甲醇无卤羰基化制乙酸甲酯新催化体系研究

Methyl acetate (MA; CH3COOCH3) as an important chemical product,is genarally produced by esterification of acetic acid and liquid carbonylation of methanol. The drawbacks of these flow charts are the high cost, long flow chart and serious corrosion. As a promising technique,the vapor carbonylation of methanol can produce MA on solide catalyst in free of halide.In this case,two types of active sites,including acid sites and metal sites are required for MA synthesis. Here,the acid sites are involved to active methanol,while the metal sites are need to active CO.In order to increase MA selectivity, the activation and the distribution as well as structure of the acid sites and metal sites are need to cooperate with each other. In this project, the Cu/mesoporous titania carbon catalyst has been designed as a new type of catalyst to catalyze the halide-free carbonylation of methanol to MA.In this catalytic system, the copper acts as metal sites to activate CO ascribing to its non-dissociatve adsorption ability for CO. And the mesoporous titania carbon material (MTC) acts as acid sites to activate methanol due to their suitable surface acidity. The copper is introduced into the pore of MTC by functionalizing the MTC with coupling agent. As the MTC has uniform and controllable mesoporous diameter, the dispersion and structure of copper can be controlled efficiently. Moreover, by changing the titania/carbon ratio, the copper loading and concentration of the surface functional group, the activation of the acid sites and the the metal sites can be adjusted to cooperate with each other.The catalytic performance of the catalysts is tested on the halide free carbonylation of methanol to MA. Through the thorough characterization of the catalysts and the deep study of the probe reaction, the structure-activity relationship and the mechnism of the adsorption-conversion of methanol and CO on the bifounctional sites will be explored. The aim of this project is hope to provide theoretical guidance for the design of bifounctional catalysts for the carbonylation of methanol to MA.

乙酸甲酯（MA）是一种重要的化学产品。甲醇无卤羰基化合成MA可在不加任何促进剂条件下由甲醇和CO直接合成MA，是未来MA合成的发展方向。此工艺要求催化剂同时具有活化甲醇的酸性中心和活化CO的金属中心，并要求两种活化中心活化能力、分布及构型匹配。本项目从反应机理出发,通过对过程双活性中心的认识，拟在介孔钛碳材料(MTC)孔道内组装铜。借助铜对CO的选择性吸附能力和MTC的酸性,实现CO和甲醇的选择性活化。利用MTC的孔道限域效应和表面性质，采用表面功能化和限域技术构建两种活性中心分布、构型及活化能力匹配的双功能催化剂。以甲醇无卤羰基化合成MA为探针反应，实现MA在新型催化剂上的选择性合成。通过对催化剂的系统表征和对探针反应的深入研究，探索甲醇和CO在催化剂表面的吸附转化与中间物种在双位活性中心上的作用机制，为甲醇无卤羰基化合成MA双功能催化剂设计提供理论指导。

针对甲醇产能过剩的现状，本项目开展了甲醇无卤羰基化制乙酸甲酯的研究。项目选取具有双位活性中心的铜/钛硅作为催化剂，实现了乙酸甲酯的无卤合成。对催化剂构效关系进行了详细研究，主要研究内容及结论如下：.1）以氯化铜为前驱体制备了铜/钛硅催化剂，对该类催化剂上铜赋存状态和催化剂表面酸性，CO吸附以及乙酸甲酯选择性之间的关系进行了研究。发现铜Cu+含量和CO吸附强度以及乙酸甲制的收率成正比；此外，铜的引入对催化剂表面酸性中心的强度，类型和数量有影响：还原前催化剂主要为弱酸，由载体和氧化铜提供，载体同时具有B酸和L酸中心，氧化铜具有L酸中心，随铜含量增加，L酸性中心数量增加，B酸减少。催化剂还原后，氧化铜转变为Cu0和Cu+，由氧化铜提供的弱酸转变为由Cu0和Cu+提供的中强酸，铜含量增加，中强酸数量增加。.2）通过对反应过程中催化剂上残留的氯含量的检测，以及制备以硝酸铜和醋酸铜制备的/钛硅催化剂，排除了氯元素在反应过程中的作用，证明铜/钛硅催化剂可以实现乙酸甲酯的无卤合成；.3) 研究了载体组成对催化剂酸性位和金属位的影响，发现随钛硅比降低，催化剂比表面增大，铜分散度增大，还原后Cu+含量增加，催化剂对CO的吸附强度增加，同时还原后催化剂主要以弱酸为主，抑制了二甲醚的生成。.4）对Cu/钛硅催化剂催化甲醇无卤羰基化的反应工艺条件，如反应压力，温度和空速进行了研究，确定了最佳反应温度为230℃，最佳反应压力为0.5 MPa。.下一步工作计划：.1）探索新的催化剂制备和处理方法，以期获得100%含量的Cu0或 Cu+，或者构建理论计算模型，深入探究铜的价态和CO吸附以及乙酸甲酯收率之间的关系；.2）采用CH3OH-TPD，TPSR以及甲醇吸附的红漫反射等手段研究酸性中心和甲醇活化之间的构效关系。.3）开展甲醇和CO的共吸附，采用在线质谱，原位红外灯手段研究两种活性中心的协同作用机制。.项目执行过程中培养博士研究生一名，发表研究性论文1篇，申请国家发明专利3项目，目前授权2项