Area of Technology:Chemical and Allied
Title of the Innovation: Simultaneous Production of US Grade Gasoline and High Purity Benzene from C6 Heart Cut of FCC Gasoline
Brief About Innovation
The MSAT – II regulations which became active on January 1, 2011 (“EPA Regulatory Announcement” – EPA420-F-07-017, February 2007), restricts the average benzene level in Gasoline sold in U.S (except California), to 0.62 % vol. Another driving force behind this technology is the conversion of conventional Naphtha Crackers to Gas Crackers due to availability of low cost feedstocks like shale gas. A light naphtha cracker produces nearly 10 times the amount of Pyrolysis Gasoline – which can be converted into aromatics – than an ethane cracker. This ongoing shift to lighter feedstocks can have a significant negative impact on heavier co-products such as aromatics, with yields cut by as much as 55%.
Currently FCC gasoline comprises nearly 10-20 % of the gasoline pool in a typical refinery. Full range FCC gasoline contains around 15-30 vol. % aromatics with up to 2 vol. % benzene and 1000 – 2000 ppm sulfur. A narrow C6 heart cut fraction of the full range gasoline will contain anywhere between 11 – 19 wt. % benzene and up to 500 ppm sulfur.
Hydro-processing routes for benzene and sulfur reduction in FCC Gasoline results in olefin saturation thus lowering the octane. Unprocessed FCC Gasoline contains reactive impurities like oxygenates, metals, chlorides, sulphur compounds, nitrogen compounds, di-olefins and organic peroxides. Due to the complex nature of this feedstock, an economic and reliable benzene removal/recovery process is difficult to develop and has not been practiced in the industry so far.
The current technology developed by CSIR serves a dual role of recovering high purity benzene and producing environmental friendly gasoline (Bz. < 0.4 wt. %, and < 5 ppm sulfur) from FCC C6 heart cut stream using extractive distillation without the requirement of a prior-hydrogenation or pre-processing step to saturate di-olefins in feedstock and reduce impurities.
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