甲醇电催化羰基化合成碳酸二甲酯工艺及电催化机理研究

Methanol is important direct or indirect product of coal devolatilization. It is an available road to obtain Chemicals or synthesis product from coal used methanol as raw material. Dimethyl carbonate(DMC) is very important as a synthetic intermediate and as a raw material in the current chemical industry. DMC is widely used as a safe carbonylation reagent to substitute for the strong toxic reagents dimethyl sulfate and phosgene for polymer synthesis such as polycarbonate and isocyanate because of it is almost non-toxicity. DMC is also a good green solvents and gasoline additives. DMC was produced by the phosgene method in the early, but phosgene was highly toxic. Therefore, phosgene-free methods have been studied and developed. In recent years, most of DMC was manufactured by the Eni Chem method and the Ube method from CH3OH and CO. These processes have a great advantage of not using phosgene, but also have some disadvantages, including reaction conditions harshly and having a lot of by-products for the Eni Chem method, and multisteps operation and use of corrosive nitrogen monoxide for the Ube method. Therefore, study and development of new method for DMC formation is very important.Advantages of the electrochemical carbonylation method is realized as environmental benign and easy to operation. For those reasons, synthesis DMC by electrolytic carbonation of methanol has been an attractive issue for sino or foreign researchers.Early approaches to the electrochemical synthesis of DMC by carbonylation of methanol were based on the redox couple Br-/Br2, but the Br2 was highly toxic and rather volatile. Pd and Cu elements were active for the electrochemical carbonylation of CH3OH to DMC in gas cell system at 70℃ had been reported, but the selectivities of those systems were rather poor, there were a lot of by-products such as CO2, DMM and MF. PdCl2/VGCF anode and CuCl2/VGCF anode were studied in the three-phase-boundary electrolysis cell at 25℃, but CuCl2/VGCF anode was not active in this system. In recent years, Au and Pd as electrocatalysts were studied in the forms of Au/VGCF anode and Pd/VGCF anode at room temperature and atmospheric pressure, but Au and Pd were very expensive, and the preparation of M/VGCF anode was very troublesome, and the most important was that the selectivities were very poor when using Au and Pd as electrocatalysts. CuCl(bipy) was reported have electrochemical activity on carbonylation of CH3OH to DMC at room temperature and atmospheric pressure, but CuCl was very unstable in the air and strong irritant to the skin. Here, we propose to find a low cost catalysis with high efficient and selectivity, investigate the catalytic mechanism. Base on the synthesis method, a new process can be proposed, all the conditions of the process will be optimism at last. This research will be benefit for extend the industry chain of coal devolatilization.

甲醇是煤直接或间接液化的重要产品，以其为原料的化学品合成是以煤为原料制取化学品的主要途径。碳酸二甲酯是高效、低毒、泛用的有机合成中间体，有良好的工业应用前景。近期开发的非光气法甲醇制取碳酸二甲酯工艺中存在毒性大、操作安全性差等问题，而电化学有机合成方法具备环境友好，操作安全等优点。为此，国内外研究者开展了甲醇电催化合成碳酸二甲酯的相关研究，但存在电催化剂价格高、反应选择性差、产物产率低等问题，未能实现工业化。本课题拟开发廉价、高效的电催化剂，提高常温常压下甲醇电催化羰基化合成碳酸二甲酯反应选择性，探索电催化反应机理，提出电催化合成过程工艺，优化工艺参数，为实现工业化生产提供理论支持。本课题立足于内蒙古自治区煤、电、稀土等资源优势，开展以甲醇为原料的电化学催化羰基化合成碳酸二甲酯工艺研究，为甲醇的非燃料利用提供新的途径。该工艺的开发应用对延伸煤制油产业链，获取高附加值的化工产品具有重要意义。

DMC被誉为21世纪有机合成的一个“新基块”，其发展将对我国的煤化工、甲醇化工、C1化工起到巨大的推动作用。而且由于其分子中含有CH3-、CH3O-、CH3OCO-、-CO-等多种官能团，因而具有良好的反应活性，具有很好的应用价值。目前，正在开发的非光气路线可分为两大类: 一类是甲醇间接氧化羰基化; 一类是甲醇直接氧化羰基化。而这两种合成方法都存在这弊端，如有毒的催化剂、催化剂失活、存在爆炸行危险等问题。所以, 开发既对环境友好, 又操作安全的DMC 新合成方法十分重要。电化学法恰恰具备这些优点。.在电化学催化甲醇羰基化合成DMC工艺过程中，催化剂的制备是核心技术内容，催化机理的探讨对催化剂的选择与制备具有指导意义，电极、电解池及电解质以及电解电压等操作参数则是工艺优化的主要内容。本项目针对这些在电化学催化甲醇羰基化合成碳酸二甲酯过程中关键性技术问题进行探索研究。.经过多年的探索研究，我们设计定制了双室电解池，之后又此电解池进行了优化设计，我们选取碳棒作为阳极、Ag/AgO作为参比电极、铜棒作为阴极。本课题组依次对金属化合物、金属配位化合物、金属有机骨架等催化剂进行了考察和研究，研究结果发现在多种金属化合物（CoCl2，NiCl2，CuCl，CuCl2和CuSO4）催化剂中，CoCl2对电化学催化甲醇氧化羰基化合成DMC具有催化活性，此研究为以后催化剂的研究奠定了基础。在多种金属配位化合物（CoCl2，NiCl2，CuCl，CuCl2和CuSO4与bipy和phen 配合）催化剂中，Cu(Phen)Cl2具有最好的催化性能。作为非均相催化剂的金属有机骨架（MOF）虽然改善了均相催化剂存在的问题，但是催化剂效率有所降低，通过GO和PANI对MOF进行改性，碳酸二甲酯的收率提高到了0.2%，这是首次将MOF引入电催化领域，并为电催化领域开阔了范围。在对电解质研究过程中，我们发现碱性越强的电解质越有利与DMC的合成。除此之外，我们还对均相催化和非均相催化的催化机理进行了多次探索和改进。. 基于以上的研究，本项目优化了电化学反应过程工艺参数，在提高选择性及产率的同时，简化产物分离过程，在制取高选择性、高电流利用率催化剂基础上，优化过程工艺参数，探索高产率的DMC合成工艺，为甲醇的非燃料利用，延长煤液化产业链条提供新的途径。