Prepn. of 2,3-di:di:methyl-1-butene from mixt. of methyl:butene(s) - by isomerisation to 2,3-di:methyl-2-butene, sepn. and reversed isomerisation, opt.on zeolite

摘要

(I) is prepd. from a hydrocarbon mixt. contg. (a) 2,3-dimethyl-1-butene and/or 2,3-dimethyl-2-butene and (b) methylpentene or methylpentenes and/or other 6C olefins with similar b.pt., by (i) treating the mixt. to isomerise any 2,3-dimethyl-1-butene in the mixt. to 2,3-dimethyl-2-butene, (ii) sepg. a prod. contg. conc. 2,3-dimethyl-2-butene, and (iii) carrying out reversed isomerisation of the 2,3-dimethyl-2-butene from step (ii), to 2,3-dimethyl-1-butene. (iv) (I) is recovered from the mixt. from step (iii) by reactive distn. Steps (i) and (iii) may be carried out on a molecular sieve based on Al and SiO2, with pore size above 0.4nm. Steps (iii) and (iv) can be combined by using in the distn. tower a catalyst bed based on a molecular sieve. The hydrocarbon mixt. has been obtd. by dimerisation of propylene. Step (iii) gives an equilibrium mixt. of 2,3-dimethyl-1-butene and 2,3-dimethyl-2-butene, and the process includes the step of recovering the conc. (I) from the equilibrium mixt., esp. by reactive distn.