Cleaning Effects of the Reactant in the Liquid-phase Isomerization of <i>m</i>-Xylene over a Silica-Alumina Catalyst under Pressure

Takaya, Haruo; Todo, Naoyuki; Hosoya, Tadasuke; Minegishi, Toshio; Yoneoka, Mikio; Oshio, Hideki

doi:10.1246/bcsj.44.2296

Cited by 8 publications

(4 citation statements)

References 3 publications

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“…Takaya et al have shown that catalyst deactivation can be avoided by carrying out the reaction in the liquid phase. 37 Thus, the activity of an ASA sample was found to be stable for prolonged reaction time. The increased stability was explained by the solvation of diphenylmethanes by liquid m-xylene.…”

Section: Resultsmentioning

confidence: 95%

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Acidity Characterization of Amorphous Silica–Alumina

Hensen

Poduval

Degirmenci³

et al. 2012

J. Phys. Chem. C

147

165

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Surface characterization of amorphous silica− alumina (ASA) by CO ads IR, pyridine ads IR, alkylamine temperature-programmed desorption (TPD), Cs + and Cu-(EDA) 2 2+ exchange, 1 H NMR, and m-xylene isomerization points to the presence of a broad range of Brønsted and Lewis acid sites. Careful interpretation of IR spectra of adsorbed CO or pyridine confirms the presence of a few very strong Brønsted acid sites (BAS), typically at concentrations lower than 10 μmol/g. The general procedure for alkylamine TPD, which probes both Brønsted and Lewis acidity, is modified to increase the selectivity to strong Brønsted acid sites. Poisoning of the m-xylene isomerization reaction by a base is presented as a novel method to quantify strong BAS. The surface also contains a weaker form of BAS, in concentrations between 50 and 150 μmol/g, which can be quantified by CO ads IR. Cu(EDA) 2 2+ exchange also probes these sites. The structure of these sites remains unclear, but they might arise from the interaction of silanol groups with strong Lewis acid Al 3+ sites. The surface also contains nonacidic aluminol and silanol sites (200−400 μmol/g) and two forms of Lewis acid sites: (i) a weaker form associated with segregated alumina domains containing five-coordinated Al, which make up the interface between these domains and the ASA phase and (ii) a stronger form, which are undercoordinated Al sites grafted onto the silica surface. The acid catalytic activity in bifunctional nheptane hydroconversion correlates with the concentration of strong BAS. The influence of the support electronegativity on the neopentane hydrogenolysis activity of supported Pt catalysts is considerably larger than that of the support Brønsted acidity. It is argued that strong Lewis acid sites, which are present in ASA but not in γ-alumina, are essential to transmit the Sanderson electronegativity of the oxide support to the active Pt phase.

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Section: Resultsmentioning

confidence: 95%

“…Further condensation of the heavy intermediates causes coke to deposit, which leads to irreversible deactivation. Takaya et al have shown that catalyst deactivation can be avoided by carrying out the reaction in the liquid phase . Thus, the activity of an ASA sample was found to be stable for prolonged reaction time.…”

Section: Resultsmentioning

confidence: 99%

Acidity Characterization of Amorphous Silica–Alumina

Hensen

Poduval

Degirmenci³

et al. 2012

J. Phys. Chem. C

147

165

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“…Catalyst coking in xylenes isomerization has been studied in detail by Takaya et al (1971Takaya et al ( , 1972a, who observed an abundance of trimethyl and tetramethyl diphenylmethanes in the coking products. If we assume that two adjacent adsorbed xylene molecules are involved in the formation of a coke precursor P, ultimately leading to coke lay-down according to the scheme AX + AX --P + Xcoke + X slow then a balance on active sites leads to the relation…”

Section: Product Distribution and Reaction Networkmentioning

confidence: 99%

Model building in complex catalytic reaction systems. A case study: p-xylene manufacture

Orr¹,

Cresswell²,

Edwards³

1983

Ind. Eng. Chem. Proc. Des. Dev.

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Ind. Eng. Chem. process Des. Dev, lg83, 22, 135-143 135 liquid-liquid dispersion. Since equal power per unit mass results in equal drop size, this implies that a bigger impeller can be employed to produce the same final drop size faster using the same amount of energy. Conclusion 1. Unsteady-state drop size, ita distribution, and the minimum transition time required to reach steady state during the initial period of liquid-liquid dispersion have been measured by using a microphotographic technique and a light transmittance method.2. The average drop size was found to follow the exponential decay rule.3. The drop size distribution changes from a very wide (multi-modal) distribution to a narrower (normal) distribution to, finally, a very narrow (skewed or log-normal) distribution as drop size becomes smaller and smaller.4. The minimum time required to reach a steady state is very strongly dependent on impeller size and speed and on tank size. At the same power input per unit mass, a larger impeller is more efficient. Nomenclature a = interfacial area per unit volume, m-l DI = impeller diameter, m DT = tank diameter, m d = particle or droplet diameter, m ds2 = Sauter mean droplet diameter defined by eq 2, m dS2* = Sauter mean droplet diameter at steady state, m I = emergent light intensity Io = incident light intensity ml, m2 = constants used in eq 1 n = number of drops N = impeller stirring speed, rpm T = fractional light transmittance = I/&,, dimensionless AT = fluctuation in T readings, dimensionless t = time, min t, = minimum transition time required to reach steady-stateGreek Letters a, 6 = constants used in eq 4 y = constant defined in eq 5 t = rate of energy dissipation per unit mass of fluid, W/kg p = viscosity, N.s/m2 p = density, kg/m3 9 = Kolmogoroffs length scale, m u = standard deviation based on dS2, m ' $d = volume fraction of dispersed phase, dimensionless Literature Cited Coulakglou, C. A.; Tavlarides, L. L. AIChE J . 1976, 22, 289. Lee, J. M. Ph.D. Dlssertatlon, University of Kentucky, Lextngtm, KY, 1978. McCoy, B. J.; Madden, A. J. Chem. Eng. Sci. 1969, 24, 416. Narslmhan, G.; Ramkrishna, D.; Gupta, J. P. A I C M J . 1980. 2 6 , 991. Roger. W. A.; Trlce. V. G., Jr.; Rushton, J. H. Chem. Eng. Prog. 1956, 52, Ross, S. L.; V e h f f , F. H.; Curl, R. L. Ind. Eng. Chem. Fundam. 1878, 77, Ramkrishna, D. Chem. Eng. Scl. 1974, 2 9 , 987. Skelland. A. H. P.; Lee, J. M. Ind. Eng. Chem. Process Des. Dev. 1978, Skelland, A. H. P.; Lee, J. M. AIChE J . 1981, 27, 99. Sprow. F. B. A I C M J . 1967, 73, 995. Vermeulen, T.; Williams, G. M.; Langlols, 0. E. Chem. Eng. Prog. 1955, 57, drop size, min 515. 101. 77, 473. 85-F.A strategy of model building In complex catalytic reaction systems is described based on the deployment of different types of laboratory reactors and independent measurement of pore diffusion within a single-pellet diffusion cell. The approach is applied to the kinetic modeling of simultaneous isomerlzation and disproportionation of a mixture of xylenes over a commercial silica-alumina catalys...

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“…20 Additionally, the liquid phase conditions allowed continuous removal of products from the catalyst bed, thus reducing carbonaceous deposits. 21 While zeolite HY was also applicable for the aromatization of larger alkyl methyl ketones, such as 2-butanone and 2-pentanone, its overall activity was still lacking regarding a potential process development for future integration into a biorefinery. 19 In the course of the catalyst development, combining high activity with long-term operational stability remains an ongoing problem that we sought to solve by using large pore amorphous aluminosilicates as acid catalysts.…”

Section: Introductionmentioning

confidence: 99%