High Space Velocity Research Articles

CO2 hydrogenation to methanol over Zr- and Ce-doped indium oxide

In recent decades, climate change has become a major issue that needs to be addressed. Many efforts have been made on the reduction of CO2 emissions and its conversion in energy carriers and high value-added products such as methane, methanol, dimethyl-ether, and hydrocarbons. The present study focuses on the development of catalysts for hydrogenating CO2 to methanol, which is a useful chemical and an alternative liquid fuel. According to the literature, In2O3-based catalysts are particularly selective in the hydrogenation of CO2 to methanol, reducing the production of CO even at high space velocities compared to the more common ternary catalysts such as Cu/ZnO/Al2O3 or Cu/ZnO/ZrO2. Therefore, the effects of CeO2 and ZrO2 on In2O3-based catalysts were investigated in the present study. The InxCe100−x and the InxZr100−x mixed oxides catalysts were synthesized via gel-oxalate coprecipitation by varying the atomic ratios between the elements. Subsequently, they were analysed with several characterisation techniques to rationalise the catalytic performances that were obtained by testing the samples in a fixed bed reactor under different reaction conditions. The addition of different amounts Ce or Zr modified the structure and morphology of the samples and promoted the adsorption of CO2 from 1.8 mmolCO2⋅gcat−1 up to 10.6 mmolCO2⋅gcat−1. ZrO2 stabilises the structure and the results suggests that the greater specific activity (168 mgCH3OH⋅gIn2O3−1⋅h−1 at 300 °C and 2.5 MPa of In40Zr60) could be ascribed to the electronic promotion of Zr. On the contrary, the addition of CeO2 did not reveal a beneficial effect on the activity. Concerning the stability, In2O3-ZrO2 binary oxides seemed to be affected mainly by sintering; whereas In2O3-CeO2 were affected by at least three deactivating phenomena: sintering, reduction of In2O3 to metallic indium and coking. Consequently, the deactivation rate of these binary oxides increased from 1.04 ⋅ 10−2 h−1 of the In100 to 4.13 ⋅ 10−2 h−1 of the In40Ce60.

Reactive Separations of CO/CO2 mixtures over Ru–Co Single Atom Alloys

Reactive separations of CO/CO2 mixtures are a promising pathway to lower the energy requirement of CO2 hydrogenation to chemicals and fuels, with applications in the U.S. Navy’s seawater-to-fuel process. With the CO/CO2 feedstock, a challenge is activating CO to produce heavier hydrocarbons while preventing CO2 methanation, requiring low-temperature Fischer-Tropsch synthesis (FTS) catalysts. In this work, we demonstrate that a Ru–Co single atom alloy (SAA) catalyst produces C5+ hydrocarbons at a rate of 11.7 μmol/s/g-cobalt (hexane basis) in a 50/50 CO/CO2 stream with ≤1% CO2 conversion. The reaction operates at a relatively low temperature (200 °C) and high gas hourly space velocity (GHSV: 84,000 mL/g/h) that is compatible with the upstream reverse water-gas shift reaction. Detailed experiments, catalyst characterizations, and density functional theory (DFT) calculations have been conducted to understand the active phase, the role of the Ru dopant, and catalyst restructuring that occurs at elevated temperatures (>200 °C). Ru dopants are found to promote the reduction of Co species, enabling catalytic activity for CO hydrogenation without pre-reduction, but may not enhance the FTS activity or desired C5+ hydrocarbon selectivity.

Flexible NiRu Systems for CO2 Methanation: From Efficient Catalysts to Advanced Dual-Function Materials.

CO2 emissions in the atmosphere have been increasing rapidly in recent years, causing global warming. CO2 methanation reaction is deemed to be a way to combat these emissions by converting CO2 into synthetic natural gas, i.e., CH4. NiRu/CeAl and NiRu/CeZr both demonstrated favourable activity for CO2 methanation, with NiRu/CeAl approaching equilibrium conversion at 350 °C with 100% CH4 selectivity. Its stability under high space velocity (400 L·g-1·h-1) was also commendable. By adding an adsorbent, potassium, the CO2 adsorption capability of NiRu/CeAl was boosted, allowing it to function as a dual-function material (DFM) for integrated CO2 capture and utilisation, producing 0.264 mol of CH4/kg of sample from captured CO2. Furthermore, time-resolved operando DRIFTS-MS measurements were performed to gain insights into the process mechanism. The obtained results demonstrate that CO2 was captured on basic sites and was also dissociated on metallic sites in such a way that during the reduction step, methane was produced by two different pathways. This study reveals that by adding an adsorbent to the formulation of an effective NiRu methanation catalyst, advanced dual-function materials can be designed.

Direct electrification of Rh/Al2O3 washcoated SiSiC foams for methane steam reforming: An experimental and modelling study

Electrified methane steam reforming (eMSR) is a promising concept for low-carbon hydrogen production. We investigate an innovative eMSR reactor where SiSiC foams, coated with Rh/Al2O3 catalyst, act as electrical resistances to generate the reaction heat via the Joule effect. The novel system was studied at different temperatures, space velocities, operating pressures and catalyst loadings. Thanks to efficient heating, active catalyst and optimal substrate geometry, complete methane conversions were observed even at a high space velocity of 200000 Nl/h/kgcat. A specific energy demand as low as 1.24 kWh/Nm3H2, with an unprecedented energy efficiency of 81%, was achieved on a washcoated foam with catalyst density of 86.3 g/L (GHSV = 150000 Nl/h/kgcat, S/C = 4.1, ambient pressure). A mathematical model was validated against measured performance indicators and used to design an intensified eMSR unit for small scale H2 production.

Platinum Nanoparticles Anchored on Covalent Triazine Frameworks Modified Cordierite for Efficient Oxidation of Hydrogen Isotopes

Catalytic oxidation is frequently employed to remove hydrogen isotopes to diminish the risk from tritium leakage and hydrogen explosion. However, Pt particle aggregation and deactivation from water are the major challenges for traditional catalysts. Herein, we design hydrophobic anchoring sites to bind Pt nanoparticles through constructing covalent triazine frameworks on cordierite for the efficient oxidation of hydrogen isotopes. The Pt nanoparticles were uniformly dispersed with a diameter of 1.8–2.4 nm on the catalyst. The catalyst has a high catalytic activity for H2/D2 oxidation at 25–65 °C and high space velocity (≤30,000 h–1). It retains stable catalytic activity in 246 h continuous and intermittent operations and exhibits a lower isotope effect (KF,H/KF,D = 1:0.7) than most of the reported Pt catalysts, indicating good catalytic activity for tritium oxidation. This work provides a Pt-anchoring nanocatalyst with high hydrophobicity for the oxidation of hydrogen isotopes, which can be an effective strategy for designing catalysts.

Platinum Nanoparticles Immobilized on Electrospun Membranes for Catalytic Oxidation of Volatile Organic Compounds.

Structured catalytic membranes with high porosity and a low pressure drop are particularly suitable for industrial processes carried out at high space velocities. One of these processes is the catalytic total oxidation of volatile organic compounds, which is an economically feasible and environmentally friendly way of emission abatement. Noble metal catalysts are typically preferred due to high activity and stability. In this paper, the preparation of a thermally stable polybenzimidazole electrospun membrane, which can be used as a support for a platinum catalyst applicable in the total oxidation of volatile organic compounds, is reported for the first time. In contrast to commercial pelletized catalysts, high porosity of the membrane allowed for easy accessibility of the platinum active sites to the reactants and the catalytic bed exhibited a low pressure drop. We have shown that the preparation conditions can be tuned in order to obtain catalysts with a desired platinum particle size. In the gas-phase oxidation of ethanol, acetone, and toluene, the catalysts with Pt particle sizes 2.1 nm and 26 nm exhibited a lower catalytic activity than that with a Pt particle size of 12 nm. Catalysts with a Pt particle size of 2.1 nm and 12 nm were prepared by equilibrium adsorption, and the higher catalytic activity of the latter catalyst was ascribed to more reactive adsorbed oxygen species on larger Pt nanoparticles. On the other hand, the catalyst with a Pt particle size of 26 nm was prepared by a solvent evaporation method and contained less active polycrystalline platinum. Last but not least, the catalyst containing only 0.08 wt.% of platinum achieved high conversion (90%) of all the model volatile organic compounds at moderate temperatures (lower than 335 °C), which is important for reducing the costs of the abatement technology.

Catalytic combustion of propane over Mg-modified Co1.5Mn1.5O4 spinel catalysts: Boosting C-H cleavage with Lewis acid and oxygen vacancies

Rational modulation of surface electronic structure can optimize the adsorption and activation of reactant molecules on the catalyst surface, which is crucial for catalytic elimination of hydrocarbons. Herein, a facile low-valence Mg doping strategy was applied to synthesize highly active and stable Co-Mn binary oxide (CMO) catalyst. Lewis acid sites and oxygen vacancies were purposefully introduced on CMO through the surface electron deficit caused by the substitution of doped Mg for host metals. For the CMO catalyst modified by appropriate amount of Mg (CMO-Mg0.05), the Co-Mn spinel with lattice expansion is significantly modified through substitution of Co or Mn ions with Mg2+, resulting in generation of abundant higher metal oxidation state species (Co3+, Mn4+) and oxygen vacancies. The best performance for catalytic propane combustion was achieved on CMO-Mg0.05 catalyst, with the T90 at 255 °C under high space velocity (60,000 ml g−1 h−1). Meanwhile, clear improvements on stability and water resistance were also achieved after the modification of Mg in CMO catalyst. Combined with C3H8-TPD, in-situ DRIFTS and various characterizations, it can be revealed that the synergistic effect of Lewis-acid sites and oxygen vacancies would remarkably promote the process of propane dissociative adsorption and mineralization. This work not only gives insight into the Mg dopants in boosting CH activation on CMO catalyst, but also provides a potential strategy for fabricating highly active hydrocarbon combustion catalysts.

Regulating the Pt-MnO2 Interaction and Interface for Room Temperature Formaldehyde Oxidation.

Formaldehyde (HCHO) is a hazardous pollutant in indoor space for humans because of its carcinogenicity. Removing the pollutant by MnO2-based catalysts is of great interest because of their high oxidation performance at room temperature. In this work, we regulate the Pt-MnO2 (MnO2 = manganese oxide) interaction and interface by embedding Pt in MnO2 (Pt-in-MnO2) and by dispersing Pt on MnO2 (Pt-on-MnO2) for HCHO oxidation over Pt-MnO2 catalysts with trace Pt loading of 0.01 wt %. In comparison to the Pt-in-MnO2 catalyst, the Pt-on-MnO2 catalyst has a higher Brunauer-Emmett-Teller surface area, a more active lattice oxygen, more oxygen vacancy activating more dioxygen molecules, more exposed Pt atoms, and noninternal diffusion of mass transfer, which contribute to the higher HCHO oxidation performance. The HCHO oxidation performance is stable over the Pt-MnO2 catalysts under high space velocity and high moisture humidity conditions, showing great potential for practical applications. This work demonstrates a more effective Pt-dispersed MnO2 catalyst than Pt-embedded MnO2 catalyst for HCHO oxidation, providing universally important guidance for metal-support interaction and interface regulation for oxidation reactions.

Engineering single-atom Pd sites in ZIF-derived porous Co3O4 for enhanced elementary mercury removal

Engineering metal-based nanoarchitectures and their atomic-scale arrangement is a promising avenue for enhanced mercury adsorbent activities. Interactions between metal single atoms and substrates result in regulated transitions between distinct reaction processes that boost mercury adsorption activity. Herein, a novel sorbent of porous Co3O4 with Palladium atomic dispersed was successfully prepared by one-step pyrolysis of zeolitic imidazolate framework 67 (ZIF-67) precursors. Via engineering single Pd atoms into ZIF-derived Co3O4 (Pd1/Co3O4-ZIF), the strong metal-support interaction (SMSI) activated the reducibility of Co3+ in porous Co3O4 to efficiently adsorb and oxidize Hg0, enhancing its mercury removal efficiency. Specifically, Pd1/Co3O4-ZIF exhibited superior sorption performance for Hg0 over a broad range of temperatures (30–350 °C) and high gaseous hourly space velocity (about 555,500 hr−1) with the average Hg0 removal efficiency higher than 98%. The strategy of constructing atomic active sites on the surface of porous metal-oxide to convert adsorbed Hg0 into HgO is a promising approach to solve the problem that Hg0 in flue gas is challenging to remove. Density functional theory (DFT) calculation further proved that the existence of a single Pd site on the surface of Co3O4 significantly reduced the energy barrier of Hg0 to HgO at the atomic level. This work contributed to a thorough comprehension of the structural and adsorption properties of the ZIF-derived Co3O4 sorbent engineering with a single atom and enabled the efficient capture of elemental mercury in flue gas by such ZIF-derived sorbent.

NH3 decomposition over Ru/CeO2-PrOx catalyst under high space velocity conditions for an on-site H2 fueling station

From a commercialization perspective, NH3 decomposition catalysts used in on-site H2 fueling stations require a high NH3 conversion of over 99.5%, space velocity (SV) of 30,000 h−1 and reaction temperature of 500 °C. To achieve this target, we present Ru catalysts supported on CeO2−PrOx composites (Ru/CP) prepared by a coprecipitation method. The Ru/CP catalysts exhibited higher activity than the Ru/CeO2 and Ru/PrOx catalysts and achieved the target with Pr content (=Pr/(Ce+Pr)) of 33−67%. STEM observations and in situ X-ray absorption fine structure analysis revealed that an increase in the Pr content in the catalysts improved the Ru dispersion but inhibited the Ru metalation, owing to a strong “metal–support interaction”. Notably, 10% of Ru in the Ru/PrOx remains an oxide even when reduced at 550 °C. These results suggest that both Ru dispersion and metalation are enhanced at the optimal Pr content, maximizing the number of Ru active sites.

β-Co(OH)2 Nanostructures with High Spin Co(II) in Distorted [CoO6] for Catalytic Ozone Decomposition

There is a high demand to synthesize ozone decomposition catalysts especially in high-space-velocity and high-relative-humidity (RH) environments. Herein, two polymorphs of cobalt hydroxide, α- and β-Co(OH)2, are synthesized and applied for ozone elimination. β-Co(OH)2 shows ∼90% ozone decomposition efficiency under high space velocity (weight hourly space velocity (WHSV) = 1,200,000 mL g–1 h–1, 25 °C, 40 ppm), which is far higher than that of α-Co(OH)2 (∼5%). β-Co(OH)2 has high spin Co(II) in distorted octahedral coordination caused by the Jahn-Teller effect, leading to a higher crystal field splitting energy level and thus contributing to the easier electron transfer between the ozone and catalyst. Moreover, β-Co(OH)2 still shows high performance (∼87%) even in humid conditions (RH ∼50%, 25 °C, 40 ppm, WHSV = 600,000 mL g–1 h–1), which is attributable to its abundant surface non-hydrogen-bonded hydroxyls weakening water molecule adsorption, providing an idea to develop highly efficient catalysts for ozone decomposition in humid environments.

Effect of morphology and simultaneous sulfation on Fe doped CeO2 for selective catalytic reduction of NOx with NH3

Researchers have been developing novel environment-friendly NH3-SCR catalysts for controlling NOx emission from fossil fuel combustion. Fe doped CeO2 catalysts with nanorod, nanocube and nanopolyhedron shape were synthesized and sulfation was conducted on porous nanorod simultaneously. Their NOx conversions were in sequence of sulfated porous nanorod (S-FeCeOx) > nanorod (R-FeCeOx) > nanopolyhedron (P-FeCeOx) > nanocube (C-FeCeOx) and presented distinct morphology dependence. S-FeCeOx catalyst possessed above 95 % NOx conversion and nearly 100 % N2 selectivity in very high gas hourly space velocity of 240, 000 mL·g−1·h−1 at 275–400 °C. The sequence of BET specific surface area was: P-FeCeOx > R-FeCeOx > S-FeCeOx > C-FeCeOx and thus the change of physical adsorption capacity may be not the main reason for high SCR catalytic activity of S-FeCeOx and R-FeCeOx. Fe doping and sulfation induced porous nanorod shape with preferentially exposed {110} faces, most oxygen vacancy defect sites and highest surface chemisorbed oxygen ratio, which contributed to the highest NOx conversion of S-FeCeOx. Fe doping mainly increased strong acid sites, and surface sulfate species significantly increased Brønsted acid sites promoting NH3 adsorption and suppressed NOx adsorption on S-FeCeOx catalyst, beneficial to both high NOx conversion and low N2O formation on it. R-FeCeOx catalyst mainly followed Langmuir-Hinshelwood mechanism, while SCR reaction mechanism was changed by sulfation and S-FeCeOx catalyst mainly followed Eley-Rideal mechanism.

Birnessite MnO2 supported on CNTs in-situ for low-temperature oxidation of ethyl acetate

The removal of ethyl acetate has received much attention because excessive emissions of ethyl acetate are harmful to the environment and human health. Efficiently removing ethyl acetate under high space velocity requires low-cost catalysts operating at low temperatures. Herein, carbon nanotubes (CNTs) supported birnessite MnO2 catalysts were in-situ prepared by the redox reaction between KMnO4 and CNTs to maximize the interaction between MnO2 and support. The good thermal stability derived from the intact CNTs structure was important for the interaction between MnO2 and CNTs, contributing to the enhanced catalytic activity for ethyl acetate oxidation. 4MnO2-CNTs showed outstanding performance for the catalytic oxidation of ethyl acetate (100 ppm), achieving 100% removal efficiency and 99% CO2 selectivity at 160 °C under 100,000 mL·g−1·h−1 space velocity. In addition, 4MnO2-CNTs exhibited an excellent catalytic stability during the 50 h test period. Based on the comprehensive characterization study, we revealed that the activity of 4MnO2-CNTs could be effectively enhanced by the higher amount of active sites (Mn3+ and surface active adsorbed hydroxyl oxygen), as well as the strong interaction between MnO2 and support and the good thermal stability derived from the introduction of the intact CNTs structure.

Non-ideal characteristics in a micro packed-bed reactor: A coupled reaction-transport CFD analysis for propane dehydrogenation

Kinetic experiments can be significantly influenced by fluidic effects and transport limitations within reactors, particularly for strongly exo- and endo-thermic reactions. This paper describes the influence non-uniform physical fields, e.g. temperature, velcocity and species concentration, on the determination of kinetic parameters for endothermic systems with propane dehydrogenation (PDH) as a model process, which was analyzed using computational fluid dynamics (CFD) method based on the porous media model. Propane conversions calculated from 3-D porous media model at various conditions have discrepancies from the reported experimental data and 1-D numerical regression. This is due to the application of kinetic parameters obtained from 1-D plug flow assumption to the 3-D model with inhomogeneous temperature distributions. In the kinetic analysis, it is found that the low space velocity may lead to backward diffusion but can be a preference to minimize the temperature gradients within the catalyst bed. On the other hand, the commonly used higher space velocity may enlarge the temperature inhomogeneity. The sensitivity of temperature distribution with various reaction conditions is further analyzed. In addition, with respect to the packed bed properties, a high thermal conductivity and low loading of catalysts can reduce the non-uniformity of temperature distribution. Therefore, it is proposed that a mixed packing scheme with lower catalyst concentration and higher thermal conductivity could effectively suppress temperature gradients in kinetic analysis. This study exemplifies the necessity to consider the non-ideal distribution of physical fields for the kinetic study of reactions with strong thermal effects.

Nitrogen-Doped Porous Carbon from Biomass with Efficient Toluene Adsorption and Superior Catalytic Performance.

The chemical composition and surface groups of the carbon support affect the adsorption capacity of toluene. To investigate the effect of catalyst substrate on the catalytic performance, two different plant biomasses, banana peel and sugarcane peel, were used as carbon precursors to prepare porous carbon catalyst supports (Cba, Csu, respectively) by a chemical activation method. After decorating PtCo3 nanoparticles onto both carbon supports (Cba, Csu), the PtCo3-su catalyst demonstrated better catalytic performance for toluene oxidation (T100 = 237 °C) at a high space velocity of 12,000 h-1. The Csu support possessed a stronger adsorption capacity of toluene (542 mg g-1), resulting from the synergistic effect of micropore volume and nitrogen-containing functional groups, which led to the PtCo3-su catalyst exhibiting a better catalytic performance. Moreover, the PtCo3-su catalyst also showed excellent stability, good water resistance properties, and high recyclability, which can be used as a promising candidate for practical toluene catalytic combustion.

Boosting the catalytic performance of Fe/Zr catalyst by tungsten addition for selective catalytic reduction of NOx with ammonia

To clarify the effect of WO3 doping over Fe/Zr catalyst, several Fe/Zr-xW catalysts were prepared via conventional wet impregnation method, and the selective catalytic reduction (SCR) performance was studied. The Fe/Zr-0.1 W catalyst showed the highest catalytic activity and achieved nearly 100 % in a wide operating temperature window of 300–500 °C, and the N2 selectivity exceeded 90 % over the entire temperature range under a high hour space velocity of 90, 000 h−1. In addition, Fe/Zr-0.1 W catalyst also exhibited superior resistance to SO2 compared to Fe/Zr catalyst without WO3 introduction. Further characterization results indicated that the Fe/Zr-0.1 W catalyst possessed larger BET specific surface area, better dispersion of active component, higher concentration of Fe3+ and more surface chemisorbed oxygen species, which might be the predominant factors for its superior catalytic performance. More importantly, WO3 doping improved the redox capacity and surface acidity, thus promoting the redox circle and enhancing the adsorption ability of NH3. According to the transient in-situ DRIFTS experiment results, the doping of WO3 increased the L-H reaction pathway on the surface of Fe/Zr catalyst during the NH3-SCR reaction. The present work could provide a new way for developing a high-performance non-vanadium SCR catalyst in practical application.

Highly Efficient Oxidation of Propane at Low Temperature over a Pt-Based Catalyst by Optimization Support.

Pt-based catalysts have attracted widespread attention in environmental protection applications, especially in the catalytic destruction of light alkane pollutants. However, developing a satisfying platinum catalyst with high activity, excellent water-resistance, and practical suitability for hydrocarbon combustion at low temperature is challenging. In this study, the Pt catalyst supported on the selected Nb2O5 oxide exhibited an efficient catalytic activity in propane oxidation and exceeded that of most catalysts reported in the literature. More importantly, the Pt/Nb2O5 catalyst maintained excellent activity and durability even after high-temperature aging at 700 °C and under harsh working conditions, such as a certain degree of moisture, high space velocity, and composite pollutants. The excellent performance of the Pt/Nb2O5 catalyst was attributed to the abundant metallic Pt species stabilized on the surface of Nb2O5, which prompted the C-H bond dissociation ability as the rate-determining step. Furthermore, propane was initially activated via oxidehydrogenation and followed the acrylate species path as a more efficient propane oxidation path on the Pt/Nb2O5 surface. Overall, Pt/Nb2O5 can be considered a promising catalyst for the catalytic oxidation of alkanes from industrial sources and could provide inspiration for designing superb catalysts for the oxidation of light alkanes.

Efficient CO catalytic oxidation by the combination of cobalt and excellent carrier Ta2O5

Small size cobalt nanoparticles are highly dispersed on different crystalline forms of Ta2O5 (amorphous, T, M, H) by impregnation method, which is then introduced to catalytic oxidation of CO. The experimental results show that Co3O4/M-Ta2O5 exhibits the highest CO conversion efficiency compared with Co3O4 loaded on amorphous-, T-, and H-Ta2O5, and the pure Co3O4 and M-Ta2O5. The temperature of 90 % CO conversion rate is approximately 170 °C at the high space velocity of 780,000 h−1. Besides, the effect of oxygen concentration, space velocity, CO concentration, as well as different ratio of Co: Ta on CO conversion have been studied. Moreover, XRD, SEM, TGA, BET and H2-TPR characterizations reveal that Co3O4 is uniformly distributed and does not change the structure crystalline of Ta2O5, and there is strong interaction between cobalt active component and Ta2O5 support, which might be beneficial for CO conversion. Furthermore, the reaction mechanism has been investigated by X-ray photon spectroscopy and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs), which suggest that Co3+ is the active component and lattice oxygen as well as adsorbed oxygen play a critical role in CO oxidation.

Experimental optimization analysis on operating conditions of CO removal process from hydrogen-rich reformate

The catalytic effects of CO preferential oxidation and methanation catalysts for deep CO removal under different operating conditions (temperature, space velocity, water content, etc.) are systematically studied from the aspects of CO content, CO selectivity, and hydrogen loss index. Results indicate that the 3 wt% Ru/Al2O3 preferential oxidation catalysts reduce CO content to below 10 ppm with a high hydrogen consumption of 11.6–15.7%. And methanation catalysts with 0.7 wt% Ru/Al2O3 also exhibit excellent CO removal performance at 220–240 °C without hydrogen loss. Besides, NiClx/CeO2 methanation catalysts possess the characteristics of high space velocity, high activity, and high water-gas resistance, and can maintain the CO content at close to 20 ppm. Based on these experimental results, the coupling scheme of combining NiClx/CeO2 methanation catalysts (low cost and high reaction space velocity) with 0.7 wt% Ru/Al2O3 methanation catalysts (high activity) to reduce CO content to below10 ppm is proposed.

Intensification of high-flux Fischer-Tropsch synthesis with axial gradient Co-loading FeCrAl monolith catalysts

FeCrAl monolith catalysts are suitable for high-flux low-temperature Fischer-Tropsch synthesis (LT-FTS) due to their high thermal conductivity and low pressure drop at high gas hourly space velocity (GHSV). In this study, the reaction and thermal performance of the catalysts with increasing Co-loading (MCINC) and decreasing Co-loading (MCDEC) at different GHSV were studied by experiment and numerical simulation. The results showed that the reaction performance of MCDEC was slightly better than that of MCINC at 28000 h−1, while the thermal performance of MCDEC was much better than MCINC. The reason was explained by the heat transfer mechanism. The dominant heat transfer mode turned to the axial convective heat transfer at 28000 h−1. The powerful axial convective heat transfer improved the transfer of the reaction heat toward the outlet and decreased the temperature of MCDEC. Conversely, it exacerbated the heat accumulation near the outlet of MCINC. Therefore, MCDEC was more suitable than MCINC for the better thermal management of high-flux LT-FTS. These results demonstrated that designing the axial gradient of Co-loading according to the GHSV is a promising approach for the thermal intensification in LT-FTS.