NL8005882A - METHOD FOR CATALYTIC REFORMING OF HYDROCARBON FRACTIONS. - Google Patents

Description

i * - r h.o. 29,542

Process for the catalytic reforming of hydrocarbon fractions.

The present invention relates to the catalytic reforming of hydrocarbon fractions. More particularly, the present invention relates to reforming in a plurality of reaction zones in series to improve the octane number of the feed.

Reforming a naphtha fraction is generally accomplished by passing the naphtha through a plurality of reaction zones in series, each zone containing a catalyst consisting of a hydrogenation dehydrogenation ring component supported on a porous solid support. Common catalysts include platinum on alumina with or without promoters such as rhenium, tin, iridium, etc. The naphtha fraction to be reformed is contacted in the first zone with a platinum-containing catalyst under reaction conditions to convert mainly naphthenes to aromatics. put. Nearly naphthene dehydrogenation, side reactions such as isomerization, hydroisomerization and hydrocracking can also take place. Usually the effluent from the first reaction zone is heated before it is fed to a subsequent reaction zone.

After a period of use in reforming, the catalyst is gradually deactivated due to the deposition of coke on the surface of the catalyst, and consequently a decrease in the octane values of the reformate product is observed.

When the octane requirements of the particular reforming system are to be continuously met, the reaction temperature of the catalyst must be raised to compensate for the loss of activity due to the coke deposit. The fastest catalyst deactivation takes place in the reactor, in which the olefin dehydro ring closure and hydrocracking are the main reactions. Consequently, even with a constant inlet temperature, the average reaction temperature increases with each subsequent reactor, because the reactions in each subsequent reactor are not as endothermic as in the previous reactor.

1 Coke deposit on the catalyst not only reduces the activity of the catalyst, but also results in a decrease in the yield of produced C 2+ gasoline product. Thus, generally, the yield of C 2+ gasoline product decreases during the reformation process until it reaches an unacceptable level, at which time it is common to regenerate all or part of the catalyst. Typical coke contents on the catalyst at the time of regeneration are 10 to 12 wt% or more on the catalyst in the last reactor and 10 or 6 wt% on the catalyst in the first reactor. Coke contents on catalysts in intermediate reactors will generally fall between these two numbers.

Generation methods either continuous or discontinuous are well known. Such methods generally involve several steps: a carbon burn by contacting the catalyst with an oxygen-containing gas at an elevated temperature until substantially all carbon has been removed; then contacting the catalyst with an oxygen-containing gas to redistribute the platinum group metal; halogen control and optionally reduction of the regenerated catalyst with a hydrogen-containing gas prior to recycling the catalyst back to the reactor (see, for example, U.S. Patent No. 5,496,096).

It is an object of the present invention to provide a reformation process with an extended operating cycle between regenerations as compared to conventional reformation processes. It is another object of the present invention to provide a method of extending the effective life of a reformation catalyst nearing the end of production.

According to an embodiment of the present invention, there is provided a reformation process wherein a 55 naphtha feed is contacted under reforming conditions in the presence of hydrogen with a reforming catalyst in a plurality of reaction zones in series, a product having a improved octane number is won from the effluent from the last reaction zone and for 4-0 deposit the course of the reforming coke on the catalyst 80 0588 2 3 * ", deactivation taking place and possible regeneration or replacement being necessary, as well as a process for extending of the life span of the catalyst in all reaction zones downstream of the first 5 zone, which includes banding the coke content on the catalyst in the first reaction zone at less than 1% by weight of the catalyst by controlling the frequency at which the catalyst is in the first reaction zone, it is regenerated or replaced with fresh or regenerated catalyst.

According to another embodiment of the present invention, there is provided a multistage process for the catalytic reforming of a naphtha feed characterized by: (a) conversion of this feed. in the presence of a catalyst and hydrogen under catalytic reforming conditions in a moving bed reaction zone, whereby the catalyst is movable by gravity flow and recovery of the resulting hydrocarbon containing effluents from the moving bed reaction zone; (b) banding the amount of coke deposited on the catalyst in the moving bed reaction zone below 1 wt% by feeding at least periodically fresh or regenerated catalyst to the upper end of the moving bed reaction zone and at least periodically withdraw an equivalent amount of coke-contaminated catalyst from the moving bed reaction zone; (c) further converting the effluent from the moving bed reaction zone under catalytic reforming conditions to a fixed bed reactor system containing at least one fixed bed reaction zone; (d) recovering a usually liquid catalytic reformed product from the effluent withdrawn from the final fixed bed reaction zone.

According to yet another embodiment of the present invention, a catalytic reforming process 1 is provided, wherein a naphtha fraction is contacted under reforming conditions in the presence of hydrogen with a reforming catalyst in a multiplicity of 80 0588 reaction zones in series, a product having an improved octane number is recovered from the effluent from the last reaction zone and coke dignified on these catalysts during the reforming process, thereby deactivating and decreasing the yield of product, as well as a method of increasing the yield, which involves maintaining the coke content on the catalyst in the first reaction zone to at least 1% by weight by controlling the frequency at which the catalyst is regenerated in the first reaction zone or is replaced by a fresh or degenerate catalyst.

Brief description of the figures

Fig. 1 illustrates the effect on the reaction temperature, the C 2+ yield and the hydrogen production of a catalyst bed containing 0, 10, 20 and 30% fresh catalyst on top of a low coked catalyst.

Fig. 2 light yield losses due to variable coke contents on the catalyst on top of a coked catalyst bed.

FIG. 3 illustrates the results of a comparison between a reformed coke catalyst and 10% fresh catalyst on top of the coked catalyst.

The present invention is applicable to those reforming systems using a plurality of reaction zones in series 25. Preheaters are preferably present between the reaction zones, so that the temperature of the feed to each reaction zone can be controlled. Preferably, each reaction zone will be contained in a separate reactor.

The present invention relates to those systems, wherein at least two reactors and preferably 3 to 5 reactors are in series. Although some or all of the reactors may be moving bed reactors, the system most preferred for all reactors is to be system / fixed bed or all reactors except the first 35 fixed bed systems / with the first a moving bed system.

In reforming systems with many reaction zones, the catalyst may vary in composition in the different reforming zones, although generally the catalyst is the same in all zones. However, the volume of catalyst generally differs from one reaction zone to the next. A conventional catalyst charge in a three reactor system can use a quarter of the total catalyst load in the first reactor, a quarter in the second reactor and half in the last reactor. The first reactor generally contains less catalyst, because the strong endothermic reaction that takes place therein results in rapid cooling of the feed. If a large volume of catalyst were present in the first reactor, the feed temperature in the lower part of the catalyst bed would be too low to allow substantial dehydrogenation reactions to take place and thus the lower part of the catalyst bed would cannot be used effectively.

To achieve the benefits of the present invention, the catalyst iii the first reaction must be replaced or regenerated with a frequency sufficient to have a coke content in the catalyst of less than 1 wt%, preferably less than 0.7 wt % and even more preferably of less than 0.5% by weight. The first reaction zone may contain 20 to 30% by volume of the total catalyst in the reaction system, although it will preferably contain only at most 20% and even more preferably at most 15% of the total catalyst mass in the reaction system.

The temperature in each of the reaction zones may be the same or different, but will generally fall in the range of from 370 to 565 ° C, and preferably in the range of from about 455 to 540 ° C. The latter reaction zone generally has the highest average catalyst bed temperature. The pressure in each of the reaction zones will usually be the same, whether atmospheric or super-atmospheric. Preferably the pressure will be in the range from 175 to 7000 kPa and more preferably between 350 and 5250 kPa. The temperature and pressure can be correlated with the liquid space velocity (LHSV) to favor any particularly desired reforming reactions and will generally be 0.01 to 10, preferably 1 to 5. It is clear that with different catalyst charge and different reaction zones, the space velocities in the individual reaction zones can vary considerably.

80 0 5 8 8 2 ♦ '* 6

Although reforming generally results in the production of hydrogen, it is usually hydrogen separated from the effluent from each of the reaction zones, usually to recycle the last reaction zone to the first or subsequent reaction zones. The hydrogen can be mixed with the feed prior to the contact with the catalyst or simultaneously with the additive; of the feed to the reaction zone. The presence of hydrogen serves to reduce the formation of coke, which tends to poison the catalyst. Hydrogen is preferably fed to the reforming reaction zone at a ratio ranging from 0.5 to 20 moles of hydrogen per mole of feed. Hydrogen can be mixed with light gaseous hydrocarbons.

The catalyst used in the reaction zones contains a platinum group component in conjunction with a porous solid support. Preferably, the platinum group component is platinum and the preferred porous solid support is a porous refractory inorganic oxide, for example, alumina. The platinum group component will be present in an amount of 0.01 to 3 wt%, and preferably 0.01 to 1 wt%.

Other components in addition to the platinum group component may be present on the porous solid support. It is particularly preferred that rhenium is present, for example in an amount of 0.01 to 5 wt%, and more preferably 0.01 to 2 wt%. Henium significantly improves the yields obtained using a platinum-containing catalyst and a platinum-renium catalyst is more fully described in U.S. Pat. No. 3,415,737. Generally, the catalyst will be provided with a reformer promoter by the addition of a halide, especially a fluoride or chloride. The halide provides limited acidity to the catalyst, which is beneficial for most reforming treatments. The promoted halide catalyst preferably contains 0.1 to 3 wt% total halide content, and the preferred halide is chloride.

40 The catalyst in the first reaction zone can be replaced 80 05 8 8 2 -? - * 7 or regenerated in situ or ex situ with a sufficient frequency to maintain less than 1% by weight of coke on the catalyst and preferably less than 0 .7 wt.% And more preferably less than 0.5 wt.%. The amount of coke on the catalyst should be calculated as the average amount of coke on the total volume of catalyst in the first reaction zone. The catalyst in the first reaction zone can be in a fixed or moving bed. When the reaction zone is a fixed bed, it may be with radial flow, upflow or downflow, and it may be desirable that a swing reactor be present and ready to be put into service when the first fixed bed reaction zone is removed from service by regeneration purposes. Of course, when the first reaction zone has a moving catalyst bed, the reaction zone can be maintained while fresh or regenerated catalyst is added to the top of the reaction zone and used coke-deactivated catalyst is withdrawn from the bottom of the zone. The other reaction zones in the system may be fixed bed or moving bed type reaction zones, but for the purposes of the present invention it is expedient when they are fixed bed reaction zones. The fixed bed reaction zones may have an upward, downward or radial flow, with radial flow being preferred.

To determine the coke or carbon content on the catalyst of the first reactor, the catalyst can be sampled when it is removed from the reactor in a moving bed reactor zone or catalyst samples can be withdrawn from the reaction zone itself without the normal reforming process to disturb. Various means are available for removing catalyst samples from reactors without stopping the reactor, see, for example, U.S. Patents Nos. 3,129,590 and 3,319.4-69. The coke or carbon content deposited on the catalyst sample can be determined by any suitable method, such as combustion of the carbon (> j and measurement of the amount of COg generated or by determining the rate at which a combustion zone proceeds through-40 a bed of coke-contaminated catalyst, as described in U.S. Pat. No. 3,414,382.

The hydrocarbon feed used in the reforming operation of the present invention can be any suitable hydrocarbon, which can be catalytically reformed at the stated conditions. Preferably, the feed is a naphtha fraction, which is a light hydrocarbonaceous oil, which generally boils within the range of 20 to 290 ° C, preferably 65 to 230 ° C. The feed can be, for example, a direct naphtha, a thermally cracked or catalytically cracked naphtha or mixtures thereof. Generally, the naphtha feed will be about 25 to 75%, and preferably about 55 to 60%, olefins, about 15% to 65%, and preferably about 25 to 55%, naphthenes, and about 5% to 20% aromatics, based on a volume percentage basis.

Catalyst regeneration methods are known and will generally involve combustion of the carbon of the catalyst by contacting the catalyst with an oxygen-containing gas at an elevated temperature of about 370 to 595 ° C. Preferably, the concentration and temperature of the oxygen are increased stepwise as the regeneration progresses. After the carbon has burned off, a gaseous halogen can be brought into contact with the catalyst. The catalyst can then be dried and reduced before it is returned to the reforming zone. Examples of suitable regeneration methods are illustrated in U.S. Pat. Nos. 3,134,732 and 3,496,096.

30 Examples

The present invention will be further elucidated by considering the following examples, which are intended to be exemplary only and not to limit the present invention. Example I shows that the presence of a small amount of fresh catalyst on a catalyst bed containing 10.9% carbon significantly increases the C 1 + yield and hydrogen production as well as the average catalyst temperature required to prepare a product with a predetermined octane, J decreases 4-0. These results indicate that the presence of a small amount of fresh catalyst upstream of a larger mass of coke-contaminated catalyst serves to significantly extend the time during which the total catalyst mass can be maintained for reforming. 5 before regeneration. Example II shows the detrimental effect on yield due to the presence of an increasing amount of coke on a small catalyst mass above a larger mass of coke deactivated catalyst. These results indicate that the less carbon is present on the catalyst in the first reaction zone, the better the overall yield. Example III is a side-by-side comparison of a catalyst bed reforming containing 10% fresh catalyst on a test catalyst bed containing 15 different levels of coke, illustrating the activity and yield benefits of a small layer of fresh catalyst present on the catalyst bed.

Example I

A middle continent naphtha with the properties listed in Table A was passed through a series of dirty reactors containing a platinum-renium reforming catalyst at reforming conditions such as a pressure of 14-00 kPa, a liquid space velocity of 2, a hydrogen to hydrocarbon molar ratio of 5 and a temperature set to obtain a reformate product with a research octane number of 98 pure.

label A.

Mid-continent naphtha

Density ° API 55 * 0 50 D-86 distillation IBP - ° C 79 10% - ° C 101 30% - ° C 134-, 5 50% - ° 0 128.5 35 70% - ° 0 14-5.5 90% - ° C 172 EP - ° C 199% olefins 43.1% naphthenes 46.8 40% aromatics 10.0 \ 8005 882 10

After 55 days of operation, part of the catalyst was removed from the last reactor in the series. The catalyst, containing an average of 10.9% by weight of coke, was tested in a very small scale reformer in three separate runs, with the top 10, 20 and JO% of the spent catalyst being replaced with an equivalent amount of fresh catalyst. The results, as shown in Fig. 1 and Table B, show that by applying a layer of fresh catalyst to a larger mass-coked catalyst (1), the activity of the total mass of the catalyst increased significantly, by 11 ° C for 10% fresh catalyst, with 13.5 ° C for 20% fresh catalyst and with 18 ° C for 30% fresh catalyst; (2) the C 4+ yield increased by 1.9 fluid volume (LV)%, from about 78.6 to 80.5 DV%; (3) the hydrogen production increased by about 11%, from 217 N dmV1 feed to 241-240 N dm / 1 feed and (4) the CH production decreased by 23-26%, from 19 2 N dm ^ / 1 feed to 14.2-14.8 N dm / 1 feed. Therefore, the presence of a small amount of fresh catalyst on top of a larger amount of coked catalyst serves to significantly increase activity, C 1 + liquid yield and hydrogen production rate, much more than can be predicted from the small amount of fresh catalyst added.

25 Table B

Laminated Bed Tests on Practically Elaborated Catalyst (EOR) _ T Cc + H0 CE., O 5 2,4 * oc LV% NdmVl MmVl

30 EWC

catalyst, 10.9 ° / ° C, 513 78.6 217 19.2 10% fresh at 90% EOR catalyst 502 80.6 241 14 20% fresh at 35 80% EOR catalyst 500.5 80.5 239.8 14.2 30 ° / o fresh at 70 ° / o EOR catalyst 495 80.5 240.1 14.8

Example II

A study was conducted to determine the effect of 40 on the yield of a varying amount of coke on the top 10% catalyst in a catalyst bed. Big. 2 \ 8005882 11

Shows the influence on the C 2+ yield and hydrogen yield associated with an increasing carbon content on the catalyst in the top 10% of the catalyst bed. Using as the standard of a catalyst bed containing 10% solid catalyst on top of 90% catalyst containing 13.3% carbon by weight, a catalyst bed containing the top 10% catalyst containing 2% carbon by weight loses 1 vol.% of the Cj + yield; a catalyst bed with the top 10% catalyst containing about 6 wt% carbon-10 loses 2% by volume of the C 2+ yield and a catalyst bed with the top 10% catalyst containing about 12 wt% carbon , loses about 3% by volume of the G ^ + yield. The hydrogen yield loss likewise increases with increasing carbon content in the top 10% catalyst in the catalyst bed. Therefore, in order to obtain the maximum yield benefit from the process of the present invention, the amount of carbon on the catalyst on top of the catalyst should be kept as small as possible.

Example III

A test was conducted to compare the performance of a bed of a coke deactivated platinum renium catalyst with an equivalent volume of catalyst containing 10% by volume fresh catalyst on top of the 90% de-23 activated catalyst. Samples of the catalyst from a technical reformer were obtained after 0, 28, 61, 89 and 122 days of use. A portion of each catalyst sample was tested at the feed listed in Table A under reforming conditions including a pressure of 14-00 kPa, a liquid space velocity of 2, a hydrogen to hydrocarbon molar ratio of 3, and a temperature which is set to obtain a reformate product having a research octane rating of 98 pure. A 10% fresh catalyst layer was placed on top of a 90% catalyst layer of the samples after 61, 89 and 122 days, respectively, and then examined under the same reforming conditions.

The results, as shown in FIG. 3, show that the catalyst beds containing 10% fresh catalyst- 8005882

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types were much more active (11 ° C after 120 hours) and more selective (4% + yield after 120 hours) than the beds, which contained only coked catalyst. The contamination rate for the beds containing 10% fresh catalyst is less than that for the coked catalyst beds, 0.083 ° C / day versus 0.185 ° C / day, indicating that the effect of the fresh catalyst is far beyond is the ratio of its volumetric presence.

From the foregoing, it can be seen that the present invention acts in a novel and effective manner to increase the activity, selectivity (C 1 + yield) or both of the total mass of catalyst in a reforming reaction zone and thus allowing allows to extend the life of most of the catalyst for regeneration or replacement is necessary.

Ö \ 8005882

Claims (8)

1. A process for catalytic reforming in which a naphtha feed is contacted under reforming conditions in the presence of hydrogen with a reforming catalyst in a plurality of reaction zones in series, a product with an improved octane number is recovered from the effluent from the last reaction zone and deposited with coke on the catalyst during the course of the reformation, thereby deactivating the catalyst and necessitating any regeneration or replacement thereof, characterized in that in order to extend the life of the catalyst in all reaction zones downstream of the first zone maintain the coke content on the catalyst in the first reaction zone at less than 1% by weight by controlling the frequency of regeneration of the catalyst in the first reaction zone or replacement with fresh or regenerated catalyst. 2. Process according to claim 1, characterized in that no more than 30% by volume of the total catalyst mass is used in the plurality of reaction zones in the first reaction zone. 3. Process according to claim 1 or 2, characterized in that a moving catalyst bed is used in the first reaction zone and at least periodically extracts, regenerates and regenerates part of the coke-contaminated catalyst from the moving part and leads back to the upper part of the moving bed. 4. Multistage process for catalytic reforming a naphtha feed in a plurality of reaction zones in series, characterized in that (a) the catalyst and hydrogen are converted into a moving bed reaction zone under catalytic reforming conditions. through which zone the catalyst is movable by gravity flow and the resulting hydrocarbon-containing effluent from the moving bed reaction zone wins, (b) the amount of coke deposited on the catalyst in the moving bed reaction zone is maintained below 1 wt% by feeding at least periodically fresh or regenerated catalyst 80 0588 2 - I Η- i 'to the upper end of the moving bed reaction zone and at least periodically feeding an equivalent amount of coke-contaminated catalyst to the lower part of the moving reaction zone bed, 5 (c) further the effluent from the moving bed reaction zone at catalytic reforming conditions reacts in a fixed bed reactor system containing at least one fixed bed reaction zone, and (d) a usually liquid catalytic reformed product from the effluent withdrawn from the last fixed bed reaction zone wins . 5. Process according to claim 4, characterized in that the coke-contaminated catalyst is regenerated from the moving bed reaction zone and recycled to the top of the moving bed reaction zone as regenerated catalyst. 6. Process according to claim 4, characterized in that a first reaction zone is used, which contains less than 30% by volume of the total catalyst in the reaction zones. 7. A process for catalytic reforming wherein a naphtha feed is contacted under reforming conditions in the presence of hydrogen with a reforming catalyst in a plurality of reaction zones in series, an improved octane product is recovered from the effluent from the last reaction zone and during the reforming coke is deposited on the catalyst and deactivates, thereby reducing the yield of product, characterized in that the coking content on the catalyst in the first reaction zone is maintained at less than 1 wt% to increase the yield. by controlling the frequency at which the catalyst is regenerated in the first reaction zone or replaced with fresh or regenerated catalyst. 8. Process according to claims 1, 4 or 7S, characterized in that a catalyst is used which contains an aluminum oxide support, with 0.01 to 3% by weight platinum and 0.01 to 5% by weight rhenium in intimate mixture thereon. dropped off. | ****** 8005882