Abstract
Ni/Al2O3 catalyst prepared by combustion method was applied in a slurry methanation reaction to study the catalytic performance, especially the regeneration performance. The catalyst properties were characterized by (X-Ray diffraction) XRD, Inductively coupled plasma atomic emission spectrometer (ICP-AES), Nitrogen adsorption-desorption, Transmission electron microscopy (TEM), Thermogravimetric analysis (TG/DTG), Temperature programmed oxidation (TPO), and H2 chemisorption before and after reaction. The results show that the catalyst deactivation was mainly due to carbon deposition, which exhibited amorphous carbon films and formed by the disproportionation of CO. The carbon deposition was formed on the catalyst surface and existed as carbon films during the reaction, then it gradually separated from the catalyst surface, generated an overlapping multi-layer three-dimensional carbon structure, which covered the active site and blocked the pores. As a result, the metal surface area of catalyst decreases, as well as the activity. The carbon deposition could be removed by oxidative calcination without destroying the catalyst structure, the active sites could be re-exposed and the catalyst activity could be recovered.
Highlights
Coal is the most abundant fossil energy on Earth, which can be used to prepare coke [1], aromatics [2], methane [3,4,5], methanol [6], ammonia [7], gasoline [8] and other chemical products through coking, gasification and liquefaction
For a slurry-bed reactor with inert liquid medium, the heat reaction could be removed in time by the liquid paraffin wrapped catalyst, which could solve the problem of overheating in the bed
It was reported that the catalyst deactivation rate in the fixed-bed methanation system is
Summary
Coal is the most abundant fossil energy on Earth, which can be used to prepare coke [1], aromatics [2], methane [3,4,5], methanol [6], ammonia [7], gasoline [8] and other chemical products through coking, gasification and liquefaction. The process of coal gasification to methane has been extensively studied in recent years [9,10,11], due to its high energy conversion efficiency, short process flow and low equipment investment of unit product. Researchers have paid more attention to the slurry-bed methanation reaction process, the reaction temperature, pressure, velocity and other reaction process [13,14]. The structure and properties of the catalyst [15,16,17,18] have been systematically studied, and it was found that the preparation method can significantly affect the specific surface area, Ni particle size, dispersion and Catalysts 2019, 9, 570; doi:10.3390/catal9070570 www.mdpi.com/journal/catalysts
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