BACKGROUND Ascorbic acid is one of the most important vitamins to monitor in dietary sources (juices and vitamins) and biological liquids. RESULTS Silica and silica-titania xerogels doped with Mo,P-heteropoly compounds (HPC) have been synthesized varying titanium(IV) and HPC content in sol. Their surface area and porosity have been studied with nitrogen adsorption and scanning electron micros...

The production of carboxylic acids by partial wet oxidation of alkali lignin at elevated temperatures and pressures was studied experimentally. Two different heteropoly acids, phosphotungstic acid (H₃PW12O40) and phosphomolybdic acid (H₃PMo12O40), were used to catalyze the oxidation of lignin under hydrothermal conditions. Factors influencing the total yield of carboxylic acids formed during th...

The selective preparation of monobenzyl glyceryl ethers, which are potential commodity chemicals with special functions, was explored to find new applications for glycerol. Among the acid catalysts investigated (sulfuric acid, heteropoly acid, Nafion(R), and zeolite), Zeolite Socony Mobil-5 (ZSM-5) afforded better results. The reaction of equimolar amounts of glycerol and benzyl alcohol at 150º...

The hydroamination reaction offers a very attractive route for the synthesis of alkylated amines and their derivatives with no byproduct formation. Heterogeneous intermolecular hydroamination reactions of alkynes with aromatic amines using different inexpensive copper salts of hetropolyacid catalysts were investigated. Among heteropoly salts, copper salts of silicotungstic acid showed highest a...

The photoreduction of silicomolybdate and other heteropoly ions by chloroplasts is insensitive to 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (DCMU). Both water and diphenylcarbazide can be used as electron source for the reduction. Three different assays for silicomolybdate reduction are described including oxygen evolution, formation of a reduced heteropoly blue silicomolybdate, or an indirect ...

Evidence is accumulating for the major influence of the identities of counterions on syntheses and properties of various heteropoly anions. An easy and convenient NMR method is presented for evaluating the extent of significant association between heteropoly tungstate species and monoatomic metallic counterions (e.g., alkali metal cations). In diamagnetic [alpha(2)-P(2)W(17)O(61)-Th(4+)-alpha(2...

This review covers the recent developments and the present state of selective oxidation of propane to acrylic acid with molecular oxygen. The current commercial manufacturing process of acrylic acid, as well as the possible oxidation pathways of propane are included as background information. Special attention is given to three classes of leading catalysts: vanadium pyrophosphate, heteropoly ac...

The effects of oxidant and organic acid additives on the oxidative cross-coupling reactions of electron rich heterocycles such as benzofuran with benzene were studied. Both regioselectivity and reaction rate could be controlled by varying the condition parameters. Furthermore, mechanistic insight was achieved via kinetic studies which indicate that reactions that are oxidized by the heteropoly ...