Abstract:

The alkylation kinetics of isobutane with mixed butenes using sulfuric acid as catalyst was investigated by batch experiments at temperatures from 276.2 K to 285.2 K under the conditions of industrial interest. With the decrease of reaction temperature, both the production of main product trimethylpentanes (TMPs) and RON of alkylates increased, and byproducts dimethylhexanes (DMHs) changed a little, but heavy ends components (HEs) reduced significantly. By using the alkylation kinetics model based on the classic carbonium ion mechanism, the concentration profiles with time regarding three groups of key alkylates, including TMPs, DMHs, and HEs, were compared against experiments. The regression results showed that the kinetics model fitted experimental data very well. An anti-Arrhenius behavior was found in the chain initiation step of the addition reaction of H⁺ to isobutene, and the apparent activation energies of itself and the reverse reaction were 45.14 kJ·mol^-1 and 41.44 kJ·mol^-1. The calculation of reaction rates of the TMPs⁺ and DMHs⁺ forming steps was added, and most of the reaction rates of chain transfer and chain termination reactions remained the same as those in literature.

Key words: alkylation, mixed butenes, reaction kinetics, carbocation, kinetics modeling, parameter estimation

摘要：

以硫酸为催化剂,间歇实验研究了276.2 ~285.2 K温度范围内混合丁烯/异丁烷烷基化反应动力学。实验结果表明,随着反应温度的降低,主产物三甲基戊烷(TMPs)生成量和烷基化油整体辛烷值增大,副产物二甲基己烷(DMHs)变化较小,高碳组分(HEs)的生成量降低明显。采用基于碳正离子反应机理建立的烷基化动力学模型对TMPs、DMHs、HEs 3类组分进行了计算分析,模拟计算结果表明,动力学模型对实验数据的拟合效果良好。链引发步骤异丁烯加氢离子反应表现出反Arrhenius行为,其本身及逆反应的活化能分别为45.14 kJ·mol^-1和 41.44 kJ·mol^-1,增加对链传递部分C₈正碳离子形成步骤的速率常数计算,部分涉及链传递和链终止反应步骤反应速率常数与文献值保持一致。

关键词: 烷基化, 混合丁烯, 反应动力学, 碳正离子, 动力学模型, 参数估值