Method of surface modification of alumina

Abstract

A method of surface modification of an alumina carrier. The method includes: 1) dissolving a soluble kazoe in deionized water to yield a kazoe aqueous solution; 2) submerging an alumina carrier in the kazoe aqueous solution and drying the alumina carrier in a vacuum environment; 3) placing the dried alumina carrier in a reactor, adding silicon tetrachloride and Grignard reagent dropwise to the reactor, sealing the reactor and heating it to a constant temperature, and maintaining the constant temperature for between 3 and 18 hours, where a volume ratio of the added silicon tetrachloride and the alumina carrier is between 0.5:1 and 5:1, the constant temperature is controlled to be between 160 and 350 C.; and 4) cooling the reactor, filtering, washing, and drying the alumina carrier in the vacuum environment.

Claims

1. A method of surface modification of alumina, the method comprising: 1) dissolving a soluble kazoe in deionized water to yield a kazoe aqueous solution; 2) submerging an alumina carrier in the kazoe aqueous solution and drying the alumina carrier in a vacuum environment; 3) placing the dried alumina carrier in a reactor, adding silicon tetrachloride and Grignard reagent dropwise to the reactor, sealing and heating the reactor to a constant temperature, and maintaining the constant temperature for between 3 and 18 hours, wherein a volume ratio of the added silicon tetrachloride and the alumina carrier is between 0.5:1 and 5:1, the constant temperature is controlled to be between 160 and 350 C.; and 4) cooling the reactor, filtering, washing, and drying the alumina carrier in the vacuum environment, whereby obtaining a surface modified alumina carrier.

2. The method of claim 1, wherein the soluble kazoe is sodium azide, potassium azide, ammonium azide, calcium azide, barium azide, or a mixture thereof.

3. The method of claim 2, wherein a weight percentage concentration of the soluble kazoe in step 1) is between 5 and 30%.

4. The method of claim 2, wherein the alumina carrier is , , , , or crystal form alumina, or a mixture thereof.

5. The method of claim 2, wherein a temperature for drying the alumina carrier in the vacuum environment is between 20 and 80 C., and a drying time is between 2 and 4 hrs.

6. The method of claim 2, wherein the constant temperature is controlled to be between 180 and 250 C.

7. The method of claim 2, wherein the volume ratio of the silicon tetrachloride and the alumina powder added in step 3) is controlled to be between 1:1 and 2:1.

8. The method of claim 2, wherein an addition volume of the Grignard reagent in step 3) is between 0.1 and 2% of the volume of silicon tetrachloride.

9. The method of claim 2, wherein in step 4), the alumina carrier is successively washed with absolute ethyl alcohol and deionized water.

10. The method of claim 2, wherein in step 4), a temperature for drying the alumina carrier in the vacuum environment is controlled to be between 20 and 80 C., and a drying time is controlled to be between 2 and 4 hrs.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) Various embodiments of this invention are described in detail as follows in reference to optimal practical examples.

EXAMPLE 1

(2) 1. Dissolving 200 g of ammonium azide into deionized water to prepare an aqueous solution having 18 wt. % of ammonium azide;

(3) 2. Pouring into above-mentioned aqueous solution 200 mL -alumina powder whose average particle size is 85 m, bulk density is 1.2 g/mL, specific surface area is 200 m.sup.2/g after preroasting treatment, completely stirring, filtering the aqueous solution, and drying it in a vacuum drying cabinet under a temperature of 50 C. for 4 hrs;

(4) 3. Placing dried alumina carrier in a stainless steel reactor, adding 200 mL silicon tetrachloride, adding dropwise 1 mL Grignard reagent, sealing the reactor, sweeping with high purity nitrogen for 10 min, then raising temperature to 250 C. with the rate of 3 C./min, and maintaining the temperature for 10 hrs; and

(5) 4. Cooling the reactor to room temperature, opening the reactor and filtering the alumina carrier, washing the alumina carrier 2 to 3 times successively with absolute ethyl alcohol and deionized water, then drying the alumina carrier in the vacuum drying cabinet with a temperature of 50 C. for 4 hrs to obtain the modified alumina carrier.

EXAMPLE 2

(6) The operation steps are the same as that in Example 1, except that in step 1), the weight percentage of the ammonium azide is raised to 25%.

EXAMPLE 3

(7) The operation steps are the same as that in Example 1, except that in step 3), the temperature in the stainless steel reactor for maintaining reaction is controlled to be 200 C.

EXAMPLE 4

(8) The operation steps are the same as that in Example 1, except that in step 3), the time for maintaining the temperature is controlled to be 4 hrs.

EXAMPLE 5

(9) 1. Dissolving 200 g calcium azide into deionized water to prepare an aqueous solution having 30 wt. % of calcium azide;

(10) 2. Pouring into the aqueous solution 300 mL cylindrical alumina carrier whose average grain size is 1.8 mm, bulk density is 0.6 g/mL, particle length is 5 to 6 mm, specific surface area is 150 m.sup.2/g, and the weight percentages of -alumina and -alumina are respectively 88% and 12% after preroasting treatment, completely stirring, filtering the aqueous solution, and drying it in a vacuum drying cabinet under a temperature of 80 C. for 2 hrs;

(11) 3. Placing dried alumina carrier in a stainless steel reactor, adding 500 mL silicon tetrachloride, adding dropwise 5 mL Grignard reagent, sealing the reactor, sweeping with high purity nitrogen for 10 min, then raising temperature to 350 C. with the rate of 3 C./min, and maintaining the temperature for reaction for 3 hrs; and

(12) 4. Cooling the reactor to room temperature, opening the reactor and filtering the alumina carrier, washing the alumina carrier 2 to 3 times successively with absolute ethyl alcohol and deionized water, then drying the alumina carrier in the vacuum drying cabinet with a temperature of 70 C. for 3 hrs to obtain the modified alumina carrier.

EXAMPLE 6

(13) The operation steps are the same as that in Example 5, except that in step 2), the spherical alumina carrier having a particle size of 3 mm is substituted for the cylindrical alumina carrier and the alumina carrier is composed of 20% -alumina and 80% -alumina in weight percentage.

EXAMPLE 7

(14) 1. Dissolving 100 g sodium azide and 100 g potassium azide into deionized water to prepare a mixed aqueous solution, where the weight percentages of sodium azide and potassium azide are both 10%;

(15) 2. Pouring into the mixed aqueous solution 200 mL -alumina powder whose average particle size is 150 m, completely stirring, filtering the aqueous solution, and drying it in a vacuum drying cabinet under a temperature of 30 C. for 3 hrs;

(16) 3. Placing the dried alumina carrier in a stainless steel reactor, adding 300 mL silicon tetrachloride, adding dropwise 2 mL Grignard reagent, sealing the reactor, sweeping with high purity nitrogen for 10 min, then raising temperature to 160 C. with the rate of 2 C./min, and maintaining the temperature for reaction for 18 hrs; and

(17) 4. Cooling the reactor to room temperature, opening the reactor and filtering the alumina carrier, washing the alumina carrier 2 to 3 times successively with absolute ethyl alcohol and deionized water, then drying the alumina carrier again in the vacuum drying cabinet with a temperature of 40 C. for 2 hrs to obtain the modified alumina carrier.

(18) The physical and chemical properties of the alumina carrier modified in Examples 1-4 have been measured. The result is showed in the following Table 1. In Table 1, the contrast sample is non-modified -alumina.

(19) TABLE-US-00001 TABLE 1 Modified -alumina Non- Physical and chemical Exam- Exam- Exam- Exam- modified properties ple 1 ple 2 ple 3 ple 4 -alumina Total specific surface 201.47 198.42 200.54 201.32 218.46 area, m.sup.2/g Average pore size, nm 7.68 8.13 8.35 8.28 8.95 Total pore volume, 0.42 0.45 0.44 0.45 0.49 mL/g Average particle size, 84.32 89.01 85.21 86.43 85.54 m Weight percentage of 6.1 8.9 3.5 1.2 silicon nitride, wt. % Abrasion resistance, 76.34 86.82 72.17 65.76 52.04 m Remark: the abrasion resistance in the table is tested in jet-ring experiment equivalent to ASTMD5757-00. The abrasion resistance is acquired by comparison with average pore diameters after abrasion.

(20) TABLE-US-00002 TABLE 2 Physical and chemical Modified Non-modified properties -alumina -alumina Total specific surface 177.3 180.5 area, m.sup.2/g Total pore volume, mL/g 0.88 0.91 Weight percentage of 7.6 silicon nitride, wt. % Abrasion resistance, m 124.52 30.21 Remark: the abrasion resistance in the table is tested in jet-ring experiment equivalent to ASTMD5757-00. The abrasion resistance is acquired by comparison with average pore diameters after abrasion.

(21) The physical and chemical properties of alumina carrier modified by steps 1) to 4) in Example 7 have been measured. The result is showed in the following Table 2. In Table 2, the contrast sample is non-modified -alumina.

(22) According to the data of Table 1 and Table 2, the alumina carrier modified in the invention, presents no apparent differences in properties of porous structure (total specific surface area, total pore volume, and average pore diameter), which means that the modified alumina carrier still keeps the properties of porous structure of original carrier and is suitable for being used as a carrier of metal catalyst. In addition, according to the test of abrasion resistance in the jet-ring experiment equivalent to ASTMD5757-00 and comparing the average pore diameters after abrasion, the data shows the average particle diameter of modified carrier is apparently bigger than that of non-modified carrier. It means that the abrasion resistance of carrier is apparently improved and the abrasion resistance is improved following the raising of mass percentage of silicon nitride.

(23) In addition, the data in Table 1 and Table 2 shows that, raising the concentration of kazoe solution is able to increase the amount of kazoe deposited on the surface of carrier. Raising the temperature or prolonging the reaction time between silicon tetrachloride and alumina is able to increase the completeness of reaction. All of these factors are able to effectively raise the weight percentage of silicon nitride, which corresponds to raising the thickness of the silicon nitride layer on the surface of alumina.

(24) While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention.