Kinetics of Reductive Alkylation of p-Phenylenediamine with Methyl Ethyl Ketone Using 3% Pt/Al₂O₃ Catalyst in a Slurry Reactor

Abstract

Intrinsic kinetics of reductive alkylation of p-phenylenediamine (PPDA) with methyl ethyl ketone (MEK) using 3% Pt/Al 2 O 3 catalyst was studied in a slurry reactor. The overall reaction involves a combination of parallel and consecutive reactions involving equilibrium noncatalytic (homogeneous) and catalytic (heterogeneous) steps. For the purpose of kinetic modeling, the effects of PPDA concentration, catalyst loading, agitation speed, and partial pressure of hydrogen were studied in a temperature range of 373-413 K. Quantitative criteria were used to ensure that the reaction occurred in the kinetic regime. Different rate equations have been considered based on the elementary steps involving catalytic and noncatalytic reactions, which lay stress on the different types of interactions occurring between the reactants and the active catalyst sites. The best-fit rate model has been proposed by rigorous optimization and model discrimination procedures, by simulating the experimental concentration-time data. For the best-fit model, the agreement between the predicted and experimental data was found to be very good over a wide range of operating conditions.

Modeling of bubble column slurry reactor for reductive alkylation of p-phenylenediamine

“…The intrinsic kinetics for the hydrogenation of PPDA to N, N -di-sec-butyl-p-phenylenediamine with 3% Pt/Al 2 O 3 catalyst have been recently studied by Patil et al (2007) using a batch slurry reactor. Based on this work, the reaction network can be described as shown in Fig.…”

“…The solubility of hydrogen in PPDA with MEK was experimentally determined (Patil et al, 2007), so the Henry's constant of solubility H e could be expressed by the following correlation in solution temperature:…”

“…The reductive alkylation reaction goes through a condensation reaction between an amine compound or its precursor and a carbonyl compound or alcohol to form an imine-a Shiff Base- (Ege, 1994), which is hydrogenated in the presence of a metallic catalyst to N-alkylated products. Reductive alkylation of nitro or amine compounds has been investigated using a wide range of alkylating agents and catalysts (Greenfield, 1994;Patil et al, 2007).…”

“…Lehtonen et al (1998) followed by Salmi et al (1999), developed a semi-batch slurry reactor model and loop reactor model for reductive alkylation of aromatic amines with short chain aldehydes (carbon chain length less than 3) using Pt/C catalyst. More detailed kinetic studies were reported from our group for reductive alkylation of aniline with acetone to N-isopropylaniline using Pd/Al 2 O 3 catalyst (Roy et al, 2005), and the more complex reductive alkylation of p-phenylenediamine (PPDA) with methyl ethyl ketone (MEK) to N, N -di-sec-alkyl-p-phenylenediamine, using Pt/Al 2 O 3 catalyst (Patil et al, 2007), wherein two amine functionalities are available for the alkylation reaction. A schematic of the reaction scheme considered in this work is shown in Fig.…”

“…The BCSR model was derived using the detailed kinetics reported in our earlier work (Patil et al, 2007) and mixing cell approach. It incorporates the gas-liquid, liquid-solid mass transfer, heat effects, and complex multistep reaction kinetics.…”