Patent GB-617090-A (GB)
Title: Improvements in the production of butadiene
IPC: C07C1/247
Filed: 1946-03-18
Abstract: In the production of butadiene by thermal dehydration of tetramethylene oxide in the vapour phase (see Group IV), a catalyst mixture of an alkali metal phosphate, an alkaline earth p  metal phosphate and phosphoric acid or a catalyst mixture of mono - calcium phosphate and mono-sodium phosphate, together with smaller proportions by weight of both phosphoric acid and butylamine phosphate is employed.  In an example, the catalyst is prepared by making a mixture of mono-calcium phosphate, mono - sodium phosphate, butylamine phosphate, and phosphoric acid into a paste with water, drying the paste, baking at 500 DEG  to 600 DEG  F. and then breaking up the solid cake into small pieces.  French Specification 844,893 is referred to.  The Specification as open to inspection under Sect. 91 defines the catalyst as one comprising an alkali metal phosphate and an alkaline earth metal phosphate together with phosphoric acid and/or a substance yielding phosphoric acid under the conditions of thermal dehydration and refers also to the use of a catalyst containing an alkali metal phosphate, an alkaline earth metal phosphate, phosphoric acid and butylamine phosphate.  This subject-matter does not appear in the Specification as accepted.ALSO:Butadiene is obtained by subjecting tetramethylene oxide to thermal dehydration in the vapour phase in the presence of a catalyst mixture of an alkali metal phosphate, an alkaline earth metal phosphate and phosphoric acid or in the presence of a catalyst mixture of mono-calcium phosphate and mono-sodium phosphate together with smaller proportions by weight of both p  phosphoric acid and butylamine phosphate.  It is preferred to admix the tetramethylene oxide with water vapour, thus 0.1 to 9 parts by weight of water may be used for each part by weight of tetramethylene oxide.  The dehydration may be effected at 200 DEG  to 800 DEG  F. and preferably at 450 DEG  to 485 DEG  F. and atmospheric, sub-atmospheric or super-atmospheric pressure, e.g. 15 to 200 lbs. per square inch may be employed.  In an example, a catalyst is prepared by mixing mono-calcium phosphate, mono-sodium phosphate, butylamine phosphate and phosphoric acid into a paste with water. The paste is dried and baked at 500 DEG  to 600 DEG  F. and the solid cake obtained is broken up into small pieces for charging into a reaction tube.  A mixture of tetramethylene oxide and water is vaporized in a preheater maintained at 460 DEG  F. and the vapours then passed into a stainless steel reaction tube containing the catalyst and maintained at a slightly higher temperature.  The products are passed through a liquid trap, a water-cooled condenser, an ice-trap to condense unchanged tetramethylene-oxide which may be recycled and then a trap cooled with a mixture of solid carbon dioxide and acetone to condense the butadiene formed. French Specification 844,893 is referred to. The Specification as open to inspection under Sect. 91 defines the catalyst as one comprising an alkali metal phosphate and an alkaline earth metal phosphate together with phosphoric acid and/or a substance yielding phosphoric acid under the reaction conditions and refers also to the use of a catalyst containing an alkali metal phosphate, an alkaline earth metal phosphate, phosphoric acid and butylamine phosphate.  This subject-matter does not appear in the Specification as accepted.