METHOD OF COUPLING METHANE DRY-REFORMING AND COMPOSITE CATALYST REGENERATION

Abstract

The present invention is related to a method of coupling methane dry-reforming and composite catalyst regeneration. A composite catalyst is filled into a reactor, and methane or a methane mixture gas is introduced therein. CaCO.sub.3 in the composite catalyst is decomposed under 600-850 C. CO.sub.2 obtained by the decomposition reacts with methane to perform methane dry-reforming reaction and produce synthesis gas containing CO and hydrogen. The composite catalyst contains CaCO.sub.3 , active nickel and alumina support. This method couples the CaCO.sub.3 decomposition reaction in calcium looping and methane dry-reforming reaction to solve the technical problem of limiting CaCO.sub.3 decomposition by high-temperature equilibrium. The decomposition of CaCO.sub.3 is enhanced, and the CO.sub.2 produced by decomposing CaCO.sub.3 is dry-reformed to produce synthesis gas to be utilized.

Claims

1-10. (canceled)

11. A method of coupling methane dry-reforming and composite catalyst regeneration, comprising: filling a first composite catalyst into a reactor, wherein the first composite catalyst comprises CaCO.sub.3 and an active nickel containing NiO supported on a support containing alumina (Al.sub.2O.sub.3); introducing a methane-containing gas into the reactor; decomposing the CaCO.sub.3 in the first composite catalyst at 600-850 C. to obtain CO.sub.2 and CaO; and performing methane dry reforming reaction by reacting the obtained CO.sub.2 with methane in the methane-containing gas to form synthesis gas containing CO and H.sub.2.

12. The method of claim 11, wherein a mass ratio of CaO, NiO and Al.sub.2O.sub.3 in the first composite catalyst is 2-7:1:1.0-3.5.

13. The method of claim 11, wherein the methane-containing gas is methane, or a mixture of methane and at least one of water vapor, CO.sub.2 and nitrogen.

14. The method of claim 11, wherein a volume ratio of the methane in the methane-containing gas is at least 10%.

15. The method of claim 11, wherein the decomposing step is performed under a pressure of 0.1-3.0 MPa, and a gas space velocity is 100-1000 h.sup.1.

16. The method of claim 11, wherein the alumina of the support reacts with the CaO obtained in the decomposing step to form calcium aluminate.

17. The method of claim 11, wherein the reactor comprises a fixed bed reactor, a fluidized bed reactor, a moving bed reactor or a bubbling bed reactor.

18. The method of claim 11, wherein the first composite catalyst is prepared by a second composite catalyst adsorbing CO.sub.2 from methane steam reforming reaction, and the second composite catalyst comprises alumina-supported CaO and NiO.

19. The method of claim 18, further comprising performing the steps of filling the first composite catalyst into the reactor, introducing the methane-containing gas into the reactor, decomposing the CaCO.sub.3 in the first composite catalyst, and performing the methane dry reforming reaction in claim 1.

20. The method of claim 11, wherein the first composite catalyst is prepared by a second composite catalyst adsorbing CO.sub.2 from flue gas decarburization process, and the second composite catalyst comprises alumina-supported CaO and NiO.

21. The method of claim 20, further comprising performing the steps of filling the first composite catalyst into the reactor, introducing the methane-containing gas into the reactor, decomposing the CaCO.sub.3 in the first composite catalyst, and performing the methane dry reforming reaction in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a schematic diagram showing the principle of the calcium looping that couples methane dry-reforming and composite catalyst regeneration.

[0030] FIG. 2 is the schematic diagram showing the principle of the reactive sorption enhanced reforming (ReSER) hydrogen production process that couples methane dry-reforming and composite catalyst regeneration.

DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention is further described as follows in combination with preferred embodiments. However, the present invention is not limited to the following embodiments.

Embodiment 1: Preparation of the Composite Catalyst

[0032] (1) 350 mL of a mixed aqueous solution containing Ni(NO.sub.3).sub.2 and CO(NH.sub.2).sub.2 having molar concentrations of 0.236 mol/L and 0.945 mol/L, respectively, were prepared. 6.76 g of polyethylene glycol was added to react in a 90 C. water bath for a period of time and then is cooled to room temperature. Deionized water and absolute ethyl alcohol were used to wash the product for several times until neutral to obtain Ni(OH).sub.2.

[0033] (2) 3.14 g Ni(OH).sub.2 prepared in Step (1) and 11.30 g nano calcium carbonate were dispersed in an ethanol aqueous solution and ultrasonically dispersed for 10 min. 37.95 g alumina sol was then added, mixed thoroughly, dried for overnight under 120 C., calcined under 500 C. for 3 h, and decomposed under 800 C. for 15 min to obtain the composite catalyst of NiOCaO/Al.sub.2O.sub.3 having a mass ratio of 2:5:3 for NiO, CaO and Al.sub.2O.sub.3.

Embodiment 2: The Composite Catalyst for ReSER Hydrogen Production

[0034] Reaction principles are shown in FIG. 2. The reaction on the left side is ReSER hydrogen production. The composite catalyst of 5 g NiOCaO/Al.sub.2O.sub.3 prepared in Embodiment 1 was filled into a fixed-bed reactor. A mixed gas of hydrogen and nitrogen was used to reduce NiO in the composite catalyst to Ni. Methane and water steam were introduced into the reactor to produce hydrogen. The flow rate of methane was 20 ml/min. The molar ratio of water over carbon was 5. The temperature was 600 C. The pressure was 0.2 MPa. The composite catalyst NiOCaO/Al.sub.2O.sub.3 was converted to the composite catalyst NiOCaCO.sub.3/Al.sub.2O.sub.3 after CO.sub.2 was saturatedly adsorbed by the composite catalyst NiOCaO/Al.sub.2O.sub.3.

Embodiment 3: The Composite Catalyst for ReSER Hydrogen Production

[0035] The composite catalyst of 5 g NiOCaO/Al.sub.2O.sub.3 prepared in Embodiment 1 was filled into a fixed-bed reactor. A mixed gas of hydrogen and nitrogen was used to reduce NiO in the composite catalyst to Ni. Methane and water steam were introduced into the reactor to produce hydrogen. The flow rate of methane was 20 ml/min. The molar ratio of water over carbon was 4. The temperature was 650 C. The pressure was 0.2 MPa. The composite catalyst NiOCaO/Al.sub.2O.sub.3 was converted to the composite catalyst NiOCaCO.sub.3/Al.sub.2O.sub.3 after CO.sub.2 was saturatedly adsorbed by the composite catalyst NiOCaO/Al.sub.2O.sub.3.

Embodiment 4: The Composite Catalyst for ReSER Hydrogen Production

[0036] The composite catalyst of 5 g NiOCaO/Al.sub.2O.sub.3 prepared in Embodiment 1 was filled into a fixed-bed reactor. A mixed gas of hydrogen and nitrogen was used to reduce NiO in the composite catalyst to Ni. Methane and water steam were introduced into the reactor to produce hydrogen. The flow rate of methane was 30 ml/min. The molar ratio of water over carbon was 3. The temperature was 600 C. The pressure was 0.2 MPa. The composite catalyst NiOCaO/Al.sub.2O.sub.3 was converted to the composite catalyst NiOCaCO.sub.3/Al.sub.2O.sub.3 after CO.sub.2 was saturatedly adsorbed by the composite catalyst NiOCaO/Al.sub.2O.sub.3.

Embodiment 5: The Composite Catalyst Adsorbing CO.SUB.2 .in Flue Gas

[0037] The reaction principles are shown in FIG. 1. The composite catalyst of 5 g NiOCaO/Al.sub.2O.sub.3 prepared in Embodiment 1 was filled into a fixed-bed reactor. Under a condition of normal pressure and 600 C., 100 mL of nitrogen-simulated mixed flue gas containing 50% CO.sub.2 was introduced into the fixed-bed reactor. The composite catalyst NiOCaO/Al.sub.2O.sub.3 was converted to the composite catalyst NiOCaCO.sub.3/Al.sub.2O.sub.3 after CO.sub.2 was saturatedly adsorbed by the composite catalyst NiOCaO/Al.sub.2O.sub.3.

Embodiment 6: The Composite Catalyst Adsorbing CO.SUB.2 .in Flue Gas

[0038] The composite catalyst of 5 g NiOCaO/Al.sub.2O.sub.3 prepared in Embodiment 1 was filled into a fixed-bed reactor. Under a condition of normal pressure and 650 C., 100 mL of nitrogen-simulated mixed flue gas containing 10% CO.sub.2 was introduced into the fixed-bed reactor. The composite catalyst NiOCaO/Al.sub.2O.sub.3 was converted to the composite catalyst NiOCaCO.sub.3/Al.sub.2O.sub.3 after CO.sub.2 was saturatedly adsorbed by the composite catalyst NiOCaO/Al.sub.2O.sub.3.

Embodiment 7: Coupling of Methane Dry-Reforming and Composite Catalyst Regeneration

[0039] The reaction principles are shown on the right side of FIG. 2. The composite catalyst of 5 g NiOCaO/Al.sub.2O.sub.3, after saturated adsorption in Embodiment 3, was filled into a fixed-bed reactor. Methane and nitrogen were introduced into the fixed-be reactor to perform reaction. The gas space velocity was 800 h.sup.1. The decomposition temperature was 800 C. The flow rate of methane was 5 mL/min. The flow rate of nitrogen was 495 mL/min. The decomposition pressure was 0.1 MPa. The complete decomposition time calcium carbonate was 35 minutes. The conversion rate of methane was 88%. The conversion rate of carbon dioxide was 81%.

[0040] A carbon deposit test was performed for the composite catalyst regenerated in Embodiment 7 on a thermogravimetric analyzer (TGA). Testing method is stated as follows: About 2 mg of samples were filled into a special platinum crucible for dewatering for 30 min under 150 C. Then, the temperature was increased to 800 C. at a rate of 15 C./min under a nitrogen atmosphere to completely decompose the calcium carbonate in the composite catalyst.

[0041] After changing to an air atmosphere, the catalyst was calcined for 30 minutes. The carbon deposit ratio was calculated by the mass difference of the catalyst before and after the reaction. The calculation formula of the carbon deposit ratio is stated below:

Carbon deposit ratio=Ma/MbMa

Mb is the mass of the composite catalyst before calcination, and Ma is the mass of the composite catalyst after calcination. The carbon deposit ratio in Embodiment 7 was calculated to be 15.08%.

Embodiment 8-14: Coupling of Methane Dry-Reforming and Composite Catalyst Regeneration

[0042] The composite catalyst of NiOCaO/Al.sub.2O.sub.3, after saturated adsorption in Embodiment 3 was filled into a fixed-bed reactor. The reaction conditions are shown in Table 1.

TABLE-US-00001 TABLE 1 Reaction Conditions and Results in Embodiment 8-14 Calcium Air carbonate Methane CO.sub.2 Carbon Reaction Methane Nitrogen space Reaction decomposition conversion conversion deposition Embodiment temperature flow rate flow rate velocity pressure time rate rate ratio 8 800 50 50 600 0.1 12 94 85 16.1% 9 800 25 75 800 0.1 18 86 80 13.3% 10 600 25 75 500 0.1 30 70 50 1.5% 11 750 10 90 100 1.5 28 89 80 2.4% 12 850 10 90 300 1 15 92 65 14.4% 13 800 100 0 1000 0.15 18 90 60 25.6% 14 800 100 0 1000 0.15 18 93.6 70 24.4%

[0043] From Table 1, it can be seen that the coupling of calcium carbonate decomposition in the composite catalyst with methane dry reforming can solve the technical problem of limiting CaCO.sub.3 decomposition by high-temperature equilibrium. Thus, the conversion rates of methane and CO.sub.2 were increased; the calcium carbonate decomposition time was shortened; and the temperature of calcium carbonate was reduced. Moreover, the carbon deposit ratio was further decreased.