A Zeolite-Based Cascade System to Produce Jet Fuel from Ethylene Oligomerization

Abstract

Jet fuel production from ethylene oligomerization opens a sustainable pathway to clean sulfur-free fuel that is increasingly in demand due to the potential renewable origin of ethylene. The key to a viable heterogeneously catalyzed process is to improve the selectivity of the jet fuel while prolonging the catalyst lifetime. To this end, we have assessed and optimized a dual-bed cascade system based on a dimerization bed that is followed by an oligomerization bed using Ni supported on Y zeolite and ZSM-5 zeolite catalysts, respectively. Our optimization approach uses different catalyst acidities, temperatures, and bed configurations for determining the best yield–conversion relationship. Under optimized dual-bed conditions, we can produce 64 wt % of jet fuel at the beginning of the reaction and maintain a 50 wt % selectivity of this fraction for over 20 h on stream. This paper also analyzes coke deposition (content and nature) at the different experimental conditions and catalyst bed arrangements using temperature-programmed combustion. We demonstrate that the dual-bed approach is effective for protecting the main oligomerization bed (ZSM-5 catalyst) from deactivation, leading to the formation of a lighter type of coke compared with that using the initial Ni2+ HY-based dimerization catalyst, which deactivates at a faster rate.

Ethylene Oligomerization: Unraveling the Roles of Ni Sites, Acid Sites, and Zeolite Pore Topology through Continuous and Pulsed Reactions

“…Conversely, the ZSM‐5 zeolite provides a better option when higher molecular‐weight products are desired [6] . Indeed, the present authors have previously applied an acidic ZSM‐5 zeolite as a secondary oligomerization catalyst in a cascade system to produce jet fuel products, obtaining yields of greater than 60 % under high ethylene conversion conditions [7] …”

“…Attempts to overcome these constraints have driven interest in gas-phase heterogeneous catalysis, wherein the zeolites have occupied a prominent place [5] due to their high thermal stability and tunable acidity and morphology. [6][7][8] Some of the most commonly reported zeolites for ethylene oligomerization are ZSM-5 [6,[9][10][11] and beta [11][12][13][14][15][16][17][18][19] zeolites due to their relatively low deactivation rates. [20][21] The ZSM-5 zeolite (MFI) contains 10-membered rings, giving it medium-sized pores intersecting straight and sinusoidal channels with cross-sections of 5.5 Å.…”

“…[6] Indeed, the present authors have previously applied an acidic ZSM-5 zeolite as a secondary oligomerization catalyst in a cascade system to produce jet fuel products, obtaining yields of greater than 60 % under high ethylene conversion conditions. [7] Despite the numerous studies on Ni/zeolite catalysts for ethylene oligomerization, several critical fundamental questions remain unanswered. For example, what are the pathways for the activation of the Ni sites or the Ni-acid site interplay in the oligomerization mechanism, [2] which is thought to occur predominantly by the Cossee-Arlman mechanism on heterogeneous catalysts?…”

“…However, these catalysts pose limitations such as instability, cumbersome separation from reaction products, and energy‐intensive reaction conditions for boosting olefin production. Attempts to overcome these constraints have driven interest in gas‐phase heterogeneous catalysis, wherein the zeolites have occupied a prominent place [5] due to their high thermal stability and tunable acidity and morphology [6–8] . Some of the most commonly reported zeolites for ethylene oligomerization are ZSM‐5 [6,9–11] and beta [11–19] zeolites due to their relatively low deactivation rates [20–21] .…”

Impacts of Ni-Loading Method on the Structure and the Catalytic Activity of NiO/SiO2-Al2O3 for Ethylene Oligomerization

“…With the gradual maturation of technologies for producing ethylene using resources other than petroleum (e.g., dehydrogenation of ethane derived from shale gas, bioethanol conversion to ethylene by catalytic dehydration, and the zeolite-catalyzed methanol-toolefin (MTO) process), the production of chemicals and liquid fuels from ethylene has attracted renewed attention [1][2][3]. Oligomerization of ethylene into long-chain olefins is one of the important reactions required for ethylene conversion and has been applied in the production of chemical intermediates, base materials, and liquid fuels [1,[4][5][6]. Currently, several million tons of linear α-olefins are produced by homogeneously-catalyzed ethylene oligomerization (EO), which comprises transition metal complexes, alkylaluminum cocatalysts, and organic solvents.…”