METHOD FOR PRODUCING BIOFUEL

Abstract

The present invention provides a method for producing a biofuel that allows an animal/vegetable fat/oil raw material containing a free fatty acid to react with a lower alcohol in the presence of a solid acid catalyst, in which the consumption of the lower alcohol is reduced and the free fatty acid and the lower alcohol are selectively esterified to reform the animal/vegetable fat/oil.

In this method, as a solid acid catalyst is used a catalyst selected from an SiO.sub.2/Al.sub.2O.sub.3 solid acid catalyst, an SiO.sub.2/Al.sub.2O.sub.3 solid acid catalyst with aluminum being partially introduced into mesoporous silica, an Al.sub.2O.sub.3/B.sub.2O.sub.3 solid acid catalyst, and a sulfated zirconia solid acid catalyst, with a molar ratio of the free fatty acid and the lower alcohol of 1 to 6.

Claims

1. A method for producing a biofuel, comprising; reacting a fat/oil containing a free fatty acid with a lower alcohol, in the presence of a solid acid catalyst, with a molar ratio of the free fatty acid and the lower alcohol is 6 or less, and performing an esterification of the free fatty acid with the lower alcohol.

2. The method for producing a biofuel according to claim 1, wherein the molar ratio of a free fatty acid and a lower alcohol is 1 to 4.

3. The method for producing a biofuel according to claim 1, wherein the solid acid catalyst is selected from an SiO.sub.2/Al.sub.2O.sub.3 solid acid catalyst, a solid acid catalyst with aluminum being partially introduced into mesoporous silica, an Al.sub.2O.sub.3/B.sub.2O.sub.3 solid acid catalyst, and a sulfated zirconia solid acid catalyst.

4. The method for producing a biofuel according to claim 1, wherein a temperature of the reaction is 150 C. or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a schematic diagram of a batch-type reactor used in the present invention; and

[0030] FIG. 2 is a circulation-type reactor used in the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0031] In a method for producing a biofuel that allows an animal/vegetable fat/oil raw material containing a free fatty acid to react with a lower alcohol in the presence of a solid acid catalyst, as a solid acid catalyst is used a catalyst selected from an SiO.sub.2/Al.sub.2O.sub.3 solid acid catalyst, a solid acid catalyst with aluminum being partially introduced into mesoporous silica, an Al.sub.2O.sub.3/B.sub.2O.sub.3 solid acid catalyst, and a sulfated zirconia solid acid catalyst, with a molar ratio of the free fatty acid and the lower alcohol of 1 to 6.

EXAMPLES

Reactor Used in the Present Invention

[0032] FIG. 1 is a schematic diagram of a batch-type reactor, having a heater provided on the outer circumference of a reactor vessel, the vessel containing a raw oil and an alcohol as well as a catalyst. A reaction is produced by controlling the temperature in the reactor vessel and the agitation speed of reaction samples by a controller.

[0033] FIG. 2 is a schematic diagram of a circulation-type reactor, having a heater provided on the outer circumference of a reactor vessel filled with a catalyst. A raw oil and an alcohol contained in each reservoir are fed into the reactor vessel by a pump and allowed to pass through a catalytic layer to produce a reaction.

[0034] A reaction liquid is depressurized through a condenser and fed into a separation tank, and reformed oil is recovered from the top of the separation tank, the lower layer is fed into a separation column, a small amount of unreacted alcohol is recovered from the top, and recovered alcohol is stored in the reservoir and fed into the reactor for another reaction.

Example of Producing a Solid Acid Catalyst Used in the Present Invention

<Aluminum-Inserted SBA-15 (A1-SBA-15 (5))>

[0035] One example of a solid acid catalyst used in the present invention is a catalyst prepared by introducing a proper amount of aluminum into mesoporous silica (SBA-15), as shown below. A polymer P123 was dissolved with hydrochloric acid and mixed with TEOS (Tetraethyl Orthosilicate). Then, to the resulting mixture was added a proper amount of hydrochloric acid solution of aluminum sulfate, neutralized with aqueous ammonia, and aluminum was introduced into the SBA-15 such that the atom ratio of aluminum and silicon is 5. Thereafter, silica crystals were grown and the polymer P123 and the like were removed by air calcination at 450 C. to obtain an aluminum-inserted SBA-15 (A1-SBA-15 (5)). With a different amount of an aluminum sulfate added, an A1-SBA-15 having a different atom ratio of aluminum and silicon is prepared.

<Sulfated Zirconia (ZrO.sub.2/SO.sub.4.sup.2)>

[0036] One example of a solid acid catalyst used in the present invention is a sulfated zirconia, as shown below. (JRC-ZRO-2 to 5) were employed as a zirconium oxide, and they were pulverized until the particle size was 32 to 50 meshes. Then, 2 g of the above zirconium oxide was collected in a conical beaker, dissolved and dispersed in a 0.5 mol/liter sulfuric acid aqueous solution, allowed to stand for one hour, and then was subjected to suction filtration for about 10 minutes to obtain a sulfated zirconia. Moreover, the sulfated zirconia obtained in the above procedures was dried at 30 C. for 24 hours and using a crucible, calcined in the air at 600 C. for 3 hours to prepare a solid acid. In addition, when nitric acid or hydrochloric acid was used in place of sulfuric acid, zirconium nitrate or zirconium hydrochloride was prepared.

[0037] Table 1 shows experimental results using a batch-type reactor.

[0038] In Table 1, the reaction time is measured by the hour, and the kinetic viscosity is measured at 40 C.

[0039] Also, Amberlyst 70 is a commercially available solid acid catalyst as a cation exchange resin shown as a comparative example.

TABLE-US-00001 TABLE 1 Properties of product Reaction condition oil Rection Reaction results Acid number Kinetic Methanol/FFA Raw oil/catalyst Reaction temperature Conversion Conversion mg KOH/g viscosity catalyst (molar ratio) (weight ratio) time (hr) ( C.) rate 1) rate 2) raw oil (mPa .Math. s) SiO.sub.2/Al.sub.2O.sub.3 6 10:1 3 150 86.1 10.5 4.28 (70:30) 2 10:1 6 150 39.1 66.8 25.1 15.2 4 10:1.5 3 150 59.9 79.0 15.9 7.33 Al.sub.2O.sub.3/B.sub.2O.sub.3 2 10:1.5 3 150 29.6 77.3 17.1 (85:15) 4 10:1 3 150 46.9 67.2 24.8 Al-SBA-15 (5) 4 10:1 3 150 10.0 76.9 18.5 Amberlyst 70 2 10:1.5 3 150 53.5 10.5 67.6 Note 1: Conversion rate 1) was for triglyceride in raw oil (%). Note 2: Conversion rate 2) was for free fatty acid (FFA) in raw oil (%). Note 3: Raw oil was palm acid oil (PAO) containing approx. 37.4% free fatty acid, and the acid number is 75.5 mm KOH/g raw oil, and the kinetic viscosity was 34.4 mPa .Math. s.

[0040] As obviously shown in Table 1, as for the solid acid catalysts such as SiO.sub.2/Al.sub.2O.sub.3 solid acid catalysts, Al.sub.2O.sub.3/B.sub.2O.sub.3 solid acid catalysts, and Al-SBA-15 solid acid catalysts with aluminum being partially introduced into mesoporous silica SBA-15, high conversion rates of free fatty acids in a raw oil are obtained.

[0041] As for the Al.sub.2O.sub.3/B.sub.2O.sub.3 solid acid catalysts, and Al-SBA-15 solid acid catalysts in particular, both the high conversion rate of free fatty acids in a raw oil and the conversion rate of a triglyceride in the raw oil can be reduced.

[0042] High conversion rates of the free fatty acids in the raw oil can be obtained by reducing the consumption of a lower alcohol, with a molar ratio of the free fatty acid and the lower alcohol of 6 or less, preferably 1 to 4.

[0043] Furthermore, a free fatty acid and a lower alcohol can selectively be esterified, with a reaction temperature of 150 C. or less, preferably 100 C. to 150 C.

Experiment by Circulation-Type Reactor

[0044] SiO.sub.2/Al.sub.2O.sub.3 solid acid catalysts with aluminum being partially introduced into mesoporous silica (Al-SBA-15) were filled in a reactor vessel of a circulation-type apparatus shown in FIG. 2, and a raw oil and a lower alcohol were fed thereinto to be esterified. Consequently, predetermined effects were obtained.

[0045] The present invention can provide a method for producing a biofuel suitable for use with diesel engines by raising the conversion rate of a free fatty acid in a raw oil to reform a fat/oil, and excellent in cost performance by reducing the conversion rate of a triglyceride in the raw oil.