REDUCE BENZENE WHILE ELEVATING OCTANE AND CO-PRODUCING PETROCHEMICALS

摘要

New challenges and opportunities will result from newly imposed regulations of the United States Environmental Protection Agency (U.S. EPA) that control benzene in the U.S. gasoline pool [1]. The new rules are already in the preliminary stages of implementation and will become fully effective in 2011. The current benzene limitation is 1.0 vol% in reformulated gasoline, which comprises about 35% of U.S. market and much of the western European market. Benzene content of regular gasoline averages 1.5 vol% in the U.S. and probably ranges from 2.0 vol% to as high as 5% in other countries outside the U.S., Western Europe and Japan. The majority of the benzene in gasoline, about 60% in the U.S. and about 75% in Europe, results from blending reformate, a high Octane Blending Component (HOBC), obtained by catalytic reforming of C C7-360°F naphtha. Reformate accounts for about 28% of the U.S. gasoline pool and about 44% of the European gasoline pool. The balance of the benzene in the gasoline pool, about 40% in US and 25% in Europe is attributed mostly to FCC gasoline. Small percentages of the benzene are attributed to coker naphtha, hydrocracker naphtha and light straight run gasoline. -As the industry is aware, the new U.S. EPA benzene limit in gasoline of 0.62 vol% became a rule on February 9, 2007. In effect this rule will require benzene saturation, removal or recovery by all U.S. refineries and will likely be followed by Canadian, European and Japanese refineries. This 0.62 vol% benzene limit is already being achieved in California and several other locations by hydrotreating a benzene containing heart cut from catalytic reformate. About 75% of U.S. and worldwide refineries having an estimated 50% of the world’s catalytic reforming capacity are not currently practicing benzene recovery from reformate and will now fall under this category [2]. Where benzene is removed from reformate to meet environmental goals, mostly for CARB gasoline, the benzene concentrate is about 20-25 vol% benzene and balance is C C6- C - C7 non aromatics. This benzene cut, typically 5% of the gasoline pool is hydrotreated, while converting benzene to cyclohexane and methyl-cyclopentane. The hydrotreated concentrate is returned to the gasoline pool but at an octane loss. The proposed concept of this presentation was initially discussed at 2003 spring meeting of NPRA, [2]. Benzene concentrate or dilute benzene is used as a feedstock for steam cracking to produce ethylene, propylene and benzene rich streams for petrochemical operations. This feedstock is very economically competitive with conventional naphtha or condensate feedstocks for steam cracking. The largest benzene derivatives are styrene, about 50-52%, cumene, about 21-23% and cyclohexane about 14-15%.