FR2460989A1 - PROCESS FOR PURIFYING A CUTTING OF AROMATIC HYDROCARBONS CONTAINING OLEFINIC AND ACETYLENE UNSATURATED HYDROCARBONS - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR PURIFYING A CUP OF AROMATIC HYDROCARBONS CONTAINING UNSATURE, OLEFINIC, POLYOLEFINIC AND ACETYLENIC HYDROCARBONS. THE INVENTION IS CHARACTERIZED IN THAT THE CUTTING OF AROMATIC HYDROCARBONS IS TREATED WITH HYDROGEN IN THE PRESENCE OF A CATALYST WITH THE SUPPORTED PALLADIUM, WHICH CATALYST, PRIOR TO ITS USE, HAS BEEN SUBJECT TO A TREATMENT BY AT LEAST ONE COMPOUND OR DERIVED FROM AT LEAST ONE ELEMENT CHOSEN FROM SULFUR, SELENIUM AND TELLURUS. THE INVENTION APPLIES IN PARTICULAR TO THE SELECTIVE HYDROGENATION OF A CUP FROM A REACTION OF CATALYTIC HYDROCARBON FLAVORING.

Description

The object of the present invention is to eliminate it by a treatment

  appropriate, undesirable products that may contain a hydrocarbon fluid

  and more precisely to eliminate a hydrocarbon fraction, very rich sn hy-

  aromatic hydrocarbons, the unsaturated constituents that it may contain, that is to say the monolefinic, polyolefinic and acetylenic hydrocarbons. Indeed, many hydrocarbon fractions very rich in aromatic compounds (benzene, toluene, xylenes, etc.) obtained by one of the various thermal or catalytic processes usually used to produce them, contain significant amounts of unsaturated products which

  are unstable and are thus producers of gums with appearance of colo-

  ration, these gums, and these colorations strongly devaluing these aromatic compounds. It is therefore necessary to subject to a treatment (to eliminate unsaturated compounds devaluing aromatic hydrocarbons) these cuts

  hydrocarbons very rich in aromatic hydrocarbons; these cuts in general

  ral; come from a catalytic reforming (or reforming) or come from a catalytic or non-catalytic aromatization reaction (for example reactions of

  production of aromatic hyrylococci from saturated or unsaturated essences

  and the "Aromising" type); these cuts can also prevent: z. steam cracking, cracking

  (cracking), the distillation of coal, etc.

  It's not so precise. the. cuts very rich in aromatics ob-

  For example, in the course of the aforesaid reactions, that is to say, in the case of severe treatments, they always contain, because of the high temperatures to which they have been subjected during such treatments, more or less of olefinic, diolefinic and also acetylenic products. And we know that these unsaturated products have te-dance to polymerize Joui, ioauire gums and resins that color and don.Lt

  l) odors to these oupe. rich in aromatic hydrocarbons, with

  sequence, devaluation of these cuts because they will no longer be used

  the petrochemical industry and could only be used as fuel

  ble. Aromatic hydrocarbons are very

  because they are essential to the development of organic chemistry.

than industrial.

  Basic arimatques, for example benzene, toluene,

  thoxylene and paraxylene, especially from petrol-catalyzed reforming

  lytic or from steam cracking species or from

  aromatization reactions (for example "aromizing") or from distilla-

  coal, etc., are intended for the manufacture of products such as plastics, detergents, cottons and fibers.

  Synthetics, etc. Aromatic hydrocarbons are used in the manufacture of

  such products after chemical transformations very often

  such as oxidation, alkylation, hydrogenation,

hydrogenation, etc.

  Thus, benzene is very widely used for the manufacture of ethylbenzene, itself intended to be converted into styrene monomer in the production of polystyrene and SBR rubber. Other uses of the

  benzene, apart from substantially equal, are the synthesis of cumene and the manufacture of

  cation of cyclohexane. Cumene leads to the manufacture of phenol and

  plastics derived from it, cyclohexane

  of adipic acid and its derivatives, in the manufacture of nylons 6 and 66. Benzene is also used for the manufacture of alkylbenzenes.

  much of which is used for the manufacture of detergents.

  For its part, toluene is used for classical synthesis and

  mainly for the manufacture of toluene diisocyanate,

  for the preparation of polyurethanes) and for the manufacture of

  phenol by oxidation of toluene.

  The xylenes, as a mixture, can be used as a solvent, in the same way as toluene. They are also used partly in the preparation

  pure xylenes, and partly as a fuel mixed with other hy-

  hydrocarbons to improve the octane number. Of the three isomers of xy-

  lene (ortho, meta and para), the most important is paraxylene, which is used to manufacture polyester fibers. Orthoxylene is almost completely

  converted into phthalic anhydride, which serves as a raw material for

  cation of the polyester resins. The third isomer, metaxylene, is

  folded for the manufacture of certain resins and additives.

  These aromatic hydrocarbons, to be used properly,

  must include specifications which guarantee their purity but

  all must not contain certain undesirable products that contaminate them, even though these products are present at very low levels, contents generally so low as the various physical methods of separation

  that exist are ineffective in eliminating them.

  As indicated above, these impurities are generally constituted by unsaturated hydrocarbons, that is to say by olefins, diole-

  fine and polyolefins as well as by acetylenic hydrocarbons, etc ...

  These hydrocarbon molecules, under the action of oxygen in the air or under the action of light, etc ...., polymerize producing gums which in particular color the aromatic hydrocarbons at the expense of their value

Merchant.

  The oldest known method for eliminating unwanted products

  cuts rich in aromatics, is the washing treatment of

  hydrocarbons with sulfuric acid.

  This way of proceeding has the disadvantage of causing losses

  of the product being treated: indeed, sulfuric acid is not only

  causes the polymerization of unsaturated products, but also provokes

  sulphonation of aromatic hydrocarbons, and consequently

  products of excellent market value.

  It has therefore quickly appeared necessary to replace this "barbaric" acid treatment with other more selective processes and in particular with selective hydrogenation processes; but these hydrogenation processes, which convert olefinic and diolefinic hydrocarbons into paraffins having the same number of carbon atoms as unsaturated hydrocarbons, do not

  are not sufficiently selective because there is also a slight

  generation of aromatic hydrocarbons. This hydrogenation is low and concerns only a small percentage of the aromatic hydrocarbons but nevertheless

  is sufficient to decrease the profitability of the operation. In addition,

  known selective hydrogenation processes do not solve the problem of hydrocarbons

  acetylenic res found in aromatic sections: acetylenic hydrocarbons cause a rapid deactivation of the catalysts used so far, due to the formation and deposition of polymers and a progressive dissolution of the active metal catalyst, especially more

  important that the acetylenic hydrocarbon content is greater.

  Thus, French Patent 1,502,462 shows that even in the case of a relatively low content of acetylenic hydrocarbons charge, a palladium catalyst on calcined alumina has already lost a large part

  its activity and selectivity after only 7 days of use.

  The present invention aims to overcome these disadvantages; it has the particular object of proposing the use of catalysts which have an initial activity substantially equal to that obtained with palladium catalysts of known type, but which remain stable over time and lead to an improved selectivity compared to that obtained in art

  prior. It is observed that the content of palladium, a metal present in the cata-

  lyser, does not vary significantly over time. The use of

  According to the invention, it is possible to obtain a minimal and negligible hydrogenation.

  aromatic hydrocarbons of the section to be treated (which section

  at least 70% by weight of aromatic hydrocarbons) and makes it possible to obtain, on the other hand, the substantially total conversion of the monoethylenic, polyethylenic and acetylenic unsaturated hydrocarbons into saturated products, the percentage of these unsaturated hydrocarbons in the section being less than% by weight. and preferably less than 1%.

  In the present process, for the hydrogenation of the

  eg at least partly in the liquid phase, a palladium catalyst

  supported, the average crystallite size of which is at least 50 Angstroms.

  This size can be measured, for example, by electron microscopy. A

  Catalyst corresponding to this definition can be prepared for example by

  corporation of a palladium compound on a carrier at the rate of 0.1 to 5%

  weight of palladium relative to the support, followed by heating activation

  at 200 to 600 ° C, preferably 200 to 500 ° C, said heating being able to take place in a neutral atmosphere, for example in nitrogen, reducing, for example in hydrogen, or oxidizing, by example in a

  gas containing free oxygen. However, an oxidizing atmosphere is preferred.

  because it allows a particularly rapid formation of palladium crystallites. It can operate under any pressure, for example under the

normal pressure.

  The method of incorporation of the palladium compound may be

  conque, for example dry mixing or in the presence of water, or impregnation with a solution of a palladium compound. The palladium compound may be any of the known and / or proposed palladium compounds for analogous use, for example palladium nitrate, palladium chloride or palladium acetylacetonate. In some cases, other metals having

  a cocatalytic effect can be added.

  The use of activation temperatures lower than those indicated

  above leads to catalysts whose average crystal size

  lites is below 45 A; these catalysts lack stability.

  The support is preferably an alumina of specific surface area

  (before incorporation of palladium and before activation)

  between 1 and 250 m 2 / g, preferably between 25 and 150 m 2 / g, with a volume of

  porous me included, for example, between 0.4 and 0.8 cm3 / g, at least 75% of the porosity corresponding to pores of average diameter between 10 and 50

  nanometers. Another type of support is silica having a specific surface area

  that between 10 and 250 m / g (before incorporation of palladium). We pre-

  generally use a very weakly acidic catalyst. This low acidity is determined by the known ammonia adsorption test of the type described for example in "Journal of Catalysis, 2, 211-222 (1963)" the method consists in heating the catalyst at 600 ° C. under vacuum. (at a pressure less than about 0.01 mm of mercury) until total outgassing (this in particular to remove water and undesirable impurities); This catalyst is then placed in a calorimeter at 32 ° C. and an amount of ammonia is introduced such that the final pressure of the equilibrium system reaches 300 ° C.

  mm of mercury (40 kilo Pascal) and measure the amount of heat released.

  Preferred supports in the context of the present invention (alumina

  do not, in particular) have a heat of neutralization by adsorption of ammonia.

  niac less than 10 calories per gram at 3200C under 40 kilo Pascal (300 mm) mercury). It should be noted that the heat of neutralization of the support used in the catalyst is substantially identical to that of the catalyst itself and that, also, the specific surface area and the pore volume of the final catalyst are substantially identical to the values given above for the support.

himself.

  The catalysts just described above are selective

  but they still saturate a significant percentage of

  aromatic bures. Thus, it is appropriate according to the invention for the catalyst, before its use for the treatment of the aromatic hydrocarbon-rich fraction, to be subjected to the action of at least one compound of at least one selected group VI A element. among sulfur, tellurium and selenium. This

  treatment is carried out after activation of the catalyst, carried out as

  diqué above, after the incorporation of palladium on platinum. We know

  that, generally, the activation of a hydrocarbon conversion catalyst

  followed by a step of reducing the catalyst with hydrogen.

  In the process of the present invention, the treatment with a derivative of

  fre or tellurium or selenium can be performed either during the

  the catalyst, either before this reduction or again after

  duction. Finally, the catalyst can be subjected to no reduction but only

  only treatment with at least one derivative of sulfur, selenium or

tellurium.

  This treatment can also be carried out with selenium, sulfur or tellurium.

  after activation of the catalyst, first reducing the

  catalyst, then continuing the reduction at the same time as one proceeds

  treatment with the sulfur, selenium or tellurium derivative, and then

  finally continuing the reduction of the catalyst in the absence of the derivative of sulfur, selenium or tellurium. We can still consider, after treatment with

  at least one derivative of the element selected from sulfur, tellurium and se-

  lenium, a catalyst sweep with hydrogen under the conditions

  usually used to carry out the reduction of the catalyst.

  The treatment with at least one derivative of at least one element chosen from sulfur, tellurium and selenium is carried out between 0 and 450 ° C., preferably between 0 ° and 300 ° C., and is continued so that the final catalyst contains 0 , 01 to 2 atoms of sulfur, selenium or tellurium per atom

of palladium.

  The reduction reaction of the catalyst when it is carried out, and when it is carried out simultaneously or not with the treatment with the compound

  or derivative of sulfur, selenium or tellurium, is also conducted at a temperature of

  between 0 and 450C and preferably between 0 and 300C.

  Preferably, according to the process of the invention, the catalyst is

  subject to a reduction, at least part of the reduction step being

  performed at the same time as the treatment with the derivative of sulfur, selenium and tellurium, at a temperature between 0 and 450C, preferably between 0 and 300C. If the reduction has started before treatment with the sulfur, selenium and tellurium derivative and / or if the reduction continues after

  treatment with the sulfur, selenium and tellurium derivative, this reduction

  following and / or preceded treatment with the sulfur derivative, the selec-

  nium or tellurium is carried out at the same temperature as the temperature of

  said treatment. We can still proceed by starting the reduction of

  and then introducing into the hydrogen a derivative of sulfur, selenium or tellurium at a temperature which may be lower than the temperature

  reduction and then gradually increase the temperature.

  to reach that of reduction.

  The compounds that can be used for the elements sulfur, selenium and tellurium are chosen from hydrides, oxides, salts containing a volatile anion and organic derivatives. For example, hydrogen

  sulfide SH2, selenium hydrogen SeH2, tellurized hydrogen TeH2, mercaptan

  tans, sulphides and oxides of selenium and tellurium.

  As in a preferred manner, the treatment with at least one derivative of at least one element chosen from sulfur, selenium and tellurium is carried out at the same time as the reduction of the catalyst, the said derivative must preferably be gaseous. or must have sufficient vapor pressure to be

  in the gaseous state under the operating conditions chosen for the treatment.

  The concentration of the derivative in the hydrogen stream in which this derivative is found is between 0.01 and 5 mol% and preferably between 0.1.

and 47. molar.

  The preferred conditions for conducting, in the presence of the catalyst treated according to the invention, the selective hydrogenation of the fillers containing

  aromatic hydrocarbons and more particularly

  this of an "Aromizing", are the following:

  - Total pressure: 1 to 50 bar and preferably 3 to 30 bar.

  Temperature: 50 to 350 ° C. and preferably 10 to 250 ° C.

  - Space velocity: from 1 to 20 and preferably 1 to 10

  (volume of liquid charge / volume of catalyst / hour).

  - H2 / hydrocarbons molar ratio of 0.05 to 5 and preferably

this from 0.01 to 1.

EXAMPLE

  The charge to be processed comes from an "Aromizing". It has the following composition by weight: Aromatic

79.50%

  (Benzene) Toluene) Aromatic C8 Aromatic C (Aromatic C1O Olefins 0.40% (mono and polyolefins) Acetylenic naphthenes Paraffins

1.00%

0.10%

  19 Z - Other features Bromine Index (Index - cut 65-90 C

-115 C

134-147 ° C

147-180 ° C

  bromine): 2200 for the total product 8.200 4.300 Acid wash color (characterized by the presence of acetylenic hydrocarbons) - 65-90 ° C cut

-115 C

134-147 ° C

147-180 ° C

  A palladium catalyst was prepared by impregnating with a nitric solution of palladium nitrate an alumina support, in beads 2 mm in diameter, having a specific surface area of 100 m 2 / g.

  and a total pore volume of 0.58 cm3 / g, so as to obtain on the basis of

  finished, a percentage of palladium equal to 0.2% by weight.

  After having finished the impregnation, the catalyst is dried at 120.degree.

  2 hours and then calcine at 400 C for 2 hours under a

dry air.

1.40%

14.60 Z

, 10 Z

23 Z

, 40%

) 79.5%

)

(79.5%

  () ler test: Part of this catalyst is loaded in a reactor, where it is reduced with hydrogen containing 3 mol% of hydrogen

  sulfide at a temperature of 250 ° C for 2 hours.

  The charge to be treated is passed over the catalyst at a space velocity of 3 volumes of liquid charge per volume of catalyst and hour, the temperature of the reaction zone being

  of 1800C and the pressure of 25 bar, with a hydrous molar ratio of

  gene / hydrocarbon charge equal to 0.1 at the reactor inlet.

  The products from the reaction zone are analyzed.

  The results obtained are presented in Single Table I,

  together with the results from the 2nd test below.

  2nd test Another part of the catalyst is charged to a reactor where it is reduced with pure hydrogen containing no sulfur, selenium or tellurium derivative, at 2500 for 2 hours. We

  passes the load to be treated defined above on this catalyst.

  under the same operating conditions as for the first test.

  The results are given in Single Table I.

TABLE I

  Weight composition in% Load test 2nd test Total aromatics 79, 50 79.35 77.80 Benzene 1.40 1.35 1.15 Toluene 14.60 14.55 13.70 Aromatic C8 35.10 35.05 34 , 80 Aromatics in C9 23.00 23.00 22.80 Aromatic in C10 5.40 5.40 5.35 Olefins 0.40 trace traces Naphthens 1, 00 1.25 2.80 Acetylenic 0.10 0.00 0 , 10 Paraffins 19.00 19.40 19.40 Aromatic hydrocarbons consumed - 0.2% 2.1% Bromine index total product 2.200 75 80 Section 65-90 C 8.200 9 8 Section 105-115 C 4.300 14 15 Section 134- 147 C 350 20 - 20 Cut 147-180 C 110 25 30

Acid wash color

  acid cutting) Cup 65-90 C 6 0 1 Cup 105-115 C 8 O 1 Cup 134-147 ° C 8 0.5 2 Cup 147-180 C 13 1 4 b: -e il The results of the Table I highlight the interest of operating

  according to the present invention: the use of the presulfided catalyst according to

  minimizes the loss of aromatics by hydrogenation and

  here puts the substantially total elimination of acetylenic hydrocarbons.

3rd and 4th test:

  The first test is repeated by replacing, in the course of

  of the catalyst, hydrogen sulphide is either hydrogen or

  selenium in the third test, either with hydrogen

  lured in the 4th test. Thus, for the treatment

  load, substantially the same results as those obtained

  in the first test, with notably the elimination of

  total acetylenic hydrocarbons.

Claims (9)

REVENDIC & TION   1.- Process for the selective hydrogenation of a hydrocarbon fraction rich in hy-   aromatic hydrocarbons containing at least one unsaturated hydrocarbon selected from the group consisting of monoolefinic, polyolefinic and acetylenic hydrocarbons, wherein said at least partly liquid phase cutting and hydrogen are contacted by a supported palladium catalyst, the catalyst containing   0.1 to 5% by weight of palladium relative to the support, the said catalyst being   before being used in the selective hydrogenation process, by at least one compound or derivative of at least one   an element selected from sulfur, selenium and tellurium, at a time   between 0 and 400 ° C, so that the catalyst   closes 0.01 to 2 atoms of the chosen element per palladium atom.   2. A process according to claim 1, wherein the aromatic hydrocarbon fraction contains at least 70% by weight of aromatic hydrocarbons and contains less than 5% by weight of unsaturated hydrocarbons chosen from   monoolefins, polyolefins and acetylenic hydrocarbons.   3. The process according to claim 2, wherein the hydrocarbon fraction contains   closes less than 1% by weight of said unsaturated hydrocarbons.   4. The process according to claim 3, wherein the hydrocarbon fraction contains   closes both monoolefins, polyolefins and acetylenic hydrocarbons. 5. A process according to claim 4, wherein the treatment with at least one compound or derivative of at least one element selected from sulfur, selenium and tellurium is carried out at a temperature between 0 and 350 ° C, the compound or derivative of sulfur, selenium and tellurium being   selected from hydrides, oxides, salts containing an anion latil and organic derivatives.   6. A process according to claim 5, wherein said treatment is effected   killed in the presence of hydrogen, with a view to simultaneously reducing the   hydrogenation of the catalyst initially prepared by incorporation of palladium on a support, the compound or derivative of the element sulfur, selenium and tellurium being chosen from compounds or volatile derivatives or having a vapor pressure sufficient to be at the gaseous state under the operating conditions chosen, the molar concentration of said compound or derivative in the hydrogen stream being between 0.01 and 5%. The method of claim 6, wherein the molar concentration of said compound or derivative in the hydrogen stream is between 0.1 and 4%.   The process according to claim 7, wherein the support of the palladium catalyst is alumina with a specific surface area of between 1 and   250 m 2 / g, with a pore volume of between 0.4 and 0.8 cm 3 / g, 75% of the   rosity corresponding to pores with a mean diameter of between 10 and nanometers, the heat of neutralization of said alumina by adsorption of ammonia being less than 10 calories per gram at 320 ° C.   under 40 kilo Pascal, the average crystallite size of the said catalyst   being at least 50 Angstroms.   9. The process according to claim 8, wherein the sulfur compound,   lenium or tellurium is selected from hydrogen sulfide SH2, hydrogen   selenium SeH2 and tellurized hydrogen TeH2.