Catalytic Combustion Technology Research Articles

Study on the combustion of toluene by acid etching assisted ultrasonic supported low content Pt catalyst

Catalytic combustion technology is an effective method for the treatment of volatile organic compounds (VOCs). However, the catalytic activity of loaded noble metal catalysts is limited by factors such as high noble metal dosage and poor stability. In this study, a method for the preparation of acid etching assisted ultrasonic loaded low-content Pt-cordierite catalysts was proposed. By comparing with the 0.5 % Pt/cordierite catalyst prepared without acid etching, it was found that the catalytic activity of toluene of the 0.5 % Pt/cordierite-HNO3 catalyst was significantly improved, and the T90 of toluene combustion was only 201 ℃, which indicated that the acid etching effectively promoted the interfacial bonding between the active component Pt and the carrier. Finally, it was confirmed by XPS that the active component Pt in the 0.5 % Pt/cordierite-HNO3 catalyst existed in multiple valence states, which effectively promoted the catalytic combustion of toluene.

Tailoring Pd/M@CoAlO core-shell catalyst morphology for efficient methane oxidation

The control of low-concentration methane (CH4) emissions is a critical component of the ‘dual carbon’ strategy, and catalytic combustion technology focused on catalyst design is recognized as a promising avenue for achieving it. However, the zeolite-based catalysts are highly prone to deactivation under hydrothermal environments, thus limiting their practical applicability. Herein, we have utilized layered double hydroxides (LDHs) as precursors and integrated them with Pd/M through a co-precipitation method to fabricate Pd/M@CoAlO composite catalysts with a core–shell structure, focused on the impact of CoAlO morphology on the activity and stability for CH4 oxidation. It revealed that the incorporation of CoAlO significantly enhanced the catalytic combustion efficiency and the hydrothermal stability of Pd/M. Furthermore, an increase in the calcination temperature led to a progressive degradation of the sheet-like or petal-shaped structure of CoAlO within the Pd/M@CoAlO composite catalysts. This structural collapse eventually resulted in the formation of CoAlO dense particles that enveloped the Pd/M, adversely affecting the adsorption of oxygen and the exposure of active sites. This work underscores the importance of morphological control, providing significant guidance for the strategic design and development of catalysts tailored for CH4 catalytic combustion.

Catalytic Hydrolysis-Oxidation of Halogenated Methanes over Phase- and Defect-Engineered CePO4: Halogenated Byproduct-Free and Stable Elimination.

Catalytic elimination of halogenated volatile organic compound (HVOC) emissions was still a huge challenge through conventional catalytic combustion technology, such as the formation of halogenated byproducts and the destruction of the catalyst structure; hence, more efficient catalysts or a new route was eagerly desired. In this work, crystal phase- and defect-engineered CePO4 was rationally designed and presented abundant acid sites, moderate redox ability, and superior thermal/chemical stability; the halogenated byproduct-free and stable elimination of HVOCs was achieved especially in the presence of H2O. Hexagonal and defective CePO4 with more structural H2O and Brønsted/Lewis acid sites was more reactive and durable compared with monoclinic CePO4. Based on the phase and defect engineering of CePO4, in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), and kinetic isotope effect experiments, a hydrolysis-oxidation pathway characterized by the direct involvement of H2O was proposed. Initiatively, an external electric field (5 mA) significantly accelerated the elimination of HVOCs and even 90% conversion of dichloromethane could be obtained at 170 °C over hexagonal CePO4. The structure-performance-dependent relationships of the engineered CePO4 contributed to the rational design of efficient catalysts for HVOC elimination, and this pioneering work on external electric field-assisted catalytic hydrolysis-oxidation established an innovative HVOC elimination route.

Thermal reactivity and gas–solid product evolution during coal catalytic combustion: An experimental study

To achieve efficient and clean coal combustion, catalytic combustion technology has received widespread attention. This paper systematically studied the influence of calcium-based compounds on the thermal reactivity and gas–solid two-phase product evolution behavior of different coal using TG-MS and FTIR analysis, combining kinetics and thermodynamics methods, the catalytic coal mechanism was discussed. Results demonstrated that both catalysts improved the combustion reactivity, the burnout temperatures of lignite, bituminous coal and anthracite were reduced by 30.75 °C, 53 °C and 25.5 °C respectively with CaO, as well as decreased by 24.75 °C, 55.5 °C and 29 °C respectively with CaCl2. Meanwhile, it was worth noting that the activation energy of three coals was also reduced. CaCl2 was more likely to bind with the C = O functional group on the surface of coal, forming CO-Ca2+ complexes, resulting in a decrease in the content of C = O and C-O. While CaO tended to absorb volatile matter, causing local overheating and promoting the breakage of side chains and bridge bonds. Besides, the calcium-based compounds advanced the gas evolution peak of combustion and the emissions of CO2, NO2 and SO2 were effectively controlled. These results aimed at providing a new reference direction for further industrial development of clean coal combustion technology.

Plasma driven exsolution of Ca as the adjacent dechlorinated site in La0.8Ca0.2MnO3 perovskite: A highly mineralization chlorobenzene oxidation catalyst

The degradation of chlorine-containing volatile organic compounds (CVOCs) catalytic combustion technology is subject to the catalyst chlorine poisoning, which is resulted from the chlorination of active phases, even though the structural stable perovskite. The reaction between Ca species and dissociated chlorine species is demonstrated as an efficient way to inhibited chlorine poisoning of the active phase. Herein, a Ca substituted partial La prepared La0.8Ca0.2MnO3 (named as L8C2MO) perovskite was treated by 5% H2/Ar plasma driven route (the treated sample was denoted as L8C2MO-P), which was applied for the chlorobenzene oxidation removal. The integrated characterization results of XRD, XPS, HRTEM, etc. confirmed that Ca (mainly exhibited as CaCO3) was successfully exsolved from La0.8Ca0.2MnO3 and simultaneously leaved oxygen vacancies on the surficial layers. The continuous catalytic oxidation experiments illustrated that the conversion efficiency of L8C2MO was unexpectedly decreased compared with that of LaMnO3 (LMO in short) sample, while that of L8C2MO-P was nearly maintained the oxidation capacity, with approximately 12 °C of 90% chlorobenzene conversion temperature (T90) higher than that of LMO. Importantly, the CO2 and inorganic chlorine species yields were significantly enhanced for L8C2MO and L8C2MO-P. The characteristic of used samples showed a possible chlorinated Ca species formation while the status of Mn phases was hardly changed, suggesting the exsolved Ca could inhibit the poison of Mn sites by binding with dissociative chlorine species. Additionally, oxygen vacancies that generated along with Ca exsolution process was definitely contributed to the deep oxidation of chlorobenzene. The possible reaction route was also studied by in situ DRIFTS and GCMS. The work provides a potential route as in situ growth of adjacent sites to protect active phases from chlorine poison in CVOCs catalytic oxidation process.

Design and Analysis of the Waste Heat Recovery System for Stenter Exhaust

In this study, combined with the exhaust adsorption, desorption and catalytic combustion technology, a waste heat recovery scheme using stenter exhaust to heat desorbed air and preheat stenter suction air was proposed. Using Aspen Plus to design the waste heat recovery system, and using Aspen EDR to design the structure of heat exchangers. The energy utilization efficiency of waste heat recovery system was evaluated through the exergy analysis, and the influence of exhaust flow rate variation on exergy efficiency of heat exchanger under different exhaust temperatures were discussed. Moreover, the influence of fluid parameter variations on the heat transfer process was also analyzed. Finally, the economic calculation was carried out and the overall energy-saving effect of waste heat recovery system was demonstrated. The results showed that the utilization of this waste heat recovery system can recover 537 kW, the exergy efficiency of desorbed air heat exchanger and preheating air heat exchanger were 51% and 58.9% respectively. In terms of the economic evaluation, the annual energy-saving economic benefits was about $ 89,312, and the static investment payback period was 1.17 years.

Thermal comfort characteristics of a catalytic combustion heater under wind-chilled exposure

Heating in wind-chilled environments is a serious task. The catalytic combustion heater (CCH) provides more efficient and cleaner in combustion compared to conventional heaters with high pollutant emission and low energy utilization. In this paper, the heating ability of CCH on human body in a wind-chilled environment (apparent temperatures between −14.8 °C and 12.4 °C) was investigated by collecting skin temperature and subjective thermal evaluation data from 23 subjects. The impact of cold air on localized heating of body parts by CCH was clarified using decision trees and dimensionless correlation coefficients. A human-computer interaction regulation strategy was proposed to simultaneously satisfy the requirements of effective heating, low energy consumption, and low pollution. Finally, CCH and a commercial heater were compared in terms of heating effectiveness and energy consumption in a real outdoor environment. The results showed that CCH effectively solved the problem of excessive cold extremities, and the temperature difference between thoracoabdominal area and extremities was reduced by 57.5–87.9% to within 2 °C. In a strong convective environment, wind speed was the decisive factor (coefficient of 0.95), inducing 46% radiant heat loss. Inputting personnel subjective perception, dynamic environmental parameters, and pollutant thresholds to adjust the injected gas flow enabled intelligent control. In a real cold scenario, the CCH saved 65.9% of energy compared to a commercial heater when achieving the same heating effect. This study provides a reference for the application of catalytic combustion technology in cold outdoor heating and also provides an important theoretical basis for the construction of heating strategies for CCH.

Increasing cerium dispersion favours lattice oxygen activity of cobalt oxides for CO catalytic combustion

Removing carbon monoxide with catalytic combustion technology is an effective and economical solution. Highly efficient conversion of CO at low temperatures can be achieved by introducing a catalyst, and its application in automotive exhaust emissions and preferential oxidation of CO in fuel cells is remarkable. In this work, catalysts were prepared by mixing the prepared cerium organic framework with Co3O4, and after calcination at 400 °C, the organic framework collapsed, resulting in a uniform dispersion of Ce on the Co3O4 nano surface. Experimental results demonstrated that the required temperature of the catalyst is 101 °C when the conversion is 90 %, and it remained stable over the 75 h tested at 100 °C. High resolution transmission electron microscopy (HRTEM) revealed that Ce/Co3O4 primarily exposed 311 surface. Combined with DFT calculations, the catalysts may improve the catalytic combustion activity of CO by multiplying the oxygen vacancies and modulating the dispersion of Ce atoms. The reaction occurred on the 311 surface predominantly. Activated CO* preferred to react with the lattice oxygen at the Ce-O-Co linkage compared to the lattice oxygen at Co-O-Co. Energy barrier for the rate dictating step in the complete catalytic cycle is 0.42 eV. This work not only provides experimental support and theoretical basis for the design of low-temperature catalytic combustion CO catalysts, but also provides new ideas for the doping of metal oxides with lanthanide metals.

Low-content Pt loading on a post-treatment-free zeolite for efficient catalytic combustion of toluene

One of the main techniques for removing volatile organic compounds (VOCs) from the environment is catalytic combustion technology. Noble metal-loaded Zeolite catalysts have a promising future in the field of VOCs catalysis. In this study, NaA, NaX, NaY and ZSM-5 were produced by a simple hydrothermal method, and Pt particles were loaded onto the zeolite. Among the four zeolite-supported Pt catalysts with similar loading loads, Pt/NaA has the best catalytic oxidation performance of toluene, and the total conversion of toluene can be achieved at 160 °C. At the same time, it has good repeatability, and stability. A series of characterizations indicate the synthesis of pure phase NaA zeolites and the presence of a number of acid sites, active oxygen and Pt0 species. The presence of these active substances promoted the adsorption and final oxidation of VOCs by the catalyst, which enabled Pt/NaA to exhibit the most excellent catalytic oxidation performance for toluene. In situ DRIFTS showed that surface reactive oxygen species in Pt/NaA acted as an important role in the catalytic oxidation of toluene. The preparation of high efficiency zeolite catalysts by simple synthesis method has broad future in the field of VOCs treatment.

Properties and mechanisms of low concentration methane catalytic combustion in porous media supported with transition metal oxides

Low concentration methane (LCM) from coal mining is hardly utilized by combustion or oxidation due to its low concentration and fluctuation. Herein, a porous media catalytic combustion technology was presented to investigate the catalytic combustion properties of LCM in porous media by developing three porous media catalysts (Fe2O3/Al2O3, CuO/Al2O3 and Co3O4/Al2O3) supported with transition metal oxides (Fe2O3, CuO and Co3O4) as active components. While the catalytic combustion mechanism was proposed by density functional theory (DFT) calculations. The results indicated that Fe2O3/Al2O3 exhibited superior high-temperature catalytic activity and thermal stability, which was capable of broadening the limit equivalence ratio of CH4 stationary combustion to 0.46 with the CH4 conversion rate over 98 %. DFT calculations revealed that the Fe atoms on the (001) surface of Fe2O3 crystals were the active center during the catalytic process, causing the adsorption and dissociation of CH4 and O2 molecules. The lattice oxygen of Fe2O3 was engaged in the formation of CO and CO2 and the adsorbed oxygen from O2 molecules dissociation facilitated H2O generation, which heightened the conversion of CH4. This study provides a promising avenue for the high-efficiency and clean utilization of LCM.

Affecting factors of electrified soot combustion on potassium-supported antimony tin oxides

Elimination of soot particulates using catalytic combustion technologies at lower temperatures remains a big challenge for diesel engines with the ever-lowering emission temperatures. We recently reported an electrified catalysis strategy that decreased the soot ignition temperature for 50% conversion (T50) to below 75 °C on potassium-supported antimony-tin oxides (K/ATO) (Mei et. al., Nature Catalysis, 2021, 4: 1002). However, the detailed affecting factors were not present for the sake of promptly enjoying this exiting progress. Herein, three important factors, including K loading amounts, electric power ramp rates and nitrogen oxides (NOx), for the Electrically Powered Programmed Oxidation (EPPO) of soot were investigated on K/ATO. First, K loading enhances soot ignition but much higher K content (>1 wt%) is detrimental due to spoiling catalyst conductivity. Second, elevating the electric power ramp rate to 0.1 W min−1 reaches an apex with the promise of the balance of soot ignition conversion and energy efficiency. Finally, NOx, a promoter in traditional thermal catalysis, is overwhelmed by the tremendous active oxygen trigged from the electrification process, showing no effects on soot ignition. These findings are instructive to rational catalyst designs and vital to accelerate the industrial applications of the newly developed electrified catalytic soot combustion in the hybrid electric vehicle (HEV) aftertreatment system.

Emission Control of Toluene in Iron Ore Sintering Using Catalytic Oxidation Technology: A Critical Review

Iron ore sintering flue gas containing large amounts of volatile organic compounds (VOCs) can form secondary photochemical smog and organic aerosols, thus posing a serious threat to human health and the ecological environment. Catalytic combustion technology has been considered as one of the most prospective strategies for VOC elimination. This paper focuses on a review of studies on catalytic removal of typical VOCs (toluene) on transition metal oxide catalysts in recent years, with advances in single metal oxides, multi-oxide composites, and supported metal oxide catalysts. Firstly, the catalytic activities of a series of catalysts for toluene degradation are evaluated and compared, leading to an analysis of the key catalytic indicators that significantly affect the efficiency of toluene degradation. Secondly, the reaction pathway and mechanism of toluene degradation are systematically introduced. Considering the site space and investment cost, the conversion of VOC pollutants to harmless substances using existing selective catalytic reduction (SCR) systems has been studied with considerable effort. Based on the current development of simultaneous multi-pollutant elimination technology, the interaction mechanism between the NH3-SCR reaction and toluene catalytic oxidation on the surface is discussed in detail. Finally, views on the key scientific issues and the challenges faced, as well as an outlook for the future, are presented. This overview is expected to provide a guide for the design and industrial application of NO/VOC simultaneous removal catalysts.

Catalytic combustion kinetics of methyl butanoate over Pd/γ-Al2O3 catalysts: An experimental and theoretical study

Catalytic combustion technology is a promising prospect for the removal of pollutants and improvement of combustion efficiency. In this study, methyl butanoate (MB), a typical biodiesel surrogate was chosen to obtain insight into the catalytic reaction mechanism of biodiesels over Pd/γ-Al2O3 catalyst. By comparing the homogeneous and catalytic combustion experiment result, it is found that the reaction temperature of the same conversion in catalytic combustion is reduced by about 400 K. The formation of a large of methyl acrylate (MA) and the significant reduction of aldehyde products reflect the change of the catalytic combustion reaction path on the surface of Pd/γ-Al2O3. Density functional theory (DFT) calculation shows that two different initial reaction paths (Pd + MB and PdO + MB) have lower energy barriers for the generation of CH3CH2CHCOOCH3 (MB2J) radicals and the MB2J goes through subsequent decomposition to form MA, which is consistent with the experimental result.

Research on Municipal Sludge Dewatering and Modified Catalytic Combustion Technology

Aiming at the problem that high moisture content of municipal sludge with flocculation structure and high water retention capacity, which makes dewatering and drying difficult, this paper carries out research on dewatering, drying and modified combustion technology of municipal sludge with the goal of resource and energy utilization. The sludge dewatering agent ZC-2T and catalytic oxidation nitrification agent ZC-4R were preferably selected as the main components of modified adjusting agent ZC-1W for industrial application of sludge energy disposal. The compounded modified adjusting agent ZC-1W has a positive contribution to improve the combustion performance of sludge mixed with raw coal, which providing important theoretical support and practical data for the large-scale industrial development and application of municipal sludge. The study will generate significant economic and social significance.

Preparation of Highly Active and Thermally Conductive Platinum Nanoparticle/Ce–Zr–Y Mixed Oxide/AAO Washcoat Catalyst for Catalytic Hydrogen Combustion Technologies

Preparation of Highly Active and Thermally Conductive Platinum Nanoparticle/Ce–Zr–Y Mixed Oxide/AAO Washcoat Catalyst for Catalytic Hydrogen Combustion Technologies

Catalytic combustion of methyl butanoate over HZSM-5 zeolites.

Catalytic combustion technology is an exciting prospect for the removal of pollutants, especially in the field of transportation. Applying zeolites in fuel combustion has gained increasing importance in heterogeneous catalysis arising from their properties such as economical practicability and high activity. However, compared with the extensively investigated homogeneous combustion, few studies have been reported to explore the catalytic combustion of large-molecule fuels, especially for the catalytic combustion of biodiesel surrogate fuels. The purpose of this feature article is to describe the catalytic combustion of methyl butanoate (one of the biodiesel surrogate fuels) over unmodified HZSM-5 zeolites with a particular focus on the catalytic reaction mechanism. Experiments and theoretical calculations were considered here to help explain the proposed catalytic mechanism. This paper can provide new insights into the catalytic mechanism of biodiesel fuels that will guide the improvement of combustion efficiency in internal combustion engines and in the control of pollutant emissions.

Non-Thermal Plasma-Modified Ru-Sn-Ti Catalyst for Chlorinated Volatile Organic Compound Degradation

Chlorinated volatile organic compounds (CVOCs) are vital environmental concerns due to their low biodegradability and long-term persistence. Catalytic combustion technology is one of the more commonly used technologies for the treatment of CVOCs. Catalysts with high low-temperature activity, superior selectivity of non-toxic products, and resistance to chlorine poisoning are desirable. Here we adopted a plasma treatment method to synthesize a tin-doped titania loaded with ruthenium dioxide (RuO2) catalyst, possessing enhanced activity (T90%, the temperature at which 90% of dichloromethane (DCM) is decomposed, is 262 °C) compared to the catalyst prepared by the conventional calcination method. As revealed by transmission electron microscopy, X-ray diffraction, N2 adsorption, X-ray photoelectron spectroscopy, and hydrogen temperature-programmed reduction, the high surface area of the tin-doped titania catalyst and the enhanced dispersion and surface oxidation of RuO2 induced by plasma treatment were found to be the main factors determining excellent catalytic activities.

Combustion of sewage sludge in a fluidized bed of catalyst: ASPEN PLUS model

This paper presents the results of the simulation of a sewage sludge combustion plant with a productivity of 6 tons per hour using the ASPEN Plus. It is shown that catalytic combustion technology can be used for the efficient utilization of mechanically dehydrated sludge with the moisture of ~75% in autothermal mode (without the use of additional fuel). At the same time, the plant for utilization of 6.0 tons of sludge per hour enables us to obtain 3.07 MW of heat energy. It is shown that the sludge moisture and its calorific value significantly affect the combustion process. Thus, at the moisture of less than 72%, additional water supply is necessary to avoid overheating of the catalyst bed. In the case of an increase in sludge moisture of more than 76%, an additional supply of fuel (for example, brown coal) is required. Also, the article discusses the emissions of harmful substances generated during sewage sludge combustion and methods for their utilization.

Roles of Oxygen Vacancies in the Bulk and Surface of CeO2 for Toluene Catalytic Combustion.

Catalytic combustion technology is one of the effective methods to remove VOCs such as toluene from industrial emissions. The decomposition of an aromatic ring via catalyst oxygen vacancies is usually the rate-determining step of toluene oxidation into CO2. Series of CeO2 probe models were synthesized with different ratios of surface-to-bulk oxygen vacancies. Besides the devotion of the surface vacancies, a part of the bulk vacancies promotes the redox property of CeO2 in toluene catalytic combustion: surface vacancies tend to adsorb and activate gaseous O2 to form adsorbed oxygen species, whereas bulk vacancies improve the mobility and activity of lattice oxygen species via their transmission effect. Adsorbed oxygen mainly participates in the chemical adsorption and partial oxidation of toluene (mostly to phenolate). With the elevated temperatures, lattice oxygen of the catalysts facilitates the decomposition of aromatic rings and further improves the oxidation of toluene to CO2.

Effect of multi-pollutant on the catalytic oxidation of dichloromethane over RuO2-WO3/Sn0.2Ti0.8O2 catalyst

Chlorine-containing volatile organic compounds emitted from combustion boilers and chemical industries will cause great harm to the ecological environment and human health. Catalytic combustion technology is one of the commonly used technologies for the treatment of CVOCs. Poor low-temperature activity, high levels of toxic by-products, and poor resistance to chlorine poisoning are common problems faced by its catalyst development. In order to effectively remove CVOCs, we constructed a RuO2-WO3/ Sn0.2Ti0.8O2 catalyst formula in which RuO2 and WO3 were supported on Sn0.2Ti0.8O2, and tested with DCM as a model molecule. By detecting the catalytic performance of RuO2-WO3/Sn0.2Ti0.8O2 series catalysts with different RuO2 loadings on DCM and corresponding characterization methods, we found that 3 wt%RuO2-5 wt%WO3/Sn0.2Ti0.8O2 catalyst had the best catalytic performance (T90% value was 291 °C, CO2 selectivity was close to 100% at 325 °C). The actual industrial environment often contains multiple gas pollutants at the same time, so it is important to study the ability of the catalyst to co-process multiple pollutants. The effects of other pollutants (propane, acetone, SO2 and NO2) in the reaction atmosphere on the catalytic oxidation performance of DCM were further studied. It was found that the RuO2-WO3/Sn0.2Ti0.8O2 catalyst could achieve the coordinated removal of acetone, propane and dichloromethane, and the effects of SO2 and NO2 on catalytic oxidation performance of DCM was revealed. It is hoped that it can serve as a reference and guidance for the subsequent industrial application of the catalyst in this system.