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

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: 7501200 C.; reaction pressure: atmospheric pressure; the weight hourly space velocity of feed gas: 100030000 ml/g/h; and fixed bed), conversion of methane is 8-50%. The selectivity of olefins is 3090%. And selectivity of aromatics is 1070%. 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.

Claims

1. A catalyst, comprising: a matrix of Si.sub.3N.sub.4, SiC, SiC.sub.xO.sub.y (in which 4x+2y=4), SiO.sub.yN.sub.z (in which 2y+3z=4), SiC.sub.xN.sub.z (in which 4x+3z=4), or SiC.sub.xO.sub.yN.sub.z (in which 4x+2y+3z=4), with the proviso that the matrix is not SiO.sub.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.sub.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.sub.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.sub.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.sub.2), carbon dioxide (CO.sub.2), water vapor (H.sub.2O), 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.

Description

DESCRIPTION OF FIGURES

(1) FIG. 1 XRD pattern of 0.5 wt. % Ca-0.5 wt. % Fe @SiO.sub.2 catalyst

(2) FIG. 2 XPS spectra of Fe doping 6HSiC(0001)

(3) FIG. 3 HRTEM image of the metal lattice-doping catalyst

EMBODIMENTS

(4) 1. Catalyst Preparation

(5) The preparation methods of silicon-based catalysts with metal dopants include the following solid phase doping technologies, such as Chemical Vapor Deposition (CVD), Vapour phase Axial Deposition (VAD), Laser induced Chemical Vapor Deposition (LCVD), metal doping sol-gel method, porous Si-based materials impregnation method, powder doping method and so on. The catalysts are marked as: A@SiO.sub.xC.sub.yN.sub.z.

(6) The preparation of A@SiO.sub.2 catalysts (example 1, 2, 3, 4, 5, 7); the preparation of A@SiOC.sub.0.5 catalysts (example 6); the preparation of A@Si.sub.3C.sub.4 catalysts (example 8, 9, 10); the preparation of A@Si.sub.3N.sub.4 catalysts (example 11); the preparation of A@SiOC.sub.0.35N.sub.0.2 catalysts (example 12); the preparation of A/SiO.sub.2 catalysts (example 13) (Active species is highly dispersed on the support.)

Example 1

(7) Chemical Vapor Deposition (CVD)

(8) The vapor phase in the high-temperature reaction furnace is formed by bubbling 30 mL/min of carrier gas (10 vol. % of H.sub.2 and 90 vol. % of He) into an 30 mL of ethanol solution dissolving 17 g of SiCl.sub.4 and 94 mg of Co.sub.2(CO).sub.8. The mist vapor mixture sprayed from the center of combustor is hydrolyzed and melted to form a uniform SiO.sub.2 material doped with Co at 1200 C. The material is melted at 1400 C. in vacuum (10 Pa) for 6 h. The Co doped silica catalyst, 0.5 wt. % Co@SiO.sub.2, is obtained after subsequent quenching in cold water.

Example 2

(9) Chemical Vapor Deposition (CVD)

(10) The vapor phase in the high-temperature reaction furnace is formed by bubbling 30 mL/min of carrier gas (10 vol. % of H.sub.2 and 90 vol. % of He) into an 30 mL of ethanol solution dissolving 17 g of SiCl.sub.4, 94 mg of Co.sub.2(CO).sub.8 and 86.9 mg Ni(CO).sub.4. The mist vapor mixture sprayed from the center of combustor is hydrolyzed and melted at 1200 C. to form a uniform SiO.sub.2 material doped with Co and Ni. The material is further melted at 1400 C. in vacuum (10 Pa) for 6 h. The Co/Ni doping silica catalyst, 0.5 wt. % Co-0.5 wt. % Ni@SiO.sub.2, is obtained after subsequent quenching in cold water.

Example 3

(11) Vapor Phase Axial Deposition (VAD)

(12) The vapor phase in the high-temperature reaction furnace is formed by bubbling 30 mL/min of carrier gas (10 vol. % of H.sub.2 and 90 vol. % of He) into an 30 mL of ethanol solution dissolving 17 g of SiCl.sub.4, 94 mg of Co.sub.2(CO).sub.8. The mist vapor mixture sprayed from the center of combustor is hydrolyzed and axial deposited on the surface of alumina support at 1200 C. to form a uniform SiO.sub.2 material doped with Co. The material is melted at 1400 C. in vacuum (10 Pa) for 6 h. The Co doping silica catalyst, 0.5 wt. % Co@SiO.sub.2, is obtained after subsequent quenching in cold water.

Example 4

(13) Vapor Phase Axial Deposition (VAD)

(14) The vapor phase in the high-temperature reaction furnace is formed by bubbling 30 mL/min of carrier gas (10 vol. % of H.sub.2 and 90 vol. % of He) into an 30 mL of ethanol solution dissolving 17 g of SiCl.sub.4, 94 mg of Co.sub.2(CO).sub.8 and 86.9 mg Ni(CO).sub.4. The mist vapor mixture sprayed from the center of combustor is hydrolyzed and axial deposited on the surface of alumina support at 1200 C. to form a uniform SiO.sub.2 material doped with Co and Ni. The obtained material is melted at 1400 C. in vacuum (10 Pa) for 6 h. The Co doping silica catalyst, 0.5 wt. % Co-0.5 wt. % Ni@SiO.sub.2, is obtained after subsequent quenching in cold water.

Example 5

(15) Metal Doping Sol-Gel Method A metal doping silica gel is formed by stirring 20 mL of tetraethoxysilane (TEOS), 120 mg of Co(NO.sub.3).sub.2.6H.sub.2O, 117.1 mg Ca(NO.sub.3).sub.2.4H.sub.2O and 30 mL ethanol in 24 g 15% nitric acid solution at 60 C. for 24 h. The gel is dried in rotary evaporator at 80 C. for 2 h and melted at 1400 C. in He atmosphere for 6 h. The Co/Ca doped silica catalyst, 0.5 wt. % Ca-0.5 wt. % Co@SiO.sub.2, is obtained after subsequent quenching in cold water.

Example 6

(16) The vapor phase in the high-temperature reaction furnace is formed by bubbling 30 mL/min of carrier gas (10% v of H.sub.2 and 90% v of He) into an 30 mL of ethanol solution dissolving 17 g of SiCl.sub.4 and 94 mg of Co.sub.2(CO).sub.8. The mist vapor mixture sprayed from the center of combustor is hydrolyzed and melted at 1200 C. to form a uniform SiO.sub.2 material doped with Co. The material is treated in a mixed gas (10% v of CH.sub.4 and 90% v of He) at 2000 C. and afterwards melted at 1400 C. in vacuum (10 Pa) for 6 h. The Co doped catalyst, 0.5 wt. % Co@SiOC.sub.0.5, is obtained after subsequent quenching in cold water.

Example 7

(17) Porous Si-Based Materials Impregnation Method

(18) The catalyst is prepared by impregnating 6 g of porous silica powder in a solution of 117 mg of Ca(NO.sub.3).sub.2.4H.sub.2O and 137.3 mg of Co(NO.sub.3).sub.2.6H.sub.2O in 10 mL of water. The slurry is dried by stirring and aging for 24 h at 120 C. and afterwards melted at 1400 C. in vacuum (10 Pa) for 6 h. The Co/Ca doped catalyst, 0.5 wt. % Ca-0.5 wt. % Co@SiO.sub.2, is obtained after subsequent melting process at 1400 C. in vacuum (10 Pa) for 6 h.

Example 8

(19) Porous Si-Based Materials Impregnation Method

(20) The metal doped is prepared by impregnating 6 g of porous silicon carbide powder in a solution of 216 mg of Fe(NO.sub.3).sub.3.9H.sub.2O in 10 mL of water. The slurry is dried by stirring and aging for 24 h at 120 C. The dry powder is melted at 2000 C. in vacuum (10 Pa) for 6 h to form a uniform SiC material doped with Fe. The Fe doping catalyst, 0.5 wt. % Fe@SiC, is obtained after subsequent quenching in rapeseed oil.

Example 9

(21) A metal doped silica gel is formed by stirring 20 mL of tetraethoxysilane (TEOS), 120 mg of Co(NO.sub.3).sub.2.6H.sub.2O, 117.1 mg Ca(NO.sub.3).sub.2.4H.sub.2O and 30 mL ethanol in 24 g 15% nitric acid solution at 60 C. for 24 h. The gel is dried in rotary evaporator at 80 C. for 2 h and melted with carbon at 2000 C. for 2.5 h to form a uniform SiC material doped with Co and Ca. The Co/Ca doping silica catalyst, 0.5 wt. % Ca-0.5 wt. % Co@SiOC.sub.0.5, is obtained after subsequent quenching in cold water.

Example 10

(22) A metal doped silica gel is formed by stirring 20 mL of tetraethoxysilane (TEOS), 120 mg of Co(NO.sub.3).sub.2.6H.sub.2O, 117.1 mg Ca(NO.sub.3).sub.2.4H.sub.2O and 30 mL ethanol in 24 g 15% nitric acid solution at 60 C. for 24 h. The gel is dried in rotary evaporator at 80 C. for 2 h and calcined with carbon at 2000 C. for 12 h to form a uniform SiC material doped with Co and Ca. The Co/Ca doping silica catalyst, 0.5 wt. % Ca-0.5 wt. % Co@SiC, is obtained after subsequent quenching in cold water.

Example 11

(23) The catalyst (0.5 wt. % Ca-0.5 wt. % Co@SiO.sub.2) mentioned in example 5 is treated in nitriding furnace at 1150-1200 C. at NH.sub.3 atmosphere for 4 h and then 1350-1450 C. at NH.sub.3 atmosphere for 18-36 h, until all become far nitride to form a uniform Si.sub.3N.sub.4 material doped with Co and Ca. The resulting powder is 0.5 wt. % Ca-0.5 wt. % Co@Si.sub.3N.sub.4.

Example 12

(24) The catalyst (0.5 wt. % Co@SiOC.sub.0.5) mentioned in example 6 is treated in nitriding furnace at 1150-1200 C. at NH.sub.3 atmosphere for 4 h and then 1350-1450 C. at NH.sub.3 atmosphere for 7.5 h to form a uniform SiOC.sub.0.35N.sub.0.3 material doped with Co. The resulting powder is 0.5 wt. % Ca-0.5 wt. % Co@SiOC.sub.0.35N.sub.0.3.

Example 13

(25) The metal loading catalyst is prepared by impregnating 6 g of silica support in a solution of 94 mg of Co.sub.2(CO).sub.8 in 10 mL of water. The slurry is stirred vigorously for 12 h and aging for 24 h at 60 C. The Co loading catalyst, 0.5 wt. % Co/SiO.sub.2, is obtained after subsequent calcination at 550 C. in air for 6 h.

(26) For the further understanding of the invention, the following examples are given for purpose of illustration only and should not be regarded as limiting in any way.

(27) 2. Catalyst Characterization

(28) a) XRD Characterization of 0.5 wt. % Ca-0.5 wt. % Fe @SiO.sub.2 Catalyst

(29) The XRD pattern of the catalyst indicates that there is only a broad diffraction peak at 23, which shows an amorphous characteristic peak of SiO.sub.2 (FIG. 1). Meanwhile, the diffraction peaks of Fe and Ca cannot be observed. All of these results are significantly different from the zeolite catalyst system.

(30) b) Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) Leaching Characterization

(31) The so-called ICP-AES acid leaching method is that the metal atoms outside the Si-based support can be dissolved in dilute nitric acid (The dilute nitric acid can only dissolves the metal, but it cannot dissolve the supports), while those protected by the Si-based support lattice or Si-based support cannot be dissolved, and meanwhile the ICP-ASE results can obtain a degree of acid leaching (i.e., a ratio of surface loadings to surface loading and doping loading). Firstly, the 0.5 wt. % Co@SiO.sub.2 catalyst was leached by dilute nitric acid, and the results showed that no Co atoms can be detected by ICP-AES, and further revealed the Co atoms have inserted the lattice of Si-based support. Subsequently, the 0.5 wt. % Co@SiO.sub.2 catalyst was leached by HF acid (the HF acid can dissolve either metal atoms or Si-based support), the results showed that all of Co atoms can be detected by ICP-AES, and the leaching amount is equal to the loading amount of the Co@SiO.sub.2 catalyst. The above results show that all of Co atoms have been inserted inside the lattice of Si-based support, and almost no Co atoms can be detected on the surface of Si-based support.

(32) c) XPS Characterization of Fe-Doped 6HSiC(0001)

(33) As can be seen from the result of XPS Si2p (FIG. 2), there is an obvious shoulder peak at the binding energy of 99.6 eV, which attributes to the FeSi.sub.x species. Furthermore, the results show Fe atom could substitute the lattice C atoms, and then the Fe atoms could bond with Si atom to form the FeSi.sub.x species.

(34) d) ICP-AES Leaching Characterization of 0.5 wt. % Co/SiO.sub.2 Catalyst

(35) Firstly, the 0.5 wt. % Co@SiO.sub.2 catalyst was leached by dilute nitric acid, and the results showed that all of Co atoms can be detected by ICP-AES, and the leaching amount is equal to the catalyst loading amount. Furthermore, the results show that all of Co atoms have dispersed on the surface of Si-based support, and almost no Co atoms can be inserted inside the lattice of Si-based support.

(36) e) High Resolution Transimission Microscopy (HR-TEM) Image of the Metal Lattice-Doping Catalyst

(37) Furthermore, HR-TEM was used to characterize the dispersion and configuration of the metal lattice-doping catalyst prepared by the metal doping sol-gel method (Example 5 of catalyst preparation), FIG. 3. As can be seen from this image, we can observe a clear crystal structure (white circles), FIGS. 3A and 3B. The HR-TEM results prove that the so-called amorphous molten state catalysts exhibited the structure with long-range disorder and short-range order.

(38) 3. Under the Oxygen-Free and Continuous Flow Conditions, Methane is Directly Converted to Olefin, Aromatics and Hydrogen.

(39) All of the above catalyst prior to use need to be ground and sieved to 20-30 mesh as a backup.

(40) All of the following reaction examples are achieved in a continuous flow micro-reaction apparatus, which is equipped with gas mass flow meters, gas deoxy and dehydration units, and online product analysis chromatography. The tail gas of reaction apparatus is connected with the metering valve of chromatography, and thus periodic and real-time sampling and analysis will be achieved. The feed gas is composed of 10 vol. % N.sub.2 and 90 vol. % CH.sub.4 without specification, in which the nitrogen (N.sub.2) is used in an internal standard. To achieve the online product analysis, the Agilent 7890A chromatography with dual detector of FID and TCD is used. The FID detector with HP-1 capillary column is used to analyze the light olefin, light alkane and aromatics; and the TCD detector with Hayesep D packed column is used to analyze the light olefin, light alkane, methane, hydrogen and N.sub.2 internal standard. According to the carbon balance before and after reaction, methane conversion, product selectivity and coke deposition selectivity are calculated by the method from the two Chinese patents (CN1247103A, CN1532546A).

Example 1

(41) The 0.75 g 0.5 wt. % Co@SiO.sub.2 catalyst prepared by the Example 1 of catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to 4840 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 8.2% of methane conversion, 47.6% and 1.0 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 26.1% and 0.2 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 26.2% and 0.1 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, and 5.4 mol/g.sub.catalyst/s of hydrogen generation rate.

Examples 2-7

(42) The 0.75 g 0.5 wt. % Co@SiO.sub.2 catalyst prepared by the Examples 2-7 of catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to the following temperatures (Table 1) at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted according to following values (Table 1). The results of methane conversion and products selectivity are as follows:

(43) TABLE-US-00001 TABLE 1 Ben- Naphtha- Methane Ethylene zene lene Exam- Temp..sup.1 WHSV.sup.2 Conv..sup.3 Sel..sup.4 Sel. Sel. ple ( C.) (ml/g/h) (%) (%) (%) (%) 2 750 1600 2.5 70 16 14 3 850 2200 5.6 65 20 15 4 900 3600 6.4 55 22 23 5 950 5100 7.9 52 23 25 6 980 8400 15.2 48 24 28 7 1050 15200 9.8 46 25 29 .sup.1Temp. denotes temperature; .sup.2WHSV denotes the weight hourly space velocity; .sup.3Conv. denotes conversion; .sup.4Sel. Denotes selectivity.

Example 8

(44) The 1.5 g 0.5 wt. % Ca-0.5 wt. % Co@SiC catalyst prepared by Example 10 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to 4840 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 8.02% of methane conversion, 46.4% and 1.2 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 26.2% and 0.2 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 27.3% and 0.1 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, and 6.4 mol/g.sub.catalyst/s of hydrogen generation rate.

Examples 9-13

(45) The 1.5 g 0.5 wt. % Ni-0.5 wt. % Co@SiO.sub.2 catalyst prepared by Example 4 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to following temperatures (Table 1) at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to following value (Table 2). The results of methane conversion and products selectivity were as follows:

(46) TABLE-US-00002 TABLE 2 Ben- Naphtha- Methane Ethylene zene lene Temp..sup.1 WHSV.sup.2 Conv..sup.3 Sel..sup.4 Sel. Sel. Example ( C.) (ml/g/h) (%) (%) (%) (%) 9 750 1600 2.2 68 16 16 10 850 2200 5.9 62 23 15 11 900 3600 6.8 51 24 25 12 950 5100 7.5 50 25 25 13 980 8400 14.3 49 23 28 .sup.1Temp. denotes temperature; .sup.2WHSV denotes the weight hourly space velocity; .sup.3Conv. denotes conversion; .sup.4Sel. Denotes selectivity.

Example 14

(47) The 0.75 g 0.5 wt. % Ca-0.3 wt. % Al@SiO.sub.2 catalyst prepared by Example 5 of catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to 4840 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. After 100 hours, the results were as follows: 7.8% of methane conversion, 46.8% and 0.9 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 27.2% and 0.2 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 25.8% and 0.1 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, and 5.2 mol/g.sub.catalyst/s hydrogen generation rate.

Example 15

(48) The 0.75 g 0.5 wt. % Co@SiOC.sub.0.5 catalyst prepared by Example 6 of catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to 4840 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 8.2% of methane conversion, 47.3% and 1.2 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 22.0% and 0.23 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 29.2% and 0.14 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, and 6.4 mol/g.sub.catalyst/s of hydrogen generation rate.

Examples 16-19

(49) The 0.75 g 0.5 wt. % Co@SiOC.sub.0.5 catalyst prepared by Example 6 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to following temperature (Table 1) at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to following value (Table 3). The results of methane conversion and products selectivity were as follows:

(50) TABLE-US-00003 TABLE 3 Ben- Naphth- Methane Ethylene zene alene Temp..sup.1 WHSV.sup.2 Conv..sup.3 Sel..sup.4 Sel. Sel. Example ( C.) (ml/g/h) (%) (%) (%) (%) 16 750 1600 3.0 72 12 16 17 850 2200 5.3 64 21 15 18 900 3600 7.1 53 24 23 19 950 5100 7.9 47 25 28 20 980 8400 15.5 45 23 32 .sup.1Temp. denotes temperature; .sup.2WHSV denotes the weight hourly space velocity; .sup.3Conv. denotes conversion; .sup.4Sel. Denotes selectivity.

Example 21

(51) The 0.75 g 0.5 wt. % Ca-0.3 wt. % Zn@SiOC.sub.0.5 catalyst prepared by Example 6 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 1000 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to 10000 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 31% of methane conversion, 52.1% and 5.7 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 21.3% and 0.8 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 26.4% and 0.6 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, and 28 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 22

(52) The 0.75 g 0.5 wt. % Ca-0.3 wt. % Co@SiOC.sub.0.5 catalyst prepared by the Example 9 of catalyst preparation method was loaded in the fix-bed reactor, and then purged with the Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas (10 vol. % CH.sub.4, 5 vol. % N.sub.2 and 85 vol. % He) was adjusted to 4840 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 7.1% of methane conversion, 51.3% and 0.1 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 14.3% and 0.01 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 7.4% and 0.003 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, 26.6% of coke selectivity, and 0.5 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 23

(53) The 0.75 g 0.5 wt. % Ca-0.6 wt. % Co@SiOC.sub.0.5 catalyst prepared by the Example 6 of catalyst preparation method was loaded in the fix-bed reactor, and then purged with the Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas (88 vol. % CH.sub.4, 2 vol. % CO, 8 vol. % N.sub.2 and 2 vol. % He) was adjusted to 4840 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 8.5% of methane conversion, 40.4% and 0.8 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 25.6% and 0.2 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 31.4% and 0.1 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, 0.4% of coke selectivity, and 5.5 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 24

(54) The 0.75 g 0.2 wt. % Mg-0.3 wt. % Zn@SiOC.sub.0.5 catalyst prepared by the Example 9 of catalyst preparation method was loaded in the fix-bed reactor, and then purged with the Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas (5.4 vol. % CH.sub.3OH, 85 vol. % CH.sub.4 and 9.6 vol. % N.sub.2) was adjusted to 4840 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 6% of methane conversion, 64.5% and 0.9 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 15.1% and 0.07 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 8.9% and 0.02 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, 3.6% and 0.05 mol/g.sub.catalyst/s of ethane selectivity, 7.8% of coke selectivity, and 9.3 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 25

(55) The 0.75 g 0.5 wt. % Ca-0.3 wt. % Co@SiOC.sub.0.5 catalyst prepared by the Example 9 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged with the Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of the feed gas (5.4 vol. % CH.sub.3OH, 85 vol. % CH.sub.4 and 9.6 vol. % N.sub.2) was adjusted to 10000 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 22% of methane conversion, 60.9% and 6.6 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 14.3% and 0.5 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 7.6% and 0.2 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, 2.3% and 0.3 mol/g.sub.catalyst/s of ethane selectivity, 14.1% of coke selectivity, and 39 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 26

(56) The 0.75 g 0.5 wt. % Mn-1.1 wt. % Fe@SiOC.sub.0.5 catalyst prepared by Example 6 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas (5 vol. % CO.sub.2, 85 vol. % CH.sub.4 and 10 vol. % N.sub.2) was adjusted to 4840 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 8.3% of methane conversion, 42.2% and 0.8 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 25.3% and 0.2 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 23.6% and 0.1 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, 3.2% and 0.06 mol/g.sub.catalyst/s of ethane selectivity, 7.1% of coke selectivity, and 2.0 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 27

(57) The 0.5 g 0.2 wt. % K-0.6 wt. % Fe@SiO.sub.2 catalyst prepared by Example 5 of the catalyst preparation method (replacing Co(NO.sub.3).sub.2.6H.sub.2O and Ca(NO.sub.3).sub.2.4H.sub.2O with KNO.sub.3 and Fe(NO.sub.3).sub.3.9H.sub.2O) was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to 10800 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 9.8% of methane conversion, 43% of ethylene selectivity, 25% of benzene selectivity, 27% of Naphthalene selectivity, 2% of ethane selectivity, and 3% of coke selectivity.

Example 28

(58) The 0.65 g 0.1 wt. % K-0.6 wt. % Pb@SiOC.sub.0.5 catalyst prepared by Example 6 of the catalyst preparation method (replacing Co(NO.sub.3).sub.2.6H.sub.2O and Ca(NO.sub.3).sub.2.4H.sub.2O with KNO.sub.3 and Pb(NO.sub.3).sub.2) was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas was adjusted to 10800 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 7.4% of methane conversion, 47% of ethylene selectivity, 23% of benzene selectivity, 28% of Naphthalene selectivity, and 2% of ethane selectivity.

Example 29

(59) The 0.65 g 0.1 wt. % K-0.6 wt. % Ti@SiO.sub.2 catalyst prepared by Example 5 of the catalyst preparation method (replacing Co(NO.sub.3).sub.2.6H.sub.2O and Ca(NO.sub.3).sub.2.4H.sub.2O with KNO.sub.3 and tetrabutyl titanate) was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. Then the weight hourly space velocity (WHSV) of feed gas was adjusted to 10800 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 7.4% of methane conversion, 47% of ethylene selectivity, 23% of benzene selectivity, 28% of Naphthalene selectivity, and 2% of ethane selectivity.

Example 30

(60) The 0.65 g 0.1 wt. % Mg-0.6 wt. % Ce@SiO.sub.2 catalyst prepared by Example 5 of the catalyst preparation method (replacing Co(NO.sub.3).sub.2.6H.sub.2O and Ca(NO.sub.3).sub.2.4H.sub.2O with Mg(NO.sub.3).2H.sub.2O and Ce (NO.sub.3).sub.3.6H.sub.2O) was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. Then the weight hourly space velocity (WHSV) of feed gas was adjusted to 10800 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 10.2% of methane conversion, 49% of ethylene selectivity, 23% of benzene selectivity, 25% of Naphthalene selectivity, 3% of ethane selectivity, and 3% of coke selectivity.

Example 31

(61) The 0.65 g 0.1 wt. % Mg-0.3 wt. % Sn@SiO.sub.2 catalyst prepared by Example 5 of the catalyst preparation method (replacing Co(NO.sub.3).sub.2.6H.sub.2O and Ca(NO.sub.3).sub.2.4H.sub.2O with Mg(NO.sub.3).2H.sub.2O and SnCl.sub.4.5H.sub.2O) was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. Then the weight hourly space velocity (WHSV) of feed gas was adjusted to 11200 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 6.2% of methane conversion, 43% of ethylene selectivity, 24% of benzene selectivity, 28% of Naphthalene selectivity, 2% of ethane selectivity, and 3% of coke selectivity.

Example 32

(62) The 0.75 g 0.5 wt. % Fe@SiC catalyst prepared by Example 5 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. Then the weight hourly space velocity (WHSV) of feed gas was adjusted to 15200 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 12.5% of methane conversion, 44% of ethylene selectivity, 22% of benzene selectivity, 24% of Naphthalene selectivity, 2% of ethane selectivity, 6% of coke selectivity, and 7.0 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 33

(63) The 0.75 g 0.8 wt. % Ca-1.1 wt. % Fe@SiOC.sub.0.5 catalyst prepared by Example 9 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas (5.0 vol. % H.sub.2O, 85.5 vol. % CH.sub.4 and 9.5 vol. % N.sub.2) was adjusted to 10000 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 12.1% of methane conversion, 34.7% and 1.2 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 25.6% and 0.3 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 25.1% and 0.2 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, 2.4% and 0.08 mol/g.sub.catalyst/s of ethane selectivity, 5.3% of CO selectivity, and 12 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 34

(64) The 0.75 g 0.5 wt. % Ca-0.5 wt. % Co@Si.sub.3N.sub.4 catalyst prepared by Example 11 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor is programmed from room temperature up to 950 C. at a heating rate of 10 C./min. Then the weight hourly space velocity (WHSV) of feed gas (90 vol. % CH.sub.4 and 10 vol. % N.sub.2) was adjusted to 5000 ml/g/h. After the WHSV being kept 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 14% of methane conversion, 40.1% and 1.3 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 22.3% and 0.3 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 26.2% and 0.2 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, 11.4% of coke selectivity, and 8 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 35

(65) The 0.75 g 0.5 wt. % Co@SiOC.sub.0.35N.sub.0.2 catalyst prepared by Example 12 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of feed gas (90 vol. % CH.sub.4 and 10 vol. % N.sub.2) was adjusted to 4840 ml/g/h. After the WHSV being kept for 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 16.2% of methane conversion, 46% and 1.4 mol/g.sub.catalyst/s of ethylene selectivity and ethylene generation rate, 27.5% and 0.35 mol/g.sub.catalyst/s of benzene selectivity and benzene generation rate, 26.5% and 0.3 mol/g.sub.catalyst/s of Naphthalene selectivity and Naphthalene generation rate, and 8 mol/g.sub.catalyst/s of hydrogen generation rate.

Example 36

(66) The 0.75 g 0.5 wt. % Co/SiO.sub.2 catalyst prepared by Example 13 of the catalyst preparation method was loaded in the fix-bed reactor, and then purged by Ar gas (25 ml/min) for 20 mins. Maintaining a constant flow rate of Ar, the reactor was programmed from room temperature up to 950 C. at a heating rate of 10 C./min. And then the weight hourly space velocity (WHSV) of the feed gas (90 vol. % CH.sub.4 and 10 vol. % N.sub.2) was adjusted to 4840 ml/g/h. After the WHSV being kept for 20 mins, the reaction results were analyzed by the online chromatography. The results were as follows: 18.5% of methane conversion, <3% of ethylene selectivity, <1% of benzene selectivity and Naphthalene selectivity, and >96% of coke selectivity.

(67) In summary, under the conditions encountered in a fixed bed reactor (i.e. reaction temperature: 7501200 C.; reaction pressure: atmospheric pressure; the weight hourly space velocity of feed gas: 100030000 ml/g/h; and fixed bed), conversion of methane is 8-50%. The selectivity of olefins is 3090%. And selectivity of aromatics is 1070%. 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.