CAREER: Reaction Kinetics Analysis of the Lebedev Process

该项目探索了使用生物可再生乙醇作为传统石油资源的替代品来生产1，3-丁二烯(BD)的潜力，1，3-丁二烯(BD)是一种重要的化学前体，用于生产用于汽车轮胎、纸张涂料、纺织品背衬和粘合剂的合成橡胶。最近石油资源的变化给BD市场带来了压力，为BD的专用生产打开了大门。一种特别有前景的技术是Lebedev工艺，它从乙醇中生产BD。然而，该工艺依赖于复杂的多组分催化剂，产品收率较低。该项目将在分子水平上绘制用于从乙醇中生产BD的反应网络图，这反过来对开发能够实现高BD产率的新催化剂至关重要。因此，该项目有潜力确保BD生产的安全性和美国的竞争力，同时支持向生物可再生原料的清洁能源过渡。此外，研究人员将开发新的课程材料，向本科生讲授催化反应器设计和生物基化学品生产。该项目团队还将开发一个模块，教育高中生和公众有关从木质生物物质中生产可再生化学品的知识。在联合碳化物公司早期工作的基础上，许多小组使用氧化镁-二氧化硅作为低成本平台，在此平台上开发列别捷夫工艺的下一代催化剂。然而，到目前为止，还没有对氧化镁-二氧化硅生产BD进行严格的反应动力学分析。根据研究小组最近发表的结果，结合文献中的观察，假设纯MgO-SiO_2催化剂上BD的生成速度受乙醇脱氢控制，而在过渡金属助剂存在下，BD的选择性被假设为由酸碱中心对催化的C-C键形成。关于C-C偶联机制和所需活性位点的性质，文献相互矛盾，本研究将从三个主要方面阐明这一点。首先，使用含有特定类型酸碱中心对的模型MgO-SiO_2催化剂的稳态反应动力学测量将被用来识别速度控制步骤，并澄清在BD生产中哪些中心对动力学意义重大的反应负责。接下来，这些催化剂将通过FTIR、XPS、LEIS和SS核磁共振进行光谱表征，以确定位置要求和丰富的表面中间体。最后，微观动力学模型将用于将宏观动力学观察与动力学同位素效应、同位素示踪研究和DFT计算提供的机械洞察力统一起来。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The project explores the potential of using biorenewable ethanol as an alternative to conventional petroleum resources for production of 1,3-Butadiene (BD) - an important chemical precursor used to produce synthetic rubbers utilized in car tires, paper coatings, textile backings, and adhesives. Recent shifts in petroleum resources have placed pressure on the BD market, opening the door to on-purpose production of BD. A particularly promising technology is the Lebedev process which manufactures BD from ethanol. However, the process relies on a complex, multicomponent catalyst and suffers from low product yields. The project will develop a molecular-level picture of the reaction network used to produce BD from ethanol, which in turn is important for developing new catalysts that can achieve high BD yields. Thus, the project has potential to ensure security and U.S. competitiveness in BD production while supporting the clean-energy transition to biorenewable feedstocks. Additionally, the investigator will develop new course materials to teach undergraduate students about catalytic reactor design and biobased chemicals production. The project team will also develop a module to educate high school students and the public about the production of renewable chemicals from woody biomass.Following on the early work of Union Carbide, many groups have used MgO-SiO2 as a low-cost platform from which to develop next-generation catalysts for the Lebedev process. However, to date a rigorous reaction kinetics analysis of BD production by MgO-SiO2 has not been performed. Based on recently published results from the investigator’s team, coupled with observations in the literature, the rate of BD formation over pure MgO-SiO2 catalysts is hypothesized to be controlled by ethanol dehydrogenation, while selectivity to BD in the presence of transition metal promoters is hypothesized to result from C-C bond formation catalyzed by acid-base site pairs. The literature is conflicted about the C-C coupling mechanism and the nature of the requisite active sites, which the study will clarify in three main thrusts. First, steady-state reaction kinetics measurements using model MgO-SiO2 catalysts containing specific types of acid-base site pairs will be used to identify rate-controlling steps and to clarify which sites are responsible for the kinetically significant reactions in BD production. Next, these catalysts will be spectroscopically characterized by FTIR, XPS, LEIS, and SSNMR to identify site requirements and abundant surface intermediates. Finally, a microkinetic model will be used to unify the macroscopic kinetics observations with mechanistic insight provided by kinetic isotope effect and isotope tracer studies and DFT calculations.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.