CN114433194A - Preparation method and application of modified ZSM-5 gold-loaded catalyst - Google Patents

Preparation method and application of modified ZSM-5 gold-loaded catalyst Download PDF

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CN114433194A
CN114433194A CN202210115585.6A CN202210115585A CN114433194A CN 114433194 A CN114433194 A CN 114433194A CN 202210115585 A CN202210115585 A CN 202210115585A CN 114433194 A CN114433194 A CN 114433194A
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gold
catalyst
molecular sieve
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祁彩霞
吴磊
孙立波
苏慧娟
孙逊
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Yantai University
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    • 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
    • B01J29/42—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 containing iron group metals, noble metals or copper
    • B01J29/44—Noble metals
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C4/00—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms
    • C07C4/02—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by cracking a single hydrocarbon or a mixture of individually defined hydrocarbons or a normally gaseous hydrocarbon fraction
    • C07C4/06—Catalytic processes
    • 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
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/12—After treatment, characterised by the effect to be obtained to alter the outside of the crystallites, e.g. selectivation
    • B01J2229/126—After treatment, characterised by the effect to be obtained to alter the outside of the crystallites, e.g. selectivation in order to reduce the pore-mouth size
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/16—After treatment, characterised by the effect to be obtained to increase the Si/Al ratio; Dealumination
    • 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
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
    • B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
    • 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
    • B01J2229/32—Reaction with silicon compounds, e.g. TEOS, siliconfluoride
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • 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
    • B01J2229/40—Special temperature treatment, i.e. other than just for template removal
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    • 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
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

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Abstract

The invention discloses a preparation method and application of a modified ZSM-5 gold-loaded catalyst. Provides a method for preparing a high-performance catalytic cracking ZSM-5 gold-loaded bifunctional catalyst by a two-step method and application thereof. Firstly, modifying the outer surface of a ZSM-5 molecular sieve by using a modifier to reduce the size of an orifice of the molecular sieve or carrying out dealumination treatment in the presence of a buffer solution to increase the strength and the content of B acid, and effectively modulating the pore diameter and the acidity of the molecular sieve under the condition of not influencing the pore structure of the molecular sieve. And then loading the gold nanoparticles on the modified molecular sieve. The prepared catalyst shows excellent low-temperature catalytic activity and propylene selectivity in the catalytic cracking production increase of propylene by hydrocarbons such as light diesel oil, n-octane and the like. The obtained catalyst can obtain a catalytic effect similar to that of a parent ZSM-5 thereof under the temperature difference of less than 100 ℃ and even 150 ℃, shows great energy-saving potential and simultaneously reduces environmental pollution. The series of catalysts realize low-temperature high yield of propylene under the dual actions of low gold loading and molecular sieve modification.

Description

Preparation method and application of modified ZSM-5 gold-loaded catalyst
Technical Field
The invention relates to a preparation method and application of a modified ZSM-5 gold-loaded catalyst. In particular to a method for preparing a catalyst by using modified ZSM-5 molecular sieve to carry gold and through a two-step method and application of the catalyst in the catalytic cracking production increase of propylene, belonging to the technical field of acid and metal bifunctional catalysts and application thereof.
Background
With the continuous change of global consumption structure, the demand of people for various deep processing products of propylene continuously increases, wherein the demand of Asia-Pacific areas is fastest, and the demand of the Asia-Pacific areas is far ahead of the demand of other areas in the world. Propylene is used primarily for the production of polypropylene, butanol, propylene oxide, etc., with polypropylene being the most downstream product of propylene, and the increase in demand being sufficient to represent the overall increase in propylene demand.
Propylene production is currently largely divided into three major routes, steam cracking, catalytic cracking and propane dehydrogenation. About 61% of propylene in the world comes from the by-product of ethylene production by steam cracking, about 34% comes from the by-product of gasoline and diesel oil production by catalytic cracking in oil refineries, about 3% comes from propane dehydrogenation unit, and about 2% comes from other units.
For more than half a century, steam cracking has been the main source of light olefins and diolefins with yields of ethylene and propylene between 24% and 55% and 1.5% and 1.8%, respectively, with the type of feedstock and operating conditions being the main factors affecting yields. The steam cracking needs high reaction temperature of 800-880 ℃, the annual energy consumption accounts for 40% of the total energy consumption of the petrochemical industry, and a large amount of CO is generated2And (5) discharging. In addition, the type of feedstock used limits the ability of steam cracking to control the propylene to ethylene ratio in light olefin production processes, which does not meet the current trend of increasing propylene demand over ethylene.
The catalytic dehydrogenation of propane to produce propylene can produce more propylene than the steam cracking of hydrocarbons, and although the production technology is increasingly regarded, the production technology is still limited to a certain extent by the propane raw material resource. The catalytic cracking reaction temperature is mostly within the range of 550-650 ℃, the propylene selectivity is high, and the adaptability of the device is strong. So the catalytic cracking process is playing an increasingly important role in increasing the propylene yield. The catalytic cracking reaction using solid acid as catalyst can control the product distribution by regulating acid quantity, acid strength, acid type and acid distribution to realize high propylene selectivity
The ZSM-5 molecular sieve with a double ten-membered ring structure shows excellent shape-selective catalytic capability due to the special pore structure. Can be adjusted by adjusting SiO2/Al2O3The ratio of (A) to (B) is such that the ZSM-5 molecular sieve has different acid properties, and in addition, the ZSM-5 molecular sieve also shows good hydrothermal stability and strong carbon deposition resistance. Modification of ZSM-5 molecular sieves has been extensively studied in a manner which affects the physicochemical properties of the catalyst and thus its catalytic performance, for example, high temperature water vapor treatment (Phys. chem. Phys. 2019,21,18758-18768), alkali treatment (Catal. Lett.2003,91,155-167), elemental modification (Microporous. Mesoporous. Mater.2019,284,316-326) and the like. The nano gold is used in CO oxidation (chem.Lett.1987, 16, 405-. And then widely used in propylene epoxidation, water gas shift reaction, selective hydrogenation, etc.
Previous work in the laboratory of the inventor (Qicai Xixia, Liu Yuhua, etc.; Chinese patent No. CN103143387A) (Chinese. J. Catal.2016,37,1747-. By loading a proper amount of La in the catalyst, not only the gold nanoparticles are stabilized and prevented from agglomerating, but also the catalytic cracking performance of the catalyst on light diesel oil and n-octane is effectively improved (Ind.Eng.chem.Res.2019,58, 14695-phase 14704). The laboratory also found that metallic gold rather than gold exhibiting a positive valence state was beneficial to n-octane catalytic cracking (J.Phys. chem.C., 2021, 125, 16013-. Patent CN103143385A (2013) also reports that small-size gold nanoparticles are loaded on high-silica zeolite molecular sieves including ZSM-5 by a negative pressure deposition precipitation method, and show higher propane conversion rate and olefin and aromatic selectivity in the reaction of preparing olefin by propane (or a mixture of propane and butane with propane content higher than 50%, or liquefied gas in oil fields) dehydrogenation.
Although the above works all prove that the nanogold shows the effects of improving the olefin yield and reducing the reaction temperature in the preparation of the olefin by catalytic cracking of the hydrocarbon, the reduction of the reaction temperature and the improvement of the propylene selection still have a great space for improvement.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a preparation method and application of a modified ZSM-5 gold-loaded catalyst, wherein the catalyst shows more excellent cracking activity, propylene selectivity and catalytic stability in catalytic cracking reaction of n-octane and light diesel oil, and the reaction temperature can be greatly reduced.
The invention is realized by the following technical scheme:
the preparation method of the modified ZSM-5 gold-loaded catalyst is characterized by comprising the steps of ZSM-5 modification and nano gold loading:
ZSM-5 modifying method
(1) The external surface modification method for treating the ZSM-5 molecular sieve parent body comprises the following steps: taking the roasted ZSM-5 molecular sieve in a modifier solution, dispersing uniformly by ultrasonic, stirring at constant temperature, washing the obtained suspension with absolute ethyl alcohol, and drying to constant weight; or,
(2) ammonium hexafluorosilicate treatment of ZSM-5 molecular sieve precursors comprising the steps of: placing the roasted ZSM-5 molecular sieve in an ammonium acetate buffer solution, stirring, adding an ammonium hexafluorosilicate solution, continuously stirring, cooling, centrifugally washing, drying to constant weight, and roasting;
secondly, the ZSM-5 modified in the step one carries the nano-gold to obtain a catalyst; the theoretical gold loading amount of the catalyst is 0.1-0.5 wt%.
And (II) adding the modified ZSM-5 molecular sieve into the gold sol by adopting a gold sol adsorption method, and stirring and adsorbing.
The preparation method of the gold sol comprises the following steps: adding HAuCl4Heating the solution to boiling; adding sodium citrate solution, and decocting until the solution turns into wine redBoiling and cooling.
The sodium citrate and HAuCl4The molar ratio of (A) to (B) is preferably 2 to 10; the boiling time is preferably 20-50 min.
The step (two) may be performed by Au (en)2Cl3As a gold precursor; the compound (Au (en)2Cl3) The preparation method comprises the following steps: stirred down to HAuCl4Adding ethylenediamine solution into the solution, stirring, adding anhydrous ethanol dropwise, stirring, centrifuging, washing with anhydrous ethanol, and drying to obtain Au (en)2Cl3。
The HAuCl4The mass ratio of the ethylene diamine to the ethylene diamine is preferably 10-30; the absolute ethyl alcohol and HAuCl4The mass ratio of (A) to (B) is preferably 10 to 20.
The step (two) can also be carried out by HAuCl4The solution is used as a gold precursor.
Preferred modifiers are those having a molecular size greater than the pore size, including octadecyltrimethoxysilane and dodecyltrimethoxysilane; the mass ratio of the ZSM-5 to the modifier is preferably 0.5-20; the mass concentration of the modifier is preferably 0.01-0.2.
The mol ratio of the ammonium hexafluorosilicate to Al in the ZSM-5 molecular sieve is preferably 0.5-2; the molar ratio of the ammonium acetate to the ammonium hexafluorosilicate is preferably 100-200.
The modified ZSM-5 gold-loaded catalyst is used for preparing propylene by catalytic cracking of n-octane or preparing propylene by catalytic cracking of light diesel oil.
The invention has the positive effects that: the invention utilizes the advantages of the nano-gold, simultaneously prepares the high-performance catalytic cracking ZSM-5 gold-loaded bifunctional catalyst by optimizing the molecular sieve carrier and then loading the gold, realizes that the catalytic effect similar to that of the parent ZSM-5 can be obtained at the temperature difference of 100 ℃ or even 150 ℃, shows great energy-saving potential and simultaneously reduces the environmental pollution. The method is simple to operate, mild in condition, high in repeatability of the obtained catalyst and good in industrial application prospect.
The invention can effectively realize the reduction of the aperture of the molecular sieve under the condition of not influencing the internal pore structure of the molecular sieve by modifying the outer surface of the ZSM-5 molecular sieve; according to the invention, the strength of B acid is greatly improved through dealumination in the presence of buffer solution, and then the gold nanoparticles are introduced, so that the propylene selectivity is greatly improved compared with that of an unmodified parent ZSM-5 at the same reaction temperature; the catalytic performance which is reduced by 100 ℃ or even 150 ℃ and is similar to that of the parent ZSM-5 is realized. The loading amount of Au in the obtained catalyst is lower (0.1-0.5%).
The invention adopts a two-step method of molecular sieve modification (outer surface modification or dealumination modification in the presence of buffer solution) and molecular sieve modification and then nano-gold loading to prepare the catalyst for preparing propylene by catalytic cracking of n-octane or light diesel, and the catalyst has the effects of obviously better catalytic cracking activity, propylene selectivity, catalytic stability and obviously reduced reaction temperature than the prior art. The series of post-treatments of molecular sieves affect the catalytic cracking performance, mainly from the aspect of the pore size (shape-selective ability) and acidity (cracking ability) of the molecular sieve, and affect the reaction path and the final product. The introduction of the nano gold further perfects the pore structure of the molecular sieve and enhances the acid B, thereby improving the cracking capability of the positive carbon particles and playing a certain role in the dehydrogenation of hydrocarbons.
In conclusion, the modified ZSM-5 gold-loaded catalyst prepared by the invention has unique technical advantages in the catalytic cracking production increase of propylene, and is more beneficial to market popularization.
Drawings
FIG. 1 is a distribution diagram of the molecular sieve pores of a ZSM-5 gold-supported catalyst prepared by an external surface modification method in example 2 of the present invention (I), wherein gold loading of 0.1 wt% is maintained, and the concentration of octadecyltrimethoxysilane is from 1 wt% to 4 wt%, wherein a is ZSM-5; ZSM-5-1% TOS; c, 0.1 percent of Au/ZSM-5-1 percent of TOS; d is 0.1 percent of Au/ZSM-5-2 percent of TOS; e, 0.1% Au/ZSM-5-3% TOS; f, 0.1 percent of Au/ZSM-5-4 percent of TOS.
FIG. 2 is a distribution diagram of molecular sieve pores of ZSM-5 supported gold catalyst prepared by outer surface modification method in example 2 of the present invention (II), keeping the concentration of octadecyl trimethoxy silane at 1 wt%, and the loading of gold nanoparticles from 0.1% to 0.5 wt%, wherein a is ZSM-5; ZSM-5-1% TOS; c, 0.1 percent of Au/ZSM-5-1 percent of TOS; d, 0.2 percent of Au/ZSM-5-1 percent of TOS; e, 0.3 percent of Au/ZSM-5-1 percent of TOS; f, 0.4 percent of Au/ZSM-5-1 percent of TOS; g, 0.5 percent of Au/ZSM-5-1 percent of TOS.
FIG. 3 is a graph (one) showing the evaluation of the catalytic cracking performance of n-octane in the Au/ZSM-5-TOS series catalyst in example 3 according to the present invention; FIG. 3 is a diagram showing: the conversion of n-octane from 1% to 4% by weight of octadecyltrimethoxysilane was maintained at a gold loading of 0.1% by weight.
FIG. 4 is a graph showing the evaluation of the catalytic cracking performance of n-octane in the Au/ZSM-5-TOS series catalyst in example 3 according to the present invention; FIG. 4 is a diagram showing: propylene selectivity from 1% to 4% octadecyltrimethoxysilane concentration with gold loading of 0.1% by weight was maintained.
FIG. 5 is a graph showing the evaluation of the catalytic cracking performance of n-octane in the Au/ZSM-5-TOS series catalyst in example 3 according to the present invention; FIG. 5 is a diagram showing: keeping the concentration of 1 wt% of octadecyl trimethoxy silane, and the normal octane conversion rate of the gold nano particles from 0.1 wt% to 0.5 wt%.
FIG. 6 is a graph (IV) showing the evaluation of the catalytic cracking performance of n-octane in the Au/ZSM-5-TOS series catalyst in example 3 according to the present invention; FIG. 6 is a diagram showing: the concentration of 1 wt% of octadecyl trimethoxy silane is maintained, and the propylene selectivity of the gold nano particles is from 0.1 wt% to 0.5 wt%.
FIG. 7 is a schematic representation of the adsorption of pyridine at 160 ℃ in the preparation of a ZSM-5 gold-supported catalyst prepared by dealumination in example 5 of the present invention, wherein a is ZSM-5; ZSM-5-F; ZSM-5-N; d is 0.3 percent of Au/ZSM-5-F;
FIG. 8 is a schematic representation of the pyridine adsorption at 350 ℃ of a ZSM-5 gold-supported catalyst prepared by the dealumination method of example 5 of the present invention, wherein a is ZSM-5; ZSM-5-F; ZSM-5-N; d is 0.3 percent of Au/ZSM-5-F;
FIG. 9 is a transmission electron micrograph (a) and an elemental map (b) of 0.3% Au/ZSM-5-F catalyst in example 5 of the present invention;
FIG. 10 is a graph (I) showing the evaluation of the catalytic cracking performance of n-octane in the Au/ZSM-5-F series catalyst under the conditions of example 6 according to the present invention, and FIG. 10 is a graph showing the conversion rate of n-octane.
FIG. 11 is a graph showing the evaluation of the n-octane catalytic cracking performance of Au/ZSM-5-F series catalysts under the conditions of example 6 of the present invention (II), and FIG. 11 is used to show the propylene selectivity.
FIG. 12 is a graph showing the results of stability tests on Au/ZSM-5-F catalyst in example 8 of the present invention.
FIG. 13 is a transmission electron micrograph of Au/ZSM-5-F catalyst in example 9 of the present invention.
Detailed Description
The invention is further illustrated by the following specific examples:
example 1 Au (en)2Cl3Preparation of the precursor
2mL of HAuCl with a concentration of 0.1g/mL was taken4And slowly dripping 0.09mL of ethylenediamine solution into the solution under the condition of magnetic stirring, continuously stirring for 30min, dripping 14mL of absolute ethyl alcohol into the solution, and stirring for 30 min. Centrifuging the obtained suspension, washing with anhydrous ethanol for 2 times, vacuum drying the obtained solid product at 40 deg.C for 12h to obtain Au (en)2Cl3And (3) powder.
EXAMPLE 2 ZSM-5 gold-loaded catalyst prepared by external surface modification
And (2) taking 10g of the calcined ZSM-5 molecular sieve, ultrasonically dispersing the molecular sieve in 100mL of 0.5-4 wt% of toluene solution of octadecyltrimethoxysilane, stirring the mixture for 6 hours at a constant temperature of 90 ℃, washing the obtained suspension with absolute ethyl alcohol, and drying the suspension for 12 hours at a temperature of 80 ℃. Then, 0.1-0.5 wt% of Au (en) prepared in example 1 is loaded by using an isometric immersion method2Cl3Soaking for not less than 24 hr, washing, drying to constant weight, and roasting at 550 deg.C. The obtained catalyst was named Au/ZSM-5-TOS.
Fig. 1 and 2 are distribution diagrams of the pore diameters of the catalyst prepared under the conditions of this example. The figure shows that the modified catalyst has more regular pore structure and is more favorable for producing propylene by shape-selective catalysis.
Example 3 application of the ZSM-5 gold-loaded catalyst prepared by the external surface modification method in the production increase of propylene by n-octane catalytic cracking.
The evaluation of the Au/ZSM-5-TOS series of catalysts was carried out in a custom-made catalytic cracking microreactor tube. The reaction temperature is 260-460 ℃, and 3g of catalyst is addedFilled in a reaction tube, and when the temperature reached a preset temperature, 0.94g of n-octane was injected into the reaction tube through a syringe and reacted for 70 s. After the completion of the feeding, high-purity N is used2Purged and separated by an ice water bath. Gas-phase products are collected by the gas bag, and liquid-phase products are collected by the colorimetric tube. The reaction products were analyzed by GC-920(X) chromatography with an OV-101 capillary column and a hydrogen flame ionization detector.
FIGS. 3 to 6 are evaluations of the catalytic cracking performance of n-octane of Au/ZSM-5-TOS series catalysts under the conditions of the present example. As can be seen from the figure, the 0.2% Au/ZSM-5-1% TOS catalyst reduces the reaction temperature by more than 100 ℃ while achieving complete conversion of n-octane.
Example 4 application of ZSM-5 gold-loaded catalyst prepared by external surface modification method in propylene yield increase in light diesel oil catalytic cracking
Evaluation of 0.2% Au/ZSM-5-1% TOS series catalysts was performed in custom made catalytic cracking micro reaction tubes. The reaction temperature is 260-460 ℃, 3g of catalyst is filled in a reaction tube, and when the temperature reaches the preset temperature, 0.94g of light diesel oil is injected into the reactor tube through an injector and reacts for 70 s. After the completion of the feeding, high-purity N is used2Purged and separated by an ice water bath. Gas-phase products are collected by the gas bag, and liquid-phase products are collected by the colorimetric tube. The reaction products were analyzed by GC-920(X) chromatography with an OV-101 capillary column and a hydrogen flame ionization detector.
Table 1 is a table for evaluating the catalytic cracking performance of light diesel oil of the catalyst under the conditions of this example. From the table, it can be found that the light diesel oil conversion rate and the propylene selectivity of the modified catalyst both show certain advantages.
Table 1 table for evaluating catalytic cracking performance of light diesel oil using modified catalyst
Figure RE-GDA0003586142000000061
Example 5 preparation of a ZSM-5 gold-supported catalyst by dealumination
10g of the calcined ZSM-5 molecular sieve is put into 200ml of ammonium acetate (3mol/L) buffer solution, evenly stirred and dropwise added at 80 DEG CA certain amount of ammonium hexafluorosilicate solution (molar ratio of ammonium hexafluorosilicate to Al in the molecular sieve: 1) was stirred for 3 hours. Cooling the solution to room temperature, centrifuging, washing, drying to constant weight, calcining to obtain ZSM-5-F catalyst (the control group catalyst is named as ZSM-5-N without adding buffer solvent), and then loading Au (en) with different concentrations by using an isometric impregnation method2Cl3Soaking for not less than 24 hr, washing, drying to constant weight, and roasting at 550 deg.C.
FIGS. 7 and 8 are the pyridine adsorption diagrams of the catalysts prepared under the conditions of this example. It can be seen from the figure that the modified catalyst B has increased acid content and strength, and the increase of the B acid is helpful for the cracking reaction. Fig. 9 is a transmission electron micrograph (a) and an elemental map (b) of the catalyst prepared under the conditions of this example. It can be seen that less Au nanoparticles are deposited on the surface of the molecular sieve, and the elemental mapping results reflect the small size of gold that is not observed to be likely to enter the channels of the analytical sieve, which can also be inferred from the pore size distribution diagram.
Example 6 application of ZSM-5 gold-loaded catalyst prepared by dealuminization method in production of propylene by n-octane catalytic cracking
The evaluation of the Au/ZSM-5-F catalyst was performed in a custom-made catalytic cracking microreactor tube. The reaction temperature is 260-460 ℃, 3g of catalyst is filled in the reaction tube, and when the temperature reaches the preset temperature, 0.94g of n-octane is injected into the reactor tube through the injector to react for 70 s. After the completion of the feeding, high-purity N is used2Purged and separated by an ice water bath. Gas-phase products are collected by the gas bag, and liquid-phase products are collected by the colorimetric tube. The reaction products were analyzed by GC-920(X) chromatography with an OV-101 capillary column and a hydrogen flame ionization detector.
FIG. 10 and FIG. 11 are graphs showing the evaluation of the catalytic cracking performance of Au/ZSM-5-F series catalysts under the conditions of this example. As can be seen from the figure, the 0.3% Au/ZSM-5-F catalyst can reduce the reaction temperature by more than 150 ℃ while realizing the complete conversion of n-octane.
Example 7 application of ZSM-5 gold-loaded catalyst prepared by dealuminization method in propylene yield increase by catalytic cracking of light diesel oil
Au/ZSM-5-F catalystThe evaluation of the reagents was performed in a custom-made catalytic cracking microreactor tube. The reaction temperature is 260-460 ℃, 3g of catalyst is filled in the reaction tube, and when the temperature reaches the preset temperature, 0.94g of light diesel oil is injected into the reactor tube through the injector to react for 70 s. After the completion of the feeding, high-purity N is used2Purged and separated by an ice water bath. Gas-phase products are collected by the gas bag, and liquid-phase products are collected by the colorimetric tube. The reaction products were analyzed by GC-920(X) chromatography with an OV-101 capillary column and a hydrogen flame ionization detector.
Table 2 shows the evaluation table of the catalytic cracking performance of light diesel oil of the catalyst under the conditions of the examples. From the table, it can be found that the light diesel oil conversion rate and the propylene selectivity of the modified catalyst both show certain advantages.
Table 2 table for evaluating catalytic cracking performance of light diesel oil using modified catalyst
Figure RE-GDA0003586142000000071
Example 8 testing of the stability of a ZSM-5 gold-loaded catalyst prepared by dealumination in the production of propylene by n-octane catalytic cracking
Stability testing of the Au/ZSM-5-F catalyst was performed in custom-made catalytic cracking microreactor tubes. The reaction temperature was 360 ℃, 3g of catalyst was packed in the reaction tube, and when the temperature reached 360 ℃, 0.94g of n-octane was injected into the reactor tube through a syringe and reacted for 70 s. After the completion of the feeding, high-purity N is used2Purged and separated by an ice water bath. Gas-phase products are collected by the gas bag, and liquid-phase products are collected by the colorimetric tube. The sample injection test is repeated, and the cycle is 15 times. The reaction products were analyzed by GC-920(X) chromatography with an OV-101 capillary column and a hydrogen flame ionization detector.
FIG. 12 is a graph showing the results of stability tests on Au/ZSM-5-F catalysts. The graph shows that the n-octane conversion rate and the propylene yield of the modified catalyst fluctuate within a certain range, and are not obviously reduced after 15 cycles.
EXAMPLE 9 ZSM-5 gold-supported catalyst prepared by gold sol method
Taking a certain amount of HAuCl4Solutions ofAdding a proper amount of deionized water, and heating to be boiled violently. Adding a certain amount of sodium citrate solution, sodium citrate and HAuCl quickly4The molar ratio of (A) to (B) is 5, boiling for 20min after the solution turns to wine red, and naturally cooling to room temperature. Adding the ZSM-5-F catalyst, stirring, adsorbing for 24h, washing and drying, wherein the theoretical gold-carrying amount is 0.5 wt%.
FIG. 13 is a transmission electron microscope image of Au/ZSM-5-F catalyst, from which it can be seen that the gold sol method can better control the size of gold nanoparticles, so that the gold nanoparticles are more uniformly dispersed.
The Au/ZSM-5 catalyst can be prepared by a deposition precipitation method, wherein the pH value of the deposition precipitation method needs to be controlled to be 9-10, or gold nanoparticles are loaded on a ZSM-5 molecular sieve by an impregnation method and need to be impregnated for more than 24 hours, or a gold sol adsorption method is adopted, and the adsorption time is controlled to be more than 24 hours. The theoretical gold-carrying amount of the catalyst is 0.1-0.5% by mass.

Claims (10)

1. The preparation method of the modified ZSM-5 gold-loaded catalyst is characterized by comprising the following steps of ZSM-5 modification and nano-gold loading:
ZSM-5 modifying method
(1) The external surface modification method for treating the ZSM-5 molecular sieve parent body comprises the following steps: placing the roasted ZSM-5 molecular sieve in a modifier solution, uniformly dispersing by ultrasonic, stirring at constant temperature, washing the obtained suspension by absolute ethyl alcohol, and drying to constant weight; or,
(2) ammonium hexafluorosilicate treatment of ZSM-5 molecular sieve precursors comprising the steps of: placing the roasted ZSM-5 molecular sieve in an ammonium acetate buffer solution, stirring, adding an ammonium hexafluorosilicate solution, continuously stirring, cooling, centrifugally washing, drying to constant weight, and roasting;
secondly, the ZSM-5 modified in the step one carries the nano-gold to obtain a catalyst; the theoretical gold loading amount of the catalyst is 0.1-0.5 wt%.
2. The process for preparing a modified ZSM-5 supported gold catalyst as claimed in claim 1, wherein: and (II) adding the modified ZSM-5 molecular sieve into the gold sol by adopting a gold sol adsorption method, and stirring and adsorbing.
3. The method of preparing a modified ZSM-5 supported gold catalyst as defined in claim 2, wherein the gold sol is prepared by: adding HAuCl4Heating the solution to boiling; adding sodium citrate solution, boiling until the solution turns to wine red, and cooling.
4. A process for the preparation of a modified ZSM-5 supported gold catalyst as claimed in claim 3, wherein: the sodium citrate and HAuCl4The molar ratio of (A) to (B) is 2-10; the boiling time is 20-50 min.
5. The process for preparing a modified ZSM-5 supported gold catalyst as claimed in claim 1, wherein: the step (two) is performed by Au (en)2Cl3As a gold precursor; the compound (Au (en)2Cl3) The preparation method comprises the following steps: stirred down to HAuCl4Adding ethylenediamine solution into the solution, stirring, adding anhydrous ethanol dropwise, stirring, centrifuging, washing with anhydrous ethanol, and drying to obtain Au (en)2Cl3。
6. The process for preparing a modified ZSM-5 supported gold catalyst as claimed in claim 5, wherein: the HAuCl4The mass ratio of the ethylene diamine to the ethylene diamine is 10-30; the absolute ethyl alcohol and HAuCl4The mass ratio of (A) to (B) is 10 to 20.
7. The process for preparing a modified ZSM-5 supported gold catalyst as claimed in claim 1, wherein: the step (two) is carried out by HAuCl4The solution is used as a gold precursor.
8. The process for preparing a modified ZSM-5 supported gold catalyst of any of claims 1 to 7, wherein the modifier is a modifier having a molecular size larger than the pore size comprising octadecyltrimethoxysilane and dodecyltrimethoxysilane; the mass ratio of the ZSM-5 to the modifier is 0.5-20; the mass concentration of the modifier is 0.01-0.2.
9. The method for preparing a modified ZSM-5 supported gold catalyst as claimed in any one of claims 1 to 7, wherein the molar ratio of ammonium hexafluorosilicate to Al in the ZSM-5 molecular sieve is 0.5 to 2; the molar ratio of the ammonium acetate to the ammonium hexafluorosilicate is 100-200.
10. The modified ZSM-5 gold-loaded catalyst is used for preparing propylene by catalytic cracking of n-octane or preparing propylene by catalytic cracking of light diesel oil.
CN202210115585.6A 2022-01-30 2022-01-30 Preparation method and application of modified ZSM-5 gold-loaded catalyst Withdrawn CN114433194A (en)

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