The way to obtain olefinic hydrocarbons

 

(57) Abstract:

Usage: chemical industry. Olefinic hydrocarbons obtained by dehydrogenation of the corresponding paraffin hydrocarbons in the presence of a catalyst composition, wt.%: Cr2O310,0-30,0; B2O30.1 to 1.5; Me2O 0,5-2,5; SiO20,5-2,0; Al2O3else, where Me is an alkaline metal. The process is carried out at a temperature of 500-650C., a pressure of 1-2 atmospheres absolute and a flow rate of 100-500 h-1. After dehydrogenation catalyst is sent for regeneration. The technical result is an increase in the yield of target products. 8 C.p. f-crystals, 1 table.

The present invention relates to the field of production of olefinic hydrocarbons, in particular olefinic hydrocarbon, C2-C20by dehydrogenation of the corresponding paraffin hydrocarbons.

Olefinic hydrocarbons are important intermediate compounds for the production of many large-scale products of polypropylene and polybutylene; synthetic rubbers; high-octane additives to motor fuels (MHBA), etc.

Traditional sources (e.g., cracking) can not meet the growing demand for olefinic hydrocarbons. the which is the dehydrogenation of the corresponding paraffin hydrocarbons.

This reaction proceeds with the absorption of heat and is governed by thermodynamic equilibrium. Environmentally acceptable outputs of olefinic hydrocarbons is achieved only at temperatures above 500oC, but the reaction rate is low and therefore requires the use of a catalyst. The catalyst should provide high outputs of olefinic hydrocarbons and possess thermal stability. The inevitable formation on the catalyst surface coke causes progressive loss of catalytic activity and the need for periodic regeneration. Regeneration is carried out usually at temperatures above 600oC, and the catalyst must maintain their characteristics under these conditions for a long time.

Known methods for producing olefinic hydrocarbons by dehydrogenation at elevated temperatures corresponding paraffin hydrocarbons in the presence of catalytic compositions based on noble metals (U.S. patent N 3531543, 4786625. European patent N 351067), and also on the basis of metal oxides in the presence of promoters, in most cases, this is caused chromium oxide (U.S. patent N 2945823, 2956030, 2991255 and the United Kingdom patent N 2162082).

However, both ODI at the stage of regeneration with the aim of preserving the activity of noble metals, for example, processing of chlorine containing substances with subsequent restoration (U.S. patent N 4438288). Structures on the basis of chromium oxide supported on aluminum oxide, silicon oxide, aluminum oxide - silicon oxide, etc. have insufficient selectivity and activity.

Closest to the proposed is a method for olefin hydrocarbons by dehydrogenation of the corresponding paraffin hydrocarbons in the presence of a catalyst composition, wt.%:

Cr2O3- 6,0-30,0

SnO - 0,1-3,5

Me2O - 0,4-3,0

SiO2- 0,08-3,0

Al2O3- Rest

The process is carried out at a temperature of from 450 to 800oC, a pressure of from 0.1 to 3 ATM. abs. and flow rate from 100 to 1000 h-1. (RF patent N 2127242, 10.03.99, bull.N 7).

The output of the olefin used in this method is not high enough due to lack of high activity and selectivity of the catalyst.

The problem solved by the present invention is to increase the efficiency of the process of dehydrogenation of paraffin hydrocarbons.

We propose a method of obtaining olefinic hydrocarbons by dehydrogenation of the corresponding paraffin hydrocarbons in the presence of a catalyst - 0,5-2,0

Al2O3- Rest

where Me is an alkaline metal.

The process is carried out at a temperature of 500-650oC, a pressure of 1-2 atmospheres absolute and bulk gas velocity from 100 to 500 h-1. After the stage of dehydrogenation catalyst is directed pas regeneration.

Preferred are embodiments of the new method:

- use a catalyst containing Al2O3in gamma; Delta; theta; gamma Delta; Delta and theta; or gamma, Delta and theta phases; use catalyst composition, wt.%:

Cr2O3- 5,0-25,0

B2O3- 0,1-0,5

Me2O - 0,8-1,6

SiO2- 0,7-1,5

Al2O3- Rest

where Me is an alkaline metal

as the alkali metal used potassium

in the composition of the catalyst used Al2O3with a specific surface area of less than 200 m2/g

the dehydrogenation and regeneration is carried out in a fluidized bed of catalyst

- dehydrogenation in a fluidized bed of catalyst is carried out at a temperature 530-620oC, atmospheric or slightly greater atmospheric pressure, the flow rate of gas from 100 to 500 h-1and time spent catalyst, and the residence time of the catalyst is from 10 to 15 minutes

- regeneration of the catalyst in the fluidized bed is carried out in the presence of air or other oxygen-containing gas at a temperature of 630-670oC, atmospheric or slightly greater atmospheric pressure, the flow rate of gas from 100 to 500 h-1and residence time of the catalyst in the regeneration zone from 15 to 45 minutes.

The use in the present conditions of the dehydrogenation catalyst, which includes boron oxide, reduces coke formation, contributes to a more complete and rapid oxidation-vostanovitel reactions on the catalyst, which increases the activity and selectivity of the process, thus increasing the yield of olefinic hydrocarbons.

Process for the catalytic system used in the new method consists in dispersing chromium compounds, alkali metal and boron on the carrier consisting of oxides of aluminum and silicon or dispersion of chromium compounds and alkali metal on a carrier consisting of oxides of aluminum, silicon and boron.

The claimed process can be applied to any dehydrogenation in a fixed, fluidized or driving oasa from the reactor, in which the dehydrogenation reaction, and the regenerator, where the catalyst surface burns the coke formed in the reactor, and recovering the activity.

The catalyst in the fluidized state, continuously circulates in the system of the reactor - regenerator. The regenerated catalyst is cooled, to sum required for the reaction heat, which allows to carry out the process continuously.

In the reactor the catalyst is maintained in fluidized condition by using vapor paraffin hydrocarbons that enter the catalyst bed through a special distribution system, providing uniform distribution over the cross section of the device.

Contact the gas after separation of the catalyst from the cyclones or other systems dust collection is cooled, heating fed to the reactor raw materials, and comes in a partition separating. Target olefins are sent to the warehouse, unreacted paraffins are recycled to the process and by-products (light hydrocarbons) can be used in the regenerator as fuel.

In the reactor the catalyst moves countercurrent with respect to the gas phase - pairs of hydrocarbons. In signapur in the reactor, and the catalyst in the fluidized state, is sent to the regenerator.

In the reactor, it is preferable to have the following operating conditions:

- temperature from 530 to 620oC (supported by a stream of regenerated catalyst having the desired temperature)

- atmospheric pressure or slightly above atmospheric

- the volumetric rate of from 100 to 250 h-1(normal m3/h gas m3catalyst)

the residence time in the reaction zone 10-15 minutes in the desorption zone 1-5 minutes

To prevent back-mixing and proximity of the operating conditions of the reactor to the model of ideal displacement is advisable to install the partitioning grid. Lattice with a free cross-sections from 10 to 50% (preferably from 10 to 30%) are installed horizontally at a distance of from 30 to 50 cm from each other.

The system of pneumatic transport from the reactor to the reactor consists of a transport line with at least one zone in which the catalyst moves in the downward direction and which is supported by the intermediate terms of the minimum fluidization to a minimum the formation of bubbles by introducing the appropriate amount of gas in the line is edenia carrier gas into the base, that significantly reduces the density of the fluid. The catalyst coming from the reactor to the regenerator, evenly distributed over the surface of the fluidized bed. Regeneration occurs within a layer by burning coke deposited on the catalyst, and heating - fuel combustion on the catalyst surface in the presence of air or other oxygen-containing gas at a temperature that is above average reactor temperature. The regenerated catalyst to the feed to the reactor is recovered at a temperature of 630-680oC for 1 to 5 minutes in order to remove compounds hexavalent chromium formed in the regenerator.

In the regenerator is also used by the countercurrent principle: air is supplied to the bottom of the apparatus, the catalyst moves downward. The fuel gas is fed to the desired height of the layer.

The gas leaving the regenerator consists of nitrogen, oxygen and combustion products. After treatment of the catalyst in the dust collection system, located in the upper part of the regenerator, the gas is used to preheat the air required for the combustion process. Prior to release into the atmosphere, the flue gases are cleaned by a filter system or other devices to reduce the soda is of oxides of nitrogen and carbon monoxide are very few and cleaning are not required. Working pressure in the regenerator is preferably atmospheric or slightly above atmospheric, the volumetric rate of gas from 100 to 500 h-1temperature 630-670oC and the residence time of the catalyst 30 to 45 minutes. The regenerated catalyst is passed to the reactor in the same way that zakochany the catalyst in the regenerator.

System reactor - regenerator made in this way allows you to maintain constant the parameters and characteristics of the process throughout the life of the installation.

If necessary, a portion of the catalyst may be discharged from the system and replaced with fresh catalyst without interrupting plant operation.

The benefits of using a process of dehydrogenation in a fluidized bed can be summarized as follows:

- no heat transfer surface, heat is transferred directly in the reaction with the regenerated catalyst; strong mixing of the fluidized bed prevents local overheating, which reduces the selectivity of

- an optimum temperature profile in the reactor

is a continuous process and there is no need to change the settings during the entire period of operation

- Usti) with virtually no decline

- reaction and regeneration occur in a variety of vehicles, so the mixing of hydrocarbon streams with streams containing oxygen is excluded

the process takes place at atmospheric pressure or slightly above, which eliminates the ingress of air into the reaction zone.

The invention is illustrated by the following examples.

Example 1.

Resulting pseudoboehmite with the addition of silicon oxide (1.5 wt%), having a particle diameter of from 5 to 250 microns, was obtained by spray-drying a suspension of pre-hydrogenated aluminum oxide, to which the hydration add silicic acid. Sample pseudoboehmite is subjected to heat treatment consisting of heating at a temperature of 150oC for 2 hours and calcination at 800oC for 4 hours in air flow.

The resulting product had a specific surface area of 170 m2/g, a porosity of 0.39 g/cm3and consisted mainly of gamma, Delta and theta transition alumina.

200 g of this alumina was impregnated, using the technique of "initial" moisture, aqueous solution (78 cm3containing of 67.1 g CrO3(and 99.8 wt.%), are 5.36 g of KOH (85%) and 0.5 g of H3BO3(and 99.8 wt.%) in neionizirovanne is sutured at a temperature of 90oC for 6 hours. The dried product was activated in a current of air at a temperature of 700oC for 4 hours.

Obtain a catalyst having the following composition, wt%:

Cr2O3- 20,0

K2O - 1,5

SiO2- 1,2

B2O3- 0,1

Al2O3- Rest

The resulting catalyst was tested in the process of dehydrogenation of isobutane and propane, performed at a temperature of 540-600oC, space velocity of the raw material 250 - 500 l of reagent/l catalizadores in laboratory quartz reactor at close to atmospheric pressure. The catalytic cycle that simulates carrying out the reaction in an industrial reactor consists of a reaction phase, in which the hydrocarbons are served within 15 minutes, the phases of the purge, when nitrogen is passed for 10 minutes to release the catalyst from the absorbed products of the dehydrogenation reaction, the regeneration phase when the regenerator the gas is fed to the regeneration air for 30 minutes (in these experiments), and again the blowdown phase when nitrogen is passed for 10 minutes to release the catalyst from the adsorbed reaction products of regeneration. Nitrogen and air are fed with the same volumetric rate as ua require regeneration at temperatures higher reaction temperatures: in this case, regeneration and restoration was carried out at 650oC, whereas the dehydrogenation was carried out at 540-600oC. the results are shown in the table.

Example 2.

Analogously to example 1 to obtain a catalyst having the following composition, wt.%:

Cr2O3- 15,0

K2O - 1,5

SiO2- 1,25

B2O3- 0,3

Al2O3- Rest

The resulting catalyst was tested in the process of dehydrogenation of isobutane and propane, as described in example 1. The results are shown in the table.

Example 3.

Analogously to example 1 to obtain a catalyst having the following composition, wt.%:

Cr2O3- 25,0

K2O - 0,8

SiO2- 1,1

B2O3- 0,6

Al2O3- Rest

The resulting catalyst was tested in the processes degidrirovaniya isobutane and propane, as described in example 1. The results are shown in the table.

Example 4

Analogously to example 1 to obtain a catalyst having the following composition, wt.%:

Cr2O3- 30,0

K2O - 1,5

SiO2- 0,5

B2O3- 0,2

Al2O3- Rest

Receive what you see in the table.

Example 5.

Analogously to example 1 to obtain a catalyst having the following composition, wt.%:

Cr2O3- 10,0

K2O - 2,5

SiO2- 1,3

B2O3- 1,5

Al2O3- Rest

The resulting catalyst was tested in the process of dehydrogenation of isobutane and propane, as described in example 1. The results are shown in the table.

Example 6.

Analogously to example 1 to obtain a catalyst having the following composition,wt. %:

Cr2O3- 20,0

K2O - 1,7

SiO2- 2,0

B2O3- 0,1

Al2O3- Rest

The resulting catalyst was tested in the process of dehydrogenation of isobutane and propane, as described in example 1. The results are shown in the table.

1. The way to obtain olefinic hydrocarbons by dehydrogenation of the corresponding Parfenovich hydrocarbons in the presence of a chromium catalyst with subsequent regeneration, characterized in that the use of the catalyst composition, wt.%:

Cr2O3- 10,0 - 30,0

B2O3- 0,1 - 1,5

Me2O - 0,5 - 2,5

SiO2- 0,5 - 2,0

Al2O3- Rest

where Me is an alkaline metal and dehydrogenation Khujand is CLASS="ptx2">

2. The method according to p. 1, characterized in that the use of catalyst containing Al2O3in gamma-, Delta-, theta-, gamma -, and Delta-Delta and theta or gamma-, Delta - and theta phases.

3. The method according to p. 1, characterized in that the use of the catalyst composition, wt.%:

Cr2O3- 15,0 - 25,0

B2O3- 0,1 - 0,5

Me2O - 0,8 - 1,6

SiO2- 0,7 - 1,5

Al2O3- Rest

where Me is an alkaline metal.

4. The method according to p. 1, characterized in that the use of catalyst containing as an alkali metal is potassium.

5. The method according to p. 1, characterized in that the use of Al2O3with a specific surface area of less than 200 m2/,

6. The method according to p. 1, characterized in that the dehydrogenation and regeneration is carried out in a fluidized bed of a catalyst.

7. The method according to p. 6, characterized in that the dehydrogenation is carried out at a temperature of 530 - 620oC, atmospheric or slightly greater atmospheric pressure, volumetric gas velocity of 100 to 500 h-1and residence time of the catalyst in the reaction zone 5 - 25 minutes

8. The method according to p. 7, characterized in that the volumetric rate of gas is 100 to 250 h-1and stay Catalina carried out in the presence of air or other oxygen-containing gas at a temperature of 630 - 670oC, atmospheric or slightly greater atmospheric pressure, volumetric gas velocity of 100 to 500 h-1and residence time of the catalyst in the regeneration zone 30 - 45 minutes

 

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