High Olefin Yield in Pyrolysis of Heavier Hydrocarbon Liquids Using Microwave as Heat Supplier

In order to expand the scope of C2H4 pyrolysis material and recycle the waste polyolefin, this study has employed microwave pyrolysis of heavier hydrocarbon liquids. Microwave pyrolysis not only maintains a stable energy supply to the reaction materials for obtaining a high conversion rate, but also avoids coking caused by local overheating. Steam may serve a dual role as diluent and heat carrier. Thus, this study has obtained higher olefin yield, higher olefin selectivity, and better operational continuity than conventional steam cracking. Light olefins (C-2(=)-C-4(=)) reached 50.65-68.64 mol% in the pyrolysis gas. The yields of C2H4 and C3H6 for heavier hydrocarbons pyrolysis were 42.80-44.76 and 12.98-13.91 wt% of the feedstock, respectively, while the maximum yields of C2H4 and C3H6 for pyrolysis of liquid products of polyolefin cracking were 47.00 and 22.83 wt%, respectively. Analysis of the pyrolysis mechanism indicates that the beta-scission reactions of free radicals are predominant, while the secondary reactions are significantly inhibited due to the enhanced heat transfer between the steam and the hydrocarbons.