Terephthalic acid from waste PET: An efficient and reusable catalyst for xylose conversion into furfural

Fe3O4@SiO2 core/shell functionalized by gallic acid: a novel, robust, and water-compatible heterogeneous magnetic nanocatalyst for environmentally friendly synthesis of acridine-1,8-diones

In this study, we conveniently prepared a novel robust heterogeneous magnetic nanocatalyst using a Fe3O4@SiO2 core/shell stabilized by gallic acid. The catalyst was completely characterized by various physicochemical techniques, including infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dynamic light scattering (DLS), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), potentiometric titration, energy dispersive X-ray microanalysis (EDX), vibrating sample magnetometer (VSM), zeta potential analysis, and BET. The potential ability of the newly developed sulfonated nanocatalyst was then exploited in the multicomponent synthesis of acridine-1,8-dione derivatives by considering the green chemistry matrix and under mild conditions. Various aldehydes and amines were smoothly reacted with dimedone, affording the desired products in good to excellent yields. The introduction of sulfonic groups using gallic acid allowed the development of a water-compatible and highly recyclable catalytic system for reactions in an aqueous environment. The prepared catalyst can be readily magnetically separated and reused eight times without significant loss of activity. High synthetic efficiency, using a recyclable and eco-sustainable catalyst under mild conditions, and easy product isolation are salient features of this catalytic system, which makes this protocol compatible with the demands of green chemistry.

Chemical features and biological effects of degradation products of biodegradable plastics in simulated small waterbody environment

A plethora of research has focused on the biosafety of biodegradable plastics (BPs), including their microplastic formation and additives leaching; however, relatively fewer studies have explored biodegradation products. This study aims to investigate the biological effects and chemical features of degradation products from three kinds of BPs, namely polyglycolic acid (PGA), poly (butylene adipate-co-terephthalate) (PBAT), and the blends of PGA/PBAT without the addition of additives, in a simulated small waterbody environment with extracted soil solution for three months. Results showed that exposure to the whole degradation remnants of three BPs had no lethal effects on zebrafish at the current BP environmental concentrations (from 0.24 to 12.72 mg plastic/L) in small waterbodies. However, from the calculated BPs environmental concentrations (from 0.57 to 43.82 mg plastic/L) in 2026, PGA and PGA/PBAT blends may cause adverse effects on the cardiovascular system such as heartbeat rate suppression in zebrafish embryos, and also lead to reduced body length and pericardial edema and spinal curvature in fish larvae. We further qualitatively analyzed the composition of degradation products, and quantitatively measured four dominant degradation monomers (glycolic acid (GA), adipic acid (A), 1,4-butanediol (B), and terephthalic acid (T)) in the degradation remnants. It was found that the observed toxicities were probably due to the presence of GA, A, and T monomers, and their concentrations can reach 0.776, 0.034, and 0.6 mg/L under the calculated future scenario, respectively. It is worth mentioning that either GA or T monomers at the above concentrations were found to cause suppressed heartbeat rate in zebrafish embryos. Collectively, though the degradation products of BPs are temporarily safe at current environmental concentrations, they may lead to non-negligible toxicity with increasing production and continual improper recycling and/or BP waste management.

Catalytic Stereoselective Conversion of Biomass-Derived 4'-Methoxypropiophenone to Trans-Anethole with a Bifunctional and Recyclable Hf-Based Polymeric Nanocatalyst

Anethole (AN) is widely used as an odor cleaner in daily necessities, and can also be applied in the fields of food additives, drug synthesis, natural preservatives, and polymeric materials' preparation. Considering environmental and economic benefits, the use of biomass raw materials with non-precious metal catalysts to prepare high-value fine chemicals is a very promising route. Here, we developed an acid-base bifunctional polymeric material (PhP-Hf (1:1.5)) composed of hafnium and phenylphosphonate in a molar ratio of 1:1.5 for catalytic conversion of biomass-derived 4'-methoxypropiophenone (4-MOPP) to AN via cascade Meerwein-Pondorf-Verley (MPV) reduction and dehydration reactions in a single pot. Compared with the traditional catalytic systems that use high-pressure hydrogen as a hydrogen donor, alcohol can be used as a safer and more convenient hydrogen source and solvent. Among the tested alcohols, 2-pentanol was found to be the best candidate in terms of pronounced selectivity. A high AN yield of 98.1% at 99.8% 4-MOPP conversion (TOF: 8.5 h^-1) could be achieved over PhP-Hf (1:1.5) at 220 °C for 2 h. Further exploration of the reaction mechanism revealed that the acid and base sites of PhP-Hf (1:1.5) catalyst synergistically promote the MPV reduction step, while the Brønsted acid species significantly contribute to the subsequent dehydration step. In addition, the PhP-Hf polymeric nanocatalyst can be recycled at least five times, showing great potential in the catalytic conversion of biomass.

Strategic Possibility Routes of Recycled PET

The polyethylene terephthalate (PET) application has many challenges and potential due to its sustainability. The conventional PET degradation was developed for several technologies to get higher yield products of ethylene glycol, bis(2-hydroxyethyl terephthalate) and terephthalic acid. The chemical recycling of PET is reviewed, such as pyrolysis, hydrolysis, methanolysis, glycolysis, ionic-liquid, phase-transfer catalysis and combination of glycolysis-hydrolysis, glycolysis-methanolysis and methanolysis-hydrolysis. Furthermore, the reaction kinetics and reaction conditions were investigated both theoretically and experimentally. The recycling of PET is to solve environmental problems and find another source of raw material for petrochemical products and energy.

Chemoenzymatic conversion of Sorghum durra stalk into furoic acid by a sequential microwave-assisted solid acid conversion and immobilized whole-cells biocatalysis

In this study, chemoenzymatic conversion of Sorghum durra stalk (SDS) into furoic acid was developed by a sequential microwave-assisted solid acid conversion and immobilized whole-cells biocatalysis method. Dry dewaxed SDS (75 g/L) was catalyzed into furfural at 57.8% yield with heterogeneous Sn-argil (2.0 wt% dosage) in n-ethyl butyrate-H₂O (1:1, v:v) biphasic system using a microwave (600 W) for 10 min at 180 °C. In this biphasic media (pH 6.5), SDS-derived furfural (125.0 mM) was biologically oxidized to furoic acid by immobilized Brevibacterium lutescens cells harboring furfural-oxidizing activity at 30 °C, and furfural was wholly transformed to furoic acid within 24 h. Finally, the recovery and reuse of the Sn-argil catalyst and immobilized biocatalysts were conducted for synthesizing furoic acid from SDS in the biphasic system. This chemoenzymatic route can be attractive for furoic acid production.

Production of furfural from xylose catalyzed by a novel calcium gluconate derived carbon solid acid in 1,4-dioxane

A novel carbon-based solid acid catalyst (SC-GCa-800) was prepared by the high-temperature carbonization of calcium gluconate followed by sulfonation with 4-diazoniobenzenesulfonate at room temperature.

Efficient Synthesis of Furfural from Biomass Using SnCl₄ as Catalyst in Ionic Liquid

Furfural is a versatile platform molecule for the synthesis of various chemicals and fuels, and it can be produced by acid-catalyzed dehydration of xylose derived from renewable biomass resources. A series of metal salts and ionic liquids were investigated to obtain the best combination of catalyst and solvent for the conversion of xylose into furfural. A furfural yield of 71.1% was obtained at high xylose loading (20 wt%) from the single-phasic reaction system whereby SnCl₄ was used as catalyst and ionic liquid 1-ethyl-3-methylimidazolium bromide (EMIMBr) was used as reaction medium. Moreover, the combined catalyst consisting of 5 mol% SnCl₄ and 5 mol% MgCl₂ also produced a high furfural yield (68.8%), which was comparable to the furfural yield obtained with 10 mol% SnCl₄. The water⁻organic solvent biphasic systems could improve the furfural yield compared with the single aqueous phase. Although these organic solvents could form biphasic systems with ionic liquid EMIMBr, the furfural yield decreased remarkably compared with the single EMIMBr phase. Besides, the EMIMBr/SnCl₄ system with appropriate water was also efficient to convert xylan and lignocellulosic biomass corn stalk into furfural, obtaining furfural yields as high as 57.3% and 54.5%, respectively.

Catalytic Processes from Biomass-Derived Hexoses and Pentoses: A Recent Literature Overview

Biomass is a plentiful renewable source of energy, food, feed and chemicals. It fixes about 1–2% of the solar energy received by the Earth through photosynthesis in both terrestrial and aquatic plants like macro- and microalgae. As fossil resources deplete, biomass appears a good complement and eventually a good substitute feedstock, but still needs the development of relatively new catalytic processes. For this purpose, catalytic transformations, whether alone or combined with thermal ones and separation operations, have been under study in recent years. Catalytic biorefineries are based on dehydration-hydrations, hydrogenations, oxidations, epimerizations, isomerizations, aldol condensations and other reactions to obtain a plethora of chemicals, including alcohols, ketones, furans and acids, as well as materials such as polycarbonates. Nevertheless, there is still a need for higher selectivity, stability, and regenerability of catalysts and of process intensification by a wise combination of operations, either in-series or combined (one-pot), to reach economic feasibility. Here we present a literature survey of the latest developments for obtaining value-added products using hexoses and pentoses derived from lignocellulosic material, as well as algae as a source of carbohydrates for subsequent transformations.