Ru(II)-functionalized SBA-15 as highly chemoselective, acid free and sustainable heterogeneous catalyst for acetalization of aldehydes and ketones

Batch and Continuous-Flow Preparation of Biomass-Derived Furfural Acetals over a TiO2 Nanoparticle-Exfoliated Montmorillonite Composite Catalyst

Furfural acetals with high octane value, high calorific value and high oxidation resistance are considered promising biofuels or fuel precursors with huge potential demand. However, there are few studies on efficient scalable catalyst systems, including continuous-flow catalyst systems, for their preparation. In this work, TiO₂ nanoparticles supported on exfoliated montmorillonite, with strong Lewis acid sites and abundant accessible Brønsted acid sites, is used to catalyze the acetalization reactions of biomass-derived furfural and alcohols. Low dosage of the catalyst made the reaction reach equilibrium in a very short time (TOF=690-1305 min^-1 ) at room temperature with the acetal as the only product. In continuous-flow reactions, the catalyst showed a stable product output with conversion close to that for the batch reaction with a short catalyst-reactant contact time of 150 s. Contrast experiments revealed that both Lewis and Brønsted acid sites on the catalyst were indispensable for maximizing the catalytic performance, and simultaneously activating both furfural and alcohol on the adjacent Lewis and Brønsted acid sites was proposed to be responsible for the high catalytic performance.

Catalytic application of sulfamic acid-functionalized magnetic Fe3O4 nanoparticles (SA-MNPs) for protection of aromatic carbonyl compounds and alcohols: experimental and theoretical studies

Protection techniques of functional groups within the structure of organic compounds are important synthetic methods against unwanted attacks from various reagents during synthetic sequences. Acetal and thioacetal groups are well known as protective functional groups in organic reactions. In this study, acetalization of carbonyl compounds with diols and dithiols and methoxymethylation of alcohols with formaldehyde dimethyl acetal (FDMA) have been carried out using sulfamic acid-functionalized magnetic Fe3O4 nanoparticles (SA-MNPs) as a heterogeneous solid acid catalyst. Products were characterized by FT-IR and NMR spectroscopies. The structural and electronic properties of some products were computed by quantum mechanical (QM) methods. Depending on the stereochemistry and electronic properties that were obtained by computational results, we have suggested that hyperconjugation plays a key role in the structural properties of 2-phenyl-1,3-dioxolane derivatives, and also the electron transfer between π-electrons of the aromatic ring with the 3d orbital of S-atoms influences the 2-phenyl-1,3-dithiane derivatives' structure.

A Review on the Catalytic Acetalization of Bio-renewable Glycerol to Fuel Additives

The last 20 years have seen an unprecedented breakthrough in the biodiesel industry worldwide leads to abundance of glycerol. Therefore, the economic utilization of glycerol to various value-added chemicals is vital for the sustainability of the biodiesel industry. One of the promising processes is acetalization of glycerol to acetals and ketals for applications as fuel additives. These products could be obtained by acid-catalyzed reaction of glycerol with aldehydes and ketones. Application of different supported heterogeneous catalysts such as zeolites, heteropoly acids, metal-based and acid-exchange resins have been evaluated comprehensively in this field. In this review, the glycerol acetalization has been reported, focusing on innovative and potential technologies for sustainable production of solketal. In addition, the impacts of various parameters such as application of different reactants, reaction temperature, water removal, utilization of crude-glycerol on catalytic activity in both batch and continuous processes are discussed. The outcomes of this research will therefore significantly improve the technology required in tomorrow's bio-refineries. This review provides spectacular opportunities for us to use such renewables and will consequently benefit the industry, environment and economy.