JP7280596B2 - Silver nanoparticle resin composite and hydrogenation catalyst - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silver nanoparticle resin composite and a hydrogenation catalyst.

Silver nanoparticles are known as catalysts for the selective hydrogenation of aldehydes. For example, in Non-Patent Document 1, by using cellulose-supported silver-iron nanoparticles as a catalyst, when an aldehyde having a carbon-carbon double bond is hydrogenated, the aldehyde is selectively hydrogenated to produce an alcohol. has been reported.

ACS Sustainable Chemistry & Engineering2016, 4, 965-973.

By the way, in Non-Patent Document 1, the selectivity of hydrogenation is studied using an aldehyde having an internal olefin, but it is known that terminal olefins and alkynes are more easily hydrogenated than internal olefins. With the catalyst of Non-Patent Document 1, it is difficult to selectively hydrogenate aldehydes having terminal olefins or alkynes. Furthermore, it has been shown that the catalyst of Non-Patent Document 1 is deactivated when it is repeatedly collected and reused, and there is room for improvement in the durability of the catalyst.

Therefore, the present invention provides a highly durable hydrogenation catalyst capable of selectively hydrogenating aldehydes, even aldehydes having terminal olefins, etc., and a silver nanoparticle resin composite used therefor. intended to provide

As a result of intensive studies, the present inventors have found that the above problems can be solved by a silver nanoparticle-resin composite comprising a polystyrene-polyethylene glycol copolymer resin and silver nanoparticles dispersed in the resin. Found it.

Such a silver nanoparticle resin composite comprises a step of supporting a silver salt on a polystyrene-polyethylene glycol copolymer resin having a coordinating group to form a silver complex, and a step of acting a reducing agent on the formed silver complex. It is preferable that it is manufactured by passing through.

The silver nanoparticle-resin composite can be suitably applied as a hydrogenation catalyst. Such a hydrogenation catalyst can selectively hydrogenate an aldehyde even if it has a terminal olefin or the like, and has high durability.

According to the present invention, even if it is an aldehyde having a terminal olefin etc., it is possible to selectively hydrogenate the aldehyde, and a highly durable hydrogenation catalyst, and a silver nanoparticle resin composite used therefor body can be provided.

Preferred embodiments of the present invention are described in detail below. However, the present invention is not limited to the following embodiments.

[Silver nanoparticle resin composite]
The silver nanoparticle-resin composite of this embodiment comprises a polystyrene-polyethylene glycol copolymer resin and silver nanoparticles dispersed in the resin. Polystyrene-polyethylene glycol copolymer resin is, for example, polystyrene on which polyethylene glycol is graft-polymerized. A polystyrene-polyethylene glycol amino resin in which an amino group is introduced at the end of a polyethylene glycol chain can be used. Polystyrene may be crosslinked.

［式（α）中、Ｚは架橋基を示し、ｐは０又は１を示す。］ Polystyrene-polyethylene glycol amino resin has, for example, a structure represented by the following formula (α).

[In the formula (α), Z represents a cross-linking group, and p represents 0 or 1. ]

In the formula (α), m and n each represent the number of repeating units of the polyethylene glycol chain, and for example, the molecular weight is about 1,000 to 100,000. In formula (α), l indicates the number of repeating units derived from polystyrene. Polystyrene may have a structure represented by the formula (α) having a polyethylene glycol chain and an amino group, or may have styrene units having no substituents, and may be crosslinked.

As the polystyrene-polyethylene glycol amino resin, conventionally known ones can be used. first name), etc. can be used.

The silver nanoparticles may be metallic silver (Ag(0)) or monovalent silver (Ag(I)). The silver nanoparticles produced by the method described below are reduced to Ag(0) when a reducing agent is applied, but may be oxidized to silver oxide (Ag ₂ O) thereafter.

The silver nanoparticles may have a size generally called nanoparticles, and for example, the average particle size can be about 1 to 100 nm.

The amount of silver nanoparticles supported in the silver nanoparticle-resin composite can be, for example, 0.05 to 1.0 mmol/g in terms of silver element.

[Method for producing silver nanoparticle resin composite]
The method for producing the silver nanoparticle resin composite is not particularly limited, but for example, a step of supporting a silver salt on a polystyrene-polyethylene glycol copolymer resin having a coordination group to form a silver complex, It can be produced through a step of allowing a reducing agent to act on.

The coordinating group is not particularly limited as long as it can coordinate with the silver salt, and examples thereof include an amino group, a carboxyl group, a thiol group and a phosphino group. Among these, an amino group or a carboxyl group is preferred, and an amino group is more preferred, from the viewpoint of ease of reduction with a reducing agent after coordination. The amino groups may be either substituted or unsubstituted amino groups. As the polystyrene-polyethylene glycol copolymer resin having an amino group, the above-mentioned polystyrene-polyethylene glycol amino resin can be suitably applied.

Examples of silver salts include silver (I) fluoride, silver (I) acetate, silver (I) tetrafluoroborate, silver (I) perchlorate, silver (I) nitrate, silver (I) carbonate, cyanide, Silver (I), silver (I) benzoate, silver (I) triflate, silver (I) hexafluorophosphate, silver (I) hexafluoroantimonate, silver (I) oxide, silver (I) nitrite, phosphorus Silver acid (I) and the like can be mentioned.

The conditions for supporting the silver salt on the polystyrene-polyethylene glycol copolymer resin having a coordinating group are not particularly limited, but it can be carried out in an appropriate solvent capable of dissolving the silver salt (eg, methanol). In addition, in order to avoid decomposition of the formed silver complex, it is desirable to carry out under light-shielding conditions.

Examples of reducing agents include ethylene glycol, formaldehyde, hydrazine, phenylhydrazine, sodium borohydride, ascorbic acid, 3-amino-1-propanol, hydrogen gas and the like.

Conditions for allowing the reducing agent to act on the silver complex are not particularly limited, but the reaction can be carried out in an appropriate solvent (for example, water) capable of dissolving the reducing agent. In addition, in order to avoid decomposition of the silver complex, it is desirable to carry out under light-shielding conditions.

(Hydrogenation catalyst)
The silver nanoparticle-resin composite described above can be suitably applied as a hydrogenation catalyst. Such hydrogenation catalysts are particularly excellent in selective hydrogenation of aldehydes, and are also capable of hydrogenating imino groups, nitro groups, azide groups, epoxy groups, terminal alkynes, aromatic ketones, and the like.

When using the silver nanoparticle-resin composite described above as a hydrogenation catalyst, either a batch method or a continuous flow method can be applied. Law should be applied. The silver nanoparticle-resin composite described above is excellent in durability, especially when applied to a long-term continuous flow method.

The catalyst amount when using the silver nanoparticle-resin composite described above as a hydrogenation catalyst is not particularly limited, but it is preferably 0.01 to 50 mol %, more preferably 0.1 to 25 mol %, in terms of silver element. It is preferably 0.5 to 10 mol %, more preferably 0.5 to 10 mol %. Here, the amount of catalyst is a ratio based on the amount of substrate.

The hydrogenation reaction described above is preferably carried out under pressurized conditions (for example, 1 to 10 MPa (10 to 100 bar)) in a hydrogen gas atmosphere. The reaction temperature for the hydrogenation reaction can be, for example, 50 to 150°C. As the reaction solvent for the hydrogenation reaction, a solvent containing water is preferable, and for example, water or a mixed solvent of water and an alcohol (eg, ethanol) can be applied.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples.

In the examples, the progress of the reaction was confirmed using gas chromatography (GC) or the like, and the reaction was continued until disappearance of the raw materials was confirmed or until it was confirmed that the reaction did not proceed any further.

(Example 1: Preparation of silver nanoparticle resin composite)
Based on Scheme 1 below, a silver nanoparticle resin composite (amphiphilic polymer-supported silver nanocatalyst (ARP-Ag)) (3) was prepared. In Scheme 1, as the polystyrene-polyethylene glycol amino resin (1), TentaGel S NH ₂ (trade name, manufactured by Rapp Polymere, amino group loading: 0.27 mmol/g) was used. Specific experimental procedures are shown below.

Polystyrene-polyethylene glycol amino resin (1) (1.7 g, 0.46 mmol-NH ₂ ) was mixed with 1N NaOH solution (17 mL), water (20 mL x 3), acetone (20 mL x 3) and methylene chloride (20 mL x 3). and dried under reduced pressure overnight. To dry methanol (MeOH) (17 mL) containing the dried resin was added a solution of silver (I) hexafluorophosphate (AgPF ₆ ) (140 mg, 0.55 mmol) in dry methanol (5 mL) under an inert atmosphere. . After covering the reaction vessel with aluminum foil, the mixture was shaken at room temperature in the dark for 2 hours. The mixture was shaken for an additional 2 hours after which diethyl ether (70 mL) was added. After removing the solvent by decantation, the remaining silver complex (2) was washed with diethyl ether (20 mL) and dried under reduced pressure.

A solution of sodium borohydride (104 mg, 2.75 mmol) in water (5 mL) was added to water (17 mL) containing the dried silver complex (2), the reaction vessel was covered with aluminum foil, and the resulting mixture was shaken at room temperature for 5 hours. The resulting resin was collected by filtration, washed with water (20 mL×3) and methylene chloride (20 mL×3), and dried under reduced pressure to obtain ARP-Ag (3). The obtained ARP-Ag(3) was analyzed as follows.

As a result of ICP analysis, the content of elemental silver in the obtained ARP-Ag(3) was 0.256 mmol/g.
TEM analysis confirmed that silver nanoparticles were formed and dispersed in the polymer matrix. The silver nanoparticles had a particle size of 2 to 10 nm and an average particle size of 4.0±1.7 nm.
As a result of XPS analysis, characteristic peaks derived from Ag 3d _5/2 and Ag 3d _3/2 were observed at 367.04 and 373.02 eV, respectively. The binding energy of Ag 3d _5/2 in ARP-Ag(3) is very close to that of Ag ₂ O (367.3 eV) and lower than that of Ag(0) metal (368.24 eV). Therefore, the oxidation number of silver nanoparticles dispersed in the polymer matrix of ARP-Ag(3) is determined to be "+1" (Ag(I)).

条件Ａ：
ＡＲＰ－Ａｇ（２３０ｍｇ，０．０５９ｍｍｏｌ），システム圧力４０ｂａｒ，反応温度１００℃，流速０．５ｍＬ／ｍｉｎ（接触時間：６２秒）
（なお、アルコール５ｂの生成の際には、システム圧力を６０ｂａｒとした。）
条件Ｂ：
ＡＲＰ－Ａｇ（２３０ｍｇ，０．０５９ｍｍｏｌ），システム圧力６０ｂａｒ，反応温度１２０℃，流速０．３ｍＬ／ｍｉｎ（接触時間：１０４秒）
条件Ｃ：
ＡＲＰ－Ａｇ（６９０ｍｇ，０．１７７ｍｍｏｌ），システム圧力６０ｂａｒ，反応温度１２０℃，流速０．３ｍＬ／ｍｉｎ（接触時間：３１２秒）
アルデヒド濃度：
ａ）５０ｍＭ，ｂ）２５ｍＭ，ｃ）１２．５ｍＭ
溶媒：
ｄ）Ｈ_２Ｏ，ｅ）Ｈ_２Ｏ／ＥｔＯＨ＝７：３，ｆ）Ｈ_２Ｏ／ＥｔＯＨ＝６：４，ｇ）Ｈ_２Ｏ／ＥｔＯＨ＝４：６，ｈ）Ｈ_２Ｏ／ｔ－ＢｕＯＨ＝７：３，ｉ）Ｈ_２Ｏ／ｔ－ＢｕＯＨ＝６：４，ｊ）Ｈ_２Ｏ／ｔ－ＢｕＯＨ＝４：６ (Example 2)
Synthesis of alcohol (5) by hydrogenation of various aldehydes (4) using ARP-Ag (3) as a catalyst was examined according to Scheme 2 below. Specific operations are shown below, taking as an example the case where benzaldehyde (4a) is used as aldehyde (4).
A cartridge was filled with ARP-Ag (3) (230 mg, 0.059 mmol Ag), set in a flow-type hydrogenation reaction system H-Cube Pro (registered trademark) (manufactured by ThalesNano), and treated with benzaldehyde (4a) (50 mM). and sodium carbonate (1 equivalent) in water (H ₂ O) was flowed at a flow rate of 0.5 mL/min (contact time: 62 seconds). Under the conditions of 100° C. and a system pressure of 40 bar (4 MPa), hydrogen supplied from a gas module (40 mL/min) was allowed to act on benzaldehyde to perform flow hydrogenation. The resulting reaction solution was collected for 108 minutes (54 mL) and extracted with diethyl ether (100 mL x 5). The resulting organic phases were combined, dried over magnesium sulfate and then isolated to give benzyl alcohol (5a) in 99% yield.
In addition, the case where benzaldehyde (4a) was used, except that the reaction conditions were changed to conditions A to C shown below, and the aldehyde concentration and solvent were changed to a) to c) and d) to j) shown below, respectively. Hydrogenation of other aldehydes (4) was carried out in a similar manner. The results are shown below. As ARP-Ag (690 mg, 0.177 mmol), three of the above cartridges were used.

Condition A:
ARP-Ag (230 mg, 0.059 mmol), system pressure 40 bar, reaction temperature 100° C., flow rate 0.5 mL/min (contact time: 62 seconds)
(Note that the system pressure was 60 bar during the production of alcohol 5b.)
Condition B:
ARP-Ag (230 mg, 0.059 mmol), system pressure 60 bar, reaction temperature 120° C., flow rate 0.3 mL/min (contact time: 104 seconds)
Condition C:
ARP-Ag (690 mg, 0.177 mmol), system pressure 60 bar, reaction temperature 120° C., flow rate 0.3 mL/min (contact time: 312 seconds)
Aldehyde concentration:
a) 50 mM, b) 25 mM, c) 12.5 mM
solvent:
d) H ₂ O, e) H ₂ O/EtOH=7:3, f) H ₂ O/EtOH=6:4, g) H ₂ O/EtOH=4:6, h) H ₂ O/t- BuOH=7:3, i) H ₂ O/t-BuOH=6:4, j) H ₂ O/t-BuOH=4:6

(Example 3)
Among the reactions shown in Scheme 2 above, the hydrogenation of benzaldehyde (4a) to benzyl alcohol (5a) was carried out in batch mode. Specific operations are shown below.
Benzaldehyde (4a) (1 mmol), sodium carbonate (1 mmol), ARP-Ag (3) (2 mol % Ag) and water (2 mL) were charged to the autoclave. The gas in the autoclave was replaced with hydrogen and pressurized to 40 bar. After the contents in the autoclave were stirred at 100° C. for 2 hours to complete the reaction, the catalyst was filtered off and the filtrate was analyzed by GC-MS. was confirmed to have been obtained.

条件Ａ：
ＡＲＰ－Ａｇ（６９０ｍｇ，０．１７７ｍｍｏｌ），システム圧力６０ｂａｒ，反応温度１２０℃，流速０．３ｍＬ／ｍｉｎ（接触時間：３１２秒）
条件Ｂ：
ＡＲＰ－Ａｇ（６９０ｍｇ，０．１７７ｍｍｏｌ），システム圧力４０ｂａｒ，反応温度１００℃，流速０．５ｍＬ／ｍｉｎ（接触時間：１８６秒）
溶媒：
ａ）Ｈ_２Ｏ／ｔ－ＢｕＯＨ＝７：３，ｂ）Ｈ_２Ｏ／ｔ－ＢｕＯＨ＝６：４ (Example 4)
According to Scheme 3 below, synthesis of alcohol (7) by hydrogenation of various ketones (6) using ARP-Ag (3) as a catalyst was studied. Specific operations are shown below, taking as an example the case where acetophenone (6a) is used as ketone (6).
Prepare three cartridges filled with ARP-Ag (3) (230 mg, 0.059 mmol Ag) (total: 690 mg, 0.177 mmol Ag), and flow hydrogenation reaction system H-Cube Pro so that these are continuous (registered trademark) (manufactured by ThalesNano), and a water-tert-butyl alcohol solution of acetophenone (6a) (12.5 mM) and sodium carbonate (1 equivalent) was added at a flow rate of 0.3 mL/min (contact time: 312 seconds). ). Under the conditions of 120° C. and system pressure of 60 bar, hydrogen supplied from a gas module (40 mL/min) was allowed to act on acetophenone (6a) to perform flow hydrogenation. The resulting reaction was collected for 167 minutes (50 mL) and extracted with ethyl acetate (100 mL x 5). The resulting organic phases were combined, dried over magnesium sulfate and then isolated to give 1-phenylethanol (7a) in 86% yield.
Further, the other ketone (6) was hydrogenated in the same manner as when acetophenone (6a) was used, except that the reaction conditions were changed to conditions A and B shown below and the solvents were changed to a) and b). gone. The results are shown below.

Condition A:
ARP-Ag (690 mg, 0.177 mmol), system pressure 60 bar, reaction temperature 120° C., flow rate 0.3 mL/min (contact time: 312 seconds)
Condition B:
ARP-Ag (690 mg, 0.177 mmol), system pressure 40 bar, reaction temperature 100° C., flow rate 0.5 mL/min (contact time: 186 seconds)
solvent:
a) H ₂ O/t-BuOH=7:3, b) H ₂ O/t-BuOH=6:4

条件Ａ：
ＡＲＰ－Ａｇ（２３０ｍｇ，０．０５９ｍｍｏｌ），システム圧力４０ｂａｒ，反応温度１００℃，流速０．５ｍＬ／ｍｉｎ（接触時間：６２秒）
条件Ｂ：
ＡＲＰ－Ａｇ（２３０ｍｇ，０．０５９ｍｍｏｌ），システム圧力６０ｂａｒ，反応温度１２０℃，流速０．３ｍＬ／ｍｉｎ（接触時間：１０４秒）
条件Ｃ：
ＡＲＰ－Ａｇ（２３０ｍｇ，０．０５９ｍｍｏｌ），システム圧力１０ｂａｒ，反応温度１００℃，流速０．５ｍＬ／ｍｉｎ（接触時間：６２秒）
条件Ｄ：
ＡＲＰ－Ａｇ（６９０ｍｇ，０．１７７ｍｍｏｌ），システム圧力６０ｂａｒ，反応温度１２０℃，流速０．３ｍＬ／ｍｉｎ（接触時間：３１２秒）
アルデヒド濃度：
ａ）１２．５ｍＭ，ｂ）２５ｍＭ，ｃ）１０ｍＭ
溶媒：
ｄ）Ｈ_２Ｏ／ＥｔＯＨ＝６：４，ｅ）Ｈ_２Ｏ／ＥｔＯＨ＝５：５，ｆ）Ｈ_２Ｏ／ＥｔＯＨ＝４：６，ｇ）Ｈ_２Ｏ／ｔＢｕＯＨ＝７：３，ｈ）Ｈ_２Ｏ／ｔ－ＢｕＯＨ＝６：４，ｉ）Ｈ_２Ｏ／ｔ－ＢｕＯＨ＝５：５，ｊ）Ｈ_２Ｏ／ｔ－ＢｕＯＨ＝４：６，ｋ）Ｈ_２Ｏ (Example 5)
According to Scheme 4 below, ARP-Ag (3) was used as a catalyst to hydrogenate the substrate (8) having two functional groups, and the chemoselectivity of this reaction was examined from the resulting product (9). bottom. Specific operations are described below, taking as an example the case where the substrate (8a) is used as the substrate (8).
A cartridge was filled with ARP-Ag (3) (230 mg, 0.059 mmol Ag), set in a flow-type hydrogenation reaction system H-Cube Pro (registered trademark) (manufactured by Thales Nano), and substrate (8) (12. 5 mM) and sodium carbonate (1 equivalent) in water-ethanol was flowed at a flow rate of 0.5 mL/min. Under the conditions of 100° C. and system pressure of 10 bar, hydrogen supplied from a gas module (40 mL/min) was allowed to act on the substrate (8a) to perform flow hydrogenation. The resulting reaction solution was collected for 46 minutes (23 mL) and extracted with t-butyl methyl ether (50 mL×5). The resulting organic phases were combined, dried over magnesium sulfate and then isolated to give the product (9a) in 95% yield.
In addition, except that the reaction conditions were changed to conditions A to D shown below, and the substrate concentration and solvent were changed to a) to c) and d) to j) shown below, respectively, the substrate (8a) was used. The hydrogenation of the other substrate (8) was carried out in a similar manner. The results are shown below. As ARP-Ag (690 mg, 0.177 mmol), three of the above cartridges were used.

Condition A:
ARP-Ag (230 mg, 0.059 mmol), system pressure 40 bar, reaction temperature 100° C., flow rate 0.5 mL/min (contact time: 62 seconds)
Condition B:
ARP-Ag (230 mg, 0.059 mmol), system pressure 60 bar, reaction temperature 120° C., flow rate 0.3 mL/min (contact time: 104 seconds)
Condition C:
ARP-Ag (230 mg, 0.059 mmol), system pressure 10 bar, reaction temperature 100° C., flow rate 0.5 mL/min (contact time: 62 seconds)
Condition D:
ARP-Ag (690 mg, 0.177 mmol), system pressure 60 bar, reaction temperature 120° C., flow rate 0.3 mL/min (contact time: 312 seconds)
Aldehyde concentration:
a) 12.5 mM, b) 25 mM, c) 10 mM
solvent:
d) _H2O /EtOH=6:4, e) _H2O /EtOH=5:5, f) _H2O /EtOH=4:6, g) _H2O /tBuOH=7:3, h) H ₂ O/t-BuOH=6:4, i) H ₂ O/t-BuOH=5:5, j) H ₂ O/t-BuOH=4:6, k) H ₂ O

From the results of Example 5, according to hydrogenation using ARP-Ag (3) as a catalyst, aldehyde is preferentially reduced even when a substrate containing both aldehyde and alkyne, olefin or aromatic ketone is used. It can be seen that Also, when a substrate containing both an aromatic ketone and an alkyne is used, the ketone is preferentially hydrogenated.
In particular, alkynes and terminal olefins are generally highly reactive to hydrogenation, and it is usually difficult to selectively hydrogenate aldehydes. From this it can be said that the hydrogenation with ARP-Ag(3) as catalyst exhibits a characteristic chemoselectivity.

なお、基質（８ｑ）を用いた場合には、生成物（９ｑ）及び（９ｑ’）が混合物として得られ、基質（８ｒ）を用いた場合には、生成物（９ｒ）及び（９ｒ’）が混合物として得られた。 (Example 6)
Hydrogenation of various substrates (8) was investigated using ARP-Ag (3) as a catalyst according to Scheme 5 below. Specific operations are shown below.
A cartridge was filled with ARP-Ag (3) (230 mg, 0.059 mmol Ag), set in a flow-type hydrogenation reaction system H-Cube Pro (registered trademark) (manufactured by Thales Nano), and substrate (8) (50 mM). and a water-ethanol solution of sodium carbonate (1 equivalent) was flowed at a flow rate of 0.5 mL/min. Under the conditions of 100° C. and system pressure of 40 bar, hydrogen supplied from a gas module (40 mL/min) was allowed to act on the substrate (8) to perform flow hydrogenation. The resulting reaction solution was analyzed using GC to determine the yield. The results are shown below.

When the substrate (8q) is used, the products (9q) and (9q') are obtained as a mixture, and when the substrate (8r) is used, the products (9r) and (9r') are obtained. was obtained as a mixture.

As is clear from the results of Example 6, by using ARP-Ag (3) as a catalyst, imino groups, nitro groups, azide groups, epoxy groups, terminal alkynes, etc. can be hydrogenated, and ARP- It was confirmed that Ag(3) has versatility as a hydrogenation catalyst.

(Example 7)
Among the reactions shown in Scheme 2 above, the hydrogenation of benzaldehyde (4a) to benzyl alcohol (5a) was carried out for a long period of time to examine the durability of the catalyst.
Specifically, the reaction was carried out for 2 weeks (336 hours) under the same conditions as in Example 2, and the reaction solution was sampled periodically to analyze the yield of benzyl alcohol (5a). 4a) was quantitatively converted to benzyl alcohol (5a), confirming that ARP-Ag (3) has excellent durability to long-term continuous flow reactions. The TON of the catalyst in this reaction is at least greater than 8560.
When the catalyst was recovered and subjected to ICP analysis, 77% of elemental silver remained in the resin even after 2 weeks of reaction. It was also confirmed that the recovered catalyst also had high catalytic activity.

Claims (2)

A silver nanoparticle resin composite comprising a polystyrene-polyethylene glycol copolymer resin (excluding one containing a branched polyalkyleneimine chain) and silver nanoparticles dispersed in the resin. A hydrogenation catalyst comprising the silver nanoparticle-resin composite according to claim 1 .