Search

CN-122006785-A - Molecular sieve domain-limited metal propane dehydrogenation catalyst and preparation method and application thereof

CN122006785ACN 122006785 ACN122006785 ACN 122006785ACN-122006785-A

Abstract

The invention discloses a molecular sieve domain-limited metal propane dehydrogenation catalyst and a preparation method and application thereof. The catalyst comprises a molecular sieve nanosheet carrier and a metal active component, wherein the metal active component comprises a first metal and a second metal, the first metal exists in molecular sieve pore channels in a single-atom form in a limited mode, and the second metal is formed around the first metal and at least partially replaces a molecular sieve framework structure. The method uses fluoride ions as mineralizer and auxiliary structure guiding agent, and realizes rapid crystallization and morphology regulation of the molecular sieve by a one-step hydrothermal method. The method is simple, convenient and environment-friendly, eliminates the traditional complicated post-load or complexing agent auxiliary route, and effectively solves the problems of easy aggregation of active centers and large synthetic pollution. The obtained catalyst has the advantages of ultrathin diffusion of the nano-sheet and chemical anchoring stability of the hetero-atom, and has excellent activity, high propylene selectivity and long-period stability in the propane dehydrogenation reaction.

Inventors

  • LI LANDONG
  • Lv Xintong
  • WU GUANGJUN
  • CHAI YUCHAO

Assignees

  • 南开大学

Dates

Publication Date
20260512
Application Date
20251222

Claims (10)

  1. 1. A molecular sieve domain-limited metal propane dehydrogenation catalyst, characterized in that the catalyst comprises a molecular sieve nanosheet carrier and a metal active component, wherein the metal active component comprises a first metal and a second metal, the first metal exists in molecular sieve pore channels in a single-atom form in a domain-limited manner, and the second metal is formed around the first metal and at least partially replaces a molecular sieve framework structure; The first metal is selected from at least one of Pt, pd, ir, rh and Ru, and the second metal is selected from at least one of Fe, co, zn, cu, mn, in and Ga.
  2. 2. The molecular sieve limited metal propane dehydrogenation catalyst of claim 1, wherein the first metal is present in an amount of 0.01 wt% -1 wt%, preferably 0.05 wt% -0.5 wt%, more preferably 0.1 wt% -0.4 wt%, the second metal is present in an amount of 0.1 wt% -20 wt%, preferably 0.2 wt% -10 wt%, more preferably 0.3 wt% -6 wt%, the remainder being a support, based on the weight of the catalyst; The silicon-aluminum ratio of the molecular sieve nanosheet carrier is greater than or equal to 50, and the molecular sieve nanosheet carrier is preferably a pure silicon molecular sieve.
  3. 3. A method for preparing a molecular sieve domain-limited metal propane dehydrogenation catalyst by fluorine-assisted rapid crystallization comprises the following steps: step 1, mixing and stirring an organic structure template agent, a silicon source and water; Step 2, mixing the fluoride ion mineralizer aqueous solution with the solution obtained in the step 1, and performing first stirring aging to obtain synthetic sol; Step 3, mixing an aqueous solution containing a first metal precursor and a second metal precursor with the synthetic sol, and performing second stirring aging to obtain metal-containing synthetic sol, wherein the first metal in the first metal precursor is at least one of Pt, pd, ir, rh and Ru, and the second metal in the second metal precursor is at least one of Fe, co, zn, cu, mn, in and Ga; and 4, carrying out hydrothermal crystallization on the metal-containing synthetic sol, carrying out solid-liquid separation on a mixture obtained by the hydrothermal crystallization, and drying and optionally roasting a separated solid-phase product to obtain the molecular sieve domain-limited metal propane dehydrogenation catalyst.
  4. 4. The method for preparing a molecular sieve limited metal propane dehydrogenation catalyst by fluorine-assisted rapid crystallization according to claim 3, wherein, The organic structure template agent is at least one of ethylenediamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrapropylammonium bromide, the silicon source is at least one of silica sol, tetraethyl orthosilicate, amorphous silica, white carbon black and silicate, and the fluoride-containing ion mineralizer is at least one of ammonium fluoride, sodium fluoride, potassium fluoride and calcium fluoride; The molar ratio of the organic structure template agent calculated by molecules in the synthesis mother liquor to the silicon source calculated by SiO 2 is T/SiO 2 =0.05-0.4:1, preferably T/SiO 2 =0.05-0.2:1; The molar ratio of water in the synthesis mother liquor to the silicon source calculated by SiO 2 is H 2 O/SiO 2 =5-100:1, preferably H 2 O/SiO 2 =20-50:1; The molar ratio of the ammonium fluoride in terms of molecules to the silicon source in terms of SiO 2 in the synthesis mother liquor is NH 4 F/SiO 2 =0.01-1:1, preferably NH 4 F/SiO 2 =0.05-1:1; and (3) mixing and stirring in the step (1) for 1-12 hours.
  5. 5. The method for preparing the molecular sieve domain-limited metal propane dehydrogenation catalyst through fluorine-assisted rapid crystallization according to claim 3, wherein the first stirring aging condition in the step 2 comprises the temperature of 25-100 ℃ for 1-24 hours, and the second stirring aging condition in the step 3 comprises the temperature of 25-100 ℃ for 1-24 hours.
  6. 6. The method for preparing a molecular sieve limited metal propane dehydrogenation catalyst through fluorine-assisted fast crystallization according to claim 3, wherein the first metal precursor is at least one of an inorganic acid, an inorganic salt, an inorganic acid salt, an inorganic complex, an organic acid salt, an organic complex, an oxide and a hydroxide of a first metal; the second metal precursor is at least one of inorganic acid salt, organic acid salt, oxide and hydroxide of a second metal; The inorganic acid salt is preferably nitrate, hydrochloride or sulfate, and the organic acid salt is preferably at least one of acetate and gluconate; Preferably, the first metal precursor is at least one of chloroplatinic acid, platinum nitrate, platinum chloride, tetraammineplatinum dichloride, platinum acetylacetonate, palladium chloride acid, palladium nitrate, palladium acetate, tetraamminepalladium nitrate, potassium tetrachloropalladate, palladium acetylacetonate, ruthenium trichloride, ruthenium acetylacetonate, rhodium trichloride, rhodium acetylacetonate, chloroiridic acid and potassium hexachloroiridate; Preferably, the second metal precursor is at least one of ferric nitrate, ferric sulfate, ferrous nitrate, ferric chloride, ferrous chloride, cobalt sulfate, cobalt nitrate, cobalt chloride, zinc nitrate, zinc sulfate, zinc chloride, manganese gluconate, manganese sulfate, manganese nitrate, manganese chloride, indium nitrate, indium chloride, gallium nitrate, and gallium chloride.
  7. 7. The method for preparing a molecular sieve limited metal propane dehydrogenation catalyst through fluorine-assisted rapid crystallization according to claim 3, wherein in the step 4, The hydrothermal crystallization condition comprises that the temperature is 90-200 ℃ and the time is 1-7 days; the drying temperature is 60-120 ℃ and the drying time is 6-12 hours; the roasting temperature is 500-700 ℃, the time is 2-10 hours, and the roasting atmosphere is air.
  8. 8. A molecular sieve limited metal propane dehydrogenation catalyst made by the method of any of claims 3-7.
  9. 9. Use of the molecular sieve domain-limited metal propane dehydrogenation catalyst of any one of claims 1-2 and 8 in the oxygen-free dehydrogenation of propane to produce propylene.
  10. 10. A process for the anaerobic dehydrogenation of propane to propylene, said process being carried out in a fixed bed reactor having a catalyst bed packed with the molecular sieve limited metalpropane dehydrogenation catalyst of any of claims 1-2 and 8, said process comprising the steps of: pretreatment is carried out on the catalyst by adopting reducing gas or inert gas before the reaction, and then raw material gas is introduced to carry out propane dehydrogenation reaction; Preferably, the reducing gas is selected from at least one of diluted hydrogen and diluted carbon monoxide, and the inert gas is selected from at least one of nitrogen, argon and helium; preferably, the pretreatment is performed at a temperature of 300-600 ℃ for 0.5-4 hours; preferably, the concentration of propane in the raw material gas is 10-100wt%, preferably 50-100wt%; Preferably, the temperature of the propane dehydrogenation reaction is 300-650 ℃, the pressure is 0-0.2 MPa, the reaction space velocity is 1-100 h -1 , and preferably 4-60 h -1 .

Description

Molecular sieve domain-limited metal propane dehydrogenation catalyst and preparation method and application thereof Technical Field The invention belongs to the field of alkane catalytic conversion, and particularly relates to a molecular sieve domain-limited metal propane dehydrogenation catalyst, in particular to a framework heteroatom anchor stable high-dispersion platinum monoatomic catalyst with molecular sieve domain-limited characteristics, a method for preparing the molecular sieve domain-limited metal propane dehydrogenation catalyst by fluorine-assisted rapid crystallization, and a catalyst for preparing propylene by propane dehydrogenation prepared by the method and application. Background Propylene is an important basic raw material for energy chemical products with high added value, called as China chemical industry chain extension. The downstream products are widely applied to the fields of industry and agriculture, daily chemicals, medical treatment, scientific research and the like, and play a key role in national economy. For a long time, the market expansion of polypropylene and other propylene derivatives drives the growth of propylene demand, and the China propylene industry maintains a high-speed expansion state. The actual propylene production comprises mainstream traditional process routes such as naphtha steam cracking, refinery catalytic cracking (FCC) separation, heavy oil catalytic cracking (DCC) and the like and emerging directional production technologies such as olefin disproportionation, methanol to olefin (MTP, MTO), propane Dehydrogenation (PDH) and the like. In recent years, the development space of coal chemical industry is restricted by the inherent three-high characteristic, and the oil-making route is slow due to the gradual reaching of the oil refining scale to the ceiling. Compared with the technology for preparing propylene by directly dehydrogenating propane, the technology has the characteristics of single raw material, single product, single process, directional synthesis and easy reverse integration, has the advantages of high propylene yield, low investment intensity, high investment return and outstanding environmental protection and cost advantages, is more in accordance with the national clean energy development route and development target, and has more competitive advantages under the policy background of energy structure optimization and upgrading and multi-energy supply. Therefore, the direct dehydrogenation of propane to propylene is the optimal directional propylene production process, is also the main direction of propylene expansion in the future, and is a key technology for realizing the efficient utilization of carbon-based energy. Propane dehydrogenation is a reaction with strong heat absorption and increased molecular number, and both the temperature increase and the pressure decrease are favorable for forward progress of the dehydrogenation reaction. The C-H bond energy of propane molecule is high, the reactivity is low, higher energy is needed for activation, the product alkene is more reactive than alkane, the deep dehydrogenation is easy to generate carbon deposition species, the conversion rate and the selectivity are difficult to be cooperatively improved, and the lower alkene yield drives the optimal design of the catalyst. Currently, the propane dehydrogenation catalysts which have been commercialized are mainly based on platinum (Pt) or chromium (Cr) based materials, represented by the olyflex process of UOP company and the Catofin process of ABB Lummus company, respectively. The chromium-based catalyst has limited popularization and application because of the problem of environmental toxicity, while the platinum-based catalyst has higher activity but high cost, and side reactions such as hydrogenolysis and the like are easy to occur in the reaction process, so that carbon (coke) is formed on the surface of the catalyst to cover active sites, and the activity is reduced, thus regeneration is required to be realized through a chloridizing combustion process frequently. In addition, the platinum species are susceptible to agglomeration and sintering under high temperature reaction conditions, further resulting in loss of catalytic activity and low production efficiency. The platinum-based catalyst auxiliary agent commonly used in propane dehydrogenation reaction is concentrated in transition metal and rare earth metal, the second metal can form alloy or metal oxide with main metal, so that active metal atoms are blocked from agglomerating to improve dispersity, the electron density of the active metal is improved to weaken interaction with olefin, the desorption rate of propylene is improved, and deep dehydrogenation and carbon deposition generation of propylene are inhibited. Bimetallic catalysts, while exhibiting the potential to exceed single metal catalysts, the introduction of a second metal and complex synthetic processes (e.g., use