WO2008003154A1

WO2008003154A1 - A process and a reactor for the production of biodiesel

Info

Publication number: WO2008003154A1
Application number: PCT/BR2007/000173
Authority: WO
Inventors: Sérgio DI BONAVENTURA
Original assignee: Etruria Indústria De Fibras E Fios Sintéticos Ltda.
Priority date: 2006-07-05
Filing date: 2007-07-04
Publication date: 2008-01-10
Also published as: BRPI0602511A

Abstract

The present invention relates to a reactor (1 ) for conversion, in continuous flow, of vegetable oils, animal fat or oils from fry into biodiesel, as well as to process of producing same.

Description

Title: "A PROCESS AND A REACTOR FOR THE PRODUCTION OF BIODIESEL"

Filed of Application

The present invention relates to a reactor for conversion, in continuous flow, of vegetable oils, animal fat or used fry oils into biodiesel, as well as to the production process. The filed of application includes the agricultural and livestock industry, chemical industry, energy sector, as well as recycling and environment-preservation activities. Description of the Prior Art The terms "biodiesel", "ecodiesel" and "diesel-Bi" apply to the alternative fuel made of methyl or ethyl ester of vegetable oils, which has been commercialized either in its pure form or as a mixture since the mid- 1990's. The raw materials for the production of Biodiesel are oils and fats of vegetable or, less frequently, of animal origin. In a simple processing step, these raw materials, which belong to the triglyceride class, are converted into esters with properties comparable to those of conventional diesel. Besides, these esters have other advantages too: they are eco-friendly products and are not harmful to engines, preserve the fossil energy resources and, since they are renewable raw materials, they guarantee employ in agriculture and in the planting and oil-processing industry.

At present, Biodiesel is the only fuel obtained from renewable raw materials that is available on the world market with an appropriate infrastructure, duly tested from the technological point of view and, what is more important: it can replace diesel from fossil origin on conventional engines, without the need for adaptations.

Biodiesel also has unforgettable advantages for the environment, namely:

- according to a study made by Shell Global Solutions, the replacement of 212,000 tons of conventional diesel with 250,000 tons of biodiesel (equivalent in oil) reduces CO2 emissions by approximately 420,000 tons;

- in Brazil, conventional diesel has been supplied with low sulfur content. In order to provide this fuel with the necessary lubricity, however, biodiesel may be added as an additive;

- the emission of particulate materials into the atmosphere is reduced by half when Biodiesel is used, and the levels of carbon monoxide and of hydrocarbons are significantly lower, especially on commercial vehicles;

- Biodiesel does not present any storage or transport problem; it is not rated as a dangerous substance of flammable liquid;

- it is biodegradable and, for this reason, it may be used even in places where legislation is applied to regulate emissions of pollutants in water, such as boats with Diesel engines.

There are four ways to produce biodiesel from oils and fats, namely: 1) direct use and mixture, 2) microemulsions, 3) thermal breakup (pyrolysis) and 4) transesterification (Ma, F. & Hanna, M., Bioresource Technology 70 (1999) 1-15). The direct use of vegetable oils as fuel has many drawbacks, such as high viscosity, low volatility and the presence of free carboxylic acids. The greatest problems related with the direct use of vegetable oils as fuel are: incomplete combustion, which leads to the formation of carbon deposits on the engine and the increase in viscosity of the oil due to the polymerization of unsaturated carboxylic acids. Although the problem of high viscosity can be solved by using microemulsions employing alcohols as surfactants, the use of these microemulsinos is limited by their instability at high temperatures and by the tendency of alcohol to absorb water at these temperatures. The thermal breakup or pyrolysis leads to the formation of paraffins, olefins and unsaturated methyl esters with a compositions similar to that of petroleum derivatives, and removes partly the environmental benefits of the use of an oxygenated fuel such as biodiesel.

Transesterification is the process most frequently employed for obtaining biodiesel from vegetable oils and animal fats. The , transesterification reaction is affected by the molar ratio between glycerides and alcohol, catalysts, temperature and reaction time, contents of water and of free carboxylic acids present in the oils and fats. It is known that the process of producing biodiesel by transesterificationis based on the employ of vegetable oils and methyl alcohol under heating. In this reaction the triglyceride is replaced by methanol, resulting in the methyl ester of the vegetable oil. In the past 10 years, this type of biodiesel came to be commercialized on a large scale in the European Union, where canola and colza seeds, with a production of 8.9 million tons in 2001 , is the most important source of raw material for the biodiesel industry. It is the only oleaginous plant that can be cultivated even under the climatic conditions found in Northern Europe. With a solidification point between -6% and -9%, the oil is quite suitable for use as fuel, which in the form of an additive guarantees a reliable operation of the engine, even at -2O⁰C. At present, 2% of the consumption of fuels in Diesel engines in Germany is already being met by Biodiesel from canola oil. The greatest producers of canola oil in the European Union are Germany (3.8 billion tons), France (3.3 million tons) and Great-Britain (1.2 million tons).

In the United States the main raw materials are soybean oil and methanol, which is a derivative of natural gas or of petroleum. In Brazil a few research groups and small producers use methanol, as in the European and American process, but together with soybean oil, babassu oil and other virgin oils, besides fry oils. The use of methanol, a toxic, poisonous alcohol of fossil origin (petroleum derivative) is one of the great disadvantages of this process, coupled to the fat that approximately 50% of the methanol consumed in this country for other purposes is imported.

An interesting alternative is the use of ethyl alcohol (ethanol), which results in ethyl ester of the oil. Ethanol, obtained from sugar-cane, is 100% renewable and guarantees greater safety in handling by virtue of its lower toxicity. Besides, in Brazil there is much sugar-cane alcohol available, this country having about 50,000 sugar-cane planters and 304 sugar-cane and alcohol mills. This country is the largest world producer of ethanol with 36% of the total produced in the world, but so far this alcohol could not be employed with efficacy as a substitute for methanol due to the low rate of conversion of vegetable oils into biodiesel and also to the difficulty of separating the phases constituted by biodiesel and the by-product called glycerin. Processes achieved in the past few years, as shown in documents Pl 0105888, WO04096962 and Pl 0104107, have increased the chances of the use of ethanol as a substitute for methanol becoming feasible, which makes Brazil a natural candidate to become a large producer of biodiesel. In addition to large plants producing ethanol, Brazil has a production of oleaginous seeds classified as one of the largest in the world, besides soybeans, also castor beans, palm (oil palm), pea-nut, cotton, sunflower, babassu, edible pine seed, forage turnip, and so on. The production of methyl esters or ethyl esters (biodiesel) is the result of a transesterification in which vegetable oil is mixed with anhydrous alcohol in excess at the molar ratio of 1 :6 with 1 % or 2% catalyst, wherein NaOH, KOH or NaOCH3 is generally employed.

When the transesterification is catalyzed by bases, it is necessary for the contents of free carboxylic acids to be low and for the triglyceride and alcohol used to be anhydrous. The presence of free acids requires a larger amount of catalyst to neutralize them, and water, in turn, causes saponification, decreasing the yield in the production of esters. The formation of soap causes an increase in viscosity and formation of gel, making the separation of the esters obtained difficult. US Patent 2,383,601 recommends the use of anhydrous alcohol when the content of free carboxylic acids is high.

As a result of the transesterofication process, one obtains at the same time methyl or ethyl esters, glycerol and alcohol dissolved in water and recovered through separation by difference in density and azeotropic distillation. In the transesterification process the two reactions, hydrolysis of the triglyceride and esterification of the released carboxylic acid, take place in a single step with a single 2-phase reaction.

A few problems, however, occur in the transesterification process when ethanol is used to replace methanol. These problems result from the tendency of the esterification reaction to reversibility when the process is carried out in batch, resulting in a yield of approximately 60% with respect to ethyl esters. The use of anhydrous ethanol in excess and the search for other catalysts have been the target of researches aiming at an improvement in the yield of the reaction. The need for subsequent rectification and dehydration of the alcohol and the cost of other catalysts are negative factors in the process. With a view to overcome the deficiencies of the batch process, especially the low yield in the formation of ethyl ester and, at the same time, to increase the productivity of industrial biodiesel plants, continuous processes have been proposed, among which the one described in US patent application 2006/0069274. This document describes a continuous process of producing ethyl esters (biodiesel) through two steps thus divided: 1) hydrolysis of the triglycerides present in the vegetable oils at a temperature of approximately 6O⁰C under atmospheric pressure, separating the triglycerides into free carboxylic acids and glycerol, and 2) esterification of the free carboxylic acids with hydrated ethyl alcohol. The reactions take place in two separate columns, filled with a heterogeneous catalyst containing calcium oxide and magnesium. The separation of the glycerol from the free carboxylic acids resulting from the first column is carried out by difference in density, and the carboxylic acids are mixed with hydrated ethanol in the second column at the molar ratio of 1:2. The ethyl esters dissolved in ethanol resulting from the second column are then separated from the water by difference in density. The ethyl ester solution mixed with ethanol is then separated by fractional distillation.

Application WO 2004/096962 describes the esterification, with an acidic solid catalyst, of carboxylic acids resulting from the palm-oil refining process at temperatures ranging from 12O⁰C and 17O⁰C. In this document it is emphasized that the addition of alcohol in stoichiometric excess is of extreme importance for the yield of the reaction. Alcohol : carboxylic acid molar rations used in the esterification reactions range from 6:1 to 12:1.

Document PI0404243 describes a continuous process of producing biodiesel from semi-refined vegetable oil, anhydrous alcohol (methanol or ethanol) and alkaline catalyst. The process uses anhydrous alcohol in excess (180 to 600 kg of alcohol per ton oil), being composed of two transesterification reactors arranged in series, responsible for the conversion of alcohol into biodiesel. After a predetermined time of contact of the oil, alcohol and catalyst, and after the balance point has been reached, the products formed in the first reactor are sent to the evaporator, where the excess alcohol is evaporated and condensed. The non-evaporated product (oil, biodiesel and glycerin residues) is then centrifuged, and separation of glycerin takes place. After separation, the biodiesel formed, just as the oil residue receive a new dosage of anhydrous alcohol and alkaline catalyst, following then to the second transesterification reactor. The process that took place in the first reactor is repeated in the second one, the biodiesel, after centrifugation and separation of glycerin, undergoing an acidic wash for removing soaps formed in the reaction with alkaline catalyst. The biodiesel is then centrifuged for separating wash water and impurities, heated and sent to a vacuum dryer, where the moisture and alcohol residue is eliminated, being at this point within the international standards.

Document PI0502891 describes a continuous process of producing biodiesel without a catalyst. In this process the mixture containing alcohol (ethanol or methanol) and vegetable oil is pumped to a tubular reactor, subjected to a pressure of 20 - 400 Bar and temperature between 15O⁰C and 45O⁰C with a residence time between 30 s and 180 min. The mixture resulting from the reaction presents an upper phase containing (predominantly) alcohol, an intermediate phase containing biodiesel and a lower phase containing glycerin. The non-reacted alcohol is separated by difference of density and evaporation, and may be led again to the reactor inlet tubing or used as fuel for keeping the temperature in the tubular reactor. In this scenario, the applicant provides a process for the production of biodiesel, which comprises reacting C1-C3 alcohol and oil of vegetable or animal origin or fat in a stoichiometric proportion, in a continuous-operation horizontal tubular reactor. Objectives of the Invention

A first objective of the present invention is to provide a reactor for the production of biodiesel, which operates continuously. A second objective of the present invention is to provide a process for the production of biodiesel, using the above-mentioned reactor, which has a reaction-medium recycle stream and uses a stoichiometric proportion of the reactants C1-C3 alcohol and oil of vegetable or animal origin or fat, with reduced input and production costs. Brief Description of the Invention

The first objective of the present invention is achieved by means of a reactor presenting tubular shape and horizontal arrangement, comprising perforated discs, arranged perpendicularly with respect to a central reaction axis, said discs defining sections in which stirring means are provided.

The second objective of the present invention is achieved by means of a process for the production of biodiesel, which comprises contacting oil of vegetable or animal origin or fat with C1-C3 alcohol in a stoichiometric proportion in a reactor as defined above. Brief Description of the Figures

The present invention will now be described in greater detail with reference to an embodiment represented in the drawings. The figures show:

- Figure 1 illustrates a process of acidic degumming of vegetable oils; - Figure 2 shows a schematic view of the reactor for producing biodiesel used in the present invention, and Figure 2 shows a sectional view of a reactor element disc;

- Figure 3 shows a flow diagram of the process of producing biodiesel of the present invention. Detailed Description of the Invention

The present invention provides a reactor 1 and a continuous process for the production of biodiesel, wherein the reactor 1 , illustrated in figure 2, has tubular shape and horizontal arrangement, comprising perforated discs 2 arranged perpendicular to a central axle 3 of the reactor 1 , said discs 2 defining sections 4 in which stirring means 5 are provided.

The reactor 1 may comprise from 2 to 10 perforated discs 2, preferably presenting a plurality of bores 6 arranged circumferentially and concentrically, through which the reaction mixture is pumped (Figure 2). The perforated discs 2, arranged perpendicularly with respect to the central axle 3, define sections 4 within the reactor 1 , where the mixture of the reactants and the reaction take place. The reactor 1 preferably comprises 3 to 11 sections 4.

Additionally, the reactor 1 comprises stirring means 5 located in the sections 4 defined by the discs 2, the preferred stirring means being stirring blades, which may be present in a number from 3 to 22 stirring blades. Said blades are usually provided with a plurality of openings 7 arranged along its length, which decreases the resistance to its movement, while favoring the mixing of the reaction medium (Figure 2). The driving of the central axle 3 of the reactor 1 promotes simultaneous movement of the perforated discs 2 and of the stirring means 5, favoring the mixing of the reaction medium and, consequently, the formation of biodiesel. The reactor 1 , which presents a diameter : length ratio (d:c) ranging from 1 :5 to 1 :15, is especially designed for the production of biodiesel in continuous condition and may be made from any material compatible with the process, such as, for instance, stainless steel, carbon steel and other materials.

The continuous process for the production of biodiesel of the present invention comprises contacting oil/fat of vegetable or animal origin with C1-C3 anhydrous alcohol in a stoichiometric proportion, using the tubular reactor described before and a catalyst, wherein one can employ, in addition to other alkaline catalysts, NaOH, KOH, NaO-CH3, methoxides or mixtures thereof. With a view to favor the efficiency of the process, a recycle stream of 20% of the reaction medium is provided in the reactor (Figure 3). A reaction-medium recycle line located at the final end of the rector, operated by a pump and controlled by a valve, is used permanently during the continuous conversion process, recycling from 10 to 30% of the reaction medium to entry of the reactor 1 (Figure 3). The process of the present invention uses, as one of the reactants, C1-C3 anhydrous alcohol, comprising methanol or ethanol or propanol or a mixture thereof. Oil / fat used in the process may be of vegetable or animal origin. When the oil / fat used is of vegetable origin, it may be of any type, being preferably chosen from peanut oil, soybean oil, maize oil, colza oil, castor oil, palm oil, cotton-seed oil, sunflower-seed oil, babassu oil, edible-pine-seed oil, forage-turnip oil or mixtures thereof. The use of vegetable fry oils as a reaction raw material too is permitted for the process in question.

Oil / fat to be used in the process may also be of animal origin, preferably ox tallow, fish oil / fat or oil / fat from poultry raising or mixtures thereof. Besides being used in the transesterification process through mixture with a catalyst and alcohol ( for conversion into biodiesel), the crude oil used as a raw material undergoes an acidic degumming process. The acidic degumming process is shown in Figure 1 and summarized in the following steps: the crude oil stored in the lung tank 21 is transferred through a pump 22 to the heater 23 at about 8O⁰C, hydrated and centrifuged, mixed with phosphoric acid at +/-0.5% (dosing system) through a dosing pump 24. The mixture of the oil with acid is carried out by means of a dynamic mixer 25, following to the acid/oil contact tank 26, where it remains for 20 minutes at 7O⁰C in a tank provided with a stirrer for hydration of the non-hydratable gums. The acid/oil mixture receives a dosage of caustic soda according to the acidity index (stoichiometric quantities) through a dosing pump 27, being again mixed in a dynamic mixer 28 and again heated through a heat exchanger 29, following to the soda/oil/acid contact tank 30, being then centrifuged 31 for removal of the gums. The centrifuged mixture is then transferred to the lung tank 32, receiving a dosage of soap sequestrants (0.2%) through a dosing pump 33, passing through a dynamic mixer 34, following to a sorting tank 35, where it undergoes a drying process with vacuum pumps. The thus obtained material is transferred to the lung tank 36, led to the press filter 37, where the removal of soaps and impurities takes place, cooled in the cooler 38 and stored in a reservoir 39, where the degummed crude oil will be used for feeding the bioconversion process (transesterification reaction), as illustrated in Figure 3. Before entering into the reactor 1 , the reactants composed of

(C1-C3) anhydrous alcohol and pre-purified oil according to the previous scheme are pre-mixed with the catalyst and a part of the reaction medium

(obtained by recycle) in a dynamic mixer at a temperature ranging from 6O⁰C to about 100⁰C, preferably at a temperature of 7O⁰C (Figure 3).

From the dynamic mixer the mixture enters into the cylindrical reactor 1 , which is pressurized with high pressure pumps, where it undergoes a number of stages and changes into biodiesel and glycerol. The reaction process takes place at a temperature ranging from about 6O⁰C to about 100⁰C, preferably at a temperature of 7O⁰C.

The presence of internal stirrers in the reactor 1 , separated by a number of perforated discs 2 having rounded bores associated to the internal work pressure of the reactor 1 , which ranges from 2 kgf/cm2 to 6kgf/cm2, regulates the displacement of the reaction medium and the product, increasing the efficiency of the reaction and reducing the residence time.

The continuous reaction process is characterized in that the residence time of the reaction medium in the reactor 1 ranged from about 20 to 40 minutes, being preferably a residence time of 30 minutes.

The flow diagram of the biodiesel production process of the present invention is shown in Figure 3. The degummed oil is initially heated to about 8O⁰C in an oil heater 15, which is led to a tank through the vacuum system 16. Later one doses the catalyst 17 and methanol 18, which are led to the dynamic stirrer 19, reaching the reactor 1. During the bioconversion process, a part of the reaction medium is recycled through the recirculation pump 20 to the mixer 19, being again led to the reactor 1. After coming out of the reactor 1 , the mixture containing biodiesel and glycerol is transferred to a lung tank 8, where the natural evaporation alcohol that possibly did not react in the process takes place. From the lung tank 8, the final procedures of purifying the biodiesel are conventionally carried out, in accordance with the following steps:

1 ) centrifuging to separate the clycerol through the centrifuge 9;

2) dosing approximately 0.2% of soap sequestrants through the dosing pump 10;

3) dynamic mixing for homogenization, using the mixer 11 ;

4) stirring and drying in an appropriate tank (heating and vacuum pump), just as in the evaporator 12; 5) filtering through the press filter 13 to retain impurities;

6) cooling by using the cooler 14;

7) biodiesel ready for consumption; and

8) storing.

Preferred embodiments having been described, one should understand that the scope of the present invention embraces other possible variations, being limited only by the contents of the accompanying claims, which include the possible equivalents.

Claims

1. A reactor characterized having a tubular shape and horizontal arrangement, comprising perforated discs (2) arranged perpendicular to a central axle (3) of the reactor (1 ), said discs (2) defining sections (4) in which stirring means (5) are arranged.

2. A reactor according to claim 1 , characterized by comprising 2 to 10 perforated discs (2).

3. A reactor according to claim 2, characterized in that the perforated discs (2) comprising a plurality of bores (6) arranged circumferentially and concentrically.

4. A reactor according to claim 1 , characterized by comprising 3 to 11 sections (4).

5. A reactor according to claim 1 , characterized in that the stirring means (5) are stirring blades.

6. A reactor according to claim 5, characterized by comprising 3 to 22 stirring blades.

7. A reactor according to claim 6, characterized in that the stirring blades (5) are provided with a plurality of openings (7) arranged along its length.

8. A reactor according to claim 1 , characterized in that the driving of said central axle (3) promotes the simultaneous movement of the perforated discs (2) and stirring means (5).

9. A reactor according to claim 1 , characterized in that the ratio between diameter and length (d:c or d:l) of the reactor (1) ranges from about 1 :5 to 1 :15.

10. A reactor according to claim 1 , characterized by operating in a continuous production condition.

11. A reactor according to claim 1 , characterized by being made from stainless steel or carbon steel.

12. A reactor according to claim 1 , characterized by having an outlet for circulation of recycle stream.

13. A process for the production of biodiesel, characterized in that it comprises contacting oil of vegetable or animal origin or fat with C1-C3 alcohol in stoichiometric proportion ion a reactor as defined in any of claims 1 to 12.

14. A process according to claim 13, characterized in that the oil of vegetable origin may be chosen from peanut oil, soybean oil, maize oil, colza oil, castor oil, cottonseed oil, sunflower-seed oil, babassu oil, edible pine seed, forage turnip, vegetable oil from fry or mixtures thereof.

15. A process according to claim 13, characterized in that the oil / fat of animal origin may be chosen from ox tallow, fish oil / fat or oil / fat from poultry raising or mixtures thereof.

16. A process according to claim 13, characterized in that the C1-C3 alcohol is anhydrous and chosen from methanol, ethanol, propanol or mixtures thereof.

17. A process according to claim 13, characterized in that it takes place at a temperature ranging from about 6O⁰C to about 100⁰C.

18. A process according to claim 13, characterized in that it takes place at a temperature of 70°c.

19. A process according to claim 13, characterized in that it takes place under a pressure ranging from 2 kgf/cm² to 6 kgf/cm².

20. A process according to claim 13, characterized in that the residence time ranges from 20 to 40 minutes.

21. A process according to claim 20, characterized in that the residence time is of about 30 minutes.

22. A process according to claim 13, characterized in that the reactants are pre-mixed before entering into the reactor (1 ).

23. A process according to claim 13, characterized by comprising a recycle stream of about 20% that returns to the feed of the reactor (1 ).

24. A process according to claim 13, characterized in that the reaction is catalyzed by sodium or potassium hydroxide or methoxides or mixtures thereof.