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CN-121991535-A - Preparation method of Pt-Pd coating slurry and Pt-Pd coating

CN121991535ACN 121991535 ACN121991535 ACN 121991535ACN-121991535-A

Abstract

The invention discloses a preparation method of Pt-Pd coating slurry and a Pt-Pd coating. The coating can inhibit coking on the inner wall of the EDC cracking furnace tube. The coating effectively isolates the contact between the catalytic active site on the metal surface and the coking matrix, has excellent anti-carbon performance, can catalyze the oxidation-reduction reaction of the coke layer and H 2 generated by the reaction, reduces the thickness of the coke layer, has uniform thickness, has the characteristics of excellent heat transfer performance, high temperature resistance, difficult falling off and simple manufacture, and is suitable for severe conditions of high-temperature cracking processes such as dichloroethane, ethylene and petrochemical industry.

Inventors

  • ZHENG LENG
  • LI YANJIE
  • ZHAO DONGKE
  • ZHANG HONGKE

Assignees

  • 万华化学(福建)异氰酸酯有限公司

Dates

Publication Date
20260508
Application Date
20241108

Claims (10)

  1. 1. A preparation method of Pt-Pd coating slurry comprises the following steps: (1) Pd (NO 3 ) 2 ·2H 2 O、PtN 2 O 6 、Mn(NO 3 ) 3 ·4H 2 O is added into the aqueous solution to prepare gel, and then the gel is prepared by stirring, dried and roasted; (2) Grinding and screening the product obtained in the step (1) to obtain powder; (3) The powder was mixed with an aluminum dihydrogen phosphate solution, and then polyvinyl alcohol was added thereto to prepare a slurry.
  2. 2. The method according to claim 1, wherein in step (1), the gel is prepared at a temperature of 80-100 ℃, preferably 90 ℃, and the stirring time is 11-13h, preferably 12h.
  3. 3. A method according to claim 1 or 2, wherein in step (1) the calcination temperature is 1100-1300 ℃, preferably 1200 ℃, and the calcination time is 1-3h, preferably 2h.
  4. 4. A method according to any one of claims 1 to 3, wherein in the aqueous solution in step (1), pd (NO 3 ) 2 concentration of 0.0001 to 0.045mol/L, ptN 2 O 6 concentration of 0.005mol/L, mn (NO 3 ) 3 ·4H 2 O concentration of 0.05mol/L, ethylene glycol concentration of 0.0689 to 0.125mol/L, and citric acid concentration of 0.0689 to 0.125 mol/L).
  5. 5. The method according to any one of claims 1 to 4, wherein the molar ratio of Pt to Pd element is 1:9 to 9:1, wherein the molar concentration of Pt is 0.005mol/L, the molar concentration of Mn is 0.05mol/L, and the molar ratio of metal cations to ethylene glycol and citric acid in the solution is (3.5 to 4.5) to (4.5 to 5.5).
  6. 6. The method according to any one of claims 1 to 5, wherein in the step (2), the particle size of the powder is 20 to 40 μm.
  7. 7. The method according to any one of claims 1 to 6, wherein the mass fraction of the aluminum dihydrogen phosphate aqueous solution is 50%, and/or the mass ratio of the powder to the aluminum dihydrogen phosphate solution in the step (3) is 1:100.
  8. 8. The method of any one of claims 1-7, wherein the slurry comprises the following composition: 0.98wt% of powder; 97.02wt% of 50% aqueous solution of aluminum dihydrogen phosphate; 2wt% of polyvinyl alcohol.
  9. 9. The preparation method of the Pt-Pd coating for inhibiting coking of the Fe-Cr-Ni alloy cracking furnace tube comprises the following steps: (a) Spraying the slurry of any one of claims 1-8 onto the pretreated surface; (b) Drying and solidifying the sample to be sprayed, heating to 500-550 ℃ at a heating rate of 5 ℃ per minute, and preserving heat for 1h; (c) And then heating to 800-850 ℃ at the heating rate of 10 ℃ per minute, and preserving heat for 2 hours to finally obtain the noble metal coating.
  10. 10. The coating according to claim 9, wherein in the step (a), a spray gun is used for spraying, the set pressure is 0.5-0.6MPa, the distance between the spray nozzle and the sample is 20-50cm, and the spray is uniformly sprayed on the surface.

Description

Preparation method of Pt-Pd coating slurry and Pt-Pd coating Technical Field The invention belongs to the field of coking inhibition of an organic matter high-temperature pyrolysis unit, and relates to slurry for preparing an anti-coking coating by spraying on the metal surface of pyrolysis equipment and a preparation method of the coating. Background Polyvinyl chloride (PVC) is the third largest synthetic polymer plastic in world production, and the main PVC production process at present is to crack ethylene into Ethylene Dichloride (EDC) and then further polymerize to form PVC, wherein the coking condition of EDC cracking furnace is an important influencing factor for inhibiting the improvement of VCM productivity and stable operation. The EDC cracking furnace has the main effects that the EDC is cracked to generate VCM at the high temperature of 500-600 ℃, the used material is high-temperature-resistant chrome-nickel alloy, iron and nickel atoms in the alloy migrate to the surface at the high temperature, so that raw material EDC and byproducts generated by cracking are generated on the surface of equipment, coke is generated under the further catalysis of metal ions, and finally the coke is further deposited on the surface of the equipment, so that the heat transfer coefficient of the cracking furnace is increased, the energy consumption of the cracking furnace is influenced, the gas phase flux of the cracking furnace is influenced, the processing capacity of the raw material is influenced, and in the more serious case, the pipeline is blocked by coking, the gas phase material flux is influenced, and the device is stopped in a linkage way. At present, few anti-coking reports are about an EDC cracking furnace, and the main coking inhibition methods at home and abroad are to add inhibitors into cracking raw materials, design and develop furnace tubes with excellent anti-carbon deposition performance, prepare coatings on the inner walls of the furnace tubes and the like by referring to anti-coking paths of other processes. The method for preparing the inhibitor is required to be continuously injected along with raw materials, the cost is high, and the manufacturing of the novel cracking furnace tube requires complex smelting process and manufacturing equipment, and is only suitable for the construction and installation of the novel cracking furnace or the reconstruction of the cracking furnace in service. The anti-coking coating is prepared on the inner wall of the cracking furnace tube by a chemical treatment method, so that the process is simple, the cost is low, the existing public engineering equipment in the cracking furnace region can be utilized, the in-service furnace tube can be repeatedly coated, and the distribution and the yield of the product are not affected. There are several reports on cracking furnace coatings, such as described in CN102046846B, CN103857971a, that by adding alloying elements to the coating, the spalling and adhesion properties of the surface are improved, but none of them promote carbon transfer of the generated carbon at the surface. Disclosure of Invention The invention aims to provide the noble metal coating slurry which can effectively inhibit the coking of an iron-chromium-nickel alloy cracking furnace tube and has low manufacturing cost. Under the reaction system, the spalling property of the coke in a pipeline and equipment can be increased, the carbon transfer of the generated coke in the system can be promoted, and the generation thickness of a coke layer is reduced. In order to achieve the purpose, the invention adopts the following technical scheme: a preparation method of Pt-Pd coating slurry for inhibiting coking of an Fe-Cr-Ni alloy cracking furnace tube comprises the following steps: (1) Pd (NO 3)2·2H2O、PtN2O6、Mn(NO3)3·4H2 O is added into the aqueous solution to prepare gel, and then the gel is prepared by stirring, dried and roasted; (2) Grinding and screening the product obtained in the step (1) to obtain powder; (3) The powder was mixed with an aluminum dihydrogen phosphate solution, and then polyvinyl alcohol was added thereto to prepare a slurry. In the step (1) of the invention, the gel is prepared at a temperature of 80-100 ℃, preferably 90 ℃ and stirred for 11-13 hours, preferably 12 hours. In the step (1) of the invention, the roasting temperature is 1100-1300 ℃, preferably 1200 ℃, and the roasting time is 1-3h, preferably 2h. In the step (1), pd (NO 3)2 concentration is 0.0001-0.045mol/L, ptN 2O6 concentration is 0.005mol/L, mn (NO 3)3·4H2 O concentration is 0.05mol/L, ethylene glycol concentration is 0.0689-0.125mol/L, and citric acid concentration is 0.0689-0.125 mol/L) in the aqueous solution. As a preferred embodiment, the molar ratio of Pt to Pd element is 1:9-9:1, the molar concentration of Pt is 0.005mol/L, the molar concentration of Mn is 0.05mol/L, and the molar ratio of metal cation to glycol and citric acid in the solution is (3.5-4.5) t