BRPI0609740A2 - A method for modifying the process by which wax crystals form in a paraffin-containing hydrocarbon liquid, fuel composition, and combination - Google Patents

Abstract

METHOD FOR MODIFYING THE PROCESS BY WHICH WAX CRYSTALS FORM IN A HYDROCARBON LIQUID CONTAINING PARAFFINS, COMBUSTIBLE COMPOSITION, AND COMBINATION. Heavy fractions of paraffinic lubricants, produced on wax removal catalysts, are effective as modifiers of existing hydrocarbon wax crystals, despite the fact that these heavy fractions have pour points above those of liquid hydrocarbons.

Description

"METHOD FOR MODIFYING THE PROCESS BY WHICH WAX CRYSTALS ARE FORMED IN A HYDROCARB ONETO CONTAINING Paraffins, FUEL COMPOSITION, AND, COMBINATION" FIELD OF INVENTION

The present invention broadly relates to the modification of low temperature properties of hydrocarbon fluids and, more particularly, to the use of a heavy fraction of paraffinic lubricants produced from a Fischer-Tropsch product as a crystal modifier. Wax

BACKGROUND OF THE INVENTION

Wax crystal modifiers are additives used in the petroleum industry to improve the cold flow properties of numerous hydrocarbon fluids such as crude oils, diesel oils, lubricating oils and the like. Basically, wax crystal modifiers work by somehow modifying the process by which wax crystals form in solutions when the temperature of the solution is lowered. For example, they may interact with the paraffins in the hydrocarbon fluid to delay the onset of crystallization; they may modify the wax morphology to a form less prone to clogging a filter or forming a gel; and they can operate to prevent fresh paraffin from sticking to the wax. Thus, wax crystal modifiers are used in lubricating oils in the form of pour point depressants, and in diesel type fuels as cold filter plugging depressants. They also find use as mist spot depressants in fuels and wax inhibitors in crude oils.

Wax crystal modifiers commonly employed include chlorinated hydrocarbons, polyolefins and ethylene vinyl ester copolymers. SUMMARY OF THE INVENTION

Surprisingly, it has been found that heavy fractions of paraffinic lubricants produced on wax removal catalysts are effective as wax crystal modifiers. In fact, it has been found that when added to a base lubricating oil, the above mentioned heavy fractions will lower the pour point of the base lubricating oil despite the fact that the heavy fraction has a pour point well above that of the base oil. .

By heavy paraffinic lubricant fractions, with wax removed, should be understood those fractions having a final boiling point exceeding 454 ° C, preferably exceeding 510 ° C and even exceeding 538 ° C after 95 weight percent, of the lubricant has been removed. Typically, the lubricant will be one having an initial boiling point exceeding 371 ° C.

In a preferred embodiment of the invention, the heavy fraction is derived from a Fischer-Tropsch product by catalytic hydroisomerization of the product to produce a lubricating oil, and distilling the lubricating oil to obtain a high boiling heavy fraction and a fraction with the lowest boiling point.

In one embodiment of the invention, the process by which the wax crystals are formed in a first paraffin-containing hydrocarbon liquid is modified by the addition of a second lubricant containing larger amounts by weight of a heavy fraction containing that of the first liquid, the second lubricant being added in an amount sufficient to modify the wax crystal formation process of the first liquid.

BRIEF DESCRIPTION OF DRAWINGS

Figures 1 to 6 are graphical illustrations of various embodiments of the invention and also depict the results of Examples 1 to 6, respectively.

DETAILED DESCRIPTION OF THE INVENTION

The wax crystal modifiers of the present invention comprise the heavy fractions of paraffinic lubricants produced on wax removal catalysts. Such paraffinic lubricants include those lubricants obtained from a mineral oil by hydrocracking, hydroisomerization, solvent extraction and hydroprocessing and combinations thereof, and lubricants obtained from polyethylene and Fischer-Tropsch paraffinic products. In a preferred embodiment of the invention, the heavy fraction of a paraffinic lubricant, suitable for use as a wax crystal modifier, is derived from a Fischer-Tropsch product that has had the wax catalytically removed.

Preferably, the Fischer-Tropsch product is obtained by conducting a Fischer-Tropsch process under conditions which are sufficient to produce products containing above 9.07 kg of 371 ° C + product by 45.36 kg of converted CO and, more preferably above 10.88 kg of 371 ° C + product per 45.36 kg of converted CO. This can be achieved by at least one of (a) proper selection of process operating conditions, and (b) catalyst selection.

Preferably the Fischer-Tropsch process is conducted at temperatures not above 221 ° C, for example from about 148 ° C to about 221 ° C. More preferably, the reaction is conducted at no more than 210 ° C. C. Operating pressures are typically in the range of from about 68.95 kPa abs to about 4137 kPa abs, preferably from about 1723 kPa abs to about 2413 kPa abs, and spatial velocities from about 1000 to 25000 abs. cm3 / cm3 / hour.

The Fischer-Tropsch process is preferably conducted in a bubbling column suspension. In bubbling column suspension reactors the catalyst particles are suspended in a liquid and the gas is fed from the bottom of the reactor through a gas distributor. Gas bubbles rise through the reactor and reagents are absorbed into the liquid and diffuse into the catalyst, where they are converted to both liquid and gaseous products. Gaseous products are recovered from the top of the column and liquid products are recovered by passing the suspension through a filter separating the solid catalyst from the liquid. An optimal method for operating a three-phase bubbling suspension column is disclosed in EP 0450860 B1, which is hereby incorporated by reference in its entirety.

Suitable Fischer-Tropsch catalysts comprise one or more Group VIII metals, such as Fe, Ni, Co and Ru, in an inorganic oxide support. In addition, the catalyst may also contain a promoter metal. A suitable catalyst for the process of the invention is titanium-supported, rhenium-promoted cobalt, having a Re: Co weight ratio in the range of about 0.01 to 1, and containing about 2 to 50% by weight of cobalt. . Examples of such catalysts can be found in U.S. 4568663; U.S. 4,992,406; and U.S. 6,111,714.

Another suitable and preferred catalyst for the Fischer-Tropsch process comprises cobalt and especially cobalt and rhenium on a support comprising mainly titanium and a small amount of cobalt aluminate. Generally, the support should contain at least 50% by weight of titania and preferably from 80 to about 97% by weight of titania based on the total weight of the support. About 20 to 100% by weight, and preferably 60 to 98% by weight of titania of the support is in the rutile crystalline phase, with the difference being the anatase crystalline phase or amorphous phases. The amount of cobalt aluminate in the binder is dependent on the amount of cobalt and aluminum compounds used in the formation of the support. Suffice it to say that sufficient cobalt is present in the support to provide a cobalt / aluminum atomic ratio of greater than 0.25, preferably from 0.5 to 2, and even more preferred about 1. Thus, in a ratio Co / Al of 0.25, about half of the aluminum oxide is present in the form of cobalt aluminate. In a Co / Al ratio of 0.5, substantially all of the alumina oxide present is present as cobalt aluminate. At Co / Al ratios above 0.5, the support will contain cobalt titanate in addition to cobalt aluminate, and will be essentially alumina free.

The support is typically formed by spray drying an appropriate aqueous suspension of titania, alumina binder material and optionally silica binder material in a heated air purged chamber at an outlet temperature of about 105 ° C to 135 ° C. Spray drying produces a spherical support with a size range of about 20 to 120 microns. This spray-dried support is then calcined at temperatures ranging from 400 ° C to 800 ° C, and preferably about 700 ° C. Then the calcined material is impregnated with an aqueous solution of a cobalt compound, preferably being cobalt nitrate in an amount sufficient to calcine at least part of the alumina to cobalt aluminate. Preferably sufficient cobalt compound is used to convert from 50% to 99+% of alumina to cobalt aluminate. Accordingly, the amount of cobalt compound added during the preparation of the support will correspond to an Co: Al atomic ratio in the range of 0.25: 1 to 2: 1, and preferably 0.5: 1 to 1: 1. In fact, it is especially preferred that the support produced be substantially free of alumina.

The calcination of the cobalt impregnated support is preferably conducted at an air temperature in the range of from about 700 ° C to about 1000 ° C, preferably from about 800 ° C to about 900 ° C.

Typically, the support should have a surface area in the range of from about 5 m2 / g to about 40 m2 / g, preferably from 10 m2 / g to 30 m2 / g. Pore volumes range from about 0.2 cm3 / g to about 0.5 cm3 / g, and preferably from 0.3 cm3 / g to 0.4 cm3 / g.

In preparing the catalyst, cobalt and rhenium promoter are combined with support by any of a variety of techniques well known to those skilled in this technology, including impregnation (either promoter co-impregnation or serial impregnation - or drying). atomization or incipient wetting techniques). Since a preferred catalyst for the fixed bed Fischer-Tropsch process is one in which the catalytic metals are present on the outside of the catalyst particle, ie in a layer not more than 250 microns deep, and preferably not more than 200 microns deep, a preferred method for catalyst preparation is the spray method described in US 5,141,050, incorporated herein by reference, or EP 0266898, also incorporated herein by reference. For suspended Fischer-Tropsch processes, the catalysts are preferably produced by impregnation with incipient wetting of spray-dried supports. When using the incipient wetness impregnation technique, organic impregnation aids are optionally employed. Such auxiliaries are described in U.S. 5,862,660, U.S. 5,856,261 and U.S. 5,863,856, all of which are incorporated herein by reference.

The amount of cobalt present in the catalyst should be in the range of 2 to 40% by weight, and preferably 10 to 25% by weight, while rhenium should be present in weight ratios of about 1/20 to 1. / 10, of the weight of cobalt.

By selecting the appropriate conditions for the Fischer-Tropsch reaction, the appropriate catalyst, or both as described above, the amount of high molecular weight waxy products formed is favored.

With a cut at 232 ° C, a waxy product is separated from the other hydrocarbons produced in the Fischer-Tropsch process and then catalytically hydroisomerized. Suitable hydroisomerization catalysts typically include at least one Group VIII hydrogenation metal component selected from Pt, Pd, Rh, Ir and preferably at least Pt on a refractory metal oxide support, or preferably in a zeolite holder. The catalyst typically contains from about 0.1 wt% to about 5 wt% metal. Examples of such catalysts include a noble metal, e.g., Pt in ZSM-23, ZSM-35, ZSM-48, ZSM-57 and ZSM-22.

A preferred catalyst is Pt in ZSM-48. The preferred preparation for ZSM-48 is disclosed in U.S. 5,075,269, incorporated herein by reference. Pt is deposited on the ZSM-48 by techniques well known in the art such as impregnation, dry techniques or incipient wetting.

The isomerization is conducted under temperature conditions from about 260 ° C to about 482 ° C, preferably from 288 ° C to 385 ° C, pressures from 6.89 to 68950 kPa of H2, preferably from 689, 5 to 17237.5 kPa H2, hydrogen gas ratios from 50 to 3500 SCF / bbl (1.42 to 99.1 Nm / bbl),

and a spatial velocity in the range of from 0.25 to 5 v / v / h, preferably from 0.5 to 3 v / v / h.

Following isomerization, the isomerized may be distilled into cuts with several ranges. The heavy fraction used as a wax crystal modifier should typically have a final boiling point after 95 weight percent has been distilled off, greater than 454 ° C, preferably greater than 510 ° C, or even higher.

In an alternative embodiment of the invention, the heavy fraction used as a wax crystal modifier may be obtained as the waxy fraction removed from a paraffinic oil with the turbidity removed. The waxy fraction may be removed by techniques known in the art such as filtration, precipitation, distillation, adsorption, and the like.

In yet another embodiment of the invention, the heavy fraction, used as a wax crystal modifier, is obtained by catalytic hydroisomerization of a polyethylene wax and distilling the isomerized, taking the heavy fraction of the material with boiling point above 566 °. Ç.

Low molecular weight polyethylene waxes are derived from high density polyethylene. They are hard crystalline materials that melt with a low viscosity. They do not contain any functional chemical groups. A range of products can be obtained using different distillation conditions. Examples are SasolWax's commercially available Polyflo® products. These polyethylene waxes may be catalytically hydroisomerized in a process similar to that described above for Fischer-Tropsch waxy feeds.

The heavy fraction, or waxy material, is added to the lubricant having its pour point lowered in an amount sufficient to lower the oil pour point. Typically this should be in the range of about 0.01 to 30% by weight based on the weight of the lubricating oil.

Base lubricating oils which may have their pour points lowered with the additive of the invention include lubricating oils derived from paraffinic Fischer-Tropsch products and conventional lubricating oils prepared from petroleum materials.

In one aspect of the invention the heavy fraction may be added to the lubricant having its pour point lowered without being separated from the paraffinic lubricant having the wax removed from which it constitutes a fraction. Accordingly, a first base lubricant containing some or no heavy fraction may be combined with a second lubricant containing a greater amount of heavy fraction than that of the first lubricant. The amount of the second lubricant combined with the first lubricant should be sufficient to lower the pour point of the first lubricant. Generally, the amount of the second lubricant added to the first lubricant is that amount which should provide a combination of lubricants containing from about 0.01 to 0.50 part by weight of a heavy fraction, preferably from about 0.10 to about 0.15%. 01 and 0.30, and even more preferred between 0.01 and 0.20.

Generally, to provide a pour point depression effect by combination, the amount of the heavy fraction in the second lubricant should be at least 0.10 parts by weight of the second lubricant, preferably 0.20 parts by weight. most preferably 0.50, and most preferably 0.70 parts by weight of the second lubricant.

Fractional amounts of the heavy fraction, ie material having a final boiling point greater than 454 ° C, may be determined by any appropriate method for determining the boiling point distribution, such as fractional distillation or simulated distribution measurement. boiling point by gas chromatographic distillation. EXAMPLES

In these Examples, the pour point was determined by the ASTM D-5950 test method and the mist point by the ASTM D5773.

In addition the Pt / ZSM-48 catalyst used was prepared according to U.S. 5075269 by adding the Pt compound by impregnation followed by calcination and reduction.

Example 1

Fischer-Tropsch wax was processed over Pt / ZSM-48 in a wide cut mode. A large boiling feed fraction, nominally a material 221 ° C and above, was hydroisomerized under conditions sufficient to reduce the pour point and the mist point of the product. The product of this broad boiling process was fractionated into 388-524 ° C and 524 ° C +. The pour point and the mist point of the fraction 388-524 ° C were -18 ° C and -6 ° C, respectively. The pour point and the fog point of the 524 ° C fraction were -9 ° C and 11 ° C, respectively. When the 524 ° C + fraction was added to the 388-524 ° C fraction, it was observed that the pour point decreased dramatically, with slight increase in the fog point, at low addition ratios. The results are shown in Figure 1.

As can be seen, with about 5% addition of the 524 ° C + fraction, a maximal pour point depression effect was observed.

Example 2

A misty Fischer-Tropsch lubricant was prepared by hydroisomerizing a nominal fraction 221 ° C over Pt / ZSM-48 at approximately 321 ° C, 1723,75 kPa man H2 and 1 LHSV. The resulting product was fractionated to yield the 538 ° C + fraction, having a pour point of -5 ° C.

A conventional catalytic wax removal base material having a viscosity of 4.33 cSt and a pour point of -20 ° C has been combined with the misted Fischer-Tropsch lubricant having a pour point of -5 ° C. ° C and a cut-off point of 538 ° C +. Pour point was significantly reduced from -20 ° C to -30 ° C with the addition of 10% by weight of heavy GTL lubricant. The results are shown in Figure 2.

Example 3

A conventional petroleum derived base material produced by catalytic wax removal having a viscosity of 5.98 cSt and a pour point of -16 ° C was combined with a misty Fischer-Tropsch lubricant fraction having a melting point. -5 ° C, a mist point of 23 ° C and a cutoff point of 538 ° C +, and prepared as described in Example 2. With about 20% addition of heavy FT oil, a maximum point reduction from -16 ° C to -24 ° C was obtained. Results are provided in Figure 3. Example 4

A conventional petroleum derived base material produced by catalytic wax removal having a viscosity of 5.98 cSt and a pour point of -16 ° C was combined with a Fischer-Tropsch lubricant that had the mist selectively removed, having a pour point of -5 ° C, a fog point of 13 ° C and a cutoff point of 510 ° C +. In this example, with only 5-10 percent addition, the maximum pour point reduction was achieved by changing the pour point from -16 ° C to a pour point of -21 ° C. The mist point in this example it was only slightly increased from -10 ° C to -10 ° C. In contrast to Example 3, where a 371 ° C + misty oil was used for pour point depression, this example shows a lower point depression response. flow rate for oil with mist removed as adsorbate. The results are shown in Figure 4. Example 5

A conventional petroleum derived catalytic wax base material having a viscosity of 5.98 cSt and a pour point of -16 ° C was combined with a misty fraction removed from a Fischer-Tropsch lubricant sample mist, prepared as described in Example 2. Prior to removal of mist the lubricant had a pour point of -5 ° C, a mist point of 36 ° C and a cutoff point of 510 ° C +. The mist removed from this lubricant had a mist point of 50 ° C and a pour point above room temperature. The results are shown in Figure 5. Example 6

Polyethylene wax, with a MW of 10000 and a melting point of approximately 110 ° C, was converted into a batch reactor on ZSM-48 catalyst for 2 hours at 346 ° C and 3447.5 kPa hydrogen man.

The product produced from this catalytic reaction had the following boiling point distribution. As can be seen from GDC data, the isomerized product contains 67% of the 371 ° C + material.

GDC% Separated, In Bulk

160 ° C 4.47

260 ° C 15.89

371 ° C 32.31

454 ° C 47.98

510 ° C 59.65

565 ° C 72.08

The total liquid product of this process had a pour point of -3 ° C and a mist point of 36.4 ° C. This product, over its full boiling range, was added to a conventional petroleum derived base material, produced by catalytic wax removal having a viscosity of 5.98 cSt and a pour point of -16 ° C. The results of these combinations are shown in Figure 6. The pour point of the resulting combination is significantly decreased at low concentrations. relative to the starting material base. Although this material has a lower initial boiling point, it is predominantly a 371 ° C material. This concentration of heavy lubricant present in this broad boiling isomerized is sufficient to achieve the desired pour point reduction response.

Claims (17)

Method for modifying the process by which wax crystals form in a paraffin-containing hydrocarbon liquid when the temperature of the liquid is decreased, which comprises adding to the liquid an effective amount of a heavy fraction of a paraffin lubricant, produced on a wax removal catalyst. Method according to claim 1, characterized in that the heavy fraction has a final boiling point above -454 ° C. Method according to claim 2, characterized in that the paraffinic lubricant is produced from a Fischer-Tropsch product. Method according to claim 2, characterized in that the heavy fraction is extracted as a waxy material from said paraffinic lubricants. Method according to claim 2, characterized in that the paraffinic lubricant is produced from a polyethylene wax. A method according to claim 3, characterized in that the hydrocarbon liquid is a base lubricating oil and where the heavy fraction is added in an amount that lowers the pour point. A method according to claim 3, characterized in that the hydrocarbon liquid is a first base lubricating oil, and the heavy fraction is added in an amount that lowers the pour point as a second base oil containing a larger fractional amount of the heavy fraction than that contained in the first lubricating oil. A method according to claim 7, characterized in that the second lubricating oil is added to the first lubricating oil in an amount sufficient to provide a combination containing from about 0.01 part by weight to about 0.5 part by weight of a heavy fraction. A method according to claim 8, characterized in that the amount of heavy fraction in the second lubricant is in the range of from about 0.10 to about 0.70 parts by weight. A method according to claim 3, characterized in that the hydrocarbon liquid is a crude oil and the heavy fraction is added in an amount sufficient to lower the wax deposition temperature. A method according to claim 3, characterized in that the hydrocarbon liquid is a diesel or heating fuel and the heavy fraction is in the form of a second base oil containing a greater fractional amount of the heavy fraction than that contained in the hydrocarbon liquid. first lubricating oil, and the second base oil is added in an amount to lower the cold filter clogging point. A method according to claim 11, characterized in that the second lubricating oil is added to the first lubricating oil in an amount sufficient to provide a combination containing from about 0.01 part by weight to about 0.5 part by weight of the heavy fraction. A method according to claim 12, characterized in that the amount of heavy fraction in the second lubricant is in the range of from about 0.10 to about 0.70 parts by weight. 14. Fuel composition, characterized in that it comprises a principal amount of a diesel or heating fuel and a heavy fraction of a paraffinic lubricant produced over a wax removal catalyst, the heavy fraction being in an amount sufficient to lower the point. clogging the fuel cold filter. Composition according to Claim 14, characterized in that the heavy fraction has a final boiling point above about 454 ° C. 16. Combination, characterized in that it is a first paraffin-containing hydrocarbon liquid and a second paraffin-containing hydrocarbon liquid, wherein the second liquid contains a heavy hydrocarbon fraction having a final boiling point greater than 454 ° C in a greater than that in the first liquid and where the amount of heavy fraction in the total combination is in the range of about 0.01 to -0.5 parts by weight. Combination according to claim 16, characterized in that the second liquid contains from about 0.10 to -0.70 part by weight of the heavy hydrocarbon fraction.