Catalytic synthesis of biodiesel from Jatropha oil in acidic ionic liquids
In February 2011, biomass group (http://brg.groups.xtbg.ac.cn/) in XTBG, CAS reported their new progress on Jatropha biodiesel production. Results were published in the international journal “Bioresource Technology” (http://dx.doi.org/10.1016/j.biortech.2011.02.079), and filed a Chinese invention patent.
Biodiesel is an environment-friendly, renewable, high-qualified and green fuel. Development of biodiesel to replace fossil fuels could strengthen the energy security in China, improve environment and promote rural economic development. Traditional methods for biodiesel synthesis use liquid acids and bases, which complicate production processes and corrode equipments, and result in many difficulties in catalyst recovery, by-product glycerol refinery and wastewater treatment. Thus, it is needed to find new catalysts which are highly-active, stable, recyclable and reusable. Recently, Dr. Feng Guo and Professor Zhen Fang found a new one-step method to transform un-pretreated and high-acid-value (13.8 mg KOH/g) Jatropha oil directly to biodiesel, using inexpensive commercial ionic liquids as solvents and catalysts. The new method could be regarded as a good alternative for the conventional and time-consuming two-step process. Acidic ionic liquid catalyzed not only the esterification of free fatty acids to methyl esters, but also the transesterification of triglycerides to biodiesel. Under the synergistic catalysis of Brønsted acid of acidic ionic liquid and Lewis acid from metal chlorides, biodiesel yield was enhanced to 88%. Methanol could be recycled after the esterification and transesterification. Ionic liquids were recovered through centrifugation and distillation. The recovered ionic liquids could be reused after drying. The experimental results provide a new way to produce biodiesel quickly and greenly from low-quality plant oils or animal fats.
Acidic ionic liquids with -SO3H functionality exhibit features as both solvents and Brønsted acids. They have some excellent properties, such as low vapor pressure, incombustibility and thermostability (-40～300 oC). Meanwhile, they are Lewis or Franklin acids. They are environment-friendly and widely used in fields like catalysis, organic synthesis, separation and electrochemistry. The application of ionic liquids in energy and chemical engineering has been developed rapidly in the last years, and will go further for a period in future. Until now, our knowledge about the influence of ionic liquid on chemical reactions is limited and still stays at an early stage. However, with their development and advancement in fundamental and applied research, ionic liquids uses as solvents and catalysts would expand explosively into more research fields.
Related references:
- F. Guo, Zhen Fang*, X. F. Tian, Y. D. Long, L. Q. Jiang, One-step production of biodiesel from high-acid value Jatropha oil in ionic liquids, Bioresource Technology, 102, 6469-6472 (2011).
(http://dx.doi.org/10.1016/j.biortech.2011.02.079)
- F. Guo, Zhen Fang. A method for biodiesel production catalyzed by ionic liquid. (Patent number: CN201010578591.1)