CN108160085B

CN108160085B - Preparation method of silicon-based nano-selenium

Info

Publication number: CN108160085B
Application number: CN201810038175.XA
Authority: CN
Inventors: 俞磊; 杨钰帆; 陈天; 杨成根; 徐清
Original assignee: Yangzhou University
Current assignee: Yangzhou University
Priority date: 2018-01-16
Filing date: 2018-01-16
Publication date: 2020-05-26
Anticipated expiration: 2038-01-16
Also published as: CN108160085A

Abstract

The invention discloses a preparation method of silicon-based nano-selenium, which relates to the technical field of chemical synthesis and is characterized in that sodium borohydride, selenium powder and silicon dioxide are used as raw materials, and sodium stearate and N, N' -diisobutylthiourea are used as auxiliary agents to synthesize a silicon-based nano-selenium material. The method is simple, the raw materials are easy to obtain, and the method can be applied to catalyzing selective oxidation of alcohols.

Description

Preparation method of silicon-based nano-selenium

Technical Field

The invention relates to the technical field of chemical synthesis, in particular to a method for synthesizing a silicon-based nano selenium material.

Background

Selenium element has unique chemical and biological activity. Recently, the catalytic activity of selenium has become a concern. The common selenium catalytic reaction mainly uses an organic selenium catalyst. The use of these catalysts is large, which results in low catalyst turnover number (TON) of the reaction, and the catalyst is difficult to recover and the utilization efficiency of the catalyst is low. In addition, the synthesis of substituted organoselenium catalysts requires the use of relatively expensive raw materials, thus limiting their industrial application prospects.

Disclosure of Invention

The invention aims to provide a preparation method of silicon-based nano selenium with high yield and low cost.

The technical scheme of the invention is as follows: mixing an ethanol solution of sodium borohydride, selenium powder, silicon dioxide, sodium stearate and N, N' -diisobutylthiourea at a freezing point environment temperature, heating to 20-50 ℃, stirring for reaction, obtaining a precipitate, performing suction filtration, and calcining at 450-550 ℃ to obtain the silicon-based nano selenium.

The invention takes sodium borohydride, selenium powder and silicon dioxide as raw materials, and sodium stearate and N, N' -diisobutylthiourea as auxiliary agents to synthesize the silicon-based nano selenium material. The method is simple, the raw materials are easy to obtain, and the method can be applied to catalyzing selective oxidation of alcohols.

The method has the following specific advantages: the reaction condition is mild, the product is easy to separate, the reaction is easy to operate, and the safety is good; the sodium hydroselenide used in the method is easy to prepare and has small dosage; finally, the method uses silicon dioxide to participate in the reaction, has easily obtained raw materials, less solid waste, low corrosivity, green and environment-friendly property, accords with the environment-friendly principle, and is suitable for industrial production.

The invention develops a method for preparing silicon-based nano selenium by taking easily available silicon dioxide as a carrier and adopting an alkaline corrosion loading method. The nano selenium material prepared by the method can catalyze selective oxidation of alcohol, wherein primary alcohol can be selectively oxidized into aldehyde without generating carboxylic acid. The invention uses easily obtained raw materials, and the synthesis application prospect of the nano-selenium material is better.

Furthermore, the mixing molar ratio of the sodium borohydride, the selenium powder and the silicon dioxide in the ethanol solution of the sodium borohydride is 100: 20-80: 1000-1200. Under the condition, selenium element can be fully dispersed, the utilization rate of selenium is improved, and the optimal catalytic effect is achieved. Tests prove that the catalyst activity of the silicon-based nano-selenium synthesized under the condition is higher, and the final silicon-based nano-selenium yield is more ideal.

More preferably, the mixing molar ratio of the sodium borohydride in the ethanol solution of the sodium borohydride to the selenium powder to the silicon dioxide is 100: 60: 1100. Under the condition, the catalyst activity of the silicon-based nano selenium is highest, and the yield of the silicon-based nano selenium is highest.

The mixing molar ratio of the sodium borohydride to the sodium stearate to the N, N' -diisobutylthiourea in the ethanol solution of the sodium borohydride is 100: 1.25-2.75: 0.1-0.6. Under the condition, a material structure with larger specific surface area is convenient to form, and the optimal catalytic effect is achieved.

The sodium stearate and the N, N' -diisobutylthiourea which are used as the reaction auxiliary agents can also greatly improve the catalyst activity of the silicon-based nano selenium under the condition of the dosage.

And when the mixing molar ratio of the sodium borohydride to the sodium stearate to the N, N' -diisobutylthiourea in the ethanol solution of the sodium borohydride is 100: 2: 0.4, the activity of the catalyst for synthesizing the silicon-based nano selenium is highest, and the yield is highest.

The concentration of sodium borohydride in the ethanol solution of sodium borohydride is 0.1-1.0 mol/L. The preferred concentration is 0.7 mol/L. Under the condition, the catalyst precursors can be combined at a proper speed, and the subsequent reduction of the catalyst activity caused by agglomeration and hardening is avoided.

The silicon-based nano-selenium catalyst has the highest activity under the condition.

In addition, the silicon dioxide is dried silica gel H or silica gel G. The dried silica gel is selected, so that the silicic acid generation caused by a small amount of moisture can be avoided, and the preparation environment of the catalyst is influenced.

The reaction temperature was conditioned at 40 ℃. Under this condition, the relevant raw materials can be contacted with each other at a proper speed, so that the activity of the formed catalyst is high.

The calcination temperature was 500 ℃. This temperature is sufficient to decompose undesirable impurities but avoids excessive temperature losses of elemental selenium, thereby maximizing catalyst activity.

The above conditions are further guarantee measures for the yield of the synthesized silicon-based nano selenium and the activity of the catalyst.

Detailed Description

The following examples illustrate the invention in more detail, but do not limit the invention further. Example 1:

under the cooling of ice-water bath, 20 mL of 0.7mol/L sodium borohydride ethanol solution, selenium powder, silica gel H (pre-dried, the water content is not more than 1%, and the molar amount is 11 times of that of sodium borohydride), sodium stearate (the molar amount is 2% of that of sodium borohydride) and N, N' -diisobutylthiourea (the molar amount is 0.4% of that of sodium borohydride) are mixed, and then the mixture is heated to 40 ℃ and stirred for reaction for 24 hours.

And (3) removing the precipitate generated in the reaction, filtering out the water phase, and calcining at 500 ℃ for 6 hours to obtain the silicon-based nano selenium material.

An electron microscope shows that the size of the silicon dioxide is greatly reduced under alkaline corrosion, and is about 20-100 nanometers. While elemental selenium is highly dispersed on silica (no peaks of crystalline selenium are observed by XRD testing), ICP indicates a selenium content of 3.890X 10^-3%。

The nano selenium is applied to alcohol oxidation, and the catalytic activity of the nano selenium is tested.

The method comprises the following specific steps: dissolving 1mmol of benzyl alcohol in 1 mL of acetonitrile, adding 20 mg of nano-selenium catalyst, adding 1mmol of aqueous hydrogen peroxide solution with the mass concentration of 30%, and reacting at 50 ℃ for 24 hours to obtain an oxidation product benzaldehyde, wherein the gas spectrum yield is 92%, and no generation of benzoic acid is observed.

Example 2: the reaction was examined under the same conditions as in example 1 for different concentrations of sodium borohydride, and the results are shown in Table 2.

TABLE 2 examination of different sodium borohydride concentrations

From the above results, the concentration of sodium borohydride in the reaction is preferably 0.7 mol/L.

Example 3: the reaction was performed under the same conditions as in example 1, and the results of the experiment were shown in Table 3.

TABLE 3 examination of the different selenium powder dosages

Molar weight of selenium powder/molar weight of sodium borohydride	20%	40%	60%	80%	100%
						Catalytic activity (yield of oxidation reaction/%)	63	78	92	88	79

From the above results, the best effect is obtained when the dosage of the selenium powder is 60% of the molar weight of the sodium borohydride.

Example 4: the reaction of the different silicas was examined under otherwise the same conditions as in example 1, the results of the experiment being shown in Table 4.

Table 4 examination of different silicas

From the above results, it was found that the effect was the best when silica gel H was used in the predried state.

Example 5: the reaction was examined under otherwise the same conditions as in example 1 for different amounts of silica, and the results are shown in Table 5.

TABLE 5 examination of the amount of silica used

From the above results, it is found that the reaction is most preferable when the amount of the sugar is 11 times the molar amount of sodium borohydride (example 1).

Example 6: the reaction of the various auxiliaries and their amounts was examined under otherwise the same conditions as in example 1, and the results are shown in Table 6.

TABLE 6 examination of the amount of auxiliary

From the above results, it is clear that the adjuvant system is most effective in sodium stearate (2.0%) and N, N' -diisobutylthiourea (0.4%). The catalyst activity is reduced by changing the amount of the auxiliary components and the type of the auxiliary.

Example 7: the reaction was examined under the same conditions as in example 1 at different temperatures, and the results are shown in Table 7.

TABLE 7 examination of the different reaction temperatures

From the above results, the reaction was best at 40 ℃.

Example 8: other conditions were the same as in example 1, and calcination at different temperatures was examined, and the results of the experiment are shown in Table 8.

TABLE 8 examination of the different calcination temperatures

From the above results, it is found that the calcination at 500 ℃ is most preferable.

Claims

1. A preparation method of silicon-based nano selenium is characterized by comprising the following steps: mixing an ethanol solution of sodium borohydride, selenium powder, silicon dioxide, sodium stearate and N, N' -diisobutylthiourea at a freezing point environment temperature, heating to 20-50 ℃, stirring for reaction, obtaining a precipitate, performing suction filtration, and calcining at 450-550 ℃ to obtain silicon-based nano selenium; the mixing molar ratio of the sodium borohydride to the selenium powder to the silicon dioxide in the ethanol solution of the sodium borohydride is 100: 20-80: 1000-1200.

2. The method of claim 1, wherein the step of preparing the silicon-based nano-selenium comprises: the mixing molar ratio of the sodium borohydride to the selenium powder to the silicon dioxide in the ethanol solution of the sodium borohydride is 100: 60: 1100.

3. The method for preparing silicon-based nano-selenium according to claim 1 or 2, wherein: the mixing molar ratio of the sodium borohydride to the sodium stearate to the N, N' -diisobutylthiourea in the ethanol solution of the sodium borohydride is 100: 1.25-2.75: 0.1-0.6.

4. The method of claim 3, wherein the step of preparing the silicon-based nano-selenium comprises: the mixing molar ratio of the sodium borohydride to the sodium stearate to the N, N' -diisobutylthiourea in the ethanol solution of the sodium borohydride is 100: 2: 0.4.

5. The method for preparing silicon-based nano-selenium according to claim 1 or 2, wherein: the concentration of sodium borohydride in the ethanol solution of sodium borohydride is 0.1-1.0 mol/L.

6. The method of claim 5, wherein the step of preparing the silicon-based nano-selenium comprises: the concentration of the sodium borohydride in the ethanol solution of the sodium borohydride is 0.7 mol/L.

7. The method for preparing silicon-based nano-selenium according to claim 1 or 2, wherein: the silicon dioxide is silica gel H or silica gel G.

8. The method for preparing silicon-based nano-selenium according to claim 1 or 2, wherein: the reaction temperature of the reaction was set to 40 ℃.

9. The method for preparing silicon-based nano-selenium according to claim 1 or 2, wherein: the calcination temperature was 500 ℃.