FR2778347A1 - Sulfuration of catalyst for use in hydrotreatment - Google Patents

Abstract

The sulfuration of the bimetallic hydrotreatment catalyst using a stoichiometric excess of sulfur in a liquid phase treatment before the final sulfuration temperature (maximum temperature before onset of coking), gives improved performance, i.e. better activity and stability. The process is applied to a petroleum refining catalyst which contains at least one group VIII metal in the oxide form. It comprises a sulfuration stage using H2S or a precursor as the sulfurizing agent, added before the catalyst attains the final sulfuration temperature. At least 130% of the stoichiometric amount of sulfur necessary for complete sulfuration is injected. Independent claims are also included for the activated catalyst obtained and its uses.

Description

The present invention relates to the field of hydrot catalysts.

used

  in the refining and petrochemical industry.

  Hydrotreatment catalysts generally comprising at least one group VIII metal and optionally at least one group VI metal and in particular those of the NiMo, CoMo, NiW and CoW type are very widely used in the refining and petrochemical industry. Among these catalysts, a distinction is made between catalysts sold in presulfurized form, and catalysts sold and loaded in

  reactors in the form of metal oxides.

  The activated and stable form of these hydrotreatment catalysts being the sulfurized form.

  when they are in the form of oxides, these catalysts must undergo a stage of

  sulfurization which can be carried out using specialized equipment, in the unit itself

  even or before loading the catalyst into the unit. This sulfurization phase can be carried out using any molecule containing sulfur and which can give hydrogen sulfide (H2S), it is indeed hydrogen sulfide which is the agent.

sulfurizing of these catalysts.

  Methods for treating catalysts in which at least one sulphurization is carried out have already been described in the literature, for example, patent EP-B-64429 describes a procedure for sulphurizing particular hydrotreatment catalysts of the NiMo, NiW, CoW type. and CoMo. In patent EP-B-64429, provision is made to carry out at least two temperature stages during the sulfurization phase. It is also described that a third level can be provided. Said sulfurization process uses a sulfurization agent which is injected onto the catalyst at a temperature T between room temperature and 180 C, the temperature is then raised to the temperature T 'of a first step between 250 C and 300 C. In this process, the quantity of sulfur injected during this first stage at temperature T 'is between - 0.2 and 2 times the quantity of sulfur theoretically necessary for the total sulfurization of metal oxides (noted QS / R ). Then, a second stage is carried out at a temperature T "higher than 300C ect higher by at least 30 to 500C than the temperature T 'of the first stage. During this second stage, the quantity of sulfur injected is between 0.1 and 3 times QS / R. Finally, it is possible to provide a third level at a temperature T "'at least 20 to 40 C higher than the temperature T" of the second level. During this third level, the quantity of sulfur injected is also included

between 0.1 and 3 times QS / R.

  The applicant has now sought to obtain a sulfurization process which would be easier to implement, for example a sulfurization process which would make it possible to

  get rid of a temperature increase process in stages.

  It has now been discovered that, surprisingly, the activity and the stability of the hydrotreatment catalysts comprising at least one metal from group VIII and optionally at least one metal from group VI and in particular those of the NiMo, CoMo, NiW type. and CoW are closely related to the sulfurization procedure used to sulfurize said catalysts. Thus, it has been found that the activity and the stability of the catalyst for hydrodesulfurization are particularly improved if said catalyst is subjected to a specific treatment beforehand. This treatment process makes

the object of the present invention.

  The expressions "group element" and "group metal" will be used

  indifferently in the present description.

  The process according to the present invention is a process for the sulfurization of a refining or petrochemical catalyst, said catalyst containing at least one metal from group VIII of the periodic table and optionally at least one metal from group VI of said classification, said metal being present as metallic oxides. Said method comprises at least one sulfurization step carried out in the presence of at least one sulfurization agent selected from the group formed by hydrogen sulfide and the hydrogen sulfide precursors. This process is carried out in such a way that, before the catalyst reaches the final sulfurization temperature. at least 130% of the stoichiometric quantity of sulfur necessary for the complete sulfurization of the catalyst

is injected onto said catalyst.

  Within the meaning of the present description, the "final sulfurization temperature" of a

  catalyst can be defined as the maximum temperature at which said sulphurization can be carried out without the catalyst thus sulphurized having too great a coking, that is to say a coking which would result in an increase in the average reaction temperature of more than 3 C. This final sulfurization temperature depends on the partial pressure of hydrogen, moreover this final sulfurization temperature is generally less than 380 C which is the temperature of

  cracking of the sulfurization charge.

  The catalyst treated according to the process of the present invention. has better performance, that is to say better activity and / or better stability. In addition, the implementation of the method according to the present invention is also easier because it

  eliminates the process of increasing the temperature in stages.

  By "activity" within the meaning of this description means the performance of the

  catalyst during the first hours of its operation in the presence of the load to be treated under the operating conditions of a given installation. By "stability"

  within the meaning of the present description, the development of the activity of the catalyst is understood to mean

  over time. By "load to be treated" within the meaning of the present description, the

  fraction of hydrocarbons which is normally sent to the catalytic reactor for

be transformed there.

  During sulfurization, the catalyst in which the metals are in the state of oxides is sulfurized. The quantity of sulfur that can be fixed varies from one catalyst to another, in particular according to its manufacturing procedure and the content of oxide (s) deposited on the support. It is possible, starting from the composition of the catalyst, to calculate the quantity of sulfur which, at most, will be tixec by the catalyst. This quantity of sulfur is the stoichiometric quantity, noted QS0. it will therefore, by definition, be the quantity of sulfur necessary for the complete sulfurization of the metal or of the mixture of metals of

oxide phase catalyst.

  These metals are, for example, molybdenum in the form of molybdenum disulfide MoS2, cobalt in the form of nonacobalt Co9S8 octosulfide, nickel in the form of nickel sulfide NiS and tungsten in the form of tungsten disulfide WS2. This QSo value can be expressed by any suitable unit and most often it is expressed either in moles of sulfur per unit mass of catalyst (for example in kilometers of sulfur per tonne of catalyst) or unit of mass of sulfur per unit of

  mass of catalyst (for example in tonnes of sulfur per tonne of catalyst).

  The catalyst treated according to the process of the present invention comprises at least one element from group VIII and optionally one element from group VI of the periodic classification (Handbook of Chemistry and Physics, 76 th Edition, 1995-1996) in the state of metal oxides. This catalyst can be in mass form, it then does not contain a support, or in supported form, the support then being an oxide

  refractory cornmme, for example alumina.

  In the following text, the notation QS / QS0 will be used, this notation represents the quantity of sulfur injected into the catalyst relative to the stoichiometric quantity of sulfur as defined above. For example, if QS / QS0 = l., It means that

  the quantity of sulfur injected is equal to the stoichiometric quantity of sulfur.

  Surprisingly, we discovered that the QS / QS0 value reached was very important. Without wishing to be linked to any theory, we can think that if a minimum value is not respected, the sulfurization of the catalvseCl- may not be sufficient and by that very fact, the catalytic performances expressed in terms

  activity and stability, may be deteriorated.

  The present invention is a process for the sulfurization of a refining or petrochemical catalyst in which the quantity of sulfur injected is determined very precisely. According to this process, the quantity of sulfur injected before the temperature reaches 250 ° C. must represent at least 130% of the stoichiometric quantity of

sulfur.

  The sulfurizing agent used is a compound capable of decomposing to give hydrogen sulphide (H2S). Indeed, the sulfurizing agent of the oxide phase is hydrogen sulphide. According to the process of the present invention, hydrogen sulfide can therefore be generated in the sulfiding zone by decomposition of a molecule containing sulfur, that is to say a precursor of hydrogen sulfide, but it can also

  be directly injected into the catalyst in the form of hydrogen sulphide.

  According to a preferred embodiment of the present invention, the sulfurization of the catalyst is carried out in the reactor where a reaction is then carried out in the presence of the sulfurized catalyst. Thus, for example during a start in the liquid phase with a gas oil, dimethyldisulfide (DMDS) is added. It is indeed known that DMDS is very easily decomposed into hydrogen sulfide, which makes it possible to carry out the sulfurization of the oxide phase. On the other hand, the sulfur contained in the gas oil itself cannot carry out the sulfurization of the oxide phase at low temperature because the sulfur molecules are too

  stable to generate hydrogen sulfide.

  All the compounds capable of forming hydrogen sulfide during their decomposition can be used in the process according to the present invention, the use of hydrogen sulfide precursors, the use of which will however be avoided.

  can be dangerous, for example. carbon disulfide (CS,) will not be used.

  In the process according to the present invention, it is therefore advisable to use a specific sulfurizing agent. Currently, most sulfurizations are carried out in the liquid phase, that is to say that the catalyst, when the sulfurization reaction takes place, is immersed in a liquid phase. This liquid phase generally comprises a hydrocarbon such as, for example, a white spirit or a gas oil. One of the main advantages of using a liquid phase is that the rise in temperature due to the exothermicity of the sulfurization reaction remains very low because the calories generated by the reaction are easily dispersed in the liquid phase. This liquid phase contains at least one precursor of H2S (for example DMDS) but it can also contain HaS in mixture with at least one precursor of H2S, for example one can use hydrogen sulfide in dissolved form in a feed containing

precursor of HiS.

  The flow rate of the sulfurization agent introduced into the reactor is calculated relative to the

  volume of catalyst loaded in the reactor where the sulfurization reaction takes place.

  The sulfurizing agent injected before the catalyst reaches the final sulfurization temperature is introduced at a chosen rate and for a period long enough for the quantity of sulfur injected to represent at least 130% of the quantity

sulfur stoichiometric.

  When a liquid sulphurizing agent is used, the flow rate of liquid, expressed in volume per hour, is generally between 0, 10 and 50 times the volume of catalyst, preferably between 0.25 and 10 and again more preferred between

  0.25 and 2 times the volume of catalyst.

  When using a gas sulfiding agent, the gas flow rate. e. xpressed in volume per hour, is much higher. The gas flow rate generally chosen is between I and 10,000 liters of gas per liter of catalyst, measured under normal conditions of temperature and pressure, and preferably between 10 and 5000 liters of gas per liter of catalyst. The increase in temperature between the start temperature and the end sulfurization temperature is carried out by means known to those skilled in the art at a rate compatible with the good mechanical strength of the unit and by eliminating the constraints caused by the expansion of the different parts of the unit. As an indication, the temperature rise is generally carried out at a rate of 5 to 25 ° C. per hour, most often continuously. Without this being compulsory. the rise in

  temperature can also be achieved by making steps.

  According to a particular embodiment, the method of sulfurization of the catalyst according to the present invention comprises a treatment with hydrogen of the catalyst, carried out before, during or after the sulfurization. Most often, this particular embodiment of the process according to the present invention is carried out by subjecting, during a first step, the catalyst to a relatively low temperature in an atmosphere containing hydrogen. A relatively low temperature means that this temperature is usually between room temperature (20 C) and a temperature generally below 250 C, often this temperature can be below 200 C and most often below 160 C. The most Current flow rate of hydrogen is between 1 and 10,000 liters of gas per liter of catalyst, measured under normal conditions of temperature and pressure. and preferably between 10 and 5000 liters of gas per liter of catalyst. The charge containing the sulfurizing agent can then be injected. To carry out the sulfurization, it is sometimes possible to use the feedstock to be treated, provided that it contains an agent capable of sulfurizing the catalyst. In the case where the sulfurization charge is the charge to be treated, a sulfur-containing compound is generally added thereto as, for example, DMDS (dimethyldisulfide). The other sulfur-containing compounds which can be used are the compounds whose dissolution in the sulfurization liquid is complete, these compounds are generally chosen from the group formed by polvsuLlftures and for example organic polysulfides called TPS, mercaptans, sulfides , disulfides, oxygenated sulfur compounds, dissolved elemental sulfur and / or

partially suspended.

  The organic polysulphides called TPS are, for example, described in the patent.

French FR 2548205.

  The feedstocks to be treated in hydrodesulfurization which can be used in the sulfurization process according to the present invention are the feedstocks resulting from the distillation of a crude oil containing substantially no olefinic compounds or diolefinic compounds. The sulfurization charge is injected as soon as possible, that is to say as soon as the

  thermal stresses on the steel when the unit is pressurized allow this.

  Previously, the conventional units used did not allow the introduction of such a charge before 210 C, in recent years the units have been constructed with materials which allow the introduction of said charge from 100 C. The temperature is then increased up to at the final sulfurization temperature by all means known to a person skilled in the art, this final sulfurization temperature generally varies and depending on the catalysts used between 220 ° C. and 380 ° C. this final sulfurization temperature can be brought to 450 ° C. and even up to 500 C with the drawbacks that these high temperatures may cause (cracking of the sulfurization charge, etc.). This temperature rise is carried out continuously or in stages. From the moment the charge is injected, the total amount of added sulfur is counted. Before the catalyst reaches the final sulfurization temperature, the quantity QS / QS0 must be at least equal to 1.3, i.e. at least 130% of the stoichiometric quantity of sulfur necessary for complete sulfurization catalyst must have been injected into the catalyst. In addition and preferably. before the temperature reaches 250 C half of the metallic particles of the catalyst must be

find in sulfurized form.

  The sulfurization of the catalysts according to the process of the present invention allows an improvement in the performance of these catalysts, in particular for the hydrodesulfurization, hydrodenitrogenation, hydrodemetallization and hydrogenation reactions of aromatic and olefinic compounds. By - performance improvement "in the sense of

  the present description means improvement of the activity and / or of the stability of the

  catalyst. When the feed to be treated contains neither olefinic compounds nor diolefinic compounds, it can sometimes be advantageous to directly use this feed to be treated for the sulfurization step. It is then very usual to add a sulfur-containing compound thereto.

  that, by decomposition in the presence of hydrogen, the H2S molecule is generated.

  The sulfurizing agent is then hydrogen sulphide generated at least in part in the sulphurization zone from a liquid feed containing at least one precursor of the hydrogen sulphide introduced into the hydrotreatment reactor. In particular, this charge can also be the charge to be treated, in which case this charge is then subjected to a hydrotreatment carried out in the presence of said sulfur catalyst. Usually, this way of operating is generally chosen when the charge is light and in particular when the charge to be treated is of the atmospheric distillate type such as naphtha,

kerosene or diesel.

  The sulfurized catalyst by the sulfurization process according to the present invention makes it possible to treat light loads such as those described above but it is quite possible to treat much heavier loads as long as they contain neither olefinic compounds nor diolefinic compounds. These charges can, moreover,

contain aromatic compounds.

  The invention also relates to the use of the catalyst according to the invention for.

  l Hydrodesulfurization of feedstocks from the distillation of petroleum crude oil containing neither olefinic nor diolefinic compounds

  The examples which follow in no way limit the scope of the invention.

Examples

  The following examples were carried out using a CoMo type catalyst deposited on alumina. To synthesize this catalyst, we used the commercial gel SB3 sold by the company Condea. This alumina gel is mixed with water and nitric acid and then kneaded for 15 minutes. The mass of water added to the gel is equal to the mass of the gel, the mass of nitric acid (HNO) added is calculated relative to the dry powder precursor of the gel, so that for 100 g of dry powder, we add 7 g of an aqueous solution of nitric acid at 68% c. At the end of this kneading, the dough obtained is passed through a cylindrical die so as to obtain extrudates with a diameter equal to 1.2 mm. The extrudates are then dried overnight at 120 ° C. and then calcined at 550 ° C. for 2 hours in air. We added molybdenum to the extruded support by dry impregnation in an aqueous medium. The molybdenum salt is ammonium heptamolybdate Mo7024 (NH4) 6,4H2O. After dry impregnation, the extrudates are dried overnight at 120 ° C. and then calcined at 550 ° C. for 2 hours in air. The cobalt is then added by dry impregnation in aqueous media using cobalt nitrate Co (NO3) 2 as a precursor. The extrudates are then dried overnight at 120 ° C. and then calcined at 550 ° C. for 11 2 hours in air. Weight contents of MoO3 and CoO with respect to the catalyst

  final are 14.0% o and 3.0% respectively.

  Two catalysts were synthesized according to the procedure described above. each of these catalysts was then subjected to sulfurization according to a different process. A first catalyst underwent sulfurization according to the process according to the present invention, the second catalyst, by way of comparative example, underwent sulfurization according to a process not according to the present invention. These two processes are described

in examples I and 2.

  For the two sulfurization processes, the sulfurization charge used is the charge to be treated. The gas oil to be treated is an atmospheric distillate which therefore does not contain olefinic compounds. It was therefore used as a sulfurization charge to which was added dimethyldisulphide (DMDS). DMDS was chosen because it is very often used industrially and we know that it decomposes very easily in the presence of hydrogen to give H2S and CH4. The hydrogen sulfide thus formed will be able

  carry out the sulfurization of the catalyst.

  EXAMPLE 1 Non-Conforming Sulfurization (Catalyst C1) The temperature of the catalyst rose from ambient temperature (25 ° C.) to approximately C under pure hydrogen. Then, the sulfurization charge, that is to say a gas oil to which 3% by weight of DMDS has been added - which corresponds to a QS / QS0 value equal to 17% - is injected at a flow rate of 40 cc / h hourly volume speed (VVH) equal to 1h-1. The temperature is then increased to 350 C (the final sulfurization temperature) at the rate of 4.5 C per minute. The temperature rise in this pilot example is carried out at a much higher speed

  faster than for industrial scale projects.

  After a very brief plateau at 350 C (about 10 minutes). the ternpératurc is lowered to 310 C, the load to be treated-that is to say the diesel used during the sulfurization but

  without adding DMDS - can then be introduced.

  The operating conditions of the sulphurization stage are as follows Total pressure (MPa) [3 VVH (hl) 2 Flow rate H, (1/1) 400 (reactor inlet) Example 2: compliant start-up (catalyst C2) The temperature of the catalyst rose from room temperature (25 C) to about C under pure hydrogen. Then, the sulfurization charge, that is to say a gas oil to which 24% by weight of DMDS has been added - which corresponds to a QS / QS0 value equal to 138% - is injected at a flow rate of 40 cc / h hourly volume speed (VVH) equal to lh'1. The temperature is then increased to 350 C (the final sulfurization temperature) at the rate of 4.5 C per minute. The temperature rise in this pilot example is carried out at a much higher speed

  faster than for industrial scale projects.

  After a very brief plateau at 350 C (approximately 10 minutes), the temperature is lowered

  up to 310 C and the sulfurization charge is replaced by the charge to be treated -that is-

  say the diesel used during sulfurization but without the addition of DMDS -.

  The operating conditions for the sulfurization stage are as follows: Total pressure (MPa) 3 VVH (hl) 2 Flow rate Hi (1/1) 400 (reactor inlet) To compare the activity of the catalysts, we have implemented a hydrodesulfurization test of an atmospheric diesel oil, the main characteristics of which are given in the following table Density at 15 C 0.856 Refractive Index at 20 C 1, .4564 Viscosity at 50 C 3.72 cSt Sulfur I.1.57 % weight Simulated distillation PI 153 C

% 2220 C

% 315 C

% 398 C

PF 448 C

  The method used in simulated distillation is the ASTM D-2887 method.

  The diesel HDS test is carried out under the following operating conditions Catalyst volume 40cm3 Total pressure 3 MPa Hourly Volume Speed 2h-1 Temperature 360 C Hydrogen flow rate 2501/1 charge The catalytic performances of the catalysts are expressed in HDS conversion (% HDS) and in activity considering that it is of order 1.5. The relationship between activity and conversion (% HDS) is as follows: Activity = [100 / (100-% HDS)] 0 5 - 1 We sulfurized two catalysts differently. In both cases, the quantity

  total sulfur injected is different but the temperature profiles are identical.

  The performance of the catalysts is compared to 360 C. In the following table, we have reported the sulfur contents in the effluents as well as the conversion into

  hydrodesulfurization (% HDS) and finally the activity of the two catalysts C I and C2.

  Cl (C2 process (non-compliant process) compliant) effluent (pprnm weight) 441 352

% HDS 97.19 97.76

  Activity 4.97 5.73 As can be seen, the catalyst C2 which has been sulfurized according to a process in accordance with the invention exhibits an HDS activity greater than that of the catalyst CI which was started with a process not in accordance with the invention, the activity obtained using catalyst C1 being equal to 79% of that obtained using catalyst C2. We also note that the process according to the present invention is a process whose implementation is easy (it is carried out in one step with a rise in temperature which does not require any particular monitoring since it consists in a rise in temperature , then maintaining this temperature for a few minutes before reducing this temperature to the temperature at which diesel is introduced at

  to treat) and which allows to obtain good yields in hydrodesulfurization (75.2%).

Claims (8)

  1- Process for the sulfurization of a refining or petrochemical catalyst, said catalyst containing at least one metal chosen from the group formed by the elements, from group VIII of the periodic table, said metal being present in the state of oxides, process characterized in that it comprises at least one step carried out in the presence of at least one sulphurizing agent chosen from the group formed by hydrogen sulphide and the precursors of hydrogen sulphide, so that, before that the catalyst reaches the final sulfurization temperature, at least 130% o of the stoichiometric quantity of sulfur necessary for complete sulfurization of the   catalyst is injected onto said catalyst.   2-A method according to claim I characterized in that the catalyst contains at least one element selected from the group formed by the elements of group VI of the   1 5 periodic classification, in the form of oxides.   3- Method according to one of claims 1 or 2 wherein the catalyst comprises an alumina-containing matrix.   4- Method according to one of claims I to 3 wherein the sulfurizing agent is   chosen from the group formed by hydrogen sulfide and the precursors of hydrogen sulfide.   - Method according to one of claims I to 4 wherein the sulfurizing agent is   hydrogen sulfide generated at least in part in the sulfurization zone from a liquid feed containing at least one precursor of hydrogen sulfide   introduced into the hydrotreatment reactor.   6- Method according to one of claims I to 5 wherein the sulfurizing agent is   contained in a charge, this charge then being subjected to hydrotreatment   carried out in the presence of said sulfur catalyst.   7- Method according to one of claims I to 6 wherein a treatment of the catalyst by hydrogen is carried out.   8- Method according to one of claims I to 7 characterized in that the sulfurization of   catalyst is carried out in a reactor where a reaction is then carried out presence of catalyst.   9- Catalyst obtained by the process according to one of claims I to 8.   - Use of the catalyst according to claim 9 or of the catalyst obtained by   Process according to one of Claims 1 to 8 for the hydrodesulfurization of feedstocks   from the distillation of crude oil containing neither olefinic compounds nor diolefinic compounds.