Acrylic acid synthesis
- Product Name:Acrylic acid
- CAS Number:79-10-7
- Molecular formula:C3H4O2
- Molecular Weight:72.06
(i) Propylene route. This route involves the two-stage oxidation of propylene:
A mixture of propylene, air and steam is fed into a reactor containing a catalyst at about 320°C to give acrolein. This intermediate is not isolated but is passed directly to a second reactor, also containing a catalyst, at about 280°C. The effluent is cooled by contact with cold aqueous acrylic acid.
Acrylic acid is extracted from the solution with a solvent and then separated by distillation. Because of the ready availability of low cost propylene, this route has become the preferred route for the production of acrylic acid. (ii) Acetylene route. This route involves the reaction of acetylene, carbon monoxide and water:
In one process, the reaction is conducted in solution in tetrahydrofuran at about 200°C and 6-20 MPa (60--200 atmospheres). Nickel bromide is used as catalyst. The solution of acrylic acid in tetrahydrofuran, after separation of the unconverted acetylene and carbon monoxide in a degassing column, passes to a distillation tower where tetrahydrofuran is taken overhead and acrylic acid is the bottom product. The reaction between acetylene, carbon monoxide and water may also be carried out by using nickel carbonyl as the source of carbon monoxide. In this case, milder reaction conditions are possible. Owing to the high cost of acetylene, this route is now of little commercial importance.
(iii) Ethylene route. This route consists of the following sequence:
The addition of hydrogen cyanide to ethylene oxide takes place at 55-60°C in the presence of a basic catalyst such as diethylamine. The reaction is exothermic and is carried out in solution to facilitate control; the solvent is conveniently ethylene cyanohydrin. The reaction mixture is neutralized and ethylene cyanohydrin is separated by distillation. The second stage of the synthesis involves the dehydration and hydrolysis of ethylene cyanohydrin; these reactions are carried out in one step by heating the cyanohydrin with aqueous sulphuric acid at about 175°C. (It is possible, of course, that the intermediate in this conversion may be acrylonitrile, as shown, or P-hydroxypropionic acid or both.) At one time this was the standard route for the preparation of acrylic acid but it has been largely displaced by the more economical propylene route.
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Yield:79-10-7 99.9%
Reaction Conditions:
with water;sodium hydroxide in hexan-1-ol at 80; for 10 h;Sealed tube;Temperature;
Steps:
1 Example 1
0.75mmol of glyceric acid was sequentially added to a 50mL high temperature and high pressure reactor.100μmol PdCl2, 10ml 57wt% hydriodic acid, sealed reaction kettle,Fill with hydrogen (3000 psi), stir and heat to 170 ° C quickly.Hold for 25h. The reaction kettle ice water bath was cooled to room temperature, the aqueous phase was collected and tested.Glyceric acid conversion rate is 100%,The yield of 3-iodopropionic acid was 99.9% (about 0.75 mmol).Take 5 ml of the aqueous phase reactant and add 10 ml of n-hexanol to extract 3-iodopropionic acid.Extract three times and combine the extractants.Take 10ml of extract (containing about 0.125mmol of 3-iodopropionic acid)Add 10ml of water to a 50mL thick-walled glass tube.And adding 0.083g of sodium hydroxide to seal the reaction kettle.Stir and heat quickly to 80 ° C for 10 h.The reaction kettle was cooled to room temperature in an ice water bath, and the aqueous phase was collected, acidified and detected.The yield of acrylic acid was 99.9% (about 0.125 mmol).
References:
CN108997108,2018,A Location in patent:Paragraph 0020; 0021; 0031; 0033; 0035; 0037; 0039; 0041
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