Separation of Meta-, Para-Cresols via Alkylation with Isobutylene

SEPARATION OF META-, PARA-CRESOLS VIA ALKYLATION WITH ISOBUTYLENE 

Butylated hydroxy toluene or BHT is a universally popular antioxidant which used to be made traditionally from pure para-cresol. Last few years, the trend has been to produce BHT by butylation of a mixture of meta-para-creso s. There are two distinct advantages  

In the alkylation process, apart from butylated cresols isobu-tylated homopolymers diisobutylene and triisobutylene are also formed. 

In the above process, usually 2 mol of isobutylene react with each mole of cresol in the presence of acidic catalyst. Dilute H2SO4 is the most popular catalyst for both alkylation and dealkylation process. Some of the plants use p-toluene sulfonic acid or even a mixture of sulfuric acid and p-toluene sulfonic acid. It is reliably learnt that at least one plant has been using some quantities of a very strong Friedel Crafts alkylation catalyst—Triflic acid or trifluoromethane 

In the commercial process, monobutylated cresols are usually recycled to the alkylators and are converted back to dibutylated cresols which are separated into BHT and dibuty-lated meta-cresol which on dealkylation produces pure meta-cresol and isobutylene, which is recycled to the alkylators. 

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