Patent GB-738157-A (GB)
Title: Improvements in or relating to preparation of acrylic acid and its anhydride
IPC: C07C51/14
Filed: 1952-03-18
Abstract: Acrylic acid and/or its anhydride is obtained by reacting together acetylene, water, and nickel carbonyl in the presence of an acid which will release carbonyl groups from the nickel carbonyl and while these are reacting introducing thereinto and reacting together at between 25 DEG  and 75 DEG  C. acetylene, carbon monoxide, and water, the carbon monoxide supplying not over 67 per cent of the total CO from both carbon monoxide and nickel carbonyl and the acetylene being introduced in an amount such as to provide a proportion of from 0.9 to 1.1 mols. acetylene per mol. of total CO.  In a modification the water is initially present in excess and acetylene and carbon monoxide are added to the reacting mixture.  In one manner of carrying out the process there are mixed in a reaction vessel water and acrylic acid preferably with an inert at least partially water-miscible organic solvent, with or without nickel carbonyl, acetylene and nickel carbonyl are passed into the mixture until the reaction is proceeding and carbon monoxide, water, and additional amounts of acetylene are then admitted.  If the reaction is to be carried out continuously nickel carbonyl is also added and reaction mixture may be withdrawn at a rate equivalent to that at which the added reactants are introduced.  By adjusting the rates of addition and withdrawal, control of the holding time and adjustment of the proportions of the reactants the product can be acrylic acid or acrylic anhydride.  At least 20 mol. per cent of carbon monoxide should preferably be used with reference to the total CO from carbon monoxide and nickel carbonyl.  The reaction is preferably carried out in the presence of a solvent, preferably a water-miscible solvent, e.g. acetone, methyl ethyl ketone, dioxane, methyl b -methoxy-propionate, the dimethyl and diethyl ethers of ethylene glycol and of polyglycols and the acetates of the monomethyl or monoethyl ethers of these glycols.  When acrylic acid is the desired product between 1.05 and 1.5 mols. of water should be used per mol. of total CO whilst if about 0.5 mol. of water is used per mol. of total CO the product is mainly acrylic anhydride.  Instead of using acrylic acid to liberate the carbonyl groups from the nickel carbonyl other acids such as hydrochloric, hydrobromic, acetic, chloroacetic and propionic acid may be used.  As soon as acrylic acid is formed in the reaction the use of another acid is no longer required.  Inert gases such as carbon dioxide, nitrogen or hydrogen may be present during the reaction.  The reaction takes place at normal pressure but increased pressures may be used.  It is preferred to use a small excess of acetylene, e.g. from 1.02 to 1.05 mols. of acetylene per mol. of total CO.  The process may be carried out by charging a reaction vessel with water, solvent (if used), an effective acid, and nickel carbonyl and acetylene is then passed into the charge. When the reaction begins water, nickel carbonyl, and acetylene are passed into the reacting mixture in approximately stoichiometric proportions along with the solvent and when the reaction is established carbon monoxide is also run in and the flow of water, solvent (when used), nickel carbonyl, acetylene, and carbon monoxide adjusted to maintain the reaction.  If the reaction is run batchwise the flow of reactants is discontinued at the appropriate time.  If the reaction is run in a continuous manner reaction mixture is taken from the reactor by overflow, acetylene is passed into the withdrawn mixture to react with the remaining nickel carbonyl.  The reaction mixture is then worked up, e.g. by adding sulphuric acid to form nickel sulphate hexahydrate and acrylic acid from the nickel acrylate and water present.  Solvent, if used, is recovered and sent back to the reactor and nickel is reconverted to nickel carbonyl and re-used. Examples describe a continuous process for the production of acrylic acid together with a small amount of acrylic anhydride using acrylic acid as the acid for liberating carbonyl groups from the nickel carbonyl and using dioxane, and methyl ethyl ketone respectively as the solvent.  In another example for the production of acrylic acid the acid used to liberate carbonyl groups from the nickel carbonyl is acrylic acid, the solvent is acetone and anhydrous hydrogen chloride is fed to the reaction mixture during the course of the reaction whereby the nickel is removed as hydrated nickel chloride.  An example is also given in which methyl ethyl ketone is used as solvent and hydrogen chloride is used as the initial acid for liberating carbonyl groups from the nickel carbonyl, the addition of the hydrogen chloride being discontinued as soon as acrylic acid is formed in the mixture. The product in this case is mainly acrylic anhydride, some acrylic acid being also formed.