Cr/MCM-22 catalyst for the synthesis of levulinic acid from green hydrothermolysis of renewable biomass resources

Advances in the green and controllable synthesis of MWW zeolite

MWW zeolite is one of the commercialized zeolites that shows great promise in heterogeneous catalysis and other interdisciplinary application fields due to its coexisting multi-channel system. The green and controllable synthesis of MWW zeolite is conducive to its more efficient and broader application. Many researchers focus on precisely controlling the dimension, interlayer hydroxyl condensation, and aluminum siting, as well as obtaining MWW with low-toxicity, readily available organic structure directing agents (OSDAs) or without OSDAs. This review summarizes recent advancements in the synthesis and application of MWW zeolite, with a particular emphasis on selecting different OSDAs, controlling the interlayer condensation degree and adjusting aluminum distribution. Future research directions and development trends of MWW zeolite are also forecasted.

Flexible Aqueous Cr-Ion Hybrid Supercapacitors with Remarkable Electrochemical Properties in all Climates

The integration of hostless battery-like metal anodes for hybrid supercapacitors is a realistic design method for energy storage devices with promising future applications. With significant Cr element deposits on Earth, exceptionally high theoretical capacity (1546 mAh g-1), and accessible redox potential (-0.74 V vs. reversible hydrogen electrode) of Cr metals, the design of Cr anodes has rightly come into our focus. This work presents a breakthrough design of a flexible Cr-ion hybrid supercapacitor (CHSC) based on a porous graphitized carbon fabric (PGCF) substrate prepared by K2FeO4 activation. In the CHSC device, PGCF acts as both a current collector and cathode material due to its high specific surface area and superior conductivity. The use of a highly concentrated LiCl-CrCl3 electrolyte with high Cr plating/stripping efficiency and excellent antifreeze properties enables the entire PGCF-based CHSC to achieve well-balanced performance in terms of energy density (up to 1.47 mWh cm-2), power characteristics (reaching 9.95 mW cm-2) and durability (95.4 % capacity retention after 30,000 cycles), while realizing it to work well under harsh conditions of -40 °C. This work introduces a new concept for low-temperature energy storage technology and confirms the potential application of Cr anodes in hybrid supercapacitors.

Levulinic Acid Is a Key Strategic Chemical from Biomass

Levulinic acid (LA) is one of the top twelve chemicals listed by the US Department of Energy that can be derived from biomass. It serves as a building block and platform chemical for producing a variety of chemicals, fuels and materials which are currently produced in fossil based refineries. LA is a key strategic chemical, as fuel grade chemicals and plastic substitutes can be produced by its catalytic conversion. LA derivatisation to various product streams, such as alkyl levulinates via esterification, γ-valerolactone via hydrogenation and N-substituted pyrrolidones via reductive amination and many other transformations of commercial utility are possible owing to the two oxygen functionalities, namely, carbonyl and carboxyl groups, present within the same substrate. Various biomass feedstock, such as agricultural wastes, marine macroalgae, and fresh water microalgae were successfully converted to LA in high yields. Finding a substitute to mineral acid catalysts for the conversion of biomass to LA is a challenge. The use of an ultrasound technique facilitated the production of promising nano-solid acid catalysts including Ga salt of molybophosphoric acid and Ga deposited mordenite zeolite, with optimum amounts of Lewis and Bronsted acidities needed for the conversion of glucose to LA in high yields, being 56 and 59.9 wt.% respectively. Microwave irradiation technology was successfully utilized for the accelerated production of LA (53 wt.%) from glucose in a short duration of 6 min, making use of the unique synergistic catalytic activity of ZnBr2 and HCl.

Electroreductive CO coupling of benzaldehyde over SACs Au-NiMn2O4 spinel synergetic composites

Electroreductive CO coupling provides a prospective strategy for biomass derivative upgrading via reducing the number of oxygen-containing functional groups and increasing their molecular weight. However, exploring superior electrocatalysts with effective reactivity and high selectivity for target products are still a challenge. In this work, single atom Au surface derived NiMn₂O₄ (SACs Au-NiMn₂O₄) spinel synergetic composites were fabricated by a versatile adsorption-deposition method and applied in electroreductive self-coupling of benzaldehyde to dibenzyl ether. The SACs Au-NiMn₂O₄ spinel synergetic composites enhanced electroreductive coupling of benzaldehyde, significantly improved the yield and selectivity of dibenzyl ether. Systematic characterizations and density functional theory calculation revealed that atomically dispersed Au occupied surface Ni²⁺ vacancies, which played a dominated role in CO coupling of benzaldehyde. Detailed calculation results showed that benzaldehyde preferred to adsorb on Ni octa-hedral sites of NiMn₂O₄ spinel synergetic structure, single atom Au surficial derivation over NiMn₂O₄ further reduced the adsorption energy (E_ads) of benzaldehyde on SACs Au-NiMn₂O₄, thus the CO coupling of benzaldehyde to dibenzyl ether was promoted. Moreover, single atom Au surficial derivation lowered the energy barrier of rate-determining step, facilitated the formation of dibenzyl ether species. Our work also paves an avenue for rational design single atom materials using spinel as support.

The Fractionation of Corn Stalk Components by Hydrothermal Treatment Followed by Ultrasonic Ethanol Extraction

The fractionation of components of lignocellulosic biomass is important to be able to take advantage of biomass resources. The hydrothermal–ethanol method has significant advantages for fraction separation. The first step of hydrothermal treatment can separate hemicellulose efficiently, but hydrothermal treatment affects the efficiency of ethanol treatment to delignify lignin. In this study, the efficiency of lignin removal was improved by an ultrasonic-assisted second-step ethanol treatment. The effects of ultrasonic time, ultrasonic temperature, and ultrasonic power on the ultrasonic ethanol treatment of hydrothermal straw were investigated. The separated lignin was characterized by solid product composition analysis, FT-IR, and XRD. The hydrolysate was characterized by GC-MS to investigate the advantage on the products obtained by ethanol treatment. The results showed that an appropriate sonication time (15 min) could improve the delignification efficiency. A proper sonication temperature (180 °C) can improve the lignin removal efficiency with a better retention of cellulose. However, a high sonication power 70% (840 W) favored the retention of cellulose and lignin removal.