On Pyrolyses Of Biocrude For Light Olefins

Exploitation and utilization of biomass energy are drawing more and more attentions with growing concerns about environment and energy problems. Hydrothermal liquefaction of algae is considered as a promising method to produce biocrude. However, high nitrogen content in this biocrude blocks it from transportation use. Biocrude post-treatments presented in literatures focus on further hydrothermal treatment of biocrude, with little significant effect. Given the nitrogen in biocrude distributing over numerous organic compounds, breaking nitrogen-containing compounds is necessary for denitrogenation of biocrude. Pyrolysis is one of the effective solutions to break chemical compound.It is necessary to investigate the composition of biocrude before pyrolysis. Real component true boiling point curve of biocrude was established according to typical full components analysis and thermogravimetric analysis. Distillation cutting simulation was performed with the aid of process simulation software and nitrogen distribution in distillate was analyzed. It was found that diesel distillate accounts for a larger proportion in the biocrude. Each distillate has a certain amount of nitrogen and enrichment of nitrogen in certain distillate was not reached through distillation. Then, according to component surrogate theory in fossil fuel research, one surrogate oils was formulated to replace complex biocrude to study product distribution of biocrude pyrolysis. The surrogate compounds used are the main ones of the bicrude.The formulated surrogate oil was used as raw material to conduct thermal pyrolysis experiments in Py-GC-MS. Influence of pyrolysis temperature on pyrolysis products was investigated before deawing some conclusions. The biocrude is good feedback to produce olefins by pyrolysis. The total olefins yield is 35-48% in the temperature range of 650-850 oC under thermal pyrolysis condition. Apart from olefins, inorganic gases, such as carbon monoxide, nitrogen and vapour, and organic gases, for instance methane, ethane and benzene, were also produced during biocrude pyrolysis process. Pyrolysis is a viable access for utilization of biocrude.Although some significant results have been obtained through pyrolysis, the threshold of high pyrolysis temperature still blocks biocrude from extensive applications. To lower pyrolysis temperature and regulate product distribution, HZSM-5 molecular sieve was employed as catalyst to carry out catalytic pyrolysis experiment in the same experimental device. Influence of pyrolysis temperature and Si/Al ratio of HZSM-5 molecular sieve on pyrolysis products was investigated in this paper with exciting conclusions. HZSM-5 molecular sieve can catalyze biocrude pyrolysis for light olefins with a total olefins yield is 50-74% at the temperatures ranging from 400 oC to700 oC and low Si/Al ratio HZSM-5. The total olefins yield of 23-54% occured at 350-650 oC and high Si/Al ratio HZSM-5. By bringing in HZSM-5 molecular sieve as catalyst, biocrude pyrolysis temperature comes down with about 200 oC, while total olefin yields improve about 20%.