CN110180530B

CN110180530B - Catalyst for preparing olefin by dehydrogenating low-carbon alkane and preparation method thereof

Info

Publication number: CN110180530B
Application number: CN201910590249.5A
Authority: CN
Inventors: 董晓燕
Original assignee: Daqing Svanda New Material Co ltd
Current assignee: Daqing Svanda New Material Co ltd
Priority date: 2019-07-02
Filing date: 2019-07-02
Publication date: 2023-05-05
Anticipated expiration: 2039-07-02
Also published as: CN110180530A

Abstract

The invention belongs to the field of catalysts, and particularly relates to a catalyst for preparing olefin by dehydrogenating light alkane and a preparation method thereof. The catalyst comprises 2-8wt% of chromium oxide, 0.5-1.0wt% of auxiliary agent and the balance of modified active carbon carrier, wherein the weight percentage of the chromium oxide is calculated by chromium element. The invention uses the modified activated carbon obtained by the microwave modification, acid modification and alkali modification treatment in sequence as a carrier, so that the surface of the catalyst has proper acidity and Cr ⁶⁺ /Cr ³⁺ The ratio of the carrier to the active component has proper interaction force, and the catalyst has excellent activity, selectivity and stability as a whole.

Description

Catalyst for preparing olefin by dehydrogenating low-carbon alkane and preparation method thereof

Technical Field

The invention belongs to the field of catalysts, and particularly relates to a catalyst for preparing olefin by dehydrogenating light alkane and a preparation method thereof.

Background

Low carbon olefins, such as propylene, are one of the basic raw materials in the chemical industry and can be used to produce a range of downstream chemicals such as high molecular polymers, olefin oxides, and the like. Meanwhile, as people pay more attention to the environment in which people depend on the environment, lead-free gasoline is initiated, MTBE (methyl tert-butyl ether) is attractive as an improver of the octane number of gasoline, and the demand is increased, so that the increase of the demand of isobutene is promoted. In summary, the demand for lower olefins and the like is increasing due to the rapid growth of downstream products in recent years. At present, the catalytic cracking process and the naphtha steam cracking process of petroleum are main sources of low-carbon olefins, but with the increasing shortage of petroleum resources, the traditional low-carbon olefin production technology has difficulty in meeting the rapidly-increasing low-carbon olefin demand, so that the development of new low-carbon olefin production technology is urgent. The method has important strategic significance for relieving contradiction between supply and demand of low-carbon olefin, optimizing energy and chemical industry structures in China and the like.

At present, catalysts for preparing olefin by dehydrogenating low-carbon alkane mainly comprise two main types of noble metal catalysts and base metal oxide catalysts, and cocatalysts used by the catalysts comprise K ₂ O、K ₂ CO ₃ MgO, etc. The former is Pt-Sn/Al disclosed in U.S. Pat. No. 3,262A ₂ O ₃ The catalyst (namely, the catalyst for the Oleflex process of the UOP) is represented, and although the conversion rate, the selectivity and the stability of the catalyst are all good, the noble metal platinum is used, so that the manufacturing cost of the catalyst is high, and the production cost is greatly increased. The latter is disclosed in British patent GB2162082A as Cr ₂ O ₃ /Al ₂ O ₃ The catalyst (namely, catalyst for the Catofin process of ABB Lummus creation) is represented, and although the conversion rate and selectivity of the catalyst are better, the production cost of the catalyst is lower, and the catalyst has certain poisoning resistance, the catalyst is deactivated very fast, frequent regeneration is required in the use process, and the energy consumption of the process is very large (regeneration period is 15-30 min).

The supported platinum-tin catalyst PtSn/MgAl (O) for the catalytic dehydrogenation of light alkane is disclosed in Chinese patent CN1185352A, wherein a carrier is MgAl (O) composite oxide, and the molar ratio of Mg to Al is 2:1-15:1, pt is 0.2 to 1.2 percent of the weight of MgAl (O) as a carrier, and the mol ratio of Pt to Sn is 0.5:1 to 1.5:1. the catalyst has high isobutene selectivity (97-98%) and high deactivation resistance for isobutane dehydrogenation reaction, but the cost of the catalyst is obviously high due to the use of noble metal platinum.

A catalyst for preparing propylene by propane dehydrogenation, as disclosed in chinese patent CN109331810a, takes tin oxide doped regular mesoporous alumina as a carrier, chromium oxide as an active component, and alkali metal oxide, alkaline earth metal oxide and fourth subgroup metal oxide as auxiliaries; the content of the tin oxide is 0.5 to 1.5 percent based on the weight of the aluminum oxide, the loading amount of the chromium oxide is 5 to 20 percent, and Cr ⁶⁺ /Cr ³⁺ The ratio is 0.5-0.6, the loading of the alkali metal oxide is 0.05-1.0%, the loading of the alkaline earth metal oxide is 0.05-1.0%, and the loading of the fourth subgroup metal oxide is 0.05-3.0%. The invention adds tin oxide in the process of forming the aluminum oxide framework structure, so that the tin oxide is fully doped in the aluminum oxide framework, thereby effectively adjusting the acid structure of the aluminum oxide and adding Cr ⁶⁺ /Cr ³⁺ The ratio of (2) is controlled within the range of 0.5-0.6, thereby inhibiting the generation of carbon deposit, having good high-temperature stability and keeping the conversion rate of propane above 40% after 120 min.

The preparation method of a low-carbon alkane dehydrogenation catalyst disclosed in Chinese patent CN108786831A comprises (1) dissolving soluble salts of Cr and La in a benzoic acid solution to obtain an impregnating solution containing Cr and La; (2) And (3) impregnating the carrier with the impregnating solution obtained in the step (1), and then drying and roasting to obtain the dehydrogenation catalyst. According to the method, a macromolecular complex taking benzoic acid as a ligand is formed by an active component Cr species and an auxiliary agent La in an acid environment, clusters of Cr and La close to each other are formed on the surface of a carrier, the Cr species stably exist on the surface of carrier alumina through strong interaction generated by the clusters, and the catalyst still has high dehydrogenation activity after multiple circulation regeneration. Cr species exist in a large amount at the pore canal with larger pore diameter, can still keep higher activity under higher carbon deposition, prolongs the single-pass operation period of the catalyst, and reduces the operation cost of the device.

Cr for preparing isobutene by dehydrogenating isobutane as disclosed in Chinese patent CN102962054A ₂ O ₃ Catalyst in which the active component Cr ₂ O ₃ 4-25% by mass percent and the balance of mesoporous carbon; the specific surface area of the mesoporous carbon is 900-3200 m ² Per g, the most probable pore diameter is 2.5-9.5 nm, the pore volume is 1.1-3.5 ml g ^-1 The mesoporosity is 70-100%. The invention adopts mesoporous carbon as a carrier, so that the surface area of the catalyst carrier and the diffusion rate of isobutene as a product are improved, and the conversion rate of isobutane can reach 26.3-58.4% at the reaction temperature of 570-660 ℃.

In general, the existing low-carbon alkane dehydrogenation olefin catalyst still has various defects in the aspects of activity, anti-carbon deposition performance, stability and the like, so that development of a new generation of low-carbon alkane dehydrogenation olefin catalyst with better performance is needed to provide more favorable supporting effect for industrial production in the chemical industry.

Disclosure of Invention

Therefore, the technical problem to be solved by the application is how to improve the activity, selectivity and stability of the catalyst for preparing olefin by dehydrogenating light alkane as much as possible on the premise of not improving the production cost, namely taking base metal oxide-chromium oxide as an active component.

The inventors of the present application have made intensive and diligent studies to solve the above-mentioned problems, and have found that a modified activated carbon can be used as a carrier for the subsequent loading of an active ingredientSo that the carrier and the active component have proper interaction force, thereby on one hand, the Cr in the catalyst can be regulated and controlled ⁶⁺ /Cr ³⁺ On the other hand, the acid functional group and the alkaline functional group which are present on the surface of the active carbon in a proper proportion are utilized, so that the active carbon has proper adsorption capacity for chromium components in the process of loading chromium oxide and proper adsorption capacity for low-carbon alkane raw materials in the process of catalytic reaction, thereby not only avoiding activity reduction caused by agglomeration of the chromium oxide in the process of reaction, but also promoting the reaction of the raw materials and the diffusion of products and avoiding side reaction and carbon deposition.

The technical scheme of the invention is as follows: the invention discloses a catalyst for preparing olefin by dehydrogenating low-carbon alkane, which comprises 2-8wt% of chromium oxide, 0.5-1.0wt% of auxiliary agent and the balance of modified active carbon carrier, wherein the weight percentage of the chromium oxide is calculated by chromium element; the auxiliary agent is selected from one or more oxides of alkali metal, alkaline earth metal, rare earth metal, sn, bi and the like.

The content of chromium oxide in the catalyst is more preferably 2 to 5wt%.

The modified activated carbon carrier is modified activated carbon obtained by microwave modification, acid modification and alkali modification treatment in sequence. The preparation process comprises the following steps:

a) Carbonization treatment

Cleaning and drying raw materials, carbonizing in a muffle furnace to obtain an active carbon precursor, and then crushing, grinding and sieving;

b) Microwave modification treatment

Loading the active carbon precursor obtained in the step a) into a microwave generator for microwave modification treatment;

c) High temperature activation

Putting the activated carbon precursor obtained in the step b) into a muffle furnace for activation treatment;

d) Acid modification treatment

Immersing the active carbon precursor obtained in the step c) into a mixed solution of hypochlorous acid and nitric acid completely, carrying out soaking treatment, and then washing and drying;

e) Alkali modification treatment

And d), completely immersing the active carbon precursor obtained in the step d) into a sodium hydroxide solution, carrying out soaking treatment, and then washing and drying to obtain the modified active carbon.

The raw materials of the modified activated carbon carrier can be wood, fruit pits, coal and semicoke, wherein fruit shells such as coconut shells or apricot pits are preferable, and the modified activated carbon carrier is used as the raw materials, so that the surface of the finally prepared modified activated carbon has more proper proportion of acidic functional groups and basic functional groups.

The drying temperature in the step a) is preferably 60-150 ℃, and the drying time is preferably 20-60min; the temperature programming is adopted in the carbonization process, the temperature rising rate is preferably 5-20 ℃/min, the temperature is firstly increased to 300 ℃, the temperature is kept for 12-24h, then the temperature is continuously increased to 500 ℃, and the temperature is kept for 12-24h; finally, the temperature is raised to 650 ℃ and kept for 12-18h.

The activated carbon precursor in step a) is sieved through a 50-80 mesh sieve.

The microwave power in the step b) is preferably 510-680W, and the microwave irradiation (i.e., microwave modification treatment) time is preferably 5-10min.

The activation temperature in step c) is preferably 700-750 ℃ and the activation time is 3-5h.

In the mixed solution of hypochlorous acid and nitric acid in the step d), the concentration of hypochlorous acid is preferably 1-1.5mol/L, and the concentration of nitric acid is preferably 2-3mol/L. The soaking time is preferably 0.5-2h; the drying temperature is preferably 60-100deg.C, and the drying time is preferably 30-60min.

The concentration of the sodium hydroxide solution in the step e) is preferably 1-1.5mol/L, the soaking time is preferably 2-6h, the drying temperature is preferably 60-100 ℃, and the drying time is preferably 30-60min.

The inventor of the application finds that by carrying out microwave modification treatment on the precursor after carbonization of the activated carbon before high-temperature activation, a plurality of closed micropores and mesopores in the activated carbon can be opened, and collapse of pore channels can be avoided in the subsequent high-temperature activation process. Thus, the activated carbon carrier can form a proper pore canal structure, and the diffusion of raw materials and products in the reaction process is facilitated.

Through research, it also developsAt present, the activated carbon after high-temperature activation is sequentially subjected to acid modification treatment and alkali modification treatment, so that the types and the amounts of oxygen-containing acidic functional groups, oxygen-containing basic functional groups and the like on the surface of the activated carbon can be purposefully modulated, the adsorption effect of the activated carbon on the activated carbon in the process of loading the chromium oxide active component can be influenced, and the surface acidity and Cr of the catalyst can be regulated and controlled on the one hand ⁶⁺ /Cr ³⁺ In a suitable range, e.g. Cr ⁶⁺ /Cr ³⁺ The ratio of (2) is in the range of 0.30-0.45, so that the deactivation rate of the catalyst can be effectively reduced under the condition of keeping high initial activity of the catalyst; on the other hand, the carrier and the active component have proper interaction force, so that the reduction of activity caused by sintering and agglomeration of the chromium oxide in the reaction process can be effectively avoided. In addition, the catalyst has proper adsorption capacity to the low-carbon alkane raw material in the catalytic reaction process, so that the reaction of the raw material and the diffusion of the product can be promoted, and the occurrence of side reaction and the formation of carbon deposit are avoided.

The invention also discloses a preparation method of the catalyst for preparing olefin by dehydrogenating light alkane, which comprises the following steps:

1) Firstly, preparing a modified activated carbon carrier;

2) Weighing soluble chromium salt and soluble precursor salt of the auxiliary agent according to the composition of the final catalyst, and adding deionized water to prepare impregnation liquid;

3) Impregnating the impregnating solution prepared in the step 2) on the modified activated carbon carrier prepared in the step 1); and then drying, roasting, and then cooling to room temperature to obtain the catalyst product.

The soluble chromium salt in the step 2) is selected from one or more of chromium nitrate, chromium oxalate, chromium sulfate, chromium chloride and the like.

The concentration of chromium ions in the impregnating solution in the step 2) is 0.5-2.0mol/L, and the concentration of metal ions in the auxiliary agent is 0.1-0.5mol/L.

The drying temperature in the step 3) is preferably 100-150 ℃, and the drying time is preferably 4-8h; the calcination temperature is preferably 500-600 ℃, and the calcination time is preferably 4-6h.

In the preparation method of the application, the molding step can be introduced after the step 3) according to the requirements on the shape and mechanical strength of the catalyst in the specific use process, and a common molding mode such as compression molding, extrusion molding, rotational molding and the like can be adopted, and a proper amount of a common molding auxiliary agent such as a binding agent such as methyl cellulose, a lubricant such as graphite and paraffin, an extrusion aid such as sesbania powder and the like can be introduced in the molding process according to the requirements.

The application also discloses application of the catalyst for preparing olefin by low-carbon alkane dehydrogenation in a process for preparing olefin by low-carbon alkane catalytic dehydrogenation, wherein the used reactor can be a fixed bed reactor, a moving bed reactor or a fluidized bed reactor, and the reaction conditions are as follows: the reaction temperature is 500-650 ℃, the reaction pressure is 0.1-0.5MPa, and the airspeed is 500-5000h ^-1 。

Compared with the prior art, the beneficial effect that this application had is:

1. the catalyst adopts modified active carbon as a carrier, so that the surface of the catalyst has proper acidity and Cr ⁶⁺ /Cr ³⁺ The ratio of the carrier to the active component has proper interaction force, and the catalyst has excellent activity, selectivity and stability as a whole.

2. The catalyst of the application adopts chromium oxide as an active component, and compared with a noble metal catalyst, the production cost is greatly reduced.

3. The chromium oxide content in the catalyst is low, the catalyst is friendly to the environment, and the adverse effect on the environment caused by unavoidable chromium loss in the preparation and use processes of the chromium-based catalyst and the treatment process of the waste catalyst can be well reduced.

4. According to the preparation method, the precursor after carbonization of the activated carbon is subjected to microwave modification treatment before high-temperature activation, so that a plurality of closed micropores and mesopores in the activated carbon can be opened, collapse of pore channels can be avoided in the subsequent high-temperature process, and the activated carbon carrier can form a proper pore channel structure, so that diffusion of raw materials and products in the reaction process is facilitated.

5. The method can effectively reduce the deactivation rate of the catalyst under the condition of keeping high initial activity of the catalyst; and can effectively avoid the reduction of activity caused by sintering and agglomeration of chromium oxide in the reaction process.

6. The catalyst has proper adsorption capacity on the low-carbon alkane raw material in the catalytic reaction process, so that the reaction of the raw material and the diffusion of the product can be promoted, and the occurrence of side reaction and the formation of carbon deposit are avoided.

Additional advantages will be set forth in part in the description which follows, and in part will be apparent from the description. The following advantages are realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.

Supplemental definition

The materials, compounds, compositions, and components described herein may be used in, or in combination with, the methods and compositions described herein, or may be used to practice and prepare the compositions, or as products obtained by the methods. It is to be understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each and every one of these compounds may not be explicitly contemplated and described herein. For example, if a certain adjunct component is disclosed and discussed, and various alternative actual forms of that component are discussed, each combination and permutation of the adjunct component and the actual form that is possible are specifically contemplated unless specifically indicated to the contrary. This concept applies to all aspects of the present application including, but not limited to, steps in methods of making and using the disclosed compositions. Thus, if there are a plurality of additional steps that can be performed, it should be understood that each of these additional steps can be performed by any specific embodiment or combination of embodiments of the disclosed methods, and that each such combination is specifically contemplated as being disclosed.

In this specification and the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:

it must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include both a reference and a plurality of references (i.e., more than two, including two) unless the context clearly dictates otherwise. Thus, for example, reference to "the pH adjustor" can include a single pH adjustor, or a mixture of two or more pH adjustor, and so forth.

"optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. For example, the phrase "optional adjunct component" means that the adjunct component may or may not be present, and the description encompasses both cases where the adjunct component is included in the composition and where the adjunct component is not included in the composition.

Unless otherwise indicated, numerical ranges in this application are approximate, and thus values outside of the ranges may be included. The numerical ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, it includes from the one particular value and/or to the other particular value. Similarly, when a particular value is expressed as an approximation by the use of the antecedent "about," it will be understood that it encompasses the particular value itself as well as the range of errors permitted in the art due to measurement or calculation. It will also be understood that the endpoints of each of the numerical ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

References in the specification and the claims to parts by weight of a particular element or component in a composition or article refer to the relationship by weight between that element or component and any other element or component in the composition or article. Thus, in a composition comprising 2 parts by weight of component X and 5 parts by weight of component Y, X and Y are present in a weight ratio of 2:5, and are present in that ratio whether or not additional components are included in the composition.

All fractions and percentages mentioned in this application are by weight, unless the context clearly indicates otherwise, or there are other meanings, or implications based on the context of the context or the manner of usage in the art, and the weight percentages of the components are based on the total weight of the composition or product comprising the components.

Reference in the present application to "comprising," "including," "having," and similar terms is not intended to exclude the presence of any optional components, steps or procedures, whether or not any optional components, steps or procedures are specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all methods claimed through use of the term "comprising" may include one or more additional steps, apparatus parts or components and/or materials. In contrast, the term "consisting of … …" excludes any component, step or procedure not specifically recited or enumerated. The term "or" refers to members recited individually as well as in any combination unless otherwise specified.

Furthermore, the contents of any of the referenced patent documents or non-patent documents in this application are incorporated by reference in their entirety, especially with respect to the definitions and general knowledge disclosed in the art (in case of not inconsistent with any definitions specifically provided in this application).

Detailed Description

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods described and claimed herein are made and evaluated, and are intended to be merely exemplary and are not intended to limit the scope of what applicants regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless otherwise indicated, parts are parts by weight, temperatures are expressed in degrees celsius or at ambient temperature, and pressures are at or near atmospheric. There are numerous variations and combinations of reaction conditions (e.g., component concentrations, solvents needed, solvent mixtures, temperatures, pressures, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the process. Only reasonable routine experimentation will be required to optimize such process conditions.

Example 1:

firstly, preparing a modified activated carbon carrier:

cleaning coconut shell raw materials, drying at 80 ℃ for 40min, carbonizing in a muffle furnace, heating to 300 ℃ in the carbonizing process, keeping for 16h, and then continuously heating to 500 ℃ and keeping for 16h; finally, heating to 650 ℃, maintaining for 14 hours, obtaining an active carbon precursor at a heating rate of 10 ℃/min, and then crushing, grinding and sieving with a 60-mesh sieve. Then the mixture is put into a microwave generator for microwave modification treatment, the microwave power is 680W, and the radiation time is 5min; then the mixture is put into a muffle furnace to be activated for 5 hours at 700 ℃. Then immersing in a mixed solution of hypochlorous acid and nitric acid, wherein the concentration of hypochlorous acid is 1.2mol/L, the concentration of nitric acid is 2.5mol/L, immersing for 1h, washing and drying at 60 ℃ for 60min. Soaking in 1.5mol/L sodium hydroxide solution for 2 hr, washing, and oven drying at 70deg.C for 50min to obtain modified active carbon carrier

Chromium oxide (calculated by Cr element) in the catalyst accounts for 2.1 weight percent of the weight of the catalyst, and the auxiliary agent K ₂ The content of O was 0.9wt%, and Cr (NO ₃ ) ₃ ·9H ₂ O，KNO ₃ Adding deionized water to prepare a mixed solution; the concentration of chromium ions in the mixed solution is 0.6mol/L, and the concentration of potassium ions is 0.3mol/L.

Impregnating the modified activated carbon carrier with the impregnating solution, drying the filter cake obtained after filtration at 100 ℃ for 8 hours, then roasting in a muffle furnace at 500 ℃ for 6 hours, and then cooling to room temperature to obtain the catalyst product.

Example 2

Firstly, preparing a modified activated carbon carrier:

cleaning apricot kernel raw materials, drying at 80 ℃ for 40min, carbonizing in a muffle furnace, heating to 300 ℃ in the carbonizing process, keeping for 16h, and then continuously heating to 500 ℃ and keeping for 16h; finally, heating to 650 ℃, maintaining for 14 hours, obtaining an active carbon precursor at a heating rate of 15 ℃/min, and then crushing, grinding and sieving with a 70-mesh sieve. Then placing the mixture into a microwave generator for microwave modification treatment, wherein the microwave power is 600W and the radiation time is 7min; then put into a muffle furnace to activate for 4h at 725 ℃. Then immersing in a mixed solution of hypochlorous acid and nitric acid, wherein the concentration of hypochlorous acid is 1.2mol/L, the concentration of nitric acid is 2.5mol/L, immersing for 1h, washing and drying at 80 ℃ for 45min. Soaking in 1.2mol/L sodium hydroxide solution for 3 hr, washing, and oven drying at 75deg.C for 45min to obtain modified active carbon carrier

The chromium oxide (calculated by Cr element) in the catalyst accounts for 3.0wt% of the weight of the catalyst, and the additive K ₂ The content of O was 0.7wt%, and Cr (NO ₃ ) ₃ ·9H ₂ O，KNO ₃ Adding deionized water to prepare a mixed solution; the concentration of chromium ions in the mixed solution is 1.0mol/L, and the concentration of potassium ions is 0.25mol/L.

And (3) impregnating the modified activated carbon carrier with the impregnating solution, drying the filter cake obtained after filtering at 120 ℃ for 6 hours, then roasting in a muffle furnace at 550 ℃ for 5 hours, and then cooling to room temperature to obtain the catalyst product.

Example 3

Firstly, preparing a modified activated carbon carrier:

cleaning coconut shell raw materials, drying at 80 ℃ for 40min, carbonizing in a muffle furnace, heating to 300 ℃ in the carbonizing process, keeping for 16h, and then continuously heating to 500 ℃ and keeping for 16h; finally, heating to 650 ℃, maintaining for 14 hours, obtaining an active carbon precursor at a heating rate of 10 ℃/min, and then crushing, grinding and sieving with a 60-mesh sieve. Then the mixture is put into a microwave generator for microwave modification treatment, the microwave power is 680W, and the radiation time is 5min; then put into a muffle furnace to activate for 3h at 750 ℃. Then immersing in a mixed solution of hypochlorous acid and nitric acid, wherein the concentration of hypochlorous acid is 1.2mol/L, the concentration of nitric acid is 2.5mol/L, immersing for 1h, washing and drying for 30min at 100 ℃. Then the mixture is completely immersed into sodium hydroxide solution with the concentration of 1.5mol/L for 2 hours, and then washed and dried for 40 minutes at the temperature of 90 ℃ to obtain the modified active carbon carrier

The chromium oxide (calculated as Cr element) in the catalyst accounts for 7.8wt% of the weight of the catalyst, and the additive K ₂ The content of O was 0.6wt%, and Cr (NO ₃ ) ₃ ·9H ₂ O，KNO ₃ Adding deionized water to prepare a mixed solution; the concentration of chromium ions in the mixed solution is 1.8mol/L, and the concentration of potassium ions is 0.15mol/L.

Comparative example 1

The preparation process is essentially the same as in example 2, except that: in the modification process of the activated carbon, the high-temperature activation step is adjusted to be after the alkali treatment step.

Comparative example 2

The preparation process is essentially the same as in example 2, except that: the alkali modification treatment step is omitted in the modification process of the activated carbon.

Comparative example 3

The preparation process is essentially the same as in example 2, except that: the acid modification treatment step is omitted in the modification process of the activated carbon.

Comparative example 4

The preparation process is essentially the same as in example 2, except that: the microwave modification treatment step is omitted in the modification process of the activated carbon.

Comparative example 5

The preparation process is essentially the same as in example 2, except that: mesoporous carbon (commercial product CMK-1) is directly used as a carrier.

Comparative example 6

The preparation process is essentially the same as in example 2, except that: alumina (alumina disclosed in ZL 201110196192.4) is directly used as a carrier.

Catalytic performance test

The catalysts prepared in examples 1 to 3 and comparative examples 1 to 6 were each tested for catalytic performance, and the test results are shown in Table 1. Wherein the life time refers to the time that the catalyst can be continuously used under the condition that the activity and the selectivity of the catalyst are basically unchanged.

The catalyst is filled in a fixed bed reactor for reaction, and the specific conditions are as follows: 550 ℃,0.1mpa,500h ^-1 (V/V) the feed gas is propane.

TABLE 1 catalyst Performance test results

As can be seen from the test results of Table 1, the catalyst of the present application has more excellent activity, selectivity and stability than the catalyst of the prior art due to the use of the modified activated carbon obtained by the microwave modification, acid modification and alkali modification treatment sequentially as the carrier.

Throughout this application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the compounds, compositions and methods described herein.

Various modifications and changes may be made to the compounds, compositions, and methods described herein. Other aspects of the compounds, compositions, and methods described herein will be apparent from consideration of the specification and practice of the compounds, compositions, and methods disclosed herein. It is intended that the specification and examples be considered as exemplary.

It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While still being apparent from variations or modifications that may be made by those skilled in the art are within the scope of the invention.

Claims

1. Use of a catalyst for producing propylene by propane dehydrogenation in a process for producing propylene by propane dehydrogenation, wherein the catalyst comprises 3.0wt% of chromium oxide and 0.7wt% of K ₂ O and the balance of modified activated carbon carrierThe weight percentage of the chromium oxide is calculated by chromium element;

the preparation process of the catalyst comprises the following steps:

cleaning apricot kernel raw materials, drying at 80 ℃ for 40min, carbonizing in a muffle furnace, heating to 300 ℃ in the carbonizing process, keeping for 16h, and then continuously heating to 500 ℃ and keeping for 16h; finally, heating to 650 ℃, keeping for 14 hours, obtaining an active carbon precursor at a heating rate of 15 ℃/min, and then crushing, grinding and sieving with a 70-mesh sieve; then placing the mixture into a microwave generator for microwave modification treatment, wherein the microwave power is 600W and the radiation time is 7min; then placing the mixture into a muffle furnace to be activated for 4 hours at 725 ℃; immersing the mixture into a mixed solution of hypochlorous acid and nitric acid, wherein the concentration of hypochlorous acid is 1.2mol/L, the concentration of nitric acid is 2.5mol/L, immersing for 1h, washing and drying at 80 ℃ for 45min; immersing the mixture into sodium hydroxide solution with the concentration of 1.2mol/L for 3 hours, washing and drying at 75 ℃ for 45 minutes to obtain the modified activated carbon carrier;

according to chromium oxide and K in the catalyst ₂ The content of O was measured to be Cr (NO ₃ ) ₃ ·9H ₂ O，KNO ₃ Adding deionized water to prepare a mixed solution; the concentration of chromium ions in the mixed solution is 1.0mol/L, and the concentration of potassium ions is 0.25mol/L;

impregnating the modified activated carbon carrier with impregnating solution, drying a filter cake obtained after filtration at 120 ℃ for 6 hours, then roasting in a muffle furnace at 550 ℃ for 5 hours, and then cooling to room temperature to obtain the catalyst;

the catalyst is filled in a fixed bed reactor for reaction, and the reaction conditions are as follows: 550 ℃,0.1mpa,500h ^-1 (V/V) the feed gas is propane.