Abstract
The current research presents an experimental approach on the mechanism, kinetic and decay of industrial Pd-Ag supported α-Al2O3 catalyst used in the acetylene hydrogenation process. In the first step, the fresh and deactivated hydrogenation catalysts are characterized by XRD, BET (Brunauer–Emmett–Teller), SEM, TEM, and DTG analyses. The XRD results show that the dispersed palladium particles on the support surface experience an agglomeration during the reaction run time and mean particle size approaches from 6.2 nm to 11.5 nm. In the second step, the performance of Pd-Ag supported α-Al2O3 catalyst is investigated in a differential reactor in a wide range of hydrogen to acetylene ratio, temperature, gas hourly space velocity and pressure. The full factorial design method is used to determine the experiments. Based on the experimental results ethylene, ethane, butene, and 1,3-butadiene are produced through the acetylene hydrogenation. In the third step, a detailed reaction network is proposed based on the measured compounds in the product and the corresponding kinetic model is developed, based on the Langmuir-Hinshelwood-Hougen-Watson approach. The coefficients of the proposed kinetic model are calculated based on experimental data. Finally, based on the developed kinetic model and plant data, a decay model is proposed to predict catalyst activity and the parameters of the activity model are calculated. The results show that the coke build-up and condensation of heavy compounds on the surface cause catalyst deactivation at low temperature.
Highlights
Ethylene is one of the most important building blocks in the chemical industry, which is widely used to produce a wide range of products and intermediates, such as polyethylene, ethylene oxide, ethylbenzene, and ethylene dichloride [1,2]
The results show that the coke build-up and condensation of heavy compounds on the surface cause catalyst deactivation at low temperature
The results showed that two different active sites are detectable based on the palladium size
Summary
Ethylene is one of the most important building blocks in the chemical industry, which is widely used to produce a wide range of products and intermediates, such as polyethylene, ethylene oxide, ethylbenzene, and ethylene dichloride [1,2]. The catalytic conversion of hydrocarbons to ethylene is beneficial, the steam thermal cracking of ethane, LPG, naphtha, and gasoline is the most popular method to produce ethylene. A wide range of hydrocarbons is produced in the thermal cracking process. The minimum required purity of ethylene in the polymerization processes to produce polyethylene is about 99.90% and the maximum allowable limit of acetylene is 5 ppm known as polymer-grade ethylene. Acetylene decreases the catalyst activity in the ethylene polymerization unit, and can produce metal acetylides as explosive compartments. In this regard, several technologies have been proposed to decrease the acetylene concentration in the effluent product from thermal
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