DK142878B - Procedure for reforming a gasoline fraction. - Google Patents

Description

(11) FOREIGN EXPRESSION 1 U2 8 7 8 DENMARK mt. ei.3 c 10 g 35/09 § (21) Note No. 4966/72 (22) Filed on 6 Oct. 1972 (24) Race day 6 Oct. 1972 (44) The application submitted and _ the petition published on 16 February. 1 9θ1

DIRECTORATE OF

PATENT AND TRADEMARK <30> Priority beaker 'from it

Oct 7 1971, 187579, US

<71> UNIVERSAL OIL PRODUCTS COMPANY, Ten UOP Plaza-Algonquin & Mt. Prospect Hoads, Des Plaines, Illinois 60016, US · (72) Inventor: Richard Earl Rausch, 678 Killarney Pass, Mundelein, 1111 = nois, US. ~ (74) Plenipotentiary in the proceedings:

The engineering firm Budde, Schou & Co .___ (54) Procedure for reforming a gasoline fraction.

The present invention relates to a catalytic reforming process in which a relatively low octane gasoline fraction is contacted with a bimetallic catalyst comprising platinum, tin and halogen under conditions selected to produce a high octane number product. More precisely, the above conditions involve the use of a critical amount of water or its equivalent to significantly improve the characteristics of the bimetallic catalyst in a process of this type. In one embodiment, the invention relates to a method for improving the performance of such a method after it has begun to deteriorate, the improvement being achieved by adding a critical amount of water or its equivalent to the process. In another embodiment, the invention relates to a reforming method utilizing said bimetallic catalyst, which is continuously started and operated by the total amount of water or its equivalent continuously entering the reforming zone and being regulated within a specified critical range below so that the stability of the process maintained at a high level throughout the duration of the reform operation.

It is well known in the art that the requirements for an optimal process for converting low octane materials into high octane materials at minimal losses to undesirable products involve a specially adapted catalytic environment designed to improve reactions for paraffins and naphthenes, which are the components of gasoline and naphthas that have the highest octane enhancing potential. For paraffins, the enhancing reactions are: isomerization to higher-branched paraffins, dehydrogenation to olefins, dehydration to aromatic compounds, and hydro-cracking to lower molecular weight paraffins. Of these, the dehydration closure reaction is the reaction which shows the maximum increase in octane number and is preferred accordingly.

For naphthenes, the main enhancing reactions involve dehydrogenation to aromatic compounds and ring isomerization and hydrogenation to aromatic compounds, but the increase in octane is not as drastic here as in paraffin dehydration leaching, because most naphthenes clear research octane is relatively high, typically in the range of 65 to 80. Accordingly, catalytic reforming operations are designed to provide an optimal mixture of the above reactions, for this purpose usually employing a multi-purpose usable catalyst having at least one metallic dehydrogenation component. and an acidic component.

A unique double-acting bimetallic composite catalyst has previously been described which has unique activity, selectivity and stability characteristics when used in hydrocarbon conversion processes of the type that have traditionally used platinum-containing composite catalysts.

Briefly, the bimetallic catalyst comprises a combination of a plate group component, a tin component, and a halogen component with a porous support material. The characteristics of this bi-metallic catalyst are nowhere more evident than in a catalytic reforming process for a gasoline fraction to produce a high octane reformate product. What is important in the previous description is that this bimetallic catalyst is extraordinarily sensitive to the presence of water in its surroundings and that it functions optimally in a reforming process when the catalyst is kept in a practically anhydrous state. It is intended that the term "practically anhydrous" should describe the situation where the total amount of water or its equivalent that continuously enters the reforming zone containing this unique catalyst is kept at a level of less than 50 ppm by weight, and preferably less than 20 ppm by weight of the hydrocarbon charge material, calculated as the weight of equivalent water in the charge material. Subsequent experiments with this catalyst have confirmed that favorable results can be obtained with this catalyst in a practically anhydrous environment, it has now been found that a catalytic reforming method using this bimetallic catalyst can be greatly improved by careful regulation of the amount of water or its equivalent introduced into the reforming zone within a relatively narrow range. More specifically, it has been observed that the initially excellent activity or selectivity characteristics shown by this catalyst in a practically anhydrous environment tend to be degraded after an initial period similar to that required for treatment of ca. 175 to approx. 5250 liters of hydrocarbon per kg. catalyst. It has now been quite surprisingly found that this performance degradation can be reversed by the addition of a critical amount of water or its equivalent to the reforming zone. Furthermore, it has also been found that this performance degradation can be completely eliminated if the process is initiated and continuously operated with a critical amount of water entering the reforming zone continuously. More specifically, it has been found that the total amount of water entering the reforming zone should be kept in the range of approx. 10 to approx. To obtain a favorable reaction of this bimetallic catalyst to the presence of water. If the amount is below this level, the activity and selectivity characteristics are not stable, and if the amount is above this level, excessive yield loss and instability will occur. In short, the present invention essentially involves the operation of a reforming process with a bimetallic catalyst which uses tin to activate a platinum group metal and with a critical saturated water continuously entering the reforming zone. It is an accompanying finding that the maximum benefits of water addition are obtained when simultaneously adding halogen to the reforming zone in an amount sufficient to maintain the molar ratio of water entering the reforming zone to halogen entering the zone, in the range of approx. 10: 1 to approx. 100: 1.

Accordingly, the present invention provides a method for catalytically reforming a gasoline fraction with a composite catalyst comprising a combination of a plate group component, a tin component, and a halogen component with a porous support material. The method allows a reversal of the activity and selectivity degradation by a reforming method of this type, i. that the activity and selectivity characteristics of a platinum, tin and halogen-containing catalyst are maintained at a high level when this catalyst is used in a catalytic reforming operation.

The present invention therefore relates to a process for reforming a gasoline fraction, wherein a process in a reforming zone maintained under reforming conditions brings a gasoline fraction and a hydrogen stream into contact with a composite catalyst comprising a combination of a plate group component, a tin component and a halogen component. with a porous support material in amounts sufficient to produce a composite material containing, on an elemental basis, from ca. 0.01 to approx. 2% by weight plate group metal, from approx. 0.1 to approx. 5% by weight of tin and from approx. 0.1 to approx. 3.5% by weight of halogen, and the process of the invention is characterized in that water or water-forming substances from any source are continuously added to the reforming zone in an amount corresponding to from approx. 10 to approx. 50 weight ppm of the gasoline fraction, calculated on the basis of equivalent water.

A particular embodiment of the present process for reforming a gasoline fraction is peculiar in that the continuous addition to the reforming zone of water or water-forming substances from any source in an amount corresponding to from ca. 10 to approx. 50 wt ppm of the gasoline fraction, calculated on the basis of equivalent water, is only started after an initial period of time in which the catalyst has excellent activity and selectivity characteristics, during which time range of approx. 175 to approx.

5 5250 liters of gasoline fraction have been treated per. kg of catalyst.

This addition of water significantly improves the activity and selectivity characteristics of the catalyst.

Other embodiments of the present invention include further details regarding suitable charge materials, essential and preferred ingredients and amounts thereof for the catalyst, essential and preferred water and halogen additives for the present process, operating conditions for use in the reforming process, and the like. These are given in the following detailed description of the essential and preferred elements of the present invention.

Before considering the various elements of the present invention in detail, it is appropriate to define several of the terms and phrases used in this specification. The term "water entering the reforming zone" means the total amount of water or substances converted into water under the conditions maintained in the reforming zone and entering the reforming zone from any source, calculated on the basis of the water and expressed as weight ppm of the gasoline fraction also entering the reforming zone. The term "activity" refers to the ability of a catalyst to produce a C, - + product of the requisite quality as measured by octane at a given severity level, where the severity level means the conditions used, i.e. reactor supply temperature, reactor pressure, hydrogen-hydrocarbon molar ratio, and liquid space velocity (VRH). It is intended that the term "selectivity" should measure the ability of the catalyst, when used in a catalytic reforming process, to produce a C ^ + yield with the required octane relative to the amount of gasoline fraction charged thereto. It is intended that the term "stability" should measure the catalyst's ability to maintain initial levels of activity and selectivity, ie. it refers to the rate of change over time of the activity and selectivity parameters. It should be noted that the terms "catalyst" and "composite catalyst" are used here in synonymous and equivalent manner.

The hydrocarbon charge material which can be reformed according to the process of the present invention is generally a gasoline fraction containing naphthenes, paraffins and aromatic compounds. These gasoline fractions may include straight run gasoline, natural gasoline, synthetic gasoline, cracked gasoline and similar charge materials. In some cases, it is advantageous to charge thermally or catalytically cracked gasoline, straight run and cracked gasoline blends, and various other mixtures of carbon atoms which are well known to one of ordinary skill in the art of reforming. 10 to approx. 220 ° C, with an initial boiling point of approx. 10 to approx. 150 ° C and a final boiling point in the range of approx. 120 to approx. 220 ° C. In many cases, this gasoline fraction is a high-boiling fraction, such as a heavy naphtha, which boils in the range of from C7 to approx. 205 C. It is also within the scope of the present invention to charge pure paraffins, pure naphthenes, or mixtures of paraffins or naphthenes boiling within the gas range of gasoline, which are to be converted into aromatic compounds, for the present process.

The concentrations of the sulfur-containing compounds, nitrogen-containing compounds and oxygen-containing compounds contained in this hydrocarbon charge material must be carefully controlled. It is generally essential that the concentrations of these pollutants be reduced to relatively low levels prior to the introduction of the charge material into the process of the present invention. Any suitable method of pre-treatment known to one of ordinary skill in the art of catalytic reforming can be used to effect the desired reduction in the amounts of contaminants. Typically, good results are obtained with a gentle hydrogenation treatment, e.g. by subjecting the hydrocarbon charge material to hydro-refining, hydrotreating and hydrodesulphurisation processes, and similar contaminant removal processes. These pretreatment methods usually involve contacting the charge material o-g with a suitably supported cobalt and / or molybdenum-containing catalyst under conditions selected to result in cleavage of C-S, C-N and C-O bonds.

The details associated with these pretreatment methods are well known to those skilled in the art and should not be repeated here, but this necessary pretreatment is mentioned here to emphasize that these contaminants in the charge material should be reduced to relatively low amounts. For sulfur-containing and nitrogen-containing pollutants, the desired amount is less than 2 wt-ppm of the charge material, and preferably less than 1 wt-ppm of the charge material of sulfur and nitrogen, respectively. The amount of water and water-forming substances found in the charge material should also be reduced to a level of less than 5 ppm, calculated as equivalent water, and preferably below 1 ppm. The purpose of removing all the water and all water-forming compounds from the hydrocarbon charge material prior to its introduction into the reforming zone is designed to facilitate careful regulation of the amount of water continuously entering the reforming zone. It is possible that the critical amount of water needed in the process of this invention can be obtained by adjusting the severity of the catalytic pretreatment so that the required amount of water or water equivalent remains in the partially treated batch material. However, this latter method would be extremely difficult to implement, except when the sulfur-containing and nitrogen-containing pollutants in the untreated material are present in extremely low amounts. In short: the hydrocarbon charge material used in the present process should be practically free of sulfur-containing, nitrogen-containing and water-forming pollutants.

An essential feature of the present process involves the use of a composite catalyst comprising a combination of a plate group component, a tin component, and a halogen component with a porous support material. When first considering the porous support material, it is preferred that the material is a porous adsorbing substrate with a large surface area, namely from approx. 25 to approx. 500 m / g.· The porous support material should be relatively refractory to the conditions used in the hydrocarbon conversion process, and it is intended to include, within the scope of the present invention, support materials traditionally used in double-acting hydrocarbon conversion catalysts such as ( 1) activated charcoal, coke or charcoal; (2) silica or silica gel, clays and silicates, including those synthetically prepared and naturally occurring, which may be acid-treated, e.g. attapulgitles, porcelains, diatomaceous earth, fuller's soil, kaolin and pumice; (5) pottery, porcelain, crushed chamottes and bauxite; (4) refractory inorganic oxides such as alumina, titanium dioxide, zirconia, chromium oxide, zinc oxide, magnesium oxide, thorium oxide, boron oxide, silica alumina, silica magnesium oxide, chromium oxide alumina, alumina boron oxide, and alumina boron oxide; (5) crystalline aluminum silicates, such as naturally occurring or synthetically produced mordenite and / or faujasite, either in the hydrogen form or in a form treated with multi-valent cations; and (6) combinations of one or more elements from one or more of these groups. The preferred porous substrates are refractory inorganic oxides, the best results being obtained with one alumina support. Suitable alumina materials are the crystalline alumina known as the gamma, eta and theta alumina, with gamma alumina providing the best results. Furthermore, in some embodiments, the alumina support material may contain smaller screens of other well known refractory inorganic oxides such as silica, zirconia and magnesium oxide.

However, the preferred support material is practically pure gamma or ethyl alumina. The preferred carriers have an apparent bulk weight in bulk of approx. 0 to about 0.7 g / cm 2 and such surface area characteristics that the average pore diameter is from approx. 20 to approx. 300 Angstroms, the pore volume is from approx. 0.1 to

ISLAND

ca. 1 ml / g and the surface area is from approx. 100 to approx. 500 m / g.

Generally, the best results are typically obtained with a carrier material consisting mainly of gamma alumina used in the form of spherical particles having a relatively small diameter (i.e., typically about 1.6 mm), an apparent bulk weight in bulk. goal of approx. 0.5 g / cm, a pore volume of approx. 0.4 ml / g and a surface area of approx. 175 m / g.

The preferred alumina support material can be made on. any suitable way and may be synthetically made or naturally occurring. Regardless of the type of alumina used, it can be activated prior to use in one or more treatments including drying, calcination and steam treatment and may be in a form known as activated alumina, activated alumina, porous alumina or alumina gel. The alumina support may e.g. is prepared by the addition of a suitable alkaline reagent, e.g. ammonium hydroxide, to a salt of aluminum, for example, aluminum chloride or aluminum nitrate, in an amount forming an aluminum hydroxide gel which, after drying and calcination, is converted to alumina. The alumina can be formed into any desired shape, e.g. bullets, pills, cakes, extrudates, powders or granules, and can be used in any desired size. For purposes of the present invention, the sphere is a particularly preferred form of alumina, and alumina spheres may be prepared continuously by the well known oil drop method comprising: forming an alumina hydrosol by any of the methods of the prior art and preferably by reacting aluminum metal with hydrochloric acid, combining the resulting hydro-sol with a suitable gelling agent and dripping the resulting mixture into an oil bath maintained at elevated temperatures. The small droplets of the mixture are preserved in the oil bath until they solidify and form hydrogel fractions. The spheres are then continuously removed from the oil bath and typically subjected to specific aging treatments in oil and an ammonia solution to further improve their physical characteristics. The resulting, aged and gelatinized particles are then washed and dried at a relatively low temperature of from ca. 150 to approx. 205 ° C and subjected to a calcination process at a temperature of from ca. 455 to approx. 705 ° C for a period of from oa. 1 to approx. 20 hours.

This treatment causes the conversion of the alumina hydrogel to the corresponding crystalline gamma-alumina, as described in U.S. Patent No. 2,620,314.

An essential component of the bimetallic catalyst is a tin component. Practically the entire tin component is preferably present in the composite material in an oxidation step which is above the oxidation step of the elemental metal. That is, the tin component should be present in the composite catalyst in either the +2 or +4 oxidation step, the latter being most likely. Accordingly, it is believed that the tin component is present in the composite material as a chemical compound, e.g. the oxide, sulfide and halide, where the tin has the necessary oxidation step, or as a chemical combination with the support material, where the tin is present in this higher oxidation step. On the basis of currently available documentation, the best results are considered to have been obtained when the tin component is present in the catalyst in the form of tin oxide.

This tin component can be incorporated into the composite catalyst in any suitable known manner, e.g. by co-precipitation or co-formation with the porous support, ion exchange with the gelatinized support or impregnation into the support either after or before it is dried and calcined. It should be noted that all conventional methods for incorporating a metallic component into a composite catalyst are intended to be included.

One preferred method of incorporating the tin component involves the co-precipitation thereof during the preparation of the preferred carrier alumina. This method typically involves adding a suitable soluble tin compound, such as stannous or stannous chloride, to the alumina hydrosol and subsequently combining the hydrosol with a suitable gelling agent and dripping the resulting mixture into an oil bath as described further above. After drying and calcining the resulting gelatinous support, an inner combination of alumina and tin oxide is obtained. A preferred method of incorporating the tin component into the composite catalyst involves the use of a soluble, decomposable compound of tin to impregnate the porous support material. Generally, the solvent used in this impregnation step is selected on the basis of its ability to dissolve the desired tin compound, and it is preferably an aqueous, acidic solution. The tin component can thus be added to the carrier by mixing the latter with an aqueous, acidic solution of a suitable tin salt or compound of tin, such as stannobromide, stannous chloride, stannic chloride, stannic chloride pentahydrate, stannic chloride diamine, stannous trichloride bromide, stannous trichloride stannous iodide, stannous sulfate and stannous tartrate. A particularly preferred impregnation solution comprises stannous or stannous chloride dissolved in a hydrochloric acid solution. Another useful impregnation solution is stannous or stannous chloride dissolved in anhydrous alcohol such as ethanol. Generally, the tin component can be incorporated either before, simultaneously with or after the addition of the plate group component to the carrier. However, it has been found that excellent results are obtained when the tin component is incorporated simultaneously with the plate group component. Indeed, it has been found that a preferred aqueous impregnation solution contains chloroplatinic acid, hydrogen chloride and stannic or stannous chloride.

Regardless of the tin compound used in the preferred impregnation step, it is important that the tin component is uniformly distributed throughout the support material. To achieve this purpose, it is necessary to add a relatively strong acid, such as hydrochloric acid, nitric acid and the like, to the impregnation in an amount calculated so as to maintain the pH value of the impregnating solution in a range of from ca. -1 or less to approx. j5, preferably below 1, and diluting the impregnation solution to a volume approximately equal to or substantially greater than the volume of the impregnated carrier. It is preferred to use a volume ratio of impregnating solution to carrier material of at least 0.5: 1 and preferably from about 0.5: 1. 1: 1 to approx. 10: 1 or greater. In the same way, it is preferable to use a relatively long contact time during the impregnation step of from approx. 15 to approx. 50 minutes or more prior to drying to remove excess solvent to ensure a high dispersion of the tin component into the support material. Similarly, the carrier is under constant agitation during this preferred impregnation step.

The bimetallic catalyst also contains a platinum group component. Although the process of the present invention is specifically directed to the use of a composite platinum containing platinum, it is intended to include other platinum group metals, i.e., palladium, rhodium, ruthenium, osmium and iridium. The platinum group component, such as platinum, may be present in the composite final catalyst as a compound such as an oxide, sulfide or halide, or as elemental metal or in combination with one or more of the other components of the catalyst. On the basis of currently available documentation, it is believed that the best results are obtained with this catalyst when practically the entire plate group component is present therein in the elemental state and the prairie reduction step described below is believed to fulfill this purpose. Generally, the amount of the plate group component present in the composite final catalyst is low compared to the amounts of the other components combined therewith. The plate group component is thus usually from about 0.01 to approx. 2% by weight of the composite final catalyst, calculated on an elemental basis. Excellent results are obtained when the catalyst contains from ca. 0.05 to approx. 1% by weight of the plate group metal. The preferred plate group component is platinum metal.

The plate group component can be incorporated into the composite catalyst in any convenient manner, e.g. co-precipitation or co-formation with the preferred carrier or ion exchange thereof or impregnation thereof. The preferred method of preparing the catalyst involves the use of a water-soluble, decomposable compound of a platinum group metal to impregnate the support material. Thus, the platinum group component can be added to the substrate by mixing the latter with an aqueous solution of chloroplatinic or chloropladic acid. Other water-soluble compounds of platinum group metals can be used in impregnation solutions and include e.g. ammonium chloroplatinate, bromoplatinic acid, platinum dichloride, platinum tetrachloride hydrate, platinum dichlorocarbonyldichloride, dinitrodiaminoplatin, palladium dichloride, palladium nitrate and palladium sulfate. The use of a platinum group compound containing halogen, such as chloroplatinic or chloropalladic acid, is preferred because it facilitates the incorporation of both the platinum group component and at least a minor amount of the halogen component in a single step. Hydrochloric acid or a similar acid is also commonly added to the impregnation solution to further facilitate the incorporation of the halogen component and to assist in the distribution of the metallic component throughout the support material. In addition, it is usually preferred to impregnate the support material after it has been calcined to minimize the risk of washing away the valuable platinum metal compounds. However, in some cases it may be advantageous to impregnate the support material when in a gelatinous state.

A fourth essential component of the bimetallic catalyst is the halogen component. Although the exact chemical association of the halogen component to the carrier is not fully known, it is common in the art to describe the halogen component as being bound to the carrier or to the other components of the catalyst in the form of the halide (e.g., the chloride or fluoride). This bound halogen can be either fluorine, chlorine, iodine, bromine or mixtures thereof. Of these, fluorine is preferred and especially chlorine. The halogen may be added to the carrier in any suitable manner either during the preparation of the carrier or before or after the addition of the other components. The halogen may e.g. is added at any stage of the preparation of the carrier or to the calcined carrier as an aqueous solution of a suitable water-soluble halogen-containing compound such as hydrogen fluoride, hydrogen chloride, hydrogen bromide or ammonium chloride. The halogen component or a portion thereof may be bonded to the support material during impregnation thereof with the plate group component, e.g. using a mixture of chloroplatinic acid and hydrogen chloride. In another case, the alumina hydrosol typically used to form the preferred alumina support material may contain halogen and thus supply at least part of the halogen component to the composite final material. For reforming, the halogen is bonded to the carrier in an amount sufficient to result in a composite final material containing from about 0.1 to about 0.5 3.5% by weight and preferably from ea. 0.5 to approx. 1.5% by weight of halogen, calculated on an elemental basis. The preferred halogen component is chlorine or a compound thereof.

With respect to the amount of tin component contained in the composite material, it is preferably sufficient to constitute from ca. 0.01 to approx. 5% by weight of the composite final material, calculated on an elemental basis, although substantially higher amounts of tin can be used in some cases. The best results are typically obtained from approx. 0.1 to approx. 1% by weight of tin. Regardless of the absolute amounts of the tin component and the platinum group component used, the atomic ratio of the tin to the pioneering group metal contained in the bimetallic catalyst is preferably selected in the range of from ca. 0.1: 1 to approx. 3: 1, with the best results obtained at an atomic ratio of approx. 0.5: 1 to 15: 1. This is especially true when the total content of the tin component plus the platinum group component of the composite catalyst is set in the range of from approx. 0.15 to approx. 2% by weight thereof, calculated on the basis of elemental tin and platinum group metal.

Regardless of how the components of the catalyst are combined with the porous support, the final catalyst is usually dried at a temperature of from 90 to ea. 320 ° C for a period of approx. 2 to approx. 24 hours or more, and finally calcined or oxidized at a temperature of about 370 to approx. 595 ° C in an air atmosphere for a period of approx. 0.5 to approx. 10 hours for converting the metallic components into predominantly oxide form. The best results are usually obtained when the halogen content of the catalyst is adjusted during the calcination step by the inclusion of a halogen or halogen-containing compound, such as hydrogen chloride or chlorine, in the air atmosphere used. When the halogen component of the catalyst is chlorine, it is particularly preferred to use a molar ratio of H 20: 1 to approx. 100: 1 during at least a portion of the calcination step to adjust the final chlorine content of the catalyst to a range of from approx. 0.5 to approx. 1.5% by weight.

It is preferred that the resulting calcined composite catalyst be subjected to a practically anhydrous reduction step prior to its use in the conversion of hydrocarbons. This step 14 is designed to ensure a uniform and finely dispersed dispersion of the metallic component throughout the support material. Preferably, practically pure and dry hydrogen (i.e. less than 20 volume ppm Έ. 50) is used as reducing agent at this stage. The reducing agent is contacted with the calcined catalyst under conditions which include a temperature of from ca. 425 to approx. 540 ° C, selected to reduce the plate group component to the metal state, while preferably keeping the tin component in an oxidized state. This reduction step can be carried out in situ as part of a commissioning sequence if measures are taken to pre-dry the plant to a practically anhydrous state and if practically anhydrous hydrogen is used. In order to minimize the danger of reducing the tin component at this stage, the duration of this step is preferably less than 2 hours and typically approx. 1 hour.

The resulting reduced composite catalyst may, in some cases, successfully undergo a pre-sulphidation step designed to incorporate from ca. 0.05 to approx. 0.5% by weight of sulfur, calculated on an elemental basis, in the composite catalyst. This presulfidation treatment preferably takes place in the presence of hydrogen and a suitable sulfur-containing compound such as hydrogen sulfide, lower molecular weight mercaptans, organic sulfides and the like. This method typically involves treating the reduced catalyst with a sulfiding gas, e.g. a mixture of hydrogen and hydrogen sulfide with approx. 10 moles of hydrogen per moles of hydrogen sulfide under conditions sufficient to effect the desired incorporation of sulfur, usually including a temperature in the range of from about. 10 to approx. 540 ° C. It is generally good practice to perform this presulfidation step under practically anhydrous conditions.

In accordance with the present invention, the catalytic reforming process involves contacting the gasoline fraction, a hydrogen stream, and water or water-forming substances with a bimetallic catalyst of the type described above in a reforming zone maintained under reforming conditions. This contact operation can be carried out by any of the systems described in the prior art to bring these reactants together with the catalyst such as a fixed mass system, a moving mass system, a fluidized catalyst system or by charge operation. Considering the danger of wear and tear of the valuable catalyst and for well-known operating advantages, the use of a fixed mass system is preferred. In this system, a hydrogen-rich gaseous stream and the charge material are preheated by any suitable preheater to the desired reaction temperature and then passed in admixture with water or a water-forming compound into the reforming zone containing a fixed mass of the bimetallic catalyst. Of course, it is to be understood that the reforming zone may be one or more separate reactors with suitable heating means therebetween to compensate for the endothermic nature of the reactions occurring in a catalytic reforming zone.

It should also be noted that the reactants are typically in the vapor phase and can be contacted with the catalyst mass in either upward, downward or radial flow directions, the latter being preferred.

In one type of operation of the present process, the reforming process is initiated and interrupted under virtually anhydrous conditions, which is achieved by careful control of the well-known sources of water involved in a catalytic reforming system. This practically anhydrous state is generally achieved by careful drying of both the catalyst and the reforming system during the initiation of the process by circulating through it a relatively dry gas stream at a relatively high temperature. In connection with this initial drying step, it is generally good practice to dry both the hydrogen-rich gas stream and the hydrocarbon charge material to relatively low levels. In many cases, the catalytic pre-treatment operation for the removal of pollutants is sufficiently effective on the hydrocarbon charge material to ensure that the amount of water, or its equivalent contained in the charge material, is less than 5 wt ppm and more typically less than 1 wt. ppm.

As a result, it is generally not necessary to dry the hydrocarbon charge material once it has been properly processed. Similarly, the hydrogen-rich stream is usually a recycle stream obtained from the discharge stream from the reforming zone, and if the hydrocarbon charge material has been properly treated, the hydrogen stream generally contains less than 10 volume ppm water and it requires no further drying. On the other hand, when the water enters the system from any source, either due to improper treatment of the charge material or due to improper drying of the catalyst or reforming zone, it is within the scope of the present invention to use suitable drying means for drying the charge material and the recycle hydrogen stream. Suitable drying means are conventional solid adsorbents or dryers with high selectivity to water, such as silica gel, activated alumina, molecular sieves, anhydrous calcium sulfate, high surface area sodium and similar materials. Regardless of how this practically anhydrous state is achieved, it is quantitatively defined as achieved when the total amount of water or its equivalent entering the reforming zone is set to a level of less than 10 wt ppm of the charge material and preferably less than 5 wt. --ppm of the charge material. In accordance with this first mode of operation, this practically anhydrous state is maintained for an initial period of time corresponding to the amount of time required to treat from ca. 175 to approx. 5250 liters of gasoline fraction per kg of composite catalyst. This anhydrous operation is generally continued until some deterioration in the activity and selectivity characteristics of the catalyst is noticed. A preferred criterion for monitoring these characteristics is usually the C + + yield, and when this parameter begins to deteriorate rapidly, this first period should be terminated. It is a preferred method to end when the value of the C 1 to 2% by volume or more in relation to the initial value. An alternative criterion that can also be used is based on the purity of the hydrogen recycling stream - a marked deviation in this last parameter from the initial value is also indicative of instability in the process. After completion of this anhydrous operation, water injection is started in the manner indicated below.

Another method of operating the process of the present invention involves the presence of the critical amount of water given below during the initiation of the process and continuously thereafter. In this mode of operation, it is necessary to carefully check all the sources of water entering the reforming zone so that a process is initiated and interrupted while the required amount of water continuously enters the zone. Any of the drying means listed above during the discussion of the first method of operation can be used to obtain the desired amount of water. As pointed out above, the water content of the charge material has generally actually been reduced to extremely low content by the catalytic pretreatment method associated with the gaseous stripping step that follows this pretreatment. In this latter case, it is usually only necessary to add the required amount of water or its equivalent to the hydrocarbon charge material to regulate the water content of the reforming zone.

Regardless of the method of operation used, it is an essential feature of the present invention that at any point in the process water or a water-forming substance is continuously introduced into the reforming zone in an amount corresponding to from ca. 10 to approx.

50 wt ppm of the hydrocarbon charge material, calculated on the basis of equivalent water. It should be noted that this amount of water is intended to include the total equivalent equivalent of water entering the reforming zone in any manner, including that contained in the hydrocarbon charge material, that present in the hydrogen stream, and which is independently introduced into the reforming zone. Depending on whether or not the recycle hydrogen stream is dried, it is usually a preferred method to add either all or part of the required amount of water to the charge material. In cases where the hydrogen is passed through only once or where the recycle hydrogen stream is dried to a content of substantially less than 5 volume ppm water and where no water is independently introduced into the zone, virtually all water entering it in the reforming zone, from that mixed with the hydrocarbon charge material. On the other hand: in the case where the recycle hydrogen stream is not dried, an amount of water introduced into the charge material will build up and accumulate in the recycle hydrogen stream until an equilibrium state is provided. Depending on the mole ratio of hydrogen to hydrocarbon used, the total amount of water entering the reforming zone in this latter case is approx. 2-6 times the amount added to the charge material under equilibrium conditions. It should be noted that at least a portion of the required amount of water may be introduced into the zone by saturating a portion of the hydrogen stream with water.

The preferred method of water regulation consists in pretreating the hydrocarbon charge material so that the amount of water or water-forming substances contained therein is substantially less than 5 wt ppm and more typically less than 1 wt ppm. The necessary water for the process of this invention is then obtained by introducing a suitable water-forming additive into the reforming zone. Generally, any water-forming additive can be used to supply the required amount of water to the reforming zone, and such additives include water and water-forming substances that win the conditions maintained in the reforming zone. Typical examples of these latter substances are oxygen and oxygen-containing organic compounds. Included in the range of suitable oxygen-containing compounds are aldehydes, ketones, alcohols, esters and the like oxygen-containing organic compounds. For the purposes of the present invention, the preferred additive is an alcohol such as an alcohol having 2-8 carbon atoms

A preferred feature of the present invention is the use of a halogen additive in association with the essential water additive. That is, it is preferred to add a halogen additive simultaneously with the water additive in an amount sufficient to result in a molar ratio of water entering the reforming zone to halogen entering the reforming zone selected in range from approx. 10: 1 to approx. 100: 1, with the best results being obtained at a molar ratio of approx. 20: 1 to approx. 60: 1, This introduction of a halogen additive into the reforming zone is most easily accomplished by adding a suitable halogen-containing compound to one of the streams entering the reforming zone. The preferred method usually consists of mixing a halogen or halogen-containing compound with the hydrocarbon charge material. Although any of the halogens can be used for the purposes of the present invention, the best results are generally obtained when the halogen additive is chlorine or a chlorine-containing compound. Any halogen additive may be used provided that, under the conditions maintained in the reforming zone, it can be converted at least partially to the corresponding halide. Hydrogen halide per se can of course also be used. Examples of suitable halogen additives are hydrogen chloride, hydrogen bromide, ammonium chloride, ammonium bromide, carbon tetrachloride and any of the alkyl halides of 2-8 carbon atoms. Typically, excellent results are obtained with an alkyl chloride of 2-8 carbon atoms.

The bimetallic catalyst reforming zone is operated under reforming conditions selected so as to produce a high octane Ct reformate. Though that print, 19 142878

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used in the reforming zone can range from approx. 0 to approx. 70 kg / cm overpressure, the preferred pressure range is from approx. 5.5 to approx. 24.5 kg / cm overpressure. Similarly, the temperature maintained at the approach to the reforming zone is selected in the range of approx. 425 to approx. 595 ° C. In addition, hydrogen is charged to the reforming zone in an amount sufficient to provide a hydrogen to hydrocarbon molar ratio of from ca. 2: 1 to approx. 20: 1, with the best results generally being obtained at a mole ratio of approx. 4: 1 to 10: 1. It should be noted that this hydrogen can be supplied to the reforming zone on the basis of a once-through flow, although the preferred method consists in obtaining the necessary hydrogen from the residual stream recovered from the reforming zone. Another relevant parameter for the operation of this reforming zone is a VRH, which can generally be selected from the range of approx. 0.1 to approx. 10 hours-1, with a value of from approx.

0.5 to approx. 5 hours 1 is preferred.

The following example serves to illustrate the advantages of the present invention.

In this example, both catalyst "A" and catalyst "B" are a combination of platinum, tin and chlorine with a gamma alumina support in amounts sufficient to result in a catalyst containing 0.6% by weight of platinum, 0.4 wt.% tin and 1 wt.% chlorine. Both catalysts are used in the form of 1.6 mm spherical particles with an apparent bulk density of 0.5 g / crrr ^, a pore volume of approx. 0.55 cm 2 / g and a surface area of about l60 m / g. Both catalysts are prepared using gamma alumina particles prepared in the manner described in U.S. Patent No. 2,620,514. Catalyst "A" is prepared by a double impregnation method using a first impregnation solution comprising an aqueous solution of stannous chloride and hydrogen chloride and a second impregnation solution comprising an aqueous solution of chloroplatinic acid and hydrogen chloride. After each impregnation, the catalyst is dried and oxidized in the manner described above. Catalyst "b" is prepared by a co-impregnation method using an impregnation solution comprising stannous chloride, hydrogen chloride and chloroplatinic acid. After impregnation, the catalyst is dried and oxidized in the manner described above. Both catalysts are pre-reduced according to the practically anhydrous method described above.

202828

The experiments described in this example are carried out in a laboratory scale and conventional design, which includes a reactor containing the catalyst, a hydrogen separation zone, a debut analyzer column and conventional heating, pumping, compression and cooling means. flow system essentially involves heating a mixture of the gasoline fraction and hydrogen recycle stream to the desired conversion temperature. The resulting mixture is then fed downstream into a reactor containing the catalyst as a fixed mass. A discharge stream is then withdrawn from the reactor, cooled to approx. 13 ° C and passed to a separation zone where a hydrogen-rich gas phase is separated from a liquid hydrocarbon phase. A portion of the gas phase is then passed through a washing plant containing large surface area sodium, and the resulting virtually anhydrous hydrogen stream is then recirculated to the reforming zone. Excess hydrogen, in addition to what is required to maintain plant pressure, is extracted as excess separator gas. Similarly, the hydrocarbon phase is taken out of the separation zone and directed to a debut analyzer column where light fractions are taken out via the top and a C 2+ product reforming stream is recovered as a bottom fraction.

In all cases, the test used is a high rigor reforming experiment designed to measure, on an accelerated basis, the activity, selectivity and stability characteristics of the catalyst under the test conditions. Each trial consists of a series of time periods of 24 hours. Each of these periods includes a 12 hour interrupted period followed by a 12 hour trial period during which a product reform is collected. The conditions used in all the experiments are: reactor pressure of 7 kg / cm overpressure, a VRH of 1.5 hours, a molar ratio of hydrogen to hydrocarbon of 4: 1 and a reactor supply temperature which is continuously adjusted throughout the experiment. to obtain and maintain a C1 + octane of 102 F1 clear. It should be emphasized that these conditions are exceptionally strict conditions designed to reveal in a very short time whether the catalyst being tested has superior reforming characteristics under the experimental conditions. In all these experiments, the same charge material is used. Its characteristics are listed in Table I. It should be noted that the charge material contains approx. 5 weight ppm equivalent water, and considering the use of recycle washes, the total amount of water entering the reforming zone in the control cases is 5 weight ppm. In all cases, of course, the experiments are initiated under carefully controlled conditions so that the other known sources of water, such as residual water in the plant and in the catalyst, are kept at negligible levels.

Table I

Density at 16 ° C, g / crn

Initial boiling point ° C 77 10 * 91 50 * 114 90 * 158

Final boiling point 191

Sulfur, weight ppm 0> 1

Nitrogen, weight ppm 0.1

Atomic compounds, vol- * 10

Paraffins, vol- * 70

Naphthenes, vol- * 20

Water, weight ppm 5

Octantal, F-l clear 40

Example

A series of experiments with different amounts of water entering the reforming zone are conducted to study the effects of different amounts of water on a reforming process using the bimetallic reforming catalyst. Experiments "A" and "B" are conducted with catalyst "A". Experiments "C" and "D" are conducted with catalyst "B". The only material difference between these experiments is the amount of water entering the reforming zone and these amounts are listed in Table II for each experiment. Furthermore, experiments "B" and "D" are carried out with 1 wt ppm t-butyl chloride added to the charge material.

The results of these experiments are listed in Tables III, IV and V expressed as reactor supply temperatures required to obtain the desired octane, expressed in ° C, C₂ + yield expressed as volume percent of the charge material and recycle hydrogen purity expressed in mole percent.

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Referring to the data in Tables III, IV and V, it can be seen that water addition can be used to stabilize the catalyst. By comparing the results of Experiment "C" with Experiment "D" it can be seen that the beneficial effects of water are evident in the figures for the temperatures required to provide the octane, for the C₂ + yield and for the hydrogen purity. In all cases, there are clearly significant improvements in the experiment in which water is added to obtain 25 weight ppm in the batch.