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.

The invention relates to a process for preparing a diisocyanate of the formula (A)

##STR00001## where R is selected from the group consisting of alkyl, aryl, and combinations thereof, comprising the following process steps in the indicated order; 1) providing an intermediate of the formula (B) with a process using lysine and urea

##STR00002##

and  where R and each R′ are independently selected from the group consisting of alkyl, aryl, and combinations thereof; and 2) thermolytic cleavage of the intermediate of the formula (B), thereby affording the diisocyanate of the formula (A),
and also to the diisocyanate directly prepared therewith.

The invention relates to a process for preparing a diisocyanate of the formula (A)

##STR00001## where R is selected from the group consisting of alkyl, aryl, and combinations thereof, comprising the following process steps in the indicated order; 1) providing an intermediate of the formula (B) with a process using lysine and urea

##STR00002##

and  where R and each R′ are independently selected from the group consisting of alkyl, aryl, and combinations thereof; and 2) thermolytic cleavage of the intermediate of the formula (B), thereby affording the diisocyanate of the formula (A),
and also to the diisocyanate directly prepared therewith.

The method for producing pentamethylene diisocyanate includes a reaction step, in which carbonyl chloride is allowed to react with pentamethylenediamine to produce a reaction mixture containing pentamethylene diisocyanate and a tar component containing a chlorine-containing component; a heating step, in which the reaction mixture is heated; and a purification step, in which the reaction mixture after the heating step is purified to separate the pentamethylene diisocyanate from the tar component, wherein in the heating step, the reaction mixture is heated without removing the tar component from the reaction mixture.

The method for producing pentamethylene diisocyanate includes a reaction step, in which carbonyl chloride is allowed to react with pentamethylenediamine to produce a reaction mixture containing pentamethylene diisocyanate and a tar component containing a chlorine-containing component; a heating step, in which the reaction mixture is heated; and a purification step, in which the reaction mixture after the heating step is purified to separate the pentamethylene diisocyanate from the tar component, wherein in the heating step, the reaction mixture is heated without removing the tar component from the reaction mixture.

Disclosed is a method for separating, with a multi-stage distillation column, a mixture containing an active hydrogen-containing compound (A) and a compound (B) that reversibly reacts with the active hydrogen containing compound (A), the method comprising distillation-separating the active hydrogen-containing compound (A) and the compound (B) with the multi-stage distillation column in the presence of an intermediate-boiling-point inactive compound (C) that has a normal boiling point between a normal boiling point of the active hydrogen-containing compound (A) and a normal boiling point of the compound (B) and is chemically inactive for both of the (A) and the compound (B).

Disclosed is a method for separating, with a multi-stage distillation column, a mixture containing an active hydrogen-containing compound (A) and a compound (B) that reversibly reacts with the active hydrogen containing compound (A), the method comprising distillation-separating the active hydrogen-containing compound (A) and the compound (B) with the multi-stage distillation column in the presence of an intermediate-boiling-point inactive compound (C) that has a normal boiling point between a normal boiling point of the active hydrogen-containing compound (A) and a normal boiling point of the compound (B) and is chemically inactive for both of the (A) and the compound (B).

The present invention relates to a process for thermally separating a mixture comprising a first main component and a second main component, where the boiling point of the first main component is lower than the boiling point of the second main components. The invention further relates to a system for thermal separation comprising a computer for control of the thermal separation which is set up to control the process of the invention. By means of predetermined thermodynamic models, pressure and temperature data are used to ascertain the proportions of first and second main component in bottom product streams.