Patent GB-684096-A (GB)
Title: Improvements in or relating to the production of mercaptans and of olefins therefrom
IPC: C07C7/17
Filed: 1949-07-18
Abstract: Mercaptans are prepared from hydrogen sulphide and olefines by introducing hydrogen sulphide into an intimate mixture of olefine in liquid state and an alkane sulphonic acid as catalyst at a conversion temperature of 0 DEG  to 60 DEG  C. in the case of tertiary olefines and 60 DEG  to 120 DEG  C. in the case of primary and secondary olefines.  The non-tertiary olefines yield thioethers as well as secondary mercaptans.  The difference in the conversion temperatures enables a mixture of tertiary olefines with other olefines of similar boiling point to be separated by reacting the mixture with hydrogen sulphide in presence of the catalyst at the lower conversion temperatures whereby tertiary mercaptans are formed and primary and secondary olefines present are unchanged. The reaction yielding tertiary mercaptans is reversed at temperatures of 80 DEG  C. upwards and accordingly tertiary mercaptans may be converted into tertiary olefines by intimately mixed the mercaptans with alkane sulphonic acid catalyst while heating at 110-140 DEG  C.  The reverse reaction enables the above separated tertiary mercaptans to be reconverted to the original tertiary olefines.  The reversability of the reaction in the case of tertiary olefines may be utilized in the recovery of hydrogen sulphide from fluid streams, in which event the olefine would be used in excess.  The reaction of olefine and hydrogen sulphide may be effected at pressures up to about 50 lbs./sq. inch. Preferred olefinic reactants are tertiary olefines containing 12-18 carbon atoms; they may be the by-products obtained in isobutylene polymerizations wherein for example the olefines of a C4 refinery stream are catalytically polymerized with phosphoric acid catalyst and in addition to iso-octene, C12-18 olefines are obtained, or they may be formed by the polymerization of isobutylene using e.g. aluminium chloride.  The olefinic reactant may be pretreated, e.g. with sulphuric acid or activated clays to remove impurities such as diolefines and peroxide.  An amount of catalyst equal to 5-25 weight per cent of the total hydrocarbon charge may be used.  The alkane sulphonic acids may be prepared as described in Specification 645,268.  When spent, they may be regenerated by blowing an inert gas, e.g. air, through the catalyst at a temperature of about 100-140 DEG  C. or by adding water, removing a resulting oil phase and then heating the catalyst at the above temperature under reduced pressure. A process described with reference to a flow sheet (not shown) comprises passing hydrogen sulphide, obtained as a by-product stream from a petrol refinery, into a vigorously stirred mixture of C12-18 olefinic polymer, containing preferably at least 50 per cent tertiary olefines, and alkane sulphonic acid and after conversion settling out a layer of catalyst which is removed for regeneration and washing the mercaptan layer with aqueous alkali and distilling to recover mercaptan from unreacted hydrocarbons. Reference is also made to the production of a tertiary mercaptan by passing hydrogen sulphide through a mixture of isobutylene trimer and alkane sulphonic acid catalyst at 30 DEG  C. and the yield is compared with those resulting when the catalyst is sulphuric acid and phosphoric acid.  In other examples, hydrogen sulphide is reacted with tetradecene-1 at 100 DEG C. in presence of ethane-sulphonic acid yielding tetradecyl mercaptan-2 and di-sec.-tetradecyl thioether; tert.-dodecyl mercaptan is refluxed at about 130 DEG  C. in presence of the same catalyst with substantial conversion to the olefine.  Di-isobutene is also mentioned as a reactant and further examples of catalysts are the sulphonic acids of methane, propane, isopropane and n-butane.  The Specification as open to inspection under Sect. 91 is not restricted to the particular conversion temperatures mentioned above.  This subject-matter does not appear in the Specification as accepted.ALSO:Hydrogen sulphide and tertiary olefines are obtained from tertiary mercaptans by intimately mixing the mercaptan with a catalytic amount of alkane sulphonic acid catalyst while heating at a temperature in the range of 110 DEG C-140 DEG C.  This reaction is reversible at temperatures below about 80 DEG C, (see Group IV(b)), and accordingly hydrogen sulphide may be recovered from H2S-containing fluid-especially gaseous-streams by intimately mixing it with tertiary olefine in the liquid phase in the presence of an alkane-sulphonic acid catalyst at 0 DEG -60 DEG C whereby the H2S is converted into the tertiary mercaptan and then decomposing the latter as above described.