High Carbon Monoxide Conversion Research Articles

Performance of Transition Metal Supported Al2O3 Coated on Honeycomb Catalysts and Its Segmentation on Exhaust Gasses Oxidation

The oxidation of carbon monoxide (CO) and unburnt hydrocarbons (HC) under segmented honeycomb catalysts was investigated using actual exhaust gas mixtures from a gasoline-fueled internal combustion engine of a motorcycle. The honeycomb catalysts were prepared through a wet process, resulting in four types coated with transition metals (Cu, Cr, Fe, and Ni) supported on Al2O3. The oxidation of CO and HC was monitored using an exhaust gas analyzer across a range of air-to-fuel ratios (AFR), from lean to rich, under stationary conditions. The results demonstrate that the honeycomb catalysts effectively decreased CO and HC concentrations in the exhaust gas. Among the transition metal oxide honeycomb catalysts, Cr and Ni exhibited high CO and HC conversion rates, surpassing those observed with Cu. The average CO and HC conversion calculations, spanning from lean to rich air-to-fuel ratios, were consistent with the actual conversion rates achieved. Furthermore, the study investigated the effect of honeycomb segmentation on CO and HC conversion. Surprisingly, the catalytic performance of Cr and Ni remained high even with longer gaps in the honeycomb. Interestingly, the conversion of CO and HC over the iron oxide honeycomb catalyst increased as the gap in the honeycomb became longer. This is likely due to an increase in the gap size and enhanced re-mixing of reactants (CO, HC, and O2) caused by recirculation. Thus, this study provides valuable elucidation on the potential application of segmented honeycomb catalysts for reducing CO and HC emissions in exhaust gases.

Edge-rich molybdenum disulfide tailors carbon-chain growth for selective hydrogenation of carbon monoxide to higher alcohols

Selective hydrogenation of carbon monoxide (CO) to higher alcohols (C2+OH) is a promising non-petroleum route for producing high-value chemicals, in which precise regulations of both C-O cleavage and C-C coupling are highly essential but remain great challenges. Herein, we report that highly selective CO hydrogenation to C2-4OH is achieved over a potassium-modified edge-rich molybdenum disulfide (MoS2) catalyst, which delivers a high CO conversion of 17% with a superior C2-4OH selectivity of 45.2% in hydrogenated products at 240 °C and 50 bar, outperforming previously reported non-noble metal-based catalysts under similar conditions. By regulating the relative abundance of edge to basal plane, C2-4OH to methanol selectivity ratio can be overturned from 0.4 to 2.2. Mechanistic studies reveal that sulfur vacancies at MoS2 edges boost carbon-chain growth by facilitating not only C-O cleavage but also C-C coupling, while potassium promotes the desorption of alcohols via electrostatic interaction with hydroxyls, thereby enabling preferential formation of C2-4OH.

Low-temperature CO oxidation by silver nanoparticles in silica aerogel mesoreactors

Low-temperature carbon monoxide (CO) oxidation on silver/silica aerogel (Ag/SiO2 AG) catalyst prepared by one-pot sol–gel synthesis followed by supercritical ethanol drying method is reported. Highly stable and sinter-proof catalyst led to easy reactant diffusion to the active sites. The Ag/SiO2 AG catalyst showed enhanced catalytic activity toward low-temperature CO oxidation by preventing agglomeration of silver nanoparticles inside pores and facilitating well-dispersed active sites to enhance the mass heat transfer in the mesopores. Catalyst pre-treatment conditions were found to play a crucial role in achieving high CO conversion efficiency at low light-off temperatures. Inverse counter-clockwise CO oxidation hysteresis was found to occur after the first run. The active sites contributing to this enhanced catalytic behavior were confirmed to be Ag0 from XPS, XRD, and TEM analysis. The catalyst exhibited good thermal stability up to 450 °C over repeated number of cycles.

Cover Feature: Theory‐Guided Machine Learning to Predict the Performance of Noble Metal Catalysts in the Water‐Gas Shift Reaction (ChemCatChem 16/2022)

The Cover Feature illustrates a theory-guided machine learning framework for water-gas shift reaction optimization. In their Research Article, J. Chattoraj, T. L. Tan and co-workers showed that purely data-driven models could violate the thermodynamic equilibrium principle as well as the models could predict non-physical carbon monoxide conversion percentage. They proposed a theory-guided machine learning model with a unique thermodynamic loss function to resolve these two problems. The proposed model showed promising reaction conditions, which could result in high carbon monoxide conversion rates. All the authors thank Zicong Marvin Wong for helping to design the cover picture. More information can be found in the Research Article by J. Chattoraj, T. L. Tan and co-workers.

Electrospun La0.8Ce0.2Fe1-xNixO3 perovskite nanofibrous catalysts for CO oxidation

Carbon monoxide (CO) is one of the main pollutants of incomplete gasoline combustion from automotive and engines. Catalytic CO oxidation is an effective way to remove CO. La0.8Ce0.2Fe1-xNixO3 nanofibrous catalysts with high thermal stability were prepared by electrospinning in this study. The influence factors of La0.8Ce0.2Fe1-xNixO3 perovskite properties on CO oxidation were investigated. Calcination temperature affects catalyst crystallinity and hence catalytic activity. Increasing calcination temperature enhances crystallinity while decreases catalytic surface area, resulting in the highest catalytic activity at the calcination temperature of 800 °C. Oxygen vacancy in the perovskite increases catalyst activity. Doping Ni up to 20 mol% increases oxygen vacancy and oxygen storage capacity while excessive doping decreases perovskite crystallinity. The nanofibrous catalyst activity can be improved via reducing fiber diameters so as to increase catalytic surface area. The advantage of nanofibrous catalysts was confirmed by comparing with conventional powder catalysts. Therefore, high CO conversion can be achieved over the nanofibrous perovskite-type catalysts.

Development of CVD Silica Membranes Having High Hydrogen Permeance and Steam Durability and a Membrane Reactor for a Water Gas Shift Reaction.

Water gas shift reaction of carbon monoxide (CO) with membrane reactors should be a promising method for hydrogen mass-production because of its high CO conversion, high hydrogen purity and low carbon dioxide emission. For developing such membrane reactors, we need hydrogen permselective membranes with high hydrogen permeance with order of 10−6 mol m−2 s−1 Pa−1 at 573 K and high steam durability. In this study, we have optimized the kind of substrates, precursors, vapor concentration, and chemical vapor deposition (CVD) time using the counter-diffusion CVD method for developing such membranes. The developed membrane prepared from hexamethyldisiloxane has a hydrogen permeance of 1.29 × 10−6 mol m−2 s−1 Pa−1 at 573 K and high steam durability. We also conducted water gas shift reactions with membrane reactors installed the developed silica membranes. The results indicated that reactions proceed efficiently with the conversion around 95–97%, hydrogen purity around 94%, and hydrogen recovery around 60% at space velocity (SV) 7000.

Gold‐Loaded Nanoporous Iron Oxide Cubes Derived from Prussian Blue as Carbon Monoxide Oxidation Catalyst at Room Temperature

AbstractThis work reports the preparation of carbon monoxide (CO) oxidation catalysts based on gold nanoparticles supported on nanoporous iron oxide cubes. By heat‐treating Prussian blue (PB) cubes at various temperatures between 250–450 °C in air, nanoporous iron oxide cubes with surface areas up to 100 m2 g−1 are obtained. Owing to the relatively large surface area and nanoporous structure, the as‐synthesized iron oxide cubes can be loaded with up to 11 wt% of Au nanoparticles without significant aggregation. When employed for CO oxidation, the Au‐loaded nanoporous iron oxide cubes exhibit a high CO conversion rate of over 95% at room temperature under 0.1 L⋅min−1 of CO gas flow, with specific activity of up to 1.79 molCO⋅gAu−1⋅h−1. The high catalytic performance of the Au‐loaded nanoporous iron oxide cubes for CO oxidation is contributed by various factors, including: (i) the high surface area of the iron oxide cubes which leads to the availability of more sites for the adsorption of oxygen molecules to react with carbon monoxide to generate more carbon dioxide (CO2); (ii) the presence of nanopores which enhances the diffusivity of the reactant molecules during the catalytic reaction and improves dispersion of the deposited gold nanoparticles while also preventing their aggregation at the same time and (iii) the small size of the deposited gold nanoparticles (2‐5 nm) which falls within the ideal size of gold nanoparticles for achieving high CO conversion.

Hydrogen production from coal-derived syngas undergoing high-temperature water gas shift reaction in a membrane reactor

In this study, a numerical model to predict the hydrogen production from water-gas shift reaction using coal-derived syngas as a feedstock was presented. The reaction was carried out in a palladium (Pd)-based membrane reactor operated at 900°C for yielding carbon monoxide (CO) conversion higher than the thermodynamic equilibrium limit. The sweep gas flow, membrane permeance, and steam-to-carbon ratio effects on the reactor performance were examined. Based on the obtained results, it was found that high CO conversion and hydrogen (H2) recovery were obtained when the reactor was operated in counter-flow mode and with high sweep gas flow rate, steam-to-carbon ratio, and membrane permeance. However, the H2S-to-H2 ratio in the reactor was found to increase with the CO conversion and can be higher than the thermodynamic limit for Pd sulfidization. Optimum operation parameters should be sought for obtaining high CO conversion and H2 recovery while preventing membrane failure due to Pd sulfidization.

Experimental study on the performance of hydrogen production from miniature methanol–steam reformer integrated with Swiss-roll type combustor for PEMFC

A miniature plate-type hydrogen production reactor using methanol as fuel was designed and tested. This reactor is composed of a catalytic combustor, vaporizer, reformer, and methanator. All components were fabricated on one piece of rectangular quartz glass plate 50mm×44mm×7mm in size. The combustor was fabricated on one side of the glass plate with a Swiss-roll type channel in which the Pt/Al2O3 particles were loaded in segmented form to catalyze the combustion. A spiral channel was fabricated on the other side of the plate and divided into three sections: a vaporizer for liquid methanol–water mixture vaporization, a reformer for methanol–steam reforming catalyzed by CuO/ZnO/Al2O3 particles and a methanator for carbon monoxide (CO) removal catalyzed by Ru/Al2O3 particles.The test results indicated that this reactor successfully produced H2 and had thermal efficiency ranging from 13% to 35%. The reactor performance depends on the feed rates to the combustor and reformer, respectively. High methanol conversion can be obtained from either a low feed rate to the reformer or a high feed rate to the combustor. However, both cases also produce high CO concentrations. The CO methanation reaction was used to reduce the CO concentration. It was found that the methanation reaction depends greatly on the reactor temperature with high temperature not being favorable to this reaction. High CO conversion and low H2 consumption with low methanol conversion result when the reaction temperature is low. Thermal management for producing suitable temperature and catalyst activity improvement in high reaction temperature for the methanator are both needed in the integrated reactor design to reduce the CO concentration down to acceptable levels for fuel cell operation.

Influence of NiO on the performance of CoO-based catalysts for the selective oxidation of CO in H2-rich gas

Abstract The catalytic properties of Ni, Co, and Co-Ni supported activated carbon (AC) catalysts for oxidation for the removal of carbon monoxide (CO) in H 2 -rich gas are investigated. Results show that Co x O y /AC and CoO–NiO/AC exhibit higher catalytic activity than NiO/AC and that CoO–NiO/AC gives high CO conversion of above 99.5% at a wide reaction temperature region of 413–463 K. The addition of nickel oxide (NiO) can lead to enriched CoO species on the surface of CoO-NiO/AC. The higher catalytic activity and selectivity of CoO-NiO/AC compared with Co x O y /AC can be attributed to NiO playing an important role.

Cu–Ce mixed oxides supported on Al-pillared clay: Effect of method of preparation on catalytic activity in the preferential oxidation of carbon monoxide

The possibility of using Al-pillared montmorillonite (Al-PILC) clay as a high-surface-area support for CuO–CeO2-based catalysts has been investigated. The preparation of the samples was done by three different methods, viz., amorphous citrate route (ACR), deposition precipitation (DP) and wet impregnation method (WIM). Samples with different CuO–CeO2 loadings (10–50wt.%) were prepared by each of the three methods. The catalytic activity of these samples was investigated for the preferential oxidation (PROX) of carbon monoxide (CO) in excess of H2. The samples prepared by DP and WIM methods show better activity than the samples prepared by ACR method. At low Cu content, the samples prepared by DP method have a slight edge over samples prepared by WIM method. The DP-30 sample shows a very high CO conversion of 96.1% at 423K. A higher dispersion of CuO–CeO2 on pillared montmorillonite clay and better reducibility of copper oxide species may be responsible for the good activity of these samples even at lower reaction temperatures. A higher O2/CO ratio increased the CO conversion but led to a reduction in oxidation selectivity. No methanation of CO or CO2 was observed at the reaction temperature. These CuO–CeO2/Al-PILC samples could be considered as comparable in performance with supported noble metal catalysts for the preferential oxidation of CO in excess hydrogen.

Biocatalytic conversion of CO to acetic acid by Clostridium aceticum—Medium optimization using response surface methodology (RSM)

Acetic acid is an important industrial feedstock which can be produced from renewable resources such as carbon monoxide (CO) for an infinite supply for future usage. The biological route of acetic acid production from CO through fermentation by acetogenic bacteria, Clostridium aceticum appeared to be potential substitution for current process technology. The fermentation medium which is responsible for sustaining and maintaining the biocatalyst growth usually accounts for 60–70% of the production cost. Therefore, efforts in creating cost effective process have been carried out by optimizing the nutrient requirements of NH 4Cl and yeast extract compositions which can still attain satisfactory responses during acetic acid fermentation. In this study, medium composition of NH 4Cl (studied ranges: 0.0–1.50 g/L) was optimized in the early stage and then followed by optimizing the yeast extract component (studied ranges: 0.0–2.00 g/L). The high-end concentration selected for each medium composition was based on the concentration consisted in the DSMZ growth medium 1496 as a guideline. Response surface methodology (RSM) which consisted of 2-D contour plot and 3-D surface plot was used to determine the optimum concentrations of NH 4Cl and yeast extract that enabled the maximum acetic acid production with high CO conversion in an actively growing culture. Fermentation when launched in medium of 0.2 g/L of NH 4Cl coupled with 1.5 g/L of yeast extract and operated for 72 h cultivation time resulted in 1.01 g/L of acetic acid production and 100% CO conversion. Optimum fermentation medium was defined as 0.2 and 1.5 g/L of NH 4Cl and yeast extract respectively in this experiment based on the 67% of response desirability achieved through RSM.

H2 enrichment from synthesis gas by Desulfotomaculumcarboxydivorans for potential applications in synthesis gas purification and biodesulfurization

Desulfotomaculum carboxydivorans, recently isolated from a full-scale anaerobic wastewater treatment facility, is a sulfate reducer capable of hydrogenogenic growth on carbon monoxide (CO). In the presence of sulfate, the hydrogen formed is used for sulfate reduction. The organism grows rapidly at 200 kPa CO, pH 7.0, and 55 degrees C, with a generation time of 100 min, producing nearly equimolar amounts of H(2) and CO(2) from CO and H(2)O. The high specific CO conversion rates, exceeding 0.8 mol CO (g protein)(-1) h(-1), makes this bacterium an interesting candidate for a biological alternative of the currently employed chemical catalytic water-gas shift reaction to purify synthesis gas (contains mainly H(2), CO, and CO(2)). Furthermore, as D. carboxydivorans is capable of hydrogenotrophic sulfate reduction at partial CO pressures exceeding 100 kPa, it is also a good candidate for biodesulfurization processes using synthesis gas as electron donor at elevated temperatures, e.g., in biological flue gas desulfurization. Although high maximal specific sulfate reduction rates (32 mmol (g protein)(-1) h(-1)) can be obtained, its sulfide tolerance is rather low and pH dependent, i.e., maximally 9 and 5 mM sulfide at pH 7.2 and pH 6.5, respectively.

Effects of heating energy and heating position on the conversion characteristics of the catalyst of a four-stroke motorcycle engine in cold start conditions

Abstract The effects of heating energy and heating position on the conversion efficiency of an electrically heated catalyst of a four stroke motorcycle engine under cold start conditions were investigated in this study. In general, during cold start, the operating temperatures of a four stroke motorcycle engine and its catalyst would not be optimized. It was found in this paper that by applying heat to the catalyst however, the reaction of the catalyst could be promoted, which, consequently, improved the conversion efficiency. The experimented parameters were heating energy, heating position, heating temperature and the carbon monoxide (CO) setting level. The heating temperatures included 100, 140 and 180 °C, while three different heating powers and six different heating positions were used. The CO levels were set as 1.0%, 1.8% and 2.3%. The best CO conversion efficiency was obtained by applying heating at the inlet of the catalyst. It was revealed that a high heating power induced a high temperature rising rate and, consequently, a high CO conversion efficiency. In terms of energy economy efficiency, however, heating at the mid-section of the catalyst gave the best results and through a relatively low heating power.

99/00135 New clean fuel from coal — direct dimethyl ether synthesis from hydrogen and carbon monoxide

Dimethyl ether (DME), which has similar physical properties to propane and is easily liquefied at low pressure, has a significant possibility as a clean and non-toxic fuel from coal or coal bed methane. Equilibrium calculation also shows a big advantage of high carbon monoxide conversion of DME synthesis compared to methanol synthesis. By using a 50 kg/day DME bench scale test plant, direct synthesis of DME from hydrogen and carbon monoxide has been studied with newly developed catalysts which are very fine particles. This test plant features a high pressure three-phase slurry reactor and low temperature DME separator. DME is synthesized at temperatures around 533--553 K and at pressures around 3--5 MPa. According to the reaction stoichiometry, the same amount of hydrogen and carbon monoxide react to DME and carbon dioxide. Carbon conversion to DME is one third and the rest of carbon is converted to carbon dioxide. As a result of the experiments, make-up CO conversion is 35--50% on an once-through basis, which is extremely high compared to that of methanol synthesis from hydrogen and carbon monoxide. DME selectivity is around 60 c-mol %. Most of the by-product is CO{sub 2} with a small amount of methanol and water.more » No heavy by-products have been recognized. Effluent from the reactor is finally cooled to 233--253 K in a DME separator and liquid DME is recovered as a product.« less

Catalytic properties and crystalline structures of manganese-promoted iron ultrafine particles for liquid-phase hydrogenation of carbon monoxide

Mn-promoted Fe ultrafine particle (UFP) catalysts for carbon monoxide hydrogenation exhibited a higher alkene selectivity and a lower methane selectivity than unpromoted Fe UFP. It was found, however, that the catalytic properties of the Mn-promoted Fe UFP catalysts, particularly the alkene selectivity, depended to a very large extent upon the level of carbon monoxide conversion. In the region of low carbon monoxide conversion, these catalysts more selectively produced olefinic hydrocarbons than in the region of high carbon monoxide conversion. Concurrently the bulk phase crystalline structures of these catalysts differed in both regions. Fe 2C was formed in the region of low carbon monoxide conversion, and mixed oxides of iron and manganese were formed in the region of high carbon monoxide conversion.