New process for prevention of premature polymerisation of styrene during its production by dehydrogenation of ethyl:benzene

摘要

A process for the prevention of premature polymerisation of styrene monomer during its production by the dehydrogenation of ethylbenzene into styrene. The process comprises: (a) passing a supply current of ethylbenzene over a dehydrogenation catalyst in a reactor, to form a current of styrene; (b) removing an exhaust effluent containing by-products consisting of H2, ethylbenzene vapour, styrene vapour, benzene, toluene, CO, CO2 and water vapour from the reactor; (c) injecting a styrene polymerisation inhibitor; and (d) compressing the exhaust effluent for the ultimate treatment stages, the gases containing no more than a trace of polystyrene. Also claimed is the system and sub-systems for the production of styrene monomer. Preferably the polymerisation inhibitor is a radical chain terminator type, of the class of sterically hindered amines. It is chosen from the following derivatives of 1-oxyl-2,2,6,6,-tetramethylpiperidine-4-yl :- -the acetate, 2-ethylhexanoate, stearate, benzoate and 4-tert-butylbenzoate; and from the bis(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl derivatives: succinate, adipate, sebacate, n-butylmalonate, phthalate, isophthalate, terephthalate and hexahydroterephthalate; and also -N, N<1>-bis(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)-adipamide, N-(1-oxyl-2,2,6,6-tetramethyl-piperidine-4-yl)caprolactam, N-(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)dodecylsuccinimide, 2,4,6-trisN-butyl-N-(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl)-s-tria zine, and 4,4<1>-ethylenebis(1-oxyl-2,2,6,6-tetramethylpiperazine-3-one). The more preferred inhibitor is the sebacate of bis(1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl).