CN104128195A - Catalyst for preparing cyanopyridine and preparation method thereof - Google Patents

Abstract

The invention relates to a catalyst for preparing cyanopyridine and a preparation method. The catalyst for the preparation of cyanopyridine of the present invention is a procatalyst composed of the vanadium oxide of the main catalyst and other transition metal oxides, alkali metal oxides, oxides of the fifth group metal elements, and phosphorus oxides, and Vector composition. Relevant experiments show that the catalyst of the invention has the characteristics of high catalytic efficiency, low production cost, wide application range, good economic benefits, remarkable energy saving, convenient use and the like.

Description

Catalyst and preparation method for preparing cyanopyridine

technical field

The invention relates to a catalyst for preparing cyanopyridine and a preparation method.

Background technique

At present, the main method of industrial production of 3-cyanopyridine is to use 3-picoline as raw material, and it is prepared by ammoxidation reaction under the action of NH ₃ , O ₂ and a catalyst, that is, 3-picoline ammoxidation method. The ammoxidation reaction refers to a type of reaction in which olefins, aromatic hydrocarbons, alkanes and their derivatives are mixed with air (O ₂ ) and NH ₃ on a catalyst to obtain cyanide compounds. The general reaction formula is:

R-CH ₃ +NH ₃ + O ₂ —— R-CN+H ₂ O

The possible reaction process of this reaction is: first, R-CH ₃ is dehydrogenated under the action of a catalyst to generate R-CH ₂ free radicals, which absorb oxygen to form R-CHO, and then R-CHO condenses with NH ₃ to form nitriles, or R-CHO is first oxidized to form R-COOH, and then reacted with _NH3 to form an amide and then hydrolyzed to form a nitrile.

The ammoxidation reaction process is a complex process, in addition to the main reaction, there are many side reactions, and the difficulty lies in the preparation of the catalyst. The catalyst for the ammoxidation reaction not only requires high conversion, but also high selectivity. The possible reaction mechanism of 3-picoline ammoxidation to 3-cyanopyridine: 3-picoline is adsorbed by the catalyst and then dehydrogenated and oxidized in multiple steps to form formaldehyde pyridine or carboxypyridine, and then undergo cyanation reaction to form the product. Oxygen that participates in the oxidation reaction is not gas-phase oxygen but lattice oxygen on the catalyst surface; ammonia that participates in the reaction in the cyanidation reaction is not gas-phase ammonia but ·NH ₂ or -NH ₂ adsorbed on the catalyst surface. According to the experimental facts, the cyanidation rate is much faster than the oxidation rate, so the steps to control the reaction rate are dehydrogenation and oxidation, and because the intermediate product of the synthesis of cyanopyridine is easily oxidized deeply, the catalyst is required to have a reasonable number of dehydrogenation centers And donate [O] center number and suitable donate [O] activity. This provides a theoretical basis for the preparation of catalysts.

The patent application (publication number CN102336706A) discloses a process for preparing 3-cyanopyridine by catalyzing the ammoxidation of 3-picoline with V-Cr or VP-based or V-Sb system molten salt as a catalyst. According to the content disclosed in the application document, this preparation method has the advantages of high thermal conductivity, high conversion rate, high selectivity and long service life. However, the application file lacks necessary technical features, so people in the industry cannot understand its specific technical content and content of invention

The invention provides a catalyst capable of efficiently catalyzing and preparing cyanopyridine.

A catalyst for preparing cyanopyridine of the present invention is composed of vanadium oxide of the main catalyst and auxiliary oxides of other transition metal oxides, alkali metal oxides, oxides of the fifth group metal elements, and phosphorus oxides. Catalyst, and carrier composition.

The transition group metal oxide in the cocatalyst of the catalyst for preparing cyanopyridine of the present invention is any oxide of iron, molybdenum, chromium or a mixture of any several oxides, and the oxide of the fifth group metal element is bismuth The oxides used are porous aluminum oxide and titanium dioxide.

The metal content and the mass percent of aluminum oxide and titanium oxide in the catalyst component for preparing cyanopyridine in the present invention are: V: Fe: Mo: Cr: Bi: K: P: Al ₂ O ₃ : TiO ₂ =1-10 %: 0.1-1%: 0.1-1%: 0.2-2%: 0.1-1%: 0.1-1%: 0.5-5%: 50-75%: 10-20%.

The content of each component of the catalyst for the preferred preparation of cyanopyridine in the present invention is: vanadium pentoxide: 28g, ferric oxide: 1.45g, molybdenum trioxide: 2.5g, chromium oxide 1.72g, bismuth oxide 2.4g, chloride Potassium, 1.5g, phosphorus pentoxide 9g, carrier Al ₂ O ₃ : 180g, TiO ₂ : 40g.

The preparation method of the catalyst for the preparation of cyanopyridine of the present invention is: take the nitrates of vanadium pentoxide, phosphorus pentoxide, potassium oxide and other metals according to the component weight, add the above-mentioned each raw material in the oxalic acid aqueous solution and stir to dissolve Then add the carrier in it, dry it after fully impregnated, then roast it at high temperature, and get the catalyst after sieving

The present invention is used to prepare the preferred preparation method of the catalyst of cyanopyridine: take by weighing 68 g vanadium pentoxide, 5g ferric nitrate, 7.5g ammonium molybdate, 9g chromium nitrate, 5g bismuth nitrate, 4.5g potassium chloride, 12g Add phosphorus pentoxide into 800mL oxalic acid aqueous solution, stir and dissolve at 60-90 ^o C, add Al ₂ O ₃ : 180g, TiO ₂ : 40g catalyst support for impregnation, and then put the impregnated solid at 100 ℃- Fully dry at 200°C, then bake at 500°C-900°C for 3-10 hours, and sieve into particles with a size of about 30 meshes.

Relevant experiments show that the catalyst of the invention has the characteristics of high catalytic efficiency, low production cost, wide application range, good economic benefits, remarkable energy saving, convenient use and the like.

Detailed ways

The present invention is illustrated in detail below through examples.

1. Catalyst preparation

Take by weighing 68 g vanadium pentoxide, 5g iron nitrate, 7.5g ammonium molybdate, 9g chromium nitrate, 4.8g bismuth nitrate, 5g bismuth nitrate, 4.5g potassium chloride, 12g phosphorus pentoxide and add in 800mL oxalic acid aqueous solution, in Stir and dissolve at 60-90 ^o C, and add 200-300g of catalyst carrier (aluminum oxide, titanium dioxide) with good high temperature resistance to impregnate. The impregnated catalyst is fully dried at 100°C-200°C, then calcined at 500°C-900°C for 3-10 hours, and sieved into particles with a size of about 30 meshes. Just made the 3-picoline ammoxidation catalyst mentioned in the present invention to prepare 3-cyanopyridine.

2. Catalyst evaluation

Using a tubular fixed-bed microreactor, the catalytic activity of the catalyst of the present invention was evaluated by taking the ammoxidation reaction of 3-picoline to prepare 3-cyanopyridine as an example.

The experimental scheme is as follows: 3-cyanopyridine is prepared using air as an oxygen source, and 3-picoline, ammonia and water as raw materials. The mixed raw material (5-10mL/h) and air (200 mL/min) are mixed in a certain ratio and then sent to a 220 ^o C preheater, and then the preheated raw material and superheated air are sent into it and filled with the above-mentioned The inventive catalyst is used for ammoxidation in a fixed-bed reactor. The ratio of raw materials for the evaluation reaction was: based on 100 mL of solution, 3-picoline: 15 mL, ammonia water (wt 28%): 42.5 mL, water: 42.5 mL. The reaction product is cooled and collected by the product collection tank, and the tail gas is absorbed by the tail gas absorption tank and then emptied. Take a sample and analyze it. The results show that the raw material conversion rate and product selectivity of the 3-picoline ammoxidation catalyzed by the catalyst of the present invention are still above 90%-98%.

The catalyst of the present invention was used to prepare the corresponding cyanopyridines from picolines with similar results.

Claims (6)

1. A catalyst for preparing cyanopyridine, consisting of the vanadium oxide of the main catalyst and a cocatalyst formed with other transition metal oxides, alkali metal oxides, oxides of the fifth group metal elements, and phosphorus oxides, and carrier composition. 2. the catalyzer preparing cyanopyridine according to claim 1 is characterized in that the transition group metal oxide used for co-catalyst is any oxide of iron, molybdenum, chromium or the mixture of any several oxides, the first The oxides of the five group metal elements are oxides of bismuth, and the carriers used are porous aluminum oxide and titanium dioxide. 3. the catalyst for preparing cyanopyridine according to claim 2, is characterized in that the mass percentage of metal content and aluminum oxide, titanium oxide in the catalyst component is: V: Fe: Mo: Cr: Bi: K: P : Al ₂ O ₃ : TiO ₂ =1-10%: 0.1-1%: 0.1-1%: 0.2-2%: 0.1-1%: 0.1-1%: 0.5-5%: 50-75%: 10 -20%. 4. the catalyst for preparing cyanopyridine according to claim 3 is characterized in that each component content of catalyst is: vanadium pentoxide: 28g, ferric oxide: 1.45g, molybdenum trioxide: 2.5g, chromium oxide 1.72g, bismuth oxide 2.4g, potassium chloride, 1.5g, phosphorus pentoxide 9g, carrier Al ₂ O ₃ : 180g, TiO ₂ : 40g. 5. the preparation method of the catalyzer of preparing cyanopyridine described in claim 3 is characterized in that taking by weighing the nitrate of vanadium pentoxide, phosphorus pentoxide, potassium oxide and other metals by component weight, adding aforementioned each raw material Stirring and dissolving in the oxalic acid aqueous solution, then adding the carrier therein, fully impregnating, drying, then roasting at high temperature, and sieving to obtain the catalyst. 6. the preparation method of the catalyzer of preparing cyanopyridine described in claim 4 is characterized in that taking by weighing 68 g vanadium pentoxide, 5g ferric nitrate, 7.5g ammonium molybdate, 9g chromium nitrate, 5g bismuth nitrate, 4.5g Add potassium chloride, 12g phosphorus pentoxide into 800mL oxalic acid aqueous solution, stir and dissolve at 60-90 ^o C, add Al ₂ O ₃ : 180g, TiO ₂ : 40g catalyst carrier for impregnation, and then impregnate the impregnated The solid is fully dried at 100°C-200°C, then calcined at 500°C-900°C for 3-10 hours, and sieved into particles with a size of about 30 meshes.