合成气与二甲醚一步制取乙醇催化剂的设计、可控合成及反应机理

With the fast economic growth, the market demands for ethanol present the explosive trend. In this project, ethanol will be directly produced from syngas (CO and H2) and dimethyl ether (DME) through tandem coupling of the two reactions for DME carbonylation to produce methyl acetate (MA) and MA hydrogenation to produce ethanol and methanol over the integrated and modified H-Mordenite (H-MOR) and Cu-based catalysts. Our aim is to rationally design and controllably synthesize the metal-modified H-MOR zeolites with the specific morphologies, sizes and pore structures. These synthesized zeolites will be selected and studied according to the results of the catalytic activity of the DME carbonylation reaction. The element kinds, micro-coordinations, spatial positions, dispersions and reducibilities of the metals, as well as the specific morphologies, crystallite sizes, axial growth directions, pore structures and acidic properties of the H-MOR zeolite, will be characterized in detail. These results will be further linked to the catalytic activities of the DME carbonylation reaction to illuminate the synergetic effect between the active metal sites and the acidic sites on the H-MOR zeolites. Moreover, we will further improve the catalytic activity of the Cu-based catalysts upon the followed MA hydrogenation reaction. The reaction conditions, as well as the regeneration conditions, of the catalysts will be evaluated and optimized. Herein, the in situ spectroscopy techniques, such as XAFS and FT-IR, will be employed to identify and characterize the adsorption/ desorption behaviors of the species adsorbed on the catalysts in the reactive atmospheres. According to these results, the reaction mechanism will be discussed and proposed. This ethanol synthesis method is a promising route to the ethanol synthesis from an environmentally friendly viewpoint. The successful implementation of this project will provide a new approach to the research level in the efficient utilization of the resources and energies, which is very important for the social and economic development in China.

目前，乙醇需求量随经济发展而急剧增长。本项目以合成气及其下游产品二甲醚为原料，通过"二甲醚羰基化制乙酸甲酯-乙酸甲酯加氢制乙醇和甲醇"反应的串联式耦合制取乙醇。首先可控合成具有特定结构的金属改性丝光沸石催化剂，解决低二甲醚羰基化反应速率和催化剂易产生积碳失活的难题，通过考察改性金属的种类、微观配位结构、空间分布、分散度和还原度以及丝光沸石的晶体定向生长轴向、表面形貌、尺寸、微-介复合孔结构和酸性质等物理化学特性，并将其与羰基化反应活性相关联，阐明金属活性中心与分子筛酸中心之间的协同作用；其次将进一步提高用于乙酸甲酯加氢反应铜基催化剂的催化性能；最后优化二甲醚羰基化和酯加氢耦合反应的条件和催化剂再生条件，原位考察反应物、中间和最终产物在催化剂上的吸附/脱附行为，提出相关催化反应机理与模型，探索乙醇绿色合成新途径。本项目的成功实施，将促进我国资源、能源可持续发展战略，具有重要的社会和经济意义。

我国化石资源结构具有富煤、贫油、少气的特点，实现煤炭高效清洁利用是我国的重大能源资源战略需求。目前，乙醇作为一种清洁燃料、汽油添加剂和重要的化学品，其市场需求量呈爆炸型增长趋势。本项目以煤基合成气及其下游产品二甲醚为原料，通过“二甲醚羰基化制乙酸甲酯–乙酸甲酯加氢制乙醇和甲醇”串联式耦合反应制取乙醇。.在工业上，在铜基催化剂上发生的酯加氢反应已经非常成熟，因此本项目的难点在于获得高二甲醚羰基化活性和稳定性的丝光沸石分子筛催化剂，突破“催化剂易积碳失活”和“低二甲醚反应速率”这两个限制工业放大的难题。本项目（1）可控合成了由厚度约为50~100nm左右的丝光沸石纳米片宏观体结构，其二甲醚羰基化反应活性比商业化丝光沸石分子筛提高了2倍以上，同时获得了较好的催化稳定性；（2）通过热水蒸气处理增加丝光沸石上的B酸性位数目，进一步提高其催化性能；（3）通过单原子锌改性丝光沸石分子筛上的酸性位分布，提高二甲醚羰基化稳定性；（4）通过单原子铜改性丝光沸石分子筛，在降低铜使用量10倍以上的同时，大幅度提高了催化剂的催化活性和稳定性；（5）经过吡啶修饰的丝光沸石分子筛催化剂稳定性大幅度提高，但其二甲醚羰基化活性会下降40~50%。本项目从分子水平上解析了吡啶在丝光沸石上的吸附行为，发现O2处酸性位与吡啶分子结合力弱，在一定温度下容易再生，使得催化剂的活性提升60%左右。.本项目提出的乙醇绿色合成工艺路线所需原料（合成气和二甲醚）价格便宜、来源广泛，且副产品中只有水和甲醇，而甲醇又可以通过脱水生成二甲醚，从而实现一个绿色环境友好的碳循环过程。本项目的成功实施，将促进我国资源、能源可持续发展战略，具有重要的社会和经济意义。