JP2003327970A - Method for producing hydrocarbon having low sulfur and mercaptan contents - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a hydrocarbon having low sulfur and mercaptan contents. <P>SOLUTION: This method for desulfurizing a hydrocarbon fraction containing sulfur compounds and olefin compounds comprises at least the following sequential processes: the first desulfurization of the fraction in the presence of hydrogen and a hydrodesulfurization catalyst under a condition that the desulfurization rate of the fraction is increased more than 90%; the separation of most of the hydrogen sulfide by-produced by the first desulfurization; and the second desulfurization of the hydrogen sulfide-removed effluent from the separation process in the presence of hydrogen and a hydrodesulfurization catalyst under a condition that the desulfurization rate of the effluent is lowered more than that on the first desulfurization. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a hydrocarbon having a low sulfur content. This hydrocarbon fraction usually contains more than 5% by weight and often more than 10% by weight of olefinic fractions. The method, among other things, reduces the sulfur and mercaptan content of the gasoline cut without reducing the yield of the gasoline and minimizes the reduction in octane number during the process, thereby reducing the overall sulfur-containing gasoline cut. Makes it possible to increase the value of. The invention is particularly concerned with gasoline to be treated,
Sulfur content exceeds 500 ppm by weight, or 100
It is a catalytic cracking gasoline that exceeds 0 ppm by weight and further exceeds 2000 ppm by weight, and the sulfur content in the desulfurized gasoline is less than 50 ppm by weight, and further 20 ppm by weight.
Applicable when less than m, especially less than 10 ppm by weight.

[0002]

BACKGROUND OF THE INVENTION Future standards for automotive fuels envision and prescribe, especially for gasoline, to significantly reduce the sulfur content of these fuels. The specification for sulfur content is currently about 150 ppm by weight, but in the coming years, it will go through a transition phase of less than 30 ppm by weight to reach a content of less than 10 ppm. Thus, the move to changing specifications for sulfur content in fuels necessitates the development of new processes for extreme desulfurization of gasoline.

The main source of sulfur in the basic constituents of gasoline is the so-called cracked gasoline, mainly the gasoline fraction resulting from the catalytic cracking process of the residues of crude oil at atmospheric or vacuum distillation. The gasoline fraction produced by catalytic cracking, which on average makes up 40% of the gasoline base, actually contributes over 90% of the sulfur content in the gasoline. Therefore, the production of low-sulfur gasoline requires a step of desulfurizing catalytically cracked gasoline. In the prior art, this desulfurization is carried out by one or several steps of contacting the sulfur compounds contained in the gasoline with a hydrogen-rich gas in the so-called hydrodesulfurization process.

On the other hand, the octane number of such gasolines is very strongly linked to their olefin content. Therefore, in order to maintain the octane number of these gasolines, it is necessary to suppress the conversion reaction of olefin to paraffin, which is inherent in the hydrodesulfurization process.

Furthermore, those gasolines are corrosive due to the presence of mercaptans. To control the corrosiveness of gasoline, it is generally necessary to have a mercaptan content of at least 1
It is necessary to reduce significantly to values below 0 ppm, ideally below 5 ppm. The mercaptans measured in desulfurized gasoline are so-called recombination, that is, the mercaptans formed by the addition reaction of hydrogen sulfide (H ₂ S) generated in the desulfurization step with the olefins present in the gasoline. The solution usually adopted to remove these mercaptans consists in hydrogenating the olefins present in the gasoline. However,
For the reasons already mentioned, this hydrogenation leads to a reduction in the octane number, which is a major obstacle to catalytically cracked gasoline.

In order to suppress the undesired olefin hydrogenation reaction, which is usually evaluated by those skilled in the art in the form of olefin saturation at the reactor outlet, and to selectively remove sulfur compounds in gasoline, many Solution has been proposed. Among these methods, the method of treating gasoline continuously in one or two reactors without separating H ₂ S in the middle can be highly evaluated. These methods are
It allows to partially solve the octane number and mercaptan problems for charges which normally contain no more than 1000 ppm of sulfur and which have a low desulfurization rate required, typically less than 90%.

In order to treat gasoline rich in sulfur (ie containing more than 1000 ppm, even more than 2000 ppm of sulfur) and finally achieve a sulfur content of less than 50 ppm, even less than 20 ppm or even less than 10 ppm, In some cases, and even more preferably, the H ₂ S formed between the hydrodesulfurization in the at least two series hydrodesulfurization reactors and the first hydrodesulfurization step
Intermediate removal may be required. This type of system achieves a high desulfurization rate, for example, 99% desulfurization rate, and produces 1% gasoline having a sulfur concentration of about 2000 ppm.
It is preferably used to obtain a sulfur concentration of about 0 ppm.

[0008] For example, the following Patent Document 1 discloses that H between at least two hydrodesulfurization steps and both hydrodesulfurization reactors.
_A method consisting of a ₂ S removal step is proposed. The hydrodesulfurization rate should be between 60% and 90% for each step. However, such a method cannot be considered to achieve desulfurization rates in excess of 99% on an industrial scale. It may be necessary to add at least one additional step to achieve stronger desulfurization, which significantly limits the economic attractiveness of the process.

US Pat. No. 6,037,037 below proposes the treatment of gasoline with a high sulfur content in a manner which also consists of a two-step hydrodesulfurization and an intermediate removal of the H ₂ S formed. The operating conditions are that the desulfurization rate and desulfurization temperature of the gasoline in the second hydrodesulfurization step are higher than those in the first step.

[0010]

[Patent Document 1] European Patent No. 0755995.

[0011]

[Patent Document 1] US Pat. No. 6,231,753.

[0012]

SUMMARY OF THE INVENTION Broadly speaking, the present invention relates to a novel process involving _two hydrodesulfurization steps and an intermediate removal of H2S, the process being: -a future standard for gasoline. , Ie 30ppm
Achieving a sulfur content of approximately 10 ppm in some countries, suppressing the hydrogenation process of olefins in the process, suppressing the decrease in octane number associated with the hydrodesulfurization process, To reduce the mercaptan content to obtain the desired sulfur content and olefin content in desulfurized gasoline,
It is possible at the same time.

More particularly, the present invention relates to a process for desulfurizing a hydrocarbon cut containing a sulfur compound and an olefin compound comprising at least the following sequential steps: -in the presence of hydrogen and a hydrodesulfurization catalyst. , First desulfurization under the condition that the desulfurization rate of the fraction is higher than 90%,-most of hydrogen sulfide (H ₂ S) generated in the first desulfurization is separated, -hydrogen sulfide is removed A second desulfurization of the effluent from the separation step in the presence of hydrogen and a hydrodesulfurization catalyst, under conditions where the desulfurization rate of the effluent is lower than that in the first desulfurization.

As described above, the present desulfurization method has a high desulfurization rate while completely suppressing the decrease in octane number due to hydrogenation of olefins and the formation of mercaptan due to recombination.
It proposes a solution for achieving desulfurization rates typically above 95%, especially above 99%. The result is gasoline with a low sulfur and mercaptan content and a high octane number.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for desulfurizing a hydrocarbon fraction containing a sulfur compound and an olefin compound, comprising at least the following sequential steps: -the presence of hydrogen and a hydrodesulfurization catalyst. the first desulfurization under the conditions min desulfurization rate is higher than 90%, - most of the separation of the first hydrogen sulfide produced by desulfurization (H 2 _S), - a separation step is removal of hydrogen sulfide A second desulfurization of the effluent in the presence of hydrogen and a hydrodesulfurization catalyst under conditions where the desulfurization rate of the effluent is lower than that in the first desulfurization.

In the method of the present invention, at least one of the hydrodesulfurization catalysts preferably contains at least one Group VIII element of the periodic table, and at least one of the hydrodesulfurization catalysts further comprises at least one. One Periodic Table VI
It is more preferable to contain a Group B element.

The hydrodesulfurization catalyst comprises at least one periodic table group VIII element selected from the group consisting of nickel and cobalt and at least one periodic table group selected from the group consisting of molybdenum and tungsten. It is particularly preferable to contain a VIB group element.

The first desulfurization of the process of the present invention is carried out at 250 ° C. and 3
At a temperature between 50 ° C. and a pressure of 1-3 MPa for 1 h
The liquid hourly space velocity of ^{−1 to} 10 h ⁻¹ and the H ₂ / HC (hydrocarbon) ratio of 50 liter / liter to 500 liter / liter are preferable, and the second desulfurization is 200
At a temperature between 0 ° C and 300 ° C, under a pressure of 1-3 MPa,
It is preferable to carry out at a liquid hourly space velocity of ¹ h ^{−1 to} 10 h ^{−1 and} an H ₂ / HC (hydrocarbon) ratio of 50 liter / liter to 500 liter / liter.

The desulfurization rate of the second desulfurization is preferably higher than 80%, more preferably the difference in desulfurization rate between the first desulfurization and the second desulfurization is at least 1% in absolute value. Such differences may be due, inter alia, to differences in temperature and / or space velocity between the first desulfurization and the second desulfurization and / or of the catalyst used in the first hydrodesulfurization step and the second hydrodesulfurization step. , Via different catalytic activities, eg due to differences in the composition or preparation of these catalysts.

The process of the present invention may optionally further comprise the additional step of selectively hydrogenating the diolefins contained in the hydrocarbon cut, which step comprises more than the first desulfurization. Also before. The method is more preferably
Furthermore, an additional step of heavier the light sulfur compounds can be included, which step is carried out prior to the first desulfurization, particularly preferably further the fraction is An additional step of separating into at least two fractions, a light fraction containing a small portion, a heavy fraction containing a majority of sulfur compounds, may be included, at least the heavy fraction Is then treated according to the first desulfurization step.

The process of the present invention is preferably applied to a charge such as a gasoline fraction produced by catalytic cracking or coking or steam cracking of a heavy hydrocarbon feedstock.

The invention may be better understood by reading the following embodiments, which are given solely for the purpose of illustration and are not limiting of the invention.

According to a preferred, but not mandatory, embodiment of the present invention, the charge to be desulfurized is optionally preliminarily subjected to selective hydrogenation of olefins (step a) and light sulfur. Worked up in a series of reactors for heavy compounding (step b). The thus pretreated charge is then distilled and fractionated into at least two fractions, namely a sulfur-poor, olefin-rich light gasoline and a sulfur-rich, olefin-depleted heavy gasoline. (Step c). The light fraction resulting from the three preceding steps usually contains less than 50 ppm, preferably less than 20 ppm of sulfur, particularly preferably 10 p
It contains less than pm of sulfur and usually does not require further processing before it is incorporated as a gasoline base. The heavy fraction resulting from the preceding three steps, which is enriched in the majority of the sulfur, is processed according to the method which is the subject of the present invention. This preferred embodiment has the advantage of further reducing octane number reduction because lightly hydrogenated olefins having up to 5 carbon atoms are not sent to the hydrodesulfurization section.

These pretreatment steps a), b) and c)
The experimental conditions for are generally as follows: 1) Selective hydrogenation (step a): This optional (optional) step of pretreating the gasoline to be desulfurized removes the diolefins present in the gasoline. It is for at least partial removal. Hydrogenation of dienes is an optional but advantageous step, which can remove almost all of the dienes present in the fraction to be treated before the hydrotreatment. The diolefins are precursors to rubbers that polymerize in hydrotreating reactors and limit their life.

This step generally comprises at least one first
It is carried out in the presence of a catalyst containing a Group VIII metal, preferably a metal selected from the group consisting of platinum, palladium and nickel, and a support. For example, alumina, silica,
A catalyst containing 1-20% by weight nickel deposited on the surface of an inert support such as silica-alumina, nickel aluminate, or a support containing at least 50% alumina is used. The catalyst is usually under a pressure of 0.4～5MPa, temperature of 50~250 ^℃, 1h ^-1 ~10h -1
Effective at liquid space velocity. Other metals of group VIB,
For example, molybdenum or tungsten may be used together to form the bimetallic catalyst. When the Group VIB metal is used in combination with the Group VIII metal, the metal is contained in an amount of 1% by weight to 20% by weight on the surface of the carrier.
Deposit at the wt% level.

The selection of operating conditions is especially important. More generally, one operates under pressure in the presence of a slight excess of hydrogen relative to the stoichiometry required to hydrogenate the diolefins. Hydrogen and the charge to be treated are injected into the reactor, preferably a fixed bed catalytic reactor, as an upflow or a downflow. The temperature is more generally between 50 and 300 ° C, preferably between 80 and 250 ° C, more preferably 1
It is between 20 and 210 ° C.

The pressure is selected such that 80% or more, preferably 95% or more of the gasoline to be treated is sufficient to maintain the liquid phase in the reactor; it is more generally 0.4 to It is greater than 5 MPa, preferably greater than 1 MPa.
Advantageous pressures are between 1 and 4 MPa (inclusive). Under these conditions, the space velocity is about ¹ to 12 h ^-1 , preferably about 4 to 10 h ^-1 .

The light fraction of the catalytically cracked gasoline fraction may contain up to several% by weight of diolefins. After hydrogenation, the diolefin content is up to 3000 ppm, and even up to 2500 ppm, preferably 1500 pp
m or less. In some cases, 500ppm
It is also possible to obtain diene contents of less than. The diene content after selective hydrogenation can optionally be reduced to below 250 ppm.

Simultaneously with the selective hydrogenation reaction of the diolefins, the double bond isomerization of the outer olefins occurs and the inner olefins are produced. This isomerization results in the formation of olefins that are more resistant to saturation with hydrogen, resulting in a slight increase in octane number (or compensation of octane number due to mild olefin loss). This is probably due to the internal olefins generally having a higher octane number than that of the terminal olefins.

According to one embodiment of the invention, the step of hydrogenating dienes usually comprises at least one catalytic reaction through which the entire charge and the amount of hydrogen necessary to carry out the desired reaction are passed. Performed in a hydrogenation catalytic reactor containing a zone.

2) Heavy sulfur compound (step b):
This optional step consists in converting the light saturated sulfur compounds, i.e. compounds having a lower boiling point than that of thiophene, to saturated compounds having a higher boiling point than that of thiophene.
These light sulfur compounds typically have 1 carbon atom.
~ 5 mercaptans, CS ₂ and 2 to 4 carbon atoms
Sulfides. This conversion is preferably carried out on a catalyst containing at least one Group VIII (group 8, 9 and 10 of the new periodic table) element on a support of the alumina, silica or silica-alumina or nickel aluminate type. carry out. The choice of catalyst is made, inter alia, to facilitate the reaction between the light mercaptans and the olefins resulting in mercaptans or sulfides having a higher boiling point than thiophene.

This optional step can optionally be carried out simultaneously with step a) on the same catalyst. For example, in the hydrogenation of diolefins, it is particularly advantageous to operate under conditions such that at least part of the mercaptan form of the compound is converted.

In this case, the temperature is generally 100 to 3
It is between 00 ° C, preferably between 150 and 250 ° C.
H_Two/ Charge ratio is 1 to 20 liters / liter, preferably
It is preferably adjusted between 3 and 15 liters / liter. Sky
Inter-speed is usually 1-10h ^-1, Preferably 2-6 h
^-1And the pressure is 0.5-5 MPa, preferably
It is between 1 and 3 MPa.

3) Separation of gasoline into at least two fractions (step c): This step is optional. If it is carried out after steps a) and b), it makes it possible to produce a desulfurized light gasoline whose mercaptan content is in most cases below 50 ppm. During this process gasoline is fractionated into at least two fractions: -a residual sulfur content is limited, preferably about 50 ppm.
Or less, more preferably about 20 ppm or less, and particularly preferably about 10 ppm or less, a light fraction; this fraction can be used without any other treatment for the purpose of reducing the sulfur content; Most (ie all of the sulfur initially present in the charge and not present in light gasoline)
A heavy fraction in which is concentrated.

This separation is preferably carried out using an ordinary distillation column. The fractionator must be capable of separating into a light sulfur distillate with a low sulfur content and a heavy fraction containing preferably the majority of the sulfur initially present in the initial gasoline.

The light gasoline obtained after the separation usually contains at least all of the olefins having up to 5 carbon atoms, preferably the compounds having up to 5 carbon atoms and at least 20% of 6 carbon atoms. Up to olefins. This light fraction obtained after steps a) and b) usually has a low sulfur content. That is, it is usually not necessary to treat this light distillate prior to its use as fuel.

The gasoline treated by a variant of the process of the invention described below is a cracked gasoline obtained directly from a cracker or pretreated according to at least one of the steps a), b) or c) above. Is.

The process of the invention comprises desulfurization steps d) and f) carried out in two separate reaction zones and an H ₂ S separation step e) between the _two hydrodesulfurization zones.

The first hydrodesulfurization step (step d) is carried out in the presence of hydrogen in the gasoline to be treated at 250 ° C to 350 ° C.
Temperature, preferably between 270 ° C. and 320 ° C., 1
It is to pass over the hydrodesulfurization catalyst at a pressure of between 3 MPa, preferably between 1.5 and 2.5 MPa. Liquid hourly space velocity during normal ^{1h -1 ~10h} -1, preferably between _{^{2h -1 ~5h -1, H 2 /}} HC ( hydrocarbon) ratio is preferably 50 liters / liter (l / l) Between ~ 500 l / l, preferably 10
Between 0 liter / liter and 400 liter / liter, more preferably 150 liter / liter-300
Between l / l. The H ₂ / HC (hydrocarbon) ratio is the ratio between the flow rate of hydrogen and the flow rate of hydrocarbon at 1 atm and 0 ° C. Under these conditions, the reaction takes place in the gas phase. The desulfurization rate achieved during this step is higher than 90%. That is, for example, gasoline initially containing 2000 ppm of sulfur will be converted to gasoline containing less than 200 ppm of sulfur. Therefore, the operating conditions during this step are adjusted depending on the properties of the charge to achieve desulfurization rates above 90%, preferably above 92%, more preferably above 94%. The effluent from this first hydrodesulfurization step is partially desulfurized gasoline, H ₂ S produced by the cracking of residual hydrogen and sulfur compounds.

Subsequent to this step is the step of separating most of the H ₂ S from the other effluents (step e). This step comprises at least 80% of the H ₂ S produced during step d),
It is preferably for removing at least 90%. Removal of H ₂ S can be accomplished, in large part, by various methods known to those skilled in the art. For example, the absorption of H ₂ S by a metal oxide body, preferably a metal oxide body selected from the group consisting of zinc oxide, copper oxide or molybdenum oxide can be mentioned. This absorber is preferably regenerable and could be regenerated continuously or discontinuously, for example by heat treatment in an oxidizing or reducing atmosphere. The absorber can be used in the form of a fixed bed or a moving bed. Another more standard method consists in cooling the effluent from step d) to produce a liquid and a gas rich in H ₂ and H ₂ S. H ₂ S can be separated from H ₂ by an amine washing device whose function is well known to those skilled in the art.

The second desulfurization step f) is for strongly desulfurizing the gasoline produced in step e) to the desired sulfur content. In this step, the gasoline produced from step e) is mixed with hydrogen at a temperature between 200 ° C. and 300 ° C., preferably between 240 ° C. and 290 ° C., 1-3 MPa,
Passing over the hydrodesulfurization catalyst, preferably under a pressure of between 1.5 and 2.5 MPa. The liquid hourly space velocity is usually between ¹ h ^{−1 and} 10 h ⁻¹ , preferably 2 to 8
h ⁻¹ and the H ₂ / HC (hydrocarbon) ratio is 50.
It is between l / l (l / l) and 500 l / l, preferably between 100 l / l and 400 l / l, more preferably between 150 l / l and 300 l / l. Under these conditions, the reaction proceeds in the gas phase. The mixture of gasoline and hydrogen treated during this step is less than 100 ppm H ₂ S, preferably 50 pp.
It contains H ₂ S of m or less. The operating conditions of this step are such that the required sulfur content can be achieved at the desulfurization rate while maintaining a lower desulfurization rate than that of the first step. The charge to be treated in this step has a much lower sulfur content than the initial charge and requires a lower desulfurization rate. Therefore, the volume of catalyst required as well as the operating temperature are lower and lower. For example, VVH in the desulfurization step f)
The (hourly volume velocity) may be 1.5 times the VVH of step d) and / or the temperature of the desulfurization step f) is for example at least 10 ° C. above that of step d), advantageously May be at least 20 ° C. lower. In most cases, the catalyst volume is fixed by industrial equipment, so that the desulfurization rate in step f) is controlled mainly by temperature. However, the above differences may be more active than those of step d) in carrying out step f) by any parameter known to affect the desulfurization rate of each of steps d) or f). By using low catalysts, adjustments can be made without departing from the framework of the invention. The difference in catalytic activity between steps d) and f) makes it possible, for example, to use a catalyst containing a smaller amount of metal or a support with a smaller specific surface area for step f) compared to the catalyst of step d). Can be obtained by Another solution may be to use a partially deactivated catalyst in step f).

The operating conditions during step f) are therefore in most cases above 80%, preferably above 85%, particularly preferably above 92% and even 95%.
It is adjusted according to the characteristics of the charge in order to achieve a desulfurization rate of more than.

The difference in desulfurization rate between the first hydrodesulfurization step and the second one is usually more than 1% in absolute value, preferably 2%.
% Or more, particularly preferably 3% or more.

Surprisingly, the Applicant has, in fact, minimized the mercaptan content in the resulting gasoline by virtue of such enforcement and restraint on the respective desulfurization rates of steps d) and f) and thus any subsequent gasoline suite. It has been found that the training process can be optional or less forced.

According to one variant of the process, fresh hydrogen is injected into the second hydrodesulfurization reactor and hydrogen is separated from the resulting gasoline, usually less than 200 ppm of H 2
It is also possible to inject this hydrogen containing ₂ S into the first hydrodesulfurization step.

The catalyst used during steps d) and f) contains at least one Group VIII and / or Group VIB element on the surface of a suitable support.

The content of Group VIII metal expressed as oxide is usually between 0.5 and 15% by weight, preferably between 1 and 10
Between% by weight. The content of Group VIB metal is usually 1.5
-60% by weight, preferably 3-50% by weight.

When the Group VIII element is present it is preferably cobalt and when the Group VIB element is present it is usually molybdenum or tungsten. The catalyst support is typically a porous solid such as alumina, silica-alumina or magnesia,
Other porous solids such as silica, titanium oxide, alone or in a mixture with alumina or silica-alumina. In order to minimize the hydrogenation of olefins present in heavy gasoline, the molybdenum density in terms of weight percent MoO ₃ per unit surface area exceeds 0.07, preferably 0.10.
It is advantageous to preferentially use catalysts above. The catalyst of the present invention is preferably 190 m ² / g or less, more preferably 180 m ² / g or less, particularly preferably 1 or less.
It has a specific surface area of 50 m ² / g or less.

After introducing the (or those) element (s), optionally in the form of a catalyst (when carrying out this step on a mixture already containing the base element), the catalyst is activated in the first step. . This activation may be by oxidation and reduction, direct reduction, or calcination alone. The calcination process is usually performed at about 100 ° C to about 600 ° C.
It is preferably carried out at a temperature between 200 and 450 ° C. with flowing air.

The catalysts are preferably used in at least partly in combination with sulfur. The introduction of sulfur can take place before or after any activation step, ie calcination or reduction. When sulfur or sulfur compounds are introduced onto the catalyst, it is preferred not to carry out any oxidation step. The sulfur or sulfur compounds can be introduced externally, ie outside the reactor for carrying out the process of the invention, or in situ, ie in the reactor used for the process according to the invention. In the latter case, it is preferred to reduce the catalyst under the abovementioned conditions and then combine it with sulfur by passing it through a charge containing at least one sulfur compound. The sulfur compound is once decomposed to fix sulfur on the catalyst surface. This charge may be gas or liquid, for example H 2
_It may be hydrogen containing ₂ S or a liquid containing at least one sulfur compound.

[0051]

EXAMPLES The advantages and advantages of the present invention will be clarified by comparing Examples 1 and 2 according to the prior art with Example 3 according to the present invention.

Example 1 (prior art): Example 1
Relates to a desulfurization method in which hydrodesulfurization is carried out in one step without intermediate separation of H ₂ S.

The hydrodesulfurization catalyst A has a specific surface area of 130 m ²
/ G, a beaded transition alumina with a pore volume of 0.9 ml / g is obtained by "solution conservative" impregnation with an aqueous solution containing molybdenum and cobalt in the form of ammonium heptamolybdate and cobalt nitrate.
The catalyst is then dried and calcined in air at 500 ° C. The content of cobalt and molybdenum in this sample is CoO
3% and MoO ₃ 10%.

100 ml of catalyst A are placed in a tubular fixed bed hydrodesulfurization reactor. The catalyst was initially charged with a charge consisting of 2% sulfur in the form of dimethyl disulfide in n-heptane, 3.4.
Under a pressure of MPa, the material is treated at 350 ° C. for 4 hours while being brought into contact with it to combine with sulfur.

The charge to be treated is a catalytically cracked gasoline having an initial boiling point of 50 ° C and a final boiling point of 225 ° C. Its sulfur content is 2000 ppm by weight and its bromine number (IB
r) is 69 g / 100 g and about 36% by weight of olefins
Equivalent to.

The charge was charged with H ₂ under a pressure of 2 MPa bar.
/ HC (hydrocarbon) ratio 300 liters / liter, VV
Treat with Catalyst A with H2h- ¹ . Table 1 shows the effect of temperature on desulfurization rate and olefin saturation.

[0057]

[Table 1] 10 with this type of gasoline that is strongly combined with sulfur
The operating conditions required to achieve ppm sulfur are high temperature (> 310 ° C.) and low VVH (2 h ⁻¹ ).
Under these conditions, it is possible to achieve desulfurization rates of more than 99%, at which time the olefins are highly saturated (greater than 85%), which is detrimental to the octane number.

Example 2 (according to the prior art) Example 2 relates to a desulfurization method according to the prior art in which hydrodesulfurization is carried out in two steps and the H ₂ S produced is separated in the middle.

Catalyst A is used under milder conditions than those of Example 1. According to the prior art, the desulfurization rate (HDS) of the second hydrodesulfurization step is higher than that of the first step. The charge to be treated is the same as the charge in Example 1.

The charge is mixed with hydrogen and passed over catalyst A in the reactor of Example 1. The operating temperature is 285 ° C. Other operating conditions are shown in Table 2. The effluent at the reactor outlet contains 239 ppm of sulfur. They are cooled and stripped to separate hydrogen and H ₂ S from the hydrocarbon phase. In that case, the stripped effluent is mixed with fresh hydrogen and reinjected into the reactor filled with catalyst A according to the operating conditions of the second step shown in Table 2. The flow rate of the charge is 1.5 compared with the flow rate of the first step.
Doubled. The experimental equipment used included an in-line sulfur analyzer capable of continuously measuring the sulfur content in the effluent. The temperature of the reactor during the second step is 10 ppm
It is adjusted to produce gasoline containing sulfur.

[0061]

[Table 2] This example shows that the method involving _two hydrodesulfurization steps and an intermediate separation of H ₂ S is more selective than the one-step method carried out in Example 1. In fact, the gasoline produced in Example 2 has the same sulfur content as the gasoline of Example 1, but the olefin saturation (HDO) is
In Example 1, it is 85.5%, while in this case it is 4%.
It is 6.7%. Therefore, the process carried out according to Example 2 can minimize the process leading to olefin saturation during hydrodesulfurization.

Example 3: In this example according to the invention, the hydrodesulfurization rate (HDS) of the first step
However, contrary to Example 2, it is higher than that of the second step.

The charges to be treated are the same as those in Examples 1 and 2.

The charge is mixed with hydrogen and passed over catalyst A in the reactor described above. The operating temperature is 300 ° C. Other operating conditions are shown in Table 3. The effluents at the reactor outlet each contain 117 ppm of sulfur. The procedure is the same as in Example 2: The distillate is cooled and stripped to separate hydrogen and H ₂ S from the hydrocarbon phase, the hydrocarbon phase is mixed with fresh hydrogen, Reinject into the reactor filled with catalyst A according to the operating conditions shown in Table 3. The flow rate of the charge is 1.5 times the flow rate of the first desulfurization step. As in Example 2, the temperature was adjusted so that gasoline containing 10 ppm sulfur was finally recovered.

[0065]

[Table 3] By the method of the present invention, i.e. by adopting a higher desulfurization rate in the first step than the desulfurization rate in the second step, the same sulfur content in the desulfurized gasoline as in the prior art illustrated by Example 2 as well as the same olefin saturation are achieved. be able to. However, the effluent produced by the process of the present invention has 30% less mercaptan content than the gasoline produced in Example 2. Therefore, by carrying out the process of the present invention, not only the saturation of olefins can be significantly suppressed, but also the mercaptan content and thus the corrosiveness of the produced gasoline can be significantly reduced / decreased.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Natali Marshall Georges             France Saint Jean Lavalle             Tou du Millenaire 12 (72) Inventor Florent Picard             France Saint Saint Folian Dozo             N'Ave New Du Shan Dumas             Ruth 30 (72) Inventor Duni Uzio             France Marry-le-Roi Squirrel             Le Saint Germain 4 F-term (reference) 4G069 AA03 AA08 BA01A BA01B                       BB06A BB06B BC59A BC59B                       BC67A BC67B CC02 DA08                       FA01 FC08                 4H029 CA00 DA00 DA02 DA03 DA09

Claims (12)

[Claims] 1. At least the following sequential steps are included:
Desulfurization method of hydrocarbon fraction containing sulfur compound and olefin compound: -First desulfurization in the presence of hydrogen and hydrodesulfurization catalyst under the condition that the desulfurization rate of the fraction is higher than 90%,- Separation of most of the hydrogen sulfide produced in the first desulfurization, the effluent from the separation step depleted of hydrogen sulfide in the presence of hydrogen and hydrodesulfurization catalyst, the desulfurization rate of the effluent is Second desulfurization under conditions lower than that of 2. The method according to claim 1, wherein at least one of the hydrodesulfurization catalysts contains at least one Group VIII element of the periodic table. 3. The method according to claim 2, wherein at least one of the hydrodesulfurization catalyst further contains at least one Group VIB element of the periodic table. 4. At least one Group VIII element of the Periodic Table selected from the group consisting of nickel and cobalt and at least one Group VIB element of the Periodic Table selected from the group consisting of molybdenum and tungsten. The method of claim 1, wherein 5. The first desulfurization is carried out at a temperature between 250 ° C. and 350 ° C. under a pressure of 1-3 MPa for 1 h ^{−1 to} 10 h.
^-1 liquid hourly space velocity, carried out in a 50 liter / liter to 500 liter / liter _H 2 / HC (hydrocarbon) ratio,
The method according to claim 1. 6. The second desulfurization is carried out at a temperature between 200 ° C. and 300 ° C. under a pressure of 1-3 MPa for 1 h ⁻¹ -10.
h- ¹ liquid hourly space velocity, 50 liters / liter to 500
Performed in liters / liter of _H 2 / HC (hydrocarbon) ratio, The method of any of claims 1-5. 7. The method according to claim 1, wherein the desulfurization rate in the second desulfurization is higher than 80%. 8. The difference in desulfurization rate between the first desulfurization and the second desulfurization is at least 1% in absolute value.
7. The method according to any one of 7. 9. The method further comprises the additional step of selectively hydrogenating the diolefins contained in the cut, the step being carried out prior to the first desulfurization. 8
The method described in any one of. 10. The method according to claim 1, further comprising an additional step of heaviening the light sulfur compound, which step is carried out prior to the first desulfurization. 11. An additional step of separating said fraction into at least two fractions: a light fraction containing a small proportion of sulfur compounds, a heavy fraction containing a majority of sulfur compounds. 11. A process according to any of claims 1 to 10, which comprises the step of treating at least the heavy fraction according to a first desulfurization step. 12. A method of applying the method according to any one of claims 1 to 11 to gasoline produced by catalytic cracking or coking or steam cracking of a heavy hydrocarbon feedstock.