MXPA99011267A - Method for regenerating a zeolitic catalyst - Google Patents

Abstract

The invention relates to a method for regenerating a zeolitic catalyst, comprising the following steps:(I) at least one partially deactivated catalyst is heated to a temperature ranging from 250 to 600°C in an atmosphere containing less than 2 vol.%oxygen;(II) the catalyst is impinged upon by a gas flow at a temperature ranging from 250 to 800°C, preferably 350 to 600°C, said gas flow having an oxygen-delivering substance content or an oxygen content or a mixture of two or more thereof ranging from 0.1 to 4 vol.%and (III) the catalyst is impinged upon by a gas flow at a temperature ranging from 250 to 800°C, preferably 350 to 600°C, said gas flow having an oxygen-delivering substance content or an oxygen content or a mixture of two or more thereof ranging from over 4 to 100 vol.%.

Description

REGENERATION OF ZEOLITE CATALYST The present invention relates to a process for regenerating a zeolite catalyst, in particular a zeolite catalyst which was used in the epoxidation of olefins with a hydroperoxide, in particular propylene with hydrogen peroxide. The regeneration is carried out by controlled combustion of the mainly organic coatings responsible for the deactivation in an inert gas atmosphere containing exactly defined quantities of oxygen or oxygen donor substances. When the reactions are carried out in the presence of catalysts, in particular in the presence of catalysts having micropores, such as titanium, silicalite, which have for example the MFI structure or titanium-containing zeolites with, for example, the BEA structure, the catalysts can be deactivated, in particular, by organic coatings. The main part of these organic coatings can be removed by calcining the catalyst or by washing with solvents (M. G. Clerici, G. Bellussi and U. Romano, J. Cata. 129 (1991), 159-167). Furthermore, EP-A 0 743 094 describes the regeneration of a molecular sieve with titanium content that was used in the catalysis of an oxidation reaction, for example the epoxidation of an olefin with hydrogen peroxide or with another oxygen compound " According to this publication, the regeneration of the deactivated catalysts described therein is carried out by combustion by means of calcination of the organic coatings present therein using molecular oxygen, a calcination temperature of more than 150 ° C. and lower than 400 ° C being used L In addition, JP-A 0 31 14 536 describes the regeneration of a titanium silicate epoxidation catalyst by combustion of the coatings from 400 to 500 ° C or by washing the catalysts at temperatures above the epoxidation temperature The solvents mentioned therein are water, alcohols, ketones, aliphatic and aromatic hydrocarbons, hydr Ocarburos containing halogen, esters, nitriles or acids. Furthermore, DE-A 44 25 672 mentions the regeneration of a catalyst used for epoxidation, in particular of propylene, by combustion thereof in an atmosphere containing oxygen at elevated temperatures. However, the regeneration processes of the prior art have some aspects which are not desirable in practice, in particular where the catalysts containing micropores, for example, the titanium silicalites used in particular in epoxidation, must be regenerated.

Some of the catalysts preferably used for the epoxidations, for example a titanium silicalite with the MFI structure or a titanium silicalite having the BEA structure, have micropores with diameters from about 0.5 to about 0.6 nm, from about 0.6 to about .7 nm [sic]. However, in both cases it is impossible to completely eliminate the oligomeric or even polymeric byproducts of the reactions catalyzed by these catalysts, in particular of the epoxidation, simply by washing with solvents at elevated temperatures. The above statements are applicable in particular to catalysts having micropores but, depending on the molecular weight and the dimensions of the oligomeric or polymeric by-products that are formed during the reaction, they are also applicable to catalysts having mesopores and / or macropores . -? However, if it is intended to eliminate these organic coatings completely, this is possible only by combustion thereof with oxygen or with oxygen donor substances. The regeneration of a highly selective zeolite catalyst having a specific structure by combustion at elevated temperatures is, however, difficult since full or local overheating of the catalyst can cause loss of selectivity as a result of partial destruction, or in extreme cases, complete of the structure inherent in the zeolite catalysts, whose destruction occurs with this overheating. If, to avoid overheating, the combustion is carried out below 400 ° C, the coatings will not be completely eliminated during relatively short calcination times The complete removal of the coatings by very prolonged calcination below 400 ° C, however It is not of commercial interest It is an object of the present invention to provide a process for regenerating a zeolite catalyst at elevated temperatures, which ensures the complete removal of the organic coatings even during relatively short-time calcification times. performed in a controlled manner so as to avoid local overheating and therefore irreversible damage to the catalyst, which causes loss of selectivity, increased formation of by-products and therefore a substantially faster deactivation of the regenerated catalyst when it is used again. We have found that this goal was achieved through the novel process. The present invention, therefore, relates to a process for regenerating a zeolite catalyst consisting of the following steps (I) and (II): (I) heating a partially or completely deactivated catalyst at 250-600 ° C in a atmosphere containing less than 2% by volume of oxygen, and (II) treating the catalyst from 250 to 800 ° C, preferably from 35 * 5 to 600 ° C, with a gas stream, containing from 0.1 to 4% in volume of an oxygen or oxygen donor substance or a mixture of two or more thereof. Preferably, the novel process consists of another step (III): (III) treating the catalyst from 250 to 800 ° C, preferably from 350 to 600 ° C, with a gas stream containing ^ from more than 4 % to 100% by volume of an oxygen or oxygen donor substance or a mixture of two or more thereof.

There are no specific restrictions with respect to the zeolite catalysts regenerated in the present process. Zeolites are known to be crystalline aluminosilicates having ordered channel and cage structures that possess micropores that are preferably smaller than about 0.9 nm. The network of these zeolites is composed of Si04 and A104 tetrahedrons that are linked by common oxygen bridges. An overview of known structures is provided, for example WM Meier, DH Olson and Ch. Baerlocher, Atlas of Zeolite Structure Types, Elsevier, 4th edition, London 1996. Zeolites that do not contain aluminum and in which some of the Si (IV ) in the silicate structure has been replaced by titanium as Ti (IV) are also known. These titanium zeolites, in particular those having MFI crystal structures, and the possibilities for their preparation are described, for example, in EP-A 0 311 983 or EP-A 405 978. In addition to silicon and titanium, these materials are also they may contain additional elements, for example aluminum, zirconium, tin, iron, cobalt, nickel, gallium, boron or small amounts of fluorine. In the zeolite catalysts preferably regenerated by the novel process, some or all of the titanium in the zeolite can be replaced by vanadium, zirconium, chromium or niobium or a mixture of two or more thereof. The molar ratio of titanium and / or vanadium, zirconium, chromium or niobium to the sum of silicon and titanium and / or vanadium and / or zirconium and / or chromium and / or niobium is, as a general rule, from 0.01: 1 to 0.1. :1. It is known that titanium zeolites having the MFI structure can be identified by specific X-ray diffraction patterns and also by an infrared (IR) skeleton vibration band at approximately 960 cm "1 and thus differ from the titanates of alkali metals or the phases of crystalline and amorphous Ti02. Preferably, the zeolites of Ti, V, Cr, Nb and Zr, particularly preferably the Ti zeolites, and especially the Ti zeolites as used in particular for the epoxidation of olefins, are regenerated by the novel process.The specific examples are Ti, V, Cr, Nb or Zr zeolites having zeolite pentasyl structure, in particular the types assigned by X-ray analysis to BEA, MOR, TON, MTW, FER, MFI, MEL, CHA, ERI, RHO, GIS, BOG, NON, EMT, HEU, KFI, FAU, DDR, MTT, RUT, LTL, MAZ, GME, NES, OFF, SGT, EUO, MFS, MCM-22 or the mixed structure MFI / MEL, those being considered particularly preferred have the MFI structure, the BEA structure, the MEL structure, the combined ITQ-4 or MFI / MEL structure. Zeolites of this type are described, for example, in the aforementioned publication of. M. Meier et al. Particularly preferred catalysts are specifically the Ti-containing catalysts, which are generally known as zeolites TS-1, TS-2, TS-3, T-S48 and TS-12 having a skeletal structure isomorphic with beta-zeolite. Other zeolite catalysts that can be regenerated in the process of the present invention are described, inter alia, in US-A 5,430,000 and WO 94/29408, the content of which in this context is incorporated herein by reference. Other titanium-containing zeolites which may be mentioned are those having the structure of ZSM-48, ZSM-12, ferrierite or β-zeolite and of orderite. Of course, it is also possible to regenerate mixtures of two or more catalysts, in particular of the aforementioned catalysts, in the novel process. There are also no specific restrictions with respect to the pore sizes or the pore size distribution of the regenerated zeolite catalysts according to the invention. Thus, catalysts having micropores, mesopores or even macropores, for example Si02 oxides containing Ti having macrophores, can be regenerated in the novel process.The novel process can be particularly and advantageously used to regenerate catalysts containing micropores. These include catalysts that contain only micropores and those that have micropores and mesopores or micropores and macropores or microporous, mesopores and macropores. The term "micropores", as used in the present application, describes pores having a diameter of 2 nm or less.The term "macropores" refers to pores having a diameter greater than about 50 nm, and the term "mesopores" refers to the pores that have a diameter from >; 2 nm to approximately 50 nm, corresponding in each case to the definition according to Puré Appl. Chem. 45 (1976), 71 et seq., In particular 79. It is also possible to regenerate the following zeolite catalysts by means of the novel process: Oxidation catalysts having a zeolite structure, as described in DE-A 196 23 611.8, which are hereby fully incorporated herein by reference with respect to the catalysts described therein. These are oxidation catalysts based on titanium silicates or vanadium silicates having a zeolite structure, reference being made to the structures previously established as preferred with respect to the zeolite structure. These catalysts have been formed by compacting processes. The processes of conformation by compaction that can be used are, in principle, all the methods for the suitable conformation, as it is generally used for the catalysts. The preferred processes are those in which the shaping is effected by extrusion in conventional extruders, for example to give the extrudates with a diameter of, usually, from 1 to 10 mm, in particular from 2 to 5 mm. If binders and / or auxiliaries are required, the extrusion is advantageously carried out by a mixing or kneading process. If required, a calcination step is also carried out after the extrusion. The extrudates obtained are, if desired, comminuted, preferably to granules or pieces having a particle diameter from 0.5 to 5 mm, in particular from 0.5 to 2 mm. These granules or these pieces and also the catalyst rocks produced by other methods contain almost no finer particle fractions than those with a particle diameter of at least 0.5 mm. In a preferred embodiment, the molded oxidation catalyst used contains up to 10% by weight, based on the total weight of the catalyst, of binders. Particularly preferred binder contents are from 0.1 to 7, in particular from 1 to 15% by weight. Suitable binders are, in principle, all the compounds used for this purpose, giving preference to the compounds, in particular oxides, of silicon, of aluminum, of boron, of phosphorus, of zirconium and / or of titanium. Of particular interest as a binder is silica, where SiO 2 can be introduced in the shaping step as a silica sol or in the tetraalkoxy silane form. The magnesium and beryllium oxides, and the clays, for example montmorillonites, kaolins, bentonites, halloysites, dickites, nacrites and anauxites, can also be used as binders. Examples of the auxiliaries for the compacting processes are extrusion aids, with a conventional extrusion aid being methylcellulose. These auxiliaries generally undergo complete combustion in a subsequent calcination step. "The titanium and / or vanadium zeolites mentioned are usually prepared by reacting an aqueous mixture of a SiO2 source, a titanium or vanadium source, such as titanium dioxide or a corresponding vanadium oxide, and a base organic containing nitrogen (compound template), for example, tetrapropylammonium hydroxide, if necessary with the addition of basic compounds, in a pressure resistant container at elevated temperatures for a period of several hours to a few days, the product being formed This is filtered, washed, dried and burned at elevated temperatures to remove the organic nitrogen base In the powder thus obtained, some or all of the titanium or vanadium is present within the skeleton of the zeolite in different amounts having coordination Four times, five times or six times Repeated washing with hydrogen peroxide solution containing sulfuric acid can be carried out osteriormente to improve _the catalytic behavior, after which the powder of titanium or vanadium zeolite must again be dried and subjected to combustion; this can be followed by a treatment with alkali metal compounds to convert the zeolite from the H form to the cationic form. The titanium or vanadium zeolite powder thus prepared is then molded as described above for the purposes of the present invention. In addition, the catalysts for oxidation based on titanium or vanadium silicates, having a zeolite structure and with a content from 0.01 to 30% by weight of one or more noble metals selected from the group consisting of ruthenium, rhodium, palladium, osmium , iridium, platinum, rhenium, gold and silver, which in the same way have been formed by processes of formed by compaction, can also be regenerated. These catalysts are described in DE-A 196 23 609.6, which is incorporated herein by reference in its entirety with respect to the catalysts described therein. The statements made in the above in relation to DE-A 196 23 611.8 are applicable with respect to the processes of conformation by compaction, binders and auxiliaries, and the structure of the catalysts for oxidation. - The oxidation catalyst described therein contains from 0.01 to 30, in particular from 0.05 to 15, especially from 0.01 to 8% by weight, based in each case on the amount of titanium or vanadium zeolites, of the noble metals mentioned. Palladium is particularly preferred therein. The noble metals can be applied to the catalysts in the form of suitable noble metal components, for example in the form of water-soluble salts, during or after the formation step by compaction. --- However, in many cases it is more advantageous that the components of the noble metals are applied only after the formation step to the catalyst mounds, particularly when a high-temperature treatment of the noble metal-containing catalyst is not desirable. . The noble metal components can be applied to the molded catalyst in particular by ion exchange, impregnation or spraying. The application can be carried out by means of organic solvents, aqueous ammonia solutions or supercritical phases, for example carbon dioxide. By using these aforementioned methods, it is completely possible to produce different types of catalysts containing noble metal. In this way, a type of coated catalyst can be produced by spraying the noble metal solution onto the molded parts of the catalyst. The thickness of this coating containing the noble metal can be substantially increased by impregnation, while the catalyst particles are substantially uniformly coated with the noble metal on the cross-section of the molded part in the case of ion exchange. The following catalysts can also be regenerated according to the invention: A molded part that contains at least one oxidic, porous material and is obtained by a process consisting of the following steps: (I) addition of a mixture containing at least an alcohol and water to a mixture containing porous oxidic material or a mixture of two or more thereof, and (II) kneading, molding, drying and calcining the mixture after addition according to step (I) The preparation of the molded parts described above starting from a porous oxidic material in powder form consists of the formation of a plastic material that contains when at least one porous oxidic material, a binder, a mixture containing at least one alcohol and water, if one or more organic substances that increase the viscosity and other additives known from the prior art are required. plastic material obtained by mixing, in particular kneaded, from the above components is preferably molded by extrusion or extrusion compression and the obtained molding is then dried and finally calcined.There are no specific limitations with respect to the porous oxidic materials which can be used to produce the molded part, as long as it is possible to produce a molded part as described in the present and starting from these materials. The porous oxidic material is preferably a zeolite, particularly preferably a zeolite of titanium, zirconium, chromium, niobium, iron or vanadium, in particular a titanium silicalite. With respect to the zeolites, in particular their structure and composition, reference is made once again to the above description of the zeolites described in connection with the application and which are to be regenerated by the novel process. Commonly, the mentioned titanium, zirconium, chromium, niobium, iron and vanadium zeolites are prepared by reacting an aqueous mixture of a SiO2 source, a source of titanium, zirconium, chromium, niobium, iron or vanadium, for example titanium dioxide or a corresponding vanadium oxide, zirconium alcoholate, chromium oxide, niobium oxide or iron oxide, and an organic base containing nitrogen as a template (template compound), for example hydroxide, of tetrapropylammonium, if it requires with the addition of basic compounds, in a pressure-resistant container at elevated temperatures for a period of from a few hours to a few days, a crystalline product being formed. This is filtered, washed, dried and subjected to combustion at elevated temperatures to eliminate the organic nitrogen base. In the powder thus obtained, some or all of the titanium or zirconium, chromium, niobium, iron and / or vanadium is present within the skeleton of the zeolite in different amounts having quadruple, quintuple or sextuple coordination. Repeated washing with hydrogen peroxide solution containing sulfuric acid can be carried out subsequently to improve the catalytic behavior, after which the zeolite powder of titanium or zirconium, chromium, niobium, iron or vanadium must be dried again and subject to combustion; this can be followed by a treatment with alkali metal compounds to convert the zeolite from the H form to the cationic form. The zeolite powder of titanium or zirconium, chromium, niobium, iron or vanadium thus prepared, is then processed into a molded part as already described. Preferred zeolites are titanium, zirconium, chromium, niobium or vanadium zeolites, particularly preferably those having a pentasyl zeolite structure, in particular the types assigned by X-ray analysis for the structure BEA, MOR, TON, MTW, FER , MFI, MEL, CHA, ERI, RHO, GIS, BOG, ~ NON, EMT, HEU, KFI, FAU, DDR, MTT, RUT, LTL, MAZ, GME, NES, OFF, SGT, EUO, MFS, MCM- 22 or the combined structure MFI-MEL. Zeolites of this type are described, for example, in the aforementioned publication of Meier and Olson. Also possible are titanium containing zeolites having the structure ZSM-48, ZSM-12, ferrierite or β-zeolite and mordenite. These zeolites are described, inter alia, in US-A 5,430,000 and WO 94/29408, the contents of which in this context are hereby incorporated by reference into their completeness. further, there are no specific restrictions with respect to the pore structure of the molded parts to be regenerated according to the invention, that is, the novel molded parts can have micropores, mesopores, macropores, micro- and mesopores, micro- and macropores or micro-, meso- and macropores, the definition of the terms mesopores and macropores also correspond to that of the aforementioned literature according to the Puré Appl. Chem. And denotes the pores that have a diameter from >; 2 nm to about 50 nm, and > approximately 50 nm, respectively. "In addition, an oxide-based material that contains silicon 1 18 having mesopores and a xerogel containing silicon can be regenerated by means of the novel process. The silicon-containing oxides having mesopores and also containing Ti, V, Zr, Sn, Cr, Nb or Fe, in particular Ti, V, Zr, Cr, Nb or a mixture of two or more thereof, are particularly preferred. . Suitable binders are in principle all the compounds used to date for such purposes. Particularly preferred compounds are oxides of silicon, aluminum, boron, phosphorus, zirconium and / or titanium. Silica is of particular interest as a binder, and SIO2 can be introduced into the forming step as silica sol or in the tetraalkoxysilane form. In addition, the oxides of magnesium and beryllium, and clays, for example, montmorillonites, kaolins, bentonites, halosites, dickites, nacrites and anauxites, can be used as binders. However, a metallic acid ester or a mixture of two or more thereof is preferably added as the binder in step (I) of the novel process. Particular examples thereof are esters of orthosilicic acid, tetraalkoxysilanes, tetraalkyl titanates, trialkyl aluminates, tetraalkyl zirconates or a mixture of two or more thereof. However, tetraalkoxysilanes are particularly preferably used as the binder in the present invention. Specific examples of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane and tetrabutoxy silane, the tetraalkoxy titanium and tetraalkoxy zirconium analog compounds and tirmethoxy-, tritetoxy-, tripropoxy- and tributoxy aluminum, with tetramethoxysilane and tetraethoxysilane being particularly preferred. The molded parts preferably contain up to about 80, particularly preferably from about 1 to about 50, in particular from about 3 to about 30% by weight, based on the total weight of the molded part, of binder, the amount of binder determined by the resulting metal oxide. The metal acid ester preferably used is employed in an amount such that the resulting metal oxide content in the molded part is from about 1 to about 80, preferably from about 2 to about 50, in particular from about 3 to about 30% by weight, based on the total weight of the molded part. As is clear from the foregoing, it is of course also possible to use mixtures of two or more of the aforementioned binders. It is essential for the production of these molded parts that a mixture containing at least one alcohol and water be used as the saponifying agent. The alcohol content of this mixture is, in general, from about 1 to about 80, preferably from about 5 to about 70, in particular from about 10 to about 60% by weight, based on the total weight of the mixture. Preferably, the alcohol used corresponds to the alcohol component of the metal acid ester, preferably used as a binder, but it is also possible to use another alcohol. There are no restrictions with regard to the alcohols that can be used, as long as they are miscible in water. Accordingly, monoalcohols of 1 to 4 carbon atoms and polyhydric alcohols miscible in water can be used. In particular, methanol, ethanol, propanol, n-butanol, isobutahol, tert-butanol and mixtures of two or more thereof are used. In the same way, the organic substance which increases the viscosity used can be any substance of the prior art suitable for this purpose. Such substances are preferably organic polymers, in particular hydrophilic, for example cellulose, starch, polyacrylates, polymethacrylates, polyvinyl alcohol, polyvinylpyrrolidone, polyisobutene and polytetrahydrofuran.

These substances mainly favor the formation of a plastic mass during the steps of kneading, molding and drying forming bridges in the primary particles and also ensures the mechanical stability of the molded parts during molding and drying. These substances are removed from the molded part during calcination. As other additives it is possible to introduce amines or amine-like compounds, for example tetraalkylammonium compounds or amino alcohols, and carbonate-containing substances such as calcium carbonate. These other additives are described in EP-A 0 389 041, EP-A 0 200 260 and WO 95/19222, which are hereby incorporated by reference in the context of the present application. In place of the basic additives, it is also possible to use acidic additives. These can, among others, effect a faster reaction of the metal acid ester with the porous oxidic material. Preferred organic acid compounds are those that can be burned by calcination after the molding step. The carboxylic acids are particularly preferred. Of course, mixtures of two or more of the aforementioned additives can also be incorporated. The order of the addition of the components of the material containing the porous oxidic material is not crucial. It is possible first to add the binder, then the organic substance to increase the viscosity, if the additive is required and finally the mixture containing at least one alcohol and water or to exchange the order with respect to the binder, the organic substance to increase the viscosity and additives. After the addition of the binder to the porous oxide powder, to which the organic substance may have already been added to increase the viscosity, the material, which is still in powder form, is homogenized from 10 to 180 minutes in a kneader or extruder. As a general rule, the process is carried out from about 10 ° C to the boiling point of the saponifying agent and at atmospheric pressure or slightly superatmospheric pressure. The remaining components are then added, and the mixture thus obtained is kneaded until an extrudable plastic material is formed. * In principle, the kneading and molding can be carried out using all the conventional kneading and molding methods or methods, of which there are many known in the prior art and used for the production of, for example, molded parts of catalyst, in general . However, the processes in which extrusion molding is carried out in conventional extruders, for example to give extrudates with a diameter of, typically, from about 1 to about 10 mm, in particular from about 2 to about 5 mm, are preferred. . These apparatuses for extrusion are described, for example, in Ullmanns Enzyklopádie der Technisc in CEIME, 4th edition, vol. 2, page 295 et seq., 1972. In addition to the use of μ extrusers, the use of an extrusion press is also preferred for molding. After the term of extrusion pressing or extrusion, the obtained moldings are dried, in general, from about 30 to 140 ° C (from 1 to 20 h, atmospheric pressure) and calcined from about 400 to "about 800 ° C. (from 3 to 10 h, atmospheric pressure.) The obtained strands or extrudates can, of course, be crushed, these are preferably crushed to obtain granules or pieces having a particle diameter from 0.1 to 5 mm, in particular from 0.5 to 2 mm. ~ These granules or these pieces and also the molded parts produced by other methods contain almost a finer particle fraction than those which have a minimum particle diameter of about 0.1 mm.In the novel process it is possible to use the catalysts in powder form, which were used as suspension, and catalysts packed in a fixed bed, in the form of a molded part, and crystallized catalysts in networks, for example a Cantal or packaged stainless steel, and coated catalysts consisting of an inert core of SÍO2, CÍ-AI2O3, highly calcined TiO2, or steatite and a coating of active catalyst consisting of a zeolite, preferably a zeolite as already described, which are regenerated. If the catalyst was used in a suspension process, it must first be separated from the reaction solution by a separation step, for example filtration or centrifugation. The at least partially deactivated catalyst powder thus obtained can then be regenerated. The stages carried out at elevated temperatures during the regeneration process are preferably carried out in rotary kilns in the case of these catalyst powders. In the regeneration of a catalyst used in a suspension process, it is particularly preferable, to couple the reaction in the suspension process and the novel regeneration process, to continuously remove from the reaction a part of the catalyst at least partially deactivated, to regenerate it externally by means of a novel process and recycling the regenerated catalyst to the reaction in the suspension process. In addition to the regeneration of the catalysts in the form of powder, the novel process can also be used to regenerate catalysts as molded parts, for example those that are packed in a fixed bed. During the regeneration of the catalyst packed in a fixed bed, the regeneration preferably takes place in the reaction apparatus itself, it being unnecessary to separate or install the catalyst for this purpose, so that it is not subjected to additional mechanical stresses. During the regeneration of the catalyst in the reaction apparatus itself, the reaction is first interrupted, any reaction mixture present is removed, regeneration is carried out and the reaction is then continued. __ In the regeneration of the catalytic powders and in the regeneration of the catalysts in molded form, the novel regeneration is carried out essentially in an identical form. In step (I), the catalyst is heated to a temperature of from about 250 to about 600 ° C, preferably from about 400 to 550 ° C, in particular from about 450 to 500 ° C, in the reaction apparatus or in an external furnace, in an atmosphere containing less than 2, preferably less than 0.57 in particular less than 0.2% by volume of oxygen The heating in step (I) is preferably carried out at a heating rate of about 0.1. to about 20, preferably from about 0.3 to about 15, in particular from 0.5 to 10 ° C / min.

- During this heating phase, the catalyst is heated to a temperature at which the generally organic coatings present begin to decompose, while at the same time the temperature is controlled by means of the oxygen content and does not increase to a damaging degree. the structure of the catalyst. After the temperature range has been reached from about 250 to about 800 ° C, preferably from about 350 to about 600 ° C, in particular from about 400 to about 600 ° C, desired to decompose the coatings, it is possible, if desired, or if necessary due to the presence of a large amount of organic coatings, leave the catalyst for another 1 to 2 hours at these temperatures in the atmosphere defined above. In step (I) of the regeneration, with or without the catalyst being left at the set temperature, most of the coatings are carbonized. The substances formed, for example hydrogen, water and carbon-containing substances, are removed from the catalyst at this stage. The removal of the coatings by carbonization, which is carried out in this step, significantly reduces the amount of energy released during the combustion of the catalyst in stages (II) and, if required, (III) of the novel process by treating the catalyst with a gas stream which has a relatively high oxygen content, so that an important step towards prevention of local overheating of the catalyst is taken simply by slowing down the heating in step (I) of the novel process. In step (II) of the novel process, the catalyst is then heated from about 250 to about 800 ° C, preferably from about 350 to about 600 ° C, with a gas stream containing from about 0.1 to about 4, preferably from about 0.1 to about 3, particularly preferably from about 0.1 to about 2% by volume of an oxygen or oxygen donor substance or a mixture of two or more thereof. The added amount of molecular oxygen or oxygen donor substances is crucial in that the amount of energy released within this stage and generated by the combustion of carbonized organic coatings results in an increase in the temperature of the catalyst, so that the temperature in the regeneration apparatus should not be outside the desired temperature range from about 250 to about 800 ° C, preferably from about 350 to about 600 ° C. Preferably, the amount of molecular oxygen or oxygen donor substances is chosen so that the temperature in the apparatus is from about 400 to about 500 ° C. As the coatings are being increasingly burned, the content of molecular oxygen or oxygen donor substances in the inert gas stream must be increased * up to 100% by volume to maintain the temperature necessary for regeneration, so that , after the end of stage (II), in the stage (III) The catalyst is treated, in the temperature range already defined with respect to step (II), with a gas stream containing from more than about 4 to 100, preferably from more than about 3 to about 20. , particularly preferably from about 2 to about 30% by volume of an oxygenate or oxygen donor substance or a mixture of two or more thereof. As a general rule, a process is adopted in which the amount of oxygen or oxygen donor substance in the feed gas stream increases continuously as the temperature in stage (II) decreases. The temperature of the catalyst as such is maintained from about 250 ~ to about 800 ° C, preferably from about 350 to about 600 ° C, in particular from about 400 to about 600 ° C, by suitable control of the oxygen content or the content of oxygen donor substances in the gas stream. - If the temperature of the exhaust gas stream in the reactor discharge decreases despite the increasing amounts of molecular oxygen or oxygen donor substances in the gas stream, the organic coatings have been completely burned. The duration of the treatment in step (II) and, if required, step (III) is generally from about 1 to about 30, preferably from about 2 to about 20, in particular from about 3 to about 10 hours in each case. In term oxygen donor substances used before includes all substances that are able to donate oxygen or remove waste containing carbon under the established regeneration conditions. Specific examples are: - Nitrogen oxides of the formula NxOy, where xyy are chosen to obtain a neutral nitrogen oxide, N2O, a stream of exit gas containing 2O from an adipic acid plant, NO, NO2, ozone or a mixture of two or more thereof. Where carbon dioxide is used as the oxygen donor substance, steps (II) and (III) are carried out from 500 to 800 ° C. In another embodiment of the novel process, the partial or completely deactivated catalyst is washed with a solvent, before heating according to step (I), to remove the desired adherent product. The washing is performed in such a way that the desired, particular products that adhere to the catalyst can be removed from it but the temperature and pressure are not chosen so high that most of the organic coating is also removed. Preferably, the catalyst is only rinsed with a suitable solvent. Thus, the solvents suitable for this washing step are all those in which the respective reaction product is easily soluble. Preferred solvents used of this type are selected from the group consisting of water, an alcohol, for example methanol, ethanol, 1-propanol, 2-propanol-, 2-methyl-2-propanol, 1-butanol, 2-butanol. , allyl alcohol or ethylene glycol, an aldehyde such as acetaldehyde or propionaldehyde, a ketone, for example acetone, 2-butanone, 2-methyl-3-butanone, 2-pentanone, 3-pentanone, 2-methyl-4-pentanone or cyclohexanone , an ether such as diethyl ether or THF, an acid, for example formic acid, acetic acid or propionic acid, an ester such as methyl formate, methyl acetate, ethyl acetate, butyl acetate or ethyl propionate, a nitrile such as acetonitrile , a hydrocarbon, for example, propane, 1-butene, 2-butene, benzene, toluene and xylene, trimethylbenzene, dichloromethane, chloroform, carbon tetrachloride, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1 -trichloroethane, 1, 1, 2-trichloroethane, 1,1,1,2-tetrachloroethane, dibromoethane, allyl chloride or chlorobenzene and, if they are misc you mix two or more of them. - The use of solvents which already act as solvents for the reaction is preferred, ie, for example, the epoxidation of olefins with the use of the catalyst to be regenerated. The following solvents can be mentioned by way of example for the epoxidation of olefins: water, alcohols, for example methane, ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol, 1-butanol, 2-butanol, allyl alcohol or ethylene glycol, and ketones such as acetone, 2-butanone, 2-methyl-3-butanone, 2-pentanone, 3-pentanone, 2-methyl-4-pentanone or cyclohexanone. The amount of solvent used and the duration of the wash step are not crucial, but both the amount of solvent and the duration of the wash step must be sufficient to remove a larger part of the desired product adhering to the catalyst. The washing step can be carried out at the reaction temperature or at comparatively higher temperatures, but the temperature should not be chosen so high that the solvent used for the washing reacts with the desired product to be eliminated. If temperatures above the reaction temperature are used, a range from 5 to 150 ° C above the reaction temperature is generally sufficient, in particular at the boiling point of the solvents used. The washing step can, if required, be repeated several times. The washing step can be carried out under atmosph, superatmosph or even supercritical pressure. The atmosph and superatmosph pressures are preferred. Where CO2 is used as a solvent, supercritical pressure is preferred. If a catalyst powder used in a suspension process is regenerated, the washing of the isolated catalyst is carried out in an external reactor. If the catalyst is packed in the form of a fixed bed in a reactor, the washing can be carried out in the reactor used for the reaction. This reactor with the catalyst to be regenerated present therein is flooded once or several times with the solvent to obtain the desired residual product. The solvent is then removed from the reactor. After finishing the washing step, the catalyst is generally dried. Although the drying process is not crucial per se, the drying temperature should not greatly exceed the boiling point of the solvent used for washing, in order to avoid the sudden evaporation of the solvent in the pores, in particular, if they are present, the micropores of the zeolite catalyst, since this can damage the catalyst too much. During the regeneration of the catalyst powders, the drying is also carried out externally in a heating device under an inert gas atmosphere. In the case of catalysts in a fixed bed, the catalyst present in the reactor is treated with a stream of inert gas at moderate temperatures. The drying of the catalyst may, but not necessarily, be carried out to completion. In the case of catalytic powders, drying as a general rule is continued until the powder is free flowing. Also in the case of catalysts installed in a fixed bed, it is generally not necessary to dry completely.

After regeneration, the catalyst can be treated by basic compounds and / or silylating agents to eliminate the acid centers. Particularly suitable compounds are dilute aqueous solutions of alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal carbonates, alkali metal or alkaline earth metal hydroxy carbonates; acetates and phosphates of Li, K, Na; and silylating esters, such as tetraalkoxy silane, tetraalkoxy monoalkylsilane and hexa ethylene disilane.

In another embodiment of the novel process, the regenerated catalyst obtained in step (III) is cooled in an inert gas stream in an additional step (IV). This stream of inert gas can contain up to 20, preferably from about 0.5 to about 20% by volume of a vaporized liquid selected from the group consisting of water, an alcohol, an aldehyde, ketone, an ether, an acid, an ester, a nitrile, a hydrocarbon, as described above with respect to washing the catalyst, and a mixture of two or more thereof. Water, alcohol or a mixture of two or more of them is preferably used as the vaporized liquid. With respect to the alcohols, aldehydes, ketones, ethers, acids, esters, nitriles or hydrocarbons which can be used preferably, reference can be made to the corresponding description of the solvents which can be used in the washing step in the novel process. In cooling according to step (IV), it is also important that the cooling is carried out slowly since excessively rapid cooling (extinguishing) can adversely affect the mechanical strength of the catalyst. In addition, the mechanical properties of the catalyst can be adversely affected by rapid flooding of the molded part of regenerated catalyst, dry by restarting the reactor for another reaction.

For this reason it is advisable to add the vaporized liquid defined above during the cooling phase. However, it is also preferred not to add the vaporized liquid until the temperature is below a threshold temperature which is defined by the boiling point of the liquid used for the vapor. The threshold temperature, as a rule, is below about 250 ° C, preferably below about 200 ° C, in particular below about 150 ° C. After the reactor and the regenerated catalyst present therein have been cooled to the reaction temperature, the reactor is filled with the reaction mixture and the reaction is continued. Although in principle all zeolite catalysts can be regenerated within the scope of the present invention, and consequently the zeolite catalysts regenerated by the novel process can also be reused for multiple reactions, the novel process is preferably used to regenerate catalysts. of zeolites which are used in the epoxidation of organic compounds having at least one CC double bond, for the hydroxylation of aromatic organic compounds or for the conversion of alkanes to alcohols, aldehydes and acids, that is, for the oxidation reactions.

Therefore, the present invention also relates to the use of regenerated zeolite catalysts by means of the process described in the present application for the epoxidation of organic compounds having at least one CC double bond, in particular for the epoxidation of lower olefins of 2 to 6 carbon atoms, for example ethylene, propylene or 2-butene, for the hydroxylation of aromatic organic compounds or for the conversion of alkanes to alcohols, aldehydes and acids.

EXAMPLES Example 1 910 g of tetraethyl orthosilicate were introduced into a four-necked flask (capacity 4 liters) and 15 g of tetraisopropyl orthotitanate were added from a dropping funnel over the course of 30 minutes with stirring (250 rpm, paddle stirrer). A colorless, transparent mixture is formed. After *, 1600 g of a solution at 20% concentration by weight of tetrapropyl ammonium hydroxide (alkali metal content <10 ppm) were added and the stirring was continued for another hour. The alcohol mixture (approximately 900 g) formed from the hydrolysis was distilled from 90 to 100 ° C. The mixture was taken to 3 liters with water and the now slightly opaque sol was transferred to a 5 liter stainless steel stirring autoclave. The closed autoclave (anchor stirrer, 200 rpm) was brought to a reaction temperature of 175 ° C at a heating rate of 3 ° C / min. After 92 hours, the reaction was complete. The cooled reaction mixture (white suspension) was centrifuged and the isolated pellet was washed repeatedly with water until neutral. The solid obtained was dried at 110 ° C in the course of 24 hours (weight obtained: 298 g). "The template that remained in the zeolite was then burned under air at 550 ° C in 5 hours (loss by calcination: 14% by weight)." According to the wet chemical analysis, the pure white product had μh Ti content of 1.5% in weight and a residual alkali content of less than 100 ppm.The yield was 97%, based on the SIO2 used.The crystallites had a size from 0.05 to 0.25 μ and the product had a band in the common IR to approximately 960 cm "1. ~ -Ej emplo 2 _. 530 g of titanium silicalite powder, synthesized according to Example 1, were kneaded with 13.25 g of silica sol (Ludox AS-40), 26.5 g of Walocel (methylcellulose) and 354 ml of water for 2 hours in a kneading The compacted material was then molded in an extrusion press to obtain 2 mm strands. The strands obtained were dried at 110 ° C for 16 hours and then calcined at 500 ° C for 5 hours. - 100 g of the resulting molded parts were processed to obtain pieces (particle size 1-2 mm) and used as a catalyst in the epoxidation of propylene with hydrogen peroxide.

For example 3 streams of 27.5 g / h of hydrogen peroxide (20% by weight), 65 g / h of methanol and 13.7 g / h of propene were passed through, at a reaction temperature of 40 ° C and a pressure of 20 bar reaction, through a cascade of reactors consisting of two reactors, each with a reaction volume of 190 ml and each packed with 10 g of catalyst according to Example 2. After leaving the second reactor , the reaction mixture was left at atmospheric pressure in a Sambay evaporator. The separated low-boiling substances were analyzed online in a gas chromatograph. The discharged liquid reaction mixture was collected, weighed and in the same way analyzed by gas chromatography. 'During all the time in the stream, the conversion of hydrogen peroxide decreased from 98% original and reached approximately 60% after 250 h. The selectivity of propylene oxide with respect to hydrogen peroxide was 95% during the time in the stream.

Example 4 The deactivated catalyst of Example 3 was installed in a quartz glass tube. The deactivated catalyst was then heated to 500 ° C in a stream of 20 liters of nitrogen gas per hour ~ ^ a heating rate of 4 ° C / min in a tubular furnace. Then, the oxygen content of the inert gas was increased to 9% by volume in the following two hours and remained there. In the next 14 hours, the oxygen content was then increased to 18% by volume and remained so. The regenerated catalyst was then cooled under inert gas, separated and used again for epoxidation.

Example 5 Currents of 25.7 g / h of 'hydrogen peroxide (20% by weight), 65 g / h of methanol and 13.7 g / h of propene were passed through, at a reaction temperature of 40 ° C and a pressure of 20 bar reaction, through a cascade of reactors consisting of two reactors, each having a reaction volume of 190 ml and each packed with 10 g of regenerated catalyst from Example 4. After leaving the second reactor, the reaction mixture was left at atmospheric pressure in a Sambay evaporator. The separated low-boiling substances were analyzed online in a gas chromatograph. The discharged liquid reaction mixture was collected, weighed and in the same manner analyzed by gas chromatography. During all the time in the stream, the conversion of hydrogen peroxide decreased from the original 98% and reached approximately 60% after 250 h. The selectivity of propylene oxide with respect to hydrogen peroxide was 95% during the time in the stream.

Example 6 The deactivated catalyst of Example 5 was installed in a quartz glass tube. The deactivated catalyst was then heated to 450 ° C in a stream of 20 1 Nitrogen gas per hour at a heating rate of 4 ° C / min in a tubular furnace, then the oxygen content of the inert gas was increased to 9% in volume during the next two hours and remained so.In the following 14 hours, the oxygen content was then increased to 18% by volume and thus remained.The regenerated catalyst was then cooled under inert gas, separated and used again for epoxidation.

Example 7 Currents of 27.5 g / h of hydrogen peroxide (20% by weight), 65 g / h of methanol and 13.7 g / h of propene were passed at a reaction temperature of 40 ° C, and a reaction pressure 20 bar, through a cascade of reactors that consisted of two reactors, each having a reaction volume of 190 ml and each packed with 10 g of regenerated catalyst from Example 6. After leaving the second reactor, the The reaction mixture was left at atmospheric pressure in a Sambay evaporator. The separated low-boiling substances were analyzed online in a gas chromatograph. The discharged liquid reaction mixture was collected, weighed and in the same way analyzed by gas chromatography. During all the time in the stream, the conversion of hydrogen peroxide decreased from 98% original and reached approximately 60% after 250 h. The selectivity of propylene oxide with respect to hydrogen peroxide was 95% during the time in the stream The described examples show that the catalytic activity of the catalysts can be restored without loss by the novel regeneration of the deactivated catalysts.

Claims (1)

1. CLAIMS A process for regenerating a zeolite catalyst consisting of the following stages (I) and (II): (I) heating a partially or completely-deactivated catalyst at 250-600 ° C in an atmosphere containing less than 2% by volume of oxygen, and (II) treating the catalyst from 250 to 800 ° C, preferably from 350 to 600 ° C, with a gas stream containing from 0.1 to 4% by volume of an oxygen or oxygen donor substance or a mixture of two or more of them, where the gas stream contains a higher amount of oxygen compared to the atmosphere in the stage (I) The process as mentioned in claim 1, which additionally consists of the next step (III): (III) treating the catalyst from 250 to 800 ° C, preferably from 350 to 600 ° C, with a gas stream containing from more than 4 to 100% by volume of an oxygen or oxygen donor substance. oxygen or a mixture of two. or more thereof The process as recited in claim 1 or 2, wherein the heating according to step (I) is carried out at a heating rate from 0.1 to 20, preferably from 0.3 to 15, in particular from 0.5 to 10 ° C / min. The process as mentioned in any of claims 1 to 3, wherein the partially or completely deactivated catalyst is washed, before heating according to step (I), with a solvent selected from the group consisting of water, an alcohol , an aldehyde, a ketone, an ether, an acid, an ester, a nitrile, a hydrocarbon or a mixture of two or more thereof The process as mentioned in any of claims 1 to 4, which also consists of the following step (IV): (V) cooling the regenerated catalyst obtained in step (III) in an inert gas stream which can contain up to 20% by volume of a vaporized liquid selected from the group consisting of water, a alcohol, an aldehyde, a ketone, an ether, an acid, an ester, a nitrile, a hydrocarbon and a mixture of two or more thereof The process as mentioned in any of the preceding claims, wherein the partial catalyst or completely des activated is maintained from 250 to 800 ° C after heating according to the step (I) and before the treatment according to the stage (II). . The process as mentioned in any of the preceding claims, wherein the oxygen donor substance is selected from the group consisting of a nitrogen oxide of the formula NxOy, where x and y are chosen to obtain a neutral nitrogen oxide, N20, a outlet gas stream containing N20 from a plant of adipic acid, NO, N02, ozone and a mixture of two or more of them. The process as mentioned in any of claims 1 to 6, wherein the oxygen donor substance is C02 and the steps (II) and (III) are made from 500 to 800 ° C. . The process as mentioned in any of the "previous claims, wherein the zeolite catalyst is selected from the group consisting of silicalite containing titanium, zirconium, vanadium, chromium or niobium having a structure MFI, BEA, MOR, _TTON, MTW, FER, CHA, ERI, RHO, GIS, BOG, NON, EMT, HEU, "KFI, FAU, DDR, MTT, RUT, 'LTL, MAZ, GME, NES, OFF, SGT, j_EU0, MFS, MCM-22 or MEL, the combined structure MFI-MEL and a mixture of two or more of the same The use of a regenerated zeolite catalyst as mentioned in any of the preceding claims for the epoxidation of organic compounds having at least one CC double bond, for the hydroxylation of aromatic organic compounds or for the conversion of alkanes to alcohols, ketones , aldehydes and acids