分子筛催化剂的孔径与生物油分子尺寸之间的差异造成分子筛催化剂的择形选择性。分子筛的孔径数据来自晶体结构分析，而生物油的分子尺寸数据很难获得，对生物油的分子尺寸进行估算十分必要。采用热裂解气质联用技术(Py-GC/MS)研究了纤维素热解生物油的组成成分，以Joback基团贡献法为基础计算了纤维素热解生物油各组成成分的动力学直径，分析了纤维素热解生物油的分子尺寸分布特性。结果表明，纤维素在350~600℃热解产生生物油的主要成分为脱水糖、呋喃衍生物和酮类化合物，生物油各组成成分的动力学直径主要分布在[0.500, 0.600) nm。当热解温度由350℃升至600℃时，动力学直径位于[0.550, 0.600) nm的生物油各组成成分的峰面积百分比由88.72%降至64.53%，位于[0.500, 0.550) nm的生物油各组成成分的峰面积百分比则由2.88%升至21.95%。纤维素催化裂解制备高品质液体燃料可选用ZSM-5, ZSM-11和IM-5等孔径尺寸0.500~0.600 nm的分子筛催化剂。
The shape selectivity of molecular sieve catalyst is caused by the difference between the pore size of molecular sieve catalyst and the molecular size of bio-oil. The data of the pore size of molecular sieve catalysts are derived from crystal structural analysis, while the data of the molecular size of bio-oil are rather difficult to obtain. It is very necessary to estimate the molecular size of bio-oil. The pyrolysis of cellulose was carried out by prolysis-gas chromatography/mass spectrometry (Py-GC/MS), and the variation of the composition of cellulose pyrolysis bio-oil with the temperature was studied. The kinetic diameter of the components of cellulose pyrolysis bio-oil were calculated on the basis of Joback group contribution method, and the characteristics of molecular size distribution were analyzed. The results showed that cellulose pyrolysis bio-oil was mainly composed of anhydrosugars, furan derivatives and ketone compounds in the temperature range from 350℃ to 600℃. The kinetic diameter of cellulose pyrolysis bio-oil were mainly distributed in the range of [0.500, 0.600) nm. When the pyrolysis temperature increased from 350℃ to 600℃, the peak area of bio-oil molecules with the kinetic diameters in the range of [0.550, 0.600) nm decreased from 88.72% to 64.53%, and the peak area of bio-oil molecules with the kinetic diameters in the range of [0.500, 0.550) nm increased from 2.88% to 21.95%. For the preparation of high-quality liquid fuels by catalytic cracking of cellulose, molecular sieve catalysts ZSM-5, ZSM-11 and IM-5 with pore size of 0.500 to 0.600 nm can be selected.
