【作者】 黄守莹；

【导师】 马新宾；

【作者基本信息】 天津大学 ， 化学工艺， 2013， 博士

【摘要】 碳酸二乙酯（DEC）作为环境友好的化学品，可用作有机合成中间体、锂电池电解液及油品添加剂等，应用前景广阔。氧化羰基化法合成DEC工艺符合绿色化学的原则，因此受到了愈来愈多的关注。Cu-分子筛催化剂用于乙醇氧化羰基化合成DEC反应，虽能避免氯流失的问题，但催化剂活性、选择性均有待提高，同时分子筛载体对活性组分的作用不明确，活性物种的形成和性质尚需深入研究。本论文考察了Cu-分子筛催化剂制备方法和载体效应对活性物种形成和催化剂性能的影响，初步提出了氧化羰基化反应Cu-分子筛催化剂的可控制备方案。分子筛载体的Br nsted酸位是影响氧化羰基化反应的首要因素。分别研究了硅铝组成的Y分子筛和β分子筛钝化前后催化剂物化性质的变化规律，通过吡啶吸附红外和活性评价建立了Br nsted酸位与DEC生成的量化关系。CO吸附红外结果表明，Br nsted酸位的分布会影响Cu活性物种的位置及形式，进而影响催化活性。孔道结构限制是除酸性外影响氧化羰基化反应的另一重要因素。对Y分子筛进行碱处理，考察其结构性质、酸性的变化规律及对催化活性的影响。结果发现，适当浓度的碱处理可在分子筛中产生缺陷位，从而大大促进微波辅助NH4NO3交换过程骨架铝的脱除，成功引入介孔和大孔结构以削弱分子扩散限制。同时超笼中-OH和非骨架铝的增加导致Cu活性位数量的增加和DEC收率的提高。结合Y、β分子筛表面酸性和孔道结构的优势，采用预置晶种法成功制备了Y-β复合分子筛，通过多种表征手段结合，证明了其兼具Y、β两种分子筛的结构特征。对合成工艺条件进行考察发现，晶化时间、凝胶硅铝组成和碱度影响着复合分子筛中两种晶相的比例，最终导致催化活性的差异。综合考虑酸性和扩散限制的影响，采用Al(NO3)3对MCM-41全硅介孔分子筛进行改性，表征结果表明Al原子的引入对分子筛规整有序的孔道结构影响甚小，却明显提高了载体表面Br nsted酸位的数量，促进了CuCl在MCM-41孔道内的高度分散，从而提升了催化剂性能。为彻底消除固体离子交换制备过程中Cl元素的影响，首次以蒸氨法制备CuY催化剂。研究表明，惰性气氛的焙烧是Cu+与分子筛骨架结合形成反应活性中心的必要条件。前驱体对催化剂的结构、化学性质影响显著。铜物种的分散度和价态与DEC收率密切相关，而中强酸位则导致副产物DEE的生成。过量的CuOx物种会导致孔道堵塞及活性位数量减少，从而不利于反应活性的提高。更多还原

【Abstract】 Diethyl carbonate(DEC), as an eco-friendly chemical, is gaining popularitybecause of burgeoning applications in chemical synthesis and lithium batteryelectrolytes, oxygenated fuel additive, etc. The direct synthesis of DEC throughoxidative carbonylation has attracted more attentions concerned within the frame ofgreen chemistry. Although utilization of Cu-doped zeolite catalysts instead of Wackertype catalyst can resolve the deactivation of catalyst and corrosion due to loss ofchlorine, the activity and selectivity of this catalyst system still need improvement forfurther industrial applications. Furthermore, the effect of supports on formation andproperties of active species need further investigation for understanding therelationship between structure and performance. This dissertation focuses onunderstanding of the support effect on Cu active species of Cu-doped zeolite and itscatalytic performance in oxidative carbonylation, aiming to realize controllablefabrication of Cu-zeolite catalyst.In order to eliminate the influences of channel structure, faujasite with variousSiO2/Al2O3ratios and Hβ before and after passivation were investigated for DECsynthesis. Combined with pyridine-adsorption IR and catalytic measurements, aquantitative relationship between amount of Br nsted acidic sites and catalyticactivities for oxidative carbonylation of ethanol has been established. CO-adsorptionIR suggested that the location of Cu active species was influenced by the distributionof Br nsted acidic sites, which also played an important role in catalytic performanceof oxidative carbonylation.NaY was modified with NaOH solutions followed by ion exchange with NH4+toHY. The textural and acidic properties of NaY and its effect on catalytic activity of thecorresponding CuY catalyst were investigated. Alkaline treatment with appropriateconcentration generated defects in the zeolite framework and promoted dealuminationduring ion exchange procedure assisted by microwave radiation, which resulted in thecreation of meso-and macropores in zeolite Y and benefited for the catalyticperformance. In addition, the increased amount of hydroxyl group in supercages andextraframework Al species favored formation of Cu active sites and further yield ofDEC.Y-β composite zeolite was synthetized using preset crystal seeds method. The characterization results demonstrated the Y-β composite zeolite had the structuralfeature of both Y and β instead of a physical mixture. Investigation of preparationconditions indicated that crystallization time, composition and alkalinity in gelaffected the proportion of Y and β in composite zeolite, which had an impact on DECproduction.By introduction of aluminum into mesoporous silica MCM-41, the amount ofBr nsted acidic sites was improved without change in ordered channel structure,which contributed to dispersion of CuCl and further catalytic performance.Preparation methods dominated the activity of CuY in oxidative carbonylation.Compared to other samples, CuY prepared by ammonia evaporation method exhibitedthe optimal catalytic properties. Thermal treatment in inert atmosphere is necessaryfor coordination of Cu+to lattice oxygen of zeolite framework. It is confirmed that thetextural properties, chemical states of active sites and acidity of CuY catalysts wereprofoundly affected by the kinds of copper precursors. Dispersion and valence of Cuspecies related to DEC yield, while moderate acid sites were responsible for DEEproduction. Excess CuOxaggregates resulted in an obvious decrease of Cu+content,surface area and pore volume, which generated a deterioration of DEC selectivity andethanol conversion.更多还原