基于分子筛制备生物柴油影响研究

发布时间：2018-01-14 11:02

本文关键词：基于分子筛制备生物柴油影响研究　出处：《山东理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：本文以油酸与乙醇的酯化反应作为探针反应,研究分子筛孔结构以及表面疏水性对分子筛催化制备生物柴油催化性能的影响,并在此基础上对分子筛进行改性,进一步提高分子筛催化性能,此外本文同时使用不同动力学模型对酯化反应进行模拟预测并对不同模型进行对比研究。实验首先选取不同硅铝比的微孔型分子筛(BEA型Beta分子筛和MFI型ZSM-5分子筛)以及微孔-介孔复合分子筛(MFI型ZRP-5分子筛)作为催化剂催化制备生物柴油,采用西勒模数计算研究分子筛孔径对反应过程中内传质阻力的影响。结果显示,硅铝比较高的分子筛催化性能较好,并且在硅铝比相同时,ZRP-5分子筛在反应过程中内传质阻力最小但催化性能最差。通过对样品表征分析与动力学模型推导证明在表面疏水性较弱的ZRP-5分子筛表面,乙醇与油酸存在竞争吸附现象,极性较弱的油酸分子较难吸附在分子筛表面,导致分子筛表面油酸覆盖程度较低,进而导致酯化反应转化率下降。在所有分子筛样品中,Beta(50)分子筛催化性能最高,在优化反应条件下(乙醇油酸摩尔比20:1,反应温度78.0°C,反应时间10.0 h,搅拌速度600 rpm,催化剂用量0.167 meq/g)最高转化率达到73.6%,且Beta(50)分子筛催化剂重复使用五次后活性组分Al没有明显流失。实验进一步采用表面包覆接枝方法对分子筛样品进行改性,制备聚苯乙烯磺酸包覆接枝分子筛。通过对样品分析表征证明,采用包覆接枝方法能够将聚苯乙烯磺酸稳定包覆在分子筛表面,且催化剂重复使用5次后,聚苯乙烯磺酸仍然能够包覆在分子筛表面。实验使用响应面法对反应条件进行优化,在优化反应条件下一次转化率最高达到96.4%(优化条件包括:反应时间4.1 h,催化剂用量47.8 wt%,乙醇油酸摩尔比15:1)。与分子筛样品以及苯乙烯系阳离子交换树脂相比,聚苯乙烯磺酸包覆接枝分子筛能够显著提高油酸转化率,并缩短反应时间。
[Abstract]:In this paper, the esterification of oleic acid with ethanol was used as a probe to study the effect of pore structure and surface hydrophobicity of molecular sieve on the catalytic performance of molecular sieve to prepare biodiesel. Further improve the catalytic performance of molecular sieve. In addition, different kinetic models were used to simulate and predict the esterification reaction, and different models were compared. Firstly, microporous molecular sieves with different Si-Al ratios were selected. BEA type Beta molecular sieve and MFI type ZSM-5 molecular sieve) and microporous / mesoporous composite molecular sieve MFI ZRP-5 molecular sieve) were used as catalysts to prepare biodiesel. The influence of molecular sieve pore size on internal mass transfer resistance in the reaction process was studied by using Schiller modulus. The results showed that the molecular sieve with higher Si-Al catalyst had better catalytic performance, and when the ratio of Si to Al was the same. ZRP-5 molecular sieve has the least internal mass transfer resistance but the worst catalytic performance in the reaction process. The characterization analysis and kinetic model analysis of the sample show that the surface hydrophobicity of ZRP-5 molecular sieve surface is weak. There is a competitive adsorption phenomenon between ethanol and oleic acid, and it is difficult for oleic acid molecules with weak polarity to adsorb on the surface of molecular sieve, resulting in low oleic acid coverage on the surface of molecular sieve. Therefore, the conversion of esterification reaction decreased. Among all the molecular sieve samples, the catalytic activity of the zeolite was the highest, and the molar ratio of ethanol to oleic acid was 20: 1 under the optimized reaction conditions. The reaction temperature was 78.0 掳C, the reaction time was 10.0 h, the stirring rate was 600rpm, the amount of catalyst was 0.167meq / g) and the highest conversion was 73.6%. The active component Al was not significantly lost after the catalyst was reused for five times. The surface coating grafting method was further used to modify the molecular sieve samples. Polystyrene sulfonic acid coated molecular sieve was prepared. The results of sample analysis and characterization showed that polystyrene sulfonic acid could be stably coated on the surface of molecular sieve by coating grafting method, and the catalyst was reused for 5 times. Polystyrene sulfonic acid can still be coated on the surface of molecular sieve. Response surface method is used to optimize the reaction conditions. Under the optimized reaction conditions, the maximum conversion rate was 96.4wt% (the optimum conditions were as follows: reaction time 4.1 h, catalyst dosage 47.8 wt%). The molar ratio of ethanol to oleic acid is 15: 1. Compared with the molecular sieve sample and the styrene cationic exchange resin, the graft molecular sieve coated with polystyrene sulfonic acid can significantly increase the conversion of oleic acid and shorten the reaction time.
【学位授予单位】：山东理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE667

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