Patent GB-609825-A (GB)
Title: The production of styrenes and other aromatic compounds
IPC: C07C4/00
Filed: 1945-11-22
Abstract: A catalyst comprising a silicate of titanium, zirconium, hafnium or thorium used in a process for decomposing asymmetric di-aryl substituted paraffins into two aromatic compounds (see Group IV (b)) may be made by precipitating the metal in oxide or hydroxide form on to a silica hydrogel or by co-precipitating the metal oxide or hydroxide along with a silica hydrogel.  The resulting silicates are washed, dried and preferably calcined at 150 DEG -500 DEG  C.  In examples: (1) hydrochloric acid is added to a solution of sodium silicate in distilled water and concentrated ammonium hydroxide then added.  The precipitated silica hydrogel is filtered off and suspended in distilled water, a solution of zirconium sodium sulphate in distilled water added and the mixture agitated.  Aqueous ammonium hydroxide solution is then added to a pH of about 8 and the zirconium silicate is filtered off, washed and dried at 170 DEG  C.; (2) hydrochloric acid is added to a solution of sodium meta-silicate in distilled water and aqueous ammonium hydroxide solution added to a pH of about 7.  The solution is made slightly acid with hydrochloric acid and the silicic acid precipitated is filtered off, washed, suspended in distilled water and a solution of titanium chloride in distilled water added with agitation of the mixture.  The pH is then adjusted to about 8 by adding aqueous ammonium hydroxide solution. The precipitated titanium silicate is filtered off, washed and dried at 175 DEG  C.  Cerium or other rare earth elements may be included in the catalysts.  Specification 569,465, [Group IV], is referred to. Reference has been directed by the Comptroller to Specifications 592,867 and 598,069, [both in Group IV].ALSO:Styrenes and other aromatic compounds are obtained by contacting a paraffin having at least two carbon atoms in the paraffin chain, or a nuclear substituted derivative thereof, at a temperature of at least 350 DEG C. with a catalyst comprising a silicate of titanium, zirconium, hafnium or thorium.  Specified starting materials are 1,1-diphenyl ethane, each of the 1 - phenyl - 1 - tolyl-; 1,1 - ditolyl-; 1 - phenyl - 1 - xylyl-; 1 - tolyl - 1 - xylyl - and 1,1 - dixylyl - ethanes; 1,1 - diphenyl propane; each of the 1-phenyl-1-tolyl-; 1,1-ditolyl; 1-tolyl-1-xylyl-; 2,2 - di - cresyl- and 2,2 - ditolyl propanes, each of the 1,1 - di - (mono- [or di-] chlorphenyl)-, 1,1 - di - (monohydroxy - phenyl)-, 1,1 - dicresyl-, 1,1 - dinaphthyl-, 1,1-dixenyl- and 1 - tolyl - 1-naphthyl-ethanes and their nuclear substituted halogen and hydroxyl derivatives.  It is desirable to employ an inert diluent, e.g. water vapour, hydrocarbons, e.g. benzene and toluene, and the fixed gases, e.g. nitrogen and carbon dioxide. Elevated or reduced pressure may be employed.  Cerium or any rare earth element may be included in the catalyst.  The silicates are prepared (see Group III) by precipitating the metal in oxide or hydroxide form on to a silica hydrogel or by co-precipitating the oxide or hydroxide along with a silica hydrogel.  The resulting silicates are washed, dried and calcined.  The catalysts are generally employed in pellet form and binders, e.g. sodium silicate, or supports, e.g. silicon carbide, non-porous aluminium oxide or highly fired ceramic materials may be used.  The catalyst is reactivated by passing heated air preferably mixed with steam or carbon dioxide through it at about 590 DEG  to 650 DEG  C.  The contact time with the catalyst calculated on the assumption that the catalyst contains 50 per cent voids and neglecting the pressure drop through the catalyst and the increase in volume occurring during the reaction is preferably between 0.004 second and 0.4 second and it is desirable to convert only a small percentage of the diaryl paraffin in one pass and recirculate it to obtain a high yield.  In examples: (1) a vaporous mixture of 1,1-di-(m-xylyl) ethane and water is passed through a tube packed with zirconium silicate at 500 DEG  C., the condensate is distilled under vacuum to yield a light oil which on fractionation in the presence of a polymerization inhibitor yields 2,4-dimethyl styrene, pure m-xylene and 1,3-dimethyl-4-ethyl benzene; (2) 1,1-di-p-tolyl ethane and steam (both preheated to 500 DEG  C.) are passed over titanium silicate heated to about 500 DEG  C., the products separated as in (1) consist of p-methyl styrene, toluene and ethyl toluene.  Specification 569,465 is referred to.  Reference has been directed by the Comptroller to Specifications 592,867 and 598,069.