RU2323777C1 - Catalyst and method to manufacture olefines from dimethyl ether in the presence thereof - Google Patents

Abstract

FIELD: CHEMISTRY.

SUBSTANCE: catalyst for synthesis of low molecular weight olefines from dimethyl ether is described. The catalyst is based on zeolites of pentasyl type with SiO₂|Al₂O₃=25-30, containing not more than 0.11% (wt.) of sodium oxide, containing zinc oxide, or zirconium oxide, or lanthanium oxide or binary mixtures thereof, and a bonding agent - aluminium oxide, component ratio being as follows, % wt.: zinc oxide 1.0-2.0 or zirconium oxide 0.5-0.8 or lanthanium oxide 0.5-0.8 or binary mixtures thereof 1.0-1.5 aluminium oxide 33.0-34.0 pentasyl type zeolite with SiO₂|Al₂O₃=25-30 and concentration of 0.11% (wt.) max sodium oxide balance. Method to manufacture low molecular weight olefines from dimethyl ether mixed with inert gas at elevated temperature and pressure in the presence of above described catalyst, dimethyl ether content in the raw material being up to 20% (vol.), is also described.

EFFECT: increase in catalyst activity and stability.

4 cl, 4 tbl, 24 ex

Description

The present invention relates to the field of production of lower olefins from non-oil feedstocks and catalysts for implementing this method.

The production of olefins is of great practical interest, since polymer fibers, plastics, rubbers, as well as non-ionic detergents, glycols, and ethylene oxide are produced on a large scale from them.

The demand for lower olefins, especially ethylene and propylene, is also increasing every year.

Currently, they are produced from petroleum feedstock either by non-catalytic pyrolysis of the gasoline fraction of oil, or by catalytic cracking of petroleum fractions upon receipt of motor fuels.

However, due to the constant increase in oil prices, the possibility of obtaining lower olefins from alternative carbon-containing raw materials of non-petroleum origin, in particular synthesis gas, attracts great attention of domestic and foreign researchers.

Most of the known developments for the production of olefins from DME are in the nature of laboratory studies.

Of the industrial developments, the most successful are Mobil's MTO methanol to olefins process, UOP and Norsk Hydro, and Lurgi, in which the process is carried out from synthesis gas obtained by natural gas conversion, mainly through methanol or methanol and dimethyl ether (DME ) An intermediate reaction for the conversion of methanol to olefins is the dehydration of methanol to dimethyl ether, followed by the conversion of dimethyl ether to lower C ₂ -C ₄ olefins, which are then converted to higher molecular weight olefins.

Analysis of numerous published patent and literature data relating to the synthesis of hydrocarbons, including lower olefins, from synthesis gas, showed that the process goes through the formation of intermediate products, which are methanol or dimethyl ether, or mixtures thereof, and foreign industrial developments can be divided into two large groups: processes using a zeolite catalyst of the ZSM-5 type and processes in which other catalysts are used to carry out this conversion.

So, in US patent No. 4072732 (C 07 With 1/20) and No. 4072733 (C 07 With 001/24) describes catalysts on traditional inorganic supports, such as Al ₂ About ₃ , SiO ₂ , ZrO ₂ , modified Al ₂ ( SO ₄ ) ₃ and Zr (SO ₄ ) ₂ . Catalysts are prepared by applying inorganic salts of Al or Zr to an inorganic substrate by impregnation.

The method of producing lower olefins from methanol and / or DME in the presence of these catalysts is carried out at T 200-400 ° C on a partially hydrated catalyst.

With a slight conversion of the feedstock (10%), the content of C ₂ -C ₄ olefins is 70 wt.%.

US patent No. 3911041 describes a zeolite catalyst modified with phosphorus compounds, for example trimethylphosphite. However, a process for preparing such catalysts requires anhydrous conditions and the use of toxic phosphorus compounds.

The disadvantages should also include a fairly low stability and selectivity for olefins. The latter indicator is due, in particular, to the significant amount of saturated and aromatic hydrocarbons formed.

Satisfactory results presented by Cai et aL, J. Appl. Cat. A: General 125,29-38 (1995) were obtained on SAPO-34 zeolite modified with additives of various metals: Ni, Ba, Ca, and Mg, which leads to an increase in olefin selectivity. The use of such a catalytic system allows to achieve a total content of C ₂ -C ₄ olefins of 90 wt.% With a conversion of feedstock close to 100 wt.%.

The disadvantage of the method for producing olefins in the presence of the described catalytic systems is the rather stringent reaction conditions (550 ° C), which is very undesirable for a zeolite-based catalyst, since coking occurs under such conditions and, as a consequence, deactivation.

Known siliceous catalyst H-FU-1, and a method for producing olefins C ₂ -C ₄ from MeOH and / or DME in its presence as described in U.S. Patent №4172856 (C 07 C 1/20). According to the patent, the highest total yield of ethylene and propylene was obtained at 425-525 ° C. The authors note that when using DME as a raw material, the conversion is higher compared to methanol.

The main drawback of the process for producing olefins C ₂ -C ₄ from MeOH and / or DME in the presence of the catalyst described above is also a high reaction temperature and consequently low stability due to coke formation. So, the drop in activity within 1 hour is about 50%.

In US patent No. 4393265 (C 07 With 1/24) as the catalyst used chabazite, modified Ba or Sr. The process is carried out in the presence of water, while the molar ratio of water to the starting material is (0.3: 1). Similarly to the previous patent, an advantage is shown in the quality of DME feedstock compared to methanol.

However, this catalyst also has low stability: in order to maintain 100% conversion at 460-550 ° C and atmospheric pressure, the catalyst should alternate with 20-60 minute regeneration cycles every 20 minutes.

US Pat. No. 4,247,731 (C 07 C 1/00) uses 13X zeolite modified with Mg and Mn in a process for producing lower C ₂ -C ₄ olefins at a temperature of 390 ° C and atmospheric pressure. The content of C ₂ -C ₄ olefins is about 72 wt.% At 60 wt.% The conversion of the feedstock, which, as in the previous patent, is preferred DME over methanol.

Using an industrial zeolite catalyst AGZ 50 containing rare earth oxides up to 2.57 wt.%, It is possible to increase the conversion of DME to 96 wt.%, And the content of C ₂ -C ₄ olefins to 94 wt.%. The patent lacks some initial data, which makes it impossible to evaluate the performance of the catalyst and its stability.

A known catalyst for the synthesis of monoolefins from methanol, dimethyl ether or mixtures thereof is described in US Pat. No. 4,613,720 (C 07 C 1/20), according to which crystalline aluminosilicate of the type chabazite, chabazite-erionite and erionite with a molar ratio of SiO ₂ | Al ₂ O ₃ = 12, containing 0.05-0.1 wt.% Sodium oxide, 0.5-3.0 wt.% Zinc oxide, rare earth oxides (REE) in an amount of 0.1-5.0 wt. .% and binder component. The catalyst is prepared by precipitation of boron-containing compounds at an atomic ratio of boron and aluminum of 1: 3.

The zeolites used in the composition of the indicated catalyst are obtained by direct synthesis or by exchanging the initial Na-form of the zeolite for an H ⁺ or NH ₄ ⁺ form.

A method of producing lower olefins in the presence of this catalyst is that a stream of methanol or dimethyl ether or a mixture thereof is fed to a zeolite catalyst with a bulk velocity of 0.5 h ⁻¹ at a temperature of 350-600 ° C and a pressure of 20-3000 kPa. In the conversion of 85 wt.% Get a mixture of low olefins - ethylene and propylene, the content of which in the products is 60 wt.%. Such results are achieved by contact of 0.3 g of feedstock per 1 g of catalyst.

The disadvantage of the described catalyst and the method for producing olefins in its presence is the low productivity of the process, the high reaction temperature and the need for catalyst regeneration every 30 minutes.

In addition, the described method leads to the formation of a large amount of water in the reaction zone, since water is added to the water that is already formed as a result of the process to ensure the stability of the catalyst.

The closest analogue is the catalyst for the synthesis of lower olefins according to US patent No. 5573990 based on zeolite type ZSM-5, modified with phosphorus, rare earth elements and a regulator of the porous structure.

The method of producing olefins - ethylene and propylene - from a mixture of methanol and dimethyl ether in the presence of this catalyst is a high-temperature, flow-through, non-cyclic process that is implemented in a system of reactors: a dehydration reactor and several adiabatic fixed-bed DME conversion reactors into which the catalyst is loaded into in the form of multi-stage packaging, and a regeneration cycle reactor.

The described catalyst has high activity and selectivity. Thus, the conversion of methanol in its presence is 100 wt.%, And the content of C ₂ -C ₄ olefins in the hydrocarbon portion of the products is 85 wt.% With a productivity of 0.7-1 tons of methanol / day for 600 hours.

The disadvantage of the described catalyst is its lack of stability and its forced regeneration every 24 hours.

In all the methods described above, including the prototype, highly diluted mixtures containing methanol and DME in an amount of not more than 3% are used as raw materials. However, for the industrial process for the production of olefins, working mixtures containing DME are all the more interesting, the higher the content of DME in them.

It should be noted that domestic development of industrial technologies for the production of lower olefins from methanol and dimethyl ether, similar to foreign ones, and there are no catalysts for such technologies at all.

Their reproduction in Russia is complicated, first of all, by the necessity of acquiring a catalyst abroad on a scale that allows introducing technology into Russian industry, which, of course, will increase the cost of the products obtained, but will not reduce the gap with the leading world companies.

Therefore, the task of creating a method for producing lower olefins from alternative non-petroleum feedstocks and catalysts exhibiting high stability with sufficient activity and selectivity is especially urgent for implementing this method in the conditions and scales of domestic industry.

The problem is solved in that a catalyst for the synthesis of lower olefins from dimethyl ether based on zeolites of the pentasil type with SiO ₂ | Al ₂ O ₃ = 30, containing not more than 0.11 wt.% Sodium oxide, which additionally contains either zinc oxide, or zirconium oxide, or lanthanum oxide, or their two-component mixtures in the following ratio of components, wt.%:

sodium oxide 0.08-0.11 zinc oxide 1.0-2.0 or zirconium oxide 0.5-0.8 or lanthanum oxide 0.5-0.8 or their two-component mixtures 1.0-1.5 aluminium oxide 33.0-34.0 silica rest

When it contains zinc oxide, boron and / or phosphorus in an amount of 0.5-1.5 wt.% With respect to the catalyst can be added to the composition of the catalyst.

The problem is also solved by the fact that in the method of producing lower olefins from dimethyl ether in a mixture with an inert gas at elevated temperature and pressure in the presence of a zeolite catalyst, the content of dimethyl ether in the feedstock is brought up to 20 vol.%, And the method is carried out in the presence of the described above the catalysts, and the process is carried out at a temperature of 340-400 ° C, a pressure of not higher than 10 atm and a feed rate of 2000-3000 hour ^-1

The invention allows

- create catalytic systems based on zeolites produced by domestic industry for the process of producing lower olefins from a mixture of dimethyl ether with an inert gas, which retain high activity. The DME conversion is 96-98 wt.% When the content of C ₂ -C ₄ olefins in the products is up to 86 wt.% Over a long period of time (100 hours). The content of the modifier in the catalyst is 0.5-1.5 wt.%.

The invention is illustrated by the examples below.

Preparation of catalysts.

Example 1-5.

The catalyst is prepared on the basis of a basic pentasil-type zeolite with a molar ratio of SiO ₂ | Al ₂ O ₃ = 30. The hydrogen form of the zeolite with a given residual content of sodium oxide in it of not more than 0.11 wt.% Is obtained by double exchange of Na ⁺ in 1 N. ammonium nitrate solution, followed by drying and calcination for 6 hours at 500 ° C. Metals are introduced into zeolite under conditions of ion exchange of its hydrogen form with aqueous solutions of salts of the corresponding metals. Modified by metal cations, the zeolite is mixed with a binder - aluminum hydroxide. The catalyst is molded by extrusion. The obtained catalyst granules are dried at 100-110 ° C for at least 6 hours, then calcined at 500 ° C for 6 hours. The composition of the obtained catalysts is given in table 1.

Table 1
The composition of the used catalysts Examples The zeolite content in the composition of the cat, wt.% Al ₂ About ₃ , wt.% Active element The content of the active component in the catalyst, wt.% one 65.0 33.0 Zn 2.0 2 65.0 34.0 Zn 1,0 3 66.0 33,2 Zr 0.8 four 66.5 33.0 Zr 0.5 5 66,2 33.0 La 0.8

Examples 6 and 8.

The catalyst is prepared analogously to example 2 with the difference that to change the acid properties of the zeolite, La and Zr are additionally introduced from aqueous solutions of the corresponding salts by the method of residual impregnation. The composition of the obtained catalysts is given in table.2.

Example 7

The catalyst is prepared analogously to example 4 with the difference that in order to change the acid properties of the zeolite, La is additionally introduced from the aqueous solution of the corresponding salt by the method of residual impregnation. The composition of the obtained catalysts is given in table.2.

table 2
The composition of the used catalysts Examples The zeolite content in the composition of the cat, wt.% Al ₂ About ₃ , wt.% Active elements The content of the active component in the catalyst, wt.% 6 65.5 33.0 Zn 1,0 La 0.5 7 65.8 33.2 Zr 0.5 La 0.5 8 65.5 33.0 Zn 1,0 Zr 0.5

Example 9-11

The catalyst is prepared analogously to example 2 with the difference that to change the acidity spectrum in the zeolite, boron and / or phosphorus is additionally added as a modifier in an amount of 0.5-1.5 wt.% With respect to the entire catalyst by impregnation.

The composition of the obtained catalysts is given in table.3.

Table 3
The composition of the used catalysts Examples The zeolite content in the composition of the cat, wt.% Al ₂ About ₃ , wt.% Active element, wt.% Modifier The modifier content in the catalyst, wt.% 9 65.5 33.0 1,0 R 0.5 10 65,2 33.0 1,0 AT 0.8 eleven 64.5 33.0 1,0 R 1,0 AT 0.5

The method of producing olefins.

Environmentally friendly lower olefins are obtained from raw materials containing up to 20 wt.% DME in the presence of the catalysts described above, and the gas mixture is fed into the reactor with a space velocity of 2000-3000 h ^-1 . The presence in the feed of various amounts of hydrogen, carbon oxides, nitrogen, methane, methyl alcohol. Their content depends on the composition of the initial synthesis gas and the mode of synthesis of DME, and in this case, special treatment of the raw material is not required.

Example 12 (comparative).

A catalyst based on domestic NTsVM (SiO ₂ | Al ₂ O ₃ = 30) with a binder Al ₂ O _{3 is} used to obtain olefins from raw materials containing dimethyl ether in a flow isothermal reactor using a gas mixture containing DME and nitrogen as feed DME concentration of 20 vol.% at a temperature of 340 ° C, a pressure of 0.3 MPa, a space velocity of the gas mixture of 2000 hours ^-1. Before the experiment, the catalyst is activated in an inert gas stream at atmospheric pressure with a temperature rise of 50 ° C per hour. Upon reaching the operating temperature, the catalyst is maintained at this temperature for 2 hours. Then the gas supply is stopped and the supply of feedstock begins.

Gaseous hydrocarbons formed during the experiment are analyzed by chromatographic method. Product identification is carried out using chromatography-mass spectroscopic analysis. Data processing is carried out using the Ekohrom computer program. The error in determining the content of individual components in the mixture does not exceed 5 rel.%. The DME conversion is 98 wt.% With the composition of hydrocarbons, wt.%: Methane 1.3; C ₂ -C ₅ olefins 38.7; paraffins 11.2.

Example 13 (comparative prototype).

The reaction is carried out analogously to example 18, where ZSM with a binder is used as a catalyst. The DME conversion is 98 wt.% With the composition of hydrocarbons, wt.%: Methane 1.1; olefins C ₂ -C ₅ 31.7; paraffins 19.4, the rest - hydrocarbons With ₆ and above.

Examples 14-24.

The catalysts obtained in examples 1-11 are used to obtain olefins from raw materials containing 10-20 vol.% DME in a flow isothermal high-pressure reactor at a temperature of 340-400 ° C, a pressure of 3 MPa, a volumetric feed rate of 2000-3000 h ^-1 . The results are presented in table 4.

Table 4
The composition of the products Examples Example cat % DME V, hour ^-1 T °, C The composition of hydrocarbons, wt.% C ₁ C ₂ = C ₃ = Olefins C _2-5 Paraffins C ₅ ⁺ fourteen one
(Zn 2.0) 10 2000 375 2.6 15.7 27.6 53.1 11.3 fifteen 2
(Zn 1.0) 10 2000 340 1.8 35.3 28.7 69.9 10.8 375 1,5 10.5 26.6 41.7 17.7 400 2.0 11.6 26.9 44.8 16,2 16 5
La 10 2000 340 1.8 16.3 23.1 49.8 21.7 375 5.7 16,4 25.5 52.3 14.6 17 four
(Zr 0.5) 10 2000 340 1,5 30.8 26.2 67.2 10,2 375 2,8 14.5 24.2 46.6 14.6 400 3,5 17.3 22.1 50,4 13.7 eighteen 3
(Zr 0.8) 10 2000 340 1.9 23.1 25.7 63.9 18.1 375 3.3 19.0 24.6 54.8 21.7 400 7.9 14.3 23.1 46.9 14.6 19 8
P twenty 3000 330 2,4 24.9 38.7 81.9 5,6 340 2,4 19.8 24.9 61.5 eleven, 400 2.6 12.9 33.9 56.2 10.9 twenty 9
AT twenty 3000 360 2.1 30.5 41.1 80.3 4.8 380 2.7 27.5 42.3 82,4 8.5 21 9
R, B twenty 3000 360 2.1 31.5 43.1 82.3 4.3 380 2.7 29.5 45.8 85,4 7.5 22 6
Zn, La 10 2000 340 2.9 20.1 26.2 56.5 21.6 375 4.2 23 30.5 69.8 4,5 400 7.9 10,2 24.3 46.1 15.0 23 7
Zr, La 10 2000 340 2,5 26 44,4 80,4 7.9 375 5 21.5 30.8 63 15.0 400 9.5 22 36,2 64.6 13.6 24 one
Zn
0.5 Zr 10 2000 340 1,5 20.6 30,4 59.6 11.0 375 1.7 16,2 25.0 50.8 14.5 400 2.6 14.6 30,0 51.3 10.7

Claims (4)

1. The catalyst for the synthesis of lower olefins from dimethyl ether based on zeolites of the pentasil type with SiO ₂ | Al ₂ O ₃ = 25-30, containing not more than 0.11 wt.% Sodium oxide, characterized in that the catalyst additionally contains zinc oxide, or zirconium oxide, or lanthanum oxide, or their two-component mixtures and a binder - aluminum oxide in the following ratio of components, wt.%: zinc oxide 1.0-2.0 or zirconium oxide 0.5-0.8 or lanthanum oxide 0.5-0.8 or their two-component mixtures 1.0-1.5 aluminium oxide 33.0-34.0 pentasil type zeolite with SiO ₂ | Al ₂ O ₃ = 25-30 and content not more than 0.11 wt.% sodium oxide rest 2. The catalyst according to claim 1, characterized in that when it contains zinc oxide, it additionally contains, as a modifier, boron and / or phosphorus in an amount of 0.5-1.5 wt.% With respect to the catalyst. 3. A method of producing lower olefins from dimethyl ether in a mixture with an inert gas at elevated temperature and pressure in the presence of a zeolite catalyst, characterized in that the content of dimethyl ether in the composition of the feedstock is adjusted to 20 vol.%, And the catalyst is used as a catalyst according to any from claim 1 or 2. 4. The method according to claim 3, characterized in that the process is carried out at a temperature of 340-400 ° C, a pressure of not higher than 10 atm and a feed rate of 2000-3000 h ^-1 .