CN117049943A - Application of low-load nickel-carbon catalyst in catalytic conversion of guaiacol under mild conditions - Google Patents
Application of low-load nickel-carbon catalyst in catalytic conversion of guaiacol under mild conditions Download PDFInfo
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- LHGVFZTZFXWLCP-UHFFFAOYSA-N guaiacol Chemical compound COC1=CC=CC=C1O LHGVFZTZFXWLCP-UHFFFAOYSA-N 0.000 title claims abstract description 161
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 98
- 229960001867 guaiacol Drugs 0.000 title claims abstract description 78
- 239000003054 catalyst Substances 0.000 title claims abstract description 59
- 230000003197 catalytic effect Effects 0.000 title claims abstract description 21
- VMWYVTOHEQQZHQ-UHFFFAOYSA-N methylidynenickel Chemical compound [Ni]#[C] VMWYVTOHEQQZHQ-UHFFFAOYSA-N 0.000 title claims abstract description 21
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 95
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 53
- 238000011068 loading method Methods 0.000 claims abstract description 28
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000001257 hydrogen Substances 0.000 claims abstract description 17
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 17
- 239000003575 carbonaceous material Substances 0.000 claims abstract description 9
- 230000035484 reaction time Effects 0.000 claims abstract description 8
- 239000003960 organic solvent Substances 0.000 claims abstract description 5
- 238000007789 sealing Methods 0.000 claims abstract description 4
- 238000001816 cooling Methods 0.000 claims abstract description 3
- 238000007599 discharging Methods 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims abstract description 3
- 239000011261 inert gas Substances 0.000 claims abstract description 3
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical group CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 28
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 11
- 239000012298 atmosphere Substances 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 7
- AOPCKOPZYFFEDA-UHFFFAOYSA-N nickel(2+);dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O AOPCKOPZYFFEDA-UHFFFAOYSA-N 0.000 claims description 7
- 239000007789 gas Substances 0.000 claims description 6
- 239000002243 precursor Substances 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 5
- 239000000843 powder Substances 0.000 claims description 5
- 238000009210 therapy by ultrasound Methods 0.000 claims description 4
- MQRWBMAEBQOWAF-UHFFFAOYSA-N acetic acid;nickel Chemical compound [Ni].CC(O)=O.CC(O)=O MQRWBMAEBQOWAF-UHFFFAOYSA-N 0.000 claims description 3
- 239000012263 liquid product Substances 0.000 claims description 3
- 229940078494 nickel acetate Drugs 0.000 claims description 3
- LAIZPRYFQUWUBN-UHFFFAOYSA-L nickel chloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Ni+2] LAIZPRYFQUWUBN-UHFFFAOYSA-L 0.000 claims description 3
- 229910000008 nickel(II) carbonate Inorganic materials 0.000 claims description 3
- ZULUUIKRFGGGTL-UHFFFAOYSA-L nickel(ii) carbonate Chemical compound [Ni+2].[O-]C([O-])=O ZULUUIKRFGGGTL-UHFFFAOYSA-L 0.000 claims description 3
- 238000003756 stirring Methods 0.000 claims description 3
- 238000003860 storage Methods 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 2
- 238000007598 dipping method Methods 0.000 claims description 2
- 238000001914 filtration Methods 0.000 claims description 2
- 238000000227 grinding Methods 0.000 claims description 2
- HPXRVTGHNJAIIH-UHFFFAOYSA-N cyclohexanol Chemical compound OC1CCCCC1 HPXRVTGHNJAIIH-UHFFFAOYSA-N 0.000 abstract description 23
- 238000000034 method Methods 0.000 abstract description 4
- 230000008901 benefit Effects 0.000 abstract description 2
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 15
- 239000000047 product Substances 0.000 description 14
- 230000000694 effects Effects 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 11
- 239000002184 metal Substances 0.000 description 11
- 238000002360 preparation method Methods 0.000 description 9
- 239000002904 solvent Substances 0.000 description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- 229920005610 lignin Polymers 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 5
- 239000007810 chemical reaction solvent Substances 0.000 description 5
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 4
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 4
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 description 4
- 125000003118 aryl group Chemical group 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000005984 hydrogenation reaction Methods 0.000 description 3
- DCQQZLGQRIVCNH-UHFFFAOYSA-N 2-methoxycyclohexan-1-ol Chemical compound COC1CCCCC1O DCQQZLGQRIVCNH-UHFFFAOYSA-N 0.000 description 2
- JYJURPHZXCLFDX-UHFFFAOYSA-N 2-methoxycyclohexan-1-one Chemical compound COC1CCCCC1=O JYJURPHZXCLFDX-UHFFFAOYSA-N 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- 238000003776 cleavage reaction Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 230000007017 scission Effects 0.000 description 2
- 238000010517 secondary reaction Methods 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- OMNGOGILVBLKAS-UHFFFAOYSA-N 2-methoxyphenol Chemical compound COC1=CC=CC=C1O.COC1=CC=CC=C1O OMNGOGILVBLKAS-UHFFFAOYSA-N 0.000 description 1
- 239000002028 Biomass Substances 0.000 description 1
- 229920002488 Hemicellulose Polymers 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000002029 lignocellulosic biomass Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 230000037361 pathway Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000002604 ultrasonography Methods 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/17—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrogenation of carbon-to-carbon double or triple bonds
- C07C29/19—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrogenation of carbon-to-carbon double or triple bonds in six-membered aromatic rings
- C07C29/20—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrogenation of carbon-to-carbon double or triple bonds in six-membered aromatic rings in a non-condensed rings substituted with hydroxy groups
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/74—Iron group metals
- B01J23/755—Nickel
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2601/00—Systems containing only non-condensed rings
- C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
- C07C2601/14—The ring being saturated
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses application of a low-load nickel-carbon catalyst in catalytic conversion of guaiacol under mild conditions. Placing guaiacol, a nickel-carbon catalyst and an organic solvent into a reactor, sealing, introducing inert gas into the reactor, and discharging residual air in the reactor; then charging 1-2 MPa hydrogen into the reactor, heating the reactor to 200-220 ℃ and keeping the temperature for 60-180 min; after the reaction is finished, naturally cooling the reactor to room temperature and decompressing; the nickel in the nickel-carbon catalyst is an active component, the carbon material is a carrier, and the nickel loading is 3-7% of the catalyst mass. The invention adopts a low-load nickel-carbon catalyst, can catalyze 100% conversion of guaiacol under mild conditions, and can obtain the cyclohexanol with a yield of approximately 90%. Compared with the conventional research, the method has the advantages of less catalyst loading, lower reaction temperature, shorter reaction time, greatly reduced cost and wide application prospect.
Description
Technical Field
The invention relates to the technical field of catalysts, in particular to application of a low-load nickel-carbon catalyst in catalytic conversion of guaiacol under mild conditions.
Background
Among renewable energy sources, biomass has received widespread attention as the only renewable resource that can be converted into liquid fuels. Both cellulose and hemicellulose in lignocellulosic biomass have been widely used in the paper industry, but produce large amounts of waste lignin. The energy crisis can be relieved and the effective utilization of wastes can be realized by converting lignin. Among them, guaiacol (2-methoxyphenol) is an important compound, which is a main component of lignin oil. Therefore, the effective conversion of guaiacol has important guiding significance for the subsequent conversion of lignin and lignin oil.
The guaiacol structure contains three types of C-O bonds, and cyclohexanol with high added value can be obtained by directionally controlling the cleavage of the C-O bonds. The preparation of highly active catalysts is critical for catalyzing the conversion of guaiacol to cyclohexanol-like chemicals. It is reported that most of common catalysts used for the reaction are noble metal catalysts, the hydrogenation activity of the catalysts is relatively low, and most of the reactions are required to be carried out under the conditions of high temperature (> 200 ℃) and high pressure (> 5 MPa), so that the conversion cost is high, and the industrialization is not easy.
Nickel-based catalysts are catalysts with good hydrogenation activity, but often require high loadings (above 10%) to promote catalytic activity and selectivity to cyclohexanol of no more than 80%. Therefore, the application of the catalyst with low cost and high efficiency in the catalytic conversion of guaiacol is the focus of the current research.
Disclosure of Invention
The invention aims to provide the application of the low-load nickel-carbon catalyst in the catalytic conversion of guaiacol under mild conditions, the load of nickel is low, the reaction conditions are mild, and the cost is reduced.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the application of the low-load nickel-carbon catalyst in the catalytic conversion of guaiacol under mild conditions comprises the following specific steps: placing guaiacol, a nickel-carbon catalyst and an organic solvent into a reactor, sealing, introducing inert gas into the reactor, and discharging residual air in the reactor; then charging 1-2 MPa hydrogen into the reactor, heating the reactor to 200-220 ℃ and keeping the temperature for 60-180 min; after the reaction is finished, naturally cooling the reactor to room temperature and decompressing; filtering the reacted liquid through a filter, and analyzing the liquid product composition and yield of the collected liquid through a gas chromatograph-mass spectrometer (GC-MS) and a Gas Chromatograph (GC); the nickel in the nickel-carbon catalyst is an active component, the carbon material is a carrier, and the nickel loading is 3-7% of the catalyst mass.
Preferably, the nickel loading in the nickel carbon catalyst is 5% of the catalyst mass.
Preferably, the nickel-carbon catalyst is prepared by the following steps: adding the nickel precursor into water, ultrasonically dissolving, then adding a carrier carbon material, and ultrasonically stirring for 5-15 min; vacuum dipping for 12-48h at room temperature after the ultrasonic treatment is finished; then transferring the mixture into a drying oven for drying for 3 to 6 hours; grinding the obtained solid into powder after drying, placing the solid powder into a tube furnace, calcining for 1-4 hours at the temperature of 450-550 ℃ in inert atmosphere, and then reducing for 1-4 hours at the temperature of 450-550 ℃ in hydrogen atmosphere; and (5) carrying out vacuum storage on the reduced catalyst.
Preferably, the nickel precursor is one or more of nickel nitrate hexahydrate, nickel chloride hexahydrate, basic nickel carbonate and nickel acetate.
Preferably, the carbon material is activated carbon.
Preferably, the hydrogen pressure is 1MPa, the reaction temperature is 200 ℃, and the reaction time is 120min.
Preferably, the organic solvent is isopropanol.
Preferably, the mass ratio of the guaiacol to the nickel-carbon catalyst is 5:3.
compared with the prior art, the invention has the following beneficial effects:
1. the invention uses a nickel-based catalyst with low loading capacity, does not need noble metal doping, has the loading capacity not exceeding 7 percent, adopts common and easily-obtained carbon materials as the carrier, and reduces the production cost of the catalyst.
2. The invention catalyzes nickel carbon with low loadThe agent is applied to the catalytic conversion of guaiacol at 200 ℃ and 1MPa H 2 Under the mild reaction condition of 2 hours, the conversion rate of the guaiacol reaches 100 percent, and the selectivity of the cyclohexanol is more than 85 percent, so that the conversion cost of the guaiacol is further reduced.
Drawings
FIG. 1 is XRD patterns of Ni/C with different loadings prepared in the examples of the present invention;
FIG. 2 is an SEM image of Ni/C with different loadings prepared according to the examples of the present invention;
FIG. 3 is a TEM image of Ni/C with different loadings prepared in the examples of the present invention;
FIG. 4 is a schematic representation of the bond energies of three C-O bonds in the guaiacol structure and the conversion of guaiacol to products;
FIG. 5 is the effect of reaction temperature on guaiacol catalytic conversion;
FIG. 6 is the effect of reaction pressure on guaiacol catalytic conversion.
Detailed Description
The invention will be described in further detail with reference to the drawings and the specific examples.
The Ni/C prepared in the following examples are named in the following manner: x Ni/C, wherein X represents nickel loading of 1%, 3%, 5% and 7%, and the catalyst preparation will be described in detail below with 5% Ni/C as an example.
Example 1: preparation of catalyst 5% Ni/C
A series of catalysts with low loading (1%, 3%, 5% and 7%) are prepared by using nickel precursors (one or more of nickel nitrate hexahydrate, nickel chloride hexahydrate, basic nickel carbonate and nickel acetate) as precursors, and carbon-based materials (activated carbon) are used as carriers of the catalysts. 0.05215g of nickel nitrate hexahydrate was placed in a beaker, 1-5mL of water was added to the beaker, and the beaker was placed in an ultrasonic apparatus to completely dissolve the nickel nitrate by ultrasound. Then adding 0.2g of carbon carrier into the beaker, putting the beaker into an ultrasonic instrument to carry out ultrasonic treatment for 5-15min, and continuously stirring the solution by using a glass rod during the process. After the ultrasonic treatment is finished, the beaker is moved into a vacuum drying oven to stand for 12-48 hours. Then the beaker is taken out and put into a blast drying oven at 110 ℃ to be dried for 3 to 6 hours. The solid obtained after the drying was ground to homogeneity with a mortar. The ground solid powder is put into a tube furnace, calcined for 3 hours at 500 ℃ in nitrogen atmosphere, and then reduced for 3 hours at 500 ℃ in hydrogen atmosphere. The reduced catalyst was placed in a vacuum dryer for storage. The nickel loading prepared by the method is 5%.
Example 2: preparation of catalyst 1% Ni/C
The preparation method was substantially the same as in example 1 except that nickel nitrate hexahydrate was added in an amount of 0.01g.
Example 3: preparation of catalyst 3% Ni/C
The preparation was substantially the same as in example 1 except that nickel nitrate hexahydrate was added in an amount of 0.0306g.
Example 4: preparation of catalyst 7% Ni/C
The preparation method was substantially the same as in example 1 except that nickel nitrate hexahydrate was added in an amount of 0.0746g.
TABLE 1 physical Properties of catalysts and supports
a The total specific surface area is calculated by the BET formula.
b At relative pressure P/P 0 Total pore volume was determined at=0.99.
c The specific micropore surface area and micropore volume were calculated using the t method.
d Total specific surface area and micropore surface area, and difference between total pore volume and micropore volume.
The physical adsorption of carbon support (C) and a series of Ni/C was characterized. As can be seen from Table 1, the specific surface area of the support was 829m 2 And/g, the specific surface area of the carrier is larger so as to be beneficial to the loading of metal. At the negative levelAfter the metal Ni is loaded, the specific surface area of the catalyst can be reduced compared with that of the carrier. The more metal supported, the more the specific surface area was reduced, indicating successful loading of metallic nickel into the carbon support. Wherein the more the metal is supported, the more the specific surface area of the micropores of the catalyst is reduced, which can indicate that the metal is more supported in the micropores.
FIG. 1 is XRD patterns of 3% Ni/C, 5% Ni/C, 7% Ni/C and carrier. As can be seen from the figure, there are more diffraction peaks of 2 crystalline nickel after loading nickel than the carrier spectrum. Typical diffraction peaks at 44.6 ° and 52.1 ° at 2θ are the (111) and (200) crystal planes of Ni, respectively, which further indicate successful loading of metallic nickel into the support.
FIG. 2 is an SEM image of 3% Ni/C, 5% Ni/C and 7% Ni/C. The porous structure of the catalyst surface can be seen from the figure. It can be seen that the porous structure of the carbon support surface remains after loading with the metal. The metal distribution on the catalyst surface can be seen from the figure, and the small round dots which are lightened in the figure are the metal nickel on the catalyst surface. Since SEM characterization can only roughly see the morphology of the metal and support, further analysis of the particle size distribution of the metallic nickel by TEM characterization is required.
FIG. 3 is a TEM image of 3% Ni/C, 5% Ni/C and 7% Ni/C. It can be seen from the figure that the dispersion of metallic nickel in the three catalysts varies with the loading. Wherein the particle size of the metallic Ni in 5% Ni/C is the smallest, 6.91nm, which indicates a more uniform dispersion of nickel in the support when the metal loading is 5%. Too little or too much metal loading can lead to uneven dispersion and increased metal particle size.
Example 5: catalytic conversion application of guaiacol
Guaiacol (50 mg), ni/C catalyst (10-40 mg) and solvents (isopropanol, n-hexane, methanol and ethanol) were placed in a reactor. After sealing, the reactor was charged with 3 times N 2 To remove residual air from the reactor. Then charging H with a certain pressure (0.1-2.0 MPa) into the reactor 2 The reactor was heated to (160-220 ℃) and maintained at that temperature (10-180 min). After the reaction is finished, the reactor is naturally cooled to room temperature and depressurized. The reacted liquid is reactedThe body was filtered through a filter and the collected liquid was analyzed for liquid product composition and yield by gas chromatography-mass spectrometer (GC-MS) and Gas Chromatograph (GC).
TABLE 2 influence of different Ni/C catalysts on the catalytic conversion of guaiacol
Reaction conditions: 50mg of guaiacol, 30mg of catalyst, 20mL of isopropanol, 200 ℃ and 1MPa H 2 ，2h.
The effect of varying loadings of Ni/C on guaiacol catalytic conversion is shown in Table 2. The guaiacol was catalytically converted using only a carbon support without any conversion. After loading the metallic nickel on the support, guaiacol begins to undergo conversion. This indicates that nickel is the active center of the reaction. At a low nickel loading of 1%, only 15.2% of the guaiacol was converted, mainly to cyclohexanol and phenol. The bond energies of the three C-O bonds in the guaiacol structure and the products resulting from the conversion of guaiacol are shown in FIG. 4. In FIG. 4, it can be seen that the bond energy of the C-O bond in the methoxy group in the guaiacol structure is the lowest, 217kJ/mol, and then the bond energy of the C-O bond in which the benzene ring is connected with the methoxy group is 356kJ/mol. And the bond energy of the C-O bond of the benzene ring connected with the hydroxyl is highest, which reaches 414kJ/mol. Figure 4 also shows possible products of guaiacol conversion, as can be seen from table 2, where cyclohexanol and phenol are the major products and 2-methoxycyclohexanone and 2-methoxycyclohexanol are the minor products during guaiacol conversion, thus classifying 2-methoxycyclohexanone and 2-methoxycyclohexanol as other products during calculation. As the nickel loading increased from 1% to 5%, the conversion of guaiacol increased gradually and 100% of the guaiacol was converted to 88% cyclohexanol at 5% ni/C catalysis. As analyzed in connection with FIG. 4, when 5% Ni/C catalyzes this reaction, the C-O bond, which is primarily the benzene ring attached to the methoxy group, is broken to form phenol, which is then further hydrogenated to form cyclohexanol. As can be seen from FIG. 4, this C-O bond energy is 356kJ/mol, which is greater than the bond energy of the C-O bonds in many other model compounds of lignin. Whereas 5% Ni/C prepared by the invention is capable of catalyzing guaiacol conversion under mild conditions, this further illustrates the catalytic advantage of 5% Ni/C. With further increasing nickel loading to 7%, the conversion of guaiacol and the yield of cyclohexanol did not change substantially. Considering the catalyst cost problem, a further investigation was conducted by selecting 5% Ni/C as the optimal catalyst.
Example 6: influence of the reaction temperature on the conversion of guaiacol
Reaction conditions: 50mg guaiacol, 30mg 5% Ni/C,20mL isopropanol, 1MPa H 2 ，2h.
The reaction temperature plays an important role in the catalytic conversion of guaiacol. 5% Ni/C was chosen as the optimal catalyst to explore the effect of temperature on the catalytic conversion of guaiacol. As can be seen from FIG. 5, the conversion of guaiacol was 40.8% at 160℃and gradually increased with further increase in temperature, and at 200℃the guaiacol was completely converted to 88% cyclohexanol. This suggests that elevated temperatures favor cleavage of the C-O bond linking the benzene ring to the methoxy group (FIG. 4). Under the action of 5% Ni/C, the invention can realize the C-O bond with higher bond energy (356 kJ/mol) under mild condition. Has a certain innovation compared with the previous research. It can be seen that cyclohexanol is the main product in this reaction system, phenol is formed at low temperature, while the selectivity of other products remains around 10% in this reaction. Guaiacol breaks the C-O bond to form phenol, which is then further hydrogenated to the main pathway of the reaction. Whereas the aromatic ring of guaiacol is hydrogenated to a secondary reaction path.
Example 7: effect of reaction time on guaiacol conversion
TABLE 3 influence of reaction time on guaiacol conversion
Reaction conditions: 50mg guaiacol, 30mg 5% Ni/C,200 ℃,20mL isopropanol, 1MPa H 2 .
The effect of reaction time on guaiacol catalytic conversion is shown in Table 3. Only 10.3% of the guaiacol was converted within 10min of the initial reaction, in which case the product contained phenol and cyclohexanol. The conversion of guaiacol gradually increased to 64.5% as the reaction time was extended to 30 min. The main product in this reaction is cyclohexanol, with a phenol yield of 15.8%, which further indicates that phenol is an intermediate product in this reaction, and that phenol is progressively hydrogenated to cyclohexanol over time. This is consistent with the above reaction temperature presumption of the path of guaiacol conversion. Under the catalysis of the reaction, the yield of other products is at most about 10%, so about 10% of the aromatic rings of the guaiacol are hydrogenated into secondary reaction paths. Most of the guaiacols are broken by C-O bonds to form phenol and cyclohexanol. Guaiacol can be completely converted to 88% cyclohexanol at a reaction time of 2 hours.
Example 8: influence of the reaction atmosphere on the conversion of guaiacol
TABLE 4 influence of the reaction atmosphere on guaiacol conversion
Reaction conditions: 50mg of guaiacol, 30mg of 5% Ni/C,180 ℃,20mL of isopropanol, 2h.
The effect of guaiacol conversion under different atmospheres was investigated. As shown in Table 4, 5% Ni/C in H was investigated 2 And N 2 Effect on guaiacol catalytic conversion under both atmospheres. It can be seen that under this reaction system, at H 2 In combination with isopropanol, the conversion of guaiacol can reach 85% with N 2 The conversion of guaiacol in combination with isopropanol was only 25.5%. It can be seen that isopropanol provides only a very small amount of active hydrogen when used as a solvent, and it is difficult to break the C-O bond in guaiacol. H 2 Active hydrogen is mainly provided in the reaction system, so that C-O bonds are cracked to generate phenol and cyclohexanol. Thus, in this reaction system, guaiacol is present in H 2 Can be better cracked to form cyclohexanol and phenol under the atmosphere.
Example 9: influence of the reaction pressure on the conversion of guaiacol
Reaction conditions: 50mg of guaiacol, 30mg of 5% Ni/C,200 ℃,20mL of isopropanol, 2h.
FIG. 6 is a graph showing the effect of hydrogen pressure on guaiacol catalytic conversion. The conversion of guaiacol was 84.6% at a hydrogen pressure of 0.5MPa, and the product contained cyclohexanol in a yield of 67.9% and phenol in a yield of 10.6%. As the pressure increased from 0.5MPa to 1MPa, the conversion of guaiacol reached 100% and the yield of cyclohexanol was 88%. The yield of phenol in the product was 0, which indicates that the increase in hydrogen pressure hydrogenates phenol to cyclohexanol. With further increases in hydrogen pressure to 2MPa, the conversion of guaiacol and the yield of cyclohexanol were not substantially changed. However, when the pressure is further increased to 3MPa, the yield of other products obtained by hydrogenation of the aromatic rings of guaiacol is increased from 9.3% to 18.7%. This indicates that too high a hydrogen pressure may cause the formation of by-products in the reaction system, thereby adversely affecting the obtaining of cyclohexanol. In summary, a hydrogen pressure of 1MPa is the optimal reaction pressure for the reaction system.
Example 10: influence of the reaction solvent on the conversion of guaiacol
TABLE 5 influence of reaction solvent on guaiacol conversion
Reaction conditions: 50mg guaiacol, 30mg 5% Ni/C,1MPa H 2 200 ℃,20mL of solvent, 2h.
Table 5 shows the effect of the reaction solvent on guaiacol conversion. In this reaction system, guaiacol does not react when methanol and ethanol are used as a reaction solvent. The conversion of guaiacol was 36% when n-hexane was used as a solvent. Whereas under the same reaction conditions, guaiacol was completely converted with isopropanol as the reaction solvent. This is due to H 2 Solubility in different solvents is different. Because of H 2 High solubility in isopropanol and conductivitySo that the conversion rate of guaiacol into active hydrogen is higher under the same reaction conditions with isopropanol as the solvent than under other solvents.
The foregoing is merely illustrative of specific embodiments of the present invention, and the scope of the invention is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present invention will be apparent to those skilled in the art within the scope of the present invention.
Claims (8)
1. The application of the low-load nickel-carbon catalyst in the catalytic conversion of guaiacol under mild conditions is characterized by comprising the following specific steps: placing guaiacol, a nickel-carbon catalyst and an organic solvent into a reactor, sealing, introducing inert gas into the reactor, and discharging residual air in the reactor; then charging 1-2 MPa hydrogen into the reactor, heating the reactor to 200-220 ℃ and keeping the temperature for 60-180 min; after the reaction is finished, naturally cooling the reactor to room temperature and decompressing; filtering the reacted liquid by a filter, and analyzing the composition and yield of a liquid product by a gas chromatograph-mass spectrometer and a gas chromatograph through the collected liquid; the nickel in the nickel-carbon catalyst is an active component, the carbon material is a carrier, and the nickel loading is 3-7% of the catalyst mass.
2. The use according to claim 1, wherein the nickel carbon catalyst has a nickel loading of 5% of the catalyst mass.
3. Use according to claim 1 or 2, wherein the nickel carbon catalyst is prepared by: adding the nickel precursor into water, ultrasonically dissolving, then adding a carrier carbon material, and ultrasonically stirring for 5-15 min; vacuum dipping for 12-48h at room temperature after the ultrasonic treatment is finished; then transferring the mixture into a drying oven for drying for 3 to 6 hours; grinding the obtained solid into powder after drying, placing the solid powder into a tube furnace, calcining for 1-4 hours at the temperature of 450-550 ℃ in inert atmosphere, and then reducing for 1-4 hours at the temperature of 450-550 ℃ in hydrogen atmosphere; and (5) carrying out vacuum storage on the reduced catalyst.
4. The use according to claim 3, wherein the nickel precursor is one or more of nickel nitrate hexahydrate, nickel chloride hexahydrate, basic nickel carbonate, nickel acetate.
5. Use according to claim 3, wherein the carbon material is activated carbon.
6. The use according to claim 1 or 2, wherein the hydrogen pressure is 1MPa, the reaction temperature is 200 ℃, and the reaction time is 120min.
7. Use according to claim 1 or 2, characterized in that the organic solvent is isopropanol.
8. The use according to claim 1 or 2, characterized in that the mass ratio of guaiacol to nickel carbon catalyst is 5:3.
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