新型二氧化钼催化剂的制备及在燃油中氧化脱硫和氧化脱氮的应用

Sulfur and nitrogen in transportation fuels is a major source of air pollution. Ultra-deep desulfurization and denitrogenation of fuels attracted many attentions not only because of increasing environmental concern and legal requirements on sulfur and nitrogen content, but also because of the application of ultra-low-sulfur fuels for fuel cell.Severe operating conditions such as high temperatures, high pressures, and high hydrogen consumption are required for traditional hydrodesulfuriztion (HDS) and hydrodenitrogenation (HDN) to achieve the ultra-deep desulfurization and denitrogenation of diesel with S and N concentration <10ppm. High capital and operating costs are inevitable. Therefore, it is necessary to develop alternative ultra-deep desulfurization and denitrogenation processes such as oxidative desulfurization (ODS) and oxidative denitrogenation (ODN). The refractory substituted DBTs and indole can be easily oxidized under mild reaction conditions (atmospheric pressure and relatively low temperature) without use of expensive hydrogen, therefore, the capital requirements for ODS and ODN are significantly less than those for deep HDS and HDN. MoO3/Al2O3 catalyst exhibited high ODS and ODN activity, compared with MoO3, MoO2 has large amounts of surface oxygen vacanies with free electrons trapped in which can adsorb peroxy oxygen in oxidant and prompt the oxidative activity. Using different reduction agents complexing agents, MoO2 with various morphologies are synthesized by hydrothermal reduction method. By investigating the hydrothermal conditions and crystallization conditions,the formation mechanisms of MoO2 with various morphologies are obtained. The oxidative desulfurization (ODS) activities and oxidative denitrogenation (ODN) activities of these catalysts are investigated.The relationships between morphologies and ODS, ODN activities are obtained by XRD, XPS, SEM, TEM. Various supports such as SiO2,mesoporous SiO2,TiO2 are introduced in the preparation of supported MoO2 catalyst using hydrothemal reduction method. The morphologies and surface structures of supported MoO2 catalysts are studied to identify the mechanisms of the interaction between MoO2 and various supports. The ODS and ODN activities of vaious sulfur-containing compounds and nitrogen-containing compounds are studied on supported MoO2 catalysts to elucidation the ODS and ODN reaction mechanism.Various metals (Ni, Co, Cu) are introduced in supported MoO2 catalysts using hydrothermal reduction method to obtain high ODS and ODN selectivity and activity.

燃油中的含硫化合物和含氮化合物燃烧时产生的SO2和氮氧化物是造成空气污染的主要原因，各国都制定了越来越严格的燃油中S、N含量标准。氧化脱硫和氧化脱氮在常温常压下进行，不耗费氢气，对于传统的高温高压加氢脱硫和加氢脱氮过程中难以脱除的烷基二苯并噻吩和吲哚等化合物具有更好的氧化脱除性能。负载型MoO3催化剂表现出良好的氧化脱硫和氧化脱氮活性，MoO2不同于MoO3，表面存在着大量氧离子空位束缚了大量自由电子，更容易吸附氧化剂中的过氧原子，提高过氧原子的氧化能力。采用水热还原法制备在不同载体上负载的不同形貌的负载型MoO2催化剂，进一步采用水热还原法在负载型MoO2上沉浸金属Me，均尚未见有文献报道。探讨负载型Me-MoO2催化剂的氧化脱硫和氧化脱氮机理，获得高选择性、高活性和高稳定性的负载型Me-MoO2燃油氧化脱硫和氧化脱氮催化剂。

近年来，环境保护标准日益严苛，部分国家和地区已要求燃料油中的硫含量低于10 ppm，深度脱硫已成为一个全球化的研究课题。氧化脱硫技术反应条件温和，工艺流程简单，非临氢操作，且可以脱除油品中含量较高、加氢脱硫难以除去的二苯并噻吩类化合物，是一种很有发展潜力的脱硫技术。本项目以二苯并噻吩（DBT）为反应探针，叔丁基过氧化氢（TBHP）为氧化剂，在固定床连续流动反应器上对催化剂进行氧化脱硫研究。分别采用氢气还原法，水合肼低温还原法，水热还原法，过氧钼酸-水热还原法等方法制备MoO2单体。结果表明，水热还原法可在温和条件下制备出纯净的MoO2，且可通过优化制备条件如反应温度，加入改性剂，晶化温度等控制MoO2的形貌，进而达到改进其催化活性的目的。经草酸改性，在最佳条件下制备的MoO2呈规则的松球状结构，氧化脱硫活性良好，在80℃时氧化脱硫转化率即可达到80%，100℃时转化率达到95%以上，远高于MoO3的催化活性。采用水合肼低温还原法，以Al2O3和SiO2-Al2O3为载体制备负载型催化剂。在最佳制备条件下，负载量为20%的MoO2/Al2O3在60℃时氧化脱硫转化率即可达到80%以上，100℃时可将模拟油品中的DBT完全脱除。以20%MoO2/SiO2-Al2O3为催化剂，40℃时氧化脱硫转化率即可达到95%以上，大大降低了反应能耗。氧化脱硫反应和MoO2催化剂的制备都秉承节能环保原则，尽量避免使用高温高压和昂贵原料，对设备成本要求低，明显降低了油品脱硫成本。进一步的研究分别采用草酸水热还原法、醇热还原法、草酸改性醇热还原法这三种方法制备出纯的VO2和V2O3单体。并采用草酸水热还原法和氢气还原法，以SiO2-Al2O3（SA）复合载体为载体制备负载型V2O3催化剂。经草酸水热还原法在最佳制备条件下，50℃时理论负载量为10%的V2O3/SA氧化脱硫转化率可达93%。