Patent GB-676353-A (GB)
Title: Improvements in the production of alcohols from olefines
IPC: C07C29/06
Filed: 1947-09-12
Abstract: Alcohols are prepared by direct hydration of olefines with aqueous sulphuric acid by feeding olefines to a hydration bath containing a predetermined initial acid and free alcohol content, allowing the hydration reaction to proceed up to or beyond an alcohol concentration at which the olefine absorption rate is a maximum, withdrawing the resultant acid/alcohol mixture and separating it into two parts, one part with added water being distilled to remove the alcohol therefrom, the acid remaining being added to the other part to form a mixture having the same composition as that of the initial hydration bath and recycling this mixture to said bath.  The process may be carried out by passing the olefine into the hydration bath containing initially A per cent alcohol until the optimum alcohol concentration B per cent corresponding to maximum absorption rate is reached and then dividing up the product as described above and returning the resultant recycle mixture to the hydration zone. Generally, when olefine-containing gases are used the gases and hydration bath are circulated in parallel or counter-flow so that the most active portion of the hydrating solution-alcohol concentration nearest B per cent-is contacted with that portion of the gases least rich in olefines.  Embodiments of this proceedure are described in examples with reference to flow sheets (not shown) whereby tertiary butanol is prepared by selective hydration of isobutylene in a cracking gas containing butane, isobutane, butylene and isobutylene wherein (1) the cracking gas, water for the hydration and a hydration bath containing 10 parts tertiary butanol and 90 parts of 40 per cent sulphuric acid are passed in parallel flow at 50 DEG  C. up a hydration tower, the hydrating liquor issuing from the top and containing substantially the optimum B per cent alcohol is treated as above described whereby an aqueous azeotrope of tertiary butanol is recovered in the distillation and the recycled mixture has the initial composition of the bath; (2) water for the hydration and aqueous 40 per cent sulphuric acid containing 19.5 per tertiary butanol (the optimum concentration B per cent at the reaction temperature employed, viz. room temperature) are passed down a hydration tower counter-currentwise to the cracking gas and the alcohol enriched hydrating solution is withdrawn and worked up as in (1); (3) the cracking gas, water for hydration and 10 per cent tertiary butanol in 50 per cent sulphuric acid are passed up a hydration tower at 50 DEG  C. in parallel flow and the residual olefinic gases and hydration solution now containing the optimum B per cent tertiary butanol are fed from the top of the tower to a second tower where they are reacted counter-currentwise yielding a more enriched hydration bath which is worked up as in (1).  A graph is given showing the variation in the rate of absorbtion of isobutylene in 40 per cent sulphuric acid containing varying amounts of tertiary butanol at 50 DEG  C.  The Specification as open to inspection under Sect. 91, relates to the direct hydration of olefines by means of a hydration bath initially containing an amount of alcohol to speed up the reaction and is not restricted to subdivision of the resulting bath into the two parts described above at the stage at or beyond which the alcohol concentration is at the optimum value.  This subject-matter does not appear in the Specification as accepted.