Aromatization catalyst and preparation method and application thereof
阅读说明：本技术 芳构化催化剂及其制备方法和应用 (Aromatization catalyst and preparation method and application thereof ) 是由 王辉 约翰·松埠 项益智 单军军 程继红 孙琦 丽萨·阮 于 2018-09-10 设计创作，主要内容包括：本发明涉及低碳烷烃生产芳烃领域,具体涉及一种芳构化催化剂及其制备方法和应用。所述芳构化催化剂包含载体以及负载在载体上的金属活性组分,其中,所述金属活性组分包括铂,所述载体包含沸石和可选的粘合剂,且载体的外表面酸度不高于12μmol/g。本发明的芳构化催化剂应用于低碳烷烃的芳构化反应时,能提高反应产物BTX的收率并相应降低甲烷的选择性,所述催化剂具有较高的活性和长期稳定性。(The invention relates to the field of aromatic hydrocarbon production by low-carbon alkane, in particular to an aromatization catalyst and a preparation method and application thereof. The aromatization catalyst comprises a carrier and a metal active component supported on the carrier, wherein the metal active component comprises platinum, the carrier comprises zeolite and an optional binder, and the acidity of the outer surface of the carrier is not higher than 12 [ mu ] mol/g. The aromatization catalyst of the invention is applied to aromatization reaction of low-carbon alkane, can improve the yield of reaction product BTX and correspondingly reduce the selectivity of methane, and has higher activity and long-term stability.)
1. An aromatization catalyst comprising a carrier and a metal active component supported on the carrier, wherein the metal active component comprises platinum, the carrier comprises a zeolite and optionally a binder, and the acidity of the outer surface of the carrier is not higher than 12 μmol/g.
2. The aromatization catalyst of claim 1 wherein the zeolite is selected from one or more of MFI, MEL, MTW, MOR, BEA, tmm N and IMF zeolites.
3. The aromatization catalyst according to claim 1 or 2 wherein the binder is selected from one or more of silica, alumina, aluminum phosphate, zirconia, titania and clay; preferably, the mass ratio of the zeolite to the binder is 100: 10-40.
4. The aromatization catalyst according to any one of claims 1-3 wherein the support is an external surface modified zeolite and the agent for modifying the zeolite is a siloxane;
preferably, the siloxane is selected from one or more of tetraethyl orthosilicate, phenyltriethoxysilane, aminopropyltriethoxysilane, and methyltriethoxysilane.
5. The aromatization catalyst according to any one of claims 1-4 wherein the amount of platinum in the aromatization catalyst is 100-1000ppm based on the total weight of the catalyst.
6. A process for preparing the aromatization catalyst of any one of claims 1-5 comprising:
1) shaping of
Forming and roasting the zeolite and the adhesive;
2) modification of
Modifying the roasted product obtained in the step 1) by using a solution containing siloxane, and then sequentially carrying out solid-liquid separation, drying and roasting to obtain the external surface modified zeolite;
3) load(s)
Loading the metal active component on the external surface modified zeolite.
7. The method of claim 6, wherein in step 2), the modification is carried out by: the siloxane-containing solution is mixed with the calcined product, and then the resulting mixture is refluxed at 20 to 200 ℃ for 0.1 to 50 hours.
8. A process for preparing the aromatization catalyst of any one of claims 1-5 comprising:
1) load(s)
Loading the active component onto a zeolite;
2) modification of
Modifying the load product obtained in the step 1) by using a solution containing siloxane, and then sequentially carrying out solid-liquid separation, drying and roasting to obtain the external surface modified zeolite loaded with active components;
3) shaping of
And forming and roasting the external surface modified zeolite and a binder.
9. The method of claim 8, wherein in step 2), the modification is carried out by: the siloxane-containing solution is mixed with the supported product, after which the resulting mixture is refluxed at 20-200 ℃ for 0.1-50 hours.
10. A process for preparing the aromatization catalyst of any one of claims 1-5 comprising:
1) modification of
Modifying zeolite with a siloxane-containing solution, and then sequentially carrying out solid-liquid separation, drying and roasting to obtain the external surface modified zeolite;
2) shaping of
Forming and roasting the external surface modified zeolite and a binder;
3) load(s)
Loading the metal active component on the roasted product obtained in the step 2).
11. The method of claim 10, wherein in step 1), the modification is carried out by: the siloxane-containing solution is mixed with the zeolite, after which the resulting mixture is refluxed at 20-200 ℃ for 0.1-50 hours.
12. Use of the aromatization catalyst of any one of claims 1-5 in a low carbon alkane aromatization reaction.
13. Use according to claim 12, wherein the lower alkane is a C2-C6 alkane, preferably ethane.
Technical Field
The invention relates to the field of aromatic hydrocarbon production by low-carbon alkane, in particular to an aromatization catalyst and a preparation method and application thereof.
Background
Typical noble metal-loaded zeolite catalysts are used to catalyze the dehydroaromatization of ethane. Light alkanes (e.g., ethane) can be produced by dehydrogenation and aromatization reactions in the presence of an aromatization catalyst to produce light aromatics (benzene, toluene, xylenes, or BTX) and olefin products, while the process produces two major products, methane and hydrogen.
Methane is of very low value compared to BTX and olefin products. Moreover, the separation of methane and/or hydrogen from ethane and other liquid products is a very energy intensive process. Unlike other light hydrocarbons, the conversion of methane is very limited under the aromatization reaction conditions of ethane, which results in the accumulation of methane in the recovery cycle of the catalyst. Thus, in the light alkane dehydroaromatization reaction, reducing the formation of low value products (such as methane) not only increases overall product yield, but also significantly reduces the expensive cost of downstream dry gas separation and the burden on the recycle loop.
From a thermodynamic perspective, aromatization of light alkanes typically requires high temperature reactions to achieve efficient conversion. However, the reaction at high temperatures results in rapid formation of coke and coke precursors, which rapidly deactivates the catalyst.
US8772563, US 8692043 and US 8871990 all disclose processes for the selective conversion of ethane to aromatics. The dehydroaromatization catalysts disclosed in these three patent documents are based on platinum-supported ZSM-5 catalysts. In order to improve the selectivity of the product aromatics, the catalysts all contain a second metal component (e.g., gallium, tin, lead, germanium, iron) to reduce the hydrogenolysis activity of platinum. Although these catalysts can significantly reduce methane formation, they also result in a decrease in catalyst activity, i.e., a decrease in ethane conversion, i.e., methane selectivity is not effectively reduced for the same ethane conversion.
Taking the dehydroaromatization catalyst disclosed in US 8692043 as an example, which improves the selectivity of aromatics by attenuating the dehydrogenation of platinum with Fe as the second metal, it is clear from table 1 describing the results that the introduction of different amounts of Fe into the catalyst significantly reduces the amount of methane formed but also results in a decrease in the catalyst activity (a significant decrease in the conversion of ethane) compared to Pt/ZSM-5. For example, co-impregnation of 0.08 wt% Fe with 0.04 wt% Pt onto ZSM-5 reduced the methane selectivity from 38.09% to 24.24%, but also the ethane conversion from 60.39% to 50.89% compared to ZSM-5 catalyst impregnated with 0.04 wt% Pt.
In addition, good catalysts also need to have high stability, and during the reaction, the rapid deactivation of the catalyst requires continuous regeneration to maintain good activity. If a catalyst with higher stability is used, the process is favorably simplified, and fixed cost and variable cost can be saved. US8772563, US 8692043 and US 8871990 also fail to solve the problem of rapid deactivation of the catalyst.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides an aromatization catalyst and a preparation method and application thereof. The aromatization catalyst is used for aromatization reaction of low-carbon alkane, not only can improve the selectivity of aromatic hydrocarbon in a product and reduce the generation of methane, but also can not cause the reduction of ethane conversion rate while reducing the selectivity of the methane, and has higher stability.
According to a first aspect of the present invention, there is provided an aromatization catalyst comprising a support and a metal active component supported on the support, wherein the metal active component comprises platinum, the support comprises a zeolite and optionally a binder, and the acidity of the outer surface of the support is not higher than 12 μmol/g.
According to a second aspect of the present invention, there is provided a process for producing the aromatization catalyst comprising:
1) shaping of
Forming and roasting the zeolite and the adhesive;
2) modification of
Modifying the roasted product obtained in the step 1) by using a solution containing siloxane, and then sequentially carrying out solid-liquid separation, drying and roasting to obtain the external surface modified zeolite;
3) load(s)
Loading the metal active component on the external surface modified zeolite.
According to a third aspect of the present invention, there is provided another method for producing the aromatization catalyst, which comprises:
1) load(s)
Loading the active component onto a zeolite;
2) modification of
Modifying the load product obtained in the step 1) by using a solution containing siloxane, and then sequentially carrying out solid-liquid separation, drying and roasting to obtain the external surface modified zeolite loaded with active components;
3) shaping of
And forming and roasting the external surface modified zeolite and a binder.
According to a fourth aspect of the present invention, there is provided a further process for producing the aromatization catalyst comprising:
1) modification of
Modifying zeolite with a siloxane-containing solution, and then sequentially carrying out solid-liquid separation, drying and roasting to obtain the external surface modified zeolite;
2) shaping of
Forming and roasting the silanization modified zeolite and a binder;
3) load(s)
Loading the metal active component on the roasted product obtained in the step 2).
According to a fifth aspect of the present invention, there is provided the use of the aromatization catalyst in a low carbon alkane aromatization reaction.
Compared with the existing aromatization catalyst, the invention reduces the acidity of the outer surface of zeolite in the catalyst, so that when the obtained aromatization catalyst is applied to the aromatization reaction of low-carbon alkane, the yield of the reaction product BTX can be improved, the selectivity of methane is correspondingly reduced, and the catalyst has higher activity and long-term stability.
Drawings
FIG. 1 is a graph comparing the stability and effect on BTX selectivity of catalyst B and catalyst A of the present invention.
FIG. 2 is a graph comparing the selectivity to methane for catalyst B and catalyst A of the present invention.
Fig. 3 is a graph comparing the effect of stability and BTX selectivity between catalyst E and catalyst C, D of the present invention.
Fig. 4 is a graph comparing the BTX yield between catalyst E and catalyst C, D of the present invention.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
According to a first aspect of the present invention, there is provided an aromatization catalyst comprising a support and a metal active component supported on the support.
In the present invention, the metal active component includes platinum (Pt) in an amount selected with reference to the existing aromatization catalyst. Generally, the amount of platinum in the aromatization catalyst may be 100 and 5000ppm based on the total weight of the aromatization catalyst. For the present invention, the content of platinum in the aromatization catalyst is preferably 100-1000ppm, and more preferably 200-800 ppm.
According to the present invention, the metal active component may include other metals conventionally used in aromatization catalysts, such as at least one of Fe, cu, Co, Sn, Zn, Mn, Ni, Ga, Bi, La, and Ce, in addition to Pt, and the contents of the other metals may be selected with reference to the prior art, and the present invention will not be described herein again.
In the present invention, the carrier may or may not contain a binder. Preferably, the mass ratio of the zeolite to the binder is 100: 10-40.
The binder is not particularly limited in the present invention, as long as the catalyst can be molded. For example, the binder may be selected from one or more of silica, alumina, aluminum phosphate, zirconia, titania, and clay.
The present invention aims to achieve the object of the present invention by controlling the acidity of the outer surface of the carrier to be not more than 12. mu. mol/g, and thus the present invention is not particularly limited to the kind of zeolite in the carrier. Typically, the zeolite may be selected from one or more of MFI, MEL, MTW, MOR, BEA, tmm N and IMF zeolites. Preferably, the zeolite has a ten-member ring topological channel structure, more preferably a molecular sieve having the structure MFI, such as ZSM-5.
According to the present invention, the support is typically prepared by surface modification of the zeolite to reduce the acidity of the external surface of the zeolite.
According to one embodiment, the support is an external surface modified zeolite and the agent for modifying the zeolite is a siloxane.
In the present invention, the siloxane can increase the external surface silica-alumina ratio of the zeolite and reduce the external surface acidity of the zeolite. Wherein the siloxane may be any silicone containing a-Si-O group. From the viewpoint of availability of raw materials, it is preferable that the siloxane is one or more selected from tetraethyl orthosilicate, phenyltriethoxysilane, aminopropyltriethoxysilane, and methyltriethoxysilane.
In this embodiment, the zeolite (unmodified) typically has a silica to alumina ratio (silica to alumina mole ratio) of from 15 to 100. In the present invention, the silicon-aluminum ratio can be measured by an ICP or XRF method.
In the present invention, the external surface acidity of the external surface-modified zeolite is preferably not higher than 5. mu. mol/g, more preferably not higher than 3. mu. mol/g, and still more preferably not higher than 1.5. mu. mol/g.
The shape of the aromatization catalyst is not particularly limited in the present invention and may be selected with reference to the prior art, for example, the shape of the aromatization catalyst may be spherical, cylindrical, strip-shaped, irregular particles, or the like.
The aromatization catalyst of the invention can be prepared by three steps of zeolite surface modification (namely surface modification), loading and forming. Wherein, the surface modification aims at reducing the external surface acidity of the zeolite to be below 12 mu mol/g, and the loading refers to that the metal active component is loaded on a carrier, and the shaping is to obtain catalyst particles which are suitable for loading in the presence of a binder. The present invention does not specifically limit the order of the above three steps as long as the aromatization catalyst is produced. To this end, the present invention also provides three methods of preparing the aromatization catalyst, depending on the sequence of the three steps.
According to a second aspect of the present invention, there is provided a process for producing the aromatization catalyst comprising:
1) shaping of
Forming and roasting the zeolite and the adhesive;
2) modification of
Modifying the roasted product obtained in the step 1) by using a solution containing siloxane, and then sequentially carrying out solid-liquid separation and roasting to obtain the external surface modified zeolite;
3) load(s)
Loading the metal active component on the external surface modified zeolite.
According to a third aspect of the present invention, there is provided another method for producing the aromatization catalyst, which comprises:
1) load(s)
Loading the active component onto a zeolite;
2) modification of
Modifying the load product obtained in the step 1) by using a solution containing siloxane, and then sequentially carrying out solid-liquid separation and roasting to obtain the external surface modified zeolite loaded with active components;
3) shaping of
And forming and roasting the external surface modified zeolite and a binder.
According to a fourth aspect of the present invention, there is provided a further process for producing the aromatization catalyst comprising:
1) modification of
Modifying zeolite with a siloxane-containing solution, and then sequentially carrying out solid-liquid separation, drying and roasting to obtain the external surface modified zeolite;
2) shaping of
Forming and roasting the external surface modified zeolite and a binder;
3) load(s)
Loading the metal active component on the roasted product obtained in the step 2).
Hereinafter, for convenience of description, the method according to the second aspect of the present invention is referred to simply as the first production method, the method according to the third aspect of the present invention is referred to simply as the second production method, and the method according to the fourth aspect of the present invention is referred to simply as the third production method.
In the three preparation methods of the present invention, the solvent in the solution containing siloxane may be selected from any solvent that does not dissolve and remains inert to the zeolite, typically an organic solvent, for example selected from cyclohexane, hexane, benzene, toluene, ethanol, etc., and the concentration of siloxane may be 0.5 to 50% by weight.
Preferably, the modification of the zeolite, zeolite-containing calcined product or supported product with the siloxane-containing solution is preferably carried out under reflux conditions, which further facilitates the uniformity of the modification.
In a first preparation method, step 2), the modification is carried out by: the siloxane-containing solution is mixed with the calcined product, after which the resulting mixture is refluxed at 20-200 ℃ for 0.1-50 hours, preferably at 50-150 ℃ for 0.5-20 hours.
In a second preparation method, step 2), the modification is carried out by: the siloxane-containing solution is mixed with the supported product, after which the resulting mixture is refluxed at 20-200 ℃ for 0.1-50 hours, preferably at 50-150 ℃ for 0.5-20 hours.
In a third preparation method, step 1), the modification is carried out by: the siloxane-containing solution is mixed with the zeolite, after which the resulting mixture is refluxed at 20-200 ℃ for 0.1-50 hours, preferably at 50-150 ℃ for 0.5-20 hours.
In the three production methods of the present invention, the step of modification is preferably repeated at least once, for example,
According to the three preparation methods of the present invention, in the step of modification, the solid-liquid separation can be performed by filtration (such as vacuum filtration) or evaporation (rotary evaporation), and the specific operation thereof is well known in the art, and the detailed description of the present invention is omitted.
In the modification step, the calcination temperature may be 150-700 ℃, preferably 400-600 ℃, and the calcination time may be 0.5-24 hours, preferably 1-5 hours.
In the three preparation methods of the present invention, the specific operation of the forming can be selected by referring to the existing catalyst forming process, and is not described herein again.
In the three production methods of the present invention, the present invention does not particularly limit the supporting as long as the metal active component can be supported on the carrier. Typically, for example, the loading may be carried out by an impregnation method.
Specifically, the zeolite or the external surface-modified zeolite may be impregnated with a solution of a compound containing the metal active component, and then the resulting mixture may be subjected to solid-liquid separation, drying, and calcination in this order.
Among the metal active component-containing compounds, non-limiting examples of the platinum-containing compound include one or more of platinum hydroxide, chloroplatinic acid, platinum nitrate, and platinum acetate. The concentration of the platinum-containing compound in the platinum-containing compound-containing solution may be 0.001 to 10% by weight, preferably 0.05 to 5% by weight.
In the loading step, the solid-liquid separation is preferably carried out in a rotary evaporator, the temperature of the rotary evaporator may be 60 to 120 ℃, and the time may be 5 to 200 minutes, preferably 20 to 80 minutes.
In the step of supporting, the temperature of the calcination may be 150-.
According to a fifth aspect of the present invention, the present invention provides use of the aromatization catalyst in a low carbon alkane aromatization reaction.
According to the application of the invention, the lower alkane can be C2-C6 alkane. Specifically, the low-carbon alkane is selected from one or more of ethane, propane, n-butane, isobutane, n-pentane, 2-methylbutane, 2-dimethylpropane, n-hexane, 2-methylpentane, 3-methylpentane, 2, 3-dimethylbutane and 2, 2-dimethylbutane. Preferably, the lower alkane is ethane.
Generally, the conditions of the lower alkane aromatization reaction may include: the reaction pressure is 0.05-2MPa, the temperature is 400-750 ℃, and the volume space velocity is 100-50000h-1Preferably 800--1。
The aromatization catalyst of the invention can not only improve the selectivity of aromatic hydrocarbon in the products of low-carbon alkane dehydrogenation aromatization reaction and reduce the generation of methane, but also can not cause the reduction of ethane conversion rate while reducing the selectivity of methane, and the catalyst has higher stability.
The present invention will be described in detail below by way of examples.
In the following examples and comparative examples,
the acidity of the external surface was determined by means of pyridine absorption Fourier transform infrared spectroscopy in Journal of Catalysis 264(2009)11-14, in which 14 mg of catalyst were pressed into 1.6 cm diameter discs and heated to 450 ℃ at 10-6Treating for 4 hours under vacuum condition of Torr; adsorbing 2,4, 6-trimethylpyridine at room temperature, then performing vacuum desorption at 200 ℃ and 1Torr, finally cooling to room temperature, and scanning a spectrogram; fourier infrared spectrum at 2cm-1The resolution of (2) is recorded.
The content of Pt and Fe in the catalyst is measured according to an ICP method;
colloidal silica was purchased from Sigma-Aldrich under the designation Ludox AS-40;
pseudo-boehmite was purchased from Sasol corporation under the brand Catapal B;
molecular sieve ZSM-5 with a silica to alumina ratio of 30 was purchased from Sigma-Aldrich and had an external surface acidity of 24.6. mu. mol/g;
molecular sieve ZSM-5 with a silica to alumina ratio of 50 was purchased from Sigma-Aldrich and had an external surface acidity of 14.8. mu. mol/g.