Catalyst for dehydrogenation of hydrocarbons and method thereof

 

(57) Abstract:

Usage: petrochemistry. The inventive catalyst for dehydrogenation of hydrocarbons includes a chromium oxide compound of alkali and/or alkaline-earth metal, zirconium dioxide and aluminum oxide, a precursor which is a compound of aluminium of the formula Al2O3nH2O, where n = 0.3 to 1.5, and further comprises at least one oxide promoter is selected from the group of niobium, tantalum, hafnium in an amount of 0.001-2 wt.%, and the catalyst has the following composition, wt.% (in terms of oxide): chromium oxide (Cr2ABOUT3)-12-23; zirconium oxide is 0.1 to 5; oxide promoter is selected from the group of niobium, tantalum, hafnium 0,001-2; the connection of alkaline and/or alkaline-earth metal of 0.5-3.5; aluminium oxide - rest. Obtaining catalyst for the dehydrogenation of hydrocarbons includes the impregnation of aluminium-containing compounds layered x-ray amorphous structure of formula A12O3mo2Oh, where n = 0.3 to 1.5, solution chromium compounds, alkaline and/or alkaline-earth metal, zirconium, drying and annealing at 700-800oC. At the stage of impregnation impose additional promoter, at least one compound of a metal from the group of niobium, cantolina catalyst for dehydrogenation of hydrocarbons with enhanced durability and having high activity and selectivity in the process of dehydrogenation of hydrocarbons. 2 S. and 11 C.p. f-crystals, 2 tab., 2 Il.

The invention relates to methods for preparing catalysts for the dehydrogenation of various hydrocarbons, in particular for dehydrogenation WITH2-C5paraffins to the corresponding olefins.

Olefins are one of the most important products of organic synthesis. They are used in the production of polypropylene, high-octane additives (methyl-tertiary-butyl ether) in gasoline and a variety of other industries.

One of the ways to obtain olefins is the dehydrogenation of paraffins. It is well known that from a thermodynamic point of view, the dehydrogenation of hydrocarbons2-C5not related to the number of effective processes. Since the reaction of dehydrogenation of indetermine, to achieve technically acceptable conversion of raw materials to the required temperature of 500-600oC. However, at these temperatures with a noticeable speed of flow and the adverse reactions of cracking and isomerization. This is because the carbon-carbon (C-C) bond is significantly less strong than the bond carbon-hydrogen (C-H). So CTI to carry out the process at low temperatures, and the reaction rate of cracking is possible to do the minimum. It must minimize the inevitable formation of a certain number of normal hydrocarbons and cyclic structure. The dehydrogenation catalyst should have high selectivity to the desired olefin with a decrease in the rate of side reactions leading to coking. The formation of coke on the catalyst requires periodic regeneration of the latter at elevated temperatures, therefore, the catalyst must be stable. Special requirements to the mechanical strength of the catalyst, because the destruction of the problems of environmental pollution.

The catalysts for the dehydrogenation of hydrocarbons containing compositions based on noble metals or combined with other elements, and chromium compounds.

However, compositions containing precious metals, have increased kekirawa ability at elevated temperatures. This leads to rapid coking of the catalyst and loss of activity and as a consequence the reduction of the lifetime.

Despite the fact that catalysts based on precious metals and gallium are a new pohorly dehydrogenation WITH2-C5paraffins are chromium oxides supported on alumina and having high mechanical strength, although chrome compounds are harmful substance. Therefore, when creating new catalysts based on chromium compounds main task is durable fixation of chromium in the media, reducing wastewater when it is received, increased activity and stability.

In the patent EP 0947247 (IPC B 01 J 23/26, 1999) proposed to increase the content of chromium oxide in the catalyst is in a certain interval of more than 30 wt. % but not more than 40 wt.%. The catalyst contains alumina and promoting additives from the group of oxides of alkaline and alkaline-earth metal, oxides of scandium, yttrium, zirconium, lanthanum, titanium, hafnium, cesium, potassium. The catalyst was prepared by double impregnation of the support with a solution of chromium compounds, drying, and calcination.

With the high chromium content decreases formation of coke and there is a simultaneous increase in the activity and selectivity of the catalyst.

The disadvantage of the catalyst is its low strength and high content of chromium compounds that are highly toxic substances, as well as complicated the way it is received.

The disadvantage of the catalyst is its low strength and lack of high activity and selectivity, bulky, complicated way of getting connected with a considerable amount of waste water and gas emissions.

Known catalyst for dehydrogenation or dehydrocyclization hydrocarbons (U.S. Patent 5378350, IPC C 10 G 35/06, B 01 J 23/00, 1995), including the oxides of chromium and aluminum, at least one compound of cesium as a promoter in an amount of 0.1-10% by weight of catalyst based on Cs2O, and at least one compound of zirconium as an additional promoter in an amount of 0.1-15% by weight of catalyst based on ZrO2.

The proposed catalyst reduces the formation of coke, suppressed side reactions, however, the disadvantages are not sufficiently high activity and selectivity of the catalyst.

Known catalyst for dehydrogenation of hydrocarbons (Patent of the USSR 1836140, IPC B 01 J 23/26, 21/06, C 07 C 5/333, 1993), which contains chromium oxide, in the amount of 25 wt.%, connection alkaline and/or alkaline-earth marks the Zirconia in the amount of 0.9 wt.%.

For the preparation of the catalyst using a carrier - aluminum oxide in the form of tablets, impregnate the carrier with a solution containing compounds of chromium and zirconium, after impregnation, the product is dried in vacuum, and then conducting heat treatment at 740oWith, after that carry out the impregnation of the catalyst compound of alkaline or alkaline-earth metal and the two-stage drying, first under vacuum and then in an atmosphere of air, the dried product is subjected to heat treatment at 740oC.

The catalyst has an increased service life by reducing formation of coke, but the method of its production is complex and multi-staged.

The closest technical solution is the catalyst for the dehydrogenation of hydrocarbons and method thereof (Patent RF 2148430, IPC B 01 J 23/26, 37/02, 2000), which contains the oxides of aluminum, chromium, a compound modifier metal, alkaline and/or alkaline-earth metal, and optionally contains compounds of silicon and/or boron. As the modifying metal catalyst contains at least one compound from the group of zirconium, titanium, iron, gallium, cobalt, molybdenum, manganese, tin, and formed during the heat treatment of aluminum compounds sposob the preparation of the catalyst is impregnated carrier based on alumina with solutions of chromium compounds, alkaline and/or alkaline-earth metal, a modifier metal, drying and annealing at 700-800oC.

The disadvantage is not a high catalyst activity.

The problem solved by the present decision, is the development of a catalyst for the dehydrogenation of hydrocarbons, which would have increased strength, activity, selectivity, and simple method of its production, which would reduce the number of stages when it is received.

This problem is solved by using a catalyst for the dehydrogenation of hydrocarbons which comprises a chromium oxide compound of alkali and/or alkaline-earth metal, zirconium dioxide and aluminum oxide, a precursor which is a compound of aluminium of the formula Al2O3nH2O, where n = 0.3 to 1.5, and further comprises at least one oxide promoter is selected from the group of niobium, tantalum, hafnium in an amount of 0.001-2 wt.%, and the catalyst has the following composition,wt.% (in terms of oxide):

The chromium oxide (CR2O3) - 12 - 23

Zirconium oxide is 0.1 to 5

The oxide promoter is selected from the group of niobium, tantalum, hafnium is 0.001 - 2

Connection alkaline and/or alkaline-earth metal - 0, the MINIA formula Al2O3mo2Oh, where n = 0.3 to 1.5, in conjunction with the compounds of the above elements and has a value of specific surface area of 50-200 m2/,

The alumina in the catalyst composition is a gamma, γ + χ - phase.

The compound of aluminium of the formula Al2O3mo2Oh, where n = 0.3 to 1.5, has a layered x-ray amorphous structure with a value of specific surface area of 50-250 m2/g and has a high chemical activity.

Compounds of chromium, alkali and/or alkaline-earth metal, zirconium and promoter uniformly distributed in the aluminum oxide and roentgenology.

The catalyst additionally contains silicon oxide in an amount of 0.01-2%.

The catalyst is preferably the following composition, wt.% (in terms of oxide):

The chromium oxide - 16

Zirconium oxide - 1

The oxide of niobium - 0,005

The potassium oxide is 1.5

Alumina - Rest

and contains silicon oxide in the amount of 0.02 wt.%.

The task is also solved using the method of producing catalyst for the dehydrogenation of hydrocarbons which comprises impregnation of aluminium-containing compounds layered x-ray amorphous structure of the formula Al2O3is ku and calcination at a temperature of 700-800oC. At the stage of impregnation impose additional promoter is at least one compound of a metal from the group of niobium, tantalum, hafnium, in the quantity necessary to obtain after heat treatment of the catalyst of the following composition, wt.% (in terms of oxide):

The chromium oxide (CR2O3) - 12 - 23

Zirconium oxide is 0.1 to 5

The oxide promoter is selected from the group of niobium, tantalum, hafnium is 0.001 - 2

Connection alkaline and/or alkaline-earth metal of 0.5 - 3.5

Alumina - Rest

As the aluminium-containing compound is used as a compound of aluminium of the formula Al2ABOUT3nH2O, where n = 0.3 to 1.5 with a value of specific surface area of 50-250 m2/,

For the preparation of the catalyst is used as a compound of aluminium of the formula Al2ABOUT3nH2Oh, where n = 0,3-1,5-containing silicon oxide in an amount of 0.01-2 wt.%.

In the catalyst after calcination chrome compounds, alkaline and/or alkaline-earth metal, zirconium, promoter uniformly distributed in the aluminum oxide and roentgenology.

The proposed solution uses a catalyst which comprises in addition to zirconium is at least one connection promoitalia in relation to the content of chromium in the catalyst, zirconium and alkali and/or alkaline-earth metals leads to the achievement of the task.

We propose a method of producing a catalyst, in which there is a formation of the structure of the catalyst during the heat treatment of aluminum compounds of the formula Al2ABOUT3mo2Oh, where n=0.3 to 1.5, with layered x-ray amorphous structure and S = 50-250 m2/g, which are uniformly distributed components of the catalyst: compounds of chromium, zirconium, alkaline and/or alkaline-earth metal compound promoter: niobium, tantalum, hafnium. The catalyst after heat treatment at a temperature of 700-800oWith preferably has a value of specific surface area S = 50-200 m2/g and a pore volume of 0.15-0.4 cm3/g and represents the gamma, γ + χ - phase with the active component in the x-ray amorphous state.

Under the connection Al2ABOUT3nH2O, where n=0,3-1,5, x-ray amorphous layered structure is understood in this connection, x-ray analysis does not detect any lines, characteristic of any crystalline phase. In Fig.1, 2 photographs particles connections A12O3mo2Oh, where n=0.3 to 1.5, at different magnification, where is the query result which is possible intercalation compounds of the catalyst components in the interlayer space between alyumogidroksidnykh packages accompanied by a shift alyumogidroksidnykh packages relative to each other. As a result of intercalation compounds of chromium, zirconium, alkaline and/or alkaline-earth metal oxide promoter: niobium, tantalum, hafnium not only evenly distributed in the alumina, but also chemically bound with the compound of aluminium. Further, when the heat treatment is thermodispersion compounds of the catalyst components, leading to the formation of highly dispersed x-ray amorphous phases catalyst components, is strongly related to the structure of aluminum oxide. The formation of the grains of the catalyst occurs both through the development of a grid of chemical bonds, so the accretion of many small particles of catalyst components. These types of structure formation - crystallization or condensation and provide the most durable structure. This explains the high mechanical strength of the resulting grains of the catalyst, as well as high thermal stability of the catalyst.

The connection of Al2O3mo2Oh, where n=0.3 to 1.5, can contain up to 2% of silicon dioxide, which has a positive effect on thermal stability of the catalyst.

The size and shape of the catalyst particles is determined AET a spheroid particles of loose porous surface and a particle size of preferably 40-200 μm. Loose porous surface of the particles contributes to a better mass transfer than the smooth surface of the particles. The obtained catalyst particles retain their shape particles of aluminum compounds of the formula Al2ABOUT3mo2Oh, where n=0,3-1,5, due pseudomorpha transition.

The catalyst for stationary layer can be prepared in the form of granules of different forms, such as tablets size 4 x 4 mm

A method of producing a catalyst for dehydrogenation of hydrocarbons includes the impregnation of aluminium-containing compounds with solutions of compounds of chromium, zirconium, alkaline and/or alkaline-earth metal promoter: niobium, tantalum, hafnium, drying and annealing at 700-800oC. as aluminium-containing compounds preferably used as a compound of aluminum layered x-ray amorphous structure of the formula Al2ABOUT3mo2Oh, where n=0.3 to 1.5.

The connection of aluminum Al2ABOUT3nH2O, where n=0.3 to 1.5, preferably has a surface 50-250 m2/,

When applying the catalyst components is simultaneous formation and modification of the catalyst. The components of the catalyst dispersed in such a way that after termoobrabotannuju stable at elevated temperature structure and uniformly distributed in the aluminum oxide. Such a catalyst composition and the structure of the catalyst can significantly increase the activity and selectivity of it, with the catalysts have high strength and low sakartveloshi, long service life thanks to high stability of the inventive catalyst components in the x-ray amorphous state.

Use as promoters of the oxides of niobium and tantalum in a joint precipitation of aluminum salts with alkali in the presence of compounds of chromium, niobium and tantalum, as in U.S. patent 3791721, does not lead to a noticeable increase in the activity of the catalyst. We received an unexpected result: a large number of promoters used for the preparation of dehydrogenation catalysts, zirconium, comprising one or more metals from the group of niobium, hafnium, tantalum, leads to a significant increase in activity of catalysts with high selectivity.

Was prepared a number of catalysts, including as a promoter only zirconium, and a number of catalysts with niobium, tantalum and hafnium without zirconium. These catalysts showed significantly less activity.

Unlike known methods, the introduction of niobium and tantalum in metalcatalyzed. Use thermoactivation aluminum compounds of the formula Al2ABOUT3mo2Oh, where n=0,3-1,5, with a specific structure, when the heat treatment which together with the compounds of the precursors of the active component is the formation of the active component and obtained high strength catalyst with high activity and selectivity.

The proposed method allows to significantly simplify the technology for producing catalyst for the dehydrogenation of paraffins compared to existing methods by eliminating several stages of preparation of media, such as the precipitation of aluminium hydroxide, spray drying or forming pellets, heat treatment of the medium in comparison with the known solutions.

The method of obtaining the proposed catalyst is simple in technological performance and is as follows.

For the preparation of the catalyst is used as a compound of aluminum layered x-ray amorphous structure of the formula Al2ABOUT3mo2Oh, where n = 0.3 to 1.5, preferably with the surface of 50-250 m2/, This compound can be obtained by any known means, for example by rapid dehydration of hydrargillite. In Fig. 1,2 pok is built by the rapid dehydration of hydrargillite, and has a size of approximately 100 microns.

As compounds of alkali metal preferably using potassium.

Oxygen-containing compound of aluminum also may partially contain a compound of silicon as an impurity, and the necessary amount of silicon, if necessary, is introduced into the catalyst by impregnation.

In the proposed method, the impregnation takes place simultaneously or sequentially all the components of the catalyst by any known methods.

Determination of the phase composition of the materials used in the technology of preparation of the catalyst dehydrogenation, conduct radiographic technique based on x-ray diffraction. Survey samples is carried out in SiC-radiation using a differential discrimination of the monochromator. The interval of angles on a scale from 2 10 to 75o, the angular velocity detector 1/60o.

Specific surface area determined by BET method, the volume of pore - water adsorption, particle size - sieve method.

The abrasion resistance is determined by the mass fraction of the loss in catalyst attrition. The method is based on the destruction of the catalyst particles in the fluidized layer and measuring the mass of particles, unisen ageme solution

Example 1

The compound of aluminium of the formula Al2ABOUT3mo2Oh, where n = 0.7, in the form of microspherical powder with a particle size of from 100 to 200 microns, with S = 150 m2/g is loaded into propitiating. There also fill in an impregnating solution containing compounds of chromium, potassium, zirconium, and niobium. All components taken in such quantities, to ensure that after calcination the catalyst composition in terms of oxides, wt. %: chrome - 16, K - 1,5, zirconium - 1.0, niobium - 0,005, alumina - rest. The catalyst after drying, calcined at 750oC. the resulting catalyst has the composition shown in table 1, and its physico-chemical and catalytic properties are presented in table 2.

Examples 2-9

The catalyst is prepared analogously to example 1, except that the method of preparation differs structure used aluminum compounds, its specific surface area, composition and number of input promoters. Data about the connection of aluminum and compounds promoters are shown in table 1, and properties of the obtained catalysts in table 2.

Example 10

The catalyst is similar to example 1, only different composition and properties of aluminum compounds, composition and number of input promostar catalyst and its physico-chemical and catalytic properties are presented in tables 1, 2. The strength of the catalyst was determined by crushing the granules at the end.

Example 11 (prototype)

The compound of aluminium of the formula Al2ABOUT3nH2O (n=0,7) amorphous structure in the form of microspherical powder with a particle size of from 100 to 200 μm in a quantity of 25 kg load in propitiating with heating and stirring. There is poured a solution containing 5 kg of chromic anhydride, 460 g of potassium alkalis, 570 g of oxynitride zirconium and 150 g of tetraethoxysilane.

The impregnation is carried out at a temperature of 20oC for 1 h followed by drying in vacuum. The dried catalyst was calcined at 700oWith 6 h in a furnace of the fluidized bed. The composition of the obtained catalyst are presented in table 1, and its physico-chemical and catalytic properties in table 2.

Thus, the catalyst for dehydrogenation of hydrocarbons has increased strength, allowing not to harm the environment, and has high activity and selectivity in the process of dehydrogenation of hydrocarbons.

1. Catalyst for dehydrogenation of hydrocarbons comprising a chromium oxide compound of alkali and/or alkaline earth metal, zirconium dioxide and aluminum oxide, pretest fact, that it additionally contains at least one oxide promoter is selected from the group of niobium, tantalum, hafnium in an amount of 0.001-2 wt. %, and has the following composition, wt. % (based on oxide):

The chromium oxide (CR2ABOUT3) - 12-23

Zirconium oxide is 0.1 to 5

The oxide promoter is selected from the group of niobium, tantalum, hafnium is 0.001-2

Connection alkaline and/or alkaline earth metal of 0.5-3.5

Alumina - Rest

2. The catalyst p. 1, characterized in that formed in the process of thermo-activation of the aluminum compounds of the formula Al2O3mo2Oh, where n = 0.3 to 1.5, in conjunction with the compounds of the above elements.

3. The catalyst p. 1, characterized in that it has a value of specific surface area of 50-200 m2/,

4. The catalyst p. 1, characterized in that the aluminum oxide in its composition represents the gamma, γ + χ - phase.

5. The catalyst PP. 1-4, characterized in that the compound of aluminium of the formula Al2O3mo2Oh, where n = 0.3 to 1.5, has a layered x-ray amorphous structure with a value of specific surface area of 50-250 m2/,

6. The catalyst p. 1, characterized in that it further contains silica in an amount of 0.01-2%.

8. The catalyst PP. 1-7, characterized in that it has the following composition, wt. % (based on oxide):

The chromium oxide - 16

Zirconium oxide - 1

The oxide of niobium - 0,005

The potassium oxide is 1.5

Alumina - Rest

9. The catalyst p. 8, characterized in that it contains silica in an amount of 0.02 wt. %.

10. The method of producing catalyst for the dehydrogenation of hydrocarbons, including impregnation of aluminium-containing compounds layered x-ray amorphous structure of the formula Al2O3nH2O, where n = 0.3 to 1.5 solutions of chromium compounds, alkaline and/or alkaline earth metal, zirconium, drying and annealing at 700-800o, Characterized in that at the stage of impregnation impose additional promoter, at least one compound from the group of niobium, tantalum, hafnium, in the quantity necessary to obtain after heat treatment of the catalyst of the following composition, wt. % (based on oxide):

The chromium oxide (CR2ABOUT3) - 12-23

Zirconium oxide is 0.1 to 5

The oxide promoter is selected from the group of niobium, tantalum, hafnium is 0.001-2

Connection alkaline and/or deliciosamente terasawa connections use the connection of aluminium of the formula Al2O3mo2Oh, where n = 0,3-1,5, with a value of specific surface area of 50-2502/,

12. The method according to p. 10, characterized in that for the preparation of the catalyst is used as a compound of aluminium of the formula Al2O3mo2Oh, where n = 0,3-1,5-containing silicon oxide in an amount of 0.01-2 wt. %.

13. The method according to PP. 10-12, characterized in that the catalyst after calcination chrome compounds, alkaline and/or alkaline earth metal, zirconium, promoter uniformly distributed in the aluminum oxide and roentgenology.

 

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