Kinetics of Liquid-Phase 1-Butene Hydroisomerization over Pd/Al₂O₃ Catalysts

Abstract

Liquid-phase 1-butene hydroisomerization to 2-butene is an important approach to utilize cheap and abundant C4 olefins (normally as by-products from refinery processes), and the reaction kinetics is critical to the development of its reactors and catalysts. Herein, kinetics experiments are performed to understand the characteristics of liquid-phase 1-butene hydroisomerization over a commercial Pd/Al2O3 catalyst, and three intrinsic kinetics models are proposed to describe the rates of the hydroisomerization and hydrogenation reactions. The results show that the selectivity toward 2-butene increases with temperature, indicating the hydrogenation reactions are suppressed due to the low partial pressure of hydrogen under high temperature. The fraction of hydrogen in reactants significantly affects 1-butene conversion and 2-butene selectivity, and thus, this effect should be included in kinetics models. Comparing the proposed power-law, dual-site Langmuir–Hinshelwood, and single-site Langmuir–Hinshelwood models, the single-site Langmuir–Hinshelwood model is the best in predicting the experiments, implying that hydroisomerization and hydrogenation reactions may occur at the same type of active sites under the reaction conditions in this work. The activation energies of the hydroisomerization reactions are lower than those of the hydrogenation reaction, and the adsorption enthalpy of butenes is smaller than that of hydrogen.

Activity and Selectivity of a Nickel SCILL Catalyst in the Competitive Hydrogenation between 1-Octene and 1-Octyne

“…A first-order reaction rate is quite common and has been demonstrated before with octyne conversion. 34,36,47,48 It can be seen from the plot that the ionic liquid reduces the LSV required to bring about a conversion comparable to that of the uncoated catalyst. This is in effect a deactivation of the nickel catalyst.…”

“…With a hydrogen pressure of 50 bar, it can be reasonably inferred that the phases are saturated with a hydrogen buffer, ensuring an abundant supply of the reactants. Moreover, the gas space velocity (GSV) for 100% hydrogen surpasses the liquid space velocity (LSV) at 2% reactants, guaranteeing that the reaction is not deficient in hydrogen, with the GSV determining the flow. ,, Additionally, the ratio of GSV to LSV is consistently maintained, establishing a fixed proportion between hydrogen and alkene/yne reactants. A 2% 1-octyne with 2% 1-octene in a hexane mixture was used in the mixed substrate reactions, while a 2% 1-octyne in a hexane mixture and a 2% 1-octene in a hexane mixture were used in the single substrate reactions.…”