WO2013081446A1

WO2013081446A1 - A process for producing biodiesel from natural oil and a system thereof

Info

Publication number: WO2013081446A1
Application number: PCT/MY2012/000275
Authority: WO
Inventors: Mohd Noor ISHENNY; Hisham Mohamed Jan BADRUL; Si Ali BRAHIM; Hasan MASITAH; Ramachandran K.B.
Original assignee: Universiti Malaya
Priority date: 2011-12-02
Filing date: 2012-11-16
Publication date: 2013-06-06

Abstract

This invention discloses a process for producing biodiesel comprising agitating a natural oil containing triglycerides with a neutral buffer solution in a reactor (123) in a presence of a biocatalyst to form free fatty acids and glycerol; removing the glycerol form the reactor (123); transesterifying the free fatty acids with methyl acetate at a predetermined temperature to obtain biodiesel and unreacted free fatty acids; removing the buffer solution and biocatalyst from the reactor (123); and completing the transesterification by reacting the unreacted free fatty acids with methanol to produce biodiesel.

Description

A PROCESS FOR PRODUCING BIODIESEL FROM NATURAL OIL AND A

SYSTEM THEREOF

FIELD OF INVENTION

The present invention relates to a process and system of producing biodiesel from natural oil. More particularly, the present invention relates to a bioprocess and system of producing biodiesel from natural oil using a biocatalytic transesterification process.

BACKGROUND OF THE INVENTION

Used oil is defined as any oil, that through use, handling or extended storage, has become unsuitable for its original purpose due to the presence of impurities, contaminants or loss of original properties. Used oil may be termed as 'waste oil' when it is inappropriately disposed, recycled or contaminated by hazardous impurities. Waste oil is bottom clean-out waste from virgin fuel storage tanks, virgin fuel oil spill cleanups, waste cooking oil, palm oil mill effluent (POME) or other oil wastes that have not actually been used. Waste oil may pose threats to the environment and may need further environmental control management before releasing them to the environment. Under the management control, waste oil can be recycled to produce useful products such as lubricant oil, hydraulic oil, transmission oil, brake fluids, motor oil, crankcase oil, gear box oil, synthetic oil and even high- grade fuel oil and cooking fuel oil.

Considerable efforts have been made to find suitable and efficient processes to produce biodiesel from waste oil. Numerous researches have been conducted to examine processes involved in biodiesel production from waste oil. However, in the current chemical process of producing biodiesel from waste oil, strong alkali and acid, excess alcohol as well as high temperature of more than 200°C are used in an esterification process to ensure complete conversion of waste oil to biodiesel. These processes require high energy, material, technology and thus high production cost. Moreover, the strong chemical used during the process is literally harmful to the environment.

Besides, there are some inventions over the prior arts relating to processes of producing biodiesel from waste oil or used oil. These patented technologies include a wide variation in their raw materials used and processes involved.

Of interest in respect to a production of fuel from waste oil is U.S. Patent Publication No. US 2004/0003534(Al). The process involves producing a fuel for diesel engine from waste oil comprising virgin fish oil, fish waste oil, or a mixture of the fish oil and virgin vegetable oil or vegetable waste oil. However, the waste oil is subjected to stirring treatment while introducing ozone, and adding an oxidation-reduction agent and a polymerization inhibitor during the stirring treatment.

There is also an invention relating to a process and apparatus for reclaiming waste oils from various sources. A U.S. Patent No. US 6132596 discloses a process and apparatus for the reclaiming and refining of waste oils that comprises raising a temperature of a feed mixture of fresh waste oil and a recycled non-volatile residue to _ cause pyro lysis of said heavy hydrocarbons contained in the feed mixture, but it is insufficient to permit substantial desired polymerization, oxidation and dehydrogenation reactions to take place in said feed mixture for a time sufficient to cause pyrolysis of the heavy hydrocarbons.contained in the feed mixture.

The use of vegetable-based or animal-based oil as raw material for biodiesel production is also known in the art. Of interest in connection with a biodiesel production process from vegetable or animal oil is U.S. Patent Publication No. 2007/0260078(Al). The process involves the use of solid transesterification and etherification catalysts to form a mixture of alkyl esters of fatty acids and alkyl ether of glycerols. However, this prior art did not focus on the pre-treatment of the vegetable or animal oil and the usage of waste oil for the production of biodiesel. However, there is no innovative invention documented regarding the use of natural oil, POME or other vegetable-based or animal-based waste oil for biodiesel production, especially for the pre-treatment of triglycerides, which is always present in the waste oil, to fatty acids. The triglycerides in waste oil has no economic value as it is substantially insoluble in water and therefore poses a critical threat to the environment if inappropriately disposed. As such, due to the ability to extract fatty acids from waste oil and even other natural oil, waste oil and natural oil have a promising value to produce biodiesel. Therefore, it is desirable for the present invention to provide a process to convert triglycerides from natural oil and waste oil to produce biodiesel using low production cost.

SUMMARY OF INVENTION

The primary object of the present invention is to provide a biodiesel production process using biocatalyst fermentation reaction. The process may also be referred to as a bioprocess.

Another object of the present invention is to provide a bioprocess to produce biodiesel that requires less energy, lower production cost and produces higher yield. Saponification is reduced due to the neutral buffer solution. A conversion rate of approximately 98% can be achieved within 1 to 3 hours.

Still another object of the present invention is to recycle POME, which is commonly disposed and environmentally harmful, to produce biodiesel and thus open another avenue for commercialization of this biodiesel to the automobile industry. Yet another object of the present invention is to produce biodiesel that has low flash point and produce a smoke-free flame and no smell when burned, which is environmental friendly as well as capable to be used as cooking fuel.

A further object of the present invention is to provide a biodiesel production process that produces biodiesel that can be used as automotive fuel without the need to mix with different petroleum-derived diesel. At least one of the preceding objects is met, in whole or in part, by the present invention, in which one of the embodiments of the present invention describes a process for producing biodiesel comprising agitating a natural oil containing triglycerides with a neutral buffer solution in a reactor in a presence of a biocatalyst to form free fatty acids and glycerol; removing the glycerol form the reactor; transesterifying the free fatty acids with methyl acetate at a predetermined temperature to obtain biodiesel and unreacted free fatty acids; removing the buffer solution and biocatalyst from the reactor; and completing the transesterification by reacting the unreacted free fatty acids with methanol to produce biodiesel. In one of the preferred embodiments of the present invention, the natural oil is agitated at a temperature range of 25°C to 50°C.

In another preferred embodiment of the present invention, the predetermined temperature of the transesterification between free fatty acids and methyl acetate ranges from 60°C to 90°C. Preferably, the predetermined temperature is 90°C.

In still another preferred embodiment of the present invention, the natural oil is derived from waste vegetable or animal oil. Preferably, the natural oil is derived from palm oil mill effluent that has 0.4% to 99.9% by weight of triglycerides. Further embodiment of the present invention is that the biocatalyst is lipase derived from Candida cylindracea.

Yet another embodiment of the present invention is the concentration ratio between natural oil and buffer solution is 0.5 - 1.5 : 1.

In still another embodiment of the present invention, the concentration ratio between biocatalyst to natural oil is 0.01 - 0.2 : 1. Preferably, the concentration ratio is 0.1 : 1. Further embodiment of the present invention is that the concentration ratio between methyl acetate to free fatty acids is 0.1 - 0.2 : 1.. Preferably, the concentration ratio is 0.1 : 1.

Another embodiment of the present invention is that the concentration ratio between methanol to unreacted free fatty acids is 0.1 - 0.2 : 1. Preferably, the concentration ratio is 0.1 : 1.

A particular embodiment of the present invention discloses a system for producing biodiesel comprising a buffer tank containing a neutral buffer solution; an oil tank containing a natural oil; an enzyme storage tank containing a biocatalyst; a reactor for mixing the buffer solution from the buffer tank, the natural oil from the oil tank and the biocatalyst from the enzyme storage tank and agitating the mixture to produce free fatty acids and glycerol; and a methyl acetate feedstock for providing methyl acetate to transesterify the free fatty acids in the reactor to form biodiesel and unreacted free fatty acids; and a methanol feedstock for providing methanol to complete the transesterification between the unreacted free fatty acids in the reactor to produce biodiesel.

Another embodiment of the present invention discloses that the system further comprising a purification tank for purifying the biodiesel produced. Yet another embodiment of the present invention discloses that the system further comprising a recycling tank for recycling the used methanol. Another embodiment of the present invention discloses that the natural oil tank comprises a palm oil mill effluent purification tank located upstream of the natural oil tank.

A further embodiment of the present invention discloses that the enzyme storage tank comprises an enzyme fermentor and an enzyme purification tank.

The biodiesel invented is an eco-friendly product as it produces no smoke and has no smell. It has a low flash point which enable it to be used for cooking. Besides, the biodiesel has a low freezing point which enable it to be stored throughout the year without any change of its properties.

One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments described herein are not intended as limitations on the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated. Figure 1 shows a schematic process flow diagram of the process and system of biodiesel production from natural oil in accordance with the embodiments of the present invention.

Detailed Description of the Invention

Hereinafter, the invention shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

According to the preferred embodiment of the present invention, a process for producing biodiesel comprising agitating a natural oil containing triglycerides with a neutral buffer solution in a reactor (123) in a presence of a biocatalyst to form free fatty acids and glycerol; removing the glycerol form the reactor (123); transesterifying the free fatty acids with methyl acetate at a predetermined temperature to obtain biodiesel and unreacted free fatty acids; removing the buffer solution and biocatalyst from the reactor (123); and completing the transesterification by reacting the unreacted free fatty acids with methanol to produce biodiesel.

The main composition in the process embodied herein is the biocatalyst. The biocatalyst is enzyme lipase produced from Candida cylindracea in the presence of palm oil. Generally, lipase is highly applicable in fat splitting as well as in synthesis of glycerides. Enzymatic hydrolysis of oil is practically more advantageous than chemical process as it requires significantly less energy while producing high quality product. A command problem of enzymatic processes is sensitivity of enzymatic reaction towards heat, alcohol, strong acid and base and it is a major challenge of existing source of lipase. However, this issue is eliminated by using this lipase produced from Candida cylindracea and_ the processing steps as claimed and described in the preferred embodiment of the present invention.

Even more, the usage of lipase is crucial to optimize production. In the production of the lipase, palm oil is used as a substrate and lipase is abundantly produced from Candida cylindracea in a culture medium of glucose, peptone, yeast extract, malt extract, agar and distilled water and through a fermentation process. The fermentation process of lipase is preferred to be carried out in a batch bioreactor in a temperature of 30°C, pH 6, aeration of 1.0 gas volume flow per unit of liquid volume per minute (wm). For a commercially obtained 7 liter batch bioreactor, a stirrer speed of 500 rotation per minute (rpm) is preferred. PH of the fermentation is controlled and maintained by constant addition of sterile 3N NaOH and 3N H2SO4 solution, where 3N comprises 99.9% of anhydrous sodium hydroxide and is commonly referred to as 3 normality. However, it should be understood that lipase produced from other processes or derived from other sources is acceptable as long as the lipase is able to withstand a moderate temperature, neutral buffer solution and able to produce high quality of end products. Preferably, the concentration ratio of biocatalyst to natural oil is 0.01 - 0.2 : 1. Most preferably, the concentration ratio is 0.1 : 1.

In one of the preferred embodiment of the present invention, the natural oil is derived waste vegetable-based oil, waste animal-based oil or any a combination thereof The natural oil is preferred to be derived from POME as it is easily obtained and commonly disposed. POME is filtered to remove charred food, dirt and other non-oil material prior to its use. Solvent extraction method may be used for extraction of residual oil from the POME. The POME has approximately a concentration of 0.4% to 99.9% by volume of oil, which can also be referred to as triglycerides. According to the another embodiment of the present invention, the natural oil is agitated for a period ranging from 10 minutes to 20 minutes at a temperature range of 25°C to 50°C. The process operates at low pressure of approximately 1 bar and in a comparatively neutral environment of buffer solution produced from weak acid and weak base. Preferably, the buffer solution is produced from a mixture of 0.01M of sodium hydroxide, 0.01M of acetic acid and distilled water. Preferably, the concentration ratio of natural oil to buffer solution is 0.5 - 1.5 : 1. Most preferably, the concentration ratio of natural oil to buffer solution is 1 : 1.

In still another embodiment of the present invention, the agitation process is preferred to be performed in a reactor (123). At the end of the agitation process, free fatty acids and glycerol are produced. Next, the free fatty acids produced from the agitation process is reacted with methyl acetate at a temperature ranging from 60°C to 90°C in order to produce biodiesel. The free fatty acids in solid form is converted to biodiesel, which is specifically known as methyl ester, by the addition of methyl acetate in a heated environment. Preferably, the temperature is approximately 90°C. The concentration ratio of methyl acetate to free fatty acids is preferred to be 0.1 - 0.2 : 1. Most preferably, the methyl acetate to free fatty acids concentration ratio is 0.1 : 1.

In a further process, methanol is added into the reactor (123) subsequent to the removal of the buffer solution and biocatalyst. Heating of the reactor (123) is stopped upon the addition of the methanol. Thus, the unreacted free fatty acids are completely transesterified to biodiesel when the temperature drops to approximately 30°C. The concentration ratio of methanol to fatty acids is preferred to be 0.1 - 0.2 :1. Most preferably, the concentration ratio is approximately 0.1 : 1.

As set forth in the foregoing description, the system as described in the embodiments of the present invention is shown in Figure 1 for making the system more easily understandable. A system for producing biodiesel comprising a buffer tank (105) containing a neutral buffer solution; an oil tank (101) containing a natural oil; an enzyme storage tank (117) containing a biocatalyst; a reactor (123) for mixing the buffer solution from the buffer tank (105), the natural oil from the oil tank (101) and the biocatalyst from the enzyme storage tank (117) and agitating the mixture to produce free fatty acids and glycerol; and a methyl acetate feedstock (119) for providing methyl acetate to transesterify the free fatty acids in the reactor (123) to form biodiesel and unreacted free fatty acids; and a methanol feedstock (121) for providing methanol to complete the transesterification between the unreacted free fatty acids in the reactor (123) to produce biodiesel.

Subsequent to the production of biodiesel, the produced biodiesel is subjected to a purification tank. The biodiesel produced is purified to remove residual water, used methanol, buffer solution and other by-products through evaporators such as vacuum evaporator (127) and thin film evaporator (131). Water removed from the system can be transferred to a steam generator (200). Preferably, water contained in the biodiesel is eliminated to approximately not more than 0.05% by volume of the biodiesel. The system further comprising a recycling tank (125) for recycling the used methanol. The used methanol may be stored in an methanol collection tank (129) to be reused in the system. The clean-up or purification process may further involve bleaching the biodiesel produced in a bleaching tank (133) and particle filtrating through a membrane filter (135) to produce a clean and high grade biodiesel. By the fermentation process as disclosed in the embodiments of the present invention, approximately 98% of triglycerides is converted to biodiesel. This high efficiency of conversion uses low energy, low production cost and helps preserve the environment by reducing the disposal of waste oil.

Upstream of the buffer tank (105) comprises a weak base input (107), a weak acid input (109) and a water input (111). These inputs are controlled to produce a neutral buffer solution to be stored in the buffer tank (105) for delivery to the reactor (123). In still another embodiment of the present invention, the natural oil tank (101) comprises a palm oil mill effluent purification tank (103) located upstream of the natural oil tank (101). The POME purification tank (103) purifies and filters POME to obtain the natural oil or can be referred to as waste oil. The obtained natural oil or waste oil is stored in the natural oil tank (101) before subjected to the process embodied herein.

Frequently, POME treatment systems are largely influenced by the cost of operation and maintenance, availability of land, and the location of the palm oil mill. Since a beneficial system as described in the embodiments of the present invention is capable of producing biodiesel from POME, it is highly desirable for palm oil mills to have this system which can not only dispose POME without harming the environment but also earning money from POME. A particular embodiment of the present invention discloses that the enzyme storage tank (113) comprises an enzyme fermentor (115) and an enzyme purification tank (117). Lipase is preferred to be produced in the enzyme fermentor (115) and purified through the purification tank (117). Purified lipase are then stored in the enzyme storage tank (113) for usage when desired.

Unlike most commercially obtained biodiesel which contain value of flash point of at least 100°C, the present invention produces a product with less flash point value by usage of 100% of waste oil. The waste oil used primarily in the present invention has no cost as it is generally a waste. The biodiesel invented herein is an eco-friendly product as it produces no smoke and has no smell when burnt. It has a low flash point value of approximately 65°C which enable it to be used as cooking fuel. Besides, the biodiesel has excellent anti-freeze property which enable it to be used and stored throughout the year especially in tropical and temperate countries, without any change of its properties. Besides being eco-friendly, the efficiency of the biodiesel produced is also comparable to that of well known commercially available products. The present invention leads to a new area of biodiesel production, which will promote the agriculture and economic growth. Due to the efficiency of the process, reasonable cost and eco-friendly of the biodiesel produced, this process as well as the system have the feasibility to be commercialized.

The present disclosure includes as contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangements of parts may be resorted to without departing from the scope of the invention.

Example

An example is provided below to illustrate different aspects and embodiments of the present invention. The example is not intended in any way to limit the disclosed invention, which is limited only by the claims.

A specification description of the biodiesel produced from the process and system as described in the embodiments of the present invention is shown in Table 1.

Table 1

Claims

A process for producing biodiesel comprising

agitating a natural oil containing triglycerides with a neutral buffer solution in a reactor (123) in a presence of a biocatalyst to form free fatty acids and glycerol;

removing the glycerol form the reactor (123);

transesterifying the free fatty acids with methyl acetate at a predetermined temperature to obtain biodiesel and unreacted free fatty acids;

removing the buffer solution and biocatalyst from the reactor (123); and completing the transesterification by reacting the unreacted free fatty acids with methanol to produce biodiesel.

A process according to claim 1, wherein the natural oil is agitated at a temperature range of 25°C to 50°C.

A process according to claim 1, wherein the predetermined temperature of the transesterification between free fatty acids and methyl acetate ranges from 60°C to 90°C.

A process according to claim 1, wherein the natural oil is derived from waste vegetable or animal oil.

A process according to claim 1, wherein the natural oil is derived from palm oil mill effluent.

6. A process according to claim 5, wherein the palm oil mill effluent has 0.4% to 99.9% by weight of triglycerides.

7. A process according to claim 1, wherein the biocatalyst is lipase produced by Candida cylindracea.

8. A process according to claim 1, wherein the concentration ratio between natural oil and buffer solution is 0.5 - 1.5 : 1.

9. A process according to claim 1, wherein the concentration ratio between biocatalyst to natural oil is 0.01 - 0.2 : 1.

10. A process according to claim 1, wherein the concentration ratio between methyl acetate to free fatty acids is 0.1— 0.2 : 1.

11. A process according to claim 1, wherein the concentration ratio between methanol to unreacted free fatty acids is 0.1 - 0.2 : 1.

12. A system for producing biodiesel comprising

a buffer tank (105) containing a neutral buffer solution;

an oil tank (101) containing a natural oil;

an enzyme storage tank (117) containing a biocatalyst;

a reactor (123) for mixing the buffer solution from the buffer tank (105), the natural oil from the oil tank (101) and the biocatalyst from the enzyme storage tank (117) and agitating the mixture to produce free fatty acids and glycerol; and

a methyl acetate feedstock (11 ) for providing methyl acetate to transesterify the free fatty acids in the reactof ^'(123) to form biodiesel and unreacted free fatty acids; and

a methanol feedstock (121) for providing methanol to complete the transesterification between the unreacted free fatty acids in the reactor (123) to produce biodiesel.

13. A system according to claim 12 further comprising a purification tank for purifying the biodiesel produced.

14. A system according to claim 12 further comprising a recycling tank (125) for recycling the used methanol.

15. A system according to claim 12, wherein the natural oil tank (101) comprises a palm oil mill effluent purification tank (103) located upstream of the natural oil tank (101).

16. A system according to claim 12, wherein the enzyme storage tank (113) comprises an enzyme fermentor (115) and an enzyme purification tank (117).