Performance of HZSM-5 agglomerated in a mesoporous matrix in the fuel production from ethylene at atmospheric pressure

Abstract

Ethylene oligomerization into liquid fuels at slightly over atmospheric pressure has been studied due to its interest to valorize online the excess of ethylene in sustainable olefins production processes and to intensify the production of fuel from refinery secondary streams. Runs were carried out in a fixed-bed reactor under the following conditions: 1.5 bar; 275–375 °C; space time, 2.7–16.2 gcatalyst h molC−1; time on stream, 5 h. The catalyst was prepared by agglomerating a HZSM-5 zeolite (SiO2/Al2O3 of 30) in a mesoporous matrix (γ-Al2O3/α-Al2O3). The hierarchical porous structure of the catalyst enables to reach a pseudo-steady state with a remarkable remnant activity after an initial deactivation period of 2–3 h. Temperature shows a relevant effect on ethylene conversion and product distribution, where a C5+ liquid fuel yield of 55% above 325 °C and 10.6 gcatalyst h molC−1 is obtained. At 325 °C, gasoline yield is 60%, with high olefin content (49%), which decreases at higher temperature, due to an increase in aromatic and paraffin concentration. Soft and hard coke analysis reveal the role of the matrix to attenuate deactivation. Moreover, above 325 °C the cracking of hard coke precursors deposited in the zeolite micropores prevails respect to their formation.