Patent Description:
Hydrocarbon feedstocks are typically combusted as a fuel. When these hydrocarbon feedstocks contain sulfur, the combustion of the feedstocks produces a pollutant of the atmosphere in the form of sulfur oxide gases. In the petroleum refining industry, it is often desirable to upgrade sulfur containing oil and fractions like heavy oils and residuum by hydrotreating to reduce the sulfur content of the fractions.

In the hydrotreating process, hydrocarbon feedstocks are contacted with a hydroconversion catalyst in the presence of hydrogen at elevated pressure and temperature. Catalysts used in hydrotreating processes generally comprise catalytically active metals from Groups <NUM>, <NUM> and <NUM> of The Periodic Table and are typically supported on a support made predominately of alumina. To achieve desulfurization, typical operating conditions hydrotreating processes have included a reaction zone temperature of <NUM> to <NUM> a pressure of <NUM> to <NUM> bar, a hydrogen feed rate of <NUM> to <NUM> normal liters of hydrogen gas per liter (Nl/l) of oil feed, and a catalyst such as nickel or cobalt and molybdenum or tungsten on a predominately alumina support.

In addition to upgrading the heavy oil or residuum stock to reduce sulfur, it is highly desirable to upgrade the hydrocarbon feedstocks to provide a low carbon residue.

Carbon residue is a measurement of the tendency of a hydrocarbon to form coke. Expressed in weight percent, carbon residue may be measured as microcarbon residue (MCR). The MCR content in a hydrotreated residual feedstock is an important parameter since the hydrotreated residue usually acts as feed to a coker or the fluid catalytic cracking (FCC) unit. Decreasing the MCR content in a hydrotreated residue decreases the amount of low value coke generated in the coker and increases the amount of gasoline generated in the FCC unit.

To this end, there remains a need to develop catalyst compositions which provide good hydrodesulfurization of heavy oil and residuum feedstocks while simultaneously providing improved MCR conversion during a hydrotreating process.

<CIT> describes improved hydrodenitrogenation catalysts comprising catalytic metals, e.g. molybdenum and nickel, on supports of co-precipitated alumina and titania with more than <NUM>% of the catalyst weight consisting of titanium oxide in the support.

<NPL>, describes the preparation of a series of NiMo/γ-Al<NUM>O<NUM>-TiO<NUM> catalysts and the testing of the catalysts in the hydrotreating of heavy gasoil FCC feed in a pilot plant fixed-bed reactor.

<CIT> describes the preparation of a catalyst for hydrotreating, especially hydrodesulfurization, of residua and heavy crudes by synthesizing the support from titanium and boehmite, to form either a titanium/alumina support (referred to as TiO<NUM>/Al<NUM>O<NUM>) or a titanium-alumina support (referred to as TiO<NUM>-Al<NUM>O<NUM>) that is thereafter provided with at least one hydrogenating metal from group VIB in oxide form and a promoter from group VIII also in oxide form.

<NPL>, describes three different methods for preparing alumina-titania binary mixed oxide supports, and the use of these supports for hydrotreating of Maya heavy crude.

The present invention is based on the finding that the use of a co-precipitated titania alumina support having a specified pore distribution unexpectedly provides an improved catalyst for hydrodesulfurization of hydrocarbon feedstocks, in particularly residuum feedstocks, during a hydrotreating process as compared to hydrodesulfurization using catalysts prepared from an alumina support having the same or substantially the same pore distribution.

Additionally, catalysts of the invention provide a reduced MCR content in residue fractions. Hydrocarbon fractions obtained from a hydrotreating process using a catalyst in accordance with the invention advantageously exhibit a reduced MCR content as compared to the MCR content of the starting hydrocarbon feedstock. Further, hydrocarbon fractions obtained from a hydrotreating process using a catalyst in accordance with the invention unexpectedly exhibit a reduced MCR content when compared the MCR content obtained using a hydrodesulfurization catalyst having the same or substantially the same pore distribution and prepared from a support containing alumina alone.

In one aspect of the present invention, a catalyst support for preparing an improved hydrodesuflurization catalyst is provided. The catalyst support comprises a co-precipitated titania alumina having <NUM> wt % or less titania, based on the total weight of the titania alumina, and has a pore distribution such that at least <NUM> volume percent of its pore volume is in pores having a diameter between about <NUM>Å and about <NUM>Å, less than <NUM>% of the pore volume is in pores having a diameter above <NUM>Å, and less than <NUM>% of the pore volume is in pores having a diameter above <NUM>Å.

In another aspect of the present invention, a process is provided for preparing an improved hydrodesulfurization catalyst. The catalyst is prepared from a catalyst support material comprising a co-precipitated titania alumina having <NUM> wt % or less titania, based on the total weight of the titania alumina. Catalysts in accordance with the present invention are prepared by impregnating catalytically active Group <NUM>, <NUM> and <NUM> metals or precursor metal compounds, and optionally, phosphorous compounds, on a support in accordance with the invention.

In another aspect of the present invention there are provided improved hydrodesulfurization catalysts for reducing the content of sulfur in a residuum hydrocarbon feed stock during a hydrotreating process.

In still another aspect of the present invention there are provided improved hydrotreating catalysts which have the ability to reduce the content of sulfur in a residuum hydrocarbon feed stock during a hydrotreating process while simultaneously reducing the content of microcarbon residue (MCR) in the hydrotreated hydrocarbon fraction.

The present invention also provides a method of making a co-precipitated titania alumina support having a distinctive pore size distribution.

In yet another aspect of the present invention improved hydrotreating processes using supported catalyst compositions in accordance with the present invention are provided.

These and other aspects of the present invention are described in further details below.

The present invention generally provides catalyst compositions comprised of catalytically active metals or precursor metal compounds of metals of Groups <NUM>, <NUM> and <NUM> of The Periodic Table, and optionally phosphorous compounds, supported on a co-precipitated titania alumina support. In one embodiment of the invention, the support material used to prepare the catalyst of the invention comprises titania alumina containing <NUM> wt % or less titania, based on the total weight of the titania alumina composition. In another embodiment of the invention, the support material comprises less than <NUM> wt % titania, based on the total weight of the titania alumina composition. In still another embodiment of the invention the support material comprises from about <NUM> to about <NUM> wt % titania, based on the total weight of the titania alumina composition.

Titania alumina supports in accordance with the present invention generally comprise at least <NUM> wt % of a co-precipitated titania alumina as described herein. Preferably, the support material comprises at least <NUM> wt %, most preferably, greater than <NUM> wt % of titania alumina, said weight percent being based on the total weight percent of the support. The support material thus can "consist essentially of" the co-precipitated titania alumina as described herein. The phrase "consist essentially of" as used herein with regards to the composition of the support material is used herein to indicate that the support material may contain co-precipitated titania alumina and other components, provided that such other components do not materially affect or influence the catalytic properties of the final hydroconversion catalyst composition.

Advantageously, titania alumina supports in accordance with the present invention possess specific properties of surface area, pore volume and pore volume distribution.

For purposes of the present invention, pore volume may be measured using nitrogen porosimetry and mercury penetration porosimetry. Typically, pores having a diameter of <NUM>Å or less are measured using nitrogen porosimetry while pores having a diameter of greater than <NUM>Å are measured using mercury penetration porosimetry.

Pore volume as described herein is the volume of a liquid which is adsorbed into the pore structure of the sample at saturation vapor pressure, assuming that the adsorbed liquid has the same density as the bulk density of the liquid. The liquid used for nitrogen porosimetry is liquid nitrogen. The procedure for measuring pore volumes by nitrogen physisorption is as disclosed and described in<NPL>.

The mercury measurement of the pore volume and the pore size distribution of the alumina support material recited in the present invention may be obtained using any suitable mercury porosimeter capable of a pressure range of atmospheric pressure to about <NUM> bar, with a contact angle, θ = <NUM>°, and a mercury surface tension of <NUM> N/m at room temperature.

Surface area as defined herein is determined by BET surface area analysis. The BET method of measuring surface area has been described in detail by <NPL>.

The surface area of titania alumina supports of the invention ranges from about <NUM><NUM>/g to about <NUM><NUM>/g. In a preferred embodiment of the invention, the surface area of the titania alumina supports ranges from about <NUM><NUM>/g to about <NUM><NUM>/g.

Titania alumina supports of the invention have a total pore volume in the range from about <NUM> cc/g to about <NUM> cc/g. In a preferred embodiment of the invention, the total pore volume of the supports ranges from about <NUM> cc/g to about <NUM> cc/g.

Supports of the invention have a distinct pore volume distribution such that generally at least <NUM>% of the total pore volume have pores in a diameter between about <NUM>Å to 130Å, less than <NUM>% of the total pore volume have pores in a diameter above <NUM>Å, as determined by nitrogen porosimetry, and less than <NUM>% of the total pore volume having pores with a diameter above <NUM>Å, as determined by mercury penetration porosimetry.

In one embodiment of the invention, at least <NUM>% of the total pore volume of the co-precipitated titania alumina support have pores in a diameter between about <NUM>Å to <NUM>Å.

In another embodiment of the invention, from about <NUM> to about <NUM>% of the total pore volume of the co-precipitated titania alumina support have pores in a diameter above <NUM>Å.

Titania alumina supports in accordance with the present invention are prepared by co-precipitating aqueous alumina sulfate and an amount of titanyl sulfate sufficient to provide <NUM> wt % or less titania in a co-precipitated titania alumina powder. In accordance with this embodiment, alumina sulfate and titanyl sulfate are mixed with an aqueous stream containing sodium aluminate and held at a pH of about <NUM> to about <NUM> and a temperature of about <NUM> to about <NUM> to precipitate a titania alumina powder. The precipitated powder is filtered, washed with water and dried at a temperature ranging from about <NUM> to about <NUM> until a powder with a moisture content of <NUM> wt % to <NUM> wt %, as analyzed by a moisture analyzer at <NUM>, is achieved.

The dried titania alumina powder is thereafter treated with a peptizing agent to peptize the alumina powder. Suitable peptizing agents include but are not limited to, strong monobasic acids (e.g. nitric acid, hydrochloric acid and the like); organic acids (e.g. formic acid, acetic acid, propionic acid and the like); and aqueous bases ( e.g. ammonium hydroxide and the like). The peptized alumina powder is then extruded and dried at a temperature ranging from about <NUM> to about <NUM> for about <NUM> minutes to about <NUM> hours.

The dried extrudate is thereafter calcined at a temperature ranging from about <NUM> to <NUM> for about <NUM> hour to about <NUM> hour to obtain a final support having the required pore structure. Preferably, the dried extrudate is calcined at a temperature ranging from about <NUM> to about <NUM> for about <NUM> to about <NUM> hours to obtain the final support.

Extruded supports in accordance with the invention may have various geometric forms, such as cylinders, rings, and symmetric and/or asymmetric polylobes, for instance, tri- or quadrulobes. Nominal sizes of the extrudates may vary. The diameter usually ranges from about <NUM> to about <NUM>, and the length ranges from about <NUM> to about <NUM>. In one embodiment of the invention, the diameter ranges from about <NUM> to about <NUM> and the length ranges from about <NUM> to about <NUM>. As will be understood by one skilled in the catalyst arts, catalyst particles produced from the supports will have a similar size and shape as the support.

Catalysts in accordance with the invention are prepared by contacting the titania alumina supports with an aqueous solution of at least one catalytically active metal or precursor metal compound to uniformly distribute the desired metal on the support. Preferably, the metals and/or metal precursors are distributed uniformly throughout the pores of the support. In a preferred embodiment of the invention, the catalysts are prepared by impregnation of the catalyst supports to incipient wetness with an aqueous solution of the desired catalytically active metal or precursor compound.

Catalytically active metal and/or precursor metals compounds useful to prepare the catalyst composition of the invention, include, but are not limited to metals or compounds of metals selected from the group consisting of Group <NUM> of The Periodic Table, Group <NUM> of The Periodic Table, Group <NUM> of The Periodic Table and combinations thereof. Preferred Group <NUM> metals include, but are not limited to, molybdenum and tungsten. Preferred Groups <NUM> and <NUM> metals include, but are not limited to, cobalt and nickel.

In a preferred embodiment of the invention the combinations of nickel and molybdenum catalytic agents are preferred. In a more preferred embodiment of the invention, the resulting catalyst comprises Mo concentrations in the range of about <NUM> to about <NUM> wt % and Ni concentrations in the range of about <NUM> to about <NUM> wt %, said wt % being based on the total weight of the catalyst composition.

Suitable precursor metal compounds of Groups <NUM> and <NUM> metals include, but are not limited to, metallic salts such as nitrates, acetates and the like. Suitable precursor metal compounds of Group <NUM> metals include, but are not limited to, ammonium molybdate, molybdic acid, molybdenum trioxide, and the like.

Catalytically active metals contemplated for use with the supports of the present invention are preferably used in the form of oxides and/or sulfides of the metals. Preferably, the catalytically active metals are used in the form of oxides.

Catalyst compositions of the invention may also comprise a phosphorus component. In this case, the impregnating solution may also contain a phosphorus compound, e.g. phosphoric acid, phosphates, and the like, in addition to the desired catalytically active metals or precursor metal compounds. Concentrations in the range of up to about <NUM> wt % of phosphorous, calculated as elemental phosphorous, based on the weight of the total catalyst composition, are suitable for use in the catalysts of the invention. In a preferred embodiment of the invention, phosphorous concentrations in the range of about <NUM> to about <NUM> wt % of phosphorous, calculated as elemental phosphorous, based on the weight of the total catalyst composition, are useful in the catalysts of the invention.

Following treatment of the supports with aqueous solutions of the catalytically active metal/s or precursor compound/s, the catalyst are optionally dried at a temperature in the range of about <NUM> to about <NUM> for about <NUM> minutes to about <NUM> hours. The dried catalyst is thereafter calcined at a temperature and for a time sufficient to convert at least part, preferably all, of the metal components or precursors to the oxide form. In one embodiment of the invention, the catalyst is calcined at a temperature in the range of about <NUM> to about <NUM> for about <NUM> minutes to about <NUM> hours. In a preferred embodiment of the invention, the catalyst is calcined at a temperature ranging from about <NUM> to about <NUM> for about <NUM> hour to about <NUM> hours.

As will be clear to a person skilled in the art, there is a wide range of variations on the impregnating method used to support the catalytic active metals on the catalyst supports. It is possible to apply a plurality of impregnating steps or the impregnating solutions may contain one or more of the component or precursors to be deposited, or a portion thereof. Instead of impregnating techniques, dipping methods, spraying methods and the like can be used. In the case of multiple impregnations, dipping, and the like, drying and/or calcining may be carried out as between steps.

Catalysts according to the invention exhibit an increased catalytic activity and stability for hydrodesulfurization of residuum feedstock during a hydrotreating process. The catalytic process of the present invention is basically directed to residuum feedstocks as opposed to gas-oil feedstocks. Residua typically have greater than <NUM> ppm metals, whereas gas-oils nearly always have less than <NUM> ppm metals content. Thus, typical feedstocks useful in the present invention are "heavy oils" which include, but is not limited to, crude oil atmospheric distillation column bottoms (reduced crude oil or atmospheric column residuum), or vacuum distillation column bottoms (vacuum residua). The metals are believed to be present as organometallic compounds, possibly in porphyrin or chelate-type structures, but the concentrations of metals referred to herein is calculated as parts per million pure metal.

Catalysts of the invention provide an increased micro carbon residue (MCR) conversion during a hydrotreating process under hydrodesulfurization conditions. Consequently, the hydrodesulfurized hydrocarbon fraction obtained exhibits a reduced MCR content as compared to the MCR content of the starting residuum feedstock. Further, hydrotreated hydrocarbon fractions obtained using the catalyst of the invention unexpectedly exhibit a reduced MCR as compared to the MCR obtainable using hydrodesulfurization catalysts prepared from a support containing alumina alone or alumina in combination with other refractory inorganic materials such as silica and magnesia.

A hydrotreating process employing the catalyst compositions of this invention may be carried out under hydrodesulfurization process conditions in an apparatus whereby an intimate contact of the catalyst composition with said residuum containing feedstock and a free hydrogen containing gas is achieved, to produce a hydrocarbon-containing fraction having a reduced level of sulfur. In a preferred embodiment of the invention, the hydrotreating process is carried out using a fixed catalyst bed. The hydrotreating process can be carried out as a batch process or a continuous process using one or more fixed catalyst beds or a plurality of fixed bed reactors in parallel or in series.

Typical hydrodesulfurization process conditions useful in the invention include, but are not limited to, temperatures between about <NUM>° and about <NUM>, hydrogen pressures between about <NUM> and about <NUM> bar, H<NUM>:oil (or residuum hydrocarbon feedstock) ratios between about <NUM> and about <NUM> Nl/l (normal liters of hydrogen gas per liter of oil feed), and space velocities (hr-<NUM>) between about <NUM> and about <NUM>. In one embodiment of the invention, the operating conditions for a hydrocarbon feedstock desulfurization process include a reaction zone temperature of about <NUM> to about <NUM>, a hydrogen pressure of about <NUM> to about <NUM> bar, and a hydrogen feed rate of about <NUM> to about <NUM> normal liters per liter of oil feed.

To further illustrate the present invention and the advantages thereof, the following specific examples are given. The examples are given as specific illustrations of the claimed invention. It should be understood, however, that the invention is not intended to be limited to the specific details set forth in the Examples.

All parts and percentages in the examples as well as the remainder of the specification that refers to solid compositions or concentrations are by weight unless otherwise specified. However, all parts and percentages in the examples as well as the remainder of the specification referring to gas compositions are molar or by volume unless otherwise specified.

Further, any range of numbers recited in the specification or claims, such as that representing a particular set of properties, units of measure, conditions, physical states or percentages, is intended to literally incorporate expressly herein by reference or otherwise, any number falling within such range, including any subset of numbers within any range so recited. Unless otherwise specified or inconsistent with the disclosure, all ranges recited herein include the endpoints, including those that recite a range "between" two values.

Aluminum sulfate solution, titanyl sulfate solution and water were mixed to form <NUM> gallons of solution containing <NUM>% aluminum and <NUM>% titanium. This aluminum and titanyl sulfate solution was added to a strike tank containing a heel of <NUM> gallons of water at <NUM>. Simultaneously, an aqueous sodium aluminate solution containing <NUM>% aluminum was added to the strike tank to maintain the slurry pH at <NUM>. After all the aluminum and titanyl sulfate solution was added, the sodium aluminate solution flow continued to bring the pH of the slurry to <NUM>.

The slurry was filtered to separate out the titania alumina mix, which was subsequently washed on the filter belt to remove residual sodium and sulfate. The resulting filter cake was then spray dried to obtain a titania alumina powder containing <NUM> titania per <NUM> of titania alumina.

The titania alumina obtained in Example <NUM> (<NUM>) was mixed with <NUM> of concentrated nitric acid (<NUM>%) and <NUM> of water for <NUM> into a wet mix. This wet mix was then extruded using a four-inch extruder into asymmetrical quadrilobe shaped extrudates (nominal diameter <NUM>"). The extrudates were dried overnight at <NUM> before being calcined at <NUM> for <NUM> hr in <NUM> liter per minute of air flow.

The calcined extrudates had the following properties: surface area <NUM><NUM>/g; total pore volume <NUM> cc/g; the pore volume in pores having a diameter between <NUM> and <NUM>Å was <NUM>% of total pore volume; the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume; and the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume. The calcined titania alumina support contained <NUM> wt % titania.

A titania alumina catalyst support prepared as described in Example <NUM> was impregnated with an aqueous metal solution containing <NUM>% Mo, <NUM>% Ni and <NUM> % P. The aqueous solution was prepared using molybdenum trioxide, nickel carbonate and phosphoric acid in water. The wet extrudates were transferred into muffle trays and covered with perforated aluminum foil. The muffle trays were placed in an oven at <NUM> overnight.

The dried extrudates were then calcined at <NUM> for <NUM> in <NUM> liter per minute of air flow. The finished catalyst was designated Catalyst A and contained <NUM>% molybdenum, <NUM>% nickel, <NUM>% titanium, and <NUM>% phosphorous. Properties of the catalyst were as described in Table <NUM> below.

A titania alumina catalyst support prepared as described in Example <NUM> was impregnated with an aqueous metal solution containing <NUM>% Mo, <NUM>% Ni and <NUM> % P. The solution was prepared from molybdenum trioxide, nickel carbonate and phosphoric acid. The wet extrudates were transferred into muffle trays and covered with perforated aluminum foil. The muffle trays were placed in an oven at <NUM> overnight.

The dried extrudates were then calcined at <NUM> for <NUM> in <NUM> liter per minute of air flow. The finished catalyst was designated Catalyst B and contained <NUM>% molybdenum, <NUM>% nickel, <NUM>% titanium, and <NUM>% phosphorous. Properties of the catalyst were as described in Table <NUM> below.

A titania alumina powder was prepared as described in Example <NUM> with the exception that the strike tank contained a heel of <NUM> gallons of water. The final titania alumina powder contained <NUM> titania per <NUM> of titania alumina. A titania alumina support was prepared as decribed in Example <NUM> except that <NUM> of the powder was mixed with <NUM> of concentrated nitric acid and <NUM> of water for only <NUM> before extrusion, drying and calcination.

The calcined extrudates had the following properties: surface area <NUM><NUM>/g; total pore volume <NUM> cc/g; the pore volume in pores having a diameter between <NUM> and <NUM>Å was <NUM>% of total pore volume; the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume; and the pore volume in pore having a diameter above <NUM>Å was <NUM>% of total pore volume.

The titania alumina catalyst support was impregnated with an aqueous metal solution containing <NUM>% Mo, <NUM>% Ni and <NUM> % P and subsequently calcined at <NUM> for <NUM>. The finished catalyst was designated as Catalyst C and contained <NUM>% molybdenum, <NUM>% nickel, <NUM>% phosphorous and <NUM>% titanium. Properties of the catalyst were as described in Table <NUM> below.

An alumina powder was precipitated as described in Example <NUM> except that the aluminum sulfate solution was mixed with only water and not titanyl sulfate. The resulted alumina powder contained no detectable amount of titania.

A portion of the alumina powder (<NUM>) was mixed with <NUM> of concentrated nitric acid and <NUM> of water for <NUM> into a wet mix. The wet mix was then extruded using a four-inch extruder into asymmetrical quadrilobe shaped extrudates (nominal diameter <NUM>"). The extrudates were dried overnight at <NUM> before being calcined at <NUM> for <NUM> hr in <NUM> liter per minute of air flow.

The calcined extrudates had the following properties: surface area <NUM><NUM>/g; total pore volume <NUM> cc/g; the pore volume in pores having a diameter between <NUM> and <NUM>Å was <NUM>% of total pore volume; the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume; and the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume,. See Table <NUM> below.

The calcined extrudates were impregnated with an aqueous metal solution prepared from molybdenum trioxide, nickel carbonate and phosphoric acid to obtain a finished catalyst designative Comparative Catalyst <NUM> which contained <NUM>% molybdenum, <NUM>% nickel, and <NUM>% phosphorous with a less than detectable titanium content.

<NUM> of a precipitated alumina powder prepared as described in Comparative Example <NUM> above was mixed with <NUM> of concentrated nitric acid, <NUM> magnesium nitrate hexahydate and <NUM> of water for <NUM> into a wet mix. The wet mix was then extruded using a two-inch extruder into asymmetrical quadrilobe shaped extrudates (nominal diameter <NUM>"). The extrudates were dried at <NUM> for two hours before being calcined at <NUM> for <NUM> hr in <NUM> liter per minute of air flow to decompose magnesium nitrate into magnesia.

The calcined extrudates had the following properties: surface area <NUM><NUM>/g; total pore volume <NUM> cc/g; the pore volume in pores having a diameter between <NUM> and <NUM>Å was <NUM>% of total pore volume; the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume; and the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume. The calcined extrudate contained <NUM> wt % magnesia.

The calcined extrudates were impregnated with an aqueous metal solution prepared from molybdenum trioxide, nickel carbonate and phosphoric acid to obtain a finished catalyst designated Comparative Catalyst <NUM> which contained <NUM>% molybdenum and <NUM>% nickel, <NUM>% P and <NUM>% magnesium. Properties of the catalyst were as described in Table <NUM> below.

<NUM> of a precipitated alumina powder prepared as described in Comparative Example <NUM> above was mixed with <NUM> of concentrated nitric acid, <NUM> of fine titania particles, and <NUM> of water for <NUM> into a wet mix. The wet mix was extruded using a four-inch extruder into asymmetrical quadrilobe shaped extrudates. The extrudates were dried overnight at <NUM> before being calcined at <NUM> for <NUM> hr in <NUM> liter per minute of air flow. The calcined extrudates had the following properties: surface area <NUM><NUM>/g; total pore volume <NUM> cc/g; the pore volume in pores having a diameter between <NUM> and <NUM>Å was <NUM>% of total pore volume; the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume; and the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume. The percentage pore volume in pores between <NUM> and <NUM>Å, and above <NUM>Å was <NUM>, and <NUM>%, respectively. The calcined extrudates contained <NUM>% titania through comulling.

The calcined extrudates were impregnated and calcined at a temperature of <NUM> to provide a finished catalyst. The catalyst was designated as Comparative Catalyst <NUM> and contained <NUM>% molybdenum and <NUM>% nickel, <NUM>% titanium and <NUM>% phosphorous. Properties of the catalyst were as described in Table <NUM> below.

Titania alumina powder (<NUM>) precipitated as described in Example <NUM> with the exception that the heel water in strike tank was at <NUM> and containing <NUM> titania per <NUM> of titania and alumina. The titania alumina powder was mixed with <NUM> of concentrated nitric acid and <NUM> of water for <NUM> into a wet mix. This wet mix is then extruded using a four-inch extruder into asymmetrical quadrilobe shaped extrudates (nominal diameter <NUM>"). The extrudates were dried overnight at <NUM> before being calcined at <NUM> for <NUM> hr. The calcined extrudates had the following properties: surface area <NUM><NUM>/g; total pore volume <NUM> cc/g; the pore volume in pores having a diameter between <NUM> and <NUM>Å was <NUM>% of total pore volume; the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume; and the pore volume in pores having a diameter above <NUM>Å was <NUM>% of total pore volume. The percentage pore volume in pores less than <NUM>Å, between <NUM> and <NUM>Å, and above <NUM>Å were <NUM>%, <NUM>%, and <NUM>%, respectively.

An impregnation solution was prepared from <NUM> of ammonium heptamolybdate, <NUM> of nickel nitrate hexahydrate, <NUM> of concentrated ammonia solution (<NUM> %) and <NUM> water. <NUM> of the impregnation solution was sprayed onto the above base. The impregnated base was subsequently calcined at <NUM> for 1hour to provide the finished catalyst. The catalyst was designated as Comparative Catalyst <NUM> and contained <NUM>% molybdenum, <NUM>% nickel, <NUM>% titanium, with less than a detectable phosphorous content. Properties of the catalyst were as described in Table <NUM> below.

Catalysts of the invention were evaluated for hydrodesulfurization and MCR residue content. After being presulfided using dimethyl disulfide, Catalyst A, Catalyst B, Catalyst C and Comparative Catalyst <NUM>, Catalyst <NUM>, Catalyst <NUM>, and Catalyst <NUM> were contacted with Arabian Light residuum feed, which feed had been passed through a standard commercial demetallation catalyst in a continuous packed bed reactor. The overall LHSV and pressure used in processing the Arabian Light residuum through the catalyst system containing the demetallation catalyst and the respective demetallation catalyst was <NUM>-<NUM> and <NUM> psig. The temperature of the reactor containing the demetallation catalyst was increased from <NUM> to <NUM>, the temperature of the reactor containing Catalysts A through C and Comparative Catalysts <NUM> through <NUM> was increased from <NUM> to <NUM> throughout the test. The properties of the Arabian light residuum are shown in Table <NUM> below.

After the catalysts had been in service for <NUM> and reached <NUM>, the results for sulfur and hydrotreated residue MCR content were recorded in Table <NUM> below.

As shown in the Table <NUM> above, the residuum fraction processed using Catalyst A contained <NUM>% MCR and <NUM>% sulfur, and the residuum fraction processed using Catalyst B contained <NUM>% MCR and <NUM>% sulfur. In comparison, the residuum fraction processed using Comparative Catalyst <NUM> contained <NUM>% MCR and <NUM>% sulfur. This shows the benefit of incorporating titanium in the support via co precipitation.

The residuum fraction processed using Catalyst C contained <NUM>% MCR and <NUM>% sulfur. This showed the effect of a decreased pore volume percentage in the range of <NUM> to <NUM>Å for Catalyst C as compared to Catalyst A. The residuum fraction processed using Comparative Catalyst <NUM> and Comparative Catalyst <NUM> contained <NUM>% and <NUM>% MCR and <NUM> and <NUM>% sulfur, respectively. The results obtained from these two examples showed that the catalyst prepared from a support containing magnesium oxide or titania along with alumina made by co-mulling are less effective to reduce sulfur and MCR as compared to a catalyst prepared from the co-precipitated titania alumina support of the invention.

Claim 1:
A process for preparing a porous support material for supporting catalytically active metals suitable for the hydrodesulfurization of residuum hydrocarbon fractions under hydrotreating conditions, which process comprises:
a) preparing a co-precipitated titania alumina powder having less than <NUM> wt % titania, based on the total weight of the titania alumina powder, by co-precipitating aqueous alumina sulfate and titanyl sulfate;
b) peptizing the titania alumina powder;
c) extruding the titania alumina powder to form a titania alumina extrudate; and
d) calcining the extrudate at a temperature from <NUM> to <NUM> for <NUM> hour to <NUM> hours to obtain a titania alumina support having less than <NUM> wt % titania, based on the total weight of the support, wherein the support has a total pore volume from <NUM> to <NUM> cubic centimeters per gram, at least <NUM>% of the total pore volume in pores having a diameter of <NUM>Å to <NUM>Å, less than <NUM>% of the total pore volume in pores having a diameter above <NUM>Å, and less than <NUM>% of the total pore volume in pores having a diameter above <NUM>Å, wherein the pore volume of pores having a diameter of <NUM>Å or less is measured using nitrogen porosimetry using the nitrogen physisorption procedure described in D. H. Everett and F. S. Stone, Proceedings of the Tenth Symposium of the Colston Research Society, Bristol, England: Academic Press, March <NUM>, pp. <NUM>-<NUM>, and the pore volume of pores having a diameter of greater than <NUM>Å is measured using mercury penetration porosimetry using a mercury porosimeter at a pressure from atmospheric pressure to <NUM> bar, with a contact angle, θ = <NUM>° and a mercury surface tension of <NUM> N/m at <NUM>, and wherein the surface area of the support determined by BET surface area analysis is from <NUM><NUM>/g to <NUM><NUM>/g.