Modified molecular sieve supported ruthenium catalyst, preparation thereof and application thereof in preparation of hydrocarbon substances from lignin
Technical Field
The invention belongs to the field of preparation of hydrocarbon substances by hydrogenation and deoxidation of lignin, and particularly relates to a modified molecular sieve supported ruthenium catalyst, and preparation and application thereof in preparation of hydrocarbon substances by lignin.
Background
Energy has been the focus of attention in the society since the 21 st century, and countries and researchers are actively seeking alternative new energy sources in order to solve the increasing shortage of non-renewable petrochemical energy sources. Biomass is the only organic carbon source which can be sustainably provided at present, and the content of lignin in biomass (about 20-30 percent) is second to cellulose, and is the most abundant natural renewable aromatic high polymer. The lignin has higher energy density, and can be used for preparing cycloparaffin and aromatic hydrocarbon by depolymerization and hydrodeoxygenation, and can be used for vehicle fuel and aviation kerosene, and the aromatic hydrocarbon with high octane number can also improve the octane number of the vehicle fuel.
Lignin has a stable molecular structure and is difficult to directly utilize, and is difficult to decompose into valuable subunits in a safe and simple manner. In recent years, the raw materials for preparing hydrocarbons are mainly reacted by model compounds, few research groups directly carry out catalytic hydrodeoxygenation on lignin, and the hydrodeoxygenation on the lignin is carried out under the conditions of high temperature and high pressure, so that side reactions and coking are easy to occur. Therefore, the key of the process for preparing the hydrocarbon fuel by hydrodeoxygenation of the lignin and the derivatives thereof is to find a suitable catalytic system. Luo et al (Green Chemistry, 2016, 18: 5845-2And 6bar N2Reacting for 4h, wherein the main product is aromatic hydrocarbon. However, the unmodified molecular sieve has smaller pore diameter, and is easy to coke in the reaction process. Wang et al (Green Chemis)try, 2015,17(12):5131-2O3HY catalyzed alkali lignin in 0.1g lignin, 0.3g Ru/Al2O3And 0.3g HY, 30ml H at 250 deg.C2O,4MPa H2Under the condition of 4 hours of reaction, the total yield is 21.83 wt%, the conversion rate reaches 81.03%, the yield of aromatic compounds is 0.88 wt%, the yield of alkylcyclohexane is 19.60 wt%, and the yield of acyclic hydrocarbon is 1.35 wt%. Although the yield of hydrocarbons is high, the use of excessive amounts of catalyst can make the economic cost prohibitive. Luo et al (RSC Adv, 2019, 9(55): 31960-: in the case of fast pyrolysis at 5,600 ℃, the overall yield is 7.63%, with 5.75% for bicyclic aromatics and 1.88% for polycyclic aromatics. However, the yield of the target product is low when the catalyst is not modified and is not loaded with active metal.
The molecular sieve catalyst has strong surface acidity, but the excessive acidity can generate side reaction and coking in the reaction process. Therefore, the chemical modification of the molecular sieve can better regulate the proportion of the B acid and the L acid, has important significance for the research of preparing hydrocarbon substances by hydrogenating and deoxidizing lignin, and can change the aperture of the molecular sieve. At present, the research on preparing hydrocarbons by catalyzing lignin hydrodeoxygenation through metal modified molecular sieves loaded with active metals is less.
Disclosure of Invention
In order to overcome the defects and shortcomings in the prior art, the invention aims to provide a preparation method of a modified molecular sieve supported ruthenium catalyst.
The invention also aims to provide a modified molecular sieve supported ruthenium catalyst prepared by the method.
The invention further aims to provide application of the modified molecular sieve supported ruthenium catalyst in preparation of hydrocarbon substances from lignin.
The purpose of the invention is realized by the following technical scheme:
a preparation method of a modified molecular sieve supported ruthenium catalyst comprises the following steps:
(1) mixing Al (NO)3)3·9H2OyiUniformly mixing an alcohol water solution and an HZSM-5 molecular sieve, standing, drying, and roasting at 500-800 ℃ for 4-8 h to obtain Al modified HZSM-5;
(2) al modified HZSM-5 was added to RuCl3·xH2Mixing the solution and the solution O uniformly, drying, then reducing the solution with hydrogen for 3 to 6 hours at the temperature of between 300 and 700 ℃, and then reducing the solution with N2/O2And passivating at normal temperature in the atmosphere of mixed gas to obtain the modified molecular sieve supported ruthenium catalyst (Ru/Al-HZSM-5).
Preferably, Al (NO) in step (1)3)3·9H2In aqueous O ethanol, Al (NO)3)3·9H2The concentration of O is 0.1-0.4 g/ml, and the volume ratio of ethanol to water is 1: 1.
preferably, the mass content of Al in the Al modified HZSM-5 in the step (1) is 1-3%.
Preferably, the standing time in the step (1) is 24-48 h.
Preferably, the drying temperature in the step (1) is 80-110 ℃, and the time is 12 h.
Preferably, the temperature rising speed of the roasting in the step (1) is 3-5 ℃/min, and the temperature reduction speed is 1-3 ℃/min.
Preferably, the loading amount of ruthenium in the modified molecular sieve-supported ruthenium catalyst in the step (2) is 2.5-10 wt%.
Preferably, the RuCl of step (2)3·xH2The solvent of the O solution is 1:1 of ethanol-water mixed solution; the RuCl3·xH2The concentration of the O solution was 0.042 g/ml.
Preferably, the step (2) of uniformly mixing refers to stirring for 12 hours at normal temperature to uniformly mix.
Preferably, the drying temperature in the step (2) is 80-120 ℃, and the time is 12 h.
Preferably, the time of the normal-temperature passivation in the step (2) is 1-2 h.
Preferably, the temperature rise rate of the hydrogen reduction in the step (2) is 1-4 ℃/min.
Preferably, N is the same as in step (2)2/O2In the mixed gas O2Content of (1%), N2/O2The flow rate of the mixed gas is 20-40 ml/min.
The modified molecular sieve supported ruthenium catalyst prepared by the method.
The application of the modified molecular sieve supported ruthenium catalyst in the preparation of hydrocarbon substances from lignin comprises the following steps:
uniformly mixing the modified molecular sieve supported ruthenium catalyst, lignin and water, and reacting for 4-12 h at the hydrogen pressure of 3-5 MPa and the temperature of 210-290 ℃; and (4) finishing the reaction, cooling to room temperature, performing solid-liquid separation, and extracting to obtain a hydrocarbon substance mixture.
Preferably, the ratio of the modified molecular sieve supported ruthenium catalyst to the lignin to the water is 0.1-0.5 g: 0.4 g: 30-40 ml.
Preferably, the rotating speed of the reaction is 400-1000 rpm.
Preferably, the reaction is carried out in an autoclave, and the cooling is carried out by rapidly cooling the autoclave to room temperature with tap water while purging the autoclave in a fume hood.
More preferably, after the temperature of the reaction is reduced, the wall of the high-pressure reaction kettle is washed by ethyl acetate, and the obtained mixed solution is extracted to obtain the hydrocarbon substances.
Preferably, the extractant used for the extraction is ethyl acetate.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the invention uses ethanol water solution to dissolve Al (NO)3)3·9H2O and RuCl3·xH2And O and ethanol have small surface tension and can easily enter a pore channel of the molecular sieve, redundant ethanol can be taken away through volatilization to form a concentration gradient, and compared with the traditional method that water is used as a solution to dissolve active center metal salt (namely ruthenium salt), the active component (ruthenium) is easier to load on the molecular sieve. The preparation process of the modified molecular sieve supported ruthenium catalyst is simple and rapid. The yield of the target product hydrocarbon substance in the lignin hydrodeoxygenation reaction reaches 14.64 percent, the yield of other oxygen-containing substances is 2.09 percent, and no obvious coking phenomenon exists.
Drawings
FIG. 1 is an XRD pattern of commercially available HZSM-5 and Al-HZSM-5, Ru/Al-HZSM-5 obtained in example 1.
FIG. 2 is an SEM photograph of commercially available HZSM-5 and Al-HZSM-5, Ru/Al-HZSM-5 obtained in example 1.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.
Those who do not specify specific conditions in the examples of the present invention follow conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like which are not indicated for manufacturers are all conventional products which can be obtained by commercial purchase.
In the following examples the hydrocarbons and oxygenates were determined by gas chromatography and mass spectrometry (GC-MS) analysis, the GC-MS detection was calculated using internal standard and n-dodecane as internal standard. The synthesized modified molecular sieve supported ruthenium catalyst is characterized by a multi-position automatic sample injection X-ray diffractometer (X' per3 Power) and an ultrahigh resolution field emission electron microscope (SU 8220).
The formula for calculating the mass percentage of alkane in the catalytic product in the following examples is: w is the mass of the target product/mass of lignin added x 100%, and in examples 12 and 18, the mass fraction of hydrocarbon species in the product was calculated again by the following calculation method: w1 equals the mass of the desired product/total product x 100% (internal standard method).
The molecular sieves purchased in the examples were dried at 110 ℃ for 12h before use.
Examples 1 to 5
0.71g of Al (NO) is weighed out3)3·9H2O in a beaker, 5ml of ethanol V: water V1: 1, weighing 3g of purchased HZSM-5 molecular sieve, pouring the weighed HZSM-5 molecular sieve into the solution, performing ultrasonic treatment and uniform stirring, standing the solution at room temperature for 48 hours, and drying the solution in a drying oven at 110 ℃ for 12 hours to obtain the modified molecular sieve carrier (Al-HZSM-5).
0.21g of RuCl was weighed3·xH2O, using 5ml of ethanol water (volume ratio is 1:1) solutionUltrasonic-assisted dissolution, weighing 2g of modified molecular sieve carrier, magnetically stirring at normal temperature for 12h, drying at 80 ℃ for 12h in a drying oven, reducing with hydrogen at 400 ℃ for 4h in a tubular furnace, and dissolving with N2/O2Mixed gas (O)2Content of 1%) at normal temperature for 1h to obtain 5 wt% Ru-loaded catalyst (Ru/Al-HZSM-5).
0.4g of organosolv lignin, 0.1, 0.2, 0.3, 0.4 and 0.5g of 5 wt.% Ru/Al-HZSM-5 catalyst and 40ml of water were placed in an autoclave, into which 2MPa H was passed2Replacing air in the kettle, repeating for 3 times, and charging 4MPa H2And (3) reacting at 270 ℃ for 8 hours, quickly cooling the reaction kettle to room temperature by using tap water after the reaction is finished, filtering, washing filter residues by using ethyl acetate, washing the filtrate by using washing liquid and the filtrate together, extracting the filtrate by using the ethyl acetate, and performing gas chromatography-mass spectrometry analysis on 1ml of extract liquor to obtain a liquid product, wherein the yield of hydrocarbon substances and oxygen-containing substances in the liquid product is shown in table 1.
TABLE 1 Effect of different catalyst dosages on the Hydrodeoxygenation of organosolv Lignin
Examples 6 to 9
Referring to example 4, 0.4g of lignin as an organic solvent, 0.4g of 5 wt% Ru/Al-HZSM-5 catalyst and 40ml of water were charged in an autoclave, to which 2MPa of H was passed2Replacing air in the kettle, repeating for 3 times, and charging 4MPa H2Respectively reacting for 8 hours at the temperature shown in the table 2, quickly cooling the reaction kettle to room temperature by using tap water after the reaction is finished, filtering, washing filter residues by using ethyl acetate, extracting the filtrate by using ethyl acetate together with washing liquid filtrate, and performing gas chromatography-mass spectrometry on 1ml of extract liquor, wherein the yield of hydrocarbon substances and oxygen-containing substances in the obtained liquid product is shown in the table 2.
TABLE 2 Effect of temperature on Hydrodeoxygenation of organosolv lignin
Examples
|
6
|
7
|
8
|
4
|
9
|
Reaction temperature/. degree.C
|
210
|
230
|
250
|
270
|
290
|
Hydrocarbon yield/wt%
|
3.66
|
4.76
|
6.7
|
12.71
|
13.35
|
Oxygenate yield/wt%
|
2.36
|
0.41
|
0.37
|
1.57
|
0.95 |
Examples 10 to 13
Referring to example 4, 0.4g of lignin as an organic solvent, 0.4g of 5 wt% Ru/Al-HZSM-5 catalyst and 40ml of water were charged in an autoclave, to which 2MPa of H was passed2Replacing air in the kettle, repeating for 3 times, and charging 4MPa H2And (3) reacting at 270 ℃, wherein the reaction time is shown in table 3, after the reaction is finished, quickly cooling the reaction kettle to room temperature by using tap water, filtering, washing filter residues by using ethyl acetate, washing the filtrate by using washing liquid, extracting the filtrate by using ethyl acetate, and performing gas chromatography-mass spectrometry analysis on 1ml of extract liquor, wherein the yield of hydrocarbon substances and oxygen-containing substances in the obtained liquid product is shown in table 3.
TABLE 3 Effect of reaction time on Hydrodeoxygenation of organosolv lignin
Examples 14 to 17
Catalyst recycle experiment: after the reaction of example 12 was completed, the residue was sufficiently washed with ethyl acetate and dried in an oven at 80 ℃ for 12 hours. The recovered catalyst was further subjected to the lignin hydrodeoxygenation reaction as in example 12, with the catalyst being recycled four times, and the hydrocarbon and oxygenate yields are shown in table 4.
TABLE 4 Effect of catalyst recycle on Hydrodeoxygenation of organosolv lignin
Examples
|
12
|
14
|
15
|
16
|
17
|
Number of catalyst cycles
|
0
|
1
|
2
|
3
|
4
|
Hydrocarbon yield/wt%
|
14.64
|
13.96
|
13.43
|
12.84
|
12.34
|
Oxygenate yield/wt%
|
2.09
|
2.98
|
3.48
|
5.09
|
5.70 |
The mass fraction, C, of the product of example 12 was calculated by a second calculation method8-C18Hydrocarbon material 70.21 wt%, C12-C18In the proportion of 50.94 wt%, C19-C25The proportion is 4.57 wt%.
Comparative example 1
0.21g of RuCl was weighed3·xH2Dissolving O in 5ml ethanol water (volume ratio 1:1) under ultrasonic assistance, weighing 2g HZSM-5 molecular sieve carrier, magnetically stirring at room temperature for 12h, oven drying at 80 deg.C for 12h in a drying oven, reducing with hydrogen at 400 deg.C for 4h in a tubular furnace, and dissolving in N2/O2Mixed gas (O)2Content of 1%) at normal temperature for 1h to obtain a 5 wt% Ru-supported catalyst (Ru/HZSM-5 catalyst).
0.4g of organosolv lignin, 0.4g of 5 wt.% Ru/HZSM-5 catalyst and 0.095g of Al (NO)3)3·9H2O and 40ml of water are added into a high-pressure reaction kettle, and 2MPa H is introduced into the high-pressure reaction kettle2Replacing air in the kettle, repeating for 3 times, and charging 4MPa H2And (2) reacting at 270 ℃ for 10 hours, quickly cooling the reaction kettle to room temperature by using tap water after the reaction is finished, filtering, washing filter residues by using ethyl acetate, washing the filtrate by using washing liquid, extracting the filtrate by using ethyl acetate, taking 1ml of extract liquid, and carrying out gas chromatography-mass spectrometry, wherein the yields of hydrocarbon substances and oxygen-containing substances in the obtained liquid product are respectively 0.28 wt% and 10.37 wt% by using a first method, and the mass percent of the hydrocarbon substances in the obtained product is 2.58 wt% by using a second method.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.