Abstract: The invention relates to a single cycle process for preparing D,L-methionine from an alkali methioninate solution obtained by alkaline hydrolysis of 5-(2-methylmercaptoethyl)hydantoin, in which the D,L-methionine is obtained by neutralizing the alkali methioninate solution with carbon dioxide at elevated temperature and subsequently crystallizing D,L-methionine in the presence of seed crystals.

Abstract: A process for preparing methionine includes the alkaline hydrolysis of 5-(2-methylmercaptoethyl)-hydantoin (methionine hydantoin) in an aqueous process solution containing alkali metal hydroxide and/or alkali metal carbonate and/or alkali metal hydrogencarbonate. The alkali metal cations in the process solution are potassium and sodium having a K/Na molar ratio range from 99/1 to 20/80.

Abstract: A process for preparing methionine includes the alkaline hydrolysis of 5-(2-methylmercaptoethyl)-hydantoin (methionine hydantoin) in an aqueous process solution containing alkali metal hydroxide and/or alkali metal carbonate and/or alkali metal hydrogencarbonate. The alkali metal cations in the process solution are potassium and sodium having a K/Na molar ratio range from 99/1 to 20/80.

Abstract: This disclosure relates to a process for preparing D,L-methionine by feeding carbon dioxide to an aqueous potassium methioninate solution obtained by hydrolysis of 5-(2-methylmercaptoethyl)hydantoin, in order to precipitate out crude methionine, which is separated off and purified. In this process an aqueous solution of the separated-off crude methionine is purified by recrystallization from a solution containing potassium ions and also a crystallization additive. The crystallization additive is a nonionic or anionic surfactant, or a mixture of different nonionic or anionic surfactants. The recrystallization occurs by introducing a 60 to 110° C.-hot methionine solution into a 35 to 80° C.-warm methionine suspension, a temperature of which is lower than that of the introduced solution, such that the temperature of the methionine suspension being maintained between 35 and 80° C. during the addition. The crystallization additive is a sorbitan fatty acid ester or a mixture of different sorbitan fatty acid esters.

Abstract: This disclosure relates to a process for preparing D,L-methionine by feeding carbon dioxide to an aqueous potassium methioninate solution obtained by hydrolysis of 5-(2-methylmercaptoethyl)hydantoin, in order to precipitate out crude methionine, which is separated off and purified. In this process an aqueous solution of the separated-off crude methionine is purified by recrystallization from a solution containing potassium ions and also a crystallization additive. The crystallization additive is a nonionic or anionic surfactant, or a mixture of different nonionic or anionic surfactants. The recrystallization occurs by introducing a 60 to 110° C.-hot methionine solution into a 35 to 80° C.-warm methionine suspension, a temperature of which is lower than that of the introduced solution, such that the temperature of the methionine suspension being maintained between 35 and 80° C. during the addition. The crystallization additive is a sorbitan fatty acid ester or a mixture of different sorbitan fatty acid esters.

Abstract: The invention relates to a process for the preparation of D,L-methionine, in which carbon dioxide is fed to an aqueous potassium methioninate solution obtained by hydrolysis of 5-(2-methylmercaptoethyl)hydantoin, in order to precipitate out crude methionine, which is separated off and purified, where, for the purposes of purification, an aqueous solution of the separated-off crude methionine is prepared and subjected to a recrystallization, characterized in that the solution from which the recrystallization takes place contains potassium ions and also a crystallization additive, where the crystallization additive is a nonionic or anionic surfactant, or a mixture of different nonionic or anionic surfactants, and that the recrystallization takes place by introducing a 60 to 110° C.-hot methionine solution into a 35 to 80° C.-warm methionine suspension, the temperature of which is lower than that of the introduced solution, the temperature of the methionine suspension being maintained between 35 and 80° C.

Abstract: The invention relates to a process for the preparation of D,L-methionine, in which carbon dioxide is fed to an aqueous potassium methioninate solution obtained by hydrolysis of 5-(2-methylmercaptoethyl)hydantoin, in order to precipitate out crude methionine, which is separated off and purified, where, for the purposes of purification, an aqueous solution of the separated-off crude methionine is prepared and subjected to a recrystallization, characterized in that the solution from which the recrystallization takes place contains potassium ions and also a crystallization additive, where the crystallization additive is a nonionic or anionic surfactant, or a mixture of different nonionic or anionic surfactants, and that the recrystallization takes place by introducing a 60 to 110° C.-hot methionine solution into a 35 to 80° C.-warm methionine suspension, the temperature of which is lower than that of the introduced solution, the temperature of the methionine suspension being maintained between 35 and 80° C.

Abstract: A process for the preparation of &bgr;,&ggr;,&dgr;-unsaturated ketones and/or &agr;,&bgr;,&ggr;,&dgr;-unsaturated ketones by the reaction of an unsaturated alcohol with an enol ether or mixture of enol ethers, with formation of ketals as a by-product, at temperatures of from 50° C. to 200° C., in the presence of an acid catalyst, whereby one or all of the reagents is/are heated to the reaction temperature of from 50° C. to 200° C. before the acid catalyst is added.

Abstract: A process for the preparation of &bgr;,&ggr;,&dgr;-unsaturated ketones and/or &agr;,&bgr;,&ggr;,&dgr;-unsaturated ketones by the reaction of an unsaturated alcohol with an enol ether or mixture of enol ethers, with formation of ketals as a by-product, at temperatures of from 50° C. to 200° C., in the presence of an acid catalyst, whereby one or all of the reagents is/are heated to the reaction temperature of from 50° C. to 200° C. before the acid catalyst is added.

Abstract: A process for the preparation of ketones corresponding to the general Formula I 1

Abstract: Process for the preparation of unsaturated 4,5-allene ketones by reaction of tertiary propargyl alcohols with alkenyl alkyl ethers or ketals in the presence of aliphatic sulfonic acids or sulfonic acid salts.

Abstract: Preparation of 2,3,5-trimethylhydroquinone diesters by rearrangement of 2,6,6-trimethylcyclohex-2-ene-1,4-dione (4-oxo-isophorone, ketoisophorone) in the presence of a solid, acid catalyst and an acylating agent, for example carboxylic acid anhydrides or carboxylic acid halides. The 2,3,5-trimethylhydroquinone diester may then optionally be saponified to the free 2,3,5-trimethylhydroquinone, which is a valuable building block in the synthesis of vitamin E.

Abstract: The invention relates to an improved method for the production of 2,3,5-trimethylhydroquinone by rearranging 4-oxo-isophorone (keto-isophorone, 3,5,5-trimethylcyclohex-2-en[e]-1,4-dione) to a trimethylhydroquinone diester and by its subsequent saponification.