Abstract
Nowadays, the solvothermal conversion of biomass has reached a good level of development, and now it is necessary to improve the process intensification, in order to boost its further growth on the industrial scale. Otherwise, most of these processes would be limited to the pilot scale or, even worse, to exclusive academic investigations, intended as isolated applications for the development of new catalysts. For this purpose, it is necessary to improve the work-up technologies, combining, where possible, reaction/purification unit operations, and enhancing the feedstock/liquid ratio, thus improving the final concentration of the target product and reducing the work-up costs. Furthermore, it becomes decisive to reconsider more critically the choice of biomass, solvent(s), and catalysts, pursuing the biomass fractionation in its components and promoting one-pot cascade conversion routes. Screening and process optimization activities on a laboratory scale must be fast and functional to the flexibility of these processes, exploiting efficient reaction systems such as microwaves and/or ultrasounds, and using multivariate analysis for an integrated evaluation of the data. These upstream choices, which are mainly of the chemist’s responsibility, are fundamental and deeply interconnected with downstream engineering, economic, and legislative aspects, which are decisive for the real development of the process. In this Editorial, all these key issues will be discussed, in particular those aimed at the intensification of solvothermal processes, taking into account some real case studies, already developed on the industrial scale.
Highlights
Nowadays, the solvothermal conversion of biomass has reached a good level of development, and it is necessary to improve the process intensification, in order to boost its further growth on the industrial scale
In the last years, increasing research has been devoted to the optimization of hydrothermal processes, in particular under sub-critical conditions, in the absence or presence of a suitable acid catalyst, for the selective production of reducing sugars or platform chemicals
Most recent advances in the production of these valuable platform chemicals will be discussed in the following paragraph
Summary
Furfural is exclusively produced from the acid-catalyzed hydrolysis of the pentosan fraction of lignocellulosic biomasses to xylose and its subsequent dehydration. Production, the formation of by-products, separation, and purification issues, as well as catalyst regeneration, have been identified as major challenges [9] To solve these drawbacks, many efficient solutions have been continuously proposed, such as that of Yan et al [10], who have performed the continuous production of 5-HMF in a flow-reactor, achieving high yields, starting from fructose or glucose, using HCl and AlCl3 as the catalysts and water as the reaction medium. (ii) an easier work-up procedures, generally by distillation, thanks to the lower boiling points of the esters; and (iii) a reduced number of process units and enhanced performances of new technological solutions, such as reactive distillation, conducive to the process intensification [18] In this way, it is possible to combine reaction and separation unit operations, allowing simpler, more efficient, economical, and cleaner production processes. We discuss more in detail about some additional choices, which should be carefully done upstream of the process development, to significantly improve the intensification phase for the production of C5 and C6 derivatives on a larger scale
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