CA1227449A - Composition for minimizing fouling of heat exchangers and other hydrocarbon processing equipment - Google Patents
Composition for minimizing fouling of heat exchangers and other hydrocarbon processing equipmentInfo
- Publication number
- CA1227449A CA1227449A CA000491498A CA491498A CA1227449A CA 1227449 A CA1227449 A CA 1227449A CA 000491498 A CA000491498 A CA 000491498A CA 491498 A CA491498 A CA 491498A CA 1227449 A CA1227449 A CA 1227449A
- Authority
- CA
- Canada
- Prior art keywords
- fouling
- distillation
- monomer
- polymerization
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Polymerisation Methods In General (AREA)
Abstract
COMPOSITION FOR MINIMIZING FOULING OF HEAT
EXCHANGERS AND OTHER HYDROCARBON PROCESSING EQUIPMENT
Abstract of The Disclosure In an improved process for purifying diene monomers by inhibiting equipment fouling wherein the purification is by distillation, wherein the improvement comprises adding a polymerization inhibiting amount of diethylhydroxylamine to the monomer being purified prior to distillation, during distillation or both.
EXCHANGERS AND OTHER HYDROCARBON PROCESSING EQUIPMENT
Abstract of The Disclosure In an improved process for purifying diene monomers by inhibiting equipment fouling wherein the purification is by distillation, wherein the improvement comprises adding a polymerization inhibiting amount of diethylhydroxylamine to the monomer being purified prior to distillation, during distillation or both.
Description
1 by ~L2;2~ Lo PI 5 0 - 2 3 - 0 0 5 7 A
COMPOSITION FOR MINCING FOULING OF HEAT
EXCHANGERS AID OTHER HYDROCARBON PROCESSING EQUIPMENT
Field of The Invention This invention relates to methods of inhibiting fouling by injecting an antifoulant composition into a stream of a hydrocarbonaceous r.taterial scheduled to be heated in a recoiler, heat exchanger, process heater, or the like. A heat exchanger and resultant products column are able to function for longer periods of time when such fouling inhibitor minimizes the formation of deposits in the heat exchanger.
BACKGROUND
Fouling of petroleum processing equipment occurs continuously during the period when petroleum or its derivatives are being processing in the equipment. Generally, fouling is caused by the gradual buildup of a layer of polymeric material resulting from the thermal polymerization of unsaturated materials which are present in the material processed. Ultimately fouling becomes a problem of such magnitude that it becomes necessary to take the equipment out of service for cleaning. Cleaning is an JO expensive, time consuming operation and consequently methods of preventing fouling, or at least significantly reducing the rate of fouling, are constantly being sought. The most economical method of reducing the fouling rate in process equipment is to add chemicals which inhibit fouling, called "antifoulants", to the feed stream being processed.
Dine compounds such as butadiene undergo undesired spontaneous polymerization (i.e., polymerization of monomers due to heat or the random generation of free radicals in the monomers) I
during storage, shipping or processing. The problem is particularly acute during purification operations at elevated temperatures such as in distillation. Spontaneous polymerization is disadvantageous not only because it causes fouling of equipment used for processing dine monomer, but also because it usually renders the monomer WIlfit for use. Accordingly, a need exists for an agent which serves to inhibit the spontaneous polymerization of dine monomers during their processing.
Prior Art I US. Patent 3,148,225 to Albert employs dialkylhydroxyl-amine for inhibiting popcorn polymers in SIR rubbers. Prior workers have understood that dialkylhydroxylamine compounds react with free radicals to prevent undesired formation of polymers.
Further inhibition of popcorn polymerization is effected by Gross (US. Patent 3,426,063~ by use of an arylhydroxylamine.
US. Patent 2,965,685 to Campbell discloses inhibition of vinyl aromatic monomer polymerization by using from 5 Pam to 5 percent dialkylhydroxylamine in the vinyl aromatic monomer. Furthermore, ~ayer-Mader (US. Patent 3,878,181) teaches termination of an aqueous emulsion polymerization of chloroprene or dichlorobuta-dine by addition of diethylhydroxylamine and Sat (US. Patent 3,849,498) discloses that dlethylhydroxylamine is effective as a polymerization inhibitor for alcoholic solutions of unsaturated alkaloids. US. Patent 3,392,204 to Elmer discloses that styrenes can be stabilized against polymerization by dosing with a small amount of a diethylhydroxylamine salt of certain carboxylic acids.
Although some of the published literature concerned with antifoulant compositions suggest that some antifoulan~s might also serve to inhibit the thermal polymerization of unsaturated I
components of the hydrocarbons liquid subjected to elevated temperatures, there has been no pattern of transfer ox technology from the polymer inhibition field to antifoulant composition technology.
Gerbrand (US. Patent 4,386,224) discloses that the color of alkyd phenols can be stabilized and discoloration inhibited by the presence of a small amount of diethylhydroxylamine.
Bert (US. Patent 3,333,001) stabilized dialkylhydroxyl-amine themselves by use of mercaptobenzothiazole.
lo US. Patent 4,400,368 (Zaida) discloses a method of removal of hydrogen sulfide and carbon dioxide from sour gases by contacting the sour gases with an aqueous solution of certain polyvalent metal chelates. The chelates life is taught to be improved by the presence of a stabilizing amount of certain nitrogen compounds including, inter alias diethylhydroxylamine.
Miller (US. Patent 3,105,810) describes the use ox amine salts of dodecyl Bunsen sulfonic acid as surfactant useful in antifoulant compositions. Gonzales (US. Patent 3,271,295) discloses substituted succinic immediacy as surfactants in anti-foul ant compositions.
Waldby (US. Patent 3,340,160) discloses an olefin polymerization inhibitor which is an aqueous solution of an alkali metal nitrite and a quinoid, amino, vitro or phenol compound.
among the amino compounds contemplated by Waldby are N,N-di-n-butylhydroxylamine, 2,4-diaminodiphenylamine, diethanolamine and monoethanolamine.
In certain olefin processing operations it is desirable to have an antifoulant or polymerization inhibitor which participates between the oil and water phase. In other words, a single inhibitor I
acting in both the oil and water phase would be desirable over adding separate water-soluble and oil-soluble inhibitors.
Accordingly, it is an object of the present invention to provide an antifoulant which acts in both the aqueous phase and the hydrocarbon phase of a water-containing hydrocarbon processing operation. It is another object of the present invention to present a method of enhancing antifoulant protection for equipment in those operations. These and other objects of the invention are set forth in the following description and examples of the invention.
Summary of The Invention The improved antifoulant effects afforded by the present invention are achieved by injecting into a stream of dine hydra-carbon scheduled for fractionation, distillation or other processing, a fouling preventing amount of a lower hydroxylamine, i.e., diethylhydroxylamine.
Detailed Description At least one major and significant advantage associated with the use of lower dialkylhydroxylamines has been overlooked extending their applications in dine process applications. This includes their partition coefficient between hydrocarbon arid water.
The advantage of lower dialkylhydroxylamines is based on the partition coefficient of the dialkylhydroxylamine in the presence of water. As an example, aqueous diethylhydroxylamine has a partition coefficient of 13:1 in favor of water. Therefore, approximately OWE of diethylhydr~ylamine would be extracted from an organic process stream which may come into contact with water through washing or which has water present as thy result of accumulation as tank bottoms water. Although this factor has been a limiting factor in efforts to translate the use of dialkyl-hydroxylamines into a majority of hydrocarbon processing units, where -there is either a water wash or caustic wash unit upstream of the hydrocarbon distillation units, it has now been discovered that diethylhydroxylamine (DOW) serves as an effective antifoulant and polymerization inhibitor in dine treatment operations, most notably for bu-tadiene treatment.
In butadiene applications, the crude butadiene distill-talon train is run at temperatures in the range of 90-175F us-don pressure conditions of 50-180 prig. Under these temperature lo and pressure conditions, DOW will not flash overhead with the desired bu-tadiene products of production, thus enabling production of purified monomer without inhibitor present. Further, inhibition of undesired fouling deposits in the lower portions of the column is achieved as well as inhibition of formation of resinous-like polymer glasses in the heat exchangers and recoilers.
The polymerization inhibitor (DOW) of the invention can be introduced into the dine monomer to be protected by any conventional method. It is generally introduced just upstream of the point of desired application by an suitable means such as by the use of a proportionating pump. The DOW polymerization in-hibltor may be added as a concentrate but it is preferable to add Kit as a solution which is compatible with the dine monomer being treated. Suitable solvents are water (if a cosolvent such as an Amarillo or Methyl pyrrolidone is used), alcohols (provided -their Boolean point is sufficiently high as -to no-t be distilled over-heed into the final recovered product), acetonitrile and other organic solvents which have boiling points higher than butadiene.
Concentration of DOW polymerization inhibitor in the solvent is desirably in -the range of about 10 -to 90 weight percent and preferably about 30 to 80 weight percent based on the total weight of DOW and solvent.
I
The DOW is used at a concentration which is effect-ivy to provide the desired protection against spontaneous polyp merization. It has been determined that amount of DELIA in the range of about 100-250 Pam based on the weight of the dine monomer being -treated affords ample protection against undesired polymerization For most applications the inhibitor is used in amourlts in the range of about 5 to 500 Pam.
Furthermore, fouling due -to both hydrocarbon phases and aqueous phases can sometimes be enhanced by use of an lo antieouliny blend of DOW and an oil soluble hydroxylamine such as di-n-butylhydroxylamine.
The following examples will serve to further ill-Stewart without limiting the invention.
Example I
Conventional butadiene recovery units processing approximately 93% crude butadiene to obtain a final product containing 99.5 % butadiene by column distillation with the operating conditions in the last of three columns being over-head 65 Sue, 118F, and 85 gym product butadiene -to storage, have been forced to shut down periodically (every 190 days) to clean recoilers and the column because of butadiene felon. injection of a sodium nitrite solution at the rate of 5 yam to the reflex return of the column did not enhance run times. Certain hydrocarbon end water soluble inhibitors were screened in the laboratory and found -to be less effect-jive than diethylhydroxylamine (see Table T ) against styrenes which was employed as a model because of its ease of handling.
Table I
Observation of Polymerization Test 1000 no Inhibitor 140F
no inhibitor phenylenediarnine ~ert-butyl catcall 3 (llethanolamine clie~hylhydroxylamine 2 It popcorn polymer growth began after 2 days extensive growth after 4 days Z) no growth in 11 days I) previously had tried a phenol/catechol on unit without success Example II
To determine top effectiveness of various hydroxylamines, the same test was repeated. Results are shown below in Table II.
Table II
Test Cone (Pam) Observation of Polymerization .
no inhibitor none polymer formed in 12 his at 100F
1) (a) DEW 100 6 days at 100F' (b) di-isopropyl-hydroxylamine 160 6 days at 100F
(c) di-n-butylhydroxyl-Amarillo 170 6 days at 100F
Finally, the volubility characteristics of compounds (a) end (c) above were determined; di~utylhydroxylamine was found LO
Lowe oily soluble not water soluble unless salted with a mineral acid or short chain carboxylic acid. Diethylhydroxylamine-- as previously mentioned -- can be made oil or water soluble but partitions in favor of water.
EXAMPLE III
As evidenced by Example I, the addition of a purely oil-soluble inhibitor proved unsatisfactory. The addition of a water-soluble oxygen scavenger used to inhibit polymerization also proved unsatisfactory. However, the addition of a hydroxylamine which can partition or the addition of a blend of hydroxylamines (one water soluble, one oil soluble) offered superior performance.
To the same unit as in Example I, 250 Pam DOW based on the weight of the butadiene monomer being processed, was added to the overhead reflex of the final product column of the three columns in series with the same operating conditions as in Example I.
The column treatment extended the run time from 190 days in two previously untreated runs to 30~ day, a 62~ increase.
COMPOSITION FOR MINCING FOULING OF HEAT
EXCHANGERS AID OTHER HYDROCARBON PROCESSING EQUIPMENT
Field of The Invention This invention relates to methods of inhibiting fouling by injecting an antifoulant composition into a stream of a hydrocarbonaceous r.taterial scheduled to be heated in a recoiler, heat exchanger, process heater, or the like. A heat exchanger and resultant products column are able to function for longer periods of time when such fouling inhibitor minimizes the formation of deposits in the heat exchanger.
BACKGROUND
Fouling of petroleum processing equipment occurs continuously during the period when petroleum or its derivatives are being processing in the equipment. Generally, fouling is caused by the gradual buildup of a layer of polymeric material resulting from the thermal polymerization of unsaturated materials which are present in the material processed. Ultimately fouling becomes a problem of such magnitude that it becomes necessary to take the equipment out of service for cleaning. Cleaning is an JO expensive, time consuming operation and consequently methods of preventing fouling, or at least significantly reducing the rate of fouling, are constantly being sought. The most economical method of reducing the fouling rate in process equipment is to add chemicals which inhibit fouling, called "antifoulants", to the feed stream being processed.
Dine compounds such as butadiene undergo undesired spontaneous polymerization (i.e., polymerization of monomers due to heat or the random generation of free radicals in the monomers) I
during storage, shipping or processing. The problem is particularly acute during purification operations at elevated temperatures such as in distillation. Spontaneous polymerization is disadvantageous not only because it causes fouling of equipment used for processing dine monomer, but also because it usually renders the monomer WIlfit for use. Accordingly, a need exists for an agent which serves to inhibit the spontaneous polymerization of dine monomers during their processing.
Prior Art I US. Patent 3,148,225 to Albert employs dialkylhydroxyl-amine for inhibiting popcorn polymers in SIR rubbers. Prior workers have understood that dialkylhydroxylamine compounds react with free radicals to prevent undesired formation of polymers.
Further inhibition of popcorn polymerization is effected by Gross (US. Patent 3,426,063~ by use of an arylhydroxylamine.
US. Patent 2,965,685 to Campbell discloses inhibition of vinyl aromatic monomer polymerization by using from 5 Pam to 5 percent dialkylhydroxylamine in the vinyl aromatic monomer. Furthermore, ~ayer-Mader (US. Patent 3,878,181) teaches termination of an aqueous emulsion polymerization of chloroprene or dichlorobuta-dine by addition of diethylhydroxylamine and Sat (US. Patent 3,849,498) discloses that dlethylhydroxylamine is effective as a polymerization inhibitor for alcoholic solutions of unsaturated alkaloids. US. Patent 3,392,204 to Elmer discloses that styrenes can be stabilized against polymerization by dosing with a small amount of a diethylhydroxylamine salt of certain carboxylic acids.
Although some of the published literature concerned with antifoulant compositions suggest that some antifoulan~s might also serve to inhibit the thermal polymerization of unsaturated I
components of the hydrocarbons liquid subjected to elevated temperatures, there has been no pattern of transfer ox technology from the polymer inhibition field to antifoulant composition technology.
Gerbrand (US. Patent 4,386,224) discloses that the color of alkyd phenols can be stabilized and discoloration inhibited by the presence of a small amount of diethylhydroxylamine.
Bert (US. Patent 3,333,001) stabilized dialkylhydroxyl-amine themselves by use of mercaptobenzothiazole.
lo US. Patent 4,400,368 (Zaida) discloses a method of removal of hydrogen sulfide and carbon dioxide from sour gases by contacting the sour gases with an aqueous solution of certain polyvalent metal chelates. The chelates life is taught to be improved by the presence of a stabilizing amount of certain nitrogen compounds including, inter alias diethylhydroxylamine.
Miller (US. Patent 3,105,810) describes the use ox amine salts of dodecyl Bunsen sulfonic acid as surfactant useful in antifoulant compositions. Gonzales (US. Patent 3,271,295) discloses substituted succinic immediacy as surfactants in anti-foul ant compositions.
Waldby (US. Patent 3,340,160) discloses an olefin polymerization inhibitor which is an aqueous solution of an alkali metal nitrite and a quinoid, amino, vitro or phenol compound.
among the amino compounds contemplated by Waldby are N,N-di-n-butylhydroxylamine, 2,4-diaminodiphenylamine, diethanolamine and monoethanolamine.
In certain olefin processing operations it is desirable to have an antifoulant or polymerization inhibitor which participates between the oil and water phase. In other words, a single inhibitor I
acting in both the oil and water phase would be desirable over adding separate water-soluble and oil-soluble inhibitors.
Accordingly, it is an object of the present invention to provide an antifoulant which acts in both the aqueous phase and the hydrocarbon phase of a water-containing hydrocarbon processing operation. It is another object of the present invention to present a method of enhancing antifoulant protection for equipment in those operations. These and other objects of the invention are set forth in the following description and examples of the invention.
Summary of The Invention The improved antifoulant effects afforded by the present invention are achieved by injecting into a stream of dine hydra-carbon scheduled for fractionation, distillation or other processing, a fouling preventing amount of a lower hydroxylamine, i.e., diethylhydroxylamine.
Detailed Description At least one major and significant advantage associated with the use of lower dialkylhydroxylamines has been overlooked extending their applications in dine process applications. This includes their partition coefficient between hydrocarbon arid water.
The advantage of lower dialkylhydroxylamines is based on the partition coefficient of the dialkylhydroxylamine in the presence of water. As an example, aqueous diethylhydroxylamine has a partition coefficient of 13:1 in favor of water. Therefore, approximately OWE of diethylhydr~ylamine would be extracted from an organic process stream which may come into contact with water through washing or which has water present as thy result of accumulation as tank bottoms water. Although this factor has been a limiting factor in efforts to translate the use of dialkyl-hydroxylamines into a majority of hydrocarbon processing units, where -there is either a water wash or caustic wash unit upstream of the hydrocarbon distillation units, it has now been discovered that diethylhydroxylamine (DOW) serves as an effective antifoulant and polymerization inhibitor in dine treatment operations, most notably for bu-tadiene treatment.
In butadiene applications, the crude butadiene distill-talon train is run at temperatures in the range of 90-175F us-don pressure conditions of 50-180 prig. Under these temperature lo and pressure conditions, DOW will not flash overhead with the desired bu-tadiene products of production, thus enabling production of purified monomer without inhibitor present. Further, inhibition of undesired fouling deposits in the lower portions of the column is achieved as well as inhibition of formation of resinous-like polymer glasses in the heat exchangers and recoilers.
The polymerization inhibitor (DOW) of the invention can be introduced into the dine monomer to be protected by any conventional method. It is generally introduced just upstream of the point of desired application by an suitable means such as by the use of a proportionating pump. The DOW polymerization in-hibltor may be added as a concentrate but it is preferable to add Kit as a solution which is compatible with the dine monomer being treated. Suitable solvents are water (if a cosolvent such as an Amarillo or Methyl pyrrolidone is used), alcohols (provided -their Boolean point is sufficiently high as -to no-t be distilled over-heed into the final recovered product), acetonitrile and other organic solvents which have boiling points higher than butadiene.
Concentration of DOW polymerization inhibitor in the solvent is desirably in -the range of about 10 -to 90 weight percent and preferably about 30 to 80 weight percent based on the total weight of DOW and solvent.
I
The DOW is used at a concentration which is effect-ivy to provide the desired protection against spontaneous polyp merization. It has been determined that amount of DELIA in the range of about 100-250 Pam based on the weight of the dine monomer being -treated affords ample protection against undesired polymerization For most applications the inhibitor is used in amourlts in the range of about 5 to 500 Pam.
Furthermore, fouling due -to both hydrocarbon phases and aqueous phases can sometimes be enhanced by use of an lo antieouliny blend of DOW and an oil soluble hydroxylamine such as di-n-butylhydroxylamine.
The following examples will serve to further ill-Stewart without limiting the invention.
Example I
Conventional butadiene recovery units processing approximately 93% crude butadiene to obtain a final product containing 99.5 % butadiene by column distillation with the operating conditions in the last of three columns being over-head 65 Sue, 118F, and 85 gym product butadiene -to storage, have been forced to shut down periodically (every 190 days) to clean recoilers and the column because of butadiene felon. injection of a sodium nitrite solution at the rate of 5 yam to the reflex return of the column did not enhance run times. Certain hydrocarbon end water soluble inhibitors were screened in the laboratory and found -to be less effect-jive than diethylhydroxylamine (see Table T ) against styrenes which was employed as a model because of its ease of handling.
Table I
Observation of Polymerization Test 1000 no Inhibitor 140F
no inhibitor phenylenediarnine ~ert-butyl catcall 3 (llethanolamine clie~hylhydroxylamine 2 It popcorn polymer growth began after 2 days extensive growth after 4 days Z) no growth in 11 days I) previously had tried a phenol/catechol on unit without success Example II
To determine top effectiveness of various hydroxylamines, the same test was repeated. Results are shown below in Table II.
Table II
Test Cone (Pam) Observation of Polymerization .
no inhibitor none polymer formed in 12 his at 100F
1) (a) DEW 100 6 days at 100F' (b) di-isopropyl-hydroxylamine 160 6 days at 100F
(c) di-n-butylhydroxyl-Amarillo 170 6 days at 100F
Finally, the volubility characteristics of compounds (a) end (c) above were determined; di~utylhydroxylamine was found LO
Lowe oily soluble not water soluble unless salted with a mineral acid or short chain carboxylic acid. Diethylhydroxylamine-- as previously mentioned -- can be made oil or water soluble but partitions in favor of water.
EXAMPLE III
As evidenced by Example I, the addition of a purely oil-soluble inhibitor proved unsatisfactory. The addition of a water-soluble oxygen scavenger used to inhibit polymerization also proved unsatisfactory. However, the addition of a hydroxylamine which can partition or the addition of a blend of hydroxylamines (one water soluble, one oil soluble) offered superior performance.
To the same unit as in Example I, 250 Pam DOW based on the weight of the butadiene monomer being processed, was added to the overhead reflex of the final product column of the three columns in series with the same operating conditions as in Example I.
The column treatment extended the run time from 190 days in two previously untreated runs to 30~ day, a 62~ increase.
Claims (4)
1. In an improved process for purifying diene monomers by inhibiting equipment fouling wherein the purification is by distillation, wherein the improvement comprises adding a polymerization inhibiting amount of diethylhydroxylamine to the monomer being purified prior to distillation, during distillation or both.
2. The process according to claim 1 wherein the diene monomer is butadiene.
3. The process according to claim 1 wherein disthyl-hydroxylamine is added to the monomer in an amount of from 5 to 500 ppm based on the weight of diene monomer treated.
4. The process according to claim 1 wherein the purification process includes a water wash or water scrubbing stream and fouling of equipment contacted by both hydrocarbon and water phases is inhibited by a polymerization inhibiting blend of diethylhydroxylamine and di-n-butylhydroxylamine.
9.
9.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US67420484A | 1984-11-23 | 1984-11-23 | |
| US674,204 | 1984-11-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1227449A true CA1227449A (en) | 1987-09-29 |
Family
ID=24705725
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000491498A Expired CA1227449A (en) | 1984-11-23 | 1985-09-25 | Composition for minimizing fouling of heat exchangers and other hydrocarbon processing equipment |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS61130242A (en) |
| CA (1) | CA1227449A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6761833B2 (en) | 2001-03-20 | 2004-07-13 | Atofina Chemicals, Inc. | Stabilization of monomers by compositions based on alkylhydroxylamines |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| ES2384453T3 (en) * | 2001-10-19 | 2012-07-05 | Zeon Corporation | Process and apparatus for separation and purification of conjugated dienes |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS50112304A (en) * | 1974-02-26 | 1975-09-03 |
-
1985
- 1985-09-25 CA CA000491498A patent/CA1227449A/en not_active Expired
- 1985-11-18 JP JP25843285A patent/JPS61130242A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6761833B2 (en) | 2001-03-20 | 2004-07-13 | Atofina Chemicals, Inc. | Stabilization of monomers by compositions based on alkylhydroxylamines |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61130242A (en) | 1986-06-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20050925 |