*3.4. Catalyst Performance Test*

A Fischer–Tropsch synthesis (FTS) system with a fixed-bed reactor was used to assess the catalytic performance. In the reactor, one gram of the prepared catalyst (Fe-C or Fe-C-K) was loaded. The catalyst was reduced for 5 h in a fixed bed reactor at 450 ◦C with a hydrogen gas flow of 30 sccm and a nitrogen gas flow of 10 sccm. The reactor was cooled to 350 ◦C to promote the reaction at 20 bar in the presence of a H2/CO (1:1 ratio). The pressure was controlled using a back-pressure regulator. A liquid product sample was taken from the two separators. Gas chromatography was used to evaluate the tail gases in real time (Shimadzu GC-2010 Plus, Kyoto, Japan). Gas chromatography–mass spectrometry was used to assess the liquid sample taken from the separator (GCMS-QP2020, Shimadzu Japan). The product selectivity was calculated using the peak area from the GCMS results. Figure 10 depicts the schematic diagram of the FTS plant that was employed in this experiment.

**Figure 10.** Schematic diagram of the FTS setup.

## **4. Conclusions**

In this study, the effects of temperature and catalyst promoters on the formation of liquid hydrocarbons were studied. The Fe-C-K-supported catalyst with potassium promoter had 72 percent gasoline (C5–C11) selectivity at high temperatures. The GCMS results show the presence of C8+ hydrocarbons with selectivities of 96 percent and 91 percent when using a Fe-C-K catalyst at low and high temperatures. As a result, this research concludes that these catalysts may have a significant impact on the generation of gasoline and diesel in the future. Lantana Camara is composed of isocaryophyllene (16.7%), germacrene D (12.3%), bicyclogermacrene (19.4%), and valecene (12.9%), and caryophyllene isomers were detected in *Lantana Camara's* essential oil composition. Because of the oily nature of "Lantana Camara," the activated carbon utilized in the catalyst preparation had a significant impact on the increased hydrocarbon production. This research concludes that the use of activated carbon as a support made from Lantana Camara in FTS catalysts has a significant influence in improving hydrocarbon selectivity.

**Author Contributions:** Conceptualization, writing—original draft, formal analysis, M.A.; funding acquisition, S.M.W.; investigation, methodology, S.M.; project administration, resources, visualization, supervision, writing—review and editing, N.I., A.I. All authors have read and agreed to the published version of the manuscript.

**Funding:** Authors are grateful to the Researchers Supporting Project Number (RSP2022R448), King Saud University, Riyadh, Saudi Arabia.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data are presented in the present research article.

**Acknowledgments:** The work was conducted at the U.S.-Pakistan Center for Advanced Studies in Energy (USPCASE), NUST. The authors appreciate the technical support by the Energy Storage and Conservation lab staff and the Advanced Energy Materials lab. Authors are grateful to the Researchers Supporting Project Number (RSP2022R448), King Saud University, Riyadh, Saudi Arabia.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

