Sustainable Synthesis of Oxalic and Succinic Acid through Aerobic Oxidation of C6 Polyols Under Mild Conditions

Polymers without Petrochemicals: Sustainable Routes to Conventional Monomers

Access to a wide range of plastic materials has been rationalized by the increased demand from growing populations and the development of high-throughput production systems. Plastic materials at low costs with reliable properties have been utilized in many everyday products. Multibillion-dollar companies are established around these plastic materials, and each polymer takes years to optimize, secure intellectual property, comply with the regulatory bodies such as the Registration, Evaluation, Authorisation and Restriction of Chemicals and the Environmental Protection Agency and develop consumer confidence. Therefore, developing a fully sustainable new plastic material with even a slightly different chemical structure is a costly and long process. Hence, the production of the common plastic materials with exactly the same chemical structures that does not require any new registration processes better reflects the reality of how to address the critical future of sustainable plastics. In this review, we have highlighted the very recent examples on the synthesis of common monomers using chemicals from sustainable feedstocks that can be used as a like-for-like substitute to prepare conventional petrochemical-free thermoplastics.

Sustainable Synthesis of 2-Hydroxymethylbenzimidazoles using D-Fructose as a C2 Synthon

D-fructose, a biomass-derived carbohydrate has been identified as an environmentally benign C₂ synthon in the preparation of synthetically useful 2-hydroxymethylbenzimidazole derivatives by coupling with 1,2-phenylenediamines. Proof of concept was established by synthesizing 23 examples using BF₃ .OEt₂ (20 mol%), TBHP (5.5 M, decane) (1.0 equiv.) in CH₃ CN at 90 °C for 1 h. The pivotal features of this method include metal-free conditions, short time, good functional group tolerance, gram scale feasibility and the synthesis of benzimidazole fused 1,4-oxazine. Control studies with conventional C₂ synthons did not produce the desired product, thus suggesting a new reaction pathway from D-fructose.

Recent Developments in Heterogeneous Catalytic Routes for the Sustainable Production of Succinic Acid from Biomass Resources

Succinic acid is a "hot molecule" identified by United States Department of Energy as a substitute for petrochemicals with great scope for its production from biomass. It is used as an intermediate for the production of a huge variety of everyday consumer products with an addressable market share of billions of dollars. Succinic acid and its derivatives are mainly used as pharmaceuticals, adhesives, solvents, intermediates for polymer synthesis, and food additives. Succinic acid is commercially produced from petrochemicals and there is a deficiency of economically viable catalytic processes for its large-scale production from biomass. Recently, a lot of biochemical routes have been devised to enhance its production from biomass resources, but such processes are time-consuming and involve tedious separation procedures. Therefore, this Review focuses on metal-based and metal-free heterogeneous catalytic routes for the synthesis of succinic acid from biomass derived products. The presence of uniform channels, cavities, active sites of various strengths, and the unique surface structure of the heterogeneous catalysts are a few of the interesting features that promote their use in industrial processes.

Selective Conversion of Cellulose to Hydroxyacetone and 1-Hydroxy-2-Butanone with Sn-Ni Bimetallic Catalysts

The high-value-added chemicals hydroxyacetone (HA) and 1-hydroxy-2-butanone (HB) were produced from agricultural waste over a Ni₃ Sn₄ -SnO_x catalyst. The Sn-Ni intermetallic compound and SnO_x acted as the active sites for HA and HB production by selectively cleaving the target C-C and C-O bonds. Approximately 70 % of the total HA and HB yield was obtained by selective hydrogenolysis of cellulose. This strategy expands the application of cellulose towards renewable production of high-value C₃ and C₄ keto-alcohols from cellulosic biomass.

Selective Oxidation of 5-(Hydroxymethyl)furfural to DFF Using Water as Solvent and Oxygen as Oxidant with Earth-Crust-Abundant Mixed Oxides

5-Hydroxymethylfurfural (5-HMF) can be considered a prominent building block: because of the presence of the alcohol and aldehyde moieties, it can be used to generate useful molecules as chemicals of industrial interest with high added value, monomers for polymers, and even fuels. This article shows how building up mixed oxides of different complexities and properties may drive the selectivity toward one of the possible products generated from 5-HMF. In particular, mixed oxides based on cerium and other metals abundant on the earth-crust perform the selective oxidation of 5-HMF to 2,5-diformylfuran (94%), using oxygen as oxidant and water as solvent. The roles of the reaction conditions (temperature, reaction time, oxygen pressure, concentration of the substrate), the chemical composition, the acidic/basic properties, and redox properties of the catalysts are discussed.

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.