Abstract: The polymerization of an ethylenically unsaturated monomer such as isoprene, butadiene and acrylonitrile is inhibited during storage or handling thereof by the addition of a dihydroxycinnamic acid or derivative thereof.

Abstract: Applicants have developed a process for inhibiting the polymerization of vinyl aromatic compound during the distillation of the vinyl aromatic compounds. The process involves adding to the vinyl aromatic compound, e.g., styrene, a nitroso compound such as N-nitroso-N, N'-di-3-pentyl-p-phenylenediamine.

Abstract: Methods and compositions for inhibiting fouling in vinyl monomers are disclosed. Alkylphosphonate esters or acids thereof are added to vinyl monomers, particularly ethylene dichloride, that are undergoing processing to inhibit fouling.

Abstract: A process including a first stage wherein a feed gas stream containing acrolein originating, for example from the gas-phase oxidation of propylene to acrolein, is fractionated into a gaseous effluent and a liquid stream in a cooling column operating such that the temperature of the liquid stream at the bottom of the column is lower than or equal to the condensation temperature of the feed gas stream, the difference in temperature not exceeding 20.degree. C. and, a second stage, wherein the gaseous effluent is condensed at a temperature that is lower than 20.degree. C., to give a liquid fraction and a purified gaseous fraction, is disclosed. An apparatus for carrying on the purification process is also disclosed.

Abstract: The polymerization of an ethylenically unsaturated monomer such as isoprene and butadiene is inhibited during storage or handling thereof by the addition of a dihydroxycinnamic acid or derivative thereof.

Abstract: A method for inhibiting the polymerization of vinyl aromatics such as styrene with a mixture of 3,5-di-tert-butyl-4-hydroxy-N,N-dimethylbenzyl amine and carboxylic acids or anhydrides thereof, in the presence of air or oxygen. The weight ratio of said 3,5-Di-tert-butylhydroxy-N,N-dimethylbenzyl amine, carboxylic acid (or carboxylic acid anhydride) and the air is 1:1 to 0.05:0.05 to 15, respectively.

Abstract: A polymerization inhibitor composition for inhibiting the polymerization of aromatic vinyl monomers at elevated temperatures comprising:(a) a benzofuroxan derivative of the formula ##STR1## wherein R is C.sub.1 -C.sub.4 alkyl or alkoxy; R.sup.1 is a nitro group; and m and n are each independently 0, 1, or 2; and(b) a solvent selected from the group consisting of toluene, xylene, ethylbenzene, vinyltoluene, divinylbenzene, alpha-methylstyrene, and a C.sub.12 -C.sub.18 hydrocarbon,and methods for inhibiting the polymerization of aromatic vinyl monomers at elevated temperatures using this composition.

Abstract: 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.

Abstract: The polymerization of a vinyl aromatic monomer such as styrene is inhibited by the addition of a composition of a benzoquinone derivative and a hydroxylamine compound.

Abstract: Vinyl aromatic monomer polymerization methods utilizing a composition of 2,6-di-tert-butyl-4-methylphenol and a substituted benzoquinonediimide compound are disclosed. Preferably, the composition is employed in an amount of 1 part to 10,000 parts per million parts monomer during distillation of styrene.

Abstract: Methods for inhibiting the polymerization of vinyl aromatic monomers in oxygen-free processing systems are disclosed. The methods comprise adding from 1 to 10,000 parts of a combination of a hydroxylamine compound and a phenylenediamine compound to the vinyl aromatic monomer.

Abstract: Vinyl aromatic monomer polymerization methods utilizing a composition of 2,6-di-tert-butyl-4-methylphenol and a substituted benzoquinonediimide compound are disclosed. Preferably, the composition is employed in an amount of 1 part to 10,000 parts per million parts monomer during distillation of styrene.

Abstract: Compositions and methods for inhibiting polymerization of vinyl aromatic monomers in oxygen-free processing systems are disclosed. The compositions comprise an oxime compound and a hydroxylamine compound and, alternatively, an oxime compound, a hydroxylamine compound and a phenylenediamine compound. The methods comprise adding either of the compositions to the vinyl aromatic monomer in an amount ranging from 1 to about 10,000 parts per million parts monomer.

Abstract: A highly polymerizable dicyclopentadiene (DCPD) monomer composition is obtained. The dicyclopentadiene so obtained is highly suitable for ring-opening polymerization by metathesis catalysts. The active DCPD yields articles with excellent physical properties upon in-mold polymerization.

Abstract: This invention is directed to a polymerization inhibitor and a polymerization inhibiting method which enables the continuous operation of a device for producing vinyl compounds over a long period of time and virtually eliminates corrosion. Further, the polymerization inhibitors according to the present invention are superior in polymerization inhibition when transferring and storing the vinyl compound products and in other cases. The polymerization inhibitor according to the present invention contains manganese dithiocarbamate or a thiuram compound as an effective component. The polymerization inhibiting method of this invention comprises individual or joint use of said inhibitors, or joint use of a copper salt, another manganese salt, or quinones in addition to said inhibitors. Further, the method may comprise jointly using copper dithiocarbamates in a manganese salt as polymerization inhibitors, or jointly using quinones in addition to the salts.

Abstract: In the production of maleic anhydride, a crude maleic anhydride is produced which contains acrylic acid and other by-products. The crude maleic anhydride is dissolved in a solvent and the acrylic acid is distilled off. To avoid the polymerization of the acrylic acid, an inhibitor of phenothiazine is added to the distillation process.

Abstract: The present invention pertains to methods and compositions for inhibiting polymerization of hydrocarbons during processing and storage. The methods comprise adding an effective amount of a hydroxyalkylhydroxylamine compound to the hydrocarbon sought to be treated.

Abstract: A method for inhibiting fouling in an organic process stream by adding certain oximes, hydrazine, erythorbic acid, carbohydrazide, or mixtures thereof. The antifoulant is added to the organic stream as an aqueous solution.

Abstract: A method of inhibiting fouling in a crude ethylene dichloride stream comprises introducing into the stream an inhibiting amount of an antifoulant selected from (A) an acylated amine (e.g., reaction product of polyisobutylene and maleic anhydride) and a polyamine (B) magnesium alkyl aryl sulfonate, and (C) a mixture of A and B.

Abstract: A process for stabilizing vinyl monomers in general, and ar-brominated styrene polymer in particular, against polymerization by mixing a vinyl monomer such as an ar-brominated styrene monomer with a stabilizing amount of iodine composition to produce a stabilized monomer and novel stabilized compositions.

Abstract: A process to purify t-butylstyrene from product containing substantial amounts of t-butylethylbenzene and small amounts of alkenyl-substituted styrene impurities by a combination of vacuum fractionation and vacuum evaporation in the presence a polymerization inhibitor, and treatment with a carbonaceous adsorbent. Such a product to be purified can be prepared by catalytically, oxidatively dehydrogenating over an alkaline pyrophosphate in the vapor phase t-butylethylbenzene containing about 95 wt. % or more of the p-isomer which can be made by alkylating ethylbenzene with isobutylene in a controlled manner in the presence of cooled concentrated sulfuric acid.

Abstract: A phenolic polymerization inhibitor is recovered from a styrene distillation residue containing the phenolic polymerization inhibitor by a method which comprises extracting the inhibitor from the styrene distillation residue with an oxygen-containing organic solvent having not more than 6 carbon atoms, adding an aromatic hydrocarbon solvent to the oxygen-containing organic solvent phase consequently obtained, and subjecting the resultant mixture to distillation thereby separating the mixture into a solution of the phenolic polymerization inhibitor in the aromatic hydrocarbon solvent and the oxygen-containing organic solvent. The recovered solution is put to use as a polymerization inhibitor either in the unmodified form or in a form separated from the aromatic hydrocarbon solvent.

Abstract: A composition having the formula ##STR1## wherein n has an average value of one to about five, is disclosed for use in reducing or eliminating the formation of reactor scale during the polymerization of vinyl chloride and comonomers. The composition is prepared by reacting phenothiazine with formaldehyde in the presence of a liquid diluent that is a solvent for the phenothiazine, but a non-solvent for the dimer of phenothiazine and formaldehyde. The process of the invention is preferably conducted in the presence of a strong acid catalyst. The formaldehyde is preferably added slowly to the reaction mixture over the course of the reaction. The product can be filtered and dried.

Abstract: Fouling of equipment used for processing of organic feed streams containing olefinic compounds is controlled by inhibiting polymerization of the olefinic compounds by carrying out the processing in the presence of from about 20 ppb to less than 1000 ppb of a stable free radical, such as a nitroxide.

Abstract: Compositions, comprised of a dinitrophenol in an aromatic hydrocarbon solvent, which compositions further comprise a sufficient amount of a phenylenediamine such that a greater amount of dinitrophenol is in solution than would be present in solution if such phenylenediamine were not present, exhibit unexpectedly desirable low temperature stability, and may be diluted with additional solvent to be employed as polymerization inhibitors for vinyl aromatic compounds.

Abstract: A process for the distillation of readily polymerizable vinyl aromatic compounds which comprises subjecting said compounds to distillation conditions in the presence of oxygen and an effective amount of asphaltene as a polymerization inhibitor.

Abstract: A process for the distillation of readily polymerizable vinyl aromatic compounds which comprises subjecting said compounds to distillation conditions in the presence of an effective amount of a pretreated polymerization inhibitor selected from the group consisting of asphalts, asphaltenes and any combination thereof. The inhibitor is pretreated by subjecting the inhibitor to a process for substantially increasing the free radical content therein.

Abstract: An extractive distillation process for selectively separating an ethylenically unsaturated hydrocarbon from a mixture containing hydrocarbon liquids having similar boiling points wherein an amine acts as a selective solvent and polymerization inhibitor. For example, styrene can be separated from a mixture of styrene and o-xylene using aminoethyl piperazine as the solvent for the distillation.

Abstract: Hydrogen chloride is recovered from a mixture with propylene by extractive distillation with an inert extraction solvent to minimize reaction between hydrogen chloride and propylene during such distillation. The temperature and pressure conditions are coordinated with the extraction solvent and amount thereof to prevent the presence of hydrogen chloride in a liquid state. The process is particularly suitable for recovering hydrogen chloride in the production of allyl chloride by thermal chlorination of propylene.

Abstract: A process for preparing vinyltoluene comprising passing ethyltoluene through a dehydrogenation zone to form vaporous crude vinyltoluene, adding from about 50 to about 100 parts per million by weight of a polymerization inhibitor such as a nitrated phenol to the vaporous crude vinyltoluene at a temperature between about 200.degree. and about 300.degree. C., condensing the vaporous crude vinyltoluene, maintaining the pH of the aqueous phase of the condensed crude vinyltoluene at a value between about 5.5 and about 6.

Abstract: Vinylaromatic compounds are stabilized against undesired polymerization by adding to the vinylaromatic compounds small amounts of zinc or nickel salts of dialkyl dithiocarbamates, specifically p-diisopropenylbenzene can be stabilized by the use of zinc dibutyldithiocarbamate.

Abstract: Hydrocarbon processing equipment is protected against fouling during the processing of hydrocarbons at elevated temperatures by adding to the equipment small amounts of the N,N'-dimer of phenothiazine or a substituted phenothiazine.

Abstract: Isopropenylstyrene, present in t-butylstyrene in small quantities as an impurity, is removed by extractive distillation using sulfolane as solvent.

Abstract: An apparatus for preparing vinyltoluene comprising passing ethyltoluene through a dehydrogenation zone to form vaporous crude vinyltoluene, adding from about 50 to about 100 parts per million by weight of a polymerization inhibitor such as a nitrated phenol to the vaporous crude vinyltoluene at a temperature between about 200.degree. and about 300.degree. C., condensing the vaporous crude vinyltoluene, maintaining the pH of the aqueous phase of the condensed crude vinyltoluene at a value between about 5.5 and about 6.

Abstract: This invention is directed to the use of mixtures of a polymerization inhibitor in the distillation of readily polymerizable vinyl aromatic monomers and more specifically to the use of mixtures containing 2,6-dinitro-4-halophenols as polymerization inhibitors for vinyl aromatic monomers such as styrene and vinyl benzenes. The invention comprises the process of subjecting the vinyl aromatic monomers to distillation temperatures in the presence of mixtures containing 2,6-dinitro-4-halophenols to inhibit polymerization.

Abstract: 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 elevated temperatures in a distillation system in the presence of a new polymerization inhibitor comprising 2,6-dinitro-p-cresol. Also disclosed is a distillation method and apparatus for use with this inhibitor.

Abstract: Vinyl aromatic compounds are stabilized against undesired polymerization by adding to the vinyl aromatic compounds small amounts of the N,N'-dimer of phenothiazine or a substituted phenothiazine.

Abstract: Vinyl aromatic compounds are stabilized against undesired polymerization by adding to the vinyl aromatic compounds small amounts of at least one N,N-diarylhydroxylamine and at least one N,N' dimer of phenothiazine or substituted phenothiazine.

Abstract: This invention is directed to the use of a polymerization inhibitor in the distillation of readily polymerizable vinyl aromatic monomers and more specifically to the use of mixtures of 2,6-dinitro-4-ethyl-phenol as a polymerization inhibitor for vinyl aromatic monomers such as styrene and vinyl benzenes. The invention comprises the process of subjecting the vinyl aromatic monomers to distillation temperatures in the presence of mixtures of 2,6-dinitro-4-ethyl-phenol and 2,6-dinitro-paracresol to prevent polymerization.

Abstract: A method for controlling the formation of polymer accumulations in a distillation column comprising accumulating liquid phase material containing a polymerization inhibitor in a seal pan; providing the seal pan with liquid-pervious weep hole means through the bottom of the pan and allowing a controlled quantity of polymerization inhibitor-containing liquid phase material to seep through the weep hole means to the underside of the seal pan; and apparatus useful for practicing the disclosed method.

Abstract: The present invention provides an improvement in methods for preparing and processing ethylenically unsaturated aromatic monomer. The improvement comprises employing 3,5-dinitrosalicylic acid or a derivative or isomer thereof as a process inhibitor. The process inhibitor is present in a concentration of about 50 to 3000 ppm, preferably about 250 to 2,000 ppm, and most preferably about 500 to 1,000 ppm.

Abstract: A method for inhibiting the formation of undesired polymer accumulations during distillative purification of vinylaromatic monomers such as styrene, alpha-alkylstyrene, vinyltoluene, divinylbenzene or the like comprising distilling the vinylaromatic monomer in the presence of a cupreous material such as metallic copper or a copper alloy, and apparatus for carrying out the method in which at least a portion of the interior of a distillation column used to purify vinylaromatic monomer, particularly in areas where there is little vapor movement, is provided with a surface layer or coating of cupreous material.

Abstract: The present invention provides an improvement in methods for preparing and processing ethylenically unsaturated aromatic monomer. The improvement comprises employing 3,5-dinitrosalicylic acid as a process inhibitor. The DNSA is present in a concentration of about 50 to 3000 ppm, preferably about 250 to 2000 ppm, and most preferably about 500 to 1000 ppm.

Abstract: A method and apparatus for inhibiting polymerization of vinylaromatic compounds during distillative purification wherein downcomers and tray bottoms of the distillation column exposed to high concentrations of liquid monomer condensate and low vapor velocities are coated with a non-wetting fluorocarbon polymer.

Abstract: Disclosed is a method of distilling readily polymerizable vinyl aromatic compounds such as styrene, .alpha.-methyl styrene, vinyl toluenes and divinylbenzenes wherein 2,2-bis(3,5-dinitro-4-hydroxy-phenyl)propane is used as a polymerization inhibitor. The invention is particularly useful for the distillation of divinylbenzene.

Abstract: A method for controlling the formation of polymer accumulations in a distillation column comprising accumulating liquid phase material containing a polymerization inhibitor in a seal pan; providing the seal pan with liquid-pervious weep hole means through the bottom of the pan and allowing a controlled quantity of polymerization inhibitor-containing liquid phase material to seep through the weep hole means to the underside of the seal pan; and apparatus useful for practicing the disclosed method.

Abstract: In a process for separating a conjugated diene from a hydrocarbon mixture containing the conjugated diene by extractive distillation using dimethyl formamide as an extractive solvent, a method for inhibiting polymerization of the conjugated diene in the dimethyl formamide at a high temperature which comprises using furfural and furfural polycondensates as polymerization inhibitors, and controlling the amounts of the polymerization inhibitors such that about 0.01 to about 2% by weight, based on the solvent, of furfural and about 0.5 to about 10% by weight, based on the solvent, of the furfural polycondensates are present in a total amount of about 1 to about 12% by weight, based on the solvent, throughout the entire separating process.

Abstract: A process for distilling vinyltoluene comprising subjecting vinyltoluene to distillation conditions in the presence of a synergistic polymerization inhibiting mixture of N-nitrosodiphenylamine (NDPA) and dinitro-para-cresol (DNPC). Preferably from about 100 to about 300 ppm by weight NDPA and about 300 to about 700 ppm by weight DNPC are dissolved in the crude vinyltoluene and the resulting solution is vacuum distilled.

Abstract: 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 elevated temperatures in a distillation system in the presence of a new polymerization inhibitor comprising 2,6-dinitro-p-cresol. Also disclosed is a distillation method and apparatus for use with this inhibitor.

Abstract: The separation of butadiene-1,3 from other C-4 hydrocarbons of lesser degree of unsaturation by extractive distillation with alkoxynitrile or aqueous alkoxynitrile as selective solvent is carried out with improved selectivity, without appreciable formation of butadiene-1,3 polymer and with consequent savings in energy by adding to the alkoxynitrile or aqueous alkoxynitrile an organic cosolvent which is dimethyl sulfoxide, sulfolane, butyrolactone, N-methyl pyrrolidone, morpholine, or trimethyl phosphate and/or an inhibitor which is 2,4-dinitrophenol or 2,4-dinitro-ortho-cresol. The organic cosolvent is present in the selective solvent composition in an amount of 5 to 30 percent by weight and the inhibitor in an amount of 0.05 to 0.6 percent by weight.