关键词: 化学反应, 催化, 固定床, 轻烃, 裂解, 乙烯, 丙烯

Abstract:

The cracking performance of light hydrocarbon model compounds such as n-paraffins, i-paraffins, naphthalenes, aromatics and n-olefins on a mesoporous catalyst based on ZSM-5 molecular sieve was investigated in a small scale fixed bed reactor. The experimental results showed that the cracking performance in the order from good to poor was:n-olefins, n-paraffins, naphthalenes, i-paraffins, and aromatics. For n-paraffins, i-paraffins and naphthalenes, the yields of total light olefins were largely different whereas the selectivities of total light olefins were all around 56.57%. The main liquid components were pentene, benzene, toluene and xylene besides unreacted feed. In case of straight-run naphtha, the yield of ethylene plus propylene and the yield of total light olefins increased with the increase in reaction temperature and the decrease in weight hourly space velocity. At a condition of reaction temperature of 680℃, a weight hourly space velocity of 4.32 h^-1 and a steam-to-oil weight ratio of 0.35, naphtha catalytic pyrolysis yielded 41.94% (mass) of total light olefins and 35.87% (mass) of ethylene plus propylene, which the ratio of propylene to ethylene at above 1.2 was much higher than that of naphtha steam cracking. A large amount of olefins and paraffins in the liquid sample of naphtha catalytic pyrolysis indicated that the liquid sample still had good cracking performance. A new characterization parameter (KF), a function of H/C atomic ratio, relative density and molecular weight of feeds, was proposed to be more suitable than KCP for characterizing catalytic pyrolysis of light hydrocarbons.

Key words: chemical reaction, catalysis, fixed-bed, light hydrocarbon, pyrolysis, ethylene, propylene