Search

CN-122006780-A - Catalyst for preparing isophthalonitrile by ammonia oxidation method, preparation method and application

CN122006780ACN 122006780 ACN122006780 ACN 122006780ACN-122006780-A

Abstract

The invention discloses a catalyst for preparing isophthalonitrile by an ammoxidation method, a preparation method and application thereof, wherein the catalyst is used for preparing isophthalonitrile by the low-temperature high-efficiency ammoxidation, and the preparation method comprises the steps of adopting an aqueous solution of Fe, co and Mn salts to load on a-BNC to obtain sub-nanometer Fe-Co-Mn ternary nitride clusters, and nitriding the sub-nanometer Fe-Co-Mn ternary nitride clusters in a mixed gas of NH 3 and H 2 at 300-340 ℃ to obtain the catalyst. The nitrogen vacancy on the surface of the nitride is utilized to activate NH 3 to generate NH 2 free radical, high-selectivity C-H amination is realized, sub-nanoclusters are anchored at B-N defect positions of the a-BNC carrier, and the whole process does not contain limited elements such as V/Mo and the like. The catalyst has the isophthalonitrile yield reaching 90.00% and selectivity 91.20% at 300 ℃, and provides a new path for green synthesis of high-end nitrile compounds.

Inventors

  • SUN HAIFENG
  • ZHAO HUI
  • FENG CHENGWEI
  • ZHOU ZHIWEI

Assignees

  • 泰州百力化学股份有限公司

Dates

Publication Date
20260512
Application Date
20260410

Claims (4)

  1. 1. A catalyst for preparing isophthalonitrile by an ammoxidation method is characterized in that an aqueous solution of Fe, co and Mn salts is loaded on a-BNC to obtain sub-nanometer Fe-Co-Mn ternary nitride clusters, and the sub-nanometer Fe-Co-Mn ternary nitride clusters are nitrided in mixed gas of NH 3 and H 2 at 300-340 ℃ to obtain the catalyst; the a-BNC is an amorphous boron nitrogen co-doped carbon carrier, wherein the atomic ratio of B to N to C is 1 (1.8-2.5): 8-12; The sub-nanometer Fe-Co-Mn ternary nitride cluster has a chemical formula of Fe a Co b Mn c N, wherein a=1.0, b=1.0, c=1.0, and the cluster size is 0.8-1.6nm; the concentration of nitrogen vacancies on the surface of the catalyst is more than or equal to 1.8X10 19 cm -3 .
  2. 2. A method for preparing a catalyst for preparing isophthalonitrile by an ammoxidation process as claimed in claim 1, comprising the steps of: (1) Mixing boric acid, melamine and glucose into deionized water according to the atomic ratio, preparing a suspension with the total solid content of 15-20wt%, transferring the suspension into a reaction kettle, performing hydrothermal reaction at 180 ℃ for 10-14 h, naturally cooling to room temperature after the reaction is finished, washing a product by deionized water for 3 times, washing by absolute ethyl alcohol for 2 times, and performing vacuum drying at 80 ℃ for 12h, placing the dried product into a tubular furnace, heating to 600 ℃ at the nitrogen flow rate of 50 mL/min, performing constant-temperature carbonization for 2-3 h at the temperature of 3 ℃ and performing natural cooling to room temperature, and grinding by a 60-mesh sieve to obtain the amorphous boron-nitrogen co-doped carbon carrier a-BNC; (2) Preparing Fe, co and Mn salts into a metal salt solution with the total metal concentration of 15wt.% according to the metal molar ratio of 1:1:1, loading the metal salt solution on an amorphous boron nitrogen Co-doped carbon carrier a-BNC by adopting an isovolumetric impregnation method, and drying at 120 ℃ for 4 hours to obtain a sub-nanometer Fe-Co-Mn ternary nitride cluster; (3) Placing the sub-nanometer Fe-Co-Mn ternary nitride cluster obtained in the step (2) in a tube furnace, introducing mixed gas of NH 3 and H 2 with the volume ratio of 9:1 and the flow rate of 80-120 mL/min, performing constant temperature treatment for 3-5H at 300-340 ℃, naturally cooling to below 100 ℃ after the reaction is finished, and cooling to room temperature under nitrogen protection instead to obtain the catalyst.
  3. 3. The method for preparing the catalyst for preparing the isophthalonitrile by the ammoxidation method according to claim 2, wherein the hydrothermal reaction temperature in the step (1) is 180 ℃, the reaction time is 12 hours, the carbonization temperature is 600 ℃, the carbonization time is 2 hours, the metal salt solution in the step (2) is one or more of nitrate, acetate or hydrochloride, the nitridation temperature in the step (3) is 320 ℃, the nitridation time is 4 hours, and the volume ratio of NH 3 to H 2 is 9:1.
  4. 4. Use of a catalyst for preparing isophthalonitrile by ammoxidation according to any one of claims 1-3, wherein the reaction temperature is 280-340 ℃, the molar ratio of metaxylene to ammonia gas to hydrogen gas=1:3.0:5.0, and the gas volume space velocity is 1300 h -1 .

Description

Catalyst for preparing isophthalonitrile by ammonia oxidation method, preparation method and application Technical Field The invention relates to the technical field of non-noble metal catalysis and green fine synthesis, in particular to an iron-cobalt-manganese nitride/amorphous boron-nitrogen-carbon heterogeneous interface catalyst for synthesizing isophthalonitrile, a preparation method and application thereof. Background Isophthalonitrile is a key intermediate for synthesizing high-performance polyimide, antidepressant drugs and fluorescent brightening agent CBS-X, and the annual demand of the world is more than 1.2 ten thousand tons and increases at 8% of annual speed. The most important industrial synthesis route is the gas phase ammoxidation (taking meta-xylene as raw material, one-step reaction): 。 The atomic economy of the route reaches 82%, no waste water is generated, and the method is a key direction of development of green technology. However, its industrialization faces a triple technical barrier: (1) The catalyst system is highly dependent on noble metal materials such as V/Mo, and the risk of environment and supply chain exists. The V-Sb-O system adopts a V 2O5-Sb2O4/C catalyst in the prior art, the IPN yield is 65-70% at 385 ℃, but V 2O5 belongs to the list of priority control chemicals (second batch), leaching toxicity exceeds standard (the release amount of V 5+ is 0.6-1.2 mg/L > national standard 0.5 mg/L), and the activity attenuation is serious (the yield of 1000 h is reduced by 25%) due to volatilization of the V component in long-term operation. (2) The activity and the selectivity of the non-V/Mo system are difficult to be compatible. The Co-Mn-Al spinel is used as a catalyst, the IPN selectivity is 68.2% at 380 ℃ and the yield is 61.5%, the Co 3+/Mn4+ has strong oxidizing property, the aromatic ring opening is easy to be initiated, and the CO x selectivity is more than 8%. The Fe-Bi-O composite oxide is used as a catalyst, bi is introduced to promote NH 3 adsorption, but Bi is easy to reduce to a metallic state, bi is lost 32% after 500-h, and the yield is reduced to the initial 54%. The fundamental problem is that the existing non-V/Mo catalyst still depends on Mars-VAN KREVELEN mechanism (lattice oxygen participates), and the activity of the lattice oxygen is in negative correlation with the selectivity, namely, high-activity lattice oxygen is easy to cause C-C bond breakage. In a word, when the existing ammoxidation catalyst is applied to m-phthalonitrile synthesis, the existing ammoxidation catalyst still faces three technical bottlenecks of high toxicity, high energy consumption and insufficient selectivity, wherein a vanadium/molybdenum-containing system has environmental risks and is easy to cause excessive oxidation, and a non-vanadium molybdenum system lacks an efficient ammonia activation path, so that both high yield and long service life are difficult to achieve. Therefore, there is a need to develop a catalyst which does not depend on the conventional ammoxidation active elements and can realize high-selectivity conversion through a new reaction mechanism at low temperature, so as to break through the limitation of the prior art and meet the urgent demands of green chemical industry and high-end material industry. Disclosure of Invention Aiming at the problems, the invention relates to a novel catalyst system for synthesizing nitrile substances by ammoxidation of aromatic hydrocarbon by using a metal nitride or nitrogen vacancy free radical path, which breaks through the dependence of V/Mo and realizes MPN selectivity of more than or equal to 90%, reaction temperature of less than or equal to 340 ℃, nontoxic element composition and 2000 h stability attenuation of less than 15%. The invention is realized mainly by the following technical scheme: the catalyst for preparing isophthalonitrile by an ammoxidation method adopts nitrate aqueous solution of Fe, co and Mn to be loaded on a-BNC to obtain sub-nanometer Fe-Co-Mn ternary nitride clusters, and the sub-nanometer Fe-Co-Mn ternary nitride clusters are nitrided in mixed gas of NH3 and H2 at 300-340 ℃ to obtain the catalyst; (1) The a-BNC is an amorphous boron nitrogen co-doped carbon carrier, wherein the atomic ratio of B to N to C is 1 (1.8-2.5): 8-12; (2) The sub-nanometer Fe-Co-Mn ternary nitride cluster has a chemical formula of Fe aCobMnc N, wherein a=1.0, b=1.0, c=1.0, and the cluster size is 0.8-1.6nm; (3) The concentration of nitrogen vacancies on the surface of the catalyst is more than or equal to 1.8X10 19cm-3. A preparation method of a catalyst for preparing isophthalonitrile by an ammoxidation method comprises the following steps: (1) Mixing boric acid, melamine and glucose in deionized water according to the atomic ratio, preparing a suspension with the total solid content of 15-20wt%, transferring the suspension into a reaction kettle, performing hydrothermal reaction at 180 ℃ for 10-14 h, naturally coolin