Deconstruction of biomass into lignin oil and platform chemicals over heteropoly acids with carbon-supported palladium as a hybrid catalyst under mild conditions

In this work, near-complete conversion of lignocellulosic biomass and high products yields were achieved through catalytic transfer hydrogenolysis (CTH) in isopropanol using a heteropoly acid SiW₁₂ synergistic with Pd/C catalyst at a relatively mild condition. The performances of various heteropoly acids and catalytic conditions were extensively examined. The results confirmed that SiW₁₂ exhibited the highest activity on disrupting C-C linkages and C-O linkages than H₂WO₄, PW₁₂, and PMo₁₂. 34.91 wt% and 43.55 wt% monophenols were achieved for hydrogenolysis of bagasse and eucalyptus, respectively, at their optimal temperature for 5 h. Characterization studies on the lignin oil revealed that the notable structural changes were observed including the breaking of the side chain alkyl-aryl ether bonds and glycosidic bonds, while methoxyl groups were retained. Additionally, particle size of feedstock also has significant impact on the distribution and yields of the monophenols.

Catalyst Development for the Synthesis of Ozonides and Tetraoxanes Under Heterogeneous Conditions: Disclosure of an Unprecedented Class of Fungicides for Agricultural Application

The catalyst H_3+x PMo_12-x ⁺⁶ Mo_x ⁺⁵ O₄₀ supported on SiO₂ was developed for peroxidation of 1,3- and 1,5-diketones with hydrogen peroxide with the formation of bridged 1,2,4,5-tetraoxanes and bridged 1,2,4-trioxolanes (ozonides) with high yield based on isolated products (up to 86 and 90 %, respectively) under heterogeneous conditions. Synthesis of peroxides under heterogeneous conditions is a rare process and represents a challenge for this field of chemistry, because peroxides tend to decompose on the surface of a catalyst . A new class of antifungal agents for crop protection, that is, cyclic peroxides: bridged 1,2,4,5-tetraoxanes and bridged ozonides, was discovered. Some ozonides and tetraoxanes exhibit a very high antifungal activity and are superior to commercial fungicides, such as Triadimefon and Kresoxim-methyl. It is important to note that none of the fungicides used in agricultural chemistry contains a peroxide fragment.

Silica gel mediated oxidative C–O coupling of β-dicarbonyl compounds with malonyl peroxides in solvent-free conditions

For the first time silica gel was observed to activate peroxides in oxidative coupling reactions. Here we report silica gel mediated oxidative C–O coupling of β-dicarbonyl compounds with cyclic diacyl peroxides affording α-acyloxy derivatives with 100% atom efficiency. The highest yields of coupling products were achieved in solvent free conditions. C–O coupling products were prepared in yields up to 86%.

Kinetic Study of the Esterification of Acetic Acid with 1-Butanol Catalysed by Alumina-Supported Tungstophosphoric Acid

The kinetics of the esterification of acetic acid with 1-butanol in the presence of alumina-supported tungstophosphoric acid (TPA) was studied. The uncatalysed reaction was shown to proceed by a second-order mechanism. In the presence of the catalyst, the reaction was found to occur between an adsorbed alcohol molecule and a molecule of acid in the bulk fluid (Eley–Rideal mechanism). It was found that alumina-supported TPA is suitable for this reaction because the activation energy was reduced from 58.0 to 37.3 kJ mol−1. The catalyst was characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscope, nitrogen adsorption study and IR spectroscopy.

Pollution by nitrogen oxides: an approach to NO(x) abatement by using sorbing catalytic materials

This article summarises the abatement of NO(x) pollution by using sorbing catalytic materials with special relevance to the challenge presented in fixed installations sources. A general vision of the origins of the different pollutants, with emphasis on nitrogen oxides formation, is presented as introduction. The impact of NO(x) pollution comprises additionally a quick view of its toxicity and environmental effects. Actual solutions are presented especially the case of the selective catalytic reduction (SCR) process with its advantages and difficulties. The new concepts for NO(x) abatement are also analysed. In such a way, updated information on solid sorbents for NO(x) removal is provided by including metal oxides, spinelles, perovskites, double-layered cuprates, zeolites, carbonaceous materials, heteropolyacids (HPAs), and supported heteropolyacids. The possibility of reducing those sorbed NO(x) is also underlined. Sorption mechanisms are analysed and clarified by emphasising convergence and disagreement points.