Process for production of Fatty Acids Methyl Esters from Raw Natural Vegetable and Recycled Oil

 

The present invention relates to the production of methyl acid esters starting from unrefined natural oils or fats as well as recycled oil.

It is well known that methyl esters of fatty acids become in the last decade very interesting. They are used mostly as biodiesel - the substitute for fossil fuel and as starting material for production of other derivatives of fatty acids such as alcohols and amides.

The process for industrial manufacturer of the above mentioned esters is very simple and consists of the reaction of triglycerides, (the main constituents of fats and oils), with methanol under the presence of catalysts. In this reaction glycerol is obtained as by product. Glycerol is also useful starting material for other chemicals and purified is valuable supplement for pharmaceutical products. The production process was developed during the last decade in order to improve the yield and economical efficiency and to make possible using of different starting materials. During the time the first used raw material - refined rapeseed oil becomes too expensive and the raw material base was therefore extended.

Classic Process

In the classic manufacturing procedure for transesterification of triglycerides basic catalyst (NaOH, KOH, NaOCH₃) are applied. These catalysts are from chemical point of view very efficient, but they have several disadvantages [G. Vicent et al Ind. Crops and Prod. 8 (1998), 29-35]:

• Free fatty acids, which are always present in same extent in raw material, are consuming catalyst for neutralization giving soaps. This by product means decreasing of yield by loosing of the part of raw material.
• On the other hand soaps are causing problems in downstream processing, specially glycerol purification. The most practical equipment for distillation of glycerol (thin - layer evaporators) are not applicable because of the presence of soaps and inorganic salts formed by neutralization of basic catalyst in the end of transesterification reaction. Difficulties in glycerol purification mean increasing the price of biodiesel. There is a possibility to remove inorganic salts by ion-exchange process, but this means again increasing of manufacturing price and decreasing the efficiency of methanol recycling and the yield of glycerol.

 

Modification

Process was then developed in order to avoid loosing of free fatty acid and to use raw materials with higher acids content. In Patent [WO 01/12581] free fatty acids are in 1 stage of process esterified by acidic catalyst, and in 2 stages acidic catalyst is removed by neutralization with base, and with excess of base transesterification reaction is carried out. In this method additional problem is removing of salt formed in neutralization of acidic catalyst.

According to Patent [U.S. 6,399,800] esterification of the free fatty acids is solved in the following manner:

• Saponification of total amount of material is carried out
• Water is removed
• Esterification of the dry saponification rest is carried out by adding corresponding alcohol and inorganic acid

Several methods for removing of free fatty acids before transesterification reaction were also known. These include separation of free fatty acids from raw oil by caustic washing, steam stripping and liquid extraction. The big disadvantage of caustic washing is loss of oil in the processing, which can amount to twice the amount of free fatty acid present in starting raw oil.

There was always the interest to discover catalyst and process, which can accept very wide range of raw materials with rather high free fatty acids content and carry out esterification and transesterification simultaneously.

 

"New process"

According to our inventive process the advantages of alkaline transesterification of triglycerides and esterification and transesterification of triglycerides with homogenous catalyst were joined together. This is reached by carrying out conversion of oils into one or maybe two steps. (See enclosed scheme.)

 

 

Advantages of "New process":	Disadvantages of "New process"
Very short reaction time, 30 min >95% reaction No salt No soap Waste is 99% water No stirring Simple distilling of glycerol	High temperature High pressure Distilling of methyl esters fatty acid if only one step reaction is used

In laboratory experiments "new process" proved to be very successful. Laboratory results esterification and transesterification in one step are shown in table below.

Batch	First stage
	monoglycerides[%]	diglycerides[%]	triglycerides[%]
B-125	3.68	0.43	0.7
B-126	3.52	0.18	0.03
B-127	3.95	0.07	0
B-128	3.1	0.17	0.05
B-129	3.11	0.2	0.01

Glycerol purity: >95%

Comparison of classic method and "New process"

	Classic process	"New process"
Raw material
Crude oil (soy, rapeseed, palm, coconut, sunflower, jatropa)	no	yes
Crude oil with more than 0.5% of free fatty acid	no	yes
Recycled oil	no	yes
Lard	no	yes
Treatment of raw material
Degumming	yes	no
Deodoration	yes	no
Bleaching	yes	no
Reduction of free fatty acid content	yes	no
Constraints of process
Soap formation	yes	no
Glycerol pretreatment for further usage	yes	no
Esterification	90%	-
Transesterification	>90%	-
Esterification and transesterification in first stage	-	>95%
Yield	90-95%	>95%
Temperature required	low	high
MeOH consumption	low	depends
First stage duration	60 – 120 min	30 min

"New process" has been presented on 31st Croatian Invention Show with International Participation - INOVA 2006, where it was awarded with bronze medal by Jury of Experts.

 

Contact

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