CN115304650A - Method for preparing ester by selective catalytic oxidative depolymerization of lignin source - Google Patents

Method for preparing ester by selective catalytic oxidative depolymerization of lignin source Download PDF

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CN115304650A
CN115304650A CN202210968756.XA CN202210968756A CN115304650A CN 115304650 A CN115304650 A CN 115304650A CN 202210968756 A CN202210968756 A CN 202210968756A CN 115304650 A CN115304650 A CN 115304650A
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sepiolite
cobalt
ester
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copper
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CN115304650B (en
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邵礼书
杨磊
盛志远
张�林
詹鹏
吴志平
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Central South University of Forestry and Technology
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07G—COMPOUNDS OF UNKNOWN CONSTITUTION
    • C07G1/00—Lignin; Lignin derivatives
    • 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
    • B01J23/75—Cobalt
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/03—Precipitation; Co-precipitation
    • B01J37/031—Precipitation
    • B01J37/035—Precipitation on carriers
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis

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Abstract

The invention belongs to the field of lignin depolymerization, and particularly relates to a method for preparing ester by selective catalytic oxidative depolymerization of a lignin source, which comprises the steps of carrying out coprecipitation on a mixed solution containing pretreated sepiolite, a copper source, a cobalt source and alkali under the assistance of ultrasound to obtain a precursor; then roasting the precursor at the temperature of 350-550 ℃ to prepare the composite catalyst; the composite catalyst is a copper-cobalt bimetallic multivalent oxide @ sepiolite material, and comprises sepiolite and copper-cobalt bimetallic multivalent oxide loaded with the sepiolite and comprising monovalent copper, divalent cobalt and trivalent cobalt; carrying out oxidative depolymerization on the lignin source under the catalysis of the composite catalyst, and then separating to obtain an ester depolymerization product. The catalyst is innovatively adopted for degrading lignin, so that the selectivity of ester degradation products can be induced, and the yield and the content of the ester products are improved.

Description

Method for preparing ester by selective catalytic oxidative depolymerization of lignin source
Technical Field
The invention relates to the field of lignin degradation, in particular to the technical field of selective degradation of lignin into ester degradation products.
Background
In the current global energy system, petrochemical energy with limited reserves still occupies a leading position, and a large amount of greenhouse gases and toxic and harmful substances are emitted in the utilization process. Among a plurality of new energy sources, biomass is the only renewable green organic carbon source in the nature, and has great potential in replacing non-renewable petrochemical resources. The lignin is a renewable aromatic macromolecule with the largest content in the nature, and has good application prospect in conversion of functional materials, biological oil and chemicals, such as lignin slow release fertilizer, lignin-based concrete alkaline water agent, lignin-based adhesive, polymer adsorbent materials and the like. The depolymerization of lignin into small-molecular organic chemicals is one of the effective ways to realize high-value conversion of lignin, and is also an important starting point for converting lignin into petroleum-based aromatic compounds to realize high added value. At present, depolymerization reports of lignin mainly include biological enzymatic depolymerization, thermal cracking, photocatalysis, catalytic reduction depolymerization, catalytic oxidation depolymerization and the like, and in the depolymerization process, how to realize controllable breakage of lignin connecting bonds and inhibition of product repolymerization are the key points of efficient depolymerization of lignin.
The lignin catalytic oxidative depolymerization reaction has a short period, the product is easy to separate, combustible hydrogen or organic micromolecule hydrogen with higher cost and strong danger is not needed to be consumed, the lignin can be converted into other high-functional chemicals such as aldehyde, ketone, organic acid and the like, and the research value is high. Therefore, catalytic oxidative depolymerization of lignin is an important direction for lignin application, and a novel catalyst with low cost, easy recovery, high conversion rate and high product selectivity is required to be developed. Besides monomeric phenol, alcohol and alkane compounds, the product of catalytic oxidative depolymerization of lignosulfonate can also generate more functional aromatic compounds and ester substances, such as vanillin, syringaldehyde and p-hydroxybenzaldehyde which can be used for synthesizing intermediates of medicines and spices; vanillyl which can be used for treating asthma and arthritis, and other organic acids such as p-coumaric acid, vanillic acid and the like, esters such as Ethyl Acetate (EA), diethyl succinate, diethyl maleate and the like are important platform compounds in the pharmaceutical and food industries, and most of the industrially produced dibasic acid (ester) is derived from petrochemical raw materials such as benzene, toluene and the like. At present, the problems of harsh conditions, low conversion efficiency, low selectivity of ester products and the like generally face from the depolymerization of lignosulfonate to ester chemicals. Therefore, a catalytic system with high conversion rate and selectivity, mild reaction conditions, good catalyst stability and low cost needs to be constructed from lignin as a raw material to ester chemicals, and the catalytic system becomes one of hot spots for catalytic depolymerization of lignin.
Disclosure of Invention
Aiming at the problems that the existing lignin degradation selectivity is not ideal and ester degradation products are difficult to obtain with high selectivity, the invention aims to provide a method for preparing ester by selective catalytic oxidative depolymerization of a lignin source, aiming at inducing the reaction of ring opening of lignin to form ester with high selectivity and improving the selectivity of the ester products.
In order to improve the selectivity of degrading lignin into ester substances and improve the yield and content of ester products, the invention provides the following scheme:
a method for selective catalytic oxidative depolymerization of a lignin source to an ester, the steps comprising:
step (1):
co-precipitating a mixed solution containing pretreated sepiolite, a copper source, a cobalt source and alkali under the assistance of ultrasound to obtain a precursor; then roasting the precursor at 350-550 ℃ to prepare the composite catalyst;
the composite catalyst is a copper-cobalt bimetallic multivalent oxide @ sepiolite material, and comprises sepiolite and copper-cobalt bimetallic multivalent oxide loaded with the sepiolite and comprising monovalent copper, divalent cobalt and trivalent cobalt;
step (2):
carrying out oxidative depolymerization on a lignin source and an oxidant under the catalysis of the composite catalyst in the step (1), and then separating to obtain an ester depolymerization product;
the oxidant is one of oxygen, ozone, hydrogen peroxide and peroxide.
The research of the invention finds that the sepiolite substrate of the composite catalyst and the supported copper-cobalt double-metal multivalent oxide are cooperated, so that the selectivity of the ring-opening depolymerization reaction of lignin can be induced effectively and the yield of the depolymerized products of esters can be improved.
In the invention, the combination of the carrier and the active ingredient of the composite catalyst is the key for synergistically improving the selectivity of depolymerizing lignin into ester. The research of the invention also finds that the selectivity of the ester-forming reaction can be further improved by controlling the preparation process of the composite catalyst, for example, pre-treating the sepiolite in advance, then co-precipitating the sepiolite with the copper source-cobalt source under the assistance of ultrasound, and roasting the sepiolite at the required temperature.
In the invention, the special structure of the sepiolite is the key for improving the degradation selectivity of the lignin esters by combining with the Cu-Co bimetal valence-change active component. For example, pre-treated sepiolite is obtained by subjecting sepiolite to a pre-baking-acidifying treatment.
Preferably, the atmosphere of the pre-roasting is at least one of nitrogen and inert gas;
preferably, the pre-roasting temperature is 300-550 ℃, and further preferably 350-400 ℃;
preferably, the pre-roasting time is 2-5h, and more preferably 3-4 h;
preferably, the acidizing acid solution is an aqueous solution of at least one of hydrochloric acid, nitric acid and sulfuric acid;
preferably, the concentration of the acid liquor is 1-3mol/L;
preferably, the time of the acidification treatment is 3-5 h;
preferably, the pretreated sepiolite is prepared by drying treatment after acidification;
preferably, the temperature for drying after acidification is 50-70 ℃, and the drying time is 11-13h.
In the invention, the copper source is water-soluble salt of copper ions, preferably at least one of chloride, sulfate, organic acid salt and nitrate of copper ions;
the cobalt source is water-soluble salt of cobalt ions, preferably at least one of chloride, sulfate, organic acid salt and nitrate of the cobalt ions;
preferably, the copper/cobalt molar ratio of the copper source to the cobalt source is 0.5-1.5; more preferably 0.7 to 1.3; more preferably 1 to 1.3.
The weight ratio of the pretreated sepiolite to the total metal is 6-8: 2 to 4, and more preferably 6 to 7. The total metal weight refers to the total weight of metal elements in the copper source and the cobalt source.
Preferably, the alkali is at least one of alkali metal hydroxide and ammonia water;
preferably, the pH of the coprecipitation stage is 8 to 11;
in the invention, coprecipitation is carried out under the assistance of ultrasound, and subsequent roasting temperature is matched, so that synergy is favorably realized, the structures of sepiolite and bimetal are adjusted, a phase of bimetal valence-variable oxide is favorably obtained, and the selectivity of the ester-forming degradation reaction of lignin is synergistically improved.
Preferably, the power of the ultrasound is 100W to 400W.
Preferably, in the step (1), the roasting atmosphere is an oxygen-containing atmosphere, preferably an air atmosphere;
preferably, the calcination temperature is 350 to 450 ℃. The catalyst obtained under the preferred conditions has better selectivity of lignin ester degradation.
The time for calcination is preferably 2 to 5 hours, more preferably 3 to 4 hours.
In the present invention, the lignin source is not particularly limited, and is, for example, a lignin sulfonate, and is preferably at least one of sodium lignin sulfonate, calcium lignin sulfonate, ammonium lignin sulfonate, and magnesium lignin sulfonate.
In the invention, the solvent for catalytic oxidative depolymerization reaction is water;
preferably, the concentration of the lignin source in the initial solution of the catalytic oxidative depolymerization reaction is 0.005-0.025 g/mL;
preferably, the weight ratio of the lignin source to the composite catalyst is 3-7: 1 to 2, and more preferably 4 to 6.
In the invention, the temperature of the catalytic oxidative depolymerization reaction is 120-250 ℃, more preferably 180-220 ℃, and even more preferably 200-210 ℃;
preferably, when the oxidant for catalytic oxidative depolymerization reaction is oxygen and/or ozone, the oxygen partial pressure in the system is 1.0-2.0 MPa;
preferably, the time of the catalytic oxidative depolymerization reaction is 3 to 5 hours.
In the invention, in the step (2), the ester depolymerization product is obtained by an extraction method;
the steps are preferably: and after the catalytic oxidation depolymerization reaction is finished, carrying out solid-liquid separation to obtain a first solution, carrying out acid precipitation treatment on the first solution, carrying out solid-liquid separation to obtain a second solution, and carrying out extraction treatment on the second solution to obtain an ester depolymerization product.
In the invention, the extraction solvent is an ester solvent, preferably at least one of ethyl acetate, tributyl phosphate and butyl acetate;
preferably, the ester depolymerization product is at least one of dibutyl phthalate, di (2-ethylhexyl) phthalate, 2' -methylenebis (6-tert-butyl-4-methylphenol), diethyl succinate, monoethyl succinate and diethyl maleate; preferably at least one of diethyl succinate, monoethyl succinate, dibutyl phthalate, di (2-ethylhexyl) phthalate and diethyl maleate.
In a more specific embodiment of the present invention, the steps comprise
1) Placing the natural sepiolite raw material into a tubular furnace, heating to 300-550 ℃ in nitrogen atmosphere, and calcining for 2-5h. Preferably, the temperature rise rate of the tube furnace is 4.9-5.1 ℃/min. The calcining temperature is 350-400 ℃, and the calcining time is 3.8-4.1h.
Dissolving calcined sepiolite in sulfuric acid solution, acidifying at 60-80 deg.C for 3-5 hr, and filtering. Drying the obtained filter cake in a vacuum drying oven at 50-70 ℃ for 11-13h. And grinding the dried filter cake into powder, and then calcining under the same conditions to finally obtain the modified sepiolite carrier. Preferably, the acidification temperature is 65-75 ℃. The acidification uses sulfuric acid with the concentration of 1.5-2.0 mol/L. The acidification time is 3.9-4h. The drying treatment in (1) is carried out in a vacuum drying oven. The drying temperature is 50-70 ℃. The drying time is 11-13h.
2) Adding sepiolite carrier, copper chloride dihydrate and cobalt chloride hexahydrate into deionized water, stirring for 0.5-1.5h (preferably 0.8-1.2 h) at 60-80 deg.C (preferably 65-75 deg.C), adding dropwise 3-7ml (preferably 4-6 ml) of NaOH with concentration of 4.5-7.5mol/L (preferably 5.5-6.5 mol/L) for 20-40min (preferably 28-32min, initial pH of 8-11), cooling, and transferring the suspension into an ultrasonic disperser (300W/15 min-310W/15 min). And then, filtering the precipitate, washing the precipitate to be neutral by using deionized water, drying a filter cake at 50-70 ℃ in vacuum for 11-13h, grinding the filter cake into powder, heating the powder to 350-550 ℃ in a tubular furnace in the air atmosphere, and calcining the powder for 3-5h to obtain the composite catalyst.
3) Taking a proper amount of the prepared composite catalyst, a proper amount of sodium lignin sulfonate and a proper amount of ultrapure water to react in a stainless steel autoclave with the rotating speed of 250-350rpm, the temperature of 180-210 ℃, and the O 2 The pressure was 1.0 to 2.0MPa, and after 3 to 5 hours of the reaction, the reaction mixture was cooled to room temperature and washed with 8 to 12ml of ultrapure water to obtain the whole depolymerization product. Filtering to separate solid and liquid products, adding 1-3ml sulfuric acid into the obtained liquid product, standing for 5-8 hours to precipitate residual sodium lignosulfonate, and filtering for the second time to obtain a total liquid product and a total solid product. Extracting the total liquid product, separating oil phase and water phase, and evaporating at 35-45 deg.C to obtain oil phase product. And performing GC-MS analysis, and calculating the conversion rate of sodium lignosulfonate and the yield of the ester chemicals.
Advantageous effects
The invention creatively takes the modified sepiolite as a substrate, and the Cu-Co bimetal valence-variable oxide is loaded on the sepiolite, so that excellent catalytic selectivity can be shown in the reaction of selectively degrading lignin into ester components, and the yield and the purity of the ester product can be effectively improved;
according to the invention, the sepiolite is pretreated in advance, and then is matched with an ultrasonic-assisted Cu-Co coprecipitation and roasting process, and further matched with the combined control of process parameters, so that the microstructure of the sepiolite can be synergistically improved, the loading is facilitated, the active ingredients of the Cu-Co bimetal valence-variable oxides are obtained, and the composite catalyst with excellent ester product solution selectivity can be prepared.
Drawings
Fig. 1 is an SEM image (c) of the natural sepiolite (a and b) and the modified sepiolite in example 1. In fig. 1 (a-b), it can be seen that the sepiolite surface has dense and thin rod-like structures, and these rod-like structures are combined in a staggered manner to form a three-dimensional network structure with uneven surface, which can be an active component carrier site. The surface topography of the modified sepiolite is shown in a figure (c), and compared with the sepiolite before modification, the stacking of the rod-shaped bodies on the surface of the modified sepiolite is relatively loose, and the gaps of a three-dimensional network space are more abundant;
FIG. 2 is XPS energy spectra of examples 1,8 and 9 screened for different active component loading amounts, which correspond to curves A, B and C respectively, and FIG. 2 shows that all XPS energy spectra can see characteristic peaks at binding energy of Si, O, cu and Co, which indicates that the basic framework of sepiolite in the catalyst is not changed drastically, and the Cu and Co components are loaded on the surface of the carrier.
The O1 s spectrum shows that all three catalysts with different loadings can be divided into three peaks, terminal oxygen (Cu/Co = O), connecting oxygen (Co/Cu-O-Co/Cu) and surface-OH oxygen species in order from low to high.
Characteristic peaks at 942eV and 963eV can be seen in a Cu 2p spectrogram, and the fact that Cu in the catalyst is mainly Cu is proved 2+ Exist in the form of (1).
Co appears in three catalysts in XPS spectrogram of Co 2p 2+ And Co 3+ Characteristic satellite peaks. The results show that Cu + And Cu 2+ And Co 2+ And Co 3+ Conversion is related to the loading, at too high a loading of active componentCu 2+ And Co 3+ The content is low;
FIG. 3 is a GC chart of ester soluble products of catalytic oxidative depolymerization of sodium lignosulfonate according to examples 1, 6 and 10, which show the best depolymerization effect under various factors. FIG. 3 shows the GC-MS product distribution of all three catalysts, and the by-products dibutyl phthalate, di (2-ethylhexyl) phthalate and 2,2' -methylenebis (6-tert-butyl-4-methylphenol) generated in the depolymerization process can be seen, and the structural formulas can be shown as (3), (4) and (5) in the figure.
30CuCoO x (ii) m-Sep350 and 30CuCoO x The GC-MS results for the/m-Sep 450 catalyst were approximately the same, indicating that catalyst preparation temperature has less effect on depolymerization. In addition, the presence of benzoic acid (7) and 9, 10-anthraquinone (6), which are intermediate products of the oxidative ring-opening process, is clearly observed, and the content of these substances decreases or even disappears as the ring-opening products increase.
30Cu 2 CoO x In a/m-Sep 350 catalyst system, the selectivity of diethyl succinate (1) and monoethyl succinate (2) is higher than that of other two catalysts, and the products also comprise hexadecanoic acid and octadecanoic acid, and the results show that the catalyst can depolymerize sodium lignosulfonate to generate a small-molecular compound, further oxidize a benzene ring to generate an ester substance by ring opening, and combine Cu and Cu in the catalyst to generate an ester substance 2+ Further presume high contents of Cu and Cu 2+ Is favorable for promoting the opening of the benzene ring of the sodium lignosulphonate to generate ester substances.
Detailed Description
In order that the manner in which the present invention is recited will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings.
In the invention, the total ester yield refers to the total yield of diethyl maleate, monoethyl succinate, diethyl succinate, ethyl octadecenoate and ethyl hexadecanoate;
the total ester yield was determined by GC-MS.
In the following cases, the total metal weight is expressed as CuCl 2 ·2H 2 O and CoCl 2 ·6H 2 The Cu and Co metal elements in the O are calculated by weight.
Example 1:
(1) Placing sepiolite (Sep) raw material in a tubular furnace, and adding into the furnace 2 Heating to 350 ℃ at the heating rate of 5 ℃/min under the atmosphere, and calcining for 4h. Taking 15g of calcined sepiolite raw material to dissolve in 150mL of H with the concentration of 2mol/L 2 SO 4 The solution was acidified at 70 ℃ for 4h and filtered. The obtained filter cake was dried in a vacuum oven at 60 ℃ for 12h. And grinding the dried filter cake into powder, and calcining under the same condition to obtain the acid-modified sepiolite carrier which is recorded as m-Sep.
(2) 3.5g of m-Sep and CuCl were weighed 2 ·2H 2 O and CoCl 2 ·6H 2 O (weight ratio of m-Sep to total metals 7, cu-Co molar ratio 1.0: 0.9), in 50mL of deionized water, stirring at 70 ℃ for 1h, then adding dropwise a 5mol/L NaOH solution, stirring to pH 9, cooling, and transferring the suspension to an ultrasonic disperser (300W/15 min). Then, filtering the precipitate, washing the precipitate to be neutral by using deionized water, carrying out vacuum drying on a filter cake at 60 ℃ for 12h, grinding the filter cake into powder, then heating the powder to 350 ℃ at a heating rate of 5 ℃/min in a tubular furnace in the air atmosphere, and calcining the powder for 4h to obtain the composite catalyst marked as 30CuCoO x /m-Sep350。
(3) Adding 0.1g of the above composite catalyst, 0.5g of sodium lignin sulfonate and 50ml of ultrapure water into a stainless steel autoclave, sealing the autoclave, and blowing oxygen (depolymerization atmosphere) at 210 deg.C and O 2 The pressure was 1.0MPa, the stirring speed was 300rpm, and after 4 hours of hydrothermal catalytic oxidative depolymerization reaction, the reaction mixture was cooled to room temperature and washed with 10ml of ultrapure water to obtain the whole depolymerization product. The solid and liquid products were separated by filtration, 2ml of sulfuric acid (about 98%) was added to the obtained liquid product, left to stand for 6 hours to precipitate the residual sodium lignin sulfonate, and filtered twice to obtain a total liquid product and a total solid product. Extracting the total liquid product, separating oil phase and water phase, and evaporating at 40 deg.C to obtain oil phase product. GC-MS analysis (northern core of the paper, 2019,52 (12): 39-49) was performed to calculate sodium lignosulfonate conversion and ester chemical yield.
Examples 2, 3:
compared with the example 1, the specific reaction process and the detection method are consistent, and the difference is only that the pretreatment condition of the step (1) is changed, and the calcination temperature is respectively adjusted to 300 ℃ and 400 ℃.
TABLE 1 conditions and results described in examples 1 to 3 of the present invention
Figure BDA0003795926680000081
Examples 4, 5:
compared with the example 1, the specific reaction process and the detection method are consistent, and the difference is only that the pretreatment condition of the step (1) is changed, and the acidification treatment time is respectively adjusted to be 3h and 5h.
TABLE 2 conditions and results described in examples 1, 4 and 5 of the present invention
Figure BDA0003795926680000082
Example 6:
compared to example 1, the difference is only that the Cu-Co molar ratio is 1.3:0.6, other operations, parameters and test methods were the same as in example 1.
Example 7:
compared to example 1, the difference is only that the Cu-Co molar ratio is 0.7:1.3, other operations, parameters and test methods were the same as in example 1.
TABLE 3 conditions and results described in examples 1, 6 and 7 of the present invention
Figure BDA0003795926680000083
Figure BDA0003795926680000091
Example 8:
compared to example 1, the only difference is that the weight ratio of m-Sep to total metal is 8:2, other operations, parameters and tests were the same as in the examples.
Example 9:
compared to example 1, the only difference is that the weight ratio of m-Sep to total metal is 6:4, other operations, parameters and tests were the same as in the examples.
TABLE 4 conditions and results described in examples 1,8 and 9 of the present invention
Figure BDA0003795926680000092
Example 10:
the only difference compared to example 1 is that in step 2, the calcination temperature of the catalyst was 450 ℃. Other operations, parameters and tests were the same as in example 1.
Example 11:
the only difference compared with example 1 is that in step 2, the calcination temperature of the catalyst was 550 ℃. Other operations, parameters and tests were the same as in example 1.
TABLE 5 conditions and results described in examples 1, 10 and 11 of the present invention
Figure BDA0003795926680000093
Figure BDA0003795926680000101
Examples 12 to 14:
compared with the example 1, the preparation process and the detection method of the specific catalyst are consistent, and the difference is that the depolymerization temperature in the step (3) is changed and is respectively adjusted to 180 ℃,190 ℃ and 200 ℃.
TABLE 6 conditions and results described in examples 1, 12 to 16 of the present invention
Figure BDA0003795926680000102
Examples 15, 16:
compared with the example 1, the preparation process and the detection method of the specific catalyst are consistent, and the difference is that the depolymerization oxygen pressure in the step (3) is changed and is respectively adjusted to be 1.5Mpa and 2.0Mpa.
TABLE 7 conditions and results described in examples 1, 15 and 16 of the present invention
Figure BDA0003795926680000103
Examples 17, 18:
compared with the example 1, the preparation process and the detection method of the specific catalyst are consistent, and the difference is that the depolymerization time in the step (3) is changed and is respectively adjusted to be 3h and 5h.
TABLE 8 conditions and results described in examples 1, 17 and 18 of the present invention
Figure BDA0003795926680000111
Comparative example 1:
compared with the example 1, the specific reaction process and the detection method are consistent, and the difference is that the catalyst in the comparative example 1 does not load the metal active component, the carrier is not modified, and only the natural sepiolite is used as the catalyst for reaction. Weighing 0.1g Sep and 0.5g sodium lignosulfonate, and 50ml ultrapure water, adding into a stainless steel autoclave, setting the temperature at 210 deg.C, and O 2 The pressure was 1.0MPa, the stirring speed was 300rpm, the reaction was cooled to room temperature after 4 hours, and washed with 10ml of ultrapure water to obtain the whole depolymerization product. The solid and liquid products were separated by filtration, 2ml of sulfuric acid (about 98%) was added to the obtained liquid product, left to stand for 6 hours to precipitate the residual sodium lignin sulfonate, and filtered twice to obtain a total liquid product and a total solid product. Extracting the total liquid product, separating oil phase and water phase, and evaporating at 40 deg.C to obtain oil phase product. And performing GC-MS analysis, and calculating the conversion rate of sodium lignosulfonate and the yield of the ester chemicals.
Comparative example 2:
compared with the comparative example 1, the specific reaction process and the detection method are consistent, and the difference is only that natural zeolite is adopted for replacing Sep and is directly used for the catalytic oxidative degradation of lignin.
Comparative example 3:
the only difference compared to example 1 is that in step (1), zeolite is used instead of Sep, and the other operations and parameters are the same as in example 1.
TABLE 9 conditions and results described in inventive example 1 and comparative examples 1 to 3
Figure BDA0003795926680000112
Figure BDA0003795926680000121
Comparative example 4:
the only difference compared to example 1 is that in step 2, only a single CuCl is added 2 ·2H 2 O, without addition of CoCl 2 ·6H 2 O, and the total mass ratio of m-SeP and metal is considered to be 7; other operations, parameters and tests were the same as in example 1: the catalyst obtained was recorded as 30Cu x O/m-Sep。
Comparative example 5:
the only difference compared to example 1 is that in step 2, only a single CoCl was added 2 ·6H 2 O, without addition of CuCl 2 ·2H 2 O, and the total mass ratio of m-SeP and metal is considered to be 7; other operations, parameters and tests were the same as in example 1: the final catalyst was recorded as 30Co x O/m-Sep。
Comparative example 6:
the only difference compared to example 1 is that in step 2, an equimolar amount of FeCl is used 3 ·6H 2 O instead of the cobalt source, the other operations, parameters and test methods were the same as in example 1.
The final catalyst was recorded as 30CuFeOx/m-Sep350.
Comparative example 7:
the only difference compared with example 1 is that in step 2, feCl3.6H2O with equal molar amount is used to replace the copper source, and the other operation, parameters and test method are the same as example 1.
The final catalyst was designated as 30CoFeOx/m-Sep350.
TABLE 10 conditions and results described in inventive example 1 and comparative examples 4 to 7
Figure BDA0003795926680000122
The product GC test results are shown in table 11:
TABLE 11
Figure BDA0003795926680000131
Ester-based: diethyl maleate, monoethyl succinate, diethyl succinate, ethyl octadecenoate and ethyl hexadecanoate; acid series: palmitic acid, stearic acid and succinic acid; benzene series: 2, 2-methylenebis (6-tert-butyl-4-methylphenol), benzoic acid and dibutyl phthalate. The acid system comprises palmitic acid, stearic acid and succinic acid. Benzene series 2,2' -methylenebis (6-tert-butyl-4-methylphenol), benzoic acid and dibutyl phthalate.
Comparative example 8:
compared with example 1, in step 2, no ultrasonic assistance was performed, and the other operations, parameters and test methods were the same as example 1.
TABLE 12 conditions and results described in inventive example 1 and comparative example 8
Figure BDA0003795926680000132
Comparative example 9:
the only difference compared to example 1 is that the temperature during the catalyst calcination stage is 300 ℃. The other operations and parameters were the same as in example 1.
The final catalyst was designated as 30CuCoOx/m-Sep300.
Comparative example 10:
the only difference compared to example 1 is that the temperature during the catalyst calcination stage is 600 ℃. The other operations and parameters were the same as in example 1. The final catalyst was recorded as 30CuCoOx/m-Sep600.
TABLE 13 conditions and results described in inventive example 1 and comparative examples 9 and 10
Figure BDA0003795926680000141
Comparative example 11:
the only difference compared to example 1 is that in step 3, the depolymerization atmosphere is nitrogen (nitrogen is used instead of the oxygen), and the other operations, parameters and tests are the same as in example 1.
Comparative example 12:
the only difference compared to example 1 is that in step 3, the depolymerization atmosphere is air (air is used instead of said oxygen), and the other operations, parameters and tests are the same as in example 1.
TABLE 14 conditions and results described in inventive example 1 and comparative examples 11 and 12
Figure BDA0003795926680000142
The above description of the embodiments is provided to facilitate understanding and use of the invention by those skilled in the art, and the present invention is not limited to the above embodiments, and all modifications and variations that fall within the scope of the claims are intended to be embraced by the present invention.

Claims (10)

1. A method for selective catalytic oxidative depolymerization of a lignin source to an ester, comprising the steps of:
step (1):
co-precipitating a mixed solution containing pretreated sepiolite, a copper source, a cobalt source and alkali under the assistance of ultrasound to obtain a precursor; then roasting the precursor at the temperature of 350-550 ℃ to prepare the composite catalyst;
the composite catalyst is a copper-cobalt bimetallic multivalent oxide @ sepiolite material, and comprises sepiolite and copper-cobalt bimetallic multivalent oxide loaded with the sepiolite and comprising monovalent copper, divalent cobalt and trivalent cobalt;
step (2):
carrying out oxidative depolymerization on a lignin source and an oxidant under the catalysis of the composite catalyst in the step (1), and then separating to obtain an ester depolymerization product;
the oxidant is one of oxygen, ozone, hydrogen peroxide and peroxide.
2. The process according to claim 1, wherein the pre-treated sepiolite is obtained by pre-roasting-acidifying sepiolite;
preferably, the atmosphere of the pre-roasting is at least one of nitrogen and inert gas;
preferably, the pre-roasting temperature is 300-550 ℃;
preferably, the pre-roasting time is 2-5h;
preferably, the acidizing acid solution is an aqueous solution of at least one of hydrochloric acid, nitric acid and sulfuric acid;
preferably, the concentration of the acid liquor is 1-3mol/L;
preferably, the time of the acidification treatment is 3-5 h;
preferably, the pretreated sepiolite is prepared by drying treatment after acidification;
preferably, the temperature for drying after acidification is 50-70 ℃, and the drying time is 11-13h.
3. The method of claim 1, wherein the copper source is a water-soluble salt of copper ions, preferably at least one of chloride, sulfate, organic acid, nitrate of copper ions;
the cobalt source is water-soluble salt of cobalt ions, preferably at least one of chloride, sulfate, organic acid salt and nitrate of the cobalt ions;
preferably, the copper/cobalt molar ratio of the copper source to the cobalt source is 0.5 to 1.5; more preferably 0.7 to 1.3;
the weight ratio of the pretreated sepiolite to the total metal is 6-8: 2 to 4.
4. The method of claim 1, wherein the base is at least one of an alkali metal hydroxide, ammonia;
preferably, the pH of the coprecipitation stage is between 8 and 11;
preferably, the power of the ultrasound is 100W to 400W.
5. The method of claim 1, wherein in step (1), the atmosphere for calcination is an oxygen-containing atmosphere, preferably an air atmosphere;
preferably, the time for calcination is 2 to 5 hours.
6. The method of claim 1, wherein the lignin source is a lignosulfonate, preferably at least one of sodium lignosulfonate, calcium lignosulfonate, ammonium lignosulfonate, and magnesium lignosulfonate.
7. The process according to any one of claims 1 to 6, wherein the solvent for the catalytic oxidative depolymerization reaction is water;
preferably, the concentration of the lignin source in the initial solution of the catalytic oxidative depolymerization reaction is 0.005-0.025 g/mL;
preferably, the weight ratio of the lignin source to the composite catalyst is 3-7: 1 to 2.
8. The method of claim 7, wherein the temperature of the catalytic oxidative depolymerization reaction is 120 to 250 ℃;
preferably, when the oxidant for catalytic oxidative depolymerization reaction is oxygen and/or ozone, the oxygen partial pressure in the system is 1.0-2.0 MPa;
preferably, the time of the catalytic oxidative depolymerization reaction is 3 to 5 hours.
9. The method of claim 8, wherein in step (2), the depolymerization product of the ester is obtained by extraction;
the steps are preferably: after the catalytic oxidation depolymerization reaction is finished, carrying out solid-liquid separation to obtain a first solution, carrying out acid precipitation treatment on the first solution, carrying out solid-liquid separation to obtain a second solution, and carrying out extraction treatment on the second solution to obtain an ester depolymerization product.
10. The method of claim 9, wherein the extraction solvent is an ester solvent, preferably at least one of ethyl acetate, tributyl phosphate, and butyl acetate;
preferably, the ester depolymerization product is at least one of dibutyl phthalate, di (2-ethylhexyl) phthalate, 2' -methylenebis (6-tert-butyl-4-methylphenol), diethyl succinate, monoethyl succinate and diethyl maleate.
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