GB1301019A - A process for the hydrogenation of pyrolysis gasoline - Google Patents

Abstract

1301019 Hydrogenation of pyrolysis gasoline SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ NV 2 March 1970 [3 March 1969] 9894/70 Heading C5E Pyrolysis gasoline, from the steam cracking of naphtha to produce ethylene and/or propylene, is selectively hydrogenated at 3 in the liquid phase to convert diolefins to monoolefins and a fraction 7 of the hydrogenated product having an initial boiling point below 80‹ C. is separated at 5, heated to a temperature not exceeding 250‹ C. at a pressure of 20-80 kg./ cm.<SP>2</SP> and hydrogenated at 9 over a sulphidic molybdenum and alumina-containing catalyst at a reaction temperature below 320‹ C. under conditions such that the stream 7 passes into the first part of the catalyst bed as a liquid and the stream is fully evaporated at a point between “ and ¥ of the height of the catalyst bed. The selective hydrogenation at 3 can be carried out at 20-50 kg./cm.<SP>2</SP> and below 160‹ C. using a sulphided catalyst, e.g. containing 5-25% nickel on alumina and/or silica. The catalyst used in the hydrogenation at 9 can comprise 3-25% molybdenum and 1-10% of W, Re, Co and/or Ni. The effluent 10 from the second hydrogenation can be subjected to a third hydrogenation at 320-375‹ C. using a desulphurization catalyst such as a sulphidic molybdenum-containing catalyst on an alumina carrier and which can also contain cobalt at a space velocity between 2 and 10. The stream 13, from which hydrogen, hydrogen sulphide have been removed at 11 and recycled to reactor 9, is separated into an aromatic rich extract phase 16 and an aromatic-poor raffinate 15 by extractive distillation at 14. The aromatic extract is separated by fractional distillation into a benzene stream 18, a toluene stream 21, a mixture of xylenes and ethyl benzene 24 and a stream 27 boiling between 170‹ and 220‹ C. In another embodiment the stream 13 can be separated into a fraction boiling above 150‹ C. and a fraction boiling below 150‹ C. which is passed to the extractive distillation unit. Suitable extractive solvents are diethylene glycol, dipropylene glycol, phenol, sulphur dioxide, N-methyl pyrrolidone, sulpholane, dimethylsulphoxide and acetonitrile and can contain up to 10% of water. Sulphur compounds, such as hydrogen sulphide, carbon disulphide, mercaptans, and dialkyl sulphides can be added to the hydrogen and gasoline feed to the second hydrogenation if the gasoline fraction from the first hydrogenation contains less than 100 p.p.m. in sulphur. The raffinate 15 can be passed to a catalytic reforming plant or recycled to the ethylene cracker. The stream 27 can be hydrogenated with a Pt or Ni catalyst to remove any aromatic compounds therein and blended with aviation gasoline or kerosine.