Hexane Isomerization over a Zeolite Catalyst

Beecher, Richard; Voorhies, Alexis

doi:10.1021/i360032a006

Cited by 31 publications

(13 citation statements)

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“…Gas and liquid products were analysed by gas chromatography. Hydrocracking products were lumped in the following cuts: C 1-4 (gas); C 5-9 (naphtha); C 10-14 (kerosene); C [15][16][17][18][19][20][21][22] (gasoil) and C 22+ (atmospheric residue). The effect of operating conditions temperature, pressure, H 2 /wax ratio and weight hourly space velocity (WHSV) was investigated by a second order factorial design, the so called central composite design (CCD) [13].…”

Section: Methodsmentioning

confidence: 99%

“…Results and discussion As shown in Fig. 2 the yields of the middle distillate (C [10][11][12][13][14][15][16][17][18][19][20][21][22] ) increases up to 80-90% of C 22+ conversion and thereafter decreases owing to greater presence of consecutive hydrocracking reactions which lead to lower molecular weight compounds such as C 5-9 fraction and gasses. The latter are almost exclusively made up of butane, isobutane and propane).…”

Section: Methodsmentioning

confidence: 99%

“…4 and 5 show graphically the effect of pressure and H 2 /wax ration on conversion of C 22+ fraction. Although the skeletal rearrangement and hydrocracking of n-paraffins occur without and with consumption of hydrogen, respectively, it is well known that rate constant for hydroisomerization/hydrocracking of n-paraffins is inversely proportional to the hydrogen pressure and the apparent reaction order with respect to hydrogen reported in literature are generally À1 [14] or slightly higher (À0.85) [15]. The negative dependence of C 22+ conversion on hydrogen pressure can be explained in terms of bifunctional mechanism where the first step is the formation of olefins at the metal site, subsequently formation of secondary carbenium at the acidic site and then the various steps leading to the final products [14,16].…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, the increase of C 22+ fraction concentration in the liquid phase at higher H 2 /wax ratios further enhances the phenomenon. MLR considering as system response the isomer content of C 10-14 and C [15][16][17][18][19][20][21][22] fractions showed that the significant factors in this case were the temperature, pressure and WHSV. The models obtained explained more than 98% of the variance of the experimental data and F values indicated a high degree meaningfulness.…”

Section: Methodsmentioning

confidence: 99%

“…The data in Tables 5 and 6 show that in both cases (i.e. C 10-14 and C [15][16][17][18][19][20][21][22] ) the temperature has a positive coefficient and plays the major effect. Differently, pressure and WHSV have an opposite effect that is higher value of these two factors lead to products with a lower isomer concentration.…”

Section: Methodsmentioning

confidence: 99%

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Hydroconversion of Fischer–Tropsch waxes: Assessment of the operating conditions effect by factorial design experiments

et al. 2005

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Hydroconversion of Fischer–Tropsch waxes: Assessment of the operating conditions effect by factorial design experiments

et al. 2005

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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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Sorption and diffusivity characteristics of acid‐leached mordenites

Satterfield

Chiu

1974

AIChE Journal

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The apparent diffusivity for the binary liquid systems benzene-cumene and cyclohexane-cumene in H-mordenite crystals at 25OC to 44OC was increased by an order of magnitude or more after the zeolite was acid-leached to increase the silica-alumina mole ratio from the range of 14 to 18 to the range of 70 to 89. The calculated diffusivities, which range from to 10-'6 cmZ/s, decrease with approach to sorption equilibrium and may be markedly reduced under some circumstances by adsorption of molecules from the bulk liquid, causing blockage of pores.Comparison of sorption capacities as a function of silica-alumina ratio as reported by various investigators indicates that considerable differences exist in the properties of acid-leached mordenites of the same silica-alumina ratio but of different origins. SCOPEH-mordenite and acid-leached mordenites have remarkable catalytic activities for acid-catalyzed reactions, but the rate and selectivity of these reactions can be profoundly affected by the rate of counterdiffusion of product and reactant molecules inside the fine pore structure of these zeolites. Acid leaching removes alumina from the silica-alumina matrix and opens up the pores of mordenites, thereby increasing the rate of diffusion. However, leaching also reduces the concenbation of acid sites, thereby presumably decreasing the intrinsic reactivity of the catalyst. The two effects act in opposite directions on the apparent reactivity of the mordenite under diffusionlimiting conditions. A principle objective of this work was to determine quantitatively the effect of acid leaching on diffusivity in mordenites. Diffusion measurements were made by observing the rate of disappearance of a hydrocarbon species A by adsorption from a dilute solution of A in B into mordenite crystals previously saturated with B-termed here adsorption measurements; or by observing the rate of appearance of B from saturated mordenite into bulk liquid consisting initially of pure A-termed here desorption measurements.Sorption capacities for benzene or cumene vapors were also determined as a function of silica-alumina ratio and compared to previous reports on sorption of these and other hydrocarbons. Sorption capacities are of interest in themselves in connection with adsorption processes, and they also provide some insight into the nature of the fine pore structure.

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Hexane Isomerization over a Zeolite Catalyst

Cited by 31 publications

References 6 publications

Hydroconversion of Fischer–Tropsch waxes: Assessment of the operating conditions effect by factorial design experiments

Hydroconversion of Fischer–Tropsch waxes: Assessment of the operating conditions effect by factorial design experiments

Kinetics of liquid phase xylene isomerization over H‐mordenite

Sorption and diffusivity characteristics of acid‐leached mordenites

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