6.2.3. Effect of Temperature

Typically, temperature is the most important parameter and has a direct effect on the selectivity and conversion. Increasing the temperature improves the reaction rate and shifts the reversible exothermic reactions toward lower equilibrium conversion. Figure 9a,b shows the effect of operating temperature on acetylene conversion, ethylene selectivity, and product distribution. Although applying higher temperature increases the rate of acetylene conversion as the main reaction, it increases rate of side reactions. Typically, applying high temperatures on the system has a considerable effect on the side reactions, so butene and butadiene formation increase sharply. Since the increasing temperature decreases selectivity, the effect of operating temperature on side reactions is more significant compared to the main reaction. *Processes* **2019**, *7*, x FOR PEER REVIEW 15 of 22 exothermic reactions toward lower equilibrium conversion. Figure 9a,b shows the effect of operating temperature on acetylene conversion, ethylene selectivity, and product distribution. Although applying higher temperature increases the rate of acetylene conversion as the main reaction, it increases rate of side reactions. Typically, applying high temperatures on the system has a considerable effect on the side reactions, so butene and butadiene formation increase sharply. Since the increasing temperature decreases selectivity, the effect of operating temperature on side reactions is more significant compared to the main reaction.

**Figure 9.** Effect of temperature on (a) acetylene conversion, ethylene selectivity, and (b) product distribution at 18 bar, hydrogen to acetylene ratio 1.2 and GHSV 5500 1/h. **Figure 9.** Effect of temperature on (**a**) acetylene conversion, ethylene selectivity, and (**b**) product distribution at 18 bar, hydrogen to acetylene ratio 1.2 and GHSV 5500 1/h.

6.2.4. Effect of Hydrogen to Acetylene Ratio

#### 6.2.4. Effect of Hydrogen to Acetylene Ratio *Processes* **2019**, *7*, x FOR PEER REVIEW 16 of 22

In general, the presence of excess hydrogen in the reactor, reduces coke build-up on the catalyst, and consequently retards the deactivation of catalysts in the hydrogenation process. Figure 10a,b shows the effect of hydrogen to acetylene ratio on acetylene conversion, ethylene selectivity, and product distribution. Increasing hydrogen concentration in the reactor increases the rate of hydrogenation reactions and results in higher acetylene conversion. Although increasing the hydrogen to acetylene ratio enhances the rate of acetylene hydrogenation, it shifts the ethylene hydrogenation toward higher conversion and decreases process selectivity. It appears that applying hydrogen rich stream increases 1-butene concentration in the reactor. In general, the presence of excess hydrogen in the reactor, reduces coke build-up on the catalyst, and consequently retards the deactivation of catalysts in the hydrogenation process. Figure 10a,b shows the effect of hydrogen to acetylene ratio on acetylene conversion, ethylene selectivity, and product distribution. Increasing hydrogen concentration in the reactor increases the rate of hydrogenation reactions and results in higher acetylene conversion. Although increasing the hydrogen to acetylene ratio enhances the rate of acetylene hydrogenation, it shifts the ethylene hydrogenation toward higher conversion and decreases process selectivity. It appears that applying hydrogen rich stream increases 1-butene concentration in the reactor.

**Figure 10.** the effect of (a) hydrogen to acetylene ratio on acetylene conversion, ethylene selectivity, and (b) product distribution at 20 bar, 45 °C and GHSV 2600 1/h. **Figure 10.** The effect of (**a**) hydrogen to acetylene ratio on acetylene conversion, ethylene selectivity, and (**b**) product distribution at 20 bar, 45 ◦C and GHSV 2600 1/h.

6.2.5. Developed Kinetic and Decay Models
