PROCESS FOR PRODUCING HIGH VISCOSITY INDEX LUBES

Abstract: A combination process for producing high viscosity index lubes from light olefins is provided wherein light olefins are first passed over a ZSM-23 catalyst and the liquid product therefrom is then processed over a ZSM-5 type catalyst to provide a lubricating oil with a higher viscosity, high Viscosity Index and low pour point in greater yield than obtained with either of the catalysts alone.

Description: This invention is directed to a combination process for the conversion of olefins over zeolite catalyst to lubricating oil of low pour point, high viscosity and high Viscosity Index (VI). High yields are attainable by this process. GB-A-2,106,132 proposes the conversion of normally gaseous olefins to high boiling hydrocarbons by two-stage contacting with an intermediate pore size silicaceous crystalline molecular sieve. U.S. Patent 4,126,644 discloses the conversion of a liquid fraction from a Fischer-Tropsch synthesis, predominantly C₅-C₁₀ olefins, over zeolites of the ZSM-5 type in order to produce higher boiling products. U.S. Patent 3,322,845 is directed towards the manufacture of high VI, low pour point lube oils from C₁₀ to C₁₈ normal alpha olefins, processing them over crystalline aluminosilicate zeolites other than those of the ZSM-5 type. The present invention provides a process for synthesizing a lubricating oil from an olefinic feedstock, which process comprises in a first stage passing the feedstock containing a C₂ to C₁₈ olefin or a mixture thereof over a catalyst comprising a zeolite having the structure of ZSM-23 to form a liquid product boiling below the lube oil range and thereafter in a second stage passing the liquid effluent from the first stage over a catalyst comprising a zeolite having the structure of ZSM-5 to form a lubricant oil product and separating said product from the second stage reaction zone. The zeolites are preferably employed in the hydrogen form. The combination process of this invention is directed to using a ZSM-23 catalyst, as described in U.S. Patent 4,076,842 to produce lube oils by converting an olefin or a mixture thereof, generally (for example C₈ to C₁₈ or C₂ to C₁₆, preferably C₂ to C₈ and especially C₃ or C₄ alpha) olefins, at elevated temperatures and pressures to a liquid product characterised by low branching having a boiling point below the lube range and which is thereafter processed over a ZSM-5 type catalyst to provide a lube oil fraction having an enhanced viscosity index. The process of the first stage of this invention, i.e., the stage wherein the olefins are contacted with the ZSM-23 catalyst, is carried out at temperatures ranging from 177°C to 343°C (350°F to 650°F) at pressures ranging from 791 to 34575 kPa (100 to 5000 psig), and preferably from 2859 to 13890 kPa (400 to 2000 psig) and at space velocities ranging from 0.1 to 10 WHSV and preferably from 0.2 to 2 WHSV. Similar process conditions may be utilized in the second stage. As stated hereinabove, the first stage in the instant combination process uses ZSM-23 catalyst. ZSM-23 catalyst is described in U.S. Patent 4,076,842 to Plank et al. The ZSM-23 catalyst utilised in this invention have essentially the same X-ray diffraction pattern as set forth in U.S. Patent 4,076,842. A substantially pure form of silicate is used for synthesis, however, a preferred commercially available product is marketed under the name of HI-SIL, a finely divided silica in hydrated form contains trace impurities of Al₂O₃ and NaCl. The original cations associated with ZSM-23 may be replaced by a wide variety of other cations according to techniques well known in the art. Typical replacing cations will include hydrogen, ammonium, and metal cations, including mixtures of the same. Of the replacing metallic cations, particular preference is given to cations of metals such as rare earth metals, manganese and calcium, as well as metals of Group II of the Periodic Table. The ZSM-23 catalyst used in the invention is preferably the hydrogen form. Typical ion exchange techniques would be to contact the ZSM-23 zeolite with a salt of the desired replacing cation or cations. Although a wide variety of salts can be employed particular preference is given to chlorides, nitrates and sulfates. Representative ion exchange techniques are disclosed in a wide variety of patents, including U.S. Patents 3,140,249, 3,140,251 and 3,140,253. The ZSM-23 zeolite is preferably admixed with an inorganic material which serves as a binder in order to provide such desirable properties thereto as improved crush resistance. The binders or matrices are extremely well known in the art and include various inorganic oxides, such as silica, alumina, magnesia, zirconia, thoria, or combinations thereof. The preferred matrix is alumina. The second stage catalyst utilized in this invention comprises zeolite ZSM-5 such as HZSM-5 having an intermediate pore size of greater than about 5 Angstroms. ZSM-5 is described in greater detail in U.S. Patent 3,702,885 and Reissue 29,948. Generally, speaking, lower or light olefins include from C₂ to C₁₆ olefins with from C₂ to C₈ being preferred. The following examples illustrate the present invention. In the examples, the zeolite was prepared in 0.16cm (1/16") extrudate form (35 wt.% alumina binder), sized with 14-25 mesh, and 4.9 g placed in the 1.55cm (3/8") ID stainless steel micro-unit reactor. The reactor fill was then treated in situ with hydrogen at 482°C (900°F) for one hour to ensure a standard dried condition before the introduction of propylene. Standard run conditions were downflow, 0.5 WHSV EXAMPLE 1 HZSM-5, 40/l SiO₂/Al₂O₃ Propylene was passed at 10443 kPa over HZSM-5 extrudate having an alpha value of about 400 for a total of four days, the first two at an average catalyst temperature of 204°C (400°F), and the last two days at 232°C (450°F). Liquid recovery was 97 wt. % The liquid was distilled, finally under vacuum to separate lube bottoms product, and portions of the bottoms were vacuum topped further to give several lube products with the following yields and properties: EXAMPLE 2 HZSM-23, 114/l SiO₂/Al₂O₃ The zeolite in this example was prepared as described in U.S. Patent No. 4,076,842, except that HI-SIL, a solid amorphous silica and aluminum sulfate were used instead of colloidal silica and sodium aluminate. The zeolite was synthesized in 24 hours at a crystallization temperature of 174°C (345°F). Propylene was charged over the extrudate catalyst for a total of four days, the first three at an average catalyst temperature of 210.56°C (411°F), and the last 238°C (461°F). Liquid recovery was 95 wt. %. Distillation of the liquid product gave the following results: Viscosity indices are higher than those of Example 1, but viscosities are lower at the same yield level (90, 120, 152 SUS at 30, 22 and 18% yield versus 170, 201 and 307 SUS at 31, 23 and 18% yield respectively). EXAMPLE 3 Propylene was charged over the extrudate catalysts of Examples 1 and 2 at 204°C (400°f) at several WHSV's and temperatures listed in the table below. The liquid products had average carbon numbers ranging from 9.1 to 11.5, well below that necessary for lubricating oils ( C₂₀). The CH₃ groups per average molecule were determined by infra-red analysis. At about the same conversion level, the liquid products from HZSM-23 have fewer methyl groups than those from HZSM-5, demonstrating that HZSM-23 makes a more linear oligomer product than HZSM-5. EXAMPLE 4 A blend of equal weights of even carbon number C₆-C₂₀ l-olefins obtained from Shell Chemical Company (labelled Neodene 6, 8 etc and ranging in normal alpha olefin content from 95.2 to 97%) was processed over the HZSM-5 extrudate catalyst of Example 1 and 10443 kPa, for 5.7 days at 0.6-0.9 WHSV, 204 to 232°C (400-450°f). The CH₃ groups per average molecule for this blend as determined by IR was 0.85. Liquid recovery was 99 wt. %. Distillation of the liquid product gave the following results. These results show that low branching leads to high yield of high viscosity index lubes, and demonstrate the advantages of the two-stage process. Viscosity is higher at the same yield level compared to HZSM-23 alone and viscosity index is higher compared to either HZSM-5 or HZSM-23 alone.

Claims: A process for synthesizing a lubricating oil from an olefinic feedstock, which process comprises in a first stage passing the feedstock containing a C₂ to C₁₈ olefin or a mixture thereof over a catalyst comprising a zeolite having the structure of ZSM-23 to form a liquid product boiling below the lube oil range and thereafter in a second stage passing the liquid effluent from the first stage over a catalyst comprising a zeolite having the structure of ZSM-5 to form a lubricant oil product and separating said product from the second stage reaction zone. The process of claim 1 wherein the feedstock comprises a C₂ to C₈ olefin or a mixture thereof. The process of claim 2 wherein the olefin is a C₃ or C₄ alpha olefin or a mixture thereof. The process of any one of claims 1 to 3 wherein the respective catalyst comprise HZSM-23 and HZSM-5.

Inventors: CHESTER, ARTHUR WARREN, GARWOOD, WILLIAM EVERETT, LUCKI, STANLEY JOHN, TABAK, SAMUEL ALLEN
Applicants: MOBIL OIL CORPORATION
Application year: 1985
Main classification: C10G71
IPC codes: C10G57, C10M105, C10G69, B01J29, C10G50, C10N20