CN102553597B - Preparation method of supported Ni-B amorphous catalyst for selective hydrogenation - Google Patents

Abstract

The invention relates to a preparation method of a supported Ni-B amorphous catalyst for selective hydrogenation. Ultrasonic waves, spray drying and microwave radiation are respectively introduced into an impregnation-reduction method to prepare the supported Ni-B amorphous catalyst. In the impregnation, drying and roasting process, the invention enhances the dispersity of the Ni precursor in the support and the interaction with the support, greatly improves the catalytic performance of the supported Ni-B amorphous alloy catalyst in the TDA (tolylenediamine) synthesis process by DNT (dinitrotoluene) hydrogenation, greatly shortens the preparation period of the catalyst, and has wide industrial prospects.

Description

A preparation method for selective hydrogenation supported Ni-B amorphous catalyst

technical field

The invention relates to a preparation method of a catalyst, in particular to a preparation method of a selective hydrogenation supported amorphous Ni-B alloy catalyst.

Background technique

Toluene diamine (TDA), also known as diaminotoluene, is widely used in industry, and its main use is as the production of toluene diisocyanate (TDI), and TDI is one of the important raw materials for the production of polyurethane. In industry, dinitrotoluene (DNT) is usually used to hydrogenate toluene diamine (TDA) in the presence of an external organic solvent and catalyst (reaction formula-1). Since the catalyst is one of the core technologies of DNT hydrogenation, in recent years, the research on DNT hydrogenation catalysts for the synthesis of toluenediamine has become a hot research topic at home and abroad.

DNT+6H ₂ →TDA+4H ₂ O (1)

Among the existing DNT hydrogenation catalysts, precious metal catalysts such as loaded palladium, platinum and rhodium have high activity, but the cost is high and easy to deposit carbon; Caustic soda extracts aluminum, causing serious environmental pollution, and it is easy to spontaneously ignite in the air, which has safety problems, and it is difficult to meet the requirements of continuous production.

Since 1980, amorphous alloys have attracted much attention as a new type of catalytic material. Among them, the supported Ni-B amorphous alloy catalyst exhibits excellent hydrogenation activity and selectivity in the field of catalytic hydrogenation, and at the same time overcomes the characteristics of small specific surface area and poor thermal stability of the non-supported Ni-B catalyst. Replace traditional framework nickel and noble metal catalysts. Therefore, it is of great practical significance to study the preparation of supported Ni-B amorphous alloy catalyst and its application in DNT hydrogenation reaction.

Patent CN1850330A discloses a supported amorphous alloy catalyst for the catalytic hydrogenation of phenol to cyclohexanone and its preparation method. The amorphous alloy catalyst is prepared by an equal-volume impregnation KBH ₄ reduction method. The preparation steps include: impregnating the metal salt precursor solution and the hydrotalcite carrier in equal volumes; drying; calcining; adding reducing agent KBH ₄ solution dropwise for reduction and washing. It has high activity and selectivity in the reaction of hydrogenation of phenol to prepare cyclohexanone.

Patent CN1196975A discloses a supported Ni-B amorphous alloy catalyst. It adopts porous material as catalyst carrier, preferably silicon oxide, aluminum oxide or activated carbon, and prepares Ni-B amorphous alloy catalyst through chemical reduction method and impregnation reduction.

Patents CN1850330A and CN1850330A adopt the conventional impregnation reduction method to prepare the supported Ni-B amorphous alloy catalyst, although the hydrogenation performance of the catalyst is improved to a certain extent. However, due to the uneven distribution of the Ni precursor in the carrier and the weak interaction with the carrier, the metal ions at the pores of the carrier are preferentially reduced during the reduction process, and the formed amorphous alloy will block the pores of the carrier. The excess reducing agent will self-decompose, thereby preventing the reduction of metal ions deposited in the deep pores of the carrier, resulting in a decrease in the content of active components and uneven radial distribution. At the same time, the catalyst preparation method is unfavorable for the industrial application of the catalyst due to many preparation steps and a long catalyst preparation period.

CN1546229A reports a preparation method of using inorganic oxides and molecular sieves as carriers, using metal Ag, Pd and Fe as inducers, and obtaining supported Ni-B amorphous alloy catalysts by electroless plating. In the obtained catalyst, Ni-B accounts for 5%-50% of the mass of the catalyst, wherein Ni/B=70:30. Although this method increases the dispersion of Ni-B on the surface of the carrier to a certain extent, in the reduction process, the reaction is carried out in the entire solution when the reducing agent reduces metal ions, so the amorphous alloy cannot be completely deposited on the carrier. A part of it aggregates and adheres to the walls of the container or deposits at the bottom of the container.

Contents of the invention

The purpose of this invention is to provide a method for preparing a supported Ni-B amorphous alloy catalyst which is uniformly dispersed on the surface of a carrier, has a strong interaction with the carrier, and greatly shortens the preparation period.

In order to overcome the problems in the preparation process of the above-mentioned supported Ni-B amorphous alloy catalyst. The present invention introduces ultrasonic wave, spray drying and microwave radiation respectively into the impregnation, drying and roasting process of preparation of supported Ni-B amorphous alloy catalyst by impregnation reduction method, which not only increases the dispersion degree of Ni precursor in the carrier and the The interaction of the support greatly improves the catalytic performance of the supported Ni-B amorphous alloy catalyst in the hydrogenation of DNT to TDA, and greatly shortens the preparation period of the catalyst, which has great industrial prospects.

The technical scheme that the present invention adopts and concrete steps are:

(1) Carrier pretreatment: Dry the 80-150 mesh SiO ₂ , Al ₂ O ₃ or activated carbon carrier at 80-120°C for 1-3 hours, and evaporate the water in the carrier to dryness;

(2) Impregnation: According to the load of Ni as 1-15wt%, nickel chloride, nickel nitrate or nickel acetate are formulated into a solution, then put into the carrier after drying, and impregnated in a medium-volume ultrasonic wave with a power of 30-100W 20-120min;

In the impregnation process, the above-mentioned metal ions can also be introduced by mixing and impregnating the soluble salt solution of Mo, Zr, Pd, Sn, Pt and other additives with the Ni solution, and the introduction amount is 0.1-30wt% of the Ni content;

(3) Drying: The impregnated suspension is dried by spray drying. The operating conditions of spray drying are: air inlet pressure 0.7-1.5MPa, air inlet temperature 220-250°C, and air outlet temperature 100-140°C;

(4) Roasting: under the condition of microwave radiation, the dried precursor is calcined at a temperature of 150-200°C for 20-100min to obtain Ni ²⁺ /carrier;

(5) Reduction: in the ice-water bath, the KBH ₄ solution of 0.5-2.5mol/L is adjusted to neutrality by the NaOH solution of 2.0mol/L, and the KBH _{4 :} Ni molar ratio is 1-5, Add it dropwise to the roasted Ni ²⁺ /carrier at a speed of 3-10ml/min. After the dropwise addition, continue to stir until no bubbles are generated. First wash with distilled water until neutral, then wash with ethanol three times and store In ethanol, the catalyst was prepared.

The application process conditions for preparing the catalyst of the present invention are: reaction temperature 80-150°C, reaction pressure 0.5-2.5MPa, methanol or ethanol as solvent, initial DNT concentration of 2-20wt%, and catalyst concentration of 0.1-10wt%.

The advantages of the present invention are as follows:

The present invention greatly improves the dispersion degree of the Ni precursor on the surface of the carrier through the ultrasonic impregnation method, and greatly shortens the impregnation time; dries the impregnated suspension by spray drying, and greatly shortens the drying time; The precursor of nickel is roasted. Due to the uniformity of microwave heating, the problem of Ni agglomeration on the surface of the carrier caused by uneven heating due to conventional heating is overcome, and the dispersion of Ni precursor in the carrier is greatly increased. The interaction with the carrier, so that the reduced Ni-B alloy can be more uniformly dispersed in the carrier.

The catalyst of the invention has high hydrogenation activity, especially high catalytic activity and selectivity for the reaction of DNT hydrogenation to prepare TDA.

Detailed ways

The specific implementation of the present invention will be further described in detail through specific examples below.

Example 1

1) Carrier pretreatment: Dry 5g of 80-100 mesh SiO ₂ carrier at 80°C for 1 hour.

2) Impregnation: Prepare 0.405g NiCl ₂ ·6H ₂ O into 10ml of aqueous solution, then put it into the dried carrier and impregnate it in an ultrasonic wave with an equal volume. The loading of Ni is 2wt%, and the impregnation time is 20min. It is 30W.

3) Drying: The impregnated suspension is dried by spray drying. The operating conditions of the spray drying are: inlet air pressure 0.7 MPa, inlet air temperature 220°C, and outlet air temperature 100°C.

4) Roasting: the dried precursor is calcined at 150° C. for 20 min under the condition of microwave radiation.

5) Reduction: adjust 2mol/L KBH ₄ solution to neutrality through 2.0mol/L NaOH solution in an ice _- water bath, and add it dropwise to the roasted Ni ²⁺ / In SiO ₂ , KBH ₄ /Ni=1 (molar ratio), after the dropwise addition, continue to stir until no bubbles are produced, wash with distilled water to neutrality, then wash with ethanol three times and store in ethanol to obtain the catalyst for future use. .

Example 2

1) Carrier pretreatment: Dry 5g of 100-120 mesh activated carbon carrier at 90°C for 2 hours.

2) Impregnation: 0.848g C ₄ H ₆ NiO ₄ 4H ₂ O and 0.018g PdCl ₂ were prepared into a 10ml mixed solution, then put into the dried carrier and impregnated with equal volume in ultrasonic wave, the loading capacity of Ni is 4wt%, the loading of Pd is 0.2wt%, the immersion time is 40min, and the ultrasonic power is 40W.

3) Drying: The impregnated suspension is dried by spray drying. The operating conditions of the spray drying are: inlet air pressure 1.0 MPa, inlet air temperature 230°C, and outlet air temperature 100°C.

4) Roasting: the dried precursor is calcined at 170° C. for 30 min under the condition of microwave radiation.

₅ ) Reduction: adjust 2mol/L KBH ₄ solution to neutrality through 2.0mol/L NaOH solution in an ice-water bath, and add it dropwise to the calcined Ni ²⁺ / In activated carbon, KBH ₄ /Ni=2 (molar ratio), after the dropwise addition, continue to stir until no bubbles are generated, wash with distilled water to neutrality, then wash with ethanol three times and store in ethanol to obtain a catalyst for future use.

Example 3

1) Carrier pretreatment: 5 g of 100-120 mesh γ-Al ₂ O ₃ carrier was dried at 100° C. for 3 hours.

2) Impregnation: 3.04g NiCl ₂ 6H ₂ O and 0.29g ZrCl ₄ were prepared into 10ml mixed aqueous solution, then placed in the dried carrier and impregnated in an equal volume in ultrasonic wave, the loading capacity of Ni was 15wt%, Zr The loading amount of is 2.5wt%, the immersion time is 80min, and the ultrasonic power is 60W.

3) Drying: The impregnated suspension is dried by spray drying. The operating conditions of spray drying are: inlet air pressure 1.2MPa, inlet air temperature 240°C, and outlet air temperature 120°C.

4) Roasting: the dried precursor was calcined at 210° C. for 40 min under the condition of microwave radiation.

₅ ) Reduction: adjust 2mol/L KBH ₄ solution to neutrality through 2.0mol/L NaOH solution in an ice-water bath, and add it dropwise to the roasted Ni ²⁺ / In γ-Al ₂ O ₃ , KBH ₄ /Ni=4 (molar ratio), after the dropwise addition, continue to stir until no bubbles are generated, wash with distilled water until neutral, then wash with ethanol three times and store in ethanol , to obtain the catalyst for use.

Example 4

1) Carrier pretreatment: 5 g of 100-120 mesh γ-Al ₂ O ₃ carrier was dried at 110° C. for 2 hours.

2) Impregnation: 4.96g Ni(NO ₃ ) ₂ ·6H ₂ O and 0.43g MoCl ₅ were prepared into 10ml mixed aqueous solution, and then put into the dried carrier and impregnated with equal volume in ultrasonic waves. The loading capacity of Ni was 20wt%, the Mo loading is 3wt%, the impregnation time is 100min, and the ultrasonic power is 70W.

3) Drying: The impregnated suspension is dried by spray drying. The operating conditions of the spray drying are: inlet air pressure 1.3 MPa, inlet air temperature 250°C, and outlet air temperature 120°C.

4) Roasting: the dried precursor was calcined at 230° C. for 50 min under the condition of microwave radiation.

₅ ) Reduction: adjust 2mol/L KBH ₄ solution to neutrality through 2.0mol/L NaOH solution in an ice-water bath, and add it dropwise to the roasted Ni ²⁺ / In γ-Al ₂ O ₃ , KBH ₄ /Ni=5 (molar ratio), after the dropwise addition, continue to stir until no bubbles are generated, wash with distilled water until neutral, then wash with ethanol three times and store in ethanol , to obtain the catalyst for use.

Example 5

1) Carrier pretreatment: Dry 5g of 140-200 mesh activated carbon carrier at 110°C for 2 hours.

2) Impregnation: 1.215g NiCl ₂ 6H ₂ O and 0.14g PtCl ₄ were prepared into 10ml mixed aqueous solution to prepare 10ml mixed aqueous solution, and then put into the dried carrier and impregnated with equal volume in ultrasonic wave, the loading capacity of Ni 6wt%, Pt loading 1.6wt%, immersion time 110min, ultrasonic power 60W.

3) Drying: The impregnated suspension is dried by spray drying. The operating conditions of spray drying are: inlet air pressure 1.4MPa, inlet air temperature 235°C, and outlet air temperature 110°C.

4) Roasting: the dried precursor is calcined at 200° C. for 60 min under the condition of microwave radiation.

₅ ) Reduction: adjust 2mol/L KBH ₄ solution to neutrality through 2.0mol/L NaOH solution in an ice-water bath, and add it dropwise to the roasted Ni ²⁺ / In activated carbon, KBH ₄ /Ni=4 (molar ratio), after the dropwise addition, continue to stir until no bubbles are produced, wash with distilled water to neutrality, then wash with ethanol three times and store in ethanol to obtain a catalyst for future use.

Example 6

1) Carrier pretreatment: Dry 5g of 100-120 mesh SiO ₂ carrier at 110°C for 2h.

2) Impregnation: 1.215g NiCl ₂ 6H ₂ O and 0.085g SnCl ₄ were prepared into 10ml mixed aqueous solution to make 10ml mixed aqueous solution, and then put into the dried carrier and impregnated with equal volume in ultrasonic wave, the loading capacity of Ni 6wt%, the Sn load is 0.8wt%, the immersion time is 60min, and the ultrasonic power is 60W.

3) Drying: The impregnated suspension is dried by spray drying. The operating conditions of the spray drying are: inlet air pressure 1.2 MPa, inlet air temperature 230°C, and outlet air temperature 100°C.

4) Calcination: Calcining the dried precursor at 200° C. for 100 min under the condition of microwave radiation.

5) Reduction: In an ice-water bath, adjust the KBH ₄ solution to neutrality through 2.0 mol/L NaOH solution in an ice-water bath, and add it dropwise to the roasted Ni ²⁺ at a rate _of 5 ml/min. /SiO ₂ , KBH ₄ /Ni=4 (molar ratio), after the dropwise addition, continue to stir until no bubbles are produced, wash with distilled water to neutrality, then wash with ethanol three times and store in ethanol to obtain the catalyst spare.

The activity evaluation results of each catalyst in the reaction of catalyzing the hydrogenation of DNT to TDA are shown in Attached Table 1:

Schedule 1

Claims (2)

1. a preparation method who is used for selecting hydrogenation support type Ni-B amorphous catalyst is characterized in that comprising the steps:

(1) carrier preliminary treatment: with 80-150 purpose SiO ₂, Al ₂O ₃Or absorbent charcoal carrier is at 80-120 ℃ of oven dry 1-3h, with the moisture evaporate to dryness in the carrier;

(2) dipping: the load capacity by Ni is 1-15wt%, and nickel chloride, nickel nitrate or nickel acetate are mixed with solution, then puts into the carrier after the oven dry, is the medium volume dipping of 30-100W ultrasonic wave 20-120min at power;

(3) drying: the suspension of dipping being finished by spray-drying carries out drying, and spray-dired operating condition is: air intake pressure 0.7-1.5MPa, EAT 220-250 ℃, leaving air temp 100-140 ℃;

(4) roasting: under 150-200 ℃ of temperature, roasting 20-100min obtains Ni at presoma under the microwave condition that drying is good ²⁺/ carrier;

(5) reduction: in ice-water bath with the KBH of 0.5-2.5mol/L ₄Solution, the NaOH solution by 2.0mol/L is with KBH ₄Solution is adjusted to neutrality, presses KBH ₄: the Ni mol ratio is 1-5, is added drop-wise to Ni after the roasting with the speed of 3-10mL/min ²⁺In/the carrier, after dropwising, continue to be stirred to without Bubble formation and finish, be washed with distilled water to first neutrality, be kept in the ethanol with after the ethanol washing three times again, make catalyst.

2. a kind of preparation method for selecting hydrogenation support type Ni-B amorphous catalyst as claimed in claim 1, it is characterized in that at dipping process also with soluble salt solution and the Ni solution hybrid infusion of Mo, Zr, Pd, Sn or Pt auxiliary agent, its metal ion is introduced carrier, and the introducing amount is the 0.1-30wt% of Ni content.