Production of Meta-Cresol

Since meto-cresol and para-cresol have more or less identical boiling points, it has not been possible as yet to recover meto-cresol from a mixture of m-p-cresols. It has already been discussed in detail that only commercial method so far employed has been to convert a mixture of m-p-cresols to BHT and pure meta-cresol by alkylating the mixture with isobutylene and thereafter dealkylating butylated meta-cresol to pure meta-cresol. This remains even today the most attractive commercial method for production of pure meto-cresol. However, the disadvantage is that this process produces pure BHT as the main product and therefore commercial feasibility of production of the co-product meta-cresol would be dictated by the demand of BHT. 

One popular commercial process for production of meto-cresol has heen via partial demethanization of isophorone, which is briefly discussed here. 

Isophorone (3,5,5-trimethyl-2-cyclohexene-l-one or 1,1,3-trimethyl-cyclohexene-3-one-5) has the following properties  

It has a light yellow color and a disagreeable camphoraceous odor. It is completely miscible with organic solvent and is only sparingly soluble in water. 

Isophorone usually contains 2-5% of the isomer j6-isophorone CAS No. [471-01-2] also known as 3,5,5-trimethyl-3-cyclohexene-l-one. 

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In USA, Union Carbide used to be the sole producer of isophorone. However, Hiils Germany has been by far the largest isophorone producer in the world. They have reportedly a capacity of 45,000 tpa. Atochem, France, SPA-SISAS, Italy and British Petroleum, England collectively produce 25,000 tpa of isophorone. Union Carbide used to produce isophorone at their Institute, W. Virginia plant. Dow Chemicals have since taken over the facilities of Union Carbide. Isophorone would continue to be an attractive and alternative feedstock for production of meta-cresol and 3,5-xylenol since acetone availability would not pose any problem. 

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