Production of Renewable Acrylic Acid via Catalytic Dehydration of Lactic Acid: Mechanistic Studies and Catalysts Design

摘要标题：通过乳酸催化脱水生产生物质绿色聚合物前体随着环境问题和碳氢化合物原料和中间体价格的持续上升，燃料和化学品的生产从化石碳源转向可再生碳源不仅具有经济意义，而且由于原油储量的减少，从环境角度来看，通过有效减少一些二氧化碳排放是非常可取的。丙烯酸及其酯是聚合物工业的主要前体，年需求量为400万吨。它们目前是通过以能源密集型原油为基础的工艺生产的。此外，天然气产量的爆炸性增长导致天然气作为碳源的使用量相对于原油突然增加，导致包括丙烯在内的许多关键化学品的产能与需求之间存在巨大差距。幸运的是，生物质转化领域的最新进展使从生物质生产各种化学品，如可再生乳酸，在技术上是可行的，在经济上也具有竞争力。特拉华大学的徐炳军教授建议发展基本的认识，制定一种利用这种乳酸作为绿色前体来制造丙烯酸的工艺。该奖项支持应对向可再生、生物质衍生原料转变的挑战所需的研究。由于乳酸和丙烯酸的结构相似，与目前的工业路线相比，以乳酸为原料通过催化脱水生产丙烯酸可能具有更高的选择性。与目前的工业工艺不同的是，从丙烯开始需要几个选择性的氧化步骤，而将乳酸转化为丙烯酸只需要一个脱水步骤。因此，催化剂和反应条件可以一步到位地优化，而不是通常发生在不同类型的活性中心上的多个反应，并在不同的条件下达到最佳性能。此外，在脱水反应中通常比部分氧化反应更容易控制选择性，因为完全氧化通常比部分氧化反应在热力学上更有利。这项工作旨在通过反应活性评价、材料合成和光谱研究相结合的方法，合理设计高效的催化剂，促进乳酸转化为丙烯酸。乳酸催化脱水合成丙烯酸的研究也将为双功能或多功能分子与催化活性中心的相互作用和选择性活化提供基本的见解，大多数生物质衍生分子属于这一类分子。因此，在拟议的研究中获得的机理见解可能导致指导原则定制催化剂的活性中心，不仅用于乳酸脱水的特定反应，而且还用于涉及多功能生物质衍生分子的广泛的其他化学转化。

Abstract Title: Production of green polymer precursors from biomass through catalytic dehydration of lactic acid to acrylic acidAs environmental concerns and the price of hydrocarbon-derived feedstocks and intermediates escalate on a continuing basis, the shift of the production of fuels and chemicals from fossil to renewable carbon sources not only makes economic sense due to price volatility and dwindling reserve of crude oil, but also is highly desirable from the environmental perspective by effectively reducing some CO2 emissions. Acrylic acid and its esters are key precursors in the polymer industry, with an annual demand of 4 million metric tons. They are currently produced through an energy intensive crude oil-based process. In addition, the explosive growth of natural gas production has led to a sudden increase in the use of natural gas relative to crude oil as a carbon source, has created significant gaps between the production capacity and demand of many key chemicals including propylene, the raw material for acrylic acid production. Fortunately, recent progress in the field of biomass conversion has made the production of various chemicals, such as renewable lactic acid, from biomass technologically feasible and economically competitive. Professor Bingjun Xu at the University of Delaware, proposes to develop the fundamental understanding to formulate a process for using this lactic acid as a green precursor to make acrylic acid. This award supports the research needed to answer the challenges of a shift to renewable, biomass-derived feedstocks. Production of acrylic acid from lactic acid via catalytic dehydration is potentially more selective compared to the current industrial route due to the structural similarity of lactic and acrylic acids. In contrast to the current industrial process, which requires several selective oxidation steps starting from propylene, only one dehydration step is needed to convert lactic acid to acrylic acid. Thus catalysts and reaction condition can be optimized for a single step rather than many reactions, which typically occur on different type of active sites and reach optimal performance under different conditions. In addition, it is generally easier to control selectivities in dehydration than partial oxidation reactions, since total oxidation is typically more thermodynamically favored than partial oxidation reactions. The proposed work aims at rationally designing efficient catalysts to facilitate the conversion of lactic acid to acrylic acid through a combination of reactivity evaluations, materials synthesis and spectroscopic investigations. The study of catalytic dehydration of lactic acid to acrylic acid will also provide fundamental insights into the interaction and selective activation of bi- or multi-functional molecules, a group to which most biomass-derived molecules belong, with catalytic active sites. Thus, the mechanistic insights gained in the proposed research could lead to guiding principles for tailoring active sites of catalysts, not only for the specific reaction of dehydration of lactic acid, but also for a broad range of other chemical transformations involving multifunctional biomass-derived molecules.