Production of Sustainable Diesel via Decarboxylation of Palm Stearin Basic Soaps

Abstract

Production of sustainable diesel was conducted via hydrogen-free decarboxylation of palm stearin basic soaps. Metal soaps are alkaline earth and transition-metal salts combined with carboxylic acids with 7−22 carbon atoms. Stearin basic soaps were prepared by direct reaction of palm stearin and mixed metal (Ca, Mg, and Zn) hydroxides. The stearin basic soaps were decarboxylated at 370 °C for 5 h to produce liquid crude bio-hydrocarbon, also known as sustainable diesel. The stearin basic soaps were characterized by Fourier transform infrared (FTIR) and thermogravimetric analysis, and the resulted liquid bio-hydrocarbons were analyzed by GC equipped with a flame ion detector. The hydroxyl band at 3678 cm −1 observed from FTIR spectroscopy indicated that the Ca/Mg/Zn ions were associated with the −OH ions in the compounds. This proved that the soaps produced from this work were basic metal soaps. The thermal stability of the soaps was examined up to 1000 °C, and the decomposition of stearin basic soaps was observed in the range of 300−500 °C. The metal contained in the basic soaps affected their thermal characteristics. Liquid crude bio-hydrocarbon with carbon chain length between 8 and 20 has been obtained from decarboxylation of stearin basic soaps. In this study, the decarboxylation of stearin basic soaps resulted in sustainable diesel as the main product. This promising process is expected to open a plethora of opportunities in the production of sustainable diesel.

The effect of Ca/Mg/Zn mixing ratio on the research octane number of bio-gasoline during basic soap pyrolysis

“…Table 2 shows that the quantity of water as a pyrolysis product is relatively low (average 2.7 wt%). This quantity also occurred in several previous soap pyrolysis studies [ 29 , 30 ]. According to Eq.…”

“…It depended on the degree of basic soap dehydration. This phenomenon was supported by several previous researchers who discovered high olefins in the liquid product of soap pyrolysis [ 21 , 29 ]. In addition, both studies carried out soap pyrolysis in a batch reactor.…”

“…Table 2 shows that the quantity of water as a pyrolysis product is relatively low (average 2.7 wt%). This quantity also occured in several previous soap pyrolysis studies [30,29]. According to equation 3, the pyrolysis of basic soap should be a hydrocarbon and mixed metal carbonate.…”

“…The yield of gaseous products reached 7.5 wt%. Meanwhile, Pratiwi [ 29 ], with the same feed, obtained a gas product of 22.8 wt%. This difference was possible due to the difference in pyrolysis temperature used.…”

“…This achievement was almost similar to the previous research. The research studied gasoline hydrocarbons from catalytic pyrolysis [ 29 ] of soapstock over corn cob-derived activated carbons. The yield of gasoline rage hydrocarbon could reach up to 91.03%-mass [ 44 ].…”