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, wherein the solid acid catalyst is 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, and an Al.sub.2O.sub.3/B.sub.2O.sub.3 solid acid catalyst.

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 a temperature of the reaction is 150° C. or less.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a batch-type reactor used in the present invention; and

(2) FIG. 2 is a circulation-type reactor used in the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) 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

(4) Reactor Used in the Present Invention

(5) 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.

(6) 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.

(7) 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.

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

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

(10) 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.

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

(12) 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.

(13) Table 1 shows experimental results using a batch-type reactor.

(14) In Table 1, the reaction time is measured by the hour, and the kinetic viscosity is measured at 40° C.

(15) Also, Amberlyst 70 is a commercially available solid acid catalyst as a cation exchange resin shown as a comparative example.

(16) 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.

(17) 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.

(18) 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.

(19) 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.

(20) 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.

(21) Experiment by Circulation-Type Reactor

(22) 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.

(23) 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.