Process for the preparation of a triaryl phosphate ester composition

A process for the preparation of a composition comprising a triphenyl and (C1-C15-alkyl) substituted triphenyl phosphate ester, the process comprising:

• a. reacting a phosphorous oxyhalide with a (C1-C15-alkyl)phenol to obtain a first product;
• and
• b. reacting the first product with phenol to obtain a triphenyl and (C1-C15-alkyl) substituted triphenyl phosphate ester composition;
• wherein,
• in step a, for every mol of phosphorous oxyhalide 1.3 to 1.6 mols of (C1-C15-alkyl)phenol are used,
• in step b, the amount of phenol required is determined by analyzing chloride anion concentration of the reaction mixture,
• steps a and b are catalyzed by a Lewis acid, and
• the phosphorous oxyhalide of step a is phosphorous oxychloride (POCl3).