Hannu Karhu

Supported ionic liquids catalysts for fine chemicals : citral hydrogenation

The quest for new concepts in catalysis involving fine chemicals production is discussed. A new approach for easy preparation of structural, heterogeneous catalysts where the selectivity profile is altered by means of different ionic liquids and the same transition metal species (Pd) is introduced. Furthermore, an novel ionic liquid, [A336][PF6], derived from a common phase-transfer catalyst, Aliquat336®, was synthesized and utilized in catalytic hydrogenation of citral.

Gas-phase hydrogenation of o-xylene over Pt/alumina catalyst, activity, and stereoselectivity

Abstract The kinetics of the gas-phase hydrogenation of o -xylene over Pt/alumina catalysts was studied at 430–520 K, a hydrogen partial pressure of 0.19–0.36, and an o -xylene partial pressure of 0.04–0.10. The catalysts were characterized by H 2 / o -xylene TPD, H 2 chemisorption, energy-dispersive X-ray analysis, and XPS. The stereoisomers, cis- and trans -1,2-dimethylcyclohexane, were the only reaction products. A reversible maximum in the o -xylene hydrogenation activity vs temperature was observed; it was explained by a decrease in the surface concentration of o -xylene at higher temperatures. The hydrogenation rate was independent of the o -xylene concentration, whereas the reaction orders with respect to hydrogen varied from 0.9 to 3 in the temperature range investigated. The stereoselectivity of the products was found to depend on temperature, reactant concentrations, and platinum precursor. The catalyst prepared from a chlorine-containing precursor exhibited a lower hydrogenation activity and selectivity toward the trans isomer. Chlorine remained on the catalyst surface, even after reduction at 673 K. Dehydrogenation and configurational isomerization of cis - to trans -1,2-dimethylcyclohexane took place at the same time as hydrogenation. Dehydrogenation and configurational isomerization reactions are enhanced by the presence of residual chlorine on the catalyst surface. The reaction pathway is proposed.

Surface modified high rectification organic diode based on sulfonated poly(aniline)

In this paper, we present a new method that combines surface modification of indium-tin oxide (ITO) and electropolymerization to prepare thin, sulfonated poly(aniline) (SPAN) films with good surface coverage. The surface modification enhances the growth of the SPAN film resulting in a better rectification signal than for SPAN films polymerized on unmodified ITO substrates. The films were characterized by FTIR, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The sulfonation degree of SPAN was determined to 29% by X-ray photoelectron spectroscopy (XPS). UV-VIS spectroscopy shows that the pH sensitivity of SPAN is suppressed due to sulfonation of the polymer backbone. It is also shown that conversion of the SPAN film to the emeraldine salt (ES) form after polymerization is crucial for obtaining a high rectification signal. This is an important practical aspect in the preparation procedure of organic electronic devices.

Physico-chemical and catalytic properties of Zr- and Cu–Zr ion-exchanged H-MCM-41

H-MCM-41 catalyst ion-exchanged by Zr and/or Cu-cations were synthesized and characterized by XPS, 27Al- and 29Si-MAS-NMR, FTIR of pyridine adsorption, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and direct current plasma atomic emission spectrometry. The catalysts were evaluated towards 1-butene skeletal isomerization after pre-treatment with hydrogen or synthetic air. The dispersion of metals after ion-exchange was reasonably good, as revealed by LA-ICP-MS. Binding energies observed by XPS indicated that after reduction or oxidation pre-treatments copper is mainly present as Cu2+, except in case of reduced Cu-H-MCM-41. Pre-treatment had no influence on the oxidation state of Zr4+ species. Zr ion-exchange decreased the concentrations of Bronsted and Lewis acid sites. As a result, the initial conversion of 1-butene was decreased, but the selectivity and stability of the catalyst were increased. As reported before, the copper introduction decreased the Bronsted acid site density, but increased the conversion. The enhancement in the catalytic activity has been connected to the presence of copper with oxidation state +1, which is formed under reaction conditions due to the hydrogen formation. This led to a peculiar effect over oxidized bimetallic Cu–Zr-H-MCM-41 at a low temperature and high weight hourly space velocity (523 K and 15 h−1, respectively): The initial conversion of 1-butene was almost zero but increased during the time-on-stream reaching the value of about 13 mol%. These observations are related to the reduction of Cu2+ species to Cu+ during the reaction. The catalyst evaluation and characterization results led to a conclusion that the presence of Zr stabilizes copper’s oxidation state of Cu+2 under reductive conditions in the bimetallic Cu–Zr-H-MCM-41 catalyst.

Synthesis of Pt-modified MCM-41 mesoporous molecular sieve catalysts: influence of methods of Pt introduction in MCM-41 on physico-chemical and catalytic properties for ring opening of decalin

MCM-41 mesoporous molecular sieve was modified with Pt using in-situ synthesis, ion-exchange and impregnation evaporation catalyst preparation methods. Physico-chemical properties of Pt-MCM-41 catalysts synthesized with different methods were investigated using characterization techniques such as X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray micro-analysis, X-ray photo-electron spectroscopy, pulse CO chemisorption and nitrogen adsorption. Under suitable designed synthesis conditions it was possible to introduce Pt in MCM-41 by in-situ, ion-exchange and impregnation methods without influencing the phase purity of MCM-41. The ring-opening of decalin was used as a test reaction to evaluate the catalytic properties of Pt-MCM-41 catalysts synthesized by ion-exchange, in-situ synthesis and impregnation evaporation methods. The Pt-MCM-41-IMP catalyst prepared by impregnation evaporation method was the most active in ring opening of decalin.