L. Matachowski

Bio: L. Matachowski is an academic researcher from Polish Academy of Sciences. The author has contributed to research in topics: Catalysis & Salt (chemistry). The author has an hindex of 14, co-authored 22 publications receiving 634 citations.

Catalytic performance of the dodecatungstophosphoric acid on different supports

Abstract: Varying amounts of tungstophosphoric acid (HPW) have been supported on Y-type zeolite and silica using the incipient wetness method. The catalytic activity of the catalysts was studied in the vapor-phase dehydration of ethanol. The reaction was carried out in a conventional flow-type reactor under atmospheric pressure at temperatures changing from 398 to 773 K. Unexpectedly, deposition of heteropolyacid on zeolite HY with the loadings decreasing from 46.8 to 0.00016 wt.% results in catalysts characterized by the same catalytic activity indicating that the catalytic behaviour is determined by few very active sites, composed of Keggin anions and lacunary Keggin anions located in the supercages opened at the surface, which has a honeycomb structure. Contrary to the series of HPW/Y catalysts, HPW supported on SiO 2 shows decreasing catalytic activity when its concentration lowers, the monolayer being catalytically inactive in acid–base reactions.

The effect of peripheral substituents in metalloporphyrins on their catalytic activity in Lyons system

Abstract: Manganese porphyrin catalysts with different number of halogens atoms substituted at the phenyl and pyrrole rings were investigated in the Lyons system in oxidation of cyclooctane with molecular oxygen (as air) to cyclooctanone and cyclooctanol without the use of sacrificial co-reductant. The catalytic activity of metalloporphyrins increases with the increase of the redox potential of metalloporphyrins in the investigated system and shows almost linear relationship with the number of the halogens on porphyrin macrocycle. On the basis of obtained results the new reaction mechanism is discussed and proposed.

Manganese porphyrins as catalysts for oxidation of cyclooctane in Lyons system

Abstract: Oxidation of cyclooctane with molecular oxygen (as air) in the presence of first generation manganese porphyrins XMn III (TTP), where X=F − , Cl − , Br − , I − , OH − , CH 3 COO − , as catalysts was investigated in the Lyons system. The catalytic activities of the metalloporphyrins in the oxidation of cyclooctane to cyclooctanone and cyclooctanol are covariant with electronegativity of halides as axial ligands and increase with the decrease of the redox potential of metalloporphyrins. It was concluded that axial ligands are involved in the reaction initiating the reaction by generating the radicals with simultaneous reduction of the manganese porphyrin. Relatively high yields of products were obtained without the use of sacrificial co-reductant.

Transesterification reaction of triglycerides in the presence of Ag-doped H3PW12O40

Abstract: Present work is concerned with examination of catalytic properties of 12-tungstophosphoric acid and its silver salts AgxH3−xPW12O40 with Ag-content ranging from x = 0.5 up to x = 3 for transesterification of triglycerides with methanol to form methyl ester (biodiesel) under mild conditions (atmospheric pressure, temperature of 50–60 °C). Reaction was studied for triacetin, a model triglyceride and for vegetable oil, castor oil. Various techniques (BET, FTIR, XRD, XPS, laser diffraction, electron microscopy, SEM, and EDS) were used to characterize as-received Ag-salts and the samples separated after the catalytic tests. Because of the presence of methanol, which is the reactant, silver salts formed colloidal dispersion during the catalytic reaction. Under such conditions, all silver salts were active for transesterification of triglycerides. The conversion of triglycerides gradually decreases as the protons in heteropolyacid are replaced by Ag+ cations. However, due to the leaching of parent H3PW12O40 upon dissolving in methanol, the contribution of homogeneous catalysis was observed, especially in the presence of Ag-salts with low silver content such as Ag0.5H2.5PW12O40. Catalytic performance of Ag-salts in methanolysis of a short-chain triglyceride, triacetin, differs remarkably from that in castor oil comprising natural, long-chain triglycerides. After transesterification of castor oil, initially crystalline particles of Ag-salts partially rearrange to “gel-type” material making their further processing difficult. Although, no “gel-type” particles are formed after reaction of triacetin, the formation of “nanowires” due to partial reduction of some of Ag+ ions is observed.

Metal-catalyzed hydrocarbon oxygenations in solutions: the dramatic role of additives: a review

Abstract: This review describes examples of remarkable acceleration of metal-catalyzed oxidation reactions by certain additives. In some cases, reactions proceed 2 or 10 times more rapidly in comparison with the process in the additive’s absence, in other cases, reactions become possible only in the presence of the additive. Varying ligands at the metal center or additives, one can not only dramatically improve yields of oxygenates but also control the selectivity of the reaction. Understanding mechanisms of the additive’s action is very important for search of new efficient catalysts and catalytic systems. Additives considered in the review can play roles of the ligands at metal ion or proton or electron transfer reagents and they mimic certain enzymes (the active center or its environment). Often the mechanism of the effect of additives on the reaction rate and the product yield is unknown, and the main aim of the review is to attract investigator’s attention in creating new efficient catalytic systems, which contain not only a metal ion but also a necessary “additive”.

Metal–organic frameworks as scaffolds for the encapsulation of active species: state of the art and future perspectives

Abstract: The use of metal–organic frameworks (MOFs) for the encapsulation of different active entities is thoroughly reviewed. Either by following ship in a bottle or bottle around a ship approaches, active species can be encapsulated in the porous framework of different MOFs. Encapsulated species vary from polymers to organometallics and from polyoxometalates to metal nanoparticles and metal oxides. The main advantages and limitations of the use of MOFs together with the synthetic approaches followed are evaluated.