(621c) Towards the Potential Coupling of Microbial Biosynthesis and Heterogeneous Catalysis for the Petroleum-Free Production of Alkylated Phenol Compounds

Amongst variegated alkylation reactions, the tert-butylation of phenol is one of particular importance to industry [1]. It has been estimated that 450,000 tonnes of tert-butyl phenols (TBP) are manufactured annually for production of innumerable chemical commodities [3]. The ortho mono-alkylated product serves a role in pesticides and fragrances; the para counterpart functions as a flavoring agent and petroleum additive, among other compounds. As for the di-alkylated products, 2,4-TBP is utilized in ultraviolet absorbers in polyolefins and PVC stabilizers, while antioxidants and pharmaceutical products make use of 2,6-TBP [2].

In the present study, petroleum-free production of alkylated phenolic compounds from glycerol was achieved by streamlined coupling of microbial biosynthesis and heterogeneous catalysis with the aim to advance biomass conversion to industrially relevant chemical products. First, bacterium E. coli was metabolically engineered to convert glycerol to phenol under mild conditions, followed by extraction of phenol from the cell culture using select polymeric resins. Desorption of phenol was achieved by washing with tertiary butyl alcohol (TBA), which serves also as a reactant in the subsequent tert-butylation reaction. The adopted polymeric resins were also evaluated as potential downstream catalysts for the production of tert-butyl phenolic products.

Catalytic activity was evaluated in batch mode at industrially relevant conditions, i.e. low temperature and pressure. Amberlyst ® 15 exhibited low to moderate phenol adsorption capacity but very promising reactivity. Achieving full conversion at 120°C within 4 h, Amberlyst ® 15 obtained over 90% selectivity to mono-alkylated products. Furthermore, full regeneration was accomplished thrice by simply washing with ethanol, highlighting the promise of Amberlyst ® 15 as a heterogeneous catalyst. The holistic approach developed by this study offers a unique opportunity to synthesize end-products directly from glycerol that cannot be achieved in such an efficient manner by using microbial biosynthesis or heterogeneous catalysis approaches alone.