Principles of catalytic dehydrogenation of alkyl aromatic hydrocarbons

Russian Chemical Bulletin -     

Sorption purification of saturated hydrocarbons to remove aromatic compounds

Prospects for use of microscopic amounts of fullerenes as a modifying additive for improving the absorption capacity of conventional adsorbents in both static and dynamic conditions of purification of saturated hydrocarbons to remove aromatic compounds were examined.     

Hydroxyaminomethylation of aromatic hydrocarbons

Conclusions The electrophilic hydroxyaminomethylation of aromatic hydrocarbons was accomplished for the first time, with toluene and m-xylene as examples.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1135–1136, May, 1967.     

Rapid determination of polycyclic aromatic hydrocarbons in the exhaust gases of direct-injecting Diesel engines by HPLC

A rapid HPLC procedure is introduced that allows the quantification of polycyclic aromatic hydrocarbons (PAH) in the exhaust gases of direct injecting Diesel engines. A branch stream of the motor exhaust gas is passed through a cooler and a filter. Then the cooler rinsing phase and the soot collected on the filter are extracted with toluene. The clean-up is carried out by solid phase extraction and thin-layer chromatography. Using this method, which is reproducible with high precision, a great number of samples may be analysed in a cost and time efficient manner, even when other rapid procedures fail.     

Sonochemiluminescence of aromatic hydrocarbons

Multibubble sonoluminescence of water and a series of aromatic hydrocarbons, viz., benzene, toluene, ethylbenzene, and m-xylene (at 25 °C), and a naphthalene melt (at 110–120 °C) was studied. An analysis of the influence of oxygen and argon on the sonoluminescence intensity and the luminescence spectra of these liquid compounds, as well as the effect of additives of ionol, ethanol, and 9,10-dibromoanthracene on m-xylene sonoluminescence, showed that a considerable contribution to the sonoluminescence of aromatic hydrocarbons is made by chemiluminescence reactions associated with their oxidation. This sonochemiluminescence is observed in both the gas phase of cavitation bubbles and the bulk solution where luminescence is retained for a long time after ultrasonication switching-off (the initial intensity of the residual chemiluminescence is up to 10% of the luminescence intensity during sonolysis). As for thermoinitiated oxidation, the afterglow of m-xylene contains the radical and molecular components.     

Multidimensional gas chromatography for the characterization of permanent gases and light hydrocarbons in catalytic cracking process

An integrated gas chromatographic system has been successfully developed and implemented for the measurement of oxygen, nitrogen, carbon monoxide, carbon dioxide and light hydrocarbons in one single analysis. These analytes are frequently encountered in critical industrial petrochemical and chemical processes like catalytic cracking of naphtha or diesel fuel to lighter components used in gasoline. The system employs a practical, effective configuration consisting of two three-port planar microfluidic devices in series with each other, having built-in fluidic gates, and a mid-point pressure source. The use of planar microfluidic devices offers intangible advantages like in-oven switching with no mechanical moving parts, an inert sample flow path, and a leak-free operation even with multiple thermal cycles. In this way, necessary features such as selectivity enhancement, column isolation, column back-flushing, and improved system cleanliness were realized. Porous layer open tubular capillary columns were employed for the separation of hydrocarbons followed by flame ionization detection. After separation has occurred, carbon monoxide and carbon dioxide were converted to methane with the use of a nickel-based methanizer for detection with flame ionization. Flow modulated thermal conductivity detection was employed to measure oxygen and nitrogen. Separation of all the target analytes was achieved in one single analysis of less than 12 min. Reproducibility of retention times for all compounds were found to be less than 0.1% (n = 20). Reproducibility of area counts at two levels, namely 100 ppm_v and 1000 ppm_v over a period of two days were found to be less than 5.5% (n = 20). Oxygen and nitrogen were found to be linear over a range from 20 ppm_v to 10,000 ppm_v with correlation coefficients of at least 0.998 and detection limits of less than 10 ppm_v. Hydrocarbons of interest were found to be linear over a range from 200 ppb_v to 1000 ppm_v with correlation coefficients of greater than 0.999 and detection limits of less than 100 ppb_v.     

High temperature catalytic synthesis of higher hydrocarbons from methane

It has been revealed that methane conversion to higher hydrocarbons over MgO catalyst involves the direct participation of heterogeneous catalyst at contact times of up to 3s and is a homogeneous reaction at 10s.

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MgO. , 3 . , 10 . .

     

Removing nitric oxide from flue gases by catalytic reduction

A Ti-W-V catalyst has been proposed for removing NO by means of ammonia reduction from flue gases from power stations and boiler systems operating with natural gas; it contains 10% W0₃ and 5% V₂O₅ deposited on anatase. The optimum NH₃/NO ration is 0.8. oxygen at levels of 0.1–7.8 vol. % does not affect the reduction of the NO. Industrial tests in flue gas from a power station show that the reduction of the NO is 96% at 240–270°C. The basic technological parameters have been determined.State Research and Development Institute for the Nitrogen Industry and Organic Synthesis Products, Moscow. Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 27, No. 5, pp. 595–598, September–October, 1991. Original article submitted July 5, 1991.     

The amidoalkylation of aromatic hydrocarbons

The Nyberg procedure (the use of trifluoroacetic acid in chloroform) for the efficient amidoalkylation of aromatic hydrocarbons is limited to substrates more nucleophilic than benzene. The reaction involves protonation of the electrophile, cleavage to a carbonium ion and alkylation of the nucleophile by the carbonium ion. Either the cleavage step or the alkylation step may be rate-determining. The present work identifies some cases where a carbonium ion is formed but fails to alkylate the nucleophile (with benzene and nitro-substituted benzenes as nucleophiles) and other cases where the reaction conditions are not sufficient to permit cleavage of the protonated electrophile (the reactions of N-phthalimidomethylamides).     

Surface ionization of aromatic hydrocarbons

The surface ionization of 14 aromatic hydrocarbons on oxidized tungsten strips was investigated. The principal relationships governing the ionization of aromatic compounds with alkyl substituents were established on the basis of the obtained mass spectra of the ions and the temperature dependence of the ion currents.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 6, pp. 733–738, November–December, 1988.     

Temperature-programmed desorption of aromatic hydrocarbons from ZSM-5 type zeolites

Temperature-programmed desorption of C₆–C₁₂ aromatic hydrocarbons from HZSM-5 and NaZSM-5 in helium stream has been studied. The role of the length, branching and number of alkyl groups was analyzed. It was shown that adsorption of aromatic ring occurs on Na-cations.     

Ultrasonic micellar extraction of polycyclic aromatic hydrocarbons from marine sediments

In this present study the extraction of polycyclic aromatic hydrocarbons (PAHs) from marine sediments with a micellar medium of Polyoxyethylene 10 lauryl ether by an ultrasound-assisted method has been studied. Factorial design experiments were used in order to optimize the extraction parameters: extraction time, surfactant concentration and surfactant volume:amount of sediment relationship. The results suggest that surfactant concentration is statistically the most significant factor. The analysis of extracts has been carried out by HPLC with UV detection. Fortified sediments gave an average recovery between 86.7 and 106.6%, with relative standard deviation of 2.02-6.83% for PAHs with a ring number higher than three.     

Pressurised liquid extraction of polycyclic aromatic hydrocarbons from contaminated soils

The reliability and efficiency of the pressurised liquid extraction technique (PLE) for extracting polycyclic aromatic hydrocarbons (PAHs) from contaminated soil has been investigated. Experimental design was used to study the influence of seven extraction variables (sample load, solvents used, solvent ratios, pressure, temperature, extraction time, and rinse volume). The results show that large sample loads in combination with small solvent volumes may result in low extraction efficiency. They also indicate that the recovery of low-molecular-mass PAHs is reduced by low extraction temperatures. The exact settings of the other variables are, however, less significant for the extraction efficiency. Repeated extractions at optimised settings of the tested variables show that PLE is an exhaustive extraction technique that generally results in high yields. In addition, extraction of a certified reference material (CRM 103-100) revealed that the method is both accurate and precise. Another finding was that adding the internal standard on top of the soil in the extraction cell causes considerable over-estimation of the concentrations when large samples are extracted with small solvent volumes. This is because the PLE-cell resembles a chromatographic column, so compounds added to the top of the soil layer have a longer distance to travel through the soil compared to the average distance of the native compounds, which are distributed evenly throughout the column. We therefore recommend that the internal standard should be added to the extract immediately after the extraction or, alternatively, carefully mixed with the sample prior to extraction.