Temperature Water Gas Shift Reaction Research Articles

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...

Optimization of Cobalt Loading in Co–CeO2 Catalyst for the High Temperature Water–Gas Shift Reaction

We varied the cobalt loading (10, 15, 25, 35 wt%) to determine the optimum loading in a Co–CeO2 catalytic system used for the high temperature water–gas shift (WGS) reaction. Severe reaction conditions were used to compare the catalytic performances including a very high gas hourly space velocity (142,663 h−1) and a high CO concentration (~38%). Among the prepared catalysts, 15% Co–CeO2 exhibited excellent catalytic activity in the temperature range of 350–550 °C without promoting the methanation reaction. In addition, this catalyst showed relatively stable activity for 50 h at 400 °C. The outstanding performance of 15% Co–CeO2 catalyst is mainly due to the highest amount of dispersed cobalt atoms on the catalyst surface. Additionally, the WGS activity was affected by the oxygen vacancy concentration.

Preparation of iron oxide nanoparticles doped by chromium for application in water–gas shift reaction

An efficient preparation method of chromium-doped iron oxide nanoparticles of controlled size, chromium content and catalytic activity was developed. The catalysts were synthesized in an acidic hydrolysis of ferric chloride in order to obtain suspensions of spherical iron oxide nanoparticles with an average size of 10 and 100nm. After purification, the suspensions were transformed into powders. Afterwards, by a wet-impregnation and calcination chromium cations were incorporated to the nanoparticle structure without changing their size. The catalysts were characterized by powder X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption (BET) and scanning electron microscopy (SEM). The activity of obtained samples was tested in a high temperature water gas shift reaction (HT-WGS) and compared with the results gained for chromium-free nanoparticles of similar sizes. The analysis of Raman spectra revealed that at elevated temperature iron hydroxyoxides are transformed to hematite (α-Fe2O3) and then, under catalytic conditions, to magnetite (Fe3O4) which is an active phase in the HT-WGS reaction. The chromium incorporated into the nanoparticles prevented a thermal sintering of nanocrystals, leading to an efficient catalyst performance. It was also shown that chromium-doped α-Fe2O3 nanoparticles of the size of 100nm, after the transformation to the magnetite phase, allowed to obtain a high carbon oxide conversion approaching the thermodynamic limit for temperatures above 500°C .

Hydrogen Production via Low Temperature Water Gas Shift Reaction: Kinetic Study, Mathematical Modeling, Simulation and Optimization of Catalytic Fixed Bed Reactor using gPROMS

Abstract The kinetics study, modeling, simulation and optimization of water gas shift reaction were performed in a catalytic fixed bed reactor. The renowned empirical power law rate model was used as rate equation and fitted to experimental data to estimate the kinetics parameters using gPROMS. A good fit between predicted and experimental CO conversion data was obtained. The validity of the kinetic model was then checked by simulation of plug flow reactor which shows a good agreement between experimental and predicted values of the reaction rate. Subsequently, considering axial dispersion, a homogeneous model was developed for simulation of the water-gas shift reactor. The simulation results were also validated by checking the pressure drop of the reactor as well as the mass concentration at equilibrium. Finally, a multi-objective optimization was conducted for water-gas shift reaction in order to maximize hydrogen formation and carbon monoxide conversion, whereas the reactor volume to be minimized. Implementation of optimal controls leads to increase in hydrogen formation at reactor outlet up to 25.55 %.

Understanding Active Sites in the Water–Gas Shift Reaction for Pt–Re Catalysts on Titania

Pt–Re clusters supported on titania have shown promise as catalysts for the low temperature water–gas shift reaction. However, the enhanced activity of the bimetallic Pt–Re catalyst versus pure Pt is not well understood. In this work, exclusively bimetallic clusters were grown on TiO2(110) by vapor-deposition of Pt on 2 ML Re clusters and Re on 2 ML Pt clusters. Temperature programmed desorption experiments with CO were used to determine the concentration of Re at the surface, given that CO dissociates on Re but not on Pt. Deposition of 2 ML Pt on 2 ML Re resulted in Re core–Pt shell structures, whereas deposition of low coverages (<0.5 ML) of Re on 2 ML Pt resulted in complete diffusion of Re into the Pt clusters. Both of these Pt on Re bimetallic clusters are thermodynamically favored by the lower surface free energy of Pt compared to Re, and both are also more active than pure Pt clusters in the WGS reaction. Postreaction XPS experiments indicate that Re in the Pt on Re clusters is not oxidized under W...

The water gas shift reaction over Pt–CeO2 nanoparticles confined within mesoporous SBA-16

Pt–CeO2 nanoparticles confined in mesoporous silica SBA-16 as successful catalysts for the single step, low temperature water gas shift reaction.

Effect of alkali on C[sbnd]H bond scission over Pt/YSZ catalyst during water-gas-shift, steam-assisted formic acid decomposition and methanol steam reforming

In previous work, Na-doping of Pt/YSZ was found to facilitate the low temperature water gas shift reaction (LT-WGS), and the promoting effect was ascribed to an electronic weakening of the CH bond of the formate species, a proposed intermediate in the catalytic cycle. Formate has also been implicated as an intermediate in steam-assisted formic acid decomposition (SAFAD) and methanol steam reforming (MSR) pathways. In the current contribution, Na-doping was also found to significantly accelerate the SAFAD reaction. The high activity of Pt/YSZ for SAFAD, as well as the promoting effect of Na, are in stark contrast to the view that formates are too stable, precluding them as intermediates for LT-WGS. With MSR, a remarkable promoting effect of Na doping was observed in the selectivity to CO2 (>90% for Na-doped relative to 22% for undoped at 300°C); however, at the doping levels used in the current work, the activity was lower for the Na doped catalyst and further optimization is needed to improve MSR conversion.

Water gas shift catalysts for hydrogen production from biomass steam gasification

Iron/ceria based catalysts were developed for high temperature Water Gas Shift (WGS) reaction in order to increase hydrogen content in the syngas at the outlet of a steam biomass gasifier working at atmospheric pressure. Alumina foam was used as support to deposit ceria and iron phase to prepare catalysts. The use of ceramic foams with different porosities (30ppi and 45ppi) assured a very low pressure drop in the process. The optimal conditions for WGS were determined in line with conditions occurring after gasification. The activity of the 45ppi catalyst in the WGS reaction at 450°C (CO conversion=50%) can be reached by the 30ppi catalyst by adjusting the gas hourly space velocity. The amount of carbon deposition observed on the catalyst, under the gas mixture representative of the syngas at the gasifier outlet, can be limited by the addition of steam (S/C ratio≥2). These conditions also led to less stable carbon. Characterizations on the spent catalyst indicated the in-situ activation of the catalyst with no over-reduction of iron oxide. The stabilization of the catalytic activity could be related to the stabilization of both the particle size and carbon deposition. The carbon formation rate (decreasing exponential curve) stabilization could be associated to the beginning of a steady state, the carbon remaining on the catalyst being at the lowest stable form.

Catalytic Activities of Bimetallic Catalysts for Low Temperature Water Gas Shift Reaction

Catalytic Activities of Bimetallic Catalysts for Low Temperature Water Gas Shift Reaction

Preparation of high temperature water gas shift catalyst with coprecipitation method in microemulsion system

In this paper nanocrystalline mesoporous iron-based high temperature water gas shift catalysts were prepared by coprecipitation method in water-in-oil (W/O) microemulsion. The prepared samples were characterized by using X-ray diffraction (XRD), N2 adsorption (BET), temperature-programmed reduction (TPR), Fourier transform infrared spectroscopy (FTIR), transmission and scanning electron microscopies (TEM, SEM) techniques. The results revealed that the Fe2O3 possessed low specific surface area and catalytic activity in high temperature water gas shift reaction. The addition of copper to Fe2O3 favored the active phase formation and significantly decreased the reduction temperature of hematite to magnetite and consequently improved the catalytic activity of Fe2O3. The incorporation of chromium in hematite increased the surface area and catalytic activity of Fe2O3. The results also showed that the prepared Fe⿿Cr⿿Cu catalyst showed higher activity than the commercial catalyst. In addition, the effects of GHSV, steam/gas ratio, and calcination temperature were investigated on the catalytic performance of Fe⿿Cr⿿Cu catalyst.

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.

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.

Ce 첨가에 따른 저온수성가스전이반응용 Cu/Zn 촉매의 활성 연구

Ce 첨가에 따른 저온수성가스전이반응용 Cu/Zn 촉매의 활성 연구

High temperature water gas shift reaction over Fe-Cr-Cu nanocatalyst fabricated by a novel method

Fe-Cr-Cu nanocatalyst was synthesized through an inorganic-precursor thermolysis approach and exploited for high temperature water gas shift reaction. The results demonstrated that the method used for the nanocatalyst fabrication led to smaller crystallite size (32.9 nm) and higher BET surface area (127.3 m2/g) compared to those of a reference sample (65.5 nm, 78.6 m2/g) prepared by co-precipitation conventional method. Furthermore, the obtained data for catalytic activity showed that the catalyst prepared via inorganic precursor has better activity than the reference sample in all studied temperatures (350-500 °C) and also exhibited higher catalytic activity than a commercial Fe-Cr-Cu catalyst in higher temperatures (more than 450 °C).

The effect of preparation method on Fe/Al/Cu oxide-based catalyst performance for high temperature water gas shift reaction using simulated waste-derived synthesis gas

The effect of preparation method on Fe/Al/Cu oxide-based catalysts was investigated for the high temperature water gas shift reaction using simulated waste-derived synthesis gas. Impregnated Fe/Al/Cu catalyst and sol–gel prepared Fe/Al/Cu catalyst were compared with a co-precipitated Fe/Al/Cu catalyst. The co-precipitated Fe/Al/Cu catalyst exhibited very high CO conversion (XCO > 85% at 450 °C) with stable activity. This performance was attributed to the high surface area, the small crystallite size of the Fe3O4, the ease of reducibility, and formation of reduced form of the Cu species.

Hydrogen production by high temperature water gas shift reaction over highly active and stable chromium free Fe–Al–Ni catalysts

High temperature water gas shift reaction is carried out over nanocrystalline chromium free Fe2O3–Al2O3–NiO catalysts with and without alkaline earth promoters. Mesoporous catalysts are prepared by coprecipitation method. The prepared catalysts are characterized using N2 adsorption (BET), temperature-programmed reduction (TPR) and desorption (TPD), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results indicate that alkaline earth promoters improve the catalytic activity and suppress the progress of methanation reaction, which is related to the increment of amount in weakly basic sites through promoter addition. Furthermore, it is found that the Fe2O3–Al2O3–NiO catalyst promoted by Ba exhibits the highest catalytic activity and the lowest methanation among the prepared catalysts and the commercial chromium containing one. In addition, the effect of Ba content on the CO conversion is investigated and the results indicate that the catalyst with 3 wt.% Ba possesses high activity and stability without any decrease in CO conversion during 50 h time on stream.

Enhancing the low temperature water–gas shift reaction through a hybrid sorption-enhanced membrane reactor for high-purity hydrogen production

The low temperature water–gas-shift reaction (LT-WGS) has been assessed by means of a hybrid sorption-enhanced membrane reactor (HSEMR) that combines both CO2 and H2 removal from the reaction zone. The performance of this reactor has been compared with that obtained by (i) a traditional and (ii) a sorption-enhanced (only CO2 is removed) reactor operating in the same operational conditions. Cu/ZnO–Al2O3 and K2CO3-promoted hydrotalcite materials have been used as a catalyst and CO2 sorbent, respectively. A self-supported Pd–Ag membrane tube has been used in order to selectively separate the H2. The CO2 sorption capacity, in the presence and absence of water vapour, of the potassium-promoted hydrotalcite has been determined by means of breakthrough experiments. The presence of water vapour enhanced the sorption capacity of the hydrotalcite in the experimental conditions used. Concerning the performance of the HSERM, results clearly show that when both CO2 and H2 are removed from the reaction zone, the hydrogen production through the reversible LT-WGS reaction is enhanced compared to either a traditional or a sorption-enhanced reactor, allowing overcoming equilibrium limitations and obtain a pure H2 stream.

High-temperature water-gas shift reaction over nanostructured Cr-free Fe2O3[sbnd]Al2O3[sbnd]CuO[sbnd]MO (M: Ba, Ca, Mg and Sr) catalysts for hydrogen production

In this paper the promotion of Fe2O3Al2O3CuO chromium free catalyst with Ba, Ca, Mg and Sr for hydrogen production via high temperature water gas shift reaction was studied. The catalysts were synthesized by coprecipitation method and characterization of the prepared catalysts were performed using X-ray diffraction (XRD), N2 adsorption (BET), temperature-programmed reduction (TPR) and transmission electron microscopy (TEM) techniques. The results revealed that addition of alkaline earth promoters decreased the BET surface area while improved CO conversion. Among the promoted catalysts, 9 wt% Ba promoted Fe2O3Al2O3CuOcatalyst exhibited higher BET surface area and catalytic activity.

Applying Taguchi robust design to the optimization of the synthesis parameters of nanocrystalline Cr-free Fe–Al–Cu catalyst for high temperature water gas shift reaction

Nanocrystalline Cr-free Fe–Al–Cu catalysts with high surface area and mesoporous structure was prepared by coprecipitation method and employed in high temperature water gas shift reaction. Several parameters such as pH, aging temperature and aging time were optimized by the Taguchi method of experimental design. The sample prepared under optimized conditions showed a high surface area of 208m2g−1, pore size of 3.76nm and theoretical particle size of 5.47nm after calcination at 400°C for 4h. This catalyst illustrated the highest CO conversion compared to other prepared catalysts. These results confirmed that the Taguchi method is an effective method of determining the optimum parameters in preparation process of high temperature water gas shift catalyst. Moreover, the effect of calcination temperature, GHSV and steam/gas ratio on the catalytic performance of optimized Fe–Al–Cu catalyst was investigated.

The effect of preparation factors on the structural and catalytic properties of mesoporous nanocrystalline iron-based catalysts for high temperature water gas shift reaction

A systematic study was done on the effect of preparation factors on the structural and catalytic properties of mesoporous nanocrystalline iron-based catalysts in high temperature water gas shift reaction. The catalysts were prepared by coprecipitation method, and the effect of the main preparation factors (pH, refluxing temperature, refluxing time, concentration of the precursors solution) was studied. The catalysts were characterized by powder X-ray diffraction (XRD), N2 adsorption (BET), Temperature programmed reduction (TPR), transmission and scanning electron microscopies (TEM, SEM) techniques. The results revealed that the preparation factors affected the textural and catalytic properties of the Fe-Cr-Cu catalyst. The results showed that the prepared catalyst with the highest activity showed higher specific surface area compared to commercial catalyst and consequently exhibited higher activity in high temperature water gas shift reaction. The TEM analysis showed a nanostructure for this sample with crystallite size less than 20 nm.