Water Gas Shift Research Articles

Strong Metal-Support Interaction between Pt and TiO2 over High-temperature CO2 Hydrogenation.

The catalytic activities and stability of oxide-supported metal catalysts are significantly affected by metal-support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal-support interaction (SMSI) and electronic metal-support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile-supported Pt nanoparticles (NP) over high-temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2-x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high-temperature reverse water-gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM-1×h-1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time-on-stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Capture and catalytic conversion of CO2 from marine and offshore applications – A review

Abstract This contribution examines recent advances in modeling fluid dynamics and capture/conversion of CO2 from marine and offshore applications in packed-bed columns/trickle-bed reactors subjected to static inclination, externally-induced rolling and heaving motions. Breaking the axial symmetry of the two-phase flow once the packed bed system is tilted results in a significant decrease in process performance, the extent of which is determined by the magnitude of the tilt and the column/reactor diameter. Only the conversion of CO2 from marine engine emissions on-board large cargo ships via catalytic cycloaddition of CO2 to styrene oxide in multiphase large-diameter trickle-bed reactors increases slightly with increasing reactor inclination. Under the externally induced column/reactor oscillations, CO2 capture/conversion performance shifts toward the steady-state solution of the vertical column/reactor as the asymmetry between the two inclined positions decreases. Oscillating (between two inclined symmetrical positions) and heaving packed-bed columns/trickle-bed reactors generate an oscillating performance around the steady-state solution of the vertical static position, which is driven by the amplitude and period of the angular and heaving motions via the continuous evolution of the intensity of the reverse secondary flow and by the magnitude of the reactor/column diameter. The catalytic conversion of CO2 captured from marine emissions via an integrated process coupling reverse water-gas shift reaction and methanol synthesis in a fixed-bed reactors network system shows a remarkable enhancement with the addition of H2O adsorbent to the reaction systems in the sorption-enhanced process periods.

Effects of water injection on reaction temperature and hydrogen production in horizontal co-axial underground coal gasification

Underground coal gasification (UCG) is process of directly recovering energy as combustible gases such as hydrogen and carbon monoxide by combusting unmined coal resources in situ. During UCG process, the temperature in the gasification zone can exceed 1,300 °C, raising concerns about the potential melting of the steel pipe for oxidant injection. To control the temperature in the gasification zone, the use of water injection as an injection agent can be an option. Injecting water during UCG process serves two purposes: it decreases the temperature in the reaction zone by the endothermic effect of water, and it enhances the production of H2 by the reduction reaction of water. However, injecting excessive amounts of water may lead to a significant decrease in the temperature in the reaction zone, consequently cannot maintain the temperature range required for the UCG reaction. This study discusses the effects of water injection on the temperature of the gasification zone and the product gas by developing a chemical reaction model of UCG using COMSOL Multiphysics® software. The model was developed based on the temperature and produced gas results obtained from laboratory-scale artificial coal seam UCG experiments. Our findings reveal that water injection significantly influences the gasification process, controlling temperature in the reaction zone and promoting H2 production through steam gasification and water-gas shift reactions. Moreover, under the experiment and analysis conditions of this study, it is revealed that water injection up to an H2O/O2 molar ratio of 3.9 can effectively control the temperature of the gasification zone with enhancing H2 production.

Catalytic enhancement of water gas shift reaction with Cu/ZnO/ZSM-5: Overcoming challenges of CO2 and H2 rich feeds

Water gas shift (WGS) reaction commonly converts CO to CO2 using H2O and produces H2 and CO2 in a catalytic fixed bed reactor. This study aims to develop a Cu/ZnO/ZSM-5 catalyst loaded in water gas shift reactor for converting typical synthesis gas produced from dry reforming of methane (DRM) at medium temperature shift (MTS, 200–350 oC) conditions and for preventing reverse reaction due to high feed concentrations of CO2 and H2. The Cu/ZnO/ZSM-5 catalyst was prepared by impregnation method with lower Cu metal loading of 5, 10, and 15 wt%, respectively, compared to commercial catalysts. The synthesized catalyst was characterized using XRF, XRD, SEM, H2-TPR, NH3-TPD, and TGA. The catalyst activity and stability for the WGS reaction were tested in the fixed bed reactor at atmospheric pressure and temperature of 325 °C. The experimental results show that CO conversion increases with increasing Cu loading. The 15 wt% Cu/ZnO/ZSM-5 catalyst showed the best results with a CO conversion of 35% and a yield of H2 of 36% and showed good stability for 32 h. Based on the TGA, the 15 wt% Cu/ZnO/ZSM-5 catalyst forms a 0.04 g carbon/g catalyst, which is much lower when compared to commercial catalyst (0.105 g carbon/g catalyst). The relative activity of the synthesized catalyst indicates 2.4 times better when compared to commercial catalysts. High concentrations of H2 and CO2 in the feed may initiate side reactions, including reverse WGS, methanation, and carbon formation, which will decrease H2 yield.

Preparation of nano Cu-Mo2C interface supported on ordered mesoporous biochar of ultrahigh surface area for reverse water gas shift reaction

High conversion rate and selectivity are challenges for CO2 utilization through catalytic reverse water gas shift (RWGS) reaction. Herein, a novel mesoporous biochar (MB) supported Cu-Mo2C nano-interface was prepared by consecutive physical activation of coconut shells followed by carbothermal hydrogen reduction of bimetal. As compared with traditional carbon materials, this MB exhibited ultra-high specific surface area (2693 m2 g–1) and mesopore volume of mesopore (0.81 cm3 g–1) with a narrow distribution (2–5 nm), responsible for the high dispersion of binary Cu-Mo2C sites, CO2 adsorption and mass transfer in the reaction system. Moderate carbothermal reduction led to the sufficient reduction of Mo ion with carbon matrix of MB and dispersive growth of nano Cu-Mo2C binary sites (~ 6.1 nm) on the surface of MB. Cu+ species were formed from Cu0 via electron transfer and showed high dispersion with simultaneous boosted bimetal loading due to the strong interaction between nano Mo2C and Cu. These were advantageous to the intrinsic activity and stability of the Cu-Mo2C binary sites and their accessibility to the reactant molecules. Under the RWGS reaction conditions of 500 °C, atmospheric pressure, and 300,000 ml/g/h gas hour space velocity, the CO2 conversion rate over Cu-Mo2C/MB reached 27.74 × 10–5 molCO2/gcat/s at very low H2 partial pressure, which was more than twice that over traditional carbon supported Cu-Mo2C catalysts. In addition, this catalyst exhibited 99.08% CO selectivity and high stability for more than 50 h without a decrease in activity and selectivity. This study offers a new development strategy and a promising candidate for industrial RWGS.Graphical

High temperature pyrolysis of sewage sludge: Synergistic effects of co-pyrolysis with rice straw and composite plastics wastes

The synergistic effect of co-pyrolysis for the mixtures of sewage sludge (SS), rice straw (RS) and composite plastic wastes (PE&PP) has been investigated with the aim of high gas yields and hydrogen generation. In this context, the applicability of high temperature pyrolysis technology was evaluated at both rotary type batch reactor and rotating screw type continuous reactor operating under the industrially relevant conditions. Gas yields have been improved at increasing the operating temperatures up to 850 °C. The gas yield of 75.06 % with its H2 portion of 32.35 % has been achieved as the best results for continuous pyrolysis unit at pilot scale. Secondary reactions such as steam de-alkylation, steam cracking, water gas shift and so on were regarded as being responsible for the high gas yields when the primary products of pyrolysis, i.e. condensable vapors, were much exposed to the hot zones inside the reactor. The dehydration of organic components involving the loss of water may supply steam to create a reactive pyrolysis atmosphere. While the pyrolysis of sewage sludge and rice straw favors CO and CO2 formation due to the high oxygen contents of these feedstocks, more methane and light olefins were produced when the plastics were added to the feedstock blends. This was ascribed to the initially generated radicals from the decomposition of sewage sludge and/or rice straw that might promote the scission reactions of plastics towards volatiles. It was shown that high temperature pyrolysis can be applied to a variety of organic wastes such as rice straw, sewage sludge and waste plastics. Conversion of wastes to hydrogen fosters the circular economy by putting the disposal costs down and creates a new route on renewable hydrogen generation.

Governing chemical reactions and mechanisms of hydrogen generation during in-situ combustion gasification of heavy oil

The global push for sustainable energy solutions has highlighted the importance of producing carbon-zero hydrogen (H2) directly from petroleum reservoirs. In-situ combustion gasification (ISCG) presents a groundbreaking method to harness the potential of heavy oil reserves for clean hydrogen production. Although simulations have demonstrated the considerable promise of ISCG, the key reactions controlling hydrogen generation require experimental validation, and the underlying mechanisms remain largely unexplored. This research aims to describe the chemical reactions and mechanisms responsible for hydrogen generation during the ISCG of heavy oil. Using a specially designed kinetic cell, we conducted combustion and gasification experiments with heavy oil and coke. The findings revealed that clay minerals in the reservoir sand act as catalysts in the oxidation reactions of heavy oil by shifting reactions to lower temperatures by approximately 20 °C. Hydrogen production began at 450 °C and peaked at 900 °C, with coke gasification and the water-gas shift reaction being the primary mechanisms. Additionally, methane was produced due to hydrogen consumption via methanation reactions, and minerals in the reservoir sands were found to inhibit hydrogen production by increasing hydrogen consumption and methane generation at temperatures above 800 °C. Controlling the reservoir temperature within an optimal range between 450 and 800 °C can enhance hydrogen generation by managing the process mechanisms. This study provides a detailed examination of the ISCG process for heavy oil, paving the way for future development of kinetic models to simulate hydrogen production through ISCG. It also emphasizes the significance of mechanistic control in enhancing hydrogen generation and suppressing hydrogen consumption reactions.

Comparative Hydrogen Production Routes via Steam Methane Reforming and Chemical Looping Reforming of Natural Gas as Feedstock

Hydrogen production is essential in the transition to sustainable energy. This study examines two hydrogen production routes, steam methane reforming (SMR) and chemical looping reforming (CLR), both using raw natural gas as feedstock. SMR, the most commonly used industrial process, involves reacting methane with steam to produce hydrogen, carbon monoxide, and carbon dioxide. In contrast, CLR uses a metal oxide as an oxygen carrier to facilitate hydrogen production without generating additional carbon dioxide. Simulations conducted using Aspen HYSYS analyzed each method’s performance and energy consumption. The results show that SMR achieved 99.98% hydrogen purity, whereas CLR produced 99.97% purity. An energy analysis revealed that CLR requires 31% less energy than SMR, likely due to the absence of low- and high-temperature water–gas shift units. Overall, the findings suggest that CLR offers substantial advantages over SMR, including lower energy consumption and the production of cleaner hydrogen, free from carbon dioxide generated during the water–gas shift process.

Reconfiguration of acid gas removal process matching the integration of coal chemical industry with green hydrogen

The focus of the acid gas removal process has shifted from decarbonization and desulfurization to desulfurization in the context of integrating coal chemical technology with green H2 without a water gas shift unit. The conventional Rectisol process, Selexol process, organic amine process, and sulfone-amine process have been reconfigured to form the R-Rectisol process, R-Selexol process, R-MDEA process, and R-Sulfolane-MDEA process to adapt to the shift of acid gas removal target. The removal efficiency of H2S and CO2, process energy consumption, and process cost are investigated to evaluate the technical and economic performance of the above four reconfigured acid gas removal processes. The results indicate that for the R-Recitsol process and R-Selexol process, both high pressure and low temperature increase the relative selectivity of H2S to CO2, thereby enhancing the selective removal of H2S. In contrast, for the R-MDEA process and R-Sulfolane-MDEA process, low pressure and low temperature improve the relative selectivity of H2S to CO2, thereby facilitating the selective removal of H2S. Under optimal operating conditions, the value of relative selectivity of H2S to CO2 of the R-Sulfolane-MDEA process is the largest, and the relative selectivity of H2S to CO2 of the R-Rectisol process, R-Selexol process and R-MDEA process are only 7.64 %, 12.85 %, and 68.40 % of the relative selectivity of H2S to CO2 of the R-Sulfolane-MDEA process, respectively. Compared to the other three reconfigured acid gas removal processes, the R-Sulfolane-MDEA process demonstrates superior advantages in both energy consumption and economic feasibility, provided that the H2S levels remain below 0.1 ppm in purified syngas. This study aims to enhance the decision-making process for gas purification methods in the coal chemical industry by considering integrated green H2 as an alternative to the water gas shift unit.

Constructing efficient Pd/Al2O3 catalyst for reverse water-gas shift via alkali-modification

The intrinsic nature of irreducible oxides (e.g. Al2O3) makes it hard to tune the charge state of supported late-transition metals, then difficult to adjust the selectivity of catalysts in CO2 hydrogenation. Herein, we find that modifying the Pd/Al2O3 catalyst with alkali metals (especially potassium) is efficient to boost the CO formation in CO2 hydrogenation. In comparison to Pd/Al2O3, approximately twenty-fold promotion in reverse water–gas shift (RWGS) rate was achieved on K-modified catalysts with proper K/Pd proportions. Combined structural characterizations demonstrate that the enhanced Pd-O interactions through K mediation stabilize the ca. 2 nm sized Pd particles as well as the electron-deficient state of Pd, which are robust enough during long-termed evaluation with undamped performance. In situ spectroscopy unveils a bi-dentate *HCOO associated reaction mechanism taking effect on alkali-modified catalysts, which contributes to ∼ 100 % of CO selectivity and 3318.1 mmol∙gPd-1∙h−1 of CO formation rate at 340°C.

In-Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water-Gas Shift Reaction.

In situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water-gas shift (RWGS) reaction. Surface oxygen atoms in various Mo-based catalysts are removed in H2-containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt-dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal -1 ⋅ h-1 at 600 °C has been achieved over in situ carbonized H-intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

In‐Situ Dynamic Carburization of Mo Oxide with Unprecedented High CO Formation Rate in Reverse Water‐Gas Shift Reaction

AbstractIn situ construction of active structure under reaction conditions is highly desired but still remains challenging in many important catalytic processes. Herein, we observe structural evolution of molybdenum oxide (MoOx) into highly active molybdenum carbide (MoCx) during reverse water‐gas shift (RWGS) reaction. Surface oxygen atoms in various Mo‐based catalysts are removed in H2‐containing atmospheres and then carbon atoms can accumulate on surface to form MoCx phase with the RWGS reaction going on, both of which are enhanced by the presence of intercalated H species or Pt‐dopants in MoOx. The structural evolution from MoOx to MoCx is accompanied by enhanced CO2 conversion, which is positively correlated with the surface C/Mo ratio but negatively with the surface O/Mo ratio. As a result, an unprecedented CO formation rate of 7544.6 mmol ⋅ gcatal−1 ⋅ h−1 at 600 °C has been achieved over in situ carbonized H‐intercalated MoO3 catalyst, which is even higher than those from noble metal catalysts. During 100 h stability test only a minimal deactivation rate of 2.3 % is observed.

Active Learning Guided Discovery of High Entropy Oxides Featuring High H2-production.

High entropy oxides (HEOs) represent a class of solid solutions comprising multiple elements, offering significant scientific potential. Due to the enormous combination types of elements, the design of HEOs with desirable properties within high-dimensional composition spaces has traditionally relied heavily on knowledge and intuition. In this study, we present an active learning (AL) strategy tailored to efficiently explore the vast compositional space of HEOs. Our approach operates as a closed-loop system, iteratively cycling through "Training, Prediction, and Experiment" stages. Across multiple AL iterations, we have successfully identified four novel HEOs from a vast array of potential compositions. These newly discovered materials exhibit exceptional stability and demonstrate outstanding performance in H2 evolution rate (251 μmol gcat-1 min-1) during the water-gas shift reaction, surpassing benchmarks set by established catalysts such as Pt/γ-Al2O3 (135 μmol gcat-1 min-1) and Cu/ZnO/Al2O3 (81 μmol gcat-1 min-1). X-ray photoelectron spectroscopy and density functional theory calculations revealed a loss of elemental identity in the selected HEOs. This catalyst discovery process underscores the efficacy of Machine Learning in accelerating the identification of HEOs with unique characteristics by effectively leveraging insights from limited experimental data.

Insights into Mechanisms of Reverse Water Gas Shift Activity Enhancement over Reverse Microemulsion‐Synthesized CuCeO2

AbstractCopper‐doped ceria (CuCeO2) catalysts with 0–26.5 Cu/(Cu+Ce) at% were synthesized via the reverse microemulsion method. X‐ray diffraction analysis of freshly synthesized and spent (post‐reaction) catalysts showed no separate phase of copper or copper oxide, indicating that Cu was incorporated into the CeO2 lattice, replacing Ce. Temperature programmed desorption experiments showed that the activation energy of CO2 desorption increased for higher Cu loadings, indicating stronger CO2 adsorption. This phenomenon was attributed to enhanced formation of oxygen vacancies due to Cu doping. X‐ray photoelectron spectroscopy further confirmed the enhanced generation of oxygen vacancies due to Cu incorporation. Catalytic performance evaluation with the H2/CO2 feed in the 300–600 °C range showed that all catalysts were 100 % selective to CO generation, with higher Cu loadings resulting in CO2 conversion close to equilibrium values at 500–600 °C. The activation energy of the reaction, determined through reaction tests, exhibited inverse relationship with the activation energy of CO2 desorption. The relationship between these two energy barriers is explored, providing valuable insights into the mechanism of RWGS activity enhancement.

Reduction of CO2 emissions by recycling low-potential heat from the Benfield CO2 removal process at a natural gas hydrogen production plant

AbstractThe EU policies related to CO2 emission strictly define the stages of carbon neutrality achieving. According to these regulations, all production installations that emit carbon dioxide will be charged additional emission fees from 2026 to fully in 2035. Analysis of the increasing emission fees shows that in some industries incurring such additional costs will result in a lack of profitability of the products. Industries directly related to the food sector, such as nitrogen fertiliser production, are strategic in the economies of all countries. Nitrogen fertilisers are produced from ammonia, which is synthesised on a large scale from hydrogen and nitrogen. Hydrogen is produced by natural gas reforming with water vapour resulting in syngas (mixture of H2, CO, CO2, H2O), which CO in the next step reacts with water vapour (water gas shift reaction) producing H2 and CO2. CO2 is separated from hydrogen using the Benfield method. The analysis of the Benfield process (one process of hydrogen production) shows a possible way to reduce CO2 emission by optimising heat balance. It was shown that in the proposed technology the heat recovery reaches 89%, while the level below 30% was reported for other available technologies. The proposed solution is based on recirculation and reuse of heat, which is lost in other technologies. The analysis is for a process balance in a medium-sized hydrogen production installation. The analysis considers also the correlations with other installations thermally linked to hydrogen production. The economic balance showed the great financial benefits of this solution. In the scenario discussed, the CO2 emission factor was reduced by 20%. Graphical Abstract

Enhanced CO2 hydrogenation reaction by Tuning interfacial Cu/ZnOx through synergistic interactions in the precursors

The Cu/ZnO/Al2O3 is a typical industrial catalyst for water–gas-shift reaction and methanol synthesis, and is also gaining momentum in CO2 hydrogenation reaction. The dynamic evolution of the phases and microstructures of the precursor of this catalyst leads to a notable synergistic effect that defines its overall catalytic function and performance. To gain insights into the role and interaction between the relevant precursors, we compared Cu/ZnO/Al2O3 catalysts using a conventional co-precipitation and a fractional precipitation method, where the latter one shows an enhanced Cu/ZnOx interface due to a thorough and strong interaction between two components in the precursor. The ZnOx decoration on Cu with unsaturated Znδ+ species boosted the methanol formation to a rate of 508 gCH3OH‧kgcat−1‧h−1 with 58 % selectivity at 513 K and 3 MPa. This work provides mechanistic insights into the synergistic interplay between the involved phases in the Cu/ZnO/Al2O3 catalyst.

Kinetic investigation of dry reforming of methane reaction over Ni–Rh/ZrO2–Al2O3 catalyst using Langmuir-Freundlich isotherm

The study involved conducting kinetic measurements for the dry reforming of methane (DRM) over a Ni–Rh/Al2O3 (85%)-ZrO2(15%) catalyst under a wide range of operating conditions (temperature: 500–900 °C, total flow rate of the inlet feed: 50–100 mL/min). The support material was prepared using the sol-gel method, followed by impregnation of Ni–Rh catalyst on the incipient wetness of the Al2O3–ZrO2 support. The calcined, reduced and spent samples were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometer (ICP-AES), N2 adsorption/desorption and CHNS analyzer, and tested for activity, yield and stability in DRM reaction. Furthermore, kinetic behavior of Ni–Rh/Al2O3–ZrO2 catalyst in DRM process was investigated by assuming DRM and reverse water-gas shift (RWGS) reactions take place on two kinds of different active sites. Experimental data were fitted using rate expressions based on the Langmuir-Freundlich (LF) isotherm for DRM and RWGS reactions. The activation energy for the DRM reaction was optimized at 43.62 kJ/mol, falling within the reported literature range of 24.73–108.9 kJ/mol. Statistical indices indicated that the kinetic model accurately predicted CO2 conversion compared to other responses, with an error of 12.054%. The computed and experimental trends for CH4 and CO2 conversions, H2 and Co yield in terms of temperature were similar with each other and the difference between the calculated and experimental trends was lower for conversions compared to yields.

Effect of Ni/Co ratio on Ce-Sc-ZrO2 catalysts for selective H2 production via methane partial oxidation

Partial oxidation of methane (POM) is a promising route for hydrogen production, and achieving a high H2 yield with an H2/CO ratio >3 is highly appealing. Optimization of Ni/Co ratios over Ce-Sc-ZrO2 (CSZ) is investigated for POM reaction and characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed reduction/oxidation/desorption, and transmission electron microscopy. The active site derived from the reduction of “strongly interacted NiO” is responsible for the dissociation of C–H (of CH4), resulting high activity towards POM. 5Ni/CSZ has the highest amount of such active sites and attains the highest activity. 5Co/CSZ catalyst has cobalt-based active sites, and there is an inert carbon deposit during the reaction, causing the least activity. 3.75 wt% Ni and 1.25 wt% Co combination over CSZ support surges the highest density of basicity, oxide vacancy, and adequate amount of active sites derived from “strongly interacted NiO”. The active sites with enhanced metal-support interaction are further grown under exposure to oxidizing gas (O2) and reducing gas (H2) during the POM reaction. The highest density of basicity and oxide vacancy involves more CO2 and H2O in the sequential oxidation of CH4 under indirect pathways. The exclusive involvement of indirect pathways of POM and inhibition of hydrogen consuming reaction (like reverse water gas shift reaction) over 3.75Ni1.25Co/CSZ results into 48 % H2 yield and 3.26 H2/CO ratio up to 24 h time on stream at 600 °C. The H2 yield doubles to ∼97 %, and the H2/CO ratio comes close to 2 over 3.75Ni1.25Co/CSZ catalyst at 900 °C.

Nickel Dynamics Switches the Selectivity of CO2 Hydrogenation.

The Reverse Water Gas-Shift reaction (CO2 + H2=CO + H2O) allows to balance syn-gas under industrial conditions. Nickel has been suggested as a potential catalyst but the temperature required is too high, more than 800ºC, limiting practical implementation but when lowering the temperature methanation occurs. Simulations via Density Functional Theory on well-defined surfaces have systematically failed to reproduce these experimental results. But under reaction conditions Ni surfaces are not static and DFT models coupled to microkinetics show that at high CO coverages drive the generation of Ni adatoms that are the active sites for methanation. At higher temperatures, the adatom population decreases, and the selectivity towards CO increases. Thus, the mechanism behind the selectivity switch is driven by the dynamics induced by reaction intermediates. Our work contributes to the inclusion of dynamic aspects of materials under reaction conditions in the understanding of complex catalytic behaviour.

Direct liquefaction behavior of Shenhua Shangwan coal under CO containing atmosphere

Direct coal liquefaction (DCL) under CO or syngas atmosphere is beneficial to reduce the cost of hydrogen production. Effects of CO on liquefaction process of Shangwan coal were investigated by comparing the liquefaction behavior in three atmospheres of CO, H2, and N2. Then, effects of different CO/H2 ratios and catalysts on the liquefaction process in syngas were investigated. The results indicated that the oil yield under CO atmosphere reached 43.1%, which was 4.2% lower than that under H2, but 10.2% higher than that under N2. The liquefaction performance was further improved by adding the Shenhua 863 catalyst. It is analyzed that CO promoted liquefaction in two ways: water-gas shift reaction and the reaction between CO and organic structures of coal. Through characterization of the products by GC-MS and FT-IR, it was found that CO makes benzenes, aliphatics, and oxygen-containing compounds in liquefied oil simultaneously increased. The effect on functional groups and free radicals concentration in the solid products was not obvious. The experimental results under syngas showed that the highest oil yield, 57.4%, can be obtained in DCL with 20% CO syngas, and further improved by increasing moisture content of coal appropriately. In addition, the Shenhua 863 catalyst had a good catalytic effect on the liquefaction process and also water-gas shift reaction.