Oxidative dehydrogenation of ethane to ethylene and preparation of multimetallic mixed oxide catalyst for such process
Oxidative dehydrogenation of light paraffins, such as ethane at moderate temperatures (<500° C.) to produce ethylene without the formation of side products such as acetic acid and/or other oxygenated hydrocarbons is achieved using tellurium-free, multimetallic catalysts possessing orthorhombic M1 phase and other crystalline structures that have an important role for obtaining high performance catalysts for the oxidative dehydrogenation of ethane to ethylene. Such catalysts are prepared using thermal and hydrothermal methods.
1. A process for the oxidative dehydrogenation of ethane to ethylene, which comprises contacting a feedstock comprising ethane and an oxidizing agent under oxidative dehydrogenation reaction conditions with a tellurium-free, multimetallic mixed oxide solid catalyst having the formula
MoV h Sb i O x (I)
wherein, h and i, respectively, are each between 0.001 and 4.0, the ratio i/h is between 0.3 and 10.0, and x represents the number determined by and consistent with the valence requirements of elements present in the multimetallic mixed oxide solid catalyst, said multimetallic mixed oxide solid catalyst having an orthorhombic M1 crystalline phase along with a pseudo-hexagonal M2 crystalline phase and an orthorhombic MoO 3 crystalline phase, and one or more additional crystalline phases, wherein a process of preparing said multimetallic mixed oxide solid catalyst comprises:
A) a process which comprises forming a tellurium-free mixture of molybdenum, vanadium and antimony metallic precursors and a compound selected from the group consisting of primary amines, secondary amines, tertiary amines, ammonia, tetra-methyl ammonium and hydrazine, and subjecting said tellurium-free mixture to
hydrothermal condition at a temperature of 100-200° C. for 6-150 hours to obtain a solid, washing and drying said solid to obtain a dried solid, and thermally activating said dried solid to form a catalyst having the pseudo-hexagonal M2 crystalline phase and the orthorhombic MoO 3 crystalline phase in addition to the orthorhombic M1 crystalline phase, wherein said thermally activating includes a first thermal treatment at a temperature from about 150° C. to about 350° C. under an oxidizing, reducing or inert atmosphere for 1-5 hours, and thereafter a second thermal treatment at a temperature from about 150° C. to 700° C. under an oxidizing or inert atmosphere for 1 to 5 hours.
2. The process of claim 1 , wherein the compound is selected from the group consisting of methylamine, dimethyl amine, tri-methyl amine, diethyl amine, or mixtures thereof.
3. The process of claim 2 , wherein said
solid is washed and dried at 80-120° C., prior to activation.
4. The process of claim 3 , wherein said hydrothermal condition is at a temperature range of 150-180° C. for 12-48 hours.
5. A process for the oxidative dehydrogenation of ethane to ethylene, which comprises contacting a feedstock comprising ethane and an oxidizing agent under oxidative dehydrogenation reaction conditions with a tellurium-free, multimetallic mixed oxide solid catalyst having the formula
MoV h Sb i A j O x (I)
wherein A represents Nb, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr, Zr, rare earth metals, alkali metals, alkaline earth metals, or a mixture thereof, h and i, respectively, are each between 0.001 and 4.0, the ratio i/h is between 0.3 and 10.0, and x represents the number determined by and consistent with the valence requirements of elements present in the multimetallic mixed oxide solid catalyst, said multimetallic mixed oxide solid catalyst having an orthorhombic M1 crystalline phase, a pseudo-hexagonal M2 crystalline phase, an orthorhombic MoO 3 crystalline phase, and one or more additional crystalline phases, wherein a process of preparing said multimetallic mixed oxide solid catalyst comprises the steps of forming a tellurium-free mixture of molybdenum, vanadium and antimony metallic precursors and thermally treating said tellurium-free mixture to form an MoVSb solid, doping said MoVSb solid with a solution containing metal cation of said metal A, as salts, oxides, hydroxides, or alkoxides to obtain a resulting mixture, drying the resulting mixture to obtain a solid and drying said solid to obtain a metal cation-doped MoVSb solid, and thermally activating the metal cation-doped MoVSb solid to form a catalyst having the pseudo-hexagonal M2 crystalline phase and the orthorhombic MoO 3 crystalline phase in addition to the orthorhombic M1 crystalline phase, where said thermally activating step includes a first thermal treatment at a temperature of from about 150° C. to about 350° C. under oxidizing and/or reducing atmosphere for 1 to 5 hours, and thereafter a second thermal treatment at a temperature of about 150° C. to about 700° C. under oxidizing or inert atmosphere for 1 to 5 hours, wherein said tellurium-free mixture includes a compound selected from the group consisting of primary amines, secondary amines, tertiary amines, ammonia, tetra-methyl ammonium and hydrazine, or mixtures thereof.
6. The process of claim 5 , wherein the solution contains metal cation of Nb, W, Sn, Cu or K.
7. The process of claim 5 , wherein said MoVSb solid is heated at a temperature range of from about 150° C. to about 600° C. prior to doping said MoVSb solid and then activating said metal cation-doped MoVSb solid at a temperature range of from about 150° C. to about 700° C. under an oxidizing or inert atmosphere for about 1 to 5 hours.
8. The process of claim 1 , wherein said oxidative dehydrogenation reaction is carried out at a reaction temperature range of about from 250° C. to 550° C.
9. The process of claim 1 , wherein said hydrothermal condition is at a temperature range of 150-180° C. for 12-48 hours.
10. The process for the oxidative dehydrogenation of ethane to ethylene, which comprises contacting a feedstock comprising ethane and an oxidizing agent under oxidative dehydrogenation reaction conditions with a tellurium-free, multimetallic mixed oxide solid catalyst, wherein the multimetallic mixed oxide has the formula
MoV h Sb i A j O x
wherein A represents Nb, W, Ga, Bi, Sn, Cu, Ti, Fe, Co, Ni, Cr, Zr, rare earth metals, alkali metals, alkaline earth metals, or a mixture thereof, h and i, respectively, are each between 0.001 and 4.0, 0.0001≦j≦2.0, the ratio i/h is between 0.3 and 10.0, and x represents the number determined by and consistent with the valence requirements of elements present in the multimetallic mixed oxide solid catalyst, said multimetallic mixed oxide solid catalyst having an orthorhombic M1 crystalline phase, along with a pseudo-hexagonal M2 crystalline phase and an orthorhombic MoO 3 crystalline phase, and one or more additional crystalline phases, and wherein a process of preparing said multimetallic mixed oxide solid catalyst comprises the steps of forming a tellurium-free mixture of molybdenum, vanadium and antimony metallic precursors and thermally treating said tellurium-free mixture to form an MoVSb solid, doping said MoVSb solid with a solution containing metal cation of said metal A to obtain an A metal cation-doped MoVSb solid, and thermally activating the A metal cation-doped MoVSb solid to form a catalyst having the pseudo-hexagonal M2 crystalline phase and the orthorhombic MoO 3 crystalline phase in addition to the orthorhombic M1 crystalline phase, wherein said tellurium-free mixture includes a compound selected from the group consisting of primary amines, secondary amines, tertiary amines, ammonia, tetra-methyl ammonium and hydrazine, or mixtures thereof.
11. The process of claim 10 , wherein the solution contains metal cation of Nb, W, Sn, Cu or K.
12. The process of claim 10 , wherein said MoVSb solid is heated at a temperature range of from about 150° C. to about 700° C. prior to doping said MoVSb solid and then activating said A metal cation-doped MoVSb solid at a temperature range of from about 150° C. to about 700° C. under an oxidizing or inert atmosphere for about 1 to 5 hours.
13. The process of claim 1 , wherein the oxidative dehydrogenation reaction is conducted at a temperature range of from 250° C. to 550° C., and at atmospheric pressure with a space-time corresponding to the ratio of multimetallic mixed oxide solid catalyst mass to inlet molar flow rate of ethane (W/F° ethane ) in a range of from 10 g cat h(mol) −1 to 800 g cat h(mol) −1 to achieve an ethane conversion above 86 mol % and an ethylene selectivity above 95 mol % without formation of acetic acid and/or other oxygenated hydrocarbons.
14. The process of claim 1 , wherein the oxidative dehydrogenation reaction is conducted at a reaction temperature range of from 250° C. to 550° C., under an operating pressure between 0.8 to 1 atm and a space-time corresponding to the ratio of multimetallic mixed oxide solid catalyst mass to inlet molar flow rate of ethane (W/F° ethane ) in a range of from 10g cat h(mol) −1 to 800 g cat h(mol) −1 with an activated multimetallic mixed oxide solid catalyst supported on a metal oxide support to achieve ethylene selectivity above 95 mol %, and ethane conversion above 71 mol %.