MXPA99006399A - Method of removing reactive metal from a metal-coated reactor system - Google Patents

Abstract

A method of removing reactive metal from a metal-coated reactor system, comprising contacting at least a portion of a metal-coated reactor system containing reactive metal with a getter to produce movable metal, and fixating the movable metal, the getter, or both. The contacting is preferably done prior to catalyst loading. A preferred coating metal comprises tin and a preferred getter comprises HCl. The invention is also a method for reducing catalyst contamination from a metal which was used to coat a reactor system. The method comprises contacting a metal-coated reactor system, witha gaseous halogen-containing compound to produce movable metal;thereafter or simultaneously, at least a portion of the movable metal is removed from the reactor system. Then a halided catalyst is loaded into the reactor system.

Description

METHOD FOR ELIMINATING REAGENT METAL FROM A SYSTEM OF REACTORS WITH METALLIC COVER FIELD OF THE INVENTION This invention is a method for removing reactive metal from at least a part of a reactor system for the conversion of hydrocarbons, with metallic coating, so that the reactive metal does not deactivate the catalyst for the conversion of the hydrocarbons. It is especially applicable to catalytic reforming processes using halide-treated catalysts.

Background and important references Platinum L-zeolite catalysts for low sulfur reformation were invented in the early 1980's. After approximately ten years of effort, and much research, the low sulfur reformation was commercialized in the early 90's. Progress towards commercialization required many. discoveries. Two key findings were the criticality of the ultralow • levels of sulfur in the feed stream, and the impact of these ultralow sulfur levels on the reactor metallurgy, that is, the discovery of the need to avoid coking, carburization and metallic powder. A preferred form for preventing coking, carburization and metal powder uses a metallic protective layer, especially one containing tin. Although the commercialization of ultra low sulfur reformation has continued, a second generation of sulfur-sensitive L-zeolite platinum catalysts was being developed. "These new catalysts are treated with halide, they allow the operation to a higher severity, they tolerate a wide range of hydrocarbon feeds, they have a high activity and a long life." Recent attempts to use this second generation of catalysts for the ultralow reformation in Sulfur resulted in an unexpected and undesirable reduction in catalyst activity After much research and experimentation it was discovered that the catalyst had been partially poisoned by the metal of the protective layer, specifically by tin, which had been used to prevent the carburetion and the metallic dust of the surface of the reactor system Somehow, some of this tin had migrated and had been deposited on the catalyst, On the contrary, when conventional L-zeolite platinum catalysts are used for the reformation with low sulfur content in a reactor system with coating tin does not observe tin migration or deactivation of the life catalyst to tin migration. The cause of these problems has now been traced to low levels of volatile hydrogen halides that, under certain conditions, are released from the catalysts themselves. These halides interact with the reactive tin and can deactivate the catalyst. Therefore, an object of the present invention is to reduce the deactivation of the catalyst by metals coming from a reactor system with metallic coating. Another object of the invention is to reduce catalyst contamination from a reactor system newly coated with metal, which would otherwise cause the deactivation of the catalyst. This new process will also improve the reproducibility of catalytic operations, since catalytic activity and life can be better predicted. It is known to use metallic coatings and metal protective coatings, especially tin coatings in hydrocarbon conversion processes. These layers provide better resistance to coking, carburation and metallic dust, especially under conditions of ultralow sulfur content. For example, Heyse et al., In WO 92/1856 coat the steel reactor systems that are to be used for the reformation with platinum L-zeolite with metallic coatings, including tin. See also U.S. Patent Nos. 5,405,525 and 5,413,700 to Heyse et al. Metal-coated reactor systems are also known to avoid carburetion, coking and metal powder in dehydrogenation and hydrodealkylation processes carried out under low sulfur conditions; see Heyse et al. ~ in U.S. Patent 5,406,014 and WO 94/15896. In Day Patent '014, Example 3 shows the interaction of a stannous coupon with hydrocarbons, methyl chloride and hydrogen at 100 and 120 ° F. The coupon was stable at methyl chloride concentrations of 1000 ppm at 1000 ° F, showing that the tin coating is stable to halogens at refurbishment temperatures. The use of catalysts treated with halogen-containing compounds for catalytic reforming is also known. See, for example, U.S. Patent No. 5,091,351 to Muraka et al. Murakawa prepares a Pt L-zeolite catalyst and then treats it with a halogen-containing compound. The resulting catalyst has a desirably long catalyst life and is useful for preparing aromatic hydrocarbons such as benzene, toluene and xylenes from aliphatic hydrocarbons of Ce-Cs in high yield. Other patents describing L-zeolite catalysts treated with thehalide include U.S. Patent Nos. 4,681,865, 4,761,512 and 5,073,652 of Katsuno et al .; U.S. Patent Nos. 5,196,631 and 5J, 260,238 of Murakawa et al; and EP 498,182 (A). None of these patents or patent applications describe any problems associated with metallic coated reactor systems. Nor do they teach the convenience or the need to remove the metal from the reactor system, especially not before loading the catalyst or before processing the hydrocarbons. In fact, the technique teaches the advantages of combining one of the coating metals, tin, with a reforming catalyst, especially with a platinum L-zeolite catalyst. US 5,279,998 to Mulaskey et al. Teaches that improvements in the activity and rate of scale are associated with the treatment on the outside of the platinum catalyst L-zeolite with metallic tin particles having an average particle size of between 1 and 5 microns (tin powder). For example, Table 1 of the Mulaskey patent shows improved catalyst performance when tin metal powder is combined with a platinum catalyst L-zeolite that has been treated with fluoride according to the process of US 4,681,865. In light of the above teachings, we were surprised to find a decrease in catalyst activity with reformation in a reactor reactor newly coated with tin using a L-zeolite catalyst treated with halide (see Example 5 below). with tin coating are known as useful for various purposes. For example, surface coating compositions, known as 'stop-offs or resists', are temporarily applied to the portions of a steel tool surface to protect it during the hardening of the box. example, in Ratliff US 5,110,854 the protective layer is a water-based alkyd resin containing tin and titanium dioxide It is also known that the reaction of tin with steel at elevated temperatures results in coated steels having iron stanides In addition to hydrocarbon processing, as already described, coated steels have been used in applications where steels with hard surfaces and / or corrosion resistant are desired. For example, Caubert in US 3 / 890,686 describes the preparation of mechanical parts having coatings consisting of three iron stanols [sic] to increase the resistance of these parts to seizure and surface wear. Coated steel is prepared by heating the steel to 1060 ° F in the presence of tin chloride (SnCl2) and hydrogenated nitrogen for 1.5 hours.The treatment of tin-coated steels is also known to further modify their properties., Galland et al., In US 4,015,950 teaches that stainless steel hot dipped in molten tin gives rise to two layers of intermetallic tinide, as an outer layer of FeSn and an inner layer consisting of a mixture of Fe (Cr, Ni , Sn) and FeSn2. The inner layer has a greater hardness. These teach that the outer layer can be removed by crushing, by reaction with 35% nitric acid with a polyamine content, or by electrochemical means, leaving behind the harder inner layer and more resistant to corrosion. Another example where tin coated steel is modified is in Carey II, et al., In US 5,397,652. In this case, the stainless steels with tin coating are shown as roofing materials and sheets for wall lining, especially for use in marine or saline environments. Carey II, et al., Teach that stainless steel-immersed in hot bath in molten tin results in a united tin coating and an underlying intermetallic alloy of chromium-iron-tin. They teach the treatment of coated steel with an oxidant solution (aqueous nitric acid) to obtain a uniform, colored stainless steel. The nitric acid preferably reacts with the united tin coating leaving behind the uniform color intermetallic alloy. None of these patents on coated steels are related to hydrocarbon conversion processing. None of the techniques described above is related to the problems associated with reactive metals from metal coatings, such as tin coatings, or the effect of these reactive metals on catalysts, especially platinum L-zeolite catalysts for the reformation . We have discovered that there are problems associated with the use of metal-coated reactor systems, especially freshly coated systems, in the presence of certain catalysts, and we have discovered the cause of and solutions for these problems. In this way, an object of the present invention is to reduce the contamination of the catalyst coming from a reactor system newly coated with metal. Another object of the invention is to ensure that contamination of the catalyst is avoided, for example when replacing a conventional catalyst with a halide-treated catalyst.

SUMMARY OF THE INVENTION In one embodiment, the invention is a method for removing reactive metal from at least a portion of a metal-lined reactor system that is used to convert chemicals, especially hydrocarbons. The method consists in contacting at least a part of a reactor system containing the reactive metal with a degasser or metal adsorbent to produce mobile metal, and fixing the moving metal, the degasser or both. The degasser reacts with the reactive metal (coming from the metal of the coating) facilitating its elimination from the reactor system. Preferably, the moving metal and the degasser are both fixed, for example by capture using a solid absorbent. Preferred metal coatings are those prepared from compositions containing tin, germanium, antimony and aluminum. Most preferably, the reactive metal consists of a tin-containing composition that includes elemental tin, tin compounds or. tin alloys. Preferably, the degasser is prepared from a gaseous halogen-containing compound; more preferably, the degasser consists of a hydrogen halide, especially HCl prepared in itself. In a preferred embodiment, a conversion catalyst is then loaded into the reactors after the reactive metal is removed, and conversion operations begin. In another embodiment, the invention is a method for removing reactive tin from at least a portion of a reactor system having freshly standated surfaces. The method consists in the steps of: a) applying a plating, painting, plating or other tin coating to a base substrate portion containing iron from a reactor system; b) heating the coated substrate to temperatures greater than 800 ° F, preferably in the presence of hydrogen to produce a reactor system having freshly standated surfaces and containing reactive tin; c) removing at least a portion of the reactive tin from the reactor system by contacting the reactive tin with a degasser to produce mobile tin; and d) absorbing or reacting mobile tin. Preferably, the reactive tin is removed by contacting the surface portion with a gaseous halogen-containing compound, such as HCl. In general, the contact is made at temperatures and flow rates sufficient to transport a significant amount of the mobile tin out of the reactor and the furnace tubes and onto an absorbent. In this case it is again preferred that the method be carried out before - loading the catalyst.

In still another embodiment, the invention is a method for reducing catalyst contamination of a metal that was used to coat a reactor system. The method consists in contacting a reactor system with metallic coating before loading the catalyst with a degasser, preferably a gas-halogen-containing compound, to produce a mobile metal; and removing and fixing at least a part of the mobile metal from the reactor system. The conversion catalyst is then charged to the reactor system and conversion operations begin with the feed being converted to the product in the reactor system. This method of preference is applied to a freshly coated reactor system. In yet another embodiment, the invention is a catalytic reforming process. The process consists of removing reactive tin from a reforming reactor system, with tin coating by contacting a tin-coated reactor system with a halogen-containing compound to produce mobile tin; mobilize and absorb mobile tin; loading a Pt L-zeolite catalyst treated with halide in the reactor system; and perform the reformation of hydrocarbons to aromatics. Among other factors, this invention is based on our observation that Pt L-zeolite catalysts treated with halide are partially deactivated during the start phase of a catalytic reforming process, especially when the start-up is carried out in a reactor newly coated with tin. This is contrary to what was observed with conventional Pt L-zeolite catalysts (which were not treated with halides); in this case the deactivation of the catalyst due to a tin coating was not observed. The technique seems to omit totally the presence of reactive metal in the reactor systems for the conversion of hydrocarbons, with metallic coatings. In addition, the art has not appreciated the need or desire to remove this reactive metal before loading the catalyst, especially before loading the halide-treated catalysts. We have found that tin-coated reactor systems, especially those with freshly prepared intermetallic tin layers, can lose tin from tin-coated surfaces when contacted with halogen-containing gases, for example, during the start-up of a Reforming process using a Pt L-zeolite catalyst treated with halide that releases acid halides, including HCl. This loss of metal results in the deposition of tin on the catalyst and reduces the activity of the catalyst. However, we have observed that after several start-up cycles, the activity of the catalyst stabilizes without further significant decrease. In this way, we believe that a reactive tin is present in the newly coated reactors. When contact is made with the hydrogen halides (e.g., HCl and / or HF), this tin is mobilized unexpectedly and deactivates the platinum catalyst. Based on these findings, we have developed simple and inexpensive procedures that quickly and efficiently remove the reactive tin from the tin-coated reactor systems, preferably before loading the catalyst. When the catalyst is then charged to the reactors and begins and the. For hydrocarbon processing, the catalyst experiences little or no deactivation from the tin coating.

DESCRIPTION OF THE FIGURES Figure 1 shows detaching HCl (far right) of a catalyst for reformation treated with halide as a function of temperature (left). The hydrogen It was added at 500 ° F at a time = 79 hours. Figure 2 shows the experimental configurations for the exploration tests described in Examples 5 and 6. Figure 3 shows total loss of tin weight of a staggered coupon as a function of the number of startup cycles, each made in Presence of Pt L-zeolite catalyst treated with halide, recent, (light circles). The line at the bottom (dark circles) is a control. See Example 7.

DETAILED DESCRIPTION OF THE INVENTION In a broad aspect, the present invention is a process for removing reactive metal from at least a part of a metal-lined reactor system. This process consists in contacting at least a part of a metal-lined reactor system with a degasser. Preferably, the degasser is a halogen-containing compound, more preferably HCl. The degasser converts reactive metal into mobile metal, which is fixed. Optionally, the mobile metal is also mobilized, for example to another place in the process equipment, before being fixed. In another embodiment, the invention is a method for reducing catalyst contamination from a metal that was used to coat a reactor system. The method consists in contacting a reactor system with metallic coating before loading the catalyst with the degasser consisting of a gaseous halogen-containing compound to produce mobile metal. The moving metal is then removed from the reactor system. In a specifically preferred embodiment, the invention is a method for reducing the contamination of a catalyst for reformation of Pt L-zeolite by tin from a reactor system newly coated with tin having intermetallic flares on the surfaces that will be in contact with it. the hydrocarbons. Although the terms' "consists of" or "" contains "are used in this. Specification, these terms are proposed to understand the terms "consisting essentially of" and "consisting of" in the various aspects and preferred embodiments of the present invention. As used herein, the term "reactor system" is proposed to include the hot sections of the chemical conversion units, especially the hydrocarbon conversion units. These units usually consist of one or more conversion reactors and one or more furnaces containing a plurality of furnace tubes for heating the feed stream. The term "reactor system" is also proposed to include the units containing furnace tube reactors where conversion occurs in the furnace tubes (i.e., inside the furnace). The "hot sections" of these units are those sections where the feed is at or above the reaction or process temperature, and / or where the hydrocarbon conversion reactions occur.

As used herein, the term "metal-lined reactor system" is intended to include reactor systems (see above) that have a plating, plating, painting or other metal-containing coating applied to at least a portion of the surfaces that are going to be in contact with the hydrocarbons at or above the temperature of the process. Preferably at least half, more preferably at least three quarters, most preferably all the surface area that will be in contact with the hydrocarbons at or above the process temperature. The term "metal-lined reactor system" is also proposed to include reactor systems having protective layers, such as intermetallic layers that are prepared from plated, plated, paintings or coatings. Depending on the metal, the reactor system having a coating applied thereto can be cured by heating, preferably in a reducing medium, to produce the intermetallic layers. The metal-lined reactor system preferably contains a base construction material (such as carbon steel, chromium steel or stainless steel) having one or more adherent metal layers bonded thereto. Examples of the metallic layers include elemental chromium, aluminized surfaces and iron-tin intermetallic compounds such as FeSn2. Freshly coated reactor systems, for example, those that have been newly stagnant, are those that have not been used for hydrocarbon processing from the coating, or from the coating and curing. As used herein the term "metal-containing coating" or "coating" is intended to include veneers, platings, paints and other coatings containing elemental metals, metal oxides, organometallic compounds, metal alloys, mixtures of these components and Similar. The metal (s) or metal compounds are preferably a key component (s) of the coating. Fluid paints that can be atomized or brushed are a preferred type of coating. As used in this; the term "halogen-containing compound" or "halogen-containing gas" includes, but is not limited to, elemental halogen, acid halides, alkyl halides, aromatic halides, other organic halides including those containing oxygen and nitrogen, salts of inorganic halides and halocarbons or mixtures thereof. Water may be present optionally. As used herein, the term "reactive metal," such as "reactive tin," is intended to include elemental metals or metal compounds that are present on the surfaces of the metal-lined reactor system and that can be mobilized in the reactor. furnace tube process or temperatures, for example, in the presence of gaseous HCl, diluted, i.e., in the presence of between about 0.1 to about 100 ppm HCl. For example, reactive tin has been observed when a halide-treated catalyst that can release HCl was used for catalytic reforming in a freshly tinned reactor system having freshly prepared intermetallic layers of stannium. When used in the context of reformation, the term "reactive tin" consists of either: elemental tin, tin compounds, tin intermetallic and decoding alloys that will migrate at temperatures between 600-1250 ° F when in contact with the degasser, and that by this means the deactivation of the catalyst occurs during the reforming operations or during the heating of the reformer's furnace tubes. In other contexts, the presence of reactive metal will depend on the specific metal, the degasser, as well as the hydrocarbon conversion process and its operating conditions. The exploration tests, as described in the examples, can be modified by the particular metal and the process of interest to determine if the reactive metal will be present during T.9. the processing and therefore cause problems. The term "mobile metal" or "mobile tin" is also used herein. This refers to the reactive metal (for example tin), after the reaction with the degasser. In general, it is the mobile metal that is fixed. Although described hereafter in terms of providing intermetallic tin layers or tin coatings, it is considered that the intermetallic layers of germanium, arsenic and antimony, especially the freshly prepared layers also contain reactive metal, and that our findings are also applicable to these metals The description herein of metallic coatings or intermetallic tin layers is merely proposed to exemplify a preferred embodiment, and it is not intended to limit the invention to tin or tin intermetallic coatings.

Degassing and Halogen Sources The "degasser" of this invention is any composition that will interact with the reactive metal and facilitate its removal from the reactor system. By contacting the degasser with the reactive metal, it converts it to a shape that is mobile and therefore can be removed from the reactor system, for example, by a flow of hot gas. As will be appreciated by those skilled in the art, the effectiveness of a degasser will depend on the contact time and temperature, the concentration of the degasser, the specific reactive metal and its chemical or physical form. Preferred degassers are halogen-containing compounds or are prepared from these compounds. Useful degassers consist of organic halides, including halocarbons, and inorganic halides, as well as inorganic halides [sic], which includes the metal halides and hydrogen halides. Some examples of the halogen-containing compounds that are useful in this invention include HCl, Cl 2 MeCl, benzyl chloride, benzoyl chloride and NH 4 Cl; HBr, Br2, MeBr, benzoyl bromide and; NH4IHF; F2, and MeF; Hl, I2, Mel, iodobenzene and NH4I; CCI4, C2C14, C2C16, C2H2C12, and CF4, CF3CI, CF2C12, CFCI3, CHFCL2, CHF2CI, CHF3, C2F-2C14, C2F4CI2 and C2H4F2. Other useful halogen-containing organic compounds include those containing heteroatoms such as oxygen and nitrogen, for example chloropyridine, acetoyl bromide and amine salts of acid halides, for example pyridine hydrochloride. Other useful degassers include metal halides such as SnCl, GeCl 4, SnHCls; transition metal halides such as iron chloride, chromium chloride, copper chloride, nickel chloride, etc., especially in their highest oxidation state; and support materials treated with halide or other solids that can produce HCl with heating. The preferred halogen-containing compounds are those that can easily produce HCl in itself; for example by reaction with hydrogen and a Pt catalyst. These include C2CI4, MeCl and CCI4. The most preferred degasser contains a hydrogen halide, more preferably HCl. It is considered that other volatile acids would also be effective degasters, especially when the "resulting mobile metal (the compound) is volatile at process temperatures." HCl can be provided as a gas, however, it is preferred to generate HCl in situ. it can be easily carried out by reacting a halogen-containing compound, such as perchlorethylene with hydrogen on a nickel or platinum catalyst, such as raney nickel or a reforming catalyst Pt on alumina, conventionally, at elevated temperatures, for example about 900 ° F. The halogen-containing compounds are preferably present in dilute concentration, Concentrations between about 0.1 and 1000 ppm are preferred, more preferably between 1 and 500 ppm, more preferably between 10 and 200 ppm. consists of hydrogen, especially when HCl is prepared in situ., hydrogen is combined with an inert gas like nitrogen. For catalysts that are irreversibly poisoned by sulfur, such as the non-acidic Pt L-zeolite catalyst, it is important to use a halogen gas that is substantially free of sulfur, preferably one having less than 10 ppb of sulfur. When HCl concentrations are too high, or temperatures too hot, undesirable removal of the protective layer can occur, leaving an underlying substrate (eg, steel) susceptible to attack. A "preferred sulfur-free gas consists of nitrogen, and the process of preference includes a step wherein the hydrogen-nitrogen gas mixture (eg 10% hydrogen in nitrogen) is used during the metal removal step, for example, a stream of nitrogen and / or hydrogen can be seeded with small amounts of the degasser.

. Although one does not wish to stick to a theory, it is considered that, especially in a newly coated reactor system containing surface intermetallics, there will be some. metal that has not reacted with the base construction metal. This unreacted coating metal is considered to be, at least in part, the reactive metal that is removed in the process of this invention. For example, when iron and nickel stanols are produced by curing / reducing tin paints on steel, a fine powder containing tin is observed on the stagnant surface. When examined by petographic analysis, the metallic surface contains small microscopic spheres of tin that are considered unreacted tin. Some of. these spheres appear to be deposited on the intermetallic surface while others are connected to the surface by what appear to be stalk roots. It is considered that this unreacted tin is removed by the process of this invention. The amount of unreacted tin and the tin powder that is present depends on a number of factors. These include the thickness of the coating, the curing conditions that were used to prepare the stanides, and the type of steel or other base metallurgy to which the tin coating was applied.The process of this invention eliminates a substantial portion of this. dust and tin that does not react from the surfaces of the reactor system, otherwise, the degasser is expected to transform the reactive metal into an inactive form, for example, the degasser can convert the reactive metal into an immobile form, which effectively he fixes it Fixation and fixing agents Fixation of the mobile metal ensures that it will not deactivate the catalyst for the conversion of hydrocarbons. The term "fixation" as used herein means intentionally immobilizing the metal or metal compounds produced from the reactive metal by means of the degasser to reduce or prevent catalyst contamination. The fixation also refers to the absorption, reaction or otherwise immobilization of the degasser. This fixation can be done using chemical or physical treatment steps or processes. The fixed metal can be concentrated, recovered or removed from the reactor system. For example, the movable metal can be fixed by contacting an adsorbent, reacting it with a compound that will immobilize the metal, or by dissolution, for example by washing the surfaces of the reactor system with a solvent and removing the dissolved mobile metal. Solid absorbers are preferred fixing agents. In a particularly preferred embodiment, a gas consisting of HCl is used as the degasser. Then the effluent HCl, the residual halogen-containing gas (if present) and the mobile metal (for example in the form of SnCl 2) are all fixed by sorption. The sorbent is a solid or liquid material (an adsorbent or absorbent) that will trap the moving metal. Solid sorbents are generally preferred as they are easy to use and subsequently facilitate the removal of the system. The choice of metal sorbent or trap depends on the specific shape of the mobile metal and its reactivity. Suitable liquid sorbents include water, liquid metals such as tin metal, caustic scrubbing solutions and other basic solvents. Suitable solid sorbents effectively immobilize the mobile metal by adsorption by reaction. The sorbent preferably has a high surface area (> 10 m2 / g), interacts strongly with the mobile metal (has a high adsorption coefficient) or reacts with the mobile metal to immobilize the metal. The sorbent preferably maintains its physical integrity after fixing the mobile metal (for example it has acceptable crushing strength, rub resistance, etc.). Suitable sorbents include metal shavings, as it can be iron shavings that will react with mobile tin chloride. Preferred sorbents include aluminas. clays, silicas, silica aluminas, activated carbon and zeolites. A preferred sorbent is basic alumina, such as potassium on alumina, especially calcium on alumina. The location of the sorbent is not crucial. For example, this can be located in one or more of the reactors, or preferably in or downstream of the last reactor, or in f a special dehydrator reactor. If the metal removal process is performed before loading the catalyst, it is preferred to place a solid sorbent in the bottom of the last reactor, or just before the heat exchangers. In this way, the reaction all surfaces are in contact with the degasser are located before the sorbent. If the elimination process is * f * done with catalyst present, it is preferred to place the solid sorbent in the upper part of each reactor bed. In this case, it is considered that the degasser would be injected near each furnace inlet and the mobile metal would be sucked before reaching the catalyst beds. In this case, a significant portion of the coated surface would be in contact with the degasser, and most of the reactive metal would be fixed. The moving metal can be fixed simultaneously as it reacts with the degasser or in one or more separate steps. For example, mobile tin, as you can Tin chloride can be formed at temperatures where the tin chloride is volatile, and the tin chloride is then immediately contacted with a solid sorbent. Otherwise, after contacting the reactive tin with HCl at approximately 600 ° F, the system The reactor can be cooled (e.g., at room temperature) and produced metal halide (e.g., tin chloride) can then be mobilized and fixed by washing it out of the reactor system with water or other suitable solvent. In another two step process, the tin chloride can be produced on the surfaces of the reactor system at a lower first temperature and then removed from the reactor system at a second higher temperature where the tin chloride is volatile. The volatile tin chloride is then fixed downstream or at the outlet of the reactor system. The amount of fixing agent is not important, as long as there is a sufficient amount to fix the mobile metal, for example, a sufficient amount of sorbent to suck the desired amount of the mobile metal. In general, too. it is advantageous to sorb any degasser, such as HCl, present in the reactor effluent.

Ways to remove reactive metal There are a variety of ways to remove reactive metal from a metal-lined reactor system. The method used and its effectiveness depend on the coating metal and the planned configuration and operations of the reactor system. For example, if the reactive metal is in the furnace tubes, these tubes can be temporarily connected in a cycle, and a heated solution or gaseous composition containing the degasser can be circulated through the cycle. It is considered here that the degasser solution can also serve as the fixing agent. After sufficient contact time, it would be drained or otherwise eliminated. Otherwise, if the "moving metal is formed as a gas, it can be fixed, for example, by sorption, during gas circulation." If the reactive metal is located inside the reactor, then it is preferred to remove this reactive metal by in contact with the surfaces with metal coating with a degasser, preferably a gas containing halogen at the conversion conditions of the hydrocarbons, for example, a support material treated with halide, such as a catalyst base - treated with halide ( that is, a catalytic metal free) can be placed in the first reactor, optionally together with a catalyst that converts halogen-containing compounds and hydrogen into HCl.The base of the halide-treated catalyst can be treated, for example, by impregnating NH4C1 in alumina After the common catalyst start-up procedures, the hydrogen halides will gradually release from the catalyst base. with halide as the temperature increases. This method models the conditions that will occur when the catalyst is present. In this case, the coated reactor system is treated in a manner similar to what will occur when the catalyst is present. It is preferred that before contacting the reactor system with the degasser, the coated reactor system is visually inspected, and where practical, any excess metal observed is manually removed. Care must be taken so that this physical separation does not cause portions of the reactor system unprotected during the processing of hydrocarbons. The elimination step "of the metal is preferably carried out in the absence of the catalysts and hydrocarbons of the process.The metal-coated steel is brought into contact, preferably after curing, with a degasser such as HCl, preferably at similar temperatures and pressures. The removal step of the metal may remove a part of the metallic coating, however, the coating that remains is significantly less susceptible to greater metal loss, for example, in the Subsequent startup cycles. It is, of course, important that a sufficiently thick coating layer remains effective for its purpose, for example, to avoid carburation, coking, and metallic dust. until most of the reactive metal is removed, preferably, the elimination continues until The metal removal rate has decreased substantially. For a freshly coated reactor system it is preferred that the weight loss of the metal be measured every 10 hours. The elimination process is performed until the metal weight loss rate is approximately 20% of the original rate of metal weight loss. There are several ways to determine when to stop adding the degasser to the reactor system. Removable, metal-coated coupons can be used to determine when to stop adding the degasser. For example, small bypass currents can be provided near the furnace and / or the reactor. A section of the bypass stream can be used to house the coated coupons. This section must be able to be isolated from the other part of the bypass current by means of valves. During the metal removal process, these valves can be closed periodically and the coupons can be separated for inspection or to determine the metal weight loss of the coupons. The actual metal weight loss curves for these coupons can be compared to the curve shown in Figure 3. The metal removal process can be completed after the weight loss of the metal is leveled, for example, when the curve begins its descent.

In commercial operations, a previous test using coated coupons in a pilot plant can be used to determine a weight loss of the target metal. In accordance with this objective, the coupons with. Removable liners can be placed in the reactor system and weighed in intervals. When the target weight loss is reached, the metal removal process is discontinued. It is preferred that the preliminary tests be performed at common temperatures of the hottest portion of the reactor system. Otherwise, visual or microscopic inspections of the surface of the reactor system can be used to determine when to stop the addition of the degasser in the metal removal process. For example, reactors can be opened and inspected. If the tin dust is still present on the surface of the reactor, the elimination operations will continue. If this powder is absent or has been converted to tin chloride (which is easily identified as it is soluble in water), then the addition of the degasser can be terminated. Our data on tin weight losses at multiple startup steps suggest that a significant portion of the reactive tin is removed relatively quickly, followed by a more gradual loss.

See Figure 3. Calculations show that this later gradual loss would only deposit approximately 50 ppm of tin in the catalyst per start step, which is expected to reduce the catalyst activity only slightly, to less than 1 ° F.

Plating, plating, paints and other coatings Metal coatings are usually applied to reactor systems to improve the operability of the process. The reactor systems of this invention have generally had metallic protective coatings applied to reduce coking, carburation and metallic dust. The invention does not apply to all coating metals. Multiple plating, plating, painting and coating processes containing metal do not produce reactive metals under the conversion / process conditions. However, simple tests such as those described in the examples will readily identify metals and coatings that require metal removal processes of this invention. The metal used in the coating will depend on the requirements of the hydrocarbon conversion process of interest, for example, its temperatures, reagents, and so on. Coating metals that melt down or under process conditions and form intermetallic complexes with the substrate material are especially preferred. These can more easily provide complete coverage of the substrate. These metals include those selected from tin, antimony, germanium, arsenic, bismuth, aluminum, gallium, indium, copper and mixtures, intermetallic compounds and alloys thereof. Preferred metal-containing coatings contain metals selected from the group consisting of tin, antimony, germanium, arsenic, bismuth, aluminum and mixtures, intermetallic compounds and alloys of these metals. Especially preferred coatings include coatings containing tin, antimony and germanium. These metals will form continuous and adherent protective layers. Tin coatings are especially preferred, they are easy to apply to steel, they are not expensive and they are benign for the environment. The most preferred metals interact with, or more preferably react with, the base material of the reactor system to produce a continuous and adherent metallic protective layer at lower temperatures or under the conditions proposed for the conversion of hydrocarbons. Coatings containing metal that are less useful include certain metal oxide coatings such as those containing molybdenum oxide, tungsten oxide and chromium oxides. In part this is because it is difficult to form adherent metallic protective layers from these oxides at temperatures at which the hydrocarbon conversion equipment is operated. "It is preferred that the coatings be sufficiently thick so that they completely cover the base metallurgy, and that_ after removing the moving metal, the resulting protective layer remains intact, so that it can protect the steel during years of operation. At the same time, thin layers are desirable. Thin layers can be produced easily, are less expensive than thicker layers and are less likely to be billed under stress. thermal. In this way, the optimum thickness of the protective layer depends on the proposed conditions of use and the specific coating metal. For example, tin paints can be applied to a (wet) thickness of between 1 to 6 mils, preferably between about 2 to 4 mils. In general, the thickness after curing is preferably between about 0.1 to 50%, more preferably between about 0.5 to 10 -20 mils, more preferably about 1 mil. It is also desirable that the coating and any of the intermetallic layers produced at least initially be firmly attached to the steel; This can be done, for example, by curing at elevated temperatures. For example, an applied tin paint can be cured in hydrogen at 1100 ° F for 24 hours. Coatings containing metal can be applied in different ways, which are well known in the art. These include electroplating, chemical vapor deposition and cathodic sublimation, to name just a few. Preferred methods for applying the coatings include painting and plating Where it is practical it is preferred that the coating be applied in a formulation similar to a paint (hereinafter "paint"). This paint can be atomized, applied by brush, formed in ingots, etc., on the surfaces of the reactor system - Tin is a preferred coating metal and is exemplified herein The descriptions in the present about tin are generally applicable to other metals such as germanium. Preferred paints contain a metal component selected from the group consisting of: a decomposable metal compound, of hydrogen, such as an organometallic compound, a finely divided metal, and a metal oxide, preferably a metal oxide which can be reduced to the process or furnace tube temperatures In a preferred embodiment, a curing step is used to produce a intermetallic protective layer bonded to the steel through an intermediate tie layer, for example, a carbide-rich tie layer. This is described in U.S. Patent No. 5,406,014 to Heyse et al., Which is incorporated herein by reference in its entirety. Some preferred coatings and paint formulations are described in US No. 803,063 to Heyse et al., Corresponding to WO 92/15653, which is also incorporated herein by reference in its entirety. An especially preferred tin paint contains at least four components or their functional equivalents: (i) a tin compound which can be decomposed with hydrogen, (ii) a solvent system, such as isopropanol, (iii) finely divided tin metal and (iv) tin oxide. As the tin compound which can be decomposed with hydrogen, organometallic compounds such as tin octanoate or tin neodecanoate are particularly useful. Component (iv), tin oxide is a porous tin-containing compound which can absorb the organometallic tin compound and can be reduced to metallic tin. The paints preferably contain finely divided solids to minimize sedimentation. The finely divided tin metal, component (iii) above, is also added to ensure that metallic tin is available to react with the "surface to be covered at temperatures as low as possible. preference is small, for example from 1 to 5 microns.When "tin paints are applied in suitable thicknesses, heating under reducing conditions will result in the migration of tin to cover small regions (for example, solders) that are not painted. This will completely cover the base metal.

Conditions of the curing process Some coating compositions need to be cured by heat treatment to produce continuous and adherent protective layers. The curing conditions will depend on the particular metallic coating as well as "of the hydrocarbon conversion process to which the invention is applied." For example, the gas flow rates and the contact time will depend on the process configuration, the coating metal, the components of the coating composition. and the. curing temperature. The curing conditions are selected to give rise to a continuous and non-interrupted protective layer that adheres to the steel substrate.The curing conditions can be easily determined.For example, the coated coupons can be The presence of hydrogen in a simple test apparatus; The formation of a continuous protective layer can be determined using petrographic analysis. As described above, it is described to contact the metal-coated reactor system with the degasser after the curing step, especially when the intermetallics are formed during the heat treatment. Tin paints are preferably cured between 900 ° F and 1100 ° F; germanium and antimony paints are preferably cured between 1000 ° F and 1400 ° F. The curing preferably takes place over a period of hours, often with temperatures in increments during the time when the paint contains reducible oxides and / or organometallic compounds containing oxygen. The reduction / curing preferably is carried out using hydrogen containing gas, more preferably in the absence of hydrocarbons. As an example of a paint cure suitable for a tin paint, the system that includes painted portions can be pressurized with flowing nitrogen, followed by the addition of a stream containing it. hydrogen. The reactor inlet temperature can be raised to 800 ° F at a rate of 50-100 ° F / h. The temperature can then be raised to 950-975 ° F at a rate of 50 ° F / h, and can be maintained for about 48 hours.

In a preferred embodiment, the reactor system coated with metal contains an intermetallic layer. This layer (which covers a base construction material as a steel substrate) contains two or more metals, the metals being present in a stoichiometric ratio, that is, as intermetallic compounds. Intermetallic compounds are well known in the art; these are more structured than molecular mixtures or alloys. In addition, these have physical properties (such as color) and chemical properties that are unique to the intermetallic phase. For example, a stacked intermetallic layer contains intermetallic tin compounds consisting of tin and at least one other metal, tin and the other metal (s) being present in the compounds having a stoichiometric ratio of two elements that varies only within a narrow range. Examples of these tin intermetallic compounds are Fe3Sn, FeSn2, Ni3Sn2, Ni3Sn, Ni3Sn4. Other examples include mixed metal intermetallic studs, for example, (Fe, Ni) xSny where Fe and Ni are freely substituted with each other, but added are present in a stechymetric relationship with tin.

Base construction material There is a wide range of base construction materials to which the process of this invention can be applied. In particular, a wide range of steels and alloys can be used in the reactor system. In general, the steels are chosen in such a way that they meet the minimum requirements of strength and flexibility necessary for the proposed hydrocarbon conversion process. These requirements in turn depend on the conditions of the process, such as the prevailing temperatures and pressures. In addition, the steel is chosen so that it is not susceptible to the expected damage from corrosion. Useful steels include carbon steel; low alloy steels such as chrome steel 1.25, 2.25, 5.7, and 9 with or without molybdenum; stainless steels series 300 that include type 304, 316 and 347; 'heat-resistant steels including HK-40, HP-50 and manurite, as well as steels treated as aluminized or chromed steels.

Conversion processes The invention is applicable to a variety of conversion processes that use catalysts to convert the feed stream into products in metal-lined reactor systems. In particular, the invention is applicable to hydrocarbon conversion processes using catalysts which can • be deactivated by reactive metal from the lining of the reactor system. Preferred hydrocarbon conversion processes include dehydrocyclization, especially dehydrocyclization of Cβ to Cs paraffins to aromatics, catalytic reformation, non-oxidative and oxidative dehydrogenation of hydrocarbons to olefins and dienes, dehydrogenation of ethylbenzene to styrene and / or dehydrogenation of isobutane. to isobutylene; conversion of light aromatic hydrocarbons; transalkylation of toluene to benzene and xylenes; hydroalkylation of alkylaromatics to aromatics; alkylation of aromatics to alkylaromatics; production of fuels and chemical substances from syngas (H2 and CO); steam reforming hydrocarbons to H2 and CO; phenylamine production from • aniline; alkylation of methanol from toluenes to xylenes; and dehydrogenation of isopropyl alcohol to acetone. The most preferred hydrocarbon conversion processes include dehydrocyclization, cyclic deformation, dehydrogenation, isomerization, hydrodealkylation and conversion of light hydrocarbons to aromatics, for example Cycllar type processing. These processes and the useful range of process conditions are well known in the art.

Preferred embodiments include those where a catalyst, preferably a platinum catalyst, is used. Preferred processes include the dehydrogenation of a C3-C4 paraffin to an olefin, for example the Oleflex® process, or the dehydrocyclization of a paraffin stream containing the feed and Cβ, C7 and / or C8 hydrocarbons in aromatics (by example the processes that produce benzene, toluene and / or xylenes) such as the Aromax® process. In a preferred embodiment, the method for removing the reactive metal is applied to a metal-coated dehydrogenation reactor system, which has a significant portion of its furnace tubes and reactor surfaces coated with the coating metal, preferably tin. The present invention is especially applicable to hydrocarbon conversion processes that require catalysts, especially catalysts treated with 'halide, having noble metals such as Pt, Pd, Rh, Ir, Ru, Os, particularly Pt-containing catalysts. These metals are usually provided on a support, for example, on carbon, in a refractory oxide support, as it can be silica, alumina, chlorinated alumina or in a molecular sieve or zeolite. The preferred catalytic processes are those using platinum on alumina, Pt / Sn on alumina and Pt / Re on chlorinated alumina; Group VIII catalysts of the noble metals supported on a zeolite such as Pt / Sn and Pt / Re on zeolites include L-type zeolites, ZSM-5, SSZ-25, SAPO, Salicalite and beta. Examples of these processes include catalytic reforming and / or dehydrocyclization processes, such as those described in U.S. Patent No. 4,456,527 to Buss et al. , and the US patent NO. 3,415,737 of Kluksdahl; catalytic processes for the isomerization of hydrocarbons such as those described in U.S. Patent No. 5,166,112 to Holtermann; and the catalytic hydrogenation / dehydrogenation processes. Metal-coated reactor systems are especially useful in processes operated under low sulfur conditions, since the coating provides better resistance to coking, carburation and metallic dust. This, in a particularly preferred embodiment of the invention, the hydrocarbon conversion process is carried out under "low sulfur" conditions. In these systems with low sulfur, the preferred feed will contain less than 50 ppm of sulfur, more preferably less than 20 ppm of sulfur and more preferably less than 10 ppm of sulfur. In another preferred embodiment, the invention is carried out under "ultra low sulfur" conditions. In this case the sulfur levels are preferably less than 100 ppb, more preferably less than 50 ppb, and more preferably below 20 ppb of sulfur, with sulfur levels below 10 ppb and especially below 5 ppb being particularly preferred. A preferred embodiment of the invention includes the use of a zeolite catalyst with medium pore size or large pore size that includes an alkaline or alkaline earth metal and is charged with one or more metals of group VIII. More preferred is the mode where this catalyst is used in reforming or dehydrocycling a stream of paraffinic naphtha containing Cβ and / or C8 hydrocarbons to produce aromatics, for example UDEX refining from C to Cs. The invention is especially applicable to ultra low low sulfur reformation using a medium or large pore zeolite catalyst containing halogens, especially a platinum catalyst on non-acidic L-zeolite treated with halide. By "intermediate pore size" zeolite is meant a zeolite having an effective pore opening in the range of about 5 to 6.5 Angstroms when the zeolite is in the H form. These zeolites allow the hydrocarbons to have some branching in the spaces zeolitic voids and can differentiate between n-alkanes and slightly branched alkanes compared to alkanes with longer branches having, for example, quaternary carbon atoms. Useful zeolites with intermediate pore size include ZSN-5 described in US Patent Nos. 3,709,886 and 3,770,614; ZSM-11 described in U.S. Patent No. 3,709,979; ZSM-12 described in U.S. Patent No. 3,832,449; ZSM-21 described in U.S. Patent No. 4,061,724; and silicalite described in US Patent No. 4, 061, 724. The preferred zeolites are silicalite, ZSM-5 and ZSM-11. A preferred Pt catalyst on zeolite is described in U.S. Patent No. 4,347,394 to Detz et al. By "zeolite with large pore size" is meant a zeolite having an effective pore opening of about 6 to 15 7? Ngstroms. Preferred large pore size zeolites that are useful in the present invention include zeolitead L, zeolite X, zeolite Y and faujasite. Y zeolite is described in US Patent No. 3,130,007 and Zeolite X is described in US Patent No. 2,882,244 Especially preferred zeolites have effective pore openings between 7 to 9 7 Angstroms In a preferred embodiment, the invention uses a zeolite catalyst with medium pore size or large pore size containing alkaline or alkaline earth metal and charged with one or more metals of group VIII.

The zeolitic catalysts used in the invention are charged with one or more metals of group VIII, for example, nickel, ruthenium, rhodium, palladium, iridium or platinum. Preferred group VIII metals are iridium and particularly platinum. If used, the preferred weight percent of platinum in the catalyst is between 0.1% and 5%. Group VIII metals can be introduced into the zeolites by synthesis, impregnation or exchange in an aqueous solution of the suitable salt. When it is desired to introduce two metals of group VIII into the zeolite, the operation can be carried out simultaneously or sequentially. Especially preferred catalysts for use in this "invention are group VIII metals on large pore zeolites, such as L-zeolite catalysts containing Pt, preferably Pt on non-acidic L-zeolite.Pt-L-zeolite catalysts halides are particularly preferred The composition of the L-zeolite type expressed in terms of molar ratios of the oxides can be represented by the following formula: (0.9-1.3) M2 / nO: Al2? 3 (5.2-6.9) Si? 2; yH2O In the above formula, M represents a cation, n represents the valence of M, and y can be any value from 0 to about 9. The zeolite L, its X-ray diffraction pattern, its properties and methods of preparation are described in detail in , for example, U.S. Patent No. 3,216,789, the content of which is incorporated herein by reference. The actual formula can vary without changing the crystalline structure. Useful Pt on L-zeolite catalysts also include those described in U.S. Patent No. 4,634,518 to Buss and Hughes, U.S. Patent No. 5,196,631 to Murakawa et al., In U.S. Patent No. 4,593,133 to Wortel and in U.S. Patent No. 4,648,960 to Poeppelmeir et al., all of which are incorporated herein by reference in their entirety. Preferably, the catalyst will be substantially free of acidity. In an especially preferred embodiment, the invention is a catalytic reforming method utilizing a Pt L-zeolite catalyst treated with halide. Before loading the catalyst and reforming, the reactive metal is removed from the reforming reactor system, with tin coating. The process consists of: a) removing the reactive metal from the reactor system for reforming, with metallic coating, by contacting the reforming reactor with metal coating with a degasser to produce mobile metal; b) slurry the mobile metal; c) charging a Pt L-zeolite catalyst treated with halide in the reactor system; d) carry out the reformation of hydrocarbons in aromatics. Preferably, the mobile metal is sorbed on a solid sorbent and the sorbent is located before the effluent heat exchanger of the feed. In a more preferred embodiment, the reforming process consists of: a) coating a reactor system for reforming with a paint containing tin; b) contacting the painted reactor system with a gas containing hydrogen at 800/1150 ° F to produce stannides; c) removing reactive tin from the reactor system for reforming by contacting the reactor system with a gaseous stream containing HCl to produce mobile tin; d) fixing the mobile tin by adsorption on a solid sorbent; e) charging the catalyst Pt L-zeolite treated with halide in the reactor system; and f) Carry out the catalytic reformation of hydrocarbons in aromatics under reforming conditions with ultra low sulfur content of less than 10 ppb of sulfur.

Thus, a preferred embodiment of the invention utilizes Pt L-zeolite catalysts treated with halogen-containing compounds, mentioned herein as halide-treated catalysts. These types of catalysts have recently been discovered. For example, U.S. Patent No. 5,091,351 to Murakawa et al., Describes the preparation of Pt L catalysts, and then treating them with a halogen-containing compound. Other related patents describing catalysts of L-zeolite treated with halide include EP 498,182 A which discloses co-impregnation with NH 4 Cl and NH 4 F; U.S. Patent Nos. 4,681,865, 4,761,512 and 5,073,652 to Katsuno et al., U.S. Patent Nos. 5,196,631 and 5,260,238 to Murakawa et al. These catalysts also include spent catalysts that have been rejuvenated by adding halogen-containing compounds (see, for example, 5,260,238). These patents are all incorporated herein by reference. The halide-treated catalysts described in these patents have been treated with halogen-containing compounds, generally with chlorine-containing and / or fluorine-containing compounds. Preferably, the catalysts have been treated with compounds containing chlorine and fluorine or with one or more compounds containing chlorine and fluorine. These halide-treated catalysts have a desirably long life and catalyst activity. These are especially useful for preparing aromatic hydrocarbons such as benzene, toluene and xylenes from aliphatic hydrocarbons of C6-Cs. We have observed that these halide-treated catalysts give off small amounts of HCl and / or HF when these special types of catalysts are heated at elevated temperatures (for example, to process conditions), or when they are brought into contact with hydrogen at temperatures above about 300-400 ° F. And, this acid halide gas thus produced reacts with the reactive metal present in the metallic coated reactor systems. Hence the need for the present invention. It should be noted that the above-described treatment with halogen-containing compounds differs from that commonly associated with platinum loading, for example, by impregnation or ion exchange with compounds containing platinum and halogen. This treatment also differs from that associated with washing solutions used during the impregnation or ion exchange of conventional catalysts, where small amounts of halides can be added.

In some applications, for example in reforming with ultra low sulfur content using non-acidic Pt L-zeolite catalysts, it is preferred that the feed for the catalyst be substantially sulfur-free, ie, the sulfur levels remain below 50. ppb, preferably below 10 ppb and more preferably below 5 ppb. Preferred conditions for the reforming process include a temperature between 700 and 1050 ° F, more preferably between 800 and 1025 ° F; and a pressure between 0 and 400 psig, more preferably between 15 and 150 psig; a recycled hydrogen velocity sufficient to produce a molar ratio of hydrogen to hydrocarbon for feeding to the reforming reaction zone between 0.1 and 20, more preferably between 0.5 and 10; and an hourly space velocity of the liquid for feeding hydrocarbons over a reforming catalyst of between 0.1 and 10, more preferably between 0.5 and 5. In order to achieve the appropriate temperatures of the reformer, it is often necessary to heat the furnace tubes to higher temperatures. These temperatures can often be in the range from 800 to 1250 ° F, usually from 850 and 1200 ° F, and most often from 900 and 1150 ° F.

To obtain a more complete understanding of the present invention, the following examples illustrating certain aspects thereof are established. It should be understood, however, that the invention is not limited in any way to the specific details of the examples.

Example IA - tinned steel using a tin paint Coupons of type 321 or type 347 of stainless steel were coated with a paint containing tin. The paint consisted of a mixture of two parts of powdered tin oxide, two parts of finely powdered tin (1-5 microns), one part of stannous neodecanoate in neodecanoic acid (20% tin Tem-Cem manufactured by Mooney Chemical Inc., Cleveland, Ohio containing 20% tin as stannous neodecanoate) mixed with isopropanol, as described in WO 92/15653. The coating was applied to the steel surface by painting and allowing the paint to dry in air. After drying the painted steel was contacted with flowing hydrogen at 1100 ° F for 40 hours to produce a stan- dard steel surface with an intermetallic content including iron stanides. Some experiments were carried out in a pilot plant with an external diameter inch reactor tube made of 316 stainless steel. The reactor tube was coated with the above-described tin-containing paint. The coating was applied to the inner surface of the pilot plant by filling the reactor tube with paint and letting the paint drain. After drying, the painted steel was cured with flowing hydrogen at 1100 ° F for 40 hours.

Example IB - Analysis of Stamped Steel The resulting tin-plated steels with their intermetallic tin layers were visually examined for coating finish. The samples were mounted on a transparent epoxy resin and then ground and polished in preparation for analysis with petographic and electron scanning (SEM) microscopes. The EDX analysis can be used to determine the chemical composition of the layers. The cross sections of the materials showed that the tin paint had been reduced to metallic tin under these conditions and a metallic protective layer (iron / nickel stannous) was formed which was continuous and adherent on the surface of the steel. The stanols containing nickel and iron were present in a thickness between about 2 to 5 microns. A nickel-poor sub-layer (2-5 microns thick) was also present. Spheres and microscopic tin globules were observed on the surface.

Example 2 Preparation of a platinum catalyst L-zeolite treated with "halide" A platinum catalyst L-zeolite treated with halide was prepared in a manner similar to EP 498, 182A1, Example 4. Experiments showed that this catalyst released HCl and HF when heated to 500 ° F in the presence of hydrogen. Figure 1 shows the release of HCl as a function of temperature. HF loss was also observed. The Gastec tubes were used to measure the concentration of HCl. The gas velocities were 1300 GHSV, in direct process. The hydrogen was added at the same time 79 hours. This catalyst was used for all the activity tests described in the following and as a source of HCl and HF in some of the following examples.

Example 3 - Standart coupon stability A newly stamped coupon was prepared using the procedure described in example 1. The coupon was weighed before stamping. After stamping the coupon, 86.5 mg by weight was increased. This coupon was placed in a stainless steel pilot plant and heated to 900 ° F in a mixture of H2 / N2. After • approximately 80 hours the coupon was weighed again. This one had lost less than 1 mg of weight. This example shows that in the absence of a degasser (such as HCl), the reactive tin does not migrate easily.

Example 4 - (comparative) A newly stamped coupon was prepared using the procedure described in example 1. The coupon was weighed before stancing. After the standar the coupon increased 84.3 mg of weight. The standarized coupon was placed in the pilot plant and heated to 1000 ° F using a mixture of H2 / N2 with a content of 1000 ppm of HCl. after 7 hours, the coupon had lost 40.3 mg of weight. Assuming, for calculation purposes, that all this weight loss was tin loss, 48% of the tin was removed after 7 hours. After 22 hours, 87% of the tin had been removed. This treatment procedure was too rigorous; This removed too much of the stannide layer. The combination of temperature and HCl concentration was too aggressive.

Example 5 - screening tests of the reformation The impact of tin on the operation of the catalyst was assessed in tests at the pilot plant. Process 1 (144-181) was carried out in a type 316 stainless steel reactor that was not stagnant. 130 [sic] of catalyst, prepared by example 2, was charged upstream of another catalyst layer of 60 [sic]. The arrangement shown in Figure 2-1 was used. The catalyst served as a source of HC1 / HF. A catalyst start-up treatment was carried out. This start-up included drying the catalyst in N2 from room temperature at 500 ° F for 79 hours; then heating the catalyst in a mixture of 10% H2 to N2 from 500 to 932 ° F at a rate of 10 ° F / H for a period of about 43 hours, and then holding the catalyst at approximately 932 ° F for 24 hours . The GHSV was maintained at 1300 hr "1 during periods of drying and reduction. Then, the entire reactor was cooled to room temperature. The upper catalyst layer was removed under a nitrogen blanket. A test run was conducted of __ catalyst using the lower catalyst only. These conditions were 100 psig, 1.6 LHSV, 3.0 H2 / hydrocarbon and a target of 46.5% weight yield of aromatics. the feed stream was a refined UDEX CSS-Ca of an extraction unit The process 2 (144-182) was established as shown in Figure 2-2 In this case, a newly stan- dard reactor and newly stan- dard type 347 stainless steel coupons were used. In this process, the ratio of the surface area stabilized to the total volume of the catalyst was equal to approximately 20 times that of a commercial scale equipment 80 ce [sic] of catalyst prepared for the example 2 was loaded upstream of a stannished coupon prepared as in Example 1. Another layer of 80 ce [sic] catalyst was loaded downstream of the stacked coupons. Then the process of starting the process 1 was carried out. After cooling, the upper catalyst layer and the coupon were removed under a layer of nitrogen. A catalyst performance test was performed (as in process 1) using only the lower catalyst. After the performance test, the lower layer of the catalyst was analyzed and found to contain about 1000 ppm of tin. After 1200 hours in the stream, the process start temperatures (SOR) were determined for processes 1 and 2 by extrapolating the off-line temperature necessary to obtain the target aromatic yield back to the same time 0.- SOR temperatures showed that_ the catalyst of process 2 was about 10 ° F less active than the catalyst of process 1. It is considered that the reactive tin had reacted with halide release, which includes HCl, from the first catalyst layer, producing mobile tin. This mobile tin had deactivated the catalyst in the second catalyst layer.

"Example 6 - Catalyst operation after pre-coupon treatment Pre-treatment conditions were developed to remove stannous reagent from standardized coupons." A newly stamped coupon that had increased 77.5 mg by weight after stamping was placed in a pilot plant. The coupon was heated to 900 ° F using an H2 / N2 mixture containing 100 ppm of HCl.The mobile tin was formed, it migrated downstream to the cooler portions of the pilot plant and detached from the plating. The pilot was cooled at different time intervals so that the coupon could be weighed. This was then reheated to 900 ° F.

- After 7.5 hours, the coupon had lost 6.3% of total tin (0.65 mg / h); after 13.5 hours, 9.0% (0.35 mg / h); after 28.5 hours, 13.4% tin (0.23 mg / h); after 44.5 hours, 16.5% (0.15 .mg / h); after 60.3 hours, 18. 8% (0.11 mg / h). When these numbers were plotted (time against tin loss in percent by weight) the maximum point on the curve was observed at approximately 15% by weight of tin loss.

The impact of a step of elimination of tin before loading the catalyst was assessed in a pilot plant test. 6 standarized coupons were prepared with 100 ppm of HCl at 900 ° F. Based on the above experiments, it was decided to remove approximately 15% by weight of tin by pretreatment. It was estimated that this would take 40 hours. After 40 hours only 6-10% by weight of tin had been removed, so that the coupons were again heated for an additional 20 hours. This process eliminated between 19-23% of tin added. These coupons were used in the next test, process 4, which is discussed later. A separate pilot plant test, process 3 (60-313), was established as in Figure 2-1 with 80 ce [sic] of Pt L-zeolite catalyst treated with halide in each bed. As in process 1, a start-up procedure was carried out. This was followed by a performance test of the catalyst using only the lower catalyst. In process 4 (60-314), the arrangement of Figure 2-2 was used with an uncoated 316 stainless steel reactor and 80 ce [sic] catalyst beds each. The six pretreated tin coupons described above were placed between the catalyst beds. The stagnant surface area / volume of the catalyst in the second bed was approximately 2 times the stagnant surface area / volume of the catalyst of a commercial reforming reactor system with coating. After following the procedures set forth in example 5, the coupons were weighed, they had lost 2-4% by additional tin weight. A performance test of the catalyst was performed using the lower layer of the catalyst. The operation of the catalyst in process 4 was compared with process 3. The conditions of the performance test were similar to those of processes 1 and 2, except that after 500 hours the severity was increased to 84% by weight of aromatics . The SOR temperatures showed that the catalyst from process 3 had the same SOR temperature as the catalyst from process 4. These results show that the reactive tin had been removed in the pretreatment process. The remaining layer of stanidone apparently did not react with the release of the halides (HCl and / or HF) from the first catalyst bed, so that deactivation of the catalyst was not observed in the second catalyst bed.

Example 7 - multiple start test The multiple start tests, using a new catalyst load each time, were performed in a stainless steel reactor that was not stagnant. The catalyst of Pt L-zeolite treated with halide (20 ce) was placed in the reactor and the newly stamped coupons of steel type 347 were prepared as in example 1 and cured at 1100 ° F. The weight gain associated with this standard was measured. This profit was assumed at 100% tin. These coupons and an uncoated type 347 stainless steel coupon were placed downstream of the catalyst bed. The stamped coupons were weighed before the test. The catalyst and coupons were first dried in nitrogen at 1300 GHSV. The catalyst was heated from room temperature to 500 ° F at this flow rate. The cups were maintained at a temperature approximately 120 ° higher than that of the catalyst during the heat treatment. This simulated the furnace temperatures relative to the catalyst temperatures under commercial conditions. Then the hydrogen was introduced and the speed of the nitrogen was decreased, keeping the total flow rate constant. The hydrogen velocity was maintained at 10% of the total flow. The catalyst was activated by treatment with this stream of hydrogen in nitrogen (H2 / N2 = 1/9) while the catalyst was heated at a rate of 10 ° F / hour from 500 ° F to 932 ° F for a period of about 43 hours Meanwhile the coupons were heated to 10 ° F / h from 600 ° F to about 1050 ° F. The catalyst was then held at approximately 932 ° F and the coupons at approximately 1050 ° F for 24 hours in the absence of feed. The reactor was then allowed to cool to room temperature under nitrogen and open. After removing the catalyst the coupons were removed and weighed. The coupons were then placed back into the reactor together with a fresh catalyst charge. The heating procedure was repeated for a second cycle. The additional cycles were performed in the same way. Figure 3 shows the results of this test. The weight loss of the tin in the coupons (for example, the weight percent of the tin loss compared to the total tin before added) is shown as a function of the number of start-up cycles. The unlined coupon showed no weight loss (dark circles). As can be seen, the loss of metal (tin) initial for the standarized coupon (clear circles) was high in the first cycle. In the last cycles this weight loss decreased. By observing Figure 3 it can be seen that the original weight loss was 12% by weight of the initial tin in the first cycle, 4% by weight in the second cycle and 2% by weight in the third cycle. This weight loss in the third cycle is approximately 10% of the initial rate of weight loss (2% vs. 12%) and would be an approximate time to interrupt metal separation operations, as most of the reactive metal has been removed.

Example 8 - calculations for commercial-scale operations The loss of tin per unit area of the coupons was calculated using the weight loss data of example 7. Based on the loss of tin per unit area, the total tin loss was calculated expected in a commercial scale plant. It was assumed that the total surface area in the reactors, furnace tubes and associated pipe would be covered by tin. Assuming that all the lost tin is deposited on the catalyst, the tin content of the catalysts and the impact of the operation of the catalyst in a commercial unit was also calculated. The results are shown below: Estimated tin content of the commercial catalyst and impact on performance Boot cycle Tin deposit Loss of the increase in estimated activity of the catalyst, ppm of the catalyst, ° F (1) 1 800 8.0 2 250 2.5 3 150 1.5 4 = 50 0.5 50 0.5 Total 1300 13.0 (1) 10 ° F of loss of activity is assumed from 1000 ppm of tin deposit in the catalyst.

This loss of activity at 13 ° F at the beginning of the process will significantly decrease the duration of the process. In addition, the impacts on the stability of the catalyst can also shorten the life of the catalyst.

Example 9 - Large scale test This example describes a large scale test and demonstrates a preferred embodiment of the invention.

A small commercial scale catalytic reformer will be operated under ultralow low sulfur reforming conditions using a L-zeolite platinum catalyst with a C3-C8 UDEX refining feed. The sulfur content of the feed stream that makes contact with the catalyst is less than 5 ppb of sulfur. The reactor system includes a sulfur / sulfur sorbent converter, followed by four reforming reactors, their associated furnaces and kiln tubes. The reactors are made of Cr steel, Mo. The furnace tubes are made of 304 stainless steel. Before loading the catalyst the reactors, the furnace tubes and the associated pipe of the reactor system are treated with a reductible tin paint. Various coupons are also placed in the reactor system. The paint is applied to the coupons and to all the surfaces of the reactor system that are going to make contact with the hydrocarbon feed at the reforming temperatures or higher. The paint consists of a part of 20% tin Ten-Cem (manufactured by Mooney Chemical Inc., Cleveland, Ohio), 2 parts of powdered stannic oxide, 2 parts of finely powdered tin metal (1-5 microns in size) ) and isopropyl alcohol (for fluidity). The Ten-Cem contain 20% tin as octanoate stannous in octanoic acid. After the paint is applied to a wet thickness of about 3 mils, the coated reactor system is heated in a mixture of fluent hydrogen and nitrogen (1/9 ratio) for approximately 24 hours and then maintained at approximately 1050 ° F. for approximately 48 hours. This is then cooled to room temperature. This procedure gives rise to stamped painted surfaces (with iron and nickel stannides). Tin migrates to cover small regions (for example, welds) that are not painted. The reactors and furnace tubes are inspected and any tin that can be easily removed is removed. The coupons are analyzed by petrographic microscopy; these show the presence of microscopic, bright tin spheres. The reactive tin is removed from this newly stannous reactive system. A bed of calcium on alumina is placed in the lower part of the last reactor and before the heat exchanger of the effluent. A degassing mixture consisting of about 1% by volume of perchlorethylene (PERC) in hydrogen is passed over a Pt catalyst on alumina at 900 ° F to generate HCl in situ. The resulting gas is diluted with nitrogen to produce a gas containing 100 ppm of HCl which is passed into the newly standed reactor system described above.

The reactor system is heated to 600 ° F for 6 hours and then maintained at 600 ° F until the reactive tin is converted to a mobile form, considered as tin chloride. The time at 600 ° F is determined using a series of newly stamped removable coupons of known tin content. When the reactive tin has been converted to stannous chloride, the addition of PERC is terminated. This is done by placing the coupons in a container connected to the transfer pipe located between the reactor and the furnace. The valves allow the separation of the coupons for the analysis. A coupon is separated every 10 hours, washed water, dried and weighed. The tin loss is plotted in percent by weight against time. This graph is used to determine when enough reactive tin has reacted and in this way when to stop the addition of the degasser. In addition, as the process nears its end, analysis using petrographic and electronic microscopy shows that the stamped surfaces of the coupons are virtually free of microscopic tin spheres. Then the reactor system is heated to 1000 ° F in H2 / N2 and then maintained at 100 ° F for 24 hours. Volatile SnCl2 is fixed by adsorption on alumina sorbent in the last reactor. After the alumina sorbent is removed, the catalysts are loaded into the reactors. The platinum catalyst L-zeolite treated halide of Example 2 is used to reform the refining feed in aromatics at temperatures between 800 and 1000 ° F. The process of separation of metals is shown effective. The catalyst shows no decrease in its activity when measured by the SOR temperature as compared to what is expected for this catalyst in a nonstandard reactor system. Although the invention has been described above in terms of the preferred embodiments, it is understood that variations and modifications may be used as the experts will appreciate. The technique. In fact there are multiple variations and modifications to the above embodiments which will be readily apparent to those skilled in the art, and which are considered in the scope of the invention as defined by the following claims.

Claims (12)

1. CLAIMS 1. A method for removing reactive metal from a metal-lined reactor system consists in contacting at least a part of a reactor system with metal coating containing reactive metal with a degasser to produce mobile metal, and fixing the mobile metal , the degasser or both.
2. 2. The method of claim 1, wherein the moving metal is fixed.
3. 3. The method of claim 1, wherein the degasser consists of or is derived from a gaseous halogen-containing compound. The method of claim 3, wherein the gaseous halogen-containing compound is selected from the group consisting of organic halides, inorganic halides, a support material treated with halide and hydrogen halides. The method of claim 4, wherein the gaseous halogen-containing compound consists of HCl. The method of claim 1, wherein the fixation of the mobile metal is by adsorption on or in reactor with a solid sorbent. The method of claim 1, wherein the metal-lined reactor system is prepared using a coating metal selected from compositions containing tin, germanium, antimony and aluminum. 8. "The method of claim 1, wherein the metal of the coating consists of metallic tin, tin compounds or tin alloys 9. The method of claim 1 further consists of loading a catalyst for the conversion of hydrocarbons. in the reactor system and converting the hydrocarbons 10. The method of claim 1 further comprises charging a catalyst for the conversion of hydrocarbons, containing platinum, with halide treatment, into the reactor system and converting the hydrocarbons. The method of claim 1 further comprises charging a catalyst for reforming in the reactor system and producing aromatics 12. A method for removing reactive tin from at least a part of a reactor system with freshly leveled surfaces, the method consists of the steps of: a) applying a tin coating by plating, painting, plating or other coating to a portion . base substrate containing iron from a reactor system; b) heating the coated substrate to temperatures greater than 800 ° F, preferably in the presence of hydrogen, to produce a reactor system having freshly standated surfaces and containing reactive tin; c) removing at least a portion of the reactive tin from the reactor system by contacting the reactive tin with a degasser to produce mobile tin; and d) slurping or reacting the mobile tin. . The method of claim 12, wherein at least some of the reactive tin is removed by treating the stannous reactor system with halogen-containing gas. The method of claim 13, wherein the halogen-containing gas consists of HCl. The method of claim 12 further comprises charging a catalyst for conversion of hydrocarbons into the reactor system and converting the hydrocarbons. . The method of claim 12, wherein the sorbent used to sorb the mobile metal in step (d) is located before a catalyst bed and the degasser is added after a catalyst bed. The method of claim 12, wherein the sorbent used to sorb the mobile metal in step (d) is located in the last reactor or before the effluent heat exchangers in the feed. A method for reducing catalyst contamination of a metal that was used to coat a reactor system, the method is to contact a reactor system with metal coating before loading the catalyst with a degasser consisting of a halogen-containing gas compound to produce mobile metal; remove the mobile metal from the reactor system; loading a co-bonding catalyst in the reactor system; and convert the feed into product in the reactor system. The method according to claim 18, where the metal is tin. A catalytic process for reforming using a platinum catalyst L-zeolite treated with halide where, before loading the catalyst and reforming, the reactive metal is removed from the reactor system for the reformation with metallic coating, the process consists in: a) eliminating the reactive metal of a reactor system for reforming, with metallic coating, by contacting the reactor system for reforming, with metal coating, with a degasser consisting of a hydrogen halide to produce mobile metal; b) mobilize and suck the mobile metal; c) charging a Pt L-zeolite catalyst treated with halide in the reactor system; and d) carry out the reformation of hydrocarbons to aromatics. The process of reformation -catalytic of the claim 20, wherein the mobile metal is sorbed over a solid sorbent consisting of alumina. The process of catalytic reformation of the claim 20, where the sorbent is located before the heat exchanger of the effluent. The process of catalytic reformation of the claim 20, where the metal is tin. A catalytic reforming process using a platinum catalyst L-zeolite treated with halide where, before loading the catalyst and carrying out the reformation, the reactive tin is removed from a reactor system for reforming, coated with tin, the process consists of in: a) coating a reactor system for the reformajé with a paint containing tin; b) contacting the painted reactor system with a gas containing hydrogen at 800/1150 ° F to produce stannides; c) removing reactive tin from the reactor system for reforming by contacting the reactor system with degasser containing a hydrogen halide to produce mobile tin; d) fixing the mobile tin by adsorption on a solid sorbent; e) charging a Pt L-zeolite catalyst treated with halide in the reactor system; and f) carry out the catalytic reformation of hydrocarbons to aromatics under reforming conditions with ultra low sulfur content of less than 10 ppb of sulfur. The catalytic reformation process of claim 24, wherein the gaseous stream containing HCl is produced from a compound containing. halogen and hydrogen by reaction with a catalyst containing platinum or nickel.