Method of producing biodiesel fuel

Abstract

A method of producing a biodiesel fuel oil, in which all fats or oils having an acid value of 20 or less can be used as a raw material, and in which no wastewater treatment is needed to thereby attain reduction of environmental load, and in which a biodiesel fuel oil conformable to quality standard levels can be obtained. The process for producing a biodiesel fuel comprises the steps of providing a fat or oil having an acid value of 20 or less as a raw material and heating the raw material oil in vacuum to thereby distill off any moistures, odorous substances and free fatty acids; bringing the raw material oil into contact with a hydrophilic adsorbent to thereby adsorb off any remaining free fatty acids and acidic substances; carrying out an ester exchange reaction in the presence of a potassium based alkali catalyst; and purifying light liquid components as a product of ester exchange reaction in accordance with a nonaqueous method.

Description

TECHNICAL FIELD[0001]The present invention relates to a method of producing a high quality fatty acid biodiesel fuel oil with a high inversion rate even from degraded oils and fats such as waste vegetable oils and the like.BACKGROUND ART[0002]Biodiesel fuel is generally obtained by subjecting vegetable oil and alcohol to an ester exchange reaction to prepare a fatty acid alkyl ester, and used as a diesel combustion fuel. Biodiesel fuel is an oxygenated fuel containing oxygen in its chemical structure, and emits minimal hazardous exhaust gas such as black smoke since it hardly contains any sulfur content. In addition, since biodiesel fuel is plant-derived, the emission of carbon dioxide is counted as zero under the stipulations provided in the Kyoto Protocol. In light of the above, biodiesel fuel is attracting attention as the alternative fuel of light diesel fuel with a low environmental load, and, in Europe and the United States, the standards and legal system for biodiesel fuel ha...

AI Technical Summary

Benefits of technology

[0048]Since heavy liquids contain most of the catalyst that was used in the reaction in addition to the glycerin as the primary component, in order to be used as fuel, generally speaking, a special boiler is required for alkali corrosion, and, when distillation under reduced pressure is performed, polyglycerol is generated, and the distillation yield is 50% or less. Moreover, if general neutralization that uses acid is performed, this will result in a high viscosity slurry or semisolid, and the filtration and removal of salt and the distillation operation will become extremely difficult. Nevertheless, according to the method of the present invention, since the salt after neutralization will take on a large crystal structure as a water-containing crystal of acid potassium salt, the acid potassium salt can be promptly separated, and the system will not become high viscosity, whereby filtration and removal can be easily performed. The subsequent distillation process can also be performed easily, and high purity glycerin can be obtained at a high yield.

[0049]With the method of producing a biodiesel fuel according to the present invention, since the ester exchange reaction in the presence of an alkali catalyst is performed after removing moisture, odorous substances and free fatty acids from the raw material oil as much as possible and the product after the reaction is refined with the nonaqueous method, degraded oils and fats having an acid value of 20 or less can be used as the raw material, and it is possible to produce a biodiesel fuel oil having a low environmental load since it does not require wastewater treatment, and capable of complying with the standard value of impurities that arise during the production in the quality standard of 2007 onward.

Problems solved by technology

Meanwhile, in Japan, approximately 10,000 tons of biodiesel fuel is being produced annually from waste vegetable oil and used, in a limited manner, by local authorities and the like.

(2) High temperature, high pressure uncatalyzed reaction

This is because the conversion ratio is insufficient in other methods.

Nevertheless, with regard to moisture, even if it is thoroughly removed by way of heating and distillation, approximately 500 ppm is the limit.

If further heating is performed in order to additionally lower the moisture value, the biodiesel itself may become decomposed during the foregoing refining process.

Moreover, a major problem that arises during the washing method is wastewater.

However, according to the Act on Prevention of Marine Pollution and Maritime Disaster of 2007, the foregoing wastewater cannot be disposed until it is completely processed, and the consequential cost increase will be enormous.

Nevertheless, when producing a biodiesel fuel oil with the production methods described in the foregoing Patent Documents, depending on the status of the raw material oil before the reaction and that status of the fatty acid alkyl ester after the reaction, it will be difficult to achieve the moisture value of 200 ppm or less, the alcohol value of 1000 ppm or less, and the acid value 0.3 or less as the biodiesel fuel standard values to be set in 2007 onward.

Nevertheless, it is difficult to obtain fresh vegetable oil or animal oil in which glycerol ester has been refined to 100%, and, pursuant to the increase in demands for biodiesel fuel oil, there is now movement of using defective oils and fats and degraded oils and fats such as waste vegetable oil as the raw material oil.

Not only will this deteriorate the reaction yield, refining will also become difficult since it also causes emulsion.

Since the esterification reaction is an equilibrium reaction, the equilibrium is shifted to the product and the yield is thereby increased by excessively using alcohol as one of the raw materials, or removing the water that is created as the side reaction product.

Nevertheless, since the foregoing reactions are basically a homogeneous reaction system in which the catalyst exists in the reaction solution in a dissolved state, there is a problem in that it is difficult to separate and collect the catalyst from the product liquid.

However, when using the foregoing solidification or a solid acid catalyst, although the esterification reaction will sufficiently progress, this alone will result in a low conversion ratio in the ester exchange reaction.

Nevertheless, the reaction is complex with two catalyst systems that completely differ in property, and the operability is inferior such needing to constantly control the first reaction based on the fatty acid content.

However, if the amount of free fatty acids is, for example, 20% or less, then it will result in overinvestment.

Moreover, since the apparatus cost is high and the operation is difficult, there is difficulty in the practical application thereof from the perspective of economic efficiency.

Nevertheless, since the foregoing reaction is a biological reaction, problems essentially remain regarding the reaction speed and conversion ratio since the reaction conditions are mild.

Nevertheless, the realization of this kind of method is difficult for the following reasons.

Nevertheless, since alkali waste will arise with this method, costs will be required for processing such alkali waste.

In addition, the process becomes difficult since a step of removing the moisture in the oils and fats prior to performing the ester exchange reaction is required after the washing step.

Although this method has high removal efficiency, with oils and fats that contain a large amount of unsaturated fatty acids; that is, oils and fats with a high iodine number (80 or higher), the raw material oil will be limited since dimers will be created and the fatty acid structure will change under the foregoing processing conditions, and it will be unsuitable as an oxidized degraded oil.

Thus, the deoxidation method in general fatty chemistry cannot be used as is as the free fatty acid removal method as the preprocessing of biodiesel fuel production that uses various types of oils and fats and their oxidized degraded oils as the raw material oil.

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