Effect of Type of Metals on Site Selective Dehydrogenation of Stearic Acid

¹ Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, 254 Phayathai Rd, Wang Mai, Pathum Wan District, Bangkok 10330, Thailand
² Green Technology Research Co., Ltd. 16 th Floor, AIA Capital Center Building 89 Ratchadaphisek Rd., Dindaeng, Bangkok 10400, Thailand

^* Corresponding author: chayakorn.kar@gmail.com

Abstract

Short-chain fatty acids (SCFAs) have been used as raw materials in wide range of chemical and medical applications. One technique to produce SCFAs is oxidative cleavage of long-chain fatty acids (LCFAs). However, unless the LCFAs are unsaturated, the yield of SCFAs is often very low because the carboxylic group of the fatty acid is more active than other part of the molecule. This work explores the idea of introducing a double bond into saturated LCFA, i.e., stearic acid, via selective dehydrogenation using commercial heterogeneous catalysts. However, cracking of the LCFA is also catalysed. Different type of metals was therefore investigated to study the effect of metals on the cracking and dehydrogenation. The experiments were conducted in an autoclave reactor under inert atmosphere. The temperature was in the range of 250–350°C. The products were analysed by gas chromatography equipped with mass spectroscopy (GC/MS). The results reveal that the introduction of double bond in the aliphatic chain of the stearic acid is possible although the yields of the unsaturated LCFAs are low. Effects of various parameters, such as temperature, pressure, and reaction time, were also investigated and reported.