Background technology
SiC is the covalent linkage compound be made up of carbon and silicon, has similar adamantine tetrahedral structural unit, thus has extraordinary chemical stability, high physical strength and hardness, and good heat-conductivity conducting performance.Compared with traditional aluminum oxide, silicon oxide, activated carbon catalyst solid support material, SiC obviously has the advantage of following aspect as catalyst support material: the heat-conductivity conducting performance that (1) is good, is conducive to the heat trnasfer of catalyzer in reaction process and the electron transmission between catalyst activity component and carrier; (2) chemical stability is good, not easily produces with active ingredient and interacts, and is conducive to keeping the stable of catalyst structure; (3) high physical strength and hardness, be conducive to the intensity and the abrasion resistance properties that improve catalyzer, the extending catalyst life-span.Based on above-mentioned advantage, SiC, as support of the catalyst, has been successfully applied in the middle of some important chemical reactions.But, in more than 100 year history of heterogeneous catalysis technology development, but seldom see the figure of SiC in industrial applications.Tracing it to its cause, is because its specific surface area of SiC that commercial methods is produced is difficult to meet the requirement of catalyst support material.Therefore, the exploitation of high-specific surface area silicon carbide has caused the attention of investigator, and relevant research is increasing.
In recent years, the development of nanotechnology, opens a frontier of specific area SiC.Nano SiC not only can increase substantially its specific surface area, and rise have more the even irreplaceable performance of some brilliance, in some chemical reaction, demonstrate unusual effect, become a kind of support of the catalyst having much potentiality.Especially the SiC of Nano microsphere structure is with the character of its uniqueness, as single dispersing, stability, Modulatory character, is self-assembled into a research field become more and more important for Materials science forward position in recent years.Kun Wang etc. are at Synthesis of nanostructured silicon carbide spheres from mesoporous C-SiO
2using tetraethoxy and furfuryl alcohol as silicon source and carbon source in nanocomposites [Chem.Commun., 2010,46,303 – 305], first synthesize C-SiO
2meso-porous nano matrix material, then obtain SiC microballoon through 1350 DEG C of carbothermic reduction reactions.But the method is at synthesis C-SiO
2need in compound system to add triblock copolymer P123, the C-SiO simultaneously synthesized
2presoma also needs through the calcination process of 550 DEG C under a nitrogen atmosphere.The method preparation process more complicated, C-SiO
2c/Si mol ratio in compound system is difficult to control.
Summary of the invention
The object of the present invention is to provide a kind of method preparing high-specific surface area SiC nanometer microsphere, it is simple to operate, favorable repeatability, is conducive to suitability for industrialized production.
For achieving the above object, the present invention adopts following technical scheme:
The present invention includes following steps: comprise the following steps:
1) by carbosphere and silicon dioxide microsphere in mass ratio (1:1) ~ (2:1) mix, obtain mixed powder; Wherein carbosphere particle diameter is 200 ~ 400nm, is 100 ~ 200nm with the particle diameter of silicon dioxide microsphere;
2) mixed powder is put into vacuum sintering furnace, argon gas is passed into by after vacuum sintering stove evacuation, and under argon shield when room temperature to 1200 DEG C by vacuum sintering stove evacuation, then continue to be warming up to 1300 DEG C ~ 1500 DEG C, sinter at 1300 DEG C ~ 1500 DEG C, then Temperature fall is to room temperature, obtains product;
3) product is calcined at 400-600 DEG C, naturally cool to room temperature, obtain high-specific surface area SiC nanometer microsphere.
Described step 2) in mixed powder is put into vacuum sintering stokehold, first mixed powder is put into corundum crucible, and keep mixed powder natural packing, mixed powder piling height controls within 10mm.
Described step 2) in reaction time be 30 ~ 90min.
In described step 3), calcining is carried out in retort furnace.
The time of calcining in described step 3) is 1-2 hour.
The present invention has following beneficial effect: the present invention is with carbosphere, SiO
2microballoon is raw material, using the carbosphere as carbon source and the SiO as silicon source
2microballoon, after mixing, inserts reaction sintering in vacuum sintering furnace, the product after sintering being calcined in atmosphere the carbon removed and remain, obtains the SiC nanometer microsphere of high-specific surface area.The present invention is simple to operate, with low cost, and favorable repeatability is conducive to suitability for industrialized production.The epigranular of the SiC nanometer microsphere obtained by the present invention, purity is high, and diameter is 200 ~ 500nm, and specific surface area can reach 25 ~ 60m
2/ g.
Embodiment
The present invention is elaborated by embodiment below in conjunction with accompanying drawing.
In the present invention, carbosphere is according to method preparation described in patent 201210235639.9, and silicon dioxide microsphere is according to method preparation described in patent 201210235695.2.
Embodiment 1
1) be that 2:1 under mechanical stirring mix with silicon dioxide microsphere according to mass ratio by carbosphere, obtain mixed powder, wherein carbosphere particle diameter is 200 ~ 400nm, SiO
2the particle diameter of microballoon is 100 ~ 200nm.
2) mixed powder is placed in corundum crucible, and keeps mixed powder natural packing, avoids pressing, mixed powder piling height is controlled as 1mm;
3) corundum crucible installing mixed powder is put into vacuum sintering furnace, pass into argon gas by after vacuum sintering stove evacuation, and vacuumize when room temperature to 1200 DEG C under argon shield, then continue to be warming up to 1300 DEG C, and react 90min at 1300 DEG C;
4) product is put into retort furnace, calcine at 400 DEG C and remove residual carbon in 2 hours, naturally cool to room temperature, obtain high-specific surface area SiC nanometer microsphere.
The SiC nanometer microsphere diameter of the present embodiment gained is at about 200nm, and specific surface area is about 60m
2/ g.
Embodiment 2
Step 1: carbosphere is mixed according to mass ratio 1:1 under mechanical stirring with silicon dioxide microsphere, obtains mixed powder; Wherein, carbosphere particle diameter is the particle diameter of 200 ~ 400nm, SiO2 microballoon is 100 ~ 200nm.
Step 2: mixed powder is placed in corundum crucible, and keep mixed powder natural packing, avoid pressing, mixed powder piling height is controlled for 10mm;
Step 3: the corundum crucible installing mixed powder is put into vacuum sintering furnace, argon gas is passed into by after vacuum sintering stove evacuation, and vacuumize when room temperature to 1200 DEG C under argon shield, then continue to be warming up to 1500 DEG C, and 30min is reacted at 1500 DEG C, then Temperature fall is to room temperature, obtains product;
4) product is put into retort furnace, calcine at 600 DEG C and remove residual carbon in 1 hour, naturally cool to room temperature, obtain high-specific surface area SiC nanometer microsphere.
The SiC nanometer microsphere diameter of the present embodiment gained is at about 500nm, and specific surface area is about 25m
2/ g.
Embodiment 3
Step 1: mixed under mechanical stirring according to mass ratio 1.5:1 with silicon dioxide microsphere by carbosphere, obtain mixed powder, wherein carbosphere particle diameter is 200 ~ 400nm, SiO
2the particle diameter of microballoon is 100 ~ 200nm.
Step 2: mixed powder is placed in corundum crucible, and keep mixed powder natural packing, avoid pressing, mixed powder piling height is controlled for 5mm;
Step 3: the corundum crucible installing mixed powder is put into vacuum sintering furnace, argon gas is passed into by after vacuum sintering stove evacuation, and vacuumize when room temperature to 1200 DEG C under argon shield, then continue to be warming up to 1400 DEG C, and 90min is reacted at 1400 DEG C, then Temperature fall is to room temperature, obtains product;
Step 4: product is put into retort furnace, calcines and removes residual carbon in 1 hour, naturally cool to room temperature, obtain high-specific surface area SiC nanometer microsphere at 500 DEG C.
The SiC nanometer microsphere diameter of the present embodiment gained is at about 300nm, and specific surface area is about 40m
2/ g.
Embodiment 4
Step 1: mixed under mechanical stirring according to mass ratio 1.2:1 with silicon dioxide microsphere by carbosphere, obtain mixed powder, wherein carbosphere particle diameter is 200 ~ 400nm, SiO
2the particle size of microballoon is 100 ~ 200nm.
Step 2: mixed powder is placed in corundum crucible, and keep mixed powder natural packing, avoid pressing, mixed powder piling height is controlled for 3mm;
Step 3: the corundum crucible installing mixed powder is put into vacuum sintering furnace, argon gas is passed into by after vacuum sintering stove evacuation, and vacuumize when room temperature to 1200 DEG C under argon shield, then continue to be warming up to 1350 DEG C, and 50min is reacted at 1350 DEG C, then Temperature fall is to room temperature, obtains product;
Step 4: product is put into retort furnace, calcines and removes residual carbon in 1 hour, naturally cool to room temperature, obtain high-specific surface area SiC nanometer microsphere at 450 DEG C.
Embodiment 5
Step 1: mixed in mechanical stirring according to mass ratio 1.7:1 with silicon dioxide microsphere by carbosphere, obtain mixed powder, wherein carbosphere particle diameter is 200 ~ 400nm, SiO
2the particle diameter of microballoon is 100 ~ 200n.
Step 2: mixed powder is placed in corundum crucible, and keep mixed powder natural packing, avoid pressing, mixed powder piling height is controlled for 8mm;
Step 3: the corundum crucible installing mixed powder is put into vacuum sintering furnace, argon gas is passed into by after vacuum sintering stove evacuation, and vacuumize when room temperature to 1200 DEG C under argon shield, then continue to be warming up to 1450 DEG C, and 70min is reacted at 1500 DEG C, then Temperature fall is to room temperature, obtains product;
Step 4: product is put into retort furnace, calcines and removes residual carbon in 1.7 hours, naturally cool to room temperature, obtain high-specific surface area SiC nanometer microsphere at 550 DEG C.
Refer to shown in Fig. 1, Fig. 1 is the SEM pattern of SiC nanometer microsphere prepared by the present invention.As seen from Figure 1: the surface irregularity of SiC nanometer microsphere prepared by the present invention, be made up of the small-particle of many diameters at 10 ~ 20nm, for the high-specific surface area of SiC nanometer microsphere provides favourable condition.
The present invention is simple to operate, favorable repeatability, is conducive to suitability for industrialized production.The SiC nanometer microsphere epigranular that the present invention obtains, purity is high, and diameter is controlled between 200 ~ 500nm, and specific surface area can reach 25 ~ 60m
2/ g.