The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Gabor A. Somorjai - One of the best experts on this subject based on the ideXlab platform.
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the structure of para Xylene and Meta Xylene adsorbed on rh 111 studied by scanning tunneling microscopy
Surface Science, 1998Co-Authors: P D Cernota, H A Yoon, Miquel Salmeron, Gabor A. SomorjaiAbstract:Abstract Scanning tunneling microscopy (STM) was used to study the adsorption of para- and Meta-Xylene on the Rh(111) surface. Para-Xylene appears in the STM images as a diamond-shaped feature with the long axis oriented along the [11 2 ] and equivalent directions. Ordered domains with three orientations differing by 120° are formed. The images of the Meta-isomer have the appearance of triangular shapes and do not form any ordered structure. Individually, however, they are oriented with one side of the triangle parallel to the compact [1 1 0] directions. The internal structure in the molecular images can be discerned. By a combination of symmetry and packing considerations, it is possible to attribute the brightest part of the molecular image as due to the methyl groups. When the two isomers are coadsorbed, they exhibit complete mixing, and the individual components can be differentiated by their shape. At low coverage, both Xylene molecules adsorb preferentially at the step edges, whereas on the terraces, they are mobile in the time scale of the STM imaging. Coadsorption with CO produces a mixed layer, and the Xylene molecules become immobile.
Ahmed K. Aboul-gheit - One of the best experts on this subject based on the ideXlab platform.
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Catalytic para-Xylene maximization: IV. Hydroisomerization of Meta-Xylene on catalysts containing platinum on differently steamed H-ZSM-5
Applied Catalysis A-general, 2001Co-Authors: Ahmed K. Aboul-gheit, S. M. Abdel-hamid, D. S. El-desoukiAbstract:Abstract The hydroconversion of Meta -Xylene was carried out using three series of catalysts containing 0.15, 0.30 or 0.60 wt.% Pt on unmodified and steam-modified H-ZSM-5 zeolite. The first series (Pt/H-ZSM-5 catalysts) contains Pt on the unmodified zeolite, whereas the second series (Pt/StH-ZSM-5) contains Pt on the steamed zeolite. The third series (StPt/H-ZSM-5) contains catalysts of the first series but treated with steam after Pt impregnation. The framework Al (Al F ) and non-framework Al (Al NF ) per unit cell (u.c.) in H-ZSM-5 and StH-ZSM-5 zeolites, as well as the XRD patterns for these zeolites were determined. The total pore volume of the catalysts was determined via thermogravimetry of the fully hydrated samples. The hydroconversion reaction was carried out using the mentioned catalysts in a pulse microreactor, atmospherically operated in a hydrogen flow at temperatures of 275–500 or 525°C. The reaction products were gas-chromatographically analyzed. The catalysts were characterized for acid sites strength distribution using temperature programmed desorption (TPD) of ammonia as well as for Pt dispersion in the support using hydrogen chemisorption and 1:1 stoichiometry. The total hydroconversiton activities of the catalysts, the selectivities for para - and ortho -Xylenes production relative to the corresponding thermodynamic equilibrium values during the whole range of reaction temperature, the level of trimethylbenzenes formation as well as of the hydrodealkylation activities producing methane, benzene and toluene were evaluated and discussed. Correlations of the catalytic activities and selectivities with the characteristics of the catalysts were undergone.
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ISOMERIZATION OF Xylene ISOMERS ON A PTRE-H-MORDENITE CATALYST
Applied Catalysis A: General, 1993Co-Authors: Ahmed K. Aboul-gheit, S. M. Abdel-hamid, Farouk M. Abdel-hayAbstract:Abstract The isomerization of three Xylene isomers was carried out on a catalyst containing 0.35 wt.-% platinum plus 0.35 wt.-% rhenium on hydrogen mordenite in a pulse catalytic microreactor positioned at the inlet of a gas chromatograph. Reactant injections were carried out at temperatures between 300 and 400 °C with hydrogen gas flow at atmospheric pressure. High ratios of para-Xylene in the product Xylene isomer's mixture relative to the corresponding thermodynamic equilibrium values (2.9–3.5) were obtained, whereas the ratios of Meta-Xylene (0.33–0.69 ) were low and those of ortho-Xylene were very low (0.093–0.18). However, relatively high dealkylation products (toluene and benzene) were obtained at higher temperatures. Disproportionation products (trimethylbenzenes) were not detected in the reaction products.
P D Cernota - One of the best experts on this subject based on the ideXlab platform.
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the structure of para Xylene and Meta Xylene adsorbed on rh 111 studied by scanning tunneling microscopy
Surface Science, 1998Co-Authors: P D Cernota, H A Yoon, Miquel Salmeron, Gabor A. SomorjaiAbstract:Abstract Scanning tunneling microscopy (STM) was used to study the adsorption of para- and Meta-Xylene on the Rh(111) surface. Para-Xylene appears in the STM images as a diamond-shaped feature with the long axis oriented along the [11 2 ] and equivalent directions. Ordered domains with three orientations differing by 120° are formed. The images of the Meta-isomer have the appearance of triangular shapes and do not form any ordered structure. Individually, however, they are oriented with one side of the triangle parallel to the compact [1 1 0] directions. The internal structure in the molecular images can be discerned. By a combination of symmetry and packing considerations, it is possible to attribute the brightest part of the molecular image as due to the methyl groups. When the two isomers are coadsorbed, they exhibit complete mixing, and the individual components can be differentiated by their shape. At low coverage, both Xylene molecules adsorb preferentially at the step edges, whereas on the terraces, they are mobile in the time scale of the STM imaging. Coadsorption with CO produces a mixed layer, and the Xylene molecules become immobile.
Velisa Vesovic - One of the best experts on this subject based on the ideXlab platform.
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viscosity measurements of ortho Xylene Meta Xylene para Xylene and ethylbenzene
The Journal of Chemical Thermodynamics, 2016Co-Authors: Xianyang Meng, Xiaoyun Gu, Jiangtao Wu, Velisa VesovicAbstract:Abstract The compressed liquid viscosities of ortho -Xylene, Meta -Xylene, para -Xylene and ethylbenzene were measured using a vibrating-wire viscometer at different temperatures and pressures. The measurements were performed over the temperature ranges of (273 to 373) K for o -Xylene and m -Xylene, (293 to 373) K for p -Xylene and (253 to 373) K for ethylbenzene, at pressures from (0.1 to 30) MPa, except for ethylbenzene for which the pressure range was up to 35 MPa. The combined expanded uncertainty of the reported viscosity is better than 2% with a confidence level of 0.95 ( k = 2). The experimental data were correlated with the empirical Andrade–Tait equation which reproduced the results with the average absolute percentage deviations of (0.25, 0.15, 0.16 and 0.23)% for o -Xylene, m -Xylene, p -Xylene and ethylbenzene, respectively. The present results are in good agreement with most of the literature values.
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Reference Correlation of the Viscosity of Meta-Xylene from 273 to 673 K and up to 200 MPa
Journal of Physical and Chemical Reference Data, 2016Co-Authors: F. L. Cao, X. Y. Meng, Velisa VesovicAbstract:A new correlation for the viscosity of Meta-Xylene is presented. The correlation is based upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory. It is applicable in the temperature range from 273 to 673 K at pressures up to 200 MPa. The overall uncertainty of the proposed correlation, estimated as the combined expanded uncertainty with a coverage factor of 2, varies from 1% for the viscosity at atmospheric pressure to 5% for the highest temperatures and pressures of interest. Tables of the viscosity, generated by the relevant equations, at selected temperatures and pressures, and along the saturation line, are provided.
D. S. El-desouki - One of the best experts on this subject based on the ideXlab platform.
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Catalytic para-Xylene maximization: IV. Hydroisomerization of Meta-Xylene on catalysts containing platinum on differently steamed H-ZSM-5
Applied Catalysis A-general, 2001Co-Authors: Ahmed K. Aboul-gheit, S. M. Abdel-hamid, D. S. El-desoukiAbstract:Abstract The hydroconversion of Meta -Xylene was carried out using three series of catalysts containing 0.15, 0.30 or 0.60 wt.% Pt on unmodified and steam-modified H-ZSM-5 zeolite. The first series (Pt/H-ZSM-5 catalysts) contains Pt on the unmodified zeolite, whereas the second series (Pt/StH-ZSM-5) contains Pt on the steamed zeolite. The third series (StPt/H-ZSM-5) contains catalysts of the first series but treated with steam after Pt impregnation. The framework Al (Al F ) and non-framework Al (Al NF ) per unit cell (u.c.) in H-ZSM-5 and StH-ZSM-5 zeolites, as well as the XRD patterns for these zeolites were determined. The total pore volume of the catalysts was determined via thermogravimetry of the fully hydrated samples. The hydroconversion reaction was carried out using the mentioned catalysts in a pulse microreactor, atmospherically operated in a hydrogen flow at temperatures of 275–500 or 525°C. The reaction products were gas-chromatographically analyzed. The catalysts were characterized for acid sites strength distribution using temperature programmed desorption (TPD) of ammonia as well as for Pt dispersion in the support using hydrogen chemisorption and 1:1 stoichiometry. The total hydroconversiton activities of the catalysts, the selectivities for para - and ortho -Xylenes production relative to the corresponding thermodynamic equilibrium values during the whole range of reaction temperature, the level of trimethylbenzenes formation as well as of the hydrodealkylation activities producing methane, benzene and toluene were evaluated and discussed. Correlations of the catalytic activities and selectivities with the characteristics of the catalysts were undergone.