CA1248513A

CA1248513A - Residual hydrocarbon demetalation and desulfurization

Info

Publication number: CA1248513A
Application number: CA000465579A
Authority: CA
Inventors: Ronald W. Plesko; Eugene A. Pasek; Robert D. Christman
Original assignee: Gulf Research and Development Co
Current assignee: Gulf Research and Development Co
Priority date: 1984-07-30
Filing date: 1984-10-16
Publication date: 1989-01-10
Also published as: NL8403107A; JPS6138629A

Abstract

RESIDUAL HYDROCARBON DEMETALATION
AND DESULFURIZATION

Abstract of the Disclosure Metals and sulfur-containing residual hydro-carbons are demetalated and desulfurized under hydro-genation conditions employing a catalyst having con-trolledmacroporosity.

Description

~2~35:1~
~1--RESIDUAI. HYDROCARBON DEMETALATION
AND DESULFURIZATION

Field of the Invention The present invention relates to a hydrogena tion catalyst, to the method of manufacture of such catalyæt and its use for the demetalation and desul-furization of asphalt-containing hydrocarbons. More particularly, this invention relates to the manufacture of a molybdenum hydrogenation catalyst containing a controlled guantity of feeder macropore~ interconnecting catalytically active micropores and the use of the catalyst in the demetalation and desulfurization of asphalt-containing hydrocarbons.

DescriDtion of the Prior Art It i~ well known in the art to remove metal6 and sulfur from petroleum asphalt-containing hydrocarbon fractions by subjectin~ them to treatment with hydrogen under elevated temperatures and pressures while in contact with a catalyst containing hydrogenating components.
l~pically, Group VI and Group VIII metals, or their oxides and sulfides, have been employed as the metallic components of the catalyst. For example, a *

4 8 5~ 3

-2-catalyst that has been utilized commercially in hydro de~ulfurization of an asphalt-containins crude oil charge i6 a nickel-cobalt-molybdenum on alumina cata-lyst. Such cataly~t and hydrodesulfurization proce~s is disclosed, for e~ample, in Re 29,315 to Carlson et al.
The life of conventional hydrodesulfurization catalysts such as de6cribed above is shortened in proportion to the concentration of metals found in the heavy oils.
These metals are adsorbed on the cataly~t, blocking the pores and deactivating the hydrode~ulfurization cata-lyst.
Hydrogenation cataly~ts previously employed a6 demetalation catalysts, such as described in U. S.
Patent 4,411,824, provide good demetalation, but the accompanying desulfurization is usually poor, requiring excessive start-of-run temperatures to achieve adequate desulfurization as high as 760F. or higher.
The recognition that large catalyst pores could be useful in the ~imultaneous demetalation and desulfurization of heavy oils is disclosed in U.S.

3,898,155 to Geoffrey R. Wilson. That reference de-scribed the simultaneous demetalation and desulfuriza-tion of heavy oils containing at least 50 ppm metals employing a catalyst composition comprising a Group VI-B
metal and at least one Group VIII metal composited with alumina, said catalyst composition having an average pore diameter greater than 100 A units, from 10-40 percent of the total pore volume in pores having a diameter greater than 600 A units, from 60-90 percent of the total pore volume in pores having a diameter in the range of 0-600 A units, and at least 80 percent of the micropore volume being in pores having a diameter of at least 100 A units.
A process for hydrodemetalation and hyrodesul-furization of a~phaltene-containing hydrocarbon~ employ-ing a bimodal cataly6t is also described in U.S.

~24~S13

4,225,421. That reference de~cribes the cataly6t as a Group VIB ~etal deposited on a support comprising alumina wherein from about 60% to about 95% of its micropore volume is in micropo~es having dia~eter~
within the range of about So A to abollt 200 A, 0% to about 15% of its micropore volume is in mlcropores having diameters within the range of about 200 A to about 600 ~, and about 3% to about 30% of the total pore volume is in macropores having diameters of 600 A or greater.

SummarY of the Invention By the invention, optimum demetalation and desulfurization of asphalt-containing hydrocarbons is obtained under hydrogenation conditions employing a catalyst comprising molybdenum and at least one Group VIII metal composited with alumina, said catalyst having a total pore volume based upon measurement by mercury penetration of at least 0.4 cc/g, a macropore volume in the range of 0.02 to 0.2 cc/cc of catalyst volume, and a micropore volume of at least 0.12 cc/cc of catalyst volume.

Brief Description of Drawinqs Figure 1 relate~ product sulfur to concentra-tion of molybdenum in 100-600 A diameter catalyst pores;
Figure 2 relates vanadium concentration in hydrocarbon product to concentration of molybdenum in micropores;
Figure 3 relates nickel concentration in hydrocarbon product to concentration of molybdenum in micropores;
Figure 4 relates concentration of vanadium in hydrocar-bon product to macropore volume; Figure 5 relatesconcentration of nickel in hydrocarbon product to macropore volume.

lZ~5:13 It has been discovered that the demetalation and desulfurization of asphalt-containing hydrocarbons can be optimized by employing a catalyst composition having a controlled molybdenum loading and a controlled distribution of macropore volume and micropore volume. As employed in this specification, the term "macropore volume" refers to that portion of the total pore volume contained in pores having a pore diameter in the range of 1000 A to 10,000 A as determined by the test procedure described in "An Instrument For the Measurement of Pore Size Distribution by Mercury Penetration" by Winslow and Shapiro in ASTM Bulletin, No. 236, February, 1959. The term "micropore volume" refers to that portion of the total pore volume contained in pores having a diameter in the range of 100-600 A units as determined by the nitrogen adsorption method described by E. V. Ballon, 0. K. Dollen, in "Analytical Chemistry" Volume 32, page 532, 1960.
The test methods described therein are referred to as the "mercury intrusion" method and "nitrogen adsorption" method, respectively.
In preparing the novel catalysts of this invention, an alumina support is employed. The alumina of this invention can contain up to about ten (10) weight percent of other component such as silica. Typically, the support should have a total pore volume as determined by mercury intrusion of 0.8 cc/gg nitrogen adsorption volume of 0.5 cc/g, a compacted bulk density of 0.5 g/cc, 95~ of the nitrogen volume being in pores having a diameter in the range of 100-600 A, a BET surface area of 200 m2/g, a macropore volume of 0.05 cc/cc of catalyst volume wherein the pore diameters are in the 2000-6000 A range and a micropore volume of 0.3 cc/cc of catalyst volume. Dependent upon . ~
., ~248513 the loading of the catalyst metals, the above described support parameters can be adjucted to produce the hereafter de6cribed catalyst.
In preparing the cataly~t, the alumina can be dried to remove any free water therefrom, typically at a temperatuxe of 250F. (121C.) for a time ranging from 1 to 24 hour6. Thereafter, the 6upport can be calcined at a temperature in the range of 800-1600F. ~427-871C.) in an oxygen atmo6phere for a period ranging from 1 to 24 hour6.
The catalysts of this invention contain molybdenum and at lea6t one metal component selected from Group VIII. Molybdenum is deposited on the alumina support 80 as to provide, based upon molybdenum triox-ide, a loading of at lea6t 0.0005 g, preferably from O.0006 to 0.0014 g, of molybdenum trioxide per 6quare meter of catalyst 6urface. The Group VIII metal is deposited on the support so as to provide a weight ratio of the Group ~III metal to molybdenum in the range of 0.10 to 0.50, preferably from 0.18 to 0.38.
The preparation of the catalyst as hereinafter described will be specifically directed to a two-step impregnation of the alumina support with the metals, although other method6 of preparation can be e~ployed.
A single impregnation 6tep can be employed or the cataly6ts can be prepared by the extrusion procedure described in the Journal of Catalysis 72, pages 255 to 265 (1981).
In the two-step impregnation of the alumina 6upport, alumina extrudates can be admixed with an aqueous solution of salts such as ammonium molybdate, ammonium heptamolybdate, molybdenum pentachloride or molybdenum oxalate. The wet impregnated al~mina can then be dried by, for example, employing a temperature of 250F. ~121C.) for a period of from 1-24 hours.

i2~513 Thereafter, the alumina ~upport impregnated with the molybdenum can be contacted wi~h a~ aqueou~
~olution of the Group VIII metal, such a~ nickel nitrate The wet catalyst can then be dried in a second drying step at 250F. (121C.) for a period of from 1-24 hours.
Following the second drying ~tep, the catalyst can then be calcined at a temperature in the range of 800-1300F.
(427-704~c.) for a period of from 1-24 hours.
The hydrogenation metal components of the prepared catalyst can be employed in sulfided or unsul-fided form. If the sulfided form is preferred, the catalyst can be presulfided after calcination, or after calcination and reduction, by methods known in the art.
For example, the sulfiding can be conducted at a tem-perature in the range of 400-700F. (204-371C.), at atmospheric or elevated pressures. Presulfiding can be conveniently effected at the beginning of an onstream period at the same conditions to be employed at the start of the demetalation and desulfurization process.
Mixtures of hydrogen and hydrogen sulfide can be employed with the relative proportions of hydrogen and hydrogen 6ulfide not being critical. Elemental sulfur or sulfur compounds, such as mercaptans or carbon disulfide, can be used in lieu of hydrogen sulfide.
The catalyst as prepared and employed in tbe asphalt-containig hydrocarbon demetalation and desul-furization process of this invention will have a total pore volume, a5 determined by mercury intrusion, of at least 0.5 cc/g, preferably in the range of 0.60 - 0.75 cc/g, a macropore volume of 0.02 to 0.20 cc/cc of catalyst volume with the macropore diameters being in the range of 1000-10,000 A, and a micropore volume of at least 0.12, pxeferably from 0.20 to 0.32, cc/cc of catalyst volume. Preferably the pore diameters of the nacropore volume will be in the range of 2000 to 6000 A
and the macropore volume will be in the range of 0.035 ~2~ 3 to 0.075 cc/cc of cataly~t volume, and the pore dia-meters of the micropore volume will be in the range of 100~400 A. ~dditionally, the catalysts of thi8 inven-tion will have a nitrogen adsorption volume of at lea~
50.3, preferably from 0.40 to 0.55, cc/g, a compacted density of at lea~t 0.4, preferably from 0.50 to 0.70 g/cc, a ~urface area of at least 100, preferably 130-17S m2/g, and the micropore volume will comprise at least 70, preferably from 80 to 95, percent of the nitrogen adsorption volume.
The effect of catalytic metals concentrations in specific pore ~tructures was determined by preparing seven catalysts in accordance with the two-step proce-dure previously described. The properties of the pre-pared alumina-supported catalysts and the properties of a commercial catalyst (No. 6) are shown below in Table 1:

1~8S13 ~ ~0 0 oo o, ~ o , o ~ o , o X
o~ o o I I I ~ n o ~ o o ~ , `o ,, o~o o , o ~, j ~o .,~o~, o ~ o , o o o o $ U~ ~ g o ~, o X o o IOn ~ o N O ~ O O ~ ~ $ ~ ~ ~
_l ~O I _~ OCO I O C~ O o~ O I :~
~3 ~3 $ ~ $ ~ ' a ~ I trl I _I ~n I o ~ o ~ o j ~ ~
~ ' ~ a O ~ o o -' -' o ~ i ~ -~ ~ ~ o ~ ~ !~
C
o~o o ~ ~ o ., . , ~o ~, o o o X o , ~ ~, ^a 'u oo ' ~ ~
~o U U - ' ., ~
~, ~ :~ ~ ~
~ ~ Ll ~
~ ~ ~ ~ O ~ g ~ ~ I U ~
Z ~ ~ ~ O ~ 1 0 I r~1 U
3 U U r~~ U O~I e ~
~- _ al~ ~ ~ U ~ O
~ ~ " a~ X a ,0 0 0 0 0 ~ O ~,1 O ~1 U ~ U O 1 0 ~ h U ~: G Cl~
~- ~ Z ~ I O --1 X x 1~ 13 U I ~-~t o ,~ ~0 ~ 00 1 * ~lC

lZ~85~3 _g _ Cataly~t~ 1-5 had large macropores (8000 A);
Catalyst6 6 and 8 had no macropores; and Catalyst 7 had small macropores (800 A~. These catalyst6 were screened in an asphalt-containing hydrocarbon demetala-tion-desulfurization trickle bed pilot plant operated at O.4 LHSV, a hydrogen pressure of 2430 p6ig and circula-tion rate of 5000 SCFB, and at a temperature of 750F.
The feedstock employed was a desalted Venezuelan crude having the following inspections:

Gravity, API 9.1 Sulfur, wt % 3.3 Nitrogen, wt% 0.61 Nickel, ppm 87 Vanadium, ppm 360 Carbon Residue 15.2 The product quality data obtained after 8 days of operation are illustrated in Figures 1-3.
Figure 1 demonstrates that the amount or size of the macroporosity has no effect on the concentration of 6ulfur in the product with desulfurization increasing as the concentration of molybdenum in the 100-600 A
diameter pores is increased. At molybdenum loadings of at least 0.0005 grams of molybdenum trioxide per square meter of surface area, desulfurization is optimized.
For these cataly~ts having a pore structure in the 100 to 600 A diameter range, the diffu6ion of organosulfur molecules i6 not a limiting factor.
Figures 2 and 3 demonstrate the criticality of employing large macropores (in pore diame~ers in the range of 1000 - 10,000 A) in the demetalation of resid-ual hydrocarbon fractions. Although the macroporosity of Catalyst 7 i8 essentially eguivalent to that of Cataly~ts 1-5, the demetalation effectiveness of Cata-lyst 7 wa~ 6ubstantially le~s, demonstrating the 6ubstan-i24~S13 tially superior diffusion capabilities of the large macropores.
~ aving establi6hed a need for large or "feeder"
macropores to permit the large, metal-containing mole-cules to react catalytically in all portions of thecatalyst particle, experiments were conducted to deter-mine the quantity of the macropore volume and the optimum size of the pores in the macropore volume. As the addition of macroporosity cau6es a decrease in the catalytically active microporosity per unit volume, the amount of macroporosity should be optimized to maintain demetalation and desulfurization catalytic activity.
A series of alumina-supported catalysts were prepared employing the previously described two-step impregnation procedure. The properties of the prepared catalysts are described in the following Table 2:

1;2~8S~3 Catalyst No. 9 10 11 12 13 14 15 16 _ _ _ Metals, wt ~
------------------ 8.0 -----------Co ~ 1.0 Pore Vol., cc/g Diameter Range, R
Nitrogen Adsorption Total 0.450.140.31 0.49 0.38 0.840.86 0.73 400-600 0.080.040.07 0.06 0.03 0.120.14 0.13 200-400 0.130.040.11 0.12 0.06 0.190.20 0.19 100-200 0.110.030.08 0.14 0.07 0.110.13 0.15 < 100 0.013 0.03 0.05 0.17 0.220.42 0.39 0.26 Mercury Intrusion Total 1.681.201.68 1.00 0.92 2.272.14 2.04 2000-4000 0.110.240.16 0.02 0.02 0.030.05 0.07 4000-6000 0.010.040.04 0.02 0.01 0.00.02 0.02 6000-10,0~0 0.00.02 0.02 0.01 0.0 0.020.01 0.01 > 10,000 0.010.03~.04 0.01 0.0 0.010.01 0.01 Compscted 0.396 0.4290.359 0.396 0.755 0.259 0.264 0.286 Density, g/cc Grams Mo in 0.600.310.44 1.01 1.03 0.80.46 0.52 100-600 A Dia.
Range per 100 cc Macropore Vol. 0.0480.1200.072 0.008 0.002 0.013 0.018 0.029 in 2000-6000 R
Diameter Range, cc/ cc Product Properties Sulfur, wt X 1.88 2.69 2.21 1.49 1.39 2.732.54 2.47 Metals, ppm Ni 31 38 42 30 42 53 50 44 85 ~

The catalysts of Table 2 were ~;creened in the previously described pilot plant in a series of run6 operated at O.5 LHSV, a hydrogen pressure of 2000 psig and circula-tion rate of 2000 SCFB, and at a temperature of 700F.
The feedstock employed was a Mexican Maya atmospheric tower bottoms fraction having the following inspections:

Gravity, API 7.5 Sulfur, wt % 4.7 Nickel, ppm 78 Vanadium, ppm 408 The sulfur and metals concentrations of each of the run products are presented in Table 2. As linear relation-ships exist between product metals and ~olybdenum content for catalyst having identical amounts and sizes of macroporosity and by employing the above product data of Table 2, the curves of Figures 4 and 5 were developed for catalysts having 0.50 grams of molybdenum in the 100 to 600 A diameter pores per 100 cc's of reactor volume and wherein the macroporosity is in the 2000 to 6000 A range. Figures 4 and 5 show that when the amount of macroporosity is less than 0.03 cc/cc of reactor volume, diffusion is inhibited, while macro-porosity in excess of 0.08 cc/cc of catalyst volume has little effect on enhancing diffusion. A range of macroporosity of between 0.035 to 0.075 cc/cc of cata-lyst volume optimizes the desired diffusion character-istics of the catalyst. Similar plots for pores in the 6000 to 10,000 A diameter range showed no recognizable trends, thereby supporting the preferred pore size range of 2000-6000 A diameter for the macropores.
Two catalysts were prepared to demonstrate the effectiveness of the invention. Cataly~t 17 was prepared by impregnating 236.0 gram~ of a calcined 1/32-inch alumina extrudate with 360 ml of an aqueous solu 1~4851 tion containing 103.96 grams of ammonium heptamolybdate (81.5% MoO3) and 45.4 ml of ammonium hydroxide. The mass was oven dried at 250F. ~121C.) and then calcined for 10 hours at 1000F. (538C.)~ The calcined mass was S then impregnated with an aqueous ~olution (326 ml) containing (a) 100.09 g of nickel nitrate hexahydrate and (b) 312.69 g of 18.31% TiO2-TiC14 ~tabilized agueous amine solution. The mass was oven dried at 250F.
(121C.) for approximately 27 hours and finally calcined for 10 hours at 1000F. (538C.).
Catalyst 18 was prepared by impregnating 187.0 grams of a 1/32-inch calcined alumina extrudate with 300 ml of an aqueous solution containing 82.17 grams of ammonium heptamolybdate (81.5% MoO3) and 35.9 ml of ammonium hydroxide. The mass was oven dried at 250F. (121C.) and then calcined for 10 hours at 1000F. (538C.). The calcined mass was then impreg-nated with 275 ml of an aqueous solution containing (a) 79.05 g of nickel nitrate hexahydrate and (b) 248.22 g of 18.01% TiO2-TiC14 stabilized aqueous 601ution. The mass was oven dried at 250F. (121C.) for approximately 27 hours and finally calcined for 10 hours at 1000F.
(538C.).
As presented in the following Table 3, the prepared cataly6t6 have the desired amounts of macro-porosity/ 0.043 and 0.041 cc/cc of catalyst volume, respectively, and microporosity, 0.20 and 0.24 cc/cc of catalyst volume, respectively. The catalysts were screened in the previously described pilot plant oper-ated at 0.3 LHSV, a hydrogen pressure of 2400 psig (169 kg/~m2) and circulation rate of 5000 SCFB (141,0000 liter~/B) using a Merey Campo crude feedstock.

Cataly~t No. 17 18 Metals, wt %
Co ___ ___ Ni 5.0 5.0 Mo 14.0 14.0 Ti 8.5 8.5 Nitrogen Adsorption Surface Area, m2/g O 130.7 134.3 Mean Pore Diameter, A 120 132 Total Pore Volume, cc/g 0.39 0.44 Pore Vol. in Diameter Ranges R, cc/g 400-600 0.028 0.021 200-400 0.104 0.116 100-200 0.175 0.205 < 100 0.083 0.098 Mercury Intrusion Pore Vol. in Diameter Ranges R, cc/g Total 0.63 0.54 2000-4000 0.033 0.049 4000-6000 0.033 0.010 6000-10,000 0.033 0.003 > 10,0000 0.038 0.006 ComDscted Bulk Density, g/cc 0.653 0.704 Gram~ Mo in 4.5 6.2 100-600 A Dia.
per 100 cc Grams MoO3/m2 0.00100 0.00127 MicropDrosity 0.20 0.24 in 100-600 A
Diameter Range, cc/cc Macroporo6ity 0.043 0.041 in 2000-6000 A
Diameter Range, cclcc 1~48513 The inspections for the feedstock a~ well as the product oils produced in the runs are pro~ided in the following Table 4. For Catalysts 17 and 18, 78.1%
and 78.9% desulfurization, re~pectively, and 83.3% and 86.9% demetalation, respectively, were obtained.

Feedstoc~ Catalyst Merey Iuspections Campo 17 18 Gravity, API 17.8 20.9 22.5 Sulfur, wt % 2.28 0.50 0.48 15 Nitrogen, wt X 0.41 0.34 0.31 Conradson Carbon 11.00 7.05 6.67 Residue, wt %
Nickel, ppm 55 17 15 Vanadium, ppm 220 29 21 20 n-Pentane Insoluble~, wt X 12.22 5.86 4.13 Days On-Stream --- 10 20 Temperature, F. --- 736 736 -The configuration of the catalyst particle used in the demetalation-desulfurization process desir-ably ha~ a high geometric surface area, and a high co~pacted density as employed in the reactor. Althrough not to be limited thereto, preferred embodiments are 1/32-inch cylinders and shaped extrudates.
The demetalation-desulfurization reactions effected pursuant to the proces6 of this invention are conducted for asphalt-containing hydrocarbons in the presence of the catalyst at a temperature that i~
maintained, after the relatively rapid elevation of te~perature employed during ~tartup, in the range of ~ ~8~13 about 600 ~o 850F. (316 to 45~C.), preferably 650 to 800F. (343~ ~o 427C~. The reactions are effected in the presence of uncombined hydrogen partial pressures in the range of 500-3000 p6ig (35.2 - 211 kg/cm2), pref-erably 1500-2500 psig (105.5 - 176 kg/cm2). ~ydrogen gas (at least 60% purity) is circulated through the reaction zone at the rate of 1000-10,000 standard cubic feet (28,250 - 282,000 liters), preferably 2000-6000 standard cubic feet (56,250 - 168,750 liters) per barrel (159 liters) of feed (SCFB). A space velocity in the range of 0.1 to 5.0, preferably 0.2 to 2.0) liquid volumes of oil per volume of catalyst per hour (L~SV) is maintained in the reaction zone.

Obviously, many modifications and variation~
of the invention, as hereinabove set for~h, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

Claims

WE CLAIM:

1. A Catalyst which comprises molybdenum and a Group VIII
metal deposited on an alumina support, said catalyst having a total pore volume as determined by mercury intrusion of at least 0.5 cc/g, a compacted density of at least 0.4 g/cc, a macropore volume of 0.035 to 0.075 cc/cc of catalyst volume, and a micropore volume comprising at least 70 percent of the nitrogen adsorption volume and at least 0.12 cc/cc of catalyst volume.

2. The catalyst of Claim 1 wherein the pore diameters of the macropores are in the range of 2,000 to 6,000 ?.

3. The catalyst of claim 2 wherein the molybdenum is deposited on the alumina support so as to provide a loading of at least 0.0005 g molybdenum trioxide per square meter of catalyst surface.

4. The catalyst of claim 3 wherein the loading is in the range of 0.0006 to 0.0014 g of molybdenum trioxide per square meter of catalyst surface.

5. The catalyst of claim 3 wherein the micropore volume is in the range of 0.20 to 0.32 cc/cc of catalyst volume.

6. The catalyst of claim 5 wherein the pore diameters of the micropore volume are in the range of 100-400 ?.

7. The catalyst of claim 3 to include a Group IVB metal deposited on said alumina.

8. A process which comprises contacting an asphalt-containing hydrocarbon containing sulfur and metals under hydrogenation conditions with hydrogen and a catalyst comprising molybdenum and a Group VIII metal deposited on an alumina support, said catalyst having a total pore volume as determined by mercury intrusion of at least 0.4 cc/g, a macropore volume of 0.02 to 0.20 cc/cc of catalyst volume, and a micropore volume of at least 0.12 cc/cc of catalyst volume.

9. The process of claim 8 wherein the macropore volume is in the range of 0.035 to 0.075 cc/cc of catalyst volume and the pore diameters of the macropores are in the range of 2000 to 6000 ?.

10. The process of claim 9 wherein the molybdenum is deposited on the alumina support 80 as to provide a loading of at least 0.0005 g molybdenum trioxide per square meter of catalyst surface.

11. The process of claim 10 wherein said catalyst also includes a Group IVB metal deposited thereon.

12. The process of claim 11 wherein the micropore volume of the catalyst is in the range of 0.20 to 0.32 cc/cc of catalyst volume.