Ajay Jha

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. CuNi/Fe2O3 exhibited the highest CO conversion with negligible CH4 selectivity at the extremely high GHSV of 101 000 h−1 (XCO = 85% at 400 °C). The high activity of CuNi/Fe2O3 catalyst is mainly due to the increase in the lattice strain and the decrease in the binding energy of lattice oxygen. In addition, X-ray photoelectron spectroscopy (XPS) results provide direct evidence for the formation of surface CuNi alloy, which plays a critical role in suppressing the methanation reaction. The detailed characterization by powder X-ray diffraction (XRD), XPS, BET, and H2 temperature-programmed reduction (TPR) techniques was used to understand the role of dopants on host iron oxides in the enhancement of catalytic activity for HT-WGS 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. The catalyst showed stable activity performance at 400 °C with 90% CO conversion without any side reactions (methanation) at a very high GHSV of 143 000 h−1, which is the highest value reported for the HT-WGS reaction. This remarkable performance is attributed to the superior reducible nature of ceria and the preferential exposure of (220) and (112) facets of CeO2 and Co3O4, respectively. The time-on-stream study substantiates that ceria stabilizes the surface area of the Co–CeO2 catalyst during the WGS reaction compared to the bulk Co3O4.

Mesoporous NiCu–CeO2 oxide catalysts for high-temperature water–gas shift reaction

Mesoporous NiCu–CeO2 oxide catalysts were synthesized by using the evaporation-induced self-assembly method applied to the high-temperature, water–gas shift reaction (HT-WGS) between 350 to 550 °C. Nickel and copper loadings on mesoporous ceria were tailored to achieve high activity and selectivity by suppressing methane formation in HT-WGS. Among the prepared catalysts, NiCu(1 : 4)–CeO2 exhibited the highest selectivity to CO2 and H2 with 85% CO conversion at a very high GHSV of 83 665 h−1. The higher activity of the catalysts was due to the mesoporous architecture, which provides more accessible active sites for the WGS reaction. Powder X-ray diffraction (XRD), small angle X-ray scattering (SAXS), N2-adsorption/desorption isotherm, high-resolution transmission electron microscopy (HR-TEM), and H2-temperature-programmed reduction (TPR) techniques were used to understand the role of mesoporosity and bimetallic composition of various NiCu–CeO2 oxides in enhancing catalytic activity for HT-WGS.

The investigation of non-noble metal doped mesoporous cobalt oxide catalysts for the water–gas shift reaction

In this study, we report an investigation of the low temperature water–gas shift (LT-WGS) reaction over a series of non-noble metal doped (Me = Mn, Fe, Co, and Ni) mesoporous Co3O4 catalysts. The effect of metal dopants on the structure and reducibility of the mesoporous Co3O4 oxide was examined using X-ray diffraction (XRD), N2-adsorption/desorption isotherm measurements, and H2-temperature programmed reduction (TPR) measurements. Experimental results revealed that among the Me-doped Co3O4 catalysts, Ni/Co3O4 demonstrated the highest catalytic performance (XCO = 93% with 47% H2 yield at 280 °C). The higher activity of the Ni-doped Co3O4 catalyst was mainly due to its smaller crystallite size (8.6 nm) and strong interaction between Co and Ni, which lead to the higher reducibility of Co3O4 compared to the other metal-doped Co3O4. To further optimize the loading of Ni- over the mesoporous Co3O4, a series of Ni(x%)/Co3O4 catalysts were prepared by varying the Ni-loading in the range of 3 to 15 wt%. Among these catalysts, 5 wt% Ni- was found to be the optimum loading, whereas higher Ni-loaded samples (10 and 15 wt%) showed a decrease in catalytic performance and hydrogen yield during the WGS reaction.