CN1260008C - Method for preparing novel Raney Ni catalyzer and its application - Google Patents

Abstract

The present invention provides a new method for preparing a Raney Ni catalyst, the nickel content of the prepared catalyst is from 70 to 90 wt%, the specific surface area is from 70 to 100m<2>/g, the pore volume is from 0.054 to 0.084cm<3>/g, the pore size distribution is within the range of 2.0 to 220 nm, and the average pore size is from 2.84 to 3.66 nm. The method comprises following steps: (i) nickel aluminum alloy is ground into particles of 80 to 100 meshes; (ii) the particles of the step (i) are added into NaOH solution, the mixture is stirring, the ratio of alloy weight (gram) to alkaline liquor volume (milliliter) is from 1:8 to 1:15, aluminum extraction is carried out on the solution by ultrasonic wave for 5 to 30 minutes, the ultrasonic frequency is from 28 to 48kHz, the water bath temperature is from 25 to 60 DEG C, after the ultrasonic wave extraction is finished, the solution is continuously stirred for 2 to 6 hours, the alkaline liquor of the upper layer is removed, and the whole process is carried out in an inert atmosphere; (iii) the particles of the step (ii) are washed to be neutral with deionized water, anhydrous alcohol is used for washing the particles to remove water, and the Raney Ni catalyst is prepared. The present invention also provides the purposes of the Raney Ni catalyst.

Description

The method for preparing novel Raney Ni catalyst and its application

technical field

The invention relates to a method for preparing a novel Raney Ni catalyst, in particular to a method for preparing a novel Raney Ni catalyst by extracting aluminum by using ultrasonic waves.

Background technique

Raney Ni catalysts have been used in industry and laboratories for decades. It is widely used in reduction reactions, such as catalytic hydrogenation and dehalogenation reactions of olefins, aromatic rings, aldehydes, ketones, nitro groups, nitrile groups, etc. It is a chemical One of the most important catalysts for production. Raney Ni catalyst has high activity and selectivity, and is cheap, so its research has always been an important part of the catalyst research field.

The conventional method for preparing Raney Ni catalyst is to extract the aluminum in the nickel-aluminum alloy with NaOH solution, and then wash it. The residue is sponge-like porous Raney Ni particles with a particle size of about 25-150 Å. The catalyst mainly contains Ni, Al (1-8 wt%), a small amount of NiO and Al ₂ O ₃ hydrate (1-20 wt%), and the total surface area is 50-130 ^m2 /g. It is worth noting that the Ni surface area only accounts for 50-100% of the total surface area. Corresponding catalysts such as Raney Co and Raney Cu can also be prepared from alloys such as cobalt-aluminum alloys and copper-aluminum alloys in a similar manner.

Regarding the preparation of skeleton catalysts, almost all patent documents focus on the preparation method, pulverization and treatment method of the alloy. The differences of the various Raney Ni catalysts reported from W1 to W8 mainly lie in the conditions of adding the alloy, the concentration of alkali, the time and temperature of aluminum extraction, and the washing conditions of the obtained catalysts. There are also many reports in the literature on modified Raney Ni catalysts, such as adding Mo, Ti, Cr, Fe, Co, B, Cu and other metals.

In recent years, the application of ultrasound in catalyst preparation is gradually attracting people's attention, but its application in RaneyNi catalyst is limited to the final cleaning (published Japanese patent 03249946A is to ultrasonically extract the good Raney Ni in deionized water And modified photoactive substances), its application in the process of extracting aluminum has not been reported so far.

Contents of the invention

The invention provides a new method for preparing Raney Ni catalyst. The nickel content of the prepared catalyst is 70-90% by weight, and the specific surface area is in the range of 70-100 ^m2 /g, preferably 75-95 m2 ^/g gram range, the pore volume is 0.054-0.085 ^cm3 /g, the pore diameter distribution is in the range of 2.0-220nm, and the average pore diameter is 2.84-3.66nm; the method includes the following steps:

(i) Grinding the nickel-aluminum alloy into 80-100 mesh particles;

(ii) Add the particles of step (i) to NaOH solution and stir, the ratio of alloy weight (grams) to lye volume (milliliters) is 1: 8 to 1: 15, and the solution is ultrasonically extracted for aluminum 5- 30 minutes, ultrasonic frequency is 28 ~ 48kHz, water bath temperature is 25 ~ 60 ° C, preferably 30 ~ 50 ° C, after the ultrasonic extraction is completed, continue to stir for 2 ~ 6 hours, then remove the upper layer of lye, the whole process is in an inert gas Carry out, preferably carry out under N ₂ protection;

(iii) The particles in step (ii) are washed with deionized water to neutrality, and then washed with absolute ethanol to remove water to obtain the Raney Ni catalyst.

The catalyst prepared by the method of the present invention has a nickel content of 70-90% by weight, a specific surface area of 70-100 ^m2 /g, preferably 75-95 ^m2 /g, and a pore volume of 0.054-0.085 cm3/ ^g . grams, the pore size distribution is in the range of 2.0-220nm, and the average pore size is 2.84-3.66nm.

The catalyst prepared by the method of the invention can be used for hydrogenation reaction, and can improve conversion rate and selectivity. Especially for the hydrogenation of benzene to prepare cyclohexane, compared with the catalyst prepared without ultrasonic extraction step, the hydrogen absorption rate and conversion rate can be increased by 54% and 82.4%, respectively.

In the above method, nickel-aluminum alloy is commercially available, its nickel content is about 40-50% by weight, and the particle size of the ground particles is about 80-100 mesh. Take a certain amount of the above-mentioned samples at a room temperature of 5-20°C, and slowly add them to the NaOH solution in an ice-water bath. Milliliters) ratio is 1:8～1:15, preferably 1:10; The frequency of ultrasonic treatment is 28～48kHz. The temperature of the ultrasonic water bath is 25-60°C, preferably 30-50°C. The ultrasonic extraction time is about 5 to 30 minutes, preferably 10 to 20 minutes, most preferably 15 minutes. The ratio of alloy weight (grams) to lye volume (ml) is 1:10. After ultrasonic extraction, continue to reflux and stir for about 2 to 6 hours, preferably 4 hours. The entire treatment process is carried out in an inert atmosphere, such as N ₂ , to prevent sample oxidation, and a reflux device is used to prevent changes in NaOH concentration. After the reaction, the supernatant was removed, and the catalyst particles were washed repeatedly with deionized water until neutral, and then washed with absolute ethanol to remove water. The prepared Raney Ni catalyst should be stored in absolute ethanol.

The Raney Ni catalyst thus obtained, determines that its Ni content range is about 70 to 90% by weight by ICP analysis, and the total specific surface area measured by the BET method is about 70 to 100 m ^/ gram, and the pore volume is 0.054 to 0.085 ^cm /g, the pore size distribution is in the range of 2.0-220nm, and mainly distributed in the range of 3.4-4.0nm.

In a preferred embodiment of the present invention, the NaOH concentration is 6.0 mol/liter, the ratio of Ni-Al alloy weight (gram) to lye volume (milliliter) is 1: 10, the frequency of ultrasonic treatment is 28kHz, the The temperature is 25°C. The Ni content range of the Raney Ni catalyst thus obtained is about 72.5 to 85.8% by weight, the specific surface area is about 88 to 96 m2 ^/ g, and the pore diameter is distributed in the range of 2.0 to 220.8 nm, and mainly distributed in the range of 3.4 to 4.0 nm. within range.

The facilitation of ultrasonic waves is mainly due to its dispersion, cleaning and microwave energy provided. The dispersion effect of ultrasonic waves is beneficial to increase the specific surface area, pore size and pore volume, and at the same time make the active site distribution of the catalyst more uniform; the cleaning effect of ultrasonic waves can make the surface of the catalyst smoother; and the energy provided by ultrasonic waves activates the metal Ni atoms as active centers ( clusters) while making the hydrogen stored in the Raney Ni catalyst more active.

Controlling the appropriate ultrasonic time in the suction filtration process of Ni-Al alloy can significantly improve the hydrogenation activity of Raney Ni catalysis, for example, in the embodiment of the present invention, the catalyst obtained by ultrasonic extraction treatment is used for benzene hydrogenation In the preparation of cyclohexane, the highest hydrogen absorption rate reached 43.0 mmol/h g, and the conversion rate reached more than 20% after 3 hours of reaction. Compared with the catalyst prepared by alkali extraction treatment without ultrasonic waves, the hydrogen absorption rate and conversion rate The highest can be increased by 54% and 82.4%, respectively. The promotion effect of ultrasound on catalytic activity is mainly attributed to the following factors: (1) the dispersion of ultrasound makes the particles of Raney Ni catalyst thinner, and the degree of dispersion increases, thereby increasing the specific surface area; (2) the cleaning effect of ultrasound makes the surface of the catalyst oxidize The aluminum layer and other impurities are reduced, and the surface is cleaner and smoother, so that more active sites are exposed on the surface of the catalyst, which is conducive to its contact and interaction with the reactants, and improves the catalytic activity; (3) ultrasonic cleaning is beneficial to remove The impurities inside the Raney Ni skeleton increase the pores and volume, which is conducive to the adsorption of reactants on the inner surface of the catalyst and improves the catalytic activity; (4) in the Ni-Al alloy, the metal Al provides part of the electrons to the metal Ni, which This situation is similar to B in Ni-B amorphous alloys. A large number of studies have shown that the electron-rich Ni active site is conducive to improving its catalytic hydrogenation activity for benzene rings. Ultrasonic treatment increases the Al content in the Raney Ni catalyst, and more importantly, the ultrasonic treatment increases the metallic Al content on the surface of Raney Ni, which leads to more electron-rich metal Ni and increases the hydrogenation activity; (5) Ultrasound provides Part of the microwave energy is absorbed by the RaneyNi catalyst, which makes the Ni atoms as the active sites and the hydrogen stored in the catalyst more active, which is conducive to improving the catalytic hydrogenation activity. However, when the ultrasonic time is too long, on the one hand, the particles will be agglomerated, and at the same time, some pore structures will be destroyed, and the storage of "active hydrogen" in Raney Ni will be reduced, resulting in a decrease in catalytic activity.

The present invention applies ultrasonic technology to the extraction aluminum process of Raney Ni catalyst for the first time, and there is essential difference with the ultrasonic cleaning of Raney Ni catalyst that has been reported (published Japanese patent 03249946A is that the Raney Ni that suction filtration is good is ultrasonically cleaned in deionized water and modify photoactive substances). This method is easy to operate and low in cost. It not only provides a new type of Raney Ni catalyst (LM Raney Ni, which is different from the reported W1-W8 type Raney Ni catalyst), but also provides a basis for the preparation of other skeleton metal catalysts and Raney Ni catalysts. A further modification of the provides a new method. The prepared LM Raney Ni has larger pore diameter and higher pore volume than Raney Ni (traditional Raney Ni) without ultrasonic treatment under the same conditions, and the specific surface area is also slightly increased; and the impurity content on the surface and in the bulk is significantly reduced .

The LM Raney Ni catalyst of the present invention not only has high activity for benzene hydrogenation, but also shows excellent catalytic activity and selectivity in many catalytic hydrogenation reactions such as acetonitrile hydrogenation, glucose hydrogenation and nitrobenzene hydrogenation, and is expected to Replace traditional Raney Ni catalyst for industrial production.

The present invention will be further described below through specific embodiments, and these examples are listed only for illustration and not to limit the present invention in any way.

specific implementation plan

Example 1

Nickel-aluminum alloy (purchased from China Pharmaceutical Group Shanghai Chemical Reagent Company (experimental reagent LR), its nickel content is about 40 to 50% by weight) is ground into 80 to 100 mesh particles, and a certain amount of the above sample is taken and neutralized in an ice bath. Under stirring, slowly add it to 6.0 mol/L NaOH solution, the ratio of alloy weight (grams) to lye volume (ml) is 1:10, after all Ni-Al alloys are added, add to the above solution Ultrasonic extraction treatment was carried out, the frequency of ultrasonic treatment was 28 kHz, the temperature of water bath for ultrasonic treatment was 25° C., and the ultrasonic times were 0, 5, 10, 15, 20 and 25 minutes, respectively. After the ultrasonic extraction was completed, the temperature was raised to 70° C., and stirring was continued for about 4 hours under reflux. Afterwards, the upper layer of lye was removed, washed repeatedly with deionized water until neutral, and then washed with absolute ethanol to remove water, thereby preparing the Raney Ni catalyst. The whole process was carried out in a _N2 atmosphere, and a reflux device was employed to prevent changes in NaOH concentration. The prepared Raney Ni catalyst is stored in absolute ethanol at 5-20°C.

The Ni content of the Raney Ni catalyst prepared by the above-mentioned method is about 72.5～85.8% by weight by ICP analysis, and the specific surface area measured by the BET method is about 88～96 m ^/ gram, and the pore size is distributed at 2.0～220.8nm, and the main distribution In the range of 3.4-4.0nm. Some structural parameters of Raney Ni catalysts obtained under different ultrasonic times are listed in Table 1.

Table 1

Raney Ni catalysts obtained under different ultrasonic times

Nickel content, specific surface area, pore size distribution and other properties Sample serial number Ultrasonic time (minutes) Ni content (weight%) Specific surface area ( ^m2 /g) Pore volume ( ^cm3 /g) Pore size distribution (nm) Average pore size (nm) 1# 0 79.1 94.247 0.0779 2.1～178.7 3.3085 2# 5 72.5 94.614 0.0793 2.1～213.9 3.3539 3# 10 83.7 96.035 0.0798 2.1～220.8 3.3247 4# 15 81.0 93.595 0.0846 2.0～110.8 3.6137 5# 20 85.8 87.986 0.0745 2.1～157.9 3.3873 6# 25 84.5 89.675 0.0821 2.0～143.8 3.6624

The above catalyst is used to hydrogenate cyclohexane from benzene, and the initial pressure of the hydrogenation reaction is $P_{h_2}=1.0\mathrm{MPa},$ The reaction temperature was controlled at 90°C, and the reaction was carried out in a 200 ml stainless steel autoclave. Initially, 0.5 g of Raney Ni catalyst, 10 ml of benzene and 30 ml of ethanol were added, and the reaction time was 3 hours. The results are shown in Table 2:

Table 2

Comparison of hydrogenation activity of Raney Ni catalysts obtained under different ultrasonic times Raney Ni samples 1# 2# 3# 4# 5# 6# Hydrogen absorption rate (mmol/h.g) 27.9 33.3 35.5 43.0 35.5 34.4 Conversion rate(%) 12.5 17.2 19.6 22.8 19.9 17.0

It can be seen from Table 2 that the Raney Ni catalyst after ultrasonic extraction treatment, in the process of benzene hydrogenation to prepare cyclohexane, the hydrogen absorption rate and conversion rate are significantly increased, and the catalyst prepared when the ultrasonic time is 15 minutes During hydrogenation to prepare cyclohexane, the hydrogen absorption rate and conversion rate reached the maximum value of 43.0 mmol/h·g and 22.8%. Compared with the Raney Ni catalyst prepared without the ultrasonic extraction step, the hydrogen uptake rate and conversion increased by 54% and 82.4%, respectively.

Example 2

Adopt the same method as embodiment 1 to prepare Raney Ni catalyst, difference is that used NaOH solution concentration is 10 mol/liter, and the ratio of alloy weight (gram) and lye volume (milliliter) is 1: 8, and ultrasonic frequency is 48kHz, ultrasonic water bath temperature is 30°C or 50°C. Some structural parameters of the catalysts prepared under these conditions are listed in Table 3.

table 3

Raney Ni catalyst obtained under different ultrasonic time and water bath temperature

Nickel content, specific surface area, pore size distribution and other properties Sample serial number Extraction time (minutes) Water bath temperature (℃) Ni content (weight%) Specific surface area ( ^m2 /g) Pore volume ( ^cm3 /g) Pore size distribution (nm) Average pore size (nm) Atomic composition (%) 7# 0 84.7 91.213 0.0671 2.1-173.3 2.9415 Al _20.9 Ni _79.1 8# 15 30 83.3 87.826 0.0726 2.2-154.2 3.3047 Al _18.2 Ni _81.8 9# 5 50 85.0 93.937 0.0667 2.1-167.3 2.8414 Al _18.5 Ni _81.5 10# 10 50 Untested Untested Untested Untested Untested Untested 11# 15 50 Untested Untested Untested Untested Untested Untested

These catalysts are used to hydrogenate cyclohexane from benzene, and the initial pressure of the hydrogenation reaction is $P_{h_2}=1.0\mathrm{MPa},$ The reaction temperature was controlled at 90° C., and the reaction was carried out in a 200 ml stainless steel autoclave, initially adding 0.5 g of Raney Ni catalyst, 10 ml of benzene and 30 ml of ethanol, and the reaction time was 3 hours. The obtained results are listed in Table 4:

Table 4

Comparison of hydrogenation activity of Raney Ni catalysts obtained under different ultrasonic times Raney Ni sample 7# 8# 9# 10# 11# Hydrogen absorption rate (mmol/h g) 31.2 39.8 41.9 35.5 30.1 Conversion rate(%) 16.1 21.7 21.5 21.2 14.9

It can be seen from Table 4 that the highest activity of the Raney Ni catalyst obtained by using 10 mol/liter of NaOH solution to extract Ni-Al alloy under the action of 48kHz ultrasonic wave is not as good as that of extracting Ni by using 10 mol/liter of NaOH solution under the action of 28kHz ultrasonic wave. -Al obtained Raney Ni catalyst, at the same time, the temperature of ultrasonic treatment water bath is too high to be unfavorable for the catalytic activity of Raney Ni catalyst.

Example 3

Adopt the same method as embodiment 1 to prepare Raney Ni catalyst, difference is that used NaOH solution concentration is 4 mol/liter, and the ratio of Ni-Al alloy weight (gram) and lye volume (milliliter) is 1: 15, The ultrasonic frequency is 48kHz, and the temperature of the water bath for ultrasonic treatment is 30°C or 50°C. Some structural parameters of each Raney Ni catalyst prepared under this condition are listed in Table 5.

table 5

Raney Ni catalysts obtained under different ultrasonic time and water bath temperature

Nickel content, specific surface area, pore size distribution and other properties Sample serial number Ultrasonic time (minutes) Water bath temperature (℃) Ni content (weight%) Specific surface area ( ^m2 /g) Pore volume ( ^cm3 /g) Pore size distribution (nm) Average pore size (nm) Atomic composition (%) 12# 0 89.2 70.761 0.0541 2.1-132.1 2.875 Al _16.2 Ni _83.8 13# 15 30 88.2 74.885 0.0590 2.2-155.5 3.1497 Al _15.5 Ni _54.5 14# 10 50 88.0 81.437 0.0701 2.1-145.3 3.2567 Al _14.6 Ni _85.4 15# 15 50 88.3 89.328 0.0763 2.1-151.7 3.4158 Al _14.0 Ni _86.0

The above catalyst is used to hydrogenate cyclohexane from benzene, and the initial pressure of the hydrogenation reaction is $P_{h_2}=1.0\mathrm{MPa},$ The reaction temperature was controlled at 90°C, and the reaction was carried out in a 200 ml stainless steel autoclave. Initially, 0.5 g of Raney Ni catalyst, 10 ml of benzene and 30 ml of ethanol were added, and the reaction time was 3 hours. The results are shown in Table 6:

Table 6

Comparison of hydrogenation activity of Raney Ni catalysts obtained under different ultrasonic time and water bath temperature Raney Ni samples 12# 13# 14# 15# Hydrogen absorption rate (mmol/h g) 32.3 46.2 35.5 39.8 Conversion rate(%) 15.1 20.2 17.4 20.0

As can be seen from Table 6, reducing the concentration of NaOH used for suction filtration and increasing the ratio of Ni-Al alloy weight (grams) to lye volume (milliliters) is conducive to improving the hydrogenation activity of the Raney Ni catalyst. High is not conducive to the catalytic activity of Raney Ni catalyst.

The specific embodiments of the present invention have been set forth above, and those skilled in the art can make modifications and changes thereto without departing from the spirit and scope of the present invention as appended claims.

Claims (7)

1. the method for preparing Raney Ni catalyst, described method comprises the following steps:

(i) nickel alumin(i)um alloy is ground to form 80～100 purpose particles;

(ii) the particle of step (i) is added in the NaOH solution and stirs, weight alloy gram number is 1: 8～1: 15 with the ratio of alkali lye volume milliliter number, this solution was carried out ultrasonic wave extracting aluminium 5～30 minutes, ultrasonic frequency is 28～48kHz, bath temperature is 25～60 ℃, the ultrasonic wave extracting finishes the back and continues to stir 2～6 hours, removes upper strata alkali lye afterwards, and overall process is carried out in inert gas;

(iii) step particle (ii) spends deionised water to neutral, removes with absolute ethanol washing and anhydrates, and makes Raney Ni catalyst.

2. the method for claim 1 is characterized in that, ultrasonic frequency is 28kHz or 48kHz.

3. the method for claim 1 is characterized in that, the bath temperature during the ultrasonic wave extracting is 30～50 ℃.

4. the method for claim 1 is characterized in that, the ultrasonic wave extracting time is 10～20 minutes.

5. Raney Ni catalyst with the preparation of method according to claim 1, the nickel content that it is characterized in that described catalyst is 70～90 weight %, specific area is at 70～100 meters ²/ gram scope, pore volume are 0.054～0.085 centimetre ³/ gram, pore-size distribution is in 2.0～220nm scope, and average pore size is 2.84～3.66nm.

6. with the application of Raney Ni catalyst in hydrogenation reaction of method preparation according to claim 1.

7. application as claimed in claim 6 is characterized in that, described hydrogenation reaction is the prepared from benzene and hydrogen cyclohexane.