CN114713275A - Modified ZSM-5 molecular sieve catalyst, preparation method and application - Google Patents
Modified ZSM-5 molecular sieve catalyst, preparation method and application Download PDFInfo
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- CN114713275A CN114713275A CN202210382853.0A CN202210382853A CN114713275A CN 114713275 A CN114713275 A CN 114713275A CN 202210382853 A CN202210382853 A CN 202210382853A CN 114713275 A CN114713275 A CN 114713275A
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- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 239000002808 molecular sieve Substances 0.000 title claims abstract description 64
- 239000003054 catalyst Substances 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 239000001509 sodium citrate Substances 0.000 claims abstract description 45
- 238000006243 chemical reaction Methods 0.000 claims abstract description 44
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims abstract description 31
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 claims abstract description 31
- 238000010438 heat treatment Methods 0.000 claims abstract description 25
- ZAFNJMIOTHYJRJ-UHFFFAOYSA-N Diisopropyl ether Chemical compound CC(C)OC(C)C ZAFNJMIOTHYJRJ-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000007788 liquid Substances 0.000 claims abstract description 22
- PAWQVTBBRAZDMG-UHFFFAOYSA-N 2-(3-bromo-2-fluorophenyl)acetic acid Chemical compound OC(=O)CC1=CC=CC(Br)=C1F PAWQVTBBRAZDMG-UHFFFAOYSA-N 0.000 claims abstract description 19
- -1 sodium citrate modified molecular sieve Chemical class 0.000 claims abstract description 19
- 238000005342 ion exchange Methods 0.000 claims abstract description 18
- 239000011148 porous material Substances 0.000 claims abstract description 18
- 238000000926 separation method Methods 0.000 claims abstract description 16
- 239000007787 solid Substances 0.000 claims abstract description 16
- 238000002156 mixing Methods 0.000 claims abstract description 14
- 238000003756 stirring Methods 0.000 claims abstract description 14
- 238000001035 drying Methods 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims description 16
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 5
- 239000002994 raw material Substances 0.000 claims description 4
- 150000001412 amines Chemical class 0.000 claims description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 2
- 238000009826 distribution Methods 0.000 claims description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims 2
- 239000000377 silicon dioxide Substances 0.000 claims 1
- 230000004048 modification Effects 0.000 abstract description 5
- 238000012986 modification Methods 0.000 abstract description 5
- 238000005265 energy consumption Methods 0.000 abstract description 3
- 238000002715 modification method Methods 0.000 abstract description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 abstract description 2
- 230000000694 effects Effects 0.000 abstract description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 abstract 2
- 239000007795 chemical reaction product Substances 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 18
- 239000007864 aqueous solution Substances 0.000 description 10
- 238000002441 X-ray diffraction Methods 0.000 description 9
- 239000000523 sample Substances 0.000 description 8
- 230000003197 catalytic effect Effects 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 229910021536 Zeolite Inorganic materials 0.000 description 2
- 150000001336 alkenes Chemical class 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 239000010457 zeolite Substances 0.000 description 2
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical group [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000012496 blank sample Substances 0.000 description 1
- 239000003729 cation exchange resin Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000011964 heteropoly acid Substances 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 239000012770 industrial material Substances 0.000 description 1
- 239000004434 industrial solvent Substances 0.000 description 1
- 239000012263 liquid product Substances 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011973 solid acid Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000003911 water pollution Methods 0.000 description 1
Images
Classifications
-
- 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
- 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
-
- 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
- B01J37/30—Ion-exchange
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
- C07C41/01—Preparation of ethers
- C07C41/09—Preparation of ethers by dehydration of compounds containing 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
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/34—Reaction with organic or organometallic compounds
-
- 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
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/38—Base treatment
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/584—Recycling of catalysts
Abstract
The invention belongs to the technical field of catalyst preparation, and particularly relates to a modified ZSM-5 molecular sieve catalyst, a preparation method and application thereof; the preparation method of the modified molecular sieve catalyst comprises the following steps: (1) mixing a ZSM-5 molecular sieve and a sodium citrate solution, heating and stirring to generate an ion exchange reaction, and performing solid-liquid separation after the reaction is finished to obtain a solid sample; (2) and (2) mixing the solid sample obtained in the step (1) with an ammonium nitrate solution, heating and stirring to perform ion exchange reaction, performing solid-liquid separation after the reaction is finished, and drying and roasting the separated solid sample to obtain the sodium citrate modified molecular sieve catalyst. The catalyst modification method is simple and controllable, and has low energy consumption and low cost. The modified molecular sieve obtained by ion exchange modification has moderate specific surface area and pore channels, the number of mesopores is increased, the modified molecular sieve has a promotion effect on the reaction process of preparing ether from alcohol, and the modified molecular sieve is used as a catalyst for preparing isopropyl ether from isopropanol, so that the conversion rate of a reaction product is improved, and the yield is improved.
Description
Technical Field
The invention belongs to the technical field of catalyst preparation, and particularly relates to a modified ZSM-5 molecular sieve catalyst, a preparation method and application.
Background
Diisopropyl ether (DIPE) as an important industrial solvent can be mixed with other solvents such as alcohol, chloroform, benzene, etc. It can be used as an extractant for extracting industrial materials because it is not readily soluble in water. By utilizing its high octane number and good anti-freezing performance, isopropyl ether can be used as an additive for gasoline. It can not only prevent lead from being added in gasoline, but also prevent tail gas from containing unburned olefin, and solve the problems caused by NOx emission and light olefin evaporation. Isopropyl ether can be used for treating wastewater of natural gas plants in the environmental protection industry so as to reduce water pollution. Due to its wide application range, isopropyl ether has long been one of the hot spots of domestic and foreign research. However, the domestic research on the production process of isopropyl ether is not yet thorough. The development of the application technology of isopropyl ether and the progress of industrialization are still in the preliminary stage.
The key point of the reaction for preparing the isopropyl ether from the isopropanol is the used catalyst, and the performance of the catalyst determines whether the high-efficiency production of the isopropyl ether product can be realized. Theoretically, the preparation of isopropyl ether from isopropanol belongs to dehydration reaction, and B acid is an active center of the reaction, so the amount of the B acid center of the catalyst needs to be increased to improve the reaction rate; on the other hand, the catalytic effect can be improved by reaming the hole. The catalyst used in the reaction of preparing isopropyl ether from isopropanol is mostly solid acid catalyst (including solid phosphoric acid, zeolite molecular sieve, heteropoly acid and cation exchange resin, etc.).
The ZSM-5 molecular sieve is a novel zeolite molecular sieve with three-dimensional crossed straight channels, has good hydrophobicity and high hydrothermal stability, and becomes one of the most important catalytic materials in the chemical industry due to the unique pore structure. The ZSM-5 molecular sieve is mainly applied to the field of light hydrocarbon production, and has poor catalytic effect in the reaction of preparing isopropyl ether from isopropanol, so improvement on the catalyst is needed.
Disclosure of Invention
Aiming at the defects of the prior art, the invention obtains a new sodium citrate modified ZSM-5 molecular sieve catalyst by modifying a molecular sieve, and the new sodium citrate modified ZSM-5 molecular sieve catalyst is used for preparing isopropyl ether by dehydrating isopropanol. The catalyst modification method is simple and controllable, and has low energy consumption and low cost; the obtained catalyst has larger specific surface area and pore channels and good catalytic activity, so that the selectivity of the reaction for preparing the isopropyl ether by dehydrating the isopropyl alcohol is improved, and the yield of the product is further improved.
The technical scheme of the invention is specifically introduced as follows.
The invention provides an application of a modified ZSM-5 molecular sieve catalyst in a reaction for preparing isopropyl ether by dehydrating isopropanol,
the modified ZSM-5 molecular sieve catalyst is prepared by the following method:
(1) mixing ZSM-5 molecular sieve and sodium citrate solution, heating and stirring to generate ion exchange reaction, and finishing the reaction
Then carrying out solid-liquid separation to obtain a solid sample;
(2) and (2) mixing the solid sample obtained in the step (1) with an ammonium nitrate solution, heating and stirring to perform ion exchange reaction, performing solid-liquid separation after the reaction is finished, and drying and roasting the separated solid sample to obtain the sodium citrate modified molecular sieve catalyst.
Preferably, in the step (1), the ZSM-5 molecular sieve is hydrothermally synthesized by a conventional organic amine template method, the raw material silicon-aluminum ratio of the ZSM-5 molecular sieve is 50-60, and the pore diameter distribution of the ZSM-5 molecular sieve is mainly 0.51-0.55nm and 0.53-0.56 nm; the concentration of the sodium citrate solution is 0.1-1 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the sodium citrate solution is 1: 40-1: 50, the heating temperature is 60-80 ℃, and the heating time is 3-4 h.
Preferably, in the step (1), the concentration of the sodium citrate solution is 0.1-1 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the sodium citrate solution is 1: 40-1: 50, heating at the temperature of 60-80 ℃ for 3-4 h; further preferably, the concentration of the sodium citrate solution is 0.5-1 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the sodium citrate solution is 1:40, the heating temperature is 80 ℃.
Preferably, in the step (2), the concentration of the ammonium nitrate solution is 0.8-1.5 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the ammonium nitrate solution is 1: 40-1: 50, heating at the temperature of 60-80 ℃ for 3-4 h; further preferably, the concentration of the ammonium nitrate solution is 0.8-1.0 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the ammonium nitrate solution is 1:40, the heating temperature is 80 ℃, and the heating time is 4 h.
Preferably, in the step (2), the drying temperature is 60-80 ℃; the roasting temperature is 400-550 ℃, and the roasting time is 3-4 h.
In the invention, in the step (1), the ion exchange of the molecular sieve is to treat the molecular sieve by using weak alkalinity of sodium citrate solution so as to remove partial silicon atoms, but in the process, Na is used for removing partial silicon atoms+Will replace H in the molecular sieve+Can become a sodium type molecular sieve which has no catalytic effect; therefore, in the step (2), NH4 in ammonium nitrate is used+With Na+Exchanging and roasting to form H+Thereby converting the molecular sieve from the sodium form to the hydrogen form.
Preferably, in the step (1) and the step (2), the ion exchange reaction and the number of times of the solid-liquid separation after the completion of the reaction are independently 1 to 3 times. More preferably, the number of ion exchanges is 3. The ion exchange times are mainly used for ensuring the treatment effect.
Preferably, the application method of the invention is as follows: adding isopropanol and a modified ZSM-5 molecular sieve catalyst into a polytetrafluoroethylene lining according to the mass ratio of 55:1-65:1, placing the polytetrafluoroethylene lining into a reaction kettle, and reacting for 5-7h in a constant-temperature drying box at the temperature of 185-195 ℃ to obtain isopropyl ether.
The invention also provides a preparation method of the modified ZSM-5 molecular sieve catalyst, which comprises the following specific steps:
(1) mixing ZSM-5 molecular sieve and sodium citrate solution, heating and stirring to generate ion exchange reaction, and finishing the reaction
Then carrying out solid-liquid separation to obtain a solid sample;
(2) and (2) mixing the solid sample obtained in the step (1) with an ammonium nitrate solution, heating and stirring to perform ion exchange reaction, performing solid-liquid separation after the reaction is finished, and drying and roasting the separated solid sample to obtain the sodium citrate modified molecular sieve catalyst.
Further, the invention provides a modified ZSM-5 molecular sieve catalyst prepared by the preparation method; the specific surface area is increased, and the pore channels are enlarged, so that the contact between the raw material and the active sites of the catalyst is increased, and the catalytic efficiency is improved.
Compared with the prior art, the invention has the following beneficial effects:
the sodium citrate modified molecular sieve is successfully prepared by carrying out ion exchange modification on the molecular sieve, the preparation method is simple and controllable, the energy consumption is low, the cost is low, the obtained sodium citrate modified molecular sieve has a micro-mesoporous composite structure, has larger specific surface area and pore channels and more three-dimensional mesoporous pore channels, can reduce the diffusion resistance of molecules in the pore channels of the molecular sieve, improves the diffusion rate of macromolecules in the pore channels of the molecular sieve, is used as a catalyst for preparing isopropyl ether by dehydrating isopropanol, can obviously improve the selectivity of a target product on the premise of ensuring the conversion rate of raw materials, and thus effectively improves the yield of the isopropyl ether.
Drawings
FIG. 1 is an XRD pattern of ZSM-5 molecular sieve raw powder of the present invention.
FIG. 2 is an XRD pattern of the sodium citrate modified molecular sieve of example 1 of the present invention.
FIG. 3 is an XRD pattern of the sodium citrate modified molecular sieve of example 2 of the present invention.
Figure 4 is an XRD pattern of the sodium citrate modified molecular sieve of example 3 of the present invention.
Detailed Description
The invention discloses a preparation method of a sodium citrate modified molecular sieve, which can be realized by appropriately improving process parameters by taking the contents of the molecular sieve as reference by a person skilled in the art. It is expressly intended that all such similar substitutes and modifications which would be obvious to those skilled in the art are deemed to be included in the invention. While the methods and applications of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations and modifications, or appropriate variations and combinations of the methods and applications described herein may be made to implement and use the techniques of this invention without departing from the spirit and scope of the invention.
The following detailed description of the invention refers to specific embodiments thereof for better understanding by those skilled in the art.
In the embodiment, the ZSM-5 carbon molecular sieve is hydrothermally synthesized by a conventional organic amine template method, the silica-alumina ratio of raw powder is 50-60, and the ZSM-5 molecular sieve is provided with vertical pore channels with the pore diameter of 0.51-0.55nm and zigzag pore channels with the pore diameter of 0.53-0.56 nm.
Example 1
A preparation method of a sodium citrate modified molecular sieve comprises the following steps:
(1) preparing a sodium citrate aqueous solution with a certain concentration: mixing a certain amount of sodium citrate with deionized water, and then stirring the mixture to ensure that the sodium citrate is completely dissolved in the water, and the solution is clear and transparent to obtain a sodium citrate water solution with the concentration of 0.1 mol/L;
(2) fully mixing a ZSM-5 carbon molecular sieve and a sodium citrate aqueous solution according to the mass ratio of 1:40, stirring and heating at 80 ℃ for 4 hours, centrifugally separating, and repeating for 3 times;
(3) preparing an ammonium nitrate aqueous solution with a certain concentration: mixing a certain amount of ammonium nitrate with deionized water, and then stirring the mixture to ensure that the ammonium nitrate is completely dissolved in water, and the solution is clear and transparent to obtain an ammonium nitrate aqueous solution with the concentration of 1 mol/L;
(4) fully mixing the ZSM-5 molecular sieve treated in the step (2) with an ammonium nitrate aqueous solution according to the mass ratio of 1:40, stirring and heating at 80 ℃ for 4 hours, performing centrifugal separation, and repeating for 3 times;
(5) and (4) drying the ZSM-5 molecular sieve subjected to centrifugal separation in the step (4) at 80 ℃ overnight, roasting the dried sample in a muffle furnace at 550 ℃ for 4h to obtain a final sodium citrate modified ZSM-5 molecular sieve sample, wherein the related results of the pore structure are shown in Table 1.
FIG. 1 is an XRD pattern of ZSM-5 molecular sieve raw powder of the present invention. FIG. 2 is an XRD pattern of the sodium citrate modified molecular sieve of example 1 of the present invention.
Example 2
Compared with the example 1, the difference is that the concentration of the sodium citrate aqueous solution is 0.5mol/L, the carbon molecular sieve modified by the sodium citrate aqueous solution is obtained, the XRD pattern is shown in figure 3, and the related result of the pore structure is shown in the table 1. Fig. 2 is an XRD pattern of the sodium citrate modified molecular sieve of example 2 of the present invention.
Example 3
Compared with the example 1, the difference is that the concentration of the sodium citrate aqueous solution is 1mol/L, the carbon molecular sieve modified by the sodium citrate aqueous solution is obtained, the XRD pattern is shown in figure 4, and the related result of the pore structure is shown in the table 1.
TABLE 1
In the table: a: BET surface area; b: micropore surface area assessed by the t-plot method; c: mesoporous surface area calculated using SEr-Sh; d: total pore volume at plpo = 0.99; e: micropore volume calculated by t-plot method; f: mesopore volume calculated using Vratal-Vicr.
As is apparent from FIGS. 1 to 4, the modified product still retains the topological structure of the ZSM-5 molecular sieve. From table 1, it can be seen that the ZSM-5 molecular sieve obtained after modification by the modification method of the present invention can form more mesoporous structures.
Application examples 1 to 4
And evaluating the catalytic effect of the modified ZSM-5 molecular sieve in the reaction of preparing isopropyl ether from isopropanol. The specific determination method is as follows:
respectively taking 0.5g of ZSM-5 raw powder and 0.5g of the sodium citrate modified ZSM-5 molecular sieve catalyst prepared in the embodiment 1-3, adding 100mL of polytetrafluoroethylene lining into isopropanol and the catalyst according to the mass ratio of 60:1, placing the mixture into a reaction kettle, reacting for 6 hours in a constant-temperature drying oven at the temperature of 190 ℃, rapidly cooling the mixture in water after the reaction is finished, and collecting a liquid product to detect the components after the temperature of the reaction kettle is reduced to the normal temperature. The test results are analyzed in table 2.
TABLE 2
Along with the increase of the concentration of the sodium citrate aqueous solution, the conversion rate of isopropanol is increased, the selectivity of isopropyl ether is improved compared with a blank sample, and the yield of isopropyl ether is obviously improved.
Claims (10)
1. An application of a modified ZSM-5 molecular sieve catalyst in the reaction of preparing isopropyl ether by dehydrating isopropanol is characterized in that,
the modified ZSM-5 molecular sieve catalyst is prepared by the following method:
(1) mixing ZSM-5 molecular sieve and sodium citrate solution, heating and stirring to generate ion exchange reaction, and finishing the reaction
Then carrying out solid-liquid separation to obtain a solid sample;
(2) and (2) mixing the solid sample obtained in the step (1) with an ammonium nitrate solution, heating and stirring to perform ion exchange reaction, performing solid-liquid separation after the reaction is finished, and drying and roasting the solid sample obtained by separation to obtain the sodium citrate modified molecular sieve based catalyst.
2. The use according to claim 1, wherein in step (1), the ZSM-5 molecular sieve is hydrothermally synthesized by a conventional organic amine template method, the raw material silica alumina ratio of the ZSM-5 molecular sieve is 50-60, and the pore size distribution of the ZSM-5 molecular sieve is mainly 0.51-0.55nm and 0.53-0.56 nm; the concentration of the sodium citrate solution is 0.1-1 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the sodium citrate solution is 1: 40-1: 50, the heating temperature is 60-80 ℃, and the heating time is 3-4 h.
3. The application of the sodium citrate as claimed in claim 1, wherein in the step (1), the concentration of the sodium citrate solution is 0.5-1 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the sodium citrate solution is 1:40, the heating temperature is 80 ℃.
4. The application of claim 1, wherein in the step (2), the concentration of the ammonium nitrate solution is 0.8-1.5 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the ammonium nitrate solution is 1: 40-1: 50, heating at the temperature of 60-80 ℃ for 3-4 h; the drying temperature is 60-80 ℃, the roasting temperature is 400-550 ℃, and the roasting time is 3-4 h.
5. The application of claim 1, wherein in the step (2), the concentration of the ammonium nitrate solution is 0.8-1.0 mol/L, and the solid-liquid mass ratio of the ZSM-5 molecular sieve to the ammonium nitrate solution is 1:40, the heating temperature is 80 ℃, and the heating time is 4 h.
6. The use according to claim 1, wherein in step (1) and step (2), the ion exchange reaction and the corresponding solid-liquid separation after the completion of the reaction are independently performed 1 to 3 times.
7. The use according to claim 6, wherein in step (1) and step (2), the ion exchange reaction and the solid-liquid separation after the completion of the reaction are carried out 3 times.
8. The application according to claim 1, characterized in that the application method is as follows: adding isopropanol and a modified ZSM-5 molecular sieve catalyst into a polytetrafluoroethylene lining according to the mass ratio of 55:1-65:1, placing the polytetrafluoroethylene lining into a reaction kettle, and reacting for 5-7h in a constant-temperature drying box at the temperature of 185-195 ℃ to obtain isopropyl ether.
9. A preparation method of a modified ZSM-5 molecular sieve catalyst is characterized by comprising the following specific steps:
(1) mixing ZSM-5 molecular sieve and sodium citrate solution, heating and stirring to generate ion exchange reaction, and finishing the reaction
Then carrying out solid-liquid separation to obtain a solid sample;
(2) and (2) mixing the solid sample obtained in the step (1) with an ammonium nitrate solution, heating and stirring to perform ion exchange reaction, performing solid-liquid separation after the reaction is finished, and drying and roasting the separated solid sample to obtain the sodium citrate modified molecular sieve catalyst.
10. A modified ZSM-5 molecular sieve catalyst prepared according to the method of claim 9.
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