DE3881180T2 - METHOD FOR IMPROVING LUBRICANTS IN A WAX ISOMERIZATION USING LOW TREATMENT GAS SPEEDS. - Google Patents

Description

The present invention relates to a process for improving the yield of lubricating oil by paraffin isomerization using low treating gas rates.

BE-A-627 517 and the corresponding GB-A-1 002 857 disclose and claim a process for converting waxy hydrocarbons to obtain an oil product having a higher isoparaffin content than the feedstock, which comprises contacting the hydrocarbons at elevated temperature and in the presence of hydrogen with a catalyst comprising a platinum group metal, a halogenatable inorganic oxide support and at least 1% by weight of fluorine, the catalysts having been prepared by contacting the support with the vapour of a fluorine compound of the general formula

(where X is carbon or sulfur and Y is fluorine or hydrogen) under conditions that do not destroy the oxide structure or produce free fluorine or volatile metal-fluorine complexes to give the catalyst containing at least 1 wt.% fluorine. Preferably, the feed contains at least 50 wt.% of the waxy hydrocarbon. Preferably, the hydrocarbons are contacted at a temperature of 500 to 1,000°F (260 to 538°C) and a pressure of 0 to 20.69 MPa (atmospheric).

The present invention comprises the use of a process for obtaining an improved yield of lubricating oil in the viscosity range of 5.6 to 5.9 mm²/s (5.6 to 5.9 cSt) at 100°C from isomerized wax comprising (1) heating the wax over an isomerization catalyst comprising a Group VI metal, Group VIII metal and mixtures supported on a halogenated refractory metal oxide support under isomerization conditions comprising a temperature in the range of 270 to 400°C, a pressure in the range of 3.45 to 20.60 MPa (500 to 3,000 psi) H₂ and a throughput in the range of 0.1 to 10 vol/vol/hour, but isomerized at a low treat gas rate in the range of 89.05 to 890.53 liters H₂ gas/liter oil (500 to 5,000 SCF/bbl H₂), and (2) fractionating the isomerize to recover a lubricating oil fraction in the boiling range of 330°C to 600°C from which, after dewaxing, oil is recovered in the viscosity range of 5.6 to 5.9 mm²/s (5.6 to 5.9 cSt) at 100°C.

The treat gas rate may be in the range of 356.21 to 712.42 liters H2 gas/liter oil (2,000 to 4,000 SCF/bbl H2), e.g., in the range of 356.21 to 534.32 liters H2 gas/liter oil (2,000 to 3,000 SCF/bbl H2).

The paraffin to be isomerized may be selected from synthetic paraffins and crude paraffins.

The catalyst may consist of a Group VIII metal on a fluorided alumina support. The Group VIII metal may be platinum and the alumina may be γ-alumina.

The isomerizate can be fractionated to obtain a lubricating oil fraction in the boiling range of 370ºC+.

It has been found that the yield of lubricating oil in the viscosity range of 5.6 to 5.9 mm²/s (5.6 to 5.9 cSt) can be improved by conducting the isomerization process at low treat gas rates as described herein. In addition to the improved yield of lubricating oil from the isomerize, the wax content of the lubricating oil fraction of the isomerize is lower when the isomerization is conducted at a low treat gas rate.

Operating at lower treat gas rates produces an increased yield of isomerizate oil in the boiling range of 370ºC+, which has a viscosity range of 5.6 to 5.9 cSt/100ºC. This oil fraction also has a reduced wax content and should therefore result in a reduced load on the dewaxer.

The paraffin that is isomerized can come from a number of sources. Synthetic paraffins from Fischer-Tropsch processes can be used, as well as paraffins obtained from the Solvent or self-cooling dewaxing of conventional hydrocarbon oils, as well as mixtures of these paraffins. Paraffins from the dewaxing of conventional hydrocarbon oils are generally called slack waxes and usually contain a significant amount of oil. The oil content of these slack waxes can generally be from 0 to 45% or more, usually from 1 to 30% oil. For the purposes of this application, the paraffins are divided into two categories: (1) light paraffinic waxes, which boil in the range of about 300 to 580°C, and (2) heavy microparaffins, which have a significant fraction (> 50%) in the boiling range above 600°C.

The isomerization is carried out over one of the standard hydroisomerization catalysts containing a hydrogenation metal component selected from Group VI and Group VIII mixtures and Group VIII metals, preferably Group VIII metals, especially Group VIII noble metals and most preferably platinum. Metal loading ranges are in the range of 0.1 to 5.0 wt.% metal, preferably 0.1 to 1.0 wt.% metal and most preferably 0.2 to 0.6 wt.% metal.

The hydrogenation metal component is supported on a halogenated, refractory, inorganic metal oxide support, preferably alumina or silica-alumina, most preferably the transition aluminas, e.g. gamma-alumina. The halogen is usually chlorine or fluorine or mixtures thereof, preferably fluorine, with the net halogen content in the range of 1 to 10 wt.% and preferably 2 to 8 wt.%.

The preferred catalyst comprises a hydrogenation metal component which is a Group VIII metal or mixture thereof, preferably a Group VIII noble metal and most preferably platinum on a fluorided alumina or alumina-containing material, preferably alumina or predominantly (ie > 50%) alumina material, most preferably γ- or eta-alumina, the catalyst being in its as-incorporated form in the paraffin feedstock. Form characterized by (1) having a hydration level of 60 or less, preferably 10 to 60, determined as the relative amount of hydrate represented by a peak in the X-ray diffraction (XRD) spectrum at 2 0 = 5.66 Å when a hydration level of 100 corresponds to an XRD peak height exhibited by a standard material consisting of 0.6 wt% Pt on 150 m²/g of γ-alumina containing 7.2 wt% F, wherein the fluorine was applied using an aqueous solution containing a high concentration of HF, ie 10% HF and more, preferably 10 to 15 wt% HF, and the material was dried at 150°C for 16 hours; (2) has a surface nitrogen content N/Al ratio of 0.01 or less, preferably 0.007 or less, and most preferably 0.004 or less, as determined by X-ray photoelectron spectroscopy (XPS); (3) has a total fluorine concentration of about 2 to about 10 wt.%; and (4) has a surface fluoride concentration present in a layer extending from the surface of the particle (e.g., 1/16 inch extrudates) to a depth of 1/100 inch of less than 3 wt.%, preferably less than 1 wt.%, most preferably less than 0.5 wt.% fluorine in that zone, provided that the surface fluoride concentration is less than the total fluoride concentration.

The fluoride content of the catalyst can be determined in several ways:

One technique analyzes the fluoridated catalyst using the oxygen combustion methodology well established in the literature. Approximately 8-10 mg of the sample is mixed with 0.1 g of benzoic acid and 1.2 g of mineral oil in a stainless steel combustion capsule which is transferred to a 300 cm³ Parr oxygen explosion calorimeter. The "sample" is deaired and subsequently burned under 30 atm of pure oxygen. The combustion products are taken up in 5 ml of deionized water. When the reaction is complete (after about 15 min), the absorbing solution is quantitatively transferred and brought to a defined volume.

The fluoride concentration of the sample is determined by ion chromatography analysis of the combustion products solution. Calibration curves were prepared by burning several concentrations of ethanolic KF standards (in the same manner as the sample) to obtain a 0 to 10 ppm calibration range. The catalyst fluoride concentration is calculated based on lossless combustion by comparing the response of the sample solution to that of the calibration curve. Loss due to combustion is determined by heating a separate sample at 800ºF (426.7ºC) for at least two hours. Ion chromatography analysis uses standard conditions for anions.

Another method uses the application of fluoride distillation followed by titrimetry. Fluorides are converted to fluorosilicic acid (H2SiF6) by reaction with quartz in phosphoric acid media and distilled as such using superheated steam. This is the Willard-Winter-Tananaev distillation. It should be noted that the use of dry (versus wet) superheated steam is critical to obtaining accurate results. When using a generator to produce wet superheated steam, the results were 10 to 20% lower. The fluorosilicic acid collected is titrated with standardized NaOH solution. A correction must be made for the phosphoric acid, which is also entrained by the steam. Fluoride values are presented on the basis of loss-free combustion after determining the combustion loss by heating a sample at 400ºC for one hour.

A preferred catalyst is a catalyst prepared by a process comprising depositing a hydrogenation metal on an alumina or alumina-containing material, calcining the metal-loaded support typically between 350 and 500°C, and preferably about 450 to 500°C, for about 1 to 5 hours, and preferably about 1 to 3 hours, and fluoridating the metal-loaded catalyst using a high pH fluorine source solution. Value to a total fluorine content of about 8 wt.% or less (e.g., 2 to 8 wt.%), preferably about 7 wt.% or less, wherein the high pH source solution has a pH of 3.5 to 4.5 and is preferably a mixture of NH₄F and HF, followed by rapid drying/heating in a flat bed or rotary kiln to ensure complete, uniform heating in air, an oxygen-containing atmosphere, or an inert atmosphere to a temperature between about 350°C and 450°C in about 3 hours or less, preferably 375 to 400°C, and maintained at the final temperature, if necessary, for a sufficient time to reduce the hydrate and nitrogen content to the recited levels (e.g., 1 to 5 hours), or using a low pH fluorine source solution having a pH of less than 3.5 using aqueous solutions of HF or suitable mixtures of HF and NH₄F to a total fluorine content of about 10 wt.% or less (e.g., 2 to 10 wt.%), preferably about 8 wt.% or less, followed by drying/heating in a flat bed or rotary kiln to a temperature of about 350 to 450°C, preferably 375 to 425°C, and holding, if desired, at that temperature for 1 to 5 hours in air, an oxygen-containing atmosphere, or an inert atmosphere. The alumina or alumina-containing material is preferably in the form of extrudates and preferably has a diameter of at least about 1/32 inch along the longest dimension of the cross section.

When the catalyst prepared at low pH is first introduced into a plant, the catalyst must be maintained at the final activation temperature, preferably at temperatures of 400 to 450ºC, for more than 5 hours, preferably more than 10 hours.

The above catalysts typically contain 0.1 to 5.0 wt.% metal, preferably 0.1 to 1.0 wt.% metal, and most preferably 0.2 to 0.6 wt.% metal.

The dried/heated catalyst has a surface nitrogen content of 0.01 or less N/Al according to X-ray photoelectron spectroscopy (XPS), preferably an N/Al of 0.007 or less (according to XPS).

After the heating step described above, the catalyst can be introduced into the isomerization reactor and rapidly brought to operating conditions. Alternatively, after the heating step described above, the catalyst prepared using the high pH solution technique can be hydrogen activated in pure or plant hydrogen (60 to 70 vol% H2) by heating to 350 to 450°C, taking care to use a short activation time, 1 to 24 hours is sufficient, and preferably 2 to 10 hours. Excessively long activation times (greater than 24 hours) have been found to be detrimental to the performance of the catalyst. In comparison, catalysts prepared using the low pH solution technique can be activated in pure or plant hydrogen at 350 to 500°C for 1 to 48 hours or longer. In fact, if catalysts prepared using low pH solutions are not heated first, it is preferred to subsequently activate the catalysts under more severe conditions, i.e., for longer periods of time and/or at higher temperatures. On the other hand, if heated first, moderate activation procedures are sufficient, such as those used for catalysts prepared by treatment with higher pH solutions.

A typical activation profile shows a time of 2 hours to go from room temperature to 100ºC, with the catalyst being held at 100ºC for 0 to 2 hours; then over a period of 1 to 3 hours the temperature is increased from 100ºC to about 350ºC and the final temperature is held for 1 to 4 hours. Alternatively, the catalyst can be activated by heating from room temperature to the final temperature of 350 to 450ºC over a period of 2 to 7 hours and the final temperature is held for 0 to 4 hours. A similar activation can be achieved by going from room temperature to the final temperature of 350 to 450ºC in one hour.

It is possible to dispense with a separate activation process entirely (provided that the catalyst has been first heated in air). In these cases, the heated catalyst is simply introduced into the reactor and heated to just above the melting point of the paraffin feed, feed and hydrogen are passed over the catalyst, and the plant is then rapidly brought up to operating conditions.

Another preferred catalyst comprises a hydrogenation metal on fluorided alumina or alumina-containing material prepared by depositing the hydrogenation metal on the support and fluoridating the metal-loaded support using acidic fluorine sources such as HF by any technique such as spraying, soaking, wetting, etc. to incorporate between 2 and 10% F, and preferably 2 to 8% F. After halogenation, the catalyst is dried, typically at 120°C, and then crushed to expose the internal surfaces; the crushed catalyst is sieved twice to remove debris and uncrushed particles. This sized catalyst is 1/32 inch or less and typically 1/64 to 1/32 inch in size along the longest dimension of its cross section.

The starting particles or extrudates can have any physical shape. Thus, particles such as cylinders, trilobes and tetralobes can be used. Extrudates of any diameter can be used and can generally be from 1/32 inch to several inches long, the length being limited only by handling considerations. It is preferred that after sizing, the particle has a length less than the initial extrudate diameter.

After deposition of the hydrogenation metal and fluoridation of the particles or extrudates, the particles or Extrudates are crushed or broken to expose the internal surfaces.

The crushing is carried out to a degree appropriate to the starting particle or extrudate. Thus, an extrudate that is 1 foot long and 1/16 inch in diameter would be sized into pieces ranging from 1/64 to 1/32 inch along the longest dimension of their cross-section. Similarly, if the extrudate is only 1/16 inch to begin with, it will suffice to simply break it in half, for example into two 1/32 inch pieces.

Alternatively, one can take a metal-loaded carrier particle that is already about 1/32 inch or smaller in size and fluoridate it using HF as described above.

In general, the sized material ranges between about 1/64 and 1/32 inch in size.

The uncalcined, size-sorted catalyst is activated in a hydrogen atmosphere such as pure hydrogen or plant hydrogen containing 60 to 70 volume percent hydrogen by heating to 350 to 500°C, and preferably 350 to 450°C, for 1 to 48 hours or longer. The hydrogen activation profiles described above can be used here in a similar manner.

This sized catalyst is unexpectedly superior in wax isomerization when compared to the uncrushed particulate or extrudate feedstock. It has also been found that 370°C+ oil products made using the sized catalyst when compared to the uncrushed or extrudate material, when starting with wax containing about 5 to 10% oil, exhibit higher viscosity indices than 370°C+ oil products made using wax as feedstock containing 0% oil (on one side) and about 20% oil (on the other side). Accordingly, to obtain products with the highest viscosity index, one would use wax containing 5 to 15% and preferably 7 to 10% oil using the "sized" Catalyst prepared using HF.

As expected, isomerization catalysts are extremely susceptible to deactivation by the presence of heteroatom compounds (i.e., N or S compounds) in the paraffin feedstock, so that such heteroatom materials must be carefully removed from the paraffin feedstock batches. When treating high purity paraffins, such as synthetic Fischer-Tropsch waxes, such precautions may not be necessary. In such cases, it may be sufficient to subject such paraffins to a very mild hydrogen treatment to ensure protection of the isomerization catalyst. On the other hand, paraffins obtained from natural petroleum sources contain certain amounts of heteroatom compounds as well as significant amounts of oil containing heteroatom compounds. In such cases, the slack waxes should be hydrotreated to reduce the heteroatom compound content to concentrations generally considered tolerable in the industry for feedstocks subjected to isomerization catalysts. Such concentrations are typically a N content of about 1 to 5 ppm and a sulfur content of about 1 to 20 ppm, preferably 2 ppm or less nitrogen and 5 ppm or less sulfur. Similarly, such slack waxes should be deoiled to an oil content in the range of 0 to 35% oil, and preferably 5 to 25% oil, prior to hydrotreating. The hydrotreating step uses typical hydrotreating catalysts such as Co/Mo, Ni/Mo, or Ni/Co/Mo on alumina under standard commercially accepted conditions, e.g. E.g., temperature of 280 to 400ºC, volume flow rate of 0.1 to 2.0 vol/vol/hr, pressure of 500 to 3,000 psig H₂, and hydrogen gas rates of 500 to 5,000 SCF/b.

It is preferred to carry out the isomerization reaction to a degree of conversion such that about 40% or less, preferably 15 to 35%, and most preferably 20 to 30% unconverted wax remains in the lube oil range boiling fraction of the isomerizate which is sent to the dewaxer. The unconverted wax fraction is calculated as (unconverted wax)/(unconverted wax + dewaxed oil) x 100. The amount of unconverted wax in the 370ºC+ oil fraction is considered to be the amount of wax removed or recovered from the oil fraction during dewaxing. The total product from the isomerisation plant is fractionated into a lube oil fraction in the 330ºC+ boiling range and preferably 370ºC+ or even higher. This lube oil fraction is preferably solvent dewaxed using a 20/80 v/v blend of MEK/MIBK and unconverted wax is recycled for further isomerization by feeding it either to the fresh feed stock tank or directly to the isomerization unit.

In principle, a wax extinction process to maximize lubricant yields would involve operation at very low severity, i.e. where conversion to fuels is at a minimum. Under these conditions, the amount of unconverted wax returned to the isomerization reactor would be large and differences in catalyst selectivity would be less important.

In practice, however, operation at very low conversion is not practical. Instead, the severity of the operating conditions is dominated by the need to produce a low pour point oil (powder point < -21ºC). It has been found that low pour points cannot be obtained from isomerizates produced at low conversion. This is unexpected because with natural oils the amount of wax present did not affect the ability to dewax oil to target low pour points. A critical determinant in achieving low pour points is that the amount of wax obtained from isomerization remaining in the 370ºC+ fraction paraffin should not exceed 40% and for low pour points may need to be as low as 15 to 25%. To maximize yield in this situation, the choice of catalyst becomes important.

After isomerization, the isomerizate is fractionated into a lube cut and a fuel cut, with the lube cut being identified as the fraction boiling in the range of 330°C to 600°C, preferably in the 370°C+ range or even higher. The lube fraction is then dewaxed. Dewaxing is accomplished by techniques that allow the recovery of the unconverted wax, since in the process of the invention this unconverted wax is recycled for further isomerization. It is preferred that this recycle wax be recycled to the feed wax storage vessel and passed through the hydrotreating unit to remove any entrained dewaxing solvent present, since such solvent can be detrimental to the isomerization catalyst. Alternatively, a separate stripper can be used to remove entrained dewaxing solvent or other contaminants. Since the unconverted wax is to be recycled, dewaxing processes that destroy the wax, such as catalytic dewaxing, are not recommended. Solvent dewaxing is used and uses typical dewaxing solvents. Solvent dewaxing uses typical dewaxing solvents such as C3 to C6 ketones (e.g. methyl ethyl ketone, methyl isobutyl ketone and mixtures thereof), C6 to C10 aromatic hydrocarbons (e.g. toluene), mixtures of ketones and aromatics (e.g. MEK/toluene), self-cooling solvents such as liquefied, normally gaseous C2 to C4 hydrocarbons such as propane, butane and mixtures thereof etc., at filter temperatures of -25ºC to -30ºC.

The preferred solvent for dewaxing the isomerizate under miscible conditions, thereby providing the highest yield of dewaxed oil at a high filter speed is a mixture of MEK/MIBK (20/80 v/v) used at a temperature in the range of -25ºC to -30ºC. Pour points below -21ºC can be achieved using lower filter temperatures and different ratios of solvents, but this comes at the cost of making the system immiscible, causing lower filter rates. Furthermore, when an isomerizate prepared from a microparaffin (e.g. brightstock slack wax) is dewaxed, it is preferred that the fraction of the isomerizate which is dewaxed is the "broad heart cut", which is identified as the fraction boiling between 330ºC and 600ºC, and preferably from 370ºC to 580ºC. The heavy bottoms fraction boiling above 580ºC to 600ºC contains significant amounts of wax and can be returned directly to the isomerization unit for further isomerization. However, if any hydrotreating or deoiling is deemed necessary or desirable, the fractionation bottoms can be sent to the fresh feedstock holding tank and combined with the wax contained therein.

It has also been found that prior to fractionating the isomerizate into various cuts and dewaxing these cuts, the total liquid product (TLP) from the isomerization unit can advantageously be treated in a second stage under mild conditions using the isomerization catalyst or simply a Group VIII noble metal on refractory metal oxide catalyst to reduce PNA and other impurities in the isomerizate and thus obtain an oil with improved daylight stability.

In this embodiment, the entire isomerizate is passed over a charge of the isomerization catalyst or only over Group VIII noble metal, e.g. transition alumina. Mild conditions are used, e.g. a temperature in the range of 170 to 270°C, preferably 180 to 220°C, at pressures of 300 to 1,500 psi H₂, preferably 500 to 1,000 psi H₂, a hydrogen gas rate in the range of 500 to 10,000 SCF/bbl and a flow rate of 0.25 to 10 vol/vol/hr, and preferably 1 to 4 vol/vol/hr. Temperatures higher than those mentioned should only be used when pressures above 1 500 psi are similarly used, but such high pressures may not be practical.

The entire isomerizate can be treated under these mild conditions in a separate dedicated facility, or the TLP from the isomerization reactor can be stored in a tank and subsequently passed through the isomerization reactor under the mild conditions. It has been found that it is unnecessary to fractionate the first stage product prior to this mild second stage treatment. When the entire product is subjected to this mild second stage treatment, an oil product is produced which, after subsequent fractionation and dewaxing, yields an oil product exhibiting a high degree of daylight stability and oxidation stability. These base oils can be subjected to subsequent hydrotreating at conventional conditions using conventional catalysts such as KF-840 or HDN-30 (e.g. Co/Mo or Ni/Mo on alumina) to remove undesirable nitrogen and/or sulfur compounds.

In the prior art, it is believed that isomerization occurs by formation of traces of reactive olefins on the surface of the isomerization catalyst. For this reason, the catalyst must contain a hydrogenation/dehydrogenation component (for example, a Group VIII metal such as platinum) and the reaction is carried out in a hydrogen-rich atmosphere.

It has been shown in the past that the volume ratio of hydrogen gas to paraffin feed (the TREAT GAS RATE) affects the reactivity of the paraffin, but it has not been shown to affect the product distribution of the hydroisomerizate.

For example, it has been observed that the selectivity to 370ºC+ oil depends only on the amount of conversion to 370ºC- material and not on any specific process parameters such as temperature, pressure or treatment gas rate. This observation suggests that the distributions of high boiling paraffin and oil are also independent of parameters such as the treatment gas rate.

However, it has now been found that the treatment gas rate has an effect on the relative yields of wax and oil in the high boiling fractions. Therefore, when a specific viscosity range of the oil such as 5.6 to 5.9 cSt/100ºC is considered, lower treatment gas rates result in increased yields of 5.6 to 5.9 cSt/100ºC oil and decreased amounts of wax in this fraction.

The increased yield of high-boiling oil and reduced yield of paraffin means several things:

(1) Paraffin is converted to oil more effectively. The overall oil yield is increased and there is less paraffin to be recycled (plant size savings).

(2) The paraffin concentration in the stream sent to the dewaxer is lowered. This means a reduced load on the dewaxer and there is less paraffin to entrain oil. Therefore, less valuable hydroisomer oil is returned to hydroisomerization.

The preferred slack wax conversion level is such that between 25 and 40 wt.% unconverted wax remains in the fraction of the isomerizate sent to the dewaxing plant. The amount of wax present in the stream sent for dewaxing can be controlled by the conversion level. Hydroisomerization can thus be carried out to produce more fuels and obtain a lower yield of residual wax. However, this results in the destruction of valuable wax and a reduction in the overall oil yield. The present invention is a process for minimizing the amount of wax present in the stream to be dewaxed without operating at higher conversion levels and this serves to preserve overall oil yields. In addition, at the same conversion level to 370ºC material, lower treat gas rates unexpectedly result in higher yields of 5.6 to 5.9 cSt/100ºC oil and lower dry wax contents of these oils.

The slack wax is preferably hydrotreated before hydroisomerization to remove nitrogen and sulfur compounds that can damage the hydroisomerization catalyst.

The isomerization is carried out between 270 and 400°C, at pressures of 500 to 3,000 psig, preferably 800 to 1,500 psig, and volume flow rates of 0.1 to 10 v/v/hr. The preferred treat gas rate is between 500 and 5,000 SCF/bbl H₂, preferably 2,000 to 4,000 SCF/bbl H₂, and most preferably about 2,000 to 3,000 SCF/bbl H₂. This range of treat gas rates allows for the exploitation of the increased reactivity of the slack wax at higher treat gas rates and the increased oil yields and lower dry slack wax contents resulting from lower treat gas rates. After isomerization, the isomerize is fractionated to obtain the increased yield of oil in the 5.6 to 5.9 cST/100ºC viscosity range.

The hydroisomer product produced at lower treat gas rates can be isomerized in a second hydroisomerization at low temperature to improve daylight stability.

This invention will be better understood from the following examples.

Examples

A hydrotreated slack wax was used in a series of hydroisomerization experiments. Relevant details on the slack wax source, pretreatment and formation of the isomerization catalyst are summarized below:

Crude oil price:

58 % Brent System Mix

14% Parentis

9% Basrah

9 % Arabic Light

10% Chamomile

The crude paraffin was obtained from 600 N distillate. Paraffin Pretreatment: Hydrogen Treatment Catalyst Hydrogen Treatment Temperature Hydrogen Treatment Pressure Hydrogen Treatment Treat Gas Rate Hydrogen Treatment Liquid Flow Rate Oil Content of Hydrotreated Paraffin Sulfur Content of Hydrotreated Paraffin Nitrogen Content of Hydrotreated Paraffin Hydroisomerization Catalyst Fluoridation Process Catalyst Volume Process Type Sulfided KF-40 (Ketjen, Ni/Mo-Alumina Catalyst Feedstock F/Alumina 1/16" Extrudates HF Impregnation of Reforming Catalyst with 10% Aqueous HF Downflow, Trickle Reactor

Catalyst pretreatment:

The catalyst was dried at 220ºC (4 hours in vacuum, then overnight in a laboratory oven at atmospheric pressure). The catalyst was placed in the reactor and heated from room temperature to 400ºC in flowing hydrogen at 300 psig pressure as follows: hold at 100ºC for 24 hours, from 100 to 400ºC at 10ºC/hour, hold at 400ºC for 3 hours, reactor cooled to 250ºC.

Details for the hydroisomerization experiments are given in the table. Three hydroisomerization products produced at treat gas rates of 2,573, 5,035 and 9,565 SCF H₂/bbl were tested. Traditionally, the amount of 370ºC material produced has been used as an indicator of conversion. The Conversion rates were very similar for the products of the two highest gas rates. The conversion rate was slightly lower for the case of the lowest gas rate (22 vs. 25 wt.% 370ºC-)

The yields of 370ºC+ oil and 370ºC+ slack wax, based on the total slack wax feed, were also very similar for the three treat gas rates. Thus, the yield of 370ºC+ oil was between 49.1 and 49.8 wt%/feed for the three cases and the similarity would not lead one to expect any significant differences in the oil products obtained. There is no reason to expect that there would be any differences between the yields of 5.6 to 5.9 cSt/100ºC oil products obtained.

Each of the products was topped and the topped material dewaxed to produce dewaxed oil with a viscosity of approximately 5.85 cSt/100ºC. The pour points of the dewaxed oils were measured as "Westcan autopours" for maximum accuracy. It was found that the yield of topped material was not the same for the three products. For dewaxed oils with the same pour point, the amount of dry wax removed also differed in the three cases. These effects resulted in different yields of oil and wax using the three treating gas rates.

Auto-pour is a more sensitive indicator of pour point than ASTM pour point. The values for dewaxing condition A show that the oils obtained at treat gas rates of 2,573 and 9,565 SCF/B were dewaxed to lower auto-pour points than the oil obtained at a treat gas rate of 5,035 SCF/B. It is generally understood that more wax must be removed to achieve the lower pour point. The oil produced at 2,573 SCF/B had the least wax of the three cases.

When comparing the three cases in the table, it must be emphasized that the test with the lowest treatment gas rate was carried out at a slightly lower level of conversion (22 wt.% 370ºC material). This means that less wax was converted to oil and light materials. If this experiment had been carried out at 25 wt.% conversion, as in the other two cases, the yield of 5.85 cSt/100ºC oil would have been even higher and the amount of wax present in the fraction would have been even lower.

In each case, even though the lowest treat gas rate experiment was conducted at a lower level of conversion, more dewaxed oil was obtained (2 to 3 wt.% of the slack wax feed to hydroisomerization). Also, less dry wax was removed from the oil during dewaxing than from products produced at higher treat gas rates. This means that hydroisomerization can be conducted at a lower level of conversion and still obtain a high oil yield, or that isomerization can be conducted at a high level of conversion, resulting in a lower dry wax content in the stream being dewaxed.

Two separate dewaxings were performed for each of the three cases to confirm the effect. MIBK (methyl isobutyl ketone) is a better solvent than MEK (methyl ethyl ketone) and this results in less wax being removed when the dewaxing solvent is pure MIBK.

The dewaxings were carried out in a simple batch dewaxing apparatus. The waxy oil was heated until completely liquefied, diluted with ketone solvent and then cooled to the required temperature in a cold bath with mixing. The mixture was filtered using a Buchner funnel which was in turn cooled by circulating solvent. The solvent was individually stripped from the paraffin and oil. Table Example Treat Gas Rate, SCF/B H₂ Catalyst Hours Temperature, ºC Pressure, psig Flow Rate LHSV Vol/Vol/Hr Wt% 370ºC Conversion/Feed Wt% 370ºC+ Oil/Feed Wt% 370ºC+ Paraffin/Feed Wt% Waxy 5.85 cSt/100ºC Oil of Feed Dewaxing Conditions Solvent Solvent:Oil Wt/Wt Filter Temperature, ºC Wt% Dry Paraffin Wt% Oil of Feed Wt% Paraffin of Feed Dewaxed Oil Viscosity Viscosity Index Auto Pour Point, ºC ASTM Pour Point, ºC

Remarks:

"Autopour" is the trademark of Hanovia Limited, Slough, England

Temperature in ºF is converted to ºC by subtracting 32 and then dividing by 1.8.

1 inch = 2.54 cm

1 SCF = 28.316 liters

Bbl = 158.97 liters

1 psi = 6.895 kPa

1 cSt = 1 mm²/s

Reference is made to the following co-pending applications:

EP-A-321 298 (European Patent Application No. 88311978.6) describes and claims a process for producing a lubricating oil basestock or blendstock which comprises contacting a slack wax under isomerization conditions with an isomerization catalyst, the catalyst comprising a fluorided hydrogenation metal loaded refractory oxide, characterized in that the slack wax has a sulfur content not exceeding 20 ppm and a nitrogen content not exceeding 5 ppm (based on the slack wax feedstock), and the catalyst is in the form of particles having sizes of about 1/32 inch or less (e.g. about 0.79375 mm and less) along the longest dimension of their cross-section. The isomerization catalyst can be prepared by either (a) depositing at least one Group VIII metal on a refractory metal oxide support in the form of extrudate particles, fluoridating the metal-loaded support using hydrogen fluoride solution, and crushing the fluoridated metal-loaded support to expose its internal surfaces and recovering sized material having particle sizes of about 1/32 inch or less (e.g., about 0.79375 mm and less) along the longest dimension of its cross-section, or (b) at least one Group VIII metal is deposited on a refractory metal oxide support in the form of extrudate particles and the metal-loaded support is fluoridated using hydrogen fluoride solution, and for the fluoridated metal-loaded support particles produced by steps (a) or (b), the resulting fluoridated metal-loaded support particles are activated by heating to a temperature in the range of 350 to 500°C in a hydrogen atmosphere for a period of 1 to 48 hours or more.

EP-A-321 302 (European Patent Application No. 88311983.6) discloses and claims a process for preparing a lubricating oil basestock or blendstock from a waxy feedstock which comprises contacting the feedstock under isomerization conditions with an isomerization catalyst, the catalyst comprising a hydrogenation metal loaded, fluorided catalyst of alumina or alumina containing material, and the catalyst as incorporated in the waxy feedstock is characterized by (1) having a hydrate level of 60 or less, preferably 10 to 60, determined as the relative amount of hydrate represented by a peak in the X-ray diffraction (XRD) spectrum at 2θ = 5.66 Å (0.566 nm), a hydrate level of 100 corresponding to an XRD peak height at 2θ exhibited by a standard material. = 5.66 Å (0.566 nm) consisting of 0.6 wt.% Pt on 150 m²/g of γ-alumina containing 7.2 wt.% F, in which the fluorine was applied using an aqueous solution containing a high concentration of HF and the material was dried at 150°C for 16 hours; (2) has a surface nitrogen content N/Al ratio of 0.01 or less as determined by X-ray photoelectron spectroscopy (XPS); (3) has a total fluorine concentration of between 2 and 10 wt.%, and (4) a surface fluoride concentration present in a layer extending from the surface of the particle to a depth of about 1/100 (0.254 mm) inch or less of less than about 3 wt.%, provided that the surface fluoride concentration is less than the total fluoride concentration.

EP-A-321 303 (European Patent Application 88311984.4) discloses and claims a process for producing middle distillate fuels from a paraffin wax comprising (a) contacting the wax with hydrogen in a hydroisomerization zone (R-1) at hydroisomerization conditions in the presence of a fluoridated Group VIII metal on alumina catalyst and converting 50 to 95 wt.% of the 700°C+ (371°C+) material present in the wax, the catalyst (i) having a total fluoride concentration in the range of 2 to 10 wt.% (e.g. 5 to 8 wt.%), the fluoride concentration in the outer surface layer to a depth of less than 1/100 (0.254 mm) inch being less than about 3 wt.% (e.g. less than 1.0 wt.%, preferably less than 0.5 wt.%), provided that the surface fluoride concentration is less than the total fluoride concentration; (ii) has an aluminum fluoride hydroxide hydrate level of greater than 60 (where an aluminum fluoride hydroxide hydrate level of 100 corresponds to the peak height in the X-ray diffraction (XRD) spectrum at 5.66 Å (0.566 nm) of a reference standard containing 0.6 wt% Pt and 7.2 wt% F on γ-alumina having a surface area of about 150 m2/g, prepared by treating a reforming grade platinum-on-γ-alumina material containing 0.6 wt% Pt on γ-alumina having a surface area of 150 m2/g by a single contact with an aqueous hydrogen fluoride solution (e.g. 10 to 15 wt% HF, such as 11.6 wt% HF solution), wherein material has been dried at 150ºC for 16 hours; and (iii) has a N/Al ratio of less than 0.005 (e.g. less than 0.002) and (b) a middle distillate product and a bottoms product having an initial boiling point of greater than 700ºF (371ºC) are recovered (D-2).

EP-A-321 305 (European Patent Application No. 88311986.9) discloses and claims a process for producing a pumpable synthetic crude oil from a Fischer-Tropsch wax containing oxygen-containing compounds, in which

(1) the Fischer-Tropsch wax (D-0) is separated into (a) a low boiling fraction containing most of the oxygenated compounds and a high boiling fraction which is essentially free of water and oxygenated compounds, and

(2) reacting the high boiling fraction from step (1) with hydrogen under hydroisomerization and mild hydrocracking conditions in the presence of a fluoridated Group VIII metal (e.g., platinum)-on-alumina catalyst (R-1) to produce a C₅+ hydrocarbon product, and

(3) the C5+ product from step (2) is combined with the low boiling fraction from step (1) to produce a pumpable, refinery-processable synthetic crude oil that can be transported at atmospheric conditions.

EP-321 306 (European Patent Application No. 88311987.7) discloses and claims a process for improving the yield of oil in the boiling range from lubricating oil basestock or blendstock produced by the isomerization of paraffin over an isomerization catalyst, in which the paraffin isomerization process is carried out over a catalyst comprising or consisting of palladium on fluorided alumina or fluorided alumina-containing support material.

EP-A-321 307 (European Patent Application No. 88311989.3) discloses and claims a process for producing lubricating oil base stocks or blend stocks having a pour point of -21ºC or below and a viscosity index (VI) of 130 and above by the isomerization of paraffin, which comprises (1) converting the paraffin into lubricating oil in an isomerization plant isomerized over an isomerization catalyst to a degree of conversion such that 15 to 35% unconverted wax, calculated as (unconverted wax)/(unconverted wax + dewaxed oil) x 100), remains in the lubricating oil range boiling isomerate fraction passed to the dewaxing unit, and the total product from the isomerization zone is fractionated into a lubricating oil range boiling lubricating oil fraction, (2) solvent dewaxing this fraction in a single solvent dewaxing step, and (3) recovering a lubricating oil product having a VI of at least 130 and a pour point of -21°C or below.

EP-A-323 092 (European Patent Application No. 88311982.8) discloses and claims a process for producing lubricating oil with a high viscosity index and a low pour point from a Fischer-Tropsch wax, in which

(a) treating the Fischer-Tropsch wax with a hydrotreating catalyst (which need not be sulfided) and hydrogen in a hydrogen treating zone (R-1) under hydrotreating conditions (which include a temperature in the range of 650 to 775°F (343.3 to 412.8°C), a hydrogen pressure in the range of 500 to 2,500 psig (3,488 to 17,238 MPa), a volume flow rate in the range of 0.1 to 2.0 vol/vol/hr, and a hydrogen to feed rate in the range of 500 to 5,000 SCF/B (89.04 to 890.4 liters H₂/liter feed)) to reduce the oxygenated compounds and trace metal concentrations in the wax and to partially isomerize the wax. and hydrocracking;

(b) reacting the hydrogen-treated Fischer-Tropsch wax from step (a) with hydrogen under hydroisomerization conditions (which include a temperature in the range of 500 to 750ºF (260 to 398.9ºC), a feed volume flow rate in the range of 0.2 to 2.0 vol/vol/hr, a gauge pressure in the range of 500 to 2 500 psig (3 488 to 17 238 MPa) and a hydrogen-to-feed rate in the range of 500 to 10,000 SCF/B (89.04 to 1788.8 liters H₂/liter feed) in a hydroisomerization zone (R-2) in the presence of a fluoridated Group VIII metal-on-alumina catalyst having (i) a total fluoride concentration in the range of 2 to 10 wt.%, the fluoride concentration in the outer surface layer to a depth of less than 1/100 (0.254 mm) inch being less than about 3 wt.%, provided that the surface fluoride concentration is less than the total fluoride concentration; (ii) has an aluminum fluoride hydroxide hydrate level of greater than 60 (e.g., at least about 100) (wherein an aluminum fluoride hydroxide hydrate level of 100 corresponds to the X-ray diffraction (XRD) peak height at 5.66 Å (0.566 nm) of a reference standard containing 0.6 wt.% Pt and 7.2 wt.% F on a gamma-alumina support having a surface area of about 150 m²/g, and which was prepared by treating reforming grade gamma-alumina having a surface area of 150 m²/g with platinum, followed by a single contact with an aqueous hydrogen fluoride solution having a high concentration of hydrogen fluoride, followed by drying at about 300°F (148.9°C), and (iii) has an N/Al ratio of less than 0.05.

EP-A-323 724 (European Patent Application No. 88311988.5) discloses and claims a process for improving the daylight stability of a lubricating oil basestock or blendstock produced by the isomerization of paraffin, which comprises hydrorefining either (a) all of the liquid product produced in the paraffin isomerization plant or (b) the lubricating oil range boiling fraction of the isomerizate, the hydrorefining using a catalyst selected from Group VIII metal on refractory metal oxide and Group VIII metal on halogenated refractory metal oxide, a temperature in the range of 170°C to 270°C, a flow rate from 0.25 to 10 vol/vol/hr, a pressure of 300 to 1 500 psi (2 069 to 10 343 MPa) H₂ and a hydrogen gas velocity of 500 to 10 000 SCF/B (89.05 to 1780.94 litres gas/litre oil).

Claims (7)

1. Use of a process for obtaining an improved yield of lubricating oil in the viscosity range of 5.6 to 519 mm²/s (5.6 to 5.9 cSt) at 100°C from isomerized paraffin which comprises (1) reacting the paraffin over an isomerization catalyst comprising a Group VI metal, Group VIII metal and mixtures supported on a halogenated refractory metal oxide support under isomerization conditions comprising a temperature in the range of 270 to 400°C, a pressure in the range of 3.45 to 20.60 MPa (500 to 3,000 psi) H₂; and a throughput in the range of 0.1 to 10 vol/vol/hour, but is isomerized at a low treat gas rate in the range of 89.05 to 890.53 liters H₂ gas/liter oil (500 to 5,000 SCF/bbl H₂), and (2) the isomerate is fractionated to recover a lubricating oil fraction in the boiling range of 330ºC to 600ºC, from which, after dewaxing, oil is recovered in the viscosity range of 5.6 to 5.9 mm²/s (5.6 to 5.9 cSt) at 100ºC. 2. Use according to claim 1, wherein the treat gas rate is in the range of 356.21 to 712.42 liters H₂ gas/liter oil (2,000 to 4,000 SCF/bbl H₂). 3. Use according to claim 1 or 2, wherein the treatment gas rate is in the range of 356.21 to 534.32 liters H₂ gas/liter oil (2,000 to 3,000 SCF/bbl H₂). 4. Use according to one of claims 1 to 3, wherein the paraffin which is isomerized is selected from synthetic paraffins and crude paraffins. 5. Use according to any one of claims 1 to 4, wherein the catalyst consists of a Group VIII metal on a fluorided alumina support. 6. Use according to any one of claims 1 to 5, wherein the Group VIII metal is platinum and the alumina is γ-alumina. 7. Use according to any one of claims 1 to 6, wherein the fractionation of the isomerate is effected to obtain a lubricant fraction in the boiling range of 370°C to 600°C.