Journal of Molecular Catalysis 

About: Journal of Molecular Catalysis is an academic journal. The journal publishes majorly in the area(s): Catalysis & Rhodium. It has an ISSN identifier of 1001-3555. Over the lifetime, 3800 publications have been published receiving 77665 citations.

Dioxygen electrocatalysis: mechanisms in relation to catalyst structure

Abstract: O/sub 2/ electrocatalysis is a particularly appropriate topic for the Berzelius lecture, in view of Berzelius' interest in both catalysis and the element oxygen. Despite extensive studies over the past century, the mechanistic aspects of the O/sub 2/ electrode reactions are not well understood; these reactions are very irreversible in aqueous electrolytes, even at temperatures of 200/sup 0/C with the best of catalysts, such as highly dispersed platinum. O/sub 2/ electrocatalysis is of critical importance to a number of applied aspects of electrochemistry, including: O/sub 2/ reduction (cathodes), anodic generation of O/sub 2/ (anodes).

A new peroxotungsten heteropoly anion with special oxidizing properties: synthesis and structure of tetrahexylammonium tetra(dipewroxotungsto)phosphate(3-)

Abstract: Preparation sous forme de monocristaux et determination par diffraction RX de la structure de [(C 6 H 13 ) 4 N] 3 {PO 4 [W(O)(O 2 ) 2 ] 4 }

The role of iron in N2O decomposition on ZSM-5 zeolite and reactivity of the surface oxygen formed

Abstract: Catalytic properties of the zeolite H-ZSM-5 doped with iron have been studied. The atomic activity of Fe in the zeolite is proved to be higher by several orders of magnitude than its activity in Fe2O3. The decomposition of N2O at low temperatures (below 300 °C) occurs in an unusual way, being accompanied by oxygen binding at the surface. There is one active site per each 4-5 Fe atoms capable of binding one oxygen atom. This form is impossible to obtain by O2 adsorption or NO decomposition. Surface oxygen generated by N2O exhibits a remarkably high reactivity. At room temperature it is involved in the O2 isotopic exchange as well as in the oxidation of CO and CH4.

On the pillaring and delamination of smectite clay catalysts by polyoxo cations of aluminum

Abstract: Two types of polyoxoaluminum solutions, base-hydrolyzed A1Cl 3 and aluminum chlorohydrate (ACH) with OH/A1 ratios of 2.42 and 2.50, respectively, have been used as reagents for the pillaring of the smectite clays montmorillonite and nontronite. Selective adsorption studies demonstrate that the method used to dry the flocculated clay layers is far more important than the choice of pillaring reagent or clay layer charge in determining the apparent pore size of pillared products. Air-drying leads to zeolite-like products with a pore opening ⪢6.2 A and 27 Al NMR spectroscopy indicates the polyoxo cation nuclearity to be larger in ACH than in base-hydrolyzed AlCl 3 , both reagents give pillared products with similar aluminum contents, pore sizes, thermal stabilities and catalytic properties. These similarities suggest the same type of oxo cations, probably Al 3 Keggin ions, are formed on the intracrystal surfaces. Also, the amount of Al bound per unit cell of pillared clay varies only over a small range (2.78 – 3.07), and the variation is not correlated with layer charge. This latter result suggests that a more or less uniform monolayer of hydrated polyoxo cations is formed in the interlayers, and that electrical neutrality is achieved through hydrolysis of the pillaring cations.

Insoluble heteropoly compounds as highly active catalysts for liquid-phase reactions

Abstract: Liquid-phase alkylation of m -xylene or trimethylbenzene with cyclohexene was studied using heteropoly compounds and other typical solid acids as the catalysts; the results are discussed in relation to the surface properties of the catalysts. Cs 2.5 H 0.5 PW 12 O 40 (abbreviated as Cs 2.5 -salt) was remarkably more active than H 3 PW 12 O 40 , zeolites, Nafion-H, SO 4 2− /ZrO 2 , H 2 SO 4 , and AlCl 3 HCl. Solid-state 31 P NMR revealed that Cs 2.5 -salt mainly consists of polyanions with one proton (Cs 2 HPW 12 O 40 ) and those without a proton (Cs 3 PW 12 O 40 ). The quantity of acid sites of Cs 2.5 -salt was determined to be 161 μmol g −1 by temperature-programmed desorption (TPD) of NH 3 , which was much greater than the estimated quantity of surface acid sites of H 3 PW 12 O 40 , and less than that of zeolites and SO 4 2− /ZrO 2 . The acid strength of Cs 2.5 -salt measured by Hammett indicators and TPD of NH 3 was smaller than that of SO 4 2− /ZrO 2 . It is presumed that the high activity of Cs 2.5 -salt is brought about by its large number of surface acid sites and its acid—base bifunctional nature, in which a caesium ion possibly increases the basicity of the heteropoly anion.