Improved flexible method for producing oil bases and distillates by hydroisomerization-conversion on a weakly dispersed catalyst followed by catalytic dewaxing

p0001The present invention relates to an improved process for producing base oils of very high quality, ie having a high viscosity index (VI), good UV stability and a low pour point, from hydrocarbon feedstocks (and preferably from hydrocarbon feeds from the Fischer-Tropsch process or from hydrocracking residues), possibly with the simultaneous production of middle distillates (diesel, kerosene particular) of very high quality, that is, ie having a low pour point and a high cetane number.

<u>prior art</u>

p0002The high quality lubricants are of fundamental importance to the functioning of modern machines, automobiles, and trucks.

p0003These lubricants are most often obtained by a series of refining steps for improving the properties of a petroleum fraction. In particular treatment of heavy petroleum fractions with high contents of linear paraffins or slightly branched is necessary to obtain base oils of good quality and with the best possible returns, by an operation aimed at eliminating the linear or very paraffins slightly branched, fillers which are then used as base oils.

p0004Indeed, the high molecular weight paraffins which are linear or very slightly branched and which are present in oils lead to high pour points and therefore to solidification phenomena for low temperature uses. To reduce the pour points, these linear paraffins or very slightly branched must be completely or partially eliminated.

p0005Another means is the catalytic treatment in the presence or absence of hydrogen and in view of their shape selectivity, zeolites are among the most used catalysts.

p0006Catalysts based on zeolites such as ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 have been described for use in such processes. All catalysts currently used in hydroisomerization are bifunctional, combining an acid function with a hydrogenating function. The acid function is provided by supports with large surfaces (150 to 800 m².g^-1 general) with a superficial acidity, such as halogenated (chlorinated or fluorinated), phosphorous-containing aluminas, combinations of boron and aluminum oxides, amorphous silica-alumina and silica-aluminas. The hydrogenating function is provided either by one or more Group VIII metals of the periodic table, such as iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, or by a combination of at least one group VI metal such as chromium, molybdenum and tungsten and at least one group VIII metal.<patcit id="pcit0001" dnum="FR2792946A"><text>FR-A- 2792946</text></patcit> discloses a base production process oil by hydroisomerization-conversion on weakly disposed catalyst. <patcit id="pcit0002" dnum="FR2698863A"><text>FR-A-2698863</text></patcit> describes the application of zeolites ZSM-48 type absorption and catalysis.

p0007The balance between the two acid and hydrogenating functions is the fundamental parameter which governs the activity and selectivity of the catalyst. A weak acid function and a strong hydrogenating function produces catalysts less active and selective as regards isomerization while a strong acid function and a weak hydrogenating function produces very active and selective catalysts as regards cracking. A third possibility is to use a strong acid function and a strong hydrogenating function to obtain a highly active catalyst is also highly selective towards isomerization. It is therefore possible, by judiciously choosing each of the functions to adjust the activity / selectivity of the catalyst.

p0008The Applicant therefore proposes, according to the method described in the invention, jointly produce middle distillates of high quality base oils of VI and pour point at least equal to those obtained with a hydrofining process and / or hydrocracking.

<u>The invention</u>

p0009We have concentrated its research efforts on the development of an improved process for manufacturing lubricating oils of very high quality and high quality middle distillates from hydrocarbon feedstocks, preferably from hydrocarbon feeds from the Fischer-Tropsch process or from hydrocracking residues dice.

p0010The present invention thus relates to a sequence of processes for the joint manufacture of high quality base oils and middle distillates (diesel especially) very high quality from oil cuts. The resulting oils have a high viscosity index (VI), low volatility, good UV stability and a low pour point.

p0011More specifically, the invention relates to a method for producing oils from a hydrocarbon feed (of which preferably at least 20% by volume has a boiling temperature at least 340 ° C), said method comprising the following successive steps:<ol><li>(A) conversion of the feed with simultaneous hydroisomerisation of at least a portion of the n-paraffins of the feedstock, said feedstock having a sulfur content less than 1000 ppm by weight, a nitrogen content of less than 200 ppm by weight, a content eh metals less than 50 ppm by weight, an oxygen content of at most 0.2 wt%, step (a) takes place at a temperature of 200-500 ° C, under a pressure of 2-25 MPa, with a space velocity of 0.1 - 10 am^-1In the presence of hydrogen at a rate of between 100-2000 I.H2 / l of feedstock, in the presence of a catalyst containing at least one noble metal deposited on an amorphous acid support, the noble metal dispersion is less than 20%.</li><li>(B) catalytic dewaxing of at least a portion de.l'effluent from step a), carried out at a temperature of 200 - 500 ° C, under a pressure of 1-25 MPa, with an hourly space velocity of 0,05-50h^-1In the presence of 50-2000 liters of hydrogen / liter of effluent entering step (b) in the presence of a catalyst comprising at least one hydro-dehydrogenating element and ZBM-30 molecular sieve.</li></ol>

p0012Step (a) is optionally preceded by a hydrotreating step typically carried out at a temperature of 200-450 ° C under a pressure of 2 to 25Mpa, at a space velocity of 0,1-6h^-1In the presence of hydrogen in the hydrogen / hydrocarbon of 100-2000 l / l, and in the presence of an amorphous catalyst comprising at least one Group VIII metal and at least one metal of group VI B.

p0013The entire effluent from step (a) may be sent in the step (b). Step (a) is optionally followed by separation of light gases from the effluent obtained at the end of step (a). Preferably, the effluent from the hydroisomerization-conversion processing is subjected to a distillation step (preferably atmospheric) to separate the compounds having a boiling point below 340 ° C (gas, gasoline, kerosene, gas oil ) products having an initial boiling point above at least 340 ° C and which form the residue. generally are thus separated at least a middle distillate fraction having a pour point of at most -20 ° C, and a cetane number of at least 50.

p0014Step (b) catalytic dewaxing is preferably applied at least to the residue obtained by distillation which contains compounds with a boiling point at least 340 ° C. In another embodiment of the invention, the effluent from step (a) is not distilled before implementing step (b). At most, it undergoes a separation of at least a portion of the light gas (flash ....) and is then subjected to catalytic dewaxing.

p0015Advantageously, the effluent from the dewaxing treatment is subjected to a distillation step preferably comprising atmospheric distillation and vacuum distillation so as to separate at least one oil fraction at a boiling point above at least 340 ° C. It often has a pour point below -10 ° C and a VI greater than 95, a viscosity at 100 ° C of at least 3cSt (or 3mm2 / s). This distillation step is essential where there is no distillation between steps (a) and (b).

p0016Advantageously, the effluent from the dewaxing treatment, optionally distilled, is subjected to a hydrofinishing treatment.

<u>Detailed Description of the invention</u>

p0017The method according to the invention comprises the following steps:

<u>Load</u>

p0018The hydrocarbon feedstock from which the oils and optionally distillates high quality means, are obtained preferably contains at least 20% by volume of compounds boiling above 340 ° C, preferably to at least 350 ° C and preferably to at least 380 ° C. This does not mean that the boiling point is 380 ° C or more but 380 ° C or more.

p0019The feed contains n-paraffins. Preferably the filler is an effluent from a Fischer-Tropsch unit. A wide variety of fillers can be treated by the process.

p0020The charge may also be for example vacuum distillates from direct distillation of crude or conversion units such as FCC, coker or visbreaking, or from aromatics extraction units, or arising hydrotreatment or hydroconversion of RAT (atmospheric residues) and / or RSV (vacuum residues), or the feed may be a deasphalted oil, or else a hydrocracking residue for example derived DSV or any mixture of loads cited above. The above list is not exhaustive.

p0021In general, fillers suitable for the target oils have an initial boiling point above at least 340 ° C and more preferably greater than at least 370 ° C.

p0022The feed to step (a) conversion-hydroisomerization must be clean. We will hear from own load charges whose sulfur content is less than 1000 ppm by weight and preferably less than 500 ppm by weight and even more preferably less than 300 ppm by weight or more to 200 ppm by weight. The nitrogen content is less than 200 ppm by weight and preferably less than 100 ppm by weight and still more preferably less than 50 ppm by weight. The filler metal content such as nickel and vanadium is extremely reduced that is to say less than 50 ppm by weight and more advantageously less than 10 ppm by weight, more preferably less than 2 ppm by weight. In the case where the amounts of unsaturated or oxygenated products may cause a too significant deactivation of the catalyst system, the filler (e.g. after the Fischer-Tropsch process) must, before entering the hydroisomerization zone undergo hydrotreated in a hydrotreating zone. Reacting hydrogen with the charge in contact with a hydrotreating catalyst whose function is to reduce the amount of unsaturated and oxygenated hydrocarbon molecules (produced for example in the Fischer-Tropsch synthesis). The oxygen content is reduced to at most 0.2% by weight.

p0023In the case where the charge to be treated is not unique in the sense defined above, it is subjected at first to a pre-hydrotreatment step, during which it is contacted, in the presence of hydrogen with at least one catalyst comprising an amorphous support and at least one metal having a hydro-dehydrogenating function provided for example by at least one element from group VIB and at least one group VIII element at a temperature between 200 and 450 ° C, preferably 250-450 ° C preferably 330-450 ° C or 360-420 ° C under a pressure of 5 to 25 MPa more preferably less than 20 MPa, preferably between 5 and 20 MPa, the space velocity being comprised between 0.1 and 6 h^-1Preferably 0,3-3h^-1, And the quantity of hydrogen introduced being such that the hydrogen / hydrocarbon is between 100 and 2000 liters / liter.

p0024The support is generally based (preferably consisting essentially of) alumina or amorphous silica-alumina; it can also contain boron oxide, magnesia, zirconia, titanium oxide or a combination of these oxides. The hydro-dehydrogenating function is preferably filled with at least one metal or metal compound of groups VIII and VIB, preferably selected (s) among; molybdenum, tungsten, nickel and cobalt.

p0025This catalyst can advantageously contain phosphorus; in fact it is known in the prior art that the compound brings two advantages to hydrotreatment catalysts: ease of preparation in particular impregnation solutions of nickel and molybdenum, and better hydrogenation activity.

p0026The preferred catalysts are the catalysts NiMo and / or NiW on alumina, also the catalysts NiMo and / or NiW on alumina doped with at least one element selected from the group of atoms formed by phosphorus, boron, silicon and fluorine, or the catalysts NiMo and / or NiW on silica-alumina, or on doped silica-titania-alumina oxide or not by at least one element selected from the group of atoms formed by phosphorus, boron, fluorine and silicon .

p0027The total concentration of metal oxides of groups VIB and VIII is between 5 and 40% by weight and preferably between 7 and 30% and the weight expressed in metal oxide between the metal (or metals) of group VI to the metal (or metals) of group VIII is preferably between 20 and 1.25 and even more preferred between 10 and 2. the phosphorus oxide concentration P₂O₅ is less than 15% by weight and preferably 10% by weight.

p0028The product obtained at the end of the hydrotreatment undergoes, if necessary, an intermediate separation of water (H₂OH₂S and NH₃ so as to cause the water contents in H₂S and NH₃ respectively to values ​​below 100 ppm, 200 ppm, 50 ppm in the feed to step (a). Can be at this level provide a optionally separation of products having a boiling point below 340 ° C so as not be treated in the step (a) a residue.

p0029In case a hydrocracking residue is treated, it is then in the presence of a filler which has already undergone a hydrotreatment and hydrocracking. The own load can then be processed directly in step (a). Generally, hydrocracking place on a zeolite catalyst, based usually zeolite Y, and in particular zeolites Y zeolites. The catalyst also contains at least one non-noble metal of group VIII and at least one group VIB metal group.

Step (a): Hydroisomerization-Conversion

<u>the catalyst</u>

p0030Step (a) takes place in the presence of hydrogen and in the presence of a bifunctional catalyst comprising at least one noble metal deposited on an amorphous acid support, the noble metal dispersion is less than 20%.

p0031During this stage the n-paraffins in the presence of a bifunctional catalyst undergo isomerization then optionally a hydrocracking for lead respectively to the formation of isoparaffins and lighter cracking products such as gas oils and kerosene. Preferably, the fraction of noble metal particles having a size less than 2 nm is at most 2 wt% of the noble metal deposited on the catalyst.

p0032Advantageously, at least 70% (preferably at least 80%, and preferably at least 90%) of the noble metal particles have a size greater than 4 nm (number%).

p0033The support is amorphous, it does not contain molecular sieve; the catalyst does not contain molecular sieve.

p0034The acid support may be chosen from the group formed by a silica-alumina, boron oxide, a zirconia alone or in admixture with each other or with a matrix (not acid for example).

p0035The amorphous acid support is generally selected from the group formed by a silica-alumina, a halogenated alumina (fluorinated preferred), an alumina doped with silicon (deposited silicon), a mixture of alumina titanium oxide, sulfated zirconia, a zirconia doped tungsten and mixtures thereof with each other or with at least one amorphous matrix chosen from the group formed by alumina, titanium oxide, silica, boron oxide, magnesia, zirconia, clay by example..

p0036Preferred supports are amorphous silica-alumina and silica-titania-alumina oxide (amorphous).

p0037The measure of acidity is well known to those skilled in the art. It can be done for example by temperature programmed desorption (TPD) with ammonia, by infrared measurement of absorbed molecules (pyridine, CO ....), catalytic cracking or hydrocracking test on model molecule. ...

p0038A preferred catalyst according to the invention comprises (preferably consists essentially of) 0.05 to 10% by weight of at least one noble group VIII metal deposited on an amorphous silica-alumina.

p0039The catalyst characteristics in more detail:<ul><li><u>Silica content:</u> the preferred medium used for the preparation of the catalyst described in the context of this patent is composed of silica SiO₂ Al and alumina₂O₃ from the synthesis. The silica content of the support, expressed as percentage by weight, is generally between 1 and 95%, advantageously between 5 and 95% and preferably between 10 and 80% and even more preferably between 20 and 70% or between 22 and 45%. This content can be accurately measured using X ray fluorescence</li><li><u>Nature of noble metal:</u> for this particular type of reaction, the metal function is provided by at least one noble metal from group VIII of the periodic classification of elements and more particularly platinum and / or palladium.</li><li><u>noble metal content:</u> the noble metal content, metal weight expressed in% relative to the catalyst is between 0.05 to 10 and more preferably between 0.1 and 5.</li><li><u>Dispersion of the noble metal</u> : Dispersion, representing the fraction of metal accessible to the reactant with respect to the total quantity of metal in the catalyst can be measured, for example, by titrating H₂/ O₂. The metal is first reduced, ie it undergoes a high temperature treatment under a hydrogen flow under these conditions such that all of the platinum atoms accessible to hydrogen are transformed into the metallic form. Then a stream of oxygen is passed under operating conditions which all the reduced platinum atoms accessible to oxygen is oxidized as PtO₂. By calculating the difference between the amount of oxygen introduced and the quantity of oxygen leaving, reaches the amount of oxygen consumed; thus, it is then deduced from this value the amount of available oxygen to platinum. The dispersion is then equal to the ratio of amount available platinum with oxygen on total catalyst platinum. In our case, the dispersion is less than 20%, it is generally greater than 1% or better than 5%.</li><li><u>Particle size measured by Transmission Electron Microscopy:</u> to determine the size and distribution of metal particles we used transmission electron microscopy. After preparation, the catalyst sample was finely ground in an agate mortar then dispersed in ethanol by sonication. samples at different locations to ensure a good representative screen are formed and deposited on a copper grid coated with a thin carbon film. The grids are then air-dried under infrared lamp before being introduced into the microscope for observation. To estimate the average size of the noble metal particles, several hundred measurements are made from dozens of photographs. All these measured enables a distribution histogram of particle size. Thus, we can precisely estimate the proportion of particles corresponding to each area of ​​particle size.</li><li><u>Distribution of noble metal</u> : The distribution of the precious metal represents the distribution of the metal inside the catalyst grain, the metal being well or poorly dispersed. Thus, it is possible to obtain poorly distributed platinum (for example detected in a crown the thickness is significantly less than the grain radius) but well dispersed that is to say that all the platinum atoms situated in ring are accessible to the reactants. In our case, the platinum distribution is good that is to say, the platinum profile, measured according to the method of the microprobe, has a distribution coefficient of greater than 0.1 preferably greater than 0, 2 and preferably greater than 0.5.</li><li><u>BET Surface</u> : The BET surface of the support is generally between 100 m²/ G and 500 m²/ G and preferably between 250 m²/ G and 450m²/ G and the supports based on silica alumina, more preferably between 310 m²/ G and 450 m²/ G.</li><li><u>total pore volume of support</u> : For silica alumina supports, it is generally less than 1.2 ml / g and preferably between 0.3 and 1.1 ml / g and even more preferably less than 1.05 ml / g.</li></ul>

p0040Preparing and shaping the silica-alumina and any media in general is made by conventional methods well known to those skilled in the art. Advantageously, prior to impregnating the metal, the support can be calcined, for example a thermal treatment at 300-750 ° C (600 ° C preferred) for a period of between 0.25 and 10 hours (2 hours preferred) 0-30% by volume of water vapor (environ7,5% preferred for silica-alumina).

p0041The metal salt is introduced by one of the usual methods for depositing a metal (preferably platinum) on the surface of a support. One preferred method is dry impregnation, which consists of the introduction of the metal salt in a volume of solution which is equal to the pore volume of the catalyst mass to be impregnated. Before the reduction operation and to obtain the size distribution of the metal particles, the catalyst undergoes a calcination in air humidified at 300-750 ° C (preferred 550 ° C) for 0.25-10 hours (preferably 2 hours). The partial pressure of H2O during calcination is for example 0.05 bar to 0.50 bar (0.15 bar favorite). Other known processing methods for obtaining the dispersion of less than 20% are suitable in the scope of the invention.

p0042In this step (a) the conversion is most often accompanied by hydroisomerisation of paraffins. The method has the advantage of flexibility: depending on the degree of conversion, the production is more directed oils or middle distillates. The conversion typically ranges between 5-90%.

p0043Before use in the reaction hydroisomerization-conversion, the metal contained in the catalyst is reduced. One preferred method for reducing the metal is treatment under hydrogen at a temperature between 150 ° C and 650 ° C and a total pressure between 0.1 and 25 MPa. For example, a reduction consists of a plateau at 150 ° C for 2 hours and then a temperature rise up to 450 ° C at a rate of 1 ° C / min and then a plateau of 2 hours at 450 ° C; throughout this reduction step, the hydrogen flow rate is 1000 1 hydrogen / l catalyst. Also note that any method of ex situ reduction is suitable.

p0044The operating conditions in which this is done step (a) are important.

p0045The pressure will be maintained between 2 and 25 MPa (usually at least 5 MPa) and preferably 2 (or 3) to 20 MPa and advantageously 2 to 18 MPa, the space velocity will range from 0.1 h^-1 and 10 am^-1 and preferably between 0.2 and 10^-1 is advantageously between 0.1 and 0.5 h^-1 and 5,0h^-1And a hydrogen rate between 100 and 2000 liters of hydrogen per liter of feedstock and preferably between 150 and 1500 liters of hydrogen per liter of feed.

p0046The temperature used in this step is between 200 and 500 ° C, preferably 250 ° C to 450 ° C, advantageously 300 to 450 ° C, and more preferably greater than 340 ° C, for example between 320-450 ° C .

p0047Stages hydrotreating and hydroisomerization-conversion may be performed on the two types of catalysts in (two or more) different reactors, and / or on at least two catalyst beds in the same reactor.

p0048The use of the catalyst described below in step (a) has the effect of increasing the viscosity index (VI). More generally, it is found that the increase in VI is at least 2 points, VI being measured on a load (residue) to the solvent dewaxed and the product from step (a) also solvent dewaxed in for a range of flow point temperature between - 15 and - 20 ° C. Is generally obtained an increase of IV of at least 5 points, and very often more than 5 points or 10 points or more than 10 points.

p0049It is possible to control the increase in VI, particularly from the measurement of the conversion. This will make it possible to optimize production towards high VI oils or oils to higher returns but with lower VI.

p0050Parallel to the increase of VI, it is usually obtained a lowering of the pour point which can range from a few degrees up to 10-15 ° C or more (25 ° C for example). The extent of reduction varies depending on the conversion and therefore the operating conditions and load.

Treatment of the effluent from step (a)

p0051In a preferred embodiment, the effluent from step (a) hydroisomerization-conversion can be completely treated in step (b) dewaxing. Alternatively, it may undergo a separation of at least a portion (and preferably at least a major part) of light gases which include hydrogen and optionally also hydrocarbon compounds with at most 4 carbon atoms. Hydrogen can be separated beforehand. The embodiment (not variant), passing in step (b) of the total effluent of step (a) is economically advantageous, since only one distillation unit is used at the end of the process . In addition, the final distillation (after catalytic dewaxing or subsequent treatments) a cold fuel is obtained. Advantageously, in another embodiment, the effluent from step (a) is distilled to separate the light gases and also separate at least one residue containing compounds with a boiling point at least 340 ° C. This is preferably an atmospheric distillation.

p0052advantageously can be distilled to obtain several fractions (gasoline, kerosene, diesel fuel, for example), to boiling point of at most 340 ° C and a fraction (called residue) to Initial boiling point above at least 340 ° C and preferably greater than 350 ° C and preferably at least 370 ° C or 380 ° C.

p0053According to a preferred variant of the invention, this fraction (residue) will then be processed in the catalytic dewaxing stage, ie without undergoing vacuum distillation. But in another embodiment, one may use a vacuum distillation.

p0054In one embodiment more focused on middle distillates production purpose, and still according to the invention, it is possible to recycle a portion of the residue from the separation step to the reactor containing the conversion-hydroisomerisation catalyst to convert and increase the production of middle distillates.

p0055In general, we call in this text middle distillates, the (the) portion (s) with an initial boiling point of at least 150 ° C. and an end before the residue, that is to ie generally up to 340 ° C, 350 ° C or preferably less than 370 ° C or 380 ° C.

p0056The effluent from step (a) can be subjected, before or after distillation, other treatments such as for example an extraction of at least a portion of the aromatic compounds.

Step (b) Catalytic Hydrodewaxing

p0057At least part of the effluent is known from step (a) effluent having optionally undergone the separations and / or treatments described above, is then subjected to a catalytic dewaxing step in the presence of hydrogen and a hydrodewaxing catalyst comprising an acid function, a hydro-dehydrogenating metallic function and at least one matrix.

p0058Note that compounds boiling above at least 340 ° C are still subject to catalytic dewaxing.

the catalyst

p0059The catalyst of the invention comprises the ZBM-30 sieve.

p0060Using the ZBM-30 molecular sieve and selected under the conditions described above, among the many existing molecular sieves already allows in particular the production of low pour point and high viscosity index in good yields the context of the method according to the invention.

p0061The content by weight of molecular sieves in the hydrodewaxing catalyst is between 1 and 90%, preferably between 5 and 90% and even more preferably between 10 and 85%.

p0062The dies used to make the catalyst shaping are by way of example and without limitation, alumina gel, alumina, magnesia, amorphous silica-aluminas, and mixtures thereof. Techniques such as extrusion, pelletization or coating, can be used to carry out the forming operation. The catalyst also comprises a hydro-dehydrogenating function provided, for example, by at least one group VIII element and preferably at least one noble element selected from the group consisting of platinum and palladium. The weight content of non-noble Group VIII metal, based on the final catalyst is between 1 and 40% preferably between 10 and 30%. In this case, the non-noble metal is often associated with at least one group VIB metal (preferably Mo or W). If there is at least one noble Group VIII metal, the weight content, with respect to the final catalyst is less than 5%, preferably less than 3% and more preferably less than 1.5 %.

p0063In the case of use of noble Group VIII metals, platinum and / or palladium are preferably located on the matrix.

p0064The hydrodewaxing catalyst according to the invention may further contain from 0 to 20%, preferably from 0 to 10% by weight (expressed as oxides) of phosphorus. metal of the combination (to) from group VIB and / or metal (s) from group VIII with phosphorus is particularly advantageous.

The treatment

p0065A residue obtained after step (a) and of the distillation and is worth to be treated in this step (b) hydrodewaxing, has the following characteristics: it has an initial boiling point 340 ° C and preferably greater than 370 ° C, a pour point of at least 15 ° C, a viscosity index of 35 to 165 (before dewaxing), preferably at least 110 and even more preferably less than 150, a viscosity at 100 ° C greater than or equal to 3 cSt (mm²/ S), an aromatics content less than 10 wt%, a nitrogen content less than 10 ppm by weight, a sulfur content below 50 ppm by weight or more to 10 ppm by weight.

p0066The operating conditions under which operates the catalytic step of the inventive method are the following:<ul><li>the reaction temperature is between 200 and 500 ° C and preferably between 250 and 470 ° C, preferably 270-430 ° C;</li><li>the pressure is between 1 <i>and</i> 25 MPa (10⁶ Pa) and preferably between 1.0 and 20 MPa;</li><li>the hourly volume rate (hvr expressed as volume of charge injected per catalyst volume unit and per hour) is between 0.05 and 50 and preferably between 0.1 and 20 h^-1 and even more preferably between 0.2 and 10 h^-1.</li></ul>

p0067They are chosen to obtain the desired pour point.

p0068The contact between the feedstock and the catalyst is performed in the presence of hydrogen. The amount of hydrogen used and expressed in liters of hydrogen per liter of charge is between 50 and 2000 liters of hydrogen per liter of feedstock and preferably between 100 and 1500 liters of hydrogen per liter of feed.

The effluent obtained

p0069The effluent leaving step (b) hydrodewaxing, is sent into the distillation train, which preferably integrates atmospheric distillation and vacuum distillation, which aims to separate the point of conversion products boiling below 340 ° C and preferably below 370 ° C, (and including in particular those formed during the catalytic hydrodewaxing step), and separate the fraction which constitutes the oil base and whose initial point boiling is greater than at least 340 ° C and preferably greater than or equal to 370 ° C.

p0070Moreover, this vacuum distillation section can separate different grades of oils.

p0071Preferably, before being distilled, the effluent leaving step (b) catalytic hydrodewaxing is, at least in part and preferably in full screen, sent to a hydrofinishing catalyst (hydrofinishing) in the presence of hydrogen so as to achieve accelerated hydrogenation of the aromatic compounds that affect the stability of the oils and distillates. However, the acidity of the catalyst must be low enough not to lead to the cracking product formation boiling point below 340 ° C so as not to degrade the final yields in particular oils.

p0072The catalyst used in this step comprises at least one Group VIII metal and / or at least one element from group VIB of the periodic table. Strong metallic functions: platinum and / or palladium, or nickel-tungsten combinations nickel-molydbène be advantageously used to achieve accelerated hydrogenation of the aromatics.

p0073These metals are deposited and dispersed on an amorphous oxide support or crystalline, such as for example, aluminas, silicas, silica-aluminas.

p0074The hydrofinishing catalyst (HDF) can also contain at least one element of group VII A of the periodic classification of elements. Most preferably these catalysts contain fluorine and / or chlorine.

p0075Contents by weight of metals are between 10 and 30% in the case of non-noble metals and below 2%, most preferably between 0.1 and 1.5%, and even more preferably between 0.1 and 1.0% in the case of noble metals.

p0076The total amount of halogen is between 0.02 and 30% by weight preferably 0.01 to 15%, or 0.01 to 10%, preferably 0.01 to 5%.

p0077Mention may be made from catalysts used in this hydrofinishing stage, and leading to excellent performance, especially for obtaining medicinal oils, catalysts containing at least one noble Group VIII metal (eg platinum) and at least one halogen (chlorine and / or fluorine), the combination of chlorine and fluorine being preferred.

p0078The operating conditions under which operates the hydrofinishing stage of the process of the invention are the following:<ul><li>the reaction temperature is between 180 and 400 ° C and preferably between 210 and 350 ° C, preferably 230-320 ° C;</li><li>the pressure is between 0.1 and 25 MPa (106 Pa) and preferably between 1.0 and 20 MPa;</li><li>the hourly volume rate (hvr expressed as volume of charge injected per catalyst volume unit and per hour) is between about 0.05 and about 100 and preferably between about 0.1 and about 30 hours^-1.</li></ul>

p0079The contact between the feedstock and the catalyst is performed in the presence of hydrogen. The amount of hydrogen used and expressed in liters of hydrogen per liter of charge is between 50 and approximately 2000 liters of hydrogen per liter of feedstock and preferably between 100 and 1500 liters of hydrogen per liter of feed.

p0080Advantageously, the temperature of the hydrofiniton step (HDF) is lower than the temperature of the catalytic hydrodewaxing step (CHDW). The difference T_HDPC-T_HDF is generally between 20 and 200 and preferably between 30 and 100 ° C. The effluent leaving HDF is sent into the distillation train.

Products

p0081Oils bases obtained according to this process have a pour point below -10 ° C, a VI greater than 95, preferably greater than 110 and even more preferably greater than 120, a viscosity of at least 3, 0 cSt at 100 ° C., an ASTM color of less than 1 and a UV stability such that the increase in the ASTM color is between 0 and 4 and preferably between 0.5 and 2.5.

p0082The UV stability test, adapted methods ASTM D1148-55 and D925-55 provides a quick method for comparing the stability of lubricating oils exposed to a source of ultraviolet rays. The test chamber consists of a metallic enclosure provided with a turntable which receives the oil samples. A bulb producing the same ultraviolet rays as those of sunlight and placed on top of the test chamber is directed downwards on the samples. Among the samples is included a standard oil with known UV characteristics. The ASTM D1500 color of the samples is determined at t = 0 and after 45 h exposure to 55 ° C. The results are transcribed for the standard sample and the test samples as follows:<ol><li>a) Initial ASTM D1500 color,</li><li>b) ASTM D1500 final color,</li><li>c) the color of growth,</li><li>d) disorder,</li><li>e) precipitate.</li></ol>

p0083Another advantage of the process according to the invention is that it is possible to achieve very low aromatics contents of below 2% by weight, preferably 1% by weight and preferably less than 0.05% by weight) and even of up to the production of white oils of medicinal quality having aromatics contents below 0.01% weight. These oils have UV absorbance values ​​at 275, 295 and 300 nanometers respectively less than 0.8, 0.4 and 0.3 (ASTM method D2008) and a Saybolt color of between 0 and 30. Particularly advantageously, therefore, the method according to the invention also allows to obtain medicinal white oils. Medical white oils are mineral oils obtained by accelerated refining, their quality is subject to different regulations aimed at ensuring their safety for pharmaceutical applications, they are devoid of toxicity and are characterized by their density and viscosity. Medicinal white oils essentially comprise saturated hydrocarbons, they are chemically inert and their aromatic hydrocarbon content is low. Particular attention is given to aromatic compounds and in particular to 6 polycyclic aromatic hydrocarbons (PAH for the Anglo-Saxon abbreviation polycyclic aromatic hydrocarbons) that are toxic and present in concentrations of one part per billion by weight of aromatic compounds in white oil. The control of the total aromatics content can be made by ASTM D 2008, this UV adsorption test at 275, 292 and 300 nanometers makes it possible to control a lower absorbance respectively 0.8, 0.4 and 0.3 (ie that white oils have aromatics contents below 0.01% by weight). These measurements are made with concentrations of 1 g of oil per liter, in a 1 cm cuvette. White oils differ by their viscosity but also by their original crude oil which can be paraffinic or naphthenic, these two parameters will lead to differences in both the physicochemical properties of the white oils considered but also in their chemical composition . Currently oil cuts, they come either from the direct distillation of a crude oil followed by extraction of aromatics with a solvent, or whether from catalytic hydroprocessing or hydrocracking process, still contain significant amounts of aromatics. In the current legislative framework of most industrialized countries, the so-called medicinal white oils must have an aromatics content below a threshold imposed by the legislation of each country. The absence of these aromatic compounds in the oil fractions is reflected by a Saybolt color specification which should be substantially at least 30 (30), a maximum UV adsorption specification which should be less than 1.60 to 275 nm on a pure product in tank 1 cm and a maximum absorption specification of extraction products by DMSO which must be less than 0.1 for the US market (Food and Drug Administration, standard No. 1,211,145). This last test consists in extracting specifically polycyclic aromatic hydrocarbons using a polar solvent, often DMSO, and control their content in the extract by measuring UV absorption in the range 260-350 nm.

figures

p0084The invention will be illustrated with the <figref idrefs="f0001 f0002">Figures 1 to 3</figref>, Representing different embodiments for the inventive treatment of a load, for example, derived from Fischer-Tropsch process or a hydrocracking residue.

<u>Figure 1</u>

p0085On the <figref idrefs="f0001">figure 1</figref>, The load between the pipe (1) into a hydrotreatment zone (2) (which may be composed of one or more reactors, and comprise one or more catalytic beds of one or more catalysts) wherein from hydrogen (e.g. via line (3)) and where is performed the step of hydrotreating.

p0086The hydrotreated feedstock is transferred via line (4) in the hydroisomerization zone (7) (which may be composed of one or more reactors, and comprise one or more catalytic beds of one or more catalysts) where is carried out in the presence hydrogen, step (a) hydroisomerization. Hydrogen can be fed via line (8).

p0087In this figure, before being introduced in the region (7), the feed to be hydroisomerized is freed of a large part of its water in the flask (5), the water leaving through line (6) and optionally ammonia and hydrogen sulphide H₂S, in the case where the feed entering through line 1 contains sulfur and nitrogen.

p0088The effluent from zone (7) is sent via a line (9) into a balloon (10) for separation of the hydrogen which is extracted via a line (11), the effluent is then distilled at atmospheric pressure in column (12) from which is extracted at the top via line (13) a light fraction containing compounds with at most 4 carbon atoms and those boiling below.

p0089It is also obtained at least one gasoline fraction (14) and at least a fraction of middle distillate (kerosene (15) and diesel (16) for example).

p0090It is obtained from the column bottom a fraction containing compounds with a boiling point at least 340 ° C. This fraction is discharged via line (17) towards the region (18) of catalytic dewaxing.

p0091The region (18) of catalytic dewaxing (comprising one or more reactors, one or more catalytic beds of one or more catalysts) also receives hydrogen through a pipe (19) for performing step (b) of the process. The effluent obtained by the outgoing line (20) is separated in a distillation train further comprising the balloon (21) for separating hydrogen via a pipe (22), an atmospheric distillation column (23) and a vacuum column (24) which processes the atmospheric distillation residue transferred via line (25), initial boiling residue above 340 ° C.

p0092It is obtained as products after distillation, an oil fraction (line 26) and lower boiling fractions, such as diesel oil (line 27), kerosene (line 28) petrol (line 29); light gas being eliminated via line (30) of the atmospheric column and via line (31) of the vacuum distillation column.

p0093The effluent via line (20) may advantageously be sent to a hydrofinishing zone (not shown) (comprising one or more reactors, one or more catalytic beds of one or more catalysts). Hydrogen can be added as desired in this area. The effluent is then transferred into the flask (21) and described the process of distillation.

p0094Order not to overburden the figure, the hydrogen recycling is not shown, either at the level of the balloon (10) to the hydrotreatment and / or hydroisomerization, and / or at the level of the balloon (21) to the dewaxing and / or hydrofinishing.

<u>Figure 2</u>

p0095We recognize references <figref idrefs="f0001">figure 1</figref> Here recovery. In this embodiment, the entire effluent from zone (7) hydroisomerization-conversion (step a) is passed directly via line (9) in the region (18) of catalytic dewaxing (step b).

<u>Figure 3</u>

p0096In the same manner as above, references to the <figref idrefs="f0001">figure 1</figref> have been retained. In this embodiment, the effluent from zone (7) hydroisomerization-conversion (step a) undergoes in the balloon (32) a separation of at least a portion of the light gases (hydrogen and hydrocarbon compounds in most 4 carbon atoms), for example by flash. The separated gases are removed via line (33) and the residual effluent is sent via line (34) in the region (18) of catalytic dewaxing.

p0097Note that on the <figref idrefs="f0001">Figures 1, 2</figref> and <figref idrefs="f0002">3</figref> a separation has been provided on the effluent from zone (18) of catalytic dewaxing. This separation can not be implemented when said effluent is subsequently treated in a hydrofinishing zone, separation having so well after such treatment. This is the separation achieved in the balls or columns 21, 23, 24.