FI86603C - Catalytic composite for hydrocarbon conversion - Google Patents

Description

86603

This invention relates to a novel catalytic composite for the conversion of hydrocarbons, and in particular to the dehydrocyclization of aliphatic hydrocarbons to aromatics. More specifically, this new composite makes it possible to convert C + paraffins to their corresponding aromas with a high degree of selectivity, which makes it possible to easily prepare large amounts of aromatics.

In the past, it has become common practice to perform the conversion of aliphatic hydrocarbons to aromatics by a well-known catalytic reforming process. The petroleum fraction is typically a full boiling fraction having an initial boiling point of 10 ° C to 38 ° C and a final boiling point of about 163 to 218 ° C. Such full boiling point naphtha contains significant amounts of paraffinic C + hydrocarbons and naphthenic C + hydrocarbons. As is well known, these paraffinic and naphthenic hydrocarbons are converted to aromatics by a variety of reaction mechanisms. These mechanisms include hydrogenation, dehydrocyclization, isomerization followed by dehydration. Thus, naphthenic hydrocarbons are converted to aromatics by dehydration! 1a. Paraffinic hydrocarbons are converted to the desired aromatics by dehydrocyclization11a and may also undergo isomerization. Thus, it is clear that the number of reactions taking place in the catalytic reforming zone is large and the typical reforming catalyst must be able to carry out numerous reactions in order to be considered useful in a commercially viable reaction system.

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Due to the complexity and number of reaction mechanisms involved in catalytic reforming, it has recently become common practice to develop highly specific catalysts tailored to convert only certain reactive compounds to aromatics. Such catalysts offer advantages over a typical reforming catalyst which must be able to participate in a number of reaction mechanisms. Ongoing research has focused on the production of a catalyst for the conversion of paraffinic hydrocarbons, especially hydrocarbons containing six or more carbon atoms, to aromatic hydrocarbons. Such a catalyst can be expected to be much more specific and lead to fewer undesirable side reactions such as hydrocracking. As can be appreciated by those of ordinary skill in the art, increased production of aromatics is desirable. The increased aromatic content of gasolines as a result of lead reduction, as well as the demands of the petrochemical industry, make C -C aromatics highly desirable products. Thus, it would be most advantageous to use a catalyst composition that is highly selective for the conversion of less valuable C + paraffins 6 to more valuable C + aromatics.

Therefore, a main object of the present invention is to provide a catalytic composite and a process for its preparation and use for the conversion of hydrocarbons. The main goal is to provide a process for the conversion of paraffinic C + hydrocarbons, in particular paraffinic C -C hydrocarbons, to their corresponding aromas.

Accordingly, a general embodiment of the present invention is directed to a catalytic composite comprising an acid-free zeolite bonded with or without a supported tris 11a, catalytically effective amounts of a Group VIII metal component a, and sufficient surface-deposited alkali metal to provide a surface-deposited alkali metal index. , which is at least 10.

I.

3,8603 An alternative general embodiment of the present invention is a hydrocarbon conversion process characterized in that, under hydrocarbon conversion conditions, the hydrocarbon feedstock is contacted with a catalyst composite containing an acid-free zeolite bonded with or without support groups. VIII metal component a and a time or layer sufficiently coated on the surface to obtain an index of the metal deposited on the surface of at least 10.

A further embodiment of the present invention comprises a process for preparing a catalyst composite which comprises doping an acid-free zeolite with or without a support matrix, catalytically effective amounts of a Group VIII metal component and sufficient metal to provide an index of at least 10 metal deposited on the surface.

These, as well as other objects and embodiments, will become apparent from the following more detailed description of the present invention.

Aluminine silicates containing Al metal metals are well known in the art. For example, U.S. Patent 3,013,986 describes an L-zeolite filled with a metal alloy. In particular, this literature reference indicates that the potassium or potassium / sodium forms of L-zeolite are the preferred starting materials for Al-metal filled L-zeolite. The literature reference teaches that a dehydrated molecular sieve can be contacted with alkali metal fumes to produce an aliquot-filled molecular sieve in which the aliquot metal is contained within the interior of a zeolite molecular sieve. However, the literature reference does not describe an acid-free zeolite doped with catalytically effective amounts of a Group VIII metal component and a surface-deposited alkali metal. Moreover, the literature reference does not suggest that such a mixture would have any use as a hydrocarbon conversion catalyst.

U.S. Pat. No. 4,866,603 to 3,376,215 discloses a hydrocarbon conversion catalyst containing a Group VIII metal and comprising a support consisting of (1) an adsorbent second inorganic oxide and (2) a mordenite-structured zeolite deposited with about 10-1000 ppm zeolite. by weight of a metal selected from the class of alkali metals, alkaline earth metals and alloys thereof. This literature reference teaches that, a support consisting of a zeolite in mordenite form and a refractory oxide is co-catalytic. In contrast, an essential feature of the present invention is the use of an acid-free zeolite. In this acid-free form, the zeolite of this invention cannot be considered catalytic. Rather, the acid-free zeolite functions by modifying the catalytic Group VIII metal of this invention. Therefore, the the literature reference does not describe a novel catalyst of this invention.

U.S. Patent 3,755,486 discloses a process for the dehydrocyclization of C 1 -C 6 hydrocarbons having at least a C backbone using 6

Li, Na or K zeolite X and Y or faujasite impregnated with 0.3-1.4% platinum. Ko. however, the literature reference fails to present the advantages obtainable by utilizing a catalytic composite consisting of an acid-free zeolite on the surface of which an aliquot metal is deposited. Similarly, U.S. Patent 3,819,507 and U.S. Patent 3,832,414, although describing processes similar to U.S. Patent 3,755,486, do not succeed in advising the use and benefits of such an acid-free zeolite doped with platinum and a surface layered ai kaiimetal 1ia.

U.S. Patent 4,140,320 describes a process for the dehydrocyclization of aliphatic hydrocarbons using an L-type zeolite having exchangeable cations, at least 90% of which are alkali metal ions selected from the group consisting of sodium, lithium, potassium, rubidium and cesium. ions, and 86603 containing at least one metal selected from the group consisting of Group VIII metals, tin and germanium. This literature reference fails to describe the catalyst composite of the present invention because the the β-ions absorbed during the catalyst reference literature are all associated with the ion exchange sites in L-zeolite 11a. It does not describe an L-zeolite with a metal layer deposited on the surface. U.S. Patent 4,417,083 describes a dehydrocyclization process using a substantially acid-free zeolite having a pore diameter greater than 6.5 Å and containing at least one metal selected from the group consisting of platinum, rhenium, iridium, tin, and germanium. In addition, the catalyst contains sulfur and time cations. However, this literature reference does not disclose any surface layered metal.

U.S. Patent No. 4,416,806 discloses yet another paraffin dehydrocyclization catalyst containing platinum, rhenium as carbonyl, and sulfur in a zeolite-free crystalline alumina silica having more than 90% compensated for time cations and having a pore diameter of greater than 6. .5 Ä. This literature reference also fails to disclose a catalytic assembly for dehydrocyclization with a metal layer deposited on the surface.

A recent U.S. Patent 4,430,200 discloses a hydrocarbon conversion catalyst containing a silica-rich zeolite, such as mordenite or zeolite Y, which is base-exchanged with a copper-containing zeolite. However, this literature reference also fails to describe an alkali-deposited catalyst. Besides, the The literature reference only describes the use of a prior art catalyst in the cracking process and not in the dehydrocyclization process.

Recent U.S. Patent 4,448,891 discloses a dehydrocyclization catalyst consisting of L-zeolite soaked in a solution having a pH of at least 11 for a time and 6,866,33 at a temperature effective to prolong the period of time that the catalyst retains its catalytic activity. In addition, the catalyst contains a Group VIII metal. However, the literature reference advises that the silica modifies the silica content of the L-zeolite and changes its structure. After some time, the literature reference mentions that the L-zeolite is washed to remove excess ions. Therefore, the the catalyst of the literature reference has not deposited an alkali metal deposited on the surface. Therefore, it does not describe the catalyst of the present invention.

In summary, therefore, there is no awareness in the art of a catalyst composite for converting hydrocarbons, in particular to dehydrocyclized aromatics of C + paraffins, which comprises an acid-free zeolite bound with or without a support matrix, catalytically effective amounts of Group VIII metal component a and sufficiently to provide an index of alkali metal deposited on the surface of at least 10. Moreover, there is no awareness in the art of the advantages available from such a new catalyst and its use.

Briefly, the present invention relates to a catalyst composite comprising an acid-free zeolite bonded with or without a support matrix, catalytically effective amounts of a Group VIII metal component a, and sufficient surface-deposited aluminum to provide an index of surface-deposited metal that is at least 10. In addition, the catalytic mixture of the present invention has a particular use as a catalyst for the dehydrocyclic ring of C + paraffins, especially C -C paraffins.

As mentioned above, an essential feature of the catalyst of this invention is that it contains an acid-free zeolite. By "acid-free zeolite" it is to be understood that substantially all cation exchange sites of the zeolite are occupied by cationic ions other than hydrogen. Preferably, these cationic ions consist of alkali metal cations, although other cationic ions may be present. Regardless of the actual cationic ions at the exchange sites, substantially all of the cationic sites in the acid-free zeolite of this invention are occupied by non-hydrogen cations, making the zeolite substantially completely cation-exchanged. Many means are known in the art for achieving a substantially fully cation-exchanged zeolite, so they need not be further elucidated here. The acid-free zeolite of this invention acts by modifying the catalytic Group VIII metal and is substantially inert in the reaction. The acid-free zeolite of this invention is believed to be non-catalytic and hence the requirement that it be acid-free.

Typical acid-free zeolites that can be used in this invention include X-zeolite, Y-zeolite and mordenite. L-zeolite is particularly preferred for the practice of this invention. The catalyst composite of this invention may also consist of a mixture of different zeolites. Of course, each zeolite used in the invention must be in the acid-free form as defined above, and therefore the cationically interchangeable sites are substantially completely cation exchanged with cationic ions other than hydrogen. As also mentioned above, the cations occupying the cationically interchangeable sites typically consist of one or more alkali metals such as lithium, sodium, potassium, rubidium and cesium. Thus, the acid-free zeolite of the present invention may consist of the sodium forms of X-zeolite, Y-zeolite or mordenite. A particularly preferred acid-free zeolite for use in this invention is the potassium form of L-zeolite. However, it is also to be understood that the acid-free zeolite of the invention may contain more than one type of time metal cation at cationically interchangeable sites, for example, sodium and potassium. As will be explained in more detail below, this may occur as a result of competing cation or changes that may occur during the deposition of the alkali metal deposited on the surface.

A preferred feature of the invention is a support matrix to which the acid-free zeolite is bound. As is well known in the art, the use of a support matrix improves the physical strength of the catalyst. In addition, the use of a support matrix makes it possible to form shaped bodies suitable for use in catalytic conversion processes. For example, the acid-free zeolite of this invention can be bound to a support matrix such that the final shape of the catalytic composite is a sphere. The use of a spherically shaped catalyst is, of course, known to be advantageous for many purposes. In particular, when the catalyst of the present invention is used in a continuous, mobile bed hydrocarbon conversion process, the spherical shape improves the ability of the catalyst to move easily through the reaction and regeneration zones. Of course, other forms may be used when preferred. Thus, the catalytic composite can be formed into extrudates, saddles, etc.

The support matrix of the present invention may consist of any of the support matrices typically used to bind zeolite-containing catalyst composites. Such support matrices are well known in the art and include clays, bauxite, refractory inorganic oxides such as alumina, zirconium dioxide, hafnium oxide, beryllium oxide, vanadium oxide, cesium oxide, chromium oxide, zinc oxide, magnesium oxide, thorium oxide, thorium oxide, magnesium oxide, chromium oxide-alumina, aluminum oxy di-boron oxide, etc. The preferred support matrix consists of silica and the particularly preferred support matrix consists of alumina. It is further preferred that the support matrix be substantially inert to the reagents that the composite is intended to convert to other components of the composite. Therefore, it is preferred that the support matrix be acid-free in order to avoid the promotion of undesirable side reactions. Such acidity can be achieved in the presence of alkali metals, such as those which form an alkali or 1i n deposited on the surface.

The acid-free zeolite can be bound to the support matrix by any method known in the art. Such methods include pelletizing, extrusion, granulation, marumarization, etc. A particularly preferred method is the so-called oil drop method.

Typically, when the zeolite is bound to the support matrix by an oil drop method, the ground zeolite is mixed with a sol containing the desired support matrix or its precursors and gelling agent. The droplets of the resulting mixture are dispersed as spherical droplets in a suspending medium, typically an oil. The gelling agent then begins to cause the sol to gel as a result of a change in the pH of the sol. The resulting gelled support matrix has bound the zeolite to itself. The suspending medium helps to maintain the spherical shape of the droplets. Useful suspending media include Nujol, Kerosene, Selected Fractions of Gas Oil, etc. Many gelling agents are known in the art and include both acids and bases. Hexame-thienetetramine is just one such known gelling agent. Hexamethylenetetramine decomposes slowly to ammonia when heated. This results in a gradual change in pH and consequent gradual gelation.

Regardless of the precise method by which the acid-free zeolite is bound to the support matrix, sufficient acid-free zeolite can be used to result in a catalyst composite containing about 25-75% by weight of acid-free zeolite based on the zeolite and the weight of the support matrix. The exact amount of acid-free zeolite that is preferably included in the catalyst composite of the invention is a function of the particular acid-free zeolite, support matrix, and particular application of the catalyst composite. Catalyst composite containing about 50-75 ρ-ϊ L-zeolite in the potassium form bound to alumina is preferably used for the dehydrocyclization of non-aromatic C 1 -C 6 hydrocarbons.

Another essential feature of the catalyst of this invention is the presence of catalytically effective amounts of a Group VIII metal component, including catalytically effective amounts of a nickel component, a rhodium component, a palladium component, an iridium component, a platinum component, or mixtures thereof. A particularly preferred Group VIII metal 1 component is the platinum component. The other components of the catalyst composite can be incorporated into the Group VIII metal component by any suitable means known in the art. For example, the platinum component can be impregnated with a suitable solution, such as dilute chlorinated acid. Alternatively, the Group VIII metal component may be doped by ion exchange, in which case some of the cation exchange sites of the acid-free zeolite may contain Group VIII metal ions. After ion exchange, the Group VIII metal can be subjected to low temperature oxidation prior to any reduction step. The other components of the Group VIII metal 1 can be alloyed either before or after the deposition of the surface-deposited precious metal described below. In addition, the Group VIII metal can be mixed with the acid-free zeolite and then the Group VIII metal-containing acid-free zeolite can be bound to the preferred support matrix.

Regardless of the precise method by which the Group VIII metal component is blended into the catalyst composite, any catalytically effective amount of the Group VIII metal component a can be used. The optimum concentration of the Group VIII metal component generally depends on which Group VIII metal component a is used in the catalyst of the invention. However, in general, about 0.01 to 5.0% by weight of the Group VIII metal component a, based on the weight of the final catalyst composite, can be advantageously used.

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It is believed that the best results are obtained when the Group VIII metal is deposited on a substantially completely acid-free zeolite instead of a support matrix. It is also preferred that the Group VIII metal component be highly dispersed. The Group VIII metal 1 i component is most effective in the reduced state. Any suitable means can be used to reduce the Group VIII metal component and many are well known in the art. For example, after doping, the Group VIII metal component may be contacted with a suitable reducing agent such as hydrogen at an elevated temperature for a period of time.

In addition to the Group VIII metal component a of the catalyst of the invention, it is contemplated in this invention that it may contain other metal components that are well known to have catalyst modifying properties. Such metal components include rhenium, tin, cobalt, indium, gallium, lead, zinc, uranium, thallium, dysprosium, and germanium, etc. components. The addition of such metal components has proven advantageous in catalytic reforming as accelerators and / or extenders. Thus, it is within the scope of this invention that catalytically effective amounts of such modifiers may be advantageously added to the catalyst of this invention to improve its performance.

Regardless of the particular Group VIII metal component or catalytic modifier doped with the catalyst of the invention, the catalyst of the present invention also contains sufficient surface-deposited precious metal to provide a surface deposition time index of at least 10 and preferably about 40. -500. It is to be understood that a surface-deposited metal or metal is meant that the alkali metal component is not attached to the cationically exchangeable site, but is instead an additional aluminum metal component relative to the amount required to occupy substantially all of the cationically exchangeable sites.

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It is further to be understood that the index of the alkali metal deposited on the surface is an indication of the amount of such alkali metal deposited on the surface. As used herein, the term "index of surface-deposited alkali metal" is defined as the soluble alkali metal

To moles per liter multiplied by the number 10 by weight of catalyst component a containing 0.5 g of acid-free zeolite when placed in 10 cm of ion-exchanged water and measured with said alkali metal sensitive electrode at 25 ° C. :in.

Any alkali metal can be used as the surface-deposited alkali metal, including lithium, sodium, potassium, rubidium, cesium, and mixtures thereof. The alkali metal deposited on the surface that gives the best results depends on the acid-free zeolite used in each case. Potassium on the surface of the potassium form of the L-zeolite is particularly preferred. In addition, sodium on the surface of the sodium form of X-zeolite or Y-zeolite can also be advantageously used.

It is to be understood that the surface metal deposited on the surface need not be the same as the metal metal cation that has occupied the cationically exchangeable sites of the acid-free zeolite. As a result, the surface metal deposited on the surface may consist of, for example, potassium, while the acid-free zeolite may consist of the sodium form of X-zeolite or Y-zeolite. Likewise, the surface-deposited alloy metal may consist of, for example, potassium and sodium on the surface of the sodium form of X-zeolite or Y-zeolite.

The surface deposited metal can be doped with the catalyst of this invention by any suitable technique. An aqueous solution of an alkali metal salt can be used using a standard ky nation technique. Either basic or neutral salts can be used. For example, when potassium is deposited on a catalyst consisting of the potassium form of L-zeolite, the impregnation solution t; 13 86603 may consist of a basic salt of potassium such as KHCO, K 2 CO 2, KOH, etc. Alternatively, a solution containing a neutral potassium salt such as KCl may be used.

In addition, it should be noted that when it is desired to obtain an alkali metal deposited on a different surface than the early metal cation associated with the cation-exchangeable sites of the acid-free zeolite, some competitive ion exchange may occur during impregnation. For example, when potassium is deposited on the surface of the sodium salt of the Y-zeolite, competitive ion exchange may occur, in which part of the potassium in the saturating solution replaces part of the sodium in the cation-exchangeable sites of the acid-free Y-zeolite. This displaced sodium in turn deposits on the surface of the zeolite along with the rest of the potassium. The net result is that the cations at the cation-exchangeable sites consist of sodium and potassium ions, while the surface-deposited alkali-1 suction consists of sodium and potassium. A catalyst having such a distribution is within the scope of this invention, but may not give the best results. However, techniques that minimize the problem of competitive ion exchange are well known in the art of catalyst preparation, and thus a more detailed explanation to those of ordinary skill in the art is not necessary.

As mentioned above, the catalyst composite 1a of the present invention has a particular use as a hydrocarbon conversion catalyst. Thus, the hydrocarbon feedstock is contacted with the catalyst composite of this invention under hydrocarbon conversion conditions. A wide range of hydrocarbon conversion conditions can be used and the exact conditions will depend on the particular feedstock and the reaction being performed. In general, these conditions include a temperature of about 260-816 ° C, a pressure of about 100-10000 kPa, and a liquid volume flow rate (calculated based on the equivalent liquid volume of the feedstock, which is contacted with the catalyst per hour divided by the 14 86603 catalyst-containing conversion zone volume) about 0.2-15 h'1. In addition, hydrocarbon conversion conditions may include the presence of a diluent such as hydrogen. When this is the case, the molar ratio of hydrogen to hydrocarbon can be about 0.5: 1 to 30: 1.

A particularly preferred application of the catalyst of this invention is its use as a dehydrocyclization catalyst, especially in the dehydrocyclization of non-aromatic C 1 -C 5 hydrocarbons. Thus, a carbon-6 8 hydrogen feedstock consisting of non-aromatic C 1 -C 6 -hydrous hydrocarbons is contacted with the catalyst of the present invention in a dehydrocyclic ratio. The dehydrocycle ring ratios include a pressure of about 100-7000 kPa, with a preferred pressure of about 283-4238 kPa, a temperature of about 427-649 kPa, and a liquid volume flow rate of about 0.1- 10 h. Hydrogen can be advantageously used as a diluent. When hydrogen is present, it can be recycled at a rate of about 1-10 moles of hydrogen per mole of hydrocarbon as feedstock.

According to the present invention, the hydrocarbon feedstock is contacted with the catalyst of the present invention in a hydrocarbon conversion zone. This contacting can be carried out using a catalyst in a fixed bed system, a moving bed system, a non-fluidized bed system or a batch type operation. The hydrocarbon feedstock and, if desired, the hydrogen-enriched gas as diluent are typically preheated to the desired reaction temperature by any suitable heating means and then passed to a conversion zone containing the catalyst of this invention.

It is, of course, to be understood that the conversion zone may be one or more reactors with suitable means in between to ensure that the desired conversion temperature is maintained at the inlet to each reactor. It is also important to know that the reagents can be contacted with the catalyst bed in either an upward, downward or radially flowing manner, with the latter being preferred. In addition, the reagents may be in the liquid phase, mixed liquid vapor phase, or vapor phase when in contact with the catalyst. The best results are obtained when the reagents are in vaporase.

In the case where the catalyst of the present invention is used in a dehydrocyclic ringing process, the dehydrocyclic ringing system comprises a reaction zone containing the catalyst of the present invention. As mentioned above, the catalyst can be used in the reaction zone in a fixed bed system, a mobile bed system, a non-fluidized bed system or a batch type operation; however, in view of the advantages of use well known in the art, it is preferable to use the catalyst of the present invention in a mobile bed system. In such a system, the reaction zone may be one or more reactors with heating means between them to compensate for the endothermic nature of the dihydrocyclization reaction that takes place in each catalyst bed. The hydrocarbon feed stream, which preferably consists of non-aromatic C 1 -C 6 hydrocarbons, is continuously charged to the reaction zone as a mobile bed. There, it is contacted with a hydrocarbon feedstock to effect dehydrocyclization.

After the dehydrocyclization hydrocarbon feedstock has been in contact with the catalyst of the present invention, it is removed as a effluent from the reaction zone and passed through a cooling medium to the separation zone. In the separation zone, the effluent can be separated into different components depending on the desired products. When hydrogen is used as a diluent in the reaction zone, the separation zone typically includes a vapor-liquid balance weight separation zone and a fractionation distillation zone. The hydrogen-enriched gas is separated from the aromatic-containing high-octane liquid product developed in the dehydrocyclization zone. After separation, at least a portion of the hydrogen-enriched gas can be recycled back to the reaction zone as a diluent. The remainder of the hydrogen-enriched gas can be recovered for use elsewhere 16 86603. The high octane liquid product containing aromatics can then be introduced into a fractionation zone to separate the aromatics from the unmodified constituents of the feedstock. These unmodified components can then be returned to the reaction zone for processing or other processes for use elsewhere.

A wide variety of hydrocarbon feedstocks can be used in the process of this invention. The exact feedstock used will, of course, depend on the precise use of the catalyst. Typically, the hydrocarbon feedstocks that can be used in this invention include naphthenes and paraffins, although in some cases aromatics and olefins may be present. Thus, the class of feedstocks that can be used includes straight distillates, natural oils, synthetic oils, etc. Alternatively, straight distillates and cracked naphthas can also be utilized. The oil feedstock may be a full boiling point naphtha having an initial boiling point of about 10-66 ° C and an final boiling point between about 163-218 ° C, or it may be a selected fraction thereof. It is preferred that the feedstocks used in this invention be treated by conventional catalytic pretreatment methods, such as hydrogen purification 1a, hydrotreating, hydrogen desulfurization, etc., to remove substantially all of the sulfur-containing, nitrogen-containing and water-producing impurities therefrom.

When the catalyst of the present invention is used as a dehydrocyclization catalyst, it is preferred that the feedstock consists essentially of paraffins. This is, of course, a consequence of the fact that the purpose of the dehydrocyclization process is to convert paraffins into aromatics. In addition, due to the value of the C -C aromatics, it is preferred that the hydrocarbon feedstock be composed of C 8 aromatics. However, regardless of this priority, the feedstock 17 86603 may contain naphthenes, α tomatoes and olefins in addition to C -C paraffins.

The following examples are provided to more fully illustrate the advantages of the present invention. It is to be understood that the following is by way of example only and is not intended to be an unreasonable limitation on the otherwise general scope of the present invention.

It is to be understood that there are three parameters that are useful in evaluating the performance of a hydrocarbon conversion catalyst, and in particular in evaluating and comparing dehydro-cyclization catalysts. The first is "activity," which is a measure of the ability of a catalyst to convert reagents under a given set of reaction conditions. Another criterion for catalyst performance is "selectivity," which is an indication of the ability of a catalyst to produce a high yield of the desired product. The third parameter is "stability", which is a measure of the ability of a catalyst to maintain its activity and selectivity over time. In the attached examples, the criterion of interest is the selectivity of the catalyst. For the purposes of the following presentation, for example, a dehydrocyclic catalyst has been taken from the catalyst of the invention, and the measure of catalyst selectivity is the conversion of paraffin reagents to aromatics.

Figure 1 is a graphical representation of the selectivity of a catalyst to produce aromatics as a function of time. It shows the performance results for catalyst A of this invention.

Example I

To more fully illustrate the advantages of the invention, the following catalyst was prepared. A catalyst support containing 50 ρ-ϊ alumina and 50 wt% L-zeolite was prepared by a standard oil drop technique a. In this technique, the zeolite was first mixed with an aiumi i ni oxide diol having an ai umi i ni pi toi content of 12, 5%. The alumina sol was acidified with sufficient HCl 86603 18 to give an Al / Cl molar ratio of 0.88. Gelling was accomplished using sufficient hexamethylenetetraamine to achieve 180% neutralization. The acidified alumina Sool i, which contained zeolite and hexamethylenetetraamine, was dispersed as droplets in an oil, whereby the droplets gelled to form spheres dropped into the oil. The spheres dropped into oil were aged in oil at a pressure of about 653 kPa and a temperature of about 140 ° C for about 1 1/2 hours. The beads were then washed with 14 liters of 0.15 molar KCl at about 95 ° C. The beads were then dried at about 110 ° C, after which the beads were heated to about 610 ° C over a 6 hour heating period. The resulting beads were then cooled to ambient temperature.

In this example, the Group VIII metal component selected for deposition on the catalyst was a platinum component. For this purpose, an ion exchange method was used to deposit a platinum component on alumina-bound L-zeolite. 60 g of oil-dropped spheres 3 prepared as described above were mixed with 320 cm of ion exchange solution. The ion exchange solution consisted of a 0.030 molar solution of P t (N H) Cl and a 0.90 molar solution of 3 4 2 KCl. The ion exchange solution was contacted with the oil droplets for 3 days at ambient temperature while maintaining the pH below about 7. The platinum-containing oil droplets were then removed from the exchange solution and rinsed 6 times with 200 cm of ion-exchanged water. The rinsed spheres were then dried at 100 ° C. After drying at 100 ° C, the catalyst was subjected to a potassium quenching step. Potassium saturation was performed using an aqueous solution of potassium chloride containing about 1.5% by weight of potassium based on the weight of the base material. The volume ratio of the impregnation solution to the catalyst composite used in the impregnation was 1: 1.

o

After impregnation, the catalyst was heated to 350 ° C over a heating period of 4 hours and then oxidized in li 86603 19 ° m 2 for 2 hours at 350 ° C. After oxidation, the catalyst was then reduced for 1.5 hours under a hydrogen atmosphere. This catalyst was designated Catalyst A. Since Catalyst A was subjected to the potassium depletion step, it was prepared according to the present invention. To determine the index of the alkali metal deposited on the surface of Catalyst A, about 1 g of this catalyst (each containing 0.5 g of acid-free zeolite) was placed in 10 cm of water at 25 ° C. An electrode sensitive to potassium ion was placed in water. The index of surface-deposited alumina was measured to be 198. In addition, the platinum content of Catalyst B was about 0.619% by weight.

Example II

To demonstrate the benefits associated with the use of Catalyst A, it was subjected to an experiment measuring its performance as a dehydrocyclization catalyst. The experiment was performed in a pilot plant with a reactor loaded with the catalyst to be tested. The reactor effluent was then analyzed by in-line gas chromatography. The feedstock 1a used in this example had the following analysis: C / C / C paraffins 0.4 wt% 3 4 5 C paraffins 69.5 wt% 6 C 1-4 naphthenes 0.7 wt% C paraffins 21.4% by weight C 1-4 naphthenes 8.0% by weight

Total 100.0 wt%

The conditions used during the catalyst testing were the reaction zone inlet temperature of 500 ° C, the liquid volume flow rate of 1.0 h and the reaction zone pressure of 446 kPa. Hydrogen was mixed with the feedstock before it was contacted with the catalyst. Sufficient hydrogen, calculated on a single pass basis, was used to provide a 5: 1 ratio of moles of hydrogen to moles of hydrocarbon feedstock. The procedure followed in the test was to first contact the catalyst with the feedstock at a reaction zone temperature of about 410 ° C. The inlet temperature of the 410 ° C reaction zone was maintained for about 7 hours for the first start. Thereafter, the temperature of the reaction zone was raised to 500 ° C over 3 hours. Once the temperature of 500 ° C was reached, it was maintained for a 12 hour test period during which the effluent from the reaction zone was analyzed by an in-line gas chromatograph 11a every hour. The results obtained from the test are shown in Figure 1. For the purposes of interpreting Figure 1 and the results therein, seiek activity is defined as grams of aromatics produced per gram of modified feed multiplied by 100. Surprisingly and unexpectedly from the results of Figure 1, it can be seen that Catalyst A of this invention has excellent selectivity for aromatics production over the 12 hour test period used in the dehydrocyclization process.

Example III

The unbound catalyst was prepared according to the present invention. 50 g of the potassium form of L-zeolite with an average crystallite size of 275 Å was slurried in a solution of 12.8 g of potassium bicarbonate and 100 cm of deionized water. The potassium / zeolite slurry was evaporated to dryness and then calcined in air at 480 ° C for 3 hours. The resulting potassium zeolite was then subjected to an ion exchange step to dop platinum on its surface. This was done by placing a potassium-saturated zeolite in 200 cm of a 0.020 M Pt (NH) Cl / 0.90 M KCl solution. After three days at 25 ° C, the potassium-saturated platinum-containing zeoHite was filtered from the ion exchange solution and rinsed with 1200 cm of deionized water. The resulting catalyst contained about 0.7% by weight of platinum and had an early metal index deposited on its surface of about 61. This catalyst prepared according to the invention was designated Catalyst "B".

I! 2i 86603

Example IV

Another catalyst was prepared by the following method.

50 g of the potassium form of L-zeolite, which already contained the surface metal already deposited on the surface, was subjected to an ion exchange step to deposit platinum on its surface. The ion exchange step was performed essentially as above using an ion exchange solution containing Pt (NH) Cl and KCl. The L-zeolite containing ion-exchanged platinum and potassium deposited on the surface was then rinsed, calcined and reduced as above. The finished catalyst contained about 0.7% by weight of platinum and the index of α 1 and 11 metal deposited on its surface was about 28. This catalyst was marked as "C".

Example V

In this example, a comparative catalyst was prepared. The potassium form of L-zeolite was subjected to ion exchange with an ion exchange solution containing platinum and KCl. Prior to ion exchange, the platinum-containing L-zeolite was subjected to a qualified wash in ion-exchanged water to ensure the removal of any potassium that the zeolite might have on the surface. The L-zeolite was calcined and then reduced as above. The finished catalyst contained approx.

1.3% by weight of platinum and the time index deposited on its surface was about 7. This catalyst was marked as "D".

Example VI

A fourth catalyst was prepared by adding 50 g of the potassium form of L-zeolite to an aqueous solution of K CO. Potassium / zeolite solution evaporated. . . ,. 2 3 was dried and placed under sieve as above. The potassium-saturated zeolite was then subjected to an ion exchange step to deposit platinum. The ion exchange solution consisted of a solution of Pt (NH 4) 2 Cl 2 / KCl. The resulting composite was then rinsed, calcined and reduced as in the above examples. The resulting catalyst contained about 0.6% by weight of platinum and the alkali metal index deposited on its surface was about 89. This catalyst was designated Catalyst "E".

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Example VII

The above four catalysts B, C, D and E were all tested to test their respective performances as dehydrocyclization catalysts. The results of this test are shown in Figure 2. Figure 2 is a graphical representation of the selectivity of a catalyst for the production of aromatics as a function of the surface metal index deposited on the surface.

The feedstock 1a used in this example had the following analysis: C ^ / C ^ / C ^ paraffins 0.4 wt% C paraffins 69.5 wt% 6 C naphthenes 0.7 wt% 6 C paraffins 21.4% by weight C 1-4 naphthenes 8.0% by weight

Total 100.0 wt%

The test was performed in a pilot plant with a reactor in which the catalyst to be tested was charged. The reactor effluent was analyzed by in-line gas chromatography.

The conditions used during the testing of the catalysts were the reaction zone inlet temperature of 500 ° C, the liquid volume flow rate of 1.0 h and the reaction zone pressure of 446 kPa. Hydrogen was mixed into the feedstock before it was contacted with the catalysts. Sufficient hydrogen, calculated on a single pass basis, was used to provide a 5: 1 ratio of moles of hydrogen to moles of hydrocarbon feedstock. The test procedure was to first contact the catalyst with the feedstock at a reaction zone temperature of 410 ° C. The inlet temperature of the 410 ° C reaction zone was maintained for 7 hours. The reaction temperature of the reaction zone was then raised to 500 ° C over 3 hours. The temperature of 500 ° C was then maintained for a 12 hour test period during which the effluent from the reaction zone was analyzed by an in-line gas chromatograph every hour.

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The results obtained from the tests are shown in Figure 1. For the purposes of Figure 1 and the following description, selectivity is defined as grams of aromatics produced per gram of converted feed multiplied by 100. Surprisingly and unexpectedly from the results of Figure 2, it can be seen that as the index of surface-deposited α1 and methylmetal increases above 10, there is an improvement in selectivity for aromatics production when catalysts are used in the dehydrocycle ringing process.

Claims (11)

1. A catalytic composite containing acidic zeolite bound to or without a carrier matrix and catalytically effective amounts of a component of a Group VIII metal, characterized in that it contains sufficient alkali metal deposited on the surface to produce an index value for the pd surface deposited alkali of at least 10. Composite according to claim 1, characterized in that the component of a group VIII metal1 consists of a platinum component. Composite according to claim 1, characterized in that the acid-free zeolite consists of L-zeolite and the alkaline metal deposited on the surface of potassium. 4. A composite according to claim 1, characterized in that the support matrix consists of alumina or silica. Composite according to claim 1, characterized in that it contains about 0.01-5.0% by weight of the component of a Group VIII metal calculated on the catalytic composite. Composite according to claim 1, characterized in that it contains sufficient alkali metal deposited on the surface of the pd to obtain an index value for the pd surface deposited alkali pd about 40-500. Catalytic composite according to any of the preceding claims, characterized in that the acid-free zeolite is an L-zeolite bonded to a support matrix formed of alumina, sufficient with the pd surface deposited potassium to obtain an index value for the pd surface deposited alkali metal. 500, and about 0.01-5.0% by weight of a platinum component calculated on the weight of the catalytic composite. 27 86603 Composite according to claim 1, characterized in that it contains about 25-75% by weight of acid-free zeolite calculated on the weight of the zeolite and the carrier matrix. Process for the conversion of hydrocarbons, characterized in that the hydrocarbon charge material is contacted under hydrocarbon conversion conditions with a catalytic composite according to any of claims 1-8. 10. A process according to claim 9, characterized in that the hydrocarbon charge material consists of non-aromatic C5-C3 hydrocarbons and said hydrocarbon conversion conditions comprise dehydrocyclization conditions. 11. A process for producing a catalytic composite, characterized in that acidic zeolite is deposited on a support matrix and, in addition, a catalytically effective amount of a component of a Group VIII metal and sufficient alkali metal to obtain an index of the surface deposited alkali is added. -lime metal of at least 10.