CN101214974A

CN101214974A - Method for preparing small crystal grain SAPO-34 molecular screen

Info

Publication number: CN101214974A
Application number: CNA2007100602970A
Authority: CN
Inventors: 李伟; 关庆鑫; 王小野; 唐珺; 李春刚; 张明慧; 陶克毅
Original assignee: TIANJIN CHEMIST SCIENTIFIC Ltd; Nankai University
Current assignee: TIANJIN CHEMIST SCIENTIFIC Ltd; Nankai University
Priority date: 2007-12-29
Filing date: 2007-12-29
Publication date: 2008-07-09
Anticipated expiration: 2027-12-29
Also published as: CN101214974B

Abstract

The invention provides a process for preparing SAPO-34 molecular sieve with small crystals, which is the process for rapidly synthesizing SAPO-34 molecular sieve with small crystals under the condition of ultrasonic wave ageing. The SAPO-34 molecular sieve with small crystals prepared through the invention can be rapidly synthesized in a comparatively short time, and the synthesized molecular sieve is uniform in dispersion. The crystal size of the invention is about one half of that of SAPO-34 molecular sieve prepared by the conventional hydrothermal method. Simultaneously, the crystallization temperature and pressure of the molecular sieve synthesized by the hydrothermal method are reduced, which enables the process for preparation can be widely applied in industrial production. The molecular sieve can be used in reaction of preparing light olefins, such as ethylene, propylene and the like from conversion of methanol.

Description

A kind of method for preparing fine grain SAPO-34 molecular sieve

Technical field

The present invention relates to a kind of method for preparing fine grain SAPO-34 molecular sieve, utilizes the ultrasonic wave burin-in process to prepare the method for fine grain SAPO-34 molecular sieve before a kind of crystallization of saying so more specifically.

Background technology

Along with the development of society, industrial production all departments also increase considerably basic material and demand for energy.Oil crisis and environmental protection need make petrochemical industry begin to seek new environmental friendliness substitute energy.Sweet natural gas is because reserves are abundant, and is pollution-free and gain great popularity, but is distributed in remote districts at China's majority, and it effectively utilizes the region constraint very big.Utilize the huge advance made in field to make in the construction of natural gas fields in recent years, and then people focus onto through methyl alcohol or dme and produce on the low-carbon alkene via Sweet natural gas-synthetic gas-methyl alcohol or dme technology comparative maturity.By the synthetic alkene of natural gas via methyl alcohol is an external in recent years important petrochemical complex novel process of developing.

Methanol-to-olefins (Methanol To Olefin, be called for short MTO) process provides one not rely on the synthesizing ethylene of oil and the approach of propylene, and this synthetic method can be in the ratio of regulating ethene and propylene in the product in a big way, to satisfy the demand in market.And methyl alcohol can be by some carbonaceous raw materials, as: these materials that can not be converted into ethene and propylene of coal, petroleum residue, Sweet natural gas or the like are made synthetic gas earlier, are made by synthetic gas again.In numerous MTO molecular sieve catalysts, SAPO-34 the active and selectivity of low-carbon alkene is considered to best.The SAPO-34 non-zeolite molecular sieve is a kind of crystallization silicoaluminophosphates of U.S. UCC company development in 1984, and its similar chabazite has the three dimensional intersection duct, and the aperture is 0.43nm, belongs to isometric system.Its octatomic ring passage of selecting shape by force can suppress the generation of aromatic hydrocarbons.In addition, ZSM-5 is little for its aperture ratio, the cell densities height, and available specific surface is big, so the speed of response of MTO is very fast.SAPO-34 has absorption property preferably, and intracrystalline saturation water pore volume is 0.3ml/g.The thermostability of SAPO-34 and hydrothermal stability are very high, and its skeleton avalanche temperature is at 1000 ℃; In 20% water vapor, processing still can keep crystalline structure under 600 ℃ of temperature.The thermostability of SAPO-34 and hydrothermal stability are very important for fluidized-bed successive reaction-regenerative operation of MTO.

Summary of the invention

The invention provides a kind of method for preparing fine grain SAPO-34 molecular sieve, it is the method for quickly synthesizing small-crystallite SAPO-34 molecular sieve under the ultrasonic wave aging condition.This molecular sieve can be used for the reaction that methanol conversion prepares low-carbon alkenes such as ethene, propylene.

Characteristics of the present invention are that prepared fine grain SAPO-34 molecular sieve is can be in the short period of time synthetic fast, and the synthetic molecular sieve is uniformly dispersed, and grain size is about 1/2nd of the prepared SAPO-34 molecular sieve size of traditional hydrothermal method.Reduce the crystallization temperature and the pressure of hydrothermal method synthesis of molecular sieve simultaneously, made this preparation method in industrial production, to be used widely.

The synthesis step of molecular sieve is as follows:

At first under certain temperature (5～80 ℃) whipped state, quantitative phosphoric acid (content is 60～85%) is joined in the deionized water, add a certain amount of pseudo-boehmite (Al then ₂O ₃Content 50～75%), stir certain hour.Treat that pseudo-boehmite slowly adds a certain amount of alkaline silica sol (SiO after dissolving fully ₂ Content 10～30%), certain ultrasonic frequency (1～99W) and temperature (5～80 ℃) continue down to stir certain hour (0.5～24h), make that solution is fully aging and disperse.Close ultrasonicly then, add a certain amount of triethylamine (content 75～99%) lentamente, continue to stir certain hour afterwards and make the solution gel.Then solution is placed the high pressure crystallizing kettle of poly-tetrafluoro liner, crystallizing kettle is put into thermostatic drying chamber, at a certain temperature (120～250 ℃) the crystallization regular hour (12～72h).Treat to take out crystallizing kettle when high pressure crystallizing kettle temperature is reduced to room temperature, product water is washed till neutrality,, put into the SAPO-34 molecular sieve that retort furnace (450～650 ℃) roasting (1～8 hour) obtains white afterwards then at the thermostatic drying chamber inner drying.

Described phosphoric acid is that content is 85% analytical pure ortho-phosphoric acid.Described pseudo-boehmite Al ₂O ₃Content is 75%.Described silicon sol is SiO ₂Content is 30% alkaline silica sol.Described triethylamine is an analytical reagent content 99%.

Adopt synthetic fine grain SAPO-34 molecular sieve of the present invention through XRD, characterization methods such as SEM confirm that the synthetic SAPO-34 of institute zeolite crystal is little, and grain-size is between 0.5～1.5 μ m.Accompanying drawing 1 is the traditional hydrothermal method X-ray powder diffraction figure at 48 hours synthetic SAPO-34 of 165 ℃ of following crystallization, has proved that the synthetic product is the SAPO-34 of pure phase.Accompanying drawing 2 is at the X-ray powder diffraction figure of ultrasonic wave 24 hours synthetic SAPO-34 of 165 ℃ of following crystallization after aging 2 hours, can prove that thus the synthetic product is the SAPO-34 of pure phase.Accompanying drawing 3 is at the X-ray powder diffraction figure of ultrasonic wave 48 hours synthetic SAPO-34 of 165 ℃ of following crystallization after aging 2 hours, can prove that thus the synthetic product is the SAPO-34 of pure phase.Accompanying drawing 4 is scanning electron microscope (SEM) photos of 48 hours synthetic synthetic of 165 ℃ of following crystallization of traditional hydrothermal method SAPO-34, by stereoscan photograph as can be seen the grain-size of synthetic SAPO-43 at 2～5 μ m.Accompanying drawing 5 is scanning electron microscope (SEM) photos at ultrasonic wave 24 hours synthetic SAPO-34 of 165 ℃ of following crystallization after aging 2 hours, by stereoscan photograph as can be seen the grain-size by synthetic SAPO-34 of the present invention between 0.5～1.5 μ m.Particle diameter than traditional hydrothermal method synthetic SAPO-34 molecular sieve reduces half, and crystallization time also shortens a lot.

Description of drawings

Accompanying drawing 1 is the traditional hydrothermal method X-ray powder diffraction figure at 48 hours synthetic SAPO-34 of 165 ℃ of following crystallization.

Accompanying drawing 2 is the X-ray powder diffraction figure at ultrasonic wave 24 hours synthetic SAPO-34 of 165 ℃ of following crystallization after aging 2 hours.

Accompanying drawing 3 is the X-ray powder diffraction figure at ultrasonic wave 48 hours synthetic SAPO-34 of 165 ℃ of following crystallization after aging 2 hours.

Accompanying drawing 4 is scanning electron microscope (SEM) photos of 48 hours synthetic synthetic of 165 ℃ of following crystallization of traditional hydrothermal method SAPO-34.

Accompanying drawing 5 is scanning electron microscope (SEM) photos at ultrasonic wave 24 hours synthetic SAPO-34 of 165 ℃ of following crystallization after aging 2 hours.

Embodiment

The present invention can describe in detail by embodiment, but they are not that the present invention is imposed any restrictions.In these embodiments, XRD is measured by Japan's D/MAX-2500 type of science x-ray diffractometer; SEM adopts day island proper Tianjin SHIMADZU ss-550 of company scanning electronic microscope.

These embodiment have illustrated the building-up process of fine grain SAPO-34.

Embodiment 1

At first under the state of 40 ℃ of stirrings, the phosphoric acid (concentration is 85% analytical pure ortho-phosphoric acid) of 5.1ml is joined in the deionized water of 27.0ml, stir the pseudo-boehmite (Al that add 5.1 grams after the 5min ₂O ₃Content is 75%), stirred 30 minutes.Treat that pseudo-boehmite dissolves the silicon sol (SiO that slowly adds 9.2ml afterwards fully ₂Content is 30% alkaline silica sol), the unlatching ultrasonic power is 99W, continues to stir 2 hours under ultransonic condition, makes solution fully wear out and dispersion.Close ultrasonic wave then, add the triethylamine (analytical reagent content 99%) of 16.5ml lentamente, continue stirring afterwards and made the solution gel in 2 hours.Then solution is placed the high pressure crystallizing kettle of poly-tetrafluoro liner, crystallizing kettle was put into 165 ℃ of thermostatic crystallizations of thermostatic drying chamber 24 hours.Take out reactor when treating that high pressure crystallizing kettle temperature is reduced to room temperature, product water is washed till neutrality, 120 ℃ of dryings 3 hours in thermostatic drying chamber are put into 550 ℃ of roastings of retort furnace afterwards and were obtained white SAPO-34 molecular sieve in 3 hours then.The ratio of its principal element is Al: P: Si=2: 2: 1. 5, and the products molecule sieve that obtains is named as A, need be kept under the exsiccant condition.

A has the feature of accompanying drawing 2, accompanying drawing 5.

Embodiment 2

Preparation process with molecular sieve-4 A is the same, and the consumption that changes silicon sol is 4.6ml, and can prepare Al: P: Si=2 under the constant situation of other condition: 2: 0.75 SAPO-34 molecular sieve, the products molecule sieve is named as B.

Embodiment 3

Preparation process with molecular sieve-4 A is the same, and the consumption that changes silicon sol is 6.1ml, and can prepare Al: P: Si=2 under the constant situation of other condition: 2: 1 SAPO-34 molecular sieve, the products molecule sieve is named as C.

Embodiment 4

Preparation process with molecular sieve-4 A is the same, and changing crystallization time is 48 hours, and can prepare Al: P: Si=2 under the constant situation of other condition: 2: 1.5 SAPO-34 molecular sieve, the products molecule sieve is named as D.D has the feature of accompanying drawing 3.

Embodiment 5

Preparation process with molecular sieve-4 A is the same, and the consumption that changes silicon sol is 12.2ml, and can prepare Al: P: Si=2 under the constant situation of other condition: 2: 2 SAPO-34 molecular sieve, the products molecule sieve is named as E.

Claims

1. the invention provides a kind of method for preparing fine grain SAPO-34 molecular sieve, it is the method for quickly synthesizing small-crystallite SAPO-34 molecular sieve under the ultrasonic wave aging condition.This molecular sieve can be used for the reaction that methanol conversion prepares low-carbon alkenes such as ethene, propylene.

The synthesis step of molecular sieve is as follows:

At first under certain temperature (5～80 ℃) whipped state, quantitative phosphoric acid (content is 60～85%) is joined in the deionized water, add a certain amount of pseudo-boehmite (Al then ₂O ₃Content 50～75%), stir certain hour.Treat that pseudo-boehmite slowly adds a certain amount of alkaline silica sol (SiO after dissolving fully ₂Content 10～30%), certain ultrasonic frequency (1～99W) and temperature (5～80 ℃) continue down to stir certain hour (0.5～24h), make that solution is fully aging and disperse.Close ultrasonicly then, add a certain amount of triethylamine (content 75～99%) lentamente, continue to stir certain hour afterwards and make the solution gel.Then solution is placed the high pressure crystallizing kettle of poly-tetrafluoro liner, crystallizing kettle is put into thermostatic drying chamber, at a certain temperature (120～250 ℃) the crystallization regular hour (12～72h).Treat to take out crystallizing kettle when high pressure crystallizing kettle temperature is reduced to room temperature, product water is washed till neutrality,, put into the SAPO-34 molecular sieve that retort furnace (450～650 ℃) roasting (1～8 hour) obtains white afterwards then at the thermostatic drying chamber inner drying.

2. according to the described phosphorus acid content of claim 1 60～85% ortho-phosphoric acid, preferred 85% analytical pure ortho-phosphoric acid.

3. be Al according to the described pseudo-boehmite of claim 1 ₂O ₃Content is 50～75%, preferred 75% pseudo-boehmite.

4. be SiO according to the described silicon sol of claim 1 ₂Content is 10～30% alkaline silica sol, preferred 30% alkaline silica sol.

5. be 75～99% according to the described triethylamine content of claim 1, preferred content is 99% analytical reagent.

6. the little crystal grain SAPO-43 of claim 1 synthetic molecular sieve can be used for the reaction of preparing light olefins from methanol.