Irena Miloslavski

Entrapment of metallic palladium and a rhodium(I) complex in a silica sol-gel matrix - Formation of a highly active recyclable arene hydrogenation catalyst

A combined palladium–rhodium catalyst, generated by silica sol–gel-co-entrapment of metallic palladium and [Rh(cod) (-Cl)]2, catalyzes under ambient conditions the hydrogenation of toluene and other simple benzene derivatives. The catalyst is perfectly recyclable and promotes at 80 ◦ C and 400 psi, also the hydrogenation of polycyclic and sterically hindered arenes that are capable of penetrating the matrix pores. A synergistic effect is assumed to exist between the two metals, as either of the entrapped metallic components is a less active catalyst than the combination of both.

Sol–gel entrapped heteronuclear transition metal catalysts

Abstract The heteronuclear complexes [(CO)4Fe(μ-PPh2)Pd(μ-Cl)2]2, [Et4N][FeCo3(CO)12] and Rh2Co2(CO)12 were physically entrapped in SiO2–sol–gel matrices. The doped materials, so formed, were utilized as recyclable catalysts for (a) selective isomerization of 1-octene, (b) selective dimerization of norbornadiene to ‘binor-S’, and (c) hydrogenation and hydrogenolysis of styrene, nitrobenzene and 1-chloronaphthalene, respectively. During the hydrogenation of the nitrobenzene and of chloronaphthalene, the dodecacarbonylbis(cobalt)dirhodium was converted into sol–gel entrapped carbonyl-free nanoparticles that efficiently catalyze the reduction of the aromatic C–C bonds.

Cuticular Surface Hydrocarbons of Desert Locust Nymphs, Schistocerca gregaria, and Their Effect on Phase Behavior

The quantity of cuticular hydrocarbons is higher in solitarious nymphs of the desert locust, Schistocerca gregaria, compared to gregarious nymphs, but the total hydrocarbon fraction of solitarious nymphs does not significantly divert behavioral transition of isolated nymphs to the gregarious phase, while gregarious hydrocarbon extracts do. This suggests that qualitative differences in composition are responsible for the biological effect. The profile of cuticular hydrocarbon components is similar in the two phases, but some peak ratios differ. Crowding of solitarious nymphs leads to rapid changes in the profile of the hydrocarbon fraction, suggesting that specific hydrocarbons are produced and secreted as a consequence. Isolating previously crowded nymphs has an opposite effect. The composition of cuticular hydrocarbons from the migratory locust, Locusta migratoria, which differs considerably from that of S. gregaria, does not induce the gregarious behavioral phase in solitarious nymphs of the latter.

Genetic characterization of gas shows in the east Mediterranean offshore of southwestern Israel

Drilling in the eastern continental margin of the Levant Basin (southeastern Mediterranean), offshore southwestern Israel encountered light oil shows, numerous vertically stacked gas pockets and, more recently, commercial gas discoveries. Chemical and stable isotopic compositions obtained for 24 gas samples from Middle Jurassic to Pliocene reservoir rocks suggest that they represent a few genetic systems which are distributed vertically in the section in accordance with the stratigraphy. These groups include bacterial gas in the Pliocene, a mixture of bacterial and thermogenic gas in the Lower Cretaceous, and thermogenic gas in the Jurassic section. The bacterial gases in the Pliocene and the Lower Cretaceous appear not to be cogenetic, and likewise the thermogenic gas in the Lower Cretaceous and the Jurassic sections. Excluding one case, where the thermogenic gas appears to represent phase separation from a probably cogenetic light oil, the relationship of either the bacterial or other thermogenic gas samples to particular potential source rocks in the section or to light oil shows encountered in the Middle Jurassic section is at this stage inconclusive.

Oil-oil correlation and potential source rocks for oils in Paleozoic reservoir rocks in the Tataria and Perm basins, Russia

Abstract We present a study of 45 oil samples from the Tataria and Perm basins in the Volgo-Ural region, Russia. Crude samples were obtained from 30 oil fields across the two basins. Samples are from variable carbonate and sandstone reservoir rocks ranging in age between Givetian (Devonian) and Kazanian (Permian) at various present-day depths. Oil-oil correlation suggests that despite the diversity of the reservoir rocks and vast geographic distribution, all oils studied are classified, in general, into a singular genetic oil family, with possible indication for secondary subdivision into two subgroups. The major characteristics of the oils, i.e. low Pr/Ph ratio, CPI ∼ 1, relatively high C 27 -sterane, low proportions of rearranged steranes, C 29 ≥C 30 -hopane, low ratio of Ts to Tm hopanes, high sulfur content and high ratio of V to Ni, all suggest a reducing and probably hypersaline depositional environment for the source rock which was likely carbonate-rich. Thermal maturity indicated for all the oils is in the upper range of the main phase of oil generation. Furthermore, the characteristics obtained for the light-end normal alkanes and mono-aromatics indicate no significant degradation for most of the samples. Hence, the relatively high specific gravity of the oil samples is not attributed to either maturity or degradation effects. Difference recorded in Pr/Ph ratio between samples from Perm basin are tentatively attributed to spatial variations in depositional environment conditions. Differences in tricyclic terpanes content in samples from both basins possibly indicate some variations in input of specific ( Tasmanites ) algae to their source rock. Preliminary examination of an extract of Devonian Domanic Formation sample corroborates the possibility that this formation is a major source rock for the oils in both the Tataria and Perm basins.

Thermal behavior of immature asphalts and related kerogens

Abstract Immature asphalts suggested to originate from early stages of catagenesis and related kerogens were submitted to various pyrolysis analyses. We have examined the idea that, under certain conditions, parts of kerogen cleave off to yield asphalt. Bulk parameters were recorded as well as gas chromatograms of the trapped pyroproducts. Thermal changes were followed through analyses of gases, condensates, and extracts formed. The residual kerogens/asphalts were examined for structural changes. Both closed and open systems experiments were conducted. Some aspects of high concentrations of organic sulfur bonded (8.0–12.9% S) and low concentrations (normal 1.5–2.1% S) and their influence on thermal behavior were studied using samples from the Dead Sea Rift Valley and Green River Shale Gilsonite. The results obtained indicate very similar thermal behavior for kerogen-immature asphalts pairs, marked differences between various modes of thermal treatment and surprisingly marginal differences between hydrous/ nonhydrous, closed system experiments.

Reactions of clay volatiles with n-alkanes

Volatiles formed on heating clay minerals contain a variety of cations and anions and are highly reactive. Gas chromatograph-mass spectrometer analysis of long-chain n-alkanes exposed to such volatiles showed that some decomposition occurred even < 250°C. Reactions with anions donated by the volatiles led to compounds containing atoms other than C and H, e.g., Cl. The products obtained from n-alkanes heated in a stream of clay volatiles to 500°C resembled those produced by corresponding alkane-clay mixtures heated to 250°C. At higher temperatures contact between the alkanes and montmorillonite or halloysite led to changes in the assemblages formed, whereas kaolinite or sepiolite had no effect. Thus, the first reactions that occurred when clays were heated with n-alkanes were apparently induced by the volatiles; at higher temperatures catalysis due to direct contact came into play with some of the clay minerals.

Long-living free radicals study of stepwise pyrolyzed melanoidins and humic substances

Abstract ESR measurements of stepwise-pyrolyzed melanoidins and humic substances (at various temperatures, mesh size, and pH values) furnished the following information: the melanoidin structure stabilizes the long-living free radicals in a manner similar to humic substances; the g and Ng values of melanoidins are similar to those of the humic substances, the cleavage of CC and CX (X = heteroatom) bonds increases the Ng value. Thermogravimetric curves, weight loss by stepwise pyrolysis, and 13C-CP/MAS NMR were found to be in good correlation with ESR data regarding the structural features of melanoidins and humic substances.

Reactions between clay volatiles and calcite reinvestigated

Calcite crystals exposed to clay volatiles react with some components of these volatiles, giving rise to a variety of surface morphologies. F, Cl, and S in different proportions were detected by electron microprobe analysis of the calcite surfaces. Under identical experimental conditions, volatiles from every clay mineral examined caused a specific morphology and chemical composition of the calcite surfaces, but these varied with temperature of the calcite. Changes in pH values and mass spectra of the volatiles after passage through calcite demonstrate that even on rapid heating some clay volatile-calcite reactions occur at temperatures as low as 150°C. Species other than those detectable by electron microprobe analysis also participate in the reactions in which CO2 is liberated.

Reactions of clay condensates with n-alkanes: comparison between clay volatiles and clay condensates

Abstract Long-chain n-alkanes were heated in the presence of clay volatiles or clay condensates, to temperatures up to 250°C in an open and 160°C in a closed system. The product assemblages obtained, which were identified by gas chromatography and gas chromatography-mass spectrometry, resembled each other and those formed on direct contact with the clay minerals. The composition of the assemblages indicates that catalytic cracking occurred. It appears that reactive species, which were previously detected and identified in the volatiles and condensates, act as acid catalysts. Under the mild conditions of the experiments the n-alkanes remained unchanged in the absence of a catalyst and catalysis by clay mineral surfaces had not yet come into play. The persistence of the reactivity of clay volatiles in the condensates implies that fluids derived from clays may catalyse processes that are removed in space and time from the immediate vicinity of the minerals.