Poisoning effects of H2S and HCl on the naphthalene steam reforming and water-gas shift activities of Ni and Fe catalysts

Xiaomin Dou,Andrei Veksha,Wei Ping Chan,Wen-Da Oh,Yen Nan Liang,Florence Teoh,Dara Khairunnisa Binte Mohamed,Apostolos Giannis,Grzegorz Lisak,Teik-Thye Lim

doi:10.1016/j.fuel.2018.12.119

Xiaomin Dou, Andrei Veksha + Show 8 more

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https://doi.org/10.1016/j.fuel.2018.12.119

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Abstract

H2S and HCl are common impurities in raw syngas produced during gasification of biomass and municipal solid waste. The purpose of this study was to investigate the poisoning effect of H2S and HCl on synthesized and commercial catalysts during steam reforming of naphthalene. Four synthesized catalysts with different loadings of Ni and Fe on alumina support and two commercial catalysts were selected and evaluated in a fixed bed reactor at 790, 850 and 900 °C. The obtained results revealed that reforming and water-gas shift (WGS) activities of catalysts did not benefit from the Fe addition. The activities were influenced differently by H2S and HCl indicating that the reactions were catalyzed by different active sites on the nickel surface. In the presence of H2S and HCl, the poisoning of naphthalene reforming activity was caused by H2S and was not affected by HCl when both compounds were present in the gas. H2S chemisorbs on nickel surface forming NiS and decreasing the accessibility of active sites to hydrocarbons. The poisoning effect was only partially reversible. On the contrary, the poisoning of WGS activity could be caused by both H2S and HCl, and the activity could be completely restored when H2S and HCl were removed from the gas. Unlike naphthalene reforming activity, which was comparable for catalysts with similar Ni loadings, WGS activity depended on the catalyst structure and was less susceptible to poisoning by H2S and HCl in case of the catalyst with strong NiO-support interactions.

Highlights

Syngas obtained during biomass/municipal solid waste (MSW) gasification is mainly a mixture of carbon monoxide, carbon dioxide, hydrogen, methane and nitrogen, which can be utilized for electric power generation or liquid fuel synthesis [1]
The specific surface areas and total pore volumes of the synthesized catalysts decreased with increasing Ni + Fe contents, which can be attributed to the impregnation of the porous alumina with loaded metal species
X-ray diffraction (XRD) patterns of the synthesized catalysts in Fig. 2 consist of broad peaks with no distinct XRD peaks and show no sharp XRD peaks indicating that alumina, nickel and iron oxides have non-crystalline and/or nanosized structures, so that alumina provides surface area for better dispersion of catalyst

Summary

Introduction

Syngas obtained during biomass/municipal solid waste (MSW) gasification is mainly a mixture of carbon monoxide, carbon dioxide, hydrogen, methane and nitrogen, which can be utilized for electric power generation or liquid fuel synthesis [1]. The biomass- and MSWderived syngas, contains significant concentrations of impurities such as tar, HCl, alkali chlorides, particulate matter, ammonia, HCN and sulfur compounds. Tar, consisting of a mixture of aromatic hydrocarbons, causes equipment failure by its condensation and corrosion upon cooling of syngas [2,3,4]. The techniques that can efficiently remove tar compounds to the acceptable levels are still under development. One of the prospective techniques is catalytic steam reforming which converts tar into H2 and CO [5,6,7]. The utilization of Ni-based catalysts enhances syngas production due to steam reforming of hydrocarbons and other catalyzed reactions, including dry reforming, WGS and Bodouard reactions [8,9,10,11,12]. Ni-based catalysts facilitate simultaneous decomposition of NH3 and HCN into N2 and H2

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