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BIPHASIC SYNTHESIS OF HYDROGEN PEROXIDE FROM CARBON MONOXIDE, WATER, AND OXYGEN CATALYZED BY PALLADIUM COMPLEXES WITH BIDENTATE NITROGEN LIGANDS

Effective and stable Pd catalysts for the biphasic synthesis of hydrogen peroxide from carbon monoxide, oxygen, and water [Eq. (a)] can be obtained by the right choice of bidentate nitrogen ligand. The best turnover numbers (578) for this reaction have been achieved with palladium complexes with 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline ligands.

A novel palladium catalyst for the synthesis of hydrogen peroxide from carbon monoxide, water and oxygen

The synthesis of hydrogen peroxide from carbon monoxide, water and oxygen in a biphasic system using palladium complexes with bidentate nitrogen ligands as catalysts was investigated. After testing a series of phenanthroline derivatives, 2,9-dimethyl-4,7-diphenylphenanthroline (8) was selected as the most efficient ligand. The palladium complex with ligand 8 showed high stability and catalytic activity (turnover number up to 600 moles of hydrogen peroxide per mole of palladium per hour) and, on the basis of a preliminary study, carried out in continuous operation mode, it appears a promising catalyst for the development of an industrial process.

Production of hydrogen peroxide from oxygen and alcohols, catalyzed by palladium complexes

Production of hydrogen peroxide has been achieved by the catalytic oxidation of primary and secondary alcohols with oxygen, in presence of a palladium catalyst. The catalyst was a complex of palladium with a bidentate nitrogen ligand and an acid cocatalyst. 2,9-Dimethyl-4,7-diphenyl-1,10-phenantroline (1) was selected as the most efficient ligand, and perfluorooctanoic acid gave the best results as cocatalyst. In this work the effects of nitrogen ligands, acid cocatalyst, alcohols, as far as temperature and oxygen pressure are concerned, are investigated.

Purification and stability of glutaryl-7-ACA acylase from Pseudomonas sp.

The enzyme glutaryl-7-ACA acylase fromPseudomonas sp. NCIMB 40474, produced by a recombinantEscherichia coli host, was purified to homogeneity. The enzyme is a tetramer composed of two couples of asymmetric dimers, each of them constituted of two subunits of mol wt 18 and 52 kDa, respectively. It was found that glutaric acid, one of the products of the substrate hydrolysis, is an effective acylase inhibitor. Between pH 6.0 and pH 10.0, the enzymatic activity is almost constant, but below pH 6.0 it progressively declines. The acylase activity decreased sharply as a function of guanidine HC1 concentration. The loss is significant even at concentrations of denaturant lower than those causing unfolding, as suggested by UV spectroscopy and fluorescence emission studies. In these conditions (low denaturant concentration and low pH) the inactivation of the enzyme is caused by the tetramer dissociation into dimers. The lability of the quaternary structure of the enzyme is a key feature that must be taken into account for the improvement of the catalyst stability.

Quinone-mediated synthesis of hydrogen peroxide from carbon monoxide, water and oxygen

Abstract An improved method for the synthesis of hydrogen peroxide from carbon monoxide, water and oxygen catalyzed by palladium complexes in presence of a quinone co-catalyst is described. Even if the reaction balance is formally the same, the mechanism of formation of hydrogen peroxide in the new process is totally different to that proposed for the reaction carried out in absence of quinones. Using 1,10-phenanthroline as a palladium ligand in a water/organic biphasic reaction medium, a dramatic enhancement of the catalyst stability was obtained operating in presence of 1,4-naphthoquinone, which prevented the formation of inactive binuclear palladium species. Additional improvements, with respect to the reaction carried out in absence of quinone, are the use of cheaper palladium ligands and the safer process conditions, since air can be used as a reagent instead of pure oxygen.

Enzymatic transformation of cephalosporin C to 7-ACA by simultaneous action of immobilized d-amino acid oxidase and glutaryl-7-ACA acylase

The enzymatic transformation of cephalosporin C (CEPH C) to 7-amino-cephalosporanic acid (7-ACA) using D-amino acid oxidase (DAO) and glutaryl-7-ACA acylase (G1-7-ACA) is reported. The enzymes have been immobilized separately on different carriers, in order to maximize the catalytic activity and the stability. The reaction has been carried out in single-step-like conditions, using the two enzymes simultaneously. The effect of catalase contamination, present in the DAO preparations, was balanced by addition of extra hydrogen peroxide. In optimum conditions, the conversion of CEPH C to 7-ACA was higher than 90%, with byproduct formation lower than 4%. The mixture of immobilized enzymes was reused in repeated reaction cycles, showing an appreciable operational stability.

Synthesis of hydrogen peroxide from carbon monoxide, water and oxygen catalysed by palladium complexes: a study of the catalyst stabilisation

Publisher Summary A new process for the one-step synthesis of hydrogen peroxide from carbon monoxide, water and oxygen has been recently reported by EniChem. The reaction was carried out in a biphasic system with the catalyst soluble in the organic phase and the produced hydrogen peroxide soluble in the aqueous phase. The organic phase was a mixture of an aromatic solvent and 2-methyl-2-butanol (a cosolvent that is necessary for the activation of the catalyst). The reaction was accelerated by an acid promoter, such as trifluoroacetic acid or toluene-4-sulfonic acid, the anion of which coordinates only weakly to the metal. Two possible deactivation mechanisms were identified, both related to the nature of the organic solvent used as reaction medium.

Selective enzymatic hydrolysis of aromatic diesters using esterase from Brevibacterium imperiale B222

SummaryA practical procedure has been developed for the chemoselective microbial hydrolysis of aromatic dicarboxylic esters to give the corresponding monoesters, using cellular lysate and whole cell of Brevibacterium imperiale B222. The produced monoesters can be transformed into hydroxyacids, useful intermediates in the synthesis of polyesters.