CN-117945425-B - Modified small-grain Y molecular sieve and preparation method and application thereof

Abstract

The invention relates to a modified small-grain Y molecular sieve, a preparation method and application thereof, wherein the preparation method comprises the following steps of (1) mixing a small-grain NaY molecular sieve, a phosphorus source and water according to the weight ratio of NaY to P 2 O 5 :1 (0.01-0.15) to 8-10, performing first exchange on an obtained first material at the temperature of below 100 ℃ to obtain a phosphorus-containing small-grain Y molecular sieve, and (2) mixing the phosphorus-containing small-grain Y molecular sieve and a rare earth source solution according to the weight ratio of NaY to RE 2 O 3 :1 (0.16-0.3), and performing second exchange on an obtained second material at the temperature of 120-240 ℃. The preparation method improves the hydrothermal stability of the small-grain Y molecular sieve, and avoids the phenomenon that the framework of the molecular sieve is dealuminized or collapsed easily when the rare earth migrates to a small cage of the small-grain molecular sieve by adopting a conventional roasting method.

Inventors

• WANG WEIJIA
• MAN ZHENG
• ZHANG XIAOXIN

Assignees

• 中国石油化工股份有限公司
• 中石化石油化工科学研究院有限公司

Dates

Publication Date

20260505

Application Date

20221031

Claims (11)

1. 1. The preparation method of the modified small-grain Y molecular sieve is characterized by comprising the following steps of: (1) Mixing a small-grain NaY molecular sieve, a phosphorus source and water according to the weight ratio of NaY to P 2 O 5 :1 (0.01-0.15) to (8-10), and performing first exchange on the obtained first material at the temperature below 100 ℃ to obtain a small-grain Y molecular sieve containing phosphorus, wherein the average grain diameter of the small-grain NaY molecular sieve is 200-700 nm, and the specific surface area is more than 700cm 2 /g; (2) Mixing the phosphorus-containing small-grain Y molecular sieve with a rare earth source solution according to the weight ratio of NaY:RE 2 O 3 =1 (0.16-0.3), carrying out second exchange on the obtained second material under the high-temperature hydrothermal condition at 120-240 ℃, and not roasting the product of the second exchange to obtain a modified small-grain Y molecular sieve; The modified small-grain Y molecular sieve comprises phosphorus and rare earth elements, wherein the content of Na 2 O is below 1.5wt%, the content of phosphorus is 1-12 wt% in terms of P 2 O 5 , and the content of rare earth elements is 14-21 wt% in terms of RE 2 O 3 based on the total weight of the modified small-grain Y molecular sieve.
2. 2. The method of claim 1, wherein in step (1), the phosphorus source is a water-soluble phosphorus-containing compound.
3. 3. The preparation method according to claim 1, wherein in the step (1), the phosphorus source is an oxyacid of phosphorus and/or an acidic phosphate, the oxyacid of phosphorus comprises one or more of orthophosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid, pyrophosphoric acid, metaphosphorous acid, hypophosphorous acid and polyphosphoric acid, and the acidic phosphate comprises one or more of ammonium phosphate, diammonium phosphate and monoammonium phosphate.
4. 4. The method according to claim 1, wherein in the step (1), the first exchange condition includes a temperature of 15-100 ℃ and a time of 5-45 min.
5. 5. The method according to claim 4, wherein in the step (1), the first exchange condition comprises a temperature of 60-80 ℃ and a time of 10-30 min.
6. 6. The method according to claim 1, wherein in the step (2), the rare earth source solution contains one or more rare earth sources selected from the group consisting of rare earth chloride, rare earth nitrate and rare earth acetate, and the rare earth elements in the rare earth sources include one or more of La, ce, pr, nd, pm, sm, eu, gd, tb, er, sc and Y.
7. 7. The method according to claim 1, wherein in the step (2), the temperature of the second exchange is 180-200 ℃ and the time is 0.5-2 hours.
8. 8. The method according to claim 1, wherein step (2) further comprises washing and drying the second exchanged product, wherein the drying temperature is 80-150 ℃ and the drying time is 8-24 hours.
9. 9. The preparation method of claim 1, wherein the modified small-grain Y molecular sieve has an average particle size of 200-700 nm.
10. 10. The preparation method according to claim 1, wherein the modified small-grain Y molecular sieve is subjected to an ammonium ion exchange and sodium removal treatment until the content of Na 2 O in the modified small-grain Y molecular sieve is 0.3 wt% or less, and the modified small-grain Y molecular sieve is subjected to an aging treatment in a steam atmosphere of 800 ℃ and 100 vol% for 17 hours, and the specific surface area retention rate of the modified small-grain Y molecular sieve after the aging treatment is 50-70%.
11. 11. Use of the modified small-grain Y molecular sieve prepared by the preparation method of any one of claims 1 to 10 in petroleum catalytic cracking.

Description

Modified small-grain Y molecular sieve and preparation method and application thereof Technical Field The present disclosure relates to molecular sieve technology, and in particular, to a modified small-grain Y molecular sieve, and a preparation method and application thereof. Background The Y-type molecular sieve is widely used as a main active component of petrochemical catalysts. In recent years, with the heavy and poor quality of raw oil, it is important to improve accessibility of active center of oil refining catalyst and raise its macromolecule cracking capability. On the other hand, the small-grain Y molecular sieve has shorter pore canal communicated with the outside, is beneficial to the diffusion of reactants and products, reduces the diffusion resistance, and effectively reduces the reaction depth and coking rate. Therefore, compared with the traditional Y-type molecular sieve, the small-grain Y-type molecular sieve has more excellent catalytic performance and becomes the key point of research and development of novel petrochemical catalytic materials. The conventional Y-type molecular sieve used in catalytic cracking catalysts typically has a crystallite size of about 1000 nm. As the grain size becomes smaller (especially the grain size is smaller than 600 nm), the structural stability is obviously deteriorated, and the framework collapse temperature of the small-grain NaY molecular sieve is obviously reduced. The modified small-grain Y molecular sieve has obviously poor hydrothermal stability and obviously lower micro-reverse activity after hydrothermal aging. The structural characteristics of the small-grain NaY molecular sieve severely restrict the application of the small-grain NaY molecular sieve in a catalytic cracking device with severe hydrothermal regeneration conditions. Patent CN106276961B discloses a modification method for improving the stability of small-grain Y molecular sieve. The method is characterized in that a small-grain NaY molecular sieve with the grain size of 100-800 nm is contacted with silicon tetrachloride to carry out gas-phase aluminum extraction and silicon supplementation, and rare earth is exchanged after washing to obtain the silicon tetrachloride gas-phase ultrastable small-grain Y molecular sieve containing rare earth. The method is difficult to ensure the uniformity of material contact in the gas-phase superstable process, and has high operation difficulty and high production cost. Patent CN104828840B discloses a modification method of small-grain NaY molecular sieve. According to the method, small crystal grain NaY with the grain size of 200-700 nm is treated by NaOH solution, ammonium is subjected to ammonium exchange and sodium washing, then aluminum is extracted and silicon is supplemented by ammonium fluosilicate liquid phase, then non-framework aluminum is removed by hydrothermal roasting, and then ammonium and sodium chloride are subjected to sodium washing, so that the ultra-stable small crystal grain Y molecular sieve containing secondary holes is obtained and can be used as an active component of hydrocracking. The method has high operation cost, relates to the treatment of fluorine-containing wastewater, and is not beneficial to clean production. Patent CN1907854a discloses a method for preparing small-grain REY with high rare earth content. According to the method, small-grain NaY molecular sieves with the grain diameters of 200-700 nm are exchanged at the temperature of 10-100 ℃ according to the weight ratio of NaY to rare earth=1:0.18-0.38, then the mixture is separated, filtrate is collected, the pH value of the filtrate is regulated to 8-11.2 to obtain rare earth precipitates, water is added into the filtrate to pulp together with a molecular sieve filter cake, then the mixture is filtered, washed and dried, baked at the temperature of 650-850 ℃, and then ammonium-exchanged and washed with sodium to obtain REY molecular sieves with the RE2O3 weight content of 14-21%. The small-grain REY is used as an active component of a catalytic cracking catalyst, and has higher heavy oil conversion capability and higher gasoline yield. Although the method can improve the stability of the small-grain Y molecular sieve by increasing the rare earth loading capacity, the high-temperature roasting process can cause the loss of crystallinity (specific surface) of the small-grain Y molecular sieve. In summary, the current modification method of the small-grain NaY molecular sieve is to directly increase the rare earth loading amount to achieve the purpose of improving the framework stability by extracting aluminum and supplementing silicon from the framework. The aluminum extraction and silicon supplementation can increase the operation difficulty and the production cost, and can bring about the problem of environmental pollution treatment. Rare earth modification is a simple and convenient method which can effectively improve the stability of the small-grain Y