Which components in naphtha increase methane production and reduce ethylene production?
Thread Content
Which components in naphtha increase methane production and reduce ethylene production? Recently, there has been no change in our COT or load, but the diene yield has decreased while methane hydrogen production has increased.
The furnace tube is coked. The temperature of the furnace tubes is uneven.
This situation is likely due to an increase in the content of isoparaffins in the raw materials; with more branched alkanes present, the ratio of methane to hydrogen in the cracking products increases, resulting in a reduced yield of diolefins. For some time, the naphtha purchased by our company was like this: the excess methane and hydrogen produced could not be utilized.
From a mechanistic standpoint, an increase in the proportion of non-linear alkanes in the feedstock leads to an increase in methane yield. Due to the reactions that occur under high-temperature thermodynamic conditions during olefin cracking, the cracking of straight-chain hydrocarbons is primarily driven by radical reactions, and the reaction time must be kept short to minimize the formation of tertiary carbon alkyl radicals. However, if the proportion of branched alkanes increases, it becomes easier to form individual methyl groups and highly stable tertiary carbon alkyl groups during cracking, and the proportion of methane produced rises when hydrogen transfer occurs. This is also why paraffinic rosin is more suitable as a raw material for ethylene cracking.