A process for preparing an aromatic isocyanate by direct carbonylation of a nitro aromatic compound by reacting the nitro aromatic compound with carbon monoxide in the presence of a catalyst, characterized in that the catalyst contains a multi metallic material comprising one or more binary intermetallic phases of the general formula A.sub.xB.sub.y wherein: A is one or more element selected from Ni, Ru, Rh, Pd, Ir, Pt and Ag, B is one or more element selected from Sn, Sb, Pb, Zn, Ga, In, Ge and As, x is in the range 0.1-10, y in is in the range 0.1-10.

The disclosure provides, inter alia, safe and environmentally-friendly methods, such as flow chemistry, to synthesize isocyanates, such as methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and tetramethylxylene diisocyanate.

The disclosure provides, inter alia, safe and environmentally-friendly methods, such as flow chemistry, to synthesize isocyanates, such as methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and tetramethylxylene diisocyanate.

A plant for preparing a purified isomeric methylene diphenyl diisocyanate monomer from a mixture of different isomeric monomers is disclosed herein. The plant can comprise a distillation apparatus, which comprises: a) a distillation column including a structured packing, b) a source for a mixture of different isomeric methylene diphenyl diisocyanate monomers, c) an evaporator, d) an overhead vapor condenser, e) optionally, an overhead vacuum system and f) a flow-controlled reflux system. The overhead vapor condenser comprises a shell and tube arrangement and is embodied so as to directly subcool the condensate to less than 47° C. The flow-controlled reflux system comprises a heater, which is embodied so as to reheat a partial stream of the condensate formed in the overhead vapor condenser up to 190° C.

A plant for preparing a purified isomeric methylene diphenyl diisocyanate monomer from a mixture of different isomeric monomers is disclosed herein. The plant can comprise a distillation apparatus, which comprises: a) a distillation column including a structured packing, b) a source for a mixture of different isomeric methylene diphenyl diisocyanate monomers, c) an evaporator, d) an overhead vapor condenser, e) optionally, an overhead vacuum system and f) a flow-controlled reflux system. The overhead vapor condenser comprises a shell and tube arrangement and is embodied so as to directly subcool the condensate to less than 47° C. The flow-controlled reflux system comprises a heater, which is embodied so as to reheat a partial stream of the condensate formed in the overhead vapor condenser up to 190° C.

A plant for preparing a purified isomeric methylene diphenyl diisocyanate monomer from a mixture of different isomeric monomers is disclosed herein. The plant can comprise a distillation apparatus, which comprises: a) a distillation column including a structured packing, b) a source for a mixture of different isomeric methylene diphenyl diisocyanate monomers, c) an evaporator, d) an overhead vapor condenser, e) optionally, an overhead vacuum system and f) a flow-controlled reflux system. The overhead vapor condenser comprises a shell and tube arrangement and is embodied so as to directly subcool the condensate to less than 47° C. The flow-controlled reflux system comprises a heater, which is embodied so as to reheat a partial stream of the condensate formed in the overhead vapor condenser up to 190° C.

The xylylene diisocyanate composition according to exemplary examples includes xylylene diisocyanate (XDI), and an acidity adjusting agent having a boiling point of 110° C. or higher, wherein the composition has an acidity of more than 100 ppm and 1,000 ppm or less based on a total weight of xylylene diisocyanate (XDI). A polymerization reaction rate is controlled through regulation of the acidity so that an optical lens having high transmittance and improved optical uniformity may be manufactured.

The xylylene diisocyanate composition according to exemplary examples includes xylylene diisocyanate (XDI), and an acidity adjusting agent having a boiling point of 110° C. or higher, wherein the composition has an acidity of more than 100 ppm and 1,000 ppm or less based on a total weight of xylylene diisocyanate (XDI). A polymerization reaction rate is controlled through regulation of the acidity so that an optical lens having high transmittance and improved optical uniformity may be manufactured.

The present invention relates to a process for preparing an isocyanate comprising the steps of (A) reacting an amine with a stoichiometric excess of phosgene using an aromatic solvent of formula C.sub.6H.sub.6-XCl.sub.X, wherein X=1 or 2, (a) as a diluent during the reaction and/or (b) as a means for cooling the reaction mixture formed from the reaction of the amine with phosgene (so-called quench) to obtain (optionally after a decompression) a liquid product mixture comprising the isocyanate and the aromatic solvent employed and a gaseous product mixture containing phosgene and hydrogen chloride; followed by (B) isolating the isocyanate from the liquid product mixture obtained in step (A) comprising the step of a final distillation in which the isolated isocyanate is obtained as a product stream, wherein in the final distillation or in a distillation step upstream of the final distillation at least one stream comprising aromatic solvent of formula C.sub.6H.sub.6-YCl.sub.Y, wherein Y=X+1, is (at intervals or continuously) discharged such that the isolated isocyanate has a mass fraction, based on its total mass, of aromatic solvent of formula C.sub.6H.sub.6-YCl.sub.Y in the range from 0.0 ppm to 9.9 ppm, preferably 0.0 ppm to 5.0 ppm, particularly preferably 0.0 ppm to 3.0 ppm.

The present invention relates to a process for preparing an isocyanate comprising the steps of (A) reacting an amine with a stoichiometric excess of phosgene using an aromatic solvent of formula C.sub.6H.sub.6-XCl.sub.X, wherein X=1 or 2, (a) as a diluent during the reaction and/or (b) as a means for cooling the reaction mixture formed from the reaction of the amine with phosgene (so-called quench) to obtain (optionally after a decompression) a liquid product mixture comprising the isocyanate and the aromatic solvent employed and a gaseous product mixture containing phosgene and hydrogen chloride; followed by (B) isolating the isocyanate from the liquid product mixture obtained in step (A) comprising the step of a final distillation in which the isolated isocyanate is obtained as a product stream, wherein in the final distillation or in a distillation step upstream of the final distillation at least one stream comprising aromatic solvent of formula C.sub.6H.sub.6-YCl.sub.Y, wherein Y=X+1, is (at intervals or continuously) discharged such that the isolated isocyanate has a mass fraction, based on its total mass, of aromatic solvent of formula C.sub.6H.sub.6-YCl.sub.Y in the range from 0.0 ppm to 9.9 ppm, preferably 0.0 ppm to 5.0 ppm, particularly preferably 0.0 ppm to 3.0 ppm.