CZ279286B6 - Process of sulfur-containing liquid hydrocarbon charge continuous hydrodesulfurization and apparatus for making the same - Google Patents

Abstract

Continuous multi-step hydrosulphurisation process comprises (a) providing a hydrosulphurisation zone maintained under hydrosulphurisation conditions and consisting of a column reactor having several reaction trays one above the other, each tray defining a respective reaction stage to hold a predetermined liquid volume and a charge of a sulphided solid hydrodesulphurisation catalyst, therein a liquid downcomer associated with each tray to allow liquid to pass the column reactor from that tray to retain solid catalyst thereon, and a gas upcomer to allow as the enter that tray from below and to agitate the mixt. of liquid and catalyst on that tray, (b) supplying liquid sulphur-contg. hydrocarbon feedstock the the uppermost one of several reaction trays, (c) supplying hydrogen-contg. gas below the lowermost one of several reaction trays, (d) allowing liquid to pass downward through the column reactor from tray to tray, (e) allowing hydrogen-contg. gas to pass upward through the column reactor from tray t, tray (f) recovering from the uppermost one of thea reaction trays an off-gas contg. hydrogen sulphide produced by the dehydrosulphurisation, and (g) recovering from the lower most reaction tray a liquid hydrocarbon product of reduced sulphur content.

Description

Process for the continuous hydrodesulfurization of a sulfur-containing liquid hydrocarbon feedstock and apparatus for carrying out the process

Technical field

The present invention relates to a process for the continuous hydrodesulfurization of a sulfur-containing liquid hydrocarbon feedstock in the presence of hydrogen and in the presence of a solid sulfided hydrodesulfurization catalyst.

BACKGROUND OF THE INVENTION

Crude oil, its direct and cracked fractions and petroleum products contain sulfur in varying amounts depending on the source of the oil and on any processing. In addition to elemental sulfur, a variety of sulfur compounds have been identified in crude oil, including hydrogen sulfide, primary C 1 -C 5 alkyl mercaptans, C 3 -C 8 secondary alkyl mercaptans, C 4 -C 6 tertiary alkyl mercaptans, cyclic mercaptans (such as cyclopentathiol, cyclohexanthiol) and cis-2-methylcyclopentanethiol), an open-chain sulfide having the formula R-S-R ', wherein R and R' are C 1 -C 4 alkyl, monocyclic sulfides, bicyclic sulfides and tricyclic sulfides, thiophenes, alkyl-substituted thiophenes, condensed thiophenes (such as benzo (b) thiophene, isothionaphthene, dibenzothiophene and benzo (b) naphtho) 2,1-d / thiophene, thienothiophenes, alkylcycloalkylsulfides, alkylarylsulfides, 1-thiaindenes, aromatic thiols (such as thiophenol) and cyclic thiophenes thiols such as cyclohexanethiol.

Generally low API masses, crude oil typically contain more sulfur than high API masses, crude oil, although there are some exceptions. In addition, the distribution of sulfur compounds in the various petroleum fractions varies mainly with the boiling point range of the individual fractions. Lighter petroleum fractions, such as naphtha, contain fewer sulfur compounds, and the content of sulfur compounds also increases with boiling point or API density, or with an increase in molecular weight of the fraction. Most sulfur compounds that have been positively detected as components of crude oil have a boiling point below about 200 ° C. Numerous other higher molecular weight sulfur compounds with a high boiling point remain unidentified in the crude oil.

For various reasons, it is necessary to treat crude oil and the petroleum fractions derived therefrom to remove sulfur compounds from it. Otherwise, subsequent processing operations may be disrupted, for example because sulfur compounds have an adverse effect on the performance of the catalyst. If the hydrocarbon fraction is to be used as a fuel, then all the sulfur compounds are converted into sulfur oxides, which have an adverse effect on air hygiene, in the combustion of the fuel.

For this reason, it is necessary to remove as far as possible any sulfur content of the crude oil-derived hydrocarbon fractions, such as gasoline fractions, diesel, gas oils and the like. Typically, such sulfur removal is performed in a manner known generally as hydrodesulfurization. In such processes,

The hydrocarbon fraction was mixed with hydrogen and passed through a hydrodesulfurization catalyst at a suitable temperature and pressure. In these processes, the intent is to break the carbon-sulfur bonds in the feed and saturate the hydrogen-formed free bonds or olefinic double bonds formed at such a degree of cleavage. In such a way the intention is to convert to the highest. to the extent possible, the contained organic sulfur compounds to hydrogen sulfide to form hydrocarbons. Typical reactions that occur during hydrodesulfurization of most types of sulfur compounds contained in crude oil are as follows:

1. Thiols

RSH + H ₂

2. Disulfides

RSSR '+ 3H ₂

3. Sulfides

RH + h ₂ s -> RH + R 1 H + 2 H ₂ S

(a) an open chain

R-S-R '+ 2H ₂

RH + R'H + H ₂ S

cyclic

bicyclic

ch ₃

CH

ch ₂ ch ₂

CH ₂ - CH - CH ₃ + H ₂ p

4. Thiophenes

CH-CH + 4H ₉

II II

CH CH \ / s

2GB 279286 B6

+ 5H ₂

--'—>

In general, cyclic sulfur compounds are more difficult to hydrogenate than open-chain compounds, and carbon and sulfur bonds are thereby more difficult to break down, the more sulfur-containing cyclic compounds have a greater number of rings.

In addition to sulfur oxides, the combustion gases of hydrocarbon fuels contain other unwanted air hygiene compounds, typically including aromatic hydrocarbons, which may be contained due to incomplete combustion with carbon particulate materials, often containing polycyclic aromatic hydrocarbons, metal compounds, oxygenated organic materials and other potentially toxic compounds.

For the current attention to environmental pollution, the strict limits set by various laws of the peoples of the world on the permissible content of impurities in hydrocarbon fuels, such as diesel, are increasing. For example, the United States Environmental Protection Agency has recently issued rules limiting sulfur content to mass. 0.05% and aromatic content to 20% by volume in diesel for diesel engines (see, for example, Higher Diesel Quality Would Contrict Refining, George H. Unzelman, Oil and Gas Journal, June 19, 1987, pp. 55-59) . Such rules require additional diesel processing and increased investment and operating costs. Further prescribed reductions of the permitted sulfur and aromatic content cannot be excluded for the future.

-3GB 279286 B6

If the hydrocarbon feed is treated with hydrogen in the presence of a suitable catalyst for hydrodesulfurization, other reactions may also take place. Therefore, the term hydrogen treatment is used as a more general term including not only hydrodesulfurization reactions but also other reactions that occur, including hydrocracking, hydrogenation and other hydrogenolysis reactions. The term hydrogen treatment is further explained in The Oil and Gas Journal, October 7, 1968, pp. 174-175. The term " nomenclature-system proposed for hydroprocessing "

There are four hydrogenolytic reactions, of which the hydrodesulfurization reaction (HDS) is probably the most important, followed by the hydrodenitrogenation reaction (HDN), the hydrodesoxygenation reaction (HDO) and the hydrodemetallization reaction (HDM). The catalysts used in such hydrogen treatment reactions include molybdenum disulfide, tungsten sulfide, sulfated nickel-molybdenum catalysts (NiMoS _x formula), and cobalt-molybdenum sulfide catalysts on alumina (Co-Mo / Al ₂ 0 ₃ ). .

However, the state of the art contemplates the simultaneous running of hydrogenation reactions, such as the hydrogenation of olefins and aromatic hydrocarbons, as disadvantageous for the hydrodesulfurization process, since the flavor content of the product is in the desired specification and the use of valuable hydrogen for non-essential hydrogenation reactions is disadvantageous. Therefore, current and future trends with regard to the use of middle distillates and heavier petroleum fractions, together with increasing stringency of regulations, will make the hydrogenation of aromatic fractions a necessary component of refining processes. Therefore, under current conditions and even more in the future, it will be desirable to combine hydrodesulfurization and aromatic hydrogenation.

In contrast to the above, except where high molecular weight residues are treated, it is common to avoid extensive hydrocracking reactions in most refining operations with hydrogen treatment, as far as possible because these operations are highly exothermic and can cause thermal damage to catalysts and reaction vessels and moreover, they can lead to the deposition of carbonaceous materials, causing a loss of catalytic efficiency. Therefore, a hydrodesulfurization plant worker reports in Refiners Seeking Improved Hydrogen Production, Oil and Gas Journal, July 20, 1987, pp. 48-49, that reactors overheat considerably in operation to the point of rupture due to undesired hydrocracking reactions.

The risk of such hydrocracking reactions may be reduced to the mimimum by ensuring that the catalyst remains adequately sulfidated.

Hydrodesulfization technology is described in numerous literature. For example:

Kinetics of Thiophene Hydrolysis on Cobalt Molybdate Catalyst

Catalyst) Charles N. Satterfield et al. AIChE Journal, Volume 14, Number 1 (January 1968), pp. 159-164.

b / Hydrogenation of aromatic hydrocarbons catalysed by Sulfided C0O-M0O3 (gamma-Al ₂ O ₃₎ (Hydrogenation of aromatic hydrocarbon sulfonate katalytovaná idovaným Co0 _MO0-3) (gamma-Al ₂ O _3). Reactivities and Reaction Networks Ajit V.Aapre et al., Ind. Eng. Chem. Process Des. Dev., Volume 20, No. 1, 1981, pp. 68-73.

c) Hydrogenation of Biphenyl Catalyzed by Sulfided CO-MoO ₃ (gamma-Al ₃ O ₂ ). The Reaction Kinetics (catalyzed hydrogenation of biphenyl-MO0 sulfidovaným Co0 ₃ (gamma-Al ₂ O _3). Reaction kinetics) Ajit V. Sapru et al., Ind. Eng. Chem. Process Des.Dev, Volume 21, No. 1, 1982, pp. 86-94.

d / Hydrogenolysis and Hydrogenation of Dibenzothiophene Catalyzed by Sulfided Co0-MO0 ₃ (gamma A1 ₂ O _3): The Reaction Kinetics) (hydrogenation and hydrogenolysis catalyzed sulfidovaným COO MO0 ₃ (gamma A1 ₂ O _3: Reaction kinetics) DH Broderick et al., AIChE Journal, Vol. 27, No. 4, July 1981, pp. 663-67.

e / Hydrogenation of.Aromatic Compounds Catalyzed by Sulfided CoO-MoO ₃ (gamma-Al ₂ O ₃ ) Hydrogenation of aromatic compounds catalyzed by sulfide CoO-MoOg (gamma-Al ₂ O ₃ ), DH Broderick et al., Journal of Catalysis, Volume 73, 1982, pp. 45-49.

An overview of hydrogen reactivity in sulfide catalysts, such as those used in hydrogen treatment, is on pages 584 to 607 of Hydrogen Effects of Catalysis, Richard B. Moyes, edited by Marcel Dekker, Inc. (1988).

An overview of industrial hydroprocessing processes is published annually in the Hydrocarbon Processing magazine, usually in the September issue. For example, reference is made to Hydrocarbon Processing, September 1984, p. 70, and to Hydrocarbon Processing in the September 1988 issue, pp. 61-91.

An overview of three known prior art hydroprocessing processes is in Hydrocarbon Processing 1988 Refining Handbook on pages 78 and 79 of Hydrocarbon Processing September 1988. According to the Chevron RDS / VRDS Hydrotreating Process, a mixture of fresh liquid hydrocarbon feedstock, treatment hydrogen and recycled hydrogen feed into the reactor in a single operation. As described, the reactor has three layers and cooling within the layer is accomplished by injecting an additional amount of recycled hydrogen. The recycled hydrogen is passed through a hydrogen sulfide scrubber. According to the HYVAHL Process method, a one-time liquid feed operation is also used. Amine scrubbers are used to remove hydrogen sulfide from recycled hydrogen. Process Unionfining Pro

-5GB 279286 B6 cess also uses once-in-time liquid feed operations. Co-current flow of hydrogen and liquid is considered. Unreacted hydrogen is recycled.

In all three processes, recycled gas is used to cool the catalyst layer and thus reduce the risk of rapid temperature rise as a result of hydrocracking. The use of recycled gas means that inert gases tend to accumulate in the circulating gas, which again means that to maintain the desired partial hydrogen pressure, the total working pressure must be increased to accommodate the circulating inert gases and that the size and cost of the recycle compressor must be increased. that increased operating costs must be tolerated.

The use of the droplet process is described in New Shell Hydrodesulphuri.sation Process Show These Features, Petroíeum Rafiner, Volume 32, Number 5 (May 1953), from page 137. Figure 1 in this article explains in more detail a four-bed catalyst reactor introducing a mixture of hot gas and gas oil at the inlet end of the layer and using cold injected gas oil between successive layers.

In the above-mentioned hydrodesulfurization processes, the conditions at the inlet end of the catalyst layer are of critical importance since the risk of hydrocracking is greatest here, especially if the sulfurization rate of the catalyst falls. This can occur, for example, when a low-sulfur feedstock is introduced into the reactor or if a feedstock in which the sulfur impurities are predominantly polycyclic compounds is used.

The hydrotreatment of the diesel feedstock is described in U.S. Pat. No. 4,243,319. It is essentially a vapor phase process.

The multi-stage hydrodesulfuration of the residue with the catalyst moving between the stages, in the opposite direction to the gas and liquid movement, is described in U.S. Pat. No. 3,809644.

U.S. Pat. No. 3,884,799 describes the conversion of black oil to low sulfur fuel oil in two reactors. Supplemental hydrogen (makeup hydrogen) is introduced into the second reactor, but mixed with hydrogen, which is from the first reactor, which is purified by removing hydrogen sulfide. Hydrogen is recovered from the first reactor and recycled to the second reactor in a mixture with inert gases that accumulate in the gas recycle loop. All condensate obtained from the first reactor is mixed with the product from the second reactor.

In a hydrodesulfurization plant with a gas recycle mode, some hydrogen sulfide is produced, typically a smaller portion of it remains in the liquid phase after product separation, while the remainder, typically a larger portion, remains in the gas phase. Even in units where interlayer cooling is carried out by cold injection of recycled gas, the hydrogen sulphide released remains in the gas / liquid mixture as this phase passes through the catalyst bed. Therefore, the hydrogen sulfide partial pressure is generally greatest at the outlet end of the catalyst layer or in the final layer when more than one catalyst layer is used. Because the efficiency of the hydrodesulfurization catalyst decreases with increasing hydrogen sulfide partial pressure, the efficiency of the catalyst is lowest at the outlet end of the layer where in fact the highest efficiency, if the last polycyclic organic compounds have, is to undergo hydrodesulfurization.

The catalysts used for hydrodesulfurization are generally also capable of influencing the hydrogenation of aromatic compounds, provided that the sulfur content is low. The conditions required for the hydrogenation of the aromatic compounds are generally similar to those required for the hydrodesulfurization. However, since the reaction is equilibrium, not supported by the use of high temperatures, the conditions required for dehydrosulfurization of cyclic and polycyclic organic sulfur compounds in conventional units do not promote hydrogenation of the aromatic compounds. In addition, since the design of conventional hydrodesulfurization units leads to high hydrogen sulfide partial pressures at the lower end of the unit, the catalyst efficiency is reduced accordingly and the conditions do not result in a significant reduction in the aroma content of the feed batch. Therefore, in Panel gives hydrotreating guides, Hydrocarbon Processing, March 1989, pp. 113-116, on page 114 it is stated:

It is an essential kinetic fact that at pressures for normal middle distillate desulfurizers (500 to 800 psig) it is difficult to achieve a more noticeable saturation of aromatic compounds. Therefore, if the charge has a flavor content well above 20%, there is not much you can do with typical hydrogen treatment units with any catalysts known to significantly reduce the flavor content.

Then you will only have the unpleasant possibilities of using high-rise units with aromatic extraction and all other alternatives.

The removal of hydrogen sulfide from the hydrodesulfurization unit with the gas recycle system is generally accomplished by scrubbing the recycle gas with an amine. If the section of the scrubber is to be large enough for the highest concentration of sulfur impurities, possibly contained in the raw material being processed, a scrubber with adequate capacity must be designed, although the unit often works with a low sulfur charge. The investment costs of such a washing machine are considerable.

It would be desirable to develop a more efficient process for hydrodesulfurization of the liquid hydrocarbon feedstock, and in particular a process in which the risk of hydrocracking reactions is substantially prevented. In addition, it is desirable to develop a hydrodesulfurization process in which the efficiency of the catalyst in the reactor is controlled in such a way that a higher degree of hydrodesulfurization at a given operating pressure in a conventional process could be achieved. It is also desirable to develop a hydrodesulfurization process that allows such an operation to simultaneously achieve a significant reduction in the flavor content of the process batch, especially a batch in which the flavor content is greater than about 20%.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process by which hydrodesulfurization can be carried out more efficiently than in the conventional process. It is also an object of the present invention to provide a hydrodesulfurization process in which the efficiency of the catalyst in the reactor is favorably controlled to improve the hydrodesulfurization of the feed. It is also an object of the present invention to provide a hydrodesulfurization process which allows a significant reduction in the flavor content of the charge while hydrodesulfurization is performed.

SUMMARY OF THE INVENTION

The principle of the continuous hydrodesulfurization process of a sulfur-containing liquid hydrocarbon feedstock in the presence of hydrogen in an amount corresponding to a 2: 1 to 20: 1 molar ratio of hydrogen: feedstock and in the presence of a solid sulphided hydrodesulfurization catalyst The invention is characterized in that the hydrodesulfurization is carried out in a plurality of superimposed and interconnected hydrodesulfurization zones, each zone containing a dose of retained solid sulfide hydrodesulfurization catalyst, the gas being introduced into the lowest of the hydrodesulfurization zones and directed to the next higher hydrodesulfurization zone upstream. to a sulfur-containing liquid hydrocarbon feed introduced into the upstream hydrodesulfurization zone and pressure and temperature conditions favorable to hydrodesulfurization are maintained in each zone and the catalyst is in each zone of the liquid in the fluidized bed by stirring in each zone of the liquid by the gas flow, from the top zone the off-gas containing hydrogen sulfide is removed and from the bottom zone the liquid hydrocarbon product with reduced sulfur content is removed.

In this process, it is essential that the amount of hydrogen is sufficient to convert all of the sulfur contained into hydrogen sulfide and to achieve the desired degree of dearomatization, and that the rate of gas rise is sufficient to maintain the catalyst νθ to the vaporized bed. The upward gas does not necessarily contain only hydrogen; it may contain recycled gas and inert gases.

Typically, the gas entering the top zone contains a sufficient amount of hydrogen sulfide and / or the liquid feed comprises a sufficient amount of sulfur-containing material from hydrogen sulfide and active sulfur-containing materials to keep the metered catalyst in sulfide form.

Active sulfur-containing materials refers to materials which rapidly release hydrogen sulfide under hydrodesulfurization conditions in the presence of a hydrodesulfurization catalyst. Examples of such materials include carbon disulfide, carbonyl sulfide (COS), alkyl mercaptans, dialkyl sulfides and dialkyl disulfides.

The solid sulfide catalyst used in the process of the present invention is preferably a catalyst selected from the group consisting of molybdenum disulfide, tungsten sulfide, cobalt sulfide, nickel / tungsten sulfide, cobalt / tungsten sulfide, sulfated nickel molybdate (NiMoS, _x ) and sulfated CoO-MoO. ₃ (gamma-Al ₂ O ₃ ) and mixtures thereof.

Typical hydrodesulfurization conditions include a pressure of about 2 to about 15 MPa and a temperature of about 240 to 400 ° C. Preferred conditions include a pressure of 2.5-10 MPa and a temperature of 250-370 ° C.

-8EN 279286 B6

The sulfur-containing liquid hydrocarbon feed may contain a mixture of saturated hydrocarbons such as n-paraffins, isoparaffins and naphthenes in various proportions. Further, it may contain one or more aromatic hydrocarbons in an amount of, for example, about 1 to 30% by volume, or even greater. If the feedstock has a low aromatic hydrocarbon content, the hydrodesulfurization reaction is the prevailing reaction. However, if the feed contains a significant amount of aromatic hydrocarbons, then at least some hydrogenation of these partially saturated or fully saturated hydrocarbons may occur simultaneously with the hydrodesulfurization. In this case, the consumption of hydrogen increases accordingly. The extent of such hydrogenation of the aromatic hydrocarbons is influenced by the choice of reaction conditions, and thus the degree of dearomatization of the feed can be influenced by the selected reaction conditions.

Thus, in the process according to the invention, the stoichiometric need for hydrogen can be functional not only in the sulfur content of the feed, but also in the aroma content. The actual hydrogen consumption depends on the hard reaction conditions chosen, i.e. the reaction temperature chosen and the reaction pressure chosen. For example, harsh conditions mean the choice of high reaction pressure or high reaction temperature or a combination of high pressure and high temperature. The higher the temperature applied to the hydrocarbon feed during hydrodesulfurization under a given hydrogen partial pressure, the closer the range of aromatic hydrogenation / or automatic dearomatization / theoretically achievable equilibrium concentration is. Thus, the amount of hydrogen consumed in the process according to the invention depends not only on the nature of the charge, but also on the roughness of the reaction conditions used.

For example, if the feedstock is a diesel feedstock, the reaction conditions used in the process of the invention are typically selected such that the sulfur content is reduced to about 0.5% by weight, or even lower, for example about 0.3% by weight. or even less, about 0.05% or less, and to reduce the flavor content to about 27% or less by volume, for example about 20% or less by volume. If the desired product is an industrial white oil, the reaction conditions are selected such that the sulfur content is reduced to a truly low level and the aroma content as much as possible. As a rule, the intention is to reduce the aroma content sufficiently to make the white oil produced colorless, substantially non-aromatic, to be a mixture of paraffinic and naphthenic oils which meet the following specification:

Saybolt's color +20

UV absorbance limits maximum absorbance per centimeter

280 to 289 ιημ 4.0 290 to 299 ιημ 3.3 300 to 329 πιμ 2.3 330 to 350 ιημ 0.8

-9EN 279286 B6

Optionally, the end product may be a white oil for medical purposes meeting the current requirements of U.S. Pat. Department of Food and Drug Administration; in such a case, the intention is to produce a product with a maximum UV absorption per centimeter at 260 to 350 nm of 0.1, measured on a dimethylsulfoxide extract using the procedure described in U.S. Pat. Pharmacopoeia. Other specifications require the sample to give as little discoloration as possible in the hot acid test using sulfuric acid and to show no reaction in the sodium lead test. To meet these stringent requirements, all aromatic hydrocarbons contained in the feed must be effectively hydrogenated.

In the process of the invention hydrogen is used in an amount which is at least equivalent to at least the stoichiometric amount of hydrogen required to desulfurize the batch to achieve the desired degree of dearomatization. As a rule, it is preferred to use at least about 1.05 times such a stoichiometric amount of hydrogen. In addition, hydrogen dissolved in the treated feedstock can be considered.

In the process of the invention, the amount of hydrogen-containing feed gas is generally about 2: 1 to about 20: 1, preferably about 3: 1 to 7: 1.

The hydrogen-containing gas can be obtained in a manner known per se, for example by steam reforming or by partial oxidation of a hydrocarbon feedstock, for example natural gas, with the following conventional steps such as water gas conversion, carbon dioxide removal and pressure adsorption.

Different hydrodesulfurization conditions can be used on different reaction trays. For example, the temperature on the top reaction tray that constitutes the first hydrodesulfurization zone may be lower than on the next lower tray, where again it may be lower than the temperature on the next tray, and this may be repeated.

The temperature may also increase from floor to floor from the uppermost floor to the immediately lower floor, but then in turn may decrease from floor to floor on the other lower floors. Thus, it is possible to operate the process such that the temperature rises from floor to floor from uppermost to next floor, but then decreases from floor to floor as the liquid descends through the column reactor. Under this mode, the batch meets progressively higher temperature conditions at substantially of the same pressure and gradually decreasing hydrogen sulfide partial pressure as it passes down the subsequent reaction trays. Since the hydrogen sulfide partial pressure is lower than on the second floor and on lower floors than on the top floor, the catalyst is effectively less sulfidated and therefore more effective on the lower floors than on the top floor. In this way, the efficacy of hydrogen sulphurization is promoted because the bottom tray conditions are much more favorable for the reaction of the remaining sulfur-containing compounds, resulting in less reactive compounds, such as sulfur-containing polycyclic compounds. In addition, lowering the temperatures on the lower trays as well as promoting catalytic efficiency on these trays due to the lower hydrogen sulfide partial pressure on these trays creates more favorable conditions for aromatic hydrogenation.

The reaction components, although supported by increasing the partial pressure of hydrogen, are limited by the equilibrium at high temperatures.

Since the hydrogen-containing gas flows to the uppermost tray from the nearest lower tray, this gas typically contains a proportion of hydrogen sulfide. Since the make-up gas is introduced below the lowest tray, the concentration of hydrogen sulfide is highest in the gas introduced to the uppermost tray. The content of organic sulfur-containing compounds is the lowest in the liquid introduced to the lowest tray, but these are the least reactive. Although sufficient hydrogen sulfide partial pressure should be maintained on the lower tray to keep the catalyst on the tray in a sufficiently sulfidated form to prevent the risk of hydrocracking on the tray, the catalyst tends to have the highest activity on the tray, so conditions on that tray are favorable not only for hydrodesulfurization but also for the hydrogenation of aromatic compounds. Therefore, under suitable working conditions, the aromatic hydrocarbon content of the feed can be greatly reduced, while at the same time efficiently removing less readily removed sulfur-containing compounds such as cyclic and polycyclic sulfur-containing compounds is achieved.

Different catalysts on different trays can be used in the process of the invention. In this case, the hydrogen sulphurization promoting catalyst rather than the aromatic compound hydrogenation is used on the top tray or on the several uppermost trays, while the catalyst which promotes the hydrogenation of the aromatic compounds is used on the lower trays.

The column reactor is equipped with means to remove the catalyst / liquid mixture from one or more of the trays. Using suitable valves and pumps, the same means may be used to dispense fresh catalyst to each tray, either to vary the amount of catalyst in accordance with batch changes, or in accordance with batch changes, or in accordance with operating conditions, or to replenish the catalyst amounts.

It is preferred that the sulfur content of the gas and liquid feed fed to the top tray is monitored to ensure that the hydrogen sulfide content is sufficient to keep the catalyst in sulfide form. Typically, the feed contains sufficient sulfur-containing compounds or the hydrogen-containing feed gas contains a sufficient amount of hydrogen sulfide, or there is a sufficient hydrogen sulfide content in both the feed and feed gas to keep the catalyst in a sufficient sulfide form. However, if for any reason there is a risk of low levels of hydrogen sulfide or active sulfur containing compounds on the top floor, sufficient hydrogen sulfide or active sulfur compounds such as carbon disulfide, carbonyl sulfide, alkyl mercaptan, dialkyl sulfide or dialkyl disulfide is added to the top stage. to restore a safe concentration of hydrogen sulfide on this palate.

Normally, it is sufficient to adjust the sulfur concentration at the top level in the form of hydrogen sulfide or an active sulfur compound to about 1 ppm and preferably about 5 ppm to about 1000 ppm. Generally, the top level sulfur concentration is from 10 ppm, for example, about 40 to 100 ppm.

-11EN 279286 B6

It is further advantageous to monitor the sulfur concentration on the at least one lower tray, for example the lower tray and, if possible, on each lower tray below the top tray and to admit to the feed on that tray optionally a sufficient amount of hydrogen sulfide or active sulfur containing additive such as carbon disulfide, carbonyl sulfide. , or an alkyl mercaptan, a dialkyl sulfide or a dialkyl disulfide, to maintain a sulfur concentration in the art of about 1 to 1000 ppm, for example about 5 to 100 ppm.

The liquid hydrocarbon feedstock may be, for example, naphtha, kerosene, middle distillates, vacuum oils, oil distillates for the production of lubricating oils, heavy components of lubricating oils made from petroleum residue, diesel fuel, atmospheric gas oils, light oils and light fuel oils.

In a preferred embodiment of the invention, the reaction trays comprise a floor inclined at an angle equal to or greater than the angle of deposition of the catalyst particles under the liquid. Each reaction tray may have a frusto-conical floor whose conicity is equal to or greater than the angle of composition of the catalyst particles under the liquid present in the tray. Alternatively, each reaction tray may have a floor and an enclosing wall, the floor comprising an inner portion that slopes downward and inwardly from the inner and outer portion of the wall, equal to or greater than the angle of deposition of the catalyst particles under the liquid.

The gas evacuation means associated with each reaction tray may comprise one or more caps of conventional design; in a particularly preferred arrangement, each such cap is connected to a relatively high riser pipe, the height of which is sufficient to prevent entrainment of the liquid from the tray in the event of a temporary interruption of gas evacuation for any reason. This relatively high riser pipe is covered by a relatively high cap, suitably inverted. The non-return valve may also be incorporated into such a riser pipe.

If the desired degree of desulphurization or dearomatization is not achieved in a single pass through the column reactor, the treated material may be reprocessed in a subsequent column reactor or other type of hydro-sulphurization reactor, possibly under harsh conditions. ·

Overview of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated by the following non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a flow diagram of a hydrodesulfurization unit for carrying out the process of the present invention; Fig. 3 is a similar vertical section through the tray of a modified column reactor design; Fig. 4 is a flow chart of the experimental unit; Fig. 5 is a diagram of the reaction tray of the unit of Fig. 4; diagram showing the relationship between the aroma content of the product and the operating temperature.

-12GB 279286 B6

It is clear to those skilled in the art that Fig. 1 is a diagram and therefore other parts of the device, such as heaters, coolers, temperature sensors, thermometers, pressure sensors, pressure valves, check valves, level gauges and the like are additionally required for the process unit. However, these additional devices are not subject of the invention and conventional such devices known in chemical plants can be used.

The hydrodesulfurization unit of FIG. 1 includes a column. a reactor vessel 1 equipped with a plurality of reaction trays 2 each carrying a portion of the particulate sulfide hydrodesulfurization catalyst and a predetermined volume of liquid. The hydrogen-containing gas is introduced into the column reactor vessel 1 via line 3. The manifolds 4 are mounted on each tray 2 and allow gas to rise through liquid on each tray 2. The treated sulfur-containing hydrocarbon feed is fed to the unit via line 5 and mixed. with recycled liquid in line 6 to form a mixed charge in line 1, which is fed to the top floor 2 of the column reactor vessel 1. The downwardly directed line 8 allows the liquid column 1 to descend from one level 2 to the next lower level 2 and finally. The trays 2 are shown in more detail in Fig. 2a 3, taking into account the different arrangement of the manifold 4 and the downwardly directed piping 8.

Thus, it is evident that the gas and liquid flow countercurrently in the column reactor vessel.

Each tray 2 is provided with a corresponding coil 10 of the heat exchanger. Each tray 2 is provided with a temperature controller 11 which controls the operation of a corresponding control valve 12 that controls the flow to the corresponding coil 10 of the heat exchanger medium supplied by line 13 to the inlet manifold 14. (For simplicity, the temperature controller 11 in FIG. 1 for the top floor 2, in practice each floor 2 has its corresponding temperature controller 11). The unit is equipped with a manifold 15 and a return line 16 for the heat exchange medium. This arrangement allows the temperature on each tray 2 to be individually controlled.

The waste gas is discharged from the top of the column reactor vessel 1 via line 17. The waste gas consists of liquid feed vapors, gaseous hydrodesulfurization reaction products including hydrogen sulphide and the inert gases contained in gas introduced through line 3. · The vapors are condensed through the condenser 18 and two-phase mixture. gas and condensate flows through line 19 into a gas and liquid separator 20 equipped with a dropper 21.

The condensate is discharged from the separator 20 via line 22 and 23 via a pump 24 and returns to the separator 20 via line 25 and 26 via a flow restrictor 27, creating a pressure in the lines 25 and 26 that is greater than that of the separator 20. line 25 returns to column reactor vessel 1 via line 28, 29 and 6 under control of a valve 30, which itself is controlled by a level gauge 31 on separator 20. A controlled amount of liquid is diverted from line 28 via line 32 equipped with valve 33 and sensor 34 flow of the selected lower tray 2; In FIG. 1, a floor at the bottom is shown as a tray 2 into which the conduit 32 leads, but the conduit 32 may also extend to another upper tray 2. The flow through the valve 33 is controlled by a flow-through valve.

meter 35, which is connected to the flow sensor 34. This supply of liquid through line 32 to the lower levels 2 of the column reactor vessel 1 represents the way through which the reactive sulfur compounds can be introduced to the lower levels 2, thereby adjusting the efficiency of the catalyst on the lower levels 2, as discussed in more detail below.

The gas from the separator 20 is discharged from the unit via line 36 and is passed through a throttle valve 37 to lines 38 and 39 through which it exits the unit. This waste gas contains hydrogen sulphide formed during the hydrodesulfurization treatment and can therefore be further processed (for example to remove hydrogen sulphide and subsequently convert hydrogen sulphide to elemental sulfur by partial oxidation).

The liquid collected in the sump 9 is discharged via line 40 and fed through control valve 41 to cooler 42. Flowmeter 43 controls control valve 41. The cooled liquid is conveyed along with desorbed hydrogen (which is less soluble in the cold liquid hydrocarbon than in the hot liquid hydrocarbon). via a line 44 to a gas / liquid separator 45. The separator 45 is equipped with a droplet entrainer 46 and a gas return line 47 which introduces gas to the bottom of the column reactor vessel 1. The liquid collected in the separator 45 flows through a line 48 equipped with a valve 49 controlled by a level gauge 50 to the separator 51 gas and liquid. This separator 51 has a dropper 52 and an outlet gas line 53 and a product line 53.

Piping 55 may be provided to control the amount of hydrogen sulfide or active sulfur containing material such as carbon disulfide, carbonyl sulfide, alkyl mercaptan RSR, alkyl sulfide RSR or dialkyldisulfide RS-SR, where R is always an alkyl group, for example n-butyl, typically in the form of a solution in a hydrocarbon solvent, optionally into a hydrodesulfurization unit, as discussed in more detail below.

In operation of the unit of FIG. 1, the liquid feed supplied by line 5 passes through the column reactor vessel 1 and finally leaves the unit via line 53. As it passes through the column reactor vessel 1, the sulfur-containing organic compounds are largely converted to hydrogen sulfide, via line 53, dissolved in the liquid product. Separation of hydrogen sulfide from the liquid product is possible in a manner known per se, for example by entrainment in a downstream processing unit (not shown). Although the hydrogen-containing gas in the χ line is substantially free of sulfur, the liquid introduced into the lowest level 2 of the column reactor vessel 1 generally contains sufficient hydrogen sulfide to ensure that the hydrodesulfurization catalyst remains adequately sulfidated on the lower level 2 to reduce it. to the minimum the risk of hydrocracking reactions on the lower tray 2 of the cylindrical reactor vessel 1. On the upper tray 2 gas is introduced from the lower tray 2 and thus contains hydrogen sulfide due to contact with the liquid phase on that tray. Therefore, as a rule, the hydrogen sulfide partial pressure on each tray 2 of the column reactor vessel 1 is sufficient to ensure sufficient sulfidation of the catalyst. However, if for any reason the hydrogen sulfide partial pressure on any tray 2 of the column reactor vessel would fall below a safe level, a suitable amount of sulfur-containing material, preferably hydrogen sulfide, carbonyl sulphide or an active sulfur-containing organic material such as alkyl mercaptan

(E.g., n-butylamercaptan), dialkylsulfide (e.g., di-n-butylsulfide) or dialkyl disulfide (e.g., di-n-butyldisulfide), typically in the form of a solution in a hydrocarbon solvent via line 54 to equalize the sulfur content of the feed on the respective tray 2 Since carbon disulfide, carbonyl sulfide, alkyl mercaptans, dialkyl sulfides and dialkyl disulfides are readily and rapidly converted to hydrogen sulfide, it is possible to ensure that the catalyst charge on each tray 2 of the cylindrical reactor vessel 1 remains adequately sulfidated so that substantially any hydrocracking hazard in the cylindrical reactor vessel is eliminated. 1.

FIG. 2 shows the construction of a tray 2 suitable for use in a relatively small cylindrical reactor vessel 6. In this case, the truncated conical septum or diaphragm 70 extends to the wall 71 of the cylindrical reactor vessel 1 and completely encloses the cross-section of the cylindrical reactor vessel 1 with the exception of the downward fluid line 72 for the upward gas line 73. The slope of the frustoconical diaphragm 70 is equal to or greater than the corresponding angle of deposition of the solids of the hydrodesulfurization catalyst under the liquid on tray 2.

The upwardly directed gas conduit 73 has an axial tube 74 which is open at its upper end and is covered by a cap 75. The annular member 76 prevents catalyst particles from sucking into the cap 75. The cylindrical partition 77 surrounds the cap 75 symmetrically and The level of liquid 78 is determined by the height of the upper end of the downwardly directed pipe 72. The downwardly directed pipe 72 is a screen 79 for returning catalyst particles to the tray 2. From the lower tray 2 (not shown) it extends through the pipe. pointing down.

The cylindrical partition 71 promotes the mixing of the liquid and catalyst slurry with the rising gas. The vertical dimension of the partition 77 is not critical, but generally should be one third to three quarters of the vertical height between the membrane 70 with the liquid level 78. It is preferred that the cylindrical partition 77 be positioned symmetrically or almost symmetrically to the vertical position. In the zone defined by the baffle 77, the fluid flow is directed generally upward, while outside the cylindrical baffle 77 the fluid flow is directed downward. Preferably, the area of the zone within the cylindrical partition 77 is approximately equal to the sum of the area outside the cylindrical partition 77.

The upward gas line 73 is equipped with a backflow prevention valve.

The temperature of the liquid and the catalyst on tray 2 can be controlled by the heat exchanger coil 82.

In operation, the ascending gas is bubbled through the liquid to tray 2 and stirred to mix the liquid and catalyst to keep the catalyst in suspension. The cylindrical partition 77 aids in good circulation of liquid to tray 2. At a suitable rate of climb, gas bubbles 83 keep most of the catalyst particles 84 in suspension. (It is recalled again that for the sake of simplicity, there are few bubbles 83 and only a few catalyst particles 84 in FIG. 2).

-15GB 279286 B6

Fig. 3 shows an alternative construction of the tray 2 of the column reactor vessel X of the unit of Fig. 1. The horizontal membrane or septum 100 extends from one wall 101 of the column reactor vessel 1 to the other wall and completely encloses the cross-section of the column reactor vessel X except for liquid and upwardly directed gas line 103. The diaphragm 100 has a frustoconical axial portion 104 surrounding an upwardly extending conduit 103 and an annular tapered portion 105 adjacent to the wall 101. The tray 2 can thus retain a volume of liquid at a level of 106 that is determined by the overflow height of the downwardly extending conduit 102 above. Each tray 2 also carries a dose of a sulfided hydrodesulfurization catalyst whose particles 107 are shown diagrammatically. Such particles 107 are kept in suspension in the liquid on tray 2 by stirring, which is achieved by an ascending gas, as described below. To prevent leakage of the overflowing liquid particles 107 into the downwardly directed conduit 102, the top of the downwardly directed conduit 102 is equipped with a screen 108. The inclination of the frustoconical portion 104 and the inclination of the annular inclined portion 105 is equal to or greater than 2.

The upwardly directed gas conduit 103 leads the upward gas to a circular manifold 109 which surrounds the truncated cone-shaped portion 104 with star-shaped tubes 110. The return of the liquid to the upwardly directed conduit 103 is passed through a built-in valve 111.

The annular exhaust sidewalls or baffles 112 and 113 are disposed in the mass of liquid on tray 2, one inside and the other outside the circular manifold 109 to promote mixing of the liquid suspension and catalyst with the rising gas. The vertical dimension of the annular withdrawal sidewall or partition 112 and 113 is not critical, but generally should be one-third to three-fourths of the vertical height between the diaphragm or partition 100 and the level level 106. It is preferred that the annular withdrawal side walls or partition

112 and 113 positioned symmetrically or almost symmetrically with the vertical position. In the annular zone between the annular side walls or baffles 112 and 113, the liquid generally flows upward and out of this zone the liquid flows downward. Preferably, the cross-sectional area of the annular withdrawal zone between the annular withdrawal walls 112 and 113 is approximately equal to the sum of the cross-sectional area within the annular withdrawal sidewall or partition 112 and outside the annular withdrawal sidewall or partition

113.

From the nearest tray 2, a downwardly directed conduit 114 is introduced. The height H of the liquid level 115 in the downwardly conduit 114 is above the liquid level 106 of the tray 2 fixed by the liquid level on the tray that feeds the downwardly conduit 114. plus a decrease in pressure in the ring distributor 109 on this tray 2 (for example on tray 2 above) and a drop in friction pressure.

The temperature on tray 2 of FIG. 3 can be controlled by the heat exchanger coil 117.

-16GB 279286 B6

In an alternative (not shown) heat exchanger coil 117 is omitted, but the external heat exchanger coil is connected to a column reactor vessel, whereby the liquid drawn from tray 2 can be pumped for temperature control purposes.

The invention is further illustrated by the following description of a preferred embodiment, but is not limited thereto. The advantages of the solution according to the invention are illustrated by the description of an example of a comparative embodiment.

DETAILED DESCRIPTION OF THE INVENTION

He did

The unit of FIG. 4 is studying the hydrodesulfurization of a synthetic mixture of organosulfur compounds (dibenzothiophene) dissolved in a saturated hydrocarbon solvent (n-hexadecene).

The liquid feed consists of a solution of dibenzothiophene (DBT) in normal hexadecane (114 g dibenzothiophene per liter of solution); the charge is stored in a storage vessel 201. Pre-prepared solution is introduced into the storage vessel 201 via line 202, then the charge is purged with dry nitrogen, through lines 202 and 203. The storage vessel 201, discharge line 204, metering pump 205 and line

206 are placed (in a circulating hot air chamber (not shown, maintaining a temperature of 50 ° C +/- 5 ° C in the chamber to avoid the risk of solids formation because the melting point of n-hexadecane is approximately 20 ° C). The flow of liquid into the column reactor vessel 207 is enabled by the metering pump 205 and the liquid is occasionally tested by a pipette (not shown) in a hot air chamber. The transfer line 206 is wrapped with an electrical resistance heater 208 so that the fluid can be preheated prior to introduction into the top of the column reactor vessel 207. The column reactor vessel 207 consists of a vertical metal cylinder 2.0 meters high and 7.5 cm in internal diameter, and It has eight sections of reaction trays 209 to 216. (The construction of one of trays 209 to 216 is shown in more detail and is described in Figure 5 below. The hydrogen-containing gas is supplied via line 212 to the bottom of the reactor.

207 (above the liquid level in the sump 218) and the desired hydrogen flow is obtained by adjusting the flow meter 219.

Whole reactor cylindrical vessel (electrically heated air bath).

207 is closed in (not shown by forced hot circulation)

The liquid advances downward from the top reaction tray 209 to the lowest reaction tray 216 by overflowing from one tray to the nearest lower tray below, and at the same time the hydrogen-containing gas rises from tray 216 to tray 209 while bubbling liquid on each tray. The liquid collected in the sump 218 at the bottom of the cylindrical reactor vessel 207 is discharged from the system via line 220 and cooled in a condenser 221 which conducts water at about 45 ° C under control of a valve 222 controlled by control signals of the level indicator. Liquid samples are taken from line 224 for analysis.

The gas phase leaves the reactor vessel 207 through line 225 and is cooled in a condenser 226 to which water is supplied

The cooled gas and condensate are passed through line 227 to drum 228. The gas phase is then passed through line 229 with pressure control valve 230; this riser pressure control valve 230 adjusts the pressure throughout the working system. The gas is fed to a flow analyzer and to a burner (not shown) for combustion of excess refinery gases. Liquid collected in drum 228 may be returned to tray 209 via line 231 under control of valve 232, controlled by level gauge sensor 223 on drum 228, or may be sampled from line 234 equipped with manually operated valve 235.

An example of the construction of one of the reaction trays 209 to 216 is shown in FIG. 5. The vertical walls of the cylindrical reactor vessel are designated 240. The trays are equipped with a feed and discharge tube 241 with a shut-off valve 242. This tube 241 is used for fouling and removal of the catalyst slurry. from the appropriate floor.

The horizontal cross-section of the cylindrical reactor vessel 207 is closed by a frustoconical membrane 243, 244. Sloping part of the membrane

243 forms an angle of 30 ° with the horizontal. Horizontal part of the membrane

244 has a diameter of 4 cm and is drawn through vertical pipes with an inner diameter of 4 mm at two points.

Tube 245 passes through the membrane in the vertical axis of the cylindrical reactor vessel and extends upwardly into the cap 246 at a distance of 22 cm. The tube 245 extends only slightly or does not extend below the lower surface of the horizontal portion 244. The cap 246 has an outer diameter of 20 mm; The 2 mm gap between the lower edge of the cap 246 and the upper surface of the portion of the membrane 244 is closed by a sieve 247, which is a fine stainless steel mesh to prevent the penetration of catalyst particles into the interior of the cap 246.

Tube 248 begins 9 cm above the horizontal portion of membrane 244 and descends below the space below the horizontal portion of membrane 244. The tube is covered by a screen 249 to prevent the introduction of catalyst particles. The height of the end of the tube 248 determines the liquid level 250 per tray. The lower end of the tube 248 is below the liquid level on the lower tray (or in the case of tray 216, the lower end of the tube 248 is below the liquid surface in the sump 218 of the cylindrical reactor vessel 207).

In operation, the tray (i.e., one of trays 209 to 216) receives fluid from the top tray through tube 248 as described above (or, in the case of tray 209, from fluid line 206); the liquid flows through the sieve 249 and drops to the nearest lower level. The gas passes through the tube 245, into the inner part of the cap 246 and through the sieve 247 and bubbles liquid through the tray; Bubble agitation keeps the catalyst particles 252 in the form of a turbulent suspension. The gaseous phase escaping through the surface of the liquid passes through the axial tube of the upper tray (or, in the case of tray 209, enters line 225). In this way, the liquid phase from tray 209 to tray 210 is repeated up to tray 216 and sump 218 and is countercurrently contacted with the gas phase extending from tray 216 up to tray 215 to tray 209 and into the conduit. 225.

After flushing the unit with nitrogen and after filling the reservoir 201 with the batch solution, the line 229 is opened to the atmosphere by opening a bypass line (not shown) around the valve 230.

-18GB 279286 B6

With valve 242 open, each tray 209-216 is filled with the catalyst slurry via line 241. In this way, 35 cm ³ of a particle size catalyst * 3 is applied to each tray 209-216.

0.1 to 0.5 mm in 290 cm n-hexadecane. The catalyst is CoO-MoO ₃ (gamma-Al ₂ O ₃ ), which is pre-reduced with hydrogen, cooled and introduced into n-hexadecane. Use 45 cm ^{3 of} n-hexadecane to wash all the catalyst in line 241 fed to the tray. The valve 242 then closes. Nitrogen is introduced into line 217 and passed through a cylindrical reactor vessel 207 and vented to atmosphere through line 229. The nitrogen stream is exchanged for a stream of hydrogen in the apparatus _? The (absolute) pressure of 3.5 MPa is slowly adjusted and the unit heater is used to raise the temperature from 30 ° C to 325 ° C over 4 hours.

Once the operating pressure is reached, after approximately 45 minutes, the hydrogen introduction rate is increased to 465 liters / h (NTP). At this point, a 10 g / l solution of carbon disulphide o is pumped on the n floor

in n-hexadecane via line 241 at a rate of 500 cm / h to ensure sufficient catalyst sulfidation. Three hours later, the feed of the carbon disulfide solution to tray 216 is stopped and liquid is introduced to tray 209 and the rate of feed liquid is stabilized at 587 cm ³ / h. During this time, the liquid level in the sump 218 rises, and the liquid then exits the cylindrical reactor vessel under the control of the level gauge-controlled actuator 223 and under the control of the valve 222.

Occasionally a sample is taken from line liquid in line 224 and analyzed for dibenzothiophene by gas chromatography. After 12 hours of continuous operation, the analysis shows that 99.1% of dibenzothiophene has been converted to sulfur-free products and only the non-quantifiable traces of the tetrahydrofibers and hexahydrofibers of dibenzothiophene are evident in the chromatographic record. During the next three-day operation, dibenzothiophene conversion gradually increases to 99.5% and is maintained at this value. '

Comparative example

In a comparative example, 280 cm @ ^{3 of the} same catalyst in the form of extrudates having a diameter of 1 mm and a length of 1-3 mm are fed into a reactor having an internal diameter of 25 mm and a catalyst bed height of 57 cm. When this conventional reactor operates at the downstream flow of liquid and gas using the same batch composition and at the same temperature, pressure and flow rate of liquid and gas as used in Example 1, only 96.4% conversion of dibenzothiophene is achieved, thereby a significantly worse performance is demonstrated compared to the countercurrent operation in the unit of the invention (more than seven times the amount of dibenzothiophene remains unconverted).

The hydrogenation of aromatic compounds in the presence of a hydrodesulfurization catalyst depends on a number of factors, including thermodynamic and kinetic factors, as well as on the efficiency of the catalyst and its efficiency.

-19GB 279286 B6

In this regard, the hydrogenation of aromatic compounds, for example aromatic hydrocarbons, is an exothermic process. In addition, the rate at which a fraction is run under certain conditions is limited by adjusting the equilibrium state under these conditions. In general, equilibrium is less favorable at high temperatures. Therefore, it is advantageous to work at lower reaction temperatures where possible.

Hydrogenation kinetics of aromatic compounds by hydrogenation reactions are favorable at high temperatures. Therefore, the rate of hydrogenation of the flavorings increases strongly with increasing temperature, at a particular hydrogen partial pressure set, provided that the concentration of the flavorings in the reaction mixture is above the equilibrium limit at the temperature considered.

The ability of a given catalyst mass, defined by the particle size range, to affect the hydrogenation of aromatics is a function of the spray particle scavenging intensity, the degree of catalyst sulfide, and the rate of hydrogen and hydrogen sulfide mass transfer to and from the catalyst surface. Generally speaking, the greatest tendency to hydrogenate flavorings has a catalyst with a low degree of sulfidization that is subjected to a turbulent biphasic (gas / liquid) mixed stream.

Fig. 6 is a diagram showing the effect of various factors on the hydrogenation reaction of aromatics. Figure 6 shows the percentage of flavorings in the product versus temperature at a given hydrogen partial pressure. Line A-A 'in Fig. 6 shows the temperature dependence at a fixed hydrogen partial pressure of the kinetically limited aroma content of the product obtained from the particular aroma charge using a fixed amount of catalyst. Line B-B 'means the equilibrium limited content of aromatics in the product from the same reaction system as a function of temperature. At each given temperature, the XY (or ΧΎ ') curve means an excess of the aroma content of the product and is therefore a measure of the strength required for the catalyst. Point 0 means the lowest aromatic content obtainable for a given system and this content is achievable only by selecting the combination of the most favorable kinetics and a less favorable equilibrium at temperature increase.

If, in some way, the efficiency of the catalyst can be promoted, for example by controlling the degree of sulfidation thereof, then a new curve is obtained, for example C-C 'with a new achievable optimum aroma content (point 0').

In practice, the crude oil-derived feedstock contains numerous different aromatics and sulfur compounds, each having its own hydrogenation and hydrodesulfurization kinetics. The prior removal of the less temperature resistant materials and hydrogen sulfide from the sulfur compounds makes it possible to use the process of the invention and to achieve significant advantages in the use of the process of the invention compared to conventional hydrodesulfurization processes known in the art.

Industrial applicability

Hydrodesulfurization process allowing a significant reduction of the aroma content in the feed with efficient hydrodesulfurization.

Claims (6)

PATENT CLAIMS A process for the continuous hydrodesulfurization of a sulfur-containing liquid hydrocarbon feed in the presence of hydrogen in an amount corresponding to a 2: 1 to 20: 1 molar ratio of hydrogen: feed and in the presence of a solid sulfided hydrodesulfurization catalyst under a hydrogen pressure of 2 to 15 MPa at 240 up to 400 ° C, characterized in that the hydrodesulfurization is carried out in a plurality of superimposed and interconnected hydrodesulfurization zones, each zone containing a dose of retained solid sulfided hydrodesulfurization catalyst, the gas being introduced into the lowest hydrodesulfurization zone and conducted to the next higher one hydrodesulfurization zones countercurrent with respect to the sulfur-containing liquid hydrocarbon feed introduced into the upstream hydrodesulfurization zone and maintaining pressure and temperature conditions effective for hydrodesulfurization and catalyst in each zone r is kept in the fluidized state in each zone by mixing with the incoming gas, a hydrogen sulphide-containing off-gas is discharged from the top zone and a reduced sulfur liquid hydrocarbon product is discharged from the bottom zone. Process according to claim 1, characterized in that a pressure of 2.5 to 10 MPa and a temperature of 250 to 370 ° C are maintained in the hydrodesulfurization zone. The process according to claims 1 and 2, wherein the solid, sulfidated catalyst is selected from the group consisting of molybdenum disulfide, tungsten sulfide, cobalt sulfide, sulfidated nickel-molybdate catalysts of the formula NiMoS _x , sulfidated CoO-MoO ₃ / gamma-Al ₂ 0 ₃ and mixtures thereof. Device for carrying out the method according to claims 1 to 3, comprising a column reactor with reaction trays arranged one above the other, each reaction tray defining a respective reaction zone and having a conduit for conducting liquid from tray to tray and a manifold for countercurrent conduction of gas from tray to tray. A tray, characterized in that each reaction tray (2) is adapted to retain a predetermined volume of liquid and has a membrane (70) inclined by an angle equal to or greater than the angle of deposition of the catalyst particles under the liquid on the reaction tray (2). Apparatus according to claim 4, characterized in that each reaction tray (2) has a frustoconical membrane (70) and the slope of the membrane (70) is equal to or greater than the angle of deposition of the catalyst under the liquid on the reaction tray (2). -21EN 279286 B6 Device according to claims 4 and 5, characterized in that the reaction trays (2) have a membrane (70) and a surrounding wall (71), wherein the inner part of the membrane (70) bends downwards and inwards from the central part and the outer part of the membrane (70) inclines downward and inwardly from the surrounding wall (71), and the inclination of the inner and outer portions of the membrane (70) is equal to or greater than the angle of deposition of the catalyst under the liquid on the reaction tray (2).