CN110237840B

CN110237840B - Preparation of platinum monatomic catalyst and application of platinum monatomic catalyst in reaction for preparing propylene through propane dehydrogenation

Info

Publication number: CN110237840B
Application number: CN201910601103.6A
Authority: CN
Inventors: 乔波涛; 郭亚琳; 黄家辉; 张军营; 刘芳
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2019-07-04
Filing date: 2019-07-04
Publication date: 2020-09-15
Anticipated expiration: 2039-07-04
Also published as: CN110237840A

Abstract

The invention relates to a preparation method of a titanium oxide supported platinum monatomic catalyst and application thereof in a reaction for preparing propylene by propane dehydrogenation. The active component platinum is dispersed on the carrier in a single atom form, and the loading rate is between 0.01 and 5 weight percent. The titanium oxide carrier is one or more than two of anatase, rutile and P25 with composite crystal phase. The catalyst has excellent carbon deposition resistance in the reaction of preparing olefin by propane dehydrogenation, can continuously run for more than 100 hours without obvious inactivation, and has high selectivity on the reaction product olefin, and the running period can be always maintained to be more than 90%. The catalyst prepared by the method has the remarkable advantages of high noble metal atom utilization rate (100 percent), good selectivity (89-98 percent), good stability (continuous operation for more than 40 hours), carbon deposit resistance and the like, and has a good application prospect.

Description

Preparation of platinum monatomic catalyst and application of platinum monatomic catalyst in reaction for preparing propylene through propane dehydrogenation

Technical Field

The invention relates to the technical field of catalysts, in particular to a preparation method of a titanium oxide supported platinum monatomic catalyst and application of the titanium oxide supported platinum monatomic catalyst in a reaction for preparing propylene by propane dehydrogenation.

Background

Propane is one of important basic raw materials in the field of petrochemical industry, and can be used for producing important chemical products such as polypropylene, acrylonitrile, propylene oxide and the like. Thus, the worldwide demand for propylene is enormous. Currently, the industrial production of propylene mainly comes from the following processes: 1) a byproduct in the process of preparing ethylene by naphtha cracking, 2) a catalytic cracking process, and 3) a process of preparing propylene (MTP) by methanol and a process of dehydrogenating propane. With the increasing demand for propylene in the world, the traditional petroleum catalytic cracking process has been unable to meet the demand of people. Recently, the breakthrough of shale gas technology has attracted attention in the process of producing propylene by propane dehydrogenation.

The dehydrogenation of propane to propylene is a strong endothermic reaction, and the reaction equilibrium is controlled by thermodynamics, so that a higher conversion rate is difficult to obtain. The reaction is generally carried out at a relatively high reaction temperature and under negative pressure in order to increase the conversion of the propane dehydrogenation reaction. However, higher temperatures can lead to the formation of propane dehydrogenation reaction by-products and carbon deposits, reducing product selectivity and leading to accelerated catalyst deactivation. Therefore, the development of a propane dehydrogenation catalyst having high activity, high selectivity, and high stability is important for industrial application of a process for producing propylene from propane.

Currently, the industrially applied Oleflex technology of UOP company mainly uses platinum supported on alumina as a main active component, and modulates the activity and stability of the catalyst by adding Sn. Although the catalyst has better reaction activity and product selectivity, the catalyst inactivation caused by carbon deposition in the catalyst reaction process can not be avoided, so that the carbon burning regeneration of the catalyst is required at very short intervals, and the industrial application value of the catalyst is greatly reduced. Chinese patents CN105709728A, CN105233844A, etc. modify the catalyst carrier to reduce the generation of catalyst by-products and improve the selectivity of the product. And CN101066532A and the like greatly improve the activity, product selectivity and reaction stability of the propane dehydrogenation catalyst by doping Sn in the molecular sieve framework. However, the carbon deposition resistance of the above-mentioned catalysts is still insufficient, and the activity of the catalyst is greatly reduced after the operation is carried out for a very short time. Greatly limiting the industrial application process.

Disclosure of Invention

The invention aims to provide a preparation method of a titanium oxide supported platinum monatomic catalyst, which is used for the reaction of preparing propylene by propane dehydrogenation and is an efficient and stable method for preparing propylene by propane dehydrogenation. The titanium oxide supported platinum monatomic catalyst provided by the invention has the advantages of low noble metal loading, extremely high (100%) Pt atom utilization rate, high activity and high selectivity, and can be used for converting propane into propylene. Meanwhile, the catalyst has very excellent carbon deposit resistance and can stably run for more than 100 hours without obvious inactivation.

In order to achieve the purpose, the invention adopts the technical scheme that:

a preparation method of a titanium oxide supported platinum-based monatomic catalyst adopts a strong electrostatic adsorption method to prepare, and comprises the following steps:

1) dropwise adding the solution A into the solution B at the flow rate of 0.1-5mL/min under the condition of stirring to form a mixture, stirring at 50-90 ℃ for 1-5h until the liquid in the mixture is completely volatilized, and stopping stirring to obtain a catalyst; the preparation method of the solution A comprises the following steps: adding a platinum metal precursor aqueous solution into an ammonia aqueous solution with the concentration of 20-30% to prepare a solution A; the preparation method of the solution B comprises the following steps: under the condition of stirring, adding the titanium oxide carrier aqueous solution into an ammonia water solution with the concentration of 20-30% until the pH value is 10-14 to prepare a solution B; the mass ratio of the platinum metal precursor to the titanium oxide carrier is 0.02-10%, preferably 0.05-1%; the concentration of the platinum metal precursor aqueous solution is 0.001-1mol/L, the volume ratio of the platinum metal precursor aqueous solution to the ammonia aqueous solution with the concentration of 20-30% is 1:100, and the concentration of the titanium oxide carrier aqueous solution in the solution B is 0.1-5000 g/L.

2) Drying the catalyst obtained in the step 1), wherein the drying temperature is 60-300 ℃, preferably 60-150 ℃, and the drying time is 1-24 hours, preferably 6-12 hours;

3) cooling the dried catalyst in the step 2) to room temperature, and then roasting in air, wherein the roasting temperature is 300-800 ℃, preferably 300-500 ℃, and the roasting time is 1-24 hours, preferably 2-6 hours.

Based on the above technical solution, preferably, the baking temperature in the step 3) is higher than the drying temperature in the step 2).

Based on the above technical solution, preferably, the titania carrier (catalyst carrier) is one or more of anatase, rutile, and P25 in a composite crystal phase.

Based on the technical scheme, the particle size of the titanium oxide carrier is preferably 20-500nm, namely the particle size of anatase is 20-500nm, the particle size of rutile is 20-500nm, and the particle size of P25 in the composite crystal phase is 20-500 nm.

Based on the technical scheme, the platinum metal precursor is preferably one or more than two of chloroplatinic acid, platinum nitrate, tetraammineplatinum chloride and tetraammineplatinum nitrate.

A platinum-based monatomic catalyst supported by titanium oxide, the active component of metal platinum is mainly dispersed on a titanium oxide carrier in a monatomic form, and the supporting rate is 0.01 wt% -5 wt%, preferably 0.05 wt% -1 wt%.

Based on the above technical solution, it is preferable that in the platinum-based monatomic catalyst supported on titanium oxide, part or all (50% or more) of platinum is dispersed in the form of a single atom on a titanium oxide support.

The invention also relates to the application of the titanium oxide supported platinum-based monatomic catalyst in the reaction for preparing propylene by propane dehydrogenation, wherein the reaction for preparing propylene by propane dehydrogenation takes propane as a reaction raw material, a supported platinum catalyst as a catalyst and a fixed bed as a reactor, and the dehydrogenation reaction is carried out within the temperature range of 300-650 ℃. The reaction product is subjected to qualitative and quantitative analysis of the product on line by gas chromatography. Wherein the reaction conditions are as follows: the reaction temperature is 300-650 ℃, preferably 400-650 ℃, more preferably 500-650 ℃, and the propane volume space velocity is 1000-6000h^-1Preferably, the following components are used: 2000-4000h^-1。

Compared with the prior art, the invention has the advantages that:

the titanium oxide-loaded platinum monatomic catalyst prepared by the invention is loaded with lower noble metal, has the remarkable advantages of high utilization rate of noble metal atoms (when all the loaded metals are monatomic dispersed, the atom utilization rate is 100%), good selectivity (89-98%), good stability (continuous operation is more than 40 hours), carbon deposition resistance and the like, and has good application prospect. The preparation method has simple flow and easy operation, the prepared supported platinum monatomic catalyst applied to the preparation of propylene by propane dehydrogenation has high metal atom utilization rate, can effectively catalyze propane dehydrogenation to prepare propylene under mild conditions, has no obvious inactivation after continuously operating for more than 100 hours under reaction conditions, has excellent carbon deposition resistance, simultaneously has very high selectivity on reaction products, can maintain the olefin selectivity to be more than 90 percent during the operation period, has obvious technical and economic effects, and is favorable for popularization.

Drawings

Figure 1 CO adsorption curve on a single atom catalyst in example 1.

FIG. 2 SEM photograph of spherical aberration of a single-atom catalyst in example 1.

FIG. 3 the selectivity versus time curve for the propane dehydrogenation reaction in example 8.

FIG. 4 the activity of the propane dehydrogenation reaction in example 8 is plotted as a function of time.

Detailed Description

The present invention will be described in detail with reference to specific examples, which are not intended to limit the scope of the present invention. Meanwhile, the embodiments only give some conditions for achieving the purpose, but do not mean that the conditions must be satisfied for achieving the purpose.

Example 1

100mg of Pt (NO)₃)₂(NH₃)₄Dissolving the solid in 50mL of deionized water to prepare a precursor solution of Pt; 2mL of the precursor solution was added to 20mL of 25% ammonia water and stirred, and the solution was designated as solution A. 2g of 100 mesh anatase titanium dioxide carrier is added into 20mL of deionized water and stirred, then 25% ammonia solution is added, and the pH value is adjusted to 10 and recorded as solution B. And dropwise adding the solution A into the stirred solution B at the dropping speed of 0.5 mL/min. After the completion of the dropwise addition, the mixture was heated in a water bath at 50 ℃ for 3 hours with continuous stirring until the liquid in the mixture was completely volatilized. The resulting solid material was dried in an oven at 80 ℃ for 10 hours and then taken out. Roasting for 4 hours at 400 ℃ in air atmosphere, wherein the heating rate is 10 ℃/min, and taking out a sample after natural cooling, and marking as CAT-1.

The prepared titanium oxide-loaded platinum-based monatomic catalyst is found to be dispersed on the carrier in the form of a platinum monatomic by an infrared and spherical aberration correction electron microscope characterization means. As shown in fig. 1: CO has two main absorption peaks on the catalyst, 2124cm^-1And 2073cm^-1. The two peaks are respectively a CO adsorption peak of positive-valence platinum and a linear adsorption peak of CO on zero-valence platinum, and are characteristic absorption peaks of single atoms. The catalyst can be judged to be a monatomic catalyst through infrared adsorption. Also, the spherical aberration correction of FIG. 2The presence of platinum on the catalyst in the form of a single atom can also be seen in the electron micrograph.

Comparative examples

The strong electrostatic adsorption method in the example 1 is changed into an immersion adsorption method, namely the total solution volume in the system is reduced, ammonia water is not added, when the Pt loading is the same as that in the example 1, the finally obtained catalyst is mainly nano particles, and has low dehydrogenation reaction activity, poor selectivity and high volatility. Comparative example is illustrated with example 1: the strong electrostatic adsorption method is the key for preparing the monatomic catalyst with high dispersion and high dehydrogenation reaction performance.

2mg of Pt (NO)₃)₂(NH₃)₄The solid was dissolved completely in 5mL of deionized water under vigorous stirring to make a precursor solution. 2g of 100-mesh anatase titanium dioxide carrier is dried in an oven at 100 ℃ for 10 hours and taken out, then the carrier is poured into a precursor solution, and after the carrier is adsorbed and saturated, the carrier is continuously stirred and is kept in a water bath at 50 ℃ for heating until water is completely volatilized. The resulting solid material was dried in an oven at 80 ℃ for 10 hours and then taken out. Roasting for 4 hours at 500 ℃ in air atmosphere, wherein the heating rate is 10 ℃/min, and taking out a sample after natural cooling, and marking as CAT-1-duibi.

Example 2

100mg of Pt (NO)₃)₂(NH₃)₄Dissolving the solid in 50mL of deionized water to prepare a precursor solution of Pt; 200. mu.L of the precursor solution was added to 30mL of 25% ammonia water and stirred, and the solution was designated as solution A. 2g of 200 mesh rutile titanium dioxide carrier was added to 25mL of deionized water and stirred, followed by addition of 25% aqueous ammonia solution and adjustment of pH to 12, and the solution was designated as solution B. And dropwise adding the solution A into the stirred solution B at the dropping speed of 1 mL/min. After the completion of the dropwise addition, the mixture was heated in a water bath at 60 ℃ for 3 hours with continuous stirring until the liquid in the mixture was completely volatilized. The resulting solid material was dried in an oven at 100 ℃ for 12 hours and then taken out. Roasting for 5 hours at 500 ℃ in air atmosphere, wherein the heating rate is 10 ℃/min, and taking out a sample after natural cooling, and marking as CAT-2.

Example 3

Mixing 100mg of H₂PtCl₆The solid is dissolved in 5mL of deionized water to prepare a precursor solution of Pt, and the precursor solution is completely added into 20mL of 25% ammonia water and stirred to obtain solution A. 1g of 50 mesh P25 carrier was added to 15mL of deionized water and stirred, followed by addition of 25% aqueous ammonia and adjustment of pH to 10, and the solution was designated as solution B. And dropwise adding the solution A into the stirred solution B at the dropping speed of 0.8 mL/min. After the completion of the dropwise addition, the mixture was heated in a water bath at 90 ℃ for 1 hour with continuous stirring until the liquid in the mixture was completely volatilized. The resulting solid material was dried in an oven at 200 ℃ for 10 hours and then taken out. Roasting for 5 hours at 500 ℃ in air atmosphere, wherein the heating rate is 10 ℃/min, and taking out a sample after natural cooling, and marking as CAT-3.

Example 4

Mixing 32mg of Pt (NO)₃)₂Dissolving the solid in 20mL of deionized water to prepare a precursor solution of Pt; 1mL of the precursor solution was added to 25mL of 25% ammonia water and stirred, and the solution was designated as solution A. 1g of 300 mesh P25 carrier was added to 25mL of deionized water and stirred, followed by addition of 25% aqueous ammonia solution to adjust the pH to 12 and recording as solution B. And dropwise adding the solution A into the stirred solution B at the dropping speed of 0.5 mL/min. After the completion of the dropwise addition, the mixture was heated in a water bath at 60 ℃ for 3 hours with continuous stirring until the liquid in the mixture was completely volatilized. The resulting solid material was dried in an oven at 100 ℃ for 10 hours and then taken out. Roasting for 4 hours at 600 ℃ in air atmosphere, wherein the heating rate is 10 ℃/min, and taking out a sample after natural cooling, and marking as CAT-4.

Example 5

35mg of PtCl₂(NH₃)₄Dissolving the solid in 20mL of deionized water to prepare a precursor solution of Pt; 5mL of the precursor solution was added to 20mL of 25% ammonia water and stirred, and the solution was designated as solution A. 1g of 100 mesh P25 carrier was added to 20mL of deionized water and stirred, followed by addition of 25% aqueous ammonia and adjustment of pH to 11, which was designated as solution B. And dropwise adding the solution A into the stirred solution B at the dropping speed of 0.9 mL/min. After the completion of the dropwise addition, the mixture was heated in a water bath at 50 ℃ for 3 hours with continuous stirring until the liquid in the mixture was completely volatilized. Drying the obtained solid substance in an oven at 120 deg.CAnd taking out after 10 hours. Roasting for 4 hours at 500 ℃ in air atmosphere, wherein the heating rate is 5 ℃/min, and taking out a sample after natural cooling, and marking as CAT-5.

Example 6

Mixing 100mg of H₂PtCl₆Dissolving the solid in 5mL of deionized water to prepare a precursor solution of Pt; 50 μ L of the precursor solution was added to 30mL of 25% ammonia water and stirred, and the solution was designated as solution A. 1g of 150-mesh rutile titanium dioxide carrier was added to 25mL of deionized water, stirred, and then added with 25% aqueous ammonia to adjust the pH to 12, which was designated as solution B. And dropwise adding the solution A into the stirred solution B at the dropping speed of 1 mL/min. After the completion of the dropwise addition, the mixture was heated in a water bath at 60 ℃ for 3 hours with continuous stirring until the liquid in the mixture was completely volatilized. The resulting solid material was dried in an oven at 200 ℃ for 12 hours and then taken out. Roasting for 5 hours at 500 ℃ in air atmosphere, wherein the heating rate is 10 ℃/min, and taking out a sample after natural cooling, and marking as CAT-6.

Example 7

The catalysts (examples 1-6, comparative example) were evaluated in a fixed bed reactor with a catalyst loading of 10ml, and the catalysts were first reduced at 550 ℃ for 2 hours before the reaction, and then reacted at 500 ℃ and 600 ℃ with introduction of a reaction gas (propane: hydrogen: 1), at a reaction pressure of normal pressure and a gas space velocity of 3200h^-1. The specific reaction results are shown in table 1 below:

TABLE 1

Example 8

The above-mentioned catalysts (example 1, example 2, comparative example) were subjected to stability evaluation in a fixed-bed reactor with a catalyst loading of 10ml, and the catalysts were first reduced at 550 ℃ for 2 hours in a hydrogen atmosphere before the reaction, and then a reaction gas (propane: hydrogen) was introduced at 580 ℃ to the reactorGas 1:1), the reaction pressure is normal pressure reaction, and the gas space velocity is 3200h^-1. The specific reaction results are shown in FIGS. 3 and 4. Therefore, the monatomic catalyst has higher reaction activity, product selectivity and reaction stability.

Claims

1. The application of the titanium oxide supported platinum-based monatomic catalyst in the reaction of preparing propylene by propane dehydrogenation is characterized in that the preparation method of the titanium oxide supported platinum-based monatomic catalyst adopts an electrostatic adsorption method and comprises the following steps:

1) dropwise adding the solution A into the solution B at the flow rate of 0.1-5mL/min under the stirring condition to form a mixture, and stirring at 50-90 ℃ for 1-5h to obtain a catalyst; the preparation method of the solution A comprises the following steps: adding a platinum metal precursor aqueous solution into an ammonia aqueous solution with the concentration of 20-30% to prepare a solution A; the preparation method of the solution B comprises the following steps: under the condition of stirring, adding the titanium oxide carrier aqueous solution into an ammonia water solution with the concentration of 20-30% until the pH value is 10-14 to prepare a solution B; the mass ratio of the platinum metal precursor to the titanium oxide carrier is 0.02-10%; the concentration of the platinum metal precursor aqueous solution is 0.001-1mol/L, the volume ratio of the platinum metal precursor aqueous solution to the ammonia aqueous solution with the concentration of 20-30% is 1:100, and the concentration of the titanium oxide carrier aqueous solution in the solution B is 0.1-500 g/L;

2) drying the catalyst obtained in the step 1), wherein the drying temperature is 60-300 ℃, and the drying time is 1-24 hours;

3) cooling the dried catalyst in the step 2) to room temperature, and then roasting in air, wherein the roasting temperature is 100-800 ℃, and the roasting time is 1-24 hours.

2. The use according to claim 1, wherein the titania support is one or more of anatase, rutile, and P25 in a composite phase.

3. Use according to claim 1, wherein the titania support has a particle size of 20-500 nm.

4. The use according to claim 1, wherein the platinum metal precursor is one or more of chloroplatinic acid, platinum nitrate, tetraammineplatinum chloride, and tetraammineplatinum nitrate.

5. Use according to claim 1, characterized in that the metallic platinum is dispersed on the titania support mainly in monoatomic form, at a loading of 0.01-5 wt%;

the titanium oxide carrier is one or more than two of anatase, rutile and P25 with composite crystal phase.

6. Use according to claim 5, wherein more than 50% of the platinum is dispersed in the form of a single atom on the titania support.

7. Use according to claim 1, characterized in that the reaction conditions are: the reaction temperature is 300-650 ℃, the pressure is 0.01-0.3MPa, and the propane volume space velocity is 1000-6000h^-1。