铑合金催化煤地下气化合成气高选择性制乙醇的理论研究

High selectively synthesis from syngas to ethanol is the important way to further improve the economic benefits in the underground coal gasification, ethanol as alternative to petroleum-derived fuels can help to solve the problem of our country's increasingly serious environmental pollution and energy shortage. Due to the low selectivity and poor conversion rate of rhodium based catalysts are difficulty to fulfill the industrialization requirement, this project is focused on improving the Rh-based catalysts for the synthesis of ethanol from syngas. Taking advantage of computational chemistry, we present the density functional theory study of the conversion from syngas to ethanol, methane, and methanol by changing the substrate of rhodium clusters with different size, shape, and electric clusters. Through the analysis of thermodynamics and kinetics，the influence of absorption energy, activation energy of the ethanol process will be discovered, which is important for optimizing low selectivity of Rh catalyst. Furthermore, Rh catalyst will be modified by promoter metals, such as Fe, as well as anti carbon deposition of Au. It will provide a valuable guide for design and synthesis of highly selectively Rh-based catalyst. This project proposes to add the anti carbon deposition of Au to catalyst. It not only enriches the rhodium catalyzed database, but also will help the ethanol development of poly-generation both petrochemical and underground coal gasification.

研发合成气高选择性制乙醇不仅是进一步提高煤地下气化经济效益的重要途径，同时乙醇作为优质的液体燃料还有助于缓解我国日益严重的环境污染和能源短缺的问题。针对常见铑催化剂选择性差、转化率低而制约工业化发展的难题，本项目拟以改善和提高铑基催化剂催化性能制乙醇为研究目标，结合计算化学优势，采用密度泛函理论从小团簇入手，以不同尺寸，形状，电性的铑团簇和铑合金表面为底物系统展开合成气乙醇化的研究。重点从热力学和动力学两方面，通过各物种吸附能、反应活化能等因素的比较，明确副反应甲烷化，甲醇化对合成气制乙醇选择性的影响，进而从理论上理清铑催化选择性差的根本原因，再借以Fe，Au等助剂对铑催化剂进行分子修饰，并以此为指导完成新型铑合金催化剂的分子设计，进而为实验高选择性铑合金催化剂提供理论指导。本项目引入抗积碳Au为助剂，丰富了铑合金的数据库，也为煤地下气化及石油化工多联产制乙醇的发展提供有价值的科学依据。

煤地下气化氢化CO高选择性制乙醇不仅是进一步提高煤地下气化经济效益的重要途径，同时乙醇作为优质的液体燃料还有助于缓解我国日益严重的环境污染和能源短缺的问题。实验发现铑对该反应具有较好的活性和选择性，加入金属铁能极大提高选择性。我们借助密度泛函理论、Clustes和Slab模型，建立CO氢化的网络关系图并研究了Rh团簇和RhFe合金团簇最稳定结构，提出H2、CO、HCO在铑团簇的吸附与解离机理、考察影响CH3CO生成的反应动力学和热力学因素。研究表明，团簇的尺寸对氢解离很重要，解离难易与配位数存在密切关系；HCO氢助解离比CO直接解离更容易；CH3CO与底物相互作用很强；CO或HCO解离成C或O原子仍是合成气制乙醇反应过程中的速率控制步。此外，我们还完成甘肃华亭煤地下气化在空气、富氧和纯氧下的煤气组分分析测试工作。以上研究结果既加深了合成气催化制乙醇的认识，又为乙醇化催化剂的研究设计提供了有价值的重要信息。