Levulinic Acid-Based "Green" Solvents for Lignocellulose Fractionation: On the Superior Extraction Yield and Selectivity toward Lignin.

The high potential use of lignin in novel biomaterials and chemicals represents an important opportunity for the valorization of the most abundant natural resource of aromatic molecules. From an environmental perspective, it is highly desirable replacing the hazardous methods currently used to extract lignin from lignocellulosic biomass and develop more sustainable and environmentally friendly approaches. Therefore, in this work, levulinic acid (a "green" solvent obtained from biomass) was successfully used, for the first time, to selectively extract high-quality lignin from pine wood sawdust residues at 200 °C for 6 h (at atmospheric pressure). Moreover, the addition of catalytic concentrations of inorganic acids (i.e., H2SO4 or HCl) was found to substantially reduce the temperature and reaction times needed (i.e., 140 °C, 2 h) for complete lignin extraction without compromising its purity. NMR data suggests that condensed OH structures and acidic groups are present in the lignin following extraction. Levulinic acid can be easily recycled and efficiently reused several times without affecting its performance. Furthermore, excellent solvent reusability and performance of extraction of other wood residues has been successfully demonstrated, thus making the developed levulinic acid-based procedure highly appealing and promising to replace the traditional less sustainable methodologies.

A 3D printed photoreactor for investigating variable reaction geometry, wavelength, and fluid flow.

Research in the field of photochemistry, including photocatalysis and photoelectrocatalysis, has been revitalized due to the potential that photochemical reactions show in the sustainable production of chemicals. Therefore, there is a need for flexible photoreactor equipment that allows for the evaluation of the geometry, light wavelength, and intensity of the vessel, along with the fluid flow in various photochemical reactions. Light emitting diodes (LEDs) have narrow emission spectra and can be either pulsed or run continuously; being flexible, they can be arranged to fit the dimensions of various types of the reactor vessel, depending on the application. This study presents a 3D printed photoreactor with the ability to adjust distances easily and switch between high-power LED light sources. The reactor design utilizes customized printed circuit boards to mount varying numbers and types of LEDs, which enables multiple wavelengths to be used simultaneously. These LED modules, comprised of heat sinks and cooling fans, fulfill the higher heat dissipation requirements of high-power LEDs. The flexibility of the reactor design is useful for optimizing the reaction geometry, flow conditions, wavelength, and intensity of photochemical reactions on a small scale. The estimates for incident light intensity under five possible reactor configurations using ferrioxalate actinometry are reported so that comparisons with other photoreactors can be made. The performance of the photoreactor for differing vessel sizes and distances, in both the flow and batch modes, is given for a photochemical reaction on 2-benzyloxyphenol-a model substance for lignin and applicable in the production of biobased chemicals.