Paolo Beltrame

Alkylation of phenol with methanol over zeolites

Abstract The reaction of phenol with methanol was carried out over five X-, six Y- and three ZSM-zeolites, in a fixed-bed continuous reactor at 250°C. Alkylation products were cresols (o>p>m), anisole, xylenols and methylanisoles. The highest conversion and the highest yields of o- and p-cresols were obtained within the initial 5 h on-stream. Selectivity to o,p-cresols in the range 40-50% at phenol conversion 40-50% was reached on some X- and Y-zeolites, the best catalyst being HY.

Alkylation of phenol with anisole over zeolites or γ-alumina

Abstract The reaction of phenol with anisole was carried out over three X-, six Y-, a ZSM-5 and a ZSM-11 zeolites, and over γ-Al 2 O 3 , in a fixed-bed continuous reactor. Alkylation products were cresols (o>p>m), xylenols and methylanisoles; also some dealkylation of anisole to phenol occurred. Selectivity to cresols and xylenols in the range 45–60% and 25–30%, respectively, at anisole conversions of around 90%, were reached with HY and HNaY zeolites, and with γ-Al 2 O 3 , when operating over fresh catalysts. Alkylations were particularly ortho-selective over γ-Al 2 O 3 .

Inhibiting action of chloro- and nitro-phenols on biodegradation of phenol: A structure-toxicity relationship

Abstract All chlorophenols and six mono- and di-nitrophenols were tested, by discontinuous kinetic measurements, as inhibitors of the phenol degradation by activated sludge. The measured values of pI50 were correlated with structural properties (logP, ϵσ) of the substituted phenols, developing a QSAR.

Kinetics of biodegradation of mixtures containing 2,4-dichlorophenol in a continuous stirred reactor

A solution containing 2,4-dichlorophenol (DCP) and phenol (or glucose), in the ratio 1:1 in terms of carbon, was fed to a completely mixed continuous flow reactor with recycle and controlled wasting of the activated sludge, operated at steady-state conditions at 20°C. A carefully adapted sludge was able to degrade DCP, besides the accompanying substrate, with no evidence of substrate inhibition in the concentration range covered (156 mg l−1 in the influent). The reactivity order was found to be glucose ⪢ phenol > DCP. The results of a series of kinetic runs with phenol + DCP were interpreted by a first-order equation for phenol and by the Monod model for DCP.

Kinetics of the hydrogen transfer reaction of cyclohexene on palladium powder

Abstract The disproportionation of cyclohexene to cyclohexane and benzene has been kinetically followed in tetrahydrofuran solution on palladium powder at 50 ° to 60 °C. The behavior of 1,3-cyclohexadiene under the same conditions has been studied too. Gas chromatography was used for the analytical determinations. The diene is noticeably more reactive than cyclohexene, and has been detected in low concentration in the reaction products from the latter. It is suggested that it is an intermediate of the reaction. Experimental results of the kinetics of cyclohexene are well accounted for by a second order rate law that takes into account the adsorption of cyclohexene and benzene on the catalyst. The adsorption coefficients for benzene are ca. five times larger than those of cyclohexene. Adsorption heats are 5.2 and 9.3 kcal/mole, respectively, for cyclohexene and benzene from the solution. The activation energy of the reaction is 14 kcal/mole. Details are given of the application of the steepest descent method for the leastsquares fitting of the kinetic equation to experimental data.

Kinetic studies for processes of liquid-phase alkylation of aromatics over solid acid catalysts

The liquid-phase alkylation of aromatics has been effected traditionally with catalysis by inorganic acids or AlCl3 and similar compounds. However the increasing importance of solid acid catalysts is changing the procedures in this field. One of the prerequisites for the development of relevant processes, and the design of reactors, is knowledge of the kinetic data in reactions catalyzed by solid acids. This review examines the information available on the kinetics of alkylations catalyzed by solid acids, mainly zeolites, supported metal chlorides and oxides, mesoporous (MCM) materials, and heteropolyacids, but also other less studied materials.

Toluene disproportionation catalysed by various zeolites

Abstract Toluene disproportionation in the gas/solid phase was performed in a flow reactor (carrier H 2 or N 2 ) over some partially exchanged X and Y zeolites and, more systematically, over decationated Y, ZSM-5 and ZSM-11 zeolites. Activity, selectivity and stability of the catalysts were tested at temperatures up to 500°C, but mostly in the range 350°–400°C. Two samples HZSM-5 showed a considerably different catalytic behaviour: with one of them, shape-selectivity effects, favouring p -xylene, were observed during progressive deactivation (carrier N 2 ); the other one, of higher and stable activity, gave xylenes in the equilibrium isomeric ratios. Using the latter zeolite, kinetic measurements were carried out in a differential reactor at 240°–300°C (carrier H 2 ). A few kinetic models were tested.

The reaction of naphthalene with benzyl alcohol over a Nafion-silica composite: a kinetic study

A Nafion-silica composite was employed as catalyst for the reaction, in a slurry batch reactor at 80 °C, of naphthalene (NA) with benzyl alcohol in cyclohexane. The products, the benzylnaphthalenes (M) and several dibenzyl derivatives (D), included dibenzyl ether that was itself shown to be a weak benzylating agent. However, dibenzyl ether has also been shown to be a critical factor in catalyst stability. The kinetics of both the reaction of benzyl alcohol to give dibenzyl ether, and the benzylation of naphthalene by benzyl alcohol or mixtures of alcohol and ether, were studied, and the measurements interpreted by kinetic models.

Influence of feed concentration on the kinetics of biodegradation of phenol in a continuous stirred reactor

Abstract The rate of phenol degradation by activated sludge was studied in a completely mixed continuous-flow reactor with sludge recycle, operated at steady-state conditions at 20°C. Monod kinetics was followed when the influent concentration ( C s °) was kept constant. When using different C s ° levels, the phenol removal rate was found to have an inverse dependence on C s °. It is suggested that this kinetic anomaly is due to inhibition of the biooxidation by some secondary reaction product(s). A kinetic model based on this concept is able to interpret experimental facts.

Kinetics of phenol degradation by activated sludge: Value of measurements in a batch reactor

Abstract Kinetic measurements on the degradation of phenol in a batch reactor were done at 20°C using an activated sludge taken from a continuous reactor where the process had shown Monod-type kinetics without substrate inhibition. When employing a sludge sample, adapted to the substrate steady concentration C s 1 , for runs with initial substrate concentration C s 0 , observed batch rates were as high as expected for C s 0 = C s 1 , but lower than expected in runs carried out at C s 0 > C s 1 1 , with indications of a transient inhibitory effect instead of a positive response to the increased substrate concentration. It is concluded that kinetic data collected in a batch reactor are of limited value for the design of a continuous biodegradation process.