PL200220B1 - Method for obtaining ethylene - Google Patents

Abstract

A method for obtaining ethylene from ethane by oxidative dehydrogenation of ethane, comprising contacting, at a temperature of 523 to 923 K, ethane and oxygen or a gas containing oxygen with a catalyst bed comprising molecular sieves, characterized in that the catalyst comprises a microporous metal silicoaluminophosphate molecular sieve with a chabazite structure, with a pore diameter of less than or equal to 0.43 nm, with atoms of silicon, manganese, cobalt and optionally atoms of at least one metal from the group comprising iron, magnesium, zinc incorporated into the aluminophosphate crystal lattice, wherein the crystal lattice of the molecular sieve also contains cations

Description

The subject of the invention is a method for obtaining ethylene from ethane by oxidative dehydrogenation of ethane.

Methods for obtaining ethylene from ethane in the presence of catalysts are known. These involve catalytic dehydrogenation or oxidative dehydrogenation of ethane.

The oxidative dehydrogenation process involves simultaneously achieving equilibrium dehydrogenation of ethane to ethylene and burning the resulting hydrogen to shift the reaction equilibrium toward ethylene. Various oxidizing gases, including oxygen, air, carbon monoxide, carbon dioxide, and nitrous oxide, are used for the oxidative dehydrogenation of ethane.

Known catalysts for the oxidative dehydrogenation of ethane include metals from groups II to VIII of the periodic table, their alloys, solid metal solutions, salts in which metal atoms exist as cations or anions, reducible or irreducible metal or phosphorus oxides with added promoters, which are salts or oxides of elements from groups I, II, and IIIb of the periodic table, or chromium. These catalysts can be formulated or deposited on supports containing oxides, carbonates, or phosphates of elements from groups IIa, IIIa, and IV of the periodic table, ceramic monoliths, and activated carbon.

Other known catalysts for oxidative dehydrogenation of ethane include zeolites with MFI, BEA, FER, MOR, and FAU structures modified with cations of cadmium, barium, lithium, sodium, potassium, iron, gallium, zinc, cobalt, and silver. MFI zeolites containing platinum, tin, or at least one metal from the group consisting of chromium, molybdenum, gallium, zinc, Group VIII metals of the periodic table, and at least one metal oxide from the group: bismuth, indium, antimony, zinc, thallium, lead, tellurium, and titanium are also known. These zeolites can be pressed or extruded using carriers such as silicon, aluminum, zirconium, titanium, hafnium, and mixtures of these oxides.

Known catalysts are also crystalline metallosilicates with the MFI structure having isomorphically substituted iron, gallium and boron atoms in the crystal lattice in place of silicon atoms, and molecular sieves of the MCM-41 type containing chromium and vanadium.

Known catalysts for oxidative dehydrogenation of ethane are MeAPO-5 aluminophosphate molecular sieves with an AFI structure containing vanadium, cobalt, and/or magnesium atoms in the crystal lattice. Depending on the catalyst used, oxidative dehydrogenation and/or ethane dehydrogenation processes are carried out at temperatures ranging from about 250 to about 800°C.

The method known from United States Patent No. 6,512,144 is a process of oxidative dehydrogenation of light paraffins, including ethane, carried out at temperatures from 250 to 650°C at pressures up to 0.5 MPa, at a weight hourly catalyst load (WHSV) from about 100 to about 10,000 h ¹ , at a paraffin to O 2 ratio from about 1:10 to about 5:1. The process involves contacting a hydrocarbon with a catalyst containing crystalline manganese phosphate in the presence of oxygen or an oxygen source. Crystalline manganese phosphate has a one-, two- or three-dimensional crystal lattice, optionally microporous, and the empirical formula in the anhydrous state is (A)v(Mn)(M) _x PyO _z , wherein A is a structure-determining factor selected from the group consisting of alkali metals, alkaline earth metals (except calcium), hydronium ion, organoammonium ions, silver, copper (II), zinc (II), nickel (II), mercury (H), cadmium (II) and mixtures thereof, M is a metal from the group: aluminum, iron, gallium, tin, titanium, antimony, silver, zinc, copper, nickel, cadmium and mixtures thereof, "x" is from 0 to about 3, "v" is from 0.1 to 10, "y" is from 0.05 to about 8.0, "z" is expressed by the formula z = 1/2(av+b+xc+5y), wherein "a" is the weighted average valence of A and ranges from 1 to about 2, "b" is the weighted average valence of Mn and ranges from 2 to about 3, "c" is the weighted average valence of M and ranges from 1 to 5. The oxygen source may be oxygen, oxygen diluted with an inert gas, or lattice oxygen from manganese phosphate.

Known methods use crystalline metalloaluminophosphates with pore diameters greater than or equal to 0.7 nm. In the channels of such molecular sieves, secondary recombination processes of dehydrogenation, alkylation, isomerization, and cyclization products can occur after ethane dehydrogenation, which reduces the selectivity of the oxidative dehydrogenation of ethane.

It has surprisingly turned out that the method according to the invention can achieve very high selectivities in the process of oxidative dehydrogenation of ethane to ethylene using pure oxygen, air or a gas containing oxygen in the molecule, optionally diluted with an inert gas, as the oxidizing agent.

The method according to the invention for obtaining ethylene from ethane by oxidative dehydrogenation of ethane, comprising contacting, at a temperature of 523 to 923 K, ethane and oxygen or an oxygen-containing gas with a catalyst bed comprising molecular sieves, is characterized in that the catalyst comprises a microporous metal silicoaluminophosphate molecular sieve with a chabasite structure, with a pore diameter of less than or equal to 0.43 nm, with atoms of silicon, manganese, cobalt and optionally atoms of at least one metal from the group comprising iron, magnesium, zinc incorporated into the aluminophosphate crystal lattice, wherein the crystal lattice of the molecular sieve also contains cations.

The molecular sieve may contain at least one type of cation from the group consisting of manganese, cobalt, iron, magnesium, zinc, lithium, sodium, potassium, rubidium, cesium, barium, cadmium, calcium, beryllium, copper, hydrogen.

In the process for obtaining ethylene from ethane according to the invention, a catalyst consisting of a mixture of metal silicoaluminophosphate sieves can be used, wherein at least one sieve has a chabazite structure.

The method of the invention can utilize a catalyst in the form of molecular sieves deposited on a support in a known manner, crystallized on the support, compressed, or formed using compounds of elements from groups IIa, IIIa, IV, and V of the periodic table, such as oxides, carbonates, silicates, phosphates, aluminosilicates, aluminophosphates, aluminosiliconphosphates, and silicophosphates. The molecular sieve can also be deposited on activated carbon or formed with activated carbon. The molecular sieve can be deposited on monolithic or metallic shapes.

The process of the invention involves the production of ethylene by oxidative dehydrogenation and/or dehydrogenation of ethane at a molar ratio of ethane to oxygen as in known processes. This may be from about 1:10 to about 10:0.1. The oxygen source may be oxygen, air, or other oxygen-containing gases.

The oxidative dehydrogenation of ethane method according to the invention involves catalytic dehydrogenation of ethane, combustion of the resulting hydrogen to produce water, and combustion of some of the dehydrogenation products, possibly cracking, to produce carbon monoxide and carbon dioxide. While combustion of some of the carbon products reduces the process efficiency, it prevents catalyst coking. Depending on the composition of the reaction gases and the process conditions, ethane conversion rates of up to 20% and ethylene selectivity of up to 90% are achieved, with trace amounts of organic oxygen-containing compounds detected in the products. Catalysts are subject to very little coking.

The method according to the invention for obtaining ethylene from ethane is illustrated by examples.

Examples I-VII

Catalysts were placed in heated, tubular, flow-through reactors. The catalysts were chabazite-structured metallosiloxane-aluminophosphate molecular sieves containing silicon, cobalt, and manganese atoms, silicon, cobalt, manganese, and iron atoms, silicon, cobalt, manganese, and zinc atoms, and silicon, cobalt, manganese, and magnesium atoms embedded in the aluminophosphate crystal lattice. The catalyst compositions were characterized by the content of Si, Co, Mn, Fe, Mg, and Zn atoms, expressed as weight percent in the dehydrated molecular sieves. After dehydrating the catalysts at 523-823 K and flushing the air contained in the catalyst pores with an inert gas, gas mixtures containing ethane, nitrogen, and oxygen in various molar ratios were passed through the sieves. The process temperatures and reactant flow rates were varied. The obtained results of ethane conversion and ethylene production selectivity are summarized in Tables 1 and 2.

Examples VIII and IX

Chabazite molecular sieves containing lithium or cadmium cations in amounts of 2.3% Li by weight and 3.2% Cd by weight, respectively, were placed in heated tubular flow reactors. After dehydrating the catalysts at 523-823 K and flushing the air contained in the catalyst pores with an inert gas, gas mixtures containing ethane, nitrogen, and oxygen in various molar ratios were passed through the sieves. The process temperatures and reactant flow rates were varied. The obtained results regarding ethane conversion and ethylene production selectivity are presented in Table 2.

Examples X-XIII

Chabazite molecular sieves were formed into extrudates using the following binders: alumina, silica, and silicoaluminophosphate. The molecular sieve contents in the catalysts were 50, 52, and 51% by weight, respectively. The extrudates were placed in heated tubular flow reactors. After dehydrating the catalysts at 523-823 K and flushing the air contained in the catalyst pores with an inert gas, gas mixtures containing ethane, nitrogen, and oxygen in molar ratios of 1/0.7/24 were passed through them.

PL 200 220 B1 the hourly catalyst load (VHSV) was 20000 h ¹ . At a temperature of 768 K, the ethane conversion rates were 10, 12 and 13%, respectively, and the ethylene production selectivities were 75.2; 74 and 78 mol%.

Example XIV

A catalyst containing 10% by weight of molecular sieves with a chabazite structure deposited on a support with the following composition: AhO3 - 67.5%, SiO2 - 25.7%, Na2O - 1.2%, BaO - 0.3%, MgO - 5.3% by weight was placed in a tubular reactor. After dehydration of the catalyst at a temperature of 523-823 K and washing out the air contained in the catalyst pores with an inert gas, a gas mixture containing ethane, nitrogen, oxygen in molar ratios of 1/4/80 was passed through it at a temperature of 923 K at VHSV = 10,000 h-1. 19.2% of ethane conversion was obtained, and the selectivity of ethylene production was 62%.

T a b l e 1

Example Catalyst Si Me Contents Process temperature C2H6:O2:N2 ratio VHSV Ethane conversion Ethylene selectivity % wt. K mol/mol/mol ή' ¹ % % And Catalyst 1 Si - 6.89 573 1/5/1.5 1000 5.6 74.3 What - 0.86 723 1/0,1/32 2000 6.5 89.4 Mn - 0.76 923 1/9/50 10000 19.0 60.2 II Catalyst 2 Si - 6.80 573 1/5/1.5 1000 6.5 80.5 What - 0.67 723 1/0,1/32 2000 7.3 85.2 Mn - 0.65 823 1/9/50 10000 20.0 60.0 Fe - 0.73 III Catalyst 3 Si- 6.50 573 1/5/1.5 1000 6.0 75.2 What - 0.65 723 1/0,1/32 2000 7.5 86.5 Mg - 0.77 823 1/9/50 10000 19.5 62.1 Mn - 0.63 IV Catalyst 4 Si - 6.20 573 1/5/1.5 1000 8.2 71.2 What - 0.90 723 1/0,1/32 2000 6.2 89.9 Mn - 0.80 823 1/9/50 10000 18.7 60.7 Zn - 0.42

T a b l e 2

Example Catalyst Si Me Contents Process temperature C ₂ H ₆ :O 2 :N ₂ ratio VHSV Ethane conversion Ethylene selectivity % wt. K mol/mol/mol h ^-1 % % 1 2 3 4 5 6 7 8 V Catalyst 5-95% Si - 6.89 Si - 7.00 573 1/5/1.5 1000 9.0 Catalyst 6-5% What - 0.86 What - 0.95 723 1/0,1/32 2000 6.0 Mn - 0.76 Mn - 0.90 823 1/9/50 10000 19.9 VI Catalyst 1-92.8% Si - 6.89 573 1/5/1.5 1000 8.7 73.1 Catalyst 6-7% What - 1.10 723 1/0,1/32 2000 7.0 90.0 Catalyst 7-0.2% Mn - 0.98 823 1/9/50 10000 18.5 63.1

PL 200 220 B1 continued from Table 2

1 2 3 4 5 6 7 8 VII Catalyst 2-50% Si - 9.02 573 1/5/1.5 1000 10.7 77.0 Catalyst 4-25% Cs - 0.35 723 1/9.9/32 2000 18.7 60.1 Catalyst 3 25% Fe - 0.35 823 1/0.08/50 10000 9.3 90.0 Mg - 0.40 Mn - 0.25 Zn - 0.20 IV Catalyst 4 Si - 6.20 573 1/5/1.5 1000 8.2 71.2 Cs - 0.90 723 1/0,1/32 2000 6.2 89.9 Mn - 0.80 823 1/9/50 10000 18.7 60.7 Zn - 0.42 IV Catalyst 4 Si - 6.20 573 1/5/1.5 1000 8.2 71.2 Cs - 0.90 723 1/0,1/32 2000 6.2 89.9 Mn - 0.80 823 1/9/50 10000 18.7 60.7 Zn - 0.42 VIII Catalyst 1 Li - 2.3 573 1/5/1.5 1000 10.0 72.0 containing lithium catims 723 1/0,1/32 2000 6.7 89.7 823 1/9/50 10000 20.0 60.5 IX Catalyst 1 Contd-3.2 573 1/5/1.5 1000 9.7 74.0 containing lithium catims 723 1/0,1/32 2000 5.6 87.3 823 1/9/50 10000 18.3 70.2

Patent claims

Claims (3)

Patent claims 1. The method of obtaining ethylene from ethane by oxidizing dehydrogenation of ethane, which consists ⁱⁿ contacting ethane and oxygen or oxygen-containing gas with a catalyst bed at sd 523 ds 923K with a catalytic bed, characterized by the use of a catalyst containing a microsphate-mixed metal filter. sits mslekulanne on the structure of chabazite, s with a psry diameter less than or equal to 0.43 nm, with silicon, manganese, xbalt atoms embedded in the aluminum phosphate lattice, and possibly cs atoms of at least one metal from the group consisting of iron, magnesium, and zinc, with the crystal lattice of the sieve mslekularnegs also contains katimas. 2. The method according to zaatm. The method of claim 1, characterized in that: kajallzajor, in which the molecular sieves contain at least one type of cs from the group consisting of manganese, ksbalt, iron, magnesium, zinc, lithium, ssd, pstas, rubidium, cesium, barium, cadmium, calcium, beryllium, copper, and sdsru. 3. A method according to the principles of The method of claim 1, characterized in that the stooute is a Kajallzajor which is a mixture of metal, glass, and metal sieves, the cs having the least one seat having a chabazite structure.