CN111111609A - 5A molecular sieve adsorbent and preparation method and application thereof - Google Patents
5A molecular sieve adsorbent and preparation method and application thereof Download PDFInfo
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- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
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- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
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Abstract
The invention relates to the field of molecular sieve adsorbents, and particularly discloses a 5A molecular sieve adsorbent and a preparation method and application thereof, wherein the 5A molecular sieve adsorbent is characterized in that the average grain diameter of a 5A molecular sieve in the adsorbent is 0.1-3.5 mu m; the content of the 5A molecular sieve in the adsorbent is more than 95 weight percent based on the dry weight of the adsorbent; the breaking rate of the adsorbent under 250N is below 7%. The 5A molecular sieve adsorbent provided by the invention has the advantages of large liquid wax adsorption capacity, good strength and the like, and the preparation method is relatively simple, has little environmental pollution and is suitable for industrial application.
Description
Technical Field
The invention relates to the field of molecular sieve preparation, and particularly relates to a 5A molecular sieve adsorbent and a preparation method and application thereof.
Background
The general energy characteristics of China are rich coal, less oil and gas. Clean utilization of coal and development of coal-to-liquid oil gas substitution are strategic choices for Chinese energy supply guarantee. In recent years, the coal-to-liquid industry in China is developed rapidly, the coal-to-liquid oil product is rich in normal paraffin, the normal paraffin is an important chemical raw material, and adsorption separation by using a molecular sieve is an important production means. The average molecular pore diameter of the 5A molecular sieve is 5A, and the molecular diameter of the n-alkane in the petroleum product and the coal-to-liquid oil product is less than 5A, so that the n-alkane can enter the pore canal of the molecular sieve. And the molecular diameter of other isoparaffin, cyclane and arene is larger than 5A, and the isoparaffin, cyclane and arene can not enter the pore channel, so that the normal paraffin can be separated and adsorbed from the petroleum oil by utilizing the adsorption characteristic of the molecular sieve.
CN87105499A discloses a method for preparing a binderless spherical A-type molecular sieve, which comprises the steps of taking inorganic ammonium salt, inorganic acid and water glass as raw materials, preparing silica hydrogel spheres by an oil column forming method, washing with water, soaking a surfactant, drying and roasting to prepare low-bulk density silica hydrogel spheres, mixing the silica hydrogel spheres with a sodium metaaluminate solution, aging and crystallizing at a certain temperature to basically convert silica into a 4A molecular sieve, and then converting the silica into a 5A molecular sieve by calcium exchange. However, the method brings about two kinds of pollution in the production process, the generated pollution is difficult to treat, particularly, ammonia nitrogen sewage which is difficult to treat is generated by using inorganic ammonium salt, and the COD of the sewage exceeds the standard due to the use of the surfactant.
CN103933932A discloses a method for preparing a 5A adsorbent by a rolling ball method, which comprises the steps of rolling ball forming powder containing a 4A molecular sieve and a binder, drying and roasting to obtain a matrix pellet, prewetting the matrix pellet, and then carrying out crystal transformation, calcium exchange, drying and roasting to obtain the 5A molecular sieve adsorbent. However, the method still has a large lifting space in the aspects of crystal transformation, adsorbent activation and the like, and is particularly seriously insufficient in the aspect of liquid wax adsorption.
Disclosure of Invention
The invention aims to overcome the problem that the existing molecular sieve adsorbent is insufficient in liquid wax adsorption capacity, and provides a 5A molecular sieve adsorbent and a preparation method and application thereof.
In order to achieve the above object, the first aspect of the present invention provides a 5A molecular sieve adsorbent, wherein the 5A molecular sieve in the adsorbent has an average crystal grain diameter of 0.1 to 3.5 μm; the content of the 5A molecular sieve in the adsorbent is more than 95 weight percent based on the dry weight of the adsorbent; the breaking rate of the adsorbent under 250N is below 7%.
In a second aspect, the present invention provides a process for preparing a 5A molecular sieve adsorbent, the process comprising:
(1) rolling ball molding is carried out on powder containing the 4A molecular sieve and a binder source to obtain small balls, and the small balls with the granularity of 0.35-0.7mm are sieved;
(2) drying and roasting the pellets to obtain matrix pellets;
(3) prewetting the substrate pellets, and then carrying out low-temperature crystal transformation to ensure that the binder in the substrate pellets is basically transformed into the 4A molecular sieve, so as to obtain 4A molecular sieve pellets;
(4) washing the 4A molecular sieve beads with water, and then performing calcium exchange to obtain 5A molecular sieve beads; and washing the 5A molecular sieve balls with water, and then drying and vacuum roasting.
In a third aspect, the present invention provides a 5A molecular sieve adsorbent prepared by the method of the present invention.
In a fourth aspect, the invention provides an application of a 5A molecular sieve adsorbent in liquid wax adsorption separation.
The preparation method has the advantages of relatively simple process and little environmental pollution, and the prepared 5A molecular sieve adsorbent has the advantages of large adsorption capacity of liquid wax (especially n-tetradecane), good strength and the like.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides a 5A molecular sieve adsorbent, wherein the average grain diameter of a 5A molecular sieve in the adsorbent is 0.1-3.5 mu m; the content of the 5A molecular sieve in the adsorbent is more than 95 weight percent based on the dry weight of the adsorbent; the breaking rate of the adsorbent under 250N is below 7%.
In a preferred embodiment of the present invention, in order to further increase the adsorption amount of the adsorbent, it is preferable that the 5A molecular sieve has an average crystal grain diameter of 0.5 to 2.5 μm; the content of the 5A molecular sieve in the adsorbent is 97-99 wt% based on the dry weight of the adsorbent; the breaking rate of the adsorbent under 250N is 4-7%.
Specific examples of the content of the 5A molecular sieve in the adsorbent include, based on the dry weight of the adsorbent: 95 wt%, 96 wt%, 96.5 wt%, 96.6 wt%, 96.8 wt%, 96.9 wt%, 97.0 wt%, 97.1 wt%, 97.2 wt%, 97.5 wt%, 97.7 wt%, 97.9 wt%, 98.1 wt%, 98.3 wt%, 98.5 wt%, 98.8 wt%, or 99 wt%, etc.
Specific examples of the breakage rate of the adsorbent at 250N include: 7%, 6.5%, 6.3%, 6.1%, 5.9%, 5.8%, 5.7%, 5.6%, 5.5%, 5.2%, 5%, 4.5%, 4.2%, or 4%, etc.
According to the present invention, in order to further increase the adsorption amount of the 5A molecular sieve adsorbent to the normal alkane, n (SiO) in the molecular sieve is preferred2)/n(Al2O3) The molar ratio is 1.92-2.2.
According to the invention, the adsorbent preferably has a fraction of molecular sieve crystallites of from 0.44 to 0.68 of more than 50% by weight.
In the present invention, it is preferable that the adsorbent is spherical.
In the present invention, the diameter of the sphere is preferably 0.1 to 0.7mm, more preferably 0.1 to 0.3mm, and still more preferably 0.1 to 0.25 mm.
According to the invention, the total pore volume of the adsorbent is preferably 0.3cm3More preferably 0.3 to 0.36 cm/g or more3/g。
In the present invention, it is preferable that the adsorbent has a specific surface area of more than 500m2/g。
According to the present invention, the n-tetradecane adsorbing amount of the adsorbent is preferably 110mg/g or more, more preferably 114-125 mg/g.
The adsorbent with the technical characteristics can be prepared by any preparation method, for example, in order to prepare a spherical adsorbent, the adsorbent can be prepared by rolling ball forming, dropping ball forming, die pressing forming and other technologies, rolling ball forming is preferably adopted for the invention, and the adsorbent can be prepared by the following steps:
(1) rolling ball molding is carried out on powder containing the 4A molecular sieve and a binder source to obtain small balls, and the small balls with the granularity of 0.35-0.7mm are sieved;
(2) drying and roasting the pellets to obtain matrix pellets;
(3) prewetting the substrate pellets, and then carrying out low-temperature crystal transformation to ensure that the binder in the substrate pellets is basically transformed into the 4A molecular sieve, so as to obtain 4A molecular sieve pellets;
(4) washing the 4A molecular sieve beads with water, and then performing calcium exchange to obtain 5A molecular sieve beads; and washing the 5A molecular sieve balls with water, and then drying and vacuum roasting.
According to the method of the present invention, the above technical solutions can achieve the object of the present invention, and in order to further increase the n-alkane adsorption capacity of the prepared 5A molecular sieve adsorbent, the average grain diameter of the 4A molecular sieve in step (1) is preferably 0.2 to 2.1 μm, and more preferably 0.5 to 1 μm.
According to the method of the present invention, the methanol adsorption amount of the 4A molecular sieve in the step (1) is preferably 190mg/g, more preferably 190mg/g and 170-.
According to the method of the present invention, in order to further increase the adsorption amount of normal alkane in the prepared 5A molecular sieve adsorbent, it is preferable that the pellets having a particle size of 0.4 to 0.6mm are sieved in the step (1).
In the present invention, the crystal transformation is a crystal transformation technique well known to those skilled in the art, and specifically refers to the conversion of a binder into a 4A molecular sieve by subjecting a matrix pellet containing the binder to an alkali treatment.
According to the method of the present invention, the method of subjecting the pre-wetted substrate beads to the transcrystallization in step (3) may be selected with reference to the prior art, and various transcrystallization methods of the prior art may be used in the present invention. For the present invention, it is preferable that the pre-wetted matrix beads are transcrystallized in step (3) so that 80 wt% or more of the binder in the matrix beads is converted into 4A molecular sieve, and it is more preferable that the pre-wetted matrix beads are transcrystallized so that 90 wt% or more of the binder in the matrix beads is converted into 4A molecular sieve.
For the present invention, preferably, the crystal transformation is performed as follows: contacting the prewetted substrate beads with an aqueous sodium hydroxide solution under conditions comprising: the concentration of the sodium hydroxide aqueous solution is 0.1-0.25mol/L, the volume ratio of the sodium hydroxide aqueous solution to the prewetted substrate pellets is 1-9:1, the contact temperature is 5-50 ℃, and the contact time is 1-10 h; more preferably, the conditions of the contacting include: the concentration of the sodium hydroxide aqueous solution is 0.13-0.15mol/L, the volume ratio of the sodium hydroxide aqueous solution to the prewetted substrate pellets is 2-3:1, the contact temperature is 20-40 ℃, and the contact time is 3-6 h.
According to the method of the present invention, in order to further increase the n-alkane adsorption amount of the finally prepared 5A molecular sieve adsorbent, the water content in the substrate beads after the substrate beads are pre-wetted in step (3) is preferably 17 wt% or more, and more preferably 18 to 23 wt%.
According to the method of the present invention, the method of the present invention has no special requirement, as long as the water content in the substrate pellet after the pre-wetting is ensured to be more than 17 wt%, the pre-wetting method of the prior art can be used in the present invention, and for the present invention, the pre-wetting in the step (3) is preferably performed as follows: putting the substrate pellets in a humid environment for sectional pre-wetting, wherein the pre-wetting humidity of the first section is 1-60% RH, and the pre-wetting time is 20-30 h; the pre-wetting humidity of the second stage is 60-100% RH, and the pre-wetting time is 10-20 h. Wherein, RH refers to relative humidity, in particular to the percentage of the water vapor amount contained in the air in the environment and the saturated water vapor amount contained in the air under the same condition; more preferably the first stage pre-wet humidity is 20-30% RH; the second stage pre-wetting humidity is 80-90% RH.
According to the method of the invention, preferably, in the step (1), the powder material containing the 4A molecular sieve and the binder source further contains a pore-forming agent, and preferably, the pore-forming agent is one or more of lignin, sodium cellulose, starch and sesbania powder. The bulk ratio of the 5A molecular sieve adsorbent can be adjusted by adding pore-forming agent into the powder.
According to the method of the present invention, the selectable ranges of the contents of the 4A molecular sieve and the binder source in the powder are wide, and in particular, the method can be performed with reference to the prior art, and for the present invention, in a preferred embodiment of the present invention, the content of the 4A molecular sieve in the powder is preferably 90 to 99 wt%, the content of the binder source is preferably 0.5 to 9 wt%, and the content of the pore-forming agent is preferably 0.1 to 8 wt%.
In the present invention, the process for preparing the powder containing the 4A molecular sieve and the binder (or further containing the auxiliary agent) can be performed according to the prior art, for example, 4A molecular sieve powder, the binder powder and the auxiliary agent powder can be mixed in a mixer (for example, a twin-screw mixer) for 1-5 h. As will be appreciated by those skilled in the art, the present invention is not described in detail herein.
In the method of the present invention, the variety of the binder source is wide, and the binder (for example, clay and/or silica alumina) in the binder source capable of being converted into the 4A molecular sieve by crystal transformation can be used in the present invention, and for the present invention, it is preferable that the binder source in the step (1) is one or more of kaolin, sodium metaaluminate, bentonite and diatomaceous earth.
According to the method of the present invention, it is preferable that the calcium exchange in step (4) is carried out as follows: contacting the washed 4A molecular sieve beads with an aqueous solution of calcium chloride under the conditions comprising: the concentration of the calcium chloride aqueous solution is 0.1-1.2mol/L, the volume ratio of the calcium chloride aqueous solution to the 4A molecular sieve balls after washing is 1-9:1, the contact temperature is 50-150 ℃, and the contact time is 1-16 h; more preferably, the conditions of the contacting include: the concentration of the calcium chloride aqueous solution is 0.5-0.6mol/L, the volume ratio of the calcium chloride aqueous solution to the 4A molecular sieve balls after washing is 2-3:1, the contact temperature is 95-99 ℃, and the contact time is 3-5 h.
The invention does not require special vessels for the calcium exchange according to the method of the invention, and can be carried out, for example, in a tank vessel or a column vessel, it being preferred for the invention that the calcium exchange is carried out in a column vessel.
According to the method of the present invention, the drying in step (4) may be performed by referring to the prior art, wherein the drying may be microwave drying, which is well known in the art, and the description of the present invention is omitted herein.
According to the method of the present invention, the method of vacuum roasting the 5A molecular sieve beads in the step (4) may be performed with reference to the prior art, however, in the research process of the present inventors, it is found that if the 5A molecular sieve beads are roasted under a certain inert atmosphere pressure and in a flowing state, moisture precipitated in the process of roasting the 5A molecular sieve beads can be rapidly taken away, so that the damage of high temperature water vapor to the 5A molecular sieve structure can be effectively avoided. Therefore, for the present invention, it is preferable that the 5A molecular sieve pellets in step (4) are calcined under an inert atmosphere pressure and in a flowing state, and the calcination condition is such that the water content of the calcined 5A molecular sieve pellets is 2 wt% or less. In the invention, the water content of the 5A molecular sieve adsorbent is expressed by 580 ℃, and the ignition loss after 1.5h is, namely the ratio of the mass loss of the ignited 5A molecular sieve adsorbent to the mass of the 5A molecular sieve adsorbent before ignition.
In the method of the present invention, it is preferable that the calcination conditions in the step (4) include: the roasting temperature is 200-; more preferably, the firing conditions include: the roasting temperature is 250-350 ℃, the roasting time is 2-3h, and the vacuum degree is- (90-100) KPa.
The roasting equipment capable of meeting the roasting conditions is a vacuum roasting furnace.
According to the method of the invention, the invention has no special requirements on the operating conditions of the vacuum roasting furnace as long as the object of the invention is achieved, and for the invention, the volume of the vacuum roasting furnace is preferably 0.1-18m3More preferably 1 to 2.8m3。
The method of the present invention may further comprise shaping the pellets obtained in step (1) before drying the pellets (also commonly referred to in the art as a polishing treatment), as required.
The shaping (also called polishing) in the invention refers to the steps of placing the small balls in a shaping machine, and after starting the equipment, the small balls are rubbed, blown to boil, extruded and ground in the shaping machine to ensure that the inner parts of the small balls become denser and the surfaces of the small balls become smoother. The method can be specifically realized as follows: a certain amount of small balls are placed in a shaping machine, the shaping machine is started at a low speed, and the small balls run at a high speed after being pretreated, which can be known by the skilled person and is not described herein again.
In the present invention, the drying and baking methods in step (2) may be performed by referring to the prior art, wherein the drying may be performed by the drying method of microwave drying as described above, and the baking may be performed by the baking method of a vacuum baking furnace as described above.
In the present invention, the purpose of washing the 4A molecular sieve beads in step (4) is mainly to remove free sodium ions by water washing, and the purpose of washing the 5A molecular sieve beads is mainly to remove chloride ions by water washing, which can be known to those skilled in the art, and the present invention is not described herein again, and is not emphasized in the specific embodiments of the present invention.
In the preparation process of the invention, a surfactant is not needed and ammonia nitrogen wastewater is not discharged, thereby effectively realizing clean production. Therefore, the method is very suitable for industrial application.
The invention provides a 5A molecular sieve adsorbent prepared by the method.
The invention provides application of the 5A molecular sieve adsorbent in liquid wax adsorption separation.
In the present invention, the calcium exchange rate refers to the percentage of sodium ions in the molecular sieve that are replaced by calcium ions, as measured by the method of the industry standard Q/SH 349550.
In the invention, the average grain diameter is measured by adopting a scanning electron microscope observation method.
The molecular sieve content of the adsorbents was tested according to the test method specified in ASTM D5357-2003(2008) e 1.
The spherical diameter is measured with a vernier caliper and directly read.
The total pore volume is determined according to the test method specified in GB/T5816-1995.
The breaking rate of the adsorbent under 250N is determined by loading about 1.5 ml of adsorbent into a stainless steel cylinder by a DL-II type particle strength tester (produced by large chemical research and design institute), naturally saturating with air, and weighing with a 297 micron sieve. During measurement, a thimble in interference fit with the stainless steel cylinder is installed, the adsorbent is poured out after being pressed once under preset pressure, the adsorbent is weighed by a sieve of 297 micrometers, and the breakage rate of the adsorbent under the set pressure is calculated according to the reduction of the adsorbent.
Example 1
(1) Putting 440kg of commercially available 4A molecular sieve raw powder (with the water content of 21 wt%, the average grain diameter of 0.6 mu m, the methanol adsorption capacity of 182mg/g), 20kg of kaolin (with the water content of 22 wt%) and 10kg of sesbania powder pore-forming agent into a double-screw mixer for mixing for 3h, taking out 50kg of the mixed material, putting into a rolling ball pot (sugar coating pot) with the caliber of 1.2m, carrying out rolling ball forming to prepare a small ball (the operating conditions in the rolling ball pot include that the rotating speed is controlled to be 30 r/min, the water adding speed is increased by 3-5 wt% per hour based on the water content of the material, stopping adding water when the final water content of the material reaches 45-50 wt%, then keeping the rotating speed of the rolling ball pot body at 30-40 r/min, continuing rotating for 3-5h), polishing for 1-2h when the ball grows to be 0.3-1.0mm in diameter, obtaining small balls with the granularity of 0.35-0.7mm by screening, according to the method, carrying out ball rolling forming in a ball rolling pot with 20 same openings to prepare the small balls, and obtaining 1 ton (the water content is 43 weight percent) of the small balls with the granularity of 0.35-0.7mm by screening;
microwave drying the pellets (the drying condition comprises that the power is 300 kilowatts, and dried purified air (the purified air can be air or inert gas) is used in the drying process to take away a large amount of water vapor generated in the drying process, the dew point of the purified air is controlled to be about 0 ℃, and the air amount of the purified air is controlled to be about 800m3H), reducing the water content of the pellets to below 18 mass%, and then feeding the pellets into a mesh belt furnace for roasting (roasting conditions include: the temperature is 550-560 ℃, and the time is 2.2h), and finally the substrate pellet (the water content is 2.3 weight percent) is obtained;
(2) placing the substrate pellets in a pre-wetting room with the air humidity of 20% RH, standing for 20h, increasing the air humidity to 80% RH, and standing for 15h to make the water content reach 20 wt%; then feeding the pre-wetted substrate pellets into a synthesis kettle to contact with a sodium hydroxide aqueous solution for crystal transformation treatment (wherein the volume ratio of the sodium hydroxide aqueous solution to the pre-wetted substrate pellets is 2.5:1, the concentration of the sodium hydroxide aqueous solution is 0.13mol/L, the temperature is 30 ℃, and the time is 3 hours), so that most of the binder is converted into the 4A molecular sieve (about 80 wt% of the binder is converted into the 4A molecular sieve), and obtaining the 4A molecular sieve pellets;
(3) washing the 4A molecular sieve beads with water to remove free sodium ions, then feeding the washed 4A molecular sieve beads into a column reactor to contact with a calcium chloride aqueous solution to perform calcium ion exchange, wherein the concentration of the calcium chloride aqueous solution is 0.55mol/L, the volume ratio of the calcium chloride aqueous solution to the washed 4A molecular sieve beads is 2:1, the contact time is 3.5h, the contact temperature is 95 ℃, the steps can be repeated for several times, and finally the calcium exchange rate of the 4A molecular sieve beads reaches 90%, so that 5A molecular sieve beads are obtained; then washing the 5A molecular sieve beads with water to remove chloride ions, and then carrying out microwave drying (the drying condition comprises that the power is 300 kilowatts, and dried purified air (the purified air can be air or inert gas) is used in the drying process to take away a large amount of water vapor generated in the drying process, so that the water vapor is purifiedThe dew point of the chemical air is controlled at about 0 ℃, and the air purification amount is controlled at 800m3H), reducing the water content of the 5A molecular sieve balls to below 18 wt%; finally, the mixture enters a vacuum activation furnace (chemical mechanical plant of Nanjing chemical industry Co., Ltd. of petrochemical industry, China) for roasting to activate and dehydrate (wherein the volume of the vacuum furnace is controlled to be 2.2m3The temperature is 350 ℃, the vacuum degree is- (90-100) KPa, the roasting time is 2h), 5A molecular sieve pellet adsorbent is obtained (the water content of the adsorbent is 1.9 wt%, the dry weight of the adsorbent is calculated, the content of the 5A molecular sieve is 96.2 wt%, the diameter is 0.1-0.25mm, the average particle size of the adsorbent is 0.16mm, and n (SiO)2)/n(Al2O3) The molar ratio is 2.02, the specific surface area is 519m2The grain size of the molecular sieve is 0.44-0.68, the mass percent of the part is 63.2%, and relevant properties such as the absorption capacity of the n-tetradecane and the like are shown in a table 1).
Example 2
5A molecular sieve adsorbent beads were prepared as in example 1 except that the prewetted air humidity in the second stage was 90% RH and left for 10h to reach a water content of 20 wt%; the other conditions were the same to obtain a 5A molecular sieve pellet adsorbent (water content of adsorbent 2 wt%, based on dry weight of adsorbent, 5A molecular sieve content 96.2 wt%, diameter 0.1-0.3mm, average particle size of adsorbent 0.17mm, n (SiO)2)/n(Al2O3) The molar ratio is 2.02, the specific surface area is 510.2m2The grain size of the molecular sieve is 0.44-0.68, the mass percent of the part is 63.2%, and relevant properties such as the absorption capacity of the n-tetradecane and the like are shown in a table 1).
Example 3
5A molecular sieve adsorbent beads were prepared as in example 1, except that pre-wetted substrate beads were fed into a synthesis kettle and contacted with an aqueous sodium hydroxide solution for a single-step crystal transformation treatment (wherein the volume ratio of the aqueous sodium hydroxide solution to the pre-wetted substrate beads was 2.5, the concentration of the aqueous sodium hydroxide solution was 0.12mol/L, the temperature was 97 ℃, and the contact time was 3 hours), and the other conditions were the same, to obtain a 5A molecular sieve bead adsorbent (the water content of the adsorbent was 1.9 wt%, based on the dry weight of the adsorbent, and the 5A molecular sieve content was 96.2 wt% based on the dry weight of the adsorbent)In an amount% of 0.1-0.3mm in diameter, 0.17mm in average particle diameter of the adsorbent, n (SiO)2)/n(Al2O3) The molar ratio is 2.02, the specific surface area is 514.9m2The grain size of the molecular sieve is 0.44-0.68, the mass percent of the part is 63.2%, and relevant properties such as the absorption capacity of the n-tetradecane and the like are shown in a table 1).
Example 4
A5A molecular sieve adsorbent pellet was prepared as in example 1 except that the temperature of the vacuum furnace was 350 ℃, the degree of vacuum was- (80-90) KPa, the calcination time was 2 hours, and the other conditions were the same to obtain a 5A molecular sieve pellet adsorbent (the adsorbent contained 2 wt% of 5A molecular sieve based on the dry weight of the adsorbent, the content of 5A molecular sieve was 96.2 wt%, the diameter was 0.1-0.25mm, the average particle size of the adsorbent was 0.16mm, and n (SiO)2)/n(Al2O3) The molar ratio is 2.02, the specific surface area is 513.2m2The grain size of the molecular sieve is 0.44-0.68, the mass percent of the part is 63.2%, and relevant properties such as the absorption capacity of the n-tetradecane and the like are shown in a table 1).
Example 5
5A molecular sieve adsorbent beads were prepared as in example 1 except that in step (3) the substrate beads were pre-wetted under conditions such that the pre-wetted substrate beads had a water content of 15.6 wt% and the other conditions were the same to give a 5A molecular sieve bead adsorbent (water content of adsorbent 2 wt%, 5A molecular sieve content 96.2 wt%, diameter 0.1-0.3mm, dry weight basis of adsorbent, average particle size of adsorbent 0.17mm, n (SiO, SiO) was 0.17mm2)/n(Al2O3) The molar ratio is 2.02, the specific surface area is 514m2The grain size of the molecular sieve is 0.44-0.68, the mass percent of the part is 63.2%, and relevant properties such as the absorption capacity of the n-tetradecane and the like are shown in a table 1).
Comparative example 1
The 5A molecular sieve adsorbent beads were prepared according to the method of example 1, except that in step (4) the 5A molecular sieve beads were calcined using a conventional muffle furnace calcination method under conditions including: the temperature was 550 ℃ and the time was 3h, the remaining conditions were the same, to give a 5A molecular sieve bead adsorbent (water content of adsorbent 1.9 wt%, based on dry weight of adsorbent,the 5A molecular sieve content is 96.2 wt%, the diameter is 0.1-0.25mm, the average particle diameter of the adsorbent is 0.16mm, and n (SiO)2)/n(Al2O3) The molar ratio is 2.02, the specific surface area is 507.2m2The grain size of the molecular sieve is 0.44-0.68, the mass percent of the part is 63.2%, and relevant properties such as the absorption capacity of the n-tetradecane and the like are shown in a table 1).
Comparative example 2
5A molecular sieve adsorbent beads were prepared as in example 1 except that substrate beads having a particle size of 0.5 to 1.3mm were obtained by sieving and the 5A molecular sieve beads were calcined in step (4) using a conventional muffle calcination procedure under conditions including: the temperature is 550 deg.C, the time is 3h, and the rest conditions are the same to obtain 5A molecular sieve pellet adsorbent (water content of adsorbent is 1.9 wt%, based on dry weight of adsorbent, 5A molecular sieve content is 96.2 wt%, diameter is 0.5-0.7mm, average particle diameter of adsorbent is 0.56mm, n (SiO)2)/n(Al2O3) The molar ratio is 2.02, the specific surface area is 505.9m2The grain size of the molecular sieve is 0.44-0.68, the mass percent of the part is 63.2%, and relevant properties such as the absorption capacity of the n-tetradecane and the like are shown in a table 1).
TABLE 1
Note: the adsorption process is carried out at room temperature, and the adsorption solution is 16 percent by weight of isooctane binary solution of n-tetradecane. Wherein, the adsorbent: the adsorption solution was 1:2 (weight ratio).
As can be seen from the results in the table, the adsorption amount of n-tetradecane in the 5A molecular sieve adsorbent beads prepared by the method of the present invention is more than 110mg/g, which is much higher than that of the 5A molecular sieve adsorbent beads prepared by the method of the prior art, and the strength of the 5A molecular sieve adsorbent beads of the present invention is much higher than that of the 5A molecular sieve adsorbent beads prepared by the method of the prior art, so that the 5A molecular sieve adsorbent beads prepared by the method of the present invention are particularly suitable for being used as an n-alkane adsorbent.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (19)
1. The 5A molecular sieve adsorbent is characterized in that the average grain diameter of the 5A molecular sieve in the adsorbent is 0.1-3.5 μm; the content of the 5A molecular sieve in the adsorbent is more than 95 weight percent based on the dry weight of the adsorbent; the breaking rate of the adsorbent under 250N is below 7%.
2. The sorbent of claim 1, wherein the 5A molecular sieve has an average grain diameter of 0.5-2.5 μ ι η; the content of the 5A molecular sieve in the adsorbent is 97-99 wt% based on the dry weight of the adsorbent; the breaking rate of the adsorbent under 250N is 4-7%.
3. The adsorbent of claim 1, wherein the molecular sieve is n (SiO)2)/n(Al2O3) The molar ratio is 1.92-2.2;
preferably, the adsorbent has a fraction of molecular sieve crystallites in the range of 0.44 to 0.68 of greater than 50% by weight.
4. The adsorbent of any one of claims 1-3, wherein the adsorbent is spherical;
preferably, the diameter of the sphere is 0.1-0.7 mm.
5. An adsorbent according to any one of claims 1 to 3, wherein the total pore volume of the adsorbent is at 0.3cm3More than g;
preferably, the adsorbent has a specific surface area of more than 500m2/g。
6. The adsorbent according to any one of claims 1 to 3, wherein the adsorbent has an n-tetradecane adsorption amount of 110mg/g or more.
7. A method of preparing a 5A molecular sieve adsorbent, wherein the method comprises:
(1) rolling ball molding is carried out on powder containing the 4A molecular sieve and a binder source to obtain small balls, and the small balls with the granularity of 0.35-0.7mm are sieved;
(2) drying and roasting the pellets to obtain matrix pellets;
(3) prewetting the substrate pellets, and then carrying out crystal transformation to ensure that the binder in the substrate pellets is basically transformed into the 4A molecular sieve, so as to obtain 4A molecular sieve pellets;
(4) washing the 4A molecular sieve beads with water, and then performing calcium exchange to obtain 5A molecular sieve beads; and washing the 5A molecular sieve balls with water, and then drying and vacuum roasting.
8. The process of claim 7, wherein the 4A molecular sieve in step (1) has an average grain diameter of 0.2-2.1 μm, preferably 0.5-1 μm.
9. The method as claimed in claim 7, wherein the methanol adsorption amount of the 4A molecular sieve in the step (1) is 190mg/g, preferably 190mg/g and 180-.
10. The method according to claim 7, wherein the water content in the substrate pellets after prewetting the substrate pellets in step (3) is 17 wt% or more, preferably 18-23 wt%.
11. The method of claim 7, wherein the pre-wetting in step (3) is performed as follows: putting the substrate pellets in a humid environment for sectional pre-wetting, wherein the pre-wetting humidity of the first section is 1-60% RH, and the pre-wetting time is 20-30 h; the pre-wetting humidity of the second stage is 60-100% RH, and the pre-wetting time is 10-20 h.
12. The method of any one of claims 7-11, wherein the pre-wetted substrate pellets are transcrystallized in step (3) such that greater than 90% by weight of the binder in the substrate pellets is converted to 4A molecular sieve.
13. The method according to any one of claims 7-11, wherein the transcrypting is performed as follows: contacting the prewetted substrate beads with an aqueous sodium hydroxide solution under conditions comprising: the concentration of the sodium hydroxide aqueous solution is 0.1-0.25mol/L, the volume ratio of the sodium hydroxide aqueous solution to the prewetted substrate pellets is 1-9:1, the contact temperature is 5-50 ℃, and the contact time is 1-10 h.
14. The method according to any one of claims 7 to 11, wherein the powder comprising the 4A molecular sieve and the binder source in step (1) further comprises a pore former;
preferably, the powder material contains 90-99 wt% of 4A molecular sieve, 0.5-9 wt% of binder source and 0.1-8 wt% of pore-forming agent;
preferably, the binder source is one or more of kaolin, sodium metaaluminate, sheep's clay and diatomaceous earth; the pore-forming agent is one or more of lignin, sodium cellulose, starch and sesbania powder.
15. The method of any one of claims 7-11, wherein the 5A molecular sieve pellets in step (4) are calcined under inert atmosphere pressure and in a flowing state, and the calcined 5A molecular sieve pellets have a water content of less than 2 wt%.
16. The method of any one of claims 7-11, wherein the firing conditions in step (4) comprise: the roasting temperature is 200-;
preferably, the firing conditions include: the roasting temperature is 250-350 ℃, the roasting time is 2-3h, and the vacuum degree is (90-100) KPa.
17. The method according to any one of claims 7 to 11, wherein the calcium exchange of step (4) is carried out as follows: contacting the washed 4A molecular sieve beads with an aqueous solution of calcium chloride under the conditions comprising: the concentration of the calcium chloride aqueous solution is 0.1-1.2mol/L, the volume ratio of the calcium chloride aqueous solution to the 4A molecular sieve balls after washing is 1-9:1, the contact temperature is 50-150 ℃, and the contact time is 1-16 h.
18. A 5A molecular sieve adsorbent prepared by the method of any one of claims 7 to 17.
19. Use of the 5A molecular sieve adsorbent of any one of claims 1-6 or the 5A molecular sieve adsorbent of claim 18 in liquid wax adsorptive separation.
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