FR2844518A1 - Desulfurization of hydrocarbon fractions, e.g. kerosene or oil, involves treatment with oxidizing agent in presence of Group IVB, VB or VIB metal oxide catalyst - Google Patents

Abstract

Desulfurization of a hydrocarbon fraction involves treating the hydrocarbon fraction with an oxidizing agent in the presence of a Group IVB, VB or VIB metal oxide catalyst.

Description

The present invention relates to a process for the desulfurization of

  hydrocarbon fractions containing sulfur at levels greater than 5 ppm and up to 5% by weight. The present process finds particular application in the treatment of petroleum fractions whose boiling temperatures are typically greater than 150 ° C., or even 5,200 ° C. In particular, the present process advantageously makes it possible to desulphurize a kerosene, or a gas oil obtained from the distillation of a crude oil or in general any product obtained

  part or all of a process for converting an oil residue.

  Due to environmental requirements, regulatory provisions in industrialized countries increasingly restrict the sulfur content in fuels and more particularly fuels such as gas oils. European specifications impose for example a sulfur content in diesel less than 50 ppm (parts per million) at present, this limitation must certainly reach 10 ppm

in the near future.

  To achieve this objective, it is conventionally used by the refiner a hydrodesulfurization process by hydrogenation in order to remove the sulfur contained in the fraction.

  hydrocarbon to be treated. The sulfur present is finally extracted from said fraction in the form of gaseous sulfur or hydrogen sulfide. These processes generally consist in hydrogenating the charge in the presence of hydrogen under pressure (2 to 10 MPa) and at temperatures generally between 300 and 400 ° C., in the presence of catalyst based on cobalt and molybdenum sulfide or nickel and molybdenum.

  The main problem associated with this type of process is their high consumption of hydrogen. This hydrogen is generally found in a limited quantity on the refinery site since generally produced in great majority only during a catalytic reforming step. Finally, the specifications relating to the sulfur contents of the products from the refinery being called upon to become more and more strict, it is to be expected that the production of hydrogen by the simple process of catalytic reforming will prove, within refinery,

  insufficient to meet demand.

  US Patent 3,551,328 describes an alternative process for desulfurization of a heavy fraction of hydrocarbon, not consuming hydrogen, in which the sulfur compounds contained in said fraction are oxidized in the presence of an oxidant. This oxidation can be carried out in the presence of a catalyst comprising an organometallic complex of a metal from groups IV-B, V-B and VI-B of the periodic table. The thermal instability of such catalysts, however, makes it necessary to carry out the oxidation at a relatively low temperature, which results in relatively long reaction times, which are hardly compatible with economic requirements.

  an industrial scale operation.

  The process which is the subject of the present invention provides an alternative solution to the hydrotreatment processes. This process consists in selectively oxidizing the sulfur compounds

  contained in a petroleum fraction or cut into sulfones and sulfoxides.

  The present process uses a more stable catalyst and also makes it possible to have

  short oxidation times compatible with industrial use.

  In its most general form, the invention relates to a process for desulfurization of a hydrocarbon fraction comprising at least one step of treatment of said fraction with an oxidizing agent in the presence of a catalyst for said oxidation, in which said catalyst comprises at least one metal oxide of chemical formula MOy, M being an element selected from the group consisting of the elements of groups IV-B, VB or VI-B of the

periodic classification.

  Preferably, the catalyst is in mass form, and more preferably consisting essentially of the active phase MOY, that is to say that it consists of at least 70% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, or even

  at least 98% by weight, with at least one metal oxide of chemical formula MOy.

  The use of such a catalyst thus makes it possible to reduce the time for bringing the 20 different reaction phases into contact by virtue of a temperature which can be understood according to the invention between room temperature (around 20 ° C.) and 200 ° C. or even 300 'VS. The

  temperature is more preferably greater than or equal to 1000C.

  The hydrocarbon fraction treated in the process according to the invention can come from the distillation of crude oil or an effluent from any cracking unit known to a person skilled in the art. It is generally called atmospheric distillate and includes the kerosene and / or diesel cut. Said hydrocarbon fraction is preferably a petroleum fraction whose boiling temperatures are between 150 and 500 ° C. More preferably, said hydrocarbon fraction comprises a weight fraction of sulfur compounds of between ppm and 5%. In the desulfurization process according to the invention, the temperature of the oxidation reaction is preferably between 40 ° C. and 300 ° C., and more preferably greater than or equal

at 1000C.

  The pressure of this step is preferably between 0.1 MPa and 5 MPa, more preferably between 0.1 MPa and 2 MPa, with or without oxygen.

  In the catalyst according to the invention, the element M is preferably selected from the group consisting of vanadium, chromium, zirconium, molybdenum, tungsten, titanium, alone or in combination. Very preferably, said catalyst comprises a molybdenum oxide. Said catalyst is preferably used in the form of powder, beads, or extrudates.

  In the desulfurization process according to the invention, the oxidizing agent is preferably selected from the group consisting of peroxides, hydroperoxides, organic peracids, ozone, oxygen, nitrogen oxides and oxidizing agents metallic, alone or in combination The process for desulfurization of a hydrocarbon fraction according to the invention preferably comprises at least the following steps: a) an oxidation of at least part of the sulfur compounds contained in said hydrocarbon fraction in the presence of at least one oxidizing agent and a catalyst

  according to one of claims 1 to 11,

  b) separation of the oxidized sulfur compounds from the products resulting from step a) by extraction, distillation or adsorption Preferably, step b) is an adsorption carried out in at least one column of adsorbent, said adsorbent being selected from the amorphous oxides such as amorphous aluminas, amorphous silicas or amorphous silica-aluminas or among crystallized oxides such as zeolites, clays, or a mixture of at least two of these. In a more

  preferred, an absorbent which can be regenerated directly by calcination will be chosen.

  The desulfurization process according to the invention can optionally further comprise a

  stage of separation of the catalyst between stages a) of oxidation and b) of separation.

  The invention will be better understood on reading the following description of an embodiment, without limitation of said invention, illustrated by FIG. 1.

  The feedstock, for example a hydrocarbon cut resulting from the atmospheric distillation of a crude oil whose boiling temperature is above 150 ° C. and containing a sulfur fraction, is injected through line 1 into a unit of oxidation A. This unit consists of one or more reactors operating continuously or discontinuously (technique 5 usually known to those skilled in the art under the term "batch"). Most often a mechanical agitation system of the phases present in the reactors and / or a recirculation system (internal or external) of the charge and / or of the reactants are provided in order to

  to have the best possible contact between the charge, the reactants and the catalyst.

  An oxidizing agent is supplied via line 2 to the oxidation unit A. An oxidation catalyst 10 is either initially present in the unit or injected at the same time as the oxidant via line 2. This oxidizing couple / catalyst is capable of selectively oxidizing the sulfur compounds contained in the hydrocarbon fraction. By way of example, the dibenzothiophenes are oxidized to sulfones according to the following reaction: Oxidant I Catalyst ss The oxidant used is advantageously selected from the class of hydroperoxides and preferably from the group consisting of hydrogen peroxide, hydroperoxide of tert-butyl

cumene hydroxide.

  The catalyst comprises at least one oxide of general formula MOy as defined above and, preferably, the element M is chosen from the group consisting of titanium, zirconium, vanadium, chromium, molybdenum and tungsten. The very preferred metal oxides are molybdenum oxide MoO3, vanadium oxide V205 or oxide of

  zirconium ZrO2, taken either separately or as a mixture.

  The catalyst is most often used in the form of beads, extrudates or powder, although any known form of the catalyst can be envisaged in the context of the present application.

  The molar ratios between the catalyst and the sulfur contained in the feed are most often between 0.0001 and 2000, preferably between 0.001 and 100. These ratios are adjusted by a person skilled in the art as a function of the flow rate of the feed and of the average temperature of unit B. The products of the oxidation reaction are conveyed by line 3 to a unit of

  separation of catalyst B. This operation is optional and is only justified insofar as the catalyst used is in powder form and supplied with the oxidant via line 2.

  In the case of a catalyst, in the form of beads or extrudates, is already present in unit A, for example in the form of a fixed bed of particles, this operation is not useful. The reaction products are then sent to a water elimination unit C by a

  line 4. Unit C can be a decanter, a coalescer or any other known means capable of promoting elimination of the water contained in the said reaction products.

  This operation is however optional since the oxidation of the sulfur-containing compounds is generally not carried out in an aqueous medium. However, said oxidation can lead to the formation of water in small quantities which can cause pollution problems.

  the absorbent during the next adsorption phase. The water is discharged through line 5.

  The products from unit C are then sent via line 6 to a unit D for separating sulfones and sulfoxides from the hydrocarbon medium. Although the use of a distillation column or a solvent extraction or any other known means of separation is possible within the framework of the present invention, a unit will preferably be used.

  adsorption. For example, columns filled with an adsorbent will be used. The adsorbent then advantageously consists of at least one amorphous oxide such as alumina, silica or silica-alumina or a mixture of these or a crystallized oxide such as a zeolite or a clay. Without departing from the scope of the invention, it is possible to envisage a mixture of these compounds in the appropriate proportions within the columns.

  The effluent, after adsorption of the sulfones, and depleted in sulfur compounds is finally

  retrieved from the unit by a line 7.

  The examples which follow illustrate in a nonlimiting manner some of the advantages of the present invention: Example 1: in accordance with the invention This example demonstrates the effectiveness of the present process for removing sulfur-containing compounds

  contained in a hydrocarbon feed.

  The feedstock is diesel fuel produced from crude oil, the distillation range of which is between 150 and 350 ° C. This diesel contains 2% by weight of sulfur.

  The oxidant / catalyst mixture is a mixture consisting of terbutyl hydroperoxide (38 g / liter of filler) and molybdenum oxide MoO3 by mass (3.2 g / liter of filler). This mixture is heated to 100 ° C. The effluent outlet no longer contains benzothiophene and dibenzothiophene but the corresponding sulfones and sulfoxides. This transformation was demonstrated by gas chromatography.

  The mixture obtained is then sent to a column containing an amorphous silica, previously activated under nitrogen at 120 ° C. This mixture is sent with a flow rate adjusted so that the ratio of the feed rate to the volume of catalyst is equal to 1 liter of feed per liter of silica per hour. At the unit outlet, the sulfur content of the unit, determined according to known techniques by combustion and chemiluminescence is equal to 5 ppm.

  Some characteristics of the feed and the effluents from the present process are shown in Table 1 Load] Effluents | Density 0.82 0.819 Sulfur (weight%) 2 0.0005

Table 1

  This comparison shows that the process claimed by the applicant makes it possible to obtain products having a very low sulfur content, conforming to specifications without

hydrogen consumption.

  Examples 2 to 4 make it possible to demonstrate that the presence of a catalyst according to the invention

  advantageously promotes the oxidation step of the sulfur compounds.

  Example 2: Oxidation without catalyst (comparative) Two grams of hydrogen peroxide are dissolved in 20 g of heptane. This mixture is placed in a flask surmounted by an ascending coolant. 3.6 g of acetic acid dissolved in 20 g of heptane are added dropwise to the flask to prepare the peracid. Then once 5 times the peracid prepared, the charge consisting of decane (107 g) containing approximately 10% by weight

  Benzothiophene (1.4 g) is added dropwise to the peracid. The mixture is kept stirring and then heated first at 50 ° C. at atmospheric pressure for 4 hours and then at 100 ° C. at atmospheric pressure for 30 hours. Chromatographic analysis at regular time intervals has shown that benzothiophene does not oxidize within 10 hours or more.

  Example 3 Oxidation with an Acid Catalyst (Comparative)

  The protocol used in this example is the same as in the previous example. However, 2 g of catalyst were added to the peracid mixture before the introduction of the charge.

  In this example, the catalyst used a sulfonic resin sold by Rohm and 15 Haas under the trade name Amberlyst 15. The mixture was heated at 50 ° C. at atmospheric pressure for 7 hours and then at 100 ° C. at atmospheric pressure for 15 hours. . Chromatographic analyzes have shown that benzothiophene does not oxidize

even after 7 hours of heating.

  Example 4: Oxidation with a catalyst according to the invention To a peracid mixture identical to that of Example 3, 0.28 g of molybdenum oxide is added. The mixture is heated to 100 ° C. at atmospheric pressure with stirring for one hour. It appears that after one hour, all of the benzothiophene present in the charge has disappeared.

Claims (14)

  1. A method for desulfurization of a hydrocarbon fraction comprising at least one step of treating said fraction with an oxidizing agent in the presence of a catalyst for said oxidation, in which said catalyst comprises at least one metal oxide of chemical formula MxO M being an element selected from the group consisting of   elements of groups IV-B, V-B or VI-B of the periodic table.   2. Desulfurization process according to claim 1, in which said catalyst is under   mass form and essentially consisting of the active phase.   3. Desulfurization process according to claim 1 or 2 wherein said hydrocarbon fraction is a petroleum fraction whose boiling temperatures are included between 150 and 500'C.   4. Desulfurization process according to any one of the preceding claims in   which said hydrocarbon fraction comprises a weight fraction of sulfur compounds of between 5 ppm and 5%.   5. Desulfurization process according to any one of the preceding claims in   which the temperature of said oxidation reaction is between 40 ° C and 300 ° C.   6. Desulfurization process according to any one of the preceding claims in   which the temperature of said oxidation reaction is greater than or equal to 1000C.   7. Desulfurization process according to any one of the preceding claims in   which the pressure of said oxidation reaction is between 0.1 and 5 MPa.   8. Desulfurization process according to any one of the preceding claims in   which element M is selected from the group consisting of vanadium, chromium,   zirconium, molybdenum, tungsten, titanium, alone or in combination.   9. Desulfurization process according to any one of the preceding claims in   which said catalyst comprises a molybdenum oxide.   10. Desulfurization process according to any one of the preceding claims in   which said catalyst is used in the form of powder, beads, or extrudates.   1. Desulfurization process according to any one of the preceding claims in   wherein said oxidizing agent is selected from the group consisting of peroxides, hydroperoxides, organic peracids, ozone, oxygen, nitrogen oxides and   metallic oxidizing agents, alone or in combination.   12. A process for desulfurization of a hydrocarbon fraction comprising at least the following steps: a) an oxidation of at least part of the sulfur compounds contained in said hydrocarbon fraction in the presence of at least one oxidizing agent and a catalyst   according to one of claims 1 to 11,   b) separation of the oxidized sulfur compounds from the products from step a) by   extraction, distillation or adsorption.   13. The desulfurization method according to claim 12 in which step b) is an adsorption carried out in at least one column of adsorbent, said adsorbent being selected from amorphous oxides such as amorphous aluminas, amorphous silicas or silicas - amorphous aluminas, or among crystallized oxides such as   zeolites, clays, or a mixture of at least two of the elements of said group.   14. Desulfurization process according to any one of claims 12 or 13 comprising   further a step of separation of said catalyst between steps a) of oxidation and b) of separation.