Acrylic acid
- Prop-2- enoic acid
- Propenoic
- Ethylene carboxylic acid
- Vinyl carboxylic acid
Colorless liquid with a pungent, acid -like odor
Liquid
1.05 g · cm -3
13 ° C
141 ° C.
4.3 hPa ( 20 ° C)
4.26
- Completely miscible with water, ethanol and diethyl ether
1.4224 (20 ° C)
Risk
10 ml · m- 3 or 30 mg · m-3
2590 mg · kg -1 ( LD50, rat, oral)
-383.8 KJ / mol
Template: Infobox chemical / molecular formula search available
Acrylic acid or propenoic acid is one of the unsaturated carboxylic acids. It is a colorless, water-miscible liquid at room temperature chemical compound with a pungent, vinegar -like odor. Acrylic acid is highly corrosive and flammable. Its salts and esters ( acrylates ) are called acrylates.
Representation
The large-scale industrial production is performed by a two-step oxidation of propene with the aid of catalysts. In the first stage, propene is reacted with air to bismuth - molybdenum oxide catalyst at temperatures of about 300 ° C to propenal ( acrolein). In the second step the oxidation of propenal of molybdenum -vanadium oxide catalyst at from 250 to 300 ° C for acrylic acid.
The presentation can also be based on Walter Reppe carbonylation of acetylene, carbon monoxide and water take place, the method has but at the present time no large-scale application:
Thermolysis of propiolactone has also become obsolete with the advent of Propenoxidationsprozesses. A novel sustainable Propiolactonsynthese of ethylene oxide and carbon monoxide could make the thermolysis of propiolactone competitive again when available inexpensive CO from CO2. The required CO could by biomass gasification, by dry reforming of methane (eg from biogas ) with CO2 according to:
Generated or by the reduction of CO2 with hydrogen from alternative sources in a reverse water -gas shift reaction.
Properties
Physical Properties
Acrylic acid is a colorless liquid, boiling at atmospheric pressure at 141 ° C. The enthalpy of vaporization is 53.1 kJ · mol -1. The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) with A = 2.69607, B = C = -121.929 621.275 and in the temperature range of 293 K to 343 K. The substance melts at 13 ° C with a melting enthalpy of 9.5 kJ · mol -1. The critical temperature is 343 ° C, the critical pressure at 52.43 bar.
Chemical Properties
Acrylic acid has a strong tendency to polymerize and is stabilized with small amounts of hydroquinone monomethyl ether.
Acrylic acid requires further special care during transport in the liquid state by means of pumps in order to prevent destruction of plant components due to spontaneous polymerization.
It should be stored below 25 ° C. It is important to ensure that the fixed point is not reached. When crystallization, stabilizer -free high-purity acrylic acid would precipitate as a solid, because the unregulated, may polymerize explosively when thawed. The polymerization enthalpy of 75 kJ · mol -1 ( 18.5 kcal / mol).
The addition reaction with hydrogen bromide to acrylic acid gives 3- bromopropanoic acid.
Safety characteristics
Acrylic acid forms flammable vapor - air mixtures. The compound has a flash point of 48-55 ° C. The explosion range is between 3.9 vol% as the lower explosive limit ( LEL) and 19.8 vol% as the upper explosive limit ( UEL). The marginal gap width was determined to be 0.86 mm. The result is thus a mapping in the explosion group IIB. The ignition temperature is 395 ° C. The fabric falls within the temperature class T2.
Use
Their main use is the polymerization superabsorbents ( application for example, in diapers ), acrylic acid esters ( which are in turn used for the preparation of polyacrylates ), and as the anionic comonomer in the preparation of polymer dispersions.
Process engineering
Since acrylic acid is processed in the chemical industry in large quantities, at the same time, however, is harmful and dangerous to the environment, and also tends to form polymers, particularly technology-based measures are required:
The latter process not only destroys the pump but potentially the entire system.