The Study Of Producing Furfural From Biomass-derived Xylose

At present primary method producing furfural is dehydration of C₅-sugar or hemicellulose on 200℃～250℃using mineral acid as catalyst. Under this condition, selectivity of preparing furfural is no t higher than 70% and that mineral acid has causticity, so it actually brings environment pollution. The selectivity of the process may be increased and the process can also be more cleaner. Three kinds solid catalysts have been investigated for dehydration of xylose to produce furfural.Different reagents were used for catalyst, such as molecular sieve (5A), clinoptilolite and calcium orthophosphate. Effects of various factors (the amount of catalyst and solvent, reaction time and temperature, stirring speed) on yield of furfural were discussed. The optimal conditions were determined using yield of furfural as an objective function. Reaction kinetics of dehydration of xylose were also studied using calcium orthophosphate as catalyst.As for preparing furfural from xylose dehydration using molecular sieve (5A) as catalyst, the optimized conditions are determined as follows: the amount of xylose 5g, the amount of molecular sieve (5A) catalyst 2.0g, water(as a solvent for xylsoe) 50ml, toluene(as furfural extract) 100ml, reaction time 4h, reaction temperature 170℃. The yield of furfural reaches 29.2% under this condition. The results showed that the selectivity of molecular sieve (5A) to furfural is high while the fractional conversion of xylose is low.As for preparing furfural from xylose dehydration using clinoptilolite as catalyst, the optimized conditions are determined as follows: the optimized conditions are determined as follows: the amount of xylose 5g, the amount of clinoptilolite catalyst 1.5g, water(as a solvent for xylsoe) 50ml, toluene(as furfural extract) 125ml, reaction time 4h, reaction temperature 170℃.The yield of furfural reaches 66% under the optimal condition. The selectivity of clinoptilolite to furfural is high.Clinoptiolite of little silica-alumina rata is propitious to experiment system according to experiment result of two molecular sieve catalysts. Catalyst of strong acidity has lower selectivity to furfural. Molecular sieve catalyst of little silica-alumina rata has good effect under this experiment system. As for preparing furfural from xylose dehydration using Calcium orthophosphate as catalyst, the optimized conditions are determined as follows: the optimized conditions are determined as follows: the amount of xylose 5g, the amount of Calcium orthophosphate catalyst 1.0g, water(as a solvent for xylsoe) 50ml, toluene(as furfural extract) 100ml, reaction time 5h, reaction temperature 180℃.The yield of furfural reaches 65.3% under the optimal condition. The selectivity of Calcium orthophosphate to furfural is high. Dehydration kinetics using calcium orthophosphate as catalyst was studied. The results show that the dehydration is a first order reaction of intrinsic kinetics and activation energy is 50.39kJ/mol, pre-exponential factor is 1.587×10⁵s^-1.Reaction rate equation is determined as follows: r = 1.587×10⁵ e ^{-5.039×104/RT} C_xylose...