CN1712393A - Production of methacrylic acid - Google Patents

Abstract

Production of methacrylic acid consists of amidation, hydrolytic reaction and distillation purification. It is characterized by using a set of continuous reactor comprising reaction vessel, tubing reactor, thermal insulating device and amide acceptor. Its advantages include easy reacting temperature control, short reacting period and higher productivity.

Description

A kind of method of producing methacrylic acid

Technical field

The present invention relates to fine chemistry industry, be specifically related to a kind of method of producing methacrylic acid.

Background technology

The basic skills of producing methacrylic acid is sulfuric acid, acetone cyanohydrin to be dropped into reactor carry out amidate action, generates Methacrylamide, and the reaction that is hydrolyzed again generates methacrylic acid, distills purification at last.Amidate action is an important process process in the methacrylic acid production process.Amidate action has two chemical reaction processes: the first step, by sulfuric acid and acetone cyanohydrin reaction, generate α-formamido-sec.-propyl sulfuric acid hydrogen ester, and this reaction is thermopositive reaction, generating heat is 60kcal/mol; In second step, the α-formamido-sec.-propyl sulfuric acid hydrogen ester that is generated by the first step continues and sulfuric acid reaction, generates Methacrylamide, and this stage is thermo-negative reaction, Δ H _Inhale=-2.5kcal/mol.In the method for existing production methacrylic acid, amidate action all adopts the method for so-called intermittent reaction, this batch production method is that two processes of amidate action are finished in same reactor, concrete processing step is: sulfuric acid, acetone cyanohydrin are dropped into reactor simultaneously, and 90 ℃-100 ℃ of controlled temperature, feed intake after the end, be warming up to 130 ℃-140 ℃, carry out the reaction of second step.The shortcoming of intermittent reaction method is that reaction time is long, and plant factor is low; Also because to be heat release with heat absorption be reflected in the same reactor for two kinds carries out, reaction is difficult to control, and the especially common the first step is reacted incomplete phenomenon, thereby causes product purity and yield lower.

Summary of the invention

The method that the purpose of this invention is to provide a kind of production methacrylic acid that adopts continuous amidate action replaces the existing intermittently method of the production methacrylic acid of amidate action that adopts, with enhance productivity, product purity and yield.

The method of production methacrylic acid provided by the invention, comprise that amidate action generates Methacrylamide, the reaction that is hydrolyzed again generates methacrylic acid, distill technical process such as purification at last, it is characterized in that the continuous reaction unit of described amidate action flow process use one cover, this device is made up of reactor, tubular reactor, warmer and acid amides susceptor; Its amidate action flow process is as follows:

The first step: with the continuously feeding simultaneously of sulfuric acid, acetone cyanohydrin to reactor, the heat that reaction produces is helped to remove by reactor chuck and pot inner coil pipe water cooler, control reaction kettle temperature is 85 ℃-105 ℃, preferred 90 ℃-100 ℃, α-resultants such as formamido-sec.-propyl sulfuric acid hydrogen ester are overflowed by upflow tube, remove tubular reactor;

Second step: the first step is reacted the α-resultants such as formamido-sec.-propyl sulfuric acid hydrogen ester that generate and is entered tubular reactor, continues and sulfuric acid reaction, generates Methacrylamide, and the interior temperature of tubular reactor this moment is controlled at 120 ℃-150 ℃, preferred 130 ℃-140 ℃; Again resultants such as Methacrylamide are sent into warmer subsequently, reaction is tending towards fully, holding temperature is controlled at about 135 ℃; Cool off material at last and enter the acid amides susceptor.

The present invention adopts the feasible heat absorption of method, the thermopositive reaction of above-mentioned continuous amidate action abundant according to reaction mechanism, and temperature of reaction control easily, shorten reaction time relatively, both improved plant factor and production efficiency, and prevented the generation of polymkeric substance again, product purity and yield significantly improve.

Embodiment

Embodiment

Sulfuric acid, acetone cyanohydrin through spinner-type flowmeter, are dropped into reactor in 2: 1 (weight ratio) ratios, because the reaction of this moment is thermopositive reaction, so unlatching cooling system, make kettle temperature remain on 90 ℃-100 ℃, resultant overflows from the reactor overflow port, enters tubular reactor; Above-mentioned resultant of reaction continues in tubular reactor and sulfuric acid generation chemical reaction, this reaction is thermo-negative reaction, with being steam heated to 130 ℃-140 ℃, because temperature is low excessively, chemical reaction is dangerous, purity is too high, cause polymerization or charing easily, so controlled temperature is a key factor; For reaction is tending towards fully, resultant enters warmer again, and holding temperature is controlled at about 135 ℃; Then cool off material and enter the acid amides susceptor, so far the flow process of amidate action is finished, and begins to enter other operation that methacrylic acid is produced.

Table 1 is the correlation data of the purity of the Methacrylamide that generates of present embodiment and traditional method amidate action.

Table 1

Method	Methacrylamide purity (%)
		The present embodiment method	????36
Traditional method	????32

Table 1 data declaration, the purity of the Methacrylamide of present embodiment obviously improves.

Table 2 is correlation datas of the present invention and produced in conventional processes methacrylic acid.

Table 2

Production method	Methacrylic acid purity (%)	Product yield (%)	Production efficiency (kg/h)
				The present embodiment method	????99.5	????88	????1000
Traditional method	????99.0	????81	????200

Table 2 data declaration, present embodiment is compared all with production efficiency and is improved significantly with purity, the product yield of the methacrylic acid of produced in conventional processes.

Claims (3)

1, a kind of method of producing methacrylic acid, comprise that amidate action generates Methacrylamide, the reaction that is hydrolyzed again generates methacrylic acid, distill the technical process of purification at last, it is characterized in that the continuous reaction unit of described amidate action flow process use one cover, this device is made up of reactor, tubular reactor, warmer and acid amides susceptor; The amidate action flow process is as follows:

The first step: with the continuously feeding simultaneously of sulfuric acid, acetone cyanohydrin to reactor, the heat that reaction produces is helped to remove by reactor chuck and pot inner coil pipe water cooler, control reaction kettle temperature is 85 ℃-105 ℃, and resultant is overflowed by upflow tube, removes tubular reactor;

Second step: the resultant of the first step reaction enters tubular reactor, continues and sulfuric acid reaction, generates Methacrylamide, and temperature is controlled at 120 ℃-150 ℃ in the tubular reactor at this moment; Again resultants such as Methacrylamide are sent into warmer subsequently, holding temperature is controlled at about 135 ℃; Cool off material at last and enter the acid amides susceptor.

2. the method for production methacrylic acid according to claim 1, it is characterized in that controlling described reaction kettle temperature is 90 ℃-100 ℃.

3. the method for production methacrylic acid according to claim 1 and 2, it is characterized in that controlling the interior temperature of described tubular reactor is 130 ℃-140 ℃.