【作者】 刘丹；

【导师】 李钢；

【作者基本信息】 大连理工大学 ， 工业催化， 2019， 博士

【摘要】 作为廉价且丰富的C1资源,CO2可与环氧化物反应合成环状碳酸酯,此反应符合原子经济性和环境友好性的理念而受到广泛关注。目前,工业上用于催化CO2环加成反应的催化剂主要为季铵盐类和金属卤化物,但这些催化体系存在催化活性不高、反应条件苛刻和催化剂难于回收等问题。研发新型、高效、稳定性和重复性优异的多相催化剂是CO2环加成反应的重要研究目标。探究催化剂的组成与催化性能的关系和阐释其在CO2环加成反应中的催化机理是此课题的研究重点。本论文基于多活性位(酸性位、碱性位)协同催化CO2与环氧化物环加成反应的思想,合成出几种新型、高效的多相催化剂。主要研究内容如下:1.针对大多数金属有机骨架材料(MOFs)活性位单一,在不添加助催化剂的条件下无法高效催化CO2环加成反应的缺点,本文采用逐步嫁接的方法制备了咪唑型离子液体功能化MIL-101-IMBr催化剂。研究结果表明:同时含有咪唑基团、Br和四配位Cr的MIL-101-IMBr-6催化剂的活性高于MIL-101(Cr),其在无助催化剂的条件下催化CO2与环氧丙烷(PO)的环加成反应,PO的转化率达95.8%,碳酸丙烯酯的选择性达97.6%。2.为了充分利用分子筛中季铵盐/季铵碱模板剂,本文合成了含有模板剂聚季铵盐-6(PDDA)和四丙基氢氧化铵(TPAOH)的介孔钛硅分子筛(MTS-1),分子筛中模板剂不高温焙烧脱除,而是作为碱性中心,与骨架钛协同催化CO2与环氧氯丙烷(ECH)的环加成反应。吸附CO2的红外表征结果显示,MTS-1可以吸附并活化CO2。研究表明,ECH的转化率随着催化剂中可接触碱性中心含量的增加而增加,同时含有骨架钛与模板剂活性中心的催化剂活性高于只含有单一活性中心的催化剂。3.为了避免TPAOH的浪费和降低催化剂合成成本,本文进一步制备了含单一碱性中心PDDA的有机无机杂化介孔钛硅催化剂Ti-mSiO2,其中,PDDA作为碱性中心,与钛物种协同催化CO2与ECH的环加成反应。研究结果表明,同时含有钛物种与PDDA的催化剂活性高于只含有单一活性位的催化剂,且其催化活性随着可接触碱性中心含量的增加而增加。4.为了改善催化剂中传质,本文以PDDA和常规表面活性剂为双模板剂,合成了酸碱双功能铁基介孔催化剂。N2物理吸附和TEM表征结果显示,所得催化剂具有孔径2-3nm的六方有序和蠕虫状介孔孔道。研究结果表明,同时含有铁物种与PDDA的Fe-HMS催化剂可高效催化CO2与ECH的环加成反应。更多还原

【Abstract】 CO2 as a cheap and abundant C1 resource can be used to synthesize five member cyclic carbonates with epoxides,which has become an attractive craft because of its sustainability and environmental friendliness.Until now,quaternary ammonium salts and metal halides are most common catalysts for COZ cycloaddition in industry,but these catalytic systems have some problems,such as low activity,harsh reaction conditions and difficult recovery of catalysts.The development of novel,efficient,stable and reproducible heterogeneous catalysts is the key issue in CO2 cycloaddition.Exploring the relationship between the composition and catalytic performance of catalysts and explaining possible mechanism in COZ cycloaddition reaction is the research focus.In this paper,several novel and effi cient heterogeneous catalysts were synthesized based on the conception of multi-functional active sites(acidic and basic sites)synergistically catalyzing cycloaddition of CO2 with epoxides.The main research contents are as follows:1.Because most metal-organic frameworks(MOFs)contain only one kind of active site,they can not efficiently catalyze CO2 cycloaddition without co-catalysts.In order to solve this problem,a kind of multi-functional sites MOF composite(MIL-101-IMBr)was successfully prepared by post-synthesis modification of MIL-101 with imidazolium-based ionic liquids.The results showed that MIL-101-IMBr-6 containing imidazole group,halogen anion and tetra-coordination Cr presented the high catalytic activity under co-catalyst free conditions for cycloaddition reaction of CO2 with propylene oxide(PO).The conversion of PO and the selectivity of propylene carbonate reached 95.8%and 97.6%,respectively.2.In order to make full use of templates in zeolite,mesoporous titanium silicate(MTS-1)containing organic templates polyquaternary ammonium salt-6(PDDA)and tetrapropyl ammonium hydroxide(TPAOH)were synthesized.Not required to be removed by calcination,the organic templates endow as-synthesized mesoporous TS-1 zeolite basic sites,which cooperate synergistically with framework Ti species,leading to an efficient bi-functional catalyst for cycloaddition reaction of CO2 with epichlorohydrin(ECH).Infrared characterization of CO2 adsorption showed that MTS-1 could activate CO2.The reaction results showed that the increased content of accessible basic sites in the catalysts was favor for the conversion of ECH,and the catalysts containing two kind of active centers,titanium species and PDDA,have excellent catalytic activity.3.In order to avoid the waste of TPAOH and reduce the cost of catalyst,the organic-inorganic hybrid mesoporous titanium-silicon catalyst(Ti-mSiO2)with a single basic center PDDA was further prepared.PDDA endow Ti-mSiO2 basic sites,which cooperate synergistically with Ti species,leading to an efficient bi-functional catalyst for cycloaddition reaction of CO2 with ECH.The reaction results showed that the catalysts containing both titanium species and PDDA have higher activity than those containing only one kind of active site,and the catalytic activity enhances with the increased content of accessible basic sites.4.In order to improve the mass transfer in catalyst,multifunctional iron-based mesoporous catalysts were synthesized by using PDDA and conventional surfactants as double templates.The results of N2 physical adsorption and TEM characterization showed that the catalyst has hexagonal ordered and wormlike mesoporous channels with pore size of 2-3 nm.The reaction results showed that the Fe-HMS catalyst containing both iron species and PDDA possesses the good catalytic performance in the cycloaddition reaction of CO2 with ECH.更多还原