Chemistry of inorganic compounds – With additive
Reexamination Certificate
1998-07-09
2001-12-11
Griffin, Steven P. (Department: 1754)
Chemistry of inorganic compounds
With additive
C423S561100
Reexamination Certificate
active
06328943
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compositions for and methods of inhibiting pyrophoric activity of iron sulfide. More particularly, the present invention relates to compositions for and methods of inhibiting the formation of pyrophoric iron sulfide by inhibiting the sulfidation of iron oxides and/or inhibiting the oxidation of iron sulfide.
BACKGROUND OF THE INVENTION
Corrosion of iron by air yields rust, or iron oxides such as goethite (∝-FeO (OH)), hematite (Fe
2
O
3
) and magnetite (Fe
3
O
4
). Exposure of these iron oxides to hydrogen sulfide rich conditions where oxygen content is low results in a sulfidation reaction which yields mackinawite (FeS
x
) which can form greigite (Fe
3
S
4
) and/or pyrite (FeS
2
). This sulfidation step is exothermic. Oxidation of these iron sulfides, as by exposures to air or oxygen rich conditions, is highly exothermic and can result in pyrophoric activity.
Hydrogen sulfide is often present in crude oil and can react with iron oxides formed in transportation, processing or storage vessels. Exposure of the resulting iron sulfides to air can result in pyrophoric activity and a potentially explosive situation. For example, the reaction of hydrogen sulfide with iron oxides present in oil tankers in the area above the liquid crude oil can result in the formation of pyrophoric iron sulfides. Upon discharge of the crude oil, exposure of the iron sulfides to air can result in pyrophoric activity in the head space and explosive results are possible. Similar conditions can exist in other crude oil handling, transporting or processing vessels. In particular, pyrophoric iron sulfides have been found in refinery units, sour water strippers and amine units in addition to oil tankers. These units have reducing atmospheres. When these units are opened up, as for repair or maintenance, exposure to air gives rise to the possibility for the pyrophoric iron sulfides to ignite flammable vapors that are still in the units.
The reactions involved in the formation of iron sulfide and its subsequent oxidation on exposure to oxygen may be represented in a simplified form as follows:
Sulfidation Reaction
Fe
2
O
3
+3 H
2
S→2 FeS+S+3H
2
O
Oxidation Reaction
4 FeS+3 O
2
→2 Fe
2
O
3
+4 S
Both of these reactions are exothermic with enthalpy, &Dgr;H, values of −168 and −635 kJ/mol, respectively. If the oxidation reaction is allowed to proceed rapidly with little dissipation of heat, high temperatures leading to glowing and sparking can be expected in the material.
Russian Patent No. 1,449,138 discloses the use of polymer/ionomers containing amide and carboxylate groups to prevent the spontaneous combustion of pyrophoric deposits of iron sulfide. The disclosed method comprises contacting pyrophoric deposits of iron sulfide with an aqueous solution of a deactivating solution of a polymer-ionomer containing amide and carboxylate groups.
SUMMARY OF THE INVENTION
The present inventors have discovered compositions for and methods of inhibiting pyrophoric iron sulfide activity. The compositions and methods of the present invention can inhibit the sulfidation of iron oxide to iron sulfides and/or the oxidation of iron sulfide. The methods of the present invention comprise contacting iron oxides and/or iron sulfide with a liquid, solution, or gaseous inhibitor comprising alkylamines, arylamines, imines; oxygen-containing compounds such as alcohols, aldehydes, esters, acids and ketones; mixed nitrogen-containing and oxygen-containing compounds such as alkanolamines, non-polymeric amides, hydroxylamines, Mannich products, polyisobutylenesuccinimides (PIBSIs), oximes; sulfur-containing compounds and phosphorus-containing compounds. The treatments of the present invention inhibit either the sulfidation and/or the oxidation reactions which can result in the formation and/or pyrophoric activity of iron sulfide.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a method for inhibiting the formation of pyrophoric iron sulfide and/or precusors thereof in the production, transportation and/or storage of petroleum products which contain hydrogen sulfide. The methods of the present invention comprise inhibiting the formation of pyrophoric iron sulfide by inhibiting the sulfidation of iron oxide to yield iron sulfides and/or the oxidation of iron sulfides by contacting the iron oxide or iron sulfide with a liquid, solution, gaseous or aerosol treatment. The treatment comprises alkylamines, arylamines, imines; oxygen-containing compounds such as alcohols, aldehydes, esters, acids and ketones; mixed nitrogen-containing and oxygen-containing compounds such as alkanolamines, non-polymeric amides, hydroxylamines, Mannich products, polyisobutylenesuccinimides (PIBSIs), oximes; sulfur-containing compounds and phosphorus-containing compounds. The amines useful in the methods of the present invention are preferably alkylamines or arylamines which have a boiling point above the temperature of the pyrophoric iron sulfide at the time of treatment, this temperature can vary from ambient temperature up. The preferred oxygen containing compounds are selected from alcohols, aldehydes, esters, acids and ketones preferably having boiling points of greater than about 170° C.
The pyrophoric nature of iron sulfide is well known. The formation of pyrophoric iron sulfide in the vapor areas of oil tankers and refinery units such as sour water strippers and amine scrubbers is considered to be the product of the reaction of hydrogen sulfide present in the hydrocarbon with rust formed by corrosion on the inner surfaces of the steel tanks or equipment. Aging of the materials sometimes increases the tendency of the pyrophoric behavior. At temperatures of 75 to 100° C. sparking can occur as soon as the sulfides are exposed to air
The present inventors discovered that the pyrophoric action of iron sulfide and/or precursors thereof can be inhibited by application of solutions, liquid compounds, aerosols, or vapors to iron sulfide solids. The use of vapor or aerosol application is desirable in liquid storage tanks where the iron sulfide can be formed in the areas above the hydrocarbon liquid.
The treatment compounds of the present invention can inhibit the sulfidation step or the oxidation step leading to pyrophoric activity of iron sulfides.
It is theorized that the treatments form coordinate bonds to the iron atom of the oxides or sulfides through the heteroatom of the treatment. When such a bond breaks, if the treatment compound has a high vapor pressure, it will evaporate, leaving an active iron atom. Such coordinate bonds are strongest for trisubstituted nitrogen compounds such as amines, less strong for nitrites and oxygen-containing compounds. While this theory is believed to be accurate, it is not intended to be limiting with respect to the scope of the present invention.
The treatment compounds of the present invention can include nitrogen-containing compounds such as alkylamines, arylamines, imines; oxygen-containing compounds such as alcohols, aldehydes, esters, acids and ketones; mixed nitrogen-containing and oxygen-containing compounds such as alkanolamines, non-polymeric amides, hydroxylamines, Mannich products, polyisobutylenesuccinimides (PIBSIs), oximes; sulfur-containing compounds and phosphorous-containing compounds.
Examples of alkylamines are n-propylamine, iso-propylamine, n-butylamine, iso-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, stearylamine, oleylamine, diethylamine, di-n-propylamine, di-iso-propylamine, di-n-butylamine, di-iso-butylamine, di-sec-butylamine, di-tert-butylamine, di-n-pentylamine, di-n-hexylamine, di-n-heptylamine, di-n-octylamine, di-n-nonylamine, di-n-decylamine, distearylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine, tri-iso-butylamine, tri-sec-butylamine, tri-tert-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-nony
Goliaszewski Alan E.
Groce Bernard C.
Parker Wiley L.
Roling Paul V.
Sintim Quincy K. A.
BetzDearborn Inc.
Greenblum & Bernstein P.L.C.
Griffin Steven P.
Nguyen Cam N.
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