CA1128751A - Magnesium hydroxide in water in oil emulsion as additive for liquid hydrocarbon - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Stable, oil dispersible, aqueous dispersions of magnesium hydroxide useful as deposit control additives for residual fuels are prepared. These slurries, of magnesium hydroxide contain generally:
A) 20-70% Mg(OH)2 having a particle size of 50 to 1.0 micron, B) 79-29% water;
C) 1.0-8.0% of a water-in-oil emulsifying agent having an HLB
value of from 2 to 11;
D) 0.1-6% of a water soluble water-in-oil emulsifying agent having an HLB value of from 10 to 40;
Said dispersion having a Brookfield Viscosity of from 100-5000 cps. (#3 spindle at 12rpm, 75°F).

Description

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~ INTRODUCTION
! ¦Magnesium containing corrosion inhibitors or the inhibition o-f fireside deposits in boilers and gas turbine units are well-known. These additives, generally being prepared as an oil soluble salt of magnesium which can be fed and dispersed into xesidual and other type o hydrocarbon uel oils for the control and inhibition of vanadium corrosion have met with some commercial success in the past.
¦ While these oil soluble compounds have been utilized, a ¦ serious factor affecting their commercial performance has been the ¦ cost and methods of preparation. Magnesium is a naturally occurring I element found in sea water and brines which are present in great abundance. While the end product of combusting the magnesium compound in a res~dual fuel oil or the like is magnesium oxide and it is believed that magneslum oxide is the active species as a Icorrosion inhibitor, the problems connected with the utilization of magnesium oxlde, such as uniformly dispersing the material into the hydrocarbon fuel have prevented commercial use With more and more emphasis being placed on obtaining alternate forms of energy and the i ~ fact that high vanadium content residual fuels are available in ¦ large quantities, it would be an advantage to the art to provide a ¦ stable and economical method for introducing magnesium into these fuels.
It has been discovered that a stable aqueous dispersion of ¦~
magnesium hydroxide can be prepared an~ that`these materials can ~e ! readily and uniformly dispersed into hydrocarbon fuel oils to providel magnesium, thus inhibiting vanadium and suluric acid corrosion, as well as rendering slag more friable and decrease the rate of slay build-up. The stable aqueous dispersions of magnesium hydroxide which are a part of the instant invention contain relatively high jj percent~yes of magnesium hydrox~ide, are storage stable over a long period of time, and are readily dispersible into residual oils to

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provide an intimate admixture o~ the magnesium compound in the residual fuel oil.
This invention seeks to provide to the art of a mag-nesium hydroxide slurry which is storage stable, dispersible ln_ to hydrocarbon fuels, and which can be prepared economic~lly.
This invention also seeks to provide to the art a stable aqueous dispersion of finely divided particles of magnes-ium hydroxide which when added to hydrocarbon fuels is dispe~s-ible therein and which acts to prevent vanadium corrosion.
In its broad concept, this invention provides a stable, oil dispersible, aqueous dispersion of finely divided particles of magnesium hydroxide useful for the prevention of vanadium corrosion in liquid hydrocarbon fuels. The composition of this invention broadly comprises the following ingredients in precent-ages by weight:
A) 20-70% MgtOH)2 having a particle size of 50 to 1.0 micron;
B) 79-29% water;
C) 1.0-8.0% of a water-in-oil emulsifying agent having an HLB value of from 2 to 11;
D) 0.1-~% of a water soluble water-in-oil emulsifying agent having an HLB value of from 10 to 40;
said dispersion having a Brookfield Viscosity of 100-5000 cps, (#3 spindle at 12rpm at 75F).

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Preferably, the composition of this in~ention comprises ~ ~ the ingredients in the following percentages hy weigh~:
! I A) 30-60 i B) 70-35%
C) 1.0-7%
D) 1.0-4%
The magnesium hydroxide employed in this invention is in the form of an aqueous slurry. A suitable material as an example is available from the Dow Chemical Company under the trade designation MHT-60. The specifications of this material as dis- ¦
closed in the Dow Chemical Company "Magnesium EIydroxide Handbook"
is found n Table I

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TABLE I

Magnesium Hydroxide I~IT-60 Magnesium hydroxide, minimum %...................................... 55 Magnesium oxide equivalent, minimum %-~-..................... ----~. 33 C~lorides (as Cl), maximum ~...................................... 0.25 Bulk density lb/gal.-.O.......... D .......................... 12.75 lb/CU ft. .................................. ..... 95 5 Specific gravity, 60% slurry--..-.......................... -.-.----- 1.53 pH range, 20% solids basis...................................... 10.5-10.7 % Total solids........ O....... ~.................. 55.0-60.0 ~ Water................................. .... 45.0-40 0 Viscosity, Poises, Stormer viscometer, 60% slurry................................ ~. 4.5-35 Particle size, Andreason sedimentation pipet - 20-30 micron range.. O..................... .......5%
10-20 micron range.. ~.......... -.......... ......15%
5-10 micro~ range.. ~..................... ......35%
2-5 micxon range... ~ .................... ......25%
~2 microns................................ O...... 20%
Grit content, slurry basis (~ dry grit on 325 mesh sie~e)............................... 0.1-0.2 Brightness, Bausch and Lomb Spectronic 20 meter, dry basis...................... .~ gl-94 .

¦ While it is noted that the particle size of this material ¦ is predominantly in the 5-10 micron range, processing this material ¦ according to steps disclosed later in this specifica-tion produce~ a ¦ material having a particle size in the less than Z mic~on size ~ang~
¦ It is to be noted that the above described magnesiwn ¦ hydroxid~ slurry is only a preferred embodiment of thi5 inven~io~
¦ and other magnesium hydroxide slurries containing fxom 20-70~ and I preferably 30-60~ by weight magnesium hydroxide can be employed.
¦ The particle size of the magnesium hydroxide slu~r~ which lS
¦ employed in the instant invention can range from 50 down to less than 2 microns. Preferably, the material shoula be a particle size !
in the range of about 30-2 microns. The magnesium hydroxide slurr~ ¦
I thus described is further processed into the unique material of this ¦ i ~ention ~ 11 t Il . I
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PREPARATION OF THE S~URRY
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While the above described magnesium hydro~ide slurri~ are stable for limi~ed periods of tume, more storage stability is generally required to insure accurate feediny of this type of material to a hydrocarbon fuel mixture. Thus, other additi~res must be utilized to insure the stability of this ma-terial and to prevent it from settling out during prolonged periods of time.
We have found that certain water-in-oil surfactants generally having a hydrophile-lipophile balance (~LB) in the range of 2-11 will act to stabilize the magnesium hydroxide slurries and thus prevent them from settling. The preferred HLB value of the materials employed should range from 4-10. Sui-table materials useful for the stabilizàtion and this part o this invention include Witcamide 5138*available from the Witco Chemical Company which is described as an alkanolamine fatty acid condensate; Surco 5024, available from the Surfact-Co which is described as a mixed atty acid diethanolamide condensate; and Monamine 853*available ~ro~
Mona Industries, Inc., described as modified alkanolamide. Other materials which should ~ind application in this section of ~he instant invention should be oil-soluble, water-dispersible non-ionic fatty alkyl alkanolamine and alkanolamide materials~
Amphoteric oil-soluble water-dispersible imidaæoline type materials may also be used. While the above ma-terials are exemplary in the manufacture of the stable magnesium hydroxide slurries of -thi~
invention it is suspected that other oil-soluble non-ionic slurries will produce stable slurries and thus this invention is not meant to be limited by the above commercial materials. The surfactarlt will generally be used at a level of from 1-~% by ~eight of the slurry and most preferably at a level oE from 2-5~ by weigh~ of the slurr~

*Trade mark _ 7 _ ~/ llZ~'751 After this surfac-tan-t has been aaded to ~he magnesi~n hydroxide dispersion, the dispersion is mixed well~ ~t this point, and optionally, a second water-in-oil emulsifying agent ha~ing a HLB value of greater than 6 and prefer~bly in the range oE 10-~0 is added to the dispersion. ~os-t preferably the HLB value o~ ~he emulsifier will range from 20-40. The addition of the second sur~actant optimizes stahility by minimizing solid settling and water-split-out after long storage periods. Utilization of the second surfactant enabl~s slurries to be maintained homo~eneously for periods of generally more than 4 months.
Surfactants which are useful as the "second surfactant"
include petroleum sulfonates, sulfated vegetable oils, complex phosphate esters, sorbitan mono fatty eskers, and alkyl phenoxy polyethylene oxy ethanol. The second surfactant employed must be water soluble or at least dispersible in water and may be anionic, non-ionic, cationic or polymeric. Preferred materials have surface active groups such as amide amine, or ammonium func-tionality.
Especially effective are amine and ammonium salts of alkyl or aryl sulfates and sulfonates. Also useful are polymeric materials such as acrylic acid-acrylate copolymers. While dispersible solid thickeners may be utilized as additives, materials such as Kelæan enhance stahility but tend to harm the products ultimate dispersibility in the hydrocarbon feature.
Whiie water has been describe~ as a part of tne magnesium hydroxide slurry which is the first component of the composition, it should be pointed out that it is also possible to start with a magnesium hydroxide powder and then disperse this material in-to water. As suchl the composition of this invention should contain 29-79% weight water and more preferably 70-35~ by weight water.
Most preferably a water level of approximately 45-55% is employed.

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As described earlier, the composition of this invention is prepaxed by merely mixing together the above men-tioned ingredients utilizing satisfactory mixing. ~fter mixing, the resultan-~composition may be stored in any type of sui~able cont~iner~ ~ox -extended pexiods of time wi~hout the need ~ox reagikation.
D~e to the presence of the "first" emulsifier the ¦ magnesium hydroxide slurries prepared according to this invention are readily dispersible into hydrocarbon fuels. The slurries may be added to a fuel line which is then mixed by either a sta~ic mi~er or centrifugal pump. Alternatively, the slurry may be added to the fuel by utilizing a chemical injector in the fuel line.
Of course, other methods have for the introduction of the oil dispersible magnesium hydroxide slurry will be apparent to those skilled in the art.
~ he slurry is generally added to the fuel oil based upon the amount of vanadium present in the oil. Dosages can be readily calculated in that the magnesium should be added at a level in that magnesium should be present(as magnesium oxide~at a level of from 1-3.0 moles per each mole of vanadium (metallic) present in the fuel oil. Preferably from 1 to 6 moles calculated as magnesium oxide should be present in the fuel oil per each mole of vanadium (as V). Most preferably from 1.5 to 3 moles of magnesium should be added per each mole of vanadium present. The additive of this invention is generally added to the fuel at a level of fxom 1~6 pints per 1000 gallons of fuel oil, but may vary considerably depend _ iny on the amount of vanadium present in the fuel oil, and the Mg concentra on of the slurry.

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EX~MPLE 1 PREPAR~TION OF MA&NESIUM HYDRO~IDE SLURRY
95 parts by weigh-t of a magnesium hydroxide slurry contain-¦ ing 55~ by weight magnesium hydroxide available fxom th~ Dow Chernic~l ¦Company under the designai:ion 60D Technicalk is mixed in a suitable ¦ container for 10 minutes. After this period of time 3 part5 by weight of Witcamide 5138 is added to the magnesium hydroxide slurry with continued mixing. After mixing for 10 minutes ~.a parts by ¦welght of S~epanol DEA*a die~hanolamine lauryl sulfate available ¦from the 5tepan Chemical Company is added. After an additional 10 minute period of time mixing the material is removed from the mixing ¦
vessel and placed in a storage tank. The resultant material had a ¦ pH of 9.6 and is completely pourable at as low ~ temperature as ¦ 32F. The material in contras-t to the starting magnesium hydroxide ¦ slurry had excellent dispersibility in fuel oil and was much more r ¦ stable~ The raw material employed after standing for 10 days yielded'~
1 20% water split-out, 35~ hard sediment, and ~5% slurry. The material' ¦ prepared according to the instant invention was still in complete suspension at the end of this time.
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EX~MPLE 2 The magnesium hydroxide slurry formed in Example 1 would be !
utilized to control vanadium corrosion in a utility boiler. The slurry of Example l would be added to residual uel oil contai~ing vanadium which was being fed to utility boiler~ The slurry was fed ¦ at a rate so as to provide 3 moles of magnesium (as MgO) for each ¦mole of vanadium pentoxide. In the fireside of the boiler itself the magnesium compound would xeact with the vanadium in the fuel oil ¦
to foxm the species 3MgO V2O~ which would be collected in the ~ particulate recovery system found in the boiler. By the use of ¦this pxogxam, deposits of vanadium in the fireside of the boiler ,¦ *Trade mark -- ]. O

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would be substantially decreased allowing increased heat transfer and thus more efficient operation of the boiler.

Claims (3)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A stable, oil dispersible, aqueous dispersion of magnesium hydroxide useful as a vanadium corrosion prevention additive for liquid hydrocarbon fuels comprising in percentages by weight:
A) 20-70% Mg(OH)2 having a particle size of 50 to 1.0 micron;
B) 79-29% water;
C) 1.0-8.0% of a water-in-oil emulsifying agent having an HLB
value of from 2 to 11;
D) 0.1-6% of a water soluble water-in-oil emulsifying agent having an HLB value of from 10 to 40;
said dispersion having a Brookfield Viscosity of 100-5000 cps, (#3 spindle at 12rpm at 75°F).

2. The stable, oil dispersible, aqueous dispersion of magnesium hydroxide of Claim 1 wherein the percentages by weight of components A-D are as follows:
A) 30-60%
B) 70-35%
C) 1.0-7%
D) 1.0-4%

3. The stable dispersible aqueous dispersions of magnesium hydroxide of Claim 1 wherein the HLB value of the water soluble water-in-oil emulsify-ing agent (D) ranges from 20 to 40.