Kinetics of the Liquid-Phase Hydrogenation of Benzene and Some Monosubstituted Alkylbenzenes over a Nickel Catalyst

Abstract

The liquid-phase hydrogenation kinetics of benzene and three monosubstituted alkylbenzenes, toluene, ethylbenzene, and cumene, was determined in a semibatch reactor operating at hydrogen pressures of 20−40 atm and at temperatures of 95−125 °C. Commercial preactivated catalyst particles of nickel−alumina were used in all experiments. The hydrogenation activity of the compounds decreased in the order benzene ≫ toluene > ethylbenzene > cumene. The main reaction product was always the completely hydrogenated cycloalkane, whereas only trace amounts of cycloalkenes were detected. The hydrogenation rates had a slow initial period followed by a period of a virtually constant rate, which decreased at the end of the reaction. The analysis of the data with a reaction−diffusion model revealed that the kinetics was influenced by pore diffusion. Rate equations based on a sequential addition mechanism of adsorbed hydrogen to the aromatic nucleus were derived, and the kinetic parameters were estimated from the reaction−diffusion model with nonlinear regression analysis. The rate equations were able to describe all the features of the experimental data.

Comparison of sorbents and isotherm models for NH3‐gas separation by adsorption

“…Therefore, the estimated parameters of all isotherm models Ž were evaluated by established statistical methods Froment and Bischoff, 1990; see also Ronnback et al, 1994;Lehtonen . et al, 1995;Toppinen et al, 1996Toppinen et al, , 1997 . The accuracy of fit was evaluated on the basis of several standard statistical val-Ž 2 .…”

Dynamic non-isothermal trickle bed reactor with both internal diffusion and heat conduction: Sugar hydrogenation as a case study

“…These kind of flux terms have been earlier used for semi-batch cases (Toppinen et al, 1996a(Toppinen et al, , 1996b.…”

Calculation of binodal lines for a multicomponent mixture by the homotopy method

“…If |dH/dT| in set (15) is smaller than ε sng ≈ 10 -5 -10 -4 , then, instead of set (15), a similar set of equations is solved, which is obtained from set (15) by replacing the lower row of the matrix by the vector [1,0]. The subscripts 0 at T k + 1 and P k + 1 in formulas (14) mean that these values lie not on the binodal line but in its close vicinity, and at each ((k + 1)th) predictor step, they serve as initial approximations for Newton's method.…”

“…Many chemical engineering processes, such as hydrogenation [1], oxidation [2], liquid-phase FischerTropsch synthesis [3,4], and liquid-phase methanol synthesis [5], are performed under conditions under which the reaction medium consists of two phases, a gas phase and a liquid phase, and has high pressure and temperature. Under these conditions, the properties of the reaction medium may deviate significantly from the properties of an ideal gas or an ideal liquid.…”