METHOD THEREOF

FIELD OF THE INVENTION

The present invention generally relates to a method of producing a solid acid catalyst and solid base catalyst. More particularly, the present invention relates to an improved method for producing a sulphated-ferric(ll l) oxide/alumina oxide solid acid catalyst and a potassium/silica oxide solid base catalyst that is suitable for use in biofuel production.

BACKGROUND OF THE INVENTION

Biodiesel production is expected to be beneficial from low quality waste feedstock. However, the presence of high free fatty acid content in waste feedstock renders the process for obtaining biodiesel to be difficult, especially by performing conventional transesterification reaction with base catalyst (e.g. sodium hydroxide). The transesterification reaction with the base catalyst leads to soap formation, which leads to increase in catalyst consumption, thus lowering catalytic efficiency and increasing viscosity of the biodiesel mixture. The transesterification reaction also leads to formation of gels, thus complicating purification of crude biodiesel. Further, base catalyzing process is very sensitive to presence of water and free fatty acids, thus leading to more usage of methanol. Brown grease obtained from the low quality waste feedstock contains high percentage of free fatty acids and water. Upon transesterification, the base catalyst will react with the free fatty acids to form soaps.

On the other hand, homogeneous catalysis system is too complicated due to the high amount of steps involved in the process. Transesterification reaction with homogenous catalysis system involved usage of neutralization agent to neutralize catalyst used and requires high amount of water to purify the product. Consequently, it will produce a large amount of waste water. Moreover, such type of catalyst could not be generated and reused. This system is also expensive due to the large amount of water usage. Catalysts typically used for producing biofuel are normally not reusable. Further, catalysts used for biofuel normally utilizes very high temperature and unable to be used for esterification and transesterification of waste with very high fat content.

See, for example, in the China patent publication no. CN 10181 1055 there is provided a promotion of transition metal, Zinc into Fe(l l) which in a catalytic test, both esterification and transesterification can occur simultaneously. The catalyst was prepared by co-precipitation method. The synthesized catalyst was used for conversion of rapeseed oil into biodiesel at high temperature of 120-200 deg C and high pressure of 3 M Pa for 2 to 18 hours. The usage of the catalyst produced by the method of the prior art requires a long period of process time under high pressure and temperature condition, which thereby utilizes more resources thus increasing biofuel production cost.

Thus, there is a long-felt need for an improved method for producing a heterogeneous solid and base catalyst and thereby overcoming the problems and shortcomings of the prior art. Although there are methods for the same in the prior art, for many practical purposes, there is still considerable room for improvement.

SUM MARY OF THE INVENTION

The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.

Accordingly, the present invention provides a method of producing a solid acid catalyst and a solid base catalyst suitable for use in biofuel production. The present invention can be characterized by the method comprising the steps of providing an ammonium ferum (I I) sulphate hexahydrate, providing an aqueous alumina oxide, impregnating the ammonium ferum (I I) sulphate hexahydrate onto the aqueous alumina oxide for forming a sulphated-ferric(l ll) oxide/alumina oxide acid catalyst, and calcining the sulphated-ferric(l l l) oxide/alumina oxide acid catalyst for forming the heterogeneous solid sulphated- ferric(l l l) oxide/alumina oxide catalyst.

Preferably, the the aqueous alumina oxide is provided in an amount ranging from 1 to 5 kg.

Preferably, the ammonium ferum(l l) sulphate hexahydrate is provided in an amount ranging from 100-600 gram. Preferably, the calcining of the sulphated-ferric(l l l) oxide/alumina oxide acid catalyst is conducted at a temperature ranging from 500 to 600 °C in air.

In another aspect of the invention, there is provided a sulphated-ferric(l ll) oxide/alumina oxide solid acid catalyst suitable for use in biodiesel production, wherein the sulphated-ferric(l l l) oxide/alumina oxide solid acid catalyst is produced by the abovementioned methods.

The present invention can be further characterized by the method comprising the steps of providing a potassium carbonate, providing an aqueous silica oxide, impregnating the potassium carbonate onto the aqueous silica oxide for forming a potassium/silica oxide base catalyst, and calcining the potassium/silica oxide base catalyst for forming the heterogeneous solid potassium/silica oxide base catalyst. Preferably, the silica oxide is provided in an amount ranging from 1 to 5 kg.

Preferably, the potassium carbonate is provided in an amount ranging from 50 to 250 gram. Preferably, the calcining of the potassium/silica oxide base catalyst is conducted at a temperature ranging from 600 to 1000 °C in air.

In another aspect of the invention, there is provided a potassium/silica oxide base catalyst solid base catalyst suitable for use in biodiesel production, wherein the potassium/silica oxide base catalyst solid base catalyst is produced by the abovementioned methods.

It is therefore an advantage of the present invention that the method allows production of solid acid and base catalyst in a short time. Further, the solid acid and base catalysts produced by the abovementioned method is reusable for up to ten times.

It is therefore another advantage of the present invention that the solid acid and base catalysts produced by the method of the present invention possess a high availability of active site and high surface area, which is favorable in producing biofuels. Further, the method of the present invention allows simpler production of solid acid and base catalysts in a shorter period in comparison to prior art methods of producing catalysts.

The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing, wherein:

Figure 1 is a flow chart of the method of preparing a sulphated-ferric(lll) oxide/alumina oxide solid acid catalyst of the present invention, according to an embodiment of the present invention.

Figure 2 is a flow chart of the method of preparing a potassium/silica oxide solid base catalyst of the present invention, according to an embodiment of the present invention. Figure 3 is a thermograph describing the physicochemical properties of acid catalyst produced by the method of the present invention, according to an embodiment of the present invention. Figure 4 is a thermograph describing the physicochemical properties of base catalyst produced by the method of the present invention, according to an embodiment of the present invention.

Figure 5 is a graph describing number of reusability of the sulphated-ferric(lll) oxide/alumina oxide solid acid catalyst produced from the method of the present invention, according to an embodiment of the present invention.

Figure 6 is a graph describing number of reusability of the potassium/silica oxide solid base catalyst produced from the method of the present invention, according to an embodiment of the present invention.

It is noted that the drawing may not be to scale. The drawing is intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

It is an object of the present invention to provide a method that allows production of solid acid and base catalyst in a short time. It is another object of the present invention that the method produces the solid acid and base catalysts that are reusable for up to ten times. It is also an objective of the present invention that the solid acid and base catalysts produced by the method of the present invention possess a high availability of active site and high surface area, which is favorable in producing biofuels.

The method of the present invention relates to a method for producing a solid acid and base catalyst that is suitable for use as catalysts in biofuel production. The method comprises the steps of preparing a sulphated-ferric(lll) oxide/alumina oxide solid acid catalyst (S04 ^2" -Fe203/Al20s) 20 and the steps of preparing a potassium/silica oxide solid base catalyst K2O/S1O23O.

The method of preparing the sulphated-ferric(lll) oxide/alumina oxide solid acid catalyst 20 comprises the steps of providing an ammonium ferum (II) sulphate hexahydrate 20 and an aqueous alumina oxide 22. Next, the ammonium ferum (II) is impregnated 24 onto the aqueous alumina oxide for forming a sulphated-ferric(lll) oxide/alumina oxide acid catalyst. The formed sulphated- ferric(lll) oxide/alumina oxide acid catalyst is then calcined 26 to form a solid version of the sulphated-ferric(lll) oxide/alumina oxide acid catalyst. The method of preparing the potassium/silica oxide solid base catalyst 30 comprises the steps of providing a potassium carbonate 32 and an aqueous silica oxide 32. Next, the potassium carbonate is impregnated 34 onto the aqueous silica oxide for forming a potassium/silica oxide base catalyst. The potassium/silica oxide base catalyst is then calcined 36 for forming the solid potassium/silica oxide base catalyst.

In order to impregnate the ammonium ferum (II) sulphate hexahydrate onto the aqueous alumina oxide, the aqueous alumina oxide is first provided in an amount ranging from 1 to 5 kg and the ammonium ferum(ll) sulphate hexahydrate is provided in an amount ranging from 100 to 600 gram. After the impregnation, the calcining of the sulphated-ferric(ll l) oxide/alumina oxide acid catalyst is conducted at a temperature ranging from 500 to 600 °C in air.

In order to impregnate the potassium carbonate onto the aqueous silica oxide, 1 to 5 kg of silica oxide and 50 to 250 gram of potassium carbonate are prepared. Then, the potassium carbonate is impregnated onto the aqueous silica oxide for forming the potassium/silica oxide base catalyst. In order to form the solid potassium/silica oxide base catalyst, calcination is conducted to the oxide base catalyst at a temperature ranging from 500 to 600 °C in air.

The sulphated-ferric(l ll) oxide/alumina oxide solid acid catalyst and potassium/silica oxide base catalyst solid base catalyst produced by the abovementioned steps are reusable up to ten times, with no effluent produced. When the sulphated-ferric(l ll) oxide/alumina oxide solid acid catalyst is used in esterification, there is no acid residue discharge or semi-crude ester produced as a by-product.

By way of example, and not necessarily of limitation, the method of the present invention may be provided as follows:

EXAMPLE 1

Methods of Producing a Fatty Acid Methyl Ester with the Sulphated-Ferric(ll l) Oxide/Alumina Oxide Solid Acid Catalyst and Potassium/Silica Oxide Base

Catalyst Solid Base Catalyst

In accordance to an embodiment of the present invention, there is provided a method for producing the fatty acid methyl ester for use in biofuel production by using the sulphated-ferric(ll l) oxide/alumina oxide solid acid catalyst and potassium/silica oxide base catalyst solid base catalyst.

Firstly, a brown grease is prepared and pretreated by heating the brown grease above 100 °C, filtered, and stored accordingly. Next, the solid base catalyst (solid sulphated-ferric(l l l) oxide/alumina oxide catalyst) and a solid acid catalyst (solid potassium oxide/silica oxide catalyst) is prepared. The solid sulphated-ferric(ll l) oxide/alumina oxide catalyst is prepared by preparing 1 to 5 kg of alumina oxide and mixed with 1 to 5 liter of distilled water to form an aqueous solution. Next, 1 -5 wt% of ammonium ferum(l l) sulphate hexahydrate was impregnated onto the aqueous alumina oxide. The mixture was stirred for 30-60 mins until the mixture is homogenous. Then, 10-50 wt% of 1 M sulfuric acid is poured into the mixture and stirred overnight. The mixture is then dried overnight at a temperature of 1 10-120 °C. The formed sulphated-ferric(l l l) oxide/alumina oxide acid catalyst is then placed in a muffle furnace for calcination at a temperature ranging from 500-600 °C for 3 hours in air. Next, a potassium/silica oxide solid base catalyst is prepared. Firstly, 1 to

5 kg of silica oxide was mixed with 6 L of distilled water to form an aqueous solution. 1-5wt% of potassium carbonate is then impregnated with the aqueous silica oxide solution and stirred for 30-60 mins until the mixture is homogenous. The homogenous mixture is then dried in an oven overnight at a temperature ranging from 100-120 °C for forming a potassium/silica oxide base catalyst. The dried potassium/silica oxide base catalyst is then placed in a furnace for calcination at a temperature ranging from 600-1000 °C for 3 hours in air.

Esterification reaction is then carried out to the pretreated brown grease in a 42 L domestic microwave, which is connected to a reflux condenser. 2L of the pretreated brown grease was poured into a 5 L reaction flask. Next, 3 wt% of solid potassium oxide/silica oxide acid catalyst and 30: 1 methanol to free fatty acid molar ratio is added to the reaction flask. Next, the reaction flask is placed in the domestic microwave that is connected to a cooling condenser. The reaction is carried out at a period of 30 minutes with microwave powered to 1 10 watt. The catalyst is then removed from the reaction flask by filtration. The remaining content in the reaction flask is then heated at a temperature ranging from 65 °C to 70 °C to remove excess methanol. Water, which is the by-product of the esterification is separated from the reaction flask by gravity separation and discharged. The final product, esterified brown grease, is then used for transesterification reaction.

Transesterification reaction is then conducted, whereby the reaction starts with pouring the esterified brown grease into a 5 L reaction flask. Then, 1 wt% of a solid potassium oxide/silica oxide catalyst and 30: 1 methanol are added into the reaction flask. The reaction flask is then placed in a domestic microwave with a power of 550 watt and connected to a cooling condenser for a period of 90 minutes. The solid potassium oxide/silica oxide catalyst is then removed from the reaction flask by filtration. Excess methanol is also removed from the reaction flask by heating the content of the reaction flask at a temperature ranging from 65- 70 °C. The remaining mixture in the reaction flask is then left overnight in a separating funnel, whereby a fatty acid methyl ester and glycerol produced by the transesterification reaction are separated into two layers. The upper layer of fatty acid methyl ester is then removed for use as an ingredient of biodiesel fuel.

By way of example, and not necessarily of limitation, the properties of the sulphated-ferric(ll l) oxide/alumina oxide solid acid catalyst is provided as follows:

EXAMPLE 2

Properties of the Sulphated-Ferric(ll l) Oxide/Alumina Oxide Solid Acid Catalyst (S04 ^2" -Fe203/Al2Q3) Prepared with the Method of the Present Invention

A test is conducted on obtaining the amount of ammonia desorbed for all synthesized acid catalyst. The result of the test is provided in the Table 1 below:

Table 1 : Amount of NH3 desorbed for all synthesized acid catalysts

Catalyst Max Desorption Ammonia Ammonia

Temperature Activation desorbed desorbed °C energy, E _d (μΓΤΐοΙ/g) (atom/g)

(kJ/mol)

5 wt% S0 ₄ ² -- 157 82.43 10.4479 6.29x10 ²⁰

10 wt% S0 ₄ ² -- 173 85.16 1 127.44 6.79x10 ²⁰

15 wt% S0 ₄ ² -- 175 76.90 1703.05 1 .03x10 ²¹

20 wt% S0 ₄ ² -- 149 73.00 472.09 2.84x10 ²⁰ Fe ₂ 03/AI ₂ 03 Further, a test is conducted for determining crystallite size of calcined S04 ^2" -Fe203/Al2C>3 catalysts with different catalyst concentration. Result of the test is provided below in Table 2: Table 2: Crystallite size of calcined S0 ₄ ^2" -Fe ₂ 03 AI ₂ 03 solid acid catalyst of different concentration.

Next, a test for determining surface area, pore diameter, and pore volume of S0 ₄ ^2" -Fe ₂ 03/AI ₂ 03 acid catalysts of varieties of concentration is conducted. The result of the test is provided in Table 3, which is provided below:

Table 3: Surface area, pore diameter, and pore volume of S0 ₄ ^2" -Fe ₂ 03/AI ₂ 03 catalysts with different concentrations.

The high surface area of the calcined S0 ₄ ^2" -Fe ₂ 03/AI ₂ 03 solid acid catalyst shows that the acid catalyst produced by the method of the present invention is suitable for use in biofuel production as the solid acid catalyst provides active sites with high availability, hence leading to higher suitability for use in esterification. A catalyst characterization result of the SCV ^' -FeaOs/AbOs acid catalyst is shown in Figure 3. The figure shows a thermograph of uncalcined S0 ₄ ^2" - Fe203/Al2C>3 acid catalyst. Figure 5 shows the result of reusability test of the solid acid S0 ₄ ^2" -Fe203/Al2C>3 catalyst produced by the method of the present invention in use for esterification for producing biofuel. The result shows that the solid acid S0 ₄ ^2" -Fe203/Al2C>3 catalyst may be reused for up to ten times with only 20% to 28% losses.

By way of example, and not necessarily of limitation, the properties of the sulphated-ferric(ll l) oxide/alumina oxide acid catalyst is provided as follows:

EXAMPLE 3

Properties of the Potassium/Silica Oxide Base Catalyst Solid Base Catalyst (K2Q/Si02) Prepared with the Method of the Present Invention

A test is conducted on obtaining the amount of carbon dioxide (CO2) desorbed for all synthesized base catalyst. The table that shows the result of the test is provided below:

Table 1 : Amount of NH3 desorbed for all synthesized acid catalysts

Further, a test is conducted for determining particle size of calcined K2O/S1O2 base catalysts based on varieties of catalyst concentration. Result of the test is provided below in Table 2: Table 2: Particle size of calcined K2O/S1O2 solid base catalyst by Debye-Scherrer equation.

Next, a test for determining surface area, pore diameter, and pore volume of K2O/S1O2 base catalysts of varieties of concentration is conducted. The result of the test is provided in Table 3, which is provided below:

Table 3: Surface area, pore diameter, and pore volume of K2O/S1O2 catalysts of different concentrations.

The high surface area of the calcined K2O/S1O2 solid base catalyst shows that the base catalyst produced by the method of the present invention is suitable for use in biofuel production, particularly in transesterification, as the solid base catalyst provides active sites with high availability, hence leading to higher suitability for use in transesterification.

A catalyst characterization result of the K2O/S1O2 base catalyst is shown in Figure 4. The figure shows a thermograph of uncalcined K2O/S1O2 base catalyst. Figure 6 shows the result of reusability test of the solid base K2O/S1O2 catalyst produced by the method of the present invention in use for transesterification for producing biofuel. The result shows that the solid base K2O/S1O2 catalyst may be reused for up to ten times with only 20% to 28% losses. While this invention has been particularly shown and described with reference to the exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.