Feasibility of sustainable reusability of Ni/char catalyst for synthetic gas production via catalytic steam gasification

Abstract

Ni/char catalyst is one of the most promising catalysts for enhancing gas production, particularly syngas from catalytic steam gasification of biomass. In the current study, one unmodified (Ni/MMchar) and two modified catalysts (Ni/NaMMchar and Ni/NaAceMMchar) were utilized to investigate the reusability potential of Ni/char catalyst for catalytic steam gasification of bamboo in a two-stage fixed-bed reactor including the changes in catalyst characteristics. N2 adsorption-desorption by BET, scanning electron microscope connected with energy-dispersive X-ray spectrometer (SEM-EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses were utilized for examining their characteristics. The findings indicated that the three catalysts could maintain the reusability potential in catalytic steam gasification of bamboo for twice cycles. The syngas reduction percentages in the second cycles of the catalysts ranged between 11.0 and 22.8 %. H2/CO ratios of all spent catalysts lined in the range of 4.10 − 2.45. The low heating values of syngas products were in the range of 8.83–8.19 MJ/Nm3. Considering the catalyst characteristics, the increasing cycles of catalyst operations induced carbon deposition, resulting in the reduction of specific surface areas. SEM-EDS images of the used catalysts appeared the coke layer and the Ni metal sintering on the surfaces. The uses of catalysts encouraged the transformation of Ni metal active site into NiO, Ni2O3 and Ni3C forms. These phenomena were the major causes of catalyst deactivation. The changes in the characteristics and catalyst activity controlled the gasification reactions, resulting in the catalyst deactivation and gaseous products.