The selectivity of hydrocarbon oxidation on metal surfaces is influenced by several factors, including temperature and gas composition. Here, we will discuss how these factors affect the selectivity of the oxidation process.1. Temperature: The temperature plays a crucial role in determining the selectivity of hydrocarbon oxidation on metal surfaces. As the temperature increases, the reaction rate also increases due to the higher energy available for the reactants to overcome the activation energy barrier. However, the effect of temperature on selectivity is not straightforward and depends on the specific reaction system and the metal catalyst involved.At low temperatures, the selectivity towards partial oxidation products such as alcohols, aldehydes, and ketones is generally higher because the activation energy for complete oxidation to CO2 and H2O is higher. As the temperature increases, the selectivity towards complete oxidation products may increase, leading to a decrease in the selectivity of partial oxidation products.In some cases, the selectivity may exhibit a maximum at an intermediate temperature, where both the reaction rate and the selectivity towards the desired product are optimized. This is because, at very high temperatures, the reaction may become non-selective, leading to the formation of various undesired by-products.2. Gas composition: The composition of the gas mixture also affects the selectivity of hydrocarbon oxidation on metal surfaces. The presence of different reactants and products in the gas mixture can influence the adsorption, desorption, and reaction processes on the metal surface, thereby affecting the selectivity.For example, the presence of oxygen in the gas mixture is essential for the oxidation process. However, the partial pressure of oxygen can influence the selectivity. At low oxygen partial pressures, the selectivity towards partial oxidation products may be higher, while at high oxygen partial pressures, the selectivity towards complete oxidation products may increase.Additionally, the presence of other gases, such as CO2, H2O, or other hydrocarbons, can also affect the selectivity by competing for adsorption sites on the metal surface or by participating in secondary reactions that lead to the formation of undesired by-products.In summary, the selectivity of hydrocarbon oxidation on metal surfaces is influenced by both temperature and gas composition. The optimal conditions for achieving high selectivity towards a specific product depend on the specific reaction system and the metal catalyst involved. Understanding these factors and their interplay is crucial for designing efficient catalytic systems for selective hydrocarbon oxidation.