Topic
Phosphotungstic acid
About: Phosphotungstic acid is a research topic. Over the lifetime, 1925 publications have been published within this topic receiving 38059 citations. The topic is also known as: Phosphowolframic acid.
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TL;DR: In this article, the effect of catalysts on the acylation of anisole with α,β-unsaturated acids was investigated using phosphotungstic acid (H 3 PW 12 O 40 ), as pure form, supported on SiO 2 and in the form of cesium salts as catalysts.
Abstract: The mechanism of the acylation of anisole with α,β-unsaturated acids, i.e. acrylic, crotonic and methylcrotonic acid, has been investigated using phosphotungstic acid (H 3 PW 12 O 40 ), as pure form, supported on SiO 2 and in the form of cesium salts as catalysts. Since α,β-unsaturated acid can either alkylate and/or acylate the aromatic compound, the influence of the catalyst on the selectivity for these two competing reactions was studied. Analysis of products obtained on the acylation of aromatic compounds with α,β-unsaturated acids shows that all the catalysts are more active for acylation than alkylation. Secondary products coming from intermolecular reactions of the acylated product with anisole as well as tertiary products coming from its further decomposition and recombination with another anisole molecule were observed. Heteropolyacids supported on silica were found to be more active and selective towards acylation reactions than zeolites HY and Hβ, even when the activity per acid site was considered. Zeolites and cesium salts from heteropolyacids favor acid polymerization reaction rather than the acylation of the aromatic compound.
35 citations
TL;DR: In this article, free standing chitosan/phosphotungstic acid polyelectrolyte membranes were prepared by an easy and fast in-situ ionotropic gelation process performed at room temperature.
35 citations
TL;DR: In this article, the self-discharge time of the PWA-TiO 2 and WO 3 was investigated under UV light (1 mW/cm 2 ) for I h in 3 wt% aqueous NaCl.
Abstract: Phosphotungstic acid (PWA) was utilized as the reductive energy storage substance instead of conventional WO, for the fabrication of an energy storage photocatalyst, which retains its reducing ability even after light irradiation. In the case where a PWA film was electrochemically charged at -0.8 V vs. Ag/AgCl for I h in 3 wt% aqueous NaCl, it showed longer self-discharge time than a WO 3 film of the same thickness. Photoelectrochemical properties of the PWA and WO 3 films coated with porous TiO 2 were also studied. The PWA and WO 3 films could be charged under UV light (1 mW/cm 2 ) for I h in 3 wt% aqueous NaCl. Although the amount of charge accumulated in the PWA-TiO 2 film was smaller than that in the WO 3 -TiO 2 film, the self-discharge time of the former was longer. Slower self-discharging process by O 2 , which may be advantageous for some applications, of the former is responsible for these results. The PWA-TiO 2 film showed relatively good durability after several cycles.
35 citations
TL;DR: In this article, a simple and cost-effective gel-casting technique has been developed to fabricate phosphotungstic acid (HPW) supported on mesoporous silica (MCM-41) electrolyte membrane for direct methanol fuel cells (DMFCs).
35 citations
TL;DR: In this paper, a simple and efficient method was developed for the synthesis of quinaldines and lepidines by a one-pot reaction of anilines with crotonaldehyde or methyl vinyl ketone using phosphotungstic acid, a Keggins-type heteropoly acid, under both thermal and microwave irradiation conditions.
35 citations