Catalytic Combustion Process Research Articles

Detailed transient numerical simulation of H2/air hetero-/homogeneous combustion in platinum-coated channels with conjugate heat transfer

Transient two-dimensional simulations of fuel-lean H2/air combustion were performed in a 2-mm-height planar channel coated with platinum, using detailed hetero-/homogeneous chemistry and transport as well as heat conduction in the solid wall. The developed model resolved, for the first time, all relevant spatiotemporal scales in a practical channel-flow reactor configuration. A parametric study was carried out to investigate the effects of wall material, inlet velocity, and inlet temperature on the fundamental catalytic and gas-phase combustion processes. Computational singular perturbation (CSP) analysis identified the key catalytic reactions affecting light-off and homogeneous ignition. Homogeneous ignition crucially depended on the OH desorbing fluxes from the catalyst, while flame propagation and stabilization involved time scales of a few milliseconds. During the short duration of the light-off event, the ensuing Stefan velocity appreciably altered the flow field. Predictions of time accurate numerical simulations were further compared against those of a code relying on the quasisteady state assumption, and the specific conditions under which the latter was invalidated were identified. Finally, CSP analysis unraveled the reasons for the high computational cost of the fully transient 2-D simulations. The surface reaction mechanism exhibited a high stiffness with fastest time scales of the order of 10-12s, pertaining to the hydrogen adsorption and to the H(s)+O(s)=OH(s)+Pt(s) reactions. These time scales were in turn six orders of magnitude shorter than the ones associated with gas-phase chemistry or with a simplified single-step catalytic reaction.

Experimental Study on Catalytic Combustion Parameters of Gasoline Vapor in Oxygen-Poor Condition

This paper studied gasoline vapor combustion catalyzed by Pd/Al2O3 in oxygen-poor condition. By adjusting the gasoline vapor and oxygen, the inlet temperature and flow rate, collecting data of temperature difference between outlet and inlet as well as the change of gas mixture, the study analyzed the various factors in the catalytic combustion process, and optimized the process control parameters. The results indicated that catalytic combustion was more efficient at the ignition temperature of 274 °C, burned 50% of gasoline vapor in oxygen-poor condition (O2 fraction was 12%).

Analysis of Criterion Number of Heat Transfer in Micro Catalytic Combustion Process

Based on a detailed chemical reaction mechanism including gas phase reaction and surface catalytic reaction, adopting the CFD software to simulate the combustion process of premixed hydrogen-oxygen in a sub-millimeter burner, and introducing a calculating model of criterion number of heat transfer, a comparative analysis of surface catalytic conditions is performed to find out the heat transfer characteristics during combustion process. The simulation results show that the effects of inlet velocity on Nux number vary regionally when gas phase reaction combined with surface catalytic reaction. As inlet velocity increases, Nux number firstly increases and then decreases in low velocity. While in high inlet velocity, the Nux number of entrance region is in the negative half shaft that means the direction of heat transfer has changed. Inlet temperature has comparatively less effects on Nux number in micro catalytic combustion process under the computational conditions. When the temperature is fixed, the Nux number with catalytic is higher than those without catalytic and the difference is more obvious in lower temperature. Key words:Micro combustion, Catalytic combustion, Criterion number of heat transfer, Dimensionless analysis

ChemInform Abstract: Ceramics in Environmental Catalysis: Applications and Possibilities

AbstractReview: 57 refs.

Microexplosions in the Upgrading of Biomass-Derived Pyrolysis Oils and the Effects of Simple Fuel Processing

The development of biofuels produced from biomass-derived pyrolysis oils (bio-oil) requires a deeper understanding of the bio-oil vaporization required for catalytic hydrodeoxygenation, reforming and combustion processes. Through the use of high-speed photography, bio-oil droplets on a 500 °C alumina disk in nitrogen gas were observed to undergo violent microexplosions capable of rapidly dispersing the fuel. High speed photography of the entire droplet lifetime was used to determine explosion times, frequency and evaporation rates of the bio-oil samples that have been preprocessed by filtering or addition of methanol. Filtration of the oil prior to evaporation significantly reduced the fraction of droplets that explode from 50% to below 5%. Addition of methanol to bio-oil led to uniform vaporization while also increasing the fraction of droplets that exploded. Experiments support the necessity of dissolvable solids for the formation of a volatile core and heavy shell which ruptures and rapidly expands to ...

Research on Exhaust Gas Temperature inside Catalytic Honeycomb Monolith Channel of Natural Gas Burner Start-up

This article discussed exhaust gas temperature and pollutant emissions characteristics of the combustion of rich natural gas-air mixtures in Pd metal based honeycomb monoliths in burner during the period of start-up process. The burner need to be ignited by gas phase combustion with the excessive air coefficient (a) at 1.3. The experimental results in catalytic monolith can be explained from SPFR. In this experiment, exhaust gas temperature and pollutant emissions were measured by thermocouple K of diameter 0.5 and the analyser every 1 minute, respectively. The finding would be applied for industrial catalytic combustion process start-up.

Ceramics in Environmental Catalysis: Applications and Possibilities

Environmental catalysis has been steadily growing because of the advances in its scientific and engineering aspects, as well as due to the new environmental challenges in the industrial era. The development of new catalysts and materials is essential for new technologies for various environmental applications. Ceramics play important roles in various environmental applications including the identification, monitoring, and quantification of pollutants and their control. Ceramics have important applications as sensors and photocatalysts, and they are extensively used as catalyst carriers and supports. Many ceramics are being explored as catalysts for pollution control applications. Their low cost, thermal and chemical stability, and capability of being tailored make them especially attractive for pollution control applications. Although a wide variety of materials have been developed as catalyst supports, this area is still of interest with new or modified catalyst supports being frequently reported. It is of equal importance to develop new or modified processes for the loading of catalysts on specific supports. Applications like chemical looping combustion (CLC) and other catalytic combustion processes are raising the demands to a new scale. We have been working on the development of both new and modified support materials, including mesoporous materials without structural order for possible applications in CLC and other catalytic reactions. Successful attempts have been made in the modification of conventional γ-Al 2 O 3 and improved synthesis processes for supporting perovskite type catalysts. Our research on environmental catalysis applications of ceramic materials and processes are also briefly discussed. The article deals with various environmental applications of ceramic based materials and structures. Synthesis, characterization, and catalytic properties of various ceramic materials including catalyst supports are discussed.

The Experimental and Numerical Approach of Catalytic Combustion on Noble Metals Disc Burners of the Turbulent Gaseous Fuel Jet Diffusion Flames

Catalytic combustion is proposed and developed as an efficient method of promoting stability and oxidation of gaseous fuel with minimum pollutants. The effect of catalytic combustion of gaseous turbulent diffusion flames over catalytic discs containing Pt, Pd, and (Pt + Pd) supported on γ-Al2O3 were experimentally and mathematically studied. These flames have proved to be highly stable over the three catalytic burners and their catalytic enhancement is found to be in the order (Pt + Pd) > Pt > Pd. The axi-symmetric thermal distribution of flames developing over these burners record higher values due to enhancing the fuel oxidizability on the noble metal sites in the reaction zone of flames via improving homogeneous-heterogeneous chemical reactions. Lower values of CO and NO are measured at the axial flames direction in the presence of catalytic burners. A numerical approach has been investigated for the catalytic combustion process on the three noble metals disc burners showing high numerical evaluation of different predicted functions. Stability limits are analyzed following a 1st-degree polynomial. The model of temperatures distribution is described by Gaussian function. For CO distribution, a non-linear four parameters model has been predicted. A differential equation for NO x indicates perfectly the location of the peak values. These models have been strictly confirmed with the experimental data.

Comparison of catalytic performance of Ag- and K-based catalysts for diesel soot combustion

Soot combustion performance of supported Ag (Ag/TiO2 and Ag/CeO2) and K (K/TiO2 and K/CeO2) catalysts under tight and loose contact conditions was evaluated by thermogravimetric analysis (TG) and the determination of the apparent activation energy as a function of soot conversion. The soot combustion performance strongly depended on the active species and contact conditions. The soot combustion proceeded by catalytic and non-catalytic combustion processes, depending on the contact conditions and the active species. Almost all the soot was catalytically combusted over Ag and K supported catalysts when they were tightly contacted with the soot, and Ag was more active catalytic species for soot oxidation than K. Under the loose contact condition, the supported K catalyst was superior to the supported Ag catalysts in the fraction of catalytically combusted soot and propagation of the combustion to the non-contact soot. Therefore, the supported K catalyst showed higher performance than the supported Ag catalyst for the removal of the majority of soot under the loose contact condition.

催化燃烧Cl-VOCs催化材料的研究进展<br>Recent Progress in Catalytic Materials for Catalytic Combustion of Chlorinated Volatile Organic Compounds

从催化剂活性组分、催化剂载体、催化剂失活三个方面，对近年来催化燃烧含氯挥发性有机物(Cl-VOCs)催化剂的研究进行了总结。贵金属催化剂用于降解Cl-VOCs的研究主要集中在选择有效载体和合成双组份贵金属催化剂，非贵金属催化剂的研究则主要着重于合成高活性过渡金属复合氧化物、钙钛矿和尖晶石等催化剂；催化燃烧Cl-VOCs时氯与活性物质生成的氯化物被认为是导致催化剂失活的重要原因，实际应用中水蒸气、积碳等对催化降解Cl-VOCs的反应活性也有很大影响。本文将为Cl-VOCs污染物催化燃烧时催化剂的合理选择及催化反应条件的优化控制提供一定参考。 he research progress in the catalytic combustion of Cl-VOCs(Chlorinated Volatile Organic Compounds) is reviewed. In this review, the effects of the active species, catalyst support, water vapor and coking on the catalytic combustion reaction were summarized. The research related to noble metal catalysts mainly focuses on developing new supports and dual noble catalysts. The research on non-noble metal catalysts concentrate on the development of transition metal mixed oxide，perovshites and spinel catalysts; The chlorination of active species is regarded as an important reason for catalyst deactivation. Besides, the effects of water vapor and coking deactivation on the catalytic combustion process are discussed with considering the practical application. This review will be helpful in choosing an appropriate catalyst and the optimal reaction conditions for the removal of Cl-VOCs by catalytic combustion with high activity and high stability.

催化燃烧Cl-VOCs催化材料的研究进展

从催化剂活性组分、催化剂载体、催化剂失活三个方面，对近年来催化燃烧含氯挥发性有机物(Cl-VOCs)催化剂的研究进行了总结。贵金属催化剂用于降解Cl-VOCs的研究主要集中在选择有效载体和合成双组份贵金属催化剂，非贵金属催化剂的研究则主要着重于合成高活性过渡金属复合氧化物、钙钛矿和尖晶石等催化剂；催化燃烧Cl-VOCs时氯与活性物质生成的氯化物被认为是导致催化剂失活的重要原因，实际应用中水蒸气、积碳等对催化降解Cl-VOCs的反应活性也有很大影响。本文将为Cl-VOCs污染物催化燃烧时催化剂的合理选择及催化反应条件的优化控制提供一定参考。 he research progress in the catalytic combustion of Cl-VOCs(Chlorinated Volatile Organic Compounds) is reviewed. In this review, the effects of the active species, catalyst support, water vapor and coking on the catalytic combustion reaction were summarized. The research related to noble metal catalysts mainly focuses on developing new supports and dual noble catalysts. The research on non-noble metal catalysts concentrate on the development of transition metal mixed oxide，perovshites and spinel catalysts; The chlorination of active species is regarded as an important reason for catalyst deactivation. Besides, the effects of water vapor and coking deactivation on the catalytic combustion process are discussed with considering the practical application. This review will be helpful in choosing an appropriate catalyst and the optimal reaction conditions for the removal of Cl-VOCs by catalytic combustion with high activity and high stability.

Variation on anthracite combustion efficiency with CeO2 and Fe2O3 addition by Differential Thermal Analysis (DTA)

Effects of CeO2 and Fe2O3 on anthracite combustion efficiency were investigated using differential thermal analysis (DTA). Based on heat release (QD) of anthracite as well as anthracite with CeO2 and anthracite with Fe2O3 additions against α-Al2O3 in DTA experiment, effects of additives CeO2 and Fe2O3 on anthracite combustion efficiency were evaluated. Under the same experimental conditions, heat releases of raw anthracite, anthracite with CeO2 and anthracite with Fe2O3 were 11.04 kJ/g, 11.30 kJ/g and 11.42 kJ/g, respectively, indicating that anthracite combustion efficiency was improved by addition of CeO2 and Fe2O3. To confirm the above results, carbon transfer was monitored using Thermogravimetric analysis Fourier transform infrared (TGA-FTIR) and Carbon-Sulfur analyzer during catalytic combustion process. The results indicated that CO2 emission was increased, whereas CO emission and residual carbon of ash were decreased, being in accordance with the results of DTA. Finally, according to analyses of ignition temperature and catalytic combustion process, the possible mechanism of catalytic combustion of anthracite was proposed.

Catalytic combustion of VOCs on non-noble metal catalysts

Volatile organic compounds (VOCs) are toxic and contribute significantly to the formation of the photochemical smog, which has remarkable impact to the air quality; therefore, the research on the removal of VOCs has attracted increasing interests during the last decade. This review covers the recent developments in catalytic combustion of VOCs over non-noble metal catalysts including mixed metal oxide catalysts, perovskite catalysts and Au-containing catalysts. The effect of water vapor, coke formation and the effect of supports on the catalytic combustion process will be discussed. The concept of an adsorption/catalytic combustion dual functional system is introduced and several examples of such systems are evaluated. To develop efficient and cost effective VOC removal technologies, further research in catalytic combustion needs to develop novel non-noble metal catalysts and adsorbents, and improve the understanding of catalytic mechanisms involved.

Influence of Carbon Sources and Catalytic Precursors on the Products Prepared by Catalytic Combustion

It is very important to study the effects of various factors on synthesis of carbon nanofibers for controlled synthesis, which plays a significant role in realizing desired nanostructures or nanodevices for applications. In this report, we employed different carbon source and different catalyst precursor solution, respectively, and studied the effects of those on carbon nanofibers that were synthesized by catalytic combustion process. We have characterized the as-grown carbon nanofibers by employing scanning electron microscopy (SEM) for deep understanding.

Effects of Catalysts on Carbon Nanofibers Synthesized by Ethanol Catalytic Combustion

It is very important to study the effects of various factors on synthesis of carbon nanomaterials for controlled synthesis, which plays a significant role in realizing desired nanostructures or nanodevices for applications. In this report, we employed iron nitrate, cobalt nitrate, nickel nitrate, iron chloride, cobalt chloride and nickel chloride as catalyst precursors, and studied the effects of catalyst precursors on carbon nanofibers that were synthesized by ethanol catalytic combustion process. The as‐grown carbon deposits have been characterized by scanning electron microscopy and transmission electron microscopy for deep understanding. The experimental results suggested that the carbon deposits synthesized by employing iron salt, cobalt salt, and nickel salt as catalyst precursors had different unique characteristics, respectively.

Effects of Concentration of Catalyst Precursors on Carbon Nanostructures

It is very important to study the effects of various factors on synthesis of carbon nanomaterials for controlled synthesis, which plays a significant role in realizing desired nanostructures or nanodevices for applications. In this report, we employed iron nitrate solution with different concentration, such as 1 mol/l, 0.1 mol/l, 0.01 mol/l, and saturated iron nitrate solution as catalyst precursor solution and studied the effects of concentration of catalyst precursor solution on carbon nanostructures that were synthesized by ethanol catalytic combustion (ECC) process. We have characterized the as-grown carbon nanostructures by employing scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for deep understanding.

Interactions Between Surface Reactions and Gas-phase Reactions in Catalytic Combustion and Their Influence on Ignition of HCCI Engine

The catalytic combustion of methane in a microchannel whose surface was coated with platinum (Pt) catalyst was studied by numerical-simulation. The effects of gas-phase reactions on the whole catalytic combustion process were analyzed at a high inlet pressure. A sensitivity analysis of the detailed mechanisms of the surface reaction of methane on Pt revealed that the most sensitive reactions affecting the heterogeneous ignition are oxygen adsorption/desorption and methane adsorption, and the most sensitive reactions affecting the homogeneous ignition are OH and H 2O adsorption/desorption. The combustion process of the homogeneous charge compression ignition (HCCI) engine whose piston face was coated with Pt catalyst was simulated. The effects of catalysis and the most sensitive reactions on the ignition timing and the concentration of the main intermediate species during the HCCI engine combustion are discussed. The results show that the ignition timing of the HCCI engine can be increased by, catalysis, and the most sensitive reactions affecting the ignition timing of the HCCI engine are OH and H 2O adsorption/desorption.

Effects of catalyst precursors on carbon nanowires by using ethanol catalytic combustion technique

Iron nitrate, nickel nitrate and cobalt nitrate were used as catalyst precursors to study their effects on carbon nanowires synthesized by ethanol catalytic combustion (ECC) process. The as-grown carbon nanowires were characterized by means of scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that relatively uniform nanowires will be formed when the catalyst precursor is iron nitrate; while helical structure or disordered structure will be formed when the catalyst precursor is nickel nitrate or cobalt nitrate.

Preparation of carbon nanotubes by ethanol catalytic combustion technique using nickel salt as catalyst precursor

A simple growth technique of carbon nanotubes (CNTs) by combustion of ethanol was developed. In the experiment, copper plate was employed as substrate, nickel nitrate (Ni(NO 3) 2) and nickel chloride (NiCl 2) as catalyst precursor, and ethanol as carbon source. The cleaned copper substrate was dipped into catalyst precursor solution for mounting catalyst precursor particles. The dip-coated substrate was then placed into ethanol flame for about 10 min after drying. The black wool-like production grown on copper plate was obtained. This route is called an ethanol catalytic combustion(ECC) process. The black powders were characterized by means of scanning electron microscopy(SEM), transmission electron microscopy(TEM), energy dispersive X-ray spectrometer(EDS) and Raman spectroscopy. The results show that the techique is much simpler and more economical to meet the future broader applications.

Catalytic technology assisted with ionization/ozonization phase for the abatement of volatile organic compounds

The catalytic combustion process of air-mixtures containing volatile organic compounds (VOCs) associated with an ionization/ozonization reactor (IOCC technique, ionization–ozonization–catalytic-combustion) has been utilized for the abatement of two very toxic industrial VOCs: acrylonitrile (ACN) and vinyl chloride (VCM). The pre-catalytic effects (electric discharge plus the action of ozone), the conventional and IOCC combustion tests were studied. Two different catalysts were used: oxide catalyst, copper–chromite (Cu–Cr), and Pt metal catalyst (0.5 wt.% Pt/γ-Al 2O 3). The abatement of ACN was markedly influenced by the pre-catalytic effects. Starting from 3 kV, an increasing abatement of ACN was observed with the voltage applied to the ionization reactor at any initial ACN concentration (500–1500 ppm). The ACN catalytic combustion, performed by the IOCC technique, led to 91 and 98% yield of CO 2 on Cu–Cr and Pt catalysts, respectively, at 260°C. Complete absence of hazardous intermediates, such as hydrogen cyanide, was observed. The Cu–Cr catalyst, at 300°C, was able to abate 57 and 23% of VCM at 10 000 and 20 000 h −1, respectively. IOCC combustion led to improved conversion. At 200°C and 3300 h −1, 98% and only 49% of VCM abatement operating according to IOCC and classical combustion was obtained, respectively. The IOCC combustion runs, performed at different initial VCM concentrations (585 and 1170 ppm), indicated a superior abatement when low VCM concentration was fed, at a given catalyst temperature and contact time. This indicated a marked influence of the pre-catalytic effects on the abatement.