Progress of research on aviation kerosene preparation using bioethanol

In recent years, the Chinese government has proposed the “dual carbon” goal of achieving a carbon peak by 2030 and carbon neutrality by 2060. In achieving this goal, the petrochemical industry is experiencing the urgent challenge regarding its development and transformation vis energy conservation and emission reduction. Biobased aviation kerosene is a sustainable and environmentally friendly alternative for reducing carbon emissions in the aviation industry, offering a notable promise for widespread adoption. This study comprehensively reviews the process for producing aviation kerosene from biomass. Vegetable oil, oil from inedible oil crops, pyrolysis oil, lignocellulosic residues, sugar, and starch biomass can be used as raw materials for the production of bioaviation kerosene. Biobased aviation kerosene can be classified into the following types according to its production technology: oil to jet (OTJ), gas to jet (GTJ), alcohol to jet (ATJ), and sugar to jet (STJ) fuels. With the rapid development of China’s bioethanol industry and abundant production, the energy supply-diversification strategy represented by ethanol and other alternative energy sources has become a guide for energy policies in various countries. The use of bioethanol as a raw material for preparing aviation kerosene is important for the environment, economy, and sustainability. This study focuses on the process of converting bioethanol into aviation fuel. It analyzes and summarizes the reaction conditions and catalysts involved in the three main reactions: ethanol dehydration to ethylene, olefin oligomerization, and hydrogenation. Currently, the ATJ process still suffers several disadvantages, such as long process flow and low conversion efficiency. The conversion route from ethanol to jet kerosene is complex and requires three different catalysts. We must develop a catalyst that can catalyze both the dehydration reaction and oligomerization hydrogenation reaction, increase the conversion efficiency, and reduce the production cost. This study introduces the carbon–carbon coupling of ethanol and hydrodeoxidation for the production of aviation kerosene, including discussions on reaction mechanisms and catalysts for the preparation of high-carbon alcohol. The Guerbet condensation reaction of ethanol is hindered by the presence of water as a by-product. Therefore, a catalyst is proposed for carbon–carbon coupling reaction of aqueous ethanol to produce high-carbon alcohols. The catalyst, with its satisfactory water resistance, can retain its activity and selectivity for high-carbon alcohols even in the presence of water and effectively inhibit the interference of water molecules, thereby increasing the efficiency and stability of the catalytic reaction. Jet kerosene is obtained via hydrodeoxidation of high-carbon alcohols, in which noble metal- and molybdenum-based catalysts exhibit satisfactory catalytic performance. Transition metals combined with Mo2C catalysts can selectively break the C–O bonds in polyols and avoid C–C bond breakage. Research and development of efficient hydrodeoxidation catalysts can facilitate the conversion of high-carbon alcohols into hydrocarbons, providing important support for the development of alternative aviation fuels. This study highlights the current challenges facing the production of ethanol-based jet fuel, such as the high production cost and the need for new catalysts. Furthermore, it proposes future development directions, offering valuable insights for the industrialization of bioethanol-based aviation kerosene production.