CERIUM-CONTAINING HYDRODESULFURIZATION CATALYSTS AND USES

Abstract

Catalysts for hydrodesulfurization (HDS), e.g., of fuel such DBT in a batch reactor, may include Ce-modified SBA CoMo-sulfided catalysts. The dispersion and catalytic activity of the active species (CoMoS.sub.2) may be influenced by the CeSi network in the support. The physico-chemical properties of such catalyststextural properties, crystallinity, metal oxide reducibility, and Mo phaseswere established, and BET surface area, X-ray diffraction (XRD), and Raman spectroscopy analysis showed up to 2.5 wt. % Ce incorporation into the Si-network in SBA-15. Up to 2.5 wt. % Ce loading on the SBA-15 support can provide large BET surface area and total pore volume. The metal oxide reducibility and MoS.sub.2 phase in the sulfided 2.5CeSCoMo catalyst indicate moderate metal-support interaction at 2.5Ce wt. %. Improved HDS activity was shown with Ce loading up to 2.5 wt. %, possibly due to Ce's facilitation of metal oxide reduction and dispersion of the MoS.sub.2 active phase via metal-support interaction.

Claims

1: A catalyst, comprising: an active component comprising Co and Mo, and suitable to catalyze hydrodesulfurization; and a support comprising at least 80 wt. %, based on the total weight of the support, mesoporous silica and cerium in a range of 0.1 to 10.0 wt. %.

2: The catalyst of claim 1, wherein the amount of cerium in support is in a range of from 1.5 to 4.5 wt. %.

3: The catalyst of claim 1, wherein the cerium is present as ceria.

4: The catalyst of claim 1, wherein the mesoporous silica has an average pore diameter in a range of from 3 to 20 nm.

5: The catalyst of claim 1, wherein the mesoporous silica is SBA-15.

6: The catalyst of claim 1, which is sulfided.

7: The catalyst of claim 1, having a BET surface area in a range of from 110 to 155 m.sup.2/g, and/or wherein the support has a BET surface area in a range of from 640 to 700 m.sup.2/g.

8: The catalyst of claim 1, having a microporous surface area in a range of from 8.5 to 20 m.sup.2/g, and/or wherein the support has a microporous surface area in a range of from 48.5 to 60 m.sup.2/g.

9: The catalyst of claim 1, having an external surface area in a range of from 100 to 145 m.sup.2/g, and/or wherein the support has an external surface area in a range of from 595 to 650 m.sup.2/g.

10: The catalyst of claim 1, having a microporous pore volume in a range of from 0.0055 to 0.0105 cm.sup.3/g, and/or wherein the support has a microporous pore volume in a range of from 0.015 to 0.0275 cm.sup.3/g.

11: The catalyst of claim 1, having a total pore volume in a range of from 0.305 to 0.375 cm.sup.3/g, and/or wherein the support has a total pore volume in a range of from 0.85 to 1.1 cm.sup.3/g.

12: The catalyst of claim 1, having an average pore size in a range of from 7.75 to 12.5 nm, and/or wherein the support has an average pore size in a range of from 6 to 8 nm.

13: A method of preparing a catalyst, the method comprising: preparing a support comprising at least 80 wt. %, based upon total support weight, mesoporous silica and cerium in a range of 0.1 to 10.0 wt. %; and impregnating the support with a solution comprising a molybdenum salt; impregnating the support with a solution comprising a cobalt salt; and heating to obtain a supported CoMo-catalyst suitable for hydrodesulfurization.

14: The method of claim 13, wherein the preparing comprises: mixing a tetraalkylorthosilicate, a surfactant, and a mineral acid, to obtain a silica sol; adding to the silica sol a cerium alkoxide in an amount in a range of from 0.1 to 10 wt. % relative to the tetraalkylorthosilicate, to obtain a cerium-containing silica sol; and heating the cerium-containing mesoporous silica sol at a temperature in a range of from 50 to 100 C.

15: The method of claim 14, wherein the tetraalkylorthosilicate comprises tetramethylorthosilicate, tetraethylorthosilicate, tetrapropylorthosilicate, and/or tetrabutylorthosilicate, wherein the surfactant is uncharged, wherein the mineral acid comprises hydrochloric acid, hydrobromic acid, sulfuric acid, and/or wherein the cerium alkoxide comprises cerium methoxide, cerium ethoxide, cerium propoxide, cerium isopropoxide, cerium sec-butoxide, and/or cerium tert-butoxide.

16: The method of claim 13, wherein the preparing comprises: mixing tetraethylorthosilicate, PEO-PPO-PPO triblock copolymer, and hydrochloric acid to form a solution; adding cerium isopropxide in an amount in the range of 0.1 to 5 wt. % relative to the tetraethylorthosilicate; and heating at a temperature in a range of from 50 to 100 C. to produce the support, wherein the support iscerium-modified mesoporous silica having an average pore diameter in a range of from 4 to 40 nm.

17: The method of claim 13, wherein the impregnating comprises: mixing a suspension of the cerium-modified silica sol in water with an aqueous solution containing equimolar amounts of cobalt (II) chloride and ammonium molybdate(VI).

18: The method of claim 13, wherein the heating comprises stirring at a temperature in a range of from 40 to 60 C. to evaporate solvent, and optionally, calcining to obtain the supported CoMo catalyst.

19: The method of claim 13, further comprising activating the supported CoMo catalyst by a method comprising: reducing the supported CoMo catalyst under a flow of hydrogen in an inert gas at a temperature in a range of 350 to 450 C., to obtain a reduced catalyst; and sulfiding the reduced catalyst, optionally with cyclohexane containing an amount of carbon disulfide in the range of 0.5 to 4 wt. % at a temperature in a range of 300 to 400 C. to produce an activated catalyst.

20: A hydrodesulfurization method, comprising: contacting a sulfur-containing hydrocarbon stream with an activated catalyst under hydrogen at a pressure in a range of 2 to 10 MPa and temperature in a range of 300 to 400 C. to thereby reduce a sulfur content of the hydrocarbon stream, wherein the activated catalyst comprises (i) an active component comprising Co and Mo, and suitable to catalyze hydrodesulfurization; and (ii) a support comprising at least 80 wt. %, based upon total support weight, mesoporous silica and cerium in a range of 0.1 to 10.0 wt. %, and the active catalyst is sulfided.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0034] FIG. 1A shows an N.sub.2 adsorption-desorption isotherm for Ce-modified supports within the scope of the invention;

[0035] FIG. 1B shows a pore volume-size distribution for Ce-modified supports within the scope of the invention;

[0036] FIG. 2A shows an N.sub.2 adsorption-desorption isotherm for Ce-modified supported CoMo catalysts within the scope of the invention;

[0037] FIG. 2B shows a pore volume-size distribution for Ce-modified supported CoMo catalysts within the scope of the invention;

[0038] FIG. 3A shows wide angle x-ray diffraction (XRD) patterns of supports: (a) SBA-15, i.e., undoped; (b) 1Ce-SBA-15; (c) 2.5Ce-SBA-15; (d) 5Ce-SBA-15; and (e) 10Ce-SBA-15;

[0039] FIG. 3B shows wide angle x-ray diffraction (XRD) patterns of supported, sulfided catalysts: (a) SCoMo, i.e., undoped; (b) 1CeSCoMo; (c) 2.5CeSCoMo; (d) 5CeSCoMo; and (e) 10CeSCoMo;

[0040] FIG. 4A shows Raman spectra of supports: (a) SBA-15, i.e., undoped; (b) 1Ce-SBA-15; (c) 2.5Ce-SBA-15; (d) 5Ce-SBA-15; and (e) 10Ce-SBA-15;

[0041] FIG. 4B shows Raman spectra of supported, sulfided catalysts: (a) SCoMo, i.e., undoped; (b) 1CeSCoMo; (c) 2.5CeSCoMo; (d) 5CeSCoMo; and (e) 10CeSCoMo;

[0042] FIG. 5A shows Fourier-transform infrared (FT-IR) spectra of supports: (a) SBA-15, i.e., undoped; (b) 1Ce-SBA-15; (c) 2.5Ce-SBA-15; (d) 5Ce-SBA-15; and (e) 10Ce-SBA-15;

[0043] FIG. 5B shows Fourier-transform infrared (FT-IR) spectra of supported, sulfided catalysts: (a) SCoMo, i.e., undoped; (b) 1CeSCoMo; (c) 2.5CeSCoMo; (d) 5CeSCoMo; and (e) 10CeSCoMo;

[0044] FIG. 6 shows H.sub.2-temperature-programmed reduction (TPR) of supported, sulfided catalysts: (a) SCoMo, i.e., undoped; (b) 1CeSCoMo; (c) 2.5CeSCoMo; (d) 5CeSCoMo; and (e) 10CeSCoMo;

[0045] FIG. 7A shows a field emissions scanning electron microscope (FE-SEM) image of a supported, sulfided 1CeSCoMo catalyst;

[0046] FIG. 7B shows an FE-SEM image of a supported, sulfided 2.5CeSCoMo catalyst;

[0047] FIG. 7C shows an FE-SEM image of a supported, sulfided 5CeSCoMo catalyst;

[0048] FIG. 7D shows an FE-SEM image of a supported, sulfided 10CeSCoMo catalyst;

[0049] FIG. 8A shows an FE-SEM image of a supported, sulfided SCoMo catalyst (undoped);

[0050] FIG. 8B shows an x-ray photoelectron spectroscopy (XPS) spectrum of supported, sulfided SCoMo catalyst (undoped) showing its Mo phases;

[0051] FIG. 9A shows an XPS spectrum of a supported, sulfided 1Ce-s-CoMo catalyst showing its Mo phases;

[0052] FIG. 9B shows an XPS spectrum of a supported, sulfided 2.5Ce-s-CoMo catalyst showing its Mo phases;

[0053] FIG. 9C shows an XPS spectrum of a supported, sulfided 5Ce-s-CoMo catalyst showing its Mo phases;

[0054] FIG. 9D shows an XPS spectrum of a 10Ce-s-CoMo sulfided catalysts showing its Mo phases;

[0055] FIG. 10A shows a hydrodesulfurization (HDS) performance plot of Ce-modified SBA-15 supported CoMo catalysts with varied Ce content, within the scope of the invention;

[0056] FIG. 10B shows the effect of process temperature on the HDS performance of 2.5CSCoMo; and

[0057] FIG. 11 shows the reaction mechanism of hydrodesulfurization (HDS) showing parallel reaction pathways.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] Catalysts within the scope of the invention may comprise: an active component comprising Co and Mo, i.e., at least 20, 30, 35, 40, 45, 50, 55, or 60% of either, with the balance of both being no more than 100% of the total active component, the active component and/or entire catalyst being suitable to catalyze hydrodesulfurization; a support comprising at least 80, 82.5, 85, 87.5, 90, 91, 92, 92.5, 93, 94, 95, 94.5, 96, 96.5, 97 wt. % or more, based upon total support weight, mesoporous silica and cerium in a range of 0.1 to 10.0 wt. %, or 1.5 to 4.5 wt. %, and/or at least 0.25, 0.33, 0.5, 0.67, 0.75, 0.85, 0.9, 1, 1.25, 1.33, 1.5, 1.67, 1.75, 1.8, 1.9, 2.0, 2.125, 2.25, 2.33, 2.4, or 2.5 wt. % and/or no more than 4.75, 4.67, 4.5, 4.33, 4.25, 4, 3.75, 3.67, 3.5, 3.33, 3.25, 3.125, 3, 2.85, 2.75, 2.67, or 2.5 wt. % Ce.

[0059] The cerium in the inventive supports may be present as ceria, i.e., a cerium oxide, though it will generally be introduced as a Ce (IV) salt, such as a cerium alkoxide. The mesoporous silica may have an average pore diameter in a range of from 2 to 40, 3 to 20, 3 to 15, 4 to 10, 5 to 9, or 6 to 8 nm, and/or the mesoporous silica may be SBA-15.

[0060] Inventive catalysts may be sulfided, though such sulfiding may be conducted immediately prior to or concurrently with implementation. Catalysts within the scope of the invention may have a BET surface area in a range of from 100 to 200, 110 to 155, 115 to 150, 120 to 145, 125 to 140, 130 to 138, or 135 to 137 m.sup.2/g, e.g., a range using any of these end points. The support may have a BET surface area in a range of from 500 to 1,000, 600 to 800, 640 to 700, 641 to 690, 642 to 680, 643 to 670, 644 to 660, 645 to 650, or 646 to 648 m.sup.2/g, e.g., a range using any of these end points.

[0061] Inventive catalysts may have a microporous surface area in a range of from 5 to 50, 8.5 to 20, 9 to 18, 10 to 16, 11 to 15, 12 to 13 m.sup.2/g (or at least 10, 11, 12, 13, 14 or 15 m.sup.2/g), e.g., a range using any of these end points. The support may have a microporous surface area in a range of from 20 to 100, 40 to 80, 48.5 to 60, 48.75 to 57.5, 49 to 55, 49.25 to 52.5, or 49.5 to 50 (or no more than 47, 45, 40, 35) m.sup.2/g, e.g., a range using any of these end points.

[0062] Inventive catalysts may have an external surface area in a range of from 50 to 200, 100 to 145, 105 to 140, 110 to 135, 115 to 130, 120 to 128, or 122 to 126 m.sup.2/g, e.g., a range using any of these end points. The support may have an external surface area in a range of from 500 to 1,000, 592 to 650, 593 to 640, 594 to 630, 595 to 620, 596 to 610, or 597 to 600 m.sup.2/g (or less than 590, 580, 570, 560, 550, 540, or 530 m.sup.2/g), e.g., a range using any of these end points.

[0063] Catalysts within the scope of the invention may have a microporous pore volume in a range of from 0.005 to 0.0200, 0.0055 to 0.0105, 0.0056 to 0.01, 0.0058 to 0.009, 0.0059 to 0.0085, 0.006 to 0.008, 0.0062 to 0.0075, 0.0064 to 0.007, or 0.0064 to 0.0068 cm.sup.3/g, e.g., a range using any of these end points. The support may have a microporous pore volume in a range of from 0.01 to 0.04, or 0.015 to 0.0275 (0.24) cm.sup.3/g, e.g., a range using any of these end points.

[0064] Inventive catalysts may have a total pore volume in a range of from 0.200 to 0.500, 0.305 to 0.375, 0.31 to 0.37, 0.315 to 0.365, 0.32 to 0.36, 0.325 to 0.355, 0.33 to 0.35, 0.335 to 0.345, or 0.339 to 0.342 cm.sup.3/g, e.g., a range using any of these end points. The support may have a total pore volume in a range of from 0.75 to 1.5, 0.85 to 1.1, 0.9 to 1.09, 0.95 to 1.08, 1.0 to 1.075, or 1.05 to 1.067 cm.sup.3/g, e.g., a range using any of these end points.

[0065] Catalysts within the scope of the invention may have an average pore size in a range of from 7 to 15, 7.75 to 12.5, 8 to 12, 8.25 to 11.5, 8.5 to 11, 8.75 to 10.5, 9 to 10.25, or 9.5 to 10 nm, e.g., a range using any of these end points. The support may have an average pore size in a range of from 5 to 10, 6 to 8, 6.05 to 7.9, 6.1 to 7.75, 6.15 to 7.5, 6.2 to 7.25, 6.25 to 7.125, 6.33 to 7, 6.4 to 6.9, 6.5 to 6.8, or 6.6 to 6.7 nm, e.g., a range using any of these end points.

[0066] Aspects of the invention include methods of preparing catalyst, the method comprising: preparing a support comprising at least 80, 82.5, 85, 87.5, 90, 91, 92, 92.5, 93, 94, 95, 94.5, 96, 96.5, 97 wt. % (or more), based upon total support weight, mesoporous silica and cerium in a range of 0.1 to 10.0 or 1.5 to 4.5 wt. %, and/or at least 0.25, 0.33, 0.5, 0.67, 0.75, 0.85, 0.9, 1, 1.25, 1.33, 1.5, 1.67, 1.75, 1.8, 1.9, 2.0, 2.125, 2.25, 2.33, 2.4, or 2.5 wt. % and/or no more than 4.75, 4.67, 4.5, 4.33, 4.25, 4, 3.75, 3.67, 3.5, 3.33, 3.25, 3.125, 3, 2.85, 2.75, 2.67, or 2.5 wt. % Ce; and impregnating the support (possibly wet, semi-formed, precipitating, and/or in suspension) with a solution comprising a molybdenum salt, preferably a molybdate; impregnating the support with a solution comprising a cobalt salt; and heating, e.g., raising the reaction temperature, drying, and/or calcining, to obtain a supported CoMo catalyst suitable for hydrodesulfurization, particularly suitable after reduction and/or sulfiding as described herein or otherwise known in the art.

[0067] The preparing may comprise: mixing a tetraalkylorthosilicate, a surfactantpreferably uncharged, and an acid, preferably a mineral acid, to obtain a silica sol; adding to the silica sol a cerium alkoxide, preferably in an amount in a range of from 0.1 to 10, 0.5 to 8, 1 to 6, 1.5 to 5, or 2 to 4.5 wt. % relative to the tetraalkylorthosilicate, to obtain a cerium-containing silica sol; and heating the cerium-containing mesoporous silica sol at a temperature in a range of from 50 to 100, 60 to 95, 70 to 90, or 75 to 85 C., and/or at least 55, 65, 75 C. and/or no more than 100, 97.5, 92.5, or 87.5 C. The ratio of cerium alkoxide, preferably cerium isopropoxide, to silicate may be selected such that the Ce atom % or ceria content, relative to Si atom % or silica content such that the molar ratio CeO.sub.2/SiO.sub.2 or the atomic ration Ce/Si is varied between 0.01-0.1, preferably 0.02-0.08, or 0.04-0.06.

[0068] The tetraalkylorthosilicate may comprise tetramethylorthosilicate, tetraethylorthosilicate, tetrapropylorthosilicate, and/or tetrabutylorthosilicate. The surfactant may comprise a poly-alkylene oxide or polymer of a mixture of alkylene oxides, e.g., ethylene oxide, propylene oxide, oxetane, 1,2-butylene oxide, 2,3-butylene oxide, and/or THF. The acid or mineral acid may comprise hydrochloric acid, hydrobromic acid, and/or sulfuric acid, but may also or alternatively comprise acetic acid, triflic acid, perchloric acid, formic acid, chloric acid, and/or nitric acid. The cerium alkoxide may comprise cerium methoxide, cerium ethoxide, cerium propoxide, cerium isopropoxide, cerium sec-butoxide, and/or cerium tert-butoxide. The percent of any of these species of the tetraalkylorthosilicate, alkylene oxide monomer, acid, and/or cerium alkoxide may be at least 75, 80, 85, 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % of a total weight of the respective genus. For example, the HCl may be 99 wt. % of the total acid weight used in the reaction. In copolymers for the surfactant, the total wt. % of components must be 100%, so the respective monomers may be 20, 25, 30, 33, 35, 40, 45, 50, 55, 60, 65, 67, or 70 wt. %, in addition to the percentages mentioned prior.

[0069] For example, the preparing may comprise: mixing tetraethylorthosilicate, PEO-PPO-PPO triblock copolymer, and hydrochloric acid to form a solution; adding cerium isopropxide in an amount in the range of 0.1 to 5, 0.5 to 4.5, 1 to 4, or 1.5 to 3 wt. % relative to the tetraethylorthosilicate; and heating at a temperature in a range of from 50 to 100 C. to produce the support, wherein the support is cerium-modified mesoporous silica having an average pore diameter in a range of, e.g., from 4 to 40, 4.5 to 30, 5 to 20, 5.5 to 15, or 6 to 10 nm.

[0070] The impregnating may comprise: mixing a suspension of the cerium-modified silica sol in water with an aqueous solution containing equimolar amounts of cobalt (II) chloride and/or other Co(II) salt described below, and ammonium molybdate(VI) and/or other Mo(IV) salt described below. The molar ratio of Co to Mo may also be, for example, in a range of 5:1 to 1:5, 4:1 to 1:4, 3:1 to 1:3, or 2:1 to 1:2.

[0071] The heating (of the catalyst reagent mixture) may comprise stirring and may be at a temperature in a range of from 40 to 60, 45 to 55, or 47.5 to 52.5 C. reaction temperature, e.g., for at least 15, 30, 45, 50, or 60 minutes and/or no more than 4, 3, 2, 1.5, or 1.2 hours, and optionally further heating to evaporate solvent, and optionally, calcining after the drying to obtain a supported CoMo catalyst within the scope of the invention. The further heating may be in the same temperature range as for the reaction, or, for example, at at least 60, 70, 80, 85, 90, 95, 100, 105, or 110 C., and the drying may be carried out for 4, 8, 12, 16, 20, 24, or 48 hours (or more). The calcining may be carried out at a temperature of at least 350, 400, 450, 500, 550, or 600 C., though generally no more than 1000, 800, 700, 600, or 550 C., and the calcining may be conducted for, e.g., 2, 3, 4, 5, or more hours. The supported catalyst material may be pressed into pellets, discs, or other shapes for transport and/or catalysis.

[0072] Inventive methods may further comprise activating the supported CoMo catalyst by a method comprising: reducing the supported CoMo catalyst under a flow of hydrogen (e.g., 5, 10, 15, 20, or 25 wt. %) in an inert gas, such as N.sub.2, He, and/or Ar, at a temperature in a range of 350 to 450, 375 to 425, or 385 to 415 C., to obtain a reduced catalyst; and sulfiding the reduced catalyst, optionally with a solution comprising cyclohexane, pet ether, decaline, gasoline, pentane, toluene, xylenes, o-diclorobenzene, and/or, containing, e.g., carbon disulfide in the range of 0.5 to 4, 1 to 3.5, or 2 to 3 wt. % at a temperature in a range of 300 to 400, 310 to 390, 320 to 380, 330 to 370, or 340 to 360 C. to produce an activated catalyst. Any known sulfiding method and/or agent suitable for CoMo catalysts may be used, for example H.sub.2S/H.sub.2, dimethyl disulfide, diethyl disulfide, and/or di-t-butyl polysulfide. The sulfiding may occur in situ during initial implementation of the catalyst in a hydrodesulfurization process or reaction.

[0073] Aspects of the invention provide hydrodesulfurization methods, comprising: contacting a sulfur-containing hydrocarbon stream, such as crude oil, fraction(s) of crude oil, or a refined product, such as gasoline, kerosene, or diesel, with an activated catalyst as described herein under hydrogen (H.sub.2) at a pressure in a range of, for example, 2 to 10, 3 to 9, 4 to 8, or 4.5 to 6 MPa (or even ambient pressure) and temperature in a range of 300 to 400 C. to thereby reduce a sulfur content of the hydrocarbon stream. The HDS temperature may be at least 300, 310, 315, 320, 325, 330, 333, 335, 340, 345, 350, 360, 365, 370, or 375 C. and/or no more than 390, 385, 380, 367, 365, 360, 355, or 350 C., or any of the lower endpoints may be the upper endpoint. The catalyst may be sufficient to remove at least 50, 60, 70, 75, 80, 85, 90, 91, 92, 92.5, 93, 94, 95, 96, 97, 97.5, 98, 99, 99.1, 99.5, or 99.9 wt. % of the sulfur in the original sulfur-containing petroleum stream after 2, 1.5, 1.25, 1, 0.75, 0.5, or 0.333 hours at 350 C. and 5 MPa H.sub.2, e.g., using no more than 50, 40, 33, 30, 25, 20, 15, 10, 5, 4, 3, 2, 1, 0.5, 0.1, 0.001, or 0.0001 wt. % catalyst relative to the weight of the original petroleum stream.

[0074] Aspects of the invention include modifying the properties of the SBA-15 support by incorporation of cerium and/or ceria, optionally using a cerium isopropoxide precursor into the support's framework, and the resultant effect on the sulfided-CoMo catalyst for HDS of DBT. Catalytic activity of such catalysts can be directly correlated to the amount of Ce and formation of effective CeOSi networks in the silica, e.g., SBA-15, support framework. The structural-activity of such catalysts can be established using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N.sub.2 physisorption, Fourier transform infrared (FTIR), Raman spectroscopy, temperature programmed reduction (TPR), and electron microscope (SEM).

[0075] Aspects of the invention provide Ce-modified SBA-15 mesoporous materials as metal (oxide) catalyst supports with different wt. % Ce loading prepared by hydrothermal synthesis. The supports may be impregnated with Mo as the active metal followed by Co as the promoter via excess wet impregnation. Up to around 2.5 wt. % Ce may be preferably incorporated into the framework of the support, such as alumina, zirconia, titania, and/or silica, esp. mesoporous silica, such as SBA-15. Larger wt. % Ce in the support may rather incorporated into the extra framework of the support, such as SBA-15. The 2.5CeSCoMo catalyst may have better active sites (MoS.sub.2 phases) for HDS. The extra framework of SiO.sub.2 is typically outside the SiOSi network. For example, the CeO.sub.2 is introduced via the hydrothermal approach to form SiOCe network (CeO.sub.2 here is in the framework of SiO.sub.2), but it was discovered that at high amounts of CeO.sub.2, SiOCe is not formed which indicates that CeO.sub.2 is deposited on the SBA-15 surface and is not in the framework. Ce loading up to 2.5 wt. % may facilitate the reduction of MoO.sub.3 and may prevent the formation of the inactive CoMoO.sub.4 phase, resulting in better Mo reduction and dispersion. The 2.5CeSCoMo may offer better HDS performance than unmodified (no Ce)SCoMo and other Ce-modified SBA-15 supported CoMo catalysts in the series. Furthermore, even at a lower process temperature (325 C.) for HDS, 2.5CeSCoMo and similar catalysts can perform better than SCoMo at 350 C., e.g., 1.1, 1.25, 1.5, 1.75, 1.8, 1.9, 2, 2.125, 2.5-fold, or greater rates. At process temperatures of 375 C., 99.27% DBT may be removed within an hour of reaction. Therefore, 2.5CeSCoMo catalysts and similarly modified/doped catalysts, may better efficiencies, potential for energy savings, and reduced refinery reaction times relative to undoped SCoMo catalysts, and other Ce-doped variants.

[0076] Inventive catalysts will generally contain less than 15, 10, 7.5, 5, 2.5, 2, 1, 0.1, 0.01, 0.001, or 0.0001 wt. % of the total carrier weight of polyoxometalate(s) of the formula (H.sub.hX.sub.xM.sub.mO.sub.y).sup.q, either individually or as a group, wherein X is P, Si, B, Ni, or Co, M is Mo, W, Ni, and/or Co, h is an integer from 0 to 12, x is an integer from 0 to 4, m is an integer 5, 6, 7, 8, 9, 10, 11, 12 and/or 18, y is an integer of 17 to 72 and q is an integer of 1 to 20.

[0077] The total catalyst and/or total carrier weight for inventive catalysts may have less than 2.5, 2, 1.5, 1, 0.75, 0.5, 0.1, 0.01, 0.001 wt. % or only detectable amounts of Cr.sub.2O.sub.3, ZrO.sub.2, V.sub.2O.sub.5, and/or NbOPO.sub.4, either individually or as a group. The amount of phosphorous in active catalysts according to the invention will generally constitute less than 10, 5, 2.5, 1, 0.5, 0.1, 0.01, 0.001, 0.0001 wt. % or only detectable amounts, relative to the active catalyst weight and/or total catalyst weight.

[0078] While the undoped support may have pores and/or an average pore size greater than 50 nm in diameter, such pores and/or an average pore size will generally be greater than 2 and less than 50 nm in diameter, such as more than 3, 4, 5, 6, 7, 8, 9, or 10 nm, and/or less than 45, 40, 35, 30, 25, 20, 17.5, 15, 12.5, 10, or 9 nm. In some cases, separately or in addition, the support may have pores and/or an average pore size no more than 2 nm in diameter, e.g., less that 2, 1.5, 1, 0.9, 0.8, 0.75, 0.6, 0.5, 0.25, or 0.1 nm.

EXAMPLES

[0079] MATERIALS: Ceric ammonium nitrate, ACS reagent grade, was procured from Riedel-de Haen AG, USA. Acetylacetone, dimethoxyethane, isopropanol, sodium hydride and sodium borohydride were procured from Fluka Chemie AG, Buchs, Switzerland. Tetraethyl-orthosilicate (TEOS), pluronic P123, i.e., a symmetric triblock copolymer comprising poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) in an alternating linear fashion, PEO-PPO-PEO, with a molar mass (Mn) of 5,800 g/mol, anhydrous cobalt chloride (98%), DBT (98%), and dodecane were purchased from Sigma-Aldrich. Ammonium molybdate (VI) tetrahydrate (99%) was purchased from ACROS organics. Deionized water was generated in-house using a Thermo Scientific Barnstead NANOPURE filter after distillation with a Labstrong FiSTREEM II Glass Still distiller.

[0080] SYNTHESIS OF SBA-15 AND CE-MODIFIED SBA-15: Mesoporous SBA-15 and series of Ce-SBA-15 (1 to 10 wt. %) catalysts were synthesized, with slight modification (e.g., the addition of cerium isopropoxide to the acidic solution mixture of TEOS and Pluronic P123, in the synthesis of SBA-15, there was no addition of cerium isopropoxide), following the procedure described in Science 1998, 279(5350), 548-552, which is incorporated in its entirety herein by reference. The SBA-15 was prepared as described in Appl. Catal. B Environ. 2017, 203, 428-441, which is incorporated in its entirety herein by reference. The series of xCe-SBA-15 supports (where x represents Ce wt. %) were prepared by following the same SBA-15 procedure, except that equivalent amount of cerium isopropoxide was added to the acidic solution mixture of tetraethyl-orthosilicate and Pluronic 123 after stirring for 1.5 hours. The cerium isopropoxide was synthesized as reported in Chem. Eng. Res. Des. 2018, 132, 479-491, which is incorporated in its entirety herein by reference.

[0081] PREPARATION OF CATALYSTS: The SBA-15 and xCe-SBA-15 supported CoMo catalysts were prepared by impregnation of the Co and Mo active phase on the supports via excess wet solution method in deionized water. The method comprises stirring equivalent amounts of CoCl.sub.2 and ammonium molybdate (VI) tetrahydrate at 50 C. for 1 hour, followed by adding an already dispersed solution of SBA-15 or xCe-SBA-15 in deionized water. The mixture, comprising the support and active catalyst metal, was further stirred until nearly all the deionized water is evaporated. The remaining solution was later dried in an oven at 80 C. for overnight, and subsequently calcined at 550 C. for 5 hours at ramping of 10 C./minute.

[0082] A description of the supports and catalysts synthesized is provided below in Table 1.

TABLE-US-00001 TABLE 1 Supports and catalysts description. Code Description SBA-15 Mesoporous silica xCe-SBA-15 Ce modified SBA-15 with xCe wt. % loading SCoMo SBA-15 impregnated with Co and Mo XCeSCoMo xCe-SBA-15 impregnated with Co and Mo

[0083] As an alternative to CoCl.sub.2, or a supplement to it, a variety of generally water soluble cobalt salts may be used, such as sulfates, halides, (bi)carbonates, (hydrogen)phosphates, hydroxides, perchlorates, borates, nitrates, oxalates, citrates, acetates, amino-acid salts, organic dicarboxylates, and/or (thio)cyanates, including (NH.sub.4).sub.2Co(SO.sub.4).sub.2, CoBr.sub.2, CoI.sub.2, CoCO.sub.3, CoF.sub.2, Co(OH).sub.2, Co(NO.sub.3).sub.2, CoC.sub.2O.sub.4, Co(ClO.sub.4).sub.2, Co.sub.3(PO.sub.4).sub.2, CoSO.sub.4, Co(BF.sub.4).sub.2, Co(SCN).sub.2, and/or hydrates of these, along with mixtures of these. In certain circumstances, Co(III) salts may be used, either as together with Co(II) salt(s) or separately, including, for example, [Co(NH.sub.3).sub.6]Cl.sub.3, [Co(NH.sub.3).sub.5C]Cl.sub.2, CoF.sub.3, Co(OH).sub.3, or the like. As an alternative to (NH.sub.4).sub.2MoO.sub.4 and/or (NH.sub.4).sub.6Mo.sub.7O.sub.24, or a supplement to it, a variety of generally water soluble cobalt salts may be used, including molybdates and other molybdenum oxides and sulfides, particularly those forming Mo(VI), such as Na.sub.2MoO.sub.4, K.sub.2MoO.sub.4, Li.sub.2MoO.sub.4, Cs.sub.2MoO.sub.4, MgMoO.sub.4, CaMoO.sub.4, MoS.sub.2, MoCl.sub.5, MoCl.sub.3, MoO.sub.2Cl.sub.2, Na.sub.2MoS.sub.4, Ag.sub.2MoO.sub.4, BaMoO.sub.4, SrMoO.sub.4, Al.sub.2(MoO.sub.4).sub.3 and/or MoO.sub.3, and/or hydrates and/or mixtures of these.

[0084] The surfactant used in the mixture for making the support may be a polyalkylene oxide, including PEO, PPO, and/or PBU, such as Pluronic-123. Such surfactants may have an Mn1,100, 1,900, 2,000, 2,700, 2,800, 3,300, or 5,800. In the case of Pluronic-123, the idealized structure may be HOPEO.sub.n-PPO.sub.mPEO.sub.pH, wherein n and/or p are in a range of 15 to 25, 18 to 22, or 20, and/or m is in a range of 60 to 80, 64 to 76, 68 to 72, or 70. Exemplary SBA-15 supports may have an average particle size <150 m; an average pore volume in a range of from 0.5 to 0.7, 0.7 to 0.9, or 0.8 to 1.00 cm.sup.3/g; average pore size of 4, 6, or 8 nm; and/or a surface area in a range of from 450 to 550, 70050, or 750 to 850 m.sup.2/g.

[0085] Characterization of Supported Catalysts

[0086] The textural properties such as surface area, pore size and pore volume of the inventive catalysts were recorded on a Micromeritics ASAP 2020 using N.sub.2 adsorption-desorption isotherms at 77 K. Prior to measurement, the catalysts were vacuum-degassed at 250 C. for 3 hour to remove impurities. The Brunauer, Emmett, and Teller (BET) method was used to calculate the surface area, and absorption branch of Barrett, Joyner, and Halenda (BJH) method was applied to calculate the pore size and pore volume of the catalysts.

[0087] X-RAY DIFFRACTION (XRD): The crystallinity of the supports and catalysts was determined by recording their XRD patterns between 10 to 90 20 using Rigaku Ultima IV X-ray diffractometer. The operation was performed at 40 kV and 40 mA with a scanning speed of 10/minute.

[0088] RAMAN SPECTROSCOPY: Raman spectra of the supports and catalysts were obtained using a HORIBA iHR320 with CCD detector Raman spectroscope. The spectroscope was operated at laser wavelength of 532 nm at room temperature.

[0089] FOURIER TRANSFORM INFRARED (FTIR) SPECTROSCOPY: The FT-IR spectra of inventive supports and catalysts were recorded on a Thermo Scientific Nicolet 6,700 FT-IR spectrometer over a wavenumber range of 400 to 4000 cm.sup.1. Samples were prepared by mixing 1% support/catalyst with KBr, pelletizing the crushed powder using an Atlas automatic press (8 ton) into a thin disc, and inserting the disc into the FTIR cell for the analysis.

[0090] TEMPERATURE-PROGRAMMED REDUCTION (H.sub.2-TPR): The catalyst oxides' H.sub.2-reducibility was determined by H.sub.2-TPR with hydrogen as a probe molecule. The H.sub.2-TPR analysis was carried out using an AutoChem II-2920 Micromeritics Chemisorption analyzer. Roughly 50 mg of respective calcined catalysts were heated to 500 C. for one (1) hour under the flow of high purity helium in order to remove impurities. After cooling to ambient temperature under the same helium flow, the gas flow was switched to 10% H.sub.2 in helium (at steady flow of 20 mL/min) and the temperature was raised to 1000 C. at 10 C./minute ramping. Under these conditions, the amount of H.sub.2 consumed at the reducible temperatures was recorded.

[0091] FIELD EMISSION SCANNING ELECTRON MICROSCOPY (FE-SEM): The morphology of sulfided catalysts were recorded on a FE-SEM instrument (TESCAN, LYRA 3) using a secondary electron (SE) imaging mode and a back scattered electron (BSE) imaging mode at an accelerating voltage of 20 kV.

[0092] X-RAY PHOTOELECTRON SPECTROSCOPY (XPS): The bonding states and binding energy of the sulfided catalysts were determined by XPS using a PHI 5000 Versa Probe II spectroscope (ULVAC-PHI Inc.). Disc-shaped pellets of samples of the catalysts were first subjected to high vacuum before the XPS analysis.

[0093] X-RAY FLUORESCENCE (XRF): The elemental composition of the sulfided catalysts were analyzed by XRF using a Bruker M4 TORNADO Micro-XRF equipped with 30 mm.sup.2 Xflash SD detector.

[0094] CATALYSTS PRESULFIDATION AND PERFORMANCE EVALUATION: The metal oxides in the catalysts, i.e., Co and Mo oxides, were reduced at 400 C. for 2 hours under a flow of 5% H.sub.2/He in a quartz tubular furnace. After the 2 hours, the furnace temperature was brought down to 350 C. and 2 wt. % CS.sub.2 in cyclohexane was flowed through the tubular furnace at the rate of 0.5 mL/min for 5 hours in order to presulfide the reduced metals. The presulfided catalysts were then pelletized to 300 to 500 microns.

[0095] The HDS performance of the presulfided catalysts was evaluated in a high-pressure Parr 4590 Micro Bench Top Reactor operated at a pressure of 5 MPa H.sub.2 and 100 rpm stirring rate. Approximately 15 mg of the presulfided catalyst was added to 15 mL of model fuel containing 1000 ppm DBT in dodecane. The model reaction was performed for 4 hours after the reaction conditions stabilized, and product was sampled at hourly intervals.

[0096] Generally, the surface area and porosity of catalysts are important for elucidating the textural properties of the material. The textural properties of the SBA-15, Ce-modified SBA-15 supports, and the supported CoMo catalysts are presented in Table 2, below.

TABLE-US-00002 TABLE 2 Textural properties of supports and catalysts. BET Microporous External Microporous Total Average Surface surface surface pore pore pore Supports area area area volume volume size catalysts (m.sup.2/g) (m.sup.2/g) (m.sup.2/g) (cm.sup.3/g) (cm.sup.3/g) (nm) SBA-15 639.1 48.3 590.7 0.023 1.07 6.71 1Ce-SBA-15 607.6 38.1 569.4 0.018 1.01 6.73 2.5Ce-SBA-15 647.1 49.7 597.4 0.024 1.06 6.65 5Ce-SBA-15 575.4 47.5 527.9 0.023 0.95 6.68 10Ce-SBA-15 532.2 27.0 505.2 0.013 0.89 6.77 SCoMo 157.7 10.4 147.3 0.0051 0.30 7.61 1CeSCoMo 117.7 8.9 108.8 0.0045 0.32 10.93 2.5CeSCoMo 136.8 12.1 124.0 0.0066 0.34 9.85 5CeSCoMo 124.9 17.2 107.7 0.0089 0.29 9.34 10CeSCoMo 131.8 17.4 114.4 0.0090 0.32 9.61

[0097] The BET surface area of the supports was observed to decrease continuously as the Ce wt. % loading increases except in 2.5Ce-SBA-15, in which the BET surface area increases by up to 8 m.sup.2/g. Possibly because low amounts of Ce ions in the sol-solution of the SBA-15 ease the incorporation of Ce into the SBA-15 framework. At high Ce ion concentrations in SBA-15 sol-solution, extra framework cerium oxide most probably forms, which could affect the surface area and pore volume of the Ce-modified SBA-15 synthesized, in addition to its catalytic properties as observed in 5Ce-SBA-15 and 10Ce-SBA-15 supports. The N.sub.2 adsorption-desorption isotherms and the pore volume-size distribution of the supports presented in FIGS. 1A and B appear to confirm this hypothesis.

[0098] The slight decrease in the BET surface area of 1Ce-SBA-15 may imply that a 1 wt. % Ce loading provides insufficient Ce ion concentration to fill into the framework of the SBA-15 via ion-exchange of the Ce.sup.3+/Ce.sup.4+ with Si.sup.4+ of the SBA-15 during the hydrolysis and condensation process. The addition of Co and Mo to the supports by the impregnation approach exemplified herein and further sulfidation of the reduced active metals, however, gave decreased surface area and pore volume in all the catalysts due to the obstruction of some surface and void spaces. The 2.5CeSCoMo catalyst showed higher surface area (136.8 m.sup.2/g) and total pore volume (0.34 cm.sup.3/g) than all the other Ce-modified SBA-15 supported CoMo catalysts (FIGS. 2A and B), thus putting the catalyst in a better position for catalytic performance.

[0099] The X-ray diffraction (XRD) patterns of the supports and catalysts were performed to determine the crystallinity and dispersion of the sulfided active metals catalysts on the SBA-15 supports. FIG. 3A to E show the XRD patterns of all the supports prepared as described above, and FIG. 3F to J show the XRD spectra of sulfided, supported catalysts. At 2.5 Ce wt. % loading, excellent metal-support interaction was achieved, however, at ceria loading of 5 and 10 wt. %, the metal-support interaction may be large enough to deter the reduction of the Mo species.

[0100] Raman spectroscopy is a sensitive tool for unraveling the molecular structure of Mo compounds. The Raman spectra of the supports are seen in FIG. 4A (a) to (e), and the Raman spectra of the supports and sulfided catalysts are seen in FIG. 4B (f) to (j). As discussed below, based on the Raman results for the sulfided, supported catalysts prepared as described herein, it may be inferred that Ce loading up to 2.5 wt. % in the catalyst supports increased the metal-support interaction to an optimum level that enhanced the molybdenum dispersion on the support, thereby easing Mo reduction and sulfidation.

[0101] Fourier transform infrared (FT-IR) spectroscopy can provide information about the functional groups present in the supports and catalysts prepared as described herein, often complementing the Raman spectroscopy. The FT-IR spectra of the supports are shown in FIG. 5A (a) to (e), and the FT-IR spectra of the supported, sulfided catalysts are presented in FIG. 5B (f) to (j). As discussed below the red shift and diminished intensity of the broad band at 1240 cm.sup.1 indicates that SiOSi bond is being substituted with SiOCe bond as the ceria loading increases, while the decrease or disappearance of the OH stretching and bending vibration indicates filling of the free voids in the mesoporous supports by Co and Mo metals.

[0102] Temperature-programmed reduction (H.sub.2-TPR) is a robust technique for studying the reducing pattern of metal oxides samples. H.sub.2-TPR was performed on the inventive catalysts to gain some insight into the reducing behavior of the Ce-modified SBA-15 supported CoMo catalysts in their oxides form. The H.sub.2-TPR profiles of the catalysts are shown in FIG. 6, and, as discussed in more detail below, the H.sub.2-TPR results suggest that ceria incorporation into SBA-15 increases the mobility and activity of surface oxygen species and that ceria incorporation aids the interaction of Co and Mo species.

[0103] Field emission scanning electron microscopy (FE-SEM) was used for morphological examination of the SCoMo (FIG. 8A) and Ce-modified SBA-15 supported CoMo catalysts (FIG. 7A to D). The FE-SEM images show hexagonally prismic and/or cylindrical short nano-rods with slight curvature, consistent with reported structures of mesoporous SBA-15. The hexagonally prismic and/or cylindrical nanorods may have average lengths in of at least 500, 600, 700, 750, 1000, 1250, 1500, 1750 nm and/or no more than 5000, 4500, 4000, 3500, 3000, 2500, 2250, 2000, and/or 1750 nm. The morphology of inventive catalysts may be that of a composite of parallel nanorods of the previously discussed lengths and cross-sectional diameters in a range of from, e.g., 0.2 to 5, 0.3 to 4, 0.4 to 3, 0.5 to 2, or 0.6 to 1 nm (these endpoints being interchangeable), agglomerated in parallel to form a composite, thicker nanorod. The length of the nano-rods was observed to increase with Ce wt. % loading on the support, indicating modified mesoporous SBA-15 properties. The particle density on the surface of the inventive catalysts due to the Co and Mo loading indicates a gradual increase in the particle density from SCoMo to 2.5CeSCoMo. However, the particle density of the catalyst surfaces decreases at higher Ce loading, i.e., 5CeSCoMo and 10CeSCoMo, which may be correlated to increased metal-support interaction from ceria loading on the SBA-15. With around 2.5 wt. % Ce, e.g., at least 0.5, 0.75, 1, 1.25, 1.5, 1.75, 1.8, 1.9, 2, 2.1, 2.125, 2.2, 2.25, 2.33, 2.40, 2.5, or 2.6 wt. % Ce, and/or up to 4.75, 4.5, 4.25, 4, 3.75, 3.5, 3.33, 3.25, 3.125, 3.1, 3.05, 3, 2.95, 2.9, 2.85, 2.8, 2.75, 2.7, 2.67, 2.625, or 2.6 wt. % Ce, the Co and Mo interaction with the support appears to be at its optimum. At around 2.5 wt. % Ce, optimum CoMo metal dispersion on the Ce-modified support. Higher Ce loading, i.e., over 5+0.5, 1, or 1.5 wt. % Ce, appears to result in stronger metal-support interactions, apparently causing aggregation of the metal crystallites and low particle density, a result which would corroborate the XRD and H.sub.2-TPR results.

[0104] X-ray photoelectron spectroscopy (XPS) spectra show various binding states and binding energies of the Mo phases in the sulfided catalysts as presented in FIG. 8B and FIG. 9A to D. Though XPS is a surface analysis technique, it is often utilized to gain some insight in to the degree of sulfidation of the Mo species. As shown in Table Si below, three Mo species, distinguished by their unique binding energies, were mapped out from the deconvoluted XPS spectra.

TABLE-US-00003 TABLE S1 Different types of Mo phases in the catalysts Percent molybdenum in various oxidation states Catalysts Mo.sup.4+ (3d.sub.5/2) Mo.sup.6+ (3d.sub.5/2) Mo.sup.6+ (3d.sub.3/2) Binding energy 229.5 eV 231.8 eV 235.6 eV SCoMo 11.51 58.24 30.25 1CeSCoMo 20.86 30.16 48.98 2.5CeSCoMo 33.44 44.59 21.97 5CeSCoMo 40.92 59.08 10CeSCoMo 44.16 55.84

[0105] Identification of peaks in the XPS spectra indicate MoS.sub.2, with MoS.sub.2, with Mo.sup.4+ (3d.sub.5/2), and MoO.sub.3 with Mo.sup.6+ (3d.sub.5/2) and Mo.sup.6+ (3d.sub.3/2), species in the developed catalysts. However, the atomic percent of the Mo species was found to vary among the SCoMo and xCeSCoMo catalysts. The XPS peak characteristic of MoS.sub.2 increased from SCoMo (undoped) up to 2.5CeSCoMo then became undetectable in higher ceria loaded catalysts. This may further explain the ease of Mo sulfidation when ceria (up to around 2.5 wt. %) is incorporated into the SBA-15 framework. The only observed XPS peak in 5CeSCoMo and 10CeSCoMo is the MoO.sub.3 peak, which is in agreement with the XRD result obtained for the catalysts.

[0106] The constituent elements in the catalysts prepared as described herein were evaluated using a non-destructive X-ray fluorescence (XRF) technique, and summarized in Table 3, below.

TABLE-US-00004 TABLE 3 Elemental composition by XRF. Elements (%) Catalysts Si O Ce Co Mo SCoMo 17.45 74.38 0.28 7.89 1CeSCoMo 17.47 75.25 0.19 0.27 6.82 2.5CeSCoMo 17.51 72.82 0.45 0.32 8.90 5CeSCoMo 15.26 76.22 0.79 0.32 7.41 10CeSCoMo 16.16 73.96 1.63 0.34 7.91

[0107] The presence of silicon and oxygen elements in large percent confirms the formation of (SBA-15) silica support in all the catalysts. The modification of the (SBA-15) silica with Ce was further verified by the increasing weight percent of elemental Ce determined in the synthesized catalysts. The disparity in the recorded weight percent, i.e., 0.19, 0.45, 0.79, and 1.63 wt. % Ce, and the theoretical weight percent, i.e., 1, 2.5, 5, and 10 wt. % Ce, may have resulted from addition of the Co and Mo metals after support modification and/or from inaccuracies in the calibration of the determination method. On average, Co appears to have been well incorporated in all the supports, and in nearly the same amount as determined by XRF. Unlike Ce, the Mo weight percent across all the catalysts, as determined by XRF was found to vary significantly. The 2.5CeSCoMo catalyst indicates the highest Mo loading of 8.90 wt. % by XRF, which is 1.01 wt. % more than the Mo loading in SCoMo, and likely due to the larger surface area of the 2.5CeSCoMo catalyst.

[0108] The 1CeSCoMo indicates an Mo loading of 6.82 wt. % by XRF, even lower than 5CeSCoMo and 10CeSCoMo. A possible reason for this observation is that, even though 1CeSCoMo has larger surface area than 5CeSCoMo and 10CeSCoMo, the metal-support interaction in the 5Ce and 10Ce catalysts may be more pronounced, as observed by XRD, H.sub.2-TPR, and Raman. This increased metal-support interaction in the 5Ce and 10Ce catalysts could attracts more Mo metal than in 1CeSCoMo catalyst.

[0109] PRESULFIDATION CATALYSTS AND PERFORMANCE EVALUATION: The performance of the inventive catalysts, evaluated by percent dibenzothiophene (DBT) removal, is shown in Table 4, below.

TABLE-US-00005 TABLE 4 Catalyst performance results: Percent DBT removal. (Process conditions: 350 C.; 5 MPa; DBT = 1000 ppm; reaction time = 4 h). Percent DBT removal (%) Catalysts 1 h 2 h 3 h 4 h SCoMo 32.43 49.65 65.49 82.50 1CeSCoMo 64.89 70.71 93.46 97.93 2.5CeSCoMo 73.54 90.42 94.6 98.14 5CeSCoMo 29.40 47.94 64.94 88.9 10CeSCoMo 36.11 50.72 83.86 89.85

[0110] Under the model reaction conditions, the hydrodesulfurization (HDS) of DBT followed a reaction performance pattern hypothesized based on the analytical determinations about the inventive catalysts. Within the first one hour of reaction after achieving the stabilized reaction conditions, SCoMo removed up to 32.43% sulfur from a 1000 ppm DBT solution of dodecane, as seen in FIG. 10A. This percent removal was almost doubled (64.89%) when 1CeSCoMo was used as the HDS catalyst. The performance further increased by 8.65% when 2.5CeSCoMo was applied as the HDS catalyst. However, reduction in catalytic activity was observed when 5CeSCoMo and 10CeSCoMo catalysts were used in the HDS reaction. The observed conversion trends continued for 4 hours in all the catalysts, and by the end of the 4th hour, 98.14% sulfur had already been removed from the 1000 ppm DBT in HDS using the 2.5CeSCoMo catalyst. The percent sulfur removal by catalyst followed the trend: 5CeSCoMo<10CeSCoMo<SCoMo<1CeSCoMo<2.5CeSCoMo.

[0111] A further study was carried out on the effect of temperature on the HDS reaction for the best performing catalyst in the study above, i.e., 2.5CeSCoMo. Results of the temperature study presented below in Table S2, as well as in FIG. 10B.

TABLE-US-00006 TABLE S2 Effect of process temperature for 2.5CeSCoMo (5 MPa; DBT = 1000 ppm; reaction time = 4 h). Percent sulfur removal (%) at different temperature Temperature ( C.) 1 h 2 h 3 h 4 h 325 64.58 75.01 87.23 95.46 350 73.54 90.42 94.6 98.14 375 99.27 100 100 100

[0112] As seen in Table S2, 64.58% of sulfur was removed after the first 1 hour of the HDS reaction at a process temperature of 325 C. This 2.5CeSCoMo removal rate is twice the activity of SCoMo at a process temperature of 350 C. Advantageously, the HDS reaction can be studied and/or conducted successfully at lower process temperatures by incorporating 2.5 wt. % Ce into the mesoporous silica, such as SBA-15, which could offer refineries substantial energy savings. At a (higher) process temperature of 375 C. using 2.5CeSCoMo in HDS, nearly complete sulfur removal (99.27%) was achieved within the first one hour of reaction. The rapid efficacy using a 2.5CeSCoMo catalyst in the HDS of DBT, could likewise offer energy savings due to decreased reaction times relative to SCoMo in HDS.

[0113] The mechanism of HDS on DBT has been reported to occur via two pathways as shown in FIG. 11: (1) one-step, direct desulfurization (DDS) involving direct CS bond cleavage to form biphenyl (BP); and (2) hydrogenation (HYD) of phenyl ring to cyclohexyl in two to three steps, then CS bond cleavage to form cyclohexyl benzene (CHB). Both of these pathways, (1) and (2), are accompanied by the release of H.sub.2S.

[0114] A detailed analysis of the product distribution after 1 hour of the model HDS reaction is summarized below in Table 5.

TABLE-US-00007 TABLE 5 Catalyst performance results: Product Distribution (%) after 1 h. (Process conditions: 350 C.; 5 MPa; DBT = 1000 ppm). Product distribution (%) Catalysts CPB CHB BP THDBT BP/CHB SCoMo 5.54 94.46 17.05 1CeSCoMo 13.82 86.18 6.24 2.5CeSCoMo 15.53 84.47 5.44 5CeSCoMo 9.68 87.90 2.42 9.08 10CeSCoMo 6.14 93.84 15.28

[0115] In each of the studied catalysts, diphenyl (BP) stands out as the significantly largest product of the HDS reaction, suggesting that a substantial part of the reaction using CoMo on silica occurs via the (one-step) DDS pathway. A trend in the BP formation across all the studied catalysts could be observed in that the amount of BP appears to decrease when Ce is incorporated to SBA-15 up to the 2.5 wt. % Ce. However, at Ce loading of 5 wt. %, the % BP increased, and at 10 wt. %, the % BP has reached almost the same amount as that of SCoMo.

[0116] The ratio of BP to cyclohexyl benzene (CHB) maintained the same trend as that observed in BP, indicating that Ce plays a role in the reaction pathway, apparently tending to lead the reaction to the HYD pathway as evidenced in the % CHB increase due to Ce loading up to 2.5 wt. %. HYD promotion of Ce may be associated with the Ce.sup.4+.Math.Ce.sup.3+ redox properties in the Ce-modified SBA-15 support. The low % CHB at 5 and 10 wt. % Ce may be associated with strong metal-support interactions weakening the Ce.sup.4+.Math.Ce.sup.3+ redox properties, hence decreasing the HYD promoter behavior of Ce.

[0117] The effect of temperature variation on the product distribution using 2.5CeSCoMo catalyst is presented in Table S3, below.

TABLE-US-00008 TABLE S3 Catalyst performance results: Product distribution (%) after 1 h for 2.5CeSCoMo at varying temperatures (Process conditions: 5 MPa; DBT = 1000 ppm). Product distribution (%) Temp CPB CHB BP THDBT BP/CHB 325 14.46 85.54 5.92 350 15.53 84.47 5.44 375 16.05 83.95 5.23

[0118] As seen in Table S3, the % CHB increases with increasing temperature, resulting in decreased BP/CHB. Typically, the DDS pathway can be modified to include a sequential HYD of BP to CHB. Although the alternate mechanism (DBT.fwdarw.BP.fwdarw.CHB) is less probable, this alternate route may explain the increased % CHB at high temperature.

[0119] A kinetic study was performed on the assumption that the HDS reaction occur completely via the parallel pathway (i.e., where as shown in FIG. 11, in the parallel pathway the hydrodesulfurization reaction occurs via both direct desulfurization pathway (DSS) and the hydrogenation pathway (HYD) at the same time), and that the reaction rate is calculated based on the pseudo-first order kinetics. Thus, calculated rate constants of the HDS reaction, k.sub.HDS (min.sup.1), DDS reaction, k.sub.DDS (min.sup.1), and HYD reaction, k.sub.HYD (min.sup.1) are presented below in Table 6.

TABLE-US-00009 TABLE 6 First-order rate constants for HDS of DBT after 1 h reaction time at 350 C. k.sub.HDS 10.sup.3 k.sub.DDS 10.sup.3 k.sub.HYD 10.sup.3 k.sub.DDS/ Catalysts (min.sup.1) (min.sup.1) (min.sup.1) k.sub.HYD SCoMo 6.53 6.17 0.36 17.14 1CeSCoMo 17.44 15.03 2.41 6.24 2.5CeSCoMo 22.16 18.72 3.44 5.44 5CeSCoMo 5.80 5.23 0.58 9.02 10CeSCoMo 7.47 7.01 0.46 15.24

[0120] The k.sub.HDS(min.sup.1) for the SCoMo catalyst was calculated to be 6.5310.sup.3, comparing well to the k.sub.HDS (8.410.sup.3 min.sup.1) reported for Ti-modified SBA-NiMo catalyst prepared and sulfided under the same conditions.

[0121] The role of Ce in the catalysts can also be expressed based on the rate constants of the HDS reaction. The k.sub.HDS (min.sup.1) was observed to increase by a factor of 3.4 from SCoMo to 2.5CeSCoMo catalysts. The increase in k.sub.HDS (min.sup.1) was in-tandem with an increase in k.sub.HYD (min.sup.1), resulting in decreased k.sub.DDS/k.sub.HYD, as observed in the BP/CHB product distribution in Table 5. However, above 2.5 Ce wt. %, the k.sub.HDS (min.sup.1) and k.sub.HYD (min.sup.1) decreased significantly.

[0122] The effect of temperature on the k.sub.HDS (min-1) for 2.5CeSCoMo catalyst was studied. As shown below in Table S4, increasing the process temperature from 350 to 375 C. increases the k.sub.HDS (min.sup.1) by a factor of 3.7. However, increasing the process temperature from 350 to 375 C. also increases the HYD pathway, thus leading to a decrease in k.sub.DDS/k.sub.HYD.

TABLE-US-00010 TABLE S4 Effect of temperature on first-order rate constants for HDS of DBT (catalyst = 2.5CeSCoMo). Temperature k.sub.HDS 10.sup.3 k.sub.DDS 10.sup.3 k.sub.HYD 10.sup.3 k.sub.DDS/ ( C.) (min.sup.1) (min.sup.1) (min.sup.1) k.sub.HYD 325 17.30 14.80 2.50 5.92 350 22.16 18.72 3.44 5.44 375 82.00 68.64 13.16 5.22

[0123] Overall, the HDS activity of 2.5CeSCoMo catalyst is unexpectedly superior to SCoMo, as evidenced by the k.sub.HDS (min.sup.1) values, among other data herein. In fact, the 2.5CeCoMo is the best performing catalyst among the series of Ce-modified SBA-15 CoMo catalyst. The performance of 2.5CeSCoMo catalyst may derive from its textural properties and a moderate metal-support interaction observed from the XRD, Raman spectroscopy, and H.sub.2-TPR results.

[0124] Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views.

[0125] FIGS. 1A and B respectively show (A) N.sub.2 adsorption-desorption isotherms and (B) pore volume-size distributions of the exemplary supports prepared within the scope of the invention. FIGS. 2A and B respectively show (A) N.sub.2 adsorption-desorption isotherms and (B) pore volume-size distributions of the exemplary supported catalysts prepared within the scope of the invention.

[0126] FIG. 3A shows XRD patterns of all the supports, i.e., SBA-15 (a); 1Ce-SBA-15 (b); 2.5Ce-SBAA-15 (c); 5Ce-SBA-15 (d); and 10Ce-SBA-15 (e), each indicating a broad diffraction peak between 20 to 30 which is a typical characteristic peak of amorphous silica. However, CeO.sub.2 diffraction peak was not observed in any of the supports, implying that ceria (up to 10 wt. % loading) has been incorporated into the mesoporous SBA-15 silica. The XRD spectra of sulfided catalystsSCoMo (f); 1CeSCoMo (g); 2.5CeSCoMo (h); 5CeSCoMo (i); and 10CeSCoMo (j)presented in FIG. 3B show the MoO.sub.3 phase pattern with a quality mark (QM) of Star, i.e., well characterized chemically and crystallographically with no unindexed lines at 20.03, for SCoMo, 5CeSCoMo, and 10CeSCoMo. However, 1CeSCoMo and 2.5CeSCoMo show an MoS2 phase pattern with a QM of I, i.e., well characterized chemically with no unindexed strong line at 20.06. The peaks intensity of the MoO.sub.3 phase follow the trend: SCoMo<5CeSCoMo<10CeSCoMo, while the peak intensity of MoS.sub.2 phase follow the trend: 1CeSCoMo<2.5CeSCoMo. This indicates that the ease of sulfidation follows the trend 2.5CeSCoMo>1CeSCoMo SCoMo>5CeSCoMo>10CeSCoMo. The observed sulfidation trend may be ascribed to the role of ceria on the metal-support interaction. At 2.5 wt. % Ce loading, the optimum metal-support interaction appears to have been achieved. However, at ceria loading of 5 and 10 wt. %, the metal-support interaction may be large enough to deter the reduction of the Mo species.

[0127] FIG. 4A shows the Raman spectra of the supports synthesized as described above: SBA-15 (a); 1Ce-SBA-15 (b); 2.5Ce-SBAA-15 (c); 5Ce-SBA-15 (d); and 10Ce-SBA-15 (e). The Raman spectra of the supports show very weak peaks at 605 and 850 cm.sup.1 which were assigned to the vibrational stretching mode of the surface hydroxyl group in SiOH and the symmetrical stretching of the SiOSi linkage respectively. Close observation of the Raman spectra of the 5 wt. % and 10 wt. % Ce-modified SBA-15 supports reveals a Raman band at 420 cm.sup.1. This band is a characteristic Raman band of cerium oxide reported elsewhere in the literature, meaning that at high ceria loading some of the cerium ions are not attached to the SiOSi framework of SBA-15. This undergirds the hypothesis that high cerium concentration most probably forms external and/or additional framework cerium oxide in the textural properties of the supports.

[0128] FIG. 4B shows the Raman spectra of the supported, sulfided catalysts synthesized as described above: SCoMo (f); 1CeSCoMo (g); 2.5CeSCoMo (h); 5CeSCoMo (i); and 10CeSCoMo (j). The Raman spectra of the sulfided catalysts showed peaks at 284, 665, 815, and 993 cm.sup.1 for SCoMo, 5CeSCoMo, and 10CeSCoMo, which are characteristic bands for MoO.sub.3, known in the literature. The Raman peaks at 284 and 665 cm.sup.1 are assigned to the wagging modes of the terminal oxygen atoms and asymmetric stretching of the MoOMo, while the bands at 815 and 993 cm.sup.1 are ascribed to the symmetric stretching and asymmetric stretching of the terminal oxygen in MoO.sub.3. The presence of the MoO.sub.3 phase in the sulfided SCoMo, 5CeSCoMo, and 10CeSCoMo catalysts indicates that some of the molybdenum species have not been completely reduced (and consequently further sulfided) in the catalysts prepared as described herein.

[0129] However, these MoO.sub.3 Raman bands were not observed in the 1CeSCoMo and 2.5CeSCoMo. Instead Raman frequencies of vibrational modes of SMoS (385 and 407 cm.sup.1) were detected. Therefore, it may be inferred that Ce loading up to 2.5 wt. % in the catalyst supports increased the metal-support interaction to an optimum level that enhanced the molybdenum dispersion on the support, thereby easing Mo reduction and sulfidation.

[0130] FIG. 5A shows the FT-IR spectra of the supports prepared as described above: SBA-15 (a); 1Ce-SBA-15 (b); 2.5Ce-SBAA-15 (c); 5Ce-SBA-15 (d); and 10Ce-SBA-15 (e). The appearance of broad peak at 3300 to 3500 cm.sup.1 in all the samples prepared may be attributed to the stretching vibration of SiOH present in the SBA-15 channels and the OH stretching of water absorbed on the surfaces of the supports and catalysts. The sharp peak observed at 1600 cm.sup.1 may be assigned to the OH bending vibration of the absorbed water molecules. The peak intensities of both OH peaks appear to decrease proportionately with ceria loading in the support, indicating that some of the SBA-15 pores may be occupied due to ceria loading. The broad band at 1240 cm.sup.1 may be assigned to the SiOSi stretching vibration, and the wavenumber of this broad band was observed to increase slightly with ceria loading. At 10Ce-SBA-15, the wavenumber is approximately 1300 cm.sup.1. In addition, the intensity of the broad band also decreases with ceria loading, also indicating that SiOSi bonds are substituted with SiOCe bonds as the ceria loading increases.

[0131] FIG. 5B shows the FT-IR spectra of the supported, sulfided catalysts prepared as described above: SCoMo (f); 1CeSCoMo (g); 2.5CeSCoMo (h); 5CeSCoMo (i); and 10CeSCoMo (j). After loading of Co and Mo onto the supports, the broad peak at 3300 to 3500 cm.sup.1 and the sharp peak at 1600 cm.sup.1 for the OH stretching and bending vibration of absorbed water molecules respectively noticeably decreased, indicating that free voids in the mesoporous supports may be filled with the loaded Co and Mo metals.

[0132] FIG. 6 shows the temperature-programmed reduction (H.sub.2-TPR) profiles of the catalysts prepared as described above: SCoMo (a); 1CeSCoMo (b); 2.5CeSCoMo (c); 5CeSCoMo (d); and 10CeSCoMo (e). Each of the metal oxide catalyst samples shows two major peaks at approximately 575 C. and 900 C., which may be respectively assigned to the reduction of molybdenum oxide: MoO.sub.3 to MoO.sub.2; and MoO.sub.2 to Moo. The reducing temperature of the inventive catalysts was observed to slightly decrease as the ceria loading increased, up to 2.5 wt. % loading, suggesting that ceria incorporation into the SBA-15 support framework increases the mobility and activity of surface oxygen species due to the redox behavior of Ce (Ce.sup.4+.Math.Ce.sup.3+) and the formation of oxygen vacancy.

[0133] By implication, more Mo species should have close contact with the Ce-modified support in the doped rather than unmodified SBA-15 support, thus resulting in less sintering and more dispersion of Mo in Ce-modified supported catalysts. However, above 2.5 wt. % Ce loading, a sharp increase in the reduction temperature was observed, implying that ceria loading up to 5 and 10 wt. % increases the metal-support interaction abruptly, inhibiting the reduction of the MoO.sub.3. These H.sub.2-TPR results support the results obtained from the wide angle XRD, discussed above. Close analysis of the SCoMo TPR profile in FIG. 6, plot (a), reveals a shoulder peak at 324.6 C., similar to a peak reported in the art. The shoulder/peak has been explained to arise from the reduction of cobalt oxide to cobalt metal, indicating that some cobalt species in the SCoMo have separated from interacting with Mo species. This 324.6 C. shoulder is absent in the Ce-modified SBA-15 supported CoMo catalysts, supporting the hypothesis that ceria incorporation into the silica aids Co and Mo interaction.

[0134] FIG. 7A to D show field emission scanning electron microscopy (FE-SEM) images of the Ce-modified SBA-15 supported CoMo catalysts, while FIG. 8A shows an FE-SEM of the SCoMo catalyst (undoped). FIG. 8B and FIG. 9A to D respectively show the x-ray photoelectron spectroscopy (XPS) spectra of the Mo phases in the sulfided catalysts SCoMo catalyst (undoped) then the various Ce-modified SBA-15 supported CoMo catalysts.

[0135] FIG. 10A shows exemplary catalyst performances for the catalysts prepared as described herein, undoped or with the various Ce modifications, for a hydrodesulfurization (HDS) reaction on dibenzothiophene (DBT) in a model fuel (dodecane)removing sulfur from a 1000 ppm DBT solution in dodecane. FIG. 10B show a study of the effect of temperature on the HDS reaction for the best performing catalyst in the study from FIG. 10A, i.e., 2.5CeSCoMo. FIG. 11 shows the reported reaction mechanism of HDS on DBT via the two proposed pathways: (1) one-step, direct desulfurization (DDS) involving direct CS bond cleavage to form biphenyl (BP); and (2) hydrogenation (HYD) of phenyl ring to cyclohexyl in two to three steps, then CS bond cleavage to form cyclohexyl benzene (CHB).

[0136] Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.