Ultrasonic oxidative desulfurization of heavy fuel oils

Abstract

The invention relates to systems and methods for ultrasonic oxidative desulfurization of heavy fuel oils. In various embodiments, the methods include combinations of ultrasonic sulfone decomposition processes and/or catalytic decomposition processes.

Claims

1. A method for desulfurization of a heavy fuel oil containing sulfur comprising the steps of: a) subjecting a heavy fuel oil to an ultrasonic oxidation process in the presence of an aqueous oxidizing agent to form a sulfone rich effluent; and b) subjecting the sulfone rich effluent to a steam catalytic sulfone decomposition process (SDP) to form a desulfurized heavy fuel oil and where the SDP process includes processing the sulfone rich effluent through a steam processing catalytic reactor having an oxidizing/desulfonating hydroprocessing (ODH) catalyst selected from any one or a combination of mixed oxides of Ni—Ce hydrotalcite, Mn hydrotalcite, Cu-hydrotalcite, V-hydrotalcite, CaCu-silicates, Ba—Cu-silicates, BiMo-oxides, K.sub.2O/hydrotalcite, K.sub.2O/Ni—Ce hydrotalcite, KCe-Zirconia and BaCe-Zirconia.

2. The method as in claim 1 where the ODH catalyst includes a solid support selected from any one of or a combination of alumina, silica and modified kaolin with controlled textural properties.

3. The method as in claim 2 where the ODH catalyst has a porosity in the range of 6-50 nm.

4. The method as in claim 1 where the ODH catalyst has a surface area in the range between 40 and 80 square meters/g.

5. The method as in claim 1 where the oxidizing agent is any one of or a combination of hydrogen peroxide, ozone, organic peroxides or peroxy acids.

6. The method as in claim 1 where step a) includes addition of an oxidizing catalyst.

7. The method as in claim 6 the oxidizing catalyst is selected from formic acid or acetic acid.

8. The method as in claim 1 where step a) includes the addition of a diluent.

9. The method as in claim 1 where the sulfone rich effluent of step a) is subjected to aqueous phase removal to recover oxidizing catalyst, water and diluent, if present.

10. The method as in claim 1 where a feed for the SDP is a water free effluent from step a).

11. The method as in claim 1 where a feed for the SDP is a water/oil effluent from step a) and where after the SDP, a sulfone free effluent is subjected to a temperature separation process to form the desulfurized oil and a vapor stream containing any one of or a combination of sulfur containing gases, steam and light hydrocarbons.

12. The method as in claim 1 where steps a) and b) are controlled to form a desulfurized heavy fuel oil having a sulfur content less that 0.5% (by weight).

13. The method as in claim 1 where the heavy fuel oil has a sulfur content greater than 0.5% (by weight) and steps a) and b) are controlled to form a desulfurized heavy fuel oil having a sulfur content less that 0.5% (by weight).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Various objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of various embodiments of the invention. Similar reference numerals indicate similar components.

(2) FIG. 1 shows a process schematic of oxidative desulfurization (ODS) of Dibenzo-thiophene (DBT) via extraction, decomposition and adsorption.

(3) FIG. 2 is a schematic flow diagram and reactor sequence for a desulfurization of heavy fuel oils in accordance with a 1st embodiment of the invention.

(4) FIG. 3 is a schematic flow diagram and reactor sequence for a desulfurization of heavy fuel oils in accordance with a 2nd embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(5) Introduction

(6) With reference to the figures, systems and methods for ultrasonic desulfurization of heavy fuel oils are described.

(7) Systems and methods of catalytic oxidative desulfurization (CODS) of heavy fuel oils can generally be carried out in two main steps including Step 1, an ultrasonic desulfurization step followed by Step 2, different decomposition steps which can include catalytic hydro decomposition (HDP) (FIG. 2) or catalytic steam decomposition (SDP) (FIG. 3).

(8) Step 1-Ultrasonic Desulfurization

(9) Generally, Step 1 is conducted within an ultrasonic oxidation reactor/zone 12. A heavy oil feed 14 (with optional diluent 14a) is introduced into an US reactor/zone 12 in the presence of an oxidizing agent 18 and preferably an oxidizing catalyst 20 together with additional water 18a. Suitable oxidizing agents include hydrogen peroxide, ozone, organic peroxides or peroxy acids. The oxidizing agents will preferably be concentrated typically in the range of 30-50% concentration in water and be introduced at roughly 50% by volume relative to the feed volume. Additional water 18a be introduced as an aqueous phase to create an aqueous phase volume and, hence additional emulsion surface area. A volume of a strong oxidizing catalyst 20 is preferably added (typically about 85% concentration and 50% volume relative to undiluted the oxidizing catalyst). Suitable oxidizing catalysts include formic acid and acetic acid.

(10) Within the ultrasonic oxidation zone 12, varying degrees of ultrasonic energy are applied sufficient to create a microemulsion of oil and aqueous phase. The sulfones will predominantly remain within the oil phase. More specifically, the sulfur atoms (typically in the divalent state) on the organic molecules are oxidized by the addition of oxygen atoms to form preferentially sulfones (hexavalent state of sulfur).

(11) Depending on the resulting viscosity of the emulsion, additional diluent 14a may be introduced to enable the mixture to be pumped and/or handled. Suitable diluents include aromatics such as toluene.

(12) As shown in FIG. 2, after reaction emulsion 22 may be separated in appropriate liquid/liquid 24 and/or gas/liquid 26 separators to form a sulfone-rich water free effluent 28.

(13) Oxidizing catalyst and water may be recycled 30.

(14) Step 2-Catalytic Sulfone Hydro-Decomposition

(15) After forming the sulfone-rich effluent 28, the sulfone rich effluent 28 is reacted with a suitable solid catalyst within a catalytic reactor 32 and hydrogen 34 enable catalytic desulfurization of the sulfones. Under suitable conditions and in the presence of the catalyst, a sulfone free effluent 36 is formed in which the sulfones are partially or totally decomposed forming preferentially SO2 and/or H.sub.2S molecules.

(16) As shown in FIG. 2, subsequent to catalytic reaction, the sulfone free effluent 36 is subjected to gas/liquid separation 38 resulting in desulfurized oil 38a and sulfur dioxide/hydrogen sulfide gas. Gases 38b and/or diluent 38c can be recovered by various techniques including adsorption or liquefaction.

(17) FIG. 3 shows an alternate embodiment utilizing catalytic steam decomposition. As shown, if the catalytic reactor 50 utilizes steam 52 to form a sulfone free effluent 54, the sulfone free effluent may utilize a high temperature separator/process 56 to form the desulfurized oil 58 and a vapor stream 60 containing any one of or a combination of sulfur containing gases, steam and light hydrocarbons. These gases may be subjected to a subsequent low temperature separation process 62 to effect separation of sulfur dioxide containing gases 64 and water 66 light hydrocarbons 68 and diluent 69.

(18) If the process uses catalytic steam decomposition process, step 1 of FIG. 3 does not require steps to remove the aqueous phase.

(19) In each case, the process steps are preferably controlled to form a desulfurized heavy oil fuel having a sulfur content less that 0.5% (by mass).

(20) Catalytic Formulations

(21) The oxidizing/desulfonating hydroprocessing catalyst and the bifunctional steam processing catalysts can be selected from: Metallic carbides, oxy-carbides and nitrides and mixtures of thereof of. Molybdenum and tungsten for the hydro processing catalysts. Bi-, tri-, tetra or penta-metallic oxides combinations having elements from the groups 1 and 2 including Na, K, Cs, Ca, Mg or Ba; elements from the groups 4, 5, 6, 7, 8, 9, 10, 11 including Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Zr or Ce and elements from groups 13, 14, 15 including Al, Si, P which maybe impregnated with noble metals including Pd and Pt or metallic carbides including those of molybdenum and tungsten for the steam processing catalysts.

(22) Examples of steam processing catalysts include: NiCe Hydrotalcite: Mixed oxides MgO.NiO.CeO.sub.2.Ce.sub.2O.sub.3. Al.sub.2O.sub.3. Mn-Hydrotalcite: Mixed oxides MgO.Mn.sub.2O.sub.3.MnO.Al.sub.2O.sub.3. Cu-Hydrotalcite: Mixed oxides MgO.CuO.Cu.sub.2O.Al.sub.2O.sub.3. V-Hydrotalcite: Mixed oxides MgO.V.sub.2O.sub.3.V.sub.2O.sub.5.Al.sub.2O.sub.3. CaCu-silicates: Mixed oxides CaO.CuO.Cu.sub.2O.SiO.sub.2. BaCu-silicates: Mixed oxides BaO.CuO.Cu.sub.2O.SiO.sub.2. BiMo-oxides: Mixed oxides Bi.sub.2Mo.sub.3O.sub.12. K.sub.2O/Hydrotalcite: Mixed oxides K.sub.2O.MgO.Mn.sub.2O.sub.3.MnO.Al.sub.2O.sub.3. K.sub.2O/NiCe Hydrotalcite: Mixed oxides K.sub.2O.MgO.NiO.CeO.sub.2.Ce.sub.2O.sub.3. Al.sub.2O.sub.3. KCe-Zirconia: Mixed oxides K.sub.2O.CeO.sub.2.Ce.sub.2O.sub.3. ZrO.sub.2. BaCe-Zirconia: Mixed oxides BaO.CeO.sub.2.Ce.sub.2O.sub.3. ZrO.sub.2.

(23) Another set of catalysts for this process, including those for hydroprocessing, can be prepared with the same suite of active components described above, using solid supports such as alumina and silica and modified kaolin with controlled textural properties (surface area and porosity are preferably in the range between 40 and 80 square meters/g and 10-50 nm, respectively). The dispersion is enhanced by slight acidification of the solid support and successive or co-impregnation with precursor solutions of the same active metals followed by drying and calcination to form the corresponding metal oxides containing catalysts. These catalysts will generally have similar performance, reduced costs and a lower environmental impact in terms of generation of metal contaminated aqueous effluents than the above described, therefore constituting a possible and more desirable path.

(24) Discussion and Examples

(25) The binding energy of the sulfone bonds O═S═O compared to the thio bonds C—S—C bonds is significantly higher as it may be derived from photoelectron spectroscopy (˜4 ev). This implies that the C—S bonds when that sulfur is previously converted into sulfones is weakened, which means that, under appropriate conditions of either mild hydrogenation or mild oxidation, S in hydrocarbons either as sulphide or thiophenic forms is less reactive than in C-(sulfone)-C.

(26) Therefore, in terms of removing S from hydrocarbons, having a pre-oxidation step of the sulfur present in petroleum fractions leading to sulfones will facilitate the extraction via rupture of the C-(sulfone) bonds with respect to the direct C—S bonds breaking, especially when sulfur is in the most abundant thiophenic form.

(27) The SO.sub.2 evolving from decomposition of sulfones is also more stable than the H.sub.2S product resulting from the direct hydro treatment or steam treatment.

(28) Applicant has shown that hydro and steam treatment after the sulfones have been formed via the Ultra Sound Assisted-Oxidation path is significantly easier (lower T requirements) or faster (higher reaction rate).

(29) Laboratory tests were carried out in continuous units, on Heavy Fuel Oil as indicated in Tables 1 and 2. Table 1 compares the results of hydrodesulfurization of a high sulfur fuel oil (HFSO) containing 3.22 wt % sulfur (Row 1) via standard hydrodesulfurization (HDS) (Experiment 1) and ultrasonic oxidation followed by catalytic hydrodesulfurization (Experiment 2) in accordance with the invention. As shown, Experiment 2 shows that a HSFO feed can produce a product having less than 0.5 wt % sulfur.

(30) TABLE-US-00001 TABLE 1 Hydrodesulfurization Sulfur Micro- content Viscosity Carbon H/C Feed/Product (wt %) @ 25 C. (wt %) ratio Feed HSFO 3.22 85090 7.69 1.0 Experiment 1 HDS Product 0.92 1304 3.36 1.32 Experiment 2 HDS Product via 0.45 942 3.25 1.26 ultrasonication and HDP

(31) The conditions for the hydrodesulfurization reactors for experiments 1 and 2: continuous flow reactor setup P=1400 PSI T=345° C. WHSV (weight hourly space velocity)=0.2 h.sup.−1 Vol. ratio H.sub.2/Oil=1150 Catalyst: 21% molybdenum carbide-nitride-oxi-carbide (21 wt %)/Al.sub.2O.sub.3 (79 wt %)

(32) Table 2 compares the results of steam processing of a high sulfur fuel oil (HFSO) containing 3.22 wt % sulfur (Row 1) via standard steam processing (Experiment 3) and ultrasonic oxidation followed by catalytic steam processing (Experiment 4) in accordance with the invention. Experiment 3 was not stable and Experiment 4 shows that a HSFO feed can produce a product having less than 0.5 wt % sulfur when subjected to a combined ultrasonication and catalytic steam processing process.

(33) TABLE-US-00002 TABLE 2 Steam Processing Micro- Sulfur Viscosity Carbon H/C Feed/Product content @ 50 C. (% w) ratio 1 HSFO Feed 0.95 1324 15.57 NA Experiment 3 Steam Reactor not stable processing Experiment 4 Steam 0.50  363 14.28 NA processing post ultrasonication sulfonation

(34) The conditions for all steam processing experiments: continuous reactor setup P=400 PSI T=370° C. WHSV=0.25 h.sup.−1 Steam/oil ratio=0.05 wt %. Catalyst Ni(7 wt %)/Ce(14 wt %)/Mg(8 wt %)/Al oxides (rest)

(35) Thus, these examples illustrate that the ultrasonic oxidation with a strong oxidizing agent as described facilitates the decomposition of the sulfones as compared to the same catalytic process without pre-oxidation forming sulfones via hydroprocessing and steam processing processes.

(36) Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses thereof, it is not to be so limited since modifications and changes can be made therein which are within the full, intended scope of the invention as understood by those skilled in the art.