Mesoporous MFI Zeolite Nanosponge Supporting

Cobalt Nanoparticles as a Fischer-Tropsch

Catalyst with High Yield of Branched

Hydrocarbons in the Gasoline Range

Jeong-Chul Kim†, ‡, Seungyeop Lee†, ‡, Kanghee Cho†, Kyungsu Na†, Changq Lee§,† and

Ryong Ryoo*,†, §

†Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS),

Daejeon 305-701, Republic of Korea

‡Graduate School of Nanoscience and Technology, KAIST, Daejeon 305-701, Republic of

Korea

§Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea

*Corresponding author: Tel +82 42 350 2830; Fax +82 42 350 8130; E-mail:

rryoo@kaist.ac.kr

1. Supporting experimental section.

(1) Preparation of desilicated MFI zeolite

Desilicated MFI zeolite was prepared by desilication method, following the procedure described

elsewhere.1 A commercial MFI zeolite sample (Zeolyst, CBV 8014, Si/Al = 40) was calcined at 823 K for 4 h to obtain the parent MFI zeolite. Desilication of MFI zeolite powder was carried out in 0.2 M NaOH aqueous solution in a polypropylene bottle and under stirring at 333 K for 0.5 h in an convection oven. This treatment was followed by immediate quenching in a water–ice bath and centrifugation to separate the zeolite powder from the solution. The residue of the desilicating agent was removed from the zeolite crystallites by subsequent redispersion in deionized water and

centrifugation cycles until neutral pH was reached. The zeolite was slurried in a 1 M NH4NO3 aqueous solution three times in all for the ion exchange to NH4

+. The NH4+-exchanged

zeolites were calcined again in air at 823 K to convert to the H+-ionic form.

(2) Synthesis of nanomorphic MTW and MRE zeolites

For the synthesis of the nanomorphic zeolite, tetraethylorthosilicate (TEOS, 95%, Junsei), sodium aluminate (53wt%, Sigma-Aldrich), sodium hydroxide, distilled water, and hexa-quaternary ammonium surfactant with the molecular formula of [C22H45-N

+(CH3)2-C6H12-N+(CH3)2-CH2-(C6H4)-

CH2-N+(CH3)2-C6H12-N

+(CH3)2-CH2-(C6H4)-CH2-N+(CH3)2-C6H12-N

+(CH3)2-C22H45](Br-)2(Cl-)4] (in short, C22N6) were mixed by the following procedure.2 Sodium hydroxide and sodium aluminate were dissolved in distilled water. To this solution, the C22N6 surfactant was added and dissolved at 333 K. After dissolution of the surfactant, the solution was cooled down to room temperature and mixed with TEOS. This mixture was vigorously mixed by hand shaking, and afterward, the resultant white gel was stirred at 333 K for 6 h. The molar composition of the gel for MTW zeolite was 100 SiO2: 1 Al2O3: 3.33 C22N6: 13 Na2O: 4500 H2O. The molar composition of the gel for MRE zeolite was 100 SiO2: 0.5 Al2O3: 1.67 C22N6: 13 Na2O: 3000 H2O. The resultant gels were transferred to a Teflon-lined autoclave and heated to synthesis temperature with tumbling. Synthesis temperature and time were varied depending on the zeolite structure. The nano MTW and MRE zeolites were obtained at 423 K for 3 d. The final products were filtered, washed with distilled water, and dried at 373 K for 12 h. The zeolite products were calcined at 853 K for 6 h to remove the remained surfactant. The zeolite was ion-exchanged three times with 1 M NH4NO3 solution and subsequently calcined again at 823 K for conversion to the H+ form.

(3) Octane hydroisomerization

The n-C8 hydroisomerization reaction was carried out in a steel fixed-bed reactor (7-mm inside diameter) under H2 at atmospheric pressure using 0.1 g of powdered catalyst. The temperature was measured using a K-type thermocouple inserted into the reactor through a thermocouple well. Prior to the reaction, the catalyst was reduced with high-purity H2 (99.999%, 50 cm3 min-1) at 673 K for 12 h. After cooling to 493 K, n-C8 (99 %, Junsei) was fed through a syringe pump (KD Scientific) as diluted by H2 flow with a H2/n-C8 molar ratio of 12. The weight hourly space velocity (WHSV) of n-C8 was 1.3 h-1. The reaction effluent was analyzed using an online gas chromatograph (GC, Younglin, Acme-6000) equipped with a flame ionization detector. The products were separated by a HP-1 column (Agilent).

(4) Catalytic measurement of FT-reaction over Co/NS-MFI and Co/γ-Al2O3 by SK Innovation FT synthesis was carried out in a continuous-flow pressurized fixed-bed reactor (inner diameter = 6.2 mm). 0.5 g of powdered catalyst supporting Co nanoparticles was loaded in the reactor and pretreated under pure H2 atmosphere (flow rate = 50 cm3 min-1) at 693 K for 12 h. After the reactor was cooled to room temperature, the syngas mixture (H2: CO: Ar = 18: 9: 1 in moles) was introduced into the catalyst bed. The pressure of the syngas mixture was increased to 2.0 MPa, then the flow rate was regulated at 20 cm3 min-1 (GHSV = 2.4 L h-1 g-1). The reactor temperature was increased to 508 K under this flow, and the FT reaction started. Product selectivity was analyzed using three different gas chromatographs. An effluent gas was collected with a tedlar bag and analyzed by a gas chromatograph (Agilent, 7890A) using a RGA system (AC analytical solutions, AC Hi-Speed RGA), equipped with FID/TCD/TCD detectors. An Al2O3 PLOT column (35 m × 0.32 mm × 8 μm; AC 21073.048) was used in connection with a sophisticated splitter and valve system. Liquid-phase products were collected in a cold trap (set to 277 K) and analyzed by a gas chromatograph equipped with MSD/FID (Agilent, 5975A) detectors. A fused-silica capillary column (50 m × 0.2 mm × 0.5 μm; HP-PONA) was used with a splitter system. Heavy hydrocarbon products remaining in the reactor were dissolved with a large amount of carbon disulfide (CS2) solvent and analyzed by a gas chromatograph using a SIMDIS system (AC analytical solutions) equipped with a FID detector. The analysis was performed according to ASTM D6352 test method with a column (5 m × 0.53 mm × 0.109 μm; AC 24001.065). The coke and adsorbed hydrocarbons of used catalysts were analyzed by thermogravimetry, after unloading the catalyst from the reactor. Carbon balances were all better than 90%. Product distributions were also investigated according to the Anderson-Schulz-Flory (ASF) distribution.

2. Supporting figures and tables

Figure S1. Characterization results of Bulk MFI zeolite: (a,b) SEM images, (c) XRD pattern, (d) argon sorption isotherm obtained at 87 K, and (e) BJH pore size distribution corresponding to the adsorption branch.

Figure S2. Solid state 31P NMR spectra of trimethylphosphine oxide (TMPO) adsorbed in (a) NS-MFI and (b) B-MFI. The NMR spectrum was deconvoluted to four individual peaks corresponding to TMPO chemisorbed onto the Brönsted acid sites and a peak corresponding to TMPO physisorbed in the zeolite sample. Among the peaks for chemisorbed TMPO, the TMPO adsorbed onto the stronger Brönsted acid sites peaked at the higher chemical shift of the NMR spectrum.

Figure S3. TEM images (left column) and Co-particle diameter distributions (right column) of (a) Co/NS-MFI which was collected after 200 h of the FT synthesis reaction, (b) Co/B-MFI and (c) Co/γ-Al2O3 catalysts which were collected after 100 h of the FT synthesis reaction.

Figure S4. Representative TEM images of (a, b) Co/NS-MFI catalyst which were collected after 100 h of the FT synthesis reaction at 573 K. Insets of TEM images in (a) is the size distribution of cobalt nanoparticles supported on NS-MFI, which were derived from TEM images.

Figure S5. The selectivity of gas products (CO2, CH4 and light hydrocarbons), plotted as a function of time on stream: (a) Co/NS-MFI, (b) Co/B-MFI and (c) Co/γ-Al2O3 (reaction conditions: GHSV = 2.4 L h-1 g-1, reaction temperature = 493 K, reaction pressure = 20 bar, and H2/CO ratio = 2)

Figure S6. (a) Product selectivity of Co/NS-MFI and Co/γ-Al2O3 catalysts, which were averaged over 50 h of FT synthesis. Reaction conditions: 0.5 g of catalyst, reactant mixture (H2: CO: Ar = 18: 9: 1 in moles), flow rate = 20 cm3 min-1, temperature = 508 K, and pressure = 2 MPa. (b) Product distributions according to carbon number of Co/NS-MFI and Co/γ-Al2O3 catalysts in FT synthesis reaction. The product distribution of Co/γ-Al2O3 catalyst followed ASF distribution. However, Co/NS-MFI did not follow ASF distribution. Chain growth probability (α) for Co/γ-Al2O3 catalyst was derived in the range of carbon number between C7 and C24. All catalytic data shown in this figure were measured with equipment at Catalyst·Process R&D Center, SK Innovation. The experimental details are described in Supporting experimental section.

Figure S7. Characterization results of DS-MFI: (a) TEM image, (b) SEM image, (c) XRD pattern, (d) argon sorption isotherm obtained at 87 K, and (e) BJH pore size distribution corresponding to the adsorption branch.

Figure S8. TEM images of (a) Co/DS-MFI (b) Co/MTW and (c) Co/MRE.

Figure S9. CO conversion over Co/DS-MFI, Co/MTW and Co/MRE, plotted as a function of time on stream (reaction conditions: GHSV = 2.4 L h-1 g-1, reaction temperature = 493 K, reaction pressure = 20 bar, and H2/CO ratio = 2).

Figure S10. Characterization results of MTW zeolite nanosponge: (a) TEM image, (b) SEM image, (c) XRD pattern, (d) argon sorption isotherm obtained at 87 K, and (e) BJH pore size distribution corresponding to the adsorption branch.

Figure S11. Characterization results of MRE zeolite nanosponge: (a) TEM image, (b) SEM image, (c) XRD pattern, (d) argon sorption isotherm obtained at 87 K, and (e) BJH pore size distribution corresponding to the adsorption branch.

Table S1. CO conversion (mmol) over Co/NS-MFI and Co/γ-Al2O3 samples and resultant product selectivity, which were averaged over 50 h of the FT reaction time.

Co/NS-MFIa Co/NS-MFIa

Average CO conversion (mmol h-1) 10.6 10.5

CO2b 10.8 9.8

CH4b 12.6 11.2

olefin (C2-C4)b 1.5 1.5

n-paraffin (C2-C4)b 3.6 2.9

olefin (C5-C11)b 30.9 6.4

i-paraffin (C5-C11)b 23.9 5.9

n-paraffin (C5-C11)b 9.6 25.0

olefin+paraffin (C12+)b 3.1 33.7

othersb,c 4.0 3.6

[a] All catalytic data shown in this figure were measured with equipment at Catalyst·Process R&D Center, SK Innovation. Reaction conditions: 0.5 g of catalyst, reactant mixture (H2: CO: Ar = 18: 9: 1 in moles), flow rate = 20 cm3 min-1, temperature = 508 K, and pressure = 2 MPa. [b] CO conversion and selectivity (C%) of individual component in product mixture, which were averaged over 50 h of reaction time. [c] Oxygenates and aromatic compounds, which were included in the product mixture. Carbon balances were all better than 90%.

Table S2. CO conversion (%) and resultant product selectivity (C%) over Co/NS-MFI sample, measured at various points of time on streama.

Reaction time (h) 25 50 75 100

CO conversion (%) 79.2 81.0 78.0 76.5

CO2b 7.6 6.5 5.0 4.6

CH4b 8.1 7.9 7.9 7.9

olefin (C2-C4)b 2.5 2.3 2.2 2.2

n-paraffin (C2-C4)b 3.3 3.5 3.2 3.2

olefin (C5-C11)b 35.4 32.8 34.2 35.6

i-paraffin (C5-C11)b 26.4 29.3 28.5 28.4

n-paraffin (C5-C11)b 8.5 9.2 10.1 9.8

olefin+paraffin (C12+)b 6.2 7.0 8.1 7.2

othersb,c 2.0 1.5 0.8 1.1

[a] Reaction conditions: 0.5 g of catalyst, GHSV = 2.4 L h-1 g-1, temperature = 493 K, pressure = 20 bar, H2/CO ratio = 2. [b] Selectivity (C%) of individual component in product mixture. [c] Oxygenates and aromatic compounds, which were included in the product mixture.

Table S3. Catalytic results of octane hydroisomerization reaction using Co/NS-MFI and Co/B-MFI as catalystsa.

Catalysts

Octane Conversiona /% Product selectivity / %

i-C7 Cracked product

Co/NS-MFI 7.2 81.0 19.0

Co/B-MFI 5.8 55.1 44.9

[a] Reaction conditions: catalyst 0.1 g, WHSV = 6.8 h-1, temperature = 493 K, pressure = 20 bar, H2/C8 ratio = 12.

Table S4. Catalytic results of n-hexadecane hydrocracking and hydroisomerization reaction using Co/NS-MFI as a catalyst a.

Catalyst Hexadecane conversion (%)

Product selectivity (%)

i-C16 Cracked product

CH4 C2-4 C5-11 C12+

Co/NS-MFI 95.1 27.2 2.5 4.8 27.1 38.4

[a] Reaction conditions: catalyst 0.5 g, WHSV = 0.47 h-1, temperature = 493 K, pressure = 20 bar, H2/C16 ratio = 240.

Table S5. Average CO conversion (mmol) and products distributions (C%) for 100 h over Co/NS-MFI and Co/γ-Al2O3 samples in the FT synthesis reactions under various reaction conditionsa.

Co/NS-MFI (473 K)d

Co/γ-Al2O3

(473K)d

Co/NS-MFI (523 K)e

Co/γ-Al2O3

(523K)e

Co/NS-MFI

(H2/CO=1)f

Co/γ-Al2O3

(H2/CO=1)e

Average CO conversion (mmol h-1)

2.3 2.9 13.7 13.9 2.3 1.6

CO2b 0.0 0.0 12.3 13.1 0.0 0.0

CH4b 14.8 9.1 19.8 14.7 8.3 5.7

olefin (C2-C4)b 5.3 2.3 1.3 1.2 3.5 1.7

n-paraffin (C2-C4)b 3.4 1.8 2.9 3.3 2.0 0.6

olefin (C5-C11)b 18.2 5.2 22.8 5.7 23.5 7.8

i-paraffin (C5-C11)b 13.7 1.5 17.0 5.9 17.4 8.1

n-paraffin (C5-C11)b 15.8 21.2 9.8 13.9 9.2 14.8

olefin+paraffin (C12+)b 23.6 58.8 10.8 42.1 33.9 61.2

othersb,c 4.2 0.1 2.3 0.1 1.2 0.1

[a] Reaction conditions: 0.5 g of catalyst, GHSV = 2.4 L h-1 g-1, pressure = 20 bar, H2/CO ratio = 2, time on stream 100 h. [b] Selectivity (C%) of individual component in product mixture, which were averaged over 100 h of reaction time. [c] Oxygenates and aromatic compounds, which were included in the product mixture. [d] Reaction temperature was 473 K, while the H2/CO ratio was retained to 2. [e] Reaction temperature was 523 K, while the H2/CO ratio was retained to 2. [f] H2/CO ratio was decreased to 1, while the reaction temperature was 493 K.

Table S6. Physicochemical properties of the desilicated MFI zeolite (DS-MFI), MTW nanosponge and MRE nanosponges.

Catalysts Si/Ala SBETb

/m2 g-1 Sext

c /m2 g-1

Vmicrod

/cm3 g-1 Vmeso

e /cm3 g-1

BAtotf

/μmol g-1

DS-MFI 14 380 180 0.09 0.18 1120

MTW 55 540 350 0.08 0.66 223

MRE 110 440 320 0.05 0.51 112

[a] Si/Al mole ratio obtained from ICP/AES analysis. [b] SBET is the BET surface area obtained from Ar adsorption in relative pressure range (P/P0) of 0.05-0.20. [c] Sext is the external surface area determined according to the t-plot method. [d] Vmicro is the micropore volume calculated from t-plot method. [e] Vmeso is the mesopore volume. [f] BAtot is the concentration of Brönsted acid sites measured by 31P NMR analysis after trimethylphosphine oxide adsorption.

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