Xylitol and gluconic acid productions via photocatalytic-glucose conversion using TiO2 fabricated by surfactant-assisted techniques: Effects of structural and textural properties

Abstract

High-value chemicals can be converted from biomass and its derivatives by various methods. In this work, gluconic acid was obtained from photocatalytic conversion of glucose with synthesized TiO2. Moreover, another high-value chemical, xylitol, was firstly found from the photocatalysis in this work. Arabinose and formic acid are other co-products obtained from the reactions. Two surfactants, polyethylene glycol (PEG) and cetyltrimethylammonium bromide (CTAB), were used in conventional sol-gel (SG), ultrasonication sol-gel (US), and hydrothermal (HD) methods to fabricate TiO2 with different structural and textural properties. Appropriate surface area and phase composition of TiO2 for production of the highest yields of gluconic acid and xylitol were investigated. It was found that all surfactant-assisted fabrications increased surface area and anatase content of TiO2 photocatalysts, resulting in high glucose conversion and high yields of xylitol, arabinose and formic acid. The highest yield of xylitol (6.45%) was obtained from US/CTAB-TiO2. Unfortunately, the yield of gluconic acid did not increase by increasing time, because it was also decomposed during photocatalysis. The moderate photocatalysis was found from SG/PEG-TiO2 (100% anatase, surface area 5.93 m2/g) that provided the highest yield of gluconic acid (7.6%) in 120 min.