The method of dehydrogenation of light paraffins

 

(57) Abstract:

To effect the dehydrogenation of light paraffins, in particular, C2-C5with the obtainment of light olefins using a catalytic system containing platinum, tin and media - alumina, with added potassium and lanthanides. The process is carried out in a reactor with a fluidized bed. Moreover, as the heat required for the reaction, using the enthalpy of the specified catalyst system, the reaction is carried out at 500 - 700oC and a pressure of 1 - 2 kg/cm2. Regeneration of the catalyst system is carried out by reduction of coke deposited on the surface of the catalytic system, the flow of air and/or oxygen if necessary when the temperature of the catalytic system to a suitable level, and after regeneration carry out the restoration of the catalytic system reducing agent. The proposed method allows to obtain the olefin from such widely available raw materials, such as natural gas with high selectivity. 4 C.p. f-crystals, 2 tab.

This invention concerns a process for the dehydrogenation of light paraffins, especially C2- C5(i.e., paraffins containing from 2 to 5 carbon atoms), in the fluidized bed with the goals of myshlennyh products such as plastics, synthetic rubbers, high-octane gasoline, antidetonation gasoline additives, detergents, etc.

In these processes, the limiting factor is often the deficiency of olefin, such as isobutylene, in the production of MTBE (methyl tertiary butyl ether).

The projected increase in the demand of industrial materials, such as MTBE, suggests that this limiting factor will become increasingly critical.

Consider the reaction of dehydrogenation by means of which receive such olefins from widely available materials, such as natural gas, is becoming increasingly important for the industry because it gives the opportunity to provide chemical industry significant amounts of light olefins.

In the dehydrogenation reaction, although it is simple stoichiometric, there are significant kinetic and thermodynamic problems. The dehydrogenation reaction is characterized by an increase of the number of moles and significant endothermically. For hydrocarbon, C2- C10the absorption of heat of reaction is about 27 to 32 kcal/mol.

This is reflected in the change in free energy, toprowoC.

Therefore, a characteristic of these processes is the necessity of holding at high temperature, i.e. in conditions where flow side reactions such as skeletal isomerization, cracking and coke formation.

Therefore, one of the main goals of the selection of the catalyst is to suppress these reactions, which contributes to dehydration.

Finally, the inevitable accumulation of coke on the catalyst surface leads to its deactivation. Therefore, each process includes periodic regeneration of the catalyst.

For these reasons, industry research focused on important themes in the development of selective catalysts, methods of supplying heat for the reaction and recycling of the catalyst.

Regarding the first theme, for a long time was used catalysts in which the active centers was a noble metal deposited on a refractory material such as alumina, silicon dioxide or magnesium oxide (U.S. patent 4438288) or oxides of transition metals (patent UK 2162082).

Of the noble metals, most attention was paid to platinum due to its visibe almost inactive, can improve operational performance and increase the lifetime platinum catalysts (U.S. patent 3998900 and 3909451).

Performance lowoperating catalysts can be further improved by appropriate modification of the well known carriers, such as titanium (European patent 441430).

With regard to the development process, the problem of heat for the reaction without the use of furnaces for heating of supply of raw materials is effectively solved by using the fluidized bed technology (F. Buonomo et. al. Dewitt 1990 Petrochemical Reriew Houston, Texas, March 27-29, 1990 ). The basics of this technology developed for catalytic cracking in a fluidized bed.

The main part of the installation is the system of the reactor - regenerator. The catalyst is continuously circulated from the reactor to the regenerator and back.

Coke deposited on the catalyst surface, the side reaction product, is burned in the regenerator and heat is supplemented by heat from combustion of a suitable fuel is accumulated in the solid phase, increasing its heat content.

The catalyst performs its functions in the reactor and, in addition, transmits reactive substances heat stored during regeneration. The Mouth Of The

Thus, the catalyst in addition to its normal role also plays the role of a carrier of heat.

Thanks to this process resolves the problem of supplying heat to the reaction system.

The catalyst used in this process must meet certain requirements, the first of which is the resistance to mechanical stress, resulting from its motion.

The method of supplying heat to the reaction system is based on the fact that the operating temperature in the regenerator is significantly higher than in the reactor. Therefore, the catalyst must be able to withstand a high temperature of about 650oC.

Finally, the mechanism of the process and the need for a regenerator had small sizes, based on the fact that regeneration should be quick and simple, i.e., to consist of the smallest possible number of stages.

Although platinum metal itself has a high catalytic activity, it has the disadvantage of high surface energy, and therefore has a tendency to the formation of large agglomerates.

Therefore, an essential task is to stabilize platinum in its active form. This is achieved by allocating meta inertia is not actually reduces the surface energy of the active site and acts only "statistically", i.e., reduces the chance encounter of two crystallites of platinum, whereas excessive activity of the medium can inhibit the catalytic activity.

In addition to media, use as stabilizers and promoters such as tin.

Finally, it should be noted that the above temperature is the temperature at the macroscopic scale. Where is the combustion of coke, creates a higher local temperature with the subsequent increase in heat load. It is known that tin also is effective in reducing both the total education of coke and surface area of platinum, covered in coke.

In practice, the production was normal to regenerate catalysts based on platinum through the regeneration process includes treatment with Halogens. The disadvantages of this process is mainly due to the use of toxic and corrosive substances such as Halogens, which leads to the complication stage of regeneration, which should include the removal of halogen, remaining on the media.

Now found that the above disadvantages can be significantly reduced by regeneration of the catalyst in ispolninos in accordance with the present invention includes: (a) contact of these paraffins with a catalytic system, containing platinum, tin and carrier - aluminum oxide in the reactor with a fluidized bed, and as the heat required for the reaction, using the enthalpy of the specified catalytic systems operating at temperatures from 500 to 700oC and at a pressure of from 1 to 2 kg/cm2b) regeneration of the specified catalyst system by combustion of coke deposited on the surface of the catalytic system, and the regeneration is carried out in a stream of air and/or oxygen, if necessary, by increasing the temperature of the catalytic system to the appropriate level (for example, by burning the respective fuel), with the subsequent recovery of the specified catalyst system reducing agent.

In addition, it was found that the formulation based on platinum, tin and aluminum can be improved by adding potassium and lanthanides. In this case, it turns out the catalyst, the better to withstand the regeneration is conducted in the atmosphere, halogen-free.

Potassium increases the selectivity to the target olefin by slowing down side reactions of isomerization.

Lanthanide, in particular lanthanum, performs various functions. It acts as a stabilizer to the surface of the olefin. Finally lanthanid increases the heat capacity of the catalyst and, if it is adequately deposited on the carrier, also increases its impact strength and density.

It is well known that lanthanum catalyzes isomerization reactions at the terminal olefinic linkages. However, the heat treatment to which he was exposed, sharply reduces its activity.

Specifically recommended the catalytic system comprises the following components:

- platinum in an amount of from 0.05 to 1 wt.%, preferably from 0.1 to 0.3%;

- tin in an amount of from 0.2 to 3 wt.%, preferably from 0.3 to 1.5%;

- potassium in an amount of from 0.05 to 2 wt.%, preferably from 0.1 to 0.5%;

element from the group of lanthanides, preferably lanthanum in an amount of from 3 to 25 wt.%, preferably from 4 to 10%;

- aluminum oxide in the amount of complement to 100%; and the carrier comprises aluminum oxide and possibly element from the group of lanthanides.

In other words, an element from the group of lanthanides can either be a part of the media, or be external to it.

In the composition of the medium can also include silicon in an amount up to 5 wt.% and/or chlorides in amounts less than 1 wt.%.

If lanthanid present in the preparation of the catalyst, the carrier can be obtained in various ways, some of which will be described below in the examples.

You can get the media containing as lanthanide and aluminum oxide uniformly distributed throughout the volume, by appropriate deposition of insoluble compounds, to obtain granules, for example by spray drying and calcination of the resulting product. On the other hand, a carrier of aluminum oxide can be obtained, for example, by spray drying a suspension of aluminum hydroxide, to which may be added a compound of silicon, such as colloidal silica, and calcining the solids. If you want, you can add lanthanid to the media - alumina later, by impregnation of the soluble salt of lanthanide, for example, nitrate, or the deposition of insoluble forms, drying and calcination.

Another way is to process the surface of the aluminum oxide volatile compound of lanthanide with subsequent calcination.

Finally, lanthanid, if it is present, you can add or separately, or in conjunction with other components (platinum, tin, and possibly potassium), and in the first case, you have done what komponentov in the system.

Here are some examples to better illustrate the invention, but which in no way limit it.

Examples

The preferred method used to obtain samples containing lanthanides described in examples 4-6 and 8-9, consists of the following stages:

a) preparation of a carrier consisting of alumina and lanthanide,

b) impregnation of the support with a solution containing Pt/Sn (K),

c) activating the catalyst,

which are as follows:

a) a Porous carrier consisting of gamma-aluminum oxide, pure or containing a certain amount of silica, impregnated with an aqueous solution of nitrate lanthanide, using the volume of solution equal to the volume of pores.

The impregnated carrier is left to stand for one hour, dried during the day, with the temperature increasing from 50 to 120oC and finally calcined for 135 min at 1000oC in a current of moist air (e.g., containing 25% by volume. of water).

b) the resulting carrier is impregnated with a solution containing platinum and tin (and possibly potassium), using the method described in paragraph (a).

To ensure a better distribution restoreposition last). As is well known, the acid acts as a competitive adsorption on the surface of the carrier. The impregnated solid carrier is dried during the day, with the temperature increasing from 50 to 120oC.

c) Activation is achieved by calcination of the solid catalyst in a muffle furnace for 2 hours at 500oC, the subsequent recovery of the calcined product for two hours at a temperature of about 660oC in a stream of a mixture of hydrogen and nitrogen (in the fluidized bed).

Since the annealing and recovery is carried out in different environments, the calcined product before you restore dried for about one hour in a stream of nitrogen at 150oC.

Before determining the catalytic activity of the sample it is pre-cooled through a complete catalytic cycle, as described below.

Samples that do not contain lanthanides described in examples 1-3 and 7, obtained using the same method as described above, except impregnation with an aqueous solution of nitrate lanthanide on stage a).

Example 1

120 g sample of Delta-aluminium oxide in the form of beads (specific surface 132 m2/g) was impregnated at room temperature the methods of the nCl22H2O (98%) and 0.97 g H2PtCl6(25% Pt).

The impregnated substance is then dried, progulivali and activated as described above. The resulting product contained 0.2 wt.% Pt and 0.7 wt.% Sn (the rest falls on the media).

Then the catalyst was tested in a reaction cycles, described below, using as a gas for regeneration of pure oxygen.

The results are shown in table 2.

Example 2

120 g sample of Delta-aluminium oxide in the form of beads (specific surface area of 120 m2/g) containing 1.6 wt.% SiO2, was treated similarly as described in example 1, and obtained a catalyst containing 0.2 wt.% Pt and 0.7 wt.% Sn. The sample was tested in the reaction cycles, described below, using for the regeneration of pure oxygen.

The results are shown in tables 1 and 2.

Example 3

The catalyst on the same media with the same composition as in example 2, was tested in a reaction cycles, described below, using the regeneration air instead of pure oxygen.

The results are shown in table 2.

Example 4

139 g of the sample of gamma-alumina in the form of beads, containing 1.5 wt. % SiO2, was soaked m is B>)3and whether the substance was dried and progulivali, as described above, receiving solid media containing 1 wt.%. La2O3and having a specific surface area of 127 m2/,

120 g of the carrier was processed as described in example 1, and obtained a catalyst containing 0.2 wt.% Pt and 0.7 wt.% Sn (the rest of the number was the media).

The catalyst was tested in a reaction cycles, described below, using the regeneration air.

The results are given in tables 1 and 2.

Example 5

120 g of the sample carrier of gamma-alumina containing 1.5 wt.% SiO2and 5 wt.% La2O3(specific surface area of 120 m2/g) prepared by the method described above, was impregnated as described in example 1, and obtained a catalyst containing 0.2 wt.% Pt and 0.7 wt.% Sn (the rest was medium).

The catalyst was tested in a reaction cycles, described below, using for the regeneration of fresh air.

The results are shown in tables 1 and 2.

Example 6

120 g of the sample of gamma-alumina containing 1.5 wt.% SiO2and 7 wt. % La2O3(specific surface area of 110 m2/g) obtained by the method described above, was soaked, as Eitel).

The catalyst was tested in a reaction cycles, described below, using the regeneration air.

The results are shown in tables 1 and 2.

Example 7

120 g of the catalyst, similar to that described in example 2 was impregnated by the method of humidification with regard to capacity with a solution containing 1.55 g KNO3, and received, a catalyst containing 0.2 wt.% Pt and 0.7 wt.% Sn and 0.5 wt.% K (the rest was medium). The catalyst was tested in a reaction cycles, described below, using for the regeneration of oxygen.

The results are shown in tables 1 and 2.

Example 8

120 g of the sample, composed of beads of gamma-alumina containing 5 wt. % La2O3(specific surface area of 120 m2/g), obtained as described above was impregnated at room temperature by the method of humidification with regard to capacity acidic solution (55 cm3containing 12 g of concentrated HCl, 1.7 g SnCl22H2O, 0.97 g H2PtCl6(25% Pt) and 1.55 g KNO3. The impregnated substance is then dried, progulivali and activated as described above. The final product contained 0.2 wt.% Pt, 0.7 wt.% Sn and 0.5 wt.% K (the rest was medium).

Then the catalyst was tested in reactr CLASS="ptx2">

Example 9

133 g of the sample of gamma-alumina composed of beads that contained 1.5% of SiO2, was soaked by the method of humidification with regard to capacity with an aqueous solution (62 cm3containing 25,31 g of the pentahydrate Pr(NO3)3. The impregnated product was dried and progulivali, as described above, and received solid media containing 7 wt.% Pr2O3with specific surface 116 m2/,

120 g of the carrier was processed as described in example 1, and obtained a catalyst containing 0.2 wt. % Pt and 0.7 wt.% Sn (the rest was medium).

The catalyst was tested in a reaction cycles, described below, using the regeneration air.

The results are shown in tables 1 and 2.

The catalyst test

Substances obtained in examples 1-9 were tested in a quartz fluidized bed reactor having a porous quartz wall. The catalytic cycle that simulates the behavior of an industrial reactor, consisted of the reaction, during which the reactor was supplied hydrocarbon (duration 15 min), stage of purging in the reactor missed the nitrogen to release the catalyst from the absorbed products (10 min), with Uchenie 30 min), and recovering in the atmosphere of hydrogen or mixtures of hydrogen with nitrogen (usually 4 minutes). Stage regeneration, recovery and reactions were separated from each other by short periods of purging with nitrogen (5 min) for security reasons, as a reaction, regeneration and restoration was carried out in the same reactor.

In the industrial process of dehydrogenation in a fluidized bed requires regeneration and restoration was carried out at a higher temperature than the reaction temperature, i.e. at a temperature of about 650oC, depending on the reaction temperature and the specific heat of the catalyst.

The reaction temperature is a function of thermodynamics of the reaction and the specific activity of the resulting catalysts. It usually varies from 540 to 580oC for dehydrogenation of isobutane (PL. 1) and from 550 to 590oC for propane dehydrogenation (PL. 2).

To the same reactor space velocity of the reacting substances is a function of the activity of the prepared catalysts and their density, and in laboratory reactors, used by us, it was changed from 200 to 600 N. l/l of catalyst per hour and usually was 400 N. l/l catalizadores.

Flux is zvishavane on the scales.

Stages of the reaction and purge gas mixture emerging from the reactor is first passed through a cooled trap to highlight the heavy products. These products are weighed, and identified them in the percentage of carbon and hydrogen and then collected them in the tank for samples. Then the amount of the substance contained in the reservoir was measured using a piston pump and analyzed by gas chromatography.

Finally, after purging with nitrogen for 10 min was selected sample of the catalyst to determine the number of formed coke.

The resulting data were entered into a personal computer to calculate the material balance conversion selectivity with respect to various products.

The data in table 1 in the column HOS (hours on stream time of reactor operation in hours) do not take into account the full catalytic cycle of pre-conditioning.

The data are shown in table 2 in the column HOS (hours on stream time of reactor operation in hours) do not take into account the full catalytic cycle of pre-conditioning of the catalyst.

1. The method of dehydrogenation of light paraffins, in particular, C2- C5pick and media - the aluminum oxide in the reactor with a fluidized bed at a temperature of 500 to 700oC and at a pressure of 1 - 2 kg cm2using as the heat required for the reaction, the heat content of the specified catalyst system, which is recovered by burning the coke deposited on the surface of the catalytic system, wherein use of the catalytic system, optionally containing an element from the group of lanthanides, and the regeneration is carried out in the current of air if necessary with increasing temperature catalytic system to the appropriate level, with the subsequent recovery of the specified catalyst system reducing agent.

2. The method according to p. 1, characterized in that the use of the catalytic system, optionally containing potassium in the following ratio, wt.%:

Platinum - 0,05 - 1

Tin - 0,2 - 3

Potassium - 0,05 - 2

Element from the group of lanthanides - 3 - 25

Aluminum oxide - 100

3. The method according to p. 2, characterized in that the use of the catalytic system, optionally containing in the structure of the carrier of silica gel in an amount up to 5 wt.% and/or chlorides in amounts less than 1 wt.%.

4. The method according to p. 2 or 3, characterized in that use katal the C group of the lanthanides, 4 - 10

Aluminum oxide - 100

5. The method according to PP.2 to 4, characterized in that the element of the group of lanthanides is a lanthanum.

 

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2 ex

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4 ex

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EFFECT: enhanced efficiency of process.

1 tbl, 13 ex

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