Introduction to the Preparation and Properties
This chapter explores the preparation of hydrogen peroxide, covering its historical context, current applications, and future prospects for in situ production It will provide an overview of the physical properties of hydrogen peroxide for clarity Additionally, the chapter will emphasize safe handling practices for peroxygen compounds, methods for the destruction of residual peroxygens, and the necessary toxicological and occupational health considerations associated with hydrogen peroxide management.
2 Industrial Manufacture of Hydrogen Peroxide
The industrial production of hydrogen peroxide began in 1818 when L J Thenard isolated it by reacting barium peroxide with nitric acid, yielding a low concentration of aqueous hydrogen peroxide This process can be enhanced using hydrochloric acid, resulting in the formation of hydrogen peroxide alongside soluble barium chloride The barium chloride is then eliminated through precipitation with sulfuric acid.
Thenard pioneered the first commercial production of aqueous hydrogen peroxide, although it wasn't until over sixty years later that his wet chemical process was utilized on a commercial scale This method of industrial hydrogen peroxide production continued to be used until the mid-20th century At the turn of the 19th century, around 10,000 metric tonnes of barium peroxide were transformed into approximately 2,000 metric tonnes of hydrogen peroxide However, Thenard's process faced significant limitations, particularly the production of only three percent m/m aqueous hydrogen peroxide solutions, which hindered its widespread adoption.
Thenard's method for producing aqueous hydrogen peroxide faced significant challenges due to prohibitively high production costs, which limited its market potential Additionally, the presence of high levels of impurities in the isolated hydrogen peroxide led to poor stability, further complicating its commercial viability.
The drawbacks of Thenard's process were significantly mitigated by Meidinger's 1853 discovery that hydrogen peroxide could be electrolytically produced from aqueous sulfuric acid Berthelot later demonstrated that peroxodisulfuric acid serves as the intermediate in this process, which is then hydrolyzed to yield hydrogen peroxide and sulfuric acid.
The first hydrogen peroxide plant utilizing the electro-chemical process began operations in 1908 at the Osterreichische Chemische Werke in Weissenstein In 1910, the Weissenstein process was modified to create the Miincher process by Pietzsch and Adolph at the Elektrochemische Werke in Munich By 1924, Reidel and Lowenstein introduced ammonium sulfate for electrolysis, leading to the production of ammonium peroxodisulfate and potassium peroxodisulfate, which were then hydrolyzed into hydrogen peroxide This innovation significantly increased hydrogen peroxide production to approximately 35,000 metric tonnes per annum.
In 1901, Manchot achieved a significant advancement in the industrial production of hydrogen peroxide by demonstrating that autoxidizable compounds, such as hydroquinones and hydrazobenzenes, react quantitatively in alkaline conditions to yield peroxides Building on this foundation, Walton and Filson proposed in 1932 a method to produce hydrogen peroxide through the alternating oxidation and reduction of hydrazobenzenes Later, Pfieiderer refined this process by developing an alkaline autoxidation technique for hydrazobenzenes, which resulted in the production of sodium peroxide, utilizing sodium amalgam to reduce azobenzene This innovative technology was commercialized by Kymmene AB at their plant in Kuisankoski, Finland.
Figure 1.2 Electrochemical manufacture of aqueous hydrogen peroxide www.pdfgrip.com
The azobenzene process faced significant challenges, particularly in the hydrogenation of azobenzene with sodium amalgam and the oxidation of hydrazobenzene in alkaline solutions These issues were effectively addressed by Riedl, who utilized polynuclear hydroquinones Building on the research of Riedl and Pfleiderer, BASF developed the anthraquinone process, commonly known as the AO process, between 1935 and 1945, achieving a pilot production of 30 metric tonnes monthly Subsequently, two large-scale plants were established in Heidebreck and Waldenberg, each designed to produce 2000 metric tonnes annually, although construction was interrupted at the end of World War II.
In 1953, E.I Dupont de Nemours established the first hydrogen peroxide plant utilizing the AO process, significantly boosting hydrogen peroxide production capacity By 1996, the global production capacity reached 1.3 million metric tonnes of 100% m/m hydrogen peroxide.
The underlying chemistry of the AO process is outlined in Figure 1.3 and a typical autoxidation plant schematic is summarized in Figure 1.4.
The AO processes consistently involve dissolving a 2-alkylanthraquinone in a suitable solvent, which is then catalytically hydrogenated to produce 2-alkylanthrahydroquinone This solution, known as the reaction carrier or working material, is typically referred to as the working solution Common industrial carriers include 2-/er/-amylanthraquinone, 2-iso-seoamylanthraquinone, and 2-ethylanthraquinone After hydrogenation, the working solution containing alkylanthrahydroquinone is separated from the catalyst and aerated with an oxygen-rich gas, such as compressed air, to regenerate the alkylanthraquinone while producing hydrogen peroxide Subsequently, the hydrogen peroxide is extracted from the oxidized working solution using demineralized water, followed by purification of the aqueous extract.
Figure 1.3 Anthrahydroquinone autoxidation process for the manufacture of aqueous hydrogen peroxide www.pdfgrip.com
The AO process involves the conversion of gaseous hydrogen and oxygen into hydrogen peroxide, which is then concentrated through fractionation to achieve the desired strength.
Selecting the appropriate quinone is crucial for optimizing several factors, including the solubility of both the quinone and hydroquinone forms, resistance to non-specific oxidation, and availability Additionally, the potential for degradation products and their regeneration into active quinones influences this decision During the hydrogenation process, various by-products can form, starting with the 2-alkylanthraquinone in the working solution This compound complexes with a palladium metal catalyst and reacts with hydrogen, resulting in the formation of a metal-containing species and 2-alkylhydroanthraquinone The latter undergoes multiple secondary reactions throughout each cycle of the process.
The 2-alkylhydroanthraquinone (A) when in contact with the catalyst will undergo a small amount of catalytic reduction (B) on the ring, initially on the unsubstituted ring, yielding a tetrahydroalkylanthrahydroquinone Unfortu-
Regenerato r Oxidize r Extracto r Stil l www.pdfgrip.com
Secondary reactions involving 2-alkylanthrahydroquinones lead to the formation of stable octa-products, which persist due to their low oxidation rate The tautomerism of 2-alkylhydroanthraquinone results in hydroxyanthrones, which can be reduced to anthrones Additionally, the epoxide produced from alkylhydroanthraquinone does not contribute to hydrogen peroxide formation and results in a loss of active quinone Consequently, strategies have been proposed to regenerate the tetrahydro compound from the epoxide.
A number of additional processes are also required to maintain the AO process For example, in order for the hydrogenation phase to run efficiently,
In the modern AO process, the hydrogenation step is crucial, as it involves the removal, regeneration, and return of part of the catalyst load to the hydrogenator During this phase, quinone decomposition products that cannot be converted back into active quinones are produced, prompting significant research into new hydrogenation catalysts and designs that often diverge from the traditional BASF principle The BASF plant utilizes a Raney nickel catalyst under slight pressure; however, due to its sensitivity to oxygen, the working solution from earlier extraction, drying, and purification stages cannot be directly introduced into the hydrogenator This solution still contains residual hydrogen peroxide, necessitating its decomposition over a supported Ni-Ag catalyst before proceeding.
Raney nickel a = pre-contact column; b = feed tank to hydrogenator; c = reactor; d = catalyst feed tank; e = oxidizer feed tank; f = safety filter; g = catalyst removal tank.
Figure, 1.6 BA SF hydrogenator www.pdfgrip.com
Figure 1.7 Destruction of residual hydrogen peroxide in the BASF process
(Figure 1.7), together with a small amount of hydrogenated working solution (which also contains 2-alkylhydroanthraquinone) Such a step removes the hydrogen peroxide completely, thus extending the life of the Raney nickel catalyst.
Raney nickel, while used as a hydrogenation catalyst in some AO plants, suffers from limited selectivity and requires stringent safety measures due to its pyrophoric nature BASF has improved its performance by pre-treating the catalyst with ammonium formate However, most AO plants prefer palladium hydrogenation catalysts for their higher selectivity, stability against hydrogen peroxide, and easier handling Degussa utilizes palladium black in their hydrogenation processes, benefiting from nearly complete hydrogen conversion, simple catalyst exchange, and non-pyrophoric properties Laporte Chemicals has advanced hydrogenation operations by using supported palladium with a particle size of 0.06-0.15 mm, facilitating easier filtration and catalyst recirculation, alongside a new design for the hydrogenation phase.
Industrial Manufacture of Hydrogen Peroxide
The industrial production of hydrogen peroxide began in 1818 when L J Thenard isolated it by reacting barium peroxide with nitric acid, yielding a low concentration of aqueous hydrogen peroxide This process can be enhanced using hydrochloric acid, resulting in the formation of both hydrogen peroxide and soluble barium chloride The barium chloride is then eliminated through precipitation with sulfuric acid.
Thenard pioneered the first commercial production of aqueous hydrogen peroxide, although it wasn't utilized on a large scale until over sixty years later This industrial method remained in use until the mid-20th century, with around 10,000 metric tonnes of barium peroxide being transformed into approximately 2,000 metric tonnes of hydrogen peroxide annually at the turn of the 19th century However, Thenard's process faced significant limitations, primarily producing only three percent m/m aqueous hydrogen peroxide solutions, which hindered its widespread adoption.
Thenard's method for producing aqueous hydrogen peroxide faced significant challenges, including prohibitively high production costs that limited market availability Additionally, the presence of high levels of impurities in the isolated hydrogen peroxide resulted in poor stability.
In 1853, Meidinger discovered that hydrogen peroxide could be produced electrolytically from aqueous sulfuric acid, addressing the disadvantages of Thenard's earlier process Berthelot later identified peroxodisulfuric acid as the intermediate formed during this reaction, which is then hydrolyzed to yield hydrogen peroxide and sulfuric acid.
The first hydrogen peroxide plant utilizing the electro-chemical process began operations in 1908 at the Osterreichische Chemische Werke in Weissenstein This process was further refined in 1910, leading to the development of the Miincher process by Pietzsch and Adolph at Elektrochemische Werke in Munich In 1924, Reidel and Lowenstein introduced a new method using ammonium sulfate during electrolysis, resulting in ammonium peroxodisulfate or potassium peroxodisulfate, which were then hydrolyzed to produce hydrogen peroxide This innovation significantly increased hydrogen peroxide production to approximately 35,000 metric tonnes per annum.
In 1901, Manchot achieved a significant advancement in the industrial production of hydrogen peroxide by demonstrating that autoxidizable compounds, such as hydroquinones and hydrazobenzenes, can quantitatively react under alkaline conditions to yield peroxides Later, in 1932, Walton and Filson introduced a method for producing hydrogen peroxide through the alternating oxidation and reduction of hydrazobenzenes Following this, Pfieiderer developed a process for the alkaline autoxidation of hydrazobenzenes that resulted in the production of sodium peroxide, utilizing sodium amalgam to reduce azobenzene This innovative technology was commercialized by Kymmene AB in a plant located in Kuisankoski, Finland.
Figure 1.2 Electrochemical manufacture of aqueous hydrogen peroxide www.pdfgrip.com
The azobenzene process faced significant challenges, particularly in the hydrogenation of azobenzene with sodium amalgam and the oxidation of hydrazobenzene in alkaline solutions Riedl successfully addressed these issues by utilizing polynuclear hydroquinones Building on Riedl and Pfleiderer's research, BASF introduced the anthraquinone process, also known as the AO process, between 1935 and 1945, achieving a pilot production of 30 metric tonnes per month Subsequently, two large-scale plants were constructed in Heidebreck and Waldenberg, each designed to produce 2000 metric tonnes annually, although construction was interrupted at the end of World War II when both facilities were only partially completed.
In 1953, E.I Dupont de Nemours established the first hydrogen peroxide plant utilizing the AO process, significantly boosting hydrogen peroxide production capacity By 1996, the global production capacity reached 1.3 million metric tonnes of 100% m/m hydrogen peroxide.
The underlying chemistry of the AO process is outlined in Figure 1.3 and a typical autoxidation plant schematic is summarized in Figure 1.4.
The AO processes involve dissolving a 2-alkylanthraquinone in a suitable solvent, which is then hydrogenated to produce 2-alkylanthrahydroquinone This solution, known as the working solution or reaction carrier, typically includes carriers like 2-tert-amylanthraquinone and 2-ethylanthraquinone After hydrogenation, the working solution is separated from the catalyst and aerated with an oxygen-containing gas to regenerate the alkylanthraquinone and produce hydrogen peroxide The hydrogen peroxide is extracted from the oxidized solution using demineralized water, followed by purification of the aqueous extract.
Figure 1.3 Anthrahydroquinone autoxidation process for the manufacture of aqueous hydrogen peroxide www.pdfgrip.com
The AO process involves the conversion of gaseous hydrogen and oxygen into hydrogen peroxide, which is then concentrated through fractionation to achieve the desired strength.
Selecting the appropriate quinone is crucial for optimizing several factors, including the solubility of both the quinone and hydroquinone forms, resistance to non-specific oxidation, and availability Additionally, the potential formation of degradation products and their regeneration into active quinones must be considered During the hydrogenation process, various by-products can arise, starting with a solution containing only the 2-alkylanthraquinone species This compound forms a complex with a palladium metal catalyst, which then reacts with hydrogen to produce a metal-containing species and 2-alkylhydroanthraquinone The latter undergoes multiple secondary reactions throughout each cycle of the process.
The 2-alkylhydroanthraquinone (A) when in contact with the catalyst will undergo a small amount of catalytic reduction (B) on the ring, initially on the unsubstituted ring, yielding a tetrahydroalkylanthrahydroquinone Unfortu-
Regenerato r Oxidize r Extracto r Stil l www.pdfgrip.com
In the presence of 2-alkylanthrahydroquinones, secondary reactions occur, leading to the formation of an octa-product (C) that remains stable due to its low oxidation rate The tautomerism of 2-alkylhydroanthraquinone produces hydroxyanthrones (D, E), which can be further reduced to anthrones (G, H) Additionally, the epoxide (F) generated from alkylhydroanthraquinone does not contribute to hydrogen peroxide formation and results in a loss of active quinone Consequently, strategies have been proposed to regenerate the tetrahydro compound from the epoxide.
A number of additional processes are also required to maintain the AO process For example, in order for the hydrogenation phase to run efficiently,
In the modern AO process, the hydrogenation step is crucial, as it involves the removal, regeneration, and return of part of the catalyst load to the hydrogenator During this phase, quinone decomposition products that cannot be converted back into active quinones are generated, prompting significant research into new hydrogenation catalysts and designs that often diverge from traditional BASF principles The BASF plant utilizes a Raney nickel catalyst under slight pressure; however, due to its sensitivity to oxygen, the working solution from prior extraction, drying, and purification steps cannot be directly introduced into the hydrogenator This solution still contains residual hydrogen peroxide, necessitating its decomposition over a supported Ni-Ag catalyst before hydrogenation.
Raney nickel a = pre-contact column; b = feed tank to hydrogenator; c = reactor; d = catalyst feed tank; e = oxidizer feed tank; f = safety filter; g = catalyst removal tank.
Figure, 1.6 BA SF hydrogenator www.pdfgrip.com
Figure 1.7 Destruction of residual hydrogen peroxide in the BASF process
(Figure 1.7), together with a small amount of hydrogenated working solution (which also contains 2-alkylhydroanthraquinone) Such a step removes the hydrogen peroxide completely, thus extending the life of the Raney nickel catalyst.
Raney nickel, while a hydrogenation catalyst, has limited selectivity, resulting in a low ratio of hydroquinone to tetrahydro compound formation BASF has addressed this issue by pre-treating the catalyst with ammonium formate, although its pyrophoric nature necessitates stricter safety measures Despite these challenges, some AO plants continue to use Raney nickel; however, most prefer palladium hydrogenation catalysts due to their superior selectivity, stability against hydrogen peroxide residues, and simpler handling Degussa predominantly utilizes palladium black, which offers near-quantitative hydrogen conversion, easy exchange, non-pyrophoric properties, and straightforward reactivation Laporte Chemicals has advanced the hydrogenation process by introducing supported palladium with a particle size of 0.06-0.15 mm, facilitating easier filtration and catalyst recirculation, alongside a new design for the hydrogenation phase.
The Laporte hydrogenator features a series of tubes that extend just beneath the liquid's surface, allowing hydrogen to be introduced at the bottom of each tube, creating small gas bubbles This process establishes a counter current flow, driven by the density differences between the solutions in the tubes and the reactor Additionally, the continuous movement of the working solution draws the palladium catalyst suspension into the tubes.