Effect of Citric Acid on MoO3/Al2O3 Catalysts for Sulfur-Resistant Methanation

Dajun Meng,Xinbin Ma,Wenxia Yu,Weihan Wang,Baowei Wang,Zhenhua Li

doi:10.3390/catal7050151

Abstract

A series of MoO3/Al2O3 catalysts with different amounts (molar ratio of CA/Mo = 0, 1, 1.5, and 2) of citric acid (CA) prepared by simultaneous impregnation were evaluated for sulfur-resistant methanation. Based on the evaluation results, catalytic activity increased accompanied with the rise of citric acid amount. Combine with the analysis of N2-physisorption, XRD, H2-TPR, XPS, and TEM, the catalyst saturated loading capacity improved, resulting in increasing dispersion of Mo species on Al2O3 surface clearly. According to H2-TPR result, the Mo oxide precursors can be more easily sulfureted when citric acid is added. Moreover, based on the Raman analysis, increasingly tetrahedrally coordinated Mo6+ species with high methanation performance are generated after citric acid treatment. These factors probably together accelerate MoO3/Al2O3 catalytic activity growth for methanation.

Highlights

With the energy shortage and contamination crisis on the environment [1], the efficient and clean use of coal resources has become increasingly significant
All samples showed typical and similar IV curves, with hysteresis loops according to the IUPAC classification system
After adding citric acid into catalysts, the Brunauer–Emmett–Teller (BET) surface area, the average pore volume, and the pore size of all catalyst samples are smaller than the Al2 O3 support

Summary

Introduction

With the energy shortage and contamination crisis on the environment [1], the efficient and clean use of coal resources has become increasingly significant. The production of synthetic natural gas (SNG). Methanation is an essential process for SNG production. Ni-based catalyst can be used for a methanation reaction [3,4], but it is extremely sensitive to sulfur and only occurs as the molar ratio of H2 /CO is no less than 3:1. Considering its good performance in water-gas shift (WGS) reactions [5], Mo-based catalysts can exhibit good methanation activity at relatively low H2 /CO. The chemical equation for sulfur-resistant methanation on Mo-based catalyst can be expressed in the following equation [6]

Methods

Results

Conclusion