Kinetics Of Catalytic Hydrogenation Research Articles

Изучение кинетических особенностей синтеза анилина на Ni-содержащем сверхсшитом полистироле

This paper presents a study of the kinetics of catalytic hydrogenation of nitrobenzene to aniline in the presence of Ni-containing catalysts based on super-crosslinked polystyrene. Aniline hydrogenation is a complex multi-stage process accompanied by the formation of a large number of both intermediate and by-products, including azobenzene, azoxybenzene, nitrosobenzene, phenylhydroxylamine and other substances. Therefor the study of the process kinetics is an important scientific and technical task necessary to increase the yield of the target product — aniline. The hydrogenation reaction of nitrobenzene was carried out in a six-cell high-pressure reactor Parr instruments, Series 5000. The products were analyzed by chromatography using a gas chromatograph Kristallux-4000M (Russia, Meta–Chrom). The effect of temperature, pressure, and concentration of the catalyst was studied; optimal reaction conditions were selected that ensure the maximum yield of aniline. Investigation of the effect of the nitrobenzene initial concentration on the rate of its transformation shows that increase of catalyst to nitrobenzene ratio from 0.2 to 0.6 kg (Cat)/kg (NB) leads to a linear increase in the rate of transformation of nitrobenzene from 0.0002 kg (NB) / (kg (Cat)*s ) to 0.0028 kg(NB)/(kg(Cat)*s), a further increase in the ratio of catalyst concentration to nitrobenzene concentration to 1.2 kg (Cat)/kg(NB) leads to stabilization of the nitrobenzene transformation rate at the level of 0.003 kg(NB)/(kg(Cat)*s). An increase in the temperature of the reaction from 90 to 160 °C contributes to a significant increase in the nitrobenzene transformation rate. The constructed dependences made it possible to calculate the apparent activation energy of the process, which amounted to be 50.4 kJ/mol and the preexponential factor, which amounted to be 15821.1 1/s. The applicability of the Langmuir–Henschelwood model to describe the basic kinetic laws of the reaction of catalytic nitrobenzene hydrogenation with the formation of aniline is studied. Numerical methods in the Matlab software allows to determine the values of preexponential factors and activation energies of the nitrobenzene hydrogenation processes, adsorption of nitrobenzene and adsorption of hydrogen, which made it possible to establish the optimal area of nitrobenzene hydrogenation process of hydrogenation of Pн2 = 15–18 atm, C(NB) = 1.2 kg(NB)/kg(Cat), t =115–120 °C providing maximum speed.

On the kinetics of catalytic hydrogenation over Pd nanoparticles regulated by various nucleosides

Aqueous-phase hydrogenation of 4-nitrophenol (4-NIP) by H2 has been investigated in the presence of Pd nanoparticles (NPs) regulated by small biological molecules. Nucleosides and their derivatives were employed as capping agents of Pd NPs, and their effect on Pd activity was evaluated. All four kinds of nucleosides exhibited obvious promoting effect on the activity of Pd NPs in comparison to that without any capping agent. The general promoting effect sequence of nucleosides and their derivatives on the activity of Pd NPs was nucleoside ≥ nucleotide > deoxynucleoside > base > deoxynucleotide. The quantitative correlation between the activity promoting effect and the structure of nucleosides and their derivatives were also studied using the method based on poly-parameter linear free energy relationships. Moreover, the kinetic behaviors of 4-NIP hydrogenation over Pd NPs regulated by different nucleosides (adenosine, guanosine, cytidine, and β-thymidine) were studied systematically and different kinetic models were developed to fit the data. The obtained kinetic data fitted well to the Langmuir-Hinshelwood (L-H) model, where the surface reaction is the rate-controlling step. The apparent activation energy, adsorption enthalpy of 4-NIP, and dissociated adsorption enthalpy of hydrogen were calculated and compared for a better understanding of the mechanism. Pd NPs regulated by cytidine showed the lowest apparent activation energy of 43.66 kJ mol−1.

Кинетика каталитического гидрирования 4-нитро-N-[2-(диэтиламино)этил]бензамида

Кинетика каталитического гидрирования 4-нитро-N-[2-(диэтиламино)этил]бензамида

Studies of Reaction Kinetics of Catalytic Hydrogenation of Isophthalonitrile for Meta-Xylenediamine Preparation

With Raney nickel catalyst and aniline solvent, the reaction kinetics of catalytic hydrogenation of isophthalonitrile (IPN) for meta-xylenediamine (MXDA) preparation is studied in this paper. The experiment is conducted in a 1L büchiglas high-pressure hydrogenation reactor under the condition of the reaction temperature (100°C) and the reaction pressure (35 bar). The results shows that the kinetics equation proposed in this paper can be used to predict the response speed of IPN accurately.

Kinetics of catalytic hydrogenation of 4-nitroaniline in aqueous solutions of propan-2-ol with acid or base additives

The effect of addition of acetic acid and sodium hydroxide to an aqueous azeotropic solution of propan-2-ol on the rate of 4-nitroaniline hydrogenation is studied. The base additive accelerates the apparent rate of nitro group reduction, while the presence of acetic acid slows the reaction rate. It is experimentally established that the rate of nitro group conversion calculated from the amount of reacted 4-nitroaniline exceeds the rate of hydrogen uptake from the gas phase in all of the studied solvents. Hydrogen bound by active sites of the catalyst surface is found to participate notably in the reactions. It is proved both experimentally and theoretically that strongly bound atomic forms of adsorbed hydrogen are most active in the reduction of the nitro group.

Kinetics of catalytic hydrogenation of benzene using copper nanoparticles as catalysts

The hydrogenation kinetics of benzene was studied using copper nanoparticles as a catalyst. Hydrogenation was carried out under steady-state conditions at different temperatures. The benzene concentration was determined using gas chromatography. The rate constants, activation energies, and conversion degrees were estimated.

Mechanism and kinetics of catalytic hydrogenation in liquid phase: Macrokinetics of reduction reactions over colloidal palladium catalyst

Mechanism and kinetics of catalytic hydrogenation in liquid phase: Macrokinetics of reduction reactions over colloidal palladium catalyst

Mechanism and kinetics of catalytic hydrogenation in liquid phase: Some of the principles of hydrogenation of unsaturated hydrocarbons over a skeletal nickel catalyst

Mechanism and kinetics of catalytic hydrogenation in liquid phase: Some of the principles of hydrogenation of unsaturated hydrocarbons over a skeletal nickel catalyst