Propylene hydrogenation on pt/α-Al ₂ O ₃ , pd/α-Al ₂ O ₃ , pt/ZrO ₂ , and pd/ZrO ₂ in the presence of H ₂ O: experimental and modeling study

Liquefied petroleum gas (LPG) is known as clean fuel and its importance will be continued in the future. However, most of LPG is currently produced from fossil resources. Thus, producing LPG from CO2 as a renewable source is significant for achieving carbon neutrality. One possible way to produce LPG from CO2 is through an indirect pathway via methanol/dimethyl ether and propylene/butene. The final step of this pathway is the hydrogenation reaction of olefins to produce paraffins. Although H2O may coexist in this reaction, there have been few studies to investigate reaction kinetics of propylene hydrogenation in the presence of H2O. Here, we measured the propylene conversion over different four catalysts: Pt/α-Al2O3, Pd/α-Al2O3, Pt/ZrO2, and Pd/ZrO2. We varied a reaction temperature and concentrations of propylene, H2 and H2O in the feed. We found that above 200 °C the propylene conversion was negatively affected by the reaction temperature and the propylene concentration, while it was positively affected by the H2 concentration. We also found that the dependence of propylene conversion on H2O concentration depended on the catalysts. To reproduce the measured results, a kinetic model based on the Langmuir-Hinshelwood mechanism was developed over Pt/ZrO2 which showed the best reaction performance among the catalysts used. A two-dimensional reactor model consisting of mass and heat balance equations was developed for exploring the desirable reactor type. The simulations showed that the externally cooled reactor with a catalyst density gradient was the most suitable for propylene hydrogenation in terms of heat management and propylene conversion.