CN100566829C - Catalyst for preparing acrylonitrile by ammonia oxidizing method - Google Patents

Abstract

The invention relates to an acrylonitrile fluidized bed catalyst prepared by ammoxidation, which mainly solves the problem that in the prior art, the reaction yield of acrylonitrile catalysts in industrial devices is not high, and gradually decreases with time, and the by-products CO ₂ , CO, and HCN increase. , The catalyst stability is not good enough. The present invention adopts the carrier selected from SiO ₂ , Al ₂ O ₃ or a mixture thereof, and the active component contained is represented by the following general formula: Mo ₁₂ Bi _a Fe _{b Nic} X _d Y _e Z _f Q _g O _x ; Wherein X is at least one selected from Mg, Co, Ca, Be, Cu, Zn, Mn or Te; Y is at least one selected from La, Ce or Sm; Z is selected from K, Rb, Na At least one of , Li or Cs; Q is selected from at least one of Ti or Zr or its technical scheme with a mixture of at least one of Nb or Sb to form a catalyst solves this problem well, It can be used in the industrial production of acrylonitrile by propylene ammoxidation.

Description

Catalyst for the preparation of acrylonitrile by ammoxidation

technical field

The invention relates to a fluidized bed catalyst for preparing acrylonitrile by ammoxidation.

Background technique

The ammoxidation of olefins to prepare α and β unsaturated nitriles was developed by BP in the 1960s. The core technology of this process is to use a catalyst whose active components contain Mo and Bi. After continuous improvement, the Mo-Bi series catalyst is very mature at present, and the process of preparing acrylonitrile by ammoxidation of propylene has been widely used in industry. In the past, the improvement of the catalyst was mainly carried out from the aspects of the activity and stability of the catalyst, such as adding transition metals to the active component to improve the activity and increase the yield of the product; adding rare earth elements to improve the redox ability; adding elements such as Na and P To improve the wear resistance of the catalyst; add Fe, Co, Ni and other elements to inhibit the sublimation of Mo, improve the stability of the catalyst, etc.

Patents CN 99119905.7, CN 99119906.5, CN 97106771.6 and CN 96101529.2 all introduced improved Mo-Bi catalysts for the ammoxidation of propylene and isobutylene to unsaturated nitrile catalysts. The advantages of these catalysts are good oxidation-reduction stability and good The reaction yield, reaction ammonia ratio and reaction temperature are lower.

Patents CN 01113194.2, CN 01113193.4 and CN 01113192.6 introduced the method of taking part of metals and organic ligands, chelating agents or surfactants in the catalyst preparation process to improve the performance of catalysts under low ammonia ratio reaction conditions.

Patents CN 03151170.8 and CN 03151169.4 describe that in the catalyst preparation process, 2-25% of solid silica with a particle size of 5-100 nanometers is added to the carrier starting material silica sol to improve catalyst performance.

Contents of the invention

The technical problem to be solved by the present invention is that the reaction yield of the prior art acrylonitrile catalyst in the industrial device is not high, and gradually decreases with time, and the by-products CO ₂ , CO, and HCN increase, and the stability of the catalyst has become the focus of the industry. One of the problems is to provide a new fluidized bed catalyst for the ammoxidation of propylene to acrylonitrile. The catalyst is suitable for operation under the conditions of lower air ratio, ammonia ratio and lower reaction temperature, and has excellent catalyst reactivity and stability.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is as follows: a catalyst for the production of acrylonitrile by ammoxidation, which is selected from SiO ₂ , Al ₂ O ₃ or a mixture thereof as a carrier, and the active component contained is represented by the following general formula:

Mo ₁₂ Bi _a Fe _b Ni _c X _d Y _e Z _f Q _g O _x

Wherein: X is at least one selected from Mg, Co, Ca, Be, Cu, Zn, Mn or Te;

Y is at least one selected from La, Ce or Sm;

Z is at least one selected from K, Rb, Na, Li or Cs;

Q is at least one selected from Ti or Zr or a mixture thereof with at least one selected from Nb or Sb;

The value range of a is 0.1~6.0;

The value range of b is 0.1~10.0;

The value range of c is 0.1~10.0;

The value range of d is 0.1~10.0;

The value range of e is 0.1~9.5;

The value range of f is >0~0.5;

The value range of the sum of e+f is 0.15～10.0;

The value range of g is >0~5.0;

x is the total number of oxygen atoms needed to satisfy the valence of other elements, and the amount of the support is 30-70% of the weight of the catalyst.

In the above technical solution, the preferred value range of a is 0.2-4.0; the preferred range of b is 0.5-5.0; the preferred range of c is 1.0-8.0; the preferred range of d is 0.5-5.0; The preferred range of values is 0.2-2.0; the preferred range of f is 0.01-0.5; the preferred range of the sum of e+f is 0.2-2.0; the preferred range of g is 0.1-4.0, and the more preferred range is 0.2-1.0; the preferred range of the amount of the carrier is 40-60% of the weight of the catalyst.

Catalysts can be prepared by coprecipitation methods familiar to those skilled in the art. The starting material of the required metal element is the corresponding water-soluble salt. The starting material of the metal element is dissolved to make a mixed salt solution, and the starting material of the carrier is prepared into a slurry by co-precipitation method. After the slurry is aged, it is spray-dried and granulated , and then calcined at high temperature to obtain the finished catalyst, the calcining temperature is 500°C-610°C.

In the embodiment given below, the investigation evaluation condition to catalyst is:

Reactor: fluidized bed reactor, inner diameter 38 mm

Catalyst filling amount: 550 grams

Reactor top pressure: 0.084MPa (gauge pressure)

Reaction temperature: 430°C

Response time: 4 hours

Raw material ratio: propylene/ammonia/air=1/1.1/9.5

WWH: 0.06 hours ^-1

The reaction product was absorbed with dilute acid at 0°C, and the product was analyzed by a combination of gas chromatography and chemical analysis. And calculate the carbon balance, when the carbon balance is (95-105)%, it is valid data.

Propylene conversion, acrylonitrile yield and selectivity are defined as:

The present invention suppresses the ammoxidation reaction through the synergistic effect of introduced rare earth elements, alkaline earth elements and alkali metal elements and at least one selected from Ti or Zr or a mixture element selected from at least one of Nb or Sb The formation of by-products in the catalyst maintains high catalyst activity, significantly improves the yield and stability of the target product of the catalyst, and achieves good technical results.

The present invention will be further elaborated below by embodiment.

Detailed ways

[Comparative Example 1]

Add 441.4 grams of (NH ₄ ) ₆ Mo ₇ O ₂₄ ·4H ₂ O to 330 grams of warm water at 70°C, stir to dissolve it, and add 1400 grams of 40% (wt.) silica sol to prepare material A.

Add 213.1 grams of Fe(NO ₃ ) ₃ ·9H ₂ O into 150 grams of 70°C hot water, stir to dissolve, then add 201.8 grams of Bi(NO ₃ ) ₃ ·5H ₂ O, 274.8 grams of Ni(NO ₃ ) ₃ · 6H ₂ O, 96.3 g of Mg(NO ₃ ) ₃ ·6H ₂ O, 72.5 g of La(NO ₃ ) ₃ ·3H ₂ O, and 18.6 g of Sm(NO ₃ ) ₃ ·3H ₂ O were stirred and dissolved to produce material B.

1.1 g of KNO ₃ , 0.9 g of NaNO ₃ and 2.0 g of CsNO ₃ were dissolved in 20 g of water and added to feed B to form feed C.

Add material C dropwise to material A under rapid stirring to form catalyst slurry. After aging at 70°C for 3 hours, it was spray-dried, and the obtained particles were calcined in a rotary calciner at 580°C for 3 hours to obtain a finished catalyst.

[Embodiments 1 to 11]

According to the same preparation process as the comparative example, the catalyst composition was prepared according to Table 1. The finished catalysts were inspected according to the above-mentioned inspection and evaluation conditions, and the initial activity results are shown in Table 2. The 250-hour stability test results of Comparative Example 1 and Example 9 are shown in Table 3.

Table 1 Catalyst

Catalyst composition Comparative example 1 Mo₁₂Bi_2.0Fe_2.5Ni_4.5Mg_1.8La_0.8Sm_0.2K_0.05Cs_0.05Na_0.05+50%SiO<sub>2</sub sub> Example 1 Mo₁₂Bi_1.2Fe_2.5Ni_4.5Co_2.0Ce_0.8Sm_0.2Ti_0.04K_0.03Na_0.05+50%SiO₂ sub>+10% Al₂O₃ Example 2 Mo₁₂Bi_0.5Fe_1.8Ni_6.0Mg_2.5La_0.8Nb_0.1K_0.1Cs_0.05Na_0.04+30%SiO₂ sub>+20% Al₂O₃ Example 3 Mo₁₂Bi_0.2Fe_2.0Ni_6.8Mg_0.8Sm_0.6Zr_0.15Cs_0.05Sb_0.2+50%SiO₂ Example 4 Mo₁₂Bi_2.0Fe_1.5Ni_4.5Co_4.0Zr_0.5La_1.5Cu_0.6K_0.02Cs_0.05Na_0.05+ 40%SiO₂+15%Al₂O₃ Example 5 Mo₁₂Bi_0.8Fe_1.0Ni_3.0Mg_1.8La_0.8Sm_0.2K_0.05Cs_0.05Nb_0.1Sb_0.3+ 35%SiO₂+10%Al₂O₃ Example 6 Mo₁₂Bi_1.2Fe_2.2Ni_5.3Mn_1.8Ce_0.8Ca_0.2Sb_0.22K_0.05Cs_0.05Na_0.05Te _0.3+50% SiO₂ Example 7 Mo₁₂Bi_0.3Fe_4.9Ni_4.5Mg_2.8Pb_0.2Ce_1.3Zr_0.07Ti_0.82K_0.05Cs_0.05Na _0.05+40% Al₂O₃ Example 8 Mo₁₂Bi_0.7Fe_2.5Ni_2.5Zr_0.9Zn_3.2Ce_0.3Na_0.05Sb_0.3+45%SiO₂ Example 9 Mo₁₂Bi_2.0Fe_3.0Ni_4.5Mg_1.8La_0.8K_0.05Cs_0.1Ti_0.3Nb_0.03+45%SiO_{2</sub sub>+5% Al₂O₃ Example 10 Mo₁₂Bi_2.0Fe_2.5Ni_4.5Mg_1.8La_1.2Sb_0.13Ti_1.0Rb_0.05Cs_0.05+25%SiO₂ sub>+25%Al₂O₃ Example 11 Mo₁₂Bi_1.7Fe_2..2Ni_5.5Mg_2.5La< sub>0.4}Ti_0.1K_0.05Cs_0.05Na_0.05+55%SiO₂

Table 2 preliminary activity investigation result

Acrylonitrile single charge (%) Acrylonitrile selectivity (%) Propylene conversion (%) Comparative example 1 76.5 78.0 98.1 Example 1 79.5 80.1 99.2 Example 2 78.6 80.6 97.5 Example 3 80.2 81.2 98.8 Example 4 83.0 83.2 99.8 Example 5 78.9 81.8 96.4 Example 6 80.6 81.8 98.5 Example 7 75.6 79.9 94.6 Example 8 79.1 80.8 97.9 Example 9 83.2 84.5 98.5 Example 10 73.5 78.4 93.8 Example 11 81.3 81.6 99.6

Table 3 Catalyst stability test result

Claims (4)

1. A catalyst for the production of acrylonitrile by ammoxidation, with a carrier selected from SiO ₂ , Al ₂ O ₃ or a mixture thereof, and the active component contained is represented by the following general formula: Mo ₁₂ Bi _a Fe _b Ni _c X _d Y _e Z _f Q _g O _x Wherein: X is at least one selected from Mg, Co, Ca, Be, Cu, Zn, Mn or Te; Y is at least one selected from La, Ce or Sm; Z is at least one selected from K, Rb, Na, Li or Cs; Q is at least one selected from Ti or Zr or a mixture thereof with at least one selected from Nb or Sb; The value range of a is 0.1~6.0; The value range of b is 0.1~10.0; The value range of c is 0.1~10.0; The value range of d is 0.1~10.0; The value range of e is 0.1~9.5; The value range of f is >0~0.5; The value range of the sum of e+f is 0.15～10.0; The value range of g is >0~5.0; x is the total number of oxygen atoms needed to satisfy the valence of other elements, and the amount of the support is 30-70% of the weight of the catalyst. 2. The acrylonitrile catalyst according to claim 1, characterized in that the value range of a is 0.2-4.0; the value range of b is 0.5-5.0; the value range of c is 1.0-8.0; d The value range of e is 0.5～5.0; the value range of e is 0.2～2.0; the value range of f is 0.01～0.5; the value range of the sum of e+f is 0.2～2.0; the value range of g is 0.1 ~4.0. 3. The catalyst for producing acrylonitrile by ammoxidation method according to claim 2, characterized in that the value of g is in the range of 0.2-1.0. 4. The catalyst for producing acrylonitrile by ammoxidation method according to claim 1, characterized in that the amount of carrier used is 40-60% of the weight of the catalyst.