KR100404548B1 - Process for preparation of lubricating base oils - Google Patents

Abstract

(a) contacting the hydrogenated hydrocarbon oil feed in a first step in the presence of a catalyst consisting of at least one Group VIII precious metal component on a refractory oxide support;

(b) contacting the liquid effluent with hydrogen in a second step in the presence of a hydrogen conversion catalyst under hydrogen conversion conditions; And

(c) recovering at least one lubricating base oil having a viscosity index of at least 80.

Description

Method for producing base oil for lubrication

The present invention relates to a process for producing a base oil for lubrication comprising two successive hydrogen conversion steps.

Two-stage hydrogen conversion processes for preparing base oils for lubrication are well known in the art, and examples of such processes are described in British Patent Specification No. 1,546,504, European Patent Application No. 0,321,298 and US Pat. No. 3,494,854; 3,459,656; 3,459,656; 3,974,060 and 4,518,485. From these specifications, the first stage of the two-stage hydrogen conversion process generally aims to remove nitrogen- and sulfur-containing compounds present in the hydrocarbon oil feed and to hydrogenate aromatic compounds present in the feed to at least some extent. It becomes clear. In the second stage, the content of the aromatic compound is further reduced in series by hydrogenation and / or hydrocracking, while dewaxing of the effluent from the first stage is also often caused by hydrogen isomers of lead molecules. Thus, the hydrogen conversion catalysts used in the first and second steps should be able to fulfill their respective objectives sufficiently. From the aforementioned prior art documents, it is evident that the first stage catalyst is normally composed of Group VIII non-noble metal components and Group VIB metal components on a refractory oxide support. The first stage catalyst generally used then comprises nickel-molybdenum, nickel-tungsten or cobalt-molybdenum on an alumina, silica-alumina or fluorinated alumina support. Suitable second stage catalysts consist of a Group VIII noble metal component, optionally together with a Group VIB metal component, on a refractory oxide support. Platinum and / or palladium are found to be useful as Group VIII metal components, either in elemental form, as oxides or sulfides. As the refractory oxide support, not only aluminosilicate (zeolitic material) but also inorganic oxides (eg silica, alumina and amorphous silica-alumina) or mixtures thereof can be used.

Although many of the aforementioned prior art two stage hydrogen conversion processes are satisfactorily performed, there is always a motivation to further improve the efficiency of the process. In particular, the first stage working temperature can be improved. Because of the relatively high working temperature applied in the first hydrogen conversion step, it is advantageous to form a multinuclear aromatic compound in this first step. These polynuclear aromatic compounds formed then have to be removed in a second stage, which means that the hydrogen conversion conditions in this second stage must sufficiently hydrogenate and / or hydrolyze the multinuclear multiaromatic compound. On the other hand, reducing the first stage working temperature will less convert the feedstock to a valuable product, which is undesirable from an economic point of view.

The present invention provides a two-stage hydrogen conversion process for preparing a base oil for lubrication, whereby the first stage can be operated at lower operating temperatures than conventionally applied, while the product has an excellent viscosity index in commercially attractive yields. The goal is still to get. It will be evident that the process depends less strictly on the equipment to be used and therefore can work at lower operating costs while still maintaining commercially attractive yields. Moreover, less formation of multinuclear aromatic species also means that these species will remain in smaller amounts in the final base oil, which is desirable given the quality of the environment and the base oil. Thus, the present invention aims to provide an improved two stage hydrogen conversion process for producing a base oil for lubrication. More particularly, the present invention aims to provide a process for producing a lubricating base oil, which allows to produce a lubricating base oil having a high viscosity index while still requiring commercially attractive yields and requiring less working conditions.

These aims have been achieved by selecting a particular first stage hydrogen conversion catalyst that is more chemically than the conventionally applied first stage catalysts and thus allows lower operating temperatures to achieve the same yields as conventional first stage catalysts.

Accordingly, the present invention relates to a method for producing a base oil for lubrication composed of the following steps:

(a) contacting the hydrocarbon oil feed with hydrogen in a first step in the presence of a catalyst consisting of at least one Group VIII precious metal component on a refractory oxide support;

(b) contacting the liquid effluent with hydrogen in a second step in the presence of a hydrogen conversion catalyst under hydrogen conversion conditions; And

(c) recovering at least one lubricating base oil having a viscosity index of at least 80.

Suitable hydrocarbon oil feeds to be used in step (a) of the process according to the invention are mixtures of high-boiling hydrocarbons such as heavy oil fractions. In particular, heavy oil fractions having a boiling range which is at least slightly above the boiling range of the base oil for lubrication are suitable as hydrocarbon oil feeds for the purposes of the present invention. It is known to use vacuum distillate fractions derived from atmospheric residues, ie distillate fractions obtained by vacuum distillation of residual fractions obtained by atmospheric distillation of crude oil as feed. The boiling point range of the vacuum distillate fraction is generally from 300 to 620 ° C, suitably from 350 to 550 ° C. However, an oil fraction of deasphalted residue, including both deasphalted atmospheric residue and deasphalted vacuum distillate, can also be used, while lead raffinate (Fischer-Tropsch lead raffinate), slack lead-in particular, Those obtained from the desalination of the hydrotreated lead distillate- and hydrocracker bottom fraction (lead hydrogen) are also suitable feedstocks for use in the process according to the invention. Suitable lead hydrogens are those having an effective blocking point of at least 320 ° C, preferably at least 370 ° C.

The catalyst to be used in the first hydrogen conversion step is a Group VIII noble metal-based catalyst. If a hydrocarbon oil feed is used that is substantially free of sulfur- and nitrogen-containing compounds, it is confirmed that this catalyst achieves optimal catalytic activity and that the catalyst is sufficiently resistant to sulfur- and nitrogen-containing compounds present in the feed. It must be sulfided before work. If the catalyst is not sulfided in this case, its sulfur-tolerance will be too low under operating conditions, and consequently will rapidly break down when the catalyst is contacted with the hydrocarbon oil feed under operating conditions. Only when the hydrocarbon oil feed is substantially free of any sulfur- and nitrogen-containing compounds when using synthetic lead as feed, the sulfidation of the noble metal-based catalyst may be unnecessary. In most cases, however, the noble metal-based catalyst must be sulfided before operation.

Sulfurization of the catalyst is described for example in European Patent Specification No. 0,181,254; 0,329,499; From 0,448,435 and 0,564,317 and from international patent applications WO 93/02793 and WO 94/25157 by methods known in the art. Sulfidation can be carried out in situ by contacting a non-sulfide catalyst with a suitable sulfiding agent, such as hydrogen sulfide. Hydrocarbon oils containing substantial amounts of sulfur-containing compounds can also be used as sulfiding agents. The oil is then contacted with the catalyst at a temperature that gradually increases from ambient temperature to a temperature of 150 to 250 ° C. The catalyst will be maintained at this temperature for 10-20 hours. Continuously, the temperature will gradually increase to the working temperature. Another option is to generally use a hydrocarbon oil feed containing significant amounts of sulfur-containing compounds as sulfiding agents. In this case, the unsulfided catalyst is contacted with the feed under conditions that are less stringent than the operating conditions, allowing the catalyst to be sulfided. Typically, the hydrocarbon oil feed consists of a compound containing at least 0.5% by weight of sulfur, said weight percentage indicating the amount of elemental sulfur relative to the total amount of feedstock to be useful as a sulfiding agent. In view of cost and efficiency, it is generally desirable to sulfide the catalyst in situ. In other words, it is preferred to first put the unsulfided catalyst into the reactor and then contact it with the sulfiding agent under suitable sulfiding conditions.

The refractory oxide support of the first stage hydrotreating catalyst may optionally be an inorganic oxide, aluminosilicate, or combination thereof, with an inert binder material. Examples of suitable refractory oxides include inorganic oxides such as alumina, silica, titania, zirconia, boria, silica-alumina, fluorinated alumina, fluorinated silica-alumina and mixtures of two or more thereof. In a preferred embodiment, acidic carriers such as alumina, silica-alumina or fluorinated alumina are used as refractory oxide carriers. The refractory oxide support may also be an alinosilicate. Both synthetic and naturally occurring alisilicates can be used. Examples are zeolite beta, posersite and zeolite Y. Preferred aluminosilicates to be used are alumina- or silica-bonded zeolites Y.

The Group VIII noble metal component of the first stage hydrogen conversion catalyst is suitably a platinum (Pt) and / or a palladium (Pd) component. If the catalyst is sulfided prior to operation, the noble metal component will generally be present as sulfides during normal operation, but some of them may be present very well in elemental and / or oxide form. In addition to the Group VIII precious metal component, Group VIII non-noble metal components and / or Group VIB metal components may also be present on the catalyst. Thus, nickel (Ni), cobalt (Co) and / or chromium (Cr), molybdenum (Mo) or tungsten (W) can also be present in the catalyst phase-suitably in their sulfided form. Of the Group VIB metals, tungsten and chromium are preferred. An example of a very suitable first stage catalyst is then a noble metal based-catalyst disclosed in European Patent Application No. 0,653,242 and International Patent Application WO 96/03208. Specific examples of suitable catalysts include PdCr and PdW on silica-bonded zeolite Y, alumina-bonded zeolite Y, fluorinated alumina-bonded zeolite Y, silica-alumina or fluorinated alumina. Other examples are Pt of silica-alumina, PtPd of silica-bonded zeolite Y, PtPd of alumina-bonded zeolite Y, and PtPd of silica-alumina. All catalysts mentioned are preferably sulfided prior to operation. Particularly preferred first stage catalysts are sulfided PdW on silica- or alumina-bonded zeolite Y, sulfided PdW on silica-alumina, and sulfided PdW on fluorinated alumina.

The second hydrogen conversion step of the process according to the invention, i.e. step (b), depends on the type of hydrogen conversion catalyst used, such as hydrogenation, hydrodesulfidization, hydrodenitrification, hydroisomerization and two of these processes. Any combination of the above may be included. Hydrolysis of the paraffinic molecule can also occur in step (b), but can occur as a (little) side reaction to one or more of the hydrogen conversion reactions mentioned above. Therefore, the hydrogen conversion catalyst to be used in step (b) will not be a particularly suitable catalyst for the hydrolysis of paraffin molecules.

The hydrogen conversion catalyst used in step (b) of the process according to the invention, ie the second stage catalyst, is in principle hydrogenated, hydrodesulfurized, hydrodenitrified and / or hydrogenated with suitable hydrocarbons for the purpose of producing a base oil for lubrication. It can be any catalyst known to be active for isomerization.

Thus, the first class of suitable second stage catalysts are hydrogenation catalysts composed of at least one Group VIII metal component and optionally at least one Group VIB metal component as the hydrogenation component (s). The catalyst may have hydrogenation activity and may also have hydrogen desulfurization and / or hydrogen denitrification activity. In general, they do not possess any suitable hydroisomerization activity. Suitable Group VIII metal components include noble and non-noble metals and / or compounds thereof, generally oxides and / or sulfides. Thus, the second stage catalyst may consist of one or more non-noble metal Group V nickel (Ni) or cobalt (Co) and / or one or more precious metal Group V Pt and Pd. In this context it is noted that if a noble metal component is present in the second stage catalyst, it is suitable for the catalyst to at least partially sulfide before operation in order to increase its sulfur resistance. It will be appreciated that the degree of sulfidation depends on the sulfur content of the first stage effluent. At sufficiently low sulfur contents of the first stage effluent, it may not be necessary to sulfide the second stage noble metal-based catalyst.

In addition to the Group VIII metal component, the second stage catalyst may also consist of a Group VIB metal component which may be Cr, Mo and / or W in elemental, oxide and / or sulfide form. The second stage catalyst support is also a refractory oxide support and comprises a support as mentioned above for the first stage catalyst. If the second stage catalyst consists of non-noble metal group VIII, it may be advantageous to use phosphorus (P) as an accelerator. Examples of suitable second stage catalysts are then NiMo (P) on alumina or fluorinated alumina, CoMo (P) on alumina, NiW on fluorinated alumina, salica-alumina, fluorinated alumina or silica-bonding. Zeolite Y phase PdW.

A second class of suitable second stage catalysts are mainly catalysts having hydroisomerization activity. If the main purpose of step (b) is to lower the pour point of the first stage effluent, ie, dewaxing, these catalysts are used. Hydroisomerization catalysts are well known in the art and are generally based on intermediate pore size zeolite materials suitably composed of at least one Group VIII metal component, preferably Pt and / or Pd. Suitable zeolitic materials then include ZSM-5, ZSM-22, ZSM-23, ZSM-25, SSZ-32, Ferrierite, Zeolite Beta, Mordenite and Silica-aluminophosphate, such as SAPO-11 and SAPO-31. Include. Examples of suitable hydroisomerization catalysts are described, for example, in international patent application WO 92/01657. Since the hydroisomerization catalyst is generally destroyed relatively quickly by sulfur-containing compounds, the first stage effluent must have a low sulfur content before it is introduced into the second stage.

The amount of other metal present on the first and second stage catalysts can vary widely. Group VIII noble metals may suitably be present on the first and second stage catalysts in amounts ranging from 0.1 to 10, preferably from 0.2 to 5 weight percent (% wt). Weight percentage here refers to the amount of metal (calculated as an element) relative to the total weight of the catalyst. Similarly, the non-noble metal Group VIII metal may suitably be present on the second stage catalyst in an amount of from 1 to 25% by weight, preferably from 2 to 15% by weight, calculated as element relative to the total weight of the catalyst. If present at all, the Group VIB metal is suitably present in the first and second stages in an amount of from 5 to 30% by weight, preferably from 10 to 25% by weight, calculated as element relative to the total weight of the catalyst.

The operating conditions in the first and second hydrogen conversion stages are those which are conventionally applied in suitable hydrogen conversion operations. Thus, the working temperature ranges from 250 to 500 ° C., the working pressure ranges from 10 to 250 bar, and the weight hourly space velocity (WHSV) ranges from 0.1 to 10 kg oil per hour per liter of catalyst (kg / l.h). Preferably 0.5 to 5 kg / l.h, and the ratio of hydrogen to oil is suitably in the range of 100 to 2,000 liters of hydrogen per liter of oil. However, as already described above, at the given final yield of the base oil for lubrication, the first stage catalyst used according to the invention lowers the first stage operating temperature, thereby forming the multinuclear aromatic species formed in this first hydrogen conversion stage. This reduces the amount of, making the conditions less severe in the second hydrogen conversion step. In this context, it is noted that the active weighting only in the first hydrotreating step of 3 ° C. can significantly reduce the amount of polynuclear aromatics formed in advance.

Before being subjected to the second stage hydrogen conversion, the liquid effluent of the first stage may first be treated to remove unwanted gaseous species such as hydrogen sulfide (H ₂ S) and ammonia (NH ₃ ). In particular, in the case of feeds containing substantial amounts of sulfur- and nitrogen-containing compounds such as vacuum distillates derived from atmospheric residues, the treatment between the steps could be very advantageous. H ₂ S can be removed, for example, by absorption in aqueous amine solution. Di-isopropanolamine solutions are very useful in this respect. However, a preferred choice is to simultaneously remove H ₂ S and NH ₃ from the effluent by passing the first stage effluent through a high pressure stripper before being introduced to the second stage. In this way, the amount of all of these unwanted gases in the first stage effluent can be effectively reduced to very low levels, suitably less than 10 ppm each. This low level of H ₂ S and NH ₃ allows the use of a second stage catalyst with higher sensitivity to sulfur and nitrogen, such as (unsulfurized) noble metal-based catalysts. Instead, the use of these types of catalysts in the second hydrogen conversion step leads to the production of higher quality base oils, such as industrial grade white oils. The use of noble metal-based catalysts in both hydrogen conversion stages would allow the production of medical oils that should be free of aromatics, nitrogen compounds and sulfur compounds if the first stage is operated at sufficiently low temperatures to prevent the formation of polynuclear aromatics. Can be.

Thus, if the liquid effluent of the first hydrogen conversion stage is treated to remove H ₂ S and NH ₃ prior to introduction into the second hydrogen conversion stage, the second stage catalyst is suitably Pt and // as Group VIII metal components. Or a Pd component. This catalyst also preferably comprises a Group VIB metal component based on W or Cr. In this mode of operation, it may be advantageous to use the same noble metal-based catalyst in the first and second hydrogen conversion stages. If H ₂ S and NH ₃ are not removed from the first stage effluent but there are few optional sulfur- and / or nitrogen-containing compounds in the feed used, the nickel or cobalt component and the Group VIB metal as Group VIII metal components Preference is given to using a second stage catalyst consisting of a molybdenum or tungsten component as a component. Suitable examples of any of these catalysts have already been described above.

Recovery of the base oil for lubrication in step (c) is generally achieved by distillation of the second stage effluent. Each lubricating base oil is then recovered as a midstream fraction. Suitably the distillation is carried out under reduced pressure. However, atmospheric distillation can also be used. The cutoff point of the distillate fraction is chosen such that each recovered base oil has the desired viscosity.

If the second stage catalyst is a hydrogenation catalyst having no or little other hydroisomerization activity, then a continuous dewaxing step (d) is required to obtain a lubricating base oil having a sufficiently low pour point. Dewapping can be accomplished by catalyst dewaxing or solvent dewaxing. Both such dewaxing techniques are well known in the art. For example, suitable catalysts for use in catalyst dewaxing include catalysts based on ZSM-5, ZSM-23 or ZSM-35. Suitable dewaxing catalysts and dewaxing processes are described, for example, in US Pat. No. 3,700,585; 3,894,938; No. 4,222,855; No. 4,229,282; No. 4,247,388; And 4,975,177. Solvent dewaxing is also a well known method of dewaxing. The most commonly applied solvent dewaxing process is the methyl ethyl ketone (MEK) solvent dewaxing route. At this time, MEK is possibly mixed with toluene and used as a dewaxing solvent. For the purposes of the present invention, preference is given to using solvent dewaxing routes.

If the second stage catalyst is a hydroisomerization catalyst, then each dewaxing step may be unnecessary after step (c). In this case, the base oil for lubrication obtained in step (c) satisfies the specification for both the viscosity index and the pour point, and thus a treatment for lowering the pour point is unnecessary in this case. As already mentioned above, the first stage effluent must have a sufficiently low sulfur content before contact with the hydroisomerization catalyst. If the hydrocarbon oil feed used in step (a) is a hydrogen lead or synthetic day raffinate, which generally has a low sulfur and nitrogen content, then the treatment between the steps for removing H ₂ S and NH ₃ may be unnecessary. The first stage effluent may be passed directly to step (b). On the other hand, if the hydrocarbon oil feed used in step (a) has a relatively high sulfur and nitrogen content, for example in the case of vacuum distillates of atmospheric residues, H ₂ S and NH ₃ are required to be removed between the steps. .

In general, the resulting lubricating base oil using the process according to the invention has a viscosity index of at least 80, preferably at least 90, and more preferably at least 95, and up to -6 ° C, and preferably up to -9 ° C. Has a pour point of.

The invention will now be further illustrated by the following examples, without limiting the scope of the invention to this particular embodiment.

Example

Hydrocarbon oil vacuum distillates obtained by vacuum flashing of atmospheric residues and having the properties indicated in Table I were calculated on fluorinated alumina carrier (4.4% wt F, basic total carrier) (all as elements relative to the total weight of catalyst) Contacted with hydrogen in the first step in the presence of a presulfurized catalyst consisting of 4.3% wt Pd and 21.9% wt W). The effluent of the first stage was treated with hydrogen in the second stage in the presence of a conventional NiMoP / alumina catalyst (3.0% wt N, 13.0% wt Mo, 3.2% wt P, all calculated as elements relative to the total weight of the catalyst). Contact was made continuously. The properties of the final product after the usual solvent dewaxing at −20 ° C. and the reaction conditions applied in both steps are provided in Tables II and III, respectively.

Table I Feedstock Characteristics

* Vk 80 and Vk 100 represent kinematic viscosity in cts as determined at 80 ° C. and 100 ° C., respectively.

Comparative Example

The procedure as described above was repeated. Only then, the first stage catalyst consists of 5.0% wt Ni and 23.1% wt W on the fluorinated alumina carrier (4.6% wt F, basic total carrier). The process conditions and the properties of the product obtained after usual solvent dewaxing at -20 ° C are listed in Tables II and III, respectively.

Table II Process Conditions

Table III Product Properties

As seen from Tables II and III, noble metal-based catalysts are used, while other methods in the present invention to obtain products with better VI and viscosity at higher yields require lower temperatures in the first step.

Claims (12)

(a) contacting the hydrogen and hydrocarbon oil feed in a first step in the presence of a catalyst consisting of at least one Group VIII precious metal component and at least one Group VIB metal component on the refractory oxide support; (b) contacting the liquid effluent with hydrogen in a second step in the presence of a hydrogen conversion catalyst under hydrogen conversion conditions; And (c) recovering at least one lubricating base oil having a viscosity index of 80 or more. The process of claim 1 wherein the first stage catalyst comprises a platinum component, a palladium component, or a platinum and palladium component as a Group VIII noble metal component. The process of claim 2 wherein the first stage catalyst comprises a tungsten component or a chromium component as a Group VIB metal component. 4. The process of any of claims 1-3, wherein the first stage catalyst is sulfided. 5. The process of claim 4 wherein the first stage catalyst is silica or alumina-bonded zeolite Y phase sulfided PdW, silica-alumina sulfided PdW or fluorinated alumina sulfided PtW. The process according to claim 1, wherein the hydrogen conversion catalyst used in step (b) further comprises at least one Group VIB metal component. The process according to any one of claims 1 to 3, wherein the hydrogen conversion catalyst used in step (b) is a hydrogenation catalyst having no hydroisomerization activity, and the dewaxing treatment of the lubricating oil recovered in step (c) (d). Additional). The process according to any one of claims 1 to 3, wherein the hydrogen conversion catalyst used in step (b) is a hydroisomerization catalyst. The process according to claim 1, wherein the liquid effluent from step (a) is first treated to remove hydrogen sulfide and ammonia before contacting with hydrogen in step (b). 10. The method of claim 9 wherein hydrogen sulphate and ammonia are removed by passing the effluent through a high pressure stripper. The process according to claim 1, wherein the hydrocarbon oil feed is a vacuum distillate fraction derived from an atmospheric residue. 4. The hydrocarbon oil feed of claim 1 wherein the hydrocarbon oil feed is hydrogen lead or synthetic lead raffinate, the effluent of step (a) is passed directly to step (b) and the hydrogen conversion catalyst is hydroisomerized. The catalyst.