Temperature Water Gas Shift Reaction Research Articles

Upgrading the low temperature water gas shift reaction by integrating plasma with a CuOx/CeO2 catalyst

Low temperature WGS reaction is kinetically limited though it is thermodynamically favored. Herein, an outstanding synergistic effect between dielectric barrier discharge (DBD) plasma and non-precious CuOx/CeO2 catalysts was observed to robustly accelerate the water gas shift (WGS) reaction at 150 °C (increase from 6% to 96% after plasma on). The apparent activation energy of the reaction was remarkablly diminished by plasma (69.6 to 15.0 kJ/mol). In-situ characterization experiments (e. g. OES and DRIFTS) revealed that the OH radicals generated by plasma-induced H2O dissociation was found to participate in the WGS reaction. In the furtherly study in DFT calculation and microkinetic modelling investigation, the OH radicals were proved to be one of the reasons for the giant increase in reaction rate. Besides, the vibrational excitation of reactants (e. g. CO) promoted by plasma could also reduce the reaction barriers of some crucial elementary reactions, thus accelerating the reaction rate.

Low-temperature Water-gas Shift Reaction Enhanced by Oxygen Vacancies in Pt-loaded Porous Single-crystalline Oxide Monoliths.

Water-gas shift (WGS) reaction at low temperature plays an important role in hydrogen production from fossil fuels and hydrogen purification for proton-exchange membrane fuel cells. However, the activation of H2 O is a critical reaction step that greatly limits the overall performance during WGS reaction. Here we fabricate porous single-crystalline (PSC) MoO3 monoliths at 1 cm scale and deposit atomic-layered Pt clusters at the lattice surface to create the interfacial system toward the low-temperature WGS reaction. The single-crystalline nature stabilizes the oxygen vacancies (VO ) at lattice and facilitates the effective activation of H2 O at the interface. We show the highest Pt-normalized activity of 0.86 molCO molPt -1 s-1 for the ultra-low temperature WGS reaction at 120 °C. The single-crystalline features with enhanced fluxion in porous architectures lead to outstanding performance without visible degradation even after continuous operation for 100 hours.

Development of Co–Nb–CeO2 Catalyst for Hydrogen Production from Waste-Derived Synthesis Gas Using Techno-Economic and Environmental Assessment

A comparative study to obtain a cost-competitive catalyst was performed to produce hydrogen via the high temperature water gas shift (WGS) reaction using synthesis gas (syngas) derived from waste. First, several selected active metals on Nb–CeO2 support and preparation methods were applied to prepare highly active and stable catalysts under severe reaction conditions. Various characterization methods were employed to understand the correlation between catalytic activity and physicochemical properties of the prepared catalysts. Among the Me–Nb–CeO2 (Me = Co, Cu, Fe, and Zn) catalysts, Co–Nb–CeO2 showed the highest activity at a high gas hourly space velocity of 315,282 mL·g–1·h–1 (temperature = 500 °C, XCO ≈ 84%). This was attributed to the high Brunauer–Emmett–Teller surface area and oxygen storage capacity of the Co–Nb–CeO2 catalyst. In addition, to investigate the effect of preparation method, various methods, including coprecipitation, incipient wetness impregnation, sol–gel, and hydrothermal methods, were applied for the synthesis of the Co–Nb–CeO2 catalyst. The Co–Nb–CeO2 catalyst prepared using the coprecipitation method exhibited high activity without significant deactivation for 60 h. This was attributed to the high oxygen storage capacity and intimate interaction between Co and the Nb–CeO2 support. Finally, techno-economic analysis and environmental impact assessment were performed for the Co–Nb–CeO2 catalysts, prepared by different preparation methods to identify the most promising catalyst for the production of hydrogen using the syngas derived from waste. By comparison with a commercial catalyst, it was shown that Co–Nb–CeO2 synthesized using coprecipitation is a promising, cost-effective, and eco-friendly catalyst with high activity.

Upgrading the Low Temperature Water Gas Shift Reaction by Integrating Plasma with a Cuox/Ceo2 Catalyst

Upgrading the Low Temperature Water Gas Shift Reaction by Integrating Plasma with a Cuox/Ceo2 Catalyst

Effects of niobium addition on active metal and support in Co–CeO2 catalyst for the high temperature water gas shift reaction

Nb promoter was introduced in the Co–CeO2 catalyst to improve its catalytic performance in the high temperature water gas shift (HT-WGS) reaction, which involves the production of hydrogen from waste-derived synthesis gas. Thereafter, the physicochemical properties of the promoter as well as those of the catalyst were investigated using various techniques. Thus, it was confirmed that the Nb promoter affects the key properties related to catalytic performance, including oxygen storage capacity (OSC) and dispersion. To maximize the positive effect of the Nb promoter, we further investigated the effect of the Nb loading amount on the performance of the catalyst. The results obtained showed that the 1.5NbCo catalyst exhibited the highest catalytic performance (XCO = 89% at 450 °C) under very severe conditions (gas hourly space velocity (GHSV) = 637,320 h−1). Additionally, this catalyst exhibited stable activity for 50 h. This its high catalytic performance could be attributed to its high OSC and Co dispersion. Therefore, it is a promising catalyst for hydrogen production via the HT-WGS reaction.

A study on the mechanical strength of Fe2O3/Cr2O3/CuO catalyst for high temperature water gas shift reaction

A study on the mechanical strength of Fe2O3/Cr2O3/CuO catalyst for high temperature water gas shift reaction

Characteristics and performance of the Co–CeO2 catalyst as a function of the promoter (La, Pr, and Zr) used in high temperature water gas shift reaction

The catalysts used to facilitate the water gas shift reaction (WGSR) are generally harmful to the environment. Therefore, catalysts that have high activity and stability in WGSR and do not pollute the environment need to be fabricated. Herein, three promoters (La, Pr, and Zr) are added into Co–CeO2 (CoCe) catalyst to improve catalytic performance in a high temperature WGSR to produce high-purity hydrogen from waste-derived synthesis gas. Various techniques are employed to confirm the changes in the properties that affect the catalytic performance. The catalytic reaction is performed at a high gas hourly space velocity to screen the performance of the promoted CoCe catalysts. The CoCeZr catalyst shows the highest CO conversion (XCO = 88% at 450 °C) due to its high Co dispersion and oxygen vacancy resulting from the addition of Zr to the CoCe catalyst; thus, it is most suitable for use in high temperature WGSR.

Ultra-low temperature water–gas shift reaction catalyzed by homogeneous Ru-complexes in a membrane reactor – membrane development and proof of concept

Supported ionic liquid-phase (SILP) catalyzed water–gas shift reaction with in situ product removal is presented. A facilitated transport membrane coated onto the smooth outside of the SiC monolith allowed preferential removal of CO2 compared to H2.

Wet chemically derived Li4SiO4 nanowires as efficient CO2 sorbents at intermediate temperatures

Lithium silicate based ceramic sorbents are potential materials for CO2 sorption in the temperature range of 500–700 °C. However, its sorption performance at temperatures <500 °C is kinetically limited due to the formation of lithium carbonate as a hard surface layer that limits the CO2 diffusion to the reaction interface. This shortcoming in temperature of application has widely impeded its practical application in industrially important reaction environments such as in petrochemical processes. In the present study, we report compositionally tuned lithium silicate nanowires wherein the formation of hard lithium carbonate layer during the sorption process is addressed through the incorporation of low melting eutectics that softens the carbonate layer and facilitates an easier pathway for the diffusion of CO2. This modification is demonstrated to overcome the kinetic limitations of CO2 sorption in lithium silicate at lower temperatures (<500 °C). The nanowire morphology of lithium silicate also facilitated enhanced CO2 capture as the diffusion path-ways for lithium are considerably shorter compared to the conventional micron sized agglomerates. Further, the compositional tuning of lithium silicate nanowires helped to realize an absorption capacity value of 300 mgg−1 at 450 °C, a value seldom achieved for lithium silicate based materials at such low temperatures. The sorption capacity could also be fully regenerated at the same temperature by a pressure swing operation. The results thus pave the possibility of using modified lithium silicate compositions as CO2 sorbents in industrially significant chemical reaction processes such as high temperature water gas shift reaction where the temperatures are generally in the range of 350–450 °C.

Performance assessment of high temperature water-gas-shift reaction for hydrogen generation and its purification in a membrane reactor/separator of hydrogen or of carbon dioxide

Abstract In the current work, the high temperature water gas shift reaction assessment for hydrogen generation and its purification was carried out in reactors integrating hydrogen or carbon dioxide perm-selective membranes. Indeed, the performance of the high temperature water gas shift reaction was analyzed under adiabatic conditions through a mathematical model developed for this purpose. The main results indicate that both membrane reactors provide under some conditions a complete carbon monoxide conversion. As a result the dual phase membrane presents a great separation capacity of carbon dioxide. This gives us the opportunity to obtain a high purity of hydrogen. Thus, it can be concluded that the concept of the membrane reactor that used for carbon dioxide separation could be a veritable competitor and a great promise candidate for replacing the Pd based membrane reactors which is used for hydrogen separation.

Parametric study of high temperature water gas shift reaction for hydrogen production in an adiabatic packed bed membrane reactor

Parametric study of high temperature water gas shift reaction for hydrogen production in an adiabatic packed bed membrane reactor

Cu substituted ZnAl2O4 ex-LDH catalysts for medium-temperature WGS – effect of Cu/Zn ratio and thermal treatment on catalyst efficiency

The effect of Cu/Zn ratio of ex-LDH oxide-based catalysts for medium–temperature water–gas shift reaction (MT–WGS) was investigated. A series of CuZnAl–LDH precursors with different Cu/Zn molar ratio were synthesized by co-precipitation and oxide (Zn,Cu)xAl2O4 catalysts were prepared via subsequent calcinations at 380 °C or 700 °C. The prepared materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetry with evolved gas analysis (TG/DTG/EGA), N2 adsorption, N2O chemisorption and temperature-programmed reduction (H2-TPR). MT-WGS activity evaluation was carried out on the basis of measurements made in a differential reactor in kinetic regime. Catalysts’ properties were investigated and effect of composition (Cu/Zn molar ratio) and the calcination temperature of CuZnAl-LDH precursors on structural transformation, active surface area and MT-WGS rate constant was shown. The highest activity of (Zn,Cu)xAl2O4 catalyst with Cu/Zn molar ratio of 1.5 calcined at mild conditions was attributed to easy reducible and accessible Cu surface.

How Do Structurally Distinct Au/α‐Fe2O3 Interfaces Determine Surface OH/H2O reactivity, Intermediate Evolution, and Product Formation in Low‐temperature Water‐gas Shift Reaction?

AbstractThree structurally distinct interfaces, i. e. Au/α‐Fe2O3‐THB‐Air, Au/α‐Fe2O3‐HS‐Air, and Au/α‐Fe2O3‐QC‐Air, with the major substrate facet being {113}, {001}, and {012} respectively, were controllably prepared. The low temperature water gas shift (WGS) reaction (100–260 °C) was applied to these unique systems to reveal how these structurally distinct interfaces can impact on the reaction behavior. With the detailed performance evaluation plus the characterizations of CO‐TPSR, XPS, and in situ‐FTIR in particular, the correlations between the evolution of different intermediates and the distinct catalytic behaviors have been established. The substrate facet structure and the Au entity largely determine the form and reactivity of surface OH/H2O species which in turn determine the formation of different intermediates and eventually the product formation. The Au/α‐Fe2O3‐THB‐Air is enriched with oxygen vacant sites, favorable for dissociative adsorption of H2O, carboxyl intermediate formation and H2 production. The Au/α‐Fe2O3‐HS‐Air is enriched with surface lattice oxygen, favorable for molecular adsorption of H2O, formate intermediate formation, and CO2 production. The Au/α‐Fe2O3‐QC‐Air interface is enriched with surface Fe sites, favorable for dissociative adsorption of H2O and evolution of stable carboxyl intermediate as well as isolated OH species at low reaction temperatures. The findings are informative to control the interfacial structure for the WGS and other reactions.

Catalytic behaviour of Mn2.94M0.06O4-δ (M=Pt, Ru and Pd) catalysts for low temperature water gas shift (WGS) and CO oxidation

Noble metal (Pt, Ru and Pd) substituted Mn3O4 catalysts have been synthesized in this work by a sonochemical route. The catalysts were characterised by XRD, XPS, TEM, H2-TPR and BET surface area analyser and the activity of these catalysts was tested towards low temperature water gas shift reaction (WGS) and CO oxidation reaction. It was observed that these catalysts have the tetragonal crystalline structure of Mn3O4 and the average particle size was found in the range of 12 nm–22 nm. H2-TPR results show that the strong metal support interaction between substituted metal and Mn3O4 leads to high reducibility and makes these catalysts active for WGS and CO oxidation. Pt substituted Mn3O4 showed higher activity towards WGS compared to other synthesized catalysts and 99.9% conversion was observed at 260 °C without methane formation. The activation energy of Mn2.94Pt0.06O4-δ was found to be 59 ± 0.6 kJ/mol. DRIFTS analysis was carried out to propose the reaction mechanism for water gas shift and CO oxidation. Redox mechanism was hypothesized for WGS and used to correlate the experimental data over Pt substituted Mn3O4. Similarly, kinetic parameters were estimated based on Langmuir-Hinshelwood mechanism for CO oxidation over Pd substituted Mn3O4 which showed better activity compare to other synthesized catalysts and 99.9% conversion was observed at 175 °C. The activation energy was calculated from Arrhenius plot which was found to be 30 ± 0.4 kJ/mol.

Process simulation of hydrogen rich gas production from producer gas using HTS catalysis

In the present article, ASPEN Plus is used to develop a process model of the hydrogen-rich gas production through cleaning and catalytic conditioning of producer gas. The process includes producer gas cleaning using venturi scrubber and sand bed filter followed by compression of the gas to 0.6 MPa using compressor. The clean producer gas along with steam undergoes high temperature water gas shift reaction to produce hydrogen-rich gas. The power law kinetic model for commercial HTS catalysts reported in the literature is used in the model. Experimental results from our previous study and those reported in the literature are used to validate the developed model for the compositions of CO & H2 in the product gas. The validated model is further simulated to study the effects of parameters such as reactor temperature, catalyst bed length and steam to CO ratio on the product gas composition. The optimum operating conditions for maximizing CO conversion are found and reported. The maximum H2 composition and CO conversion predicted by the model are 27.029% 97.5479% respectively and the corresponding operating conditions are reactor; temperature of 350 °C, S/CO of 8 and GHSV 1000 h−1.

Catalytic Pd0.77Ag0.23 alloy membrane reactor for high temperature water-gas shift reaction: Methane suppression

A catalytic membrane reactor was constructed using inner coated Pd0.77Ag0.23 (mass fraction) alloy membrane on Al2O3 hollow fiber substrate, prepared by electroless plating method and packed with Ni-Phyllosilicate catalyst for high temperature water gas shift (WGS) reaction. The performance of the ultra-thin ∼1 µm membrane was evaluated in a temperature range of 300–500 °C and hydrogen partial pressure of 50–200 kPa. The membrane showed high hydrogen permeance of 5.11 × 10−4 mol.m−2 s−1 Pa−0.65 at 100 kPa pressure and 500 °C. WGS reaction was carried out using the membrane reactor at temperature range of 400–500 °C, the effect of pressure, steam to carbon ratio and GHSV on CO conversion and methane formation were evaluated. Results showed increase in H2 permeation with increase in temperature and pressure, which eventually helps surpass the thermodynamic equilibrium CO conversion at high temperatures. H2 recovery and CO conversion decreased with increase in GHSV from 2896 h−1 to 11008 h−1. In this study, the shifting of equilibrium conversion and suppressed methane formation is also demonstrated at a temperature range of 400–600 °C. WGS reaction was performed in a catalytic membrane reactor at 600 °C for 100 h and it was found to be stable in terms of CO conversion and H2 recovery for the entire range of investigation. Finally, the membrane was tested for its performance using a reformate gas mixture similar to the gasification plant without any diluents and the conversion was found to be enhanced by 28% in terms of CO conversion at 500 °C using a membrane reactor.

Nickel‐based Catalysts for High‐temperature Water Gas Shift Reaction‐Methane Suppression

AbstractThis article provides a critical review of Ni‐based catalysts employed in high temperature and ultra‐high temperature water gas shift reaction (WGS) for hydrogen production and methane suppression. The promotional role of nature and type of active metal and support for WGS reaction is discussed with respect to activity and selectivity. This review mainly covers the recent strategic catalytic formulations like promotion with alkali metals, alloying with another metal and core@‐shell‐like structures for suppressing methanation during WGS reaction. The change in nature and strength of CO adsorption over modified Ni‐surfaces is discussed using available in situ CO‐DRIFTS results. The various WGS reaction and CO methanation pathways are also presented together with insights gained from computational DFT studies.

Ternary oxide-supported bimetallic nickel-copper catalysts for a single step high temperature water gas shift of biogas reformate

Promoted ternary oxide based bimetallic catalysts with nominal composition of 3%Ni5%Cu/CeZrM (where M = La, Mg, Y, Gd or Ca) were prepared by surfactant-assisted route and tested for the high temperature water gas shift reaction. The catalysts were initially screened at 500 °C at atmospheric pressure in a packed bed tubular reactor using 30%CO/70%N2 gas. The Ca promoted catalyst showed the best performance, and was subsequently tested using simulated reformate gas of composition: 46.2%CO, 8.5%CH4, 7.2%CO2 and 38.1%H2 (obtained from biogas dry reforming). Effects of catalyst preparation method: (i.e. impregnation method (atmospheric pressure or vacuum), surfactant/metal ratio (S/M = 0–1.25) and calcination temperature (425–650 °C) were tested. Operating conditions: (i.e. reaction temperature (450–550 °C), steam/CO molar ratio and reactor pressure (atmospheric–250 psi) were also studied. Structure-activity relationships developed to correlate catalyst characteristics to performance showed that catalyst activity was highly dependent on Cu reducibility, support basicity and metal dispersion.

Preparation of highly dispersed Cu/SiO2 doped with CeO2 and its application for high temperature water gas shift reaction

Highly dispersed Cu/SiO2 catalysts doped with CeO2 have been successfully prepared via in-situ self-assembled core-shell precursor route. The prepared catalysts were characterized by XRD, SEM, TPR, chemisorption and XPS techniques. The results showed that our newly developed method could not only prepare highly dispersed supported metal catalysts but also highly dispersed supported CeO2 on silica. The highly dispersed CeO2 showed strong interaction with highly dispersed Cu. The synergy between the highly dispersed CeO2 and the highly dispersed Cu exhibited high catalytic activity for high temperature water gas shift reaction compared to the catalysts prepared with the routine method of incipient impregnation.

A Structured Cu-Based/γ-Al2O3/Al Multifunctional Catalyst for Steam Reforming of Dimethyl Ether: Investigation on in-Situ CO Reduction Strategy

A plate-type Cu/Ni/γ-Al2O3/Al catalyst exhibited a good stability in steam reforming of dimethyl ether (DME SR); however, a high CO concentration (ca. 26%) was detected. As such, a multifunctional catalyst combined DME SR and high temperature water gas shift reaction (HT-WGSR) was developed in this work. It is found that the reaction temperature regions of Fe-based and Cu-based catalysts coupled perfectly, and thus resulted in an in situ CO reduction during DME SR process. Meanwhile, the CO reduction mechanism was proposed over the Fe-doped Cu-based multifunctional catalyst. Furthermore, the effects of iron loading on the physicochemical properties and performance of catalysts were extensively investigated. The results show that the proper amount of iron doping was helpful in improving the dispersion of Cu, and thus enhancing the catalytic performance and decreasing CO concentration. Finally, it is found that the optimized Cu/NiO/Fe3O4/γ-Al2O3/Al multifunctional catalyst has excellent stability during a 2...