Selective photocatalytic conversion of CO2 to olefins: a feasibility study

寻求可持续资源以满足不断增长的全球人口的需求是本世纪人类面临的主要挑战之一。全世界都在关注二氧化碳排放对气候变化的影响，这意味着迫切需要减少我们对石油作为化学品来源的依赖。石油占化学原料的绝大多数，但要成为真正可行的替代原料，必须是可持续的，即“有能力满足21世纪的能源需求，同时不损害子孙后代的能源需求。”最近的英国第四次碳预算设定了雄心勃勃的目标，即到2025年将二氧化碳排放量在1990年的水平上减少50%。利用二氧化碳作为化学原料是一种特别有吸引力的策略，可以改善碳排放，同时提供可持续、安全和有用的碳捕获。目前用于化学合成（主要是尿素）的二氧化碳利用率仅占二氧化碳排放量的2%，但预测预测这些方法每年可减少300-700亿吨（兆吨）二氧化碳，远远超过核能、风能和纤维素生物燃料技术（每年约5000万吨）二氧化碳减排的综合潜力。事实上，最近的CS3白皮书“可持续发展的全球社会”强调光催化二氧化碳转化为化学品是一个全面的基础材料化学研究必不可少的领域。烯烃及其聚合物是世界上最大的单一化学商品，2010年全球乙烯和丙烯的生产能力估计分别为1.23亿吨和7700万吨/年。从石油中生产乙烯和丙烯的商业过程包括将石脑油、汽油和冷凝物蒸汽或催化裂化成碳氢化合物混合物，然后进行蒸馏。蒸汽裂解是化学中最耗能的过程，占该行业一次能源使用的8%，每年二氧化碳排放量为1.8 -2亿吨！光催化CO2还原（PCR）提供了一种潜在的经济和环境友好的CO2利用过程，促进塑料和聚合物中的长期碳夹带，并创建新的化学品供应链，而不依赖于目前对石油，煤炭和天然气的依赖。这项可行性研究将开发新型光催化剂，对实现CO2选择性光还原为乙烯（即2CO2 + 2H2O -> C2H4 + 3O2）至关重要，从而支持TranSChem计划资助申请的重新提交，该申请旨在将这种纳米结构无机光催化剂与生物色素的特殊光收集特性结合起来，在新型太阳能光反应器中最大限度地强化CO2 PCR到烯烃的过程。

The quest for sustainable resources to meet demands of a constantly rising global population is one of the main challenges for mankind this century. Worldwide concern over the impact of CO2 emissions on climate change means there is an urgent need to reduce our dependency on oil as a source of chemicals. Oil accounts for the vast majority of chemical feedstocks, however to be truly viable alternative feedstocks must be sustainable, that is "have the ability to meet 21st century energy needs without compromising those of future generations." The recent UK Fourth Carbon Budget set the ambitious target of a 50 % cut in CO2 emissions by 2025 compared with 1990 levels. CO2 utilisation as a chemical feedstock is a particularly attractive strategy to ameliorate carbon emissions while offering sustainable, safe and useful carbon capture. Current CO2 utilisation for chemical synthesis (principally urea) accounts for only 2 % of emitted CO2, but forecasts predict such approaches could mitigate 300-700 Mt (megatons) CO2 per year, far larger than the combined potential for CO2 abatement by nuclear, wind and cellulosic biofuel technologies (~50 Mt CO2 per year). Indeed the recent CS3 White Paper "A Sustainable Global Society" highlights photocatalytic CO2 conversion to chemicals as an area where comprehensive fundamental materials chemistry research is essential.Olefins and their polymers are the single largest chemical commodity in the world, with global ethene and propene production capacity in 2010 estimated to be 123 and 77 Mt/year respectively. Commercial ethene and propene manufacture from oil involves steam or catalytic cracking of naphtha, gasoil and condensates to hydrocarbon mixtures followed by distillation. Steam cracking is the most energy-consuming process in chemistry, accounting for 8% of the sector's primary energy use and annual CO2 emissions of 180-200 Mt! Photocatalytic CO2 reduction (PCR) offers a potentially economical and environmentally-benign CO2 utilisation process, facilitating long-term carbon entrainment within e.g. plastics and polymers, and the creation of new chemical supply chains free of current dependencies on oil, coal and natural gas.This feasibility study will develop novel photocatalysts critical to achieving the selective photoreduction of CO2 to ethene (i.e. 2CO2 + 2H2O -> C2H4 + 3O2), thereby underpinning resubmission of the TranSChem Programme Grant application that seeks to integrate such nanostructured inorganic photocatalysts with the exceptional light-harvesting properties of biological pigments, inside novel solar photoreactors for maximum process intensification of CO2 PCR to olefins.