Kinetic modelling of a complex consecutive reaction in a slurry reactor: Hydrogenation of phenyl acetylene

doi:10.1016/0009-2509(86)85044-8

Chemical Engineering Science

Volume 41, Issue 12, 1986, Pages 3073-3081

https://doi.org/10.1016/0009-2509(86)85044-8 Get rights and content

Abstract

Kinetics of hydrogenation of phenyl acetylene to styrene to ethyl benzene using Pd/C catalyst has been reported. The experiments were carried out in a mechanically agitated autoclave over a temperature range of 15–45°C. Effect of catalyst loading, H₂ pressure, concentrations of reactants and products on the rate of hydrogenation as well as the concentration profile in a batch reactor was investigated. The analysis of initial rates showed that the data were in kinetic regime for 0.1% Pd/C catalyst. For interpretation of the kinetics, the observed concentration time data were directly used and the rate parameters evaluated using a simulation model for the batch reactor. It was found that the rate of hydrogenation was strongly inhibited in the presence of phenyl acetylene, while styrene and ethyl benzene showed negligible effects. The activation energies observed for the two consecutive steps were 51.5 and 53.6 kJ/mol, respectively.

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The palladium azolate/carboxylate network (Pd-dmpzc) catalyses the selective hydrogenation of phenylacetylene to styrene in water. Under optimised conditions, at a Pd:NaBH₄ ratio of 1:100 at 40 °C, Pd-dmpzc provided much better results than Pd(OAc)₂ or PdCl₂(CH₃CN)₂. Analysis of the recovered catalyst revealed the presence of different Pd²⁺ species and Pd⁰ NPs which contributed in the catalytic reaction.
Activity and selectivity of carbon supported palladium catalysts prepared from bis(Η<sup>3</sup>-allyl)palladium complexes in phenylacetylene hydrogenation
2018, Catalysis Communications
Citation Excerpt :
It was the case in our previous work too [5]. In some other works, a constant catalyst activity establishes not at once, as in our case, but during next hydrogenation runs [34]. Carbon-supported palladium catalysts containing 9.1 wt% of Pd synthesized by reduction of bis(η3-allyl)palladium complexes as precursors with hydrogen demonstrated good figures in selective liquid-phase hydrogenation of PA to ST. Their performance obeys direct specific surface area effect: the more Pd specific surface area the greater their activity and selectivity.
Liquid phase hydrogenation of phenylacetylene was investigated on a series of 9.1 wt% Pd/C catalysts prepared from bis(η³-allyl)palladium complexes, as well as commercial Russian Pd/C catalyst (GIPKH-108). Pd/C catalysts were characterized by oxygen absorption and SEM. All prepared Pd/C catalysts demonstrated very high selectivity to styrene. The reduction temperature of palladium precursor has a significant effect on the palladium dispersity, but the substituent near terminal carbon atom of allyl ligand affects the dispersity more essentially than reduction temperature. Pd/C catalyst prepared from bis[(η³-allyl)palladium acetate] showed highest metal dispersity, activity and selectivity in the hydrogenation of phenylacetylene to styrene.
Palladium nanoparticles supported on ceria thin film for capillary microreactor application
2018, Chemical Engineering Research and Design
Ceria thin film in capillary microreactor was developed as a catalyst support for palladium nanoparticles (Pd NPs) by sol–gel approach. The thickness of Pd/CeO₂ film deposited in capillary of 250 μm internal diameter is 200 nm as measured by scanning electron microscope (SEM), and the particle size of Pd NPs as determined by the transmission electron microscope (TEM) images is 4.2 nm. The Pd/CeO₂ immobilized capillary was tested for hydrogenation of phenylacetylene in a microreactor at temperature range of 30–60 °C. Higher selectivity toward ethylbenzene was recorded at higher temperature. The reaction rate of 1.89 × 10⁻³ mol g⁻¹ s⁻¹ was obtained for 158 ppm phenylacetylene hydrogenation at 60 °C and 0.50 ml min⁻¹ hydrogen flow rate. The ceria thin film was stable even after 6 days.
Acetophenone hydrogenation on Rh/Al<inf>2</inf>O<inf>3</inf> catalyst: Intrinsic reaction kinetics and effects of internal diffusion
2016, Chemical Engineering Journal
Acetophenone hydrogenation on 1% Rh/Al₂O₃ catalyst was conducted using various support sizes to study intrinsic kinetics and internal diffusion effects. In the first part of this work, results from different noble metals and supports were compared, and the 1% Rh/Al₂O₃ was selected. From experiments at 60–100 °C, 1.1–4.1 MPa $P_{H_{2}}$ and 0.04–0.4 M C_AP.o using powder catalysts, intrinsic reaction kinetic modeling with the Langmuir–Hinshelwood mechanism was conducted. The selected kinetic model included dissociative and non-competitive hydrogen adsorption, along with saturated active sites for organic species, and surface reaction as the rate determining step. With the obtained intrinsic reaction kinetics, internal diffusion effects were investigated using two catalyst particle sizes and diffusion–reaction models. The properties of the egg-shell type catalyst particles, including metal dispersion, were characterized and utilized in the models. The concentration–time profiles calculated from models developed in this work correspond well with the experimental results, explaining the effects of internal diffusion inside catalyst particles on reaction rates and selectivity, and are suitable for future use in trickle-bed reactor modeling studies.
Revisiting the reaction kinetics of selective hydrogenation of phenylacetylene over an egg-shell catalyst in excess styrene
2015, Chemical Engineering Science
Citation Excerpt :
In a previous study on the kinetics of selective hydrogenation of pygas over a commercial egg-shell catalyst (Zhou et al., 2010b), it was found that the effect of internal diffusion limitations was noticeable although the thickness of the active layer was only 60 μm. To date, a few studies have been devoted to the kinetics of selective hydrogenation of phenylacetylene (Chaudhari et al., 1986; Jackson and Shaw, 1996; Wilhite et al., 2002; Berenblyum et al., 2015), and the activation energies reported in the literature vary greatly, being 9.7–54.6 kJ/mol for the hydrogenation of phenylacetylene to styrene and 23.2–53.6 kJ/mol for the hydrogenation of styrene to ethylbenzene. Despite the fact that different types of catalysts may have different activation energies, the contribution of the effect of mass transfer processes should not be overlooked, especially for the selective hydrogenation reactions that have high reaction rates (Vergunst et al., 2001).
Selective hydrogenation of phenylacetylene is an important reaction for the removal of a small amount of phenylacetylene from styrene monomer. In this work, the kinetics of phenylacetylene hydrogenation over an egg-shell Pd/Al₂O₃ catalyst in the presence of excess styrene was investigated by using a laboratory-scale fixed-bed reactor. The liquid-phase residence time distribution (RTD) in the reactor under different operating conditions was measured by tracer pulse method, and the Peclet number was determined based on the experimental data and the RTD model. The kinetic experiments showed that an increase in temperature and pressure or a decrease in the liquid hourly space velocity gave rise to increased conversion of phenylacetylene and decreased concentration of styrene. A rigorous mathematical model combining reaction kinetics, external mass transfer, intraparticle diffusion as well as axial dispersion of the liquid phase was developed to describe the selective hydrogenation of phenylacetylene in the reactor, and the kinetic and adsorption parameters involved in the kinetic model were estimated by minimization of the sum of squares of relative residuals between observed and model-derived concentrations of different components. The kinetic model can describe the phenylacetylene hydrogenation over the Pd/Al₂O₃ catalyst very well, and the activation energies for the hydrogenation reactions of phenylacetylene to styrene, styrene to ethylbenzene and phenylacetylene to ethylbenzene were 48.6, 52.2 and 57.9 kJ/mol, respectively.
Surface dynamics of the intermetallic catalyst Pd<inf>2</inf>Ga, Part II - Reactivity and stability in liquid-phase hydrogenation of phenylacetylene
2014, Journal of Catalysis
Citation Excerpt :
It is 0.58 for pure Pd powder, meaning that double bond hydrogenation occurs clearly faster than triple bond hydrogenation. This is typically for Pd catalysts, e.g., in the gas-phase hydrogenation of acetylene [37] and was also reported for the liquid-phase hydrogenation of phenylacetylene [38]. The ability to form hydrides makes Pd highly reactive toward alkene hydrogenation [39].
The catalytic properties of unsupported Pd₂Ga for the liquid-phase hydrogenation of phenylacetylene are investigated after different pre-treatments with focus on the stability of the catalyst during reaction. The surface of as-prepared Pd₂Ga consists mainly on Pd and oxidized Ga species. Under the conditions of the liquid-phase hydrogenation of phenylacetylene, the intermetallic surface cannot be reformed in situ by reduction of Ga oxide. After a reductive pre-treatment in 5% H₂/Ar at 400 °C, an almost clean Pd₂Ga surface can be obtained. Its hydrogenation activity is significantly lowered compared to elemental Pd, which is due to the intrinsic adsorption properties of the intermetallic surface. However, residues of H₂O or O₂ lead to oxidation of this surface. Excluding these impurities, the decomposition can be suppressed. In this case, the bulk material of Pd₂Ga gets cracked during phenylacetylene hydrogenation. The controlled modification of the crystal and the electronic structure of Pd by formation of the intermetallic compound Pd₂Ga are accompanied with a decreased stability.

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Kinetic modelling of a complex consecutive reaction in a slurry reactor: Hydrogenation of phenyl acetylene

Abstract

J. Catalysis

J. chem. Engng Japan

A.I.Ch.E. J.

Ind. Engng Chem. Prod. Res. Dev.

Ind. Engng Chem. Proc. Des. Dev.

J. chem. Engng Japan