468115 The Role of Co-Catalysts in the Metathesis of Butenes to Propylene

Wednesday, November 16, 2016
Grand Ballroom B (Hilton San Francisco Union Square)
Faisal H. Alshafei1, Mohammed R. Alalouni1, Munir D. Khokhar1, Shaikh A. Ali2, Brian S. Hanna3, Maxim P. Bukhovko3 and Sohel K. Shaikh1, (1)Research & Development Center, Saudi Aramco, Dhahran, Saudi Arabia, (2)Chemistry Department, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia, (3)Aramco Services Company: Aramco Research Center - Boston, Cambridge, MA

The metathesis of ethylene and 2-butenes over a WO3/SiO2 catalyst is an important industrial reaction for the production of on-purpose propylene to supplement traditional supply routes such as steam cracking and fluid catalytic cracking (FCC). Over the years, various metal oxides have been proposed as catalysts with the most common being oxides of tungsten, rhenium and molybdenum supported on silica, alumina or Si-Al. In addition to the primary catalysts, co-catalysts comprising of various compounds including metal oxides, hydroxides and nitrates such as CaO, MgO, Y2O3, Ca(OH)2 and NaNO3 have been shown to enhance metathesis activity.

The primary objective of this research study is to develop an industrially pertinent co-catalyst for the valorization of C4 raffinate streams to propylene via cross- and self-metathesis as opposed to conventional ethylene metathesis. In this study, we examined the influence of adding various co-catalysts to study their effect on the rate of propylene formation. Various preparation techniques were employed to synthesize the co-catalysts. Catalytic performance was correlated to surface area and pore volume (BET), basicity measurements (CO2-TPD), chemical and electronic states measurements (XPS), particle morphology (SEM) and crystallinity (XRD).

The obtained results prove that appropriately synthesized co-catalysts with controlled microstructures when added to a primary metathesis catalyst, augment the metathesis performance. A novel reaction mechanism explaining the contribution of activators to the formation of the metal-carbene species will be presented. This research effort provides insight into the design of fine-tuned and catalytically active metathesis co-catalyst systems.

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