Inhibitors of vapor space polymerization

Abstract

An inhibitor composition is provided for mitigating undesired polymerization in the vapor space during the purification of reactive vinyl monomers. The polymerization inhibitor composition includes at least a first inhibitor compound having a stable nitroxide radical and a second inhibitor comprising a phenylenediamine. Methods of inhibiting polymerization of monomers in a vapor space using the disclosed compositions are also provided.

Description

[Technical field]

[0001] The present disclosure relates generally to compositions comprising a blend of polymerization inhibitors and methods of using the same to inhibit undesired polymerization in vapor space regions. More particularly, the present disclosure relates to compositions comprising at least one compound having a stable nitroxide radical and a phenylenediamine useful for inhibiting polymerization of ethylenically unsaturated monomers in vapor space regions. [Background technology]

[0002] Ethylenically unsaturated monomers are typically produced in a three-stage process consisting of (i) reaction, (ii) recovery, and (iii) purification. Distillation operations at high temperatures are often included in the recovery and purification stages. The process involves fractional distillation of the monomer. In the upper section of the distillation column, the purified monomer vapor condenses into a liquid pool before being transferred to a storage facility. Some of the condensed monomer stream descends the column. In the vapor space region of the distillation column, the liquid monomer pool is likely to generate spontaneous free radicals or peroxide-initiated free radicals. Current polymer inhibitor technology is limited to liquid flow in the lower section of the process column. The inhibitor is typically trapped in the lower section of the distillation column because it is non-volatile, and the inhibitor does not reach the highly reactive monomer pool in the vapor space region. With conventional inhibitors, the trapped monomer is not treated to mitigate undesired polymerization. For this reason, reactive monomers polymerize unnecessarily through radical polymerization, especially at high temperatures or when in contact with rust on the surfaces of process equipment such as distillation column trays.

[0003] This polymerization is especially severe in the presence of polymerization initiators such as organic peroxides, which are ubiquitous in the recycle stream that was previously exposed to atmospheric oxygen. Conventional polymerization inhibitors such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (HTEMPO) and 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl (OTEMPO) are generally effective. Premature polymerization of these monomers is generally controlled by reducing premature polymerization of the monomers by injecting a polymerization inhibitor directly into the liquid hydrocarbon stream. However, these polymerization inhibitors (HTEMPO and OTEMPO) are not volatile. In the field, the process is accelerated when the liquid monomer condenses on trays far above the bulk liquid that is treated with the non-volatile polymerization inhibitor. This problem is exacerbated when the trays have rust or there is residual polymer in the cracks and corners. Equally important, existing polymer in equipment cracks, dead legs, and hold-up pools of liquid monomers causes rapid accumulation of contaminant polymer due to the Norris-Tromsdorff effect. Due to accelerated polymerization, the growing polymer contaminants cause mechanical damage and potential release of large amounts of heat, resulting in fire or explosion. Complete inhibition of tray corrosion or complete removal of polymer from hard-to-reach locations in the purification column means that it is difficult to stop unwanted polymerization in the vapor space. Summary of the Invention

[0004] A method for inhibiting polymerization of monomer in the vapor space section of a distillation column is provided, the method comprising adding to the monomer a composition as described herein, the composition comprising a first inhibitor compound comprising a stable nitroxide radical and a second inhibitor compound comprising a phenylenediamine.

[0005] In some embodiments, the first inhibitor compound has Formula (I): [ka] The In the formula, R1 is C1 to C 22 alkyl or aryl, and the alkyl and aryl are C1-C 22 It is optionally substituted with one or more alkyl or aryl.

[0006] In some embodiments, the first inhibitor is 1-oxyl-2,2,6,6-tetramethylpiperin-4-ol, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-ethoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-propoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-butoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-pentoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-hexyl ... Methylpiperidine-1-oxy, 4-heptyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-octyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-nonyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-decyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-undecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-dodecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-tridecyloxy 4-tetradecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-pentadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-hexadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-heptadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-octadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-nodecyloxy-2,2,6,6-tetramethylpiperidine 4-decyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-icosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-henicosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-docosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-(phenoxy)2,2,6,6-tetramethylpiperidine-1-oxy, 4-(benzyloxy)-2,2,6,6-tetramethylpiperidine-1-oxy, 2,2,6,6-tetramethyl-4-(naphthalene-2-yloxy)piperidin-1-oxy, and any combination thereof.

[0007] In some embodiments, the first inhibitor has Formula III: [ka] is a compound of In the formula, R3 is -O· or -OH, and R4 is C1-C 22 alkyl or aryl, and the alkyl and aryl are C1-C 22 It is optionally substituted with one or more alkyl or aryl.

[0008] In some embodiments, the first inhibitor is 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl acetate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl propanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl butyrate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl pentanoate, 1-oxyl-2 ,2,6,6-tetramethylpiperidin-4-yl hexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl heptanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl octanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl nonanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl decanate canoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl undecanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl dodecanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 2-ethylhexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl stearate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl benzoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl palmitoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl behenoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 4-tert-butylbenzoate, and any combination thereof.

[0009] In some embodiments, the second inhibitor compound is a phenylenediamine of formula (IV) or formula (V): [ka] In the formula, X1 and X2 are independently C1 to C 22 alkyl or aryl, and the alkyl and aryl are C1-C 22 It is optionally substituted with one or more alkyl or aryl.

[0010] In some embodiments, X1 and X2 are independently C1 to C 22 alkyl or phenyl, and alkyl and phenyl are C1-C 22 It is optionally substituted with one or more alkyl or aryl.

[0011] In some embodiments, X1 and X2 are independently C1 to C 10 alkyl or phenyl, and alkyl and phenyl are C1-C 22 It is optionally substituted with one or more alkyl or aryl.

[0012] In some embodiments, X1 and X2 are independently C1-C5 alkyl or phenyl, and alkyl and phenyl are C1-C 22 It is optionally substituted with one or more alkyl or aryl.

[0013] In some embodiments, the second inhibitor is selected from the group consisting of 1,2-phenylenediamine, 1,4-phenylenediamine, N,N'-di-methyl-p-phenylenediamine, N,N'-di-sec-butyl-1,4-phenylenediamine, N,N'-di-1,4-dimethylpentyl-1,4-phenylenediamine, N,N'-di-acetyl-1,4-phenylenediamine, N-tert-butyl-N'-phenyl-1,4-phenylenediamine, N,N'-di-phenyl-1,4-phenylenediamine, and any combination thereof.

[0014] In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 80% by weight.

[0015] In some embodiments, the second inhibitor compound is present in the composition at a concentration of about 0.01% to about 50% by weight.

[0016] In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is from about 100:1 to about 1:100.

[0017] In some embodiments, the composition further comprises an organic solvent.

[0018] In some embodiments, the composition further comprises an ethylenically unsaturated monomer selected from the group consisting of vinyl acetate, acrylonitrile, acrylates, methacrylates, 1,3-butadiene, styrene, isoprene, acrylic acid, methacrylic acid, and any combination thereof.

[0019] A method of inhibiting monomer polymerization is provided that includes adding a composition to a process stream in a monomer purification process. The composition includes a first inhibitor compound that includes a stable nitroxide radical and a second inhibitor compound that includes a phenylenediamine.

[0020] In some embodiments, the process stream comprises a monomer.

[0021] In some embodiments, the process stream further comprises one or more additional components selected from an acid, an organic solvent, and water.

[0022] In some aspects, the monomer is an ethylenically unsaturated monomer.

[0023] In some embodiments, the composition is added to a process stream such that the concentration of the first inhibitor compound is from about 0.1 ppm to about 10,000 ppm.

[0024] In some embodiments, the composition is added to a process stream such that the concentration of the second inhibitor compound is from about 0.1 ppm to about 10,000 ppm.

[0025] In some embodiments, the monomer is selected from the group consisting of vinyl acetate, acrylonitrile, acrylates, methacrylates, 1,3-butadiene, styrene, divinylbenzene, isoprene, cyclopentadiene, dicyclopentadiene, acrylic acid, methacrylic acid, and any combination thereof.

[0026] The foregoing has outlined rather broadly the features and technical advantages of the present disclosure so that the detailed description of the embodiments that follow may be better understood. Additional features and advantages of the present disclosure will be described hereinafter which form the subject of the claims of this application. It should be appreciated by those skilled in the art that the concept and specific aspects disclosed may be readily utilized as a basis for modifying or designing other aspects for carrying out the same purposes of the present disclosure. It should also be appreciated by those skilled in the art that such equivalent aspects do not depart from the spirit and scope of the present disclosure as set forth in the appended claims. [Brief description of the drawings]

[0027] A detailed description of the invention is hereinafter described with specific reference to the following drawings.

[0028] [Figure 1] 1 shows various formulations of vapor space polymerization inhibitors. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Various aspects of the present disclosure are described below. The relationship and function of the various elements of the aspects may be better understood by referring to the following detailed description. However, it should be understood that the aspects are not limited to those explicitly described herein, and in some cases, details that are not necessary for understanding the aspects disclosed herein, such as, for example, conventional synthesis and / or compounding, may be omitted.

[0030] During the extractive distillation of reactive conjugated diene monomers, vapor space polymerization can occur, leading to undesirable contamination. There is a need for a polymerization inhibitor that can effectively inhibit vapor space polymerization. The compositions and methods disclosed herein can inhibit or reduce emulsion polymerization.

[0031] As used herein, "vapor space" typically refers to the area of ​​a distillation equipment that is in contact with vapor rather than a liquid process stream.

[0032] A method of inhibiting monomer polymerization is provided that includes adding a composition to a process stream in a monomer purification process. The composition includes a first inhibitor compound that includes a stable nitroxide radical and a second inhibitor compound that includes a phenylenediamine.

[0033] The present disclosure relates to a composition comprising a blend of polymerization inhibitors and a method of using the same to inhibit the polymerization of ethylenically unsaturated monomers. The polymerization inhibitor composition of the present disclosure comprises at least one compound having a thermally and chemically stable nitroxide radical and a phenylenediamine. The polymerization inhibitor composition may be a blend of multiple components including components in addition to the aforementioned compound having a stable nitroxide radical and a phenylenediamine.

[0034] A "polymerization inhibitor" in the presence of polymerizable monomers inhibits the polymerization of these monomers during an induction period under quenching conditions. After the induction period following complete consumption of the polymerization inhibitor, polymer formation occurs at the same rate as if no polymerization inhibitor was present at all.

[0035] Polymerization inhibitors and retarders may generally be considered "polymerization inhibitors," that is compounds capable of inhibiting or reducing the formation of polymer from one or more radically polymerizable compounds.

[0036] The term "fouling" refers to the formation of polymers, prepolymers, oligomers, and / or other materials that become insoluble in a stream and / or precipitate from the stream and deposit in the equipment under the conditions of operation of the equipment. Similarly, the inhibitor compositions of the present disclosure may be referred to as "antifoulants" because they inhibit or reduce the formation of foulant polymers.

[0037] Compositions of the Disclosure The present disclosure relates to a composition for inhibiting monomer polymerization, the composition comprising a first inhibitor compound having a stable nitroxide radical and a second inhibitor compound having a phenylenediamine. In some aspects, the composition used herein is particularly useful for inhibiting vapor space polymerization in a distillation column. In some aspects, the composition is for inhibiting monomer polymerization, the monomer being an ethylenically unsaturated monomer. For example, the composition of the present disclosure is useful for inhibiting the polymerization of ethylenically unsaturated monomers, including, but not limited to, vinyl acetate, acrylonitrile, acrylate esters, methacrylate esters, 1,3-butadiene, styrene, isoprene, acrylic acid, (meth)acrylic acid, and combinations thereof.

[0038] In some embodiments, the first inhibitor compound having a stable nitroxide radical has formula (I): [ka] is a compound of In the formula, R1 is H, C1 to C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 Alkynyl, C1-C 22 Cycloalkyl, aryl, -C1~C 22 Alkylene aryl, -C(O)(C1-C 22 Alkyl), -C(O)(C1-C 22 alkenyl), -C(O)(C1-C 22 alkynyl), -C(O)(C1-C 22 -C(O)(cycloalkyl), -C(O)(aryl), or -C(O)(C1-C 22 alkylenearyl), where the alkyl, cycloalkyl, and aryl are C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 It is optionally substituted with one or more of alkynyl, or aryl.

[0039] The term "aryl" refers to monocyclic, bicyclic (fused), and tricyclic (fused or spiro) hydrocarbon ring systems having a total of 5 to 14 ring carbon atoms, in which at least one ring in the system is aromatic, and in which each ring in the system contains 3 to 7 ring carbon atoms. The term "aryl" can be used interchangeably with the term "aryl ring."

[0040] In certain embodiments, R1 is -C(O)(C1-C 22 Alkyl), -C(O)(C1-C 22 alkenyl), -C(O)(C1-C 22 alkynyl), -C(O)(C1-C 22 -C(O)(cycloalkyl), -C(O)(aryl), or -C(O)(C1-C 22 alkylenearyl), where the alkyl, cycloalkyl, and aryl are C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 Optionally substituted with one or more of alkynyl, and aryl.

[0041] In some embodiments, R1 is C1-C 22 alkyl or aryl, and the alkyl and aryl are C1-C 22 It is optionally substituted with one or more alkyl or aryl.

[0042] In some embodiments, R1 is H. In some embodiments, R1 is C1-C 22 In some embodiments, R is C1-C 22 In some embodiments, R is C1-C 22 In some embodiments, R is C1-C 22 Cycloalkyl, cycloalkyl being C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R1 is aryl, and aryl is optionally substituted with one or more of C1-C22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R1 is optionally substituted with one or more of -C1 to -C2. 22 Alkylene aryl, aryl being C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R1 is optionally substituted with one or more of -C(O)(C1-C 22 In some embodiments, R1 is -C(O)(C1-C 12 In some embodiments, R1 is -C(O)(C1-C6 alkyl). In some embodiments, R1 is -C(O)(methyl). In some embodiments, R1 is -C(O)(ethyl). In some embodiments, R1 is -C(O)(propyl). In some embodiments, R1 is -C(O)(butyl). In some embodiments, R1 is -C(O)(C1-C6 alkyl ... 22 In some embodiments, R1 is -C(O)(C1-C alkenyl). 22 In some embodiments, R1 is -C(O)(C1-C 22 cycloalkyl), where cycloalkyl is C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R1 is -C(O)(aryl), and aryl is C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R1 is optionally substituted with one or more of -C(O)(C1-C 22 alkylenearyl), wherein aryl is C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 It is optionally substituted with one or more of alkynyl, or aryl.

[0043] Examples of compounds of formula (I) include 1-oxyl-2,2,6,6-tetramethylpiperin-4-ol, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-ethoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-propoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-butoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-pentoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-hexyl ... Piperidine-1-oxy, 4-heptyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-octyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-nonyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-decyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-undecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-dodecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-tridecyloxy- 2,2,6,6-tetramethylpiperidine-1-oxy, 4-tetradecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-pentadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-hexadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-heptadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-octadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-nodecyloxy-2,2,6,6-tetramethylpiperidine ethylpiperidine-1-oxy, 4-decyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-icosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-henicosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-docosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-(phenoxy)2,2,6,6-tetramethylpiperidine-1-oxy, 4-(benzyloxy)-2,2,6,6-tetramethylpiperidine-1-oxy, or 2,2,6,Examples include, but are not limited to, 6-tetramethyl-4-(naphthalen-2-yloxy)piperidin-1-oxy.

[0044] In other embodiments, the first inhibitor compound has formula (II): [ka] The In the formula, R2 is H, C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 Alkynyl, C1-C 22 Cycloalkyl, aryl, -C1~C 22 Alkylene, -C(O)(C1-C 22 Alkyl), -C(O)(C1-C 22 alkenyl), -C(O)(C1-C 22 alkynyl), -C(O)(C1-C 22 -C(O)(cycloalkyl), -C(O)(aryl), and -C(O)(C1-C 22 alkylene), wherein the alkyl, alkylene, and aryl are selected from C1 to C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 It is optionally substituted with one or more of alkynyl, or aryl.

[0045] In certain embodiments, R2 is -C(O)(C1-C 22 Alkyl), -C(O)(C1-C 22 alkenyl), -C(O)(C1-C 22 alkynyl), -C(O)(C1-C 22 -C(O)(cycloalkyl), -C(O)(aryl), and -C(O)(C1-C 22 alkylene), where the alkyl, alkylene, cycloalkyl, and aryl are C1 to C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 It is optionally substituted with one or more of alkynyl, or aryl.

[0046] In some embodiments, R2 is H. In some embodiments, R2 is C1-C 22 In some embodiments, R2 is C1-C 22 In some embodiments, R2 is C1-C 22 In some embodiments, R2 is C1-C 22 Cycloalkyl, cycloalkyl is C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R2 is aryl, and aryl is optionally substituted with one or more of C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R2 is optionally substituted with one or more of -C1 to -C6. 22 alkylene, the alkylene being C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R2 is -C(O)(C1-C 22 In some embodiments, R2 is -C(O)(C1-C 12 In some embodiments, R2 is -C(O)(C1-C6 alkyl). In some embodiments, R2 is -C(O)(methyl). In some embodiments, R2 is -C(O)(ethyl). In some embodiments, R2 is -C(O)(propyl). In some embodiments, R2 is -C(O)(butyl). In some embodiments, R2 is -C(O)(C1-C6 alkyl ... 22 In some embodiments, R2 is -C(O)(C1-C alkenyl). 22 In some embodiments, R2 is -C(O)(C1-C 22 cycloalkyl), where cycloalkyl is C1-C 22 Alkyl, C1-C 22Alkenyl, C1-C 22 In some embodiments, R2 is -C(O)(aryl), and aryl is C1-C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 In some embodiments, R2 is optionally substituted with one or more of -C(O)(C1-C 22 alkylene), wherein the alkylene is C1 to C 22 Alkyl, C1-C 22 Alkenyl, C1-C 22 Optionally substituted alkynyl, or aryl which is optionally substituted with one or more aryl.

[0047] In some embodiments, the compound of formula (II) is selected from the group consisting of 2,2,6,6-tetramethylpiperine-1,4-diol, 4-methoxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-ethoxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-propoxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-butoxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-pentoxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-hexyl ... 4-Heptyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-Octyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-Nonyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-Decyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-Undecyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-Dodecyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-Tridecyloxy-2,2,6,6-tetramethylpiperidine- 1-ol, 4-tetradecyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-pentadecyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-hexadecyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-heptadecyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-octadecyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-nodecyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-decyloxy-2,2,6,6- tetramethylpiperidin-1-ol, 4-icosyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-henicosyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-docosyloxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-(phenoxy)-2,2,6,6-tetramethylpiperidin-1-ol, 4-(benzyloxy)-2,2,6,6-tetramethylpiperidin-1-ol, or 2,2,6,6-tetramethyl-4-(naphthalen-2-yloxy)piperidin-1-ol.

[0048] In certain embodiments, the compositions of the present disclosure include compounds of formula (I) and (II), respectively, where R1 and R2 are the same. For example, in some embodiments, the compositions of the present disclosure include compounds of formula (I) and (II), respectively, where R1 and R2 are each independently -C(O)(C1-C 22 In certain embodiments, the compositions of the present disclosure include first and second inhibitor compounds of formula (I) and (II), respectively, where R1 and R2 are different.

[0049] The presently disclosed compounds of formula (II) having hydroxylamines have advantages over the corresponding nitroxides (compounds of formula (I)), such as the ability to provide additional polymerization inhibition, as more fully described below. A common synthetic route to generate hydroxylamines of nitroxides is the reduction of the corresponding nitroxide with a reducing agent such as: [ka]

[0050] The hydroxylamines of nitroxides have the potential to provide additional polymerization inhibition in the presence of carbon- and oxygen-centered radical initiators, as compared to the corresponding nitroxides, as discussed below. [ka]

[0051] Nitroxide hydroxylamines are excellent hydrogen donors and therefore efficient antioxidants due to their weak NO-H bond in the compound. As antioxidants, nitroxide hydroxylamines react easily with oxygen-centered radicals, such as peroxide radicals, while being converted to their corresponding nitroxides. Nitroxides are generally known as the most effective inhibitors due to their superior inhibition ability through scavenging carbon-centered free radicals at a rate that is mostly diffusion-controlled. This rate is orders of magnitude faster than phenolic compounds. However, their kinetic advantage is not always advantageous. For example, they may lose their advantage when oxygen-centered radicals are present as the primary free radicals. Another issue of concern with nitroxides is their consumption through uninhibited and undesired reactions with process stream components or other inhibitor additives. As a result, for a given inhibition efficacy, high nitroxide inhibitor dosages are often required, thereby making their use economically unattractive or even infeasible.

[0052] Essentially, each hydroxylamine of a nitroxide is equivalent to one hydrogen donor plus one nitroxide polymerization inhibitor when both oxygen- and carbon-centered radicals are present, which is an attractive incentive provided by the hydroxylamine of a nitroxide: one hydroxylamine of a nitroxide can eliminate one oxygen-centered radical and one carbon-centered radical, whereas the nitroxide can only eliminate carbon-centered radicals.

[0053] In some embodiments, the first inhibitor has Formula III: [ka] is a compound of In the formula, R3 is -O· or -OH, and R4 is C1-C 22 alkyl or aryl, and the alkyl and aryl are C1-C 22It is optionally substituted with one or more alkyl or aryl.

[0054] In some embodiments, R3 is -O. In some embodiments, R3 is -OH.

[0055] In some embodiments, R4 is C1-C 22 C1-C optionally substituted with one or more alkyl or aryl 22 In some embodiments, R4 is C1-C 22 Aryl is optionally substituted with one or more alkyl or aryl.

[0056] Examples of compounds of formula (III) include 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl acetate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl propanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl butyrate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl pentanoate, 1-oxyl- 2,2,6,6-tetramethylpiperidin-4-yl hexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl heptanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl octanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl nonanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4- yl decanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl undecanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl dodecanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 2-ethylhexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl stearate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl benzoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl palmitoate, 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl behenoate, or 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 4-tert-butylbenzoate.

[0057] In some embodiments, the second inhibitor compound is a phenylenediamine of formula (IV) or formula (V): [ka] In the formula, X1 and X2 are independently C1 to C 22 alkyl or aryl, and the alkyl and aryl are C1 to C 22 It is optionally substituted with one or more alkyl or aryl.

[0058] In some embodiments, the second inhibitor compound is a phenylenediamine of formula (IV). In some embodiments, the second inhibitor compound is a phenylenediamine of formula (V).

[0059] Examples of phenylenediamines include, but are not limited to, 1,2-phenylenediamine, 1,4-phenylenediamine, N,N'-di-methyl-p-phenylenediamine, N,N'-di-sec-butyl-1,4-phenylenediamine, N,N'-di-1,4-dimethylpentyl-1,4-phenylenediamine, N,N'-di-acetyl-1,4-phenylenediamine, N-tert-butyl-N'-phenyl-1,4-phenylenediamine, and N,N'-di-phenyl-1,4-phenylenediamine.

[0060] In some embodiments, the composition comprises 2,2',6,6'-tetramethylpiperidinyl-1-oxyl and an alkyl substituted 1,4-phenylenediamine.

[0061] In some embodiments, the composition consists essentially of a first inhibitor compound and a second inhibitor compound, hi other embodiments, the composition consists of an organic solvent, a first inhibitor, and a second inhibitor.

[0062] In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 80% by weight. In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 70% by weight. In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 60% by weight. In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 50% by weight. In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 40% by weight. In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 30% by weight. In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 20% by weight. In some embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 10% by weight.

[0063] For example, in certain embodiments, the first inhibitor compound is present in the composition at a concentration of about 0.01%, about 0.1%, about 1%, about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, or about 80% by weight.

[0064] In some embodiments, the second inhibitor compound is present in the composition at a concentration of about 0.01% to about 50% by weight. In some embodiments, the second inhibitor compound is present in the composition at a concentration of about 0.01% to about 40% by weight. In some embodiments, the second inhibitor compound is present in the composition at a concentration of about 0.01% to about 30% by weight. In some embodiments, the second inhibitor compound is present in the composition at a concentration of about 0.01% to about 20% by weight. In some embodiments, the second inhibitor compound is present in the composition at a concentration of about 0.01% to about 10% by weight.

[0065] For example, in certain embodiments, the second inhibitor compound is present in the composition at a concentration of about 0.01%, about 0.1%, about 1%, about 5%, about 10%, about 15%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, or about 50% by weight.

[0066] In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 100:1 to about 1:100. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 90:1 to about 1:90. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 80:1 to about 1:80. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 70:1 to about 1:70. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 60:1 to about 1:60. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 50:1 to about 1:50. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 40:1 to about 1:40. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 30:1 to about 1:30. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 20:1 to about 1:20. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 10:1 to about 1:10. In some embodiments, the molar ratio of the first inhibitor compound to the second inhibitor compound is about 1:1.

[0067] In some embodiments, the composition also comprises 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethylpiperidin-1-ol, 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidin-1-ol, 4-acetoxy ... The composition further comprises one or more additional compounds selected from the group consisting of bis-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-acetoxy-2,2,6,6-tetramethylpiperidin-1-ol, 4-propionoxy-2,2,6,6-tetramethylpiperidine-1-oxyl, 4-propionoxy-2,2,6,6-tetramethylpiperidin-1-ol, and bis((2,2,6,6-tetramethylpiperidine-1-oxyl)-4-yl)oxalate. In some embodiments, the composition also comprises 2,2,6,6-tetramethylpiperidine-1-oxyl. In some embodiments, the composition also comprises 2,2,6,6-tetramethylpiperidin-1-ol. In some embodiments, the composition also comprises 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl. In some embodiments, the composition also includes 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-ol. In some embodiments, the composition also includes 4-oxo-2,2,6,6-tetramethylpiperidin-1-oxyl. In some embodiments, the composition also includes 4-oxo-2,2,6,6-tetramethylpiperidin-1-ol. In some embodiments, the composition also includes 4-acetoxy-2,2,6,6-tetramethylpiperidin-1-oxyl. In some embodiments, the composition also includes 4-acetoxy-2,2,6,6-tetramethylpiperidin-1-ol. In some embodiments, the composition also includes 4-propionoxy-2,2,6,6-tetramethylpiperidin-1-oxyl. In some embodiments, the composition also includes 4-propionoxy-2,2,6,6-tetramethylpiperidin-1-ol.In some embodiments, the composition also includes bis((2,2,6,6-tetramethylpiperidine-1-oxyl)-4-yl) oxalate.

[0068] The composition may optionally include one or more organic solvents. Those skilled in the art will appreciate that there are many organic solvents that are compatible with the compositions of the present disclosure. For example, in some embodiments, the one or more organic solvents are selected from vinyl acetate, dimethyl phthalate, dimethylformamide, toluene, xylene, highly aromatic naphtha, acetonitrile, ethyl acetate, acetone, dichloromethane, tetrahydrofuran, hexane, dimethyl sulfoxide, N-methyl-2-pyrrolidone, and combinations thereof. In certain embodiments, the composition also includes vinyl acetate. In certain embodiments, the composition also includes dimethyl phthalate. In certain embodiments, the composition also includes dimethylformamide. In certain embodiments, the composition also includes toluene. In certain embodiments, the composition also includes xylene. In certain embodiments, the composition also includes highly aromatic naphtha. In certain embodiments, the composition also includes acetonitrile.

[0069] In some embodiments, the composition also includes one or more ethylenically unsaturated monomers. Those skilled in the art will understand that there are many monomers that are compatible with the compositions of the present disclosure. For example, in some embodiments, the one or more ethylenically unsaturated monomers are selected from vinyl acetate, acrylonitrile, acrylates, methacrylates, 1,3-butadiene, styrene, isoprene, (meth)acrylic acid, and combinations thereof. In certain embodiments, the composition also includes vinyl acetate. In certain embodiments, the composition also includes acrylonitrile. In certain embodiments, the composition also includes an acrylate. In certain embodiments, the composition also includes a methacrylate. In certain embodiments, the composition also includes 1,3-butadiene. In certain embodiments, the composition also includes styrene. In certain embodiments, the composition also includes isoprene. In certain embodiments, the composition also includes (meth)acrylic acid.

[0070] The composition of the present disclosure is stable and remains a useful polymerization inhibitor even under acidic conditions.Therefore, the composition of the present disclosure is useful for inhibiting premature polymerization of monomers during manufacturing processes, especially during processes carried out under acidic conditions.For example, the composition of the present disclosure is useful for inhibiting polymerization of acrylates, which may include, but are not limited to, acrylonitrile, acrylic acid, methyl methacrylic acid and its esters, and vinyl acetate.

[0071] In some embodiments, the compositions disclosed herein do not include 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl. In some embodiments, the compositions disclosed herein do not include 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl. In some embodiments, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl and 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxyl are not added to the ethylenically unsaturated monomer.

[0072] The present disclosure also relates to a method of inhibiting polymerization of a monomer comprising adding a composition of the present disclosure to the monomer, hi some aspects, an effective amount of a composition of the present disclosure is added to the monomer, where an effective amount is any amount sufficient to inhibit polymerization of the monomer.

[0073] In some aspects, the monomer is an ethylenically unsaturated monomer. In some aspects, the monomer is an ethylenically unsaturated monomer selected from vinyl acetate, acrylonitrile, acrylate esters, methacrylate esters, 1,3-butadiene, styrene, divinylbenzene, isoprene, cyclopentadiene, dicyclopentadiene, acrylic acid, (meth)acrylic acid, and combinations thereof, which are disclosed. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of vinyl acetate. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of acrylonitrile. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of acrylate esters. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of methacrylate esters. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of 1,3-butadiene. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of styrene. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of isoprene. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of acrylic acid. In some aspects, the methods disclosed herein are useful for inhibiting the polymerization of (meth)acrylic acid.

[0074] The compositions of the present disclosure can be added to the fluid manually or automatically. The compositions can also be added continuously and / or intermittently. Automatic addition may be accomplished through the use of a chemical injection pump. The chemical injection pump may be programmed to add a specific amount of the polymerization inhibitor composition or any of its components to the fluid at a certain time interval. In an alternative embodiment, the chemical injection pump can be manually controlled to add a specific amount of the polymerization inhibitor composition or any of its components to the fluid. Adding the presently disclosed polymerization inhibitor composition to a monomer inhibits polymerization of the monomer.

[0075] In some aspects, the monomers are provided as a neat solution, while in other aspects, the monomers are provided in a solution, hereinafter referred to as a "monomer solution."

[0076] In some embodiments, the monomer solution also includes one or more additional components selected from an acid, an organic solvent, water, and combinations thereof. For example, in some embodiments, the monomer solution includes one or more organic solvents selected from vinyl acetate, dimethyl phthalate, dimethylformamide, toluene, ethyl toluene, xylene, highly aromatic naphtha, acetonitrile, ethyl acetate, acetone, dichloromethane, tetrahydrofuran, hexane, dimethyl sulfoxide, N-methyl-2-pyrrolidone, and combinations thereof. In some embodiments, the monomer solution includes one or more acids selected from hydrochloric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, perchloric acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, ethanoic acid, caprylic acid, undecylic acid, lauric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, and suberic acid. In some embodiments, the monomer solution includes water.

[0077] In some embodiments, the monomer solution has a pH value of about 1 to about 7. In some embodiments, the monomer solution has a pH value of about 1 to about 6. In some embodiments, the monomer solution has a pH value of about 2 to about 6. In some embodiments, the monomer solution has a pH value of about 3 to about 6. In some embodiments, the monomer solution has a pH value of about 4 to about 6. In some embodiments, the monomer solution has a pH value of about 5 to about 6.

[0078] In some embodiments, the composition is added to the monomer such that the concentration of the first inhibitor compound is about 0.1 ppm to about 10,000 ppm. In some embodiments, the composition is added to the monomer such that the concentration of the first inhibitor compound is about 0.1 ppm to about 5,000 ppm. In some embodiments, the composition is added to the monomer such that the concentration of the first inhibitor compound is about 0.1 ppm to about 1,000 ppm. In some embodiments, the composition is added to the monomer such that the concentration of the first inhibitor compound is about 0.1 ppm to about 500 ppm.

[0079] In some embodiments, the composition is added to the monomer such that the concentration of the second inhibitor compound is about 0.1 ppm to about 10,000 ppm. In some embodiments, the composition is added to the monomer such that the concentration of the second inhibitor compound is about 0.1 ppm to about 5,000 ppm. In some embodiments, the composition is added to the monomer such that the concentration of the second inhibitor compound is about 0.1 ppm to about 1,000 ppm. In some embodiments, the composition is added to the monomer such that the concentration of the second inhibitor compound is about 0.1 ppm to about 500 ppm.

[0080] The disclosed method is useful for inhibiting premature polymerization of monomers during the extraction process. During the extraction process, a solvent is used to separate the components. The polarity difference between the extraction solvent and the hydrocarbon layer leads to emulsion formation, thereby increasing the risk of emulsion polymerization.

[0081] The methods of the present disclosure are also useful in preventing the premature polymerization of styrene during the manufacturing and purification processes.

[0082] The disclosed method is also useful in butadiene extraction processes. This utility stems from the balanced partition coefficient between the polar organic phase and the organic phase.

[0083] In some embodiments, the compositions disclosed herein are used in the distillation purification of olefins. For example, the compositions can be added to a process stream prior to entering a distillation unit, or the compositions can be added to a process stream within a distillation unit. EXAMPLES

[0084] Example 1: Various formulations were screened for vapor space polymerization inhibition. Volatile nitroxide free radicals and alkyl-substituted 1,4-phenylenediamines were found to exhibit synergistic effects and to be superior to commercially available vapor space polymerization inhibitors such as dialkylhydroxylamines and the nitroxide free radical HTEMPO.

[0085] The isoprene was passed through an alumina column to remove 4-tert-butylcatechol (TBC). Approximately 100 ppm of active inhibitor was added to the TBC-free isoprene (approximately 125 g). The solution was purged with nitrogen. Several popcorn polymer seeds weighing approximately 0.15 g were added to the top of the sample kit. The tube was sealed and heated to 80° C. for 3 days with an adjusted stirring speed of 250 rpm. The weight gained in the kit reflected the inhibitor performance on popcorn-type polymer formation.

[0086] Figure 1 shows that the combination of volatile nitroxide free radicals and alkyl-substituted 1,4-phenylenediamines showed synergistic effects. In Figure 1, HTEMPO ester refers to 4-acetoxyl-2,2',6,6'-tetramethylpiperidinyl-1-oxyl, 8550-36-2 refers to 15% by weight of 4-acetoxyl-2,2',6,6'-tetramethylpiperidinyl-1-hydroxyl and 5% by weight of di-sec-butyl-4,4'-phenylenediamine, DEHA is N,N'-diethylhydroxylamine, and PDA is di-sec-butyl-4,4'-phenylenediamine.

[0087] All of the compositions and methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. The present invention can be embodied in many different forms, and certain preferred embodiments of the present invention are described in detail herein. The present disclosure is an exemplification of the principles of the present invention, and is not intended to limit the invention to the specific embodiments exemplified. In addition, unless expressly stated otherwise, the terms "a" or "an" are intended to include "at least one" or "one or more." For example, "inhibitor" is intended to include "at least one inhibitor" or "one or more inhibitors."

[0088] Any ranges expressed in either absolute or approximate terms are intended to encompass both, and any definitions used herein are intended to be illustrative, not limiting. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein should be understood to encompass any and all subranges subsumed therein, including all fractional and whole values.

[0089] Any composition disclosed herein can comprise, consist of, or consist essentially of any element, component, and / or ingredient disclosed herein, or any combination of two or more of the elements, components, or ingredients disclosed herein.

[0090] Any method disclosed herein may comprise, consist of, or consist essentially of any method steps disclosed herein, or any combination of two or more of the method steps disclosed herein.

[0091] The transitional phrase "comprising," which is synonymous with "including," "containing," or "characterized by," is inclusive or open-ended and does not exclude additional, unrecited elements, components, ingredients, and / or method steps.

[0092] The transitional phrase "consisting of" excludes any element, component, ingredient, and / or method step not specified in the claim.

[0093] The transitional phrase "consisting essentially of" limits the scope of the claim to certain elements, components, ingredients, and / or steps, and those that do not materially affect the basic and novel characteristics of the claimed invention.

[0094] As used herein, the term "about" refers to a cited value that is within error resulting from the standard deviation found in their respective testing measurements; where such error cannot be determined, "about" may refer, for example, to within 5% of the cited value.

[0095] Moreover, the present invention encompasses all possible combinations of any or all of the various aspects described herein. It should also be understood that various changes and modifications to the preferred embodiments of the invention described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its intended advantages. Accordingly, such changes and modifications are intended to be covered by the appended claims.

Claims

1. A method for inhibiting vapor-space monomer polymerization, wherein the method is The process includes adding the composition to the process flow in a monomer purification process. A method wherein the composition comprises a first inhibitor compound containing a stable nitroxide radical and a second inhibitor compound containing phenylenediamine.

2. The first inhibitor compound is defined by formula (I): 【Chemistry 1】 It is, In the formula, R １ However, C １ ~C ２２ It is alkyl or aryl, and the alkyl and the aryl are C １ ~C ２２ The method according to claim 1, wherein the molecule is optionally substituted with one or more alkyl or aryl atoms.

3. The first inhibitor is 1-oxyl-2,2,6,6-tetramethylpiperin-4-ol, 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-ethoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-propoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-butoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-pentoxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-hexyloxy-2,2,6,6-tetramethylpiperidine Zin-1-oxy, 4-heptyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-octyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-nonyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-decyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-undecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-dodecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-tridecyloxy-2, 2,6,6-tetramethylpiperidine-1-oxy, 4-tetradecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-pentadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-hexadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-heptadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-octadecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-nodecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-nodecyloxy-2,2,6,6-tetramethylpiperidine-1-oxy Tylpiperidine-1-oxy, 4-decyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-icosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-henicosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-docosyloxy-2,2,6,6-tetramethylpiperidine-1-oxy, 4-(phenoxy)2,2,6,6-tetramethylpiperidine-1-oxy, 4-(benzyloxy)2,2,6,6-tetramethylpiperidine-1-oxy, 2,2,6,The method according to claim 1 or 2, selected from the group consisting of 6-tetramethyl-4-(naphthalene-2-yloxy)piperidine-1-oxy and any combination thereof.

4. The first inhibitor is given by formula III: 【Chemistry 2】 It is a compound of, wherein R ３ is -O· or -OH, and R ４ is C １ to C ２２ alkyl or aryl, and the alkyl and the aryl are optionally substituted with one or more of C １ to C ２２ alkyl or aryl, the method according to claim 1.

5. The first inhibitor is 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylacetate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylpropanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylbutyrate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylpentanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylpentanoate. Methylpiperidine-4-ylhexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylheptanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-yloctanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylnonanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-yldecanoate, 1-oxy The method according to claim 1 or 4, selected from the group consisting of 1-2,2,6,6-tetramethylpiperidine-4-ylundecanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-yldodecanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl2-ethylhexanoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylstearate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylbenzoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylpalmitoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-ylbehenoate, 1-oxyl-2,2,6,6-tetramethylpiperidine-4-yl4-tert-butylbenzoate, and any combination thereof.

6. The second inhibitor compound is phenylenediamine of formula (IV) or formula (V), 【Transformation 3】 In the formula, X １ and X ２ However, independently, C １ ~C ２２ It is alkyl or aryl, and the alkyl and the aryl are C １ ~C ２２ The method according to claim 1 or 2, wherein the molecule is optionally substituted with one or more alkyl or aryl atoms.

7. The method according to claim 1 or 2, wherein the second inhibitor is selected from the group consisting of 1,2-phenylenediamine, 1,4-phenylenediamine, N,N'-dimethyl-p-phenylenediamine, N,N'-di-sec-butyl-1,4-phenylenediamine, N,N'-di-1,4-dimethylpentyl-1,4-phenylenediamine, N,N'-diacetyl-1,4-phenylenediamine, N-tert-butyl-N'-phenyl-1,4-phenylenediamine, N,N'-diphenyl-1,4-phenylenediamine, and any combination thereof.

8. The method according to claim 1 or 2, wherein the first inhibitor compound is present in the composition at a concentration of about 0.01% to about 80% by weight.

9. The method according to claim 1 or 2, wherein the second inhibitor compound is present in the composition at a concentration of about 0.01% to about 50% by weight.

10. The method according to claim 1 or 2, wherein the molar ratio of the first inhibitor compound to the second inhibitor compound is about 100:1 to about 1:

100.

11. The method according to claim 1 or 2, wherein the composition further comprises an organic solvent.

12. The method according to claim 1 or 2, wherein the process flow further comprises an ethylenically unsaturated monomer selected from the group consisting of vinyl acetate, acrylonitrile, acrylate, methacrylate, 1,3-butadiene, styrene, isoprene, cyclopentadiene, dicyclopentadiene, acrylic acid, methacrylic acid, and any combination thereof.

13. The method according to claim 1 or 2, wherein the process flow further comprises one or more additional components selected from an acid, an organic solvent, and water.

14. The method according to claim 1 or 2, wherein the composition is added to the process stream such that the concentration of the first inhibitor compound is about 0.1 ppm to about 10,000 ppm.

15. The method according to claim 1 or 2, wherein the composition is added to the process stream such that the concentration of the second inhibitor compound is about 0.1 ppm to about 10,000 ppm.

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