JP2005154302A - Method for oxidizing glucide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for converting a glucide in excellent productivity by catalytic oxidation exhibiting high yield and selectivity even under a mild condition. <P>SOLUTION: In the method for producing a glucide, a catalyst composed of superfine particle of gold is used. For example, gluconic acid is produced from glucose in a high yield and high selectivity at room temperature under a mild condition of normal pressure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a method for oxidizing saccharides using gold ultrafine particles as a catalyst, and a method for producing gluconic acid using the oxidation method in producing glucose by oxidizing raw material glucose.
Gluconic acid or a gluconic anhydride easily obtained by dehydration of gluconic acid is a useful compound used in a wide range of applications such as health foods, food additives, coagulants, and detergents.

  Carbohydrates play an important role not only as an energy source but also in life activities such as maintenance of cell structure and immune response. In recent years, functional products using carbohydrates have been actively developed, especially in the fields of food, medicine / pharmaceuticals, agriculture, various industrial fields, and environmental fields. Although there is no time, from a technical point of view, glycosylation that introduces specific monosaccharides into other substrates, oligomerization or polymerization of monosaccharides, or introduction of amino groups, acetyl groups, fluorine atoms, etc. into carbohydrates Chemical conversion is fundamental, and conversion to a carboxyl group by introduction of a fluorine atom, amino group, acetyl group or the like into the hydroxyl group of glucose, or oxidation of a formyl group or a hydroxymethyl group is typical. Production of various useful substances has been attempted from glucose, which is a typical monosaccharide. For example, gluconic acid, glucuronic acid, vitamin C, dextran, cellulose, and glucosamine can be produced from glucose. Further, α-arbutin having a whitening effect can be produced from glucose and hydroquinone (see, for example, Patent Document 1).

  Among these, gluconic acid is glucose fermentation (see, for example, Patent Document 2), air oxidation using palladium, a platinum catalyst, etc. (see, for example, Patent Documents 3 and 4, Non-Patent Documents 1 and 2), bromine or hypochlorous acid It is manufactured by chemical oxidation with bromic acid or the like (see, for example, Non-Patent Document 3). Commercially, fermentation using microorganisms of the genus Aspergillus or Gluconobacter has been successful. However, the fermentation method has a long production time of several days consisting of the growth time of microorganisms and the conversion time to gluconic acid, and a part of glucose is consumed for the growth of microorganisms. There is a drawback in that it needs to be removed and takes time for purification.

On the other hand, the chemical method has the advantage that the reaction time is shorter and the productivity is higher than the fermentation method, but the yield is not sufficient and there are many impurities, and the selectivity of the reaction is improved and the chemical method is improved. Attempts have been made to solve the drawbacks (see, for example, Patent Documents 5 and 6). The method of Patent Document 5 uses an activated carbon-supported catalyst composed of palladium and bismuth as an oxidation catalyst, and it is described that the selectivity when glucose is oxidized at 50 ° C. for 1 hour exceeds 99%. Further, the method of Patent Document 6 uses a catalyst in which bismuth, palladium, and platinum are supported on activated carbon, and it is described that the selectivity reaches 98%. As described above, the selectivity of the oxygen oxidation reaction is improved as compared with the conventional case, and an improvement in productivity can be expected. However, in any case, it is necessary to use two or three kinds of metal atoms as a catalyst component. Therefore, it takes time to prepare the catalyst, and there is a problem that the reaction results are not stable and a problem that the selectivity is lowered by repeated use. Therefore, it has been desired to provide an oxidation catalyst composed of a single metal atom.
JP-A-5-176785 Japanese Patent Publication No.33-7620 Japanese Patent Publication No. 60-92239 Japanese Examined Patent Publication No. 62-228098 JP-A-2-72137 Japanese Patent Laid-Open No. 10-180094 Chemistry of Organic Fluorine Compounds II, Monograph1, American Chem. Society, 1995, p.187 Busch, DRP 702729, (1939), DRP / DRBP Org. Chem .: 3 1320 Heyns Heinemann, JLACBF, Justus Liebigs Ann. Chem., 558 (1947) 190 Ruff, CHBEAM, Chem. Ber., 32 (1899), 2274

  An object of the present invention is to provide a method for converting a carbohydrate having excellent productivity by catalytic oxidation, which exhibits high yield and selectivity even under mild conditions.

As a result of intensive studies to solve the above problems, the present inventors have used nano-sized gold ultrafine particles (for example, see JP-A-10-180094), which have recently been confirmed to have a catalytic action, as catalysts. When used, the oxidation reaction easily proceeds from glucose even under mild conditions at room temperature and normal pressure, and gluconic acid is produced with high selectivity, and the activity decrease is small even when the catalyst is repeatedly used. As a result, the present invention has been achieved. That is, the present invention relates to a saccharide oxidation method using the nano-sized ultrafine gold particles shown in the following (1) to (5) as a catalyst, and a method for producing gluconic acid from glucose as a raw material using the oxidation method. .
(1) A method for oxidizing a carbohydrate, characterized by using ultrafine gold particles as a catalyst.
(2) The carbohydrate oxidation method according to (1), wherein the primary particle diameter of the gold ultrafine particles observed by a transmission electron microscope (TEM) is 10 nm or less.
(3) The method for oxidizing a saccharide according to (1) or (2), wherein a catalyst in which gold ultrafine particles are supported on silica, titania, zirconia, or activated carbon is used.
(4) The method for oxidizing a saccharide according to any one of (1) to (3), wherein the saccharide is a monosaccharide, an oligosaccharide, a polysaccharide, or a derivative thereof.
(5) A method for producing gluconic acid using the saccharide oxidation method using gold ultrafine particles as a catalyst according to any one of (1) to (4) when gluconic acid is produced by oxidizing glucose as a raw material.

  According to the present invention, a saccharide, particularly glucose, can be selectively oxidized under mild conditions using a gold catalyst that is composed of a single element, is easy to prepare, and is relatively inexpensive. Further, since the catalyst life is long, the productivity of gluconic acid is high, and the industrial significance is great.

  The catalyst used in the present invention is gold ultrafine particles having a primary particle diameter of 10 nm or less as observed by TEM. For use in the intended reaction, the primary particle diameter is preferably 10 nm or less, and particularly preferably 1 to 5 nm. When the primary particle diameter is 10 nm or more, the selectivity and activity of the reaction are lowered, which is not preferable. Gold particles having such a primary particle diameter can be prepared by a known method. For example, a precipitate obtained by dropping an aqueous solution of chloroplatinic acid and an aqueous solution of a transition metal into a sodium carbonate solution is washed, Drying and calcination (M. Haruta et al., J. Catal., 115, 301 (1989)) or impregnation method in which activated carbon is suspended in water, an aqueous solution of chloroauric acid is heated and then reduced with formaldehyde (GJ Hutchings et al., Chem. Commun., 2002, 696) can be applied. In addition, nano-sized particles can be easily obtained using microwaves.

Furthermore, an amorphous alloy method (M. Shibata et al., Chem. Lett., 1985, 1605) for obtaining Au—ZrO ₂ by oxidizing Au—Zr alloy, and after forming gold thiol clusters, sol-gel In addition to the gold thiol cluster method (JJ Pietron et al., Nano Lett. 2, 545 (2002)), which incorporates gold into titania by the method, sodium hydroxide aqueous solution is added dropwise to an aqueous solution of chloroauric acid, and a carrier is added. A chemical surface immobilization method, a gold complex CVD method (so-called gas phase grafting method), a gold phosphine complex precipitation method (liquid phase grafting method), and the like can also be used.

  The gold ultrafine particles are usually used by being supported on a suitable carrier. As a carrier suitable for this purpose, for example, general inorganic oxides or activated carbon is preferable. Specific examples include silica, alumina, titania, zirconia, calcia, magnesia, yttria and the like. Particularly preferred are activated carbon or carbon nanotubes or carbon nanohorns which are nano-sized carbon, silica, titania, zirconia, yttria and the like.

  The amount of gold atoms carried on the support is preferably 0.01% by weight or more. Usually, 0.5 to 5% by weight is supported and used, but if it can be supported, there is no particular problem even if 5% by weight or more is used. If there is no adverse effect on activity, selectivity, etc., atomic species other than gold may be included, and examples of atoms used with gold include Pd and Bi.

  The substrate for the oxidation reaction may be a carbohydrate containing a hydroxymethyl group or a formyl group. For example, glucose, fucose, N-acetylglucosamine, N-acetylgalactosamine, N-acetylneuraminic acid, erythrose, threose, ribose , Arabinose, xylose, allose, lyxose, altrose, mannose, gulose, idose, galactose, talose, psicose, fructose, sorbose, tagatose, unsaturated sugars such as hexaenos with unsaturated bonds, branched sugars such as apiose, deoxy There are two monosaccharides including disaccharides such as sugars, amino sugars, thio sugars, condensed sugars, monosaccharide anhydrides, and other monosaccharides, or disaccharides such as maltose, sucrose, and lactose that are linked to other saccharide units. From about several oligosaccharides, When polysaccharides such as open air, glycogen, and cellulose, complex carbohydrates in which these sugars are bound to proteins and lipids, and sugar derivatives such as nucleosides, ribonucleic acids, and deoxyribonucleic acids bound to nucleobases have a hydroxymethyl group or a formyl group Can be used. Glucose is particularly preferred as a substrate if it is limited to the production of gluconic acid. The substrate glucose may be any of D-form, L-form, racemate, or a mixture thereof.

  The catalyst is charged in a fixed bed or added to and coexisted in the reaction solution. The reaction can be carried out in a batch system, a semi-batch system, or a continuous system, and the reaction can also be performed under normal thermal reaction or irradiation with microwaves and / or electromagnetic waves in the vicinity of the microwaves. The reaction temperature is preferably from room temperature to 150 ° C. or less, particularly preferably from room temperature to 100 ° C. Air or oxygen is used for the oxidation. The gas is introduced at normal pressure or under pressure to carry out the reaction. Usually, bubbling under normal pressure is preferred for safety.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to only these examples.
[Analysis conditions]: The oxidation products of glucose were analyzed under the following conditions using capillary electrophoresis.
Capillary: Fused Silica 50μm × 72cm
Buffer: HP Basic Anion Buffer (part number 5064-8209)
Voltage: -25KV
Temperature: 20 ° C
Detector Signal 350 nm, 20 nm; Reference 275 nm, 10 nm

Reference Example 1 Preparation of gold ultrafine catalyst 1 4 g of activated carbon (Kuraray Coal, Kuraray Co., Ltd.) was charged in a 500 ml four-necked flask equipped with a dropping funnel, a reflux tank and a thermometer, and 2 g of sodium citrate was dissolved in 300 ml of water. The aqueous solution was added and stirred for 10 minutes. An aqueous solution prepared by mixing 50 ml of water and 2 ml of a 0.1 M chloroauric acid aqueous solution was added to the dropping funnel and added dropwise over 30 minutes. After completion of dropping, the mixture was further stirred for 30 minutes. Next, an aqueous solution obtained by mixing 40 ml of a 0.1 M aqueous sodium hydroxide solution and 10 ml of water was added dropwise over 30 minutes and stirred for 30 minutes. An aqueous solution obtained by mixing 2 g of formaldehyde solution (37% concentration) and 50 ml of water was added dropwise over 30 minutes, and after completion of the addition, the mixture was heated to 70 ° C. The mixture was further stirred at that temperature for 10 minutes. Stirring was stopped, the mixture was allowed to cool to room temperature, and filtered. It was washed twice with 200 ml of water and dried at 90 ° C. for 5 hours to obtain an ultrafine gold catalyst 1 (3.68 g). The amount of gold supported on this catalyst was 1 wt%, and the primary particle diameter of the gold particles as observed by TEM was 8 nm.

Reference Example 2 It carried out according to the preparation literature (Preparation of Catalysts VI, 227) of the gold ultrafine particle catalyst 2 . A four-necked flask was charged with 200 ml of pure water, 1 ml of 0.05 M chloroauric acid aqueous solution, and 20 ml of 0.1 M sodium hydroxide aqueous solution to adjust the pH to 11. After stirring the liquid temperature at 70 ° C. for 10 minutes, 2 g of titania (Nippon Aerosil Co., Ltd. P25) was added and stirred for 2 hours. After cooling to room temperature, solid-liquid separation was performed with a centrifuge. The precipitate was fully dried and calcined at 400 ° C. for 3 hours. Blue-violet titania-supported gold ultrafine particle catalyst 2 (1.34 g) was obtained. The amount of gold supported was 1 wt%, and the primary particle diameter of the gold particles as observed by TEM was 9 nm.

Example 1
Glucose was dissolved in 10 ml of water by putting 1.8 g of glucose and gold ultrafine particle catalyst 1 (0.197 g) in a 100 ml four-necked flask containing a stirrer chip (substrate: gold = 1000: 1). In a separate container, 0.4 g of sodium hydroxide was dissolved in 10 ml of water and added to the 4-neck flask reactor. Oxygen was bubbled at 1 atmosphere, and the reaction was started while stirring at 600 rpm. After reacting for 1 hour at room temperature, the suspension containing the catalyst was centrifuged. The supernatant was filtered through a 0.45 μm membrane filter and the product was analyzed. As a result, the glucose conversion was 100% and the selectivity for gluconic acid was 99%.

Example 2
The reaction was performed in the same manner as in Example 1 except that the ultrafine gold catalyst 2 was used as the catalyst. The conversion was 99% and gluconic acid selectivity was 99% at room temperature for 1 hour.

Comparative Example 1
The same procedure as in Example 1 was performed except that 5% activated carbon-supported Pd was used as a catalyst and Pd was added at a ratio of 1000: 1 with respect to the substrate. As a result, the glucose conversion was 20% and the gluconic acid selectivity was 20%.

Example 3
After recovering the catalyst, the reaction described in Example 1 was repeated 10 times. Almost no decrease in the activity of the catalyst was observed, and the glucose conversion was 99% and the gluconic acid conversion was 99%.

Claims (5)

  A method for oxidizing a carbohydrate, characterized by using gold ultrafine particles as a catalyst.   The method for oxidizing a carbohydrate according to claim 1, wherein the primary particle diameter of the gold ultrafine particles observed with a transmission electron microscope (TEM) is 10 nm or less.   The method for oxidizing a saccharide according to claim 1 or 2, wherein a catalyst in which gold ultrafine particles are supported on silica, titania, zirconia, or activated carbon is used.   The method for oxidizing a saccharide according to any one of claims 1 to 3, wherein the saccharide is a monosaccharide, an oligosaccharide, a polysaccharide, or a derivative thereof.   A method for producing gluconic acid using the method for oxidizing carbohydrates using gold ultrafine particles as a catalyst according to any one of claims 1 to 4 in producing gluconic acid by oxidizing raw material glucose.