Study of the Co-pyrolysis characteristics of oil shale with wheat straw based on the hierarchical collection

Abstract

To reveal the co-pyrolysis characteristics of oil shale mixing with wheat straw in different reaction steps, three temperature stages of 348 °C-T1, 476 °C-T2 and 521°C-T3, which were obtained through the thermogravimetric analysis results, were chosen as the collection temperature of the liquid products. The volatiles of each temperature stage would be condensed and collected separately and successively for the depiction of the detailed co-pyrolysis characteristics. Through the comprehensive analysis of the product distributions and their GC-MS, NMR experimental results, the main formation temperature stages of the co-pyrolysis products are T1 and T2 respectively. The synergistic effects of T1 stage mainly consist of the catalytic effect of minerals in oil shale and the effect of micro-molecule free radicals on kerogen macromolecular restructuring process, while the synergistic effect of T2 stage comes from the catalysis of bio-char on the cracking process of the critical bitumen. Moreover, the synergistic effects significantly enhanced the H/C atomic ratio from 1.571 to 1.668 in bio-oil, causing a transfer of oxygen from pyrolytic oil to pyrolysis gas and promoting the generation of long straight carbon chains in shale oil.