RU2238797C2 - Improvements in catalysis of dehydrogenetion - Google Patents

Abstract

FIELD: dehydrogenation of hydrocarbons.

SUBSTANCE: the invention is dealt with catalysts used in dehydrogenation of hydrocarbons and with the methods of application of the catalysts. The regenerated catalyst used for dehydrogenation of the hydrocarbons contains a catalytic component picked out of the group consisting of platinum, rhodium, iridium, palladium, ruthenium and osmium, deposited on a carrying agent containing porous aluminum oxide, that has a specific surface of more than 100 m²/g , volume of pores with diameters less than 6 nm (60А) makes less than 0.05 cm³/g, volume of pores with diameters within the limits of 6-35 nm (60-350 А) makes more than 0.50 cm³/g, and where volume of pores with diameters within the limits of 6-35 nm (60-350 А) makes more than about 70% of bulk volume of pores. The method of production of olefin by dehydrogenation of the hydrocarbons with application of the mentioned above catalyst is also described. The invention ensures a favorable balance of selectivity, activity and thermal stability of the catalyst.

EFFECT: the invention ensures a favorable balance of selectivity, activity and thermal stability of the catalyst.

46 cl, 1 tbl, 9 ex

Description

Description

This application claims the privilege of provisional application US No. 60/151113, filed August 27, 1999, provisional US application No. 60/155877, filed September 24, 1999, and US provisional application No. 60/179984, filed February 3, 2000, all of which are currently still under consideration and incorporated by reference.

Field of Invention

This invention relates to catalysts applicable in the dehydrogenation of paraffins, and to methods of using catalysts. The catalysts of the invention provide a combination of selectivity, thermal stability and initial activity of the catalytic layer per unit volume, which is very advantageous. In one preferred embodiment, the invention relates to the dehydrogenation of substantially linear paraffins having between about 9 and 15 carbon atoms per molecule, and to monoolefins derived from such paraffins, which find particular use in the production of biodegradable detergents. Thanks to the use of the catalysts and methods of the invention, it is possible to achieve excellent reaction selectivity in a process that includes catalyst regeneration.

BACKGROUND OF THE INVENTION

Many chemical processes that are practiced on an industrial scale involve the use of one or more catalysts to produce intermediate or commercial products. This is the case, in particular, in oil-dependent industries. Due to the typically processable, large volumes, partial improvements in the implementation of catalytic processes can provide commercially significant beneficial effects. Examples of important catalytic hydrocarbon conversion processes include alkylation processes, hydrogenation processes, dehydrogenation processes, and isomerization processes.

Although catalysts, by definition, are not directly consumed in the chemical reactions that they promote, in the above and other processes, the catalysts often gradually become less active during their use due to one or more mechanisms known to those skilled in the art. In some cases, it is possible, by undertaking specific steps, such as coke removal, acid washing or calcination, to recover most of the lost activity so that the useful life of the catalyst is extended. Such steps are often referred to as “regeneration” of the catalyst. Mostly, it is highly desirable to use catalysts that respond well to regeneration in order to reduce the costs associated with replacing the catalyst. However, in many processes, catalyst regeneration is not feasible. For example, the catalyst, which in other respects could be regenerated by burning accumulated coke, does not have sufficient thermal stability to adequately withstand the high local temperatures that develop under conditions of efficient coke burning.

This invention relates to catalytic materials useful in the dehydrogenation of paraffins (saturated hydrocarbons). Paraffin dehydrogenation is often carried out with the aim of introducing one or more olefin bonds, either in order to obtain an olefin product that is useful on its own, or to provide an effective "capture" on the molecule for subsequent reaction with some other substances. This invention, in particular, relates to heterogeneously catalyzed dehydrogenation of paraffins in the range of detergents (paraffins with the number of carbon atoms in the range of 9-15) to obtain products that contain a single unsaturated bond per molecule (monoolefins). The resulting monoolefins (monoolefins of the detergent range) are useful for reaction with other organic products that include aromatic nuclei to produce alkylbenzenes. Such alkylbenzenes having substantially linear alkyl substituents attached to benzene rings are useful for conversion to alkylbenzenesulfonates, which are used in detergent formulations for both industrial use and consumer products. Alkylbenzenes, obtained mainly from linear paraffins, are particularly preferred in the production of detergents, since their sulfonates have a very high degree of biodegradability. As used herein, the term “substantially linear” means that the type and degree of branching present in the paraffin that must be dehydrogenated to produce olefins for subsequent use in the production of alkylbenzenesulfonates is limited to those which provide alkylbenzenesulfonates with a degree of biodegradability that is acceptable in accordance with existing standards promulgated by industry and regulatory authorities. Alkylbenzenes containing a single alkyl substituent attached to the benzene ring (monoalkylbenzenes) are preferred, as is known in the art, as they tend to provide favorable detergent characteristics. Mixtures of alkylbenzenes, consisting predominantly of monoalkylbenzenes with linear alkyl substituents, are also recognized as preferred, and they are the types most widely used by the detergent industry. Such mixtures are commonly referred to by those skilled in the art as “linear alkylbenzene” or “LAB”.

The production of monoolefins in the dehydrogenation process typically involves contacting saturated hydrocarbons with a suitable catalyst under reaction conditions favorable to the formation of monoolefins. However, the production of a monoolefin is inevitably accompanied by some formation of undesirable by-products, such as diolefins, aromatics, and cracking products. The amount of diolefin formed depends mainly on the structure of the paraffin and the degree of conversion, and a relatively weak regulation of diolefin formation is possible by other reaction conditions. The formation of cracking products can be minimized by using a catalyst and eliminating extremely high temperatures. The formation of aromatic compounds is significantly affected by both the selectivity of the catalyst and the reaction conditions used. It is well known in the art that great economic benefits can be realized through the use of a highly selective dehydrogenation catalyst, which minimizes the formation of aromatic compounds at a given level of paraffin conversion. Specific benefits associated with lower aromatics formation include lower paraffin consumption, lower monoolefin consumption in aromatic side reactions during alkylbenzene production, higher purity of recycle paraffin, and less extensive inhibition and clogging of the catalyst.

Many catalysts useful for paraffin dehydrogenation are known in the art. Typically, known catalyst materials contain one or more finely divided active metals or metal oxides deposited on the surface of the particles with respect to an inert carrier material such as silica or alumina. Alternative means known in the art by which the main component (s) of the catalyst or its precursors can be obtained in a finely divided state on the surface of an appropriately pre-treated support include methods such as precipitation, adsorption from an aqueous solution and ion-exchange techniques using support materials Zeolite® (molecular sieve). Typically, after one or more substances are deposited on a selected carrier to obtain a crude catalyst, the raw catalyst material is subjected to any heat treatment at an elevated temperature for a suitable time, often in the presence of a controlled atmosphere, which may be inert, oxidizing or reducing.

Previous experience is replete with examples of aluminum oxides and silicon dioxide with various particle sizes, crystalline phases, pore structures, etc. combined with a very wide variety of other components deposited on their surfaces. In many cases, the precipitated components contain at least one main catalytic component and at least one additional component, such as an activator, attenuator or modifier.

Typically, the performance of a catalyst is largely determined by three critical properties that are easily distinguishable and known to those skilled in the art of catalysis. These properties are 1) selectivity, 2) activity, and 3) thermal stability.

In the case of paraffin dehydrogenation to produce a monoolefin, the selectivity of the catalyst is a measure of its ability, under appropriate reaction conditions, to maximize the fraction of all converted paraffin, which is converted to a monoolefin. Since an increase in the formation of an undesirable by-product leads to a decrease in the formation of a monoolefin with a given paraffin conversion, selectivity is improved if the formation of a by-product decreases with a given paraffin conversion. Thus, comparisons of catalyst selectivity can be made by the amounts of by-products formed during the same paraffin conversion in experiments that use different catalysts, but which are essentially equivalent in the sense of other reaction conditions. When comparing various weakly acidic catalysts, the most important difference will usually be between the amounts of aromatic compounds formed during a given paraffin conversion. When comparing selectivities in a series of alternative catalysts, it is especially convenient to express selectivities in comparison with a single standard catalyst. So, for each alternative catalyst that detects an improvement in selectivity, the degree of improvement can be expressed as the percentage by which the alternative catalyst reduces the formation of aromatic compounds during a given paraffin conversion under standard reaction conditions compared to a standard catalyst.

In the case of paraffin dehydrogenation, the activity of the catalyst is a measure of its ability to promote paraffin conversion. In a continuous process under any specific reaction conditions, higher catalyst activity is manifested in higher conversion over a given amount of catalyst. For practical purposes, the most important measure of catalytic activity is volumetric activity, indicating activity per unit volume of catalyst layer. Under given conditions of a continuous reaction, a catalyst with a higher volumetric activity is capable of providing a higher conversion of paraffin over a catalyst bed of a given volume. Alternatively, this makes it possible to reduce the volume of the catalyst bed (reactor size) necessary to obtain a given paraffin conversion. Factors that significantly affect the volumetric activity of the catalyst include specific surface area, bulk density, types and weight percentages of active metals included in the composition, distribution of active metals within the carrier granules, and degree of diffusion resistance associated with the pore structure. Since dehydrogenation catalysts lose activity during normal use, comparisons of the activity of different types of catalysts should be made with comparable degrees of catalyst deactivation. This can be done by comparing the conversion limits of paraffin for experiments of equal duration, which begin with a fresh catalyst and in which standard reaction conditions are used.

The dehydrogenation catalyst must have a high degree of thermal stability in order to adequately withstand the elevated temperatures that it encounters during its normal use. High thermal stability is especially important if the catalyst is regenerated by burning accumulated coke, i.e. a procedure that usually tends to produce unusually high local temperatures. The lack of thermal stability leads to an excessive loss of activity at a time when the catalyst is exposed to high temperatures. One process that contributes to the loss of activity during thermal exposure involves agglomeration (coalescence) of particles of the active component (s). Another process involved is the degradation of the structure of the carrier such that some catalytic particles are trapped in unacceptable places within the surrounding layers of carrier material. In any case, the size of the catalytic surface available for the reaction is reduced. The thermal stability of a particular catalyst can be determined by comparing the activities of the presented samples from the same batch, which were subjected to the appropriate treatment, leading to high temperature aging, and were not subjected to such an effect.

It is known that in the catalytic dehydrogenation of paraffins of the detergent range, the percentage conversion to monoolefins in one pass through the reactor is limited by equilibrium. Although the conversion restriction can vary significantly under different reaction conditions, the actual percentage of monoolefin in the products is usually not more than about twenty weight percent. It is also well known that the formation of a monoolefin in such a process is accompanied by the formation of various less desirable by-products, including diolefins, aromatics and hydrocarbons with carbon numbers below the range of detergents that form in cracking reactions. As used herein, the term "conversion" means the mass percentage of the paraffin in the range of detergents in the feedstock, which is converted in one pass into products other than paraffins in the same range of carbon atoms. In cases where the feedstock contains substances other than the paraffins of the detergent range, these components of the feedstock are ignored in the calculation of conversion and selectivity. Generally, a higher conversion and higher selectivity are preferred, but an increase in conversion leads to a decrease in selectivity.

A well-known problem encountered in the production of detergent range olefins by catalytic dehydrogenation of paraffins is the loss of catalyst activity during paraffin processing. The catalyst may lose activity due to the presence of strong catalytic poisons, such as sulfur compounds, in the feed, and this loss of activity is usually limited by controlling the purity of the feed. However, even when the feed contains extremely small amounts of such poisons, the catalyst tends to be deactivated to a large extent due to the formation of coke on the catalytic surfaces. The rate of coke formation can vary widely depending on the combination of the selected reaction conditions. As a rule, a lower coke formation rate is preferable since it reduces the various costs associated with the regeneration or replacement of the catalyst and makes it easier to maintain the conversion conditions and other reactions within optimum limits for extended periods of operation.

One method used in prior art paraffin dehydrogenation processes to reduce catalyst deactivation is to mix varying amounts of hydrogen with the vaporized paraffin feed before being introduced into the catalytic reaction zone. US Pat. No. 4,343,724 teaches, for example, that such hydrogen has a “dual function” - both diluting paraffin and “suppressing the formation of hydrogen-deficient carbon deposits" on the catalyst. In many cases, the amount of added hydrogen used in the examples of the patent was very large, for example 4-8 moles of hydrogen per mole of hydrocarbon. Extreme inconveniences accompany such large hydrogen additives, including the detrimental effect on the equilibrium of monoolefin formation, the increased size of most parts of the processing equipment for a given capacity, and the increased energy and maintenance costs associated with the extraction, compression, and recycling of hydrogen. Therefore, it is very beneficial to reduce the molar ratio of hydrogen to hydrocarbon (H ₂ : HC ratio) used in this process. US Pat. No. 5,324,880 suggests the use of H ₂ : HC ratios in the range of 0.5-1.9, and even lower ratios such as those in the range of 0.3-0.5 are applicable under certain conditions. However, it seems that some additional amount of hydrogen is always necessary in order to maintain the catalyst in an active state.

Typically, the activity of a paraffin dehydrogenation catalyst decreases when used until the residual activity becomes insufficient to maintain further economical operation without prior replacement or regeneration of the catalyst. Since the cost of a fresh catalyst charge for an industrial-sized reactor system can easily reach hundreds of thousands of dollars, it is highly desirable to extend the useful life of a given catalyst bed by regenerating it one or more times before its final replacement. The costs reduced by catalyst regeneration include the costs of acquiring a new catalyst, reducing the time and labor associated with replacing the catalyst, processing the spent catalyst to recover the noble metal, and recovering the loss of the noble metals during the processing of the spent catalyst. Moreover, the need to use expensive equipment to add catalyst without shutting down the reactor can be avoided, and occasionally occurring episodes of catalyst poisoning are less costly since regeneration of the catalyst is often sufficient to restore normal operation.

The ability of a catalyst to regenerate efficiently is commonly referred to as catalyst regenerability. In order to be able to regenerate, the catalyst must have a high degree of thermal stability, so that the loss of activity due to thermal decomposition is minimal during high-temperature regeneration procedures, such as burning stored coke. Since some loss of activity during each regeneration is unavoidable, another requirement for regeneration is a sufficient amount of activity in the fresh catalyst to compensate for the loss of activity that occurs during regeneration. The catalyst, which is highly regenerated, is able to maintain an adequate level of activity over a number of many work cycles and regenerations taking place. No laboratory test can fully quantify the degree of catalyst regeneration. However, an acceptable estimate of the regenerability can be achieved in the laboratory by measuring the initial activity and thermal stability at a temperature characteristic of the proposed regeneration procedure.

In the production of monoolefins by dehydrogenation of a range of detergents, significant economic benefits can be realized through the use of a catalyst that has favorable characteristics with respect to selectivity, volumetric activity, thermal stability and regenerability. In practice, however, previously known catalysts had disadvantages, at least with respect to one of these properties. Catalysts that were regenerable had insufficient selectivity, and catalysts with relatively high selectivity had insufficient bulk activity, thermal stability, or regenerability. Thus, the discovery of a catalyst with favorable characteristics with respect to all four of these properties, as described herein, represents a major benefit in the dehydrogenation of paraffins and in the production of alkylbenzene for use in the detergent industry.

Previous experience with catalytic reactions involving hydrocarbons includes US Pat. which is attached to this link. Patents of the prior art relating to catalysts applicable for the dehydrogenation of hydrocarbons include US patents nos. 3274287, 3315007, 3315008, 3745112 and 4430517, the entire contents of which are incorporated by reference.

Prior experience with the dehydrogenation of paraffins of the detergent range to form monoolefins includes US Pat. No. 3,761,531, which is incorporated by reference in its entirety. This patent describes a dehydrogenation process comprising contacting a hydrocarbon under dehydrogenation conditions with a catalytic composite comprising a combination of catalytically effective amounts of a platinum group component, a metal component of group IV-A, a metal component of group VA and an alkaline or alkaline earth metal component with a carrier material based aluminum oxide. It indicates that the preferred alumina-based support material has a relatively low apparent bulk density, with a bulk density in the range of about 0.3 to about 0.4 g / cm ³ being particularly preferred, and bulk density should be used for best results. about 0.33 g / cm ³ . Although the catalysts described in US Pat. No. 3,761,531 exhibit an acceptable degree of selectivity for the desired reaction, they typically exhibit relatively low bulk activity and / or thermal stability. Therefore, such catalysts cannot be considered recoverable. In normal practice, after a single reaction cycle, a layer of such a catalyst is replaced with a fresh catalyst. Such a reset is expensive both in terms of the cost of the catalyst and in the sense of the reactor shutdown time known from experience.

Other patents that relate to catalysts and methods applicable in the dehydrogenation of paraffins of a range of detergents to form monoolefins are US Pat. The catalysts described in US patent 3920615, have an acceptable selectivity, but they are considered insufficient in volumetric activity and / or regenerability. The catalysts described in the other three patents mentioned above are highly rated for volumetric activity and regenerability, but they have insufficient selectivity, which is undesirably low.

The following US patents, which are incorporated by reference in their entireties, are useful for explaining the differences between the prior art and the present invention: 3293319, 3448165 (especially column 5, lines 26-33); 3,576,766 (special art. 5, lines 31-60); 3647719 (particular art. 4, line 68 - art. 5, line 4); 3,649,566 (esp. Art. 5, lines 13-24); 3761531 (special art. 4, line 68 - art. 5, line 17); 3,776,594 (special art. 2, lines 46-60 and example 1); 3,825,612 (special art. 5, lines 26-38); 3998900 (particular art. 5, line 60 - art. 6, line 3); 4,048,245 (special art. 6, lines 39-51); 4,070,413 (special example 1); 4125565 (particular art. 6, lines 38-51); 4,136,127 (esp. Art. 6, lines 41-54); 4172853 (special art. 6, line 61 - art. 7, line 6); 4,177,218 (special example 1 and art. 3, line 56 - art. 4, line 14); 4207425 (particular art. 6, lines 33-54); 4,216,346 (special art. 6, lines 40-54); 4,227,026 (special art. 6, lines 36-50); 4268706 (special art. 6, lines 38-52, art. 7, line 27 - art. 8, line 59 and art. 19, lines 3-10); 4312792 (special art. 6, line 63 - art. 7, line 9, art. 7, line 54 - art. 9, line 19 and art. 19, lines 22-28); 4341664 (special art. 6, line 62 - art. 7, line 8, art. 7, line 53 - art. 9, line 18 and art. 19, lines 1-8); 4343724 (special art. 6, line 61 - art. 7, line 7, art. 7, line 52 - art. 9, line 17 and art. 19, lines 14-21); 4396540 (special art. 6, line 61 - art. 7, line 7, art. 7, line 52 - art. 9, line 17 and art. 19, lines 5-11); 4,486,547 (special art. 6, line 56 - art. 7, line 23); 4551574 (special art. 6, line 60 - art. 7, line 25); 4,595,673 (special art. 6, lines 15-43); 4,608,360; 4677237 (special art. 6, lines 25-33) and 4827072 (special art. 10, line 31 - art. 11, line 11). The rights to these patents are intended to be assigned to UOP, LLC. With the exception of US Pat. No. 4,070,413, these prior art patents have claims limited to the inclusion of one or more elements other than platinum group metals, group IB metals and alkali metals. The remaining US Pat. No. 4,070,413 has a claims limited to the use of a particular steamed alumina carrier. In each of these patents, the content relates to the shape and size of the catalyst particles, more preferably 0.16 cm (1/16 inch) spheres. Some of these patents (US Pat. Nos. 4,268,706, 4,312,792, 4,316,664, 4,343,724 and 4,396,540) indicate that 1/16 inch extrudates are also preferred. In all examples, 0.16 cm (1/16 inch) spheres were used, and there is no indication in these patents that extrudates are even preferable to spheres. Only one of the patents, US Pat. No. 4,608,360, discusses the distribution of pore sizes and indicates that more than 55% of the total pore volume should be pores with diameters of 60 nm (600 Angstroms) or more. Higher selectivity is attributed to such a pore structure in Example III of this patent. The indication regarding the average pore size is variable and not very specific. The indicated limits for the average pore diameter include 2-3 (20-30), 2-30 (20-300) and 2-300 (20-3000) nm (Angstrom). The most preferred bulk densities for the spheres were below 0.5 g / cm ³ in some of the previously issued patents and about 0.3 g / cm ³ in all other patents. The bulk density limits indicated for the extrudates were 0.4-0.85 or 0.5-0.85 g / cm ³ .

The following US patents, the entire contents of which are incorporated by reference, are also useful in explaining the differences between the prior art and the present invention: 5677260 (especially column 4, lines 50-59); 3,458,592; 3,662,018; 3,527,836; 3,274,287 (special art. 3, line 66 - art. 4, line 20 and example IV); 3,315,007 (esp. Art. 3, lines 25-56 and example I); 3,315,008 (esp. Art. 3, lines 12-44); 3,585,253; 3632662 (particular art. 2, lines 50-61 and art. 3, lines 26-31); 3920615 and 5324880. The catalysts disclosed in US Pat. No. 5,677,260, the rights of which are likely to be assigned to Indian Petrochemicals, include an unusually large number of additional elements, and they closely resemble the various catalysts disclosed in the patents, the rights to which, probably should be assigned to UOP, LLC. They prefer spheres of 0.16 cm (1/16 inch) with a bulk density of about 0.3 g / cm ³ . It is mentioned that the preferred pore distribution should be “mesoporous”, however, no further definition is given. US Pat. Nos. 3,458,592, 3,662,018 and 3,527,836, the rights of which are likely to be assigned to Texas and British Petroleum, claim catalysts with molecular sieve supports.

Among the listed patents originally assigned to Monsanto Company, the earliest: 3274287, 3315007 and 3315008 do not mention the use of copper in combination with platinum and a carrier, while the later ones: 3585253, 3632662, 3390615 and 5324880 disclose this. These patents indicate that the volume of macropores (the volume enclosed in pores with average diameters above 70 nm (700 Angstroms)) should be at least 0.05 cm ³ / g and that higher volumes of macropores are preferred. They do not say anything about bulk density. US 3,920,615 teaches that selectivity is improved by calcining to a specific surface of less than 150 m ² / g. Although such calcination affects the structure of the pores, the specific final structure of the pores is determined simply by establishing the specific surface. Permissible changes in the starting materials and the order of operations significantly affect the relationship between the specific surface and the pore structure.

SUMMARY OF THE INVENTION

Although the prior art patents established and described hereinabove in the Background to the Invention section contain rich information regarding the composition and use of various catalysts useful in paraffin dehydrogenation, there is nothing in the prior experience that would indicate or even confirm that a high degree of volumetric activity, thermal stability and selectivity, still not observed, could be provided by the catalyst in accordance with this invention, to tory comprises one or several elements: platinum, rhodium, iridium, palladium, ruthenium, and osmium ( "platinum group elements") deposited on a porous alumina carrier, selected so as to provide a finished catalyst surface area of more than 100 m ² / g, the pore volume with diameters below 60 Angstroms is less than 0.05 cm ³ / g, the pore volume with diameters in the range of 6-35 nm (60-350 Angstroms) is more than 0.50 cm ³ / g, and the pore volume with diameters in the range of 6-35 nm (60-350 Angstroms) is more than 70% of the total pore volume. In a preferred embodiment, the pore volume with diameters in the range of 6-35 nm (60-350 Angstroms) is more than 75% of the total pore volume. In a preferred embodiment, the bulk density of the catalyst package is more than 0.50 g / cm ³ . In fact, previous experience leads to just the opposite conclusion that such a catalyst should have relatively low activity and selectivity, due to the lack of pores with diameters of more than 60 or 70 nm (600 or 700 Angstroms). Therefore, the beneficial effects achieved through the use of catalysts, as described further below, in accordance with this invention, were completely unexpected.

This invention relates to a catalyst useful in the dehydrogenation of paraffin hydrocarbons, which in one form contains a porous alumina support and a main catalytic component containing one or more elements selected from the group consisting of platinum, palladium, osmium, ruthenium, iridium and rhodium deposited on a carrier, said catalyst has a specific surface area of more than 100 m ² / g, a bulk density of the package of more than 0.50 g / cm ³ , a pore volume with diameters below 6 nm (60 Angstroms) of less than 0.05 cm ³ / g, pore volume with diameters in the range of 6-35 nm (60-350 Angstroms) of more than 0.50 cm ³ / g, and a pore volume with diameters in the range of 6-35 nm (60-350 Angstroms) of more than about 70% of the total pore volume.

The catalysts disclosed herein possess a combination of thermal stability and bulk activity that is substantially comparable to that provided by the most stable and active prior art catalysts applicable in the manufacture of monoolefins of a range of detergents from paraffins of a range of detergents. So, one of the advantages of the catalysts prepared according to the guidelines given here is that they are particularly well suited for use in a process that involves regeneration of the catalyst. An additional advantage is that they provide higher selectivity than prior art catalysts that have comparable thermal stability and bulk activity. Thus, the advantages of catalyst regeneration mentioned above can always be realized in combination with excellent initial catalyst selectivity in the production of mono-olefins of a range of detergents from paraffin starting materials. In addition, in any dehydrogenation process that uses the catalysts of this invention, despite the fact that the catalyst regeneration process is contained or not, the high volumetric activity of the catalysts prepared according to the invention can help to achieve longer reaction cycles or a higher average conversion in the reactor of a given size. Alternatively, the size of the reactor can be reduced without compromising average productivity. In addition, any necessary fine-tuning of volumetric activity can easily be accomplished by varying the Pt load. Such improvements are completely in the competence of specialists in this field. The high selectivity of the catalyst inherent in the catalysts of the invention is clearly advantageous, since it can be used to achieve either greater productivity at a given cost of the starting material per pound (unit mass) of the product, or to reduce the consumption of the feedstock at a given performance. In a preferred embodiment, the catalysts of the invention provide both high catalyst selectivity and a relatively low pressure drop. A low pressure drop tends to improve the selectivity of the reaction by providing a lower average reaction pressure, and this in some cases can also help to reduce the overall energy consumption associated with the process.

Detailed Description of Preferred Options

This invention relates to the formation of monoolefins by catalytic dehydrogenation of paraffins having from 9 to 15 carbon atoms per molecule. The monoolefins thus obtained can subsequently be used in the manufacture of alkylbenzene-based detergent compositions. The catalysts of this invention use known metals or their combinations as the main catalytic components for the dehydrogenation of paraffins in combination with a porous alumina support selected to provide a unique specific combination of structural characteristics in the finished catalyst. In a preferred embodiment, the main catalytic component is platinum.

Alumina catalyst carrier

The catalysts of the invention are supported catalysts, i.e. they contain at least one active catalytic material that is supported on an inert carrier (“catalyst carrier”). In accordance with this invention, the catalyst carrier is porous alumina selected to provide specific physical properties in the finished catalyst that have been found to provide beneficial catalyst performance related to selectivity, activity, and regenerability. The specific physical properties of the finished catalyst of the invention include limitations on the microstructure of the finished catalyst, including its specific surface area and pore structure.

It is well known that the microstructure of the finished catalyst depends on the initial properties of the support material in its initial state before exposure to the reagents, conditions, and operations used in the process of producing the catalyst, some of which are well known to specialists in the preparation of catalysts, including impregnation with a catalytically active metal ( metals), calcination stages, hydrothermal treatments, etc. The microstructure of the starting alumina can be changed significantly during the preparation of the catalyst. Thus, the choice of alumina to obtain the catalyst according to the invention should be made strictly on the basis of a detailed description that characterizes the microstructure of the resulting finished catalyst. The starting alumina for use in the catalysts obtained in accordance with the invention can be from any source and can be obtained by a method ensuring that the resulting finished catalyst has a unique set of physical properties precisely established here. Most preferably, starting alumina with a relatively narrow pore size distribution is used. Various methods are known for producing alumina with a controlled and narrow pore size distribution. Some of these methods are described by D.L. Trimm and A. Stanislaus in Applied Catalysis 21, 215-238 (1986), which are incorporated by reference in their entireties. A particularly preferred alumina for producing the catalysts of the invention and for achieving the desired combination of physical properties set forth herein is the type manufactured by Engelhard Corporation of Iselin, New Jersey, designated "AE-30" grade.

The catalysts obtained in accordance with the invention have a distinct superior selectivity in combination with a very low pore content with diameters of more than 60 nm (600 Angstroms). For example, in catalysts B, C, E, and F shown in the table below, such pores comprise less than 10.5% of the total pore volume. According to the invention, the starting support is chosen to provide a finished catalyst structure that preferably has a very low volume content (less than 20.00% of the total pore volume, including every one-hundredth of a percentage between 20.00% and 0.00%) of pores with diameters more than 60 nm (600 Angstroms). Based on previous experience in this technical field, it would be expected that such a pore structure would result in an undesirably low catalyst selectivity. Therefore, the high selectivity achieved in accordance with the invention, in the absence of a significant amount of such large pores, was a complete surprise.

The relatively high bulk density of the package (more than 0.50 g / cm ³ , and including every hundredth g / cm ³ between 0.50 and 0.80) presented in the catalysts according to one form of the invention, is very advantageous due to its beneficial effect for bulk activity. Although some prior art catalysts had bulk densities of packing comparable to those of the present invention, such prior art catalysts had insufficient activity per unit mass, selectivity or thermal stability. Therefore, the fact that the preferred catalysts obtained in accordance with the invention have a relatively high bulk density of the package, while providing excellent activity per unit mass, selectivity and thermal stability, is a notable improvement in the art.

The main catalytic component

The catalysts prepared according to the invention contain a main catalyst component containing one or more elements selected from the group consisting of ruthenium (Ru), rhenium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum ( Pt), ("platinum group metals"). Although prior experience with dehydrogenation is replete with patents that contain claims regarding the use of one or more platinum metals, in one form or another, deposited on various supports, Pt is the only metal used commercially to any measurable degree as the main catalytic component for the dehydrogenation of paraffins in the range of detergents. According to this invention, it is preferable to include platinum and, most preferably, use platinum and only platinum as the main catalytic component. However, according to the invention, it is also possible to use other platinum group metals, either individually or in various combinations, as the main catalytic component of the catalyst of the invention. Although preferred amounts of the main catalytic component, expressed as a mass percentage based on the total weight of the finished catalyst, are precisely defined here for the preferred embodiments of this invention, the use of any amount of the main catalytic component between 0.01% and 3.0% by weight of the total weight of the finished catalyst, including every one hundredth of a percentage between them, is covered by the scope of this invention. In any case, the main catalytic component is located on the carrier with such a distribution so as to provide catalytic surfaces that are easily accessible to the reaction mixture.

When platinum is the main catalytic component, the platinum content of the finished catalyst, expressed as a mass percentage of the total weight of the finished catalyst, is variable and preferably ranges from about 0.02% to 2.00%, including every one-hundredth of therebetween. more preferably between about 0.20% and 1.00%, including every one hundredth of a percentage between them, even more preferably between about 0.40% and 0.70%, including every one hundredth of a percentage between them, most preferably 0.55 % Such levels can be achieved by a person skilled in the art without resorting to excessive experimentation, since methods for changing said experimentally determined variable are well known.

Activating component

Despite the fact that the catalysts obtained in accordance with this invention may contain only a carrier and a main catalytic component, it is preferable to include an activating component that functions so as to improve the performance of the catalyst. A suitable activating component may be selected from one or more metals, such as scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, silver, lanthanum, hafnium, tantalum, tungsten, ruthenium and gold. However, it is particularly preferable to include an activating component that contains one or more metals selected from elements such as copper, silver and gold (Group I-B). The main function of the activating component used here is to improve the activity and / or selectivity of the catalyst through various effects on the main catalytic component. For example, the activating component can be used to improve the dispersion of the main catalyst component and / or to improve the distribution of the main catalyst component within the granules of the catalyst carrier. In order to achieve the desired effect of improving the activity and selectivity of the catalyst, the activating component must be deposited on the catalyst support. Regardless of the activating component selected, the catalyst of the invention may contain any amount of activating component between 0.10% and 5.00% of the total weight of the finished catalyst, including every one-hundredth of a percent therebetween. However, it is most preferable to use copper and only copper as an activating component, since copper is both highly effective as an activator and has a relatively low cost. When copper is used, the concentration of copper in the finished catalyst material, expressed as the mass percentage of the total catalyst, is preferably in the range of about 0.10% -5.00%, including every one-hundredth of the percentage between them, more preferably between about 0.50% and 4.00%, including every one hundredth of a percentage therebetween, even more preferably between about 1.00% and 3.00%, including every hundredth of a percentage between them, most preferably about 2.00%. Such concentrations in the finished catalyst are readily attainable by those skilled in the art without resorting to undue experimentation through the use of conventional techniques used to deposit metals on catalyst supports, as more fully described in the examples.

Acid control component

In order to provide a catalyst according to the invention, which has the most favorable combination of selectivity, activity and regenerability, it is necessary to control the degree of acidity of the finished catalyst. If the acidity of the hydrogenation catalyst of the invention is too high, acid-catalyzed side reactions such as cracking and isomerization will be promoted during the dehydrogenation process to a degree that reduces the economics of the process and production efficiency. According to one form of the invention, alkali metals or mixtures thereof are preferred as acid control agents, since the oxides of these elements are basic in nature and highly effective in neutralizing the effects of various acid particles that are commonly found in or on a catalyst. Other metals whose oxides are alkaline in nature, such as alkaline earth metals, can also be used as acid control agents, but they are less preferred than alkalis, as they are generally less effective. Regardless of the selected acid control agent (s), the acid control agent (s) is preferably added to the catalyst at the time of preparation using techniques known to those skilled in the art, and as mentioned here, and the amount of acid control agent present in the finished catalyst may be any the amount between 0.001% and 1,000% by weight of the total weight of the finished catalyst, including every thousandth of a percentage between them.

Some available starting aluminas already contain sufficient alkali as an impurity, such as sodium, for example, to provide an effective degree of acidity control. Therefore, the addition of an acid control agent to the starting alumina during catalyst preparation may not be necessary in all cases. However, it is usually preferable to include an additional acid control component containing one or more alkali metals in order to provide a greater degree of protection against potential acidification of the catalyst. If an added acid control component is used, it is preferably deposited on the surface of the support during catalyst preparation using similar or the same techniques as are known in the art and applicable to the deposition of metals on catalyst supports.

According to a preferred form of the invention, it is particularly desirable to use added potassium as an acid control component. When using added potassium, its amount is preferably in the range of about 0.01% -2.00%, including every one hundredth of a percentage of them, more preferably in the range of about 0.05% -1.00%, including every hundredth of a percentage between them, and even more preferably in the range of about 0.10% -0.60%, including every one-hundredth of a percentage between them, most preferably about 0.20%. In this specification and the appended claims, the amount of potassium added is conveniently expressed as a percentage by weight of metal of the total weight of the finished catalyst, although it is assumed that potassium should be present in the catalyst in the form of an oxide or salt. If other alkali metals or mixtures of alkali metals are added instead of potassium, suitable amounts can easily be determined using equivalent masses of elements to be used without undue experimentation.

Catalyst Granule Shape and Size

Specialists in the field of catalysis know that the size and shape of the granules of the catalyst may vary. Catalysts previously used in industry for the dehydrogenation of paraffins of the detergent range had essentially spherical porous alumina carriers with an average granule diameter in the range of about 0.16 cm to about 0.32 cm. Known methods for producing spherical alumina granules include such methods as the agglomeration of a moistened alumina powder and an oil-drop method (the formation of hydrogel spheres from a liquid precursor discharged dropwise into a heated oil bath). Extrudates are obtained by converting powdered alumina into an extrudable dough by various known methods and then extruding the dough through a die under suitable conditions. When the extrudate emerges from the head, it can be cut into segments of any desired length using, for example, rotary or reciprocating knife devices at the exit point of the extruder. Extrudates having a wide variety of cross sections can be obtained by changing the shape of the head. For example, circular and three-blade cross sections are just two of the most commonly produced profiles. It is well known that granule size and granule shape have an important influence on the performance of the catalyst. Shorter diffusion paths within the granules are usually associated with higher catalyst selectivity, and diffusion paths can be shortened by using smaller granules and / or using granule shapes that have higher surface to volume ratios. However, it is also necessary to take into account the influence of the size and shape of the granules on the mechanical strength of the granules and on the pressure drop through the catalyst bed. For example, smaller catalyst granules result in a higher pressure drop, and granular shapes other than spherical tend to result in lower mechanical strength. Therefore, optimization of the size and shape of the granule for a given process often requires a balance of effects on selectivity, pressure drop and catalyst strength. The most favorable balance can change significantly when technological conditions change. However, for any particular case, the best balance is easily determined by specialists through routine experimentation.

Granules of the catalyst of any size and shape, applicable for the dehydrogenation of paraffins in the range of detergents, can be used, according to the guidelines given here, in the practice of this invention. If spheres are used, preferred spherical diameter limits are between 1.0 and 4.0 millimeters, including every tenth of a millimeter in the gap, most preferably 2.5 mm. However, for the purposes of the invention, it is most preferable to use extrudates.

It is preferable to use an extrudate with the greatest length in the range between 1.0 and 10.0 millimeters, including every tenth of a millimeter in the gap. It is more preferable to use an extrudate having an approximately circular cross-section, a diameter between about 1.0 and 4.0 millimeters, including every tenth of a millimeter in the gap, and a length sufficient to provide an average length to diameter ratio of about 1-4. Such extrudates having an average diameter of about 1.60 millimeters and an average length to diameter ratio in the range of about 2.00-4.00 (including every hundredth in the gap) are particularly preferred, most preferably an average length to diameter ratio of 3.00.

Properties of the finished catalysts according to the invention

The finished catalyst obtained in accordance with this invention has a specific surface area of more than 100 m ² / g, and preferably in the range of 120-200 m ² / g, including each whole m ² / g between them. A range of 135-150 m ² / g, including each whole in the range, is particularly preferred.

The catalysts according to the invention can be conveniently characterized as having a specific pore volume, the average diameters of which lie inside the first range of diameters, and another specific pore volume, the average diameters of which lie inside the second range of diameters. The pore volume within the second range of diameters can be further characterized as a percentage of the total pore volume related to the specified second range of diameters. In the catalyst of the invention, the pore volume having diameters below 6 nm (60 Angstroms) is less than 0.05 cm ³ / g, and the pore volume having diameters below 6 nm (60 Angstroms) is less than 0.02 cm ³ / g is more preferred and a pore volume having diameters below 6 nm (60 Angstroms) of less than 0.01 cm ³ / g is most preferred. The pore volume having diameters in the range of 6-35 nm (60-350 Angstroms) is more than 0.50 cm ³ / g and more preferably in the range of 0.60-0.80 cm ³ / g, including every hundredth cm ³ / g between them, most preferably about 0.69 cm ³ / g.

When expressed as a percentage of the total pore volume available in the catalyst according to one embodiment of the invention, the pore volume with diameters in the range of 6-35 nm (60-350 Angstroms) is more than 75.00%. More preferably, the pore volume with diameters in the range of 6-35 nm (60-350 Angstroms) is more than 80.00%. Even more preferably, pore volumes with diameters in the range of 6-35 nm (60-350 Angstroms) are more than 84.00% with a most preferred range of 86.00-89.00%, including every one-hundredth of a percent in the range. Percentages of pore volume here are expressed as a percentage of the total pore volume of the catalyst. Measurement of pore volumes is carried out by the mercury method, such a method is known to specialists in the field of catalysts.

According to a generally accepted understanding of prior experience, catalysts having a combination of properties (including pore distribution) possessed by the catalysts of this invention would presumably have to detect an undesirably low catalyst selectivity. Moreover, they would presumably have to have an unacceptably high diffusion resistance due to the lack of pores with diameters greater than about 60 (600) or 70 (700) nm (Angstrom). Therefore, it was unexpected that the catalysts of the invention were found to have excellent selectivity with the concomitant low content of large pores.

Other properties of the finished catalyst

Other physical properties are useful for further characterizing the catalysts of the invention, including bulk density. In a preferred embodiment, the catalyst of the invention has a bulk density of more than 0.50 g / cm ³ . Particularly preferred bulk density of the package in the range of 0.50-0.65 g / cm ³ including every hundredth g / cm ³ in the interval, with the most preferred bulk density of the packaging of 0.57 g / cm ³ . Bulk packing densities above 0.50 g / cm ³ tend to set limits on both the density of the granules and the volume of voids of the catalyst layer, which leads to favorable effects with respect to the volumetric activity of the catalyst.

The bulk densities of the packaging are established here based on measurements made by the following method. The catalyst in an amount in the range of 900-1000 ml is poured into a calibrated vibrating graduated cylinder of 1000 ml. Vibration of the cylinder is continued until the volume becomes constant. Read the final volume of the catalyst sample and determine the mass of the catalyst sample. The bulk density of the package is calculated by dividing the mass of the sample by the final volume of the sample. The measurements are carried out on samples that were protected from atmospheric moisture after their final calcination during the preparation of the catalyst.

Another characteristic of the catalysts of the invention is that they are regenerable. For the purposes of this description and the appended claims, a catalyst is “regenerable” if its response to a practical regeneration procedure is favorable enough to make it economically feasible to regenerate the catalyst at least once during its useful life. The degree of regeneration can be quantified by the decrease in the duration of the cycle associated with regeneration. For the purposes of this description and the appended claims, the “reduction in cycle time” characteristic of the first catalyst regeneration is the percentage reduction in cycle time that is observed when comparing the first and second operating cycles, achieved with the same catalyst loading when two cycles are carried out under conditions which are both economically viable and essentially equivalent in the sense of both average paraffin conversion and other working conditions, with the exception of the activity of kata izatora. In such a pair of cycles, the first cycle begins with a fresh catalyst, continues without regeneration, and ends at the point in time selected to provide an economically viable combination of cycle length and average paraffin conversion. The second cycle begins after the first regeneration, continues without additional regeneration, and ends at the point in time selected to provide the average paraffin conversion, approximately the same as during the first cycle. In each case, periods of downtime within the cycles are not included in the calculation of cycle times or average conversions. The preferred and / or economically long cycle time for a given set of conditions is easily determined by a mid-level specialist in the field of catalytic processes.

As determined by this method, the reduction in cycle time associated with the first regeneration of the catalyst of the invention is preferably not more than 50% of the duration of the first cycle. The catalysts according to the invention in a more preferred embodiment are characterized as having a decrease in cycle time characteristic of the first regeneration, not more than 35% of the duration of the first cycle. The catalysts according to the invention, corresponding to an even more preferred embodiment, are characterized as having a decrease in the cycle duration characteristic of the first regeneration, not more than 20% of the duration of the first cycle.

As for the catalyst obtained in accordance with the preferred embodiment, where the main catalytic component is Pt, it is well known that the conditions for the preparation of the catalyst must be precisely selected in order to provide a catalyst with adequate mechanical strength and a high degree of dispersion of Pt. According to the invention, any distribution of Pt in the carrier can be used provided that it results in a suitable dispersion of Pt that has adequate thermal stability. Preferably, the distribution of Pt is as uniform as possible. More specifically, the highest local concentrations of Pt should be kept low enough to avoid excessive agglomeration of Pt under conditions of application and regeneration of the catalyst. The purity of the starting alumina material and the conditions for the preparation of the catalyst must also be selected in order to ensure adequate thermal stability of the support structure in the finished catalyst; stability should be sufficient to avoid excessive Pt occlusion during catalyst application. Similar considerations are also relevant if other platinum group metals are used, and these considerations are known to those skilled in the art of preparing and using supported catalysts.

Catalyst Preparation

Typically, many methods for preparing a catalyst containing a platinum group metal on an alumina support can be used to prepare the catalysts of the invention. However, the complete processing of the catalyst precursors must be sufficiently consistent with that specified here to produce a finished catalyst material having a unique combination of physical characteristics and properties (including pore size distribution) that is within the limits limited by the claims of this invention. A new combination of properties possessed by the catalysts described herein is necessary to provide a catalyst material that has relatively high degrees of bulk activity, selectivity, thermal stability, and regenerability. While the preferred preparation method according to the invention is described in Example II below, significant changes can be made to the preparation method without departing from the scope of the claimed invention, which should be understood by those skilled in the art after reading this description and the attached claims, since many basic principles the preparation of catalysts known in the art can be used to prepare the catalysts of the invention. In any case, it is preferable to choose the impregnation conditions, which result in favorable distributions of the added components in the carrier, as well as a high degree of dispersion of the main catalytic component.

The catalysts obtained in accordance with the preferred form of the invention contain a carrier, a main catalytic component, an acid control component and optionally an activating component. These components are often discussed here only in relation to their constituent elements, but it should be understood that these elements may be present in different degrees of oxidation or as components of various chemical compounds or complexes at various stages of the preparation or use of catalysts.

Various known methods for combining catalyst supports with added catalyst components are considered by those skilled in the art. Some of these methods that are applicable to the preparation of catalysts containing one or more platinum group metals deposited on a porous alumina support can be used to precipitate added catalyst components (including soluble metal particles bound to the complex or not bound to the complex) upon receipt of the catalysts according to this invention. For example, a suitable alumina catalyst carrier may be immersed in a solution containing one or more metal decomposable metal salts to be used when heated. In one embodiment, the activating component and the main catalytic component can be satisfactorily deposited on the catalyst support simultaneously using a solution containing both components. In some cases, better results are obtained if the activating component is applied first followed by a calcination step, after which the calcined material is impregnated with a solution containing the main catalytic component. Although it is possible to apply the main catalyst component first, followed by the application of the activating component, this procedure is usually not preferred. As described in Example II below, excellent results are achieved by the method where the activating component and the acid control component are simultaneously added to the support in the first impregnation step and the main catalyst component is then added in the second impregnation step. As a rule, it is most preferable to add the main catalytic component after any calcination step, which significantly reduces the specific surface area of the support in order to reduce the risk of wasteful capture of some or all of the main catalyst component by the support during calcination.

Despite the fact that in accordance with the invention can be used any decomposable by heating soluble metal salts, which must be deposited on a carrier of aluminum oxide, the best results are usually achieved when using salts that do not contain halogen. Halogen-containing salts such as chloroplatinic acid, although applicable, are usually not particularly preferred, because their use leads to the fact that the catalyst contains at least some halogen ions, and the presence of halogen ions in the catalyst material, even in small quantities may potentially promote unwanted adverse reactions. Similarly, metal sulfates are unfavorable because the sulfate ion is only difficult to remove from the catalyst material, and the presence of sulfate ions in the catalyst, even in small amounts, can be unfavorable. The most preferred catalyst impregnation solutions containing Group IB metals are solutions containing nitrates, such as copper nitrate or silver nitrate, dissolved in aqueous ammonium hydroxide. The most preferred solutions containing platinum metals are those obtained by dissolving diammine dinitrites, such as platinum diamine, Pt (NH ₃ ) ₂ (NO ₂ ) ₂ or palladium diamine, Pd (NH ₃ ) ₂ (NO ₂ ) ₂ , in aqueous hydroxide ammonium

When using an aqueous ammonia solution of platinum diammine dinitrite (as in examples I-III below), the following solution preparation method gives good results. Platinum diammine dinitrite is dissolved in a hot concentrated aqueous solution of ammonium hydroxide to obtain a homogeneous intermediate mother liquor in which the concentration of Pt is slightly higher than that intended for use for impregnation of the catalyst. The mother liquor can then optionally be kept at a temperature in the range of about 65-85 ° C (“aged”) for up to about four hours, resulting in some approximation to the equilibrium distribution of the complexes present in the solution. The amount of solution required to impregnate the catalyst is conveniently provided by diluting a suitable amount of the intermediate mother liquor with deionized water, while maintaining a temperature suitable for maintaining homogeneity, such as about 65 ° C. If desired, the diluted solution may be heated or cooled to some other temperature for the catalyst impregnation step. In any case, it is preferable that the solution is homogeneous when it is brought into contact with the catalyst carrier. It will be appreciated by those skilled in the art that the most preferred cooking method may vary depending, for example, on the desired particle size of the catalyst. The specialist belongs to the choice of the most suitable method and solution concentrations for a given set of conditions.

During a given impregnation step, the amount of solution used can vary widely. It is preferable to use a sufficiently large volume of solution to ensure uniform deposition of metal salts. A procedure was found to be very satisfactory when, in each case, a solution volume was used that is equal to the amount necessary for complete saturation of the carrier material. According to this procedure, the amount of metal deposited on the carrier during the impregnation step is simply equal to the total amount of metal present in the solution that is used for the impregnation step. The amount of solution required to saturate the carrier material can be easily determined by tests conducted on a small sample of carrier material. If the selected metal salt (such as a basic carbonate, as just one example) is in any case not sufficiently soluble to allow the desired amount of metal to be precipitated in one application, the metal can be deposited in several stages by drying and / or calcining the catalyst material between in such stages.

In the various examples cited herein, calcination conditions are described in terms of a specific calcination temperature and either a precisely set calcination time or calcination time sufficient to provide the stated effect. Those skilled in the art will appreciate that slightly different calcination temperatures could also be used with substantially equivalent results. In some cases, compensating changes in the calcination time might be required, and such changes are well known in the art. When calcination is carried out in order to achieve catalyst particles having a specific specific surface, the progression of the specific surface can easily be tracked by testing material samples at appropriate intervals using techniques known to those skilled in the art, such as the BET method with nitrogen as an adsorbed substance. When treatment at elevated temperatures is used to remove volatile or decaying impregnation by-products such as nitrites, nitrates, ammonia and the like, a similar test of small amounts of catalyst granules at selected intervals can be undertaken to evaluate success, or, as option, specialists can trust those conditions that are well known and recognized as sufficient for such removal, provided that the finished catalyst has the physical limitations set forth in the claims . Although air calcination is shown in various examples, the invention also provides for the use of other atmospheres during calcination, since the use of other atmospheres, including oxidizing, reducing and inert atmospheres, is known to those of ordinary skill in calcining catalysts. Calcination is usually carried out at a temperature between 300 and 1200 ° C, preferably between 400 and 1000 ° C, including every degree of temperature in the specified range. The duration of the calcining treatment can be any period of time between 0.5 and 24 hours, but preferably it is between forty-five (45) minutes and 4 hours. It is understood that the average temperature during calcination will be higher than the average temperature during any drying treatment.

Example I - Prior Art

This example illustrates the preparation and use of a dehydrogenation catalyst on an alumina support corresponding to what is known from the prior art. All parts used herein are parts by weight, unless otherwise indicated. The alumina carrier used was obtained from LaRoche Industries, Inc., grade A-302, spheres 5-8 mesh. Specifications for said support include bulk density of at least 0.673 g / cm ³ , specific surface area of at least 270 m ² / g and macropore volume of at least 0.18 cm ³ / g. 104.6 parts of said catalyst support are loaded into a suitable catalyst coating drum. The first impregnation solution is prepared from 0.666 parts of potassium nitrate, 8.23 parts of copper (II) nitrate trihydrate, 23.0 parts of concentrated aqueous ammonium hydroxide (28% NH ₃ ) and a sufficient amount of deionized water to provide a final solution volume equal to , which is necessary to fill the pores of the carrier, as determined by the test on a small sample of alumina. When the carrier is treated in a drum for coating, the entire first impregnation solution is sprayed onto the granules for a period of about seven minutes. After a few more minutes of processing in a drum, sufficient to effect complete absorption of the solution by granules, the granules are dried at 138 ° C to a moisture content of 3% or less and then calcined in air at about 675 ° C for a time sufficient to reduce their specific surface to a range of 180-220 m ² / g, as determined by tests on small samples carried out during the calcination process. After cooling to ambient temperature and sieving to remove fines, the resulting calcined intermediate granules are again placed in a coating drum and impregnated a second time with a hot (50-60 ° C) aqueous ammonia solution of platinum diammine dinitrite containing 0.37 parts of platinum using the procedure the same procedure for the first impregnation. The resulting granules are then dried at 113 ° C. to a moisture content of 5% or less and then calcined in air at about 455 ° C. for a time sufficient to remove decaying impregnation by-products such as nitrites and nitrates. Finally, the granules are cooled and sieved to obtain 100 parts of the finished catalyst. The resulting catalyst has the following measured properties: 0.25% K, 2.1% Cu, 0.37% Pt and a specific surface area of 218 m ² / g. Some additional properties typical of a conventional catalyst of this type can be found in the table below (Catalyst A).

This catalyst is tested using it for dehydrogenation of a conventional paraffin mixture, which contains hydrocarbons that contain 10, 11, 12 and 13 carbon atoms per molecule, in a laboratory reactor with recycle under the following conditions: catalyst temperature 444-445 ° C, overpressure 54 , 5-55 / 3 kPa (7.9-8.1 psi), molar ratio of hydrogen to hydrocarbon 0.69-0.71, paraffin consumption 79-80 g / g catalyst / hour and duration five hours experience. The limits of normal paraffin conversion achieved are 7.5-11.00% and the conversion limits to aromatic by-products are 1.02-1.93%.

Example II

This example illustrates the preparation and use of a dehydrogenation catalyst on an alumina support according to the invention. The procedure of Example I is repeated except that the carrier is an extrudate from Engelhard Corporation, grade AE-30, having an approximately circular cross-section with diameters of about 0.16 cm (1/16 inch) and length to diameter ratios mainly in the range of 2-4 . The duration of the first calcination is selected so that at least it is a period of time sufficient to remove decaying impregnation by-products, and the amount of platinum in the second impregnation solution is increased to provide a higher platinum content in the finished catalyst. The total amount of support used and the amount of copper (II) nitrate and potassium used in the first impregnation solution are slightly reduced as required to provide the resulting catalyst having the following properties: 0.23% K, 2.07% Cu, 0.54% Pt, specific surface 144 m ² / g, bulk density 0.57 g / cm ³ , macropore volume 0.06 cm ³ / g, total pore volume 0.78 cm ³ / g, pore volume zero for pores with diameters below 6 nm (60 Angstroms) and a pore volume of 0.69 cm ³ / g for pores with diameters in the range of 6-35 nm (60-350 Angstroms) (equal to 88.5% of the total pore volume).

The dehydrogenation characteristics for the specified catalyst are tested using the same feedstock and conditions as those used in Example I. The limits of normal paraffin conversion achieved are 10.9% -15.5%. The increase in conversion in comparison with example I is proportional to the increase in mass of Pt in the reactor. Therefore, there is no loss of Pt utilization efficiency at a higher Pt content. The conversion limits to aromatic by-products are 1.23-2.44%. With this paraffin conversion, the conversion to aromatic by-products is 36% lower than in Example I. Therefore, the selectivity of the catalyst according to the invention was found to be much better than that of the catalyst prior art from example I.

Example III

The procedure of example II is repeated except that a different batch medium is used. The resulting catalyst has the following properties: 0.27% K, 2.08% Cu, 0.52% Pt, specific surface area 143 m ² / g, bulk density 0.56 g / cm ³ , macropore volume 0.07 cm ³ / g, total pore volume 0.78 cm ³ / g, pore volume zero for pores with diameters below 6 nm (60 Angstroms) and pore volume 0.68 cm ³ / g for pores with diameters in the range of 6-35 nm (60 -350 Angstroms) (equal to 87.2% of the total pore volume). The limits of normal paraffin conversion achieved are 10.8-15.3% and the conversion limits to aromatic by-products are 0.92-2.17%. With this paraffin conversion, the conversion to aromatic by-products is 51% lower than in Example I. This further illustrates the advantage of the selectivity of the catalyst of this invention compared to the prior art catalyst of Example I.

Example IV

The procedure of example II is repeated except that a different extrusion type support of 0.16 cm (1/16 inch) is used, which provides a higher specific surface area in the finished catalyst. The resulting catalyst has the following properties: 0.32% K, 2.19% Cu, 0.65% Pt, specific surface area 297 m ² / g, macropore volume 0.07 cm ³ / g, total pore volume 0.77 cm ³ / g, pore volume 0.20 cm ³ / g for pores with diameters below 6 nm (60 Angstroms) and pore volume 0.48 cm ³ / g for pores with diameters in the range of 6-35 nm (60-350 Angstroms ) (equal to 62.3% of the total pore volume). The limits of normal paraffin conversion achieved are 9.3-14.6% and the conversion limits to aromatic by-products are 1.1-3.0%. With this paraffin conversion, the conversion to aromatic by-products is about 20% lower than in Example I. This 20% decrease in the formation of aromatic compounds is significantly less than the decrease by 36% and 51% shown in Examples II and III. This illustrates the less favorable selectivity, which is achieved when the diameter of the granules remains the same as in examples II and III, but the pore size distribution of the catalyst is not consistent with the invention.

Example v

Two catalysts are prepared from different portions of the same batch of Kaiser KA 101 alumina pellets. For catalyst S (standard specific surface), the granules are calcined at 600 ° C. for 2 hours to obtain modified granules with a specific surface area of 190 m ² / g macropore volume 0 , 18 cm ³ / g and bulk density of 0.67 g / cm ³ . The modified granules are impregnated with an aqueous ammonia solution of platinum diammine dinitrite and copper (II) nitrate, dried at 120 ° C and calcined at 450 ° C for two hours to obtain a finished catalyst containing 0.45% Pt and 2.0% Cu. The specified catalyst is tested using it for dehydrogenation of normal dodecane in a laboratory reactor with a piston feed stream under the following conditions: catalyst temperature 450 ° C, overpressure 63 kPa (10 psi), molar ratio of hydrogen to hydrocarbon 8.0 , the dodecan feed rate 32 of the volume of liquid per volume of the catalyst layer per hour and the duration of the experiment 25 hours. The limits of normal paraffin conversion achieved are 13.0-14.3% and the conversion limits to aromatic by-products are 0.21-0.56%.

For catalyst L (low specific surface area), the granules are calcined at 1000 ° C. for 6 hours to obtain modified granules with a specific surface area of 48 m ² / g, a macropore volume of 0.25 cm ³ / g and a bulk density of 0.69 g / cm ³ . The conversion of the modified granules to the catalyst is used, resulting in the levels of Pt and Cu and the test conditions of the catalyst are the same as for catalyst S, except that a higher temperature of the catalyst is used during part of the dehydrogenation process. For catalyst L, the experiment is started at 460 ° C. in an attempt to compare with the conversion achieved with catalyst S. However, despite the higher temperature, the highest conversion achieved is only 14%. Therefore, the volumetric activity of catalyst L is significantly lower than that of catalyst S. After 2 hours, the temperature is reduced in 3 hours to 450 ° C. and this temperature is then maintained for the rest of the experiment. The range of normal paraffin conversion achieved at 450 ° С is 9.1-11.3%. The conversion to aromatic by-products for the entire experiment is 0.04-0.30%. These results show that although the selectivity of the catalyst is improved by calcining the prior art support to a reduced specific surface area, as described in patent No. 3920615, the improvement of selectivity is accompanied by a significant decrease in activity achieved with a given mass of Pt. This disadvantage is eliminated in the catalyst of this invention, as explained in Example II.

Example VI

Samples of the catalyst from example II and the prior art catalyst prepared as described in example I are aged for two hours in a nitrogen atmosphere at 540 ° C. The dehydrogenation characteristics for each catalyst before and after aging are tested using the same feedstocks and conditions as those used in Example I. Paraffin conversions after 100 minutes of use are used for comparisons. For the catalyst of Example II, the indicative result of aging is a decrease in conversion from 12.6% to 11.4%, without aging, the reduction in conversion achieved is 9.5%. For another catalyst, a significant result of aging is a decrease in conversion from 9.7% to 9.0%, without aging, a decrease in conversion achieved is 7.2%. This suggests that both catalysts exhibit excellent thermal stability. A slight difference between the two results is considered insignificant.

Example VII

The procedure of example II is repeated except that the order of addition of metals is changed. In the first impregnation step, only potassium is added instead of potassium and copper. In the second impregnation step, copper and platinum are added instead of only platinum. The resulting catalyst has the following properties: 0.37% K, 2.66% Cu, 0.76% Pt, specific surface area 123 m ² / g, bulk density 0.58 g / cm ³ , macropore volume 0.05 cm ³ / g, total pore volume 0.78 cm ³ / g, pore volume zero for pores with diameters below 6 nm (60 Angstroms) and pore volume 0.69 cm ³ / g for pores with diameters in the range of 6-35 nm (60-350 Angstroms) (equal to 88.5% of the total pore volume).

The limits of normal paraffin conversion achieved are 9.5–13.0% and the conversion limits to aromatic by-products are 0.98–2.04%. With this paraffin conversion, the conversion to aromatic by-products is 32% lower than in Example I. This illustrates the change in the catalyst preparation process that is possible in the field of the invention without any significant damage to selectivity.

Example VIII

The procedure of example II is repeated except that the diameter of the carrier is increased from about 0.16 cm (1/16 inch) to about 0.32 cm (1/8 inch). The resulting catalyst has the following properties: 0.25% K, 2.1% Cu, 0.54% Pt, specific surface area 133 m ² / g, packing bulk density 0.54 g / cm ³ , macropore volume 0.07 cm ³ / g, total pore volume 0.78 cm ³ / g, pore volume zero for pores with diameters below 6 nm (60 Angstroms) and pore volume 0.68 cm ³ / g for pores with diameters in the range of 6-35 nm (60-350 Angstroms) (equal to 87.2% of the total pore volume). The limits of normal paraffin conversion achieved are 7.8-11.6% and the conversion limits for aromatic by-products are 0.92-1.92%. With this paraffin conversion, the conversion to aromatic by-products is 17% lower than in Example I. This illustrates the advantage of the selectivity of the catalyst of this invention compared to the prior art catalyst of Example I in the absence of any noticeable difference in granule diameter.

Example IX

A single-stage adiabatic piston downdraft reactor is charged with two types of catalysts in separate layers. Catalyst P is used for the lower layer and catalyst N is used for the upper layer. By weight, the resulting hybrid catalyst layer contains 75.7% of catalyst P and 24.3% of catalyst N. Catalyst P is a prior art catalyst prepared as described in Example I, and catalyst N is prepared in accordance with the invention. The catalyst P has the following properties: 0.24% K, 1.8% Cu, 0.46% Pt, specific surface area 213 m ² / g and bulk density of the package 0.74 g / cm ³ . Catalyst N has the following properties: 0.30% K, 1.8% Cu, 0.54% Pt, specific surface area 142 m ² / g and bulk density 0.58 g / cm ³ . In the first operating cycle, a hybrid catalytic layer is used for dehydrogenation of normal paraffin under conditions within the following ranges: inlet temperature in the catalyst layer 429-454 ° C, overpressure inlet 57.2-63 kPa (8.3-10.0 lb / square inch gage), the molar ratio of hydrogen to hydrocarbon is 0.47-1.06, the consumption of paraffin is 4.9-5.3 g / g of catalyst / hour and the limits of paraffin conversion are 8.25-11.90%. The cycle duration is 32 days (23 days for C10-13 paraffin and 9 days for SP-14 paraffin) and the average paraffin conversion of 10.72%. After the first cycle, the catalyst is regenerated by burning accumulated coke, treated with hydrogen, and then used for the second working cycle. In the second cycle, the limits of the operating conditions are as follows: temperature at the inlet to the catalyst bed 437-454 ° C, overpressure at the inlet 52.4-73.1 kPa (7.6-10.6 psi), molar the ratio of hydrogen to hydrocarbon 0.33-1.11, the consumption of paraffin 4.9-5.3 g / g of catalyst / hour and the conversion of paraffin 7.90-12.10%. The cycle duration is 29 days (20 days for C10-13 paraffin and 9 days for SP-14 paraffin) and the average paraffin conversion of 10.54%. A comparison of the two cycles shows that regeneration restores a significant portion of the catalyst activity that is lost during the first cycle. Moreover, cycle times and average conversions fit well into practical operating limits. Therefore, the hybrid layer does not exhibit any insufficient regenerability, and the results show an acceptable degree of regenerability of the catalyst according to the invention.

Structural details

The data in the table below are presented in order to discuss in more detail the effects of specific structural changes in the finished catalysts. Catalyst A represents the best known regenerated catalyst of the prior art for the dehydrogenation of paraffins of a range of detergents. The indicated reduction to zero of aromatic compounds is based on the result achieved in example I, and other properties are determined using another typical sample, which is obtained by the method of example I. Catalysts B-F are catalysts from examples II, III, IV, VII and VIII, respectively. In all cases, a more significant reduction in aromatic compounds is equivalent to a higher selectivity of the catalyst.

Catalysts B, C, E and F are all prepared in accordance with the invention. For each of these catalysts, the selectivity is significantly higher than for catalyst A of the prior art. Compared to catalysts B and C, catalyst E has a selectivity slightly lower, obviously because it is obtained using a less optimal order of addition of metals.

Compared to catalysts B and C, catalyst F has lower selectivity due to the larger diameter of its granules. Compared to catalyst A, catalyst F has a slightly smaller diameter, but the resulting diffusion advantage is greater than that recoverable due to the greater length of its granules. Thus, it can be easily seen that the selectivity advantage is at least as much as shown in the table for catalyst F compared to catalyst A, is the result of a more favorable porous structure of catalyst F.

Catalyst D is not in accordance with the invention, since the pore volume for diameters of 6 nm (60 Angstroms) is not in the required range. Compared to catalyst A, catalyst D has better selectivity due to the smaller diameter of its granules. However, since catalysts B, C, and D have very similar pellet shapes and diameters, the lower selectivity of catalyst D compared to catalysts B and C clearly demonstrates that the pore structure of catalyst D is less favorable.

The comparisons discussed above show that the pore structures of catalysts B, C, E, and F prepared in accordance with the invention provide higher selectivity than the pore structures observed in catalysts A and D. For catalysts B, C, E, and F, significantly more the low content of pores with diameters below 6 nm (60 Angstroms) is obviously a very important contribution to higher selectivity. In catalyst A, a significantly higher macropore content> 70 nm (> 700 Angstroms) is not able to compensate for the detrimental effect on the selectivity of a relatively high pore content of less than 6 nm (60 Angstroms). This inefficiency of macropores is completely surprising and unexpected from the point of view of the previous idea that significant pore volumes are associated with better selectivity. For example, US Pat. No. 4,608,360 requires that at least 55% of the total pore volume of the catalyst be associated with pores having average diameters of about 60 nm (600 Angstroms) or more.

The loss of the former strong confidence in very large pores in connection with the teachings of the invention is advantageous due to some of the disadvantages inherent in very large pores. Compared to smaller pores, very large pores contain a large amount of empty space, which can be considered as unused space, since it is no longer considered necessary for high selectivity of the reaction. Counting per unit volume of catalyst, very large pores provide a smaller specific surface area of the support, which is necessary in order to properly stabilize fine platinum crystallites, which are necessary for high catalytic activity. Therefore, in a catalyst with a high content of very large pores, an increase in the platinum content, in order to provide a higher initial activity, leads to such a close collection of crystallites that it adversely affects the thermal stability of the platinum dispersion. Another disadvantage of very large pores is their tendency to reduce the mechanical strength of the catalyst granules.

In catalysts B, C, E and F, a very large pore content in the range of 6-35 nm (60-350 Angstroms) is not associated with low selectivity. Therefore, it can be concluded that pores in this range are surprisingly capable of very effectively contributing to the low diffusion resistance, which is necessary for high selectivity.

Another surprising aspect of the catalysts of this invention, which will undoubtedly be taken into account by those skilled in the art after reading and understanding this description, is the great extent to which the micropore content, defined here as pores with diameters of less than 6 nm (60 Angstroms), can be reduced. Some catalysts prepared in accordance with the invention are substantially devoid of such micropores. Despite the fact that it was previously known that selectivity could be increased by harder calcination, apparently due to a decrease in the micropore content, all previous attempts in this direction gave relatively unfavorable results. If the calcination was stiff enough to provide a significant increase in selectivity, the specific surface was reduced so much that the activity and thermal stability were undesirably low. If the calcination was less stringent, the increase in selectivity was less than desired. It has now been found that a very high degree of micropore reduction and an increase in selectivity can be achieved in combination with a final specific surface area sufficient to provide both high activity and high thermal stability.

The bulk packing density of the catalyst of the invention is higher than that of most prior art dehydrogenation catalysts. This property, combined with the new porous structure, makes it possible to achieve a very high level of volumetric activity without noticeable damage to thermal stability or selectivity. High bulk density, low macropore volume and low micropore volume result in a previously inaccessible level of a favorably located specific surface area of the carrier per unit reaction volume.

This makes it possible to introduce a large amount of platinum into a reactor of a given size without any significant damage to the average efficiency per unit mass of platinum.

Useful Process Features

Any various combinations of equipment, feedstock and operating conditions that can be used with prior art catalysts to produce mono-olefins of a range of detergents by paraffin dehydrogenation can also be used with the catalysts of the invention. However, it is preferable to use a process that involves regeneration of the catalyst at economically advantageous intervals. The following sections describe various preferred process characteristics for a process that involves catalyst regeneration.

Reactor design

In order to practice the present invention, the reactor or reactors used should preferably be designed for adiabatic piston flow. One reason for this is that access of reaction mixtures with a higher degree of conversion to hotter walls leads to lower selectivity of the reaction. Another reason is that exposure to such mixtures of higher catalyst temperatures existing near the adiabatic reactor inlet leads to a decrease in the selectivity of the reaction and causes an unacceptably high degree of catalyst deactivation under the conditions of this process. Another reason is that selectivity tends to be highest when any increase in conversion occurs at the lowest possible average olefin to paraffin ratio, i.e. when back mixing is minimized. A fourth reason is that the portion of the adiabatic reactor downstream of the site where the largest conversion occurs provides a favorable lower temperature environment where the preferred excess initial catalyst activity can be maintained.

Any other structural elements of a reactor suitable for use with platinum-catalyzed dehydrogenation of the paraffin range of detergents can also be used in the practice of this invention. The direction of flow may be downward, upward or radial. The ratio of the layer depth in the flow direction to the cross-sectional area of the layer at a specific depth can vary widely. The catalyst bed may be fixed or mobile, but it should not be fluidized, as this would be incompatible with piston flow operation.

It is preferable to use cylindrical continuous-flow reactors with a fixed bed and a downward flow with a length to diameter ratio selected so as to minimize problems with wall effects, formation of local through flows, excessive back mixing, excessive thermal feedback, or insufficient turbulence outside the catalyst granules. It is also preferred that the feed paraffin be completely vaporized and uniformly mixed with added hydrogen before contact with the catalyst bed.

Paraffin Feedstock

The detergent range paraffin used as a feedstock can be of any origin and of any variety suitable for use in platinum-catalyzed dehydrogenation. Paraffins useful as starting materials for dehydrogenation using the catalysts of the invention include all paraffins having from 2 to 20 carbon atoms per molecule, whether they are straight chain or branched paraffins. Although it is contemplated that any paraffin that is commonly known to be capable of undergoing catalytic dehydrogenation is suitable for use in accordance with the invention, the preferred starting material is paraffins suitable for preparing alkylbenzenes as intermediates in the manufacture of sulfonated alkylbenzenes for detergents, and normal paraffins are particularly preferred feedstocks. "Detergent range paraffin" means paraffins with total carbon atoms ranging from 9 to 15 inclusive, i.e. saturated hydrocarbon molecules that contain 9, 10, 11, 12, 13, 14 or 15 carbon atoms per molecule. Total carbon atoms ranging from 10 to 14 are particularly preferred. Mixtures with a range of carbon numbers can be used, and it is preferable to limit the width of the range of numbers of carbon atoms in such mixtures to four or less carbon atoms. The paraffins used can be fresh (not previously used in the dehydrogenation process) or recycle (non-converted paraffin recovered from an earlier dehydrogenation product). Mixtures containing fresh and recycled paraffins in any proportions can also be used.

Since the various ranges are set forth in this specification and the appended claims, it is useful to define all established ranges as having specific limits, including those values that are extreme in the established range. For example, the expression “any number of carbon atoms between 9 and 15” means 9, 10, 11, 12, 13, 14, and 15. Similarly, percent ranges also include extreme values used to limit the range.

The number of stages and the amount of catalyst

It is preferable to use either a single reaction step or two successive steps with suitable means for reheating between steps. If two stages are used, various aspects of reactor designs and operating conditions may be similar or different. In a preferred method of operation, a series of many duty cycles and alternating catalyst regenerations can be completed without any interruption for adding or removing the catalyst. At the beginning of this series, the types and amounts of catalyst loaded into the reactor or reactors should be such that there is an excess of catalyst activity. Such an excess of initial activity is necessary to compensate for the deactivation of the catalyst, which occurs during each working cycle, and from cycle to cycle. The preferred excess initial activity is its excess, which provides the most favorable balance between the duration of the cycles, the number of cycles in the series and the tendency to an excessively deep reaction, known from experience, at the beginning of each cycle due to excess activity.

Paraffin wax

Any degree of conversion per passage and any conversion control that is suitable for platinum-catalyzed dehydrogenation of the paraffins of the detergent range can be used in the practice of this invention. The conversion during one stage could be very low in some cases, for example about 1%. The total conversion during all stages of the dehydrogenation process could reach 20% or higher. The preferred paraffin conversion range throughout the combined steps is from about 5% to about 20%. The conversion can be kept almost constant during the processing cycle or changed in any desired way. The best time-based transformation control program within the work cycle is significantly dependent on other conditions used and can be determined by routine experimentation.

Various methods for controlling conversion during the processing cycle are well known. Such methods include adjusting the temperature of the reaction, reversible poisoning of the catalyst, periodic or continuous addition of catalyst during processing. Any such means may be used in the practice of this invention. In a preferred method, processing cycles begin with a substantial excess of activity of the catalyst bed, and operating conditions are closer to the start of the cycle by relatively low temperature limits, which provides a high tolerance for excess catalyst activity. In this way, good results can be achieved without relying on either reversible poisoning or the addition of catalyst during processing.

Catalyst hydrogen regeneration and treatment

A preferred method of regenerating the catalyst is to burn accumulated coke using a diluted oxygen source such as a mixture of air with nitrogen and / or recycle coke combustion products. The oxygen content and the temperature of the gas inlet can be adjusted to provide a suitable peak temperature inside the combustion zone of coke. In a preferred method of operation after burning out coke and before introducing the initial paraffin, the catalyst is treated with pure or recycle hydrogen for about an hour or more at a temperature comparable to that which should be at the beginning of the next processing cycle. Hydrogen treatment is also used to prepare the new catalyst for use. The specific conditions for catalyst regeneration and hydrogen treatment in any particular circumstances can be determined by routine experimentation.

Added hydrogen

It is known that in the traditional industrial dehydrogenation of paraffins of the detergent range, a certain amount of hydrogen is added to the initial dehydrogenation mixture in order to maintain the catalyst in an active state. Without reference to any theory, it is generally assumed that the actions of hydrogen go beyond mere dilution. In particular, hydrogen probably plays a role in suppressing the formation of coke on the surfaces of the catalyst and in maintaining the platinum in the required metallic state.

The amount of hydrogen added can vary widely, and the H ₂ : HC ratio can be constant or variable throughout the reaction cycle. The H ₂ : HC ratio is defined here as the molar ratio of added hydrogen to hydrocarbons in the range of detergents in the feed mixture. Although much higher ratios can be used, it is preferable to use relatively low H ₂ : HC ratios in the range of about 0.3 to 1.9. It is particularly preferred to use H ₂ : HC ratios in the range of about 0.4 to 1.0. Among the advantages of relatively low H ₂ : NS ratios are smaller equipment sizes, lower energy costs and the ability to work efficiently at lower temperatures. Lower operating temperatures are particularly advantageous near the start of operating cycles when there are large amounts of excess catalyst activity.

The hydrogen used in this invention may be from any source and any variety suitable for use in platinum-catalyzed dehydrogenation of paraffins. Suitable types include hydrogen produced by another process; hydrogen generated during the dehydrogenation process, isolated or recycled, and hydrogen of different purities. For economic reasons, it is usually preferable to use hydrogen generated in the process. The degree of purification or treatment of recycled hydrogen before reuse should be selected in order to optimize the overall efficiency of the process.

Temperature and pressure

Any temperature at the entrance to the catalyst bed suitable for platinum-catalyzed dehydrogenation of the paraffins of the detergent range can be used in the practice of this invention. For operations with a single reaction stage, it is preferable to use inlet temperatures that do not exceed 460 ° C. For operations with two or more reaction stages, it is preferable to use inlet temperatures that do not exceed 450 ° C. The advantages of these temperature limits include reduced yield loss before cracking reactions, lower energy costs, reduced coke formation rates, reduced equipment maintenance costs and improved catalyst efficiency.

For best results, it is usually necessary to change the inlet temperature during the duty cycle. Typically, the lowest temperature is used at the beginning of the cycle to suppress an excessively deep reaction, and higher temperatures are used later to compensate for the decrease in catalyst activity. At each point in time during the working cycle, the inlet temperature necessary for a particular reaction stage strongly depends on the enhancement of the desired conversion during the stage, the desired conversion at the output of the stage, the total pressure and the Na: HC ratio, all this is interconnected with the inlet temperature and determines whether the exit temperature of the stage is high enough to provide the desired conversion that must be achieved before the conversion is prevented by the effects of equilibrium of the reaction. For any particular situation, the optimal program of adjusting the inlet temperature can be determined by routine experimentation by a specialist taking into account this description.

Any general pressure suitable for platinum-catalyzed dehydrogenation of the paraffins of the detergent range can be used in the practice of the invention. Preferably, the pressure is at least one atmosphere due to excessive costs and the dangers associated with operating at pressures below atmospheric. It is also preferable to use pressures below about three atmospheres because of the advantages of chemical equilibrium. It is particularly preferred that the pressures at the final stage of the reaction are as low as practicable, i.e. from about 1 atmosphere to about 1.8 atmospheres.

MCHOR

Mass hourly volumetric flow rate (MCHR) is defined here as the mass of initial paraffin entering the specific catalyst bed per hour per unit mass of catalyst in that layer (both masses are measured in the same units). When the CDM increases, the conversion in the catalyst bed of a given activity tends to decrease. The choice of the value of MCHOR also fixes the value of such alternative parameters as hourly volumetric flow rate of liquid (COR) or contact time. Any MCHR suitable for platinum-catalyzed dehydrogenation of a paraffin range of detergents can be used in the practice of this invention. Values ranging from about 1 to about 20 are preferred. The best value for use in any particular situation can be determined by routine experimentation in light of this description.

Duty cycles

The action of a process with a particular catalyst bed from the time it is charged or regenerated to its removal or re-regeneration is referred to herein as a duty cycle. The duration of such a cycle refers to the time it takes to process the raw material and does not include periods of downtime. The duration of the cycle can vary widely, and the most favorable cycle time greatly depends on the life of the catalyst at the beginning of the cycle, and on the operating conditions used during the cycle. Although any cycle time can be used, it is preferable to use a cycle time of more than about 200 hours, since shorter cycles lead to an excessive reduction in the percentage of time during which the reactor is available for processing paraffin. Significantly longer cycles are possible, for example 1000 hours or more. When the cycle time increases, it becomes more difficult to maintain the conversion and operating conditions in the optimal range, since the catalyst is deactivated.

Product Extraction and Application

The olefins obtained in accordance with this invention can be recovered or used in any suitable way. Suitable applications include conversion to alkylbenzenes for use in detergents and conversion to various other products. Suitable product recovery methods include various effective combinations of steps selected from condensation, gas-liquid separation, fractional distillation, selective adsorption, solvent extraction, and selective chemical reactions. In a preferred method, the gaseous dehydrogenation reaction mixture is cooled to obtain a hydrocarbon-rich liquid phase and a hydrogen-rich gaseous phase. The gaseous phase is partially removed and partially recycled, with or without further purification, to the dehydrogenation process. The liquid phase is optionally subjected to selective hydrogenation to convert diolefins to monoolefins and, in any case, fractionated to remove low boiling cracking products. The remaining mixture containing olefins and paraffins of the detergent range is contacted with benzene and an acid catalyst under suitable alkylation conditions to convert the olefins mainly into alkyl benzene. The alkylation mixture is then separated by suitable means, including fractional distillation, into the product fraction of alkylbenzene, the fraction of unconverted paraffin, the fraction of unconverted benzene and other components such as recovered catalyst and various by-products. The benzene and paraffin fractions are recycled, with or without further purification or blowing, in the alkylation and dehydrogenation steps, respectively. In a particularly preferred method, the acid alkylation catalyst is hydrofluoric acid, which is recovered from the alkylation mixture, at least partially purified, and returned to the alkylation step.

Although the invention has been shown and described with respect to specific preferred embodiments, it is obvious that equivalent changes and modifications may become apparent to those skilled in the art after reading and understanding this description and the appended claims. This invention includes all of these modifications and changes and is limited only by the following claims.

Claims (48)

1. A regenerated catalyst applicable in the dehydrogenation of hydrocarbons containing a main catalytic component that contains one or more elements selected from the group consisting of platinum, rhodium, iridium, palladium, ruthenium and osmium, deposited on a solid support containing porous alumina, characterized in that said regenerated catalyst has a specific surface area of more than 100 m ² / g, a pore volume with diameters below 6 nm (60

) is less than 0.05 cm ³ / g, pore volume with diameters in the range of 6-35 nm (60-350

) is more than 0.50 cm ³ / g, and where the pore volume with diameters in the range of 6-35 nm (60-350

) is more than about 70% of the total pore volume. 2. The catalyst according to claim 1, further comprising an acid control component selected from the group consisting of alkali metals and alkaline earth metals deposited on said support. 3. The catalyst according to claim 1 or 2, additionally containing an activating component containing one or more elements selected from the group consisting of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium , niobium, molybdenum, silver, lanthanum, hafnium, tantalum, tungsten, rhenium and gold deposited on the specified media. 4. The catalyst according to any one of claims 1 to 3, where the specified main catalytic component contains platinum. 5. The catalyst according to any one of claims 1 to 4, where the specified main catalytic component contains a mixture of at least two different elements selected from the group consisting of platinum, rhodium, iridium, palladium, ruthenium and osmium. 6. The catalyst according to any one of claims 2 to 5, wherein the acid control component is selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and barium. 7. The catalyst according to claim 6, where the acid control component is potassium. 8. The catalyst according to any one of claims 2 to 7, wherein the acid control component is a mixture of at least two elements selected from the group consisting of alkali metals and alkaline earth metals. 9. The catalyst according to any one of claims 3 to 8, where the activating component is selected from the group consisting of copper, silver and gold. 10. The catalyst according to claim 9, characterized in that said activating component is copper. 11. The catalyst according to any one of claims 1 to 10, where the main catalytic component is present in an amount between 0.01 and 3.00% of the total mass of the catalyst, including every one-hundredth of a percent in the gap. 12. The catalyst according to claim 4 or any item dependent on it, which contains between 0.002 and 2,000% of platinum of the total mass of the catalyst, including every one hundredth percent of the gap. 13. The catalyst according to item 12, which contains between 0.20 and 1.00% platinum of the total mass of the catalyst, including every hundredth of a percentage in the gap. 14. The catalyst according to item 13, which contains between 0.40 and 0.70% of platinum of the total mass of the catalyst, including every hundredth of a percentage in the gap. 15. The catalyst according to any one of claims 2-14, wherein said acidity controlling component is present in any amount between 0.001 and 1,000% of the total weight of the catalyst, including every thousandth percent in the range. 16. The catalyst according to claim 7 or any item dependent on it, where the potassium is present in an amount in the range from about 0.10 to about 0.60% of the total weight of the finished catalyst, including every one hundredth percent in the interval. 17. The catalyst according to any one of paragraphs.3-16, where the specified activating component is present in an amount between 0.10 and 5.00% of the total mass of the catalyst, including every one hundredth percent of the gap. 18. The catalyst of claim 10 or any item dependent on it, where copper is present in an amount of from 1.00 to 3.00% of the total mass of the catalyst, including every one-hundredth percent of the gap. 19. The catalyst according to any one of claims 1 to 18, where the bulk density of the package is more than 0.50 g / cm ³ . 20. The catalyst according to any one of claims 1 to 19, where the pore volume with diameters in the range of 6-35 nm (60-350 A) is more than about 75% of the total pore volume. 21. The catalyst according to claim 20, where the pore volume with diameters in the range of 6-35 nm (60-350 A) is more than 80% of the total pore volume. 22. The catalyst according to any one of claims 1 to 21, where the reduction in the duration of the cycle associated with the first regeneration of the catalyst is not more than 50% of the duration of the first cycle. 23. The catalyst according to item 22, where the decrease in the duration of the cycle associated with the first regeneration of the catalyst is not more than 35% of the duration of the first cycle. 24. The catalyst according to item 23, where the reduction in the duration of the cycle associated with the first regeneration of the catalyst is not more than 20% of the duration of the first cycle. 25. The catalyst according to any one of claims 1 to 24, where the catalyst exists in the form of spheroids having diameters in the range of 1.0-4.0 mm, including every tenth of a millimeter in the gap. 26. The catalyst according to any one of claims 1 to 24, where the catalyst exists in the form of an extrudate with a largest diameter of 1.0 to 10.0 mm, including every tenth of a millimeter in the gap. 27. The catalyst according to any one of claims 1 to 26, where the specific surface is in the range from 135 to 150 m ² / g, including each whole 1 m ² / g in the gap. 28. A method for producing an olefin by dehydrogenation of a hydrocarbon, which comprises the steps of a) producing a hydrocarbon; b) preparing a catalyst according to any one of the preceding claims; and c) contacting said catalyst with said hydrocarbon under conditions effective to cause dehydrogenation of said hydrocarbon to produce an olefin. 29. The method according to p, where the hydrocarbon is paraffin. 30. The method according to clause 29, where the paraffin has a straight or branched chain and is a paraffin in the range of detergents. 31. The method according to clause 30, where the specified hydrocarbon contains paraffin with a straight chain range of detergents. 32. The method according to p, where the hydrocarbon contains at least one unsaturated hydrocarbon. 33. The method according to any one of p-32, where the hydrocarbon contains a mixture of hydrocarbons, where unsaturated hydrocarbons are present in an amount of less than 25.00% of the total weight of the hydrocarbon. 34. The method according to clause 33, where the hydrocarbon contains a mixture of hydrocarbons, where unsaturated hydrocarbons comprise at least 50.00% of the mixture of the total mass of hydrocarbon. 35. The method according to any one of p-34, where the specified catalyst is placed inside the reactor, where the reactor includes a) an inlet, which serves a stream of feedstock containing gaseous hydrocarbon; b) means for maintaining the catalyst in a substantially stationary position; and c) an outlet where exhaust gases containing at least one olefin leave said reactor. 36. The method according to clause 35, where the hydrocarbon contains a saturated hydrocarbon. 37. The method according to clause 35 or 36, additionally containing stage d) extraction of paraffin from the specified exhaust gases. 38. The method according to clause 35 or 36, additionally containing stage d) extraction of the monoolefin from the specified exhaust gases. 39. The method according to any one of claims 35-38, further comprising the steps of e) extracting the monoolefin from said off-gas to obtain a depleted effluent that contains a lower percentage of monoolefins than said off-gas, and f) re-directed said depleted off-gas stream to the specified input. 40. The method of claim 39, further comprising the step of adding gaseous hydrocarbon to the depleted effluent before the step of re-directing said depleted effluent to said inlet. 41. The method according to any one of claims 35-40, wherein said feed stream contains hydrogen in an effective amount to maintain said catalyst in an active state. 42. The method according to paragraph 41, where the molar ratio of hydrogen to hydrocarbon is in the range from 0.3 to 1.9. 43. The method according to any one of claims 35-42, wherein the hydrocarbon is paraffin and which further comprises the steps d) recovering unreacted paraffins from said effluent; and e) re-directing unreacted paraffins to said inlet of said reactor. 44. The method according to any one of claims 35-42, further comprising steps d) recovering unreacted paraffins from said effluent; e) mixing fresh paraffins with said unreacted paraffins until a mixture is formed; and f) feeding said mixture to said inlet. 45. The method according to any one of claims 28-44, further comprising the step of regenerating said catalyst. 46. The method according to item 45, where the regeneration of the specified catalyst includes heating the catalyst in an oxygen-containing atmosphere to a temperature sufficient to cause oxidation of at least part of the coke present on the surface of the specified catalyst. Priority on points: 08/27/1999 according to claims 1-27; 02/03/2000 according to paragraphs 28-46.