多相无碱催化丙三醇一步合成乳酸酯研究

发布时间：2018-08-14 13:11

【摘要】：生物质作为一种丰富的可再生资源,可部分替代化石资源。从而减轻化石资源过度消耗带来的环境和经济压力。由生物质转化制备燃料或者化学品引起众多研究者的兴趣。其中,研究生物质转化制备高附加值化学品备受关注。乳酸(酯)是一种重要的平台化合物,具有广泛用途。丙三醇作为生物柴油的主要副产物,年产量大。研究催化丙三醇转化制备乳酸(酯)具有重大的科学意义和应用价值。论文设计并制备了Au/Sn-USY双功能催化剂,用于无碱一步催化丙三醇转化制备乳酸酯。研究了催化剂制备条件、反应条件等对催化剂结构及催化性能的影响。Au溶胶pH的影响:当Au溶胶的pH较低(pH=1)或较高(pH=7)时均会导致形成较大的Au纳米颗粒(10 nm),使催化剂活性降低,pH=3或5时,Au纳米颗粒尺寸较小(10 nm)。PVA与Au质量比的影响:PVA与Au的质量比等于1时,Au颗粒平均尺寸为6.2 nm,PVA的量过低或过高时,将导致Au纳米颗粒长大。Sn含量的影响:当Sn含量为0 wt%到2 wt%时,Sn主要进入分子筛骨架,形成Lewis酸性位;当Sn含量超过2 wt%(如3 wt%或4 wt%)时,过量的Sn与脱铝后介孔周围的Si-OH作用,形成非骨架Sn。这部分非骨架Sn与Au之间通过相互作用,使Au均匀分散于分子筛的介孔周围,得到颗粒尺寸较小,且分布均匀的纳米Au颗粒。将制备条件优化后的催化剂用于目标反应,并对反应时间、反应温度、催化剂量等条件进行优化,发现在160 oC条件下,反应10 h,乳酸甲酯收率可达79%,选择性达90%。论文进一步对低温条件下催化丙三醇转化制备乳酸酯进行了研究,课题组已经实现了1,3-二羟基丙酮(DHA)室温转化制备乳酸酯,因此,本文重点研究低温催化丙三醇转化制备DHA。以不同来源的CuO为载体,制备Au/CuO催化剂,在甲醇溶剂中,低温催化丙三醇转化为DHA。发现不同来源的CuO载体,形貌及物理化学性质差异较大,对Au的催化氧化性能影响显著。以醋酸铜热分解得到的CuO负载Au后活性较好,50 oC条件下,反应4 h,丙三醇转化率可达55%,DHA收率为33%。实现了醇溶剂中,低温催化丙三醇转化为中间产物DHA。
[Abstract]:As a kind of abundant renewable resources, biomass can partly replace fossil resources. Thus reducing the environmental and economic pressure caused by excessive consumption of fossil resources. The production of fuels or chemicals from biomass has attracted interest from many researchers. Among them, graduate student material conversion to produce high added-value chemicals has attracted much attention. Lactic acid (ester) is an important platform compound with a wide range of applications. As the main by-product of biodiesel, glycerol has a large annual output. It is of great scientific significance and application value to study the synthesis of lactic acid (ester) by catalytic conversion of glycerol. In this paper, Au/Sn-USY bifunctional catalyst was designed and prepared, which was used to catalyze the conversion of glycerol to lactate without alkalinity. The preparation conditions of the catalyst were studied. Effects of reaction conditions on Catalytic structure and Catalytic performance. Effects of au sol pH: when au sol pH is lower (pH=1) or higher (pH=7), larger au nanoparticles will be formed (10 nm), can reduce catalyst activity at pH 3 or 5 au). The effect of the mass ratio of PVA to au on the particle size is smaller (10 nm). When the mass ratio of PVA to au is equal to 1, the average size of au particles is 6.2 nm, the amount of PVA is too low or too high. The effect of Sn content on the growth of au nanoparticles: when Sn content is from 0 wt% to 2 wt%, the Sn mainly enters the framework of molecular sieve to form the acidic site of Lewis, and when Sn content exceeds 2 wt% (for example, 3wt% or 4wt%), Excessive Sn acts with Si-OH around mesoporous after dealumination to form non-skeleton SnS. Through the interaction between non-skeleton Sn and au, au particles are dispersed around the mesoporous structure of molecular sieve, and the particles are smaller in size and uniformly distributed. The optimized catalyst was used in the target reaction and the reaction time, reaction temperature and catalyst quantity were optimized. It was found that under the condition of 160oC, the yield of methyl lactate could reach 79% and the selectivity was 90% under the condition of 160oC for 10 h. In this paper, the preparation of lactate by catalytic conversion of glycerol to lactate at low temperature has been studied. The room temperature conversion of 1h3- dihydroxyacetone (DHA) to lactate has been realized. Therefore, this paper focuses on the study of catalyzing the conversion of glycerol at low temperature to prepare lactate. The CuO catalyst was prepared by using CuO from different sources as the carrier. The catalyst was used to catalyze the conversion of glycerol to DHA in methanol solvent at low temperature. It was found that the morphology and physicochemical properties of CuO carriers from different sources varied greatly, which had a significant effect on the catalytic oxidation of au. Under the condition of 50 鈩，

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