BACKGROUND OF THE INVENTION
This patent application claims priority to U.S. Provisional Patent Application Ser. No. 60/639,909 filed on Dec. 29, 2004, which is incorporated by reference in its entirety.
1. Technical Field of the Invention
This invention relates generally to the field of catalytic treatment of heavy hydrocarbons to produce desirable hydrocarbon products, in particular, a novel catalyst operable to catalytically treat de-metallized oil (DMO) and Vacuum Gas Oil (VGO) Blend.
2. Description of the Prior Art
The flexibility of hydrocracking as a process for refining petroleum has resulted in its phenomenal growth during the past 15 years. Through catalytic treatment, feedstocks can be converted to lower boiling or more desirable products. Hydrocarbon feedstocks suitable for such treatment range from residue to naphtha. Products include such widely diverse materials such as gasoline, kerosene, middle distillates, lubricating oils, fuel oils, and various chemicals.
Commercial hydrocracking is typically carried out in a single stage reactor or in a two-stage reactor with the stages in series. Numerous hydrocracking catalysts have been explored to treat various hydrocarbons, to reduce undesirable side effects of the catalytic treatment and/or to extend the life of the catalyst. Development has also led to catalysts suitable for severe operating conditions. Efforts for cost effectiveness are ongoing. The choice of catalysts and of the particular process scheme will depend on many factors such as feed properties, desired products properties, size of the hydrocracking unit, and various other economic considerations.
- SUMMARY OF THE INVENTION
While hydrocracking has been investigated in the past for the purpose of hydrocracking medium and heavy vacuum gas oil (VGO), there is a need to address heavier and different hydrocarbons such as de-asphalted oil (DAO) or de-metallized oil (DMO) to convert this into suitable product for gasoline lines, jet fuels and diesel oils according to geographical and seasonal variations in demand. LPG and lubricating bases would also be desirable products. A catalyst would be advantageous that is capable of handling large hydrocarbon molecules and heavy poly-aromatic molecules, in particular, DMO. A catalyst that can process VGO/DMO feed blend would be particularly advantageous. As it is notable that the world market is tending toward heavier hydrocarbons, a catalyst suitable for such heavy hydrocarbons would be advantageous.
The current invention includes a catalyst for and a process for hydrotreating/hydrocracking heavy hydrocarbons. The catalyst is particularly useful for treating de-metallized oil (DMO) and is particularly useful in VGO/DMO hydrocarbon blend. The catalyst acts to catalytically convert the VGO/DMO blend to shorter-chain valuable hydrocarbon products. The catalyst includes a catalytic support material, a catalytic metal impregnated upon the catalytic support material, and a promoter metal on the catalytic support material to enhance catalytic conversion. The combination of the catalytic support material with catalytic metal and promoter metal is operable to catalytically convert VGO/DMO into hydrocarbon products having shorter carbon chains.
In a preferred embodiment, the catalytic metal component includes molybdenum and the promoter metal includes nickel.
Regarding the catalytic support materials, a particularly preferred catalytic support material includes MCM-41 mesoporous material. γ-alumina was used as binder for all catalyst prepared in this research. The amount of γ-alumina used was around 70% of the total catalyst support for the test runs. In a particularly preferred embodiment, the USY zeolite is in an absence of γ-zeolite.
In another preferred embodiment, the catalytic support material is β-zeolite. In another preferred embodiment, the catalytic support material is USY zeolite. In yet another preferred embodiment, the catalytic support material is amorphous silica alumina, also called ASA. ASA has a non-uniform structure with low acidity and high surface area. The non-uniform structure tends to create acidic sites that are not available to large molecules, which leads to inferior performance of ASA alone as compared to MCM-41 or a combination of MCM-41 with ASA. Similarly, the USY and β-zeolite supports suffer from drawbacks related to the microporous nature of the supports which makes the catalyst less efficient for large molecules since it is diffusion limited. These supports used alone tend to plug rapidly, thereby deactivating the catalyst. However, the MCM-41 support material overcomes these flaws. In a preferred embodiment, the catalytic support material is solely ultra stable Y zeolite, MCM41 mesoporous material, β-zeolite, amorphous silica alumina or combinations thereof. A particularly preferred embodiment includes a single catalytic support material that is substantially all MCM-41. This material is mesoporous that is well-structured and has uniform morphology with high surface area. It also has low acidity as compared to beta and USY support materials. The invention includes the use of proper support material and a balance between acidic and metallic function with the proper distribution of metals throughout the support material. This is accomplished through the very well-structured morphology features of MCM-41 support material, which contains both acidic and metallic site that are accessible to the large hydrocarbon molecules found in VGO and DMO. For this reason, high conversion is achieved. Advantageously the lower acidity of MCM-41 as compared to other support materials drives conversion toward selectivity towards mid distillates and limits the production of undesirable light gases.
In a preferred embodiment of the invention, the catalytic metal is in a sulfide form. For example, molybdenum in the form of molybdenum sulfide is preferred.
In a preferred embodiment, promoter metals include solely nickel.
The catalyst of the invention is particularly useful for VGO/DMO hydrocarbon blend contains at least 10% DMO by volume. Test runs have been made for VGO/DMO hydrocarbon blend contains at least 15% DMO by volume.
Impregnation of the catalytic metal and the promoter metal onto the catalytic support is accomplished through methods known in the art, such as co-impregnation method. The process of catalytically converting a heavy hydrocarbon containing de-metallized oil includes the steps of introducing the heavy hydrocarbon containing de-metallized oil into a reactor stage and introducing the catalyst into the reactor stage. The catalyst introduced into the reactor stage includes the catalytic support material, the catalytic metal impregnated upon the catalytic support material, and the promoter metal on the catalytic support material to enhance catalytic conversion. The catalytic support material with catalytic metal and promoter metal operate to catalytically convert at least a portion of the de-metallized oil into hydrocarbon products having shorter carbon chains.
The process reaches and maintains a pre-defined temperature in the reactor operable to achieve conversion. In a preferred embodiment, the pre-defined temperature is at least 390 degrees C. In a more particularly preferred embodiment, the pre-defined temperature is at least 400 degrees C.
BRIEF DESCRIPTION OF THE DRAWINGS
In a preferred embodiment, a majority of the pores of the catalyst support are located within 20 to 50 Angstrom (Å) and the catalyst support has a large surface area as measured through pore size distribution. Table 1 shows examples of preferred embodiments.
|TABLE 1 |
|Prepared Catalysts Textual Characteristics |
| || || ||Average |
| ||BET Surface Area ||Pore Volume ||Pore Diameter |
|Sample ||(m2/g) ||(cm3/g) ||(A0) |
|NiMo-ASA ||186 ||0.33 ||36 |
|NiMo-MCM-41 ||324 ||0.40 ||25 |
|NiMo-β ||313 ||0.41 ||26 |
|NiMo-USY ||300 ||0.35 ||23 |
So that the manner in which the features, advantages and objects of the invention, as well as others that will become apparent, may be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of the invention's scope as it may admit to other equally effective embodiments.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 depicts a schematic of a preferred embodiment of the process with the catalyst of the invention.
Several catalysts were prepared using nickel (Ni)/molybdenum (Mo) metals loadings along with the four different support materials identified above. The four catalyst formulations created in this manner were characterized using gas sorption analyzer, temperature programmed reduction (TPR) and temperature programmed de-sorption (TPD). Moreover, the catalyst formulations were tested in a batch reactor and compared against a commercial catalyst. The outcome of this work showed that the formulation including MCM-41 catalyst support, resulting in NiMo-MCM-41, has performed better than the commercial catalyst on heavy hydrocarbons, in particular, VGO/DMO blends. NiMo-MCM-41 showed higher hydrodesulfurization (HDS) and hydrogenation activities. In addition, it had higher conversion and higher diesel yield than commercial catalyst.
Most of the hydrocracking catalysts of commercial interest are dual functional in nature, consisting of both a hydrogenation-dehydrogenation component and an acidic support. The reactions catalyzed by the individual components are quite different. In specific catalysts, the relative strengths of the two components can be varied. The reactions occurring and the products formed are influenced by the balance between these two components.
|TABLE 2 |
|Acidity for all prepared catalysts |
|Catalyst ||Acidity (mmol/g) ||Peak Temperature (° C.) |
|NiMo-MCM-41 ||0.33 ||264 |
|NiMo-ASA ||0.50 ||252 |
|NiMo-β ||0.56 ||233 |
|NiMo-USY ||0.59 ||238 |
Table 2 shows the TPD of ammonia for all of the prepared hydrocracking catalysts. The acidity of the prepared catalysts ranges from 0.33 mmol/g (NiMo-MCM-41) to 0.59 mmol/g (NiMo-USY). The lower acidity of NiMo-MCM-41 catalyst is expected since MCM-41 is a silica based material and has low amount of alumina. Therefore, NiMo-MCM-41 catalyst has lower amount of γ-alumina than the other prepared catalysts.
The catalytic metal, such as molybdenum, and the promoter metal, such as nickel, provide the hydrogenation-dehydrogenation functions. As noted, this is preferably in the sulfide form. Other group VIA and group VIIIA metals are useful as promoter metal and catalytic metal. These metals catalyze the hydrogenation of the feedstock, making it more reactive for cracking and heteroatom removal, as well as reducing the coking rate. They also initiate the cracking by forming a reactive olefin intermediate via dehydrogenation.
Since hydrocracking of industrial feedstocks is to be carried in presence of hydrogen sulfide and organic sulfur compounds, it is preferred that the metal site be in a metal sulfide form of the VIA group promoted by a nickel or cobalt sulfide.
The reactions that occur during the hydrocracking process take three major routes. First, non-catalytic thermal cleavage of C-C bonds via hydrocarbon radicals, with hydrogen addition (hydropyrolysis). Second, monofunctional C-C bond cleavage with hydrogen addition over hydrogenation components consisting of metals, oxides or sulfides (hydrogenolysis). Third, bifunctional C-C bond cleavage with hydrogen addition over bifunctional catalysts consisting of a hydrogenation component dispersed on a porous, acidic support. In addition to the above reactions, there are other reactions that take place during the hydrocracking process. These can include hydrodesulfurization, hydrodeintrofication, hydrodeoxigenation, olefin hydrogenation and partial aromatic hydrogenation.
|TABLE 3 |
|Experimental Design |
| ||Catalyst Systems |
| ||Com- ||NiMo- ||NiMo- ||NiMo- ||NiMo- |
| ||mercial ||MCM-41 ||USY ||β ||ASA |
| || |
|Catalyst || || || || || || |
|γ-alumina binder, || || ||70 ||70 ||70 ||70 |
|wt % |
|Support, wt % || || ||30 ||30 ||30 ||30 |
|NiO, wt % || || ||2.5 ||2.5 ||2.5 ||2.5 |
|MoO3, wt % || || ||12 ||12 ||12 ||12 |
|Ni, wt % || || ||2 ||2 ||2 ||2 |
|Mo, wt % || || ||8 ||8 ||8 ||8 |
|Atomic Ratio || || ||0.2 ||0.2 ||0.2 ||0.2 |
|Surface Area, || || ||324 ||300 ||313 ||186 |
|Pore Vol., cm3/g || || ||0.4 ||0.35 ||0.41 ||0.33 |
|Pore Size, || || ||25 ||23 ||26 ||36 |
|Acidity, || || ||0.33 ||0.59 ||0.56 ||0.5 |
|Batch Reactor ||— ||— |
|No. of Runs || ||5 ||1 ||1 ||1 ||1 |
|Temperatures, || ||410 ||410 ||410 ||410 ||410 |
|deg. C. |
|Pressures, kg/cm2 || ||150 ||150 ||150 ||150 ||150 |
|Feed weight, g || ||100 ||100 ||100 ||100 ||100 |
|Catalyst weight, g || ||3 ||3 ||3 ||3 ||3 |
The commercial catalyst that was used for comparison is DHC-8 from Universal Oil Products (UOP) Company. γ-alumina was used as binder for all catalyst prepared in this test shown above. The amount of γ-alumina used was 70% of the total catalyst support.
|TABLE 4 |
|Feedstock Definition |
| || || ||VGO/DMO |
|Feedstock Properties ||VGO ||DMO ||85%/15% |
|Specific Gravity ||0.92-0.93 ||0.96-0.97 ||0.93-0.94 |
|Total Nitrogen, wt ppm ||700-900 ||1300-2100 ||1100-1200 |
|Total Sulfur, wt % ||2-3 || 3-3.5 ||2.6-2.8 |
|ASTM Distillation, D2887 |
|5%, ° C. ||279 ||402 |
|50%, max ° C. ||472 ||596 ||495 |
|90%, max ° C. ||543 ||678 ||615 |
|Ni + V wt. ppm ||<1 || 8.0-13.5 ||2-3 |
|Tested catalysts conversion for 800-900° F. cut and 900-1050° F. cut
|| 1Conversion %
|Cut Range, ° F.
Among the four catalyst formulations described above that are encompassed within the invention, NiMo-MCM-41 catalyst had the lowest acidity and the highest surface area. This is attributed to the fact that MCM-41 is a silica-based material and has low amounts of alumina. This is one of the advantages of MCM-41 being mesoporous and having low acidity. The mesoporous feature along with the lower acidity of NiMo-MCM41 catalyst promotes the highest conversion and the lowest gas make.
While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.