Two-step Process for Etherification of Phenolic-oil with Methanol under Catalysis of Alumina-Supported Metal Salts

A novel two-step process for etherification of phenolic-oil is put forward, to avoid the hindering effect of alkoxyphenols to the etherification of alkylphenols. In the first step, the phenolic-oil with both of alkylphenols and alkoxyphenols is to be converted to primary product rich in alkylphenols. In the second step, the primary product oil is further converted to arylethers-enriched oil by etherification of alkylphenols with methanol. For the first step, Na2SO3/Al2O3 is found to be the best catalyst among 7 tested alumina-supported metal salts and the reaction conditions are optimized as 500oC with GHSV of 1944 h-1, under which alkoxyphenols almost completely disappeared and the content of alkylphenols reaches up to 70.07%. For the second step with catalyst of KH2PO4/Al2O3, high content of arylethers (62.87%) is obtained in product oil under the optimized conditions of 450oC with GHSV of 1819 h-1. Characterization of the catalysts shows that Na5AlO4 is generated in the catalyst of Na2SO3/Al2O3 after calcination at 700oC for 8 h, and Na5AlO4 is verified as the essential substance in promoting the selective conversion of alkoxyphenols to alkylphenols. Stronger acid site favors the conversion of alkoxyphenols to alkylphenols, while the acid site in weaker acidity is more beneficial to the etherification of alkylphenols, and the catalysts with transition metal like Fe and Co are more promotive to the reaction of hydrodeoxygenation.