**3.1 Steam reforming**

The SRM approach produces a higher H2:CO ratio of 3:1 compared to the ratio required for Fischer-Tropsch (F-T) synthesis of 2:1 [80]. Due to its endothermic nature, SRM requires an extensive energy input so it is very expensive. In addition, a higher H2O:CH4 ratio is required to achieve a higher H2 output, making the SRM process less favorable and speeding up the activation of catalysis. Moreover, SRM faces corrosion problems and requires a desulfurization unit [81].

### **3.2 Partial oxidation of methane**

In the case of POM approach, this process is suitable for producing larger amounts of hydrocarbons and naphtha. Typically, POM has a very short residence time, high selectivity, and high conversion rates [82]. However, the exothermic nature of the reaction causes the induction of hot spots in the catalyst and makes it difficult to control the process. In addition, POM requires a cryogenic unit to separate oxygen from air. In the case of POM, this process is suitable for producing larger amounts of hydrocarbons and naphtha. POM typically has a very short period of residence, high selectivity and high conversion rates. The exothermic nature of the response, however, allows warm spots in the catalyst to be induced and makes the method hard to regulate and POM requires a cryogenic unit to separate oxygen from air [83].
