Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G67/00—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only
  • C10G67/02—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only plural serial stages only
  • C10G67/06—Treatment of hydrocarbon oils by at least one hydrotreatment process and at least one process for refining in the absence of hydrogen only plural serial stages only including a sorption process as the refining step in the absence of hydrogen

Definitions

• the present invention relates to a process for producing hydrocarbons with a low sulphur content.
• Said hydrocarbon fraction contains an olefin fraction that generally exceeds 5% by weight, usually 10% by weight, a sulphur content of more than 100 ppm by weight and a nitrogen content of more than 20 ppm by weight.
• the process allows all of a gasoline cut containing sulphur to be upgraded, reducing the sulphur content of said gasoline cut to very low levels, without reducing the gasoline yield, and minimizing the reduction in the octane number during said process.
• the invention is of particular application when the gasoline to be treated is a cracked gasoline containing more than 300 ppm by weight or more than 500 ppm by weight of sulphur, and a nitrogen content that is generally more than 50 ppm by weight, or more than 100 ppm by weight, preferably more than 150 ppm by weight, or 200 ppm by weight or more.
• the principal sources of sulphur in gasoline bases are cracked gasolines, principally the gasoline fraction deriving from a process for catalytic cracking of a residue from atmospheric distillation or vacuum distillation of crude oil.
• the gasoline fraction derived from catalytic cracking which represents an average of 40% of gasoline bases, contributes more than 90% of the sulphur in that gasoline.
• the production of low sulphur gasoline requires a step for desulphurizing catalytically cracked gasoline. That desulphurization is conventionally achieved by one or more steps for bringing the sulphur-containing compounds contained in said gas into contact with a gas that is rich in hydrogen in a hydrodesulphurization process.
• the octane number of said gasolines is very closely linked to their olefin content. Preserving the octane number of said gasolines thus necessitates limiting reactions transforming olefins to paraffins, which reactions are inherent to hydrodesulphurization processes.
• the present invention for the same degree of saturation of olefins at the reactor outlet and for the same operating temperature for the hydrodesulphurization reactor, it is possible to increase the catalyst activity by prior reduction in the nitrogen-containing compounds present in the gas.
• eliminating basic nitrogen-containing compounds prior to hydrodesulphurization can limit the degree of olefin saturation for a fixed sulphur content at the reactor outlet. The present invention is thus of particular application to the treatment of gasoline cuts with a high nitrogen-containing compound content.
• the present invention relates to a process that can achieve at least one of the following advantages and preferably all simultaneously:
• the present desulphurization process proposes a solution to obtaining high degrees of desulphurization while limiting the octane number loss due to olefin hydrogenation. This results in the production of a low sulphur gasoline with a high octane number.
• the present invention provides a process for desulphurizing a gasoline feed comprising at least 150 ppm by weight of sulphur-containing compounds using a hydrodesulphurization catalyst, characterized in that said feed undergoes prior denitrogenation treatment under conditions such that the amount of nitrogen-containing compounds present in said feed when it is brought into contact with said hydrodesulphurization catalyst does not exceed 150 ppm by weight.
• the denitrogenation treatment is carried out immediately prior to said contact (hydrodesulphurization).
• step e for example when said treatment is carried out immediately prior to said contact (step e) and possibly f)), at least one step selected from the group constituted by:
• step e) and possibly step f)) is preferably carried out with at least the heavy fraction from step c).
• step d denitrogenation treatment
• step e contact
• step f contact
• said contact is preferably carried out with at least said heavy fraction from step c).
• said contact is made in at least two steps e) and f), regardless of the envisaged implementation.
• said hydrodesulphurization catalyst comprises at least one element from group VIII of the periodic table, and advantageously, said hydrodesulphurization catalyst comprises at least one element from group VIB of the periodic table.
• said group VIII element is selected from the group constituted by nickel and cobalt and said at least one group VIB element is selected from the group constituted by molybdenum and tungsten.
• the conditions for said contact are generally as follows: a temperature in the range 200° C. to 450° C., a pressure in the range 1 to 3 MPa, an hourly space velocity in the range 1 h ⁇ 1 to 10 h ⁇ 1 , and a H 2 /HC ratio (ratio of hydrogen to hydrocarbons, expressed in litres per litre) in the range 50 l/l to 500 l/l.
• the present process can advantageously be applied to gasoline from catalytic cracking or from cokefaction of a heavy hydrocarbon feed or from steam cracking.
• the feed to be desulphurized is optionally pre-treated in a concatenation of reactors for selective diolefin hydrogenation (step a) and for rendering light-sulphur-containing compounds heavier (step b)).
• the feed that has optionally been pre-treated is then distilled and fractionated into at least two cuts (step c)): a light gasoline that is depleted in sulphur and rich in olefins, and a heavy gasoline that is rich in sulphur and depleted in olefins.
• the light fraction from the three preceding steps generally contains less than 100 ppm of sulphur, preferably less than 50 ppm of sulphur, and highly preferably, less than 20 ppm of sulphur, and in general does not need subsequent treatment prior to its incorporation as a gasoline base.
• the heavy fraction from the three preceding steps, which contains the major portion of the sulphur, is treated using the process of the present invention.
• This preferred implementation has the advantage of further minimizing the octane number loss as light olefins containing 5 carbon atoms, which are readily hydrogenated, are not sent to the hydrodesulphurization section.
• Step a) is optional and is principally intended to eliminate the diolefins present in the gasoline. This step can maximize the service life of catalysts used in the downstream steps. Steps b) and c) are also optional, but if they are carried out prior to step e), they can minimize the overall octane number loss in the process.
• Denitrogenation step d) is carried out before contact with the hydrodesulphurization catalyst (steps e) and/or f)) or before at least one of steps a), b) and/or c), so that the amount of nitrogen-containing compounds does not exceed 150 ppm (expressed by weight), preferably 125 ppm, more preferably 100 ppm.
• the process of the invention comprises at least the two steps d) and e).
• Step d) corresponds to a step for at least partial elimination of the nitrogen contained in the gasoline;
• step e) corresponds to a step for hydrotreatment of the pre-treated gasoline.
• This optional pre-treatment step for the gasoline to be desulphurized is intended to at least partially eliminate the diolefins present in the gasoline.
• Diene hydrogenation is an optional but advantageous step, which can eliminate the vast majority of the dienes present in the cut to be treated prior to hydrotreatment.
• Diolefins are precursors to gums, which polymerise in the hydrotreatment reactors and limit their service life.
• This step generally takes place in the presence of a catalyst comprising at least one group VIII metal, preferably selected from the group constituted by platinum, palladium and nickel, and a support.
• a catalyst comprising at least one group VIII metal, preferably selected from the group constituted by platinum, palladium and nickel, and a support.
• a catalyst containing 1% to 20% by weight of nickel deposited on an inert support such as alumina, silica, silica-alumina, a nickel aluminate or a support containing at least 50% alumina.
• This catalyst operates at a pressure of 0.4 to 5 MPa, at a temperature of 50° C. to 250° C., with an hourly space velocity of the liquid of 1 h ⁇ 1 to 10 h ⁇ 1 .
• a further group VIB metal such as molybdenum or tungsten can be combined therewith to form a bimetallic catalyst.
• This group VIB metal if combined with a group VIII metal, will be deposited in an amount of 1% by weight to 20% by weight.
• the operating conditions usually, we operate under pressure in the presence of a quantity of hydrogen that is in slight excess with respect to the stoichiometric value necessary to hydrogenate the diolefins.
• the hydrogen and the feed to be treated are injected as upflows or downflows into a reactor, preferably with a fixed catalyst bed.
• the temperature is most generally in the range 50° C. to 300° C., preferably in the range 80° C. to 250° C., more preferably in the range 120° C. to 210° C.
• the pressure is 0.4 to 5 MPa, preferably more than 1 MPa.
• An advantageous pressure is in the range 1 to 4 MPa, limits included.
• the space velocity is of the order of 1 h ⁇ 1 to 12 h ⁇ 1 , preferably of the order of 4 h ⁇ 1 to 10 h ⁇ 1 .
• the light fraction of the catalytically cracked gasoline cut can contain up to a few % by weight of diolefins.
• the diolefins content is reduced to less than 3000 ppm, or less than 2500 ppm and more preferably less than 1500 ppm. In some cases, a content of less than 500 ppm can be achieved.
• the diene content after selective hydrogenation can even be reduced to less than 250 ppm.
• the diene hydrogenation step is carried out in a catalytic hydrogenation reactor that comprises a catalytic reaction zone preferably traversed by the entire feed and by the quantity of hydrogen necessary to carry out the desired reactions.
• Certain nitrogen-containing compounds are also transformed during this step. This is the case, for example, with slightly basic nitriles which, through hydrogenation, are transformed into amines which are more basic.
• This optional step consists of transforming light saturated sulphur-containing compounds, i.e., compounds with a boiling point that is lower than that of thiophene, into saturated sulphur-containing compounds with a boiling point that is higher than that of thiophene.
• Said light sulphur-containing compounds are typically mercaptans containing 1 to 5 carbon atoms, CS 2 and sulphides containing 2 to 4 carbon atoms.
• This transformation is preferably carried out over a catalyst comprising at least one group VIII element (groups 8, 9 and 10 of the new periodic table) on an alumina, silica or silica-alumina or nickel aluminate type support.
• the choice of catalyst is made so as to promote the reaction between light mercaptans and olefins, which results in mercaptans or sulphides with boiling points that are higher than thiophene.
• This optional step can possibly be carried at the same time as step a), in the same reaction bed and with the same catalyst.
• it may be particularly advantageous to operate, during the diolefin hydrogenation, under conditions such that at least a portion of the mercaptans are transformed.
• the temperatures are generally in the range 100° C. to 300° C., preferably in the range 150° C. to 250° C.
• the H 2 /feed ratio is adjusted to between 1 and 20 litres per litre, preferably to between 3 and 15 litres per litre.
• the space velocity is generally in the range 1 h ⁇ 1 to 10 h ⁇ 1 , preferably in the range 2 h ⁇ 1 to 6 h ⁇ 1
• the pressure is in the range 0.5 to 5 MPa, preferably in the range 1 to 3 MPa.
• step b) renders possible separation of a portion of the nitrogen-containing compounds from the IP-60° C. fraction.
• This optional step carried out after steps a) and b), can produce a light desulphurized gasoline, generally containing less than 5 ppm of mercaptans.
• the gasoline is fractionated into at least two fractions:
• a light fraction containing a limited residual sulphur content preferably less than about 50 ppm, more preferably less than about 20 ppm, highly preferably less than about 10 ppm, and which enables said cut to be used without carrying out (an)other treatment(s) aimed at reducing the sulphur content; this light fraction is generally depleted in light nitrogen-containing compounds;
• Said separation is preferably carried out using a conventional distillation column.
• This fractionation column can separate a light fraction of the gasoline containing a small fraction of sulphur from a heavy fraction preferably containing the major portion of the sulphur initially present in the initial gasoline.
• the light gasoline obtained following separation generally contains at least all of the olefins containing five carbon atoms, preferably compounds containing five carbon atoms and at least 20% of olefins containing six carbon atoms.
• this light fraction obtained after steps a) and b) has a low sulphur content, i.e., it is not in general necessary to treat the light cut before using it as a fuel.
• the nitrogen-containing compounds present in gasoline are principally from the following families: nitrites, amines, pyrroles, pyridines and anilines. These compounds are generally present in the gasoline in an amount of 20 to 400 ppm. Most of these compounds are basic; thus, they can be eliminated by separation in an acidic medium.
• the step for eliminating nitrogen from the gasoline can thus consist of washing the gasoline with an aqueous solution containing an acid compound. Examples of acids that can be cited are phosphoric acid, sulphuric acid, hydrochloric acid and formic acid. Any type of acid that is soluble in water and has sufficient acidity to protonate nitrogen can be used for this operation.
• This operation is carried out by bringing the gasoline to be treated into contact with the acid, for example in a washing column.
• the washing conditions are optimized so that the gasoline that is recovered contains less than 150 ppm of nitrogen, preferably less than 100 ppm by weight, and more preferably less than 50 ppm of nitrogen, or less than 20 ppm.
• Step d) can also be accomplished by treating the gasoline on a solid with a sufficient Lewis or Brönsted acidity to fix the nitrogen-containing compounds.
• solids that can be used are ion exchange resins, strong acids on mineral supports such as phosphoric acid on silica, or silica aluminas in the zeolitic or amorphous form. This list is only given by way of illustration, and the scope of the present invention encompasses the use of any other known technique for eliminating all or a portion of the nitrogen-containing compounds present in a hydrocarbon fraction.
• the gasoline traverses a guard mass that is in general use in a fixed bed, the basic nitrogen-containing compounds are protonated and become fixed on the mass. Once saturated, the mass can be regenerated, or more simply, replaced with a fresh mass.
• the choice of mass, its length of use and the operating conditions are optimized so that the gasoline produced during step d) contains less than 150 ppm of nitrogen, or 100 ppm of nitrogen, preferably less than 50 ppm of nitrogen, more preferably less than 20 ppm of nitrogen.
• the choice of mass, its service life and the operating conditions are optimized so that at least 50%, preferably 70% and more preferably at least 90% of the nitrogen-containing compounds are eliminated during this step.
• step a) is carried out before step d).
• Certain nitrogen-containing compounds such as nitrites are transformed during step a) to form the corresponding amines.
• the observed reaction is as follows:
• Step d) can also include separation, generally by distillation, of the gasoline to be treated.
• the basic compounds present in the cracked gasoline are concentrated in the heavy fraction of the gasoline. Said heavy fraction is eliminated by distillation, and can thus at least partially eliminate the basic nitrogen-containing compounds.
• step d), which consists of distillation produces at least two fractions:
• the hydrodesulphurization step (step e)) consists of passing the gas to be treated, in the presence of hydrogen, over a hydrodesulphurization catalyst at a temperature in the range 200° C. to 350° C., preferably in the range 250° C. to 320° C. and at a pressure in the range 1 to 3 MPa, preferably in the range 1.5 to 2.5 MPa.
• the liquid space velocity is generally in the range 1 h ⁇ 1 to 10 h ⁇ 1 , preferably in the range 2 h ⁇ 1 to 5 h ⁇ 1 ;
• the H 2 /HC ratio is 50 litres/litre (l/l) to 500 l/l, preferably in the range 100 l/l to 450 l/l, and more preferably in the range 150 l/l to 400 l/l.
• the H 2 /HC ratio is the ratio between the hydrogen flow rate at 1 atmosphere and at 0° C. and the hydrocarbon flow rate. Under these conditions, the reaction takes place in the gas phase.
• the operating conditions during this step are adjusted as a function of the characteristics of the feed to be treated, to accomplish the desired degree of desulphurization.
• the effluents from said hydrodesulphurization step are partially desulphurized gasoline, residual hydrogen and the H 2 S produced by decomposition of the sulphur-containing compounds.
• the catalysts used during step e) comprise at least one group VIII element and/or at least one group VIB element on a suitable support.
• the amount of group VIII metal, expressed as the oxide, is generally in the range from 0.5% to 15% by weight, preferably in the range 1% to 10% by weight.
• the amount of group VIB metal is generally in the range 1.5% to 60% by weight, preferably in the range 3% to 50% by weight.
• the group VIII element, when present, is preferably cobalt, and the group VIB element, when present, is generally molybdenum or tungsten.
• the catalyst support is normally a porous solid such as an alumina, a silica-alumina, or other porous solids, such as magnesia, silica or titanium oxide, used alone or as a mixture with alumina or silica-alumina.
• a catalyst in which the density of the molybdenum, expressed as the % by weight of MoO 3 per unit surface area, is more than 0.07 and preferably more than 0.10.
• the catalyst of the invention preferably has a specific surface area of less than 200 m 2 /g, more preferably less than 180 m 2 /g, and highly preferably less than 150 m 2 /g.
• the catalyst used is preferably in an at least partially sulphurized form.
• the sulphur or sulphur-containing compound can be introduced ex situ, i.e., outside the reactor in which the process of the invention is carried out, or in situ, i.e., in the reactor used for the process of the invention.
• Sulphurization consists of passing a feed containing at least one sulphur-containing compound, which once decomposed fixes sulphur on the catalyst.
• This feed can be gaseous or liquid, for example hydrogen containing H 2 S, or a liquid containing at least one sulphur-containing compound.
• Hydrodesulphurization step e) can be followed by a supplemental step aimed at improving the final degree of desulphurization. This step is compulsory after step e) and can be carried out with or without intermediate H 2 S elimination.
• Step f) comprises at least one step for decomposing saturated sulphur-containing compounds deriving from step e). Said sulphur-containing compounds are transformed into H 2 S over a catalyst and under conditions such that the olefins are only very slightly hydrogenated.
• the degree of hydrogenation (saturation) of olefins in this step is generally less than 20%, and preferably less than 10%.
• This hydrodesulphurization step (step f)) generally consists of passing the gasoline to be treated, in the presence of hydrogen, over a hydrodesulphurization catalyst, at a temperature in the range 250° C. to 450° C., preferably in the range 300° C. to 360° C. and at a pressure in the range 1 to 3 MPa, preferably in the range 1.5 to 2.5 MPa.
• the liquid space velocity is generally in the range 1 h ⁇ 1 to 10 h ⁇ 1 , preferably in the range 1 h ⁇ 1 to 5 h ⁇ 1 ; the H 2 /HC ratio is in the range 50 litres/litre (l/l) to 500 l/l, preferably in the range 100 l/l to 450 l/l, and more preferably in the range 150 l/l to 400 l/l. Under these conditions, the reaction takes place in the gas phase. The operating conditions during this step are thus adjusted as a function of the characteristics of the feed to be treated in order to reach the desired degree of desulphurization.
• the catalyst used during step e) comprises at least one group VII element selected from the group constituted by nickel, cobalt, iron, molybdenum and tungsten.
• the amount of group VIII metal, expressed as the oxide, is generally in the range 1% to 60% by weight, preferably in the range 1% to 40% by weight.
• the catalyst support is normally a porous solid such as an alumina, a silica-alumina or other porous solids such as magnesia, silica or titanium oxide, used alone or as a mixture with alumina or silica-alumina.
• the catalyst of the invention preferably has a specific surface area in the range 25 to 350 m 2 /g.
• the catalyst is preferably at least partially in the sulphurized form.
• the sulphur or a sulphur-containing compound can be introduced ex situ, i.e., outside the reactor in which the process of the invention is carried out, or in situ, i.e., in the reactor used for the process of the invention.
• Sulphurization consists of passing a feed containing at least one sulphur-containing compound, which once decomposed fixes sulphur on the catalyst.
• This feed can be gaseous or liquid, for example hydrogen containing H 2 S, or a liquid containing at least one sulphur-containing compound.
• Example 1 in accordance with the prior art
• Example 2 in accordance with the invention.
• Example 1 concerns a desulphurization process with no preliminary nitrogen elimination.
• a hydrodesulphurization catalyst A was obtained by impregnating a transition alumina in the form of beads with a specific surface area of 130 m 2 /g and with a pore volume of 1.04 ml/g, with an aqueous solution containing molybdenum and cobalt in the form of ammonium heptamolybdate and cobalt nitrate. The catalyst was then dried and calcined in air at 500° C. the amount of cobalt and molybdenum in this sample was 3% of CoO and 10% of MoO 3 .
• the treated feed was a catalytically cracked gasoline with an initial boiling point of 50° C. and an end point of 225° C.
• the sulphur content was 1450 ppm by weight and its bromine index (BrI) was 69 g/100 g.
• This gasoline had a nitrogen content of 180 ppm of nitrogen including 165 ppm of basic nitrogen (the term “basic nitrogen” means the nitrogen included in compounds comprising a nitrogen-containing group with a basic nature).
• the total nitrogen was assayed using American standard method ASTM 4629, and the basic nitrogen was assayed using ASTM 4739.
• Example 2 was carried out in accordance with the invention, i.e., most of the basic nitrogen-containing compounds were eliminated during an acid washing step carried out prior to desulphurization.
• Example 2 The feed that was treated was the same as that of Example 1.
• This gasoline contained 180 ppm of nitrogen, including 165 ppm of basic nitrogen.
• 50 kg of this gasoline was mixed, in a batch reactor, with 100 kg of a 10% by weight concentrated sulphuric acid solution in distilled water. The mixture was stirred for 15 minutes then allowed to settle. The aqueous phase in the lower portion of the reactor was drawn off. The remaining gasoline was washed with 50 kg of distilled water. After settling, the water was separated from the gasoline.
• Example 1 The reactor used in Example 1 was charged with fresh catalyst A and sulphurized using the same procedure as that described in Example 1.
• Example 2 This feed was treated over catalyst A, at a pressure of 2 MPa, a H 2 /HC ratio of 300 l/l and a HSV of 2 h ⁇ 1 .
• the operating conditions applied in Example 2 were identical to the operating conditions of Example 1.
• Table 2 shows the influence of temperature on the degrees of olefin desulphurization and saturation.
• Sulphur content BrI of in desulphurized Degree of desulphurized Degree of olefin Temperature gasoline desulphurization gasoline saturation o (° C.) (ppm by weight) (HDS-%) (g/100 g) (HDO-%) 280 160 89.0 48.2 30.1 290 97 93.3 43.1 37.5 300 59 95.9 37.4 45.8

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• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

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• 2002
  • 2002-06-07 FR FR0207054A patent/FR2840620B1/fr not_active Expired - Fee Related
• 2003
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  • 2003-06-06 BR BR0301675-7A patent/BR0301675A/pt not_active Application Discontinuation
  • 2003-06-06 JP JP2003162438A patent/JP4834285B2/ja not_active Expired - Fee Related
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