WO2010115320A1

WO2010115320A1 - Integral porous adsorbent and preparation method therefor

Info

Publication number: WO2010115320A1
Application number: PCT/CN2009/072601
Authority: WO
Inventors: 何静; 安哲
Original assignee: 北京化工大学
Priority date: 2009-04-10
Filing date: 2009-07-02
Publication date: 2010-10-14
Also published as: CN101518728A; CN101518728B

Abstract

An integral high specific surface area porous adsorbent comprises an integral self-supporting metal oxide skeletal structure consisting of metal oxide obtained through thermal decomposition of metal nitrate. The metal oxide is Co₃O_4,In₂O_3,ZnO, Cr₂O₃ or NiO. The adsorbent is prepared with a chiral silicon oxide template. The adsorbent has a high specific surface area and a uniformly distributed pore diameter, and thus a large adsorption capacity. The adsorbent is used for adsorbing hydrogen gas, carbon monoxide, acetylene gas, ketones, aldehydes or ether solvents or macromolecular polar organic pollutants.

Description

Monolithic porous adsorbent and preparation method thereof

The invention belongs to the technical field of porous adsorbents, and particularly relates to a monolithic high specific surface area porous adsorbent and a preparation method thereof. In particular, the present invention relates to an adsorbent having a monolithic self-supporting structure and a high specific surface area. Background technique

Adsorbent materials are one of the hotspots in today's scientific research, for a wide range of applications, such as: integral filled adsorbents for specialty gas cylinder materials, energy storage adsorbents, and water and atmospheric purification adsorbents. The materials currently used as adsorbents mainly include silicate materials, molecular sieve materials, metal skeleton materials, and porous metal oxide materials.

There is an urgent need for a monolithic sorbent for specialty gas cylinder materials, and the preparation of sorbent materials faces two major challenges. On the one hand, the material lacks a monolithic structure and the three-dimensional order of the pore structure is poor; on the other hand, the specific surface area of the material needs to be improved and the pore size distribution is not uniform. In view of the above two challenges, the inventors have proposed a method for synthesizing a monolithic self-supporting pore-shaped structure adsorbent material by template orientation of a chiral silicon-based material, whereby the adsorbent material obtained has a high specific surface area and The pore size distribution is uniform. Summary of the invention

SUMMARY OF THE INVENTION The object of the present invention is to provide a monolithic high specific surface area porous adsorbent and a preparation method thereof. The adsorbent of the present invention has a large specific surface area and a uniform pore size distribution, and has a simple process and a low cost.

The monolithic high specific surface area porous adsorbent according to the present invention has a monolithic self-supporting porous metal oxide skeleton structure having a high specific surface area, and the composition of the adsorbent is a metal oxide which is heated by a metal nitrate A metal oxide obtained by decomposition transformation.

In the monolithic high specific surface area porous adsorbent of the present invention, the metal oxide exists in the form of a spiral, and metal can be formed by intertwining between the metal oxide spirals without any external force. An oxide rod, i.e., a monolithic high specific surface area porous adsorbent of the present invention. Therefore, the adsorbent of the present invention exhibits an integral self-supporting structural feature.

The present invention is not particularly limited to the spiral direction of the metal oxide spiral, and may be left-handed or right-handed. In general, the average pitch of the metal oxide helix in the adsorbent of the present invention may be from 100 to 200 nm, preferably from 100 to 180 nm, more preferably from 110 to 150 nm; the metal oxide spiral is flat The average diameter may be from 1 to 5 nm, preferably from 2 to 5 nm, more preferably from 3.5 to 4.5 nm.

In the monolithic high specific surface area porous adsorbent of the present invention, the average size of the metal oxide rod in the radial direction is generally 110-180 nm; the length of the axial direction of the formed metal oxide rod of the present invention is There is no particular limitation and it may be any length, but in general, the metal oxide rod may have a length of 200 to 500 nm.

In the monolithic high specific surface area porous adsorbent of the present invention, a large amount of pores exist between the metal oxide spirals or inside each metal oxide spiral, and the pores are formed in the absorbent of the present invention. At least a portion of the absorption material absorbing space, the pores having a maximum pore size of generally 2-5 nm. The presence of the above pores allows the monolithic high specific surface area porous adsorbent of the present invention to have a specific surface area of generally 50 to 200 m ² /g.

The composition of the monolithic high specific surface area porous adsorbent of the present invention is a metal oxide, and the metal oxide may be a metal oxide obtained by thermal decomposition conversion of a metal nitrate, and examples of the metal oxide include but not It is limited to cobalt trioxide (Co ₃ 0 ₄ ), indium trioxide (In ₂ 0 ₃ ), zinc oxide (ZnO), chromium trioxide (Cr ₂ O ₃ ), and nickel oxide (NiO).

The preparation method of the monolithic high specific surface area porous adsorbent of the invention comprises:

(1) Preparation of chiral silica template

Cetyltrimethylammonium bromide, sodium silicate, mesitylene, ethyl acetate, and deionized water are more uniform than 0.12-0.50: 0.15-0.50: 0.18-1.0: 0.3-3.0: 1000 The mixture is crystallized at a temperature of 15 to 40 ° C for 10 to 48 hours, and the reaction product is subjected to solid-liquid separation, and then the solid product is washed and dried to obtain a first solid powder.

The solid-liquid separation may be carried out by a method generally used in the art, preferably by centrifugal separation; the washing may be carried out using deionized water as a washing solvent; the drying is preferably vacuum drying, and the vacuum drying may be carried out at a temperature of 15 to 30 °C.

The concentrated solid nitric acid and hydrogen peroxide are mixed in a molar ratio of 2.0-4.0: 4.0-6.0 to the first solid powder obtained, and under microwave irradiation, the pressure is controlled to 1.0-1.5 MPa and the temperature is 100-25 CTC to remove hexadecane. The reaction product is subjected to solid-liquid separation by trimethylammonium bromide, and then the solid product is washed and dried to obtain a chiral silica template.

The concentrated nitric acid is used in an amount of 0.05-0.25 mol with respect to 1 g of the first solid powder; the concentration of the concentrated nitric acid may be a concentration well known to those skilled in the art, generally 15 mol/L; The concentration of hydrogen peroxide can be a concentration commonly used in the art, generally 30% by weight. The microwave radiation can be carried out in a microwave radiation apparatus well known to those skilled in the art, which typically has a time of 2-7 min. The separation can be carried out by methods commonly used in the art, preferably by centrifugation. The washing may use deionized water as a washing solvent; The drying temperature may be from 25 to 60 °C.

(2) Preparation of monolithic high specific surface area porous adsorbent

The metal nitrate solution is mixed with the obtained chiral silica template for 0.5-10 hours to obtain a uniformly mixed mixture, and the resulting mixture is dried at 50-15 CTC, and then calcined at 400-60 CTC to obtain a second solid. powder.

The amount of the metal nitrate in the metal nitrate solution is 5-15 mol with respect to 1 g of the chiral silica template; the concentration of the nitrate solution in the present invention is not particularly limited, and is generally 0.5-1.0. Mol/L. The drying time may be from 1 to 15 hours; the calcination is preferably carried out in a muffle furnace, and the calcination time may be from 3 to 8 hours.

The 2 mol/L NaOH solution is mixed with the obtained second solid powder, and subjected to a reaction for 0.5 to 3.0 hours to remove the chiral silica template, and the reaction product is subjected to solid-liquid separation, and then the solid product is washed and dried. The adsorbent of the present invention is obtained.

The NaOH solution is generally used in an amount of from 1 to 4 mL based on 1 g of the second solid powder. The separation can be carried out by methods commonly used in the art, preferably by centrifugation. The washing may employ deionized water as a solvent for washing; the drying may be carried out at a temperature of 25 to 60 °C.

The monolithic high specific surface area porous adsorbent obtained in the step (2) has a maximum pore diameter of 2-5 nm and a specific surface area of 50-200 m ² /g.

According to the preparation method of the present invention, a metal nitrate as a metal oxide precursor is filled in a pore of the chiral silica template by using a chiral silica having a spiral pore as a template, and the metal is calcined. The nitrate is converted to a metal oxide and the chiral silica template is removed to obtain the monolithic high specific surface area porous adsorbent of the present invention. Therefore, the monolithic high specific surface area porous adsorbent obtained according to the preparation method of the present invention inherits the spiral pore structure of the chiral silica template, that is, the metal oxide may exist in the form of a spiral; After the chiral silica template, a large number of pores may be formed between the metal oxide spirals or each metal oxide spiral, and the pores may be used as adsorbents of the present invention for adsorbing substances. Adsorption space. Therefore, the production method of the present invention can impart a monolithic self-supporting structure to the adsorbent of the present invention.

In the chiral silica template having a spiral channel used in the present invention, the most porous pore size of the pore may be 1-5 nm; the presence of the spiral channel makes the chiral silica template of the present invention The specific surface area is generally from 600 to 1200 m ² /g.

The present invention is not particularly limited to the spiral direction of the spiral-shaped pores in the chiral silica template. It may be left-handed or right-handed; the average pitch of the spiral channels may be determined according to the requirements of the adsorbent to be prepared, but is generally 100-200 nm, preferably 100-180 nm, and more preferably 110-150. Nm.

The monolithic high specific surface area porous adsorbent of the present invention has a large adsorption amount, and the adsorbable gas includes hydrogen, carbon monoxide and ethylene, and the adsorbable solvent includes a ketone solvent, an aldehyde solvent and an ether solvent, etc., and the like The monolithic high specific surface area porous absorbent can also act as a special adsorbent to adsorb macromolecules, polar organic pollutants and specific gas molecules.

The method for preparing the monolithic high specific surface area porous adsorbent of the present invention is not only simple in process but also low in cost, and the integral filled adsorbent of the special gas cylinder material can be further put into practical use. DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a high resolution transmission electron micrograph of the monolithic high specific surface area porous adsorbent prepared in Example 1. Figure 2 is a high resolution transmission electron micrograph of the monolithic high specific surface area porous adsorbent prepared in Example 2. detailed description

The invention will be described in detail below by way of examples.

The microstructure of the prepared adsorbent and chiral silica template was determined on a JEOL JEM-2010 transmission electron microscope. The specific operating conditions were as follows: Operating voltage was 200 kV. The test sample was dispersed in ethanol using an ultrasonic cleaner before the experiment. The ethanol solution was dropped on a porous ultrafine carbon network. A low temperature nitrogen uptake/desorption experiment was performed on a Quantachrome Autosorb-1 system, and the sample was degassed at 20 CTC for 3 hours before the experiment. Example 1

a. 0.002 mol of cetyltrimethylammonium bromide, 0.002 mol of sodium silicate, 0.004 mol of mesitylene, 0.003 mol of ethyl acetate, and 150 mL of deionized water were placed in the flask in turn. And uniformly mixed, the flask was placed in a water bath at 30 ° C for 10 hours for crystallization;

b. After the reaction is completed, the product is centrifuged, washed 5 times with deionized water, and the obtained slurry is dried in a vacuum oven at 25 ° C to obtain a white first solid powder;

c Take 0.3334 g of the first solid powder in a polytetrafluoroethylene reactor, add 0.023 mol of concentrated nitric acid (15 mol/L) and 0.034 mol of hydrogen peroxide (30% by weight), mix well, and contain the above reaction. The reaction kettle is placed in a modulated WX-4000 microwave system, and the pressure and temperature are controlled to not exceed 1.3 MPa and 180 ° C, respectively, and the reaction is 2 min; d. After the temperature and pressure are lowered to normal temperature and normal pressure, the reaction solution is taken out, the reaction solution is centrifuged, the supernatant is discarded, and washed with deionized water to pH=7. The slurry was dried at 25 ° C to obtain a chiral silica template. The average pitch of the spiral pores of the chiral silica template was determined by high-resolution transmission electron microscopy to be 120 nm, and the most suitable pore size was 4.3 nm; e. The chiral silica template of g was dispersed into 1 mL of a cobalt nitrate solution having a concentration of 0.8 mol/mL, and stirred at 25 ° C for 0.5 hour, and the resulting mixture was dried at 80 ° C for 1 hour, and the obtained solid was placed. It is placed in a porcelain crucible and placed in a muffle furnace, heated from room temperature to 450 ° C, kept for 7 hours, and naturally cooled to room temperature to obtain a second solid powder;

f. The obtained second solid powder was placed in 2 mL of a 2 mol/L sodium hydroxide solution, and stirred at 25 ° C for 2 hours to remove the chiral silica template, centrifuged and washed with deionized water until The solution was dried at 25 ° C at pH = 7, to obtain a monolithic high specific surface area porous adsorbent of the present invention.

It can be seen from the high-resolution transmission electron micrograph shown in FIG. 1 that the monolithic high specific surface area porous adsorbent of the present invention is composed of a plurality of three cobalt oxide spiral wires intertwined with each other, wherein the average diameter of the tricobalt trioxide spiral is about 4.0 nm. Left and right, the average pitch is 116 nm, and the average radial dimension of the metal oxide rod formed by the entanglement of the cobalt trioxide spiral is 130 nm. Example 2

b. After the reaction is completed, the product is centrifuged and washed 5 times with deionized water, and the obtained slurry is dried in a vacuum oven at 25 ° C to obtain a white first solid powder;

c Take 0.3334 g of the first solid powder in a polytetrafluoroethylene kettle, add 0.023 mol of concentrated nitric acid (15 mol/L) and 0.034 mol of hydrogen peroxide (30% by weight), mix well, and contain the above reactants. The reaction kettle is placed in a modulated WX-4000 microwave system, and the pressure and temperature are controlled to not exceed 1.3 MPa and 180 ° C, respectively, and the reaction is 2 min;

d. After the temperature pressure drops to normal temperature and normal pressure, the reaction solution is taken out, the reaction solution is centrifuged, the supernatant is discarded, and washed with deionized water to pH=7. The slurry was dried at 25 ° C to obtain a chiral silica template. The average pitch of the spiral pores of the chiral silica template was determined by high-resolution transmission electron microscopy to be 120 nm, and the most suitable pore size was 4.3 nm; e. The chiral silica template of g was dispersed into 0.8 mL of a 0.8 mol/mL indium nitrate solution, and stirred at 25 ° C for 1 hour, and the resulting mixture was dried at 80 ° C for 1 hour, and the obtained solid was placed in porcelain. Juxtaposition in the crucible In a Mafu furnace, heated from room temperature to 450 ° C, kept for 6 hours, naturally reduced to room temperature, to obtain a second solid powder; f. The second solid powder obtained was placed in 2 mL of 2 mol / L of hydroxide The sodium solution was stirred at 25 ° C for 2 hours to remove the chiral silica template, centrifuged and washed with deionized water to pH = 7, and dried at 25 ° C to obtain the monolithic high specific surface area porous adsorbent of the present invention.

It can be seen from the high-resolution transmission electron micrograph shown in FIG. 2 that the monolithic high specific surface area porous adsorbent of the present invention is composed of a plurality of indium trioxide spirals having different pitches, wherein the indium trioxide spiral is The average diameter is about 4.0 nm, and the average pitch is 118 nm. The average radial size of the metal oxide rod formed by the intercalation of indium trioxide is 160 nm. Example 3

The monolithic high specific surface area porous adsorbent prepared in Example 1 and Example 2 was subjected to a low temperature nitrogen adsorption/desorption experiment. The specific surface area and the most probable pore diameter data are shown in Table 1 below.

Table 1

Specific surface area (m ² /g) 1100 95 151

4.3 4.1 3.8 (nm) From the data in Table 1, the monolithic high specific surface area porous adsorbent of the present invention has a high specific surface area, and the specific surface areas of the adsorbents prepared by Example 1 and Example 2 are 95, respectively. m ² /g and 151 m ² /g, the most probable apertures are 4.1 nm and 3.8 nm, respectively.

Claims

Claim

What is claimed is: 1. A monolithic high specific surface area porous adsorbent, characterized in that the adsorbent has a monolithic self-supporting metal oxide skeleton structure, the composition of the adsorbent is a metal oxide, and the metal oxide is a metal nitrate. A metal oxide obtained by thermal decomposition.

The adsorbent according to claim 1, wherein the adsorbent has a most pore diameter of 2 to 5 nm and a specific surface area of 50 to 200 m ² /g.

The adsorbent according to claim 1 or 2, wherein the metal oxide is Co ₃ 0 ₄ , In ₂ 0 ₃ , ZnO, Cr ₂ O ₃ or NiO.

4. The adsorbent according to claim 1, wherein the metal oxide is present in the form of a spiral having an average pitch of 100 to 200 nm, an average diameter of the metal oxide spiral It is 1-5 nm.

5. A method of preparing the adsorbent of claim 1 wherein the method comprises:

(1) Preparation of chiral silica template

(1-a) Cetyltrimethylammonium bromide, sodium silicate, mesitylene, ethyl acetate and deionized water molar ratio 0.12-0.50: 0.15-0.50: 0.18-1.0: 0.3-3.0 : 1000 sequentially mixed uniformly, crystallized at a temperature of 15-40 ° C for 10-48 hours, the reaction product is subjected to solid-liquid separation, and then the solid product is washed and dried to obtain a first solid powder;

(1-b) uniformly mixing the concentrated nitric acid and hydrogen peroxide with a molar ratio of 2.0-4.0: 4.0-6.0 with the obtained first solid powder under microwave irradiation at a pressure of 1.0-1.5 MPa and a temperature of 100-25 CTC. Reacting to remove cetyltrimethylammonium bromide, subjecting the reaction product to solid-liquid separation, and then washing and drying the solid product to obtain a chiral silica template;

(2) Preparation of monolithic adsorbent

(2-a) The metal nitrate solution is mixed with the obtained chiral silica template for 0.5-10 hours to obtain a uniformly mixed mixture, and the resulting mixture is dried at a temperature of 50-15 CTC, and then at 400-60 CTC. Calcination at a temperature to obtain a second solid powder; (2-b) mixing a 2 mol/L NaOH solution with the obtained second solid powder, and reacting for 0.5 to 3.0 hours to remove the chiral silica template, subjecting the reaction product to solid-liquid separation, and then performing solid product separation Washing and drying to obtain an adsorbent.

6. The method according to claim 5, wherein in step 1-b, the concentrated nitric acid is used in an amount of 0.05-0.25 molo relative to 1 g of the first solid powder.

7. The method according to claim 5, wherein, in the step 2-a, the amount of the metal nitrate in the metal nitrate solution is 5-15 mol with respect to 1 g of the chiral silica template.

The method according to claim 5, wherein the calcination time in the step 2-a is from 3 to 8 hours.

9. The method according to claim 5, wherein in step 2-b, the NaOH solution is used in an amount of from 1 to 4 mL with respect to the second solid powder of lg.

10. The method according to claim 5 or 7, wherein the chiral silicon oxide template has a spiral channel, the spiral channel has an average pitch of 100-200 nm, and the average inner diameter of the spiral channel is 1-5 nm.