GB1560627A - Hydrodesulphurization catalysts - Google Patents

Description

(54) HYDRODESULFURIZATION CATALYSTS (71) We, AMERICAN CYANAMID COMPANY, a Corporation organised and existing under the laws of the State of Maine, United States of America, of Berdan Avenue, Township of Wayne, State of New Jersey, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to improvements in the catalytic hydrodesulfurization of residual oil for sulfur removal and particularly to improvements in the catalysts for use in such process.

United States Patent No. 3,966,644, to W.R. Gustafson, described catalysts for hydrodesulfurization of residual oils and described several methods for making those catalysts.

A preferred catalyst described in that patent for use in hydrodesulfurization of petroleum residuums, was prepared by precipitating alumina over a heel of silica hydrogel, washing the precipitate, adding ammonium molybdate with water and spray drying the mixture. The dried powder was mixed with nitric acid and water and the mixture was extruded, dried calcined and the calcined extrudate was impregnated with cobalt salt solution, dried and calcined again. The trilobal particle shape described in detail in the Gustafson patent is a preferred shape for catalysts of the present invention.

In U.S. Patent No, 3,980,552 to Grant A. Mickelson, it was demonstrated again that catalysts made by the method described above would have higher activity in the hydrodesulfurization of residual oils than catalysts of similar composition which had been prepared by prior art methods.

The method for making superior catalyst as described by Gustafson and Mickelson involved two calcining steps as well as an extra imbibing step, and thus involved more expense in preparation than the prior art methods. We have now found that catalysts having about the same physical properties as the earlier improved catalyst and about the same catalytic activity for the residual oil hydrodesulfurization process, can be prepared by a simpler method which requires only a single calcining step. An unexpected result with our new catalyst is a considerable improvement in the rate of decay of the catalytic activity when using the present catalyst in continuous processing as compared with the use of a catalyst prepared by the method described by Gustafson.Mickelson postulated the importance of certain structural relationships between pore volume, pore diameter, total surface area, external surface area, and volume of the catalyst particles, which were said to be critical to the activity and catalyst life when the catalysts were used for the hydrodesulfurization of certain residual oils. It was supposed that the catalyst making method described was critical to obtain the structural relationships needed for optimum activity and catalyst life.

As defined by Mickelson, the process for which these catalysts are designed, is the hydrodesulfurization of residual oils which contain 1-20 weight percent asphaltenes and 10 to 500 ppm metals by contacting the said residual oil, in admixture with 500 to 8,000 standard cubic feed (SCF) hydrogen per barrel (B) of the residual oil, at a temperature in the range from 6500F. to 8500F. and under pressure in the range from 1,000 to 3,000 pounds per square inch (psig), with a catalyst which is a sulfided composite of 1-7 weight percent CoO and 5-20 percent MoO3 supported on a carrier consisting essentially of activated alumina or of activated alumina and 1 to 5 percent by wt. silica and which is further characterized by:: a. total surface area in the range from 150 to 350 m2/g; b. pore volume from 0.3 to 0.8 ml/g; c. average pore diameter from 40 to 100 A; d. pore volume in pores above 100 A diameter of from 0.01 to 0.1 ml/g; and e. external surface area to volume ratio in the range from 70 to 160 sq. in. area per cubic inch volume. (in-l) and preferably from 100 to 150 ini The process of the present invention differs significantly from the process defined by Mickelson only by the differences in the respective methods for making the catalyst.

According to the present invention the catalyst for the defined process is made by the following steps: i) slurrying alumina hydrogel in aqueous solution of ammonium molybdate. In a preferred embodiment, silica gel in also present in the slurry in amount to make about one to five percent by wt. silica in the calcined catalyst.

ii) partially drying the slurry to a water content in the range from 10 to 40 percent by weight. A preferred drying method for this step is spray drying; iii) mulling the partially dried hydrogel with cobalt salt solution in amount sufficient to give the desired Co concentration in the finished catalyst, i.e. in the range 1 to 7 percent by wt. and with acid at pH in the range from 3.6 to 6.0 to make an extrudable mixture; iv) extruding the mulled mixture to make extrudates having the above defined ratio of external surface area to volume, i.e. 70 - 160 in-l. The preferred particle size is: max. diameter from 0.03 to 0.06 in. and length from 0.1 to 0.25 inch. The preferred die shape for the extrusion is one that forms a polylobal cross-section as described by Gustafson and particularly the three lobe cross-section.

v) drying and calcining the extrudates at calcining temperature in the range from 900" to 1400"F.

As will be seen from the foregoing description, a significant difference of the present process is the fact that cobalt is incorporated in the mixture in the muller. The particular catalyst requirements for hydrodesulfurization of residual oils had previously been thought to require the extra steps of imbibing cobalt after the first sintering step and sintering again in order to obtain the structural qualities needed for highest activity in a fixed bed catalyst.

The present invention combines the advantages of relatively less expensive manufacture with the retention of equally high activity, as compared with the use of the catalysts prepared as described by Gustafson or Mickelson.

A specific embodiment of the invention is set out in detail in the Example which follows.

EXAMPLE Dilute aqueous sodium silicate is reacted with 25 percent sulfuric acid and the resulting hydrogel is filtered and washed to remove sodium and sulfate. Thirty pounds of the washed silica hydrogel (containing 2.2 Ibs. ignited solids) are added to 600 Ib. of water at 920F. in an agitated reactor. Three hundred sixty-six Ibs. of aluminum sulfate solution (7.5who equivalent Al2O3) is added into the reactor over a period of about one hour and simultaneously, sodium aluminate solution (26% Awl,03 - 26% NaOH) is added with the rates of addition of the two solutions regulated to maintain pH between 8.3 and 8.7. The addition of the two solutions is held as uniform as practicable throughout the addition.

Additional sodium aluminate is added at the end to increase pH to 10.3-10.5. Final temperature is 127"F. The resulting silica-alumina hydrogel is filtered and washed twice; before the second filtration, pH is adjusted to 7.0 with HNO3. A slurry is made of the twice filtered silica-alumina hydrogel and ammonium molybdate solution is added in an amount to make about 13 percent by wt of MoO3 based on the ignited solids content of the silica-alumina hydrogel in the slurry. After thorough mixing, this slurry is partially dried to about 78 percent solids by spray drying to produce spray-dried powder.

In a muller, a mixture of the following ingredients is mixed and mulled for 45 minutes: 550 Ibs. of spray dried powder made as described above.

80 Ibs. of catalyst fines recycled from the calcining step of a previous preparation of the same catalyst.

550 Ibs. of water 11 Ibs. of 60% nitric acid.

115 libs. of cobalt nitrate solution (14.8% CoO equivalent) 1.5 Ibs. of polyacrylamide flocculant (American Cyanamid Company Superfloc 16).

pH in the muller is about 4.6-5.0.

The mulled mixture is extruded through a die shaped to produce extrudates having the trilobal cross section described in the Mickelson and Gustafson patents. The maximum diameter of the particles is about 0.50 in. (av. 0.049) and the average particle length is about 0.14 in. (after calcining). The extruded shapes are dried in a belt drier at temperatures ranging from about 200"F. at the inlet to about 2650F at the outlet, for about 30 minutes.

The dried particles are calcined for 30 to 60 minutes in a rotary calciner with maximum shell temperature about 1175"F.

A typical catalyst prepared by the foregoing procedure has the following properties: Chemical Analysis: CoO % by wt. 3.4 MoO3 % by wt. 13.4 SiO2 % by wt. 1.2 Impurities measured less than 1% Physical Analysis Total Surface Area M2/gm 309 Pore Volume ml/gm 0.52 Pore volume of all pores having over 100 Angstrom pore diameters ml/gm 0.043 Average pore diam eter, Angstroms 67 External surface area to volume ratio in-' 148 A sample of the catalyst prepared as described and having the chemical and physical properties described was tested in a standardized laboratory test, scientifically controlled, in which the catalyst sample is contacted with residual oil containing 1-20 wt. percent asphaltenes and 10 to 500 in admixture with 500 to 8,000 SCF/B hydrogen, at temperature in the range from 650"F. to 850"F. under pressure in the range from 1,000 to 3,000 psig. This is a test not significantly different from that described in Example 1 of the Mickelson U.S.

Patent No. 3,980,552. The initial activity of this catalyst as calculated from test results is found to be 97.4% relative to the activity of laboratory standard catalyst assigned a value of 100%. A preferred catalyst having chemical and physical properties which do not vary significantly from those properties described above but prepared by the method described in the Gustafson and Mickelson patents, is tested under comparable conditions in the same test and its relative activity is found to be 97.0%.

The same two catalysts are compared in a variation of the same test in which, as the continuous reaction proceeds over a period of several days and the catalyst activity declines, the temperature is increased from time to time as needed to maintain a constant reaction rate at constant feed rate.

This test is standardized and a relative activity decay rate is calculated as a percentage of the decay rate obtained using a laboratory standard catalyst. For the catalyst prepared by the present invention the relative activity decay rate determined by this test is 82%. By the same test procedure, the preferred prior art catalyst, prepared by the Gustafson method, was found to have a relative activity decay rate of 89%. These results reveal a significantly lower decay rate for the catalyst of the invention as compared with the decay rate of the Gustafson catalyst. Thus the catalyst prepared as described herein is found to have equivalent activity and superior catalyst life as compared with the Gustafson catalyst, for use in the catalytic hydrodesulfurization of residual oils for removal of sulfur, as described.

WHAT WE CLAIM IS: 1. A process for the hydrodesulfurization of a residual petroleum feedstock containing 1-20 weight percent asphaltenes and 10-500 ppm metals, which comprises contacting said feedstock in admixture with 500-8,000 SCF/B of hydrogen at a temperature of 650"-850"F.

and a pressure of 100-3,000 psig, with a catalyst consisting essentially of a sulfided composite of 1-7 weight percent CoO and 5-20 weight percent MoO3 supported on a carrier

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. 0.14 in. (after calcining). The extruded shapes are dried in a belt drier at temperatures ranging from about 200"F. at the inlet to about 2650F at the outlet, for about 30 minutes. The dried particles are calcined for 30 to 60 minutes in a rotary calciner with maximum shell temperature about 1175"F. A typical catalyst prepared by the foregoing procedure has the following properties: Chemical Analysis: CoO % by wt. 3.4 MoO3 % by wt. 13.4 SiO2 % by wt. 1.2 Impurities measured less than 1% Physical Analysis Total Surface Area M2/gm 309 Pore Volume ml/gm 0.52 Pore volume of all pores having over 100 Angstrom pore diameters ml/gm 0.043 Average pore diam eter, Angstroms 67 External surface area to volume ratio in-' 148 A sample of the catalyst prepared as described and having the chemical and physical properties described was tested in a standardized laboratory test, scientifically controlled, in which the catalyst sample is contacted with residual oil containing 1-20 wt. percent asphaltenes and 10 to 500 in admixture with 500 to 8,000 SCF/B hydrogen, at temperature in the range from 650"F. to 850"F. under pressure in the range from 1,000 to 3,000 psig. This is a test not significantly different from that described in Example 1 of the Mickelson U.S. Patent No. 3,980,552. The initial activity of this catalyst as calculated from test results is found to be 97.4% relative to the activity of laboratory standard catalyst assigned a value of 100%. A preferred catalyst having chemical and physical properties which do not vary significantly from those properties described above but prepared by the method described in the Gustafson and Mickelson patents, is tested under comparable conditions in the same test and its relative activity is found to be 97.0%. The same two catalysts are compared in a variation of the same test in which, as the continuous reaction proceeds over a period of several days and the catalyst activity declines, the temperature is increased from time to time as needed to maintain a constant reaction rate at constant feed rate. This test is standardized and a relative activity decay rate is calculated as a percentage of the decay rate obtained using a laboratory standard catalyst. For the catalyst prepared by the present invention the relative activity decay rate determined by this test is 82%. By the same test procedure, the preferred prior art catalyst, prepared by the Gustafson method, was found to have a relative activity decay rate of 89%. These results reveal a significantly lower decay rate for the catalyst of the invention as compared with the decay rate of the Gustafson catalyst. Thus the catalyst prepared as described herein is found to have equivalent activity and superior catalyst life as compared with the Gustafson catalyst, for use in the catalytic hydrodesulfurization of residual oils for removal of sulfur, as described. WHAT WE CLAIM IS:

1. A process for the hydrodesulfurization of a residual petroleum feedstock containing 1-20 weight percent asphaltenes and 10-500 ppm metals, which comprises contacting said feedstock in admixture with 500-8,000 SCF/B of hydrogen at a temperature of 650"-850"F.

and a pressure of 100-3,000 psig, with a catalyst consisting essentially of a sulfided composite of 1-7 weight percent CoO and 5-20 weight percent MoO3 supported on a carrier

consisting essentially of activated alumina, said catalyst being further characterized by: a. a total surface area from 150 to 350m2/g; b. a pore volume from 0.3 to 0.8 ml/g; c. an average pore diameter from 40 to 100A; d. a pore volume in pores above 100A diameter of from 0.01 to 0.1 mUg; and e. a particle-form shape having a ratio of external surface area to volume of from 70 to 160 reciprocal inches; said catalysts having been prepared by the steps of: i) slurrying alumina hydrogel in aqueous solution of ammonium molybdate; ii) partially drying the slurry to a water content in the range from 10 to 40 percent by weight; iii) mulling the partially dried hydrogel with cobalt salt solution in amount sufficient to give the desired CoO concentration in the final catalyst, i.e. in the range 1 to 7% CoO by wt. and with acid at pH in the range from 3.6 and 6.0 to make an extrudable mixture iv) extruding the mulled mixture to make extrudates having the above defined ratio of external surface area to volume, i.e. 70-160 in.; and v) drying and calcining the extrudates at calcining temperature in the range from 900" to 1400"F.

2. A process according to Claim 1, wherein said catalyst comprises from one to five percent by wt. of silica.

3. A process according to Claim 1 or Claim 2, wherein said catalyst is extruded to have a polylobal cross-section.

4. A process according to Claim 3, wherein said catalyst is extruded to have a trilobal cross-section.

5. A process according to any preceding claim, wherein the slurry is partially dried in said step (ii) by spray drying.

6. A process according to any preceding claim, wherein the extrudates have a ratio of external surface area to volume in the range from 100 to 150 reciprocal inches.

7. A process according to any preceding claim, wherein the extrudates have a maximum overall diameter about 0.05 inches and average length about 0.14 inches and ratio of external surface area to volume about 150 reciprocal inches.

8. A process for the hydrodesulfurization of a residual petroleum feedstock, according to Claim 1 and substantially as described in the Example herein.