FR2492837A1 - PROLONGED SERVICE TIME REFORMING METHOD WITH REGENERATION - Google Patents

Abstract

THE INVENTION RELATES TO A REFORMING PROCESS WITH AN EXTENDED SERVICE LIFE, WITH REGENERATION. IN A MULTI-ZONE CATALYTIC REFORMING PROCESS, THE C-PRODUCT YIELD OR CATALYST SERVICE LIFE IN ALL REACTION ZONES DOWNSTREAM OF THE FIRST ARE HIGH BY KEEPING LESS THAN 1 COKE WEIGHT ON THE CATALYST IN THE FIRST REACTION ZONE BY ADJUSTING THE FREQUENCY OF REGENERATION OR REPLACEMENT. APPLICATION TO CATALYTIC REFORMING OF HYDROCARBON FRACTIONS.

Description

1.

  The present invention relates to catalytic reforming

  tics of hydrocarbon fractions. It concerns more particularly

  the reforming process in several reaction zones in series, with a view to improving the octane number of the charge.

  The reforming of a fraction of naphtha is generally

  The process is carried out by passing naphtha through a plurality of reaction zones in series, each containing a catalyst comprising a hydrogenation-dehydrogenation component attached to a porous solid support. Typical catalysts include platinum attached to alumina with or without activating agents such as rhenium, tin, iridium, etc. The naphtha fraction to be reformed is contacted in the first reaction zone with a platinum-containing catalyst under reaction conditions suitable for converting naphthenes primarily to aromatics. In addition to the dehydrogenation of naphthenes, side reactions such as isomerization, hydroisomerization and hydrocracking may also occur. Normally, the effluent of the first reaction zone is heated before

  to be introduced into a subsequent reaction zone.

  After a period of use in the reforming, the catalyst is gradually deactivated because of the formation of a coke deposit on its surface and is observed therefore

  a drop in the octane numbers of the product reformate.

  If the octane requirements imposed on the system

  reforming facilities must be continuously satisfied.

  The reaction temperature of the catalyst must be high in order to compensate for the decrease in activity due to the formation of the coke deposit. The fastest deactivation of the

  catalyst occurs in the reactor where dehydrogenation

  cyclization and hydrocracking of paraffins constitute the

  main reactions. Therefore, even when the temperature

  the intake temperature is constant, the average reaction temperature increases from reactor to reactor because the reaction that takes place in each reactor of the series is not as

  endothermic only in the previous reactor.

  2. The formation of a coke deposit on the catalyst

  not only to reduce the activity of the catalyst

  but also to reduce the yield of C + gasoline produced. As a result, the C5 + gasoline yield generally decreases during the course of

  until it reaches an unacceptable level.

  table, level for which the usual practice is to regenerate all or part of the catalyst. At the time

  regeneration, the proportions of coke fixed are normally

  10 to 12% by weight or more on the catalyst in the last reactor and 5 or 6% by weight

  on the catalyst found in the first. The proportions

  coke concentrations on catalysts in intermediate reactors generally fall between these two

beaches.

  Regeneration operations, whether continuous or discontinuous operations, are generally well known in the art. such operations generally involve several steps - carbon removal by contact combustion of the catalyst with a high oxygen gas at an elevated temperature until the carbon has been substantially completely removed; subsequent contact of the catalyst with an oxygen-containing gas to redistribute the platinum group metal; an adjustment of the amount of halogen, and optionally a reduction of the regenerated catalyst with a hydrogen-containing gas before the return of the catalyst to the reactor <see, for example, the United States patent

No. 3,496,096).

  The object of the present invention is to find a reforming process having a prolongation of the cycle of

  work between two regenerations, in comparison with procedures

  ordinary reforming dice. Another object of the invention is to find a method for prolonging the useful life of a

  reforming catalyst that approaches the end of the cycle.

  According to an embodiment applied to a reforming process in which a naphtha feedstock is brought into contact, under reforming conditions in the presence of hydrogen, with a reforming catalyst in several reaction zones in series, a product of the improved octane number is taken from the effluent of the last reaction zone and, during this reforming, coke is deposited on the catalyst by deactivating it and requiring its final regeneration or its replacement, the present invention proposes the

  the process of extending the service life of the

  a catalyst in all reaction zones downstream from the first, which method consists in maintaining the coke level on the catalyst in the first reaction zone at a value of less than 1% by weight of the catalyst by adjusting the frequency with which the catalyst catalyst in the first reaction zone is regenerated or replaced by

  fresh or regenerated catalyst.

  According to another embodiment, the present invention provides a multistage process for the catalytic reforming of a naphtha feed, which process comprises: (a) reacting said feedstock in the presence of a catalyst

  and hydrogen under catalytic reforming conditions.

  in a moving bed reaction zone in which the catalyst moves by gravity flow and collecting the resulting hydrocarbon effluent exiting the moving bed reaction zone; (b) maintaining the amount of coke deposited on the catalyst in the moving bed reaction zone to a value of less than 1% by weight by introduction at least

  periodic catalyst fresh or regenerated by the

  upper limit of the moving bed reaction zone and

  at least periodically withdraw an equivalent quantity

  coke contaminated catalyst slurry through the lower end of said moving bed reaction zone; (c) continuing the reaction of the effluent from the moving bed reaction zone under catalytic reforming conditions in a fixed bed reactor system containing at least one fixed bed reaction zone; (d) separating a normally liquid reformate from the effluent

  withdrawn from the last fixed bed zone.

4.

  According to yet another embodiment

  catalytic reforming process wherein a naphtha fraction is contacted under reforming conditions, in the presence of hydrogen, with a reforming catalyst in a plurality of reaction zones in series, a product of The improved octane is separated from the effluent of the last reaction zone and, during this reforming, coke is deposited on the catalyst and deactivates it thereby reducing the product yield, the present invention provides a process for increasing said yield. which consists in keeping the coke level on the catalyst in the first reaction zone at a value of less than 1% by weight by controlling the frequency with which the catalyst is present.

  in the first reaction zone is regenerated or is replaced

  by fresh or regenerated catalyst.

  In the accompanying drawings: FIG. 1 illustrates the effect produced on the reaction temperature, the C.sub.2 + product yield and the hydrogen production of a catalyst bed containing 0, 10, 20 and 30% of fresh catalyst over a catalyst layer loaded with coke; FIG. 2 illustrates the yield losses due to variable coke rates on the catalyst at the top of a coke laden catalyst bed; FIG. 3 illustrates the results obtained by comparing a reforming carried out with a catalyst charged with coke and a reforming carried out with 10% of fresh catalyst over

a catalyst loaded with coke.

  The present invention can be applied to reforming systems in which a plurality of reaction zones in series are used. Preheaters are preferably present between the reaction zones so that the temperature of the feed introduced into each reaction zone can be adjusted. Preferably, each reaction zone is located in a separate reactor. The present invention is directed to systems in which at least two reactors and preferably 3 to 5 reactors are installed in series. Although some reactors or all 5. reactors may be moving-bed reactors, the most preferred system is one in which all reactors are fixed-bed or all but the first are fixed-bed reactors.

the first is moving bed.

  In multi-zone reforming systems, the catalyst composition may vary in

  different reforming zones, although generally the cata-

  lyser be the same in all -zones. However, the catalyst volume generally differs from one reaction zone to the next. The usual loading of the catalyst in a three-reactor system can be divided into a quarter of the total catalyst load in the first reactor, a quarter in the second reactor and half in the last reactor. Generally, the first reactor contains less catalyst because the very endothermic reaction that takes place causes rapid cooling of the charge. If a large volume of catalyst was present in the first

  reactor, the temperature of the feed in the lower portion

  the catalyst bed would be too low for significant dehydrogenation reactions to take place and, therefore, the lower portion of the catalyst bed

would not be exploited effectively.

  To benefit from the advantages of the present invention, the catalyst in the first reaction zone must be replaced or regenerated with sufficient frequency to maintain a coke content in the catalyst of less than 1% by weight, preferably less than 0, 7% and in particular less than 0.5% by weight. The first

  The reaction zone may contain up to 30% by volume of

  total lyser found in the reactor system, although

  that it preferably contains only a proportion that does not

  than 20% and, even better, only 15% of the

  total mass of catalyst in this system.

  The temperature may be the same in each of the reaction zones or it may be different, but in general it is in the range of 371 to 5661C and preferably in the range of about 454 to 5380C. The terminal reaction zone generally has the highest average temperature of the catalyst bed. The pressure in each of the reaction zones is usually the same, and it is equal to or greater than the atmospheric pressure. Preferably, the gauge pressure is in a range of 0.175 to 7 MPa and especially in the range of 0.35 to 25 MPa. The temperature and pressure can be correlated with liquid hourly space velocity (LHSV) to promote particularly desirable reforming reactions and this rate is generally in the range of 0.01 to 10 and preferably in the range of from 1 to 5. It is obvious that when the catalyst charge distribution and the reaction zones are different, the space velocities in the individual reaction zones can

vary greatly.

  Although reforming generally results in the production of hydrogen, it is common to recycle hydrogen separated from the effluent of any of the reaction zones, usually the terminal zone, into the

  first reaction zone or in subsequent zones.

  The hydrogen can be mixed with the feedstock before contacting the catalyst or at the same time as introducing feedstock into the reaction zone. The presence of hydrogen

  has the effect of reducing the formation of coke which tends to

  sound the catalyst. Hydrogen is preferably introduced into the reforming reaction zone in a proportion ranging from 0.5 to 20 moles of hydrogen per mole of

  charge. Hydrogen can be mixed with hydro-

light gaseous carbides.

  The catalyst used in the reaction zones comprises a platinum group component in combination 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 is

  present in an amount of 0.01 to 3% by weight and preferably

from 0.01 to 1% by weight.

  Other components in addition to the group component

  platinum may be present on the porous solid support.

  7. The presence of rhenium is particularly preferred, for example in a proportion of 0.01 to 5% by weight and in particular of 0.01 to 2% by weight. Rhenium significantly improves the yields obtained when using a platinum-containing catalyst, and a platinum-rhenium catalyst is described in detail in US Pat. No. 3,415,737. Generally, the catalyst is activated. for reforming by the addition of a halide, especially a fluoride or a chloride. The halide gives the catalyst a limited degree of acidity which is beneficial for most

  reforming operations. The catalyst activated by a halogen

  genius preferably contains 0.1 to 3% by weight of halide

  total, and the halide is preferably a chloride.

  The catalyst located in the first reaction zone can be replaced or regenerated in situ or ex situ, with sufficient frequency to maintain a deposit on it

  less than 1% by weight of coke, preferably a lower

  0.7% by weight and in particular less than 0.5% by weight

  weight. The amount of coke on the catalyst must be expressed

  the average amount of coke relative to the total catalyst volume in the first reaction zone. The catalyst in the first reaction zone may be arranged in a fixed bed or in a moving bed. If the reaction zone is a fixed bed, the flow may be radial, upward or downward and it may be advantageous for an oscillating reactor to be present and ready for operation when the first fixed bed reaction zone is withdrawn. service for its regeneration. Naturally, if the

  first reaction zone comprises a mobile bed of catalytic

  However, this reaction zone can be kept in service while fresh or regenerated catalyst is added to the upper part of the reaction zone and the spent catalyst, deactivated by the coke, is withdrawn from the base. The other reaction zones of the system may be fixed bed or moving bed reaction zones, but for the purposes of the present invention, it is advantageous that they be fixed bed reaction zones. The fixed bed reaction zones may be upflow, downflow or

  radial, the latter flow mode being preferable.

  8. To determine the proportion of coke or carbon deposited on the catalyst of the first reactor, a sample of this catalyst may be taken at the time of discharge from the reactor in a moving bed reaction zone or samples may be taken. catalyst of the reaction zone itself without interrupting the normal reforming process. Various means are available for taking catalyst samples from reactors without involving the shutdown of these reactors; see, for example, U.S. Patent Nos. 3,129,590 and 3,319,469. The amount of coke or carbon deposited on the catalyst sample can be determined by any convenient means, for example by burning carbon and

  determination of the amount of CO2 produced or by

  the rate at which a combustion zone progresses in a catalyst bed contaminated with coke, as described in US Pat.

No. 3 414 382.

  The hydrocarbon feed used in the operation

  reforming the present invention can be any hydro-

  suitable carbide capable of being catalytically reformed under the conditions indicated. Preferably, the filler is a naphtha fraction which is a light hydrocarbon oil boiling generally in a range of 21 to 2881C and preferably in the range of 66 to 2321C. The feed may be for example a straight-run naphtha, a naphtha

  thermally cracked or catalytically cracked or mixtures thereof.

  Generally, the naphtha feed contains about 25 to 75% and, preferably, about 35 to 60% paraffins, about 15 to 65% and preferably about 25 to 55% naphthenes and about 5 to 20% aromatics. the percentages being

expressed on a volume basis.

  Catalyst regeneration processes are well known in the art and generally involve the removal of carbon from the catalyst by combustion, by contacting the latter with an oxygen-containing gas at an elevated temperature of about 37%. at 5931C. Preferably, the oxygen concentration and the temperature are 9.

  elevated in stages as regeneration progresses.

  After removal of the carbon by combustion, a halogen gas may be introduced in contact with the catalyst. Then, the catalyst can be dried and reduced before being returned to the reforming zone. Advantageous examples of regeneration processes are illustrated in US patents

  No. 3,134,732 and 3,396,096.

EXAMPLES

  The present invention is illustrated in more detail by the following examples which are given by way of non-limiting example. Example 1 demonstrates that the presence of a small amount of fresh catalyst at the top of a catalyst bed containing 10.9% carbon has the effect of substantially increasing the C 5 + product yield.

  and hydrogen production as well as lowering the temperature

  catalyst, which is necessary to form a

  product of predetermined octane number. These results indicate

  that the presence of a small amount of fresh catalyst upstream of a larger mass of coke-contaminated catalyst can significantly prolong the period during which the total mass of catalyst can be maintained in the reforming service before to be regenerated. Example 2 demonstrates the harmful effect

  performance by the presence of a growing quantity

  of coke on a small mass of catalyst lying above a larger mass of coke deactivated catalyst. These results indicate that the overall yield is even better than the amount of carbon present on the catalyst in the first reaction zone is lower. Example 3 is a parallel comparison of the reforming with a catalyst bed

  containing 10% fresh catalyst over a bed of cat-

  a cofactor containing various proportions of coke, which illustrates the advantages, in terms of activity and yield, of the presence of a small layer of fresh catalyst at the

  upper part of the catalyst bed.

10.

EXAMPLE 1

  A Mid-Continent naphtha is passed through

  both the characteristics shown in Table I in a series of fouled reactors containing a platinum and rhenium reforming catalyst under reforming conditions involving a pressure of 1.4 MPa, a liquid hourly space velocity of 2, a molar ratio of hydrogen to hydrocarbon equal to 3, and a temperature adjusted so as to obtain as product a reformate whose research octane number is equal to 98 (without additive).

TABLE I

  Mid-Continent Naphtha Density at 15.6 C 0.7587 Distillation D-86 Eb. initial, C 78.9

%, C 101.1

%, C 115

50%, C 128.3

%, OC 145.5

  % A oC 172.2 Eb. Final, C 198.9 Paraffins,% 43.1 Naphthenes,% 46.8 Aromatic,% 10.0 After 55 days of effective running a portion of the catalyst is discharged from the last reactor of the series. Catalyst carrying an average of 10.9% coke is tested in a miniature pilot reformer in three runs

  in which the 10, 20 and 30% of the upper layer

  the spent catalyst are replaced by an equiva-

  worth of new catalyst. The results shown in Fig. 1 of the accompanying drawings and in Table 2 show that when a new catalyst layer is placed over a fairly large mass of catalyst carrying a coke deposit, (1) the activity of the mass total catalyst increases significantly, 10.5 C for 10% of new catalyst, 12.1 C 11.

  for 20% of new catalyst and 17.6 C for 30% of catalyst.

  new lyser; (2) the yield of C5 + product increases by 1.9% by volume of liquid, from about 78.6 to 80.5% by volume of liquid; (3) hydrogen production increases by about 11%, from 216.6 m3 / m3 of load to 241.4-239.8 m3 / m3 of load, and (4) methane production decreases

  from 23 to 26%, from 19.2 m3 / m3 of load to 14.2%

  14.8 m3 / m3 of load. Thus, the presence of a small amount of new catalyst over a larger amount of coke-bearing catalyst has the effect of substantially increasing the activity, the liquid C5 + yield and the

  rate of hydrogen production, much more than

  provide for the small amount of new catalyst added.

TABLE II

  Laminate bed tests on a catalyst at the end of the cycle Toi, C C5 +, H2, CH4, volume m3 / m3 m3 / m3 liquid,% Catalyst at the end of the cycle

(FDC), 10.9%

of C 512.8 78.6 216.6 19.2

% of

  new catalyst on 90% of catalyst

FDC 502.2 80.6 241.4 14.6

% of

  new catalyst on 80% of catalyst

FDC 500.5 80.5 239.8 14.2

% of

  new catalyst on 70% of catalyst

FDC 495 80.5 240.1 14.8

  In FIG. 1, the dots on the graph with 10%, 20% and 30% values and 12. of which the abscissa is 55 days, correspond to the proportion of new catalyst in the top layer. The curves

  correspond to the test catalyst alone.

EXAMPLE 2

  A study was conducted to determine the effect on performance by a variable amount of

  coke on the 10% of catalyst occupying the top position

  in a catalyst bed. Figure 2 illustrates the effect on C5 + efficiency and hydrogen yield in association with the presence of an increasing amount of

  carbon on the catalyst in the upper layer represents

  as much as 10% of the catalyst bed. Using as a control a catalyst bed carrying 10% of new catalyst over 90% of catalyst containing 13.3% by weight of carbon, it is found that a catalyst bed whose upper layer represents 10% of the catalyst contains 2% of catalyst. % by weight of carbon loses 1% by volume of C5 + yield; that a catalyst bed whose upper layer representing 10% of the catalyst contains about 6% by weight of carbon loses 2% by volume of C + yield; and that a catalyst bed having an upper layer of 10% of the catalyst containing about 12% by weight of carbon loses about 3% by volume of the C5 + yield. The loss of hydrogen yield also increases at the same time that the carbon content in the upper layer represents 10% of the catalyst in the catalyst bed. Thus, in order to make the most of the process of the invention with respect to efficiency, the amount of carbon on the catalyst at the top of the catalyst bed should be kept as low as possible. In FIG. 2, the abscissa indicates the percentage by weight of carbon in the upper layer

representing 10% of the bed.

EXAMPLE 3

  An experiment was conducted to compare the performance of a coke deactivated platinum and rhenium catalyst bed 13 with an equivalent volume of catalyst representing 10% by volume of new catalyst deposited on 90% of the deactivated catalyst. Catalyst samples were taken from an industrial reformer after about 0, 28, 61, 89 and 122 days of service. A portion of each catalyst sample was tested on the feed indicated in Table I under reforming conditions involving a pressure of 1.4 MPa, a liquid hourly space velocity of molar ratio of hydrogen to hydrocarbon equal to 3, and a temperature adjusted to obtain as product a reformate having a research octane number equal to 98 (without additive). A layer of 10% new catalyst was deposited on a% catalyst layer from the respective samples taken after 61, 89 and 122 days, and then the catalyst obtained

  has been tested under the same conditions of refor-

  mage. As shown in FIG. 3 of the accompanying drawings, the catalyst beds containing 10% new catalyst are much more active (110C after 120 hours) and more selective (C5 + yield equal to 4% after 120 hours) than the beds. containing the catalyst carrying a coke deposit. The fouling rate of the beds containing 10% new catalyst is lower than that of the catalyst beds carrying a coke deposit <0.0820C per day against 0.180C per day.

  this indicates that the effect of the new catalyst is wide-

  disproportionate to its volumetric presence.

  In FIG. 3, the curves in solid line correspond to the test catalyst bearing quantities

  coke variables and the broken line curves correspond to

  the presence of 10% of new catalyst on 90% of

test catalyst.

  It is apparent from the above results that the present invention operates in an original and effective way to increase activity, selectivity (C 5 + yield) or both characteristics of the total mass of catalyst in a reforming reaction zone. thus allowing to extend the service life of the catalyst mass before

  regeneration or replacement is necessary.

  14. It goes without saying that the present invention has been described only for explanatory purposes, but in no way limiting and that many modifications can be made without it.

get out of his frame.

15.

Claims (8)

  1. - Reforming process in which-a charge   naphtha is placed in contact under conditions   reforming in the presence of hydrogen with a reforming catalyst in a plurality of reaction zones in series, an improved octane product is obtained from the effluent of the last reaction zone and, during the   reforming, coke is deposited on the catalyst   and ultimately requiring its regeneration or replacement, characterized in that it consists in extending the service life of the catalyst in all reaction zones downstream of the first zone by maintaining the proportion of coke on the catalyst in the reaction zone. first reaction zone, to a value of less than 1% by weight by adjusting the frequency at which the catalyst in the first reaction zone is regenerated or is replaced with new or regenerated catalyst.   2. - Process according to claim 1, characterized   in that the first reaction zone contains not more than 30% by volume of the total mass of catalyst   found in the various reaction zones.   3. - Process according to claim 1, characterized   in that the first reaction zone comprises a moving bed of catalyst, and a portion of the coke-contaminated catalyst is removed at least periodically in the lower portion of the moving bed, regenerated and re-introduced.   in the upper portion of the moving bed.   4. - Multistep process for the catalytic reforming of a charge formed of a naphtha in several reaction zones in series, characterized in that it consists in (a) reacting the charge in the presence of a catalyst and hydrogen under catalytic reforming conditions in a moving bed reaction zone in which the catalyst can move by gravity and recovering hydrocarbon effluent produced from the moving bed reaction zone; (b) maintaining the amount of coke deposited on the catalyst in the moving bed reaction zone below 1% 16.   by weight by at least one periodic introduction of catalytic   or at least periodically withdrawing an equivalent amount of coke-contaminated catalyst from the lower end of said moving-bed reaction zone; (c) continuing the reaction of the moving bed reaction zone effluent under catalytic reforming conditions in a fixed bed reactor comprising at least one fixed bed reaction zone, (d) recovering a catalytic reformate normally liquid effluent withdrawn from the last reaction zone to fixed bed.   5. - Process according to claim 4, characterized   in that the coke-contaminated catalyst withdrawn from the moving bed reaction zone is regenerated and returned to the upper part of the moving bed reaction zone as regenerated catalyst.   6. - Process according to claim 4, characterized   in that the first reaction zone contains less than   % by volume of the total catalyst of the reaction zones.   A process for increasing the yield in a reforming process in which a naphtha feedstock is contacted under reforming conditions in the presence of hydrogen with a reforming catalyst in a plurality of reaction zones in series, a product an improved octane number is obtained from the effluent of the last reaction zone and, during reforming, coke is deposited on the catalyst and deactivates it, thereby reducing the product yield, characterized in that it consists in increasing the yield by maintaining the proportion of coke on the catalyst in the first reaction zone to a value of less than 1% by weight by adjusting the frequency at which the catalyst of the first reaction zone is   regenerated or replaced with new or regenerated catalyst.   8. - Process according to any one of the   Claims 1, 4 and 7, characterized in that the catalyst comprises an alumina support on which 0.01 to 3% by weight platinum and 0.01 to 5% by weight are mixed. rhenium weight.