High-temperature Water Gas Shift Reaction Research Articles

In situ characterization of catalysts and membranes in a microchannel under high-temperature water gas shift reaction conditions

Microreactor technology with high heat transfer in combination with stable catalysts is a very attractive approach for reactions involving major heat effects such as methane steam reforming and to some extent, also the high temperature water gas shift (WGS) reaction. For this study Rh/ceria catalysts and an ultrathin hydrogen selective membrane were characterized in situ in a microreactor specially designed for x-ray absorption spectroscopic measurements under WGS conditions. The results of these experiments can serve as a basis for further development of the catalysts and membranes.

Chromium free high temperature water–gas shift catalyst for the production of hydrogen from waste derived synthesis gas

A comparative study between monometallic (Me−CeO2, Me=Zn, Cu, Fe and Co) and Ni-doped bimetallic (Me−Ni−CeO2) catalysts has been performed in the high temperature water-gas shift (HT−WGS) reaction using waste derived synthesis gas. Experimental results revealed that Me−Ni−CeO2 exhibited higher catalytic performance than simple Me−CeO2 catalysts. Within the Me−Ni−CeO2 series, Co−Ni−CeO2 exhibited excellent and stable catalytic performance (CO conversion>90%) at a very high GHSV of 143,000h−1. The existence of high concentration of Ce3+ ions and oxygen vacancies on the catalyst surface were responsible for the increased WGS activity of Co−Ni−CeO2. In addition, Co−Ni−CeO2 maintains a stable performance for 50h. However, commercial Fe2O3-Cr2O3 catalyst showed a steep decline from their initial CO conversion values 15–10% within 5h.

Resolving the Reaction Mechanism for H2 Formation from High-Temperature Water–Gas Shift by Chromium–Iron Oxide Catalysts

The reaction mechanism of the high-temperature water–gas shift (HT-WGS) reaction catalyzed by chromium–iron oxide catalysts for H2 production has been studied for 100 years with two reaction mechanisms proposed: redox and associative (involving surface HCOO*). Direct experimental support for either mechanism, however, is still lacking, which hinders a thorough understanding of catalytic roles of each elements and the rational design of Cr-free catalysts. The current study demonstrates, with temperature-programmed surface reaction (TPSR) spectroscopy (CO-TPSR, CO+H2O-TPSR, and HCOOH-TPSR), for the first time that the HT-WGS reaction follows the redox mechanism and that the associative mechanism does not take place.

ChemInform Abstract: Iron‐Based Catalysts for the High‐Temperature Water‐Gas Shift (HT‐WGS) Reaction: A Review

AbstractReview: 173 refs.

Determining Number of Active Sites and TOF for the High-Temperature Water Gas Shift Reaction by Iron Oxide-Based Catalysts

This study demonstrates, with C16O2/C18O2 isotope switch and H2-TPR experiments, for the first time that (i) the high-temperature water–gas shift (HT-WGS) reaction by copper–chromium-iron oxide catalysts follows a redox mechanism dominated by the surface layer, (ii) the number of catalytic active sites can be quantified by the isotopic switch, and (iii) the turnover frequency (TOF) can be determined from knowledge of the number of sites. The quantitative TOF values reveal that chromium is only a textural promoter, whereas copper is a chemical promoter.

High temperature water–gas shift without pre-reduction over spinel ferrite catalysts synthesized by glycine assisted sol–gel combustion method

Selected metal ions (Ni, Co, Mn, Mg, or Zn) were introduced into iron oxide (spinel lattice) and the resulting materials screened for catalytic activity for the high temperature water–gas shift reaction using waste-derived syngas. The active phase of spinel ferrite catalysts was directly synthesized by the glycine assisted sol–gel combustion method under a reducing atmosphere. Among the prepared catalysts, NiFe2O4 catalyst showed the highest CO conversion (81%) with stability even at a very high gas hourly space velocity of 40,057 h−1. This result was primarily due to the inverse spinel structure and easier reducibility of NiFe2O4 catalyst.

High-temperature water gas shift reaction on Ni–Cu/CeO2 catalysts: effect of ceria nanocrystal size on carboxylate formation

The WGS mechanism strongly depends on the Ni–Cu surface composition.

Iron-Based Catalysts for the High-Temperature Water–Gas Shift (HT-WGS) Reaction: A Review

This article critically reviews the literature on iron-based catalysts for the high-temperature water–gas shift (HT-WGS) reaction. The reaction mechanism, reaction intermediates, rate-determining step, kinetics, active site, and promoters are covered. Unlike the low-temperature water–gas shift (LT-WGS) reaction by Cu/ZnO catalysts that has received intensive analysis with modern in situ and operando spectroscopy and DFT studies, the corresponding HT-WGS reaction by Fe-based catalysts still lacks a fundamental understanding because of the absence of modern catalysis studies of this important catalytic system. Given the role of the WGS catalysts on production of H2 for a hydrogen economy, it is imperative that the fundamental molecular-level understanding of the HT-WGS catalyst be advanced.

The Effect of Metal on Catalytic Performance Over MFe<SUB>2</SUB>O<SUB>4</SUB> Catalysts for High Temperature Water-Gas Shift Reaction

The Effect of Metal on Catalytic Performance Over MFe<SUB>2</SUB>O<SUB>4</SUB> Catalysts for High Temperature Water-Gas Shift Reaction

Possibility of Methane Production from Steam and Carbon Dioxide by Using Solid Oxide Electrolysis Cells

To overcome global warming issue and energy shortage problem, economical hydrogen production technologies from renewable energy or unused fossil fuel with carbon capture technology are being developed all over the world. However it becomes the large problem that it is necessary to reconstruct energy infrastructures for production, transportation and usage of hydrogen and to entail a vast cost. Against this problem, for effectively utilizing existing energy infrastructures, we are developing a methane producing technique from water and carbon dioxide by using renewable electricity instead of hydrogen production. Specifically, solid oxide electrolysis cell (SOEC) technology for producing syn-gas with high efficiency has been developed and we have succeeded in trial manufacture tubular SOECs whose sin-gas production rate is more than 3.5 sccm/cm2 at the operating temperature of 750 oC and electrolytic voltage of 1.35V. Therefore, in this paper, the numerical models of an SOEC methane production system and a conventional methane production system were made in reference to performance of the tubular SOECs and dependence of performance of the each system on operating conditions, such as operating temperature, feed gas composition, is analyzed and compared with each other. The methane producing system which combined a water electrolysis system with a high temperature water-gas shift reactor was considered as a conventional system. From the result of the analysis, advantage of SOEC methane production system is clarified.

Modeling and simulation of H2S effect in high-temperature water–gas shift reaction using coal-derived syngas

In this study, a model including hydrogen sulfide (H2S) effect on high-temperature water–gas shift reaction (WGSR) performance was built using coal-derived syngas as feedstock. Based on this model, it was found that the H2S coverage rate increases with the decrease in reaction temperature, leading to more significant carbon monoxide (CO) conversion reduction at low reaction temperature. It was also found that the H2S effect can be ignored when the reaction temperature is in the range at which reverse WGSR occurs. In such a temperature range, CO conversion for both with and without the H2S effect approaches equilibrium result. Through parametric studies using this model, it was found that CO conversion depends significantly on the residence time which can be adjusted by varying the flow rate, steam to carbon molar ratio, inlet pressure of syngas and reactor size. For syngas with fixed CO/H2 molar ratio, CO conversion was found to decrease with the increase in carbon dioxide (CO2) content.

Operational Feasibility Analysis of Stand-Alone Methanol Fuel Processors with Flexible Waste Heat Recovery Schemes

To develop a compact and portable fuel processor, two types of stand-alone methanol fuel processor using a combination of an autothermal methanol reformer, a high-temperature water–gas shift reactor, and an internal burner are presented. On the basis of different waste heat recovery schemes, designs 1 and 2, a flexible waste heat recovery design (design 2) by utilizing the split waste heat flow is verified to reduce the waste heat loss. The specific optimization algorithm for maximizing hydrogen yield is taken into account to determine the optimum operating conditions of designs 1 and 2. Through the feasibility analysis at different operational scenarios, the conflict between the optimum operating conditions and the region of operational feasibility can be found. The simulations show that the flexible waste heat recovery design with additional operating variables can raise 11% hydrogen yield and reduce 3.3% waste heat loss.

Preparation of Mesoporous Chromium Promoted Magnetite Based Catalysts for High Temperature Water Gas Shift Reaction

In this paper, the effects of three main preparation factors (pH of the precipitation, aging time and calcination temperature) were investigated on the structural and catalytic properties of mesoporous nanocrystalline magnetite based catalysts in HT-WGS (high temperature water gas shift) reaction. The catalysts were characterized by powder X-ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), temperature-programmed reduction (TPR) and scanning electron microscopy (SEM) techniques. The XRD analysis confirmed the preparation of catalysts directly in active magnetite phase. The results revealed that increasing pH value and decreasing in calcination temperature increased the BET surface area and improve the catalytic activity. However, for the aging time there is an optimum point. It was found that the catalyst prepared at pH value of 10 under aging time of 5h and calcined at 400 °C possessed the highest activity compared to the other prepared catalysts. In addition this catalyst showed the higher activity compared to the commercial one. This catalyst exhibited high stable catalytic performance during 20 h time on stream in high temperature water gas shift reaction.

Enhancing the catalytic performance of cobalt oxide by doping on ceria in the high temperature water–gas shift reaction

The high temperature water–gas shift (HT-WGS) reaction was performed using a Co–CeO2 catalyst, prepared through a co-precipitation method.

Hydrogen production by the water-gas shift reaction using CuNi/Fe2O3 catalyst

Incorporation of both Cu and Ni together into the crystalline lattice of Fe2O3 results in a significant increase in the catalytic activity and also suppresses the methanation reaction in the high-temperature water-gas shift (HT-WGS) reaction.

Synthesis of Improved Catalytic Materials for High-Temperature Water-gas Shift Reaction

In this investigation, we report the preparation and characterization of Co-, Cuand Mn-substituted iron oxide catalytic materials supported on activated carbon. Co-precipitation method and low temperature treatment were used for their synthesis. The influence of chemical composition, stoichiometry, particle size and dispersity on their catalytic activity was studied. Samples were characterized in all stages of their co-precipitation, heating and spend samples after catalytic tests. The obtained results from room and low temperature Mossbauer spectroscopy were combined with analysis of powder X-ray diffraction patterns (XRD). They revealed the preparation of nano-sized iron oxide materials supported on activated carbon. Relaxation phenomena were registered also for the supported phases. The catalytic performance in the water-gas shift reaction was studied. The activity order was as follows: Cu0.5Fe2.5O4 > Co0.5Fe2.5O4 > Mn0.5Fe2.5O4. Catalytic tests demonstrated very promising results and potential application of studied samples due to their cost-effective composition.

Study of a Mn–Cr/TiO2 mixed oxide nanocatalyst prepared via an inorganic precursor complex for high-temperature water–gas shift reaction

Abstract The influence of three preparation methods on the properties and reaction performances of a titania-supported Mn–Cr bimetallic nanocatalyst for high-temperature water–gas shift reaction has been studied. Impregnation, co-precipitation and thermal decomposition of the [Mn(H2O)6]3[Cr(NCS)6]2·H2O/TiO2 precursor as an inorganic precursor complex were utilized for the preparation of the Mn–Cr/TiO2 catalysts. The calcined catalyst and the precursor that were used for its preparation were characterized by powder X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller specific surface area measurements, thermal gravimetric analysis, differential scanning calorimetry and Fourier transform–infrared spectroscopy. The high-temperature water–gas shift activity was appraised in the temperature range from 280 to 420 °C. The results showed that thermal decomposition of inorganic precursor complexes is more advantageous than impregnation and co-precipitation methods for the preparation of Mn–Cr/TiO2 catalysts for high-temperature water–gas shift reaction.

Performance of spinel ferrite catalysts integrated with mesoporous Al2O3 in the high temperature water–gas shift reaction

Abstract The present study focuses on the use of spinel ferrite (MFe 2 O 4 ) catalysts (M = Ni, Co, Fe, or Cu) integrated with mesoporous alumina for the high temperature water–gas shift (WGS) reaction. Among these catalysts, copper ferrite integrated with mesoporous alumina exhibits outstanding performance. To optimize the Cu/Fe ratio in the copper ferrite catalyst, we prepared different Cu x Fe (3− x ) O 4 -MA catalysts ( x = 0.5, 1.0, 1.5, 2.0, or 2.5) by varying the Cu/Fe mole ratio. Of the various Cu/Fe catalysts, the 1:1 mole ratio of Cu/Fe exhibited the highest CO conversion (84%) and 100% selectivity to CO 2 at a very high GHSV of 42,000 h −1 . The improved performance of the catalyst is correlated with its easier reducibility.

Simplified direct pyrolysis method for preparation of nanocrystalline iron based catalysts for H2 purification via high temperature water gas shift reaction

The high-temperature water gas shift reaction is an important step in industrial processes and gas purification. Although the chromium promoted Fe2O3 catalysts have been widely used in this reaction, but preparation of catalyst directly in the active phase (Fe3O4) is of great importance from technical viewpoint. In this paper, facile direct pyrolysis method was employed for synthesis of nanocrystalline Fe3O4 based catalysts with different Fe/Cr and Fe/Cu ratios for high temperature water gas shift reaction. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption (BET), temperature-programmed reduction (TPR), thermal gravimetric and differential thermal analyses (TGA/DTA) and scanning electron microscopy (SEM) techniques. XRD analysis showed that this simple preparation method allows obtaining the catalyst directly in the active phase with chromium and copper incorporated into magnetite lattice. Moreover, the effect of chromium and copper contents on the structural properties and catalytic performance of the catalysts was investigated. It was found that, among the catalysts evaluated the catalyst with Fe/Cr=10 and Fe/Cu=20 ratio possessed higher activity compared to commercial catalyst and showed high stability during 10h time on stream. In addition, the effect of reduction and calcination temperatures, GHSV and steam/gas ratio on the catalytic performance was evaluated.

Heat integration and optimization of hydrogen production for a 1 kW low-temperature proton exchange membrane fuel cell

Heat integration and process optimization for the hydrogen production units of 1kW low-temperature proton exchange membrane fuel cells (LT-PEMFCs) were studied. Hydrogen is produced from methane in a process consisting of a steam methane reforming reaction (SMR), a high-temperature water–gas shift reaction (HWGS), a low-temperature water–gas shift reaction (LWGS), and a preferential oxidation reaction (PROX). Using commercial Aspen Plus® software, the process was designed and simulated with the objective of energy recovery. Furthermore, the unit operation parameters were discussed based on the mass/heat balances. Pinch analysis was applied for heat integration and process optimization to improve the energy recovery level of the hydrogen production system. By integrating system heating, a maximum energy recovery network (MER) and also a relaxed network were developed. The efficiencies of the hydrogen production systems designed with these MER and relaxed networks were 84.3% and 80.1%, respectively. Compared with the MER design, the relaxed network greatly simplifies the hydrogen production process and reduces the exchanger number from 18 to 9. The penalty in terms of power for relaxation is 120W. Sensitivity analysis shows that heat loss and the steam-to-carbon (S/C) ratio are the primary factors influencing the system efficiency, i.e., a 5% heat loss may result in a 7% efficiency drop, and increasing the S/C ratio from 2.5 to 3.0 may result in a 2.5% efficiency drop. The conversion of methane (XCH4) and the relative deviation from chemical equilibrium for the WGS reactions (both HWGS and LWGS) are secondary factors: efficiency drops 3.5% at XCH4=0.8 and at 0.9 of the WGS equilibrium, compared with equilibrium conditions. Finally, the minimum pinch temperature difference (ΔTmin) and reaction temperatures have little impact on system efficiency. Therefore, the device insulation and catalyst performance are very important for system performance.