Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Aluminum containing
Reexamination Certificate
2000-01-03
2001-03-27
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Aluminum containing
C502S081000, C502S341000, C502S355000, C423S139000, C423S265000, C423S275000, C423SDIG001
Reexamination Certificate
active
06207612
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the treatment of crude hydrocarbon streams and particularly to an adsorbent material that is effective to remove troublesome components often present in such streams.
In the production of oil from underground sources, after a well has been drilled to tap into the oil-bearing rock formations, it is often necessary to break up the formations to allow the oil to flow to the well bore. This is accomplished by the use of “frac fluids” which, as the name implies, have the purpose of fracturing the rock formations in which the oil is located. These frac fluids are often based on a hydrocarbon carrier liquid and contain proppants and phosphate derivatives as gelling agents to ensure that the frac fluids do not become widely dispersed in the formations but stay adjacent the well bore. The frac fluids are pumped into the well under pressure sufficient to accomplish the above purpose and are then pumped out of the well for re-processing. However such removal is not usually complete and at least a portion of the crude extracted from the well will be contaminated by the phosphate derivatives.
The frac fluids may also be contaminated by metal values which are also present in many phosphate-containing gelling agents and the removal of such metal values is desirable since they can poison catalysts used in subsequent refining components of the refinery or be deposited in the equipment used to further process the oil. The phosphate contaminants are particularly undesirable since they are often in an acidic form or a polymerized form that either lead to corrosion damage to distillation or other refining equipment in an oil refinery unless expensive stainless steel materials are used, or cause the deposition of gummy residues that interfere with the efficient operation of the refinery components.
The “sweetening” of an oil, that is the removal of sulfur-containing contaminants such as mercaptans, is carried out by an oxidation process conducted in an alkaline environment. A desirable preliminary to such a process is the removal of naphthenic acid values from the oil to be “sweetened” and a method for the accomplishment of this removal is described in U.S. Pat. No. 5,389,240. This patent teaches passing the oil through a bed of a solid solution of at least one divalent metal oxide selected from alkaline earth metal oxides, and the oxides of cobalt, iron, nickel and zinc, and aluminum oxide. One example of such a material is hydrotalcite
An adsorbent medium has now been developed that provides improved performance over the materials described in the prior art in terms of its ability to absorb metal values, phosphate derivatives and acids. These capabilities can also be provided in the form of porous shaped media suitable for incorporation in a tower adapted for continuous operation with sufficient crush strength to withstand loading and recycling operations.
SUMMARY OF THE INVENTION
The absorbent media of the invention comprise from 50 to 96% by weight of alumina and from 50 to 4% by weight of alkaline earth metal oxides selected from calcia and magnesia in CaO:MgO proportions by weight of from 90:10 to 50:50, and have a BET surface area of at least 100 m
2
/gm.
The term “absorbent” as used herein is intended to cover activities in which an impurity in a hydrocarbon flow is physically trapped within the pores of the medium, adsorbed on to the surface of the pores of the medium, or reacts chemically with the material of the medium to produce components that are not further transported by the flow of which the impurity was a component.
The proportions of the components are calculated of the basis of the weights of components added initially stoichiometrically adjusted to the oxides that remain after firing to produce the media of the invention. In general terms this gives a reasonably accurate translation as can be seen from the following chart.
Boehmite
CaCO
3
MgCO
3
→
Al
2
O
3
CaO
MgO
90
8.2
1.8
92.2
6.6
1.2
60
36
4
65.9
31.1
3.0
96
3.6
0.4
97.1
2.6
0.3
96
2.0
2.0
97
1.6
1.4
The first three formulations were made using dolomitic limestone and the fourth used plain dolomite. As can be seen the relative proportions do not change very significantly when going from the precursor materials to the final fired product.
The media can have any desired shape depending on the application. They can for example be in the form of short rods or pellets, hollow cylinders, rings, saddles and the like. A particularly useful shape is described in U.S. Pat. No. 5,304,423. Alternatively they can have the form of monoliths with multiple through passages that can be assembled into beds. Such monolith media are however often less preferred for applications such as those primarily intended for the media of the present invention.
The invention further comprises a method of making such media which comprises a) forming an aqueous slurry mixture of from 50-97% by weight of a hydrated alumina component, such as for example a boehmite, with from 50 to 3% by weight of a mixture of calcium carbonate and magnesium carbonate wherein the relative weight proportions of the calcium and magnesium carbonates are from 10:1 to 50:50, the weights of the boehmite and carbonate mixture being based on the solids weight in the slurry;
b) peptizing the slurry by addition of an acid;
c) extruding the peptized slurry to form the desired media shapes; and
d) drying to remove water and then firing the shapes at a temperature of 650 to 850° C.
The hydrated alumina component can be selected, for example, from any of the commercial boehmite products which are commonly assigned the formula AlOOH or more accurately Al
2
O
3
.H
2
O.
The mixture of calcium and magnesium carbonates is conveniently supplied by a powdered form of dolomite or preferably dolomitic limestone, which is a mixture of dolomite, (in which the calcium and magnesium metal atoms are present in nominally equal numbers) and calcite, with the calcite predominating and a few percentage points of impurities such a s silica and iron. When calcined during the firing stage this mixture decomposes to the respective oxides. The products of the invention could therefore, in theory, be made by incorporating the oxides or hydroxides into the boehmite slurry. This would however require more acid to peptize the slurry and thus is a less preferred option.
To aid dispersion of the carbonates in the boehmite sol, it is preferred that they be supplied in the form of a powder of about 50 microns average particle size or finer. A commercial dolomitic limestone that is commercially available from National Lime and Stone Company under the trade name Bucyrus Microfine, (99% passing through 325 mesh screen), is particularly suitable. This material contains the calcium and magnesium carbonates in a roughly 6:1 weight ratio
The acid added to cause peptization of the slurry, which is essentially a dispersion of the calcium/magnesium-containing component in a boehmite sol, can be any of those generally know to peptize such sols. Because the firing would lead to decomposition of the acid, it is preferred that mineral acids such as nitric, hydrochloric or sulfuric acids be avoided and a strong organic acid such as acetic or, better, formic acid is used to cause peptization. The peptized sol in effect becomes a stable gel which can be formed, for example by extrusion, to produce shapes that will retain their shape during drying and firing. Enough is preferably added to reduce the pH to 5 or lower.
The drying of the shapes is preferably carried out under conditions that will allow the water to be removed without disruption of the shape. This implies drying at a fairly low temperature of about 100° C. (though up to 50° C. higher can be used in most circumstances) for prolonged periods of up to two days though usually a drying period of 10-24 hours is adequate.
Firing of the dried shapes should be long enough to form calcium and magnesium oxides from their respective carbonates and to drive off any bound water and convert the boehmite to the gamma alumina
Reid John S.
Szymanski Thomas
Bell Mark L.
Bennett David
Hailey Patricia L.
Norton Chemical Process Products Corporation
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