果糖催化脱水制5-羟甲基糠醛(5-HMF)是生物质转化制高附加值化合物过程中的一个重要反应.采用自制的介孔SBA-15,浸渍法制备了Nb/SBA-15催化剂,再经磷酸化处理制得Nb-P/SBA-15催化剂,研究了该催化剂在果糖脱水制5-HMF反应中的性能.SEM、TEM、BET和XRD表征结果表明,Nb/SBA-15和Nb-P/SBA-15完好地保留了SBA-15的微观结构,其内孔道直径为10nm,铌酸在孔内表面分布均匀;负载铌和磷酸化后,孔壁变薄.NH3-TPD结果显示,Nb/SBA-15经磷酸预处理后,不仅弱酸性位有所增加,而且产生了中强酸和强酸性位,使得在含水两相体系果糖脱水反应中,Nb-P/SBA-15比Nb/SBA-15具有更高的催化活性和5-HMF选择性.同时考察了反应温度、溶剂比例、反应时间对果糖脱水的影响,结果表明,以水/MIBK(V/V=1/2)为溶剂时,160℃下反应1.5h,果糖转化率和5-HMF收率分别高达96.1%和92.6%.Nb-P/SBA-15经循环使用四次后仍具有较好的催化活性,表明该催化剂具有较高的耐水稳定性.%Dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) is one of the pivotal reactions in conversion of biomass towards valuable platform compounds.In this work, Nb/SBA-15 was prepared via incipient wetness impregnation with self-made SBA-15 as support;Nb/SBA-15 was further treated with phosphoric acid and calcined at 450 ℃, to obtain the Nb-P/SBA-15 catalyst.The Nb-P/SBA-15 catalyst was characterized by SEM, TEM, BET, XRD and NH3-TPD;its performance in the dehydration of fructose to 5-HMF was then investigated.The results indicate that the microscopic structure of SBA-15 is well preserved in Nb/SBA-15 with an internal channel diameter of about 10 nm and the niobic species are highly dispersed on the surface of the channels;the wall of channels became thinner after impregnation of Nb and treatment with phosphoric acid.After the treatment with phosphoric acid, the weak acid sites are increased, moreover, the medium and strong acidic sites are generated in Nb-P/SBA-15;as a result, for the dehydration of fructose in a water/MIBK biphasic system, Nb-P/SBA-15 exhibits higher catalytic activity and selectivity to 5-HMF.By reaction at 160 ℃ for 1.5 h, with a water/MIBK volume ratio of 1/2, the conversion of fructose and the yield of 5-HMF reach 96.1% and 92.6%, respectively.Moreover, the Nb-P/SBA-15 catalyst also exhibits excellent stability in view of water tolerance;it still demonstrates high catalytic activity and selectivity to 5-HMF even after successive recycling for four times.
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