Method for preparing pyridine bases

Abstract

The invention relates to a method for preparing pyridine bases. The pyridine bases are prepared by taking formaldehyde, acetaldehyde and ammonia as raw materials through the steps of carrying out chemical synthesis on the formaldehyde, the acetaldehyde and the ammonia in a fixed bed reactor in the presence of a catalyst at a temperature of 350 to 550 DEG C so as to obtain a high-temperature gas containing the pyridine bases; condensing the high-temperature gas so as to obtain a solution containing the pyridine bases, and carrying out ammonia absorption and steam stripping on the uncondensable ammonia-containing gas; then recovering the obtained ammonia and feeding the ammonia to the fixed bed reactor to be used as raw materials; extracting the obtained solution by benzene, then respectively obtaining a benzene solution containing the pyridine bases and a water solution containing a small amount of ammonia, benzene and pyridine bases, etc., after the solutions are processed, feeding the solutions to a combustion furnace to burn at a temperature of 1000 to 1200 DEG C; then discharging the solutions; feeding the benzene solution containing the pyridine bases into a benzene stripper to carry out steam stripping, then respectively obtaining benzene and pyridine base liquor, feeding the pyridine base liquor into different rectifying towers to carry out rectification under normal pressure or negative pressure, then respectively obtaining pyridine, 3-picoline and 2-picoline. The method in the invention has the advantages of low material consumption, high total yield, less catalyst consumption, and low energy consumption, and is simple in operation.

Description

Technical field: [0001] The invention relates to a preparation method in the field of chemical industry, in particular to a method for preparing pyridine base. Background technique: [0002] Pyridine base is a general term for mixtures containing pyridine, 3-picoline, 2-picoline, 4-picoline, 2,4-lutidine, etc. Pyridine base is a nitrogen-containing heterocyclic core common compound of nitrogen-containing heterocyclic pesticides, medicines, veterinary drugs and three-drug intermediates, commonly known as the "chip" of heterocyclic three-drugs and three-drug intermediates. It is also an important raw material for daily chemicals, food spices, feed additives, and radial tires. Statistics show that there are more than 50 types of pesticides that only use pyridine bases, and more than 50 types of synthetic medicines. Important food and feed additives such as niacin and nicotinamide still rely on imports because there is not enough supply of pyridine bases. The manufacturing pro...

AI Technical Summary

Problems solved by technology

[0015] The most critical step of producing pyridine base by the above method is the synthesis process of pyridine base. According to the existing method for producing pyridine base, if a single fixed bed is used for production, a large amount of carbon will be separated out in the process of synthesizing pyridine base. Deactivation must be stopped for treatment, so it can only be produced intermittently; if a fluidized bed reactor is used, the catalyst will collide and easily break into fine catalysts during the production process, and the fine catalysts will be carried out with the synthesis gas, resulting in larger catalysts Loss, because the price of catalyst is as high as 400,000-500,000 yuan / ton, and the amount of catalyst replenishment is large, and the cost is high

In addition, the common production process unprocesses the non-condensable gas in the synthesis gas and the extracted aqueous solution containing a small amount of ammonia, benzene and pyridine alkali, etc., and recycles the useful components directly to the incinerator for incineration, resulting in high raw material consumption and high energy consumption. , thus increasing the cost of producing pyridine base

Because the ammonia in the non-condensable gas in the synthesis gas and the ammonia and benzene in the raffinate have not been recovered, even after incineration, the pollution to the environment is still very serious