Kinetics of Liquid - Phase Hydrogenation of Straight Chain C10 to C13 Di-Olefins Over Ni/Al2O3 Catalyst

Straight chain C10 to C13 di-olefins were selectively hydrogenated to increase the mono-olefins content in the feed to alkylation reactor in the process of production of Linear Alkyl Benzene (LAB). The reaction was carried out in a liquid phase up-flow fixed bed reactor at temperature of 448-503 °K and pressure of 1.08-1.96 MPa, which keeps hydrogen dissolved in the hydrocarbon feed. Under the above process conditions the reactor will be virtually two phase (solid-liquid) instead of three phase (solid-liquid-vapour). Kinetics of hydrogenation of straight chain C10 to C13 di-olefins on nickel alumina (Ni/Al2O3) catalyst was studied in the temperature range of 458-488 °K. The reaction scheme considered includes two consecutive hydrogenation reactions. Various rate models based on the modified Power Law, Horiuti-Polanyi mechanism & proposed by Somers. A.; were derived for the two consecutive hydrogenation reactions and subjected to model discrimination. Parameter estimation was done utilizing the Levenberg-Marquardt Algorithm for global convergence using MATLAB software. Out of the various models tested, rate model based on power law with modification fitted the data well. The estimated rate constants of the best model are thermodynamically sound and statistically consistent.

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Liquid-Phase Hydrogenation of 1-Phenyl-1-propyne on the Pd1Ag3/Al2O3 Single-Atom Alloy Catalyst: Kinetic Modeling and the Reaction Mechanism

Nanomaterials ◽

10.3390/nano11123286 ◽

2021 ◽

Vol 11 (12) ◽

pp. 3286

Author(s):

Alexander V. Rassolov ◽

Igor S. Mashkovsky ◽

Galina N. Baeva ◽

Galina O. Bragina ◽

Nadezhda S. Smirnova ◽

...

Keyword(s):

Reaction Mechanism ◽

Liquid Phase ◽

Reaction Kinetic ◽

Single Atom ◽

Kinetic Characteristics ◽

Liquid Phase Hydrogenation ◽

Alkyne Hydrogenation ◽

Kinetics Of ◽

Al2o3 Catalyst ◽

Single Atom Alloy

This research was focused on studying the performance of the Pd1Ag3/Al2O3 single-atom alloy (SAA) in the liquid-phase hydrogenation of di-substituted alkyne (1-phenyl-1-propyne), and development of a kinetic model adequately describing the reaction kinetic being also consistent with the reaction mechanism suggested for alkyne hydrogenation on SAA catalysts. Formation of the SAA structure on the surface of PdAg3 nanoparticles was confirmed by DRIFTS-CO, revealing the presence of single-atom Pd1 sites surrounded by Ag atoms (characteristic symmetrical band at 2046 cm−1) and almost complete absence of multiatomic Pdn surface sites (<0.2%). The catalyst demonstrated excellent selectivity in alkyne formation (95–97%), which is essentially independent of P(H2) and alkyne concentration. It is remarkable that selectivity remains almost constant upon variation of 1-phenyl-1-propyne (1-Ph-1-Pr) conversion from 5 to 95–98%, which indicates that a direct alkyne to alkane hydrogenation is negligible over Pd1Ag3 catalyst. The kinetics of 1-phenyl-1-propyne hydrogenation on Pd1Ag3/Al2O3 was adequately described by the Langmuir-Hinshelwood type of model developed on the basis of the reaction mechanism, which suggests competitive H2 and alkyne/alkene adsorption on single atom Pd1 centers surrounded by inactive Ag atoms. The model is capable to describe kinetic characteristics of 1-phenyl-1-propyne hydrogenation on SAA Pd1Ag3/Al2O3 catalyst with the excellent explanation degree (98.9%).

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