Boron-Hyperdoped Silicon for the Selective Oxidative Dehydrogenation of Propane to Propylene

Propylene (C₃H₆) is one of the most important building blocks in the petrochemical industry. It is used in the production of many industrial products, such as polypropylene, propylene oxide and isopropanol [1]. Propylene is traditionally produced from steam cracking and fluid catalytic cracking in petroleum refineries. However, both technologies suffer from low selectivity, high energy consumption and significant production of CO₂ emissions. Direct production of C₃H₆ from the dehydrogenation of propane is currently of great interest in an effort to close the C₃H₆ supply and demand gap in the US. Oxidative dehydrogenation of propane (ODHP) reactions have attracted extensive attention as they are more resistant to coke deposition compared to non-oxidative DHP reactions and they are not limited by equilibrium.

Boron containing catalysts have the highest reported selectivity to C₃H₆ in the ODHP reaction, but their productivity still remains low. Herein, a series of boron-hyperdoped silicon catalysts with boron concentrations of 15, 25 and 42 at.% were synthesized by a laser pyrolysis method that enables boron concentration exceeding the solubility limit of boron in silicon [2]. The boron-hyperdoped silicon catalysts demonstrated high catalytic activity towards the ODHP reaction, which we attribute to enriched BOx and B-OH species present at the catalyst surface. Specifically, 42 at.% boron-hyperdoped silicon showed around 3.7 times higher C₃H₆ productivity (3.01 g_C₃H₆g_cat^-1h^-1) at 500℃ compared to commercial hexagonal boron nitride (0.82 g_C₃H₆g_cat^-1h^-1) under the same reaction conditions (WHSV = 28.2 g_C₃H₈g_cat^-1h^-1, C₃H₈:O₂:Ar = 1:1.5:3.5). Moreover, boron-hyperdoped silicon catalysts showed higher C₃H₆ productivity and at lower reaction temperatures compared to most reported ODHP catalysts (Fig. 1).

References

[1] J.T. Grant, J.M. Venegas, W.P. McDermott, I. Hermans, Chem. Rev., 118 (2017) 2769-2815.

[2] P. Rohani, S. Banerjee, S. Sharifi-Asl, M. Malekzadeh, R. Shahbazian-Yassar, S.J.L. Billinge, M.T. Swihart, Adv. Funct. Mater., 29 (2019) 9.