Multistage nanoreactor catalyst and preparation and application thereof

Abstract

The present disclosure discloses a multistage nanoreactor catalyst and preparation and application thereof, belonging to the technical field of synthesis gas conversion. The catalyst consists of a core of an iron-based Fischer-Tropsch catalyst, a transition layer of a porous oxide or porous carbon material, and a shell layer of a molecular sieve having an aromatization function. The molecular sieve of the shell layer can be further modified by a metal element or a non-metal element, and the outer surface of the molecular sieve is further modified by a silicon-oxygen compound to adjust the acidic site on the outer surface and the aperture of the molecular sieve, thereby inhibiting the formation of heavy aromatic hydrocarbons. According to the disclosure, the shell layer molecular sieve with a transition layer and a shell layer containing or not containing auxiliaries, and with or without surface modification can be prepared by the iron-based Fischer-Tropsch catalyst through multiple steps. The catalyst can be used for direct preparation of aromatic compounds, especially light aromatic compounds, from synthesis gas; the selectivity of light aromatic hydrocarbons in hydrocarbons can be 75% or above, and the content in the liquid phase product is not less than 95%; and the catalyst has good stability and good industrial application prospect.

Claims

1. A multistage nanoreactor catalyst, comprising a structure of a core layer, a shell layer and a core-shell transition layer; wherein the core layer is an iron-based catalyst having Fischer-Tropsch activity, a weight of the core layer being 0.1% to 80% of a total weight of the catalyst; wherein the shell layer is a molecular sieve, a weight of the shell layer being 0.1% to 80% of the total weight of the catalyst; and wherein the core-shell transition layer is a porous oxide or porous carbon material, a weight of the transition layer being 0.01% to 35% of the total weight of the catalyst.

2. The multistage nanoreactor catalyst according to claim 1, wherein the iron-based catalyst having Fischer-Tropsch activity is a supported or unsupported catalyst comprising additives.

3. The multistage nanoreactor catalyst according to claim 1, wherein the molecular sieve is one or a mixture of two or more of ZSM-5, MCM-22, MCM-49, and SAPO-34 zeolite molecular sieves.

4. The multistage nanoreactor catalyst according to claim 1, wherein the molecular sieve comprises additives.

5. The multistage nanoreactor catalyst according to claim 4, wherein an outer surface of the molecular sieve has a silicon-oxygen compound.

6. The multistage nanoreactor catalyst according to claim 4, wherein the additives are selected from the group consisting of P, V, Cr, Mn, Fe, Co, Cu, Zn, Ga, Ge, Zr, Mo, Ru, Pd, Ag, W, Re and a combination thereof, and a weight of the additives is 0.01% to 35% of the weight of the shell layer.

7. The multistage nanoreactor catalyst according to claim 3, wherein the molecular sieve comprises additives.

8. The multistage nanoreactor catalyst according to claim 1, wherein the molecular sieve is a zeolite molecular sieve, and silica-alumina ratio of the zeolite molecular sieve is 10 to 500.

9. The multistage nanoreactor catalyst according to claim 1, wherein the porous oxide of the core-shell transition layer is selected from the group consisting of silicon oxide, aluminum oxide, zirconium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium oxide and a combination thereof, and a thickness of the transition layer is 0.1 to 1000 nm.

10. The multistage nanoreactor catalyst according to claim 1, wherein an outer surface of the molecular sieve has a silicon-oxygen compound, wherein a weight of the silicon-oxygen compound is 0.01% to 20% of the weight of the shell layer.

Description

BRIEF DESCRIPTION OF FIGURES

(1) FIG. 1 is a schematic diagram showing the structure of a multistage nanoreactor catalyst in an embodiment of the present disclosure.

DETAILED DESCRIPTION

Examples 1˜6: Preparation of Multistage Nanoreactor Catalyst for Direct Conversion of Synthesis Gas to Aromatic Compounds

(2) Product analysis: the products left from the reactor were condensed in a cold trap, while the uncondensed components were analyzed on-line by a gas chromatography with TCD and FID detectors. In detail, the unreacted CO, formed CO.sub.2 and CH.sub.4, and inert gas N.sub.2 were separated by a packed column of TDX-01 and detected by TCD, and the N.sub.2 was used as internal standard substance for calculation of CO conversion. C1-C5 hydrocarbons were separated using an HP-PLOT/Al.sub.2O.sub.3 capillary column. The condensed hydrocarbons were collected after reaction and analyzed by another gas chromatography off-line which connected with an FID and a capillary column of HP-1 or FFAP for further separation of para-, ortho- and meta-xylene.

(3) (1) The total CO conversion X.sub.CO was calculated as:
X.sub.CO=((A.sub.CO/A.sub.N.sub.2).sub.in−(A.sub.CO/A.sub.N.sub.2).sub.out)/(A.sub.CO/A.sub.N.sub.2).sub.in×100

(4) where (A.sub.CO/A.sub.N.sub.2).sub.in and (A.sub.CO/A.sub.N.sub.2).sub.out are the peak area ratio of CO to N.sub.2 at the inlet and outlet of reactor, respectively.

(5) The selectivity of CO converted to CO.sub.2 (S.sub.CO to CO.sub.2) was calculated as:
S.sub.CO to CO.sub.2={(A.sub.CO.sub.2/A.sub.N.sub.2).sub.out×f.sub.CO.sub.2/((A.sub.CO/A.sub.N.sub.2).sub.in−(A.sub.CO/A.sub.N.sub.2).sub.out×f.sub.CO}×100

(6) where (A.sub.CO.sub.2/A.sub.N.sub.2).sub.out is the peak area ratio of CO.sub.2 to N.sub.2. f.sub.CO.sub.2 and f.sub.CO are the correction factors of CO.sub.2 and CO, respectively.

(7) (3) The selectivity of CO converted to hydrocarbons (S.sub.CO to HC) was calculated as:
S.sub.CO to HC=100−S.sub.CO to CO.sub.2

(8) Definitely, the CO.sub.2-free selectivities of CO converted to CH.sub.4, C.sub.2-C.sub.6 in gas phase, and hydrocarbons in liquid phase, namely the CO.sub.2-free hydrocarbon distribution, were calculated as:

(9) a) The CO.sub.2-free selectivity of CO converted to CH.sub.4 was calculated as:
S.sub.CO to CH.sub.4=(A.sub.CH.sub.4/A.sub.N.sub.2).sub.out×f.sub.CH.sub.4/((A.sub.CO/A.sub.N.sub.2).sub.in−(A.sub.CO/A.sub.N.sub.2).sub.out)×f.sub.CO)×100/S.sub.CO to HC

(10) Where S.sub.CO to CH.sub.4 is the selectivity of CH.sub.4. (A.sub.CH.sub.4/A.sub.N.sub.2).sub.out is the on-line TCD peak area ratio of CH.sub.4 to N.sub.2. f.sub.CH.sub.4 is the correction factor of CH.sub.4.

(11) b) The CO.sub.2-free selectivities of CO converted to C.sub.2-C.sub.6 hydrocarbons in gas phase were calculated as:
S.sub.CO to C.sub.n=A.sub.C.sub.n.sup.FID1×f.sub.C.sub.n.sup.FID1/(A.sub.CH.sub.4.sup.FID1×f.sub.CH.sub.4.sup.FID1)×S.sub.CO to CH.sub.4

(12) Where A.sub.C.sub.n.sup.FID1 and A.sub.CH.sub.4.sup.FID1 are the on-line FID peak areas of C.sub.n (n=2-6) and CH.sub.4, respectively; f.sub.C.sub.n.sup.FID1 and f.sub.CH.sub.4.sup.FID1 are the correction factors of C.sub.n (n=2-6) and CH.sub.4 in on-line FID, respectively.

(13) a) The CO.sub.2-free selectivities of CO converted to total hydrocarbons in liquid phase were calculated as:
S.sub.CO to C.sub.liquid phase=100−S.sub.CO to CH.sub.4−Σ.sub.n=2.sup.6S.sub.CO to C.sub.n

(14) b) The CO.sub.2-free selectivities of CO converted to detailed hydrocarbons in liquid phase were calculated as:
S.sub.CO to C.sub.n=A.sub.C.sub.n.sup.FID2×f.sub.C.sub.n.sup.FID2/Σ.sub.n=5.sup.nA.sub.C.sub.n.sup.FID2×f.sub.C.sub.n.sup.FID2×S.sub.CO to C.sub.liquid phase

(15) Where A.sub.C.sub.n.sup.FID2 is the off-line FID peak area of C.sub.n (n>=5); f.sub.C.sub.n.sup.FID2 is the correction factors of C.sub.n (n>=5) 4 in off-line FID.

Example 1

(16) Dissolve 200.0 g of ferric nitrate nonahydrate and 5.92 g of manganese nitrate hexahydrate into 500 mL of deionized water, precipitate by using 6 mol/L ammonia water as a precipitant at pH=8.0, age, filter, wash and dry at 120° C. for 12 h, and finally calcine at 500° C. for 5 h to obtain a precipitated FeMn catalyst having an iron-manganese atomic ratio of 96 to 4.

(17) Admix 5.0 g of the prepared FeMn catalyst into 50 mL of ethyl orthosilicate solution, continuously stir, then perform rotary evaporation to remove the solvent, dry and calcine to obtain a sample having a SiO.sub.2 coating. Next, admix the sample into 50 mL of solution containing tetrapropylammonium hydroxide template, ethyl orthosilicate, Al.sub.2O.sub.3, NaOH and H.sub.2O in a ratio of 0.3:1.0:0.03:0.015:130, stir for 4 h, then charge into a hydrothermal kettle, seal, heat to 180° C., and hydrothermally crystallize for 48 h. Filter the solid product after crystallization and cooling, wash till the pH value of the washing liquid is 8, then dry at 120° C. for 12 h, and calcine at 500° C. for 5 h to obtain a catalyst sample A with the weight percentage of a core layer being 66%, the weight percentage of a transition layer being 9% and the weight percentage of a shell layer being 25%.

Example 2

(18) Admix 5 g of the precipitated FeMn catalyst prepared in Example 1 into 50 mL of aluminum isopropoxide trihydrate solution, continuously stir, then perform rotary evaporation to remove the solvent, dry and calcine to obtain a sample having an Al.sub.2O.sub.3 coating. Next, admix the sample into 50 mL of solution containing tetrapropylammonium hydroxide template, ethyl orthosilicate, Al.sub.2O.sub.3, NaOH and H.sub.2O in a ratio of 0.3:1.0:0.03:0.015:130, stir for 4 h, then charge into a hydrothermal kettle, seal, heat to 180° C., and hydrothermally crystallize for 48 h. Filter the solid product after crystallization and cooling, wash till the pH value of the washing liquid is 8, then dry at 120° C. for 12 h, and calcine at 500° C. for 5 h to obtain a catalyst sample B with the weight percentage of a core layer being 64%, the weight percentage of a transition layer being 8% and the weight percentage of a shell layer being 28%.

Example 3

(19) Take 5 g of 20 wt % Fe 1 wt % K/SiO.sub.2 supported iron-based catalyst prepared using an—incipient wetness impregnation method. Admix the sample into 50 mL of aluminum isopropoxide trihydrate solution, continuously stir, then perform rotary evaporation to remove the solvent, dry and calcine to obtain an iron catalyst sample having an Al.sub.2O.sub.3 coating.

(20) Next, admix the sample into 50 mL of solution containing tetrapropylammonium hydroxide template, ethyl orthosilicate, Al.sub.2O.sub.3, NaOH and H.sub.2O in a ratio of 0.3:1.0:0.05:0.010:130, stir for 4 h, then charge into a hydrothermal kettle, seal, heat to 180° C., and hydrothermally crystallize for 48 h. Filter the solid product after crystallization and cooling, wash till the pH value of the washing liquid is 8, then dry at 120° C. for 12 h, and calcine at 500° C. for 5 h to obtain a catalyst sample C with the weight percentage of a core layer being 74%, the weight percentage of a transition layer being 6% and the weight percentage of a shell layer being 20%.

Example 4

(21) Take 5 g of the catalyst sample A in Example 1, admix into 5.2 mL of zinc nitrate solution by an incipient wetness impregnation method, perform rotary evaporation to dryness, dry at 120° C. for 12 h, and calcine at 500° C. for 5 h to obtain a catalyst sample containing 3% of metallic Zn element by weight in the shell layer molecular sieve; next, admix the sample into an n-hexane solution containing 2 wt % of ethyl orthosilicate, stir for 4 h, perform rotary evaporation to dryness, dry at 120° C. for 12 h, and calcine at 500° C. for 10 h to obtain a catalyst D.

Example 5

(22) Take 2 g of the catalyst sample B in Example 2 to support a gallium nitrate solution by an ion exchange method, perform rotary evaporation to dryness, dry at 120° C. for 12 h, and calcine at 500° C. for 5 h to obtain a catalyst sample containing 2.5% of metallic Ga element by weight in the shell layer molecular sieve, next, admix the sample into 15 mL of n-hexane solution containing 2 wt % of ethyl orthosilicate, stir for 4 h, perform rotary evaporation to dryness, dry at 120° C. for 12 h, and calcine at 500° C. for 10 h to obtain a catalyst E.

Example 6

(23) Take 2 g of the catalyst sample C in Example 3 to support a zinc nitrate solution by an ion exchange method, perform rotary evaporation to dryness, dry at 120° C. for 12 h, and calcine at 500° C. for 5 h to obtain a catalyst sample F containing 4% of metallic Zn element by weight in the shell layer molecular sieve.

Examples 7˜11: Application of Invented Catalysts in Conversion of Synthesis Gas to Aromatic Hydrocarbons

(24) Mold the prepared catalyst under the pressure of 6.5 MPa, crush and sieve to obtain a sample of 40 to 60 meshes. Add 1.0 g of the catalyst into a continuous flow reactor, wherein the catalyst was pre-reduced with one or more of hydrogen, carbon monoxide, methane, ethane and ethylene gas for a certain period of time, and then cooled to the reaction temperature for continuous reaction. The reaction gas consisted of 45 vol % CO, 45 vol % H.sub.2 and 4 vol % N.sub.2, with N.sub.2 as the internal standard gas for calculating the conversion rate of CO. The product was analyzed on line under atmospheric pressure by a gas chromatograph equipped with a thermal conductivity cell and a hydrogen ion flame detector after cold trap, and the product in the cold trap was analyzed off line by another gas chromatograph equipped with a hydrogen ion flame detector.

Example 7

(25) Put 1 g of the catalysts A to F into a pressurized fixed bed reactor respectively, heat to 400° C. at 5° C./min in an H.sub.2 atmosphere, and reduce under atmospheric pressure at the space velocity of 1000 h.sup.−1 for 10 h. Then, cool, introduce a reaction gas for reaction, and continuously react at the pressure of 1.0 MPa, the space velocity of 5000 h.sup.−1 and the temperature of 300° C. for 30 h, wherein the CO conversion rate and the selectivity of each product were shown in Table 1.

Example 8

(26) Put 1 g of the catalyst D into a pressurized fixed bed reactor, heat to 400° C. at 5° C./min in an H.sub.2 atmosphere, and reduce under atmospheric pressure at the space velocity of 1000 h.sup.−1 for 10 h. Then, cool, introduce a reaction gas for reaction, continuously react at the pressure of 1.0 MPa, the space velocity of 5000 h.sup.−1 and the temperatures of 250° C., 300° C., 350° C. and 400° C. for 30 h, and investigate the influence of the reaction temperatures. The CO conversion rate and the selectivity of each product were shown in Table 1.

Example 9

(27) Put 1 g of the catalyst E into a pressurized fixed bed reactor, heat to 400° C. at 5° C./min in an H.sub.2 atmosphere, and reduce under atmospheric pressure at the space velocity of 1000 h.sup.−1 for 10 h. Then, cool, introduce a reaction gas for reaction, continuously react at the space velocity of 5000 h.sup.−1, the temperature of 300° C. and the pressures of 0.5 MPa, 1.0 MPa, 2.0 MPa and 3.0 MPa for 30 h, and investigate the influence of the reaction pressures. The CO conversion rate and the selectivity of each product were shown in Table 1.

Example 10

(28) Put 1 g of the catalyst D into a pressurized fluidized bed reactor and a slurry bed reactor respectively, heat to 400° C. at 5° C./min in an H.sub.2 atmosphere, and reduce under atmospheric pressure at the space velocity of 1000 h.sup.−1 for 10 h. Then, cool, introduce a reaction gas for reaction, and continuously react at the pressure of 1.0 MPa, the space velocity of 5000 h.sup.−1 and the temperature of 300° C. for 30 h, wherein the CO conversion rate and the selectivity of each product were shown in Table 1. The results were used for comparing the reaction results of the catalyst in different reactors. The results showed that the results in the slurry bed reactor and the fluidized bed reactor were similar, but both are lower in the aromatic hydrocarbon selectivity than the fixed bed (Example 7).

Example 11

(29) Put 1 g of the catalyst D into a pressurized fixed bed reactor, heat to 400° C. at 5° C./min in an H.sub.2 atmosphere, and reduce under atmospheric pressure at the space velocity of 1000 h.sup.−1 for 10 h. Then, cool, introduce a reaction gas for reaction, and continuously react at the pressure of 1.0 MPa, the space velocity of 5000 h.sup.−1 and the temperature of 300° C. for 500 h. The CO conversion rate and the selectivity of each product were shown in Table 1.

Comparative Example 1

(30) Tablet, mold, crush and sieve the precipitated FeMn catalyst and FeK/SiO.sub.2 catalyst prepared in Example 1 and Example 3 respectively, add 1.0 g of respective catalyst of 40 to 60 meshes into a pressurized fixed bed reactor, heat to 400° C. at 5° C./min in an H.sub.2 atmosphere, and reduce under atmospheric pressure at the space velocity of 1000 h.sup.−1 for 10 h. Then, cool, introduce a reaction gas for reaction, and continuously react at the temperature of 300° C., the pressure of 1.0 MPa and the space velocity of 5000 h.sup.−1 for 30 h, wherein the CO conversion rate and the selectivity of each product were shown in Table 2.

Comparative Example 2

(31) Admix 5 g of the precipitated FeMn catalyst sample prepared in Example 1 into 50 mL of solution containing tetrapropylammonium hydroxide template, ethyl orthosilicate, Al.sub.2O.sub.3, NaOH and H.sub.2O in a ratio of 0.3:1.0:0.03:0.015:130, stir for 4 h, then charge into a hydrothermal kettle, seal, heat to 180° C., and hydrothermally crystallize for 48 h. Filter the solid product after crystallization and cooling, wash till the pH value of the washing liquid is 8, then dry at 120° C. for 12 h, and calcine at 500° C. for 5 h to obtain a catalyst sample G with the weight percentage of a core layer being 71% and the weight percentage of a shell layer being 29%. Tablet, mold, crush and sieve the catalyst G, add 1.0 g of the catalyst of 40 to 60 meshes into a pressurized fixed bed reactor and a slurry bed reactor respectively, heat to 400° C. at 5° C./min in an H.sub.2 atmosphere, and reduce under atmospheric pressure at the space velocity of 1000 h.sup.−1 for 10 h. Then, cool, introduce a reaction gas for reaction, and continuously react at the temperature of 300° C., the pressure of 1.0 MPa and the space velocity of 5000 h.sup.−1 for 30 h, wherein the CO conversion rate and the selectivity of each product were shown in Table 2.

(32) TABLE-US-00001 TABLE 1 Reaction performance of different catalysts for conversion of synthesis gas to aromatic hydrocarbons. CO Hydrocarbon product distribution (CO.sub.2-free C-mol %) Temperature Pressure/ conversion xylene Catalyst ° C. MPa rate/% methane olefin alkane benzene toluene o- m- p- A.sub.9+ other A 300 1 63 15.4 0.3 15.3 10.6 21.5 3.9 1.2 28 2.3 1.5 B 300 1 59 14.5 0.4 14.2 11.7 22.4 3.5 1.7 27.5 2.1 2 C 300 1 38.2 15.8 0.4 15.2 9.9 18.8 3.1 2.1 30.1 2.2 2.4 D 300 1 69.4 13.5 0.4 10.5 13.5 18.2 4.6 1.3 32.5 3.6 1.9 E 300 1 67 11.2 0.6 7.5 14.8 20.7 4.3 2.6 34.5 2.6 1.2 F 300 1 49.8 12.1 0.2 11.1 12.8 21.8 4.6 1.8 30.9 2.9 1.8 D 250 1 26.1 10.7 2.3 9.8 13.3 23.3 0.7 1.9 26.8 9.6 1.6 D 350 1 83 17 0.3 23.3 7.8 17.3 3.6 2.2 24.5 2.5 1.5 D 400 1 91 22.5 0.3 34.7 8.2 15.2 2.3 0.9 14.2 0.9 0.8 E 300 0.5 50 13 1.5 16 5.9 31.1 2.0 1.3 25.6 3 0.6 E 300 2 75.5 12.5 0.4 14.5 7.9 22.4 2.1 2.3 34.6 2.4 0.9 E 300 3 83 11 0.2 13 8.1 25.2 3.4 2.1 33.2 2.8 1 D 300 1 69.4 13.5 0.4 10.5 13.5 18.2 2.8 1.9 33.7 3.6 1.9 D* 300 1 56.5 15.5 1.2 12.5 8.8 18.2 3.5 0.6 27.1 8.2 4.4 D** 300 1 58.1 16.3 1.6 11.8 9.5 18.8 4.2 1.1 24.6 8.1 4 D*** 300 1 64 13.5 0.5 11 14.1 19.2 3.8 0.9 30.9 2.1 4 Reaction space velocity: 5000 h.sup.−1; average value of reacting 10 to 30 h. *, fluidized bed reactor; **, slurry bed reactor; ***, continuously reacting for 500 h.

(33) TABLE-US-00002 TABLE 2 Comparative experiment results. CO Hydrocarbon product distribution (CO.sub.2-free C-mol %) Temperature Pressure/ conversion xylene Catalyst ° C. MPa rate/% methane olefin alkane benzene toluene o- m- p- A.sub.9+ other FeMn 300 1 57.6 14.5 45.6 34.9 0 0 0 0 0 0 5   FeK/SiO.sub.2 300 1 35.1 20.1 48 29.6 0 0 0 0 0 0 2.3 G 300 1 60 13 1.2 15 6.9 18.3 7.2 5.1 10.2 18.9 4.2 G** 300 1 62 14.5 1.5 14.5 7.3 16.2 4.5 6.4 9.4 20.9 4.8 Reaction space velocity: 5000 h.sup.−1; average value of reacting 10 to 30 h. **, slurry bed reactor.

(34) It can be seen from the comparison of the examples and the comparative examples in Tables 1 and 2 that the catalyst containing the transition layer oxide and with the molecular sieve layer being modified internally and externally has higher selectivity to light aromatic hydrocarbons, the highest BTX selectivity is 76.9%, and particularly, the selectivity to xylene reaches 30% or above, accounting for 80 to 90% of the xylene. The catalysts with the molecular sieve layers not being modified internally and externally show more heavy aromatic hydrocarbon products.

(35) The disclosure described and claimed herein is not to be limited in scope by the specific aspects herein disclosed. Any person skilled in the art can make modifications without departing from the spirit and scope of the disclosure. The scope of protection of the present disclosure should therefore be defined by the claims.