**Ourmazd Dehghani, Mohammad Reza Rahimpour \* and Alireza Shariati**

Department of Chemical Engineering, Shiraz University, Shiraz 71345, Iran; ourmazd1@yahoo.com (O.D.); shariati@shirazu.ac.ir (A.S.)

**\*** Correspondence: rahimpor@shirazu.ac.ir; Tel.: +98-713-2303071

Received: 4 February 2019; Accepted: 19 February 2019; Published: 5 March 2019

**Abstract:** The current research presents an experimental approach on the mechanism, kinetic and decay of industrial Pd-Ag supported α-Al2O<sup>3</sup> 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-Al2O<sup>3</sup> 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.

**Keywords:** acetylene hydrogenation; kinetic model; catalyst decay; process modeling
