CA1338488C - Hydroxyalkylhydroxylamine oxygen scavenger in aqueous mediums - Google Patents
Hydroxyalkylhydroxylamine oxygen scavenger in aqueous mediumsInfo
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- CA1338488C CA1338488C CA 611613 CA611613A CA1338488C CA 1338488 C CA1338488 C CA 1338488C CA 611613 CA611613 CA 611613 CA 611613 A CA611613 A CA 611613A CA 1338488 C CA1338488 C CA 1338488C
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Abstract
An improved oxygen scavenger for aqueous mediums is disclosed which is a hydroxyalkylhydroxylamine. The material may be catalyzed with a dioxo compound such as hydroquinone, benzoquinone, 1,2-naphthoquinone-4-sulfonic acid, pryrogallol and t-butylcatchol.
Hydroxyalkyl substituted hydroxylamines of the general formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 where n ranges from 0 to about 10 have been found to be effective oxygen scavengers for aqueous systems such as industrial water systems.
Hydroxyalkyl substituted hydroxylamines of the general formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 where n ranges from 0 to about 10 have been found to be effective oxygen scavengers for aqueous systems such as industrial water systems.
Description
1338~88 ~ R-587 HYDROXYALKYLHYDROXYLAMINE OXYGEN SCAVENGER
IN AQUEOUS MEDIUMS
Field of the Invention The present invention relates to oxygen scavengers for aqueous systems. More particularly, the present invention relates to the use of catalyzed and non-catalyzed hydroxyalkylhydroxylamines as oxygen scavengers in aqueous systems such as boiler systems.
Background of Invention From a corrosion point of view, the presence of certain dissolved gases, even in small amounts, is undesirable in water systems which contact metal surfaces~ For example, metal surfaces in contact with oxygen containing water can experience severe pitting in industrial water systems. Pitting is highly localized corrosion affecting only a small area of the total metal surface.
This can be a serious problem causing metal failure even though only a small amount of metal is lost and the overall corrosion rate is relatively low. ~
'~' With respect to oxygen, the severity of attack will depend upon the concentration of dissolved oxygen in the water, pH and temperature. As water temperature increases, as for example in a water heating system such as a boiler, enough driving force is added to the corrosion reaction that small amounts of dissolved oxygen in the water can cause serious problems. Oxygen pitting is considered a most serious problem in boiler systems, even where only trace amounts of oxygen are present.
Deaeration is a widely used method for removing oxygen from an oxygen-containing aqueous medium. It is particularly useful for treating boiler feedwater and can be either mechanical or chemical.
While vacuum deaeration has proven to be a useful mechanical deaeration method for treating water distributing systems, boiler feedwater is treated using pressure deaeration with steam as the purge gas. According to the pressure deaeration method for preparing boiler feedwater, the water is sprayed into a steam atmosphere and is heated to a temperature at which the solubility of oxygen in the water is low. Typically greater than 99% of the oxygen in the feedwater is released to the steam and is purged from the system by venting.
Mechanical deaeration is considered an important first step in removing dissolved oxygen from boiler feedwater. However, as already noted, as water temperature increases, even trace amounts of dissolved oxygen can cause serious problems~ Accordingly, supplemental chemical deaeration is required.
1338~88 For hoilers operated below 1000 pounds per square inch (psi), catalyzed sodium sulfite is commonly used as an oxygen scavenger for the chemical deaeration of the feedwater. The oxygen/sulfite reaction can be effectively catalyzed by iron, copper, cobalt, nickel, and/or manganese~ While the sodium sulfite oxygen scavenger is often used with success, this material does have recognized limitations. At boiler operating pressures of 900 to 1000 psi and above, increased dissolved solids from the sulfite/oxygen reaction product can become a significant problem~
Also, at high pressures the sulfite decomposes in the boiler to form sulfur dioxide and hydrogen sulfide, both of which can cause corrosion in the return condensate system~
Hydrazine is also used as an oxygen scavenger~ Hydrazine does not have the above noted high pressure limitation of sodium sulfite~ For example, since the products of the hydrazine/oxygen reaction are water and nitrogen, no solids are added to the boiler water~ Hydrazine as an oxygen scavenger does, however, have its own limitations~ A major problem relates to the toxicity of hydrazine~
Also, the hydrazine/oxygen reaction is very slow at low temperatures which may encountered in some sections of a boiler system~ The decomposition products of hydrazine are ammonia and nitrogen~ The ammonia can be aggressive to copper or copper bearing metallurgies that are found in condensate systems~
In recent developments, the use of certain compounds such as dioxo-aromatic compounds or organically substituted derivatives thereof has become known~ The group "dioxo-aromatic" consists of benzoquinone, napthoquinone, hydroquinone and catechol~ The phrase "organically substituted derivatives thereof" includes any dioxo-aromatic compound having an organic substituent with a carbon atom attached directly to the aromatic ring. An example of such a derivative is 4-tert-butylcatechol~ The use of quinones and diols as catalysts for the hydrazine/oxygen reaction in an aqueous medium is well known, for example, U.S. Patent No. 3,551,349 to Kallfass~
U.S. Patent NoA 3,843,547 to Kaufman discloses the use of a combination of an aryl amine compound and a quinone compound as a catalyst for a hydrazine oxygen scavenger.
Indeed, in the context of the prior art, wherein the use of quinones as catalysts for hydrazine/oxygen scavengers is well known, it was also discovered that some dioxo-aromatic compounds performed very well alone as oxygen scavengers. Such compounds are less toxic than hydrazine and also demonstrate greater reactivity at room temperature. The use of dioxo-aromatic compounds in combination with select neutralizing amines, classified as "mu-amines", is described in U.S. Patents Nos. 4,279,767 and 4,289,645 to Muccitelli.
The use of hydroxylamine, certain of its water soluble salts and derivatives of hydroxylamine which serve as oxygen scavengers, is disclosed in U.S~ Patent No. 4,067,690~ The hydroxylamines described as useful as oxygen scavengers have the general formula RlR2NOR3 wherein Rl, R2 and R3 are either the same or different and selected from the group consisting of hydrogen, lower alkyl having between 1 to about 8 carbon atoms, and aryl such as phenyl, benzyl, and tolyl. The hydroxylamine oxygen scavengers disclosed in U.S~ Patent No~ 4,067,690 may be catalyzed with a number of well known catalysts as used in sodium sulfite or hydrazine boiler water treatment such as hydroquinone and benzoquinone as well as alkaline metal hydroxides, water soluble metal salts.
Summary of the Invention The present invention is directed to the discovery that hydroxylamines having hydroxyalkyl substitutions provide effective oxygen scavengers~ The material may be catalyzed with a small amount of a dioxo compound. The oxygen scavengers of the present invention have relatively high boiling points.
The present inventors have discovered that hydroxyalkyl-hydroxylamines are more effective oxygen scavengers than the prior art oxygen scavenger N,N-diethylhydroxylamine (DEHA) and simialr alkyl hydroxylamines~ As with the prior art oxygen scavengers, catalysts such as hydroquinone may be employed. The catalyzed hydroxyalkylhydroxylamines of the present invention have relatively high boiling points so they are more resistant to flashing out of the aqueous phase than prior art oxygen scavengers. The prior art problem of the low solubility of hydroquinone in aqueous mediums is minimized by the use of low concentrations of hydroquinone as a catalyst for the hydroxyalkylhydroxylamine oxygen scavenger of the present invention.
-1~38488 The preferred hydroxyalkylhydroxylamine of the present invention are N,N-bis(2-hydroxypropyl)hydroxylamine (HPHA), N,N-bis(2-hydroxyethyl)hydroxylamine (HEHA), and N,N-bis(2-hydroxybutyl)hydroxylamine (HBHA)~
Description of the Preferred Embodiments The present inventors have discovered that hydroxyalkylhydroxylamines either alone or catalyzed, provide improved oxygen scavenging under conditions encountered in a typical boiler system~ The oxygen scavengers of the present invention combine low toxicity and low volatility, are relatively easy to manufacture, and add no solids to the boiler system~ They also provide good oxygen scavenging ability at typical deaerator temperatures and moderate reactivity at room temperatures which minimizes storage and handling problems~
The improved oxygen scavengers of the present invention comprise a hydroxyalkylhydroxylamine of the general formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 wherein n can range from 0 to about 10. A catalyst may be employed to accelerate the reaction of the hydroxyalkylhydroxylamine with oxygen to rates which are of practical use in low temperature areas of a boiler system or when reaction times are short. Catalyst which have been found to be effective include hydroxylated aromatics as well as copper.
Preferred hydroxyalkylhydroxylamines include:
N,N-bis(2-hydroxyethyl)hydroxylamine (n=0);
N,N-bis(2-hydroxypropyl)hydroxylamine (n=l); and -N,N-bis(2-hydroxybutyl)hydroxylamine (n=2).
N,N-bis(2-hydroxypropyl)hydroxylamine is particularly preferred Catalysts which have been found to be effective include hydroquinone, benzoquinone, pyrogallol, copper ( I I ) and 1,2-naphthoquinone-4-sulfonic acid. 1,2-naphthoquinone-4-sulfonic acid has been found to be particularly effective.
The hydroxyalkylhyroxylamine of the present invention can be added to an aqueous system in amounts ranging from about 5 parts per billion up to about 100 parts per million. Preferrably the hydroxyalkylhydroxylamine is added to an aqueous system in concentrations ranging from about 5 up to about 200 parts per billion. The ratio of hydroxyalkylhydroxylamine to catalyst can range from 0 up to about 25% catalyst.
The effectiveness of the hydroxyalkylhydroxylamine oxygen scavengers of the present invention is evidenced by the following examples wherein oxygen scavenging ability was tested at both room temperature and at temperatures corresponding to those expected in a typical boiler system deaerator. The present invention will now be further described with reference to a number of specific examples which are to be regarded as illustrative and not as restricting the scope of the invention.
Test Method Utilized The testing at room temperature was performed using a room temperature oxygen scavenging apparatus which consists of a three necked flask fitted with a dissolved oxygen electrode in one neck, a 1338~88 pH electrode in a second neck, and a rubber septum at a third neck.
Aerated, demineralized water in the flask was adjusted to a fixed pH
with sodium hydroxide and held at an equilibrium temperature fixed by a water bath surrounding the flask~ Following injection of a scavenger/catalyst mixture through the rubber septum, the dissolved oxygen concentration was recorded as a function of time~ The numbers shown in the following tables are based upon the initial rates of reaction for each scavenger with dissolved oxygen. The rate is measured by the slope of the plot of log (oxygen concentration at a given time divided by initial oxygen concentration) versus the time in minutes~ Because the rate of oxygen removal is measured, larger negative values indicate faster, more desirable reaction rates Test Conditions for Tables 1, 2 and 3 Temperature: 28C (83C) pH: 10~0 pH adjustment with 1 N NaOH
water: air saturated, demineralized scavenger concentration: 6~3 x 10-4 molar organic catalyst concentration: 5.1 x 10~5 molar 1~38488 g Initial Reaction Rates of HPHA/Catalyst Combination Treatment Rate HPHA alone, no catalyst -0.003 HPHA/hydroquinone -0.619 HPHA/1,2-naphthoquinone-4-sulfonic acid -0~786 HPHA/benzoquinone -0.569 HPHA/copper (II)* -0.260 HPHA/pyrogallol -0.204 HPHA/t-butylcatechol -0.062 * copper was tested at 2 ppm in combination with 3.6 ppm hydroxyethylidenediphosphonic acid.
Reaction Rates for the Series n = 0 to 2, N,N-bis(2-hydroxyalkyl)hydroxylamines with Hydroquinone Catalyst Treatment Reaction Rate HEHA/no catalyst -0.002 HEHA/HQ -0.337 HPHA/no catalyst -0.003 HPHA/HQ -0.619 HBHA/no catalyst -0.002 HBHA/HQ -0.550 lo 1338488 Initial Reaction Rates of Various Hydroxylamine/Catalyst Combinations Treatment Rate Diethylhydroxylamine/hydroquinone -0.215 Hydroxyethylhydroxylamine/hydroquinone -0.354 Dipropylhydroxylamine/hydroquinone -0.163 Hydroxypropylhydroxylamine/hydroquinone -0.619 Dibutylhydroxylamine/hydroquinone -0.162*
Hydroxybutylhydroxylamine/hydroquinone -0.426**
Hydroxybutylhydroxylamine/hydroquinone -0.550***
* ~ Stock prepared in ethanol due to low aqueous solubility ** Stock prepared in ethanol.
*** Stock prepared in water.
The data in Tables 1, 2, and 3 shows the desirability of a catalyst when the reaction temperatures are low. Also, the hydroxyalkylhydroxylamines of the present invention are unexpectedly shown to be significantly more reactive than the corresponding alkylhydroxylamines~ The significantly higher rate of reaction of the hydroxyalkylhydroxylamines with dissolved oxygen when compaired to their non-hydroxylated alkyl analogs was unexpected.
Experiments which approximate typical deaerator conditions were run in moderate a temperature scavenging test apparatus similar to those described in U.S. Patent No. 4,289,645.
Test Conditions for Table 4 and 5 Temperature: 135C (275F) pH: (25C): 8~0 Residence time at 275F: 6 min Flow rate: 167 mL/min Initial dissolved oxygen: 30 +/- 4 parts per billion Reaction coil: 40 ft x 1/2 in 316 stainless steel tube Total time in system: 9 minutes pH buffer: 1,059 ppm KH2P04/286 ppm NaOH
Buffer injection rate: 2.0 +/- 0.2 mL/min into 167 mL/min Catalyst concentration: 6.7 x 10-8 molar Scavenger concentration: 8.3 x 10~7 molar HPHA Testing in Moderate Temperature Oxygen Scavenging Test Apparatus 02 w/out 02 with 02 Removed Scav Catalyst Scav Scav ppb DEHA None 31.0 25.5 4.5 HPHA None 31.0 14.0 17.0 HPHA HC 31.5 10.0 21.5 HPHA HC 26.0 4.0 22.0 HPHA NS 29.8 5.0 24.8 HPHA PYRO 29.3 4.0 25.3 HPHA PG 30.0 4.0 26.0 HPHA PG 28.0 7.5 20.5 (HQ = hydroquinone, NS = 1,2-naphthoquinone-4-sulfonic acid, PYRO =
pyrogallol and PG = propylgallate) -1338~88 The data in Table 4 shows that even at elevated tempertures, the non-hydroxylated hydroxylamine, DEHA, has little activity without a catalyst present. Conversely, HPHA, a hydroxylamine with hydroxylated alkyl substituent, shows good oxygen scavenging reactivity with or without the presence of a catalyst.
Hydroxylamine Testing in Moderate Temperature Oxygen Scavenging Test Apparatus 2 w/out 2 w/out 2 Removed Scav Catalyst Scav Scav ppb DEHA HQ 27.0 12.0 15.0 DEHA HQ 32.0 16.0 16.0 HEHA HQ 30~5 10.0 20~5 DPHA HQ 32.0 20~0 12.0 HPHA HQ 26.0 4.0 22.0 HPHA HQ 31.5 10.0 21.5 DBHA HQ 30.5 19.0 11.5 HBHA HQ 30.0 3.5 26.5 Tables 4 and 5 illustrate the superior reactivity of the hydroxylamines having hydroxylated alkyl substituents over the analogous non-hydroxylated materials, even at elevated temperatures.
As can be seen in all the Tables, the catalyst selected, in all cases, accelerates the reaction of a hydroxyalkyl-hydroxylamine. The effect is found at both room temperature and at temperatures representative of deaerator temperatures in a boiler system.
13~8~88 While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention~
IN AQUEOUS MEDIUMS
Field of the Invention The present invention relates to oxygen scavengers for aqueous systems. More particularly, the present invention relates to the use of catalyzed and non-catalyzed hydroxyalkylhydroxylamines as oxygen scavengers in aqueous systems such as boiler systems.
Background of Invention From a corrosion point of view, the presence of certain dissolved gases, even in small amounts, is undesirable in water systems which contact metal surfaces~ For example, metal surfaces in contact with oxygen containing water can experience severe pitting in industrial water systems. Pitting is highly localized corrosion affecting only a small area of the total metal surface.
This can be a serious problem causing metal failure even though only a small amount of metal is lost and the overall corrosion rate is relatively low. ~
'~' With respect to oxygen, the severity of attack will depend upon the concentration of dissolved oxygen in the water, pH and temperature. As water temperature increases, as for example in a water heating system such as a boiler, enough driving force is added to the corrosion reaction that small amounts of dissolved oxygen in the water can cause serious problems. Oxygen pitting is considered a most serious problem in boiler systems, even where only trace amounts of oxygen are present.
Deaeration is a widely used method for removing oxygen from an oxygen-containing aqueous medium. It is particularly useful for treating boiler feedwater and can be either mechanical or chemical.
While vacuum deaeration has proven to be a useful mechanical deaeration method for treating water distributing systems, boiler feedwater is treated using pressure deaeration with steam as the purge gas. According to the pressure deaeration method for preparing boiler feedwater, the water is sprayed into a steam atmosphere and is heated to a temperature at which the solubility of oxygen in the water is low. Typically greater than 99% of the oxygen in the feedwater is released to the steam and is purged from the system by venting.
Mechanical deaeration is considered an important first step in removing dissolved oxygen from boiler feedwater. However, as already noted, as water temperature increases, even trace amounts of dissolved oxygen can cause serious problems~ Accordingly, supplemental chemical deaeration is required.
1338~88 For hoilers operated below 1000 pounds per square inch (psi), catalyzed sodium sulfite is commonly used as an oxygen scavenger for the chemical deaeration of the feedwater. The oxygen/sulfite reaction can be effectively catalyzed by iron, copper, cobalt, nickel, and/or manganese~ While the sodium sulfite oxygen scavenger is often used with success, this material does have recognized limitations. At boiler operating pressures of 900 to 1000 psi and above, increased dissolved solids from the sulfite/oxygen reaction product can become a significant problem~
Also, at high pressures the sulfite decomposes in the boiler to form sulfur dioxide and hydrogen sulfide, both of which can cause corrosion in the return condensate system~
Hydrazine is also used as an oxygen scavenger~ Hydrazine does not have the above noted high pressure limitation of sodium sulfite~ For example, since the products of the hydrazine/oxygen reaction are water and nitrogen, no solids are added to the boiler water~ Hydrazine as an oxygen scavenger does, however, have its own limitations~ A major problem relates to the toxicity of hydrazine~
Also, the hydrazine/oxygen reaction is very slow at low temperatures which may encountered in some sections of a boiler system~ The decomposition products of hydrazine are ammonia and nitrogen~ The ammonia can be aggressive to copper or copper bearing metallurgies that are found in condensate systems~
In recent developments, the use of certain compounds such as dioxo-aromatic compounds or organically substituted derivatives thereof has become known~ The group "dioxo-aromatic" consists of benzoquinone, napthoquinone, hydroquinone and catechol~ The phrase "organically substituted derivatives thereof" includes any dioxo-aromatic compound having an organic substituent with a carbon atom attached directly to the aromatic ring. An example of such a derivative is 4-tert-butylcatechol~ The use of quinones and diols as catalysts for the hydrazine/oxygen reaction in an aqueous medium is well known, for example, U.S. Patent No. 3,551,349 to Kallfass~
U.S. Patent NoA 3,843,547 to Kaufman discloses the use of a combination of an aryl amine compound and a quinone compound as a catalyst for a hydrazine oxygen scavenger.
Indeed, in the context of the prior art, wherein the use of quinones as catalysts for hydrazine/oxygen scavengers is well known, it was also discovered that some dioxo-aromatic compounds performed very well alone as oxygen scavengers. Such compounds are less toxic than hydrazine and also demonstrate greater reactivity at room temperature. The use of dioxo-aromatic compounds in combination with select neutralizing amines, classified as "mu-amines", is described in U.S. Patents Nos. 4,279,767 and 4,289,645 to Muccitelli.
The use of hydroxylamine, certain of its water soluble salts and derivatives of hydroxylamine which serve as oxygen scavengers, is disclosed in U.S~ Patent No. 4,067,690~ The hydroxylamines described as useful as oxygen scavengers have the general formula RlR2NOR3 wherein Rl, R2 and R3 are either the same or different and selected from the group consisting of hydrogen, lower alkyl having between 1 to about 8 carbon atoms, and aryl such as phenyl, benzyl, and tolyl. The hydroxylamine oxygen scavengers disclosed in U.S~ Patent No~ 4,067,690 may be catalyzed with a number of well known catalysts as used in sodium sulfite or hydrazine boiler water treatment such as hydroquinone and benzoquinone as well as alkaline metal hydroxides, water soluble metal salts.
Summary of the Invention The present invention is directed to the discovery that hydroxylamines having hydroxyalkyl substitutions provide effective oxygen scavengers~ The material may be catalyzed with a small amount of a dioxo compound. The oxygen scavengers of the present invention have relatively high boiling points.
The present inventors have discovered that hydroxyalkyl-hydroxylamines are more effective oxygen scavengers than the prior art oxygen scavenger N,N-diethylhydroxylamine (DEHA) and simialr alkyl hydroxylamines~ As with the prior art oxygen scavengers, catalysts such as hydroquinone may be employed. The catalyzed hydroxyalkylhydroxylamines of the present invention have relatively high boiling points so they are more resistant to flashing out of the aqueous phase than prior art oxygen scavengers. The prior art problem of the low solubility of hydroquinone in aqueous mediums is minimized by the use of low concentrations of hydroquinone as a catalyst for the hydroxyalkylhydroxylamine oxygen scavenger of the present invention.
-1~38488 The preferred hydroxyalkylhydroxylamine of the present invention are N,N-bis(2-hydroxypropyl)hydroxylamine (HPHA), N,N-bis(2-hydroxyethyl)hydroxylamine (HEHA), and N,N-bis(2-hydroxybutyl)hydroxylamine (HBHA)~
Description of the Preferred Embodiments The present inventors have discovered that hydroxyalkylhydroxylamines either alone or catalyzed, provide improved oxygen scavenging under conditions encountered in a typical boiler system~ The oxygen scavengers of the present invention combine low toxicity and low volatility, are relatively easy to manufacture, and add no solids to the boiler system~ They also provide good oxygen scavenging ability at typical deaerator temperatures and moderate reactivity at room temperatures which minimizes storage and handling problems~
The improved oxygen scavengers of the present invention comprise a hydroxyalkylhydroxylamine of the general formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 wherein n can range from 0 to about 10. A catalyst may be employed to accelerate the reaction of the hydroxyalkylhydroxylamine with oxygen to rates which are of practical use in low temperature areas of a boiler system or when reaction times are short. Catalyst which have been found to be effective include hydroxylated aromatics as well as copper.
Preferred hydroxyalkylhydroxylamines include:
N,N-bis(2-hydroxyethyl)hydroxylamine (n=0);
N,N-bis(2-hydroxypropyl)hydroxylamine (n=l); and -N,N-bis(2-hydroxybutyl)hydroxylamine (n=2).
N,N-bis(2-hydroxypropyl)hydroxylamine is particularly preferred Catalysts which have been found to be effective include hydroquinone, benzoquinone, pyrogallol, copper ( I I ) and 1,2-naphthoquinone-4-sulfonic acid. 1,2-naphthoquinone-4-sulfonic acid has been found to be particularly effective.
The hydroxyalkylhyroxylamine of the present invention can be added to an aqueous system in amounts ranging from about 5 parts per billion up to about 100 parts per million. Preferrably the hydroxyalkylhydroxylamine is added to an aqueous system in concentrations ranging from about 5 up to about 200 parts per billion. The ratio of hydroxyalkylhydroxylamine to catalyst can range from 0 up to about 25% catalyst.
The effectiveness of the hydroxyalkylhydroxylamine oxygen scavengers of the present invention is evidenced by the following examples wherein oxygen scavenging ability was tested at both room temperature and at temperatures corresponding to those expected in a typical boiler system deaerator. The present invention will now be further described with reference to a number of specific examples which are to be regarded as illustrative and not as restricting the scope of the invention.
Test Method Utilized The testing at room temperature was performed using a room temperature oxygen scavenging apparatus which consists of a three necked flask fitted with a dissolved oxygen electrode in one neck, a 1338~88 pH electrode in a second neck, and a rubber septum at a third neck.
Aerated, demineralized water in the flask was adjusted to a fixed pH
with sodium hydroxide and held at an equilibrium temperature fixed by a water bath surrounding the flask~ Following injection of a scavenger/catalyst mixture through the rubber septum, the dissolved oxygen concentration was recorded as a function of time~ The numbers shown in the following tables are based upon the initial rates of reaction for each scavenger with dissolved oxygen. The rate is measured by the slope of the plot of log (oxygen concentration at a given time divided by initial oxygen concentration) versus the time in minutes~ Because the rate of oxygen removal is measured, larger negative values indicate faster, more desirable reaction rates Test Conditions for Tables 1, 2 and 3 Temperature: 28C (83C) pH: 10~0 pH adjustment with 1 N NaOH
water: air saturated, demineralized scavenger concentration: 6~3 x 10-4 molar organic catalyst concentration: 5.1 x 10~5 molar 1~38488 g Initial Reaction Rates of HPHA/Catalyst Combination Treatment Rate HPHA alone, no catalyst -0.003 HPHA/hydroquinone -0.619 HPHA/1,2-naphthoquinone-4-sulfonic acid -0~786 HPHA/benzoquinone -0.569 HPHA/copper (II)* -0.260 HPHA/pyrogallol -0.204 HPHA/t-butylcatechol -0.062 * copper was tested at 2 ppm in combination with 3.6 ppm hydroxyethylidenediphosphonic acid.
Reaction Rates for the Series n = 0 to 2, N,N-bis(2-hydroxyalkyl)hydroxylamines with Hydroquinone Catalyst Treatment Reaction Rate HEHA/no catalyst -0.002 HEHA/HQ -0.337 HPHA/no catalyst -0.003 HPHA/HQ -0.619 HBHA/no catalyst -0.002 HBHA/HQ -0.550 lo 1338488 Initial Reaction Rates of Various Hydroxylamine/Catalyst Combinations Treatment Rate Diethylhydroxylamine/hydroquinone -0.215 Hydroxyethylhydroxylamine/hydroquinone -0.354 Dipropylhydroxylamine/hydroquinone -0.163 Hydroxypropylhydroxylamine/hydroquinone -0.619 Dibutylhydroxylamine/hydroquinone -0.162*
Hydroxybutylhydroxylamine/hydroquinone -0.426**
Hydroxybutylhydroxylamine/hydroquinone -0.550***
* ~ Stock prepared in ethanol due to low aqueous solubility ** Stock prepared in ethanol.
*** Stock prepared in water.
The data in Tables 1, 2, and 3 shows the desirability of a catalyst when the reaction temperatures are low. Also, the hydroxyalkylhydroxylamines of the present invention are unexpectedly shown to be significantly more reactive than the corresponding alkylhydroxylamines~ The significantly higher rate of reaction of the hydroxyalkylhydroxylamines with dissolved oxygen when compaired to their non-hydroxylated alkyl analogs was unexpected.
Experiments which approximate typical deaerator conditions were run in moderate a temperature scavenging test apparatus similar to those described in U.S. Patent No. 4,289,645.
Test Conditions for Table 4 and 5 Temperature: 135C (275F) pH: (25C): 8~0 Residence time at 275F: 6 min Flow rate: 167 mL/min Initial dissolved oxygen: 30 +/- 4 parts per billion Reaction coil: 40 ft x 1/2 in 316 stainless steel tube Total time in system: 9 minutes pH buffer: 1,059 ppm KH2P04/286 ppm NaOH
Buffer injection rate: 2.0 +/- 0.2 mL/min into 167 mL/min Catalyst concentration: 6.7 x 10-8 molar Scavenger concentration: 8.3 x 10~7 molar HPHA Testing in Moderate Temperature Oxygen Scavenging Test Apparatus 02 w/out 02 with 02 Removed Scav Catalyst Scav Scav ppb DEHA None 31.0 25.5 4.5 HPHA None 31.0 14.0 17.0 HPHA HC 31.5 10.0 21.5 HPHA HC 26.0 4.0 22.0 HPHA NS 29.8 5.0 24.8 HPHA PYRO 29.3 4.0 25.3 HPHA PG 30.0 4.0 26.0 HPHA PG 28.0 7.5 20.5 (HQ = hydroquinone, NS = 1,2-naphthoquinone-4-sulfonic acid, PYRO =
pyrogallol and PG = propylgallate) -1338~88 The data in Table 4 shows that even at elevated tempertures, the non-hydroxylated hydroxylamine, DEHA, has little activity without a catalyst present. Conversely, HPHA, a hydroxylamine with hydroxylated alkyl substituent, shows good oxygen scavenging reactivity with or without the presence of a catalyst.
Hydroxylamine Testing in Moderate Temperature Oxygen Scavenging Test Apparatus 2 w/out 2 w/out 2 Removed Scav Catalyst Scav Scav ppb DEHA HQ 27.0 12.0 15.0 DEHA HQ 32.0 16.0 16.0 HEHA HQ 30~5 10.0 20~5 DPHA HQ 32.0 20~0 12.0 HPHA HQ 26.0 4.0 22.0 HPHA HQ 31.5 10.0 21.5 DBHA HQ 30.5 19.0 11.5 HBHA HQ 30.0 3.5 26.5 Tables 4 and 5 illustrate the superior reactivity of the hydroxylamines having hydroxylated alkyl substituents over the analogous non-hydroxylated materials, even at elevated temperatures.
As can be seen in all the Tables, the catalyst selected, in all cases, accelerates the reaction of a hydroxyalkyl-hydroxylamine. The effect is found at both room temperature and at temperatures representative of deaerator temperatures in a boiler system.
13~8~88 While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention~
Claims (27)
1. A composition which is useful for reducing the amount of oxygen in an oxygen-containing aqueous medium, said composition comprising a hydroxyalkylhydroxylamine having the formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 wherein n ranges from 0 to about 10, said composition being added to said aqueous medium in an amount of from about 5 parts per billion up to about 100 parts per million.
2. The composition of claim 1 wherein said composition further includes a catalyst in an amount sufficient to increase the oxygen scavenging efficiency of said hydroxyalkylhydroxylamine.
3. The composition of claim 2 wherein said catalyst is selected from the group of hydroxylated aromatics consisting of hydroquinone; benzoquinone;
1,2-naphthoquinone-4-sulfonic acid; pyrogallol; and t-butylcatechol.
1,2-naphthoquinone-4-sulfonic acid; pyrogallol; and t-butylcatechol.
4. The composition of claim 1 wherein said hydroxyalkylhydroxylamine is selected from the group consisting of N,N-bis(2-hydroxyethyl)hydroxylamine;
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
5. The composition of claim 2 wherein the ratio of hydroxyalkylhydroxylamine to catalyst ranges from a trace up to about 25%
catalyst.
catalyst.
6. A composition which is useful for reducing the amount of oxygen in an oxygen-containing aqueous medium, said composition comprising: a hydroxyalkylhydroxylamine having the formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 wherein n ranges from 0 to about 10; and a catalyst selected from the group consisting of hydroxylated aromatics and copper.
7. The composition of claim 6 wherein said catalyst is present in an amount sufficient to increase the oxygen scavenging efficiency of said hydroxyalkylhydroxylamine.
8. The composition of claim 6 wherein said hydroxyalkylhydroxylamine is selected from the group consisting of N,N,-bis(2-hydroxyethyl)hydroxylamine;
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
9. The composition of claim 6 wherein said catalyst is selected from the group of hydroxylated aromatics consisting of hydroquinone; benzoquinone;
1,2-naphthoquinone-4-sulfonic acid; pyrogallol; and t-butylcatechol.
1,2-naphthoquinone-4-sulfonic acid; pyrogallol; and t-butylcatechol.
10. The composition of claim 6 wherein said composition is added in an amount of from about 5 parts per billion up to about 100 parts per million.
11. The composition of claim 6 wherein the ratio of hydroxyalkylhydroxylamine to catalyst ranges from a trace up to about 25%
catalyst.
catalyst.
12. A composition which is useful for reducing the amount of oxygen in an oxygen containing aqueous medium, said composition comprising: water; a hydroxyalkylhydroxylamine having the formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 wherein n ranges from 0 to about 10; and a catalyst selected from the group consisting of hydroxylated aromatics and copper, said catalyst present in an amount sufficient to increase the oxygen scavenging efficiency of said hydroxyalkylhydroxylamine.
13. The composition of claim 12 wherein said catalyst is selected from the group of hydroxylated aromatics consisting of hydroquinone;
benzoquinone; 1,2-napthoquinone-4-sulfonic acid; pyrogallol; and t-butylcatechol.
benzoquinone; 1,2-napthoquinone-4-sulfonic acid; pyrogallol; and t-butylcatechol.
14. The composition of claim 13 wherein said hydroxyalkylhydroxylamine is selected from the group consisting of N,N,-bis(2-hydroxyethyl)hydroxylamine;
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
15. The composition of claim 12 wherein said hydroxyalkylhydroxylamine is added to said aqueous medium in an amount of from about 5 parts per billion up to about 100 parts per million
16. The composition of claim 12 wherein the ratio of hydroxyalkylhydroxylamine to catalyst ranges from a trace up to about 25%
catalyst.
catalyst.
17. A method of reducing the amount of oxygen in an oxygen containing aqueous medium comprising adding to said oxygen containing aqueous medium a hydroxyalkylhydroxylamine having the formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 wherein n ranges from 0 to about 10 and a catalyst selected from the group of hydroxylated aromatics and copper.
18. The method of claim 17 wherein said catalyst is present in an amount sufficient to increase the oxygen scavenging efficiency of said hydroxyalkylhydroxylamine.
19. The method of claim 17 wherein said hydroxyalkylhydroxylamine is selected from the group consisting of N,N,-bis(2-hydroxyethyl)hydroxylamine;
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
20. The method of claim 17 wherein said catalyst is selected from the group of hydroxylated aromatics consisting of hydroquinone; benzoquinone;
1,2-napthoquinone; pyrogallol; and t-butylcatechol.
1,2-napthoquinone; pyrogallol; and t-butylcatechol.
21. The method of claim 17 wherein said composition is added to said aqueous medium in an amount of from about 5 parts per billion up to about 100 parts per million.
22. The method of claim 17 wherein the ratio of hydroxyalkylhydroxylamine to catalyst ranges from a trace up to about 25%
catalyst.
catalyst.
23. A method of reducing the amount of oxygen in an oxygen containing aqueous medium comprising adding to said oxygen containing medium:
water; a hydroxyalkylhydroxylamine having the formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 wherein n ranges from 0 to about 10; and a catalyst selected from the group consisting of hydroxylated aromatics and copper, said catalyst present in an amount sufficient to increase the oxygen scavenging efficiency of said hydroxyalkylhydroxylamine.
water; a hydroxyalkylhydroxylamine having the formula HON-[CH2-CH(OH)-(CH2)n-CH3]2 wherein n ranges from 0 to about 10; and a catalyst selected from the group consisting of hydroxylated aromatics and copper, said catalyst present in an amount sufficient to increase the oxygen scavenging efficiency of said hydroxyalkylhydroxylamine.
24. The method of claim 23 wherein said catalyst is selected from the group of hydroxylated aromatics consisting of hydroquinone; benzoquinone;
1,2-naphthoquinone-4-sulfonic acid; pyrogallol; and t-butylcatechol.
1,2-naphthoquinone-4-sulfonic acid; pyrogallol; and t-butylcatechol.
25. The method of claim 23 wherein said hydroxyalkylhydroxylamine is selected from the group consisting of N,N,-bis(2-hydroxyethyl)hydroxylamine;
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
N,N-bis(2-hydroxypropyl)hydroxylamine; and N,N-bis(2-hydroxybutyl)hydroxylamine.
26. The composition of claim 23 wherein said composition is added to said aqueous medium in an amount of from about 5 parts per billion up to about 100 parts per million.
27. The composition of claim 23 wherein the ratio of hydroxyalkylhydroxylamine to catalyst ranges from a trace up to about 25%
catalyst.
catalyst.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US36938489A | 1989-06-21 | 1989-06-21 | |
| US07/369,384 | 1989-06-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1338488C true CA1338488C (en) | 1996-07-30 |
Family
ID=23455255
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 611613 Expired - Fee Related CA1338488C (en) | 1989-06-21 | 1989-09-15 | Hydroxyalkylhydroxylamine oxygen scavenger in aqueous mediums |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1338488C (en) |
-
1989
- 1989-09-15 CA CA 611613 patent/CA1338488C/en not_active Expired - Fee Related
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