Maximizing production of high-quality tar from catalytic upgrading of lignite pyrolysis volatiles over Ni-xCe/Y under CH4/CO2 atmosphere

Abstract In this paper, a novel process for integrating lignite pyrolysis volatiles upgrading with methane dry reforming (MDR) was carried out over Ni-Ce bimetallic catalysts in a fixed-bed reactor. The effects of Ni-xCe/Y catalysts on CH4/CO2 conversions, products distributions and tar compositions were investigated. The results indicated that the Ni-Ce bimetallic catalysts could significantly decrease coke deposit and obviously improve tar components, especially for light aromatics (LAs). The Ni-7Ce/Y catalyst exhibited better catalytic performance in pyrolysis volatiles upgrading in the respects of high light tar yield, selectivity to LAs, the resistance of coke deposition and the removal of heteroatoms in tar. The resultant high-quality tar could be attributed to the moderate acidity with suitable ratio of Bronsted/Lewis acid sites, better dispersion and strong interaction of Ni and Ce species on supports. The 2H NMR and GC–MS results confirmed that methane dry reforming participated in the tar formation, especially aromatic rings. This work could provide more insights into catalytic upgrading of lignite pyrolysis volatiles and sufficient utilization of CH4/CO2 greenhouse gases.