Biomass valorization derivatives: Clean esterification of 2-furoic acid using tungstophosphoric acid/zirconia composites as recyclable catalyst

2-Furoic acid esters, which are biomass derived, are used in the flavoring and fragrance industry or as synthesis intermediates in the pharmaceutical industry. A series of zirconia samples modified with different contents of tungstophosphoric acid (TPA) and two different preparation methods (ZrPEGTPA30(T100), ZrPEGTPA60(T100), ZrTPA30PEG(T100), and ZrTPA60PEG(T100)) were synthesized from zirconium propoxide via sol-gel reactions using polyethylene glycol as template. They were characterized by different physicochemical techniques (BET, FT-IR, P-31 MAS NMR and potentiometric titration), and their activities were tested in the synthesis of n-butyl-2-furoate as the model compound, among which ZrTPA30PEG(T100), (mesoporous acid zirconia modified catalyst) was the most active catalyst. The effect of various parameters such as catalyst loading, mole ratio of 2-furoic acid to n-butanol, and temperature was studied under optimized conditions. Several other alkyl 2-furoates were produced from esterification of 2-furoic acid with different alcohols using these catalysts, and the effect of alcohol structure over the conversion reaction was considered. The use of a solid acid catalyst made the procedure environmentally benign. The catalysts ZrPEGTPA30(T100) and ZrTPA30PEG(T100) were reused without appreciable loss of the catalytic activity (three runs). The methodology represents a green and efficient alternative for the conversion of bio-based 2-furoic acid into valuable esters. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.