基于Lewis酸催化机制设计合成丙烷脱氢氧化物催化剂

Propylene is a basic material in the petrochemical industry and its market demand is increasing each year. Propane dehydrogenation is an economical, feasible and effective route for the production of propylene, which has recently attracted lots of attention in the field of petrochemical industry. Although Pt and Cr based catalysts have been commercialized for propane dehydrogenation process, the high cost of Pt and toxic Cr significantly limit their wide application. In order to overcome these problems, this proposal aims at the development of novel metal oxide catalysts for propane dehydrogenation based on Lewis acid catalyzed dehydrogenation mechanism. The catalysts will be controlled synthesized from soft chemistry approach in order to precisely tune their micro-structure at different levels, and the structure-activity relationship will be established, which will provide basic understanding for the design and synthesis of propane dehydrogenation catalyst. Upon the optimization of preparation parameters, efficient metal oxide catalysts with high activity, selectivity and stability will be finally achieved, which will deliver conversion above 40% and selectivity above 90% under the reaction temperature below 630 C, H2/C3H8 ratio below 0.5 and gas hourly space velocity above 800 h-1; meanwhile the deactivated catalyst is completely regenerable. Therefore, the study in this proposal will provide fundamental knowledge and technology solution for the development of a new generation of catalyst for propane dehydrogenation.

丙烯是石油化工基本原料其需求量逐年增长，丙烷脱氢是生产丙烯非常有竞争力的路线，正成为石化产业关注的焦点。为了突破传统Pt基催化剂成本高和Cr基催化剂环境污染等问题，本项目基于对Lewis酸催化脱氢机制的认识，创制高效、经济、环境友好的丙烷脱氢酸性氧化物催化材料，包括负载型本征Lewis酸性氧化物和掺杂型缺陷Lewis酸性氧化物，发展软化学可控合成策略在多尺度上调控催化剂的多级结构，建立催化剂的构-效关系，为催化材料设计合成提供科学基础。通过对合成条件的优化，开发出活性好、选择性高和稳定性强的两类氧化物催化剂，在反应温度630度以下、H2/C3H8比小于0.50、气体空速大于800h-1的反应条件下，单程转化率大于40%，选择性大于90%，且催化剂能完全再生，为新一代丙烷脱氢制丙烯技术的开发奠定理论基础和技术支撑。

丙烯是石油化工基本原料其需求量逐年增长，丙烷脱氢是生产丙烯非常有竞争力的路线，正成为石化产业关注的焦点。为了突破传统Pt基催化剂成本高和Cr基催化剂环境污染等问题，本项目基于对Lewis酸催化脱氢机制的认识研制了四类高效丙烷脱氢催化剂：Sn分子筛催化剂、γ-Al2O3负载的Ga2O3催化剂、Y和La掺杂的ZrO2催化剂和本体型Al2O3催化剂。通过XRD、Raman、BET、ICP、SEM-EDX、NH3-TPD、XPS、Py-FTIR、HRTEM等手段确定了这几类催化剂的结构，详细考察了这四类催化剂在丙烷脱反应中的催化性能，解释了催化剂的构-效关系。主要研究结论如下：. （1）通过对分子筛脱Al补Sn合成了Sn-Beta、Sn-ZSM-5、Sn-Y和Sn-MOR分子筛。丙烷脱氢的性能与分子筛的Lewis酸性直接关联，高Lewis酸量有利于丙烷脱氢反应。各类分子筛中Sn-Beta具有最佳的催化活性，丙烷转化率高达40%，丙烯选择性达到92%，并且在长达72 h的反应中没有发现失活，表现出极佳的稳定性。. （2）通过浸渍法制备一系列的Ga2O3/Al2O3催化剂，这些催化剂具有强的Lewis 酸性。负载量为 5%的Ga2O3/Al2O3催化剂具有最优的丙烷脱氢性能，其初始丙烷转化率为65%，丙烯选择性一直稳定在90%；经过多次再生，丙烷转化率和丙烯选择性都基本保持稳定状态，Ga2O3-γ-Al2O3催化剂催化可实现高效的多次循环再生。. （3）研究了丙烷在具有Lewis酸性Al2O3的丙烷脱氢性能。γ-Al2O3-200催化剂综合性能最好，反应24 h后的转化率仍然高达35%，选择性一直保持83%，且具有良好的再生性能。因此，γ-Al2O3-200是一种有一定潜力的丙烷脱氢制丙烯催化剂。. （4）通过水热法制备了一系列LaλZr100-λOx和YλZr100-λOx催化剂，La元素成功“进入”ZrO2的晶体结构中并高度分散，提高了催化剂的比表面积和缺陷位点，从而产生了强Lewis酸性位。丙烯选择性稳定在93%以上，催化剂能够经完全再生，其再生前后的结构并未改变，说明LaλZr100-λOx催化剂结构稳定且高效。. 上述研究证明了具有Lewis酸性的氧化物是一类高性能的丙烷脱氢催化剂，为新型丙烷脱氢催化剂的研制提供了理论支撑。