Optimization of furfural selectivity from xylose using titanium niobium mixed oxide catalysts via statistical response surface methodology

This study examines factors influencing the dehydration of xylose to furfural in the toluene-water biphasic system using titanium-niobium mixed oxide catalyst materials synthesized via a sol–gel method. The influence of reaction time (30–180 min), temperature (30–180 °C), catalyst dosage (0–3.4 wt%), and xylose concentration (3.4–6.8 wt%) on the optimization of furfural (FUR) yield and selectivity was studied in a batch model using multivariate experimental design approach. The quadratic models obtained by response surface methodology with central composite design (RSM–CCD) gave precise predictions of the effects of parameters (reaction time, temperature, catalyst dosage, and xylose concentration) on optimal FUR yield and selectivity. The highest coefficient of correlation of 0.9994, 0.9990, and 0.7877 were obtained for furfural yield, selectivity, and xylose conversion responses, respectively. The analysis of variance (ANOVA) test revealed that the models were statistically significant with a p-value < 0.0001. The optimum operating conditions obtained were 180 min reaction time, 180 °C reaction temperature, 6.8 wt% xylose loading, and 3.4 wt% catalyst dosage, resulting in maximum furfural yield, selectivity, and xylose conversion of 52.43, 57.43 and 91.09%, respectively, with a desirability of 1.000. Results revealed that catalyst loading, xylose concentration, reaction time, and temperature significantly impact furfural yield and selectivity. The activation energy obtained for this study was 91.4 ± 0.9 kJ·mol⁻1 (95% CI). The catalyst could be regenerated by calcination between cycles and tested over five runs; performance decreased modestly through three cycles and then stabilized. Nb-Ti mixed oxide catalyst improves furfural yield and selectivity from xylose in a toluene–water system. Optimal conditions (180 °C, 180 min, 6.8 wt% xylose, 3.4 wt% catalyst) maximize selectivity of 57.4% and xylose conversion 91.1%. Catalyst regenerated by calcination and reused five times; activity dropped slightly then stabilized.