CN100344596C

CN100344596C - Method for preparing methylal using combined continuous distillation and liquid-liquid extraction

Info

Publication number: CN100344596C
Application number: CNB2006100380684A
Authority: CN
Inventors: 顾正桂
Original assignee: Nanjing Normal University
Current assignee: Nanjing Normal University
Priority date: 2006-01-26
Filing date: 2006-01-26
Publication date: 2007-10-24
Anticipated expiration: 2026-01-26
Also published as: CN1807378A

Abstract

The present invention relates to a technology for preparing methylal by combining continuous reaction distillation and liquid-liquid extraction, which comprises the following steps: an acid catalyst is added into a reaction kettle at one time, formaldehyde is added into the reaction kettle continuously, methanol is added through a distillation column, and the temperatures of the bottom and the top of the reaction distillation apparatus are respectively controlled at 50 to 55 DEG C and 35 to 42 DEG C; after reaction distillation, a distillate containing high content of methylal, methanol and water is obtained at the tower top, glycerol or dimethanolamine is used as an extraction agent, the distillate is extracted by a liquid-liquid extraction tower, methylal is obtained as the top of the extraction tower, and the extraction agent and a mixed liquid of methanol and water are recovered by a regeneration tower for circularly use. In an optimized scheme, the acid catalyst is methylbenzenesulfonic acid. The mass contents of methylal, methanol and water in the tower top distillate are respectively 92%, 6% and 2%, and the yield of methylal reaches more than 97%. The technology overcomes the defects of long reaction period and low yield of traditional technologies. The new technology for preparing methylal by combining continuous reaction distillation and liquid-liquid extraction has the advantages of short reaction period, high speed rate and high yield.

Description

Successive reaction rectifying and liquid-liquid extraction are in conjunction with the method for preparing methylal

Technical field

The present invention relates to a kind of organic chemical industry's technology, be specifically related to a kind of successive reaction rectifying and liquid-liquid extraction in conjunction with the method for preparing methylal.

Background technology

Traditional methylal synthesis technique is taked following four kinds of methods: methylene dichloride is the method for synthesizing dimethoxym ethane the earliest, because backward in technique, yield is lower, so this method does not have industrialization; Dimethyl sulfoxide method, because methyl-sulphoxide is unstable to acid, heating can generate formaldehyde, so also there is not industrialization; Calcium Chloride Method, reaction yield can reach 86.5%, but because long reaction time, aftertreatment inconvenience is not so also there is industrialization; The acid catalysis interrupter method, yield is lower, production cycle is longer, the energy consumption height, but China produces the main path of methylal, and content is approximately about 55%, through reaching about 99% after azeotropic distillation, drying and the precise distillation, this process energy consumption height, technology are complicated, the dry by product that generates, regeneration cost height.The deficiency of traditional technology is that reaction production thing purity is low, purification process is complicated, the dry by product that generates utilizes the cost height.

Summary of the invention

In order to remedy the above-mentioned deficiency of prior art, the present invention will provide a kind of methylal preparation technology that can carry out suitability for industrialized production, and methylal yield that this processing method is produced and purity are all than higher, and the reaction times is short, energy consumption is low.

The scheme of finishing the foregoing invention task is: the present invention has designed new methylal production technique, i.e. successive reaction rectifying and liquid-liquid extraction are in conjunction with the flow process of producing methylal.This reaction time is short, yield is high, and sepn process is simple, energy consumption is low.Once can obtain the methylal more than 92%, in conjunction with liquid-liquid extraction, the purity of product can reach more than 99.7%.

Successive reaction rectifying and liquid-liquid extraction are in conjunction with the technology of producing methylal, and step is as follows:

Disposable adding acid catalyst in reactor, formaldehyde adds in the reactor continuously, and methyl alcohol adds from the rectifying column middle part; The temperature of reaction and rectification device still and cat head is controlled at 50～55 ℃, 35～42 ℃ respectively;

Behind the reactive distillation, cat head gets the higher methylal of distillate (about 92%), methyl alcohol (about 6%) and water (about 2%);

At the liquid-liquid extraction tower, be extraction agent with glycerol and dimethanolamine, above-mentioned distillate is extracted, extraction tower obtains the methylal more than 99.7%;

Extraction agent and methanol-water mixed solution reclaim through regenerator column again, and extraction agent recycles: the mass content that the regenerator column overhead distillate contains methylal, first alcohol and water is respectively 10%, 67.5%, 22.5%, and the methylal yield reaches more than 99%.

Acid catalyst described in the above scheme can be: hydrochloric acid, sulfuric acid, toluene sulfonic acide and Phenylsulfonic acid.In the prioritization scheme, acid catalyst is selected toluene sulfonic acide for use.

Further improve: regeneration overhead first alcohol and water can further reclaim processing, and methyl alcohol returns reaction and rectification device and uses.

The reactive distillation processes condition:

(1) temperature and reaction times are to the influence of building-up process

Alcohols and aldehydes is under the use of acid, and the carbonyl addition generates unsettled hemiacetal in acid and the aldehyde, and hemiacetal is further reaction under the katalysis of acid, forms unsettled acetal, and the reaction that generates acetal is thermopositive reaction, so adopt low temperature to help improving speed of reaction.Add under volume ratio 1.5: 1,5.5% condition of toluene sulfonic acide in methanol/formaldehyde/, at first consider the influence of temperature building-up process for the adding total amount.Adopt rhythmic reaction, the reaction times is 5 minutes, reacts and finishes back employing batch distillation, extracts 35～42 ℃ of cuts of boiling range, and through stratographic analysis, temperature and distillate composition (wt%) relation are seen shown in Figure 2, and normal temperature helps reaction, but temperature effect is less.Under these conditions, control reaction temperature is at 50～55 ℃, and reaction finishes the back and adopts batch distillation to extract 35～42 ℃ of cuts, the rhythmic reaction time (minute) see shown in Figure 3 to the influence of synthesizing dimethoxym ethane composition (wt%).When the reaction times reached 5 minutes, the methylal content in the reactant remained unchanged substantially, and this reaction process speed is very fast, and the reaction times is controlled at and can reaches reaction end in 5 minutes, so it is feasible to adopt successive reaction rectifying to produce methylal.

(2) influence of material flow comparison distillate yield

Employing methyl alcohol is excessive, and reaction fractionating tower still, top temperature are controlled at respectively about 50～55 ℃, 35～42 ℃, and toluene sulfonic acide (98%) adding is controlled at 5.5% of reinforced total amount; Methyl alcohol (99.5%, V/V)/formaldehyde (37%, when V/V) volume flow ratio increased, saw shown in Figure 4, and to add throughput ratio be 1.4～1.6: 1 comparatively suitable so get, and recommends employing 1.5: 1 by the methylal yield.

(3) selecting the throughput ratio of methanol/formaldehyde/is 1.5: 1, under the constant condition of temperature of reaction condition, add toluene sulfonic acide (98%) amount to distillate methylal yield influence see shown in Figure 5.Be controlled at the about 5.3～5.7% comparatively suitable of reinforced total amount from the add-on of result's toluene sulfonic acide, recommend to adopt 5.5%.

(4) can adopt other acid substitution toluene sulfonic acide to make catalyzer, but yield decreases, other mineral acid can't utilize again.

Successive reaction rectifying of the present invention and liquid-liquid extraction are in conjunction with the technology of preparation methylal, reaction time is short, purity is high, yield is high, under the certain condition of reaction fractionating tower temperature, stirring velocity, toluene sulfonic acide consumption and methanol/formaldehyde/throughput ratio, cat head once can get the above methylal of 92% (wt%), reaction yield can reach more than 97%, reactive distillation cat head distillate can get the above methylal of 99.7% (wt%) through liquid-liquid extraction.

Description of drawings

Fig. 1 is reactive distillation and liquid-liquid extraction bonded process flow sheet;

Fig. 2, Fig. 3, Fig. 4, Fig. 5 are respectively temperature, reaction times, methanol/formaldehyde/flow and when add the influence curve figure of toluene sulfonic acide amount to the methylal yield.

Embodiment

Embodiment 1, successive reaction rectifying and liquid-liquid extraction are in conjunction with preparation methylal technology, with reference to Fig. 1: 37～40% formaldehyde is pressed the speed of 68ml/min, 5.5% (mass ratio) that the toluene sulfonic acide catalyzer is pressed the reaction mass total amount adds in the reactor 1,99.5% methyl alcohol adds from rectifying column 4 the 5th (feed entrance point can be adjusted), adding V/V is 101ml/min, behind the reactive distillation, cat head gets distillate and contains higher methylal and first alcohol and water, with the glycerol is extraction agent, through 5 extractions of liquid-liquid extraction tower, extraction cat head methylal content can reach more than 99.7%.Extraction agent and methanol-water mixed solution are again through regenerator column 6 recycling uses.Regeneration overhead first alcohol and water can further reclaim processing.Reaction and rectification device still, top temperature are controlled at 50～55 ℃, 35～42 ℃ respectively.Overhead distillate contains methylal, methyl alcohol and water and is respectively 92%, 6%, 2% (being mass rate), more than the methylal yield to 97%.2 is electric agitator among the figure, and 3 is chuck.

Embodiment 2, and is substantially the same manner as Example 1, but catalyzer is used sulfuric acid instead, and extraction agent is used dimethanolamine instead; The methanol/formaldehyde/volume flow ratio is 1.4: 1.

Embodiment 3, and is substantially the same manner as Example 1, but the methanol/formaldehyde/volume flow ratio is 1.6: 1.

Embodiment 4, and is substantially the same manner as Example 1, but the methanol/formaldehyde/volume flow ratio is 1.5: 1.

Claims

1, a kind of successive reaction rectifying and liquid-liquid extraction combine and prepare the methylal method, and step is as follows:

In the disposable adding reactor of acid catalyst, formaldehyde adds in the reactor continuously, and methyl alcohol adds from rectifying column, and the temperature of reaction and rectification device still and cat head is controlled at 50～55 ℃, 35～42 ℃ respectively;

Behind the reactive distillation, the distillate of cat head contains methylal, first alcohol and water;

Extraction agent and methanol-water mixed solution reclaim through regenerator column again, and extraction agent recycles; The regenerator column overhead distillate contains methylal, first alcohol and water;

Described acid catalyst is selected from: toluene sulfonic acide or sulfuric acid.

2, according to described successive reaction rectifying of claim 1 and the liquid-liquid extraction preparation methylal method that combines, it is characterized in that: the add-on of described acid catalyst is 5.5% of a reaction mass quality total amount; Described methanol/formaldehyde/adds volume ratio: the formaldehyde of 99.5% methyl alcohol/37～40%=1.4～1.6: 1.

3, according to described successive reaction rectifying of claim 2 and the liquid-liquid extraction preparation methylal method that combines, it is characterized in that: said acid catalyst adopts toluene sulfonic acide; It is 1.5: 1 that described methanol/formaldehyde/adds volume ratio.

4, according to claim 1 or 2 or 3 described successive reaction rectifying and the liquid-liquid extraction preparation methylal method that combines., it is characterized in that: the adding speed of formaldehyde is 68ml/min, the adding speed of methyl alcohol is 101ml/min.