Abstract
Heterogeneous catalytic conversion of lignocellulosic components into valuable chemicals and biofuels is one of the promising ways for biomass valorization, which well meets green chemistry metrics, and can alleviate environmental and economic issues caused by the rapid depletion of fossil fuels. Among the identified biomass derivatives, furfural (FF) and 5-hydroxymethylfurfural (HMF) stand out as rich building blocks and can be directly produced from pentose and hexose sugars, respectively. In the past decades, much attention has been attracted to the selective hydrogenation of FF and 5-hydroxymethylfurfural using various heterogeneous catalysts. This review evaluates the recent progress of developing different heterogeneous catalytic materials, such as noble/non-noble metal particles, solid acids/bases, and alkali metal salts, for the efficient reduction of bio-based furanic aldehydes to alcohols. Emphasis is laid on the insights and challenges encountered in those biomass transformation processes, along with the focus on the understanding of reaction mechanisms to clarify the catalytic role of specific active species. Brief outlook is also made for further optimization of the catalytic systems and processes for the upgrading of biofuranic compounds.
Highlights
Selective conversion of reproducible bio-resources into fuels and valuable chemicals has caused great attention because of the rapid economic development of world accompanying with the everincreasing demand for energy from fossil resources (Li et al, 2018a,b; He et al, 2019a)
The aim of this review is to provide a comprehensive overview of the production of BHMF or furfuryl alcohol (FFA) from the hydrogenation of 5-hydroxymethylfurfural or FF
The results showed that catalytic transfer hydrogenation can be used to selectively hydrogenate 5-hydroxymethylfurfural into BHMF
Summary
Selective conversion of reproducible bio-resources into fuels and valuable chemicals has caused great attention because of the rapid economic development of world accompanying with the everincreasing demand for energy from fossil resources (Li et al, 2018a,b; He et al, 2019a). This review evaluates the recent progress of developing different heterogeneous catalytic materials, such as noble/non-noble metal particles, solid acids/bases, and alkali metal salts, for the efficient reduction of bio-based furanic aldehydes to alcohols. There have been many reports on the different reaction mechanisms for the production of FF from xylose (Marcotullio and De Jong, 2010; Yang et al, 2012), but most studies using heterogeneous catalysts are based on a cyclized dehydration mechanism that gradually releases three molecules of water (Marcotullio and De Jong, 2010) This mechanism typically uses Brønsted acid catalysts, while some modifications have been made to the Lewis acid catalysts to produce FF. In order to decrease the chromium content of the Crcontaining catalyst while showing comparable catalytic activity, Huang et al studied the application of TiO2 supported copper chromite catalyst in the selective hydrogenation of FFA, and the conversion of FF was 100% and the yield of FFA was 79% under the reaction conditions of 140◦C for 2 h (Huang et al, 2007). The bimetallic CuCo/C-873 catalyst has a significant loss in catalytic activity over four consecutive
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