Reaction characteristics of maximizing light olefins and decreasing methane in C₅ hydrocarbons catalytic pyrolysis

When converting C₅ hydrocarbons to light olefins by catalytic pyrolysis, the generation of low value-added methane will affect the atomic utilization efficiency of C₅ hydrocarbons. To improve the atomic utilization efficiency, different generation pathways of light olefins and methane in the catalytic pyrolysis of C₅ hydrocarbons were analyzed, and the effects of reaction conditions and zeolite types were investigated. Results showed that light olefins were mainly formed by breaking the C₂–C₃ bond in the middle position, while methane was formed by breaking the C₁–C₂ bond at the end. Meanwhile, it was discovered that the hydrogen transfer reaction could be reduced by about 90% by selecting MTT zeolite with 1D topology and FER zeolite with 2D topology under high weight hourly space velocity (WHSV) and high temperature operations, thus leading to the improvement of the light olefins selectivity for the catalytic pyrolysis of n-pentane and 1-pentene to 55.12% and 74.60%, respectively. Moreover, the fraction ratio of terminal C₁–C₂ bond cleavage was reduced, which would reduce the selectivity of methane to 6.63% and 1.83%. Therefore, zeolite with low hydrogen transfer activity and catalytic pyrolysis process with high WHSV will be conducive to maximize light olefins and to decrease methane.