GB2090766A - Porous hydroprocessing catalyst containing halloysite - Google Patents

Abstract

A shaped calcined catalyst suitable for use in the demetalation of asphaltene-containing feedstocks is made from the tubular form of the clay halloysite by dispersing the rods of that clay, either alone or in admixture with a second fibrous clay, such as attapulgite, and optionally a binder oxide, such as alumina, so that the rods of halloysite and of the second clay, when present, are randomly oriented with respect to each other, prior to shaping and calcining the porous catalyst mass.

Description

SPECIFICATION Porous hydroprocessing catalyst containing halloysite This invention relates to a catalyst for hydrotreatment and hydrodemetalation of hydrocarbonaceous feedstocks. More particularly, this invention relates to catalysts and catalyst supports fabricated from halloysite.

Impurities such as metals, sulfur and nitrogen are contained in hydrocarbonaceous materials including crude oils, heavy oils, cracked oils, deasphalted oils, residual oils, shale oils, coal and partially liquefied coal and the like. These impurities are discharged into the atmosphere when the hydrocarbon is burned, creating a major source of pollution. They also tend to rapidly foul catalysts used for processing of the hydrocarbon or treating the exhaust from combusted hydrocarbons. The removal of these undesirable impurities as early as possible in the processing of the hydrocarbonaceous materials is therefore highly desirable.

When metals such as nickel, iron and vanadium are present, they tend to deposit on the interior surface of the pores of hydroprocessing catalysts, tending to plug the pore mouths thereby reducing activity. It is desirable, therefore, that a substantial volume of the pores have a pore mouth diameter greater than 200 Angstroms. The majority of the pores should be preferably smaller than about a 1000 Angstroms because large pores tend to decrease the mechanical crush strength of the catalyst bodies, and also decrease surface to volume ratios.

Catalysts that effectively treat asphaltene containing fractions are desirable because many known crude oil reserves worldwide are high in asphaltenes. Additionally, various synthetic fuel processes tend to create fractions high in asphaltenes.

Catalysts containing clay materials have been suggested for hydroprocessing heavy hydrocarbon feeds.

For example, U.S. Patent No. 4,152,250 to Inooka suggests the use of a catalyst containing the mineral sepiolite (Meershaum), a fibrous magnesium silicate clay and transition metals and/or Group Il-B metals.

Another clay which has been suggested in halloysite. Halloysite is an aluminum silicate clay that frequently occurs naturally in a rod like form. The basic formula is Al2Si205(OH)4.

In U.S. Patent No.4,098,696, a synthesis of the plate form of halloysite is disclosed. In U.S. Patent No.

3,891,541 a demetalation catalyst is disclosed that is formed from halloysite and alumina. The pore structure contains pores with a diameter of between about 180 Angstroms to about 300 Angstroms. The pore diameters are said to be an artifact of the alumina.

This invention provides a method for the hydroprocessing of hydrocarbonaceous feedstocks containing asphaltenes. It also provides a catalyst and catalyst support useful, for example, in hydroprocessing hydrocarbonaceous feedstocks containing asphaltenes.

In accordance with one aspect of the invention there is provided a shaped calcined porous catalyst comprising dispersed rods of halloysite optionally codispersed with another fibrous clay containing rods having a length in the range from 1 to 5 microns and a diameter in the range from 50 to 100 Angstroms, and from 0-15 percent by weight of a refractory inorganic oxide binder. The weight percentage is based on the total weight of the halloysite and the oxide binder and the other fibrous clay when present.

In one embodiment of this invention a catalyst is prepared by (a) preparing a mix of halloysite and a fibrous second clay, halloysite preferably having predominantly rods having a length within the range of 0.5-2 microns and a diameter within the range of 0.04-0.2 microns, and the fibrous second clay having predominantly rods having a length within the range of 1-5 microns and a diameter within the range of 50-100 Angstroms, (b) adding sufficient liquid to said mix to form a slurry of no more than 25 percent solid, and then vigorously agitating the slurry to substantially disperse the rods, (c) removing enough water from the slurry to form an easily shapable mass, shaping the mass, and (d) drying and calcining the shaped body.

It is preferred that attapulgite be used as the fibrous second clay.

In the catalyst of the invention, the codispersed rods of halloysite are preferably composed predominantly of fibers with a length range of 0.5-2 microns and a diameter range of 0.04-0.2 microns, whilst the fibrous second clay is predominantly composed of fibers having a length range of 1-5 microns and a diameter range of 50-100 Angstroms. Halloysite must be in the tubular form. A preferred second clay is fibrous attapulgite. It is preferred that the composition be at least 5 percent attapulgite. It is preferred that the binder oxide be alumina. It is preferred that the catalyst body have a total pore volume of at least 0.35 cc/g and at least 60 percent of the volume of the pores is present in pores having diameters of 200-700 Angstroms.This invention also comprises a method for hydroprocessing hydrocarbonaceous feedstocks comprising contacting the feedstocks with molecular hydrogen under hydroprocessing conditions in the presence of a catalyst having codispersed rods of halloysite having rods predominantly in the range of 0.5-2 microns with a diameter range of 0.04-0.2 microns and a fibrous second clay having rods in the range of 1-5 microns and a diameter range of 50-100 Angstroms.

It is preferred that the composition includes least one catalytic transitition metal preferably a metal selected from Group VI-B or VIII of the Periodic Table. It is preferred that the composition have a pore volume of at least 0.35 cc/g of which at least 70 percent of the pore volume is present in pores having a diameter of 200-700 Angstroms and at least 70 percent of those pores have diameters of 300-700 Angstroms.

Hydrocarbon feedstocks containing at least one percent by weight asphaltenes can be processed by contacting feedstocks with hydrogen under hydroprocessing conditions in the presence of a catalyst in accordance with the invention.

The catalyst composition of the present invention involves the rod form of halloysite processed alone or in combination with a fibrous clay so that the rods are dispersed. "Dispersed rods" are defined herein to mean rods of halloysite which have been substantially completely disassociated from one another and are substantially randomly oriented with respect to one another.

The tubular or rod form of halloysite is readily available from natural deposits. It frequently comprises bundles of tubular rods or needles consolidated or bonded together in a weakly parallel orientation. It has been discovered that if these bundles of rods are broken up by mechanical means and re-oriented in a substantially random orientation with respect to one another, a catalyst support with superior asphaltene hydroconversion properties results. Halloysite occurs naturally in tubular rods that are approximately 1 micron long and 0.1 micron in diameter with a centrally located hole penetrating the rod from about 100 Angstroms to about 300 Angstroms in diameter resulting in a scroll-like rod, in contrast to fibrous clays like attapulgite and sepiolite which are non-tubular. The exact dimensions vary from rod to rod and are not critical.It is critical that the rod form, rather than the platy form, of halloysite be used.

When halloysite rods or other rods of similar dimensions are agitated in a fluid such as water to disperse the rods, the dispersion can be shaped, dried and calcined to provide a porous body having a large pore volume present at 200-700 Angstroms diameter pores. When the shaping is by extrusion, however, it has been found that mixtures of dispersed clay rods of the halloysite type, do not extrude well. The rods on the surface of the extruded bodies tend to realign, destroying the desirable pore structure at the surface of the catalyst. This is defined herein as a "skin effect".It has been discovered, however, that if a fibrous second clay with longer, narrower and presumably more flexible, fibers is codispersed with the halloysite-type clay, the resulting composition is easily extrudible, and there is no significant skin effect. "Codispersed" is defined herein as having rod- or tube-like clay particles of at least two distinct types substantially randomly oriented to one another.

The second fibrous clay should have long slender fibers typically about 1-5 microns in length with a diameter range of about 50-100 Angstroms. Clays for use as the second component include attapulgite, crysotile, immogilite, palygorskite, sepiolite and the like.

In addition to the halloysite component and the second fibrous clay component of the present catalyst, an inorganic binder oxide may be added to increase crush strength. Inorganic binder oxides are defined as refractory inorganic oxide such as, silica and oxides of elements in Group 2a, 3b and 3a of the Periodic Table as defined in Handbook of Chemistry and Physics, 45th Edition. Preferable binder oxides include: silica, alumina, magnesia, zirconia, titania, boria and the like. An especially preferred binder oxide is alumina. It has been discovered that the amount of asphaltene adsorbed onto a catalyst support of dispersed rods of halloysite is related to the amount of binder oxide used. When the amount of binder oxide exceeds about 15 percent of the total weight of halloysite and binder oxide, the amount of asphaltenes adsorbed is severely reduced.It has been found that an especially preferable amount of binder oxide is about 5 percent. As more binder oxide is added to the catalyst support, the pore sizes tend to cluster around smaller distributions. A catalyst support with 25 percent alumina has substantially all of its pores less than 100 Angstroms in diameter.

If an inorganic oxide component is to be present into the composition of the present invention, codispersal of the rods of the fibrous clay is preferably carried out in the presence of an aqueous hydrogel or the sol precursor of the inorganic oxide gel component. The preferred inorganic oxide is alumina. Mixtures of two or more inorganic oxides are suitable for the present invention for example, silica and alumina.

Afunction of the inorganic oxide gel component is to act as a bonding agent for holding or bonding the clay rods in a rigid, three-dimensional matrix. The resulting rigid skeletal framework provides a catalyst body with high crush strength and attrition resistance.

A catalyst support made from halloysite alone or in combination with a fibrous clay can contain any catalytic reactive transition metal. The catalytic metal components can be added during any stage of preparation. Catalystic metals can be added as powdered salts or oxides during the agitation stage or by impregnation of the catalyst body by adding a metal containing solution after the catalyst bodies have been formed. Preferred catalystic metals are those of Groups Vl-B and VIII of the Periodic Table. When preparing hydroprocessing catalyst, it is preferable that the composition include at least one metal of the group of chromium, molybdenum, tungsten and vanadium, and at least one metal of the group of iron, nickel and cobalt, such as cobalt-molybdenum, nickel-tungsten or nickel-molybdenum.

The metal component can be added to the catalyst composition at any stage of the catalyst preparation by any conventional metal addition step. For example, metals or metal compounds can be added to the slurry as solids or in solution, preferably before dispersion of the clay rods. Alternatively, an aqueous solution of metal can impregnate the dried or calcined bodies. The metals can be present in reduced form or as one or more metal compounds such as oxides or sulfides. One preferred method is impregnating the calcined catalyst bodies with a solution of phosphomolybdic acid and nickel nitrate.

Preparation of the catalyst with dispersed rods is accomplished by creating a mixture of tubular halloysite a fibrous second clay and if desired, binder oxide and enough water to form a slurry of about 20 weight percent solid content. As the mixture is violently agitated the slurry is observed to thicken. Agitation is continued until the slurry stops thickening with continued agitation. This takes about 10 minutes of agitation.

This thickening is indicative of dispersal of the rods. Excess water in the slurry is removed by evaporation until a moldable plastic mass is formed. The bodies are then shaped by spheridizing, pelletizing and similar procedures and then calcined. It has been observed that a catalyst body made exclusively of dispersed rods of halloysite tends not to extrude well. The rods tend to realign on the surface of the extruded mass, and this skin effect decreases the average pore diameter at the surface of the extruded mass. Alternatively, the halloysite mass can be dried and calcined; and the calcined mass broken up to produce catalyst bodies. The final product is a catalyst body with the characteristics of dispersed rods of halloysite. It is preferable that the binder oxide be added to the halloysite as the gel or the sol precursor to the gel at the agitation stage of the slurry.

Referring to Table I, the pore size distribution for unprocessed halloysite and pore size distribution for halloysite with dispersed rods are compared. It will be noted that in unprocessed halloysite most of the pore size is in the 200-400 Angstrom range. On the other hand, halloysite with dispersed rods has most of its pores distributed from 400-600 Angstroms. In halloysite with dispersed rods there is a substantial amount of pore volume provided by pores having diameters in the range of 100-300 Angstroms. It is believed that these pores are from the central hole present in halloysite rods. The presence of these smaller pores is not a gauge of the thoroughness of dispersion of the rods.

TABLE I Pore Size Distribution (Expressed as percentage of Total Pore Volume) With Pore Size Diameter Unprocessed Dispersed Rods > 600Angstroms 4% > 1% 500-600 Angstroms 2% 22% 400-500Angstroms 13% 29% 300-400 Angstroms 19% 18% 200-300 Angstroms 44% 14% < 200 Angstroms 17% 17% Total Pore Volume .26 cc/g .39 cc/g It will also be noted that the halloysite with dispersed rods has a substantially greater total pore volume than the natural halloysite.

It is believed that the pores in the range of 200 Angstroms to about 700 Angstroms impart especially good deasphalting properties to the catalyst support. One explanation is that demetalation and desulfurization reactions tend to be fast, therefore, pores significantly larger than the molecules tend to allow rapid diffusion into and out of the pores. Large pores are preferable in demetalation catalysts since the metals removed from the feedstocks tend to deposit on the surface of the catalyst support, thereby rapidly plugging the mouths of the smaller pores. Since there is no substantial amount of pore volume in pores greater than 1000 Angstroms, there is less problem with mechanically weak catalyst bodies and attendant attrition.

The catalyst support and catalyst of this invention are versatile and can be used for conversion of a variety of hydrocarbonaceous feeds. This catalyst is especially useful in hydroprocessing of heavy fractions which contain more than one precent by weight asphaltenes. Asphaltenes are defined herein to mean any hydrocarbon fraction that is insoluble in n-heptane whether or not it is soluble in benzene. Any feedstock containing asphaltenes can be treated by use of this catalyst whether or not the asphaltenes have been previously separated from the remainder of the feedstock.

The feedstocks with more than about 10 percent asphaltenes are especially suitable for upgrading by use of the present invention. Suitable feedstocks include those oils that have an API gravity below about 25 or a Conradson carbon residue of at least 7 percent. Particularly suitable are those feedstocks that boil at greater than 550"C. Suitable feedstocks include: crude petroleum, vacuum and atmospheric residua from petroleum, coal-liquids, shale oil, topped crudes and the like.

The present invention is especially suitable for any of the numerous hydroconversion processes that use molecular hydrogen. The generic conditions are exposing the feedstockto hydrogen at a partial pressure ranging from 0 to 200 atmospheres at between 200"C and 540"C, and hydrogen to oil feed ratio of from zero to 9,000 standard cubic liters per liter of oil and an hourly liquid space velocity from about 0.1 to about 25 reciprocal hours. Among the specific uses for which this catalyst is suitable are hydrocracking, hydrodesulfurization, hydrodenitrification, hydrodemetalation, and hydroconversion of asphaltenes. The present catalyst is especially suitable for hydrodemetalation and hydrocracking of asphaltenes.

The following examples are for illustrative purposes only and should not be considered to be limiting.

Example I This example illustrates the preparation of a catalyst support containing only halloysite without a binder oxide or catalytic metals.

Naturally occurring halloysite from Dragon Iron Mine, Utah, &num;13 powder is placed in a blender with enough water to make a slurry of about 20 weight percent solid content. The slurry is vigorously agitated in a Waring blender until it reaches a constant thickness. After removal from the blender, the clay containing slurry is dried and calcined and shaped into catalytic bodies.

Example II This example illustrates preparation of a catalyst support containing halloysite and a binder oxide. Dragon Halloysite #13 powder is placed in a blender. Enough 5 percent alumina by weight alumina hydrogel is added to form a mixture that is 5 percent by dry weight alumina. The alumina hydrogel is prepared conventionally, as by peptizing a commercially available alumina by a vigorous agitation with a peptizing agent such as nitric acid or formic acid, or by precipitation of the hydrogen from an aluminum nitrate solution with a base such as ammonium hydroxide. Enough water is then added to make a slurry that is no more than about 20 percent solid content. The mixture is then vigorously agitated in a Waring blender until the slurry no longer visibly thickens.Once the halloysite rods are adequately dispersed, the slurry will not get any thicker. Normally this takes about 10 minutes of agitation. Excess water is evaporated from the slurry to form a plastic, workable mass. The mixture is heated to 500"C for three hours and the calcined mass is broken up into catalyst particles.

Example 111 A mixture of 50 g of halloysite &num;13 from the Dragon Iron Mine, Utah, 10 g of attapulgite from Gadsden City, Florida, and 25 g of alumina sol (20 percent Catapal alumina by weight) in 500 ml of water was agitated in a Waring blender for 10 minutes. At this point the slurry mixture had stopped visibly thickening. The slurry was slowly evaporated dry at 110"C to a thick paste which could be easily extruded. The paste was extruded, and dried and calcined at 500"C.

Example IV This example illustrates the deasphaltening properties of a catalyst support made from dispersed rods of halloysite.

A calcined catalyst support prepared by the general method illustrated in Example I was impregnated by a solution of phosphomolybdic acid and cobalt nitrate. The impregnated catalyst contained 2 percent by weight of cobalt and 6 percent by weight of molybdenum. The support was employed for hydrometalizing a feedstock comprising Arabian Atmospheric Residue in a microreactor. The temperature was 3820C, the pressure of hydrogen was 112 atmospheres, the hydrogen flow was 90 standard liters per liter of feed and the liquid hourly space velocity was 0.86 reciprocal hours. The concentration of impurities in the feedstock was reduced after hydrogen processing the feedstock in the presence of the catalyst. Table II shows the concentrations of the impurities in the feedstock before and after hydrodemetalation.

TABLE II V,ppm N,ppm % S % Asphaltene Feed 83 22 4.4 7.2 Product 57 18 3.9 5.3 Table III shows the concentrations of impurities in the asphaltene fraction of the feedstocks when the heptane insoluble asphaltenes are separated and analyzed separately.

TABLE lil V,ppm N,ppm % S Asphaltenes From Feed 1030 300 10.5 Asphaltenes From Product 760 250 8.8 It will be appreciated that the asphaltene left behind was cleaner than the asphaltene in the initial feedstock.

Analysis of the catalyst particles revealed that the metals deposited on the catalyst support tended to be evenly distributed throughout the particles, rather than on the surface only.

Example V A series of catalysts were made according to the general method of Example II except that varying amounts of alumina were used in each preparation. The catalysts were then placed in toluene solutions of asphaltenes and the absorbance at 550 nm is monitored with respect to time according to the method of Saint-Just(lnd. Eng. Chem. Prod. Res. Div. 1980, 19,71).550nm is chosen becausetheabsorbanceofthis wavelength of light has been correlated to the concentration of vanadium, which in turn has been correlated to the concentration of asphaltenes.

Table IV shows the absorbance of light at 550 nm at varying time intervals for various halloysite catalysts that have varying amounts of alumina. As the catalyst adsorbs asphaltenes, the solution becomes progressively more clear, therefore, absorbing less light. Therefore, the better catalyst compositions for deasphaltening action will have lower final light absorbances.

TABLE IV Time (minutes) 0 5 10 15 20 30 Halloysite with 1.0 0.28 0.14 0.08 0.06 0.04 0% alumina Halloysite with 1.0 0.22 0.01 0.05 0.04 0.03 5% alumina Halloysite with 1.0 0.67 0.56 0.49 0.43 0.36 10% alumina Halloysite with 1.0 1.0 1.0 1.0 1.0 1.0 25% alumina Halloysite with 5% alumina (extruded) 1.0 0.92 0.85 0.82 0.79 0.73 It can be seen that the best asphaltene absorbance is for the catalyst composition with 0-5 percent alumina content, and asphaltenes are absorbed progressively more poorly for the catalyst supports with higher amounts of alumina. The extruded halloysite shows decreased light absorbance with time, indicating that asphaitene absorption onto the catalyst support is taking place, but it is considerably inferior to the 5 percent alumina catalyst that has been shaped by alternate means.This is apparently due to a skin effect on the extruded catalyst body that tends to realign the dispersed rods during extrusion. The results of this absorbance test can be roughly correlated to the pore size distribution of the catalyst support, which should be large enough to adsorb molecules the size of asphaltene molecules. It will also be noted that there is no decrease in light adsorbance in the 25 percent alumina catalyst. It is thought that the pore sizes are too small to allow the catalyst body to preferentially adsorb asphaltenes. The light absorbance characteristics of this series of dispersed rod catalysts indicate that dispersed rods of halloysite can be superior catalyst supports for hydroprocessing if the catalyst support contains no more than about 15 percent binder oxide.

Example VI The catalyst of Example Ill is tested for absorbance. The absorbance of 550 nanometers (nm) of a solution of asphaltenes dissolved in toluene is followed with time according to the method of Saint-Just (Ind. Eng.

Chem. Prod. Res. Div., 1980, 19, '71). The wave length of light chosen has been correlated to concentration of vanadium in solution, which has in turn been correlated to asphaltene concentration. Various catalysts are added. A reduction in the absorbance means that the catalyst preferentially adsorbs asphaltene materials from the toluene solution. The results are tabulated in Table V. It can be appreciated that the extruded halloysite/attapulgite mixture adsorbs asphaltenes much better than the extruded halloysite. It has been shown that good demetalation catalysts will always show a marked decrease in the absorbance of the toluene solution when tested in this manner.

TABLE V Solution Absorbance at 550 NM Catalystcomposition 0mien 5Min lOMin 15Min 20Min 30 Mn Halloysite with 1.0 0.92 0.85 0.82 0.79 0.73 5% alumina extruded Halloysite 80%, 1.0 0.535 0.39 0.31 0.255 0.19 Attapulgite 20 Halloysite 50%, 1.0 0.48 0.34 0.27 0.22 0.165 Attapulgite 50%

Claims (14)

1. A shaped calcined porous catalyst comprising dispersed rods (as hereinbefore defined) of the fibrous clay halloysite optionally codispersed with another fibrous clay containing rods having a length in the range from 1 to 5 microns and a diameter in the range from 50 to 100 Angstroms.

2. A catalyst as claimed in Claim 1, wherein at least 5 weight percent of said other fibrous clay is present based on the total weight of the catalyst.

3. A catalyst as claimed in Claim 2, wherein said other fibrous clay is attapulgite.

4. A catalyst as claimed in Claim 1,2 or 3 and further comprising up to 15 weight percent of a refractory inorganic oxide binder based on the total weight of the catalyst.

5. A catalyst as claimed in Claim 4, wherein the binder is alumina.

6. A catalyst as claimed in any preceding claim and further comprising at least one catalytic transition metal.

7. A catalyst as claimed in Claim 6, wherein the transition metal is selected from Group Vl-B and/or Group VIII of the Periodic Table.

8. A catalyst as claimed in any preceding claim, having a total pore volume of at least 0.35 cc/gm, of which at least 60 percent of the pore volume is present as pores having a diameter in the range from 200 to 700 Angstroms.

9. A catalyst as claimed in any one of Claims 1 to 7, having a pore volume of at least 0.35 cc/gm, of which at least 70 percent of the pore volume is present as pores having a diameter in the range from 200 to 700 Angstroms and at least 70 percent of said pores have a diameter in the range from 300 to 700 Angstroms.

10. A catalyst as claimed in any preceding claim, wherein said halloysite is composed predominantly of rods having a length in the range from 0.5 to 2 microns and a diameter in the range from 0.04 to 0.2 microns.

11. A method of preparing a catalyst as claimed in any preceding claim, which comprises adding to the halloysite and, when present in the catalyst, said other fibrous clay, binder and/or transition metal sufficient water to create a slurry of no more than 25 weight percent solid content; vigorously agitating the resulting slurry until the slurry ceases to thicken; drying the slurry to create a dry mass; shaping the dried mass; and calcining the shaped mass to form the required shaped catalyst.

12. A method of preparing a catalyst in accordance with Claim 1, substantially as described in any one of the foregoing Examples I to V.

13. A method of hydroprocessing a hydrocarbonaceous feedstock containing more than one percent by weight asphaltenes comprising: contacting said feedstock under hydroprocessing conditions with a shaped calcined porous catalyst as claimed in any one of Claims 1 to 10.

14. A method of hydroprocessing a hydrocarbonaceous feedstock comprising: contacting the feedstock with molecular hydrogen under hydroprocessing conditions in the presence of a shaped calcined porous catalyst as claimed in any one of Claims 1 to 10.