Hydroisomerization of normal pentane over a zeolite catalyst

Voorhies, Alexis; Bryant, Philip A.

doi:10.1002/aic.690140607

Cited by 25 publications

(8 citation statements)

References 18 publications

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“…At 0 mol % benzene, the experimental results obtained (Table III) indicate a range of 3.97-4.05 which is reasonably close to the equilibrium values, allowing for experimental errors and predictive errors in the equilibrium calculations. The result implies that branching from 2MP to 2,3DMB is rapid in Pt/mordenite, an observation in accordance with the results obtained by other researchers (Voorhies and Bryant, 1968; Nagy et al, 1984). Benzene addition to the feed increases the 2MP/2.3DMB ratio at higher benzene concentrations.…”

Section: Resultssupporting

confidence: 91%

Competitive reaction in intrazeolitic media

Chen¹,

Martin²,

Kim³

et al. 1988

Ind. Eng. Chem. Res.

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The effects of an aromatics cofeed on paraffin hydroisomerization and hydrocracking over Pt/ mordenite are studied as an example of competitive reaction in intrazeolitic medium. Preferential adsorption by the aromatic (benzene) modifies catalytic site distributions available for the paraffin (n-hexane) reaction and also affects diffusional characteristics in the one-dimensional channel structure of the zeolite. A significant inhibition of the hexane reaction is observed. The hexane isomer distribution in the presence of the aromatic is rationalized using concepts of coreactant induced size and shape selectivity modifications.

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Section: Resultssupporting

confidence: 91%

Competitive reaction in intrazeolitic media

Chen¹,

Martin²,

Kim³

et al. 1988

Ind. Eng. Chem. Res.

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“…Significant progress in paraffin isomerization capability was achieved in the 1960's. This progress resulted from the employment of a crystalline zeolite base in the dual-function type catalyst which classically was defined as a dispersed metal on a high-surface-area amorphous base (Rabo et al, 1961;Voorhies and Beecher, 1969;Voorhies and Bryant, 1968; and dual-function type catalysts have generally been used for aromatic isomerization.…”

Section: Conclusion and Significancementioning

confidence: 99%

Kinetics of liquid phase xylene isomerization over H‐mordenite

Hopper¹,

Shigemura²

1973

AIChE Journal

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A study of the kinetics for the liquid phase isomerization of ortho-xylene over H-mordenite has been made at 505OK, 2.76 X lo5 N/m2, and 23 mole *% toluene diluent. This is the first known study reporting kinetic data for the liquid phase isomerization of xylene over a zeolite catalyst. High activity is indicated by the SOTo achievement of para-xylene equilibrium at 505OK, 2.76 X 105 N/m2, and 0.767 X kg/s/kg. Although high selectivity has previously been reported for a specifically prepared zeolite catalyst, the 99+ Yo selectivity of the isomerization reaction with H-mordenite as indicated by no Cg+ aromatics and less than 0.5 mole yo benzene in the product is most significant. Catalyst deactivation was also significant. Reaction rate constants are reported for a first-order reversible triangular model among the xylene isomers with catalyst deactivation incorporated into the model. J. R. HOPPER SCOPEOrtho and para-xylene are important chemical intermediates. New catalysts which offer high activity and selectivity can alter the optimum economic decision for their production. The objective of this study was to establish a kinetic model for xylene isomerization over a zeolite catalyst-H-mordenite. The study was performed under conditions of liquid phase, toluene diluent, and relatively lower temperature (505OK) for which kinetic data have not been previously reported but for which high activity and selectivity were recently demonstrated with an undisclosed zeolite catalyst (Grandio et al., 1971). H-mordenite is known to have high initial activity for this reaction (Hansford and Ward, 1968), but the selectivity is not reported. Catalyst deactivation, if it existed, was to be incorporated into the model. The results of this study can provide further insight into the catalytic properties of Hmordenite and quantitative kinetic information on the magnitude of the activity, selectivity, and catalyst deactivation which are of major value in process optimization and control evaluations. CONCLUSIONS AND SIGNIFICANCEThe isomerization of ortho-xylene over H-mordenite was investigated at 505OK, 2.76 X 105 N/m2 and about 23 mole '% toluene diluent. The most significant observation was the 99+ yo selectivity to the isomerization reaction and no formation of Cg+ aromatics. The activity was very good with an 807' achievement of para-xylene equilibrium at a space velocity of 0.767 X 10-3 kg/s/kg. Catalyst deactivation was significant. The reaction was modeled by the first-order reversible interconversion triangular reaction scheme among the isomers. The catalyst deactivation was correlated by an exponential decay function of the feed/ catalyst ratio. The model in compact notation is expressed as l 6 r . -2 BOk e-ak(e17) R~~ The reaction model constants given in Table 4 show the conversion of ortho to para-xylene occurs primarily by the series of 1, 2 methyl shifts first to meta-xylene and then to para-xylene.Hydrocarbon isomerization reactions have received considerable attention in the past two decades. Significant progress in p...

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“…The effect of temperature on the overall isomerization rate of n-pentane was evaluated by use of a previous!)' developed expression for this reaction (Voorhies and Bryant, 1968). The results are illustrated in Arrheniustype plots in Figure 3 for each catalyst.…”

Section: Methodsmentioning

confidence: 99%

Hydroisomerization of Cyclohexane and n-Pentane over Series of Mordenite Catalysts of Varying Silica-Alumina Ratio

Hopper¹,

Voorhies²

1972

Product R&D

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Four palladium-hydrogen mordenite catalysts of varying silica-alumina mole ratio were evaluated in the hydroisomerization reactions of cyclohexane and n-pentane. A kinetic model was developed for the cyclohexane reaction over these catalysts. One batch of sodium mordenite was used as the source from which each of the catalysts was prepared. The standard or parent mordenite preparation was caustic-leached to remove silica, producing a catalyst with a lower silica-alumina ratio than the standard mordenite, and two other catalysts with higher silica-alumina ratio than the standard mordenite were made by acid-extracting alumina from the standard mordenite preparation. Each of the catalysts contains about 1/2 wt % palladium. Isomerization rates were temperature sensitive for all of the catalysts, and energies of activation were presented for both the cyclohexane and n-pentane reactions. The effect of the partial pressure of the hydrocarbons and hydrogen was represented by a dual-site adsorption model. Isomerization activity was observed to initially increase with an increase in silica-alumina ratio and then decrease with additional increase in the ratio. It is felt that the reduction in surface area and active acid sites at the higher alumina extraction is primarily responsible for the loss in activity at the higher silica-alumina ratio. A general relationship for both reactions is not apparent.AAolecular sieve zeolites have in the past decade been demonstrated to be outstanding catalysts for isomerization reactions (Voorhies and Bryant, 1968; Beecher and Voorhies, 1969;Rabo et al., 1961). Mordenites particularly are active isomerization catalysts (Voorhies and Bryant, 1968; Beecher and Voorhies, 1969;Benesi, 1965). Thus, these catalytic qualities have prompted a number of kinetic studies by use of zeolites for isomerization reactions. Voorhies and Bryant (1968) have reported on the isomerization of -pentane, and Beecher and Voorhies (1969) on the isomerization of hexanes.Modifications of the SÍO2/AI2O3 ratio in the mordenite are also particularly interesting because of the changes in catalytic activity which have resulted. Beecher et al. (1968) have investigated activity changes for decalin and decane hydrocracking fora change in SÍO2/AI2O3 from 12 to 66. The cracking activity was greater at the higher ratio. Weller and Brauer (1969), however, observed that n-hexane cracking activity went through a maximum as the SÍO2/AI2O3 ratio was increased over a much narrower range. Eberly and Kimberlin (1970) reported that cumene cracking activity increased with SÍO2/AI2O3 ratio.However, Kranich et al. (1970) and Bierenbaum et al. (1971) observed from differential conversions a loss of cracking activity for cumene at high SÍO2/AI2O3 ratios. et al. (1971) reported on the effect of S1O2/AI2O3 ratio on acidic properties of mordenite and isomerization activity for -pentane; Kranich et al. (1970) investigated activity changes with SÍO2/AI2O3 ratios for butene isomerization; and Piguzova et al. (1969) on the change in isomeriza...

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Hydroisomerization of normal pentane over a zeolite catalyst

Cited by 25 publications

References 18 publications

Competitive reaction in intrazeolitic media

Competitive reaction in intrazeolitic media

Kinetics of liquid phase xylene isomerization over H‐mordenite

Hydroisomerization of Cyclohexane and n-Pentane over Series of Mordenite Catalysts of Varying Silica-Alumina Ratio

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