Coking of solid acid catalysts and strategies for enhancing their activity

The development of practically viable solid acid catalysts as environmentally safer alternatives to liquid superacids continues to be a challenge. The major barrier in this regard is the rapid deactivation of the catalyst due to fouling by hydrocarbonaceous compounds, or coke. This paper reviews coke formation pathways on solid acid catalysts for low temperature (<110°C) processes such as gasoline alkylate production from isobutane and C3/C4 olefins, and skeletal isomerization of n-butane. The formation of coke precursors from feed impurities is also included. The use of near-critical reaction media to effectively balance the coke precursor formation rate with coke precursor removal rate (thereby enhancing catalyst activity) is discussed. Our results suggest that near-critical operation in conjunction with rational catalyst design (manipulating parameters such as pore structure and acidity) and proper choice of reactor configuration (stirred reactor minimizing olefin concentration) have excellent potential for enhancing catalyst activity and product selectivity.