Bio-ethanol Upgrading Catalysed by Multifunctional Zeolites

自2015年以来，全球以生物质为原料的生物乙醇产量每年已超过250亿加仑。化学工业对化石燃料的依赖所产生的负面环境影响意味着，使用可再生能源的压力越来越大。因此，将生物乙醇升级为高价值的化学品和燃料引起了学术界和工业界的极大兴趣。生物乙醇主要用作汽油的替代可再生燃料添加剂。不幸的是，生物乙醇对大多数发动机具有腐蚀性，因此在没有适当的发动机改装的情况下，只能在汽油中添加低含量的乙醇(10%)。此外，生物乙醇的能量密度比汽油低(70%)，而且可溶于水，这可能会导致储罐中的分离和稀释问题。相比之下，从生物乙醇中提取的生物丁醇是一种更好的汽油发动机可再生添加剂；它的能量密度是汽油的90%，无腐蚀性，与水的相容性有限，因此可以在更高浓度下混合，甚至可以作为独立的生物燃料使用。目前，以贵金属为基础的催化剂通常用于乙醇转化为丁醇。然而，这些催化剂对于工业生产生物丁醇来说是不可持续的，它们的生产和处置被认为是环境和经济问题。因此，从地球上丰富的无毒材料开发有效的催化剂将克服这一过程商业化的主要障碍。沸石是一种微孔铝硅酸盐材料，在催化裂化等一系列工业过程中用作可持续催化剂。它们高度稳定的笼状结构允许形状选择催化，并且它们可以被结构修饰以容纳大量不同的活性中心，从而能够催化多步反应过程。最近达勒姆大学泰勒小组的工作表明，沸石负载的氧化锌(ZnO)可以产生非常稳定的乙醇脱氢催化剂(超过120小时)，这是乙醇制丁醇反应级联反应的第一步。本项目旨在对这些氧化锌/沸石催化剂进行进一步的改性，增加活性中心，以完成乙醇到丁醇的完整级联反应。这将包括丰富的地球，额外的骨架金属位置，以及骨架路易斯酸位。该项目将确定不同催化组分的性质和位置如何影响整体催化功能，这将为未来的催化剂设计提供结构功能模型。不同催化功能的位置将通过各种不同的合成方法进行控制。该项目将利用流动反应器和在线分析相结合的方法探索乙醇多步转化为丁醇的过程，并将通过原位红外光谱探索反应机理。该项目涵盖了生物能源、催化、化学反应动力学和机理、功能陶瓷和无机物等多个EPSRC研究领域。这项研究的主题是能源和制造未来，主要目标是开发用于生物燃料生产的催化剂。

Since 2015, global production of bioethanol from biomass-based feedstocks has exceeded 25 billion gallons per year. The negative environmental impacts derived from the chemical industry's dependence on fossil fuels means that there is an ever-increasing pressure to utilise renewable alternatives. Consequently, the upgrading of bioethanol into higher value chemicals and fuels is of great interest in both academia and industry. Bioethanol is predominantly used as a drop-in renewable fuel additive to gasoline. Unfortunately, bioethanol is corrosive to most engines and so only low levels (10%) can be added to gasoline without suitable engine modification. Additionally, bioethanol has a lower energy density (70%) than gasoline and is water miscible, potentially causing problems with separation and dilution in storage tanks. Contrastingly, biobutanol, derived from bioethanol, is a much better renewable additive for gasoline engines; it has 90% the energy density of gasoline, is non-corrosive and has limited miscibility with water so it can be blended at higher concentrations, or even be used as a stand-alone biofuel. Currently, precious metal based, catalysts are typically utilised for the conversion of ethanol to butanol. These catalysts however are unsustainable for industrial manufacture of biobutanol, and their production and disposal are considered both environmentally and economically problematic. Development of effective catalysts from earth abundant, non-toxic materials would therefore overcome a major barrier in the commercialisation of this process. Zeolites are microporous aluminosilicate materials used as sustainable catalysts in a range of industrial processes such as catalytic cracking. Their highly stable, cage-like structure allows for shape-selective catalysis, and they can be structurally modified to accommodate numerous different active sites, resulting in an ability to catalyse multistep reaction process.Recent work in the Taylor group at Durham University has shown that zinc oxide (ZnO) supported on zeolites gives rise to very stable ethanol dehydrogenation catalysts (over 120 hours), which is the first step in the ethanol to butanol reaction cascade. This project aims to modify these ZnO/Zeolite catalysts further, with additional active sites to complete the full ethanol to butanol cascade pathway. This will include earth abundant, extra framework metal sites, as well as framework Lewis acid sites. The project will determine how the nature and location of the differing catalytic components affects overall catalytic function, which will provide structure function models for future catalyst design. The location of the different catalytic functionalities will be controlled via a variety of different synthetic approaches. The multistep conversion of ethanol to butanol will be explored using flow reactors coupled with online analysis, and mechanistic pathways will be probed by in-situ infrared spectroscopy.This project spans multiple EPSRC research areas including bioenergy, catalysis, chemical reaction dynamics and mechanisms, and functional ceramics and inorganics. The research falls under the themes of Energy and Manufacturing the Future, with the primary goal being development of catalysts for biofuel production.