Dibromoethane To Ethylene In The New Technology Of High-carbon Hydrocarbons

Ethylene is one of the main intermediate chemicals used as a raw material in the petrochemical industry, it is commercially produced by the thermal cracking of naphtha and saturated hydrocarbons, due to thermodynamic limitations, thermal cracking temperatures as high as 850℃. Higher hydrocarbons is a clean fuel, the majoy process for the conversion of nature gas to liquiud fuels is initial from syngas, which is called Fischer-Tropsch process, but this is an energy consuming process, more than one fourth of natural gas must be burned to generate heat for the steam reforming of natural gas. So it is necessary to find new pathways and starting materials to produce ethylene and higher hydrocarbons liquid fuels. To solve the shortage of the raw material of ethylene as well as increase the utilize efficient of natural gas.In this paper, we discussed a non-syngas process to synthesize ethylene and higher hydrocarbons from ethane which was the second component of natural gas. The characteristic of the process was to choose HBr/H₂O as a medium. The process include two reaction steps. In the first reaction, ethyl bromide was produced from the reaction of ethane, HBr, and oxygen, and in the second reaction, ethyl bromide became ethylene and higher hydrocarbons through the dehydrogen bromide reaction of ethyl bromide. In this paper, we mainly discussed the first step.Catalyst was the key of the reaction. Firstly, We investigated the influence of the support of the catalyst, The results show that when we choosed SiO₂ as support, the main production was ethylene, while choosed HZSM-5(Si/Al=360) as support the main products was higher hydrocarbons. Then we modified SiO₂ and HZSM-5 with different metals and investigated the effection of Si/Al ratio, metal content and the preparation of catalyst respectively. After we choosed appropriate catalysts we investigated the effection of the reaction temperature and the reaction time.Under the reaction condition, when we choosed 12.0%ZnO/SiO₂-450-8 as catalyst, the conversion of ethyl bromide was over 80.9% and the selectivity of ethylene was over 98.0% under the conditions of 260℃, while the conversion of ethyl bromide was over 98.3% and the selectivity of ethylene. was over 98.0% under the conditions of 300℃; when we choosed 8.0%ZnO/HZSM-5-450-8 (Si/Al=360) as catalyst, the conversion of ethyl bromide was over 98.0% and the products included alkanes, olefins and aromatics with five to thirteen carbon atoms, under the conditions of 300℃.In this paper, we also discussed the mechanism of condensation of ethyl bromide to synthesize higher hydrocarbons. According to several experiments, we tend to believe that the reaction mechanism was similar to the "carbon pool" mechanism. However, we still do not know in detail. The research work is still in progress in this aspect.