Tom Tat La - English Study On The Treatment Of Exhaust Gases Containing Aromatic Vocs (Benzene And Toluene) Using Cu (Co)-Mnox Catalysts.pdf

As a result, the thesis proposes combining catalytic oxidation and adsorption methods to eliminate aromatic VOCs, such as benzene and toluene, from the exhaust gas mixture produced durin

MINISTRY OF EDUCATION AND TRANING

HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY

TRAN THI THU HIEN

STUDY ON THE TREATMENT OF EXHAUST GASES CONTAINING AROMATIC VOCs (BENZENE AND TOLUENE)

USING Cu (Co)-MnO x CATALYSTS

Major: Environmental Engineering Code: 9520320

THE ABTRACT OF ENVIRONEMENTAL ENGINEERING

DOCTORAL DISSERTATION

Hà Nội – 2024

The dissertation was accomplished in

Ha Noi University of Science and Technology

Supervisors:

1 Prof Dr Le Minh Thang

2 Assoc Prof Dr Ly Bich Thuy

Reviewer 1: Assoc Prof Dr Duong Cong Hung

Reviewer 2: Assoc Prof Dr Le Minh Cam

Reviewer 3: Assoc Prof Dr Nguyen Thi Viet Nga

The dissertation was defended before the scientific committee

at the level of University at Ha Noi University of Science and Technology at 8:30 am on 16th October 2024

The dissertation information can be found at following libraries:

1 Tạ Quang Bửu Library- Ha Noi University of Science and Technology

2 Viet Nam national library

Người hướng dẫn khoa học: GS TS Lê Minh Thắng

PGS.TS Lý Bích Thủy

INTRODUCTION

1 The necessity of the study

VOCs (BTEX) are a concern because they can harm human health and the environment if their concentration exceeds certain levels Some VOCs, such as benzene, are considered potential substances that can cause cancer They can cause severe damage to the liver, kidneys, brain, nervous system, antibody system, and cancer risk [1] Additionally, some VOCs can contribute to environmental phenomena by producing secondary pollutants such as peroxyacetyl nitrate (PAN), the main components of photochemical smog Therefore, controlling VOCs is necessary and has been researched for

a long time

Nowadays, waste tyres are one of the wastes that have become

a growing environmental concern A favorable and adequate disposal method for waste tires is pyrolysis, an environmentally friendly and efficient method In addition, the exhaust gas from the waste tyre pyrolysis process contains many VOCs, incredibly aromatic compounds, which can harm human health if released into the environment untreated

Numerous techniques have been researched and implemented

to eliminate VOCs Catalytic oxidation is an advanced environmental engineering technique that effectively oxidizes and breaks down harmful organic compounds, precisely aromatic VOCs, to prevent the release of pollutants into the environment Once the adsorption process reaches saturation, the adsorbent must be desorbed and treated using oxidation As a result, the thesis proposes combining catalytic oxidation and adsorption methods to eliminate aromatic VOCs, such

as benzene and toluene, from the exhaust gas mixture produced during the waste tire pyrolysis process

Therefore, the thesis "Study on the treatment of exhaust gases containing aromatic VOCs (benzene and toluene) using Cu (Co)-MnOx catalysts" is necessary to study and develop the catalysts that exhibit high catalytic activity at low reaction temperatures for the effective treatment of aromatic VOCs in industrial exhaust gases such

as waste tire pyrolysis aims to improve the air environment, toward the goal of environment protection

2 The objectives of the study

The thesis aims to study and develop a high-activity catalyst system at a low reaction temperature to remove aromatic VOCs that can be applied on an industrial scale, focusing on improving the air environment and toward environmental protection goals

The objectives of the study are:

• Synthesis of non–noble catalysts and evaluate their catalytic activity for the toluene complete oxidation;

• Optimize the composition of catalysts by studying the influence factors such as the synthesis method, the molar ratio

of each metal component and sulfur compound on the catalytic activity;

• Synthesis of non–noble catalysts supported on cordierite or activated carbon (AC) and evaluate their activity for toluene and benzene complete oxidation process on a laboratory scale;

• Evaluate the performance of non–noble catalysts supported

on cordierite and activated carbon for treating exhaust gas mixture from (containing benzene, toluene) the waste tire pyrolysis process on pilot scale

3 Content research

Content 1: Synthesis of manganese oxide and non–noble catalysts and

evaluation of their catalytic activity for the complete oxidation of toluene to select the catalyst for VOC oxidation

Content 2: Synthesizing mixed manganese and copper oxide catalysts

in powder form involves identifying an appropriate synthesis method and determining the optimal molar Cu/Mn ratio to optimize catalyst composition Following that, the impact of the sulfur compound on the catalytic activity of the CuMnOx12 catalyst was investigated Furthermore, the synthesis of the CuMnOx12 catalysts supported on cordierite and AC was carried out, and their activity for the complete oxidation of toluene and benzene was evaluated on a laboratory scale

Content 3: Synthesizing mixed manganese and cobalt oxide catalysts

in powder form involves determining the optimal molar Co/Mn ratio

to optimize the catalyst composition Additionally, the CoMnOx91 catalysts supported on cordierite were synthesized, and their activity for the complete oxidation of toluene and benzene was evaluated on a laboratory scale

Content 4: Evaluate the performance of the catalyst system (15%

CoMnOx91/cordierite catalyst for the oxidation unit and 7% CuMnOx12/AC catalyst for the adsorption unit) for treating exhaust gas mixture containing aromatic VOCs (toluene, benzene) from the

waste tyre pyrolysis process on a pilot scale

4 Research methods

- Inheritance method: conduct a literature review

- Experimental research:

+ Perform a laboratory-scale study;

+ Conduct a pilot scale study

- Methods of analysis, evaluation, and comparison

5 The research object and scope of the study

The research object:

• Popular VOCs represented for the BETX group: toluene, benzene;

• Non-noble catalysts in powder form (focus on CuMnOx and CoMnOx catalyst) and non-noble catalysts are supported on substrate or support (focus on CuMnOx12/cordierite, CoMnOx91/cordierite, CuMnOx12/AC catalyst);

• The treatment of exhaust gases containing aromatic VOCs (benzene and toluene)

The scope of study:

• Synthesizing non–noble catalysts in powder form by some synthesis methods such as hydrothermal, co-precipitation, thermal evaporation, and sol-gel and evaluating their catalytic activity on a laboratory scale;

• Synthesizing non–noble catalysts supported on the substrate

or support (cordierite, AC) by the impregnation method and evaluating their catalytic activity on a laboratory scale;

• Evaluating the catalyst's performance for a specific exhausted gas treatment process (the exhausted gas mixture from the waste tyre pyrolysis process) on a pilot scale

6 The science and practical significance

The scientific significance

• The thesis has developed the effective CuMnOx and CoMnOx

catalyst with the optimal Cu/Mn and Co/Mn ratio for the complete oxidation of toluene and benzene;

• The thesis has determined the influence of sulfur compounds

on the catalytic activity of the CuMnOx catalyst;

• The thesis has examined the process of treating exhaust gases containing aromatic VOCs from the waste tire pyrolysis using catalysts supported on cordierite and activated carbon Practical significance

• The thesis has decreased the treatment temperature of the VOCs by combining the complete oxidation and adsorption processes

6 The new contribution of the dissertation

• Development of CuMnOx, CoMnOx, CuMnOx/cordierite, CuMnOx/AC, and CoMnOx/cordierite with a suitable ratio of Mn/Cu, and Co/Mn exhibited high catalytic activity at low temperatures in toluene, benzene oxidation process, and benzene adsorption process (completely oxidize benzene, toluene at 250 oC over CuMnOx12, CoMnOx91 catalysts and completely oxidize benzene, toluene at 350 oC for the 23% CuMnOx12/cordierite, 15% CoMnOx91/cordierite, the 7% CuMnOx12/AC catalyst achieves a 46.57% benzene conversion, with 13.47% YCO2 at 150 °C) and stable activity for a long examination period;

• Exploration of the influence of sulfur compounds on the catalytic activity of CuMnOx 12 catalysts in the benzene oxidation process (the introduction of 800 ppm SO2 caused a 20% decrease in benzene conversion, while the presence of

2000 ppm H2S led to a 30% reduction);

• Development of a treatment method which is a combination

of catalytic complete oxidation and adsorption methods (application of the most active catalysts in this study: 15% CoMnOx91/cordierite and 7% CuMnOx12/AC catalyst) for treatment of exhaust gases mixture containing aromatic VOCs (toluene, benzene) from waste tire pyrolysis in a pilot system

8 Structure of the dissertation

The structure of the dissertation comprises of

Introduction

Chapter 1 Literature review

Chapter 2 Experiment

Chapter 3 Results and discussion

Conclusions and Recommendations

CHAPTER 1 LITERATURE REVIEW

1.1 Overview of volatile organic compounds (VOCs)

Volatile organic compounds (VOCs) are organic substances that quickly evaporate at room temperature According to the US-EPA, VOCs are carbon compounds, excluding carbon monoxide, carbon dioxide, carbonic acid, metal carbides or carbonates, and ammonium carbonate, that participate in photochemical reactions in the atmosphere, except for those considered to have negligible photochemical reactions [13] This study focuses on toluene and benzene, the substances represented by aromantic VOCs, seriously influencing human health and the environment Especially removing benzene to protect human health is an urgent task that is needed for the goal of sustainable development and environmental protection

1.2 Overview of VOCs control methods and engineering

VOCs control methods and engineering consist of prevention, concentration and recovery, and oxidation

1.3 Overview of catalytic oxidation of VOCs

1.3.1 Mechanisms and kinetics of catalytic oxidation of VOCs

Three main mechanisms have been proposed for the catalytic oxidation of VOCs:

-The Langmuir-Hinshelwood mechanism

-The Eleye Rideal mechanism

-Mars-van Krevelen model

1.3.2 Catalyst for the VOCs oxidation

1.3.2.1 The noble–based catalyst

The noble-based catalyst (Pt, Pd, Au, Ag, etc.,.) often exhibited high efficiency for removing VOCs at low temperatures However, they have high manufacturing costs, limited source materials, and are easily influenced by many substances in the feed stream

1.3.2.2 The non - noble metal-based catalyst

The non-noble metal oxides are potential catalysts for replacing noble metals in VOC oxidation They have various sources, low prices, and high activity Almost non-noble metal-based catalysts are an excellent alternative to noble metals in VOC oxidation due to their high activity, sulfur stability, and heat resistance Although their

activity is less than noble oxides, they are less poisonous and have good resistance to catalytic poisoning

1.3.2.3 The mixed non-noble metal oxide catalyst

Many studies have shown that combining manganese oxide with other transition metal oxides like copper and cobalt can improve the properties and performance of the catalyst The catalyst has active oxygen species related to Cu [89], and the presence of manganese oxide can promote CuO reduction and play a particular role in oxygen donors [90] According to Li et al [67], the CoMnOx catalyst has higher activity than Mn3O4 and Co3O4 In addition, forming the Co-

Mn solid solution enhanced the electron transfer between cobalt and manganese ions, promoting redox ability [76]

CHAPTER 2 EXPERIMENT

The research process can be divided into three stages:

• Synthesis and evaluate the catalytic activity of the non - noble metal-based catalysts

• Synthesis and evaluate the catalytic activity of the non – noble metal-based catalysts supported on the substrate/support

• Evaluate the catalytic activity of catalyst on pilot scale

2.1 The synthesis of the catalyst

2.1 Chemical substances and substrates, supports

Three nitrate salts of copper (99%), cobalt (99%), and manganese were employed as the precursors, which were supplied by Xilong Chemical Co., ltd (China) The commercial porous materials, namely activated carbon (AC), were supplied by Tra Bac JSC, and cordierite was provided by Hanoi University of Science and Technology

2.1.2 The non – noble metal based catalyst

- The non – nobal metal based catalyst: NCO-1.5, NCO-1.0, NCO-0.5, α-MnO2 120, α-MnO2 150, β-MnO2, MnO2

- The manganese-based catalyst in powder form

CuMnOx catalyst (CuO, CuMnOx HT, CuMnOx CP 1, CuMnOx CP

2, CuMnOx TE, CuMnOx 13, CuMnOx 12, CuMnOx 11, CuMnOx 21

và CuMnOx 31) and the CoMnOx catalyst (Co3O4, CoMnOx 13, CoMnOx 12, CoMnOx 11, CoMnOx 21, CoMnOx 31)

- The manganese-based catalyst/cordierite or AC

CuMnOx/cordierite (5% CuMnOx12/ cordierite, 10% CuMnOx12/ cordierite, 23% CuMnOx12/ cordierite, 37% CuMnOx12/ cordierite, CuMnOx12 powder (cordierite));

CuMnOx/AC (7% CuMnOx/ AC cordierite, 20% CuMnOx/ AC cordierite and 25% CuMnOx/ AC cordierite, CuMnOx12 powder (AC));

and the CoMnOx/cordierite (8% CoMnOx31/ cordierite, 11% CoMnOx31/ cordierite,15% CoMnOx31/ cordierite, and CoMnOx 31 powder)

2.2 Catalyst characterization

2.2.1 N 2 Adsorption/ Desorption isotherm method (BET)

BET surface areas were measured on an ASAP Micromeritic (LIKAT, Rostock University ) and a Micromeritics Gemini VII 2390 device (GeViCat center, Hanoi University of Science and Technology)

2010-2.2.2 X-ray diffraction

This work mainly recorded XRD patterns using a D8 Advance Bruker device (Faculty of Chemistry, Hanoi University of Science, Vietnam) and the X’-Pert diffractometer manufactured at the Leibniz Institute for Catalysis (LIKAT)

2.2.3 Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX)

In this study, The samples were performed on a JCM-7000 NeoScope™ Benchtop SEM device, a JEOL brand magnified 35,000 times at GeViCat center, Hanoi University of Science and Technology

2.3.4 Hydrogen temperature – programmed reduction

In this thesis, the TPR-H2 profiles of the catalysts were measured using an AutoChem 2920 II– Micromeritics device at the GeVicat Center, Hanoi University of Science and Technology

2.3.5 Fourier transform infrared spectroscopy (FT- IR)

FTIR spectra were measured using a Nicolet IS50 FT-IR spectrometer at the GeViCat center

2.2.6 Electron paramagnetic resonance (EPR)

EPR spectra were measured by EMX, micro X system (Brucker, Germany), (GeViCat center, Việt Nam)

2.2.7 Thermal analysis (TGA)

TGA curves in this thesis were recorded using a NETZSCH STA 449 F3 (Leibniz Institute for Catalysis, Germany and NETZSCH STA 449F5 (GeViCat center, Vietnam)

2.3 Evaluation of the catalytic activity

2.3.1 Evaluation of the performance of direct oxidation of VOCs over the manganese-based catalyst

3 VOCs tank; 5 the micro reactor; 6 the furnace; V1 – V9 Valse

7 The temperature controller of the furnace; 8 GC with TCD; 9 Flow measuring device

1: MFC1.Mass flow controller for the flow of O2 ; 2, 4: MFC2, MFC4.Mass flow controller for the flow of N2 ; 10: MFC10 : Mass flow controller for the flow of SO2 (H2S)

Fig 2.12 Schematic diagram of the direct oxidation of VOCs process

2.3.2 Evaluation of the performance of the combined adsorption– oxidation process of VOCs

For the combined adsorption-oxidation process, the evaluation of catalytic activity involved two steps, as shown in Fig 2.12 Firstly, VOCs were adsorbed on the catalyst's surface, and then the adsorbed VOCs were desorbed and oxidized into CO2 and H2O at the reaction temperature

2.3.3 Evaluation of the performance of a combination of the VOCs oxidation–adsorption process over the manganese-based catalyst on

a pilot scale

Fig 2.13 Schematic of the exhaust gas mixture treatment system

for the waste tyre pyrolysis process

CHAPTER 3 RESULTS AND DISCUSSION

3.1 Catalyst characterization and selection of catalysts for VOCs oxidation

The catalytic activity of the non - noble metal based- catalysts were determined based on both the toluene conversion and the percent

of toluene that can be converted into CO2 at temperature ranges from

150 oC to 400 oC Experiment data showed that amongst investigated samples with pure manganese oxide and mixed oxide catalysts, the CuMnOx12 and CoMnOx31 catalysts possess the highest toluene conversion Thus, the manganese-based catalysts (the CuMnOx and CoMnOx catalysts) were chosen to investigate the VOC oxidation process

H2O

Table 3.6 Catalytic activity of mixed non-noble metal oxide catalysts compared to manganese oxide catalyst

Conditions

Temperature( o C) / Toluene conversion (%)

α- MnO

2

150

5000 toluene ppm

GHSV = 5700 mL/(g.h) 300

oC/100

NCO – 1.5 5000 toluene

ppm

GHSV = 5700 mL/(g.h) 300

oC/100

CoMnOx91 5000 toluene

ppm

GHSV = 5700 mL/(g.h) 250

Total H2 consumption (mmol/g) a

Cu/Mn molar ratio b

The results of the composition of the catalysts and their BET surface area can be seen in Table 3.7 The analysis revealed that the weight percentage of the catalyst is nearly the same as the calculated weight percentage In addition, the CuMnOx 12 catalyst prepared using the sol-gel method had the largest surface area with a value of 25.15 m2/g

ª ª ª

It has been observed that the presence of the spinel phase in

Cu1.5Mn1.5O4 (ICDDPDF No 35-1172) can be indicated [143] In addition, the exits of the other phase are also identifiable through its diffraction peak

In Fig 3.20, this signal was attributed to isolated Cu2+ ions in octahedral coordination with tetragonal distortion The lack of EPR signal characteristics for Mn species revealed that they most likely exist as Mn4+ [137, 144]

The results obtained from the profile of the H2-TPR profile (Fig 3.21) indicate that these interactions in the spinel catalyst may reduce the reduction temperature, leading to a faster reaction When the preparation method was changed, the Mn-Cu spinel and sub-