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CN-122010137-A - Y-type molecular sieve for small crystal grains and preparation method thereof

CN122010137ACN 122010137 ACN122010137 ACN 122010137ACN-122010137-A

Abstract

The invention discloses a small-grain Y-shaped molecular sieve and a preparation method thereof, wherein the raw materials comprise sodium silicate, aluminum sulfate and small-grain seed crystal, wherein the small-grain seed crystal is prepared by mixing sodium silicate, sodium aluminate and aqueous alkali according to the mass ratio (silicon dioxide: aluminum oxide=15.5-16.5:1, sodium oxide: silicon dioxide=0.75-0.79:1, water: silicon dioxide=13.5-13.9:1) and is obtained by inducing nucleation, slow growth, standing at a constant temperature of 27-28 ℃ and storing for 2 weeks (the seed crystal has been applied for patent of the invention and patent number is CN 118877905B). Then, the small-grain seed crystal, sodium aluminate, sodium silicate and aluminum sulfate are mixed together according to the mass ratio (silicon dioxide: aluminum oxide=8.3-8.4:1, sodium oxide: silicon dioxide=0.50-0.51:1, water: silicon dioxide=23.5-24:1) and the seed crystal ratio of 0.5-4.0%, and then the mixture is statically crystallized for 40-50 h at 100+/-2 ℃ in a normal pressure reaction kettle to obtain a small-grain NaY molecular sieve (phi 300 nm), and after filtering and washing, the obtained small-grain Y molecular sieve has large and more mesopores on the outer surface, is suitable for exchange reaction at low temperature (0-50 ℃), has high reaction speed, is more energy-saving and environment-friendly, and has more development space in the fields of catalytic cracking, hydrogenation agents and adsorbents.

Inventors

  • ZHAO KE
  • LIU CHEN

Assignees

  • 湖南省天怡新材料有限公司

Dates

Publication Date
20260512
Application Date
20260316

Claims (9)

  1. 1. The seed crystal for preparing the small-grain Y-type molecular sieve is characterized in that the seed crystal is prepared from sodium silicate, aluminum sulfate and small-grain seed crystal according to the mass ratio of sodium silicate, sodium aluminate and aqueous alkali (silicon dioxide: aluminum oxide=15.5-16.5:1, sodium oxide: silicon dioxide=0.75-0.79:1 and water: silicon dioxide=13.5-13.9:1). Slowly adding a liquid alkali solution with the mass fraction higher than 48% into a sodium silicate solution with the mass fraction higher than 27%, setting up a cold water bath for reaction, starting stirring, slowly dropwise adding 18.5% -27% of sodium aluminate solution through a separating funnel when the system temperature is lower than 25 ℃, controlling the reaction temperature to be 23-25 ℃, adding deionized water according to the calculated amount, and uniformly stirring. And standing for more than 2 weeks at the temperature of 27-28 ℃ after stirring is stopped.
  2. 2. The seed crystal for preparing the small-grain Y-type molecular sieve according to claim 1, wherein the molar ratio of the silica to the aluminum oxide in the raw material is 16:1, the molar ratio of the sodium oxide to the silica in the raw material is 0.78:1, and the molar ratio of the water molecules to the silica in the raw material is 13.75:1.
  3. 3. The preparation method of the small-grain Y-type molecular sieve is characterized by comprising the following steps of: calculating the required quality of various raw materials according to a certain proportion according to the raw material analysis index; dropping sodium aluminate solution into sodium silicate solution through a separating funnel, controlling dropping speed, and ensuring good fluidity of a reaction system; adding aluminum sulfate and part of deionized water into a reaction system, uniformly stirring and heating to 96 ℃; adding the seed crystal of claim 1 or 2 to the reaction system, and supplementing a calculated amount of deionized water; Continuously heating the reaction system to 100 ℃, and carrying out normal-pressure static crystallization for 40-50 h under the condition of 100+/-2 ℃; And (3) when the temperature of the reaction system is reduced to 50-70 ℃, carrying out solid-liquid separation on a Buchner funnel, eluting a filter cake by using deionized water at 60-70 ℃ at the same time, and drying to obtain a small-grain Y-shaped molecular sieve finished product.
  4. 4. The method for preparing a small-grain Y-type molecular sieve according to claim 3, wherein the seed crystal is used in an amount of 0.5% -4% of the total mass of the feedstock.
  5. 5. The method of preparing a small-grain Y-type molecular sieve according to claim 3, wherein the water is used for leaching the deionized water with a volume not less than 1 time, and the leached filter cake is dried under the environment not higher than 250 ℃.
  6. 6. The method for preparing the small-grain Y-type molecular sieve according to claim 3, wherein the ratio of the substances of the silica to the alumina is 8.35-8.40:1, the ratio of the substances of the sodium oxide to the silica is 0.50-0.52:1, and the ratio of the substances of the water to the silica is 23-24:1.
  7. 7. The method for preparing the small-grain Y-type molecular sieve according to claim 6, wherein the method comprises the following steps: the ratio of the materials added in the preparation method is that the mass ratio of the sodium oxide to the silicon dioxide is 0.51:1.
  8. 8. The method for preparing a small-grain Y-type molecular sieve according to claim 6 or 7, wherein the BET specific surface area of the molecular sieve is 789-806 m 2 /g, the mesoporous specific surface area of the molecular sieve is 39-50 m 2 /g, the crystallinity of the molecular sieve is 55.3% -74.7%, and the silicon-aluminum ratio of the molecular sieve is 4.20-5.08.
  9. 9. A small-grain Y-type molecular sieve prepared using the preparation method of claim 8.

Description

Y-type molecular sieve for small crystal grains and preparation method thereof Technical Field The invention belongs to the technical field of molecular sieves, and particularly relates to a Y-shaped molecular sieve for small grains and a preparation method thereof. Background The Y-type molecular sieve is an artificially synthesized Faujasite (FAU) structure capable of withstanding the impact of high temperature steam during catalytic cracking regeneration. The less aluminum atoms, the lower the negative charge density of the framework, the reduced hydrophilicity, the increased acid strength and the framework collapse temperature of more than 800 ℃. The structural stability and acidity of the catalyst are greatly improved by introducing rare earth ions, the yield of the catalytic cracking gasoline is improved by 10% -20%, and then skeleton aluminum is removed by high-temperature hydrothermal or chemical treatment to generate secondary holes, so that the mass transfer of the molecular sieve in heavy oil macromolecule cracking is faster, and the technology is further broken through. Y-type molecular sieves have been the core component of Fluid Catalytic Cracking (FCC) and hydrocracking catalysts since commercialization. Along with the increasing weight and inferior quality of crude oil, huge colloid and asphaltene molecules in the raw materials are difficult to enter a longer pore canal in the traditional micron-sized crystal (1-6 mu m), the paths of reactants diffusing to an active center and products diffusing out are long, secondary cracking and carbon deposition are extremely easy to cause, the device is forced to be regenerated at high temperature and frequently, and the economic and clear oil yield is reduced. It was found that after the grain size was reduced, a significant nonlinear change in its physicochemical properties occurred. The stacking of the small-grain molecular sieve generates abundant intergranular mesopores, provides a rapid channel for macromolecules, and simultaneously increases the active sites directly exposed on the outer surface, so that the macromolecules can react at the inlet. The crystal grain is reduced, the diffusion time is shortened, the hydrogen transfer reaction is greatly inhibited, and the yield of olefin can be improved. In the rapid nucleation growth process of small grains, the framework is easy to generate more defects, which often means that more acid centers are exposed, and the subsequent modification is facilitated. In the prior art, chinese patent application CN121536943A discloses a method for synthesizing a nano flaky NaY molecular sieve, which utilizes high-speed shearing to mix and disperse materials, synthesizes the nano flaky NaY molecular sieve under the condition of no template agent, has strict performance requirements on high-rotating-speed equipment, has a limited bottleneck in industrialization in equipment failure rate and long-time stable operation, and has limited advantages in the subsequent catalysis process. In view of the specificity and performance advantages of the small-grain molecular sieve, the development of a production method which has low cost, short production process and capability of mass industrialization is very important. Disclosure of Invention The invention aims to develop a preparation method of a small-grain Y-type molecular sieve with low cost and short production process by deep utilization of small-grain seed crystals. The technical scheme adopted for solving the technical problems is as follows: The seed crystal for preparing the small-grain Y-type molecular sieve comprises raw materials including sodium aluminate, sodium silicate, sodium hydroxide and deionized water, wherein the mass ratio of silicon dioxide to aluminum oxide in the raw materials is 15.5-16.5:1, the mass ratio of sodium oxide to silicon dioxide in the raw materials is 0.75-0.79:1, and the mass ratio of water to silicon dioxide in the raw materials is 13.5-13.9:1. Further, the molar ratio of the silica to the alumina in the raw material is 16:1, the molar ratio of the sodium oxide to the silica in the raw material is 0.78:1, and the molar ratio of the water molecules to the silica in the raw material is 13.75:1. Further, the concentration of the sodium aluminate solution is 18.5% -27%, the concentration of the sodium silicate solution is above 27%, and the concentration of the sodium hydroxide solution is more than 48%. The invention aims to prepare a small-grain Y-type molecular sieve, which comprises the following steps: calculating the required quality of various raw materials according to a certain proportion according to the raw material analysis index; dropping sodium aluminate solution into sodium silicate solution through a separating funnel, controlling dropping speed, and ensuring good fluidity of a reaction system; adding aluminum sulfate and part of deionized water into a reaction system, uniformly stirring and heating to 96 ℃; Adding the