Direct Catalytic Conversion Of Cellulose Into Formic Acid By Supported Phosphotungstic Acid Catalyst

This study aims to prepare phosphotungstic acid supported on hydrotalcite (PTA-HT) for one-pot hydrothermal cellulose conversion into formic acid (FA). In this study, different percentages of PTA on HT (1, 5, 10, 15, 20, 25, and 33%) were prepared and the catalytic activity was observed for two different parameters such as time (1 to 5 hours) and reaction temperature (160 to 240 °C). The prepared catalysts were characterized using Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), Brunauer-Emmet-Teller (BET) and field emission scanning electron microscopy-energy dispersive X-ray spectrometry (FESEM-EDX), while the production of FA was determined using ultra high-performance liquid chromatography (UHPLC). To avoid bias, raw PTA and calcined HT were compared with varying percentages of supported PTA. PTA-HT was successfully prepared through the impregnation method as confirmed by XRD, FTIR, BET and FESEM-EDX. According to the results, the optimum condition for cellulose conversion into formic acid was when 25% PTA-HT was applied at 220 °C for 4 hours, with a 30% cellulose conversion and 18 % FA yield. Due to the acidity and redox properties of PTA, it has been demonstrated that PTA-HT increased the catalytic activity by two-fold when compared to calcined HT alone (8%). The significance of this finding opens new suggestion of bifunctional catalyst in cellulose conversion into FA.