Synthesis of olefins from oxygen-free direct conversion of methane and catalysts thereof

Patent metadata

Field	Value
Publication number	US-9932280-B2
Application number	US-201314003551-A
Country	US
Kind code	B2
Filing date	Jul 24, 2013
Priority date	May 13, 2013
Publication date	Apr 3, 2018
Grant date	Apr 3, 2018

Abstract

Provided is a method for the preparation of a metal lattice-doping catalyst in an amorphous molten state, and the process of catalyzing methane to make olefins, aromatics, and hydrogen using the catalyst under oxygen-free, continuous flowing conditions. Such a process has little coke deposition and realizes atom-economic conversion. Under the conditions encountered in a fixed bed reactor (i.e. reaction temperature: 750˜1200° C.; reaction pressure: atmospheric pressure; the weight hourly space velocity of feed gas: 1000˜30000 ml/g/h; and fixed bed), conversion of methane is 8-50%. The selectivity of olefins is 30˜90%. And selectivity of aromatics is 10˜70%. There is no coking. The reaction process has many advantages, including a long catalyst life (>100 hrs), high stability of redox and hydrothermal properties under high temperature, high selectivity towards target products, zero coke deposition, easy separation of products, good reproducibility, safe and reliable operation, etc., all of which are very desirable for industrial application.

First claim

We claim:

1. A catalyst, comprising:
a matrix of Si 3 N 4 , SiC, SiC x O y (in which 4x+2y=4), SiO y N z (in which 2y+3z=4), SiC x N z (in which 4x+3z=4), or SiC x O y N z (in which 4x+2y+3z=4), with the proviso that the matrix is not SiO 2 ,
one or more metal dopant(s) residing in the matrix,
a plurality of active species, each of the plurality of active species is formed by replacing a Si, C, O, or N atom in the matrix with an individual atom metal dopant(s) atom so that the metal dopant(s) element is confined in a lattice of the doped matrix,
wherein an amount of the metal dopant(s) ranges from 0.4 wt % to 1.9 wt % to of a total weight of the catalyst, wherein x ranges from 0 to 1, y ranges from 0 to 2, and z ranges from 0 to 4/3,
wherein the catalyst is in an amorphous state,
wherein the metal dopant(s) is selected from a group consisting of Li, Na, K, Mg, Al, Ca, Sr, Ba, Y, La, Ti, Zr, Ce, Cr, Mo, W, Re, Fe, Co, Ni, Cu, Zn, Ge, In, Sn, Pb, Bi, and Mn,
and wherein the catalyst is active in converting methane to olefins.

2. The catalyst according to claim 1 , wherein the catalyst further comprises one or more metals or metal compounds supported on a surface of the matrix, wherein the supported metal compound is selected from the group consisting of metal oxides, metal carbides, metal nitrides, metal silicides, and metal silicates.

3. The catalyst according to claim 2 , wherein the supported metal or the metal in the supported metal compound is selected from the group consisting of Li, Na, K, Mg, Al, Ca, Sr, Ba, Y, La, Ti, Zr, Ce, Cr, Mo, W, Re, Fe, Co, Ni, Cu, Zn, Ge, In, Sn, Pb, Bi, and Mn.

4. The catalyst according to claim 1 , wherein the catalyst is prepared by a chemical vapor deposition method comprising mixing silicon vapor or SiCl 4 with a vapor of the metal dopant(s) or a vapor of a volatile salt of the metal dopant(s); and reacting the mixture with a water vapor to obtain a solid.

5. The catalyst according to claim 1 , wherein the catalyst is prepared by a vapor phase axial deposition method comprising mixing silicon vapor or SiCl 4 with a vapor of the metal dopant(s) or a vapor of a volatile salt of the metal dopant(s); exposing a substrate of corundum, silicon carbide, or silicon nitride to the mixture; and reacting the mixture with a water vapor to form a solid deposited on the substrate.

6. The catalyst according to claim 4 , wherein the volatile metal salt is selected from the group consisting of metal carbonyls, metal alkoxides of carbon atom number from 1 to 5, and metal organic acid salts of C atom number from 1 to 5.

7. The catalyst according to claim 1 , wherein the catalyst is in a form of particles of size in the range of 10 nm-10 cm.

8. The catalyst according to claim 1 , wherein the amount of the metal dopant(s) ranges from 0.5 wt % to 1.6 wt % of a total weight of the catalyst.

9. The catalyst according to claim 1 , wherein the individual metal dopant(s) atom in each of the plurality of active species bonds with atoms adjacent to the replaced Si, C, O, or N atom.

10. The catalyst according to claim 1 , wherein the metal dopant(s) is a transition metal.

11. The catalyst according to claim 1 , wherein the metal dopant(s) is Fe or Co.

12. A method of conversion of methane to olefins, comprising:
reacting a methane feedstock comprising methane in presence of a catalyst of claim 1 ; and
obtaining a product stream comprising olefins, aromatics, and hydrogen.

13. The method according to claim 12 , wherein a reaction temperature ranges from 750° C. and 1200° C.

14. The method according to claim 12 , further comprising a step of pretreating the catalyst in a feed gas comprising hydrocarbons selected from the group consisting of alkanes with 2 to 10 carbon atoms, alkenes with 2 to 10 carbon atoms, alkyne with 2 to 10 carbon atoms, monohydric alcohol with 1 to 10 carbon atoms, dihydric alcohol with 2 to 10 carbon atoms, aldehyde with 1 to 10 carbon atoms, carboxylic acid with 1 to 10 carbon atoms, and aromatics with 6 to 10 carbon atoms, at a temperature ranging from 800° C. to 1000° C. under a pressure ranging from 0.1 MPa to 1 MPa in a weight hourly space velocity of feed gas ranging from 500 ml/g/h to 3000 ml/g/h.

15. The method according to claim 12 , wherein the methane feedstock comprises methane, optionally an inert gas, optionally a non-inert gas, and is substantially oxygen free,
wherein the inert gases is selected from a group consisting of nitrogen (N 2 ), helium (He), neon (Ne), argon (Ar), krypton (Ke), and a mixture thereof,
wherein the non-inert gases is selected from a group consisting carbon monoxide (CO), hydrogen (H 2 ), carbon dioxide (CO 2 ), water vapor (H 2 O), monohydric alcohol with 1 to 5 carbon atoms, dihydric alcohol with 2 to 5 carbon atoms, alkanes with 2 to 8 carbon atoms, and a mixture thereof.

16. The method according to claim 12 , wherein the conversion of methane is carried out in a fluidized bed, a moving bed, or a fixed bed, at a pressure ranging from 0.05 MPa to 1 MPa, and a weight hourly space velocity of the methane feedstock ranging from 1000 ml/g/h to 30000 ml/g/h.

17. The method according to claim 12 , wherein the metal dopant is selected from the group consisting of alkali metals, alkaline earth metals, and transition metals.

18. The method according to claim 15 , wherein the methane feedstock comprises 5-100% of methane by volume, 0 to 95% of inert gas by volume, and 0-15% of the non-inert gas by volume.

19. A method of preparing a catalyst of claim 1 , comprising the steps of:
dissolving a liquid silicon source and a metal salt selected from the group consisting of metal nitrates, metal halides, metal sulfates, metal carbonates, metal hydroxides, metal organic acid salts having 1 to 10 carbon atoms, and metal alkoxides having 1 to 10 carbon atoms in a mixture of water and ethanol wherein a weight content of water in the mixture is 10-100%;
obtaining a sol gel from the mixture after hydrolysis and condensation;
drying the slurry to obtain a powder;
melting the powder at a temperature ranging from 1300° C. to 2000° C. to a molten mixture;
cooling the molten mixture to a solid; and
grinding the solid to particles.

20. A method for preparing a catalyst according to claim 1 , comprising the steps of:
providing a porous silicon-based material selected from the group consisting of silica, silicon carbide, silicon nitride, and a mixture thereof;
impregnating the porous silicon-based material in a solution comprising a salt of the metal dopant to obtain a slurry;
drying the slurry to obtain a powder;
melting the powder at a temperature ranging from 1300° C. to 2000° C. to a molten mixture; and
cooling the molten mixture to a solid.

Assignees

• Dalian Inst Chem & Physics Cas

Inventors

• Bao Xinhe
• Guo Xiaoguang
• Fang Guangzong
• Deng Dehui
• Ma Hao
• Tan Dali

Classifications

• C07C2523/75

  Cobalt · CPC title

• B01J23/755

  Nickel · CPC title

• B01J35/002

  Operations & Transport · mapped topic

• B01J23/78

  with alkali- or alkaline earth metals · CPC title

• B01J37/348

  Electrochemical processes, e.g. electrochemical deposition or anodisation · CPC title