EP0069943B1 - Hydrocarbon-hydrogenation process - Google Patents

Abstract

Unsaturated hydrocarbons and mixtures in which the latter are present are treated with anion exchangers prior to hydrogenation and are then hydrogenated catalytically in a known manner. The treatment with anion exchangers is carried out at 0 DEG -120 DEG C. and at a space velocity of 0.1 to 10 l of hydrocarbons to be hydrogenated per l of exchanger, per hour. The process avoids other, energy-intensive pretreatments, for example distillation of the hydrocarbons to be hydrogenated, or washing, and can be carried out in simple equipment. A considerable prolongation of the catalyst operating time is achieved in the subsequent catalytic hydrogenation.

Description

The invention relates to a process for the hydrogenation of unsaturated hydrocarbons, in which these unsaturated hydrocarbons are treated with anion exchangers before a catalytic hydrogenation known per se.

In the hydrogenation of olefinic, diolefinic or acetylene-containing hydrocarbon fractions, progressive poisoning and deactivation of this catalyst occurs due to the deposition of impurities or the formation of polymers on the catalyst, which leads to relatively short catalyst service lives. This is particularly true for the selective hydrogenation of diolefinic cracked gasoline fractions, which occur, for example, in the production of ethylene by cracking naphtha, gas oils, etc.

Various processes for the selective hydrogenation of these cracked gasoline fractions and their pretreatment before use in this partial hydrogenation are known (Asinger, the Petrolchemical Industry, Akademie-Verlag Berlin, p. 618 ffl. These include thermal pretreatments, separation of polymers by distillation, washing of polymers from the hydrogenation catalyst by using trickle phases or liquid phase hydrogenations, partially hydrogenated hydrocarbon streams being recycled, the general improvement of the hydrogenation catalytic converters.These processes achieve catalyst service lives of a few months to a year and only occasionally even longer, but this requires a relatively high amount of pretreatment , for example a high energy expenditure in the separation of polymers by distillation and a high investment expenditure in the return of hydrogenated product streams.

The hydrogenation of acetylene-containing or also olefinic hydrocarbons also leads, through the formation of polymers and the impurities contained, to the coating of the catalyst surface or to the poisoning of the catalyst and thus to unsatisfactory catalyst service lives. For example, in the hydrogenation of the dimers and oligomers of the C ₃ and C ₄ olefin oligomerization, only catalyst service lives of a few months are achieved.

Our own experiments, with intimate mixing of the hydrocarbon fraction to be hydrogenated with an alkaline aqueous solution as pretreatment before the actual hydrogenation, did not lead to any significant improvement in the catalyst service life.

It is therefore completely surprising that treating the unsaturated hydrocarbons intended for the hydrogenation with an anion exchanger results in a considerable increase in the catalyst life.

Accordingly, a process for the hydrogenation of hydrocarbons was found, which is characterized in that unsaturated hydrocarbons and hydrocarbon mixtures from cracker fractions with anion exchangers at a temperature of 0 to 120 ° C., a pressure

from 1 to 100 bar and a space velocity (LHSV) from 0.1 to 10 1 hydrocarbons per 1 exchanger and then catalytically hydrogenated in a known manner.

The anion exchangers which can be used according to the invention can be natural or synthetic, inorganic or organic anion exchangers. Examples of natural or artificial inorganic anion exchangers are: natural or artificial scapolites or hydroxylapatites, iron oxide gels, carbon anion exchangers such as ammonium carbons, clay minerals, insoluble salts, such as phosphates, zirconium oxide hydrates, aluminum oxide and others.

Examples of organic anion exchangers are gel or macroporous styrene / divinylbenzene resins, condensation resins made from phenols and formaldehyde, cellulose anion exchangers with the functional group -OC _z H ₄ N (C ₂ H ₅ ) ₂ or -OCH ₂ C ₆ H ₄ NH ₂ or another strongly basic functional group, called (meth) acrylic resins or epichlorohydrin / polyamine condensates.

All of these resins are cross-linked and thus made insoluble. Instead of the divinylbenzene crosslinker mentioned, it is also possible, for example, to use trivinylbenzene or trivinylcyclohexane. The crosslinker is generally present in an amount of about 0.3 to 80% by weight, preferably 1 to 65% by weight, particularly preferably 2 to 50% by weight, based on the total amount of the comonomers. Anion exchangers with one of the matrices mentioned contain, for example, quaternary ammonium groups -NH ₃ ⁺ , such as -N (CH ₃ ) ₃ ⁺ or -N (CH ₃ ) ₂ CH ₂ CH ₂ OH ⁺ , or tertiary amino groups -NR ₂ , as functional groups -N (CH ₃ ) ₂ . The matrices can also carry alkylene amine or imino groups or unsubstituted amino groups. Anion exchangers of the types described have, for example, total capacities for ion exchange of about 0.5 to 6 val / P resin. Such described anion exchangers and their recovery or production processes have long been known (Houben-Weyl, Methods of Organic Chemistry, Volume 1, page 256; F. Helfferich, Ion Exchange, Mc-Graw-Hill, Book Company, New York 1962 ).

Anion exchangers, in particular synthetic organic anion exchangers, are available in many variations and in a large number of types as commercial products from many manufacturers. Such anion exchangers can be used individually or as a mixture of several.

According to the invention, synthetic organic anion exchangers are preferably used. Anion exchangers which have a matrix of styrene / divinylbenzene and have a gel-like or macroporous structure are used in a particularly preferred manner.

The anion exchangers mentioned can be loaded with various ions, for example with hydroxyl, chloride, bromide, sulfate, acetate or formate ions. Mixtures of different ion exchangers which are loaded with various of the anions mentioned by way of example can also be used. Mixtures of the same anion exchanger can also be used which the resin particles present in the mixture are loaded with various of the anions mentioned by way of example. Finally, it is also possible to use anion exchangers which, as a result of partial loading with salts of the various anions mentioned as examples, contain different anions in a resin particle. Anion exchangers or mixtures of anion exchangers are preferably used in which hydroxyl ions are present as an anion, in whole or in part, on different resin particles or on the same resin particle, optionally in addition to one or more other anion (s). For example, a proportion of at least 10%, preferably at least 50%, particularly preferably 100% hydroxyl ions, based on the total number of anions, may be mentioned.

Unsaturated hydrocarbons which are treated according to the invention include olefinic, diolefinic or acetylenic hydrocarbons, or hydrocarbons which contain one or more acetylenic bonds in addition to one or more olefinic bonds. Such unsaturated bonds can be either terminal or non-terminal. Such hydrocarbons can also be used as a pure substance fraction, as a mixture with one another or as a mixture with other substances. Such other substances can be, for example, saturated hydrocarbons, hydrogen, carbon monoxide, carbon dioxide, nitrogen or noble gases. Unsaturated or saturated hydrocarbons that can be treated according to the invention can be either branched or straight-chain. Their chain length is not critical for the implementation of the method according to the invention. A chain length of 2 to 30, preferably 2 to 24, carbon atoms may be mentioned by way of example. Examples of such hydrocarbons and hydrocarbon mixtures mentioned are fractions such as those formed during the cracking of various cracking feedstocks or are produced from them, further fractions such as those obtained in the selective hydrogenation of cracking gasoline and cracking gasoline fractions, and furthermore fractions such as those used in the oligomerization of C ₃ - and / or C ₄ -olefins or olefin fractions with the aid of acidic catalysts. The process according to the invention is preferably carried out by using such cracking fractions and oligomerization products with unsaturated bonds, which may also contain paraffins, naphthenes and / or aromatics as mixture components.

The inventive method is conducted at a temperature of for example 0 to 120 ° C, preferably 10 to 50 ° C, particularly preferably from 20 bar to 30 ⁰ C and at a pressure of 1 to 100, preferably 1 to 15 bar, particularly preferably 1 to 5 executed in cash. When carrying out the process according to the invention, the hydrocarbons to be treated are at least partially in the liquid phase, for example at least 30%, preferably at least 80%, particularly preferably completely, based on the total amount of the hydrocarbons or the mixture proportions.

To carry out the process according to the invention, the hydrocarbons from. be driven upwards or downwards through a bed of the anion exchange particles. Here, the anion exchange particles can be arranged in a fixed bed, floating bed or in a fluidized bed. The apparatus to be used to carry out the process according to the invention can be very simple, such as a cylindrical reactor without internals. Of course, the anion exchanger can also be used in different beds, which are arranged, for example, on different bottoms of a cylindrical reactor. Further, between two such beds each distributor plates to secure Stel _- Lung be located a uniform wetting of the different beds of anion exchanger.

The process according to the invention can be applied in the same way and with the same advantage to unsaturated hydrocarbons or the abovementioned mixtures which are then to be subjected to a selective hydrogenation or a full hydrogenation.

The bed of anion exchangers is filled with the unsaturated hydrocarbon to be treated or one of the mixtures mentioned with a space velocity LHSV (Liquid Hourly Space Velocity) of 0.1-10, preferably 0.5-5, particularly preferably 1-2 f hydrocarbons per f exchanger loaded per hour.

After treatment with an anion exchanger, the unsaturated hydrocarbons or the abovementioned mixtures are subjected to catalytic selective hydrogenation or full catalytic hydrogenation in a known manner. The conditions for such a hydrogenation are known to the person skilled in the art. For example, 1 to 10 moles of hydrogen are used per mole of the double or triple bond to be hydrogenated. For example, it is carried out at 10 to 350 ° C and 1 to 200 bar. Examples of hydrogenation catalysts are noble metal catalysts such as palladium or platinum, Raney catalysts such as Raney nickel, Raney cobalt, Raney iron or mixtures of such Raney catalysts, optionally with the addition of promoters, or sulfidic hydrogenation catalysts such as cobalt sulfides, nickel sulfides, molybdenum sulfides or Mixtures of these, called. In a known manner, such hydrogenation catalysts can be used as such or in combination with an inert support. As inert carriers are SiO _z , A1 ₂ 0 ₃ , burnt MgO, carbonates such as CaC0 ₃ or BaC0 ₃ , sulfates such as BaS0 ₄ or activated carbon. Such a catalytic hydrogenation can be carried out, for example, in the gas phase, the trickle phase or the liquid phase with a solid or suspended catalyst.

When using the process according to the invention, all previously known processes for pretreating the hydrogenation material with the aim of increasing the catalyst service life can be dispensed with. In comparison with the previous pretreatment processes, a significant increase in the Catalyst service life achieved. For example, in the selective hydrogenation of pyrolysis gasoline using the process according to the invention, the catalyst service life is at least doubled. Likewise, the treatment of oligomers of the C ₃ and C ₄ oligomerizations before the full hydrogenation leads to a considerable, for example a 2- to 5-fold increase in the catalyst service lives.

The method according to the invention is energetically and thus financially cheaper than previously known pretreatment methods. For example, the elimination of the energy-consuming and thus expensive distillation of the hydrogenation product should be mentioned.

The process according to the invention can be carried out in a simple and inexpensive apparatus and thus, in contrast to many previously conventional pretreatment processes, requires only a small investment.

Finally, due to the longer catalyst downtimes, many of the operational downtimes that were previously necessary can be eliminated.

Examples

The treatment according to the invention is explained in connection with the hydrogenations described below.

a) Examples of the selective hydrogenation of cracked petroleum fractions

The hydrogenation equipment consisted of: insert piston pump, preheater, hydrogenation reactor, cooler and separator. VA reactors, inner diameter 15 mm, length 700 mm with electric heating or with double jacket were used as hydrogenation reactors. The lower half of the reactor (about 340 mm in length, corresponds to 60 m! Catalyst) was filled with a Pd catalyst on Al ₂ O ₃ . The reactor room above was filled with Al ₂ O ₃ balls and served as an additional preheater.

The hydrogenation was carried out in the trickle phase with a hydrogen obtained in cracking plants with approx. 15% CH ₄ at 26 bar and an LHSV (Liquid Hourly Space Velocity) of 5. The bromine number (g Br _z / 100 g) of the hydrogenated product was used as the criterion for the hydrogenation performance. The product used was pyrolysis gasoline, which was to be selectively hydrogenated to a diene number of at most 1. This corresponds to a result of comparison measurements a reduction of the bromine number to 40-45 g _Br2 / 100 g. When determining the service life of the catalyst, the inlet temperature was raised from 30-60 ° C. to 110-160 ° C., depending on the hydrogenation activity, the catalyst being considered deactivated if the temperature exceeded 100 ° C.

Example 1 (for comparison)

Untreated pyrolysis gasoline was used, as described above, for the selective hydrogenation of the diolefins. The catalyst contained 5 g Pd / f on Al ₂ O ₃ , impregnated only on the surface. Fresh hydrogen was added to the reactor as exhaust gas was removed. The amount of exhaust gas was 200 ℓ / h. The hydrogenation was started at an inlet temperature of 60 ° C. The bromine number rose after 5 days of operation to over 50 g Br _∋ / 100 g, whereupon the inlet temperature had to be raised several times by 10-15 ° C. After a running time of 6 weeks, the inlet temperature of 110 ° C was exceeded. During the entire period were almost without exception only bromine numbers> 50 g Br ₂ / g reaches 100th

The bromine numbers and inlet temperatures over the term are summarized in Table 1:

Example 2 (for comparison)

Like example 1, noble metal catalyst, 5 g Pd / run Al ₂ O ₃ , but soaked. As in Example 1, the inlet temperature had to be raised several times by 10-15 ° C after a week of running. After a running time of approx. 4 weeks, the inlet temperature of 110 ° C was exceeded.

The bromine numbers and inlet temperatures over the term are summarized in Table II:

Example 3 (for comparison)

Like example 1, but distilled pyrolysis gasoline was used in the hydrogenation. The inlet temperature was initially 60 ° C, but the amount of exhaust gas and thus the amount of fresh hydrogen had to be throttled to 30 ℓ / h due to the high initial activity. It had only reached the "normal amount" of 200 ℓ / h due to the equipment after about 6 weeks. Analogous to Examples 1 and 2, the inlet temperature had to be gradually increased by 10-1 5 ° C, but the time intervals were considerably longer. The experiment was terminated after 15 weeks g at an inlet temperature of 100 ° C and a bromine number of 47 g _Br2 / 100.

The bromine numbers and inlet temperatures over the term are summarized in Table III:

Example 4

As in example 3, but undistilled pyrolysis gasoline was used, which had previously been pretreated using an anion exchanger. This anion exchanger pretreatment takes place in a fixed bed reactor at 20 ° C practically without pressure using an ion exchange mixture consisting of a part of weakly basic, macroporous ion exchanger based on polystyrene in the OH form (Bayer Lewatit MP 62) and a part of strongly basic gel-like ion exchanger Polystyrene base in the CI 'form (Bayer Lewatit M 500). The pretreatment reactor consisted of a glass tube 350 mm long and 35 mm wide and was completely filled with the anion exchange mixture.

Due to the high initial activity, the amount of exhaust gas had to be reduced to approx. 40 ℓ / h and the inlet temperature to 30 ° C. After about 4 weeks, the inlet temperature was raised to 40 ° C. After 20 months of operation, the amount of exhaust gas was still 120 V / h instead of the “normal amount” of 200 ℓ / h caused by the apparatus. After 20 weeks running, the inlet temperature was still 40 ° C, the bromine numbers varied between 38 to 45 g of Br _2/100 g, however, were generally at about 40 g Br _z / 100 ml.

b) Examples of the full hydrogenation of olefinic oligomer fractions

The hydrogenation equipment consisted of: insert piston pump, preheater, hydrogenation reactor, cooler and separator. VA reactors, 25 mm inside diameter, 700 mm length, with double jacket were used as hydrogenation reactors. The reactors were filled with 400 ml of catalyst. The free space above was filled with AI ₂ 0 ₃ balls. These served simultaneously as a liquid distributor and as an additional preheating zone.

The hydrogenation was carried out in the trickle phase with a trimer from a C ₄ oligomerization (isododecene) as the starting product and with a hydrogen obtained in cracking plants with approx. 15% methane at 26 bar and an LHSV of 1.5. The feed was preheated to 180 ° C and hydrogenated at a reactor temperature of 220 ° C. The criterion for the hydrogenation performance, the bromine number (g _Br2 / 100 g) serving of the hydrogenated product. A bromine number of 0.1 g _Br2 / 100 g was regarded as the limit of the product specification, and exceeding this limit value was considered as deactivation of the catalyst.

Example 5 (for comparison)

As previously described, untreated isododecene was used to fully hydrogenate the olefins in the hydrogenation apparatus. The catalyst contained 18 g Pd / ℓ on A1 ₂ 0 ₃ , impregnated only on the surface. Fresh hydrogen was added to the reactor as exhaust gas was removed. The amount of exhaust gas was 200 i / h.

The course of the bromine number over the catalyst runtime is summarized in the following table:

Example 6

As in Example 5, but the isododecene feed was treated with an anion exchanger before entering the hydrogenation. This anion pre-cleaning was carried out in a fixed bed reactor at 20 ° C practically without pressure using an anion exchange mixture consisting of a part of weakly basic, macroporous ion exchanger based on polystyrene in the OH form (Bayer Lewatit MP 62) and a part of strongly basic, gel-like ion exchanger based on polystyrene in the CI 'form (Bayer Lewatit M 500).

Gegenüber Beispiel 5 ist eine erhebliche Verlängerung der Katalysatorlaufzeit durch die Behandlung des Einsatzproduktes mit Anionentauscher erreicht worden.The reactor consisted of a glass tube 350 mm long and 35 mm wide and was completely filled with the anion exchange mixture.

Compared to Example 5, a considerable increase in the catalyst runtime has been achieved by treating the feed product with an anion exchanger.

Claims (7)

1. Process for the hydrogenation of hydrocarbons, characterised in that hydrocarbons and hydrocarbon mixtures consisting of cracked fractions are treated with anion exchangers at a temperature of 0 to 120°C, under a pressure of 1 to 100 bars and at a space velocity (LHSV) of 0.1 to 10 f of hydrocarbons per ℓ of exchanger and are then hydrogenated catalytically in a known manner.

2. Process according to claim 1, characterised in that the anion exchangers used are those having a matrix composed of styrene/divinylbenzene and a gel or macroporous structure.

3. Process according to claim 1 and 2, characterised in that it is carried out at 10 to 50°C.

4. Process according to claim 1 to 2, characterised in that it is carried out at 20 to 30°C.

5. Process according to claims 1 to 4, characterised in that mixtures which contain unsaturated hydrocarbons and originate from cracking plants are used.

6. Process according to claims 1 to 4, characterised in that mixtures which are obtained by partial hydrogenation and contain unsaturated hydrocarbons, are used.

7. Process according to claims 1 to 4, characterised in that mixtures which are obtained by catalytic oligomerisation of C₃ and/or C₄ olefines and which contain unsaturated hydrocarbons, are used.