Disclosed is a process for the distillation of readily polymerizable vinyl aromatic compounds and a new polymerization inhibitor therefor. The process comprises subjecting a vinyl aromatic compound to distillation conditions in a distillation system and adding to the system the new polymerization inhibitor comprising a mixture of N-nitroso diphenyl amine and a dinitro-O-cresol.

Polymerization inhibitor for vinyl aromatic compounds

Disclosed is a method for inhibiting polymerizable (meth)acrylic acid and esters thereof from polymerizing during their production, transportation and storage by using as the inhibitor (A) at least one N-oxyl compound, (B) at least one phenol compound, and (C) at least one phenothiazine compound in combination with one another. (A) is selected from 2,2,6,6-tetramethylpiperidinooxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidinooxyl, and 4,4',4''-tris-(2,2,6,6-tetramethylpiperidinooxyl)phosphite, and combinations thereof and the phenol compound is hydroquinone and/or methoquinone. The combined use of the three inhibitors provides an inhibiting effect which is superior to their use alone or in pairs.

Method for inhibiting polymerization of (meth)acrylic acid and esters thereof

Compositions and methods for inhibiting the polymerization of vinyl aromatic monomers in oxygen-free processing systems are disclosed. The compositions comprise a hydroxylamine compound, a phenylenediamine compound and a vinyl aromatic monomer. The methods comprise adding to the monomer bis-N,N'(hydroxypropyl)hydroxylamine.

Compositions and methods for inhibiting vinyl aromatic monomer polymerization

Method for minimizing fouling of heat exchanger

A stabilized acrylic acid composition is provided in which the polymerization of the acrylic acid is inhibited during the distillation process for purifying or separating the acrylic acid as well as during transport and storage. The compositions of the present invention comprise three components: (A) acrylic acid, (B) a stable nitroxyl radical, e.g., the nitroxyl radical 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (CAS registry number 2226-96-2) (HTEMPO), and (C) a dihetero-substituted benzene compound having at least one transferable hydrogen, e.g., a quinone derivative such as the mono-methyl-ether of hydroquinone (MEHQ). During the distillation process, transport and storage, components (B) and (C) are present in a polymerization-inhibiting amount. During the distillation process, oxygen (D) is preferably added with components (B) and (C).

Stabilized acrylic acid compositions

The inhibition of the polymerization of acrylic acid and a process for stabilizing the distillation of acrylic acid using a combination of a polymerization inhibitor, such as diphenylamine or its derivatives, and an oxygen-containing gas, or mixtures of polymerization inhibitors, such as diphenylamine or its derivatives, with benzoquinone and/or hydroquinone mono-methylether, and an oxygen-containing gas are disclosed.

Polymerization inhibition of acrylic acid

A PROCESS IS PROVIDED FOR INHIBITING POLYMERIZATION OF A POLYMERIzABLE UNSATURATED ACID SUCH AS ACRYLIC ACID, AND A PROCESS FOR STABILIZING DISTILLATION OF A POLYMERIZABLE UNSATURATED ACID SUCH AS ACRYLIC ACID, USING A COMBINATION OF POLYMERIZATION INHIBITORS, I.E., BENZOQUINONE AND HYDROQUINONE MONOMETHYL ETHER AND PREFERABLY WITH AIR (OR OXYGEN) PRESENT IN SPECIFIED AMOUNTS. THE PROCESS IS ALSO USEFUL WITH OTHER ACIDS SUCH AS METHACRYLIC ACID.

Stabilization of unsaturated acids by distillation with a combined polymerization inhibitor

A process for inhibiting polymerization of acrylic acid or esters thereof and a process for stabilizing a distillation operation of acrylic acid or esters thereof through the joint use of multiple polymerization inhibitors, i.e., hydroquinone, phenol and air (or oxygen) in specified amounts.

Stabilization of acrylic acid or esters thereof

This invention relates to the method of accelerating the separation of two layers, one being an organic solvent phase which contains an unsaturated organic acid, and the other being an aqueous phase from which the acid has been extracted. The accelerated separation of the phases is accomplished by adding an alkali metal salt or ammonium salt in minute amounts to the aqueous solution, containing acrylic acid, or methacrylic acid, and impurities such as other organic acids, before or after commingling said solution and said solvent. Other metal salts, though effective for ultimately increasing the amount of product extracted because of the "salting-out" effect, may actually delay separation of the phases. Small amounts of the useful salts do not induce polymerization as do somewhat larger amounts.

Accelerating separation rate of two liquid phases in the extraction of aqueous acrylic acid

Distillation of a polymerisable unsatd. acid is effected while introducing hydroquinone monomethyl ether and benzoquinone into the upper part of the distillation zone, and, if desired, an oxygen-contg. gas into the lower part of the distillation zone. Specif., the acid is acrylic or methacrylic acid. The wt. ratio of benzoquinone to hydroquinone monomethyl ether is 0.1:20-20:0.1, pref. 1:10-10:1. The total amount of these two cpds. in the distilln. zone at a given instant is at least 5 ppm based on liquid in the zone. The added cpds. inhibit the polymsn. of the unsatd. acid in the vapour phase at high temps. Distilln. can be effected continuously without blockages in the columns.

Susumu Otsuki

Papers

Polymerization inhibition of acrylic acid

Stabilization of unsaturated acids by distillation with a combined polymerization inhibitor

Stabilization of acrylic acid or esters thereof

Accelerating separation rate of two liquid phases in the extraction of aqueous acrylic acid

Unsatd acid distillation - using hydroquinone monomethyl ether benzoquinone and oxygen-contg gas as polymn inhibitors