US20100242348A1

US20100242348A1 - Method of increasing transesterification conversion of oils

Info

Publication number: US20100242348A1
Application number: US12/796,982
Authority: US
Inventors: Yi-Hung Chen; Ching-Yuan CHANG; Yu-Hang HUANG; Rong-Hsien LIN
Original assignee: National Kaohsiung University of Applied Sciences
Current assignee: National Kaohsiung University of Applied Sciences
Priority date: 2007-01-16
Filing date: 2010-06-09
Publication date: 2010-09-30

Abstract

A method that can effectively increase the transesterification conversion of oils comprises the following steps of setting a rotating packed bed reactor for performing centrifugal rotation, centrifugally rotating the rotating packed bed to rotate relative to the container by the drive shaft; heating the oils and additives being heated to arrive at a temperature range approximately between 40 degrees Celsius to 100 degrees Celsius before entering the rotating packed bed; injecting the oils and the additives; performing the transesterification reaction, wherein the oils and the additives are delivered by a centrifugal force to pass through the stainless steel filler in the packed reaction region; performing the transesterification reaction with a rotation speed range of approximately 300 rpm to 1500 rpm; inducing a phase separation; and collecting the effluent at the outlet of the rotating packed bed reactor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part patent application of U.S. application Ser. No. 12/014,052 filed on Jan. 14, 2008, the entire contents of which are hereby incorporated by reference for which priority is claimed under 35 U.S.C. §120.

FIELD OF THE INVENTION

The present invention relates to, and more particularly to biodiesel, and more particularly to a method of increasing transesterification conversion of oils by using a rotating packed bed reactor.

BACKGROUND OF THE INVENTION

Increasing growth of industries, transportations and commercial activities have resulted enormous quality of petroleum consumption. But due to limited petroleum resources, the petroleum price has risen sky-high in recent years. The rising of fuel prices and the pressing need of cutting carbon dioxide emissions are the two essential issues our industries must address and solve quickly. Many studies are conducted regarding alternative fuels. Biodiesel is one alternative fuels that are considered to replace petroleum fuel.
Biodiesel is converted from edible oils such as vegetable oil and animal fat by alcoholysis to form modified oils that can be used as renewable fuel. Because the edible oils are derived from carbon dioxide in the atmosphere via photosynthesis mechanism of plants, the gases discharged from the burning of biodiesel make nearly null increase in the greenhouse effect. However, petroleum fuels are drawn from carbon stores in the earth's crust and used accompanying the release of carbon dioxide to the atmosphere. Therefore, biodiesel is also beneficial for environmental protection.
Because of high viscosity of edible oils (27.2-53.6 mm²/5 at 38° C.)., edible oils are not suitable to be used directly as fuel oils for vehicles and usually can undergo transesterification process to reduce viscosity. A conventional transesterification process uses a mechanical agitating device to mix edible oils in batch type operation with additives for modification of edible oils. However, the conventional transesterification process takes a long period of time due to immiscibility of oils and additives while transesterification conversion of edible oils may not be sufficient. Hence, manufacturing costs of oil modification increase and productivity of biodiesel is limited.
Ramshaw et al. (U.S. Pat. No. 4,400,275) discloses an apparatus for effecting mass transfer between two fluid phases which is principally designed for the gas-liquid system. The apparatus taught in Ramshaw has only one liquid feed pipe and one gas inlet on the peripheral wall of the device. The method and the equipment taught in Ramshaw et al. were difficult to be utilized for transesterification, wherein the two immiscible liquids including the oils and additives require individual distribution systems in order to enter to the reactor for the elimination of the significant interference between the immiscible liquids during the transportation. Furthermore, the high transesterification conversion of the oils is achieved by performing the rapid separation after the transesterification reaction.
It is clear that the conventional methods cannot be used in two different immiscible liquids. Moreover, those conventional methods cannot improve the transesterification conversion of edible oils. It is one the main objectives of the present invention to introduce a method that can improve the transesterification conversion of oils. In other words, the present invention provides a method and equipment that can overcome all shortcomings of the prior arts and increase the transesterification convention of oils.

SUMMARY OF THE INVENTION

In view of the foregoing shortcomings of the conventional designs, the present invention provides a method that can effectively increase the transesterification conversion of oils. Further the present invention utilizes a rigid baffle inside the peripheral wall of the high gravity reactor to carry out the rapid and preliminary phase separation based on the high centrifugal speed and distinct density difference between two immiscible liquids. The method comprises the following steps of:

- (a) setting a rotating packed bed reactor for performing centrifugal rotation, in which the rotating packed bed reactor further comprises a container, a drive shaft and a rotating packed bed, wherein the container further comprises an upper side, a lower side, a peripheral wall, two feeds being formed in the upper side of the container, an outlet being formed in the lower side of the container, and a rigid baffle being formed in an inner side of the peripheral wall; and
  - the rotating packed bed is connected to the container through the drive shaft, wherein the rotating packed bed comprises an inner wall acting as a passage for oils and additives, a packed reaction region being formed along a radial direction of the rotating packed bed and packed with a stainless steel filler for rotating along with the drive shaft;
- (b) centrifugally rotating the rotating packed bed to rotate relative to the container by the drive shaft;
- (c) heating the oils and additives being heated to arrive at a temperature range approximately between 40 degrees Celsius to 100 degrees Celsius before entering the rotating packed bed;
- (d) injecting the oils and the additives, wherein the oils and the additives are individually injected into the rotating packed bed through bored holes of the two feeds located at the upper side of the container;
- (e) performing the transesterification reaction, wherein the oils and the additives are delivered by a centrifugal force to pass through the stainless steel filler in the packed reaction region;
- (f) performing the transesterification reaction with a rotation speed range of approximately 300 rpm to 1500 rpm;
- (g) inducing a phase separation, wherein an effluent is left from the rotating packed bed, and then the phase separation is carried out on the rigid baffle by the centrifugal force; and
- (e) collecting the effluent at the outlet of the rotating packed bed reactor, wherein the effluent comprises transesterified and separated oils.

The transesterification method of the present invention utilizes a specific design of a rotating packed bed reactor to increase the transesterification conversion of oils.
These features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth thereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order for the advantages of the invention to be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that theses drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:

FIG. 1 is a block diagram of a method of increasing transesterification conversion of oils in accordance with a preferred embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of a rotating packed bed reactor in accordance with a preferred embodiment of the present invention; and

FIG. 3 is a schematic cross-sectional view inside the rotating packed bed reactor in accordance with the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a block diagram of a method of increasing transesterification conversion of oils in accordance with a preferred embodiment of the present invention. The method of the present invention comprises steps of packing a stainless-steel filler, centrifugally rotating a rotating packed bed via a drive shaft, injecting oils into the rotating packed bed, performing a transesterification reaction and collecting an effluent at an outlet of the rotating packed bed reactor.
FIG. 2 of the application illustrates a rotating packed bed reactor (10) of the present invention, wherein the rotating packed bed reactor (10) comprises a container (11), a rotary driver (20), a drive shaft (23) and a rotating packed bed (15). The container (11) has an upper side, a lower side, a peripheral wall, an oil feed (12), an additive feed (21) and an outlet (14). The oil feed (12) and additive feed (21) are formed centrally through the upper side of the container (11). The outlet (14) is formed through the lower side of the container (11).
The rotating packed bed (15) with an inner wall and a packed reaction region (16) is powered to rotate by a rotary driver (20) and rotatably mounted in the container (11). The inner wall of the rotating packed bed (15) allows passage of oils and additive. The packed reaction region (16) is formed along the radial direction of the rotating packed bed (15) and packed with a stainless-steel filler. The oil and additive are injected into the rotating packed bed (15) through the openings of the oil feed (12) and additive feed (21) located along the axis of the rotation as shown in FIG. 2 so that the oil and the additive are delivered via the centrifugal force by passing through the stainless steel filler in the packed reaction region (16).
The transesterification reaction is carried out in the packed reaction region (16). The effluent is induced to carry out the phase separation on the rigid baffle (17). Then the effluent is collected at the outlet (14).
For the transesterification reaction, the reactants initially form a two-phase liquid system. The poor diffusion between the phases results in a slow reaction rate while the vigorous mixing intensity is significant in this reaction region. When the fatty acid methyl esters have been generated in the transesterification reaction, they act as a mutual solvent for the reactants and a single-phase system is formed. As the single phase is established, the influence of the mixing becomes insignificant to the transesterification.
On the other hand, the coagulation of glycerol (by-product) starts to form the glycerol phase, which is positive to the chemical equilibrium shift towards the transesterification reaction. By using the present method, the reactants would be intensively mixed within a very short time in a rotating packed bed (15) so the transesterification reaction could proceed quickly. Then the great centrifugal force contributes to the formation of the glycerol phase on the rigid baffle (17) to obtain high conversion of oils. Furthermore, the time required for the satisfactory phase separation would be significantly reduced after collecting at the outlet.
The schematic cross-sectional view of the flow pattern inner part of the rotating packed bed reactor is illustrated in FIG. 3. FIG. 3 shows the components including the oil feed (12), additive feed (21), packed reaction region (16), ester phase layer (24), glycerol phase layer (25), and rigid baffle (17). The solids lines with arrows depict the flow pattern. The liquids were sprayed onto the inner ring of the rotating packed bed (15) and thrown outward by the centrifugal force. It is presumed that the reactants would be intensively mixed within a very short time in the rotating packed bed (15) while the transesterification reaction could quickly proceed. Afterward, the high centrifugal force on the effluent can contribute to the phase separation on the rigid baffle (17).
In other words, the present invention provides a method of increasing transesterification conversion of oils which uses oils and additives as raw materials, in which the method comprises of: heating the oils and additives, injecting the oils and the additives into a high gravity field, performing transesterification reaction, inducing a phase separation, and post-treating effluent to obtain biodiesel, preferably highly converted oils, characterized in that the transesterification reaction is carried out under a high gravity reactor. The oils and additives are heated to arrive at a temperature of about 40 degrees Celsius to about 100 degrees Celsius, and the oils and the additives acting as reactants are injected into a rotating packed bed of the high gravity reactor, sprayed to the inner edge of the rotating packed bed through bored holes of individual distributors, and delivered by a centrifugal force to pass through stainless steel filler where the oils react in the transesterification reaction with the additives. Therefore, the transesterification reaction taught in the present invention requires less reaction time and obtains higher transesterification conversion.
The present invention utilizes a rigid baffle inside the peripheral wall of the high gravity reactor to carry out the rapid and preliminary phase separation based on the high centrifugal speed and distinct density difference between two immiscible liquids. The method of the present invention comprises the following steps of:

- (a) setting a rotating packed bed reactor for performing centrifugal rotation, in which the rotating packed bed reactor further comprises a container, a drive shaft and a rotating packed bed, wherein the container further comprises an upper side, a lower side, a peripheral wall, two feeds being formed in the upper side of the container, an outlet being formed in the lower side of the container, and a rigid baffle being formed in an inner side of the peripheral wall; and
- (b) the rotating packed bed is connected to the container through the drive shaft, wherein the rotating packed bed comprises an inner wall acting as a passage for oils and additives, a packed reaction region being formed along a radial direction of the rotating packed bed and packed with a stainless steel filler for rotating along with the drive shaft;
- (c) centrifugally rotating the rotating packed bed to rotate relative to the container by the drive shaft;
- (d) heating the oils and additives being heated to arrive at a temperature range approximately between 40 degrees Celsius to 100 degrees Celsius before entering the rotating packed bed;
- (e) injecting the oils and the additives, wherein the oils and the additives are individually injected into the rotating packed bed through bored holes of the two feeds located at the upper side of the container;
- (f) performing the transesterification reaction, wherein the oils and the additives are delivered by a centrifugal force to pass through the stainless steel filler in the packed reaction region;
- (g) performing the transesterification reaction with a rotation speed range of approximately 300 rpm to 1500 rpm;
- (h) inducing a phase separation, wherein an effluent is left from the rotating packed bed, and then the phase separation is carried out on the rigid baffle by the centrifugal force; and
- (i) collecting the effluent at the outlet of the rotating packed bed reactor, wherein the effluent comprises transesterified and separated oils.

The method disclosed in the present invention has been carried out and proved it effectiveness in several experiments. The following are some of experiments carried out by utilizing the method in accordance with a preferred embodiment of the present invention.
A soybean oil was modified in accordance with the present invention to perform a test of transesterification conversion. The additive comprises methanol and an alkali metal compound. The filler is stainless steel wire. Test conditions and results are shown in Table 1.

TABLE 1

Test conditions and results

Example	1	2	3	4	5

Oil	Soybean	Soybean	Soybean	Soybean	Soybean
	oil	oil	oil	oil	oil
Oil flow rate	180	180	180	180	180
(ml/min)
Methanol flow	46	46	46	46	46
rate (ml/min)
Alkali metal	KOH	KOH	KOH	KOH	KOH
compound
Alkali metal	1.63	1.63	1.63	1.63	1.63
compound input
rate (g/min)
Filler	Stainless	Stainless	Stainless	Stainless	Stainless
	steel wire	steel wire	steel wire	steel wire	steel wire
Rotating speed	300	900	1500	900	900
(rpm)
Reaction	58	58	58	40	40
temperature (° C.)
Transesterification	86.38	90.31	91.26	90.05	89.51
conversion (%)

As shown above, various rotating speeds of 300, 900, and 1500 rpm and reaction temperatures of 40 and 58° C. were carried out to obtain the transesterification conversion in the range of 86.38-91.26%.
Results in Table 1 show that transesterification conversion in accordance with the present invention being at least 86.38%, while transesterification reaction was continuously performed.

TABLE 2

Test conditions and results

	Reaction time (min)	Transesterification conversion (%)

	0	0
	3	75.3
	6	81.4
	9	82.6
	12	83.2
	60	85.6

A conventionally mechanical agitating device was used to perform a batch transesterification reaction to serve as a comparison. Soybean oil of 2949 ml was mixed with methanol of 756 ml and KOH of 27 g in the mechanical agitating device. Results in Table 2 show that the conventional reactor only can achieve the transesterification conversion of 85.6% even after a reaction time of an hour. Therefore, it is clear from the results of the tables that the present invention requires less reaction time and obtains higher transesterification conversion.
Various oils were modified in accordance with the present invention as another test of transesterification conversion. Test conditions and results are shown in Table 3.

TABLE 3

Test conditions and results

Example	6	7	8	9	10	11

Oil	Palm	Sunflower	Lard	Olive	Canola	Sesame
	oil	oil	oil	oil	oil	oil
Oil flow rate	180	180	180	180	180	180
(ml/min)
Methanol flow	46	46	46	46	46	46
rate (ml/min)
Alkali metal	KOH	KOH	KOH	KOH	KOH	KOH
compound
Alkali metal	1.63	1.63	1.63	1.63	1.63	1.63
compound input
rate (g/min)
Filler	Stainless	Stainless	Stainless	Stainless	Stainless	Stainless
	steel wire	steel wire	steel wire	steel wire	steel wire	steel wire
Rotating speed	900	900	900	900	900	900
(rpm)
Reaction	40	40	40	40	40	40
temperature (° C.)
Transesterification	86.45	89.17	85.24	81.43	81.71	80.10
conversion (%)

As shown above, various oils including palm oil, sunflower oil, lard oil, olive oil, canola oil, and sesame oil were carried out to obtain the transesterification conversion in the range of 80.10-89.17%. The modes proposed herein can provide useful information for any person in the art to perform the best mode based on the control of the operation conditions.
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the exemplary embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the invention as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention.
Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “one embodiment,” “an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment, different embodiments, or component parts of the same or different illustrated invention. Additionally, reference to the wording “an embodiment,” or the like, for two or more features, elements, etc. does not mean that the features are related, dissimilar, the same, etc. The use of the term “an embodiment,” or similar wording, is merely a convenient phrase to indicate optional features; which may or may not be part of the invention as claimed.
Each statement of an embodiment is to be considered independent of any other statement of an embodiment despite any use of similar or identical language characterizing each embodiment. Therefore, where one embodiment is identified as “another embodiment,” the identified embodiment is independent of any other embodiments characterized by the language “another embodiment.” The independent embodiments are considered to be able to be combined in whole or in part one with another as the claims and/or art may direct, either directly or indirectly, implicitly or explicitly.
Finally, the fact that the wording “an embodiment,” or the like, does not appear at the beginning of every sentence in the specification, such as is the practice of some practitioners, is merely a convenience for the reader's clarity. However, it is the intention of this application to incorporate by reference the phrasing “an embodiment,” and the like, at the beginning of every sentence herein where logically possible and appropriate.
Thus, while the present invention has been fully described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiment of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made, without departing from the principles and concepts of the invention as set forth in the claims.

Claims

1. A method of increasing transesterification conversion of oils which uses oils and additives as raw materials, comprising the following steps of: heating the oils and additives, injecting the oils and the additives into a high gravity field, performing a transesterification reaction, inducing a phase separation, and post-treating effluent to obtain biodiesel, preferably highly converted oils, characterized in that the transesterification reaction is carried out under the high gravity field.

2. The method of claim 1, wherein the whole transesterification reaction is carried out in a high gravity reactor.

3. The method of claim 1, wherein the oils and additives are heated to arrive at a temperature of about 40 degrees Celsius to about 100 degrees Celsius

4. The method of claim 2, wherein the oils and the additives acting as reactants are injected into a rotating packed bed of the high gravity reactor, and sprayed to the inner edge of the rotating packed bed through bored holes of individual distributors, and delivered by a centrifugal force to pass through stainless steel filler where the oils are converted in the transesterification reaction with the additives.

5. The method of claim 1, wherein the high gravity field comprises a centrifugal acceleration of about 50 m/s²to about 10,000 m/s².

6. The method of claim 4, wherein rotation speed of the rotating packed bed is about 300 rpm to about 1500 rpm.

7. The method of claim 1, wherein the phase separation is carried out on a rigid baffle installed in an inner side of the peripheral wall of the high gravity reactor.

8. The method of claim 1, wherein the post-treatments comprise one or more of separating, neutralizing, washing and distilling.

9. The method of claim 1, wherein the oils comprise a triglyceride, an organic acid or a mixture thereof.

10. The method of claim 9, wherein the triglyceride is selected from a group consisting of olive oil, canola oil, tung oil, rapeseed oil, Chinese tallow tree oil, soybean oil, sesame oil, ricinus oil, rice bran oil, palm oil, coconut oil, jatropha oil, algae oil, tallow oil, lard oil and sunflower oil.

11. The method of claim 9, wherein the organic acid is selected from a group consisting of stearic acid, lauric acid, myristic acid, oleic acid, palmitic acid, linoleic acid and linolenic acid.

12. The method of claim 1, wherein the additives comprise an alcohol and a homogeneous catalyst.

13. The method of claim 12, wherein the alcohol is methanol, ethanol, propanol, isopropanol or butanol.

14. The method of claim 12, wherein the homogeneous catalyst is an alkali metal compound or an inorganic acid.

15. The method of claim 14, wherein the alkali metal compound is a sodium hydroxide, potassium hydroxide or sodium methoxide.

16. The method of claim 14, wherein the inorganic acid is sulfuric acid, nitric acid or phosphoric acid.