AlPO4-Ti02 Catalysts IV. The Alkylation of Phenol with Methanol

Campelo, J.M.; García, A.; Luna, Diego; Marinas, J. M.; Moreno, María Ángeles Esteban

doi:10.1016/s0167-2991(09)60821-1

Cited by 16 publications

(2 citation statements)

References 6 publications

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“…By contrast, in the alkylation of activated arenes, such as phenol, diphenols and aniline, with olefins or with alcohols, the selectivity for the para-electrophilic substitution is lower than expected [58]. Indeed, on amorphous acid catalysts, the selectivity to o-cresol can even approach 100% [8,59,60]. The low selectivity to p-cresol in phenol methylation has been attributed to different reasons [61,62] and specifically: i) The alkylation at heteroatom is an intermediate step in C-alkylation by the olefin or by the alcohol [63].…”

Section: Performance Of Beta-2 and Beta-3 Catalysts In Phenol Methylamentioning

confidence: 90%

Methylation of phenol over high-silica beta zeolite: Effect of zeolite acidity and crystal size on catalyst behaviour

Bregolato

Bolis

Busco

et al. 2007

Journal of Catalysis

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A systematic investigation has been carried out, aiming at elucidating several aspects of the gas/solid methylation of phenol over high Si/Al ratio BEA-structured zeolite in protonated form. The catalysts have been characterized by several techniques, such as XRD, SEM, BET, ICP, FT-IR, TGA, micro-calorimetry and modelling by ab initio calculations. The correlation between these characteristics and kinetics and mechanistic features of the catalytic reaction, as well as of catalyst deactivation, showed that these zeolites are very active for the present reaction, leading to cresols and anisole as primary products. As catalyst deactivation proceeds, the selectivity to cresols and anisole increases substantially, together with a rapid decrease of selectivity to poly-alkylated species. Catalyst surface acidity is prevalently made of medium-to-low-strength silanolsbased acid sites of Brønsted type. High-strength Lewis acid sites are either almost absent, especially when metal cations partially substitute for protons, or play a role essentially in catalyst deactivation. Stacking faults in the zeolite framework, generated by the 2 intergrowth of at least two BEA polymorphs, lead to an increase of the concentration of silanols-based acid sites. Deactivation is essentially due to the interaction of phenol and oxygenated products with the strong Lewis acid sites. For time-on stream values longer than a few hours, self oligomerisation-cyclisation of methanol to olefins and aromatics, followed by further alkylation to aromatic C atoms, contributes more significantly to catalyst deactivation. At higher temperature all the zeolites deactivate at a comparable rate, whereas at lower temperature initial catalytic activity is higher for larger crystal size zeolite, due to the longer diffusion time of bulkier coke precursors within zeolite pores. At any conversion level and at any temperature the anisole/cresols ratio is systematically lower for the larger crystal size zeolite, since the secondary transformations of anisole to cresols, by both intra-molecular rearrangement and inter-molecular alkylation of phenol, is favoured by the longer residence time of anisole within the zeolite pores.

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Section: Performance Of Beta-2 and Beta-3 Catalysts In Phenol Methylamentioning

confidence: 90%

Methylation of phenol over high-silica beta zeolite: Effect of zeolite acidity and crystal size on catalyst behaviour

Bregolato

Bolis

Busco

et al. 2007

Journal of Catalysis

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“…The surface of catalysts should possess both basic and acidic (mainly Lewis) properties to secure a high yield of C-methylated phenol derivatives. The catalyst selectivity is attributed to a presence of acidic centres possessing weak and medium strength [17]. For catalysts exhibiting mainly Brönsted acidic sites, especially strong, the selectivity towards C-methylated products decreased with temperature [16].…”

Section: Introductionmentioning

confidence: 98%

Glycothermal Synthesis and Catalytic Properties of Nanosized Zn1−x Co x Al2O4 (x = 0, 0.5, 1.0) Spinels in Phenol Methylation

2011

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Zn 1-x Co x Al 2 O 4 (x = 0, 0.5, 1.0) spinels were synthesised under microwave-assisted solvothermal conditions using 1,4-butanediol as reaction medium. The results of XRD and HRTEM have indicated nanocrystallinity of prepared materials (average crystallite size in the range 6-16 nm), and N 2 adsorption-desorption measurements have revealed high feature of their surface area and mesoporous nature. Acid-base properties of prepared materials were determined using TPD-NH 3 method and cyclohexanol test. All studied spinels that underwent examination were active in phenol methylation but Co-substituted zinc aluminate (Zn 0.5 Co 0.5 Al 2 O 4 ) was found to be the most efficient in the selective formation of orthomethylated products. It could be ascribed to its dominant basic character and the presence of weak and strong acid centres, and the highest surface area as well.

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Heterogeneous catalytic methylation of catechol

Porchet

Su²,

Doepper

et al. 1994

Chem Eng & Technol

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It has been shown that, after a partial deactivation, y-alumina ( y-A1203) is a good catalyst for selective methylation of 1,2-benzenediol in the temperature range of 260 -310 "C. The main products are the desired 3-methyl-I ,2-benzenediol and 2-methoxyphenol, which may be converted in another step into 3-methyl-I ,2-benzenediol, giving an overall selectivity for the desired products of 80 to 90%. The catechol forms a strongly chemisorbed surface species on y-alumina and its steric adsorption model correlates with the kinetic data.

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AlPO4-Ti02 Catalysts IV. The Alkylation of Phenol with Methanol

Cited by 16 publications

References 6 publications

Methylation of phenol over high-silica beta zeolite: Effect of zeolite acidity and crystal size on catalyst behaviour

Methylation of phenol over high-silica beta zeolite: Effect of zeolite acidity and crystal size on catalyst behaviour

Glycothermal Synthesis and Catalytic Properties of Nanosized Zn1−x Co x Al2O4 (x = 0, 0.5, 1.0) Spinels in Phenol Methylation

Heterogeneous catalytic methylation of catechol

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