WO2009147816A1 - Heteropoly acid decomposition catalyst and method for manufacturing diesel fuel oil using said catalyst - Google Patents

Abstract

Disclosed is a heteropoly acid catalyst/carrier composite prepared by sintering a carrier composed of Nb₂O₅ and WO₃ at a temperature in the range of 723‑823 K, and a Keggin type of heteropoly acid catalyst with which it is possible to lower the environmental load and easily separate the solid acid catalyst during manufacture, and that can be achieved at an economic reaction rate without wasting resources or energy when manufacturing diesel fuel oil by using a solid acid catalyst of a heterogeneous system to convert fatty acid triglycerides in oil and grease into fatty acid monoesters with an ester exchange reaction. Also disclosed is a fatty acid monoester manufacturing method using said composite.

Description

Heteropoly acid decomposition catalyst and method for producing diesel fuel oil using the same

The present invention relates to a heteropolyacid decomposition catalyst for converting fatty acid glycerides (mainly fatty acid triglycerides) into fatty acid monoesters by transesterification and a method for producing biodiesel fuel using the same.

In order to suppress the increase in CO ₂ , biofuels are required to be put to practical use. In particular, a method for obtaining fatty acid monoesters (so-called biodiesel) from plant-derived fats and oils (fatty acid triglycerides) by transesterification (1) is promising ( Non-patent document 1, Non-patent document 2). The small-molecule alcohol as a secondary raw material may be natural gas-derived methanol, petroleum-derived ethanol, bioethanol, or the like. In the case of using bioethanol, theoretically, an increase in CO ₂ (= CO ₂ generated by combustion) -The amount of CO ₂ absorbed by the plant by photosynthesis is zero, which is the most efficient. Even if natural gas or petroleum-derived alcohol is used, since most of the energy is generated from fats and oils, the amount of increase in CO ₂ is very small compared to current diesel fuel (light oil).

Chemical formula 1 shows the reaction of fatty acid triglyceride + small molecule alcohol → fatty acid monoester + glycerin. For example, if x = 17, y = 33, m = 2, and n = 5, the reaction is to make ethyl oleate from triolein (main component such as palm oil) and ethanol.

The advantages of biodiesel over bioethanol are that bioethanol requires a special engine or engine modification, whereas biodiesel can be used directly with current diesel engines, per biodiesel weight and cultivated land The energy density per area is large, and it takes a long time to obtain ethanol from a plant using an enzyme, whereas reaction (1) can be carried out at a practical speed if a good catalyst is used. It is. Biodiesel not only has the same performance as the current diesel fuel (diesel oil) but also is superior to diesel oil in that it does not contain sulfur.

Reaction (1) proceeds without catalyst under supercritical (very high pressure, high temperature) conditions (Patent Document 1, Non-Patent Document 3), but is not practical because it requires equipment and energy to maintain high pressure and high temperature. . Therefore, conventionally, a homogeneous base catalyst such as KOH has been used in the reaction (1) (Non-patent Document 4). When a homogeneous base catalyst is used, the catalyst is dissolved in the raw material solution, and the lower layer containing a large amount of glycerin is removed from the solution obtained after the reaction (containing the product and catalyst) to obtain biodiesel fuel oil. The lower layer contains a catalyst and is a base solution that is harmful to the environment, so it consumes energy and resources such as adding acid to desalinate and incinerate for detoxification.Furthermore, local governments use biodiesel from waste tempura oil, for example. When making it outside the chemical factory, measures to use dangerous acids and bases are necessary. That is, since the environmental load of the homogeneous catalyst is high, this causes a drawback.

Therefore, an attempt has been made to use a solid catalyst that can be easily separated from the solution. Conventionally proposed as solid catalysts are roughly divided into two groups, solid bases and solid acids.

Examples of the solid base include calcium oxide (Non-Patent Document 5, Non-Patent Document 6), alkali-type zeolite (Non-Patent Document 7), alkali-modified alumina (Non-Patent Document 8, Non-Patent Document 9), and the like. Although the reaction proceeds at the reaction rate, if water or carboxylic acid is mixed in the raw material, dissolution into the solution occurs, and the solid catalyst loses the active component and becomes irreversibly deactivated. Further, when the obtained biodiesel fuel is used as it is for an internal combustion engine, precipitation of inorganic components becomes a problem. Natural vegetable fats and oils and waste tempura oil are used as raw materials for biodiesel fuel production, but water and carboxylic acid are inevitably mixed in both. In order to avoid this, some pretreatment for removing water and carboxylic acid from the raw material of reaction (1) is required. Further, since the solid base catalyst is deactivated by carbon dioxide when exposed to air, a pretreatment of the catalyst is necessary immediately before the reaction. Improvements in solid base catalysts have also been made, but it is difficult to essentially solve these problems.

Since the solid acid catalyst does not have the above problem (Non-patent Document 10), it is considered that practical use is easy if a sufficient reaction rate can be realized. In addition, unlike a homogeneous catalyst, an apparatus for continuously producing biodiesel fuel by a fixed bed tube type flow reaction or a tank type flow reaction is considered to be easily possible. For this purpose, a solid acid catalyst that reaches a sufficient conversion rate within a contact time of about 10 hours is practically required. If this is achieved, it will be easy to place small plants not only in chemical factories but also in local government waste oil collection sites, etc. For the above reasons, a search for a solid acid catalyst that promotes the reaction (1) has been conducted. Various substances are known as solid acids, but examples reported in the reaction (1) include acidic ion exchange resins (Patent Document 2, Non-Patent Document 11), WO ₃ ZrO ₂ (Non-Patent Document). 12), sulfated zirconia, and acid-type zeolite (Non-Patent Document 13, Non-Patent Document 14). Both have low activity and are not practical.

The prior patent document (Patent Document 2) describes that a solid acid catalyst can be used as a catalyst for the ester reaction, but the examples only include acidic ion exchange resins and clays, There is no feasible description for other solid acid catalysts.

Thus, there is no example which performed reaction (1) reaction at a practical speed using the solid acid catalyst with which separation from a product is easy (nonpatent literature 15, nonpatent literature 16). In manufacturing, there is no known method that does not waste resources and energy, has a low environmental impact, and performs at a practical speed.

JP 2008-7658 A JP-A-6-313188

The present invention converts a fatty acid triglyceride into a fatty acid monoester by a transesterification reaction using a heterogeneous solid acid catalyst, and has a low environmental burden and excellent stability, and has a high conversion or yield. An object of the present invention is to find a method for producing biodiesel fuel using the solid acid catalyst.

As a result of diligent research to solve the above-mentioned problems, the present inventors have found that fatty acid triglycerides contained in plant-derived oils and fats are converted to fatty acid monoesters by transesterification with alcohol at a temperature of 723 K to 823 K. It has been found that by using a complex containing a Keggin-type heteropolyacid decomposition catalyst containing niobium that has been subjected to a calcination treatment and an inorganic support, a good effect can be obtained for the transesterification reaction of the above-mentioned problem. As a result, the inventors have found a method for producing a good biodiesel fuel by using the present invention, and have made the present invention.

That is, according to the present invention, a catalyst having high catalytic activity and not dissolved during the target transesterification can be obtained by calcining the Keggin type heteropolyacid catalyst at a temperature of 723 K to 823 K. it can.

_{HPNbW / NbW (H 4 PNbW 11} O 40 40wt% / WO 3 36wt% -Nb 2 O 5 24wt%, 773K fired) in a batch reaction with, is a graph showing the relationship between the reaction time and the ethyl oleate yield . It is a diagram showing a relationship between firing temperature and ethyl yield oleate HPNbW _/ NbW in a batch-type reaction _{(H 4 PNbW 11 O 40 40wt} % / WO 3 36wt% -Nb 2 O 5 24wt%). HPNbW _/ NbW in a batch-type reaction _{(H 4 PNbW 11 O 40 40wt} % / WO 3 36wt% -Nb 2 O 5 24wt%, 773K firing) is a diagram showing the relationship between pre-treatment temperature and ethyl yield oleate. The relationship between ethanol / triolein mol ratio and ethyl oleate yield in batch reaction using HPNbW / NbW (H ₄ PNbW ₁₁ O _{40 40} wt% / WO ₃ 36 wt% -Nb ₂ O ₅ 24 wt%, 773K calcined) FIG. Batch reaction (reaction time) in the case of using no catalyst (no catalyst) and HPNbW / NbW (H ₄ PNbW ₁₁ O _{40 40} wt% / WO ₃ 36 wt% -Nb ₂ O ₅ 24 wt%, 773 K calcined) It is a figure which shows the comparison of the ethyl oleate yield in ethanol / triolein molar ratio 15,50 in 8h). In batch reaction, the relationship between the weight ratio of H ₄ PNbW ₁₁ O _{40 in} HPNbW / NbW and the yield of ethyl oleate (weight ratio of Nb ₂ O ₅ and WO ₃ is 4: 6, firing temperature is constant at 773K) FIG. It is a reference figure which shows the transesterification reaction apparatus used for the fixed bed flow-type reaction. It is a figure which shows the time-dependent change of the triolein conversion, yield, and mass balance in the fixed bed flow reaction which uses HPNbW / NbW as a catalyst. (A) Reaction temperature is 377K, (b) Reaction temperature is 394K.

Keggin-type heteropolyacid catalyst and heteropolyacid catalyst / support complex The first embodiment of the present application has the chemical formula:

[In the above formula, X is a single or plural kinds of atoms selected from a hydrogen atom or an alkali metal atom, P is phosphorus, Nb is niobium, W is tungsten, and O is an oxygen atom. ]

And a fatty acid glyceride contained in fats and oils of a Keggin-type heteropolyacid catalyst having n in the range of 0.8 to 2.2 and a carrier consisting of Nb ₂ O ₅ and WO ₃ The present invention relates to a heteropolyacid catalyst / support complex calcined at a temperature of 723 K to 823 K for conversion to a fatty acid monoester by an ester exchange reaction.

The Keggin heteropolyacid catalyst according to this embodiment is modified to a heteropolyacid decomposition catalyst by baking the Keggin heteropolyacid catalyst at a temperature of 723K to 823K.

“Heteropolyacid” is a polymer polyoxoacid (Y ₁ M _m O _n ) _x- type polyacid in which a heteroelement is inserted into a metal oxoacid skeleton. Here, Y represents a hetero element, M represents a poly element, and O represents oxygen.
“Keggin type” is one of the crystal structures of heteropolyacids and is distinguished from other “Dawson type” crystal structures.

“Heteropolyacid decomposition catalyst” is a heteropolyacid-decomposed post-calcination heteropolyacid in which a part or the whole of the crystal structure is changed from an original structure to an amorphous structure by thermal decomposition. It refers to an acid catalyst (K. Okumura, et al., J. Catal., 245, 75 (2007)).

The catalyst used in the transesterification reaction is more preferably in the form of a “heteropolyacid catalyst / support complex” in which a Keggin type heteropolyacid is supported on a support. This is because the separation of the catalyst is facilitated in the reaction by the tank reactor, and in the tubular reactor, the catalyst is filled in the reactor and is easily fixed. The heteropolyacid that is a raw material of the heteropolyacid catalyst according to the present embodiment is a Keggin type heteropolyacid containing niobium as a poly element,

[In the above formula, X represents a single atom or plural kinds of atoms selected from a hydrogen atom or an alkali metal atom, and preferably a hydrogen atom. P represents phosphorus, Nb represents niobium, W represents tungsten, and O represents an oxygen atom. n is a numerical range of 0.8 to 2.2, preferably n = 1. ]

(Hereinafter referred to as “HPNbW”) is preferable from the viewpoint of high catalytic activity and low solubility during reaction (see Example Table 3). Here, the numerical range of n in the composition means a range of errors that can occur in the preparation of the heteropolyacid, and preferably indicates that n = 1. As the alkali metal atom, lithium, sodium, potassium, rubidium, cesium, and francium of Group 1A of the periodic table are selected. The heteropolyacids selected in the present embodiment are not limited to those having substantially the same composition ratio, and similar Keggin-type heteropolyacids may have the same or higher effects. It does not exclude acid catalysts. The heteropolyacid catalyst / support complex according to the present embodiment is a complex comprising the above heteropolyacid catalyst and an inorganic carrier supporting the heteropolyacid catalyst.

The inorganic carrier supporting the heteropolyacid may be any inorganic carrier as long as it does not inhibit the transesterification reaction, is stable to the reaction, and functions as a carrier. , Nb ₂ O ₅ and WO ₃ (hereinafter referred to as “Nb ₂ O ₅ —WO ₃ ” or “NbW”). This is because dissolution or decomposition of the catalyst after the catalytic reaction can be prevented (see Example Table 3).

Therefore, the heteropolyacid catalyst / support complex is most preferably an “HPNbW / NbW” type complex using a combination of “HPNbW” type heteropolyacid and “NbW” inorganic carrier as raw materials.
The preferred heteropolyacid catalyst / support complex (HPNbW / NbW) described above is

(I) A Keggin type heteropolyacid catalyst (for example, H ₄ PNbW ₁₁ O ₄₀ ) and an inorganic carrier raw material (for example, WO ₃ , Nb ₂ O ₅ , niobium oxalate and ammonium tungstate) are mixed in water to form an aqueous solution. Process,
(Ii) drying the aqueous solution;
(Iii) a step of firing at a specific temperature;

A heteropolyacid catalyst / support complex comprising a heteropolyacid decomposition catalyst prepared by a preparation method comprising: According to this preparation method, the heteropolyacid decomposition catalyst has a structure supported not only on the surface of the inorganic carrier but also inside the carrier. This preparation method is preferable in that the bond between the supported heteropolyacid and the carrier becomes strong and the durability is excellent.
On the other hand, as other preparation methods,
(I) a step of impregnating an inorganic carrier with a Keggin-type heteropolyacid in the solution (ii) a step of drying the solution;
(Iii) a step of firing at a specific temperature;

It may be a heteropolyacid catalyst / support complex including a heteropolyacid decomposition catalyst prepared by a preparation method comprising: In this case, the heteropolyacid decomposition catalyst has a structure supported on the surface of the inorganic carrier. Moreover, a preparation method other than the above may be used as long as the desired heteropolyacid catalyst / support complex is obtained.

The specific firing temperature in the firing step is a temperature around 723K to 823K, preferably 760K to 790K, and most preferably around 773K. By carrying out the calcination treatment under these specific conditions, it is possible to suppress the dissolution of the catalyst during the transesterification reaction while maintaining high catalyst activity, and to obtain a much higher durability of the catalyst than before calcination. FIG. 2 of an example described later describes comparative experimental data on the basis of the numerical range for catalyst activity and Table 3 for the solubility of the catalyst (see Examples). The unburned heteropolyacid (catalyst number 2) is completely dissolved in the catalyst during the transesterification reaction, so the effect of the baking step at the specific temperature is clear.

When the transesterification is carried out with the heteropolyacid catalyst / support complex, the composition ratio of HPNbW / NbW is such that the raw material before the preparation is a Keggin heteropolyacid (H _{3 + n} PNb _n W _12-n O ₄₀ ) is 30% to 50% by weight, WO _{3 of the} inorganic carrier raw material is 25% to 45% by weight, and Nb ₂ O ₅ of the inorganic carrier raw material is 15% to 35% by weight. % Range is preferred. More preferably, H _{3 + n} PNb _n W _12-n O ₄₀ is in the range of 35 wt% to 45 wt%, WO ₃ is 32 wt% to 40 wt%, and Nb ₂ O ₅ is in the range of 20 wt% to 28 wt%. . Most preferably, the weight ratio of the heteropolyacid catalyst (H _{3 + n} PNb _n W _12-n O ₄₀ ) is an amount in the vicinity of 40% by weight with respect to the whole heteropolyacid catalyst / support complex showing the highest catalytic activity. . FIG. 6 of an example described later describes comparative experimental data that is the basis for the numerical range (see the example).

Raw material alcohol As the alcohol used in the present invention, an alcohol having 1 to 4 carbon atoms, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butyl alcohol or the like is preferably used. In particular, it is preferable to use methanol or ethanol in terms of reactivity and economy. The raw material alcohol may be of mineral origin or biological origin.

-Raw material fats and oils The raw material used for this embodiment is fats and oils and contains fatty acid glyceride. The fatty acid glyceride is a glyceride of a saturated or unsaturated aliphatic carboxylic acid, and the carbon chain of the carboxylic acid moiety may have any length, but preferably has a carboxylic acid moiety having C14 to C24 carbons. Fatty acid triglyceride. However, in general, fatty acid diglycerides and fatty acid monoglycerides mixed in fats and oils together with fatty acid triglycerides as main components can also be used as raw materials for the transesterification reaction of the present application in the same manner as fatty acid triglycerides. Examples of oils and fats used in the present invention include soybean oil, corn oil, coconut oil, olive oil, peanut oil, sesame oil, sunflower oil, linseed oil, palm oil, rapeseed oil, castor oil, coconut oil, and other plant-derived oils and fats, Animal fats and oils such as beef tallow, pork tallow, whale oil and fish oil, synthetic fats and oils, and mixtures thereof. The content ratio of the fatty acid triglyceride contained in the oil and fat may be any ratio. Moreover, the used waste oil of these fats and oils can be selected as an effective raw material especially as an environmental measure. If the fats and oils are plant or animal-derived fats and oils, the consumption of fossil fuels can be reduced by the biodiesel fuel oil of the product oil.

A method for producing a fatty acid monoester and a method for producing a biodiesel fuel oil The second embodiment of the present invention is a method for producing a fatty acid monoester from a fatty acid glyceride and an alcohol in the presence of the above heteropolyacid catalyst / support complex. About.

In the production of the fatty acid monoester, for example, a heatable reactor (reaction tube) containing the above heteropolyacid catalyst / support complex, an oil and fat containing fatty acid glycerides, and a raw alcohol are introduced into the reactor. A transesterification apparatus for converting fatty acid glycerides into fatty acid monoesters can be used.

The reactor may be a batch tank reactor, a fixed bed flow tube reactor, or a tank flow reactor, but in consideration of industrial practicality, the fixed bed may be used. A continuous flow tubular reactor or a tank flow reactor is preferred.

In the production of fatty acid monoesters using a transesterification reactor, when the amount of fatty acid glycerides and HPNbW / NbW introduced into the reactor is fixed, generally, the higher the amount of alcohol, the higher the yield of fatty acid monoesters. It is said that the reaction rate becomes faster. However, an excessive increase in alcohol requires a large amount of energy for distillation and circulation of the unreacted surplus alcohol and increases costs, which is not preferable from the viewpoints of the global environment and economics. Therefore, it is necessary to set the amount of the raw material alcohol to an optimum condition in relation to the fatty acid glyceride. For example, the raw alcohol and the raw fat / oil are preferably introduced into the reactor so that the molar ratio of raw alcohol / fatty acid glyceride is in the range of 6 to 50 (in the alcohol / fatty acid group molar ratio is in the range of 2 to 17). More preferably, it is in the range of 9-30 (in the alcohol / fatty acid group mol ratio, in the range of 3-10), and most preferably in the range of 12-15 (in the alcohol / fatty acid group mol ratio, in the range of 4-5. ). FIG. 7 shows a reference diagram of the transesterification reactor (10) in the case of a fixed bed flow type tubular reactor.

The transesterification reactor (10) has a pump (13) capable of introducing each raw material into a reaction tube (15) from a tank (11) containing raw oil and fat and a tank (12) containing raw material alcohol. ), A pressure gauge (14), and a device including a pressure valve. Here, as long as the introduction of the raw material can be stably maintained at the inlet portion of the reaction tube, the raw material tank and the raw material introduction device may have any structure.

The transesterification reaction is monitored by a pressure gauge (14), a flow meter attached to the reactor, a thermometer, etc., so that the introduction of each raw material can be operated by a pressure valve, a back pressure valve (18), etc. An apparatus is preferred.

Furthermore, the reaction tube (15) of the reactor (10) is equipped with an electric furnace (17). The electric furnace and the heating method using the electric furnace may be any structure and method as long as the entire reaction tube (reactor) or a specific part can be kept at a high temperature safely and stably.

When the transesterification reactor (10) is a reaction tube (15) of a tubular reactor as shown in FIG. 7, the heteropolyacid catalyst (16) filled in the reaction tube is supported on an inorganic carrier. Particularly preferred is a heteropolyacid catalyst / support complex. This is to prevent the catalyst from dissolving in the liquid phase during the reaction, and to facilitate handling by filling and fixing the catalyst in the reaction tube.

The heating temperature of the reactor in the transesterification reaction apparatus is appropriately selected according to the relationship between the catalyst, the raw material fat and the raw material alcohol, and is an HPNbW / NbW type heteropolyacid catalyst / support complex, where the raw fat and oil is a fatty acid triglyceride When the raw alcohol is ethanol, the temperature is preferably 350 K to 580 K (see Example, FIG. 8).

The third embodiment of the present application relates to a method for producing diesel fuel oil including a step of converting fatty acid glycerides contained in fats and oils into fatty acid monoesters using the above heteropolyacid catalyst / carrier complex.

The raw material fats and oils may be any fats and oils as long as they contain fatty acid glycerides such as fatty acid triglycerides. Biodiesel fuel oil can be produced by selecting oils derived from plants or animals. Moreover, used waste oil can be used as raw material fats and oils in the range in which the contaminants and moisture contained in the fats and oils do not hinder the operation in terms of the catalytic activity and flow rate of the transesterification reaction apparatus. In this embodiment, the purpose is mainly to obtain a fatty acid monoester corresponding to a fraction of diesel fuel oil. However, in the case of raw oils and fats containing a large amount of light components, production of kerosene containing abundant oxygen atoms Can also be used.

According to the fuel oil production method described above, resources and energy are not wasted by reducing the load on the environment and facilities due to the use of strong bases, strong acids, etc., unlike conventional biodiesel fuel production processes, Since no special process is required to separate the catalyst from the product oil (reaction liquid layer), there is no environmental impact such as waste generation due to the neutralization reaction of the strong base catalyst. Since the catalyst can be easily separated without dissolving in water or liquid phase, it is advantageous in that fuel oil can be produced at a practical reaction rate. Further, when producing biodiesel fuel using plant or animal-derived fats and oils as raw materials, it is advantageous in that there are no fatal problems in the catalytic reaction even if the raw materials contain a small amount of carboxylic acid or water.

As described above, according to the present invention, the structure of the heteropolyacid catalyst is changed by calcining the Keggin type heteropolyacid catalyst at a temperature of 723 K to 823 K, and the transesterification reaction between the fatty acid glyceride and the alcohol is performed. A catalyst having high catalytic activity can be obtained. In addition, by supporting a heteropolyacid catalyst on an inorganic carrier to form a heteropolyacid catalyst / carrier complex, it is possible to obtain a catalyst that has high catalytic activity and does not dissolve during the intended transesterification reaction.

Further, according to the present invention, the catalyst can be easily separated from the produced oil by the transesterification reaction apparatus provided with the heteropolyacid catalyst or the heteropolyacid catalyst / support complex, and for ethanol distillation and circulation. The energy required can be greatly reduced. Therefore, a practical catalytic reaction can be performed by the transesterification reaction apparatus.

Furthermore, according to this invention, the process of converting the fatty acid glyceride contained in fats and oils (especially biologically derived fats and oils) into fatty acid monoester by using said heteropolyacid catalyst or heteropolyacid catalyst / carrier complex is included. It is a method for producing diesel fuel oil, and a method for producing an environmental load can be provided.

Hereinafter, the present invention will be illustrated in more detail, but the present invention is not limited to the examples.

Batch type reaction (batch type tank type reaction) (1) Catalyst The catalyst used is as described in Table 1.

Incidentally, unfired _H in Table 1 4 _PNbW 11 _{O 40} (Catalyst No. 2, the feed heteropolyacid catalyst No. 1 and 2) were synthesized by the following method.

An aqueous solution of Na ₂ WO ₄ · 2H ₂ O (100 g), Na ₂ HPO ₄ · 12H ₂ O (50 g) and niobium oxalate (160 ml) was stirred at 353 K for 4 hours while adding a 24% aqueous hydrochloric acid solution (150 ml). . Diethyl ether and a small amount of concentrated hydrochloric acid were added to the reaction product solution to obtain the product as a filtered precipitate. The composition of H ₄ PNbW ₁₁ O ₄₀ · 13H ₂ O was confirmed by inductively coupled plasma (ICP) analysis and thermogravimetric (TG) analysis.

(2) Raw material In the present Example, ethanol (Wako Pure Chemicals special grade) was used as alcohol, and it was used without dehydrating.
Triolein (Tokyo Kasei) with relatively few impurities was used as the raw material fat. The composition of each component contained in Triolein is as shown in Table 2.

As shown in Table 2, hereinafter, triolein contained in the raw material will be expressed as “OOO”, dioleo-renolinoin as “OOL”, diolein as “OO”, and oleorelinoline as “OL”. *

(3) Reaction operation (batch-type reaction) 0.2 g of catalyst, 4.7 g (0.10 mmol) of ethanol, 1.76 g of triolein (“OOO” 1.5 mmol + “OOL” 0.32 mmol + “OO” 0.28 mmol + “ OL "(0.03 mmol) (that is, ethanol / triolein mol ratio = 50, alcohol / fatty acid group mol ratio = 17), each in a small container, sealed in an autoclave with a capacity of 100 cm ³ under a nitrogen atmosphere, and a temperature of 373 K And stirred for 8 h. The internal pressure of the autoclave increased with the vaporization of ethanol, and in all cases was about 0.3 MPa. After cooling, a known amount of ethyl decanoate (internal standard substance) was added to the product solution, diluted with an analysis solvent (2-propanol + hexane, volume ratio 5: 4), and solid components were separated by filtration. The filtrate was analyzed by liquid chromatography.

In the case of pretreatment, the catalyst is treated for 1 hour at a predetermined temperature in a nitrogen stream in the glass tube, then the cock at the inlet and outlet of the glass tube is closed and allowed to cool, and ethanol is trioated as described above in a nitrogen atmosphere. Sealed together with rain in an autoclave and reacted in the same manner. In addition, in order to evaluate the influence by ethanol / triolein mol ratio, the reaction operation which changed only the quantity of ethanol suitably was performed similarly.

(4) Analysis According to the method described in the literature (M. Holczapek, P. Jandera, J. Fischer and B. Prokesz, J. Chromatogr., A, 858, 13 (1999)), ethyl decanoate was used as an internal standard substance. Analysis was performed using high performance liquid chromatography.

(5) Experimental results [comparison with catalyst]
The activities of various catalysts were compared at a reaction temperature of 373 K and a reaction time of 8 h. In the transesterification reaction, “OOO” + ethanol → ethyl oleate + “OO”, “OO” + ethanol → ethyl oleate + monoolein (C ₁₇ H ₃₃ COOC ₃ H ₅ (OH) ₂ , hereinafter “O”), “O” + ethanol → ethyl oleate + glycerin sequentially produces ethyl oleate (target product), and “OOL” and “OL” also react, but Table 3 is easy to compare In addition, the conversion rate of “OOO”, the yield of ethyl oleate, and the mass balance of C ₁₇ H ₃₃ CO groups (groups contained in “OO” and “OL” were also added. However, “O” could not be quantified. (Not considered).

As shown in Table 3, a small amount of ethyl oleate was produced even under the condition of “no catalyst (catalyst number 0)”.

HPNbW / NbW (catalyst number 1), Nb ₂ O ₅ —WO ₃ (catalyst number 4), zeolite β (catalyst number 12), silica alumina (catalyst number 15), sulfated zirconia (catalyst number 16), silica-supported doson The type heteropolyacid (Catalyst Nos. 9 to 11) and the Keggin type heteropolyacid Cs salt (Catalyst No. 8) were not dissolved as far as they were visually recognized, but the uncalcined heteropolyacid (Catalyst No. 2) was dissolved.

Among the solid catalysts that did not dissolve, HPNbW / NbW (Catalyst No. 1), Keggin-type heteropolyacid Cs salt (Catalyst No. 8), and sulfated zirconia (Catalyst No. 16) exhibited high activity (ethyl oleate yield). The other solid catalysts showed little activity. Among them, the activities of HPNbW / NbW and Keggin type heteropolyacid Cs salt were the highest. However, although the Keggin heteropolyacid Cs salt could be filtered in the examples described in Table 3, this material usually consists of particles smaller than 1 μm in diameter, suspended in many solutions without precipitation, and industrial It is known that it is difficult to filter using a filter cloth (N. Horita, M. Yoshimune, Y. Kamiya and T. Okuhara, Chem. Lett., 34, 1376 (2005). ). For this reason, there is no advantage as a solid acid catalyst in a fine particle state, and it is not suitable as a catalyst of the present invention. Accordingly, HPNbW / NbW (Catalyst No. 1), which is the heteropolyacid catalyst / support complex of the present invention, showed the highest activity among the solid acid catalysts that can be easily separated from the product. HPNbW / NbW clearly showed high activity as compared with acidic ion exchange resins, WO ₃ / ZrO ₂ , sulfated zirconia, zeolite and the like described in the prior literature (see paragraph [0008]).

“Uncalcined” HPNbW (catalyst number 2), which is a raw material of the heteropolyacid catalyst / support complex HPNbW / NbW, showed high activity, but was completely dissolved after the reaction was completed. It is not suitable as a catalyst for the transesterification reaction to be converted into Various heteropolyacids, which are similar compounds, also showed activity but were completely dissolved. On the other hand, HPNbW (Catalyst No. 3) calcined without an inorganic carrier is inferior to HPNbW / NbW (Catalyst No. 1) in that it is partially dissolved during the reaction, but has high activity. It can be used for exchange reactions. Nb ₂ O ₅ —WO ₃ (catalyst number 4), which is an HPNbW / NbW carrier, was inactive as a catalyst.

[Catalytic activity of HPNbW / NbW]
FIG. 1 shows the relationship between the reaction time and the ethyl oleate yield in a batch reaction using HPNbW / NbW (H ₄ PNbW ₁₁ O _{40 40} wt% / WO ₃ 36 wt% -Nb ₂ O ₅ 24 wt%, 773 K calcination). Up to about 20 h of reaction time, the ethyl oleate yield increased slowly to about 65%. Even when the ethanol / triolein molar ratio was 15, the ethyl oleate yield showed the same tendency as in the case of the molar ratio of 50 until the reaction time was about 12 h.

The catalytic activity of HPNbW / NbW strongly depended on the calcination temperature, and the activity was low regardless of whether the calcination temperature was low or high with 773K as the maximum (FIG. 2). The measurement was carried out by changing the pretreatment temperature while keeping the firing temperature constant at 773K. The activity was shown when the pretreatment temperature was lower than 773K, but the activity decreased at 823K (FIG. 3). As described above, the activity of the present catalyst is sensitive to the calcination temperature (thermal history), and the catalyst activity largely changes with the peak at around 773K. When pretreatment is performed at a temperature higher than this temperature, the thermal change proceeds and the activity is lost.

Further, when the influence of ethyl oleate yield was investigated by changing the ethanol / triolein mol ratio, high activity was maintained in the range of ethanol / triolein mol ratio of about 9 to about 30 (FIG. 4). This tendency was the same even when the reaction time was 6 hours. Even under the condition of “no catalyst” (catalyst number 0), when the batch reaction was carried out with an ethanol / triolein mol ratio of 15, the triolein conversion was higher than in the case of a mol ratio of 50. The yield of ethyl oleate was 6.4% at a mol ratio of 50 and 9.7% at a mol ratio of 15 and was low (FIG. 5). ). This is because in the batch reaction under the condition of “no catalyst”, many unidentified peaks were observed in the analysis by high performance liquid chromatography, so the excess triolein that did not react with ethanol in the transesterification reaction is unknown. It was speculated that it was changed to a substance. On the other hand, HPNbW / NbW has high catalytic activity in the transesterification reaction even when the ethanol / triolein molar ratio is lowered (FIG. 5). It is possible to produce a product. Therefore, efficient production of fatty acid monoesters becomes possible with HPNbW / NbW.

On the other hand, when the composition ratio of HPNbW and the carrier was changed, HPNbW had a high activity in the range of 30 to 50% by weight of the total weight, and the composition ratio showing the highest activity was around 40% by weight (Fig. 6). When HPNbW was 100% (catalyst number 3), the catalyst activity was high, but a part of the catalyst was dissolved in the liquid phase.

Therefore, the optimal composition ratio of HPNbW is around 40% by weight with respect to the total weight of the heteropolyacid catalyst / support complex.

Fixed bed flow reaction (1) Catalyst The catalyst used is the same as described in Example 1 (Table 1).

(2) Raw materials In this example, as in Example 1, ethanol (Wako Pure Chemicals special grade) was used as the alcohol, and triolein (Tokyo Kasei) was used as the fat.

(3) Reaction operation (fixed bed flow reaction)
7.4 g of HPNbW / NbW heteropolyacid decomposition catalyst was set in the reaction tube (inner diameter 7.6 mm, length 150 mm) of the apparatus of FIG. 7, ethanol was 0.60 gh ⁻¹ (13 mmol · h ⁻¹ ), Triolein 0.23gh ⁻¹ (“OOO” 0.19 mmol · h ⁻¹ + “OOL” 0.042 mmol · h ⁻¹ + “OO” 0.037 mmol · h ⁻¹ + “OL” 0.0042 mmol · h ^-1 ) (ie, ethanol / triolein molar ratio = 50, alcohol / fatty acid group molar ratio = 17). The reaction tube was kept at a predetermined reaction temperature with an electric furnace, and the pressure in the system was kept at 0.4 MPa (gauge pressure 0.3 MPa) at the start of circulation by a back pressure valve at the outlet. Shortly after the start of distribution, the pressure rose to about 0.6 MPa due to the pressure loss of the catalyst and the filter. In addition to a column filter (pore size 2 μm), a filter paper (5C, retention particle size 1 μm) is set at the catalyst outlet, and an empty reaction tube (inner diameter 4 mm, length 14 cm, front and rear column filter 2 μm) A 5C filter paper having a retention particle diameter of 1 μm was disposed to separate the solid and the liquid. The exit liquid was sampled and analyzed by liquid chromatography.

(4) Analysis The analysis was performed in the same manner as in Example 1.

(5) Experimental results Persistence of catalytic activity, ease of catalyst separation]

FIG. 8 shows the results of a fixed bed flow-type reaction using HPNbW / NbW of the heteropolyacid catalyst / support complex. (A) shows the time-dependent change results of the conversion rate, yield, and mass balance at 373 K, and (b) at 393 K at a slightly elevated reaction temperature. At 377 K, the yield of ethyl oleate was about 80% in the initial stage, but it rapidly decreased gradually and gradually reached about 20% after 150 hours. At 394K, the ethyl oleate yield was slightly higher. Thus, although the reaction rate was reduced, the activity was observed even after one week.

The decrease in reaction rate is thought to be due to catalyst deterioration. However, the fact that activity was observed even after one week in this condition in the fixed bed flow-type reaction indicates the practical applicability of HPNbW / NbW.

From the above, the practical sustainability of the catalytic activity of the present invention was confirmed, and it was revealed that it can be applied to an actual apparatus. It was also clarified that the catalyst can be easily separated from the product oil.

According to the present invention, a catalyst having high catalytic activity and not dissolved during the target transesterification by calcining the Keggin type heteropolyacid catalyst at a temperature of 723 K to 823 K, and its solid acid catalyst It is possible to provide a method for producing biodiesel fuel with a low environmental load using

DESCRIPTION OF SYMBOLS 10 Fixed bed flow type reaction apparatus 11 Oil and fat (triolein) tank 12 Alcohol (ethanol) tank 13 Pump 14 Pressure gauge 15 Reaction tube 16 Catalyst fixed layer 17 Electric furnace 18 Back pressure valve

Claims (6)

1. Chemical formula:
   

   

   [In the above formula, X is a single or plural kinds of atoms selected from a hydrogen atom or an alkali metal atom, P is phosphorus, Nb is niobium, W is tungsten, and O is an oxygen atom. The fatty acid glycerides contained in the fats and oils of a Keggin type heteropolyacid catalyst having a composition represented by the formula (1), wherein n is in the range of 0.8 to 2.2, and Nb ₂ O ₅ and WO ₃ A heteropolyacid catalyst / support complex calcined at a temperature of 723 K to 823 K for conversion to a fatty acid monoester by transesterification with.
2. The heteropolyacid catalyst / support composite according to claim 1, wherein the heteropolyacid catalyst is supported on the support in an amount of 30 to 50% by weight based on the total weight of the entire composite including the support. .
3. The fatty acid glyceride is a fatty acid triglyceride, fatty acid diglyceride and / or fatty acid monoglyceride composed of saturated or unsaturated fatty acid having C ₁₄ to C ₂₄ carbon, and the alcohol is methanol or ethanol. Heteropolyacid catalyst / support complex.
4. A method for producing a fatty acid monoester, comprising a step of producing a fatty acid monoester from a fatty acid glyceride and an alcohol in the presence of the heteropolyacid catalyst / carrier complex according to any one of claims 1 to 3.
5. The method for producing a fatty acid monoester according to claim 4, wherein the molar ratio of alcohol / fatty acid glyceride is in the range of 6-50.
6. A method for producing diesel fuel oil, comprising the step of converting fatty acid glycerides contained in fats and oils into fatty acid monoesters using the heteropolyacid catalyst / carrier complex according to any one of claims 1 to 3.

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