The replacement of fossil resources that currently provide more than 90% of our energy needs and feedstocks of the chemical industry in combination with reduced emission of carbon dioxide is one of the most pressing challenges of mankind. Biomass as a globally available resource has been proposed as an alternative feedstock for production of basic building blocks, which could partially or even fully replace the currently utilized fossil-based ones in well-established chemical processes. The destruction of lignocellulosic feed followed by oxygen removal from its cellulose and hemicellulose content by catalytic processes results in the formation of initial platform chemicals (IPCs). However, their sustainable production strongly depends on the availability of resources, their efficient or even industrially viable conversion processes, and replenishment time of feedstocks. Herein, we overview recent advances and developments in catalytic transformations of the carbohydrate content of lignocellulosic biomass ...

Catalytic Conversion of Carbohydrates to Initial Platform Chemicals: Chemistry and Sustainability

Alternative Monomers Based on Lignocellulose and Their Use for Polymer Production.

A wide variety of commodity chemicals can be produced from the catalytic oxidation of carbohydrates or carbohydrate derived molecules including formic acid, acetic acid, glycolic acid, gluconic acid, glucaric acid, malonic acid, oxalic acid, 2,5-diformylfuran (DFF), 5-hydroxymethyl-2-furancarboxylic acid (HFCA), 5-formyl-2-furancarboxylic acid (FFCA), and 2,5-furandicarboxylic acid (FDCA). This review will highlight the recent research progress in the development of new routes for the production of organic acids and furan compounds via catalytic oxidation reactions. Particular attention will be paid to these one-pot reactions with the requirements of an acidic site and a metal site. For the one-pot transformation of cellobiose or lignocellulose into gluconic acid, these reactions were performed via a one-step strategy using a single catalyst containing an acidic site and a metal site. However, a two-step strategy was adopted for the oxidative transformation of carbohydrates into DFF or FDCA in order to avoid the oxidation of the carbohydrates. The first step was performed for the dehydration of carbohydrates into 5-hydroxylmethylfuran (HMF) in the presence of an acid catalyst, and the second step was performed for the oxidation of HMF into DFF or FDCA with a metal catalyst.

Catalytic oxidation of carbohydrates into organic acids and furan chemicals

Platform molecules have recently been in the focus of numerous investigations as intermediates for transformation of lignocellulosic biomass into fuels and chemicals. Herein we focus on challenges associated with technical implementation of the production of selected platform molecules. 5-(Hydroxymethyl)-furfural, furfural and levulinic acid were chosen to illustrate pitfalls and limitations of currently available catalytic reaction systems. Owing to the prominent reactivity, high polarity and high boiling points of most biomass-derived platform chemicals, the design of efficient, economic and environmentally benign chemical processes offers a number of difficulties. Challenges include not only a selective synthesis of such platform chemicals and their further transformation into potential products but also methods to allow an energy efficient product separation and sufficient catalyst stability under the applied reaction conditions. In this review we discuss three approaches to tackle the integration of catalytic transformations, reaction engineering and product separation. First, extraction-assisted synthesis methods are discussed. In the next step the integration of such extraction-assisted approaches into reaction cascades is considered. Finally, one-pot transformations of lignocellulose-derived carbohydrates into value-added products without isolation of the intermediate platform chemicals are outlined. The present status of predictive tools facilitating the selection of suitable solvent systems for extraction systems is discussed to outline current opportunities and constraints of a theoretical process design and optimization. In summary, this review provides an overview of recent progress with regard to strategies for process integration of chemo-catalytic biomass valorisation and highlights challenges associated with such approaches.

Cellulose and hemicellulose valorisation: an integrated challenge of catalysis and reaction engineering

Biomass is a promising feedstock for the next generation drop-in liquid fuels and renewable chemicals, and hence the development of economically viable technologies for the production of commodity and specialty chemicals from sustainable biomass have received significant attention in recent years. Although biomass transformation into drop-in biofuels involves multiple processing steps in which biomass is first depolymerized and converted to furfurals (5-hydroxymethylfurfural, furfural), catalytic upgrading of furfurals is the most important step in achieving end products of the desired fuel properties. Several research papers have been published in the past decade reporting homogeneous and heterogeneous catalytic processes for upgrading furfurals to relevant drop-in fuel candidates such as, 2,5-dimethylfuran (DMF), 2-methylfuran (2-MF), 5-ethoxymethylfurfural (EMF), γ-valerolactone (GVL), ethyl levulinate and long chain hydrocarbon alkanes. Although process technologies for the production and upgrading of...

Upgrading Furfurals to Drop-in Biofuels: An Overview

Efficient conversion of carbohydrates into 5-ethoxymethylfurfural in ethanol catalyzed by AlCl3

Synthesis of 5-ethoxymethylfurfural from 5-hydroxymethylfurfural and fructose in ethanol catalyzed by MCM-41 supported phosphotungstic acid

In this study, we have developed a new and green method for the synthesis of 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) from fructose using cellulose sulfuric acid as catalyst. Firstly, HMF was synthesized from fructose, and a high yield of 93.6 % was obtained in DMSO for 45 min in the presence of cellulose sulfuric acid. Cellulose sulfuric acid also showed high catalytic activity for the synthesis of EMF. EMF was obtained in a high yield of 84.4 % by the etherification of HMF under the optimal reaction conditions. More importantly, a high EMF yield of 72.5 % was also obtained from fructose through one-pot reaction strategy, which integrated the dehydration of fructose into HMF and the followed etherification of HMF into EMF. The reaction work-up was very simple and the catalyst could be reused several times without the loss of its catalytic activity.

Cellulose sulfuric acid as a bio-supported and recyclable solid acid catalyst for the synthesis of 5-hydroxymethylfurfural and 5-ethoxymethylfurfural from fructose

The paper deals with oxidation of the biomass-derived model molecule 5-(hydroxymethyl)furfural (HMF) catalyzed by the trimetallic mixed oxide RuCo(OH)2CeO2. The catalyst RuCo(OH)2CeO2 was prepared through alkali hydrolysis of RuCl3, Co(NO3)2, and Ce(NO3)2 and characterized by X-ray diffraction and transmission electron microscopy techniques. RuCo(OH)2CeO2 showed high catalytic activity for aerobic oxidation of HMF under mild conditions (in the case of atmospheric oxygen pressure). Various reaction parameters such as the reaction temperature, catalyst amount, solvent, and oxidant were explored. Results demonstrated that the oxidant and solvent showed a remarkable effect on the aerobic oxidation of HMF to 2,5-diformylfuran (DFF). Under optimal conditions, DFF was obtained in a high yield of 82.6% with HMF conversion of 96.5% after 12 h at 120 °C. More importantly, the catalyst could be reused several times without significant loss of its catalytic activity.

Kecheng Huang

Papers

Efficient conversion of carbohydrates into 5-ethoxymethylfurfural in ethanol catalyzed by AlCl3

Synthesis of 5-ethoxymethylfurfural from 5-hydroxymethylfurfural and fructose in ethanol catalyzed by MCM-41 supported phosphotungstic acid

Cellulose sulfuric acid as a bio-supported and recyclable solid acid catalyst for the synthesis of 5-hydroxymethylfurfural and 5-ethoxymethylfurfural from fructose

Aerobic Oxidation of Biomass-Derived 5-(Hydroxymethyl)furfural into 2,5-Diformylfuran Catalyzed by the Trimetallic Mixed Oxide (Co–Ce–Ru)