Continuous process for producing biodiesel fuel

Abstract

A continuous process for producing biodiesel fuel with a conversion of triglycerides in biodiesel above 99.90% by weight in the transesterification step, which comprises the following steps:a) providing a triglyceride source at a triglyceride concentration above 99.0% by weight;b) subjecting triglycerides to a transesterification reaction with methanol, ethanol, or the mixtures thereof, at a molar ratio of triglycerides:alcohol 1:3-3.5, in the presence of 0.7 to 1.0% by weight of sodium or potassium hydroxide as catalyst, under ultrasonic cavitation conditions in an ultrasonic cavitation reactor with 2 to 8 serial cavitation cells, at a temperature of 45 to 60° C., at a pressure of 1.5 to 2 MPa (15-20 atm) and during a period of time of 15 to 30 seconds;c) recovering the product of step b) and subjecting it to mechanical agitation operation, at a temperature of 45 to 60° C. for a maximum of 10 minutes, up to the completion of the transesterification reaction, thus obtaining a conversion of triglycerides in biodiesel above 99.90% by weight;d) decanting and / or centrifuging the product resulting from step c) to remove glycerin;e) purifying biodiesel obtained in step d) by exchange resins; andf) removing by distillation methanol and water from the product of step e) and recovering the biodiesel fuel thus obtained.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a continuous process for obtaining biodiesel fuel.[0002]This semi-synthetic type of fuel is used in pure form or blended with diesel fuel (also known as gasoil) for the operation of diesel engines.[0003]The advantages of biodiesel fuel, compared to its fossil equivalent, diesel, have been known for many years:[0004]This fuel derives from renewable resources.[0005]It can be blended with diesel fuel at any rate, without altering the normal operation of the engine.[0006]Biodiesel reduces dioxide emissions to the atmosphere, which are the main cause of the greenhouse effect that produces global warming, as well as sulfur and carcinogenic aromatic component emissions.[0007]Finally, biodiesel is biodegradable, i.e. it is beneficial to the environment, and can be perfectly blended with gasoil: it neither starts nor bursts easily because it has a high ignition point or temperature.[0008]Biodiesel is obtained from new or used veget...

AI Technical Summary

Problems solved by technology

Even though there are many technologies for carrying out the transesterification reaction, all of them have technical drawbacks and economic disadvantages.

These sudden decompressions may cause small gas bubbles, which subsequently collapse.

This physical phenomenon results, at liquid volume level, in a violent agitation and the subsequent mixture of the liquid.

Firstly, the need of an agitated-tank-type reactor after the cavitation reactor, designed for a residence time of about 1 hour, in order to obtain an acceptable triglyceride conversion, implies large and expensive structures for biodiesel production at industrial scale.

Secondly, the need of a reactor downstream from the cavitation reactor for obtaining acceptable levels of final conversion in the transesterification reaction (96-98%), within a considerably high residence time (1 hour), indicates that the conversion of triglycerides in biodiesel within the cavitation reactor is far from being optimal.

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