CA2307695C - Demetallation of hydrocarbon streams - Google Patents

Abstract

A method for the removal of metals from hydrocarbon stream by passing the oil over a bed of high surface area ceramic material at elevated temperatures. Contact with the ceramic material causes the metals to be absorbed on to the surface of the material and undergo a chemical reaction. The oil after contact with the material contains little or no metals. The metals can be removed from the material by reversing the chemical reaction with the addition of hot steam. The steam has the added benefit of enhancing the material and making it more reactive towards the next metal laden petroleum feedstock. The steam/metal stream can be collected and concentrated to efficiently dispose of the metals taken from the oil.

Description

TITLE OF THE INVENTION
Demetallation of Hydrocarbon Streams FIELD OF THE INVENTION
This invention relates to methods of treating hydrocarbon streams BACKGROUND OF THE INVENTION
Hydrocarbon streams from within a refinery, chemical plant, recycling plant and many other industries may contain significant amounts of elemental organic or inorganic metals. These metals can cause a variety of problems which include, but are not limited to tower fouling, catalyst deactivation, change in metallurgical properties, environmental pollution and toxic contamination. Removal of these metals may greatly enhance catalyst life spans, add value to recycled streams and reduce the impact of these streams on the environment.
SUMMARY OF THE INVENTION
This invention is directed to the treatment of a hydrocarbon stream to remove metals from the stream. There is therefore provided according to a first aspect of the invention a method for the removal of metals from a hydrocarbon stream by passing the oil over a bed of absorbent material, preferably ceramic material, preferably at elevated temperatures, such as between 20 C and 450 C, and, preferably at a temperature between 250 oC and 350 C.
Contact with the ceramic material causes the metals to be absorbed on to the surface of the material and undergo a chemical reaction. The oil, after contact with the material, contains little or no metals. The metals can be removed from the material by reversing the chemical reaction with the addition of hot steam. The steam has the added benefit of enhancing the material and making it more reactive towards the next metal laden petroleum feedstock. The steam/ metal stream can be collected and concentrated to efficiently dispose of the metals taken from the oil.
According to an aspect of the invention, there is provided a method of removing metals from a hydrocarbon stream. The hydrocarbon stream is contacted with an

2 absorbent material that is insoluble in the hydrocarbon stream, the absorbent material being formed from a basic material selected from the group consisting of alkaline earth compounds, alkaline metal compounds, group IIIA element compounds, group IVA
element compounds and group VIA element compounds. The Absorbent material chemically reacts with metals in the hydrocarbon stream and binds to the metals, thus removing them from the hydrocarbon stream.
According to an aspect of the invention, there is provided a method of removing metals from a hydrocarbon stream, the method comprising the step of contacting the hydrocarbon stream with an absorbent media, wherein the absorbent media is insoluble in the hydrocarbon stream and comprises alumina, calcia and magnesia.
According to a further aspect of the invention, there is provided the step of regenerating the absorbent material by contacting the absorbent material with a flow of steam. Preferably, before regenerating the absorbent material, the absorbent material is cleaned by contacting the absorbent material with a hydrocarbon solvent stream, such as toluene. Regeneration may be enhanced by contacting the absorbent material with methanol.
These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a graph showing variation of phosphorus and iron over time while distilling contaminated oil in the presence of absorbent material; and Figure 2 is a bar graph showing the amounts of phosphorus in distillate and residue after being distilled in the presence of various media.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
There will now be described preferred embodiments of the invention, with reference to the examples, by way of illustration only and not with the intention of limiting what is claimed. In this patent document, "comprising" means "including". In addition, a reference to an element by the indefinite article "a" does not exclude the

3 possibility that more than one of the element is present. The label Cx means a hydrocarbon with X carbon atoms. The label Cx+means hydrocarbons having more than X carbon atoms. "Absorbent" in relation to a material means that the material contains pores, with a surface area that promotes absorption, and that the material has the property of attracting metals from the hydrocarbon stream.
Metals are removed from a hydrocarbon stream by contacting the stream with a material that is insoluble in the hydrocarbon stream. The removal of the metals is accomplished at temperatures ranging from 20 C to 450 C, a preferred temperature being between 250 C and 350 C. The types of metals removed from petroleum streams include, lead, copper, aluminum, silicon, iron, chromium, zinc, magnesium, nickel, sodium, calcium, vanadium, mercury, phosphorus and manganese. A hydrocarbon stream consists of C5 + The absorbent material is preferably made up of one or more alkaline earth oxides. The material should contain a large surface area and large pore size distribution to allow efficient removal of the metals and easy flow of the oil through the material. The material should be placed in a hot hydrocarbon stream to facilitate the removal of the metals within the stream. A preferred method would be within an absorber bed.
It is believed that the removal of the metal from the hydrocarbon stream is based on the reaction between the metal and the inorganic material. Both the metal and the material can be polar in a non-polar medium; this accelerates the absorption of the metals on to the surface of the material. The metal will bind to the material, undergo a chemical reaction and become trapped within the matrix of the material. With additional heat, this reaction can be accelerated.
Once the level of absorption starts to fall, the material can be regenerated by cleaning with a hydrocarbon solvent and then treatment with steam. A
hydrocarbon solvent such as toluene may be used at 300 C to clean out the heavy hydrocarbons present within the material. Various solvents may be used, particularly aromatic rich solvents such as XYSOLTM hydrocarbon solvent available from Enerchem International Inc. Once clean, the material can be regenerated with hot (150 C) steam.
Steam is applied by flowing it over the absorbent material until the absorbent material is cleaned.
A flow for 8 hours has been found to clean the absorbent material. It is believed that the

4 reaction to absorb the metals is fully reversible. By using steam to rehydrate the surface of the material, the metals can be desorbed from the surface of the material.
It has also been found that the use of hot methanol (150 C) between the solvent wash and the steam wash removes any residual oil and helped the steam penetrate the material. A small percentage of methanol in the steam had the same effect. Any alcohol is believed to be adequate for the purpose, which is to cut the hydrocarbons away from the ceramic, making it easier for the steam to work.
The function of the absorbent material is two fold, it provides a large surface area to collect and trap the metals. It also provides a catalytic medium in which the metals can thermally react with the surface of the material.

Examples and Analysis Analysis for metals was done by ICP with identification of the individual elements by Metro Tech Systems Ltd. of Calgary, Alberta, Canada.
Examples 1-4 all use a hydrocarbon stream API =48, containing various amounts of metal contaminants. The stream was pumped through a heated SS 1/2 inch x 25 cm column packed with 8g of sample #9945546. Experiments 1-3 used the same 8g of material. The stream was collected and cooled and then analyzed by ICP. The %
removed for the stream was then calculated.
Expermient #1: First run starts at 274 C. At 60 hours, the temperature was raised to 302 C. At 120 hours the temperature was raised to 316 T. Flow rate =3.1 mL/min.
Hydrocarbon stream contains Pb =2ppm, Fe =24 ppm. Zn =2 ppm 1. Percent of ppm removed ppm Hours ppm Pb ppm Fe Zn Experiment #2: After 200 hours the column was cleaned with toluene and regenerated by contact with steam.
Second regenerated run at 316 C, flow rate =3.1 mL/min Hydrocarbon stream contains

5 Pb =2 ppm, Fe =24ppm, Zn =2 ppm 2.Percent PPM removed-Regenerated run ppm Hours ppm Pb ppm Fe Zn

6 100 100 100

7 Experiment: #3: After 162 hours another hydrocarbon stream replaced the first one. The flow through experiment was continued for an additional 24 hours.
The replacement hydrocarbon stream contains Al =223 ppm, Ca -37 ppm, Fe 116 ppm, Mg =49 ppm, Mn 1 ppm, Na =39 ppm, Pb 3 ppm, Zn =2 ppm.
3. Percent ppm removed Hours Al Ca Fe Mg Mn Na Pb Si Zn Experiment #4: Another hydrocarbon stream containing Hg =6ppm, Cu =2.6 ppm, Fe =

8.9 ppm Zn 3.1 ppm, and P =8.2 ppm was pumped through a column containing sample #9945546 (8g) for 6 hrs at various temperatures with a flow rate of 3.1 mL/min.

4. Percent Removed Hours 1 3 5 6 Temp. C 110 210 280 280 Element Hg 50% 66% 77% 85%
Cu 81% 96% 100% 100%
Fe 0% 30% 100% 100%
Zn 100% 100% 100% 100%
P 100% 100% 100% 100%

Experiment #5: Pilot plant removal of entrained metals in a hydrocarbon stream A hydrocarbon stream was brought into the plant to be reprocessed, API gravity =45-50, water =1- 10% and solids 1-3%. Once the S&W (sediment & water) is removed the fluid is pumped through two heat exchangers and a line heater to obtain a temperature between 249 to 316 C. The hot hydrocarbon stream is passed through a bed containing sample #9945546, approximately 66 cubic feet. The volume processed was between 38 barrels per day. The pressure on the stream is 75-90 psi and at this pressure at least 50-60% of the stream is vapour. The Vapour stream is separated and is not passed through the absorber bed. The vapour and the liquid stream are recombined and sent to a fractionation tower.
After a total volume of 2300 barrels was processed and the % metals removed was as follows P=98 %, Na =72 %, Fe =95 %, AI =97 %, Cu =92 %, Zn =99 %, Ca =94 %, Mg =98 %, Si =77 %, Pb =49 % and Cr =89 %.
A sample taken after 19000 barrels contained Fe, Ca, Na, Mg, Fe, Si, and Al.
After passing through the bed the % removed was, P=96%, Ca=90%, Na=73%, Mg 96 %, Fe =92 %, Si =15 % and Al =95 %.
Experiment #6: A crude oil from northern Alberta containing Zn, Ni, Na and V
was placed in an autoclave with crushed sample #9945546 (10g) and heated to under nitrogen (100 psi). After 30 minutes the sample was analyzed and the %
metals removed was 15 was Zn =45 %, Ni =21 %, Na =76 % and V =24 %.

Example V. A bed of used sample #9945546 (8g) which contained Hg, Cu, Fe, Zn and P
was washed with steam (200 C) at 60g/ hour for 8 hours. The water was collected and analyzed by ICP. Metals found in the water included Hg, Cu, Fe, Zn and P.

A preferred material is an alumina based absorbent material containing up to 50 %
alkaline earth metal oxides. The preferred media have a BET surface area of at least 100 m2/gm. BET is a common method of multilayer physical absorption data. The most preferred media, identified as sample #9945546, contain calcia and magnesia in weight ratios from 9:1 to 1:1.
It is preferred to carry out the reaction in a fixed bed, for example an absorber bed. In a typical application, the absorber is placed after a heater of some kind, or after a

9 process that involves heating the hydrocarbon stream, to make use of the heated fluid exiting the heater.
The following information on the nature of the preferred material was obtained from Norton Chemical Process Products Corporation.
The absorbent media comprises 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 m2/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. In general terms this gives a reasonably accurate translation as can be seen from the following chart.
Boehmite CaCO3 MgCO3 -> A1203 CaO MgO
90 8.2 1.8 92.2 6.6 1.2 60 36.0 4.0 65.9 31.1 3.0 96 3.6 0.4 97.1 2.6 0.3 96 2.0 2.0 97.0 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 USP 5,304,423. Alternatively they can have the form of monolith 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.
A method of making such media comprises a) forming an aqueous slurry mixture of from 50-97 % by weight of a hydrated alumina component, such as for example a 5 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;

10 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 AIOOH or more accurately A1203H20.
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 as 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 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 MicrofineTM, (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

11 generally know to peptize such sols. Because the firing would lead to decomposition of the acid, it is preferred that the 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 form of some other intermediate allomorph or amorphous form. It is however preferred that the firing should not be under conditions that would lead to the formation of the alpha form or sintering since this leads to a loss of porosity and leaves the alumina in a less active form. The firing temperature therefore is preferably at a maximum temperature of from 500 C to 800 C and for a period of time until no further weight loss occurs. Generally heating at the firing temperature for 30 minutes to 5 hours is long enough to decompose essentially all the carbonate and drive off all the bound water.
The surface area of the fired product is at least 100m2/gm such as above about 200 m2/gm and preferably from 200 to 250 m2/gm.
Description of Preferred Embodiments The invention is now further described with particular reference to the following non-limiting examples which illustrate the capabilities of the media for the effective removal of contaminants from hydrocarbon streams.
Example 1 A sol was made by mixing 450 gm of boehmite sold by LaRoche Chemicals under the trademark "VERSAL " were mixed with 200 gm of deionized water. In this sol were dispersed 50 gm of dolomitic limestone available from National Lime and Stone

12 Company as BucyrusTM Microfine and the sol was peptized by the addition of 22.5 gm of formic acid dissolved in 200 gm of deionized water. The mix was then extruded in a coil press and the resulting coil was extruded again through a die to give a strand that was cut into one quarter inch long pellets or rods. These rods were dried at a little over 100 C
for about 10 hours. They were then fired in a kiln at 700 C for a period of about an hour.
The BET surface area of the media obtained was measured at 219 m2/gm. The apparent porosity was 78.5% , the water absorption was 103.4%, the apparent specific gravity was 3.54 gm/cc and the material density was 0.76 gm/cc. Analysis of the material showed 92.2% by weight of alumina, 6.6% by weight of calcia and 1.2% by weight of magnesia.
Several more samples were made in different forms from essentially the same mix and in one case with a slightly different firing schedule. Also in Sample #3, a corn starch temporary binder was added to the slurry at a level of 5 % by weigh based on the dry solids weight of the slurry. The process and the properties of the media are set forth in the following table.

SAMPLE #1 #2 #3 #4 #5 #6 #7 SHAPE ROD RING RING RING RING RING ROD
Diam.mm 6.4 37 38.1 38.4 3.56 3.15 ID mm - - 27.2 - 28.2 1.52 -Length mm 6.4 - 30.5 - 36.8 3.81 3.99 SA cc/gm 219 238 274 199 228 242 212 Poros. % 78.5 77.6 77.7 80.6 79 82.2 81.8 H2O Ab. % 103.4 99.5 103.4 113.3 110.6 140.9 128.3 App. SG 3.54 3.48 3.38 3.62 3.42 3.28 3.52 Mat. Dens. 0.76 0.78 0.76 0.71 0.72 0.59 0.64 FPCS rod kg 13.2 - - - - - 3.18 FPCS ring kg - 2 5.9 4.54 4.54 0.45 -

13 Dry Temp Dry Time hr 10 10 10 10 10 10 10 Fire Temp Fire Time hr 1 1 1 1 1 1 1 In the above table: "H2O Abs. %" means water absorption percentage "Poros" means apparent porosity "App. SG" means apparent specific Gravity "Mat. Dens." means material density "FPCS" indicates the flat plate crush strength measured according to ASTM D-4179 This demonstrates that the above formulation can be fired to produce media with a high surface area in a variety of sizes and shapes with a reasonable crush strength if the right sizes are chosen.
From these samples, #I was selected to be evaluated in the removal of phosphate contaminants from a hydrocarbon stream. The evaluation was performed by distilling oil which had been deliberately contaminated by the addition of tri-decyl phosphate such that the phosphorus content was 0.4 mmole or (78ppm). The contaminated oil was distilled in a 500 ml flask in the presence of 4 % by weight of media made from the formulation under investigation. The fractions boiling in three temperature ranges were examined: 20-65 C; 65-370 C and 370 C and higher for contamination. The amounts of phosphorus measured in these ranges were: none; 0.3 ppm and 0.5 ppm. Barely a trace of residue remained.
In a different experiment the same media were used to evaluate iron and phosphorus removal from an oil over a protracted period. The results are shown in Figure 1 and indicate that, even after 138 hours, the phosphate level was reduced to a low and acceptable level and the iron level remained at essentially zero. It is calculated from this

14 data that 2000gm of the media could treat 6400 m3 of contaminant containing oil before they would need to be regenerated.
In addition, sample #5 was evaluated using the same procedure. The phosphate removal achieved by 8gm of the media was initially 90 % and was still >75 %
after 200 hours of flow during which 46.3kg of oil containing 47 ppm of phosphate were treated. In the same period the amount of iron contamination removed, which was initially at a level of 26 ppm, was initially over 90 % and after 200 hours had risen to 95 %. The media were then regenerated by heating the media in steam and after that, no trace of iron, zinc or lead remained in the media.
Finally Samples #1 and #5 and a repeat of Sample #5 were evaluated alongside a sample containing no media at all. In each case the same amount of oil contaminated with 78 ppm of phosphorus was distilled. The results which are shown in Figure 2 indicate clearly that the media were effective in binding up the phosphorus since the bulk of it was to be found neither in the distillate nor in the residue in the flask.
Example 2 In this Example a further series of media were made using essentially the process described in Example 1 with the minor difference discussed below. The products were examined to determine their physical properties which are recorded in the following Table.

SAMPLE #8 #9 #10 SHAPE ROD RING RING
SA cc/gm 109 115 112 Poros. % 66.3 67.6 79.4 H2O ab. % 63.5 68.7 103.1 App. SG 3.1 3.04 3.75 Mat. Dens. 1.05 0.99 0.77 FPCS rod 18 kg FPCS ring 2.7 kg 2.5 kg Dry Temp. 100 C 100 C 100 C
Dry Time 10 hr 10 hr 10 hr Fire Temp 700 C 700 C 1000 C
Fire Time hr 1 hr 1 hr 1 hr In Sample #8, the Versal boehmite component was mixed with 50% by weight of dolomitic limestone and the dispersion was peptized with 2.5 % by weight of formic acid.
In Sample #9, the same solid components were used in the same percentages as in 5 Sample #8 but the formic acid addition was doubled to 5 %.
In Sample #10, only 10% of the dolomitic limestone was added to the Versal boemite and 4.5 % of the formic acid was used.
Immaterial modifications may be made to the invention described here without departing from what is claimed.

Claims (15)

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

1. A method of removing metals from a hydrocarbon stream, the method comprising the step of:
contacting the hydrocarbon stream with an absorbent material that is insoluble in the hydrocarbon stream, in which the absorbent material is formed from a basic material selected from the group consisting of alkaline earth compounds, wherein the absorbent material chemically reacts with metals in the hydrocarbon stream and binds to the metals, thus removing the metals from the hydrocarbon stream.

2. The method of claim 1 in which the absorbent material is a ceramic comprising 50 to 96% alumina by weight and 50 to 4% of alkaline earth metals selected from calcia and magnesia.

3. The method of any one of claims 1-2 in which the absorbent material has a BET
surface area of at least 100 m2/gm.

4. The method of any one of claims 1-3 further comprising the step of:
regenerating the absorbent material by contacting the absorbent material with a flow of steam.

5. The method of claim 4 further comprising the step of, before regenerating the absorbent material, cleaning the absorbent material by contacting the absorbent material with a hydrocarbon solvent stream.

6. The method of claim 5 in which the hydrocarbon solvent is toluene.

7. The method of any one of claims 5-6 further comprising preparing the absorbent material for regeneration by contacting the absorbent material with methanol.

8. The method of claim 7 in which the methanol is contacted with the absorbent material with the steam.

9. The method of any one of claims 4-8 further comprising the steps of:
processing the steam to concentrate the metals, and disposing of the metals.

10. The method of any one of claims 1-9 in which the hydrocarbon stream has a temperature between 20°C and 450°C.

11. The method of any one of claims 1-9 in which the hydrocarbon stream has a temperature between 250°C and 350°C.

12. A method of removing elements including aluminum, iron, sodium, phosphorus, magnesium and zinc from a hydrocarbon stream, the method comprising the steps of:
contacting the hydrocarbon stream with an absorbent material that is insoluble in the hydrocarbon stream, in which the absorbent material is formed from a basic material selected from the group consisting of alkaline earth compounds, wherein the absorbent material chemically reacts with the elements in the hydrocarbon stream and binds to the elements, thus removing the elements from the hydrocarbon stream;
washing the absorbent material with a hydrocarbon solvent stream; and regenerating the absorbent material by contacting the absorbent material with a flow of steam.

13. The method of claim 12 in which the hydrocarbon solvent comprises aromatic hydrocarbons.

14. The method of claim 12 or 13 further comprising preparing the absorbent material for regeneration by contacting the absorbent material with methanol.

15. The method of claim 14 in which the absorbent material is contacted by the methanol delivered with steam.