Bioenergy systems for the future 10 formation of hydrogen rich gas via conversion of lignocellulosic biomass and its decomposition products

Bioenergy systems for the future 10 formation of hydrogen rich gas via conversion of lignocellulosic biomass and its decomposition products Bioenergy systems for the future 10 formation of hydrogen rich gas via conversion of lignocellulosic biomass and its decomposition products Bioenergy systems for the future 10 formation of hydrogen rich gas via conversion of lignocellulosic biomass and its decomposition products Bioenergy systems for the future 10 formation of hydrogen rich gas via conversion of lignocellulosic biomass and its decomposition products

Formation of hydrogen-rich gas via conversion of lignocellulosic biomass and its decomposition products 10 J Grams, A.M Ruppert Lodz University of Technology, Lodz, Poland 10.1 Introduction In recent years, the increased interest in the use of renewable energy sources has been observed It is related to the rapid depletion of fossil fuels and growing energy demand One of the most promising alternatives for traditional energy resources is lignocellulosic biomass The advantages of such a feedstock are usually associated with global availability, relatively low price, and limited influence on the increase in the greenhouse effect On the other hand, hydrogen is considered one of the most environmentally friendly energy carriers Moreover, it can be used in a number of chemical processes, including the production and valorization of platform molecules originating from biomass Unfortunately, currently, its main production methods are steam reforming of natural gas or coal gasification It is widely known that such processes require the use of traditional carbon resources and due to that affect considerably the quality of the environment Taking that into account researchers began the studies focused on the development of methods that allow for direct production of hydrogen from lignocellulosic feedstock The literature data shows that it can be formed by high temperature treatment or in milder conditions, that is, formic acid decomposition where arising H2 can be used as a reducing agent in different industrial processes related to the valorization of intermediates formed in lignocellulosic processing In the further part of this chapter, both mentioned directions will be discussed in more detail 10.2 High-temperature conversion of lignocellulosic biomass towards hydrogen-rich gas The production of hydrogen by high-temperature methods can be attractive from both economic and environmental points of view (Ni et al., 2006) However, the efficient conversion of lignocellulosic biomass is not an easy task due to the problems with obtaining high yield and selectivity of occurred reactions The literature data Bioenergy Systems for the Future http://dx.doi.org/10.1016/B978-0-08-101031-0.00010-7 © 2017 Elsevier Ltd All rights reserved 346 Bioenergy Systems for the Future demonstrate that pyrolysis and gasification are the most popular methods of the hightemperature processing of lignocellulosic feedstock (Bridgwater, 2012; Saxena et al., 2008; Balat et al., 2009) In this case, the feedstock is heated in the presence of inert gas or gasifying agent (i.e., oxygen or steam), respectively It leads to the production of permanent gases, bio-oil, and carbonaceous residue as demonstrated in Eq (10.1): Lignocellulosic biomass ! H2 + CO + CO2 + CH4 + Cn Hm + bio À oil + tars + char (10.1) However, it should be noted that thermal conversion of lignocellulosic biomass is a very complex process that proceeds in several steps (Wang et al., 2014) The first one consists of the decomposition of the feedstock in the temperature range of 300–500°C that results in the formation of thermally produced oxygenates In the further part of the process, the oxygenates are submitted to dehydration and cracking reactions Moreover, decarboxylation, decarbonylation, and oligomerization processes can proceed (Ruddy et al., 2014) They lead to the arising of liquid fraction containing water, hydrocarbons, and their derivatives (i.e., carboxylic acids, ketones, aldehydes, alcohols, esters, ethers, sugars, among others) In the case of the formation of gaseous products, steam reforming, dry reforming, water-gas shift, and methanation play a major role (Zhao et al., 2009) It results in the production of gas mainly consisted of hydrogen, carbon oxide, carbon dioxide, methane, and lower amount of light hydrocarbons The presence of hydrogen mixed together with other gaseous compounds makes it necessary to separate and purify this component before its use in industrial processes or as a fuel It can be performed by different methods including membrane separation, absorption of carbon dioxide, or drying (Ni et al., 2006) The composition of the gaseous products obtained in the thermal conversion of lignocellulosic feedstock depends on the final temperature of the process, heating rate, residence time, and type of biomass, among others (Ni et al., 2006; Saxena et al., 2008; Czernik and Bridgwater, 2004; Huber et al., 2006) Therefore, the change of the conditions of lignocellulosic biomass treatment makes it possible to control the concentration of particular chemical compounds in the formed mixture However, due to the fact that described process consists of a high number of chemical reactions, both desired and undesired, this control is not satisfactory It also affects the profitability of the hydrogen production That is why the scientists undertook research aimed at developing new methods of high-temperature conversion of lignocellulosic biomass that involved the use of heterogeneous catalysts The literature data demonstrates that an application of the catalyst leads to the increase in the efficiency of hydrogen production (Fig 10.1) It can be produced directly from lignocellulosic feedstock or by the conversion of earlier formed biooil in steam reforming process There are numerous examples of the studies concerning an application of the catalysts to the steam reforming of model bio-oil compounds, such as acetic acid, acetone, ethanol, ethyl acetate, benzene, xylene, phenol, glycerol, or glucose (Chen and He, 2011; Braga et al., 2016; Nabgan et al., 2016; Gao et al., 2016; Zou et al., 2015; Seung-hoon et al., 2014) Formation of hydrogen-rich gas 347 Lignocellulosic biomass Intensification of gas production, higher selectivity to H2 Thermal decomposition, cracking, reforming, water-gas shift Liquid phase (oxygenates) Gaseous products (H2, CO, CO2, CH4, C2Hx) Tar and char Intensification of cracking, dehydration, decarboxylation, decarbonylation Fig 10.1 Influence of the catalyst on the efficiency of lignocellulosic biomass conversion process 10.2.1 Effect of the type of catalyst At first, the high-temperature treatment of lignocellulosic biomass was conducted without the use of catalysts However, it was observed that an addition of natural minerals such as dolomite or olivine increased the conversion of tar formed during the decomposition of biomass (Yoon et al., 2010) In spite of the fact that those materials are cheap and thermally stable, their performance in the mentioned process was moderate In the further part of the studies, an influence of zeolites and various mesoporous materials was investigated (Adam et al., 2006; Jeon et al., 2013; Iliopoulou et al., 2012) Although it was demonstrated that the efficiency of thermal conversion of biomass can be increased when the supported catalysts containing the metallic phase are used, there are several examples of an application of noble metals as an active phase of the catalysts for fast pyrolysis of biomass (Kaewpengkrow et al., 2014; Lu et al., 2010) However, the literature data exhibit that due to the lower price and high performance in described process nickel is the most commonly used metal for high-temperature conversion of lignocellulosic biomass (Melligan et al., 2012; Swierczynski et al., 2007; Wu et al., 2013) Obviously, it should be noted that an application of nickel is associated with several drawbacks A deactivation of the catalyst by carbon deposit formation is the most important of them This process cannot be fully eliminated during the conversion of lignocellulosic feedstock in the presence of metallic catalyst However, it can be noticeably reduced by the choice of the suitable support for Ni The influence of the support on the activity and stability of the 348 Bioenergy Systems for the Future catalysts in high-temperature conversion of biomass will be discussed in the further part of this work The mechanism of catalytic conversion of lignocellulosic material is not fully understood yet Although the performed studies suggest that intermediates formed during initial decomposition of biomass are adsorbed on the surface of the catalyst and undergo dehydrogenation reaction (Ruppert et al., 2014) Swierczynski et al (2007) demonstrated that the presence of nickel catalyst facilitates the cleavage of CdO and CdC bonds in the molecules of primary products of the decomposition of lignocelluloses Subsequently, the smaller products formed in cracking reaction are easier dehydrogenated, and this way, larger amount of hydrogen can be obtained Considering other components of gaseous phase formed in thermal treatment of lignocellulosic feedstock, it should be noted that the presence of catalyst promotes reforming reaction that leads to a decrease in the methane content comparing with the process performed without catalyst Furthermore, water-gas shift reaction can proceed in the presence of residual water originated from the mixture of primary products of biomass decomposition The investigations performed by Wang et al (2014) suggested that intermediates containing oxygen formed in dehydration step were rather subjected to decarbonylation in the presence of H-ZSM5 material in comparison with the reaction performed without catalyst In the latter case, decarboxylation path was more favored Chen and He in their work (Chen and He, 2011) described the possible mechanism of hydrogen formation in reforming of oxygenates originating from biomass decomposition in the presence of metallic catalyst In the investigations, ethylene glycol was chosen as a model compound This molecule can be adsorbed on the surface of the catalyst via two carbon atoms or one carbon atom and one oxygen atom, which results in the formation of two bonds with an active phase A desired pathway of dehydrogenation of oxygenates consists of the formation of hydrogen and carbon oxide via the cleavage of CdC bond In this case, the subsequent conversion of carbon oxide to carbon dioxide and the production of additional amount of hydrogen via water-gas shift reaction are also observed The second possibility is associated with the cleavage of CdO bond and the formation of alcohol In the following step, the CdC or CdO breaking can proceed in the alcohol molecule It results in the formation of hydrogen and carbon dioxide or light alkanes, respectively The next path can lead to the production of acids that can be transformed into alkanes, carbon oxides, hydrogen, and water Taking that into account, it seems that hydrogen production can be considerably enhanced by the initial dehydrogenation of primary products of biomass decomposition and subsequent cleavage of CdC bonds while their dehydration and successive breaking of CdO bonds does not affect H2 formation so positively In spite of that the authors of the mentioned publication presented also the results of theoretical calculation concerning the ability of different metals to the cleavage of CdC and CdO bonds It was noted that catalytic properties of particular elements strictly depend on numerous factors such as the composition of the feedstock, type of the precursor of the catalyst, its preparation method, type of the support, metal loading, and conditions of thermal treatment of biomass Therefore, it is difficult to refer these results to the real reaction systems Formation of hydrogen-rich gas 349 Considering that an issue of hydrogen production from lignocellulosic biomass has been already raised in several reviews mentioned earlier, the following part of this chapter will be focused on the presentation of the examples of the latest developments related to the use of heterogeneous catalysts in this process (Fig 10.2) 10.2.1.1 Bimetallic containing nonnoble metals and perovskie-type catalyst Li et al (2014) investigated an influence of the addition of copper to the catalyst prepared from hydrotalcite-like compounds containing nickel, magnesium, and aluminum on its performance in steam reforming of lignocellulosic biomass tar derived from pyrolysis of cedar wood The obtained results revealed that Ni-Cu/Mg/Al catalyst possessed the higher activity than monometallic systems The best catalytic performance was observed for the sample with copper-to-nickel ratio ¼ 0.25 The authors concluded that the most important factor for the enhancement of the catalytic activity was the formation of Ni-Cu alloy that led to higher dispersion of nickel, increase in the amount of the active sites on the catalyst surface, and its higher affinity to the oxygen Bimetallic catalysts based on nonnoble metals Catalysts containing noble metals Efficiency improvement of high temperature conversion of biomass Modification of support of nickel catalyst Development of new multi-step processes increasing H2 yield H2 Fig 10.2 Routes of the application of heterogeneous catalysts for the improvement of the efficiency of hydrogen production in high-temperature conversion of lignocellulosic biomass 350 Bioenergy Systems for the Future During the steam reforming process, the large molecules existing in tar undergo dissociation and fragmentation on the surface of an active phase Simultaneously, steam dissociates on the metal particles giving hydrogen and oxygen atoms that can interact with hydrocarbon fragments and form the next portion of hydrogen and carbon monoxide molecules Due to the presence of Ni-Cu alloy, the smaller nickel species are formed on the catalyst surface It increases an ability of the catalyst to the creation of nickel active sites (better metal dispersion) and adsorption of hydrogen Thus, a dissociation of tar takes place more efficiently Furthermore, the smaller bimetallic particles demonstrate higher affinity to oxygen in comparison with bigger nickel species It promotes the decomposition of tar fragments adsorbed on the catalyst surface and limits the formation of carbon deposit The coke resistance of bimetallic catalyst can be also enhanced due to the presence of smaller nickel crystallites because coke formation is stimulated by larger Ni particles than steam reforming reaction The stability of Ni-Cu/Mg/Al catalyst was also linked with no aggregation of bimetallic species during the reaction The similar investigations of the steam and dry reforming of model pyrolysis gas with the use of Ni/Fe/Ce/Al2O3 catalyst were described by Xu et al (2015) In this case, the role of the second metal (iron) consisted of the promoting of cracking of pyrolysis intermediates and deposited carbon, which results in the increase in hydrogen production It was suggested that iron oxide can react with water and hydrocarbon molecules according to the reactions (10.2), (10.3): Fex OyÀ1 + H2 O ! Fex Oy + H2 (10.2) ð2n + mÞFex Oy + Cn H2m ! ð2n + mÞFex OyÀ1 + nCO2 + mH2 O (10.3) Moreover, it was demonstrated that the presence of iron can enhance the conversion of methane and selectivity to hydrogen and carbon dioxide in both steam reforming and water-gas shift reactions Lang et al (2015) developed iron catalyst for water-gas shift reaction for hydrogen enrichment in a gas from steam gasification of biomass They used ceramic foams impregnated by ceria The presence of ceria allowed for the increase in the surface area of the support and formation of relatively well-dispersed crystallites of iron However, the submission of the synthesized catalyst to the activity test resulted in the increase in iron oxide species from about 30 to 45 nm Hydrogen-rich gas was also produced by catalytic steam reforming of bio-oil or bioslurry (containing both bio-oil and biochar with the ratio of 9:1) with the use of perovskite-type materials (La1ÀxKxMnO3 or LaCo1ÀxCuxO3) (Chen et al., 2016a; Yao et al., 2016) The advantage of perovskites is their stability at high temperatures that prevents agglomeration of metal atoms in the structure of the catalyst submitted to thermal treatment The smaller metal species suppress the formation of carbon deposit that enhances the activity of the catalysts Moreover, the substitution of lanthanum present in the structure of the perovskite by potassium can lead to the enhancement of the oxygen mobility and surface area of the prepared material Both tested systems allowed for the production of hydrogen with the yield up to 70%–75% of the stoichiometric yield Formation of hydrogen-rich gas 351 The mixture of KAl and NiAl catalysts was applied in the steam gasification of wheat straw (Lv et al., 2014) that was conducted in double-bed reactor In the first step, the mixture of catalysts and biomass (gasification bed) was fluidized Subsequently, intermediates were directed to the reforming bed for further conversion The obtained results showed that owing to the use of such reaction system it is possible to obtain about 97% efficiency of carbon conversion Moreover, it was suggested that KAl promotes decomposition and cracking of biomass and primary products, NiAl favors reforming of tar and light hydrocarbons, while both catalysts enhance water-gas shift reaction The examples of the application of bimetallic containing nonnoble metals and perovskite-type catalyst to the high-temperature conversion of biomass are also presented in Table 10.1 10.2.1.2 Modification of support of Ni catalyst As mentioned earlier, Ni-based systems are the most popular groups of catalysts used in the high-temperature conversion of lignocellulosic biomass In recent years, the main attention of the researchers focused on the investigation of the influence of Application of bimetallic containing nonnoble metals and perovskite-type catalyst to the high-temperature conversion of biomass Table 10.1 No Catalyst Feedstock Ni-Cu/Mg/Al Cedar wood Ni/Fe/Ce/Al2O3 Model pyrolysis gas Model gas Fe/CeO2 supported on ceramic foam La1ÀxKxMnO3 LaCo1ÀxCuxO3 KAl, NiAl Bio-oil from fast pyrolysis of pinewood sawdust Bioslurry (90 wt% bio-oil, 10 wt% biochar) Wheat straw Process, products, and remarks regarding the influence of catalyst Reference Steam reforming of biomass tar Steam and dry reforming of model pyrolysis gas Water-gas shift for hydrogen enrichment Steam reforming of bio-oil Li et al (2014) Steam gasification of bioslurry Yao et al (2016) Steam gasification in double-bed reactor Lv et al (2014) Xu et al (2015) Lang et al (2015) Chen et al (2016a) 352 Bioenergy Systems for the Future support on the catalytic performance of such materials including catalyst activity, stability in high-temperature range, and susceptibility to deactivation (Table 10.2 and Fig 10.3) The studies performed in our group (Matras et al., 2012) revealed that ZrO2 was the most promising support of the nickel catalyst applied to the cellulose pyrolysis process conducted in a stirred batch reactor at the temperature range up to 700°C The Ni/ZrO2 sample appeared the most active among the investigated materials (Ni/Al2O3, Ni/SiO2, Ni/CeO2, Ni/TiO2, and Ni/MgO) However, in this case, nickel was introduced on the surface of commercial oxides The commercial ZrO2 possessed low Modification of support of Ni catalyst used in high-temperature conversion of biomass Table 10.2 No Catalyst Feedstock Process, products, and remarks regarding the influence of catalyst Cellulose Pyrolysis Matras et al (2012) Ni supported on ZrO2, Al2O3, ZrO2Al2O3, SiO2, CeO2 Ni/ZrO2 Cellulose Ruppert et al (2014) Ni/CeO2-ZrO2 Cellulose Ni/MexO-ZrO2 (Me ¼ Ca, Mg, Na, and K) Cellulose Ni/Mesoporous material (SBA-15, SBA-16, KIT-6, and MCM-41) Ni/CaAlOx Cellulose Pyrolysis Catalysts were prepared by different methods (precipitation with organic template, precipitation with NaOH, calcination of zirconium salt) Pyrolysis CeO2 was introduced into ZrO2 structure by impregnation, precipitation, and sol-gel method Pyrolysis Dopants were introduced on the catalyst surface by impregnation method Pyrolysis Wood sawdust Pyrolysis-steam reforming in fixed-bed two-stage reactor Reference Grams et al (2016a) Ryczkowski et al (2016) Grams et al (2016b) Chen et al (2016b) Formation of hydrogen-rich gas 353 Nickel catalyst Type of support Different metal oxide supports Application of mesoporous silicas Modification of ZrO2 by cerium and various alkali and alkaline earth metals Development of optimal method of ZrO2 synthesis (precipitation, calcination of Zr salts, use of organic template) Fig 10.3 Routes of the modification of the support of Ni catalysts for high-temperature conversion of lignocellulosic biomass surface area equal about m2/g (considerably lower than SiO2 or Al2O3) and monoclinic phase It indicated the high potential of the use of zirconium oxide as a catalyst support in the described process Therefore, in the next step of our studies, the investigations were focused on the choice of the optimal method of ZrO2 synthesis ensuring the formation of the material having the best physicochemical properties, which would allow for the achievement of the highest hydrogen yield in the hightemperature treatment of lignocellulosic biomass The zirconium oxides were prepared by precipitation with organic template, precipitation with sodium oxide, and calcination of zirconium salt (Ruppert et al., 2014) The obtained results exhibited that the highest hydrogen yield was achieved in the presence of the catalyst where nickel was introduced on the support synthesized from ZrOCl2 by precipitation with NaOH, which was followed by calcination at 700°C in air Such system contained tetragonal zirconia phase, relatively small crystallites of nickel oxide, and retained surface area in the reaction conditions In contrast, the catalyst containing ZrO2 prepared with the use of organic template showed the highest surface area, but it was not stable during the reaction and decreased of about 40% after the reaction Moreover, in the last case, zirconium oxide was amorphous It is believed that these differences were the reasons of low activity of that material Another crucial aspect was related to the ability of migration of zirconium ions on the surface of the active phase The XPS results revealed that the highest migration tendency was characteristic for tetragonal phase of zirconia (followed by monoclinic and amorphous) It was responsible for the closer contact between support and metallic phase during the reaction that can be associated with higher stability of the catalyst and the enhancement of the catalytic activity 354 Bioenergy Systems for the Future The next step of the studies was devoted to the investigation of the effect of the addition of various dopants to the structure of zirconium oxide In the first case, ZrO2 was doped by CeO2 (Grams et al., 2016a) The supports containing 15 and 50 wt% of cerium oxide were prepared by three different methods such as impregnation, precipitation, and sol-gel As in the previous cases, nickel (20 wt%) was introduced onto the support surface by impregnation method, and the activity of the catalysts was tested in high-temperature conversion of cellulose in the atmosphere of inert gas It was demonstrated that an addition of cerium oxide to the zirconium oxide support considerably increased the amount of the formed hydrogen comparing with the Ni/ZrO2 catalyst The production of the highest amount of H2 was observed in the case of the materials containing supports prepared by sol-gel and impregnation methods It was suggested that zirconium oxide promotes the activity of nickel in the reforming reaction Support containing ZrO2 can accumulate H2O molecules (which are present in the reaction mixture) and produce hydroxyl groups participating in the hydrogen formation process On the other hand, literature data show that cerium oxide, due to its high oxygen storage/release capacity and thermal stability, can limit the coke formation and increase an efficiency of carbon deposit removal (Ebiad et al., 2012; Shao et al., 2014) It was also observed in the described measurements where Ni/ZrO2 catalyst loses its activity in high-temperature conversion of cellulose noticeably faster than the material consisted of Ni supported on CeO2-ZrO2 The performance of Ni/ZrO2 catalyst in the hydrogen production from biomass can be also enhanced by the modification of zirconia support by alkali and alkaline earth metals (Ryczkowski et al., 2016) As in the previous case, it is related to the inhibition of carbon formation process (Nichele et al., 2014) An addition of alkali metals leads to the formation of oxygen vacancies that can be responsible for the arising of OH and O radicals able to stop the accumulation of carbon species on the catalyst surface Moreover, dopants take part in the formation of basic sites responsible for carbon dioxide chemisorption and facilitation of the gasification of accumulated coke (Liu et al., 2008) The adsorbed CO2 can also shift an equilibrium of the reactions that take place in the high-temperature biomass conversion and additionally increase the hydrogen production The obtained results revealed that in spite of the substantial decrease in the surface area the presence of calcium resulted in the production of higher amount of hydrogen in comparison with the catalysts containing sodium or potassium Further studies, performed by Chen et al (2016b), showed also that an addition of Ca can be responsible for the increase in CO selectivity and simultaneous drop in CO2 production in pyrolysis-steam reforming of wood sawdust The other group of the investigations was devoted to the application of mesoporous silicas as supports for nickel catalyst used in the cellulose conversion to hydrogen-rich gas (Grams et al., 2016b) The samples containing SBA-15, SBA-16, KIT-6, and MCM-41 were tested The obtained results revealed that an introduction of Ni on the surface of mesoporous support can increase H2 yield in comparison with the catalyst supported on commercial SiO2 The highest amount of hydrogen was produced in the presence of 20% Ni/SBA-15 and 20% Ni/KIT-6 samples It was demonstrated that catalytic performance of the studied materials depended not only on surface Formation of hydrogen-rich gas 357 sulfur present in the feedstock Moreover, the formation of Ni-Pt species can be responsible for the further improvement of the efficiency of secondary reactions (i.e., cracking or reforming of biomass volatiles and tars produced in the initial step of the process), which allows the enhancement of hydrogen production It is also associated with the increase in the selectivity of the process toward hydrogen and carbon oxide rather than to the formation of coke 10.2.1.4 Development of new methods of lignocellulosic biomass conversion Literature data demonstrate that not only new but also commercially available catalysts can be used for the production of hydrogen-rich gas via high-temperature treatment of lignocellulosic feedstock (Table 10.3) However, in this case, the studies are rather focused on the development of new methods of lignocelluloses conversion Chen et al (2015) investigated simultaneous gasification of gas and char formed in the pyrolysis of cotton stalks in entrained flow-bed reactor Apart from the application of commercial Ni/MgO catalyst that was responsible for the increase in the efficiency of steam reforming, the authors mentioned about the catalytic activity of char It was demonstrated that simultaneous gasification of char and pyrolysis gas allowed for the increase in the total conversion of carbon from 79% (observed in the case of two-stage pyrolysis and steam reforming process) to about 92% The presence of char influenced the composition of tar by the promotion of transformation of polycyclic aromatic compounds to low-ring or even low-chain compounds The described changes, resulting from the interactions between pyrolysis gas and char, led also to considerable decrease in the carbon deposit formation on the surface of nickel catalyst and almost twofold growth in the yield of the produced hydrogen Nanda et al (2016) performed studies on subcritical and supercritical water gasification of pinewood and wheat straw That process has already been conducted previously, but in the present case, biomass submitted to gasification was additionally impregnated by nickel salt It was showed that the efficiency of the incorporation of Ni into the structure of lignocelluloses depended on the amount of lignin that hinders the penetration of the material by dopants This is why pinewood containing more lignin accumulated lower amount of nickel in comparison with wheat straw It is worth noting that wheat straw possessed also higher content of alkali metals such as sodium, potassium, calcium, and magnesium The presence of the catalyst resulted in substantial increase in the total gas yield (about 60%) and the amount of hydrogen (even 100%) with simultaneous growth in the gasification efficiency of carbon (about 65%) The highest hydrogen yield was achieved at 500°C with biomass-to-water ratio 1:10 and longer residence time that enhanced cracking reaction The higher temperature of supercritical water promoted the production of hydrogen, carbon dioxide, and methane due to the increase in the efficiency of water-gas shift and methanation processes The efficiency of the hydrogen production can be also increased by the use of the integrated process consisted of continuous fast pyrolysis of pinewood sawdust 358 Bioenergy Systems for the Future followed by in-line steam reforming of the pyrolysis vapors with the use of commercial Ni/Al2O3 catalyst doped by calcium (Arregi et al., 2016) In this case, the first step of biomass conversion is conducted in a conical spouted-bed reactor, while the second one in a fluidized-bed reactor The char formed during pyrolysis is continuously removed from the reaction system The main product of this step is bio-oil (about 75 wt%) that is passed together with gases (about wt%) to steam reforming unit However, some part of that fraction can be lost due to not complete vaporization that influences the efficiency of the whole process According to the authors of that work, the advantage of the proposed system in comparison with gasification process is the production of gases that are free of tars It was showed that the use of steam in the pyrolysis process does not significantly affect the distribution of produced substances that is similar to that obtained with the use of nitrogen as a fluidizing agent An application of nickel catalyst increases the conversion of the volatiles present in the reaction mixture and hydrogen yield The optimization of the reaction conditions (temperature, steam-to-biomass ratio, and space time) allows for the formation of about 96% of theoretically possible amount of H2 taking into account stoichiometry of the occurred reactions 10.3 Hydrogen not only as a source of energy When hydrogen is produced for energy purposes, very often, the gasification of the bio-based feedstock is the process of choice There are however plenty other than energy-based applications for hydrogen-rich gas, and among them are all reactions that require external use of hydrogen, fuel cell applications, or many others It can be even considered that hydrogen can play pivotal role in future biorefinery schemes and its demand can increase Many processes based on cellulose valorization concerning platform molecule production (e.g., sugar alcohols) or biofuel additives (e.g., γ-valerolactone) require hydrogen Just mentioning the process of biofuel manufacture, where for the reduction of oxygen-containing compounds, a great amount of reductant typically represented by molecular fossils delivered hydrogen is required Therefore, it is essential that hydrogen for those purposes will be also bio-based Hydrogen can be obtained from carbohydrates via reforming reaction; however, this process requires harsh conditions and noble metal catalysts (Nguyen-Phan et al., 2016) On the other hand, formic acid (FA) can be used for hydrogen storage, hydrogen donor, or molecular hydrogen for many reactions It can be easily obtain from lignocellulosic biomass One way of its synthesis is acid-catalyzed hydrolysis of cellulose where sugars formed in the first step undergo subsequent processes to form equimolar amount of formic and levulinic acids (Weingarten et al., 2012) Much higher yield of FA (up to 60%–70%) can be obtained when hydrolysis is combined with high oxygen pressure Glucose of hydroxymethylfurfural formed in the first step of cellulose hydrolysis is subsequently oxidized to formic acid ( Jin et al., 2008) (Scheme 10.1) Formation of hydrogen-rich gas 359 O C6 sugar H2O O O OH –HCOOH H2O 5-Hydroxymethylfurfural OH O HO O HO O OH OH O OH H2O2 O OH + O Levulinic acid OH Formic acid O + H 2O OH Formic acid Cellulose Scheme 10.1 Two different ways of the synthesis of formic acid from biomass 10.3.1 Factors which influence the decomposition of FA The decomposition of formic acid has been mostly characterized by two reaction pathways: dehydrogenation (reaction 10.4) to form H2 and CO2 and dehydration (reaction 10.5) to form H2O and CO: HCOOH ! H2 + CO2 (10.4) HCOOH ! H2 O + CO (10.5) CO + H2 O Ð CO2 + H2 (10.6) CO + 3H2 ! CH4 + H2 O (10.7) CO2 + 4H2 ! CH4 + 2H2 O (10.8) 2HCOOH ! HCHO + CO2 + H2 O (10.9) In real reaction conditions, however, the situation is much more complex Subsequent water-gas-shift reaction (WGS, reaction 10.6) can occur In the presence of some catalysts like Ru, it has been also identified that Fischer-Tropsch reaction can take place (reactions 10.7, 10.8) Although less often, it is also mentioned in the literature that the formation of formaldehyde is possible due to the reaction of formate ions (HCOOÀ) (reaction 10.9) (Redondo et al., 2014) However, those important issues of side reactions are mostly omitted by researchers, and only very few such examples have been described (Zhang et al., 2013; Yi et al., 2013; Bulushev et al., 2013; Ciftci et al., 2013) While the side reactions decrease the hydrogen selectivity, CO is also a poison of the catalyst active centers Therefore, the design of selective catalysts for this process still remains a great challenge FA decomposition has been performed in a broad range of temperatures from room temperature to 300°C, mostly in the gas phase and flow system ( Jia et al., 2013, 2014) It was demonstrated that FA decomposition in the gas phase starts at 80°C and is finished in the temperature range of 200–260°C The reaction was mostly found to be zero-order In the gas phase, the reaction conditions seem not to have a deciding influence on the catalyst performance It was 360 Bioenergy Systems for the Future observed that neither the temperature nor the FA concentration has much influence on the process selectivity (Bulushev et al., 2010; Ojeda and Iglesia, 2009) In the aqueous phase, the reaction has been examined to a lesser extent, but the conditions are often milder (25–90°C) It is expected however that it proceeds in a different way, as solvent effects may change the reaction rate by several orders of magnitude or completely alter the mechanism for reactions in aqueous phase In the gas phase on metal surface, HCOOÀ was identified as a reactive intermediate, and the decomposition of HCOOÀ into CO2 and H2 was the rate-limiting step in this reaction By contrast, in the liquid phase, HCOOÀ is rather considered only a spectator that adsorbs on the catalyst surface (Hu et al., 2012) Additionally, the presence of water is reported to lower the activation barrier of the decarboxylation reaction in comparison with dehydration, therefore shifting the selectivity of FA decomposition toward hydrogen path (Akiya and Savage, 1998) The presence of water—beside influencing the reaction pathways—can also change the reactivity of the catalyst itself It was observed by us that some metals in its presence can significantly lower their activation barrier for hydrogenation or dehydrogenation reactions, for example, Ru that consequently is much more active in aqueous phase (Michel et al., 2014) It was also noted that, in the case of some metals, the selectivity of the FA decomposition can be significantly improved in the presence of water; for example, Ir gave 98.3%–99% selectivity for H2, additionally giving CO-free H2 at the temperatures of 110–150°C (Solymosi et al., 2011) 10.4 Catalysts used for FA decomposition Both hetero- and homogeneous catalysts, with mono- and bimetallic nanoparticles, supported on various materials or just as bulk nanoparticle catalysts, were tested in FA decomposition 10.4.1 Homogeneous catalysts Work concerning homogeneous catalysts was recently described in review paper summarizing the recent discoveries on that topic Homogeneous catalysts used for this reaction are restricted mainly but not only to different Ru complexes formed in situ Among different examples, it is interesting to mention Ru catalysts formed from [Ru (H2O)6]2 or commercial RuCl3xH2O with two equivalents of meta-trisulfonated triphenylphosphine (mTPPTS), which especially with the addition of HCOONa, resulted in excellent activity (Fellay et al., 2008, 2009) Czaun et al used homogeneous ruthenium trichloride and triphenylphosphines as catalyst precursors in emulsion and in biphasic (aqueous/organic) systems Activity and reaction selectivity of in situ formed Ru(HCO2)2(CO)2(PPh3)2, Ru(CO)3(PPh3)2, and Ru2(HCO2)2(CO)4(PPh3)2 catalysts were as well as in previous case additionally improved by the addition of the surfactants, especially sodium dodecyl sulfate to the biphasic system of toluene/water (Czaun et al., 2014) Also in another example, tetranuclear ruthenium complex [Ru4(CO)12H4], identified as active species formed in situ from precursors and additional CO resulted from FA decomposition, showed superior Formation of hydrogen-rich gas 361 activity in reaction that was boosted by the addition of NaCOOH Although the catalysts showed high activity and very often high selectivity in the reaction conditions, their separation from reactants and reaction products and their reuse would be challenging Additionally, the necessity of using surfactants or other adducts like HCOONa pushed scientist for more intensive development of heterogeneous catalysts 10.4.2 Heterogeneous catalysts Consequently, the large part of research concerns the use of different heterogeneous catalysts based mostly on the following metals: Pt Ag, Pd, Rh, Au Cu, Ni, and Fe (Zhang et al., 2013; Ojeda and Iglesia, 2009; Park et al., 2002; Gazsi et al., 2011; Luo et al., 2012; Boddien et al., 2011) The earlier work on this topic was classified in some reviews ( Johnson et al., 2010; Grasemann and Laurenczy, 2012; Enthaler et al., 2010) The recent research can be categorized into the following areas: (a) the search of selective catalysts producing CO-free gas, which are operating in ambient-temperature conditions mainly for fuel cell applications; (b) basic research focusing on understanding the principles of the catalytic active sites for this reaction and related mechanisms of FA decomposition; and (c) formic acid decomposition and its direct use for hydrogenation reactions—mainly one-pot reactions (Wa˛chała et al., 2016) (Fig 10.4) There are many methodologies of preparing selective catalysts One of the methods is based on synthesis modification in a way that would allow to obtain ultrafine welldispersed nanoparticles of the metal Zhu et al (2014) synthesized highly dispersed Pd nanoparticles deposited on nanoporous carbon MSC-30 They exchange the ligand of the chlorine precursor of Pd to hydroxide ones by the addition of NaOH The excellent catalytic properties were assigned not only to enhanced electronic interaction of chlorohydroxypalladium(II) complex and support that led to small nanoparticles but also to the crucial role of the carbon support Authors obtained high TOF value of 750 hÀ1 at 25°C and evidenced also that formic acid was decomposed exclusively to H2 and CO2 Also in the work of Cao and coworkers, the high activity of the catalyst was attributed to small metal particles Working on gold deposited on zirconia catalysts, they applied slightly modified deposition-precipitation method for synthesizing ultradispersed gold catalysts consisting in gold subnanoclusters deposited on zirconia They were able to reach TOF values as high as 1590 hÀ1 for the reaction performed in 40°C (Bi et al., 2012) Another approach was related with changing the properties of the metal by its doping/alloying with a second one Recent studies pointed out that Pd-based catalysts, such as Pd-Au (Huang et al., 2010; Zhou et al., 2008; Yuan and Liu, 2013) and Pd-Ag (Tedsree et al., 2011; Xu et al., 2014; Zhang et al., 2013), showed great potential, especially by selectively producing almost CO-free H2 Additionally, the activity of such bimetallic catalysts was much higher than monometallic counterparts Especially a lot of research was devoted to the Ag-Pd system Many different modifications, synthesis approaches, and component ratios were considered From recent examples, the work of Zhang et al is highly interesting that investigated the AgPd nanoparticles prepared via coreduction of organic precursors of 362 Bioenergy Systems for the Future Approaches for catalysts design for formic acid decomposition Small metal particles Uniform particles of the very small average size in average of 2–5 nm Activity improvement assigned mainly to small nanoparticles and support influence Alloy structure (a) Synergistic effect between two metals in the formed alloy responsible for increase of activity (b) Increased dispersion identified (c) Search of optimum composition of two metals for optimum performance Further modifications of synthesis Further improvement of bimetal composition CO free catalyst for low temperature purposes Highly dispersed Ag-Pd hollow spheres anchored on graphene Core shell structure -Synthesis with PVP or PVA used as stabilizing agents or via thermal modification Average diameter 18 nm, and wall nm Activity increase due to higher availibility of active sites and specific interactions of bimetal with the support Activity increase mainly due to (a) Charge transfer from the metal cores to Me shell This can strength the adsorption and bridge the formate via stronger back donation and increase the amount of produced hydrogen (b) Change in particle size distribution (c) Change of CO adsorption strength Fig 10.4 Schematic representation of the factors that influence the design of the catalysts used in formic acid decomposition the metals, assisted by the presence of oleic acid 1-octadecene used as surfactants where the latter one holds also as in situ reducing agent By this way, they managed to obtain uniform particles of the very small average size of 2.2 nm Very high activity (TOF 382 hÀ1 for reaction at 50°C) and selectivity observed with this material were attributed to the very small NPs size, and synergistic effect between those two metals in the formed alloy was also identified, with an optimum composition of Ag42Pd58 (Zhang et al., 2013) In another example, the group of Chen ( Jiang et al., 2016) managed to synthesize highly dispersed AgPd hollow spheres anchored on graphene by using facile one-pot hydrothermal route Those hollow nanoparticles (NPs) had an average diameter of about 18 nm and a wall thickness of about nm The excellent activity of NPs was attributed not only to the presence of this very thin shell that increases the availability of active sites for regents but also to specificity of the interactions of bimetallic particles with the graphene layer and the very good dispersion of Formation of hydrogen-rich gas 363 NPs on this support Bimetallic nanoparticles belong to a group of highly important nanomaterials that are largely unexplored Besides, numerous possible combinations of metallic elements in nanoparticles and electronic interactions among metals, bimetallic NPs may produce totally new physical and chemical properties Moreover, change in the particle morphology constitutes another way of tailoring their physicochemical properties For the above reasons, the choice of the synthesis method plays an important role in obtaining the catalysts with desired properties Therefore, a lot of place in the literature was dedicated to the investigations of many different synthesis methods, as it has been recognized that controlling the bimetallic structures plays a crucial role in achieving the demanding properties Especially, bimetallic core-shell structure that contains an inner core of one metal element and an external shell of the other metal element has shown some unique physical and chemical properties The design of the catalysts is therefore crucial, and that is why there were several interesting reports that claim that unique catalytic properties can be obtained when the coreshell structure is implemented This synthesis was investigated for several different alloys like Pd-Au or Pd-Ag (Huang et al., 2010) Authors claimed that such a structure allows superior activity for hydrogen generation The different methods were investigated with the use of stabilizing agent or just with the different reduction/calcination steps combined with chemical or thermal reduction In the later case, advantage was taken from the ability of metals to migrate in certain conditions For example, in the case of Au-Pd systems, Pd has ability to migrate during calcination steps as it is more easily oxidized than Au and forms the surface PddO bonds By tuning, the conditions of subsequent reduction are possible to influence the composition of the core versus shell (Herzing et al., 2008; Hilaire et al., 1981) By implementing this approach, PdAu@Au core-shell structure was synthesized by the use of chemical reduction without the presence of stabilizing agent Such catalysts showed superior activity and high H2 selectivity in the formic acid decomposition (Huang et al., 2010) Also, Ag@Pd core-shell synthesized by the approach using PVP as a stabilizing agent was proved to be much more active in FA decomposition than the corresponding alloy possessing the same composition or Pd alone (Tedsree et al., 2011) Despite that many researches have been done in this area, the question emerges why alloy could shape selectivity There are several explanations of the activity improvement One of the explanations is related with the existence of a synergistic effect between two metals in the alloy For example, in the case of Ag-Pd, the electrons can transfer from Ag to Pd, so that the bimetallic system was strongly modified in the way that it becomes more active In some reports, this close interaction of two metals is claimed to be responsible for activity and selectivity increase ( Jiang et al., 2016) On the other hand, it is claimed that the addition of, for example, Ag and Au, reduces the size of nanoparticles in comparison with the corresponding monometallic systems (Zhou et al., 2008) Although the same information can be found for Ag-Pd, some reports claimed that the effect of Au addition is better than that of Ag judging the particle size effect, which may be one of the reasons for the better performance of Pd-Au/C compared with Pd-Ag/C (Zhou et al., 2008) Additionally, the adsorption strength of CO is changed for such a bimetallic composition, being much weaker 364 Bioenergy Systems for the Future so that Ag and Au not form stable complexes with CO ( Judai et al., 2003) and that is why such a catalyst is more resistant to poisoning Tedsree et al explained the activity of metals and bimetallic systems by the use of density functional theory (DFT) Based on the previous findings of the group of Norskov (Ruban et al., 1997), they systematize the activity of metals in FA dehydrogenation as Pd > Rh > Pt % Ru > Au > Ag and relate this difference to the distance of the d-band center to the Fermi level The closer was the d-band center to the Fermi level of a metal, the higher was the adsorption the optimum was reached for Pd, which is in agreement with the literature as palladium is one of the most often used monometallic catalysts for FA decomposition (Larsen et al., 2006; Tedsree et al., 2011) Based on the same principle, authors explained the activity increase of the coreshell structure of bimetallic particles particularly Ag-Pd They explained it by the charge transfer from the metal cores to Pd shell, which is the reason for the net difference in the work function This can strengthen the adsorption and bridge the formate via stronger back donation, and the same can increase the amount of produced hydrogen 10.5 Decomposition of formic acid to hydrogen and subsequent hydrogenation reaction There are some interesting examples in the literature showing the use of formic acid as direct hydrogen source for hydrogenation reactions They are mostly related with biomass valorization approach where the increase of sustainability by the use of internal hydrogen source is especially desirable As formic acid is obtained in equimolar amount with levulinic acid in cellulose hydrolysis process, it is therefore very often directly used for LA hydrogenation γ-Valerolactone, a product of this hydrogenation, has many potential applications among them and is considered as a platform molecule for conversion to many useful chemicals such as polymers of high thermal stability or biofuels (Ruppert et al., 2015; Luo et al., 2015; Alonso et al., 2013) The challenge of this process is often related with the use of the same catalysts for FA decomposition and LA hydrogenation This is however not the only requirement When FA decomposition is done in batch reactor, a high conversion of formic acid is required before the LA hydrogenation can take place The reason of that is related with the nature of FA adsorption Formic acid can in the easy and strong way adsorb dissociatively on metal surfaces in the form of formate at the temperature as low as À193°C (Sun and Weinberg, 1991; Avery et al., 1982) For comparison, levulinic acid and hydrogen have a much weaker energy of adsorption (Ruppert et al., 2016) As a result, the surface of the catalyst is completely covered by formate until a high enough (very often full) conversion is reached in formic acid dehydrogenation, liberating catalytic sites for H2 and the levulinic acid It can be even said that formate acts as an inhibitor for the LA hydrogenation when the same catalysts is used (Ruppert et al., 2016) Therefore, intensive search for adequate catalyst for these subsequent reactions can be observed Both hetero- and homogeneous catalysts were investigated in this reaction Ruthenium-based homogeneous catalysts, such as [(η6-C6Me6)Ru(bpy)(H2O)][SO4] or RuCl3/PPh3, were proved to be efficient for this reaction (Mehdi et al., 2008; Formation of hydrogen-rich gas 365 Deng et al., 2009; Tang et al., 2014) However, drawbacks such as poor stability and a weak resistance to water and to mineral acids that are often present in real biomass feedstock after hydrolysis process consequently forced scientists to develop more stable heterogeneous catalysts Considering the heterogeneous catalysts, Ru was shown to be the most active among Pd-Pt ones when reaction was performed in batch reactor in aqueous phase It was also demonstrated that the further modification of Ru can influence the activity in both dehydrogenation and subsequent hydrogenation reactions Ru/C that was reduced at higher temperature was much more active in formic acid dehydrogenation This could be related to the presence of larger nanoparticles of the metal than after a lower-temperature treatment Luo et al (2013) suggested that the H2 production from HCOOH could be then favored on larger particles, so on (0001) facets, which was also observed in the literature before for other oxophilic metallic surfaces like Ni for which the activity predicted by DFT calculations was higher on Ni(111) surfaces versus Ni(211) Also, Au catalysts were tested in mentioned process Du et al was evaluating different oxides and active carbon as support for metallic Au nanoparticles Du et al (2011) evidenced that the role of the support is crucial and that zirconia was the most promising one, with an excellent 99% GVL yield being achieved over Au/ZrO2 after h of reaction at 150°C with equimolar amount of FA to LA Ag and Ag-Ni catalytic systems were also investigated, and high activity with almost full GVL yield was shown over 10% Ag 20% Ni supported as well on zirconia after h of reaction performed at 220°C The outstanding performance of Ag-Ni-ZrO2 catalyst was attributed to the surface synergy between Ag and Ni Not only noble metals were investigated Upare et al showed that nickel-promoted copper-silica can be very active in described process Authors tested their nanocomposites in high temperature of 285°C in vapor phase in the flow system The high activity and stability were attributed to synergetic effect between the two metals, and they claimed additionally that the addition of Ni was preventing the sintering of the nanoparticles (Upare et al., 2015) Also, bimetallic nanoparticles of Ni-Pt and Ni-Ru supported on ZrO2 and gammaAl2O3 were investigated in the solvent-free hydrogenation of levulinic acid using formic acid as a hydrogen source A conversion of 35% with a selectivity to GVL over 99% was obtained on 0.6 Ni-1.9 Ru/gamma-Al2O3 in the flow reaction at 50 bar of hydrogen at 90°C for 20 Authors indicated that the catalytic performance was depending on the metal dispersion on the surface and textural and surface properties of the support material (Al-Najia et al., 2016) 10.6 Summary The two showcases of hydrogen production were discussed in this chapter One of them is based on high-temperature processes Here, we highlighted the new methods of lignocellulosic treatment that prevent the catalysts deactivation and development of new stable catalysts based mainly on nonnoble metals Moreover, we described the 366 Bioenergy Systems for the Future influence of the catalysts support on the efficiency of the performed reactions In the second approach, we discussed the application of formic acid as a hydrogen source We concentrated on its use for direct hydrogenation reactions mainly in liquid phase We focused on the development and use of novel catalysts for this process The new synthesis methods aiming at metal nanoparticle formation were highlighted Also, bimetallic catalysts were described taking into account experimental and theoretical approach Presented studies showed a huge potential for the catalyst application for hydrogen production processes Their use can considerably limit the costs of the nowadays and future chemical technologies and improve the efficiency of the H2 formation Therefore, we believe that the increase of bio-based hydrogen production will take the major place in the future biorefinery schemes References Adam, J., Antonakou, E., Lappas, A.A., Stocker, M., Nilsen, M.H., Bouzga, A., Hustad, J.E., Rye, G., 2006 In situ catalytic upgrading of biomass derived fast pyrolysis vapours in a fixed bed reactor using mesoporous materials Microporous Mesoporous Mater 96, 93–101 Akiya, N., Savage, P.E., 1998 Role of water in formic acid decomposition AICHE J 44, 405–415 Al-Najia, M., Yepezb, A., Balub, A.M., Romerob, A.A., Chena, Z., Wildea, N., Lic, H., Shihc, K., Gl€asera, R., Luquebb, R., 2016 Insights into the selective hydrogenation of levulinic acid to γ-valerolactone using supported mono- and bimetallic catalysts J Mol Catal A: Chem 417, 145–152 Alonso, D.M., Wettstein, S.G., Dumesic, J.A., 2013 Gamma-valerolactone, a sustainable platform molecule derived from lignocellulosic biomass Green Chem 15, 584–595 Arregi, A., Lopez, G., Amutio, M., Barbarias, I., Bilbao, J., Olazar, M., 2016 Hydrogen production from biomass by continuous fast pyrolysis and in-line steam reforming RCS Adv 5, 25975–25985 Avery, N.R., Toby, B.H., Anton, A.B., Weinberg, W.H., 1982 Decomposition of formic acid on Ru(001): an EELS search for a formic anhydride intermediate Surf Sci 122, 574–578 Balat, M., Balat, M., Kirtay, E., Balat, H., 2009 Main routes for the thermo-conversion of biomass into fuels and chemicals Part 1: pyrolysis systems Energy Convers Manage 50, 3147–3157 Bi, Q.-Y., Du, X.-L., Liu, L.-M., Cao, Y., He, H.-Y., Fan, K.-N., 2012 Efficient subnanometric gold-catalyzed hydrogen generation via formic acid decomposition under ambient conditions J Am Chem Soc 134, 8926–8933 Boddien, A., Mellmann, D., G€artner, F., Jackstell, R., Junge, H., Dyson, P.J., Laurenczy, G., Ludwig, R., Beller, M., 2011 Efficient dehydrogenation of formic acid using an iron catalyst Science 333 (6050), 1733–1736 Braga, A.H., Sodre, E.R., Santos, J.B.O., Marques, C.M.P., Bueno, J.M.C., 2016 Steam reforming of acetone over Ni- and Co-based catalysts: effect of the composition of reactants and catalysts on reaction pathways Appl Catal B 195, 16–28 Bridgwater, A.V., 2012 Review of fast pyrolysis of biomass and product upgrading Biomass Bioenergy 38, 68–94 Bulushev, D.A., Beloshapkin, S., Ross, J.R.H., 2010 Hydrogen from formic acid decomposition over Pd and Au catalysts Catal Today 154, 7–12 Formation of hydrogen-rich gas 367 Bulushev, D.A., Beloshapkin, S., Plyusnin, P.E., Shubin, Y.V., Bukhtiyarov, V.I., Korenev, S.V., Ross, J.R.H., 2013 Vapour phase formic acid decomposition over PdAu/γ-Al2O3 catalysts: effect of composition of metallic particles J Catal 299, 171–180 Chen, D., He, L., 2011 Towards an efficient hydrogen production from biomass: a review of processes and materials ChemCatChem 3, 490–511 Chen, Z., Zhang, S., Chen, Z., Ding, D., 2015 An integrated process for hydrogen-rich gas production from cotton stalks: the simultaneous gasification of pyrolysis gases and char in an entrained flow bed reactor Bioresour Technol 198, 586–592 Chen, G., Yao, J., Liu, J., Ya, B., Shan, R., 2016a Biomass to hydrogen-rich syngas via catalytic steam reforming of bio-oil Renew Energy 91, 315–322 Chen, F., Wu, Ch., Dong, L., Vassallo, A., Williams, P.T., Huang, J., 2016b Characteristics and catalytic properties of Ni/CaAlOx catalyst for hydrogen-enriched syngas production from pyrolysis-steam reforming of biomass sawdust Appl Catal B 183, 168–175 Ciftci, A., Ligthart, D.A.J.M., Pastorino, P., Hensen, E.J.M., 2013 Nanostructured ceria supported Pt and Au catalysts for the reactions of ethanol and formic acid Appl Catal B: Environ 130–131, 325–335 Czaun, M., Goeppert, A., Kothandaraman, J., May, R.B., Haiges, R., Surya Prakash, G.K., Olah, G.A., 2014 Formic acid as a hydrogen storage medium: ruthenium-catalyzed generation of hydrogen from formic acid in emulsions ACS Catal 4, 311–320 Czernik, S., Bridgwater, A.V., 2004 Overview of applications of biomass fast pyrolysis oil Energy Fuels 18, 590–598 Czernik, S., French, R., 2014 Distributed production of hydrogen by auto-thermal reforming of fast pyrolysis bio-oil Int J Hydrogen Energy 39, 744–750 Czernik, S., French, R., Feik, C., Chornet, E., 2002 Hydrogen by catalytic steam reforming of liquid byproducts from biomass thermoconversion processes Ind Eng Chem Res 41, 4209–4215 Deng, L., Li, J., Lai, D.M., Fu, Y., Guo, Q.X., 2009 Catalytic conversion of biomass-derived carbohydrates into gamma-valerolactone without using an external H2 supply Angew Chem Int Ed Engl 48 (35), 6529–6532 Dı´az-Rey, M.R., Cortes-Reyes, M., Herrera, C., Larrubia, M.A., Amadeo, N., Laborde, M., Alemany, L.J., 2015 Hydrogen-rich gas production from algae-biomass by low temperature catalytic gasification Catal Today 257, 177–184 Du, X.L., He, L., Zhao, S., Liu, Y.M., Cao, Y., He, H.Y., Fan, K.N., 2011 Hydrogenindependent reductive transformation of carbohydrate biomass into γ-valerolactone and pyrrolidone derivatives with supported gold catalysts Angew Chem Int Ed Engl 50 (34), 7815–7819 Ebiad, M.A., Abd El-Hafiz, D.R., Elsalamony, R.A., Mohamed, L.S., 2012 Ni supported high surface area CeO2-ZrO2 catalysts for hydrogen production from ethanol steam reforming RSC Adv 2, 8145–8156 Enthaler, S., von Langermann, J., Schmidt, T., 2010 Carbon dioxide and formic acid—the couple for environmental-friendly hydrogen storage? Energy Environ Sci 3, 1207–1217 Fellay, C., Dyson, P.J., Laurenczy, G., 2008 A viable hydrogen-storage system based on selective formic acid decomposition with a ruthenium catalyst Angew Chem Int Ed 47, 3966–3968 Fellay, C., Yan, N., Dyson, P.J., Laurenczy, G., 2009 Selective formic acid decomposition for high-pressure hydrogen generation: a mechanistic study Chem Eur J 15, 3752–3760 Gao, N., Wang, X., Li, A., Wu, Ch., Yin, Z., 2016 Hydrogen production from catalytic steam reforming of benzene as tar model compound of biomass gasification Fuel Process Technol 148, 380–387 368 Bioenergy Systems for the Future Gazsi, A., Ba´nsa´gi, T., Solymosi, F., 2011 Decomposition and reforming of formic acid on supported Au catalysts: production of CO-free H2 Phys Chem C 115 (31), 15459–15466 Grams, J., Niewiadomski, M., Ryczkowski, R., Ruppert, A.M., Kwapi nski, W., 2016a Activity and characterization of Ni catalyst supported on CeO2-ZrO2 for thermo-chemical conversion of cellulose Int J Hydrogen Energy 41, 8679–8687 Grams, J., Potrzebowska, N., Goscianska, J., Michalkiewicz, B., Ruppert, A.M., 2016b Mesoporous silicas as supports for Ni catalyst used in cellulose conversion to hydrogen rich gas Int J Hydrogen Energy 41, 8656–8667 Grasemann, M., Laurenczy, G., 2012 Formic acid as a hydrogen source—recent developments and future trends Energy Environ Sci (8), 8171–8181 Herzing, A.A., Carley, A.F., Edwards, J.K., Hutchings, G.J., Kiely, C.J., 2008 Microstructural development and catalytic performance of AuÀPd nanoparticles on Al2O3 supports: the effect of heat treatment temperature and atmosphere Chem Mater 20 (4), 1492–1501 Hilaire, L., Legare, P., Holl, Y., Maire, G., 1981 Interaction of oxygen and hydrogen with Pd-Au alloys: an AES and XPS study Surf Sci 103, 125–140 Hu, Ch., Ting, S.-W., Chan, K.-Y., Huang, W., 2012 Reaction pathways derived from DFT for understanding catalytic decomposition of formic acid into hydrogen on noble metals Int J Hydrogen Energy 37, 15956–15965 Huang, Y., Zhou, X., Yin, M., Liu, C., Xing, W., 2010 Novel PdAu@Au/C core–shell catalyst: superior activity and selectivity in formic acid decomposition for hydrogen generation Chem Mater 22, 5122–5128 Huber, G.W., Iborra, S., Corma, A., 2006 Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering Chem Rev 106, 4044–4098 Iliopoulou, E.F., Stefanidis, S.D., Kalogiannis, K.G., Delimitis, A., Lappas, A.A., Triantafyllidis, K.S., 2012 Catalytic upgrading of biomass pyrolysis vapors using transition metal-modified ZSM-5 zeolite Appl Catal B 127, 281–290 Irmak, S., Meryemoglu, B., Ozsel, B.K., Hasanoglu, A., Erbatur, O., 2015 Improving activity of Pt supported metal catalysts by changing reduction method of Pt precursor for hydrogen production from biomass Int J Hydrogen Energy 40, 14826–14832 Jeon, M.-J., Jeon, J.-K., Suh, D.J., Park, S.H., Sa, Y.J., Joo, S.H., Park, Y.-K., 2013 Catalytic pyrolysis of biomass components over mesoporous catalysts using Py-GC/MS Catal Today 204, 170–178 Jia, L., Bulushev, D.A., Podyacheva, O.Yu., Boronin, A.I., Kibis, L.S., Gerasimov, E.Yu., Beloshapkin, S., Seryak, I.A., Ismagilov, Z.R., Ross, J.R.H., 2013 Pt nanoclusters stabilized by N-doped carbon nanofibers for hydrogen production from formic acid J Catal 307, 94–102 Jia, L., Bulushev, D.A., Beloshapkin, S., Ross, J.R.H., 2014 Hydrogen production from formic acid vapour over a Pd/C catalyst promoted by potassium salts: evidence for participation of buffer-like solution in the pores of the catalyst Appl Catal B: Environ 160–161, 35–43 Jiang, Y., Fan, X., Xiao, X., Qin, T., Zhang, L., Jiang, F., Li, M., Li, S., Ge, H., Chen, L., 2016 Novel AgPd hollow spheres anchored on graphene as an efficient catalyst for dehydrogenation of formic acid at room temperature J Mater Chem A 4, 657–666 Jin, F., Yun, J., Li, G., Kishita, A., Tohji, K., Enomoto, H., 2008 Hydrothermal conversion of carbohydrate biomass into formic acid at mild temperatures Green Chem 10, 612–615 Johnson, T.C., Morris, D.J., Wills, M., 2010 Hydrogen generation from formic acid and alcohols using homogeneous catalysts Chem Soc Rev 39 (1), 81–88 Judai, K., Abbet, S., W€orz, A.S., Heiz, U., Giordano, L., Pacchioni, G., 2003 Interaction of Ag, Rh, and Pd atoms with MgO thin films studied by the CO probe molecule J Phys Chem B 107, 9377–9387 Formation of hydrogen-rich gas 369 Kaewpengkrow, P., Atong, D., Sricharoenchaiku, V., 2014 Effect of Pd, Ru, Ni and ceramic supports on selective deoxygenation and hydrogenation of fast pyrolysis Jatropha residue vapors Renew Energy 65, 92–101 Lang, Ch., Secordel, X., Zimmermann, Y., Kiennemann, A., Courson, C., 2015 Hightemperature water–gas shift catalysts for hydrogen enrichment of a gas produced by biomass steam gasification C R Chim 18, 315–323 Larsen, R., Ha, S., Zakzeski, J., Masel, R.I., 2006 Unusually active palladium-based catalysts for the electrooxidation of formic acid J Power Sources 157, 78–84 Li, D., Koik, M., Che, J., Nakagawa, Y., Tomishig, K., 2014 Preparation of Ni–Cu/Mg/Al catalysts from hydrotalcite-like compounds for hydrogen production by steam reforming of biomass tar Int J Hydrogen Energy 39, 10959–10970 Liu, S., Guan, L., Li, J., Zhao, N., Wei, W., Sun, Y., 2008 CO2 reforming of CH4 over stabilized mesoporous Ni–CaO–ZrO2 composites Fuel 87 (12), 2477–2481 Lu, Q., Tang, Z., Zhang, Y., Zhu, X., 2010 Catalytic upgrading of biomass fast pyrolysis vapors with Pd/SBA-15 catalysts Ind Eng Chem Res 49, 2573–2580 Luo, Q., Feng, G., Beller, M., Jiao, H.J., 2012 Formic acid dehydrogenation on Ni(111) and comparison with Pd(111) and Pt(111) Phys Chem 116 (6), 4149–4156 Luo, Q., Wang, T., Beller, M., Jiao, H., 2013 Hydrogen generation from formic acid decomposition on Ni(2 1), Pd(2 1) and Pt (2 1) J Mol Catal A: Chem 379, 169–177 Luo, W., Sankar, M., Beale, A.M., He, Q., Kiely, C.J., Bruijnincx, P.C.A., Weckhuysen, B.M., 2015 High performing and stable supported nano-alloys for the catalytic hydrogenation of levulinic acid to γ-valerolactone Nat Commun 6, 6540–6549 Lv, X., Xiao, J., Du, Y., Shen, L., Zhou, Y., 2014 Experimental study on biomass steam gasification for hydrogen-rich gas in double-bed reactor Int J Hydrogen Energy 39, 20968–20978 Matras, J., Niewiadomski, M., Ruppert, A., Grams, J., 2012 Activity of Ni catalysts for hydrogen production via biomass pyrolysis Kinet Catal 53, 565–569 Mehdi, H., Fa´bos, V., Tuba, R., Bodor, A., Mika, L.T., Horva´th, I.T., 2008 Integration of homogeneous and heterogeneous catalytic processes for a multi-step conversion of biomass: from sucrose to levulinic acid, γ-valerolactone, 1,4-pentanediol, 2-methyltetrahydrofuran, and alkanes Top Catal 48, 49–54 Melligan, F., Hayes, M.H.B., Kwapinski, W., Leahy, J.J., 2012 Hydro-pyrolysis of biomass and online catalytic vapor upgrading with Ni-ZSM-5 and Ni-MCM-41 Energy Fuels 26, 6080–6090 Michel, C., Zaffran, J., Ruppert, A.M., Matras-Michalska, J., Jedrzejczyk, M., Grams, J., Sautet, P., 2014 Role of water in metal catalyst performance for ketone hydrogenation: a joint experimental and theoretical study on levulinic acid conversion into gammavalerolactone Chem Commun 50, 12450–12453 Nabgan, W., Amran, T., Abdullah, T., Mat, R., Nabgan, B., Gambo, Y., Moghadamian, K., 2016 Acetic acid-phenol steam reforming for hydrogen production: effect of different composition of La2O3-Al2O3 support for bimetallic Ni-Co catalyst J Environ Chem Eng (3), 2765–2773 Nanda, S., Reddy, S.N., Dalai, A.K., Kozinski, J.A., 2016 Subcritical and supercritical water gasification of lignocellulosic biomass impregnated with nickel nanocatalyst for hydrogen production Int J Hydrogen Energy 41, 4907–4921 Nguyen-Phan, D.T., Baber, A.E., Rodriguez, J.A., Senanayake, S.D., 2016 Hydrogen from oxygenated molecules Au and Pt nanoparticle supported catalysts tailored for H2 production: from models to powder catalysts Appl Catal A Gen 518, 18–47 370 Bioenergy Systems for the Future Ni, M., Leung, D.Y.C., Leung, M.K.H., Sumathy, K., 2006 An overview of hydrogen production from biomass Fuel Process Technol 87, 461–472 Nichele, V., Signoretto, M., Pinna, F., Menegazzo, F., Rossetti, I., Cruciani, G., Cerrato, G., Di Michele, A., 2014 Ni/ZrO2 catalysts in ethanol steam reforming: inhibition of coke formation by CaO-doping Appl Catal B 150–151, 12–20 Ojeda, M., Iglesia, E., 2009 Formic acid dehydrogenation on Au-based catalysts at nearambient temperatures Angew Chem 121, 4894–4897 Park, S., Xie, Y., Weaver, M.J., 2002 Electrocatalytic pathways on carbon-supported platinum nanoparticles: comparison of particle-size-dependent rates of methanol, formic acid, and formaldehyde electrooxidation Langmuir 18 (15), 5792–5798 Redondo, A.B., Fodor, D., Brown, M.A., van Bokhoven, J.A., 2014 Formaldehyde, methanol and methyl formate from formic acid reaction over supported metal catalysts Catal Commun 56, 128–133 Ruban, A., Hammer, B., Stoltze, P., Skriver, H.L., Nørskov, J.K., 1997 Surface electronic structure and reactivity of transition and noble metals J Mol Catal A: Chem 115, 421–429 Ruddy, D.A., Schaidle, J.A., Ferrell, J.R., Wang, J., Moens, L., Hensley, J.E., 2014 Recent advances in heterogeneous catalysts for bio-oil upgrading via “ex situ catalytic fast pyrolysis”: catalyst development through the study of model compounds Green Chem 16, 454–490 Ruppert, A., Niewiadomski, M., Grams, J., Kwapinski, W., 2014 Optimization of Ni/ZrO2 catalytic performance in thermochemical cellulose conversion for enhanced hydrogen production Appl Catal B 145, 85–90 Ruppert, A.M., Grams, J., Je˛drzejczyk, M., Matras-Michalska, J., Keller, N., Ostojska, K., Sautet, P., 2015 Titania-supported catalysts for levulinic acid hydrogenation: influence of support and its impact on g-valerolactone yield ChemSusChem 8, 1538–1547 Ruppert, A.M., Je˛drzejczyk, M., Sneka-Płatek, O., Keller, N., Dumon, A., Michel, C., Sautet, P., Grams, J., 2016 Ru catalysts for levulinic acid hydrogenation with formic acid as a hydrogen source Green Chem 18, 2014–2028 Ryczkowski, R., Niewiadomski, M., Michalkiewicz, B., Skiba, E., Ruppert, A.M., Grams, J., 2016 Effect of alkali and alkaline earth metals addition on Ni/ZrO2 catalyst activity in cellulose conversion J Therm Anal Calorim 126, 103–110 Saxena, R.C., Seal, D., Kumar, S., Goyal, H.B., 2008 Thermo-chemical routes for hydrogen rich gas from biomass: a review Renew Sust Energ Rev 12, 1909–1927 Seung-hoon, K., Jae-sun, J., Eun-hyeok, Y., Kwan-Young, L., Ju, M.D., 2014 Hydrogen production by steam reforming of biomass-derived glycerol over Ni-based catalysts Catal Today 228, 145–151 Shao, S., Shi, A., Liu, C., Yang, R., Dong, W., 2014 Hydrogen production from steam reforming of glycerol over Ni/CeZrO catalysts Fuel Process Technol 125, 1–7 ´ , Liliom, N., Ugrai, I., 2011 Production of CO-free H2 from formic acid Solymosi, F., Koo´s, A A comparative study of the catalytic behavior of Pt metals on a carbon support J Catal 279, 213–219 Sun, Y.-K., Weinberg, W.H., 1991 Catalytic decomposition of formic acid on Ru(001): transient measurements J Chem Phys 94 (6), 4587–4599 Swierczynski, D., Libs, S., Courson, C., Kiennemann, A., 2007 Steam reforming of tar from a biomass gasification process over Ni/olivine catalyst using toluene as a model compound Appl Catal B 74, 211–222 Tang, X., Zeng, X., Li, Z., Hu, L., Sun, Y., Liu, S., Lei, T., Lin, L., 2014 Production of γ-valerolactone from lignocellulosic biomass for sustainable fuels and chemicals supply Renew Sustain Energy Rev 40, 608–620 Formation of hydrogen-rich gas 371 Tedsree, K., Li, T., Jones, S., Chan, C.W.A., Yu, K.M.K., Bagot, P.A.J., Marquis, E.A., Smith, G.D.W., Tsang, S.C.E., 2011 Hydrogen production from formic acid decomposition at room temperature using a Ag–Pd core-shell nanocatalyst Nat Nano 6, 302–307 Upare, P.P., Jeonga, M.-G., Hwanga, Y.K., Kimb, D.H., Kima, Y.D., Hwanga, D.W., Lee, U.-H., Changa, J.-S., 2015 Nickel-promoted copper–silica nanocomposite catalysts for hydrogenation of levulinic acid to lactones using formic acid as a hydrogen feeder Appl Catal A: Gen 491, 127–135 Wa˛chała, M., Grams, J., Kwapinski, W., Ruppert, A.M., 2016 Influence of ZrO2 on catalytic performance of Ru catalyst in hydrolytic hydrogenation of cellulose towards γ-valerolactone Int J Hydrog Energy 41 (20), 8688–8695 Wang, K., Kim, K.H., Brown, R.C., 2014 Catalytic pyrolysis of individual components of lignocellulosic biomass Green Chem 16, 727–735 Weingarten, R., Conner Curtis Jr., Wm, Huber, G.W., 2012 Production of levulinic acid from cellulose by hydrothermal decomposition combined with aqueous phase dehydration with a solid acid catalyst Energy Environ Sci 5, 7559–7574 Wu, C., Wang, Z., Huang, J., Williams, P.T., 2013 Pyrolysis/gasification of cellulose, hemicellulose and lignin for hydrogen production in the presence of various nickel-based catalysts Fuel 106, 697–706 Xu, L., Luo, Z., Fan, Z., Zhang, X., Tan, C., Li, H., Zhang, H., Xue, C., 2014 Triangular Ag-Pd alloy nanoprisms: rational synthesis with high-efficiency for electrocatalytic oxygen reduction Nanoscale (20), 11738–11743 Xu, X., Jiang, E., Wang, M., Xu, Y., 2015 Dry and steam reforming of biomass pyrolysis gas for rich hydrogen gas Biomass Bioenergy 78, 6–16 Yao, J., Liu, J., Hofbauer, H., Chen, G., Yan, B., Shan, R., Li, W., 2016 Biomass to hydrogenrich syngas via steam gasification of bio-oil/biochar slurry over LaCo1ÀxCuxO3 perovskitetype catalysts Energy Convers Manage 11, 343–350 Yi, N., Saltsburg, H., Flytzani-Stephanopoulos, M., 2013 Hydrogen production by dehydrogenation of formic acid on atomically dispersed gold on ceria ChemSusChem 6, 816–819 Yoon, S.J., Choi, Y.-Ch., Lee, J.-G., 2010 Hydrogen production by steam reforming of biomass-derived glycerol over Ni-based catalysts Energy Convers Manage 51, 42–47 Yuan, D.W., Liu, Z.R., 2013 Atomic ensemble effects on formic acid oxidation on PdAu electrode studied by first-principles calculations J Power Sources 224, 241–249 Zhang, S., Metin, O., Su, D., Sun, S.H., 2013 Monodisperse AgPd alloy nanoparticles and their superior catalysis for the dehydrogenation of formic acid Angew Chem Int Ed 52, 3681–3684 Zhao, M., Florin, N.H., Harris, A.T., 2009 The influence of supported Ni catalysts on the product gas distribution and H2 yield during cellulose pyrolysis Appl Catal B 92, 185–193 Zhou, X., Huang, Y., Xing, W., Liu, C., Liao, J., Lu, T., 2008 High-quality hydrogen from the catalyzed decomposition of formic acid by Pd-Au/C and Pd-Ag/C Chem Commun 30, 3540–3542 Zhu, Q.-L., Tsumoria, N., Xu, Q., 2014 Sodium hydroxide-assisted growth of uniform Pd nanoparticles on nanoporous carbon MSC-30 for efficient and complete dehydrogenation of formic acid under ambient conditions Chem Sci 5, 195–199 Zou, J., Yu, B., Zhang, S., Zhang, J., Chen, Y., Cui, L., Xu, T., Cai, W., 2015 Hydrogen production from ethanol over Ir/CeO2 catalyst: effect of the calcination temperature Fuel 159, 741–750 ... stability of the catalyst and the enhancement of the catalytic activity 354 Bioenergy Systems for the Future The next step of the studies was devoted to the investigation of the effect of the addition... activity and stability of the 348 Bioenergy Systems for the Future catalysts in high-temperature conversion of biomass will be discussed in the further part of this work The mechanism of catalytic conversion. .. loading, and conditions of thermal treatment of biomass Therefore, it is difficult to refer these results to the real reaction systems Formation of hydrogen- rich gas 349 Considering that an issue of