Patent GB-747493-A (GB)
Title: Improved oxo aldehyde synthesis
IPC: C07C11/08
Filed: 1953-04-02
Abstract: Aldehydes are prepared by a carbonylation process from a mono-olefinic feed-stock containing a minor proportion of polyolefines inhibiting carbonylation of the feed-stock, which comprises treating the feed-stock in a hydrogenation zone with a hydrogen gas containing carbon monoxide in the presence of a non-carbonyl forming hydrogenation catalyst at elevated temperatures and pressures whereby the polyolefines contained in the feed-stock are substantially converted to mono-olefines and passing the hydrogen-treated feed-stock to a carbonylation zone wherein the treated feedstock is reacted with carbon monoxide and hydrogen at elevated temperature and pressure in the presence of a carbonylation catalyst to form aldehydes containing at least one more carbon atom than the mono-olefines in the treated feed-stock; the aldehydes may then be hydrogenated to alcohols.  The pretreatment of the feed-stock results in reduction of the carbonylation inhibition and reaction times, increased yield of aldehydes of improved colour and elimination of resin-forming bodies.  Feedstocks which may be treated include olefine fractions, especially the C6-18 fractions, obtained by thermally cracking wax, cracked petrolatum fractions, butene fractions containing butadienes and the liquid stream from the lowpressure cracking of gas oil.  The preferred pretreatment catalysts are the sulphide type of hydrogenation catalysts, e.g. molybdenum sulphide on active carbon and tungsten sulphide; platinum and palladium are also mentioned.  Suitably, the catalyst is contacted with the feed-stock in the liquid or vapour phase at 200 DEG  to 500 DEG  F. and at pressures up to the aldehyde synthesis pressures of 2500 to 3500 p.s.i.g. in the presence of a hydrogen-carbon monoxide mixture, which is preferably the carbonylation synthesis gas or hydrogen-fortified synthesis gas. The carbonylation is preferably carried out at about 350 DEG  to 450 DEG F. under pressures of about 2500 to 3500 p.s.i.g., using a synthesis gas containing H2 and CO in equal volumes, the catalyst being preferably in the form of a fatty acid salt, e.g. of stearic, palmitic, oleic or naphthenic acid such as the cobalt salt, though cobalt carbonyl, cobalt oxide, cobalt carbonate, cobalt acetate or formate or aqueous solutions containing the cobalt carbonyl anion are also suitable.  The hydrogenation of the aldehydes to alcohols is effected at temperatures between 150 DEG  and 550 DEG  F. under pressures of about 1500 to 4500 p.s.i.g. with such catalysts as metallic nickel or cobalt, tungsten, molybdenum and nickel sulphides and copper chromite.  A process described with reference to apparatus (not shown) comprises feeding synthesis gas and olefinic feed-stock having, say, 2 to 25 per cent of polyolefinic compounds into a hydrogenation reactor under synthesis temperature and pressure using molybdenum sulphide catalyst, the residence time being sufficient to reduce the polyolefine content of the feed to below inhibiting proportions; the reaction mixture is then fed to a gas-liquid separator from which the liquid passes to an oxo reactor while part of the gas is recycled to the hydrogenator and the remainder with more synthesis gas passes to the oxo reactor which contains a cobalt catalyst. The synthesis product is fed to a decobalting zone where it is treated in various specified ways for removal of cobalt and thereafter the aldehydes are converted into alcohols.  If desired, the hydrogenation pretreatment and carbonylation may be effected in the one vessel, the pretreatment catalyst and feedstock being supplied to the bottom of the reactor and cobalt catalyst introduced downstream in the direction of flow, all the synthesis gas being fed in at the bottom or part being fed at the bottom and the remainder introduced downstream.  An example describes the carbonylation of an olefinic naphtha, obtained by steam cracking and clay treating, and shows the reduction of the inhibition period when the feed-stock is pretreated as above described.  Experiments are also described showing the inhibiting effects of (1) polyolefines in a crude C7-8 olefine fraction; and (2) 2-methyl-1:3-pentadiene in a heptene fraction obtained by copolymerization of propylene and butylene, in conventional carbonylations.  Specification 684,958 is referred to.