柠檬酸改性USY催化纤维素合成乙酰丙酸乙酯

摘要

Ultra-stable Y zeolite ( USY ) was dealuminated by citric acid of 0. 2 mol/L, and the dealuminated USY( DUSY) was used as solid acid catalyst for the synthesis of ethyl levulinate( EL) from cellulose.The initial USY and modified DUSY were characterized by X ray diffraction (XRD),Fourier translation-infrared spectroscopy ( FT-IR ) , Brunner-Emmet-Teller ( BET ) measurements, pyridine adsorption infrared spectroscopy(Py-IR) and NH3-temperature programmed desorption(NH3-TPD).The porous structure of USY was enriched,and the Lewis acidity was also enhanced. Meanwhile,the catalytic ability of USY for the synthesis of EL from cellulose was improved. Moreover, the conditions of EL synthesis from cellulose catalyzed by DUSY were optimized.Under the conditions of cellulose 0. 6 g,DUSY 0. 3 g,at 220 ℃ for 3 h,36. 1％ of the EL yield was achieved,and DUSY could be used repeatedly. Furthermore,EL synthesis from different carbohydrates was compared,the EL yield from fructose,glucose, sucrose and inulin were 50. 7％,41. 0％,47. 9％ and 42. 9％,respectively.%以0.2 mol/L浓度的柠檬酸对超稳Y型(USY)分子筛进行脱铝改性,并对改性获得的脱铝超稳Y型分子筛(DUSY)催化纤维素合成乙酰丙酸乙酯(EL)进行试验研究.利用X线衍射(XRD)、傅里叶变换红外光谱(FT IR)、比表面积测试(BET)、吡啶吸附红外光谱(Py IR)、氨气程序升温脱附(NH3 TPD)等对改性前后的USY进行表征.结果显示:柠檬酸改性能够丰富USY的多孔结构,增强Lewiss(L)酸位,提高催化纤维素合成EL的能力.此外,优化了DUSY催化纤维素合成EL的工艺条件,在纤维素加入量0.6 g、DUSY用量0.3 g、反应温度220℃、反应时间3 h的条件下,EL的产率达到36.1％,且DUSY可重复使用.进一步对DUSY催化不同碳水化合物合成EL进行比较,发现果糖、葡萄糖、蔗糖和菊糖转化合成的EL产率分别为50.7％、41.0％、47.9％和42.9％.