CN108947786B - Method for preparing acrolein by glycerol dehydration - Google Patents
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/51—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by pyrolysis, rearrangement or decomposition
- C07C45/52—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by pyrolysis, rearrangement or decomposition by dehydration and rearrangement involving two hydroxy groups in the same molecule
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- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
Abstract
The invention discloses a method for preparing acrolein by catalyzing glycerol dehydration through a hollow-structure ZSM-5 nano molecular sieve, which comprises the following steps: firstly, preparing a ZSM-molecular sieve, then uniformly mixing and stirring the prepared ZSM-5 molecular sieve and an alkaline substance aqueous solution, stirring and carrying out alkali treatment at 40-80 ℃, centrifugally washing after treatment, drying and roasting to prepare a ZSM-5 nano molecular sieve with a hollow structure; finally, glycerin is dehydrated to prepare acrolein under the catalysis of a ZSM-5 molecular sieve with a hollow structure. The ZSM-5 molecular sieve with the hollow structure prepared by the invention is beneficial to the mass transfer and diffusion of each reaction molecule in the chemical reaction, thereby effectively improving the conversion rate of glycerol, the yield of acrolein and the inactivation resistance of the catalyst.
Description
Technical Field
The invention relates to the field of reactions for preparing acrolein by high-value conversion and utilization of glycerol and dehydration of glycerol, in particular to preparation and application of a hollow ZSM-5 molecular sieve deactivation-resistant catalyst.
Background
For over 150 years, the development of the chemical and energy industries has been extensively dependent on fossil resources, such as coal, natural gas, and petroleum, so that over-exploitation of fossil resources has created various global environmental problems. Biomass is an abundant carbon neutral renewable resource that can be used for the production of energy and chemicals. In recent years, much research has been devoted to the shift from social dependence on fossil raw materials to the utilization of renewable biomass resources. Among the numerous applications of biomass, biodiesel has been produced industrially on a large scale. In 2012, the global biodiesel production was 2270 ten thousand tons and increased rapidly, with an estimated 3690 ten thousand tons by 2020. The biodiesel produced industrially is prepared with vegetable oil and animal fat as material and short chain alcohol (methanol, ethanol, etc.) in sodium hydroxide or sodium methoxide as catalyst, and through ester exchange reaction at alkali temperature and high temperature (230-250 deg.c) to produce corresponding fatty acid methyl ester or ethyl ester, washing and drying. The production process generates about 10 wt% of by-product crude glycerol, which becomes the main source of biomass crude glycerol at present. The biomass crude glycerol is not widely regarded due to small market share and low price. To prevent this waste of resources and at the same time to ensure the sustainability of biodiesel production, during the last decade, numerous studies on the conversion of glycerol into chemical value-added products have been proposed.
Glycerol can be converted to high value-added chemicals by steam reforming, hydrogenolysis, oxidation, dehydration, esterification, carboxylation, acetylation, and chlorination. Such as hydrogenation of glycerol to 1, 2-propanediol and 1, 3-propanediol, oxidation of glycerol to dihydroxyacetone and glyceric acid, and dehydration of glycerol to acrolein. In addition to the above chemicals, some commercially important C3 chemicals, such as acrylic acid, lactic acid, acrylonitrile, ethanol, allyl alcohol, 1-propanol, propylene, can also be produced by catalytic conversion of glycerol. Based on the rapid development of glycerol conversion technology, glycerol is gradually becoming a potential renewable chemical resource for producing various high value-added chemicals. Therefore, the use of glycerol to produce high value-added chemicals can partially compensate for the gap created by the excessive cost of fossil fuel production. One of the important uses of glycerol is the preparation of acrolein, an important chemical intermediate, for the production of acrylic acid, esters, methionine, perfumes, polymers or detergents, etc.
The current industrial production method of acrolein is to use Bi/Mo mixed oxide as catalyst to oxidize propylene in gas phase, the selectivity of acrolein can reach 85%, and the conversion rate of propylene is above 95%. In addition, another approach is to obtain acrolein by dehydration of glycerin by gasification using a solid acid catalyst. In the solid acid catalyst, the B acid site is more favorable for improving the activity and selectivity of the reaction than the L acid site, when the glycerin molecule is combined with the acid site, firstly a molecule of water is removed from the molecule, then the molecule isomerization is carried out, and finally the terminal hydroxyl is removed to generate the acrolein. Several types of catalysts proposed in recent years include molecular sieves, heteropolyacids, acidic heteropoly salts, phosphoric acid-based materials and oxides. Of these, molecular sieves, particularly ZSM-5 molecular sieves, have received attention for their high selectivity and catalytic stability for the production of acrolein. However, severe coking is one of the important causes of catalyst deactivation. For this reason, the objective of this study was to design a solid acid molecular sieve catalyst with higher resistance to deactivation.
Disclosure of Invention
In order to solve the defects of the prior art, the invention provides the ZSM-5 nano molecular sieve with the hollow structure, which has the advantages of uniform and regular thin wall outside, fast mass transfer, large specific surface area, good catalytic activity and inactivation resistance, and can effectively improve the conversion rate of glycerol and the yield of acrolein.
In order to achieve the purpose, the invention adopts the following technical scheme:
(1) deionized water and NaAlO2Uniformly mixing and stirring, adding 25-40% by mass of tetrapropyl ammonium hydroxide aqueous solution, and fully stirring to obtain a mixed solution; dropwise adding tetraethyl orthosilicate into the mixed solution, fully stirring to completely hydrolyze the tetraethyl orthosilicate, putting the mixed solution into a hydrothermal kettle, crystallizing at the temperature of 100-120 ℃ for 2-8h, then heating to the temperature of 170-200 ℃ for crystallization for 3-5d, centrifugally washing, drying and roasting to obtain the Na-ZSM-5 molecular sieve; two-stage heating is adopted, and low-temperature crystallization is favorable for promoting nucleation of the molecular sieve, so that a molecular sieve product with uniform size and smaller particle size is obtained. If the low-temperature crystallization process is cancelled, the product size is larger, the specific surface area is smaller, mass transfer in the reaction process is not facilitated, and the coking phenomenon is aggravated, so that the reaction activity of the catalyst is reduced, and the service life of the catalyst is prolonged.
(2) Mixing and stirring the Na-ZSM-5 molecular sieve and an inorganic alkali aqueous solution uniformly, heating and heating, continuously stirring, centrifugally washing after finishing alkali treatment, drying, and roasting to obtain a hollow Na-ZSM-5 molecular sieve;
(3) stirring the Na-type molecular sieve and an ammonium nitrate solution for 4-6H at 40-80 ℃, performing ammonium exchange, centrifugally washing, drying and roasting to obtain an H-type molecular sieve, wherein the method is suitable for conventional ZSM-5 molecular sieves and hollow ZSM-5 molecular sieves;
(4) the hollow ZSM-5 molecular sieve (0.5g) prepared above was placed in the middle section of a mini fixed bed reactor. Before introducing the glycerol aqueous solution, introducing nitrogen at the temperature of 270-320 ℃ to purge the catalyst for 30-60min, injecting the glycerol aqueous solution into a reactor by an injection pump, carrying out contact reaction with a ZSM-5 molecular sieve catalyst, condensing a reaction product mixture, collecting the condensed reaction product mixture into a collector, and carrying out qualitative and quantitative analysis by timing sampling through a gas chromatography.
Preferably, in the step (1), the deionized water and the NaAlO are added2The molar ratio of the tetrapropylammonium hydroxide aqueous solution to the tetraethyl orthosilicate is as follows: (600-1000): (0.25-1): (2-4): 10.
preferably, in the step (2), the inorganic base is one or a mixture of sodium hydroxide and potassium hydroxide.
Preferably, in the step (2), the ratio of the molecular sieve to the inorganic alkali solution is: 1g of molecular sieves corresponds to 30mL of a 0.2M solution.
Preferably, in the step (2), the molecular sieve is put into an inorganic alkali solution for alkali treatment, the heating temperature is 40-60 ℃, and the stirring time is 4-6 h.
As the optimization of the technical proposal, in the step (2) and the step (3), the roasting temperature is 500-600 ℃, and the roasting time is 6-8 h.
Preferably, in the step (4), the concentration of the aqueous glycerol solution is 20 to 30%.
Preferably, in the step (4), the glycerin aqueous solution is injected into the reactor at a rate of 3 to 5mL/min, and the nitrogen carrier gas flow rate is 30 to 50 mL/min.
The invention has the following advantages:
the invention firstly prepares ZSM-5 nano molecular sieve, and then adopts an alkali treatment method to prepare ZSM-5 molecular sieve with a hollow structure, wherein the ZSM-5 molecular sieve has a uniform and regular thin-wall structure, the wall thickness is about 15-25nm, the molecular sieve particles are shaped like oblate truncated cones, the cross section outer diameter is 190-230nm, and the specific surface area is 400-600 m-2/g, external surface area of 160-180m2Per g, almost twice that of the samples without alkali treatment (85-95 m) 2In terms of/g). The hollow catalyst has high catalytic activity, small mass transfer resistance on the diffusion of each substance molecule when being used for glycerin catalytic reaction, effectively improved conversion rate of glycerin and yield of acrolein, and excellent deactivation resistance.
Drawings
FIG. 1: SEM electron micrographs before and after treatment of the nano ZSM-5 molecular sieve, (a) solid ZSM-5, (b) hollow ZSM-5 (example 1);
FIG. 2: TEM micrograph of hollow ZSM-5 molecular sieves (a) solid ZSM-5, (b) (c) hollow ZSM-5 (practical example 2) (scale bar 100, 200 and 50 nm).
Detailed Description
The features of the present invention are described below by way of examples, and the present invention is not limited to the following examples.
Example 1
The preparation method of the anti-coking hollow ZSM-5 molecular sieve catalyst and the application of the catalyst in the reaction of preparing acrolein by glycerol dehydration comprise the following steps:
(1) deionized water and NaAlO2Uniformly mixing and stirring, adding 25% by mass of tetrapropyl ammonium hydroxide aqueous solution, and fully stirring to obtain a mixed solution; dropwise adding tetraethyl orthosilicate into the mixed solution, fully stirring to completely hydrolyze the tetraethyl orthosilicate, putting the mixed solution into a hydrothermal kettle, crystallizing at 120 ℃ for 2 hours, then heating to 170 ℃ for crystallization for 3 days, centrifugally washing, drying and roasting to obtain the Na-ZSM-5 molecular sieve; wherein, deionized water and NaAlO 2The molar ratio of the tetrapropylammonium hydroxide aqueous solution to the tetraethyl orthosilicate is as follows: 500: 0.5: 2: 10;
(2) putting 1g of Na-ZSM-5 molecular sieve into 20mL of 0.1M inorganic alkaline aqueous solution, mixing and stirring uniformly, heating to 60 ℃, continuing stirring for 4 hours, after the alkali treatment is finished, centrifugally washing, drying, and roasting for 6 hours at 500 ℃ to obtain a hollow Na-ZSM-5 molecular sieve; wherein the inorganic base is sodium hydroxide.
(3) Stirring the Na-type molecular sieve and an ammonium nitrate solution at 60 ℃ for 4H, performing ammonium exchange, centrifugally washing, drying, and roasting at 500 ℃ for 6H to obtain the H-type molecular sieve, wherein the method is suitable for conventional ZSM-5 molecular sieves and hollow ZSM-5 molecular sieves.
(4) The hollow ZSM-5 molecular sieve (0.5g) prepared above was placed in the middle section of a mini fixed bed reactor. Before introducing 20% glycerol aqueous solution, introducing nitrogen at 300 ℃ to purge the catalyst for 30min, injecting the glycerol aqueous solution at the speed of 3mL/min by using an injection pump, introducing the glycerol aqueous solution into a reactor at the flow rate of 40mL/min by using nitrogen, carrying out contact reaction with a ZSM-5 molecular sieve catalyst, condensing a reaction product mixture, collecting the reaction product mixture into a collector, and performing qualitative and quantitative analysis by timing sampling through a gas chromatography.
The ZSM-5 molecular sieve obtained by the method has a hollow structure, uniform and regular thin wall, wall thickness of about 25nm, cross section outer diameter of about 220-230nm, specific surface area of 400-500m 2/g, external surface area of 160-165m2(ii) in terms of/g. The results of the scanning electron microscope are shown in FIG. 1.
The catalyst is adopted to ensure that the glycerol conversion rate reaches 100 percent and the acrolein yield reaches 93 percent in the glycerol dehydration reaction. Particularly, in the reaction of 30 hours, the yield of the acrolein is still kept at 90%, and the coking amount of the catalyst after the thermogravimetric analysis reaction is 10.8 wt%, so that the catalyst is not deactivated.
Example 2
The preparation method of the anti-coking hollow ZSM-5 molecular sieve catalyst and the application of the catalyst in the reaction of preparing acrolein by glycerol dehydration comprise the following steps:
(1) deionized water and NaAlO2Uniformly mixing and stirring, adding 25% by mass of tetrapropyl ammonium hydroxide aqueous solution, and fully stirring to obtain a mixed solution; dropwise adding tetraethyl orthosilicate into the mixed solution, fully stirring to completely hydrolyze the tetraethyl orthosilicate, putting the mixed solution into a hydrothermal kettle, crystallizing at 120 ℃ for 4 hours, then heating to 170 ℃ for crystallization for 4 days, centrifugally washing, drying and roasting to obtain the Na-ZSM-5 molecular sieve; wherein, deionized water and NaAlO2The molar ratio of the tetrapropylammonium hydroxide aqueous solution to the tetraethyl orthosilicate is as follows: 1000: 0.2: 1: 10;
(2) putting 1g of Na-ZSM-5 molecular sieve into 30mL of 0.2M inorganic alkaline aqueous solution, mixing and stirring uniformly, heating to 80 ℃, continuing stirring for 6 hours, after the alkali treatment is finished, centrifugally washing, drying, and roasting at 600 ℃ for 4 hours to obtain a hollow Na-ZSM-5 molecular sieve; wherein the inorganic alkali substance is potassium hydroxide.
(3) Stirring the Na-type molecular sieve and an ammonium nitrate solution at 60 ℃ for 4H, performing ammonium exchange, centrifugally washing, drying, and roasting at 600 ℃ for 4H to obtain the H-type molecular sieve, wherein the method is suitable for conventional ZSM-5 molecular sieves and hollow ZSM-5 molecular sieves.
(4) The hollow ZSM-5 molecular sieve (0.5g) prepared above was placed in the middle section of a mini fixed bed reactor. Before 15% of glycerol aqueous solution is introduced, nitrogen is introduced at 280 ℃ to purge the catalyst for 60min, the glycerol aqueous solution is injected by a syringe pump at the speed of 5mL/min, the nitrogen carries the glycerol aqueous solution into the reactor at the flow rate of 30mL/min, the glycerol aqueous solution is in contact reaction with the ZSM-5 molecular sieve catalyst, a reaction product mixture is condensed and then collected into a collector, and the mixture is sampled at regular time and is subjected to qualitative and quantitative analysis through gas chromatography.
The ZSM-5 molecular sieve obtained by the method has a hollow structure, uniform and regular thin wall, wall thickness of about 15-20nm, cross section outer diameter of about 200-210nm, specific surface area of 550-600m2(g) external surface area of 180-2(ii) in terms of/g. The transmission electron microscopy results are shown in FIG. 2.
The obtained catalyst has the glycerol conversion rate of 100 percent and the acrolein yield of 85 percent in the glycerol dehydration reaction. Particularly, in the reaction of 30 hours, the yield of acrolein was still maintained at 78%, and the amount of coking of the catalyst after the reaction was 8.9 wt% by thermogravimetric analysis, and no deactivation was observed.
Example 3
The preparation method of the anti-coking hollow ZSM-5 molecular sieve catalyst and the application of the catalyst in the reaction of preparing acrolein by glycerol dehydration comprise the following steps:
(1) deionized water and NaAlO2Uniformly mixing and stirring, adding 25% by mass of tetrapropyl ammonium hydroxide aqueous solution, and fully stirring to obtain a mixed solution; dropwise adding tetraethyl orthosilicate into the mixed solution, fully stirring to completely hydrolyze the tetraethyl orthosilicate, putting the mixed solution into a hydrothermal kettle, crystallizing at 100 ℃ for 6 hours, then heating to 170 ℃ for crystallization for 3 days, centrifugally washing, drying and roasting to obtain the Na-ZSM-5 molecular sieve; wherein, deionized water and NaAlO2The molar ratio of the tetrapropylammonium hydroxide aqueous solution to the tetraethyl orthosilicate is as follows: 600: 0.25: 2.5: 10;
(2) putting 1g of Na-ZSM-5 molecular sieve into 30mL of 0.15M inorganic alkaline aqueous solution, mixing and stirring uniformly, heating to 50 ℃, continuing stirring for 6 hours, after the alkali treatment is finished, centrifugally washing, drying, and roasting at 600 ℃ for 8 hours to obtain a hollow Na-ZSM-5 molecular sieve; wherein the inorganic alkali substance is a mixture of sodium hydroxide and potassium hydroxide, and the molar ratio of the inorganic alkali substance to the potassium hydroxide is 1: 1.
(3) Stirring the Na-type molecular sieve and an ammonium nitrate solution at 60 ℃ for 4H, performing ammonium exchange, centrifugally washing, drying, and roasting at 500 ℃ for 6H to obtain the H-type molecular sieve, wherein the method is suitable for conventional ZSM-5 molecular sieves and hollow ZSM-5 molecular sieves.
(4) The hollow ZSM-5 molecular sieve (0.5g) prepared above was placed in the middle section of a mini fixed bed reactor. Before introducing a 20% glycerol aqueous solution, introducing nitrogen at 300 ℃ to purge the catalyst for 60min, injecting the glycerol aqueous solution at the speed of 3mL/min by using an injection pump, introducing the glycerol aqueous solution into a reactor at the flow rate of 50mL/min by using the nitrogen, carrying out contact reaction with a ZSM-5 molecular sieve catalyst, condensing a reaction product mixture, collecting the reaction product mixture into a collector, and performing qualitative and quantitative analysis by timing sampling through a gas chromatography.
The ZSM-5 molecular sieve obtained by the method has a hollow structure, uniform and regular thin wall, wall thickness of about 15-20nm, cross section outer diameter of about 190-200nm, and specific surface area of 500-550m2(g) an external surface area of 170-2/g。
The catalyst is adopted to ensure that the glycerol conversion rate reaches 100 percent and the acrolein yield reaches 83 percent in the glycerol dehydration reaction. Particularly, in the reaction of 30 hours, the yield of the acrolein is still kept at 75%, and the coking amount of the catalyst after the reaction is analyzed by thermogravimetry is 6.8 wt%, and the catalyst is not deactivated.
Example 4
The preparation method of the anti-coking hollow ZSM-5 molecular sieve catalyst and the application of the catalyst in the reaction of preparing acrolein by glycerol dehydration comprise the following steps:
(1) the procedure was as described in step (1) of example 1.
(2) Putting 1g of Na-ZSM-5 molecular sieve into 20mL of 0.3M inorganic alkaline aqueous solution, mixing and stirring uniformly, heating to 60 ℃, continuing stirring for 4 hours, after the alkali treatment is finished, centrifugally washing, drying, and roasting for 6 hours at 500 ℃ to obtain a hollow Na-ZSM-5 molecular sieve; wherein the inorganic base is sodium hydroxide.
(3) The procedure was as described in step (3) of example 1.
(4) The procedure was as described in step (4) of example 1.
The obtained ZSM-5 molecular sieve has a hollow structure, uniform and regular thin wall and approximate wall thickness20nm, the cross-sectional outer diameter is about 220-230nm, and the specific surface area is 450-520m2/g, external surface area 165-175m2/g。
The catalyst is adopted to ensure that the glycerol conversion rate reaches 100 percent and the acrolein yield reaches 95 percent in the glycerol dehydration reaction. Particularly, in the reaction of 30 hours, the yield of acrolein is still kept at 92%, and the coking amount of the catalyst after the thermogravimetric analysis reaction is 11.5 wt%, so that the catalyst is not deactivated.
Example 5
The preparation method of the anti-coking hollow ZSM-5 molecular sieve catalyst and the application of the catalyst in the reaction of preparing acrolein by glycerol dehydration comprise the following steps:
(1) the procedure was as described in step (1) of example 1.
(2) The procedure was as described in step (2) of example 1.
(3) The procedure was as described in step (3) of example 1.
(4) The hollow ZSM-5 molecular sieve (0.5g) prepared above was placed in the middle section of a mini fixed bed reactor. Before introducing 20% glycerol aqueous solution, introducing nitrogen at 320 ℃ to purge the catalyst for 30min, injecting the glycerol aqueous solution at the speed of 5mL/min by using an injection pump, introducing the glycerol aqueous solution into a reactor at the flow rate of 40mL/min by using nitrogen, carrying out contact reaction with a ZSM-5 molecular sieve catalyst, condensing a reaction product mixture, collecting the reaction product mixture into a collector, and performing qualitative and quantitative analysis by timing sampling through a gas chromatography.
The catalyst is adopted to ensure that the glycerol conversion rate reaches 100 percent and the acrolein yield reaches 88 percent in the glycerol dehydration reaction. Particularly, in the reaction of 30 hours, the yield of acrolein was maintained at 82%, and the amount of coking of the catalyst after the thermogravimetric analysis was 14.5 wt%, and no deactivation was observed.
Comparative example 1
The catalyst adopts ZSM-5 nano molecular sieve which is not subjected to alkali treatment (the alkali treatment process without the step (2)) and the silicon-aluminum ratio and the glycerol dehydration reaction conditions are the same as those of the example 1.
The ZSM-5 molecular sieve obtained in the above way does not have a hollow structure, and the results of a scanning electron microscope and a transmission electron microscope are shown in figures 1 and 2. The external diameter of the cross section is about 180-210nm, and the specific surface area is 400-500m2Per g, external surface area of85-95m2/g。
Analysis shows that the conversion rate of the glycerol in the dehydration reaction of the glycerol by adopting the catalyst reaches 100 percent, and the yield of the acrolein reaches 79 percent. But after 30 hours of reaction, the yield of the acrolein is reduced to 53 percent, the coking amount of the catalyst is 4.9wt percent after the thermogravimetric analysis reaction, and the catalytic activity of the catalyst is obviously reduced.
Comparative example 2
The catalyst used was commercially available Nankai micron size sieve (NKF-5) and the silica to alumina ratio and the glycerol dehydration reaction conditions were the same as in example 1.
Analysis shows that the catalyst has glycerin converting rate up to 86.3% and acrolein yield up to 62.8% in glycerin dewatering reaction. However, after 10 hours of reaction, the catalyst was deactivated and the acrolein yield was reduced to 42%.
The ZSM-5 molecular sieve with the hollow structure prepared by the invention is beneficial to the mass transfer and diffusion of each reaction molecule in the chemical reaction, thereby effectively improving the conversion rate of glycerol, the yield of acrolein and the inactivation resistance of the catalyst.
And (4) analyzing results:
compared with a sample which is not treated by alkali, the hollow ZSM-5 molecular sieve prepared by the invention has larger hollow volume and specific surface area, thereby having stronger capacity of accommodating carbon deposition and ensuring that the glycerol dehydration reaction can keep higher acrolein yield for a longer time.
Claims (14)
1. The method for preparing the acrolein by dehydrating the glycerol is characterized in that a hollow ZSM-5 molecular sieve deactivation-resistant catalyst is adopted, and the preparation process of the catalyst comprises the following steps:
(1) deionized water and NaAlO2Uniformly mixing and stirring, adding 25-40% by mass of tetrapropyl ammonium hydroxide aqueous solution, and fully stirring to obtain a mixed solution; adding tetraethyl orthosilicate into the mixed solution drop by drop, fully stirring to completely hydrolyze the tetraethyl orthosilicate, putting the mixed solution into a hydrothermal kettle, crystallizing at the temperature of 100-120 ℃ for 2-8 h, then heating to the temperature of 170-200 ℃ for crystallization for 3-5 d, centrifugally washing, drying, roasting, Preparing Na-ZSM-5 nano molecular sieve;
(2) mixing and stirring the Na-ZSM-5 molecular sieve and an inorganic alkali aqueous solution uniformly, heating to raise the temperature, continuously stirring, centrifugally washing after finishing alkali treatment, drying, and roasting to obtain a hollow Na-ZSM-5 nano molecular sieve;
(3) stirring the Na-type molecular sieve and an ammonium nitrate solution for 4-6H at 40-80 ℃, performing ammonium exchange, centrifugally washing, drying and roasting to obtain an H-type molecular sieve;
placing the prepared hollow ZSM-5 molecular sieve in a micro fixed bed reactor, before introducing a glycerol aqueous solution, introducing nitrogen at the temperature of 280 plus 300 ℃ to purge the catalyst for 30-60 min, then heating the reactor to the reaction temperature, injecting the glycerol aqueous solution into the reactor by an injection pump, loading the glycerol aqueous solution into the reactor by nitrogen, carrying the nitrogen into the reactor to contact and react with the ZSM-5 molecular sieve catalyst, and condensing a reaction product mixture and then collecting the condensed reaction product mixture into a collector.
2. The method of claim 1, wherein: in the reaction system in the step (1), the deionized water and the NaAlO2The molar ratio of the tetrapropylammonium hydroxide aqueous solution to the tetraethyl orthosilicate is as follows: (400-1000): (0.2-1): (1-4): 10.
3. the method of claim 1, wherein: in the step (2), the inorganic alkali is one or a mixture of sodium hydroxide and potassium hydroxide; the proportion of the molecular sieve to the inorganic alkali solution in the step (2) is as follows: 1 g of molecular sieves corresponds to (10-40) mL (0.1-0.3) M of solution.
4. The method of claim 3, wherein: the proportion of the molecular sieve to the inorganic alkali solution in the step (2) is as follows: 1 g of molecular sieve corresponds to 30 mL of a 0.2M basic solution.
5. The method of claim 1, wherein: and (3) putting the molecular sieve in the step (2) into an inorganic alkali solution for alkali treatment, wherein the heating temperature is 40-80 ℃, and the stirring time is 2-8 h.
6. The method of claim 5, wherein: the heating temperature is 40-60 ℃, and the stirring time is 4-6 h.
7. The method of claim 1, wherein: in the step (2) and the step (3), the roasting temperature is 450-.
8. The method of claim 7, wherein: the roasting temperature is 500-600 ℃, and the roasting time is 6-8 h.
9. The method of claim 1 or 2, wherein: in the glycerol dehydration process, the reaction temperature is 270-320 ℃.
10. The method of claim 9, wherein: the reaction temperature is 280-300 ℃.
11. The method of claim 1 or 2, wherein: in the dehydration process of the glycerol, the concentration of the glycerol aqueous solution is 10 to 30 percent.
12. The method of claim 11, wherein: the concentration of the glycerol aqueous solution is 20-30%.
13. The method of claim 1 or 2, wherein: in the dehydration process of the glycerol, when the dosage of the molecular sieve catalyst is 0.5 g, the injection speed of the glycerol aqueous solution into the reactor is 3-10 mL/min, and the flow speed of the nitrogen carrier gas is 20-50 mL/min.
14. The method of claim 13, wherein: the injection speed is 3-5 mL/min, and the nitrogen flow rate is 30-50 mL/min.
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| CN107175126A (en) * | 2016-03-09 | 2017-09-19 | 中国科学院大连化学物理研究所 | A kind of preparation methods of Zn/ without stick ZSM-11 molecular sieve catalysts |
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