CN110639510A - Method for preparing monatomic catalyst through re-dispersion of Pt nanoparticles - Google Patents

Abstract

The invention discloses a method for preparing a single-atom catalyst by redispersion of Pt nano-particles, and belongs to the technical field of Pt catalysts. The method includes the following steps: (1) preparing a catalyst containing Pt nanoparticles; (2) redispersing the catalyst containing Pt nanoparticles at a high temperature with a mixture of air, water and HCl to obtain a Pt single-atom catalyst. The method for preparing single-atom catalyst by redispersion of Pt nanoparticles provided by the present invention has the advantages of simple operation and remarkable effect, can effectively disperse Pt nanoparticles into Pt single atoms, and is suitable for newly preparing single-atom Pt catalysts. Also suitable for regeneration of platinum-based catalysts that have been deactivated after use.

Description

A method for preparing single-atom catalyst by redispersion of Pt nanoparticles

technical field

The invention belongs to the technical field of Pt catalysts, and relates to a method for preparing a single-atom catalyst by redispersing Pt nanoparticles.

Background technique

Platinum catalyst is a kind of catalyst often used in chemical, petroleum and chemical reaction processes. It has high catalytic activity, good selectivity, and the catalyst is simple and convenient to make, and the amount of catalyst used is small. It can be improved by changing and improving the manufacturing method. performance. Therefore, it is widely used in reaction processes such as ammonia oxidation, petroleum hydrocarbon reforming, oxidation and hydrogenation of unsaturated compounds, and removal of carbon monoxide and nitrogen oxides in gases.

Catalytic reforming is one of the petroleum refining processes, that is, under the condition of catalyst, the molecular structure of hydrocarbons in gasoline fraction is rearranged into new molecules, so that the light gasoline fraction obtained by crude oil distillation is converted into rich aromatic hydrocarbons. of high-octane gasoline. The platinum catalyst is an excellent catalyst in the catalytic reforming reaction, but with the progress of the reaction, Pt will accumulate seriously at high temperature and in a water-containing atmosphere. The Pt is seriously aggregated in the medium, and the maximum grain size of Pt reaches 90 nm, and the catalyst activity is greatly reduced. In order to restore the activity of the catalyst, the aggregated Pt particles need to be redispersed.

USP4444897 discloses a Pt-Ir-based catalyst redispersion method. After the catalyst is reduced, it is treated with helium gas containing HCl and water in an oxygen-free atmosphere, and finally treated with a gas containing HCl and oxygen to make the active components Redispersed.

CN 106268883 B discloses a high-Pt dispersion method, which comprises subjecting an alumina carrier loaded with active components to ionizing radiation treatment, and then performing water chlorine activation and reduction to obtain a platinum-based agent with higher platinum dispersion.

CN107362834A discloses a method for recovering the activity of continuous reforming catalysts in use. In this method, the used catalysts are scorched, soaked in hydrochloric acid at 30°C for 2 hours, the waste liquid is removed, dried, and finally activated with water chlorine at 510°C for 4 hours , to obtain the activated catalyst. Experiments show that this method can effectively restore the activity of continuous reforming catalysts.

Existing catalyst redispersion methods have various defects and deficiencies. Patent USP4444897 uses helium gas containing HCl and water in an oxygen-free atmosphere, and the cost of industrially using helium gas is relatively high; patent CN 106268883 B needs to pre-load the active component The alumina carrier is treated with ionizing radiation, and the steps are cumbersome; the patent CN107362834 A is soaked in hydrochloric acid at 30 ° C for 2 hours, and the waste liquid is removed and dried. The steps are cumbersome and difficult to handle online.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for redispersing Pt clusters into single atoms or preparing single-atom Pt catalyst. operation and can effectively redisperse Pt clusters into single atoms. The invention can provide technical support for the deactivation regeneration (redispersion) of platinum-based catalysts in industrial catalytic reforming. The object of the present invention is achieved through the following technical solutions.

A method for preparing a single-atom catalyst by redispersion of Pt nanoparticles is characterized in that, comprising the following steps: (1) preparing a catalyst containing Pt nanoparticles; (2) using the catalyst containing Pt nanoparticles using air, water, HCl The mixture is redispersed at high temperature to obtain a Pt single-atom catalyst.

Further, the Pt content in the Pt-based catalyst is 0.01-3 wt.%.

Further, the temperature used for the redispersion treatment is 400 to 600°C, preferably 450 to 550°C.

Further, the preparation method of the medium used in the redispersion treatment is as follows: air passes through the HCl aqueous solution to obtain saturated air containing HCl.

Further, the concentration of the HCl aqueous solution used in the redispersion preparation treatment medium is: 0.01-0.5 mol/L, preferably 0.01-0.2 mol/L.

Further, the medium gas-agent ratio used in the redispersion treatment is 1000:0.5-1000:10. Gas-to-agent ratio: The ratio of the amount of gas passing through the catalyst bed per hour to the volume of the catalyst.

Further, the redispersion treatment time is 2-15h.

In order to simulate the catalyst deactivated due to the severe accumulation of Pt in the reaction, the present invention performs hydrothermal aging on the newly prepared catalyst to obtain a catalyst containing Pt nanoparticles. The catalyst containing Pt nanoparticles obtained in step (1) is subjected to redispersion treatment in step (2) after hydrothermal aging treatment; the hydrothermal aging conditions are: the hydrothermal aging temperature is 400-700° C., and the hydrothermal aging medium contains The amount of water is 5-40v%, the aging time is 10-72h, and the air-agent ratio is 1000:0.5-1000:10.

The method for preparing single-atom catalyst by redispersion of Pt nano-particles provided by the invention has the advantages of simple operation and remarkable effect, can effectively disperse Pt nanoparticles into Pt single-atom, and is suitable for newly preparing single-atom Pt catalysts. Also suitable for regeneration of platinum-based catalysts that have been deactivated after use.

Description of drawings

Figure 1 is the HAADF STEM image of the platinum catalyst after hydrothermal aging for 24 h.

Figure 2 is the HAADF STEM image of the platinum catalyst after 8h redispersion treatment.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings.

Example 1

Aging of the catalyst

The catalyst prepared by the impregnation method was placed in a quartz tube reactor. The catalyst loading was 100ml, the hydrothermal aging temperature was 500°C, the moisture content of the aging medium was 20v%, the gas-agent ratio was 1000:1, and the hydrothermal aging time was 24h.

The HAADF STEM image of the aged platinum catalyst is shown in Figure 1. It can be seen from the figure that after hydrothermal aging for 24 h, Pt is seriously accumulated on the platinum catalyst, which is in the form of large particles.

Example 2

Redispersion of Pt Nanoparticles

The aged catalyst, that is, the catalyst containing Pt nanoparticles, was placed in a quartz tube, the catalyst loading was 100ml, the heating temperature was set to 400°C, the gas-to-agent ratio was 1000:0.5, and the concentration of the HCl solution was 0.02mol/L. , the air is passed through the HCl solution to obtain saturated air containing HCl, and then enters the quartz tube to contact with the catalyst, and the redispersion treatment time is 2h.

Example 3

Redispersion of Pt Nanoparticles

The aged catalyst, that is, the catalyst containing Pt nanoparticles, was placed in a quartz tube, the catalyst loading was 100ml, the heating temperature was set to 500°C, the gas-to-agent ratio was 1000:1, and the concentration of the HCl solution was 0.05mol/L. , the air is passed through the HCl solution to obtain saturated air containing HCl, and then enters the quartz tube to contact with the catalyst, and the redispersion treatment time is 5h.

Example 4

Redispersion of Pt Nanoparticles

The aged catalyst, that is, the catalyst containing Pt nanoparticles, was placed in a quartz tube, the catalyst loading was 100ml, the heating temperature was set to 500°C, the gas-to-agent ratio was 1000:1, and the concentration of HCl solution was 0.2mol/L. , the air is passed through the HCl solution to obtain saturated air containing HCl, and then enters the quartz tube to contact with the catalyst, and the redispersion treatment time is 8h.

The HAADF STEM image of the redispersed platinum catalyst is shown in Figure 2, from which it can be seen that the Pt particles are effectively dispersed and are in a single atomic state. Combining Fig. 1 and Fig. 2, it is fully demonstrated that for Pt particles with serious accumulation, the redispersion treatment method of the present invention can effectively disperse the Pt particles into single atoms.

Example 5

Redispersion of Pt Nanoparticles

The aged catalyst, that is, the catalyst containing Pt nanoparticles, was placed in a quartz tube, the catalyst loading was 100ml, the heating temperature was set to 550°C, the gas-to-agent ratio was 1000:2, and the concentration of HCl solution was 0.01mol/L. , the air is passed through the HCl solution to obtain saturated air containing HCl, and then enters the quartz tube to contact with the catalyst, and the redispersion treatment time is 10h.

Claims (10)

1. a method for preparing single-atom catalyst by redispersion of Pt nanoparticles, is characterized in that, comprises the steps: (1) prepare the catalyst containing Pt nanoparticles; (2) use air, water, The HCl mixture is redispersed at high temperature to obtain a Pt single-atom catalyst. 2. The method according to claim 1, wherein the Pt content in the Pt-based catalyst is 0.01-3 wt.%. 3 . The method according to claim 1 , wherein the temperature used in the redispersion treatment is 400-600° C. 4 . 4 . The method according to claim 1 , wherein the temperature used in the redispersion treatment is 450-550° C. 5 . 5 . The method according to claim 1 , wherein the method for preparing the medium used in the redispersion treatment is as follows: passing air through an aqueous HCl solution to obtain saturated air containing HCl. 6 . 6 . The method according to claim 5 , wherein the concentration of the HCl aqueous solution used in the redispersion preparation treatment medium is: 0.01-0.5 mol/L. 7 . 7 . The method according to claim 5 , wherein the concentration of the HCl aqueous solution used in the redispersion preparation treatment medium is: 0.01-0.2 mol/L. 8 . 8 . The method according to claim 1 , characterized in that, the medium gas-to-agent ratio used in the redispersion treatment is 1000:0.5-1000:10. 9 . 9 . The method according to claim 1 , wherein the redispersion treatment time is 2-15 h. 10 . 10. method according to claim 1, is characterized in that, the catalyst that contains Pt nano-particles that step (1) obtains, after hydrothermal aging treatment, adopts step (2) redispersion treatment; Hydrothermal aging condition is: The hydrothermal aging temperature is 400～700℃, the water content of the hydrothermal aging medium is 5～40v%, the aging time is 10～72h, and the air-agent ratio is 1000:0.5～1000:10.

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