1-Butene oligomerization over ZSM-5 zeolite: Part 1-Effect of reaction conditions

The demand for middle distillates (kerosene and diesel) in comparison to gasoline fractions is increasing constantly, particularly in the majority of European countries. Thus, maximizing the production of middle distillates in the refining process is of immediate interest to refiners. However, the production of liquid fuels, for instances using a catalytic cracker, always generates a significant amount of lighter fractions, in particular of olefinic nature. Thus, the use of oligomerization reactions to convert the lighter olefin cuts into middle distillates to incorporate in the diesel pool is a promising process for the production of clean diesel fractions. In this work, 1-butene oligomerization over H-ZSM-5 zeolite has been investigated in a differential reactor operating at ambient pressure. The effect of the reaction conditions, such as reaction temperature, contact time and partial pressure was studied on the activity, selectivity and stability of the catalyst. The results show that an increase in the reaction temperature and/or partial pressure and in the contact time produces an improved catalyst activity. The data also show that high partial pressure improves the selectivity to C-8(+). Moreover, when increasing the temperature from 150 degrees C to 200 degrees C the C-8(+) hydrocarbons selectivity increases, whereas above this temperature it decreases as expected, due to the competition of cracking reactions. Furthermore, a decrease in contact time between the reaction mixture and the acid sites of the catalyst caused the C-8(+) hydrocarbons fraction in the product to increase. The highest selectivity towards C-8(+) hydrocarbons (similar to 86 wt.%) was obtained with H-ZSM-5, at 200 degrees C and 50 kPa of partial pressure and for the lowest value of contact time analyzed (12.5 x 10(-3) h). In this way, the operating conditions must be tuned in order to achieve a significant conversion and selectivity in desired fraction (C-8(+)). (C) 2013 Elsevier Ltd. All rights reserved.