Current Catalysis - Volume 1, Issue 2, 2012

A short account of discovery, development of basic mechanistic concepts, and variants of Phase Transfer Catalysis is presented.

Palladium was impregnated to precipitated iron catalyst as a promoter. The catalysts were tested in a fixed bed reactor to convert CO and H2 into hydrocarbons. Compared with pure iron catalyst, more CH4 and less olefins in C2-C4 hydrocarbons are produced from the iron catalyst promoted only by Pd. The olefin ratio in C2-C4 hydrocarbons of the catalysts promoted by Pd, Zn and Cu is between the values of pure iron catalyst and Pd-promoted iron catalyst. It means that the influence of Pd on the hydrocarbon distribution can be adjusted by the coexistence of Zn and Cu. Temperatureprogrammed reduction by H2 was used to detect the influence of Pd on iron catalysts.

The catalytic effect of the aluminium chloride reagents R1AlCl2 (R1 = Cl, Me, Et) on the dienophilic reactivity of the >C=C< functionality of indolizine and >C=P- functionality of 2-phosphaindolizine in their Diels-Alder (DA) reaction with 1,3-butadiene has been investigated theoretically at the DFT (B3LYP/6-31+G**) level. The activation barriers of the DA reactions of the uncomplexed dienophiles with 1,3-butadiene are quite high. Co-ordination of the aluminium reagent to the carbonyl group of indolizine or 2-phosphaindolizine raises the activation barriers further. On the other hand, co-ordination of the aluminium catalyst to the σ2, λ3-P atom of 2-phosphaindolizine lowers the activation barrier making the DA reaction possible. Electronic structure calculations of indolizine, 2-phosphaindolizine and their complexes to the aluminium catalyst indicate, that this behavior can be explained by a combination of energetic and stereoelectronic influences of the catalyst on the lowest unoccupied molecular orbital (LUMO) of the dienophiles. Co-ordination of the aluminium catalyst to the dienophile lowers the orbital energy of the LUMO in any case making it energetically more feasible for the normal electron demand DA-reactions. However, O co-ordination polarizes the spatial distribution of the LUMO away from the dienophilic center while P co-ordination increases the orbital contribution of the >C=P fragment to the LUMO.

A Rh phosphine complex, derived from the Wilkinson's catalyst, has been immobilized by ion-exchange on the ammonium form of a Al-MCM-41 sample. Ammonium ions have been exchanged by cholamine ions, which act as an amine ligand, and then the Wilkinson's catalyst has been immobilized by substitution of a phosphine ligand by the anchored amine. This is a novel immobilization procedure, as a ligand, instead of the whole complex, is tethered to the support by ion exchange. The obtained hybrid catalyst has been characterized by Elemental Analysis, DRIFTS and XPS. The quantitative exchange of ammonium by cholamine and coordination of Rh to amines has been observed. Most of the anchored Rh is considered to be coordinated to the ligand tethered to the support and a small proportion seems to be interacting with the protonated ligand or with the support surface. The catalyst has been tested in the hydrogenation of cyclohexene and in the hydroformylation of 1-octene. In the first case the catalyst is active and reusable, while a strong Rh leaching takes place in the second one.

From the viewpoint of sustainable development, chemical fixation/utilization of CO2 in an environmentally benign manner has been drawing much interest, especially in the field of organic chemistry. In this review, 100% atom economical routes such as the reaction of CO2 and aziridines to prepare oxazolidinones and polyurethanes with more consideration given to the catalytic strategies and insight into the reaction mechanism are reviewed in the context of CO2 conversion into useful chemicals. High atom efficiency of the reaction and wide application of the CO2-derived products are the main driving force for the constant interest paid to catalytic conversion of CO2 into fuels, value-added chemical, polycarbonate materials.

RuCl3·3H2O-catalyzed stereoselective transfer semihydrogenation of diarylacetylenes with HCOOH as hydrogen source affording trans-stilbenes in good to high yields is developed.

Biotransformation of (+)-α-pinene to (+)-verbenone using shaking cultures of Cladosporium cladosporides (MTCC 1003) was investigated. Cladosporium cladosporides showed specific transformation of (+)-α-pinene with 86.8±3.0% conversion (relative integrated area gas chromatography–mass spectrometry (GC-MS)) of (+)-verbenone in 7 day incubation. The amount of verbenone formed was observed at 1, 3, 5 and 7th day where it is gradually increased. Verbenol was formed as intermediate product and slowly biocatalyzed to verbenone.

Hydrocarbons representative of jet fuel were produced by both catalytic cracking and one-step catalytic hydrocracking of soybean oil in a lab-scale flow reactor. The yield of kerosene/jet fuel hydrocarbons by catalytic cracking over a commercialized ZSM-5 was as high as 21%. Both temperature and space velocity exhibited irregular effects on the product distribution. Steady state was not attained and significant amounts of tar and coke were generated during the reaction. A bifunctional hydrocracking catalyst with 1.1% ruthenium supported on ZSM-5, prepared by an impregnation method, produced a 16% yield of jet fuel, which is comparable to yields over commercialized sulfided NiMo catalysts while at a much lower pressure of 650 psi. Compared to the catalytic cracking process over ZSM-5, steady-state flow reaction was obtained with less tar and polymerized products.

A series of Cu/ (MgO-Al2O3) hydrotalcite catalysts have been prepared by impregnation technique with a Cu loading ranging between 5 to 25wt%. The prepared catalysts have been characterized by BET technique, X-Ray diffraction, temperature programmed reduction (TPR) and N2O pulse chemisorption techniques. Cyclohexanol dehydrogenation and nitrobenzene hydrogenation (individual reactions) and coupling of these two reactions have been performed over these catalysts in vapor phase at atmospheric pressure and at 548K. XRD results reveal the intactness of hydrotalcite structure in reduced and used catalysts with Cu loadings below 15wt%. The beauty of the coupling reaction is to yield cyclohexanone and aniline from cyclohexanol and nitrobenzene respectively with stoichiometric quantity of H2 usage for nitrobenzene hydrogenation. The catalyst with 10wt% Cu loading showed higher activity in the coupling reaction which could be attributed to the better Cu dispersion, smaller Cu particle size and relatively more number of Cu active species presented on the surface of the catalyst.