Metal Oxide Oil Slurries

This invention is a highly stable metal oxide oil slurry useful in reducing slag, facilitating removal of deposits from boiler tubes, and reducing corrosion on the heating surfaces of boilers. Such a slurry consists essentially of about 50% by weight magnesium oxide or the entity of magnesium oxide and alumina oxide, together with an oil-soluble emulsifier such as an alkanolamide or an alkanol with a carbon chain greater than a C.sub.3 alcohol, an oil-soluble dispersant such as a C.sub.12 -C.sub.22 entity selected from an unsaturated or saturated fatty acid such as oleic acid. Also, as a necessary constituent is an anionic surfactant such as magnesium lauryl sulfate in an oil base such as No. 2 fuel oil. The alkanolamide is fashioned from heating alkanolamines and fatty acids either in a 1:1 ratio or 2:1 ratio. The reactant amino alcohol is in the range C.sub.10 -C.sub.24. The alcohol itself is greater than C.sub.3 and up to C.sub.16, with a preferred range C.sub.12 -C.sub.16. The acid which is reacted to produce the alkanolamide is selected from a C.sub.12 -C.sub.22 entity such as oleic acid, etc. The alcohol defined as greater than C.sub.3 and which reacts with the amine to produce the alcohol amine may be greater than C.sub.3 and up to C.sub.16 and it is noted that the optimum detergent range is C.sub.12 -C.sub.16.

Specialty oil slurries have been successfully developed for the application of reducing slagging, facilitating removal of slag and deposit from the fireside of the boiler tubes and reducing corrosion on the heating surfaces of the boilers. A generalized recipe of a typical composition is set out below.

A preferred oil is heavy aromatic naphtha.

Also, a recipe of more particular components is set out below:

The emulsifier and wetting agent are preferably non-ionic surfactants; for example, alkanolamides or alcohols of chain links greater than C.sub.3. The oil-soluble dispersant and stabilizer are preferably unsaturated and saturated fatty acids of chain link C.sub.12 -C.sub.22 ; for example, oleic acid. The oil-insoluble thickening and stabilizing agents are anionic surfactants preferably salts of alkyl sulfates and alkyl aryl sulfonates; for example, magnesium lauryl sulfate.

The slurry is stable at ambient temperature and at 135.degree. F. for an extended period of time (greater than three months). It is believed that the slurry as formed is stabilized through the formation and interaction of hydrophilic cores with lypophilic tails of the micelles. For example, a stable slurry was obtained by mixing 1 part alkanolamide with 4 parts oleic acid, 43 parts No. 2 fuel oil, 45.45 parts magnesium oxide, 4.55 parts alumina trihydrate, and 2 parts magnesium lauryl sulfate. The slurries are sterically stabilized by this new technique involving the formation of micelles and micelle-like network structures. A uniqueness was found in its good stability at moderate temperatures as shown above and also a smoother manufacturing process and good pourability.

With reference to the emulsifiers, a preferred alkanolamide is Witcamide 5138 (Witco Chemical Company). In the area of the metal oxide a preferred embodiment of alumina trihydrate is Alcoa C-330.

While it is noted that the particle size of the MgO material is predominantly in the 4-6 micron range, processing this material according to steps disclosed later in this specification produces a material having a particle size in the less than 2 micron size range.

It is to be noted that the above-described magnesium oxide slurry is only a preferred embodiment of this invention and other magnesium oxides containing from 20-70% and preferably 30-60% by weight magnesium oxide-hydroxide can be employed. The particle size distribution of the magnesium hydroxide slurry which is employed in the instant invention can range from 50 down to less than 2 microns. Preferably, the material should be a particle size in the range of about 30-2 microns. The magnesium hydroxide slurry thus described is further processed into the unique material of this invention.

The hydrocarbon oil utilized in this invention and which permits utilization of the parameter heavy oil and high aromatic oil is justified by reference to the ASTM detailed requirements for fuel oil. It is noted that in the gradation which appears in Perry's Chemical Engineers Handbook, 5th edition, 1973, page 9-9 (reproduced below) No. 5 and 6 are heavy oils so that the terms "high" and "heavy" have definite meaning in the oil industry.

A number of exemplary recipies were made up embodying this example:

Standard Procedure of Making Slurries

Mix emulsifier and dispersant with oil until homogeniety is achieved, usually 10 minutes.

Charge MgO and Al.sub.2 O.sub.3.3H.sub.2 O to the mixture and mix for one-half hour.

Charge thickener and continue mixing for 15 minutes.

Store the slurry in a closed container.

Mix 2% emulsifier, 43% oil, with 5% oleic acid.

Charge MgO until viscosity reaches .about.8,000 cps.

Observe stability at room temperature and at 135.degree. F.

Mix 1 to 4% thickener to either single or dual surfactants-slurry.

Record the viscosity increases.

Observed stability at room temperature and at 135.degree. F.