A review of recent advances in water-gas shift catalysis for hydrogen production

Abstract

The water-gas shift reaction (WGSR) is an intermediate reaction in hydrocarbon reforming processes, considered one of the most important reactions for hydrogen production. Here, water and carbon monoxide molecules react to generate hydrogen and carbon dioxide. From the thermodynamics aspect, pressure does not have an impact, whereas low-temperature conditions are suitable for high hydrogen selectivity because of the exothermic nature of the WGSR reaction. The performance of this reaction can be greatly enhanced in the presence of suitable catalysts. The WGSR has been widely studied due do the industrial significance resulting in a good volume of open literature on reactor design and catalyst development. A number of review articles are also available on the fundamental aspects of the reaction, including thermodynamic analysis, reaction condition optimization, catalyst design, and deactivation studies. Over the past few decades, there has been an exceptional development of the catalyst characterization techniques such as near-ambient x-ray photoelectron spectroscopy (NA-XPS) and in situ transmission electron microscopy (in situ TEM), providing atomic level information in presence of gases at elevated temperatures. These tools have been crucial in providing nanoscale structural details and the dynamic changes during reaction conditions, which were not available before. The present review is an attempt to gather the recent progress, particularly in the past decade, on the catalysts for lowtemperature WGSR and their structural properties, leading to new insights that can be used in the future for effective catalyst design. For the ease of reading, the article is divided into subsections based on metals (noble and transition metal), oxide supports, and carbon-based supports. It also aims at providing a brief overview of the reaction conditions by including a table of catalysts with synthesis methods, reaction conditions, and key observations for a quick reference. Based on our study of literature on noble metal catalysts, atomic Pt substituted Mn 3 O 4 shows almost full CO conversion at 260°C itself with zero methane formation. In the case of transition metals group, the inclusion of Cu in catalytic system seems to influence the CO conversion significantly, and in some cases, with CO conversion improvement by 65% at 280°C. Moreover, mesoporous ceria as a catalyst support shows great potential with reports of full CO conversion at a low temperature of 175°C.

Improved Water–Gas Shift Performance of Au/NiAl LDHs Nanostructured Catalysts via CeO2 Addition

“…In regard to industrial application, aiming to achieve high CO conversion, the up-to-date WGS reaction is performed through a two-stage WGS converter system using both different temperatures and catalysts. There is a high temperature shift stage (350–450 °C, Fe 2 O 3 -Cr 2 O 3 , residual CO of about 2–5%), followed by a low temperature shift stage (180–250 °C, Cu-ZnO-Al 2 O 3 , residual CO content < 1%) with interstage cooling [ 3 , 4 , 5 , 6 , 7 ].…”

“…A variety of catalysts combining noble or transition metals (Pt, Rh, Au, Pd, Fe, Cu, Ni, Co) with different oxides or mixed oxides can catalyze the WGS reaction, as described in many scientific reviews and numerous papers. The process parameters and recent advances in WGS catalysis, the design of novel and effective catalyst compositions, the preparation approaches, the nature of the support, the catalyst precursors and promoter additives (if there) as well as their impact on the performance in the WGS reaction have been debated and clarified [ 5 , 6 , 7 , 8 , 9 ].…”

Improved Catalytic Activity of the High-Temperature Water Gas Shift Reaction on Metal-Exsolved La0.9Ni0.05Fe0.95O3 by Controlling Reduction Time

“…Fossil fuels, which are the primary source of energy [1], pollute the environment, induce global warming, and are not renewable. One alternative clean energy source is hydrogen [2,3]. It has a high energy yield of 122 kJ/g [4], which is about 2.75 times higher than that of traditional hydrocarbon fuels [5,6].…”

“…Physical characteristics of the reduction-treated LNF samples. Nanoparticle size is calculated from the Scherrer formula based on the XRD measurement;2 Nanoparticle size is statistically analyzed using the ImageJ program based on the SEM images;3 The population of the NPs per um 2 is calculated by the ImageJ program based on the SEM images.…”

Zr and Fe on Pt/ CeO 2 ‐MO x / Al 2 O 3 catalysts for WGS reaction

“…Within the H 2 energy vector, the water gas shift (WGS) reaction (1) stands as chief process representing a bottleneck regarding H 2 technology implementation into portable devices. 1,2 WGS fundamental understanding should be considered to develop active and stable catalysts able to surpass the WGS intrinsic limitations, for example, high contact times and catalyst deactivation issues. 3 On the WGS reaction, the water dissociation is known as the rate-limiting step.…”