NO139384B - ANALOGICAL PROCEDURE FOR THE PREPARATION OF PHARMACOLOGICALLY ACTIVE PROPANEL DERIVATIVES - Google Patents

Description

Process for catalytic desulphurisation of hydrocarbon oils.

The invention relates to the catalytic desulfurization of hydrocarbon oils by bringing sulfur-containing hydrocarbon oils at elevated

temperature and in the presence of water vapor i

contact with a hydrogenation/dehydrogenation catalyst.

It is known to desulphurise hydrocarbon oils by contacting these oils with a

catalyst at elevated temperature and

pressure together with hydrogen. This process, known as hydrodesulfurization, suffers

due to the fact that the necessary hydrogen is in short supply and often expensive.

In this connection, it is further proposed that the necessary hydrogen is produced by, in a previous step, passing

the hydrocarbon oil to be desulphurised

a temperature above 450° C over a catalyst together with steam. The hydrogen

which was formed by the reaction of the hydrocarbon oil with steam is then used in a

second step for desulphurisation at a temperature below 450° C. This two-step process suffers from the shortcoming that

for desulphurisation, two separate reactors are needed, which are operated at different temperatures

temperatures.

Finally, it has been proposed to carry out the catalytic desulphurisation of the hydrocarbon oils without the use of free

hydrogen, as the hydrocarbon oils are carried

over a hydrogenation/dehydrogenation catalyst in the presence of steam at

a temperature between 350° and 450° C. One

However, a technical and financial shortcoming of the process is that it usually happens

rapid decrease in the activity of the catalyst

tet and as a result it must be regenerated after only a short period of operation.

It has now been found that the service life of the catalyst can be extended considerably by using a hydrogenation/dehydrogenation catalyst containing one or more alkali metal compounds.

The invention thus relates to a method for catalytic desulphurisation of hydrocarbon oils by contacting sulphur-containing hydrocarbon oils at elevated temperature and in the presence of water vapor with a hydrogenation/dehydrogenation catalyst. The method is characterized by the sulfur-containing hydrocarbon oil being contacted with a hydrogenation/dehydrogenation catalyst containing one or more alkali metal compounds, at temperatures in the range of 250° to 450° C.

Suitable hydrogenation/dehydrogenation catalysts are those that contain one or more metals from groups V-VIII in the periodic table, e.g. chromium, tungsten, molybdenum, manganese, iron, nickel and cobalt, if necessary in whole or in part in the form of their compounds with each other and/or one or more other elements such as oxygen and sulphur.

Particularly useful are catalysts which comprise at least one sulphide of an element from side group VI of the periodic table and at least one sulphide of metals from the group consisting of iron, nickel and cobalt. A combination of cobalt sulphide and molybdenum sulphide, which may be in the form of thiomolybdate, is preferably used. The catalytically active metal components are preferably placed on a carrier. Suitable carriers are, for example, natural and/or synthetic aluminum oxide-containing materials. These materials may also contain silicon oxide. Particularly useful are carriers which completely or practically consist of aluminum oxide, namely which contain 90% by weight. or more aluminum oxide.

According to the invention, the above-mentioned catalysts are used in combination with one or more alkali metal compounds. Particularly useful alkali metal compounds are the carbonates and/or compounds such as the hydroxides, which can easily be transferred to the corresponding carbonates. This transfer can be carried out by a special pre-treatment with carbon dioxide and/or by transfer during the desulphurisation process itself. In the latter case, it will usually be necessary to add carbon dioxide to the starting material as desulphurisation takes place simultaneously with the formation of carbon dioxide. The alkali metal carbonates can also be obtained by starting from such organic salts as formates and acetates. In the conventional production of catalysts, a calcination is usually carried out in the presence of air so that the organic salts are thereby transferred into the corresponding carbonates.

The alkali metal compounds are used in amounts from 18-20 wt. (calculated as carbonates) of the finished catalyst. Amounts of more than 15 wt.%, especially from 20 to 40 wt.%, are generally applicable.

Of the alkali metal compounds, those with lithium, sodium and potassium are particularly relevant. These compounds can either be used as such or in the form of mixtures, with or without other alkali metal compounds.

The alkali metal compounds can be incorporated into the catalyst in different ways. As a rule, any commonly used method can be followed. It can thus e.g. a method is used in which e.g. aluminum oxide as carrier material is impregnated with a solution containing a mixture of a cobalt and a molybdenum salt and of the alkali metal compound or compounds. The impregnated material is then dried and calcined, the salts being transferred to the corresponding metal oxides and/or carbonates, after this step the catalysts can be sulphided in a known manner, e.g. by passing over a mixture of hydrogen and hydrogen sulphide, carbon disulphide, butyl mercaptan etc.

The preparation of the catalyst is preferably carried out by dry mixing of particles of the various components. Good catalysts can be obtained, e.g. by finely grinding a cobalt-molybdenum catalyst placed on aluminum oxide and mixing the powder obtained with a powdered alkali metal compound such as e.g. water-free soda. The resulting mixture is, after any addition of a lubricating agent such as e.g. stearic acid or graphite, compressed into pellets that can be calcined and sulphided.

It should be noted that these alkali metal containing catalysts have been found to have both a longer service life and a better desulfurization activity than the corresponding catalysts containing no alkali metal compound or less than 10 wt. hence. This is shown in Ex. 1, 2 and 3 where Na2CO;.., Li2CO;J> and K,CO;J> respectively mixtures thereof are used as the alkali metal compounds in the hydrogenation/dehydrogenation catalyst for the desulphurisation of a technical xylene contaminated with thiophene. The same favorable effect appears from Ex. 4 which describes the desulphurisation of a kerosene fraction in approx. 200 hours without any appreciable decrease in activity for the Na 2 CO 2 -containing Co-Mo-Al 2 O 2 -catalyst.

It has been found that the particle size of the powdered components in the dry mixture is an important factor in the production of the catalysts. It has been found that, as a rule, catalysts are produced from particles smaller than the corresponding approx. 30 mesh sieve according to A.S.T.M. Standard Sieves more active than those made from coarser-grained powders. This is shown in the experiments described in Ex. 5.

It has further been found that it is unnecessary to combine the Co-Mo-Al20;:! catalyst and the alkali carbonate in a composite pellet. The same favorable results can be obtained by carrying out the desulphurisation in the presence of a mixture of Co-Mo-Al 2 O 2 catalyst particles and particles of alkali carbonate and/or particles of e.g. a carrier material such as aluminum oxide containing the required amount of alkali carbonate. As can be seen from the results of the experiments described in Ex. 6 leads to removal of the alkali carbonate particles, e.g. by sieving the catalyst mixture, immediately to a reduction in the activity of the Co-Mo-AUO.j catalyst, while on the other hand it appears that the catalyst's activity can be partially restored by adding the alkali carbonate particles again.

As the use of the catalyst in the form of fine particles can lead to an unwanted pressure drop under operating conditions with fixed beds ('fixed bed'), a catalyst prepared by mixing dry alkali carbonate powders with powdered Co-Mo-Al20,, catalysts and pelletizing this mixture.

It is noted that during the preparation of the catalysts according to the invention, the calcination step can be avoided. In those cases where this step is included, the calcination is carried out, if desired in the presence of air, at temperatures in the range from 100° to 800° C, preferably in the range from 400° to 600° C. As can be seen from Ex. 7, the desulfurization activity of a catalyst calcined at 650°C is considerably lower than the activity of a catalyst calcined at 500°C.

The catalysts according to the invention are applicable for the desulphurisation of hydrocarbon oils such as e.g. coal tar fractions, gasolines, kerosenes, gas oils and residual oils which may contain sulfur compounds of very different composition. It has been found that both acylic sulfur compounds such as mercaptans, sulphides and disulphides, which usually react quite well, and also the more stable cyclic sulfur compounds such as thiophene, benzothiophene and derivatives thereof are transferred.

In addition to the above-mentioned advantages, the high selectivity of desulphurisation should also be mentioned. This means that of the food mixture to be desulphurised, only the sulphur-containing molecules are reacted, as the hydrocarbon molecules remain intact. If it thus e.g. is assumed from a mixture of benzene and thiophene, practically only the thiophene is decomposed.

The process is carried out at temperatures in the range from 250° to 450° and in the presence of steam, the temperature range from 375° to 425° C being preferred. The ratio between the molar amounts of steam and hydrocarbon oil is determined based on, among other things, a., the oil's sulfur content. Usually 5-250 gram molecules of steam are used per grams of sulfur in the feed mixture.

As already stated, it has previously been proposed to use sulphur-containing hydrocarbon oils using hydrogen formed in an earlier process step by passing the hydrocarbon oil to be desulphurised at a temperature above 450° C together with steam over a catalyst.

The present method differs from the aforementioned processes not only in that desulphurisation takes place in one step but also in that the desulphurisation mechanism appears to be of a completely different nature. While desulphurisation in the hitherto well-known way is carried out by direct conversion with hydrogen, in the present process it takes place with the help of steam, presumably by some form of hydrolysis in which the water's OH groups take the place of the sulfur atom which is bound to the carbon atom and the free valence of the sulfur atom which is liberated in this way is desaturated with the remaining hydrogen atom in the water molecule.

This assumption of a different mechanism is supported by the experiments in Ex. 8 from which it appears from the desulphurisation of hydrocarbon oils in the presence of a Co-Mo-Al;)0;, catalyst by means of hydrogen is adversely affected if the catalyst also contains an alkali metal compound. In contrast, if the same alkali metal-containing catalyst is used with steam instead of hydrogen, the desulfurization is greatly improved. The theory that the desulphurisation mechanism does not take place by means of a direct conversion with hydrogen is further confirmed by the fact that when the hydrocarbon oil is passed over, for example, a Co-Mo-AlL)0.., catalyst together with steam at temperatures between 250° and 450° C , as used in the method according to the invention, hardly any hydrogen is formed. Larger amounts of hydrogen are only formed at temperatures above 450° C.

The process is carried out at a pressure that can vary from atmospheric pressure to 75 atm.abs. or more. It has been found that higher pressures have a favorable effect on the stability of the catalyst. The technical desulphurisation of hydrocarbon oils is therefore preferably carried out at a slightly higher pressure, e.g. 20 atm. abs. or more, and preferably in the range from 50-75 atm. abs.

The activity of the present alkali-containing catalysts will of course be reduced after longer use and this reduction appears to be greater as the hydrocarbon oil to be desulphurised has a higher boiling range. During the desulphurisation of gas oils and higher-boiling hydrocarbon oil fractions, the activity of the catalysts thus appears to decrease relatively quickly. As can be seen from the experiments described in Ex. 9, the activity is maintained much longer if the desulphurisation with steam is carried out at a higher pressure. Suitable pressure is in the range 70-150 atm.abs. For technical reasons, the pressures used in practical implementation for the latter case will not usually exceed 100 atm. abs.

The desulfurization reaction can be carried out in vapor phase, liquid phase, or partially in vapor and partially in liquid phase depending on the feed mixture to be desulfurized and the operating conditions.

The process is preferably carried out continuously. The fluid volume velocities can vary within wide limits. Typically, liquid-volume rates of between 0.25 and 4 kg of oil per liter of catalyst per hour.

The catalysts can be used in a fluidized or suspended state, but immobile catalyst layers are preferred. Due to the relatively low reaction temperatures, it is also possible for the hydrocarbon oils to remain completely, or almost completely, in the liquid phase during desulphurisation without requiring very high pressures. To carry out the desulphurisation in the liquid phase, the trickling technique described in e.g. British patent specification 657 521 particularly applicable. According to this technique, the hydrocarbon oil is passed over the catalyst in whole or in part in the liquid phase together with the water vapour.

Although the desulphurisation according to the invention can be carried out without the addition of hydrogen, if desired, a certain amount of hydrogen or hydrogen-containing gas, which in itself is insufficient for the considered desulphurisation, can be added to the supplied water vapour.

The process according to the invention is illustrated by means of the following examples.

Example 1.

The starting material was technically xylene contaminated with approx. 10 volume percent thiophene. This starting material was continuously introduced into the top of a tower equipped with an immobile catalyst layer, at a temperature of 400° C. and a pressure of 20 atm. abs. along with water vapor. The liquid volume rate was 0.44 kg of liquid starting material per liter of catalyst per hour, with 0.2 kg of water vapor per liters of starting material (9 grammol. H 2 O per gram atom S) was added. The reaction gases were cooled at the bottom of the tower and the liquid and gaseous components separated.

The base catalyst used was a commercially available cobalt-molybdenum catalyst placed on aluminum oxide (alumina) and which contained 3.9% by weight. cobalt oxide, 12.6 wt. molybdenum oxide, the rest being aluminum oxide. Starting from this catalyst, a number of catalysts with varying contents of sodium carbonate were produced. For this purpose, the Co-Mo catalyst was mixed in powder form with the required amounts of similarly powdered sodium carbonate and was then compressed to 3 x 3 mm by pelletizing after the addition of 1 wt. stearic acid. Before compaction, the powdered components passed a 40 mesh sieve (A.S.T.M. Standard Sieves). The pellets were calcined for 3 hours at 500° C in a muffle furnace in the presence of air and were finally sulphided by introducing hydrogen containing 10 volume percent hydrogen sulphide at atmospheric pressure and temperatures from 100° to 350° C.

In this way, catalysts were prepared which contained 1, 5, 10, 25, 50 and 75% by weight respectively. sodium carbonate.

The desulphurisation results of the experiments with these catalysts are given in Table I.

The achieved desulphurisation was determined after an operating period of 4-6 and 22-24 hours, respectively. By percentage desulphurisation it is meant here and in the following examples:

The stability of the catalyst is determined by the difference between the percentage desulphurisation after 4-6 hours and after 20-24 hours. The smaller this difference, the greater the stability. It has been found that in the presence of 10 wt. sodium carbonate in the catalyst, there is already a noticeable improvement in stability and that at 25 wt. there is no reduction in activity at all. The catalyst with 50 wt. sodium carbonate even showed an increased activity after 20-24 hours, while, on the other hand, at very high concentrations (75% by weight) a certain reduction in activity was observed. It should be noted that the initial activity of the catalyst, which was expressed by the percentage desulfurization after 4-6 hours, is favorably affected by the presence of sodium carbonate in amounts varying from 25-50 wt.

Example 2.

In the same way as described in ex. 1, experiments were carried out with Co-Mo catalysts in which 50% by weight had been incorporated. lithium carbonate respectively 25

wt. potassium carbonate. The results of the experiments were now the following:

These results show that as a result of the application of 50 wt. lithium carbonate, a remarkably stable catalyst was obtained which even showed an increased percentage of desulphurisation after 22-24 hours. The activity of this catalyst was further higher than the activity of the Co-Mo catalyst as such, as this was expressed in the percentage desulphurization for the catalyst after 4-6 hours, namely as 85 against 91. The catalyst with 25 wt. potassium carbonate exhibits the very high activity of 97 per cent desulphurisation which was not reduced after 22-24 hours.

Example 3.

Co-Mo catalysts containing mixtures of alkali carbonates were prepared and calcined in the same manner as described in Ex. 1. The sulphidation was carried out by passing over hydrogen containing 10 volume percent hydrogen sulphide, at a pressure of 10 atm. abs. and gradually increasing temperatures from room temperature to 375° C. The sulphidation process, which took 4 hours, was carried out in the same reactor that was used for the desulphurisation of the sulphurous hydrocarbon oil.

Desulfurization tests were carried out with the base catalyst of Co-Mo-Al 2 O:. as used in Ex. 1 and with this catalyst containing 25 wt. carbonate in the form of mixtures of equal amounts of Na2CO,,-K2CO:i, Li2CO;l-K2aO:, and Li2C03 - Na2CO.t, respectively.

A mixture of thiophene and xylene in vapor form containing 4.5 wt. sulfur was passed over the catalysts together with steam. The reaction products were collected and analyzed for their sulfur content.

The test conditions were:

due to the higher volume velocities used in the above tests, the data in Table III are not completely comparable with the data in Tables I and II. The experiments show, however, that mixtures of alkali carbonates are as effective as the individual carbonates for improving the activity and stability of the Co-Mo-Al 2 O 3 catalyst.

Example 4.

This example shows the beneficial effect of Na2C03 in the sulfided Co-

Mo-Al2CX, catalyst which was used for steam desulphurisation of a kerosene fraction from the Middle East containing 0.24 wt. sulphur. As can be seen from Table 4, a commercial Co-Mo-Al,O.rcatalyser (1.5 mm extruded pieces with about 3.6 wt.% CoO, 12.6 wt.% MoO:i) is clearly less stable than the same catalyst containing 25 wt. Na2CO;. according to the invention.

Example 5.

Catalyst pellets were prepared by mixing powders with three different particle sizes of the same Co-Mo-Al 2 O;i catalyst that was used in ex. 1 together with similarly powdered anhydrous lithium carbonate in a ratio of 75% by weight. Co-Mo-Al 2 O 3 catalyst and 25 wt. Li 2 CO 8 . Pellets of size 3x3 mm were made which were calcined for 3 hours at 500° C in the presence of air. After being sulphided, the three catalysts were tested in exactly the same way as described in ex. 3. The food mixture was again a mixture of thiophene and xylene containing 4.5% by weight. sulphur. The results were as follows:

Example 6.

In the previous examples, the desulphurisation experiments were carried out with catalysts containing Co-Mo-Al2Oo and alkali carbonate in a composite pellet. In this example, it is shown that instead of these composite pellets, catalysts can be used consisting of a mixture of Co-Mo-Al2O3 particles and separate particles of alkali carbonate or of particles containing alkali carbonate and another immaterial such as e.g. aluminum oxide ("alumina").

The following experiments were carried out: a) A reactor was filled with 75 grams of Co-Mo-Al2O.r particles (40-80 mesh) mixed with" 25 grams of Li^COi particles (less than 200 mesh). After sulphidation with a H2S -H2-mixture containing 10% by volume H,S, a test was carried out under the same conditions as described in Ex. 3, with a thiophene/xylene mixture (4.5% by weight sulphur) again being used as feed mixture. b) After a 24 hour test period, the reactor was cooled and the Co-Mo-Al2Oa particles were separated from the Li2CO3 particles by sieving. use of thiophene/xylene as feed mixture.

c) The sample was again interrupted after 24 hours and a new portion of 25 grams of Li2C03

(< 200 mesh) was added to and mixed with the Co-Mo-Al 2 O 3 particles. The sample was resumed after sulphidation in the manner indicated above.

The desulfurization results set out in Table VI show that: 1) It is not necessary to combine Co-Mo-Al20,j and Li2COs in a composite pellet to achieve d"a stabilizing effect of Li2CO;i. likely to decrease the activity in the sulphided Co-Mo-Al2O3 catalyst. 3) Addition of new Li 2 CO 3 to the de-activated Co-Mo-Al 2 O 3 particles partially restores their activity.

In another experiment (No. 23), a mixture of powdered Co-Mo-Al 2 O 3 catalyst (100-200 mesh particles) and particles (100-200 mesh) consisting of a mixture of Al 2 O 3 and anhydrous Na 2 CO 3 were added to the reactor. The final particles were produced by pelletizing a mixture of powdered Al 2 O 3 and anhydrous Na 2 CO 3 followed by crushing and recovery of the desired fraction by sieving.

The data in Table VI show that the addition of sodium carbonate in the form of particles containing Na2C03 and Al2O3 resulted in stabilization of the Co-Mo-Al263 catalyst

2) Removal of Li2C03 leads to instant clean.

Feed mixture: Mixture of thiophene and xylene containing 4.5% by weight of sulphur.

Catalyst composition and pretreatment: Co-Mo-Al2O3 commercially available (approx. 3.6% by weight CoO, approx. 12.6% by weight MoO3). Before each sample, the reactor contents were sulphided according to the method described in Ex. III.

Example 7.

To demonstrate the impact of

the calcination temperature during manufacture

of the catalysts according to the invention, the following desulphurisation experiments were carried out.

Feed mixture: thiophene + xylene, containing 4.5% by weight of sulphur.

Catalyst: 100 ml of pelletized (3x3 mm) catalyst, consisting of 75 wt% Co-Mo-Al2O3 + 25 wt% Na2CO3 sulfided with a 10 vol% H2SH2 mixture before use. The original Co-Mo-Al 2 O 3 component contained 3.6 wt% CoO and 12.6 wt% MoO 3 .

Example 8.

In order to demonstrate the different character of a desulphurisation with free hydrogen and the desulphurisation according to the invention, experiments were carried out with an extruded (1.5 mm diameter) Co-Mo-Al2O;i catalyst containing approx. 3.6 wt.

CoO and 12.6% by weight. MoO;H and with it

same catalyst after pulverization and

repelletisation together with 25 wt.

powdered anhydrous Na2CO, followed by calcination at 500° C. for 3 hours.

With each type of catalyst, a desulphurisation experiment was carried out in the presence of supplied hydrogen as well as an experiment in the presence of steam. The feed mixture was in all cases a direct-distilled gas oil (boiling range 250°—375° C A.S.T.M.) from the Middle East, containing 1.48 wt. sulphur.

All catalysts were sulphided before use in the manner described in Ex. III.

Experiment 27 constitutes an example of

the well-known hydrogen treatment ("hydrotreating") of oil fractions with addi-

put hydrogen. Experiment 28 shows that for such a hydrogenation process the catalyst containing an alkali carbonate according to the invention is not applicable. On

on the other hand, it is alkali carbonate alcohol

dige catalyst better suited for dedusting

the ling with steam.

Example 9.

To show the beneficial impact of

increased pressure on the stability of the catalyst

according to the invention, desulfurization experiments were carried out with a direct-distilled heavy gas oil (boiling range 250° C—375° C A.S.T.M.) from the Middle East. Goose-

then was combined with steam over sulfi-

dert Co-Mo-Al2O;i catalyst (3x3 mm pellets, base catalyst as in Ex. 3) containing 25 wt. Na2CO;.j or Li2CO.,

under conditions as listed in Table IX.

In all cases the volume velocity was 0.43

kg per liters per hour.

In Table IX three series of experiments are shown, each comprising one sample at low and one at higher pressure. In each series, it appears that the higher pressures have a favorable effect on the catalyst's stability. As the series differ with regard to catalyst composition or reaction conditions, the data show that the influence of pressure is a general relationship.

Claims (13)

1. Method for catalytic desulphurisation of hydrocarbon oils by bringing sulphur-containing hydrocarbon oils at elevated temperature and in the presence of steam into contact with a hydrogenation-dehydrogenation catalyst, characterized in that the sulphur-containing hydrocarbon oil is brought into contact with a hydrogenation/dehydro- generation catalyst containing one or more alkali metal compounds, at temperatures in the range of 250° to 450° C, preferably 375° to 425° C. 2. Method according to claim 1, characterized in that the hydrogenation/dehydrogenation catalyst contains at least one sulfide of an element from side- group VI in the periodic table and at least one sulphide of a metal from the group consisting of iron nickel and cobalt. 3. Method according to claim 2, characterized in that the hydrogenation/dehydrogenation catalyst contains a combination of cobalt sulphide and molybdenum sulphide. 4. Method according to any one of the preceding claims, characterized in that the catalytically active components are placed on a carrier which consists wholly or partly of aluminum oxide ("alumina"). 5. Method according to any one of the preceding claims, characterized in that the finished catalyst contains alkali metal compounds in amounts from 10 to 80 wt. (calculated as carbonates) and in particular from 20 to 40 wt. 6. Method according to any one of the preceding claims, characterized in that the final catalyst contains lithium, sodium and/or potassium carbonate as the alkali metal compound. 7. Method according to any of the preceding claims, characterized in that the catalyst is produced by dry mixing of particles of the various catalyst components. 8. Method according to claim 7, characterized by the particles being smaller than the equivalent of a 30 mesh sieve (A.S.T.M. Standard Sieves). 9. Method according to claim 7 or 8, characterized in that the catalyst is produced by crushing a cobalt-molybdenum catalyst placed on aluminum oxide, dry mixture of the resulting pool with a powdered alkali metal compound and compacting the mixture into pellets which can be calcined and sulphided. 10. Method according to any of the preceding claims, characterized in that the desulfurization is carried out in the presence of 5-250 gram molecules of water vapor per gram atom of sulfur in the sulfur-containing hydrocarbon oil. 11. Method according to any of the preceding claims, characterized in that the desulfurization is carried out at a pressure of 20 atm. abs. or higher. 12. Method for desulphurisation of gas oil and higher boiling hydrocarbon oil fractions, according to any of the preceding claims, characterized in that the desulphurisation is carried out at pressure in the range from 70-150 atm. abs. 13. Method according to any of the preceding claims, characterized in that the desulfurization is carried out continuously and using liquid volume rates between 0.25 and 4 kg of oil per liter of catalyst per hour.