Production of fatty acid and fatty acid ester

The present invention concerns a process for forming a fatty acid, a fatty acid ester or a mixture thereof from a starting material comprising soap, as well as use of the formed mixture.

Biodiesel is mainly the methyl ester of fatty acids that is formed through the transesterification of long-chained fatty acids with an alcohol (methanol). The fatty acid esters of natural fats consist mainly of triglycerides, whereby a water-soluble glycerol that is unacceptable as biodiesel is released in the transesterification. Further, an alcohol (methanol) mixed into the aqueous glycerol solution and salts of fatty acids (later soap) are released in the process. This fraction containing glycerol, alcohol and soap still has, particularly with regard to the soap, a high energy content. Theoretically, 10% by weight of glycerol is generated from the triglyceride. Depending on the process conditions, the proportion of the soap can vary greatly and rise up to tens of percent from the original total amount of triglyceride. Since the soap compounds are dispersed and partly dissolved in the aqueous solution of the formed glycerol, their separation from the aqueous solution is difficult. The soap disrupts the phase between the fat-soluble fatty acid esters and the water-soluble glycerol and tends to form different degrees of emulsions, creating a challenging problem in large-scale processes with regard to separation techniques. Removal of the alcohol, such as methanol, would also require expensive vacuum distillation. Thus, it can be concluded, that manufacturing biodiesel using the afore-described method in modern technology is underutilization of the most energy-rich parts of the raw material. Purification of the compounds generated in the process in order to increase their value of use is highly uneconomical already merely with regard to the purification steps required.

To a great extent due to the aforementioned reasons, no cost-effective solutions for the utilization of the mixture of aqueous glycerol, soap and alcohol (methanol) have been found.

There are no business economically advantageous solutions for transforming the multi-component mixtures containing glycerol as a component into commercial products. The significance of this technological deficiency is emphasized particularly as the interest grows towards renewable sources of energy raw materials in addition to the fossil raw materials.

The present invention concerns a process for forming a fatty acid, a fatty acid ester or a mixture thereof from a starting material comprising soap.

More specifically, the process according to the present invention is characterized by what is stated in the characterizing part of claim 1.

The use according to the invention, on the other hand, is characterized by what is stated in claims 15 and 16.

The invention provides a new solution to a problem that relates to a process wherein esters of fatty acids are produced according to an established method using methanol or other short-chained alcohols from glycerolipid-containing fat by treating them with alkali metal alkoxides. Glycerol and other alcohols as well as a water-soluble alkali metal salt of fatty acids, soap, are formed in the process. The glycerol and the soap of the mixture decrease the utilization degree of the total carbon contained in the original fat used in the process and, thus, the economic efficiency of the process. An essential disadvantage of the utilization of the glycerol that is formed in the production of biodiesel, compared with pure glycerol, is the water, the soap and the toxic methanol or other short-chained alcohol it contains as impurity.

It is known that the presence of soap in water and in a mixture containing water-insoluble oil prevents the separation of the aqueous and the oil phases from each other. In the aqueous solution of an impure polyhydric alcohol, the soap disrupts the phase between the water and the lipid formed from fatty acid esters so that separating the phases becomes complicated and, even at the best case, it contains water and other components that better dissolve in the aqueous phase.

An advantage of the invention is an integrated unit operation entity, by means of which an ester that is formed from a hydrocarbon-chain-containing fatty acid and short-chain alcohols can be reformed from a difficulty energy-economically utilizable impure glycerol minor flow, which is released from the transesterification of organic fats. The apparatus used in the process is simple and the technology associated with it is known with regard the production and the use. The process according to the invention is not bound to production scale, but it is readily scalable.

The invention enables, inter alia, the recovery of the energy-rich soap and the recycling into alcohol esters of fatty acids or free fatty acids. A process technical and economical advantage of the invention is that, by means of it, the total utilization of the carbon of the fraction consisting of compounds that contain alcoholic groups and containing impurities can be solved for the manufacturing of fatty acid esters and fatty acids by a process that neither demands energy requiring unit operations, such as heating, nor pressurized unit operations and, which for functioning requires only the use of such chemicals, which can be incorporated into the inner circulation of the process according to the invention.

Compared to the prior art, in every aspect the invention more efficiently fulfils the principles of sustainable development by intensifying the total utilization of the raw materials and by thus decreasing the need for using other raw materials. The process according to the invention consists of a functional entity having the prerequisites for updating the production costs of fatty acids and alcohol esters thereof to a level accepted by consumers.