NL8702577A - PROCESS FOR CYCLICALLY REGENERATING CATALYTIC CRACKING OF HYDROCARBONS WITHOUT ADDITION OF HYDROGEN. - Google Patents

Description

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{S 2909-830 Ned.

P&C

Short designation: Process for cyclic regenerating catalytic cracking of hydrocarbons in the absence of added hydrogen.

Division of patent application 7701714.

The invention relates to a process for the cyclic regenerative catalytic cracking of hydrocarbons in the absence of added hydrogen, wherein the catalyst coming out of the reactor goes through an external circuit, which contains a regenerator and is returned to the reactor 5, and in which circuit a platinum group metal or rhenium or a compound of such metal is added at a concentration sufficient to catalyze the oxidation of carbon monoxide in the regenerator, but insufficient to act as a catalyst poison in the cracking operation.

Such a method is described in the older, non-prepublished Dutch patent application 7701071, which was published on August 4, 1977. According to this patent application, the metal is added as a solid in the form of powders, flakes, pills or agglomerates, but preferably in a liquid as a solution or dispersion. Incidentally, the use of a small amount of one of the said metals in the preparation of a cracking catalyst or in the cracking process is known from Dutch patent application 7412423, which was filed for inspection on March 24, 1975. According to the latter application, the metal in question can also are incorporated into the catalyst by adding it to the hydrocarbon charge 20 in the form of a metal compound soluble therein.

A favorable improvement of this method has now been found.

The invention therefore relates to a process of the type described in the preamble, which is characterized in that the metal or metal compound is added to the catalyst while it is in a side stream.

According to a preferred embodiment, a side stream drawn from the circulating mass of cracking catalyst in a contact zone is impregnated with a solution of a compound of the metal to be incorporated in a solvent. The side stream may be from various parts of the circuit, but preferably the side stream is taken from a catalyst stripping zone or from a coke deposition catalyst line. Furthermore, it is preferable that the side stream be in a single closed vessel. This vessel may in turn communicate with the reactor, regenerator, spent catalyst line, or regenerated catalyst standpipe.

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It is further preferred that the catalyst be fluidized in the contact zone.

Particularly suitably, the catalyst can be combined in the side stream with a solution of the metal compound concerned in a solvent boiling between 60 ° C and 316 ° C at the prevailing pressure. This enhances the activity of the metal for carbon monoxide combustion and prevents possible loss of some of the metal or deposition of the metal in a location other than on the catalyst.

Of course, the various suitable metals do not all have the same effect on the combustion of carbon monoxide. Platinum is the strongest and this metal and its compounds are therefore preferred.

Suitable metal compounds include metal halides, nitrates, amine halides, oxides, sulfates, phosphates and other water-soluble inorganic salts; metal carboxylates .. with 1-5 carbon-15 atoms and metal alcoholates. Organometallic compounds are also suitable, such as metal di-ketetonates, carbonyl compounds, netallences, olefin complexes with 2-20 carbon atoms, ethyl complexes, alkyl or arylphosphine complexes and carboxylates with 1-20 carbon atoms. As suitable, relatively simple and inexpensive compounds are mentioned, chloroplatinic acid and tetra-20-tetmine platinum dichloride.

Suitable solvents in the present process are water or organic solvents boiling between 60 ° C and 316 ° C. Suitable organic solvents are, for example, monovalent and polyvalent alcohols, esters, ethers, hydrocarbons and mixtures thereof.

As further explained below, it is advantageous to use mixtures of solvents, for example water and ethylene glycol, benzene and cumene or t-butanol and water.

The reason that it is important that the solvents used boil between 60 ° and 316 ° C at the pressure in the contact zone is that it is essential to cool the side stream of the hot circulating cracking catalyst to a temperature below 316 ° C. The advantage of this is that decomposition of the compound of the metal serving as a promoter for the CO combustion is avoided before this compound has adequately contacted the catalyst and is optimally distributed over its surface. The optimum temperature for contacting the solution of the compound of the promoter metal with the side stream of the cracking catalyst therefore varies depending on the thermal stability of the metal compound concerned and on the choice of the solvent and sometimes with the nature of the cracking catalyst itself. For example, a% / U L is 0 / / i -4.

- 3 - particularly high efficacy observed with tetrammine platinum dichloride

using water as a solvent at a temperature of 135 ° C

or higher, which temperature is approximately the boiling point of water under an excess pressure in the contact zone of about 2.1 kg / cm. In general, it is preferable to carry out the contacting step under conditions such that at least part of the solvent wets the catalyst.

For contact treatment, the side stream of the cracking catalyst can be cooled indirectly using a cooler using air or other heat transfer material. Direct cooling of the side stream is also possible with the aid of injected inert gas or water.

It is also possible to use a combination of direct and indirect cooling.

Of course, at least some direct cooling occurs upon contact of the side stream of the cracking catalyst with the promoter metal compound solution. The desired cooling can therefore be achieved to a great extent or even entirely by simply diluting the solution of the metal compound with a considerable excess of solvent and injecting proportionally larger portions of solution into the contact zone.

Advantageously, mixtures of solvents of different volatility are used, for example a small amount of glycerol in combination with a predominant amount of water. In this case, the water acts as a co-solvent and coolant, while the less volatile glycerol ensures that the promoter metal compound does not decompose until adequate contact with the catalyst is achieved. The cooling effect due to evaporation of the solvent can be further improved by choosing a solvent which decomposes endothermically in contact with hot cracking catalyst. Examples of this are tert-butanol, which decomposes to isobutene and water, and isopropanol, which forms propylene and water. These endothermically decomposing solvents can be used alone or in admixture with other solvents.

As far as boiling point is concerned here, this means in the case of solvent mixtures the temperature at which at least 95% of the solvent mixture distills. Insofar as this further refers to a boiling point or boiling range without mentioning a pressure, this means that this boiling temperature applies at the pressure in the contact zone, which pressure is usually approximately 69 - 345 kPa gauge pressure. Although the catalyst-containing side stream can be taken from any part of the hot circulating catalyst mass, it has been found to be advantageous to use a side stream of coke-deposited catalyst. Therefore, it is preferable to take the side stream from the reactor or from the catalyst line 6702577-4 - Λ> with coke deposit. When the side stream is withdrawn from the reactor, it is preferable to drain the catalyst from the stripping zone to avoid problems due to the presence of volatile hydrocarbons. That is, the coke-deposited catalyst at contact with the solution of the combustion promoter metal should be practically free of gas oil or reaction products thereof.

The discharged side stream is fed to a contact zone and contacted there with the solution. The solution can be introduced through a device that promotes intimate contact, for example a spray nozzle. It is desirable to keep the catalyst in the contact zone in a fluidized state because it promotes uniform temperature and good distribution of the metal compound on the catalyst. Solvent evaporation aids fluidization.

After impregnation, the side stream is recycled and mixed again with hot circulating catalyst mass. At the high temperature that occurs again, decomposition will take place, thereby providing the active form of the promoter. Due to the particularly small amount of metal present, it is not possible to accurately determine the nature of the metal in its active form, i.e. whether the metal is present as elemental metal, sulfide, oxide or other form.

The metal serving as a combustion promoter may be present on all or only part of the catalyst particles. The concentration present in the entire system must be large enough to effect the combustion of carbon dioxide, while of course the other conditions in the regenerator, such as the temperature and the amount of air or oxygen, must be sufficient to sustain this combustion. On the other hand, the metal should not be present in such an amount that the cracking action in the reactor is adversely affected. Furthermore, of course, the activity of the 7 metals involved is different from one another. Therefore, for the least active of these metals, the upper limit is about 100 ppm, while for the highly active metals platinum and irridium, this upper limit is about 10 ppm.

Figures 1 and 2 of the drawing further illustrate the prior art fluid cracking catalyst (FCC) system, while Figures 3 and 4 illustrate two embodiments of the invention.

In Figure 1, a hydrocarbon material 2, for example a preheated gas oil, boiling in a range of 316 ° - 538 ° C, is introduced into riser 4 at the bottom, and mixed there with hot regenerated catalyst, which is fed through the control valve 8 provided standpipe 6. The mixture 8702577 e- -½ - 5 - flows upwards with a temperature of at least 510 ° C and the residence time of the mixture in the riser reactor is 1-10 seconds. At the top of the reactor are one or more cyclones 14 and the gas phase obtained therefrom is discharged via space 16 through line 18. The catalyst separated in the cyclone is passed via dip tubes 20 to a densely fluidized catalyst bed 22 located around the upper part of the riser reactor 4. The catalyst bed 22 moves downwardly to a volatiles removal zone 24 countercurrent with ascending stripping gas. This stripping gas is introduced via line 26. The stripping effect is further improved by partitions 28 which are arranged in the zone 24.

The stripping gas flows to one or more cyclones 32 and the fine catalyst particles separated therein are recycled through dip tube 34.

The stripped catalyst is fed via line 36 to a fluidized catalyst bed in a regeneration zone 42. This line 36 is provided with a control valve 38.

The tangentially introduced catalyst is mixed in the fluidized bed in the regenerator with hotter catalyst, which undergoes the exothermic regeneration, and then flows down the vertical axis of the regenerator in a circular or swirling motion through the discharge funnel 40, which is located in the near the regeneration gas distribution grid. In the embodiment shown in Figure 2, the catalyst introduced tangentially through line 36 causes circulating movement of the catalyst in a clockwise direction. In the regeneration zone 42, in which there is a densely fluidized bed of catalyst particles 44, which are fluidized by the oxygen-containing regeneration gas, which is introduced via manifold 46, the density of the mass of suspended catalyst particles can be varied using the input gas volume. Above the dense bed there is a dilute phase of suspended catalyst particles 48. Depending on the rate of the regeneration gas, the boundary between the fluidized bed and the above diluted phase is clearer or more blurred.

In the bottom part of the regeneration vessel there is a distribution grid 50 for the regeneration gas. Oxygen-containing combustion gas is separated in the cyclones at the top of the regenerator from entrained catalyst particles, the latter of which are returned via dip tubes.

The term "circulating mass catalyst" therefore includes the catalyst in riser 4, in the dense bed 22, the dense bed 24, the dense bed in the regenerator 44, as well as the catalyst material in the conduits 36 and 6 and the catalyst material suspended in the dilute phase and the cyclones, as well as in the reactor portion. The regenerator operates at a temperature above 538 ° C and the reactor at a temperature above 427 ° C.

In Figs. 3 and 4, the catalyst portion shown in Fig. 1 is shown simplified, and the numbers already discussed in that Fig. Represent the same elements and are not discussed here again.

According to Figure 3, coke-deposited catalyst flows from line 10 36 into line 70, which is provided with a control valve 71 for controlling the rate of the side stream. The material passing through the valve is passed through line 72 through heat exchanger 73 and cooled therein. The cooled catalyst flows through line 74 into vessel 75, which is provided with a nozzle, nozzle or other means 78, which serves to deliver the solution of the compound of the combustion promoter metal supplied through line 77. Pipe 79, which is connected to the delivery member 78, also projects into the vessel 75. This pipe, which can be separated from or combined with the pipe 77, serves to inert compressed air, steam, nitrogen, volatile solvent or other dispersing medium into the vessel 75 to keep the catalyst therein in a fluidized state. The catalyst thus treated and cooled is then passed through line 80 to the regenerator and re-incorporated into the circulating mass.

Although it is shown in Figure 3 that the side stream is taken from the line 36, which comes from the stripping zone 24, the side stream may as well be directly from the reactor vessel 81, from the regenerator, from the regenerated catalyst line 6, or generally taken from any suitable point in the hot circulating catalyst mass. Likewise, instead of via line 80 to the regenerator, the side stream can also be recycled to another suitable portion of the catalyst loop, for example, to line 6 for regenerated catalyst.

The vessel 75 may suitably be provided with a temperature measuring device, for example a thermocouple 76.

Figure 4 illustrates another embodiment. Here, a vessel 90, 35 communicating with conduit 91 is attached to the stripping zone of reactor vessel 91, the contents of the stripping zone and vessel 90 communicating freely through conduit 91. The lines 77 and 79 and the dispenser 78 are the same as discussed in Figure 3. The lines 77 and 79 insert into the vessel 90 and the drain 78 is located in this vessel.

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In this system, fluidized catalyst flows from the stripping zone 24 into the vessel 90 and contacts the solution of the metal compound (combustion promoter) and is returned to the stripping zone by the same conduit. The pipe 91 can of course also be arranged at a different location than is indicated in the drawing; this line can also be attached to the regenerator. It is preferred, however, that the attachment be at such a point that the contents of the vessel 90 communicate with a fluidized bed of hot coke catalyst.

It is noted that the invention also applies to systems with other types of regenerators, for example a riser regenerator intended for the complete combustion of carbon monoxide. Furthermore, if desired, the present method of applying metal to the catalyst can be combined with the use of make-up catalyst on which such a metal has already been deposited during the preparation. The present method can be used to control the combustion of carbon monoxide in the regenerator, and this control is achieved by suitable coupling means which control the flow rate in the side stream or the pumping speed or the concentration of the solution of a compound of the combustion promoter. metal depending on the composition of the flue gas.

Unless otherwise noted, all parts and percentages listed in the examples below are by weight.

EXAMPLE I

In this example and the following examples, a continuously operating FKK pilot plant was used. The pilot plant consisted of a regenerator, a riser reactor (corresponding to element of Fig. 1) which communicated with a volatile material removal zone (corresponding to zone 24 of Fig. 11 and lines corresponding to lines 6 and 36 vein Fig. 1- Equilibrium catalyst was obtained from a commercial catalytic cracking plant and used in this example and the following examples: The catalyst was a representative commercial material of the rare earth exchanged faujasite type, the faujasite was dispersed in a matrix of silica-35 alumina The composition was as follows: 8702577 - 8 -

* - X

61.3% Si 2 / 35.9% Al 2 O 2 / 2.77% 2 O, 0.51% Na, 359 ppm nickel and 404 ppm vanadium.

In this example, a vessel in the form of a tube as shown in Fig. 1 was used; this tube was attached to and communicated with the dense bed in the regenerator. The tube had a volume of 25 cm.

The vessel was equipped with a nitrogen inlet tube to keep the catalyst in the tube in a fluidized state.

Before starting to contact the catalyst and impregnate it with the compound of the combustion promoter metal, the pilot plant was started with a mass of 3500 g of the catalyst described above and charged with a large boiling range gas-oil fraction. a crude Mid-Continent oil; the operating conditions were set as follows:

15 Reactor temperature, ° C approx. 538 ° C

. Temperature in volatile removal zone approx. 538 ° C

; material, ° C

Regenerator temperature, ° C approx. 677 ° C

Catalyst residence time in riser, seconds 7.0 20 Oil residence time in riser, seconds. 4.5

Catalyst to Oil Weight Ratio 6.0

A solution of 6 mg of platinum in the form of tetramine platinum dichloride in 250 ml of water was placed in a stock. The solution was pumped as a jet in the above described 25; fluidized catalyst containing tube; the pump speed was set so that the temperature of the contact zone was about 177 ° C, as indicated by determination of the surface temperature. Before entering the solution, the temperature of the contact zone was about 482 ° C. The set pump speed was 66 ml / hour? introduction of the solution was terminated after 231 ml of solution was pumped into the contact zone. Catalyst samples were taken from the volatile removal zone at hourly intervals and tested for catalytic activity in the combustion of carbon monoxide. The results are shown in the table below.

8702577 «* η - 9 -

TABLE

Monster Mb. Impregnation time ppm CO2 / CO

P _ ratio 1 0 minutes 0 2.7 2 30 minutes 0.22 4.7 3 60 minutes 0.44 3.7 5 4 90 minutes 0.66 3.9 5 120 minutes 0.88 3.6 6 150 minutes 1.10 4.7

EXAMPLE II

The procedure of Example 1 was repeated with a fresh charge equilibrium catalyst, except that instead of the wide boiling gas oil fraction, a heavy vacuum gas oil obtained from a crude sulfur containing West Texas oil was used. Bee . in this test, 6 mg of platinum in the form of tetraammine platinum dichloride was dissolved in 180 ml of water. The solution was pumped at a rate of 119 ml / hour for 1 hour; after this 1 hour period, the temperature in the contact zone was about room temperature. A catalyst sample taken from the volatile material removal zone after 1 hour showed no increased efficacy in promoting the combustion of CO. The impregnation was continued for a second egg hour period, with 78 ml of the above solution being pumped into the tube. At the end of this period, the temperature of the contact zone was about 177 ° C.

A catalyst sample taken after 2 hours of impregnation gave a CO2 / CO ratio of 6.3, compared to a catalyst ratio of 2.7 before impregnation. The calculated content of the sample promoter metal was 1.9 ppm.

EXAMPLE III

In this example, the tubular vessel used for the contact treatment was attached to the zone of the pilot plant in which volatile material is removed. Untreated equilibrium catalyst was introduced into the system. The system was set up as described in Example I, but using the heavy vacuum gas oil used in Example II.

- A solution of 2 mg of platinum in 250 ml of water was pumped into the tube at a rate of 90 ml / hr at 90 ml / h to be contacted with the catalyst until 135 ml of the solution was consumed. The temperature in the contact zone was initially about 204 ° C and then dropped to about 104 ° C, at which point the test was terminated and a catalyst sample was taken. The calculated platinum content of the sample was 0.31 ppm; the sample gave a CC / CO ratio of 410.

EXAMPLE IV

Example III was repeated with a fresh batch of equilibrium catalyst, but the flow rate of the solution used for the contact treatment and the flow rate of the nitrogen were adjusted so that the temperature of the contact zone was in the range of about 204 ° -316 ° C keep it. A sample of the final catalyst, whose calculated platinum content was 0.29 ppm, gave complete combustion of carbon monoxide, that is, the CQ / CO ratio was infinite.

8702577

Claims (9)

1. Process for cyclic regenerative catalytic cracking of hydrocarbons in the absence of added hydrogen, wherein the catalyst coming out of the reactor passes through an external circuit, which contains a regenerator and is recycled to the reactor, and in that circuit a metal from the platinum group or rhenium or a compound of such metal is added at a concentration sufficient to catalyze the oxidation of carbon monoxide in the regenerator, but insufficient to act as a catalyst poison in the cracking operation, characterized in that the metal is or adding the metal compound to the catalyst while it is in a side stream. · 2. Process according to claim 1, characterized in that the side stream is taken from a catalyst stripping zone. 3. Process according to claim 1, characterized in that the side stream is obtained from a coke catalyst pipe. Method according to claims 1-3, characterized in that the side stream is contained in a single closed vessel. 5. Process according to claim 4, characterized in that the vessel is in communication with the reactor, the regenerator, the spent catalyst line or a regenerated catalyst standpipe. 6. Process according to claims 1-5, characterized in that the catalyst is fluidized in the side stream. 7. Process according to claims 1-6, characterized in that the additive is combined with the catalyst in the form of a solution of a compound of the respective metal in a solvent which is at the prevailing pressure between 60 ° C and 316 ° C boils. Process according to claim 7, characterized in that an amount of solution is used which is sufficient to cool the side stream to the boiling point or boiling range of the solvent at the prevailing pressure. 9. Process according to claim 7 or 8, characterized in that an organic compound is used as solvent, which decomposes endothermically on contact with a hot cracking catalyst. 8702577