Practical issues in catalytic and hydrothermal biomass conversion: concentration effects on reaction pathways

Converting biomass to biofuels and chemicals calls for practical and simple processes, since it must compete economically with both burning and anaerobic bacterial digestion. Here we employ concentrated glucose solutions as a biomass model compound, using a pressure-controlled batch reactor setup for hydrothermal and catalytic upgrading. We examine the hydrothermal, acid-catalysed and base-catalysed reactions of concentrated glucose giving gases, tar (biofuels), and char products, and show that working at practical (i.e., high) feed concentrations has a strong effect on the reaction pathways

Interrelation of chemistry and process design in biodiesel manufacturing by heterogeneous catalysis

The pros and cons of using heterogeneous catalysis for biodiesel manufacturing are introduced, and explained from a chemistry and engineering viewpoint. Transesterification reactions of various feed types are then compared in batch and continuous process operation modes. The results show that the reaction chemistry and process kinetics characterising a particular feedstock are determinant factors for obtaining high-grade biodiesel. When using heterogeneous catalysis, the biodiesel quality of a particular feed can be controlled by customising the process design and operation conditions

Current pretreatment technologies for the development of cellulosic ethanol and biorefineries

Lignocellulosic materials, such as forest, agriculture, and agroindustrial residues, are among the most important resources for biorefineries to provide fuels, chemicals, and materials in such a way to substitute for, at least in part, the role of petrochemistry in modern society. Most of these sustainable biorefinery products can be produced from plant polysaccharides (glucans, hemicelluloses, starch, and pectic materials) and lignin. In this scenario, cellulosic ethanol has been considered for decades as one of the most promising alternatives to mitigate fossil fuel dependence and carbon dioxide accumulation in the atmosphere. However, a pretreatment method is required to overcome the physical and chemical barriers that exist in the lignin–carbohydrate composite and to render most, if not all, of the plant cell wall components easily available for conversion into valuable products, including the fuel ethanol. Hence, pretreatment is a key step for an economically viable biorefinery. Successful pretreatment method must lead to partial or total separation of the lignocellulosic components, increasing the accessibility of holocellulose to enzymatic hydrolysis with the least inhibitory compounds being released for subsequent steps of enzymatic hydrolysis and fermentation. Each pretreatment technology has a different specificity against both carbohydrates and lignin and may or may not be efficient for different types of biomasses. Furthermore, it is also desirable to develop pretreatment methods with chemicals that are greener and effluent streams that have a lower impact on the environment. This paper provides an overview of the most important pretreatment methods available, including those that are based on the use of green solvents (supercritical fluids and ionic liquids)

Reaction Pathways During Hydrothermal; Upgrading of Biomass

BiotechnologyApplied Science