Extended Data Fig. 5: Unusual kinetic behavior exhibited by 3%SOMC.
From: Promoting active site renewal in heterogeneous olefin metathesis catalysts
a, Reaction orders for ethylene/2-butene cross-metathesis. Red: ethylene reaction order plot with y(C2H4) = 0.2 to 0.5 and y(C4H8) = 0.5. Blue: 2-butene reaction order plot with y(C4H8) = 0.2 to 0.5 and y(C2H4) = 0.5. Reaction conditions: 10 mg catalyst, pretreated at 550 °C under 100 mL/min He for 1 h, 100 mL/min total gas flow rate (balance He), WHSV = 0.0038 mol C4H8/gcat.s, T = 330 °C. b, Effect of adding 2-butene to a propylene self-metathesis reaction at steady-state. The increase in ethylene yield is modest (ca. 1.5x with 20% 2-butene co-feed) but significant, stable and fully reversible, consistent with observations for better promoters such as i4ME as discussed in the text. There are two possible alternative sources of additional ethylene production upon 2-butene addition that can both be eliminated as they are too small to account for the magnitude of the increase in ethylene yield. Firstly, traces of ethylene impurities (ca. 30 ppm determined by GC-FID on a bypass run) present in the 2-butene source are 2-3 orders of magnitude too small. Secondly, 1-butene, whether as a feed impurity or generated in situ by isomerization, can undergo cross-metathesis with propylene to yield a 1:1 ratio of pentenes and ethylene. However, the mole fraction of pentenes in the product stream is 0.0002, an order of magnitude too small. Reaction conditions: 10 mg catalyst, pretreated at 550 °C under 100 mL/min He for 1 h, 25 mL/min C3H6 + 25 mL/min He or (15 mL/min He + 10 mL/min C4H8), WHSV = 0.0019 mol C4H8/gcat.s, T = 330 °C.
