Propylene-Permeable Catalytic Carbon Molecular Sieve (CMS) Membrane Reactors for Low Temperature Propane Dehydrogenation

丙烯是许多商业产品的起始材料，通常来自石油裂解双产物。然而，目前双相产品的供应预计无法跟上不断增长的需求。有意合成丙烯的另一种途径是从丙烷开始的，现在可以从低成本的天然气中获得。然而，将丙烷转化为丙烯，使用一种称为脱氢的过程，需要高温才能获得30-50%的低收率。在这个项目中，研究人员的目标是开发改进的催化剂和分离膜，以在更低的温度和更高的产量下生产丙烯。这种较低的温度还有一个额外的好处，就是在反应过程中减少不需要的副产物，比如焦炭。研究人员计划通过优化低温操作的催化剂结构和优化分离材料的孔径来实现这些目标，从而从起始材料丙烷中去除产物丙烯。这种分离策略的额外好处是推动反应继续生产丙烯。从该项目中获得的基本概念和技术将为材料发现和技术开发开辟新的途径，可以将天然气转化为增值化学品。该提案旨在通过减少在高温下因焦炭形成而导致的膜失活来提高丙烷脱氢（PDH）反应的丙烯收率。PIs假设控制Pt-Cu/沸石脱氢催化剂的结构和活性将导致低温丙烷活化，并从热力学上抑制副反应和焦炭的形成。为了验证这一假设，研究人员将合成具有不同合成参数的Pt-Cu/沸石催化剂，以控制催化剂的组成和性能。催化剂将使用固定床微反应器系统进行测试，反应器流出物将使用同时进行的气相色谱和质谱分析进行表征。在第二个目标中，将创建具有高刚性孔结构的新型聚酰胺衍生碳分子筛（CMS）膜，以在350-450℃下提供具有吸引力的丙烷/丙烯分离性能。这些膜的渗透性和选择性将通过热重分析研究C3H6/C3H8的高温吸附动力学和等温线来评估。Pt-Cu/沸石催化剂和（CMS）膜将在膜反应器中一起进行评估，以证明协同催化-运输。所提出的活动的结果将是基本理解(i)在PDH条件下碳分子筛和熵扩散选择性之间的结构-性质关系，（ii）单原子金属合金催化剂对低温C3H8活化的影响，（iii）丙烯和/或H2浓度对丙烷活化和焦化的动力学影响，以及（iv） PDH反应器中的协同催化转运。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Propylene is a starting material for many commercial products and is often derived from petroleum cracking biproducts. However, the current supply of biproducts is not expected to keep pace with growing demand. An alternative route to intentional propylene synthesis starts with propane, now available from low-cost natural gas. However, transforming propane to propylene, using a process called dehydrogenation, requires high temperatures to obtain even low yields of 30-50%. In this project, the investigators aim to develop improved catalysts and separation membranes to produce propylene at lower temperatures and higher yields. These lower temperatures have the additional advantage of reducing unwanted side-products, such as coke, during the reaction. The investigators plan to accomplish these aims by optimizing the catalysts structure for low-temperature operation and optimizing the pore size in the separation material to remove the product, propylene, from the starting material, propane. This separation strategy has the added benefit of driving the reaction to continue to produce propylene. The fundamental concepts and technologies obtained from this project will open new avenues of material discovery and technique development that can transform natural gas into value-added chemicals.This proposal aims to improve propylene yield from propane dehydrogenation (PDH) reactions by reducing membrane deactivation due to coke formation at high reaction temperature. The PIs hypothesize that controlling the structure and activity of Pt-Cu/zeolite dehydrogenation catalysts will result in low temperature propane activation and thermodynamically suppress side reactions and coke formation. To test this hypothesis the investigators will synthesize Pt-Cu/zeolite catalysts with varying synthesis parameters in order to control catalyst composition and properties. The catalysts will be tested using a fixed-bed microreactor system and reactor effluents will be characterized using concurrent gas chromatographic and mass spectrometric analysis. In a second aim, novel polyamide-derived carbon molecular sieve (CMS) membranes with highly-rigid pore structure will be created to provide attractive propane/propylene separation performance at 350-450 degrees C. The permeability and selectivity of these membranes will be evaluated by studying the high-temperature C3H6/C3H8 adsorption kinetics and isotherms using thermogravimetric analysis. The Pt-Cu/zeolite catalysts and (CMS) membranes will be evaluated together to demonstrate cooperative catalysis-transport in a membrane reactor. The outcome of the proposed activities will be fundamental understanding of (i) the structure-property relationships between carbon molecular sieve and entropic diffusion selectivity under PDH conditions, (ii) effects of single-atom metal alloy catalysts on low temperature C3H8 activation, (iii) kinetic effects of propylene and/or H2 concentration on propane activation and coking, and (iv) cooperative catalysis-transport in PDH reactors.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.