The present invention provides a process for preparing di- and polyamines from the diphenylmethane series by converting aniline and formaldehyde in the absence of an acid catalyst to give aminal and water, removing the aqueous phase and further processing the organic aminal phase to give the di- and polyamines of the diphenylmethane series, in which use of a coalescence aid in the phase separation of the process product obtained in aminal reaction reduces the proportion of water and hence also of water-soluble impurities in the organic phase containing the aminal. The di- and polyamines of the diphenylmethane series obtained by acid-catalyzed rearrangement and workup after further processing of the aminal phase are outstanding suitably for preparation of the corresponding isocyanates.

The present invention relates to a method for operating a phosgene generator for producing phosgene by reacting carbon monoxide with chlorine in the gas phase on an activated carbon catalyst arranged in a reaction chamber, in which method, after a predefinable operating period, the phosgene production is at least temporarily interrupted by shutting down the phosgene generator over a shutdown period and, after a predefinable downtime, is resumed by starting up the phosgene generator over a start-up period, wherein the method is characterized in that the activated carbon catalyst, before the phosgene generator is started up, is freed of chlorine by adding carbon monoxide so that, during the start-up period, a maximum concentration of chlorine in the gas stream immediately downstream of the reaction chamber of 1000 ppmv is not exceeded. The invention also relates to the use of the phosgene thus obtained in the production of polycarbonate and isocyanates.

The present invention relates to a method for operating a phosgene generator for producing phosgene by reacting carbon monoxide with chlorine in the gas phase on an activated carbon catalyst arranged in a reaction chamber, in which method, after a predefinable operating period, the phosgene production is at least temporarily interrupted by shutting down the phosgene generator over a shutdown period and, after a predefinable downtime, is resumed by starting up the phosgene generator over a start-up period, wherein the method is characterized in that the activated carbon catalyst, before the phosgene generator is started up, is freed of chlorine by adding carbon monoxide so that, during the start-up period, a maximum concentration of chlorine in the gas stream immediately downstream of the reaction chamber of 1000 ppmv is not exceeded. The invention also relates to the use of the phosgene thus obtained in the production of polycarbonate and isocyanates.

The purification method of an aldehyde compound of the present invention includes a step of neutralizing a reaction solution containing an aldehyde compound by adding water and a base compound to the reaction solution, and a step of distilling the neutralized reaction solution, in which the reaction solution is obtained by reacting a compound represented by the following Formula (a1) or (a2) with hydrogen and carbon monoxide in the presence of a metal compound of groups 8 to 10 and a phosphorus compound, the phosphorus compound is represented by Formula (R.sup.1O).sub.3P, and the base compound is at least one kind selected from among carbonate and hydrogen carbonate of metals of group I on the periodic table and carbonate and hydrogen carbonate of metals of group II on the periodic table. ##STR00001##

The purification method of an aldehyde compound of the present invention includes a step of neutralizing a reaction solution containing an aldehyde compound by adding water and a base compound to the reaction solution, and a step of distilling the neutralized reaction solution, in which the reaction solution is obtained by reacting a compound represented by the following Formula (a1) or (a2) with hydrogen and carbon monoxide in the presence of a metal compound of groups 8 to 10 and a phosphorus compound, the phosphorus compound is represented by Formula (R.sup.1O).sub.3P, and the base compound is at least one kind selected from among carbonate and hydrogen carbonate of metals of group I on the periodic table and carbonate and hydrogen carbonate of metals of group II on the periodic table. ##STR00001##

A mutant lysine decarboxylase produced by replacing at least one of the amino acids in SEQ ID NO:4 with another amino acid.

A mutant lysine decarboxylase produced by replacing at least one of the amino acids in SEQ ID NO:4 with another amino acid.

A mutant lysine decarboxylase produced by replacing at least one of the amino acids in SEQ ID NO:4 with another amino acid.

Monoisocyanate impurities are removed from a process stream obtained when solvent is separated from a polyisocyanate product. The monoisocyanates are reacted with amine compounds at specific molar ratios to produce ureas. The ureas can be discarded by burning, landfilling or otherwise. Alternatively the ureas can be recycled back into the polyisocyanate manufacturing process, where they are formed into biuret compounds that can remain with the polyisocyanate product.

Monoisocyanate impurities are removed from a process stream obtained when solvent is separated from a polyisocyanate product. The monoisocyanates are reacted with amine compounds at specific molar ratios to produce ureas. The ureas can be discarded by burning, landfilling or otherwise. Alternatively the ureas can be recycled back into the polyisocyanate manufacturing process, where they are formed into biuret compounds that can remain with the polyisocyanate product.