单糖化学催化制取运输燃料

Chemocatalytic Transformation of Sugars to Transportation Fuels

农作物秸秆和林业废弃物是资源量大、可再生的非粮生物质。它们由半纤维素、纤维素和木质素组成,源于这些生物质的单糖不仅可以经过生物催化过程制备纤维乙醇,还是化学催化法制备传统烃类运输燃料的重要平台。本文首先介绍了木质生物质酶法和酸催化法水解制备单糖的工艺特点,然后详细介绍了近几年来开发的从单糖出发制取烃类生物燃料的各种新型催化方法,如单糖经HZSM-5分子筛直接催化重整制备液体烃类,以及单糖经乙酰丙酸和酯化加氢工艺、经多元醇和水相脱水加氢(APD/H)工艺、经糠醛类化合物和羟醛缩合加氢工艺、经单官能团化合物和催化提质工艺。对这些催化方法的工艺条件、催化剂组成和化学反应进行了总结评述。考虑到由单糖制备C6以上烃类可以直接或混配为传统的液体燃料,本文对这两条工艺路线进行了重点介绍,总结了过程所发生的反应和脱氧机理,并探讨了工业化过程中需要注意的科学难题。

Agricultural and forest residues consisting primarily hemicellulose, cellulose, and lignin are abundant, renewable non-food biomass resources. Fermentable sugars origin from raw materials can be converted into ethanol by biocatalystic process. Moreover, sugars have the potential to serve as precursors of conventional transportation fuels. In this review, the process of hydrolytic conversion of woody biomass into simple sugars with the use of an acidic or enzymatic catalyst is firstly introduced. Then, several novel chemocatalytic methods converting sugars to hydrocarbons are described, such as sugar feed directly reformed over HZSM-5 catalyst, or via Levulinic acid and subsequent esterification/hydrogenation process, polyols and subsequent aqueous-phase dehydration/hydrogenation （APD/H） process, furan derivatives and subsequent aldol condensation/hydrogenation process, monofunctional compounds and subsequent catalytic upgrading steps. These chemical routes have been explored in recent years, in the presence of solid-phase catalysts（including metal and/or acid/base active sites） under carefully controlled conditions that avoid unwanted by-products. The corresponding catalysts, process conditions, chemistries for the selective conversion are summarized in this review. More attention is paid on the current developing of two catalytic approaches for the conversion of sugars to C6＋ alkanes due to targeted highenergy hydrocarbons mixtures can be used directly or blended seamlessly to make conventional liquid fuels. The reactions involved in the catalytic processes, deoxygenation mechanism, as well as the chemical and engineering barriers of industry are discussed.