Short Contact Time Catalytic Partial Oxidation of Methane over

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Kinetics, Catalysis, and Reaction Engineering

Short contact time catalytic partial oxidation of methane over rhodium supported on ceria based 3-D printed supports Corey Leclerc, and Rohan Gudgila Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.9b01169 • Publication Date (Web): 29 Jul 2019 Downloaded from pubs.acs.org on July 31, 2019

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Industrial & Engineering Chemistry Research

Short Contact Time Catalytic Partial Oxidation of Methane over Rhodium Supported on Ceria Based 3-D Printed Supports Corey A. Leclerc1,* and Rohan Gudgila2 1Department

of Chemical Engineering & Department of Materials Engineering

2Department

of Petroleum Engineering

New Mexico Institute of Mining & Technology, 801 Leroy Place, Socorro, NM 87801

Keywords: short contact time, 3-D printing, rhodium, hydrogen, catalytic partial oxidation

* To whom correspondence should be addressed: Tel: (575) 835-5293. Fax: (575) 835-5210. E-mail: [email protected]

Abstract Three different ceria containing catalyst supports and an alumina (control) support have been deposited with rhodium and used in the short contact time catalytic partial oxidation of methane. The goal of this paper is to compare reactor performance from powder catalyst studies to determine how they translate into structured high gas hourly space velocity catalysts operating at millisecond contact times. The supports were synthesized by 3-D printing of powders allowing for the first time the use of a catalyst support in the form of a monolith entirely composed of ceria. The ceria containing supports demonstrated some of the enhanced activity demonstrated as powders and showed superior methane conversion and hydrogen selectivity as compared to the alumina support. The use of 3-D printing to translate powder catalysts into structured supports is promising.

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1. Introduction Short contact time catalytic partial oxidation (SCT-CPO) is a promising route to produce synthesis gas from a wide range of fuels. In catalytic partial oxidation, a fuel is reacted with oxygen at ratios that are much higher than is required for complete combustion leading to the production of hydrogen and carbon monoxide. Equation 1 shows the reaction for methane: 𝐶𝐻4 +

1

2𝑂2 𝐶𝑂 + 2𝐻2

∆𝐻 = ―41 𝑘𝐽/𝑚𝑜𝑙

(1)

For most fuels, the reaction is exothermic. The heat generated from the reaction is sufficient to maintain catalyst lightoff. In fact, the reactor operates nearly adiabatically leading to exit temperatures >600°C. Even with a residence time that is on the order of milliseconds, the reactor often achieves ~90% conversion of fuel, nearly 100% conversion of oxygen, and ~90% selectivity to hydrogen. This is true for a wide range of fuels from methane 1, to alcohols 2 3, to liquid fuel surrogates 4 5 6, and gaseous fuel surrogates 7. Rhodium was found to be the catalyst that provides the highest yields of hydrogen with the most robust stability 8. In order to achieve high gas hourly space velocities, the catalyst is deposited on a structured support, such as a reticulated foam. Indeed it has been shown that reticulated foams achieve the highest activity as compared to straight channel monoliths 9. One limitation regarding reticulated foams is the material available. Bodke et al. also showed that zirconia demonstrated superior performance as a support for a rhodium catalyst though it was not much better than alumina 9. In that study, less than 10 materials were available for reticulated foams. The literature on powder catalysts is much more expansive when it comes to choice of materials. In this regard, structured supports are limited. Ceria has been used as a support for powder catalysts in catalytic partial oxidation. Pantaleo et al. found that the use of a ceria support led to less carbon deposition on the catalyst surface 10. They attribute the reduction in carbon to the oxygen mobility in ceria supplying oxygen to remove the carbon. Costa et al. found that ceria further promoted CO oxidation to carbon dioxide in ethanol partial oxidation 11. Additionally, ceria has been shown to promote water gas shift activity 12. In a separate study, Moral et al. found that alumina was better than ceria as a support for a rhodium catalyst in the oxy-dry reforming of methane 13, but they did not specify why that was so. To combine the fluid dynamic benefits of structured supports with the material availability of powders, several groups have coated ceria on monoliths or reticulated foams. Nguyen et al. co-precipitated ceria with rhodium for methyl acetate short contact time catalytic partial oxidation 6. They found that ceria enhanced the conversion of methyl acetate. Similarly, Scarabello et al. found that ceria reduced the catalyst lightoff temperature and increase methane conversion for partial oxidation when they coated a structured support with ceria 14. Other groups have synthesized similar catalysts for related catalytic processes. Vita et al. added ceria to a cordierite monolith using rhodium as a catalyst for the steam reforming and oxidative steam reforming of methane 15 16. Similarly, Moraes et al. added a mixture of ceria and silica to a cordierite foam to enhance a rhodium catalysts 17. Robocasting is a process by which ceramic powders are 3-D printed in layers forming a support structure ideal for catalysts. In fact, Ferrizz et al. showed that these 3-D printed supports have superior mass transfer capabilities compared to straight channel monoliths 18. A major benefit of these supports is the ability to 3-D print essentially any ceramic powder into the desired support structure. This enables the 2 ACS Paragon Plus Environment

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ability to determine catalytic activity under conditions with little to no mass and heat transfer limitations (powder catalysts), then measure their activity under severely mass and heat transfer limiting systems like short contact time reactors. In this work, we have used 4 different catalyst supports prepared by 3-D printing of powders. Two of the supports contain ceria which has not been previously available. Though depositing ceria on alumina foams has been carried out and has shown more activity, this work compares 2 ceria containing supports with an alumina support and another alumina support with ceria deposited on the surface. Based on previous literature findings that ceria 1) enhances carbon burnoff, 2) promotes the oxidation of CO to CO2, 3) enhances methane conversion, and 4) enhances the water-gas shift reaction, this work seeks to determine how ceria enhances the short contact time catalytic partial oxidation of methane on rhodium.

2. Experimental Section 2.1 Reactor Set-up The reactor consists of a 40 cm quartz tube. The catalytic support is placed between two blank alumina supports, wrapped in alumino-silica paper (Unifrax), and pushed into the middle of the reactor. A K-type thermocouple (Omega) is inserted through the downstream blank alumina support to make contact with the back face of the catalytic monolith. Mass flow controllers (Tylan) meter nitrogen (Airgas), air (Airgas), and methane (Airgas) to the reactor at total flow rates from 2 to 8 standard liters per minute. The gases exiting the reactor are sampled with a gas tight syringe and immediately injected into an Agilent 7890 gas chromatograph. The gas chromatograph has a split/splitless injector using helium as the carrier gas. All gases except CO2 move through the first column (Poraplot Q) and on to a second column (Molsieve). Once those gases have passed through column 1 to column 2, a valve switches the outlet of column one to the thermal conductivity detector (TCD) from column 2. The carbon dioxide then exits the column to the TCD. After the carbon dioxide is detected on the TCD, the valve switches back to supplying flow to column 2. The remaining products leave column 2 to the TCD. All products except for water and hydrogen are measured directly. The water is calculated by closing the atomic oxygen balance. The molecular hydrogen is calculated by closing the atomic hydrogen balance. The carbon balance is calculated and must be within 3%. Each data point presented is the average value of three separate reactor runs. The error bars represent the range one standard deviation above and one below the average value. The conversion of methane is calculated based on the difference of the feed flow in minus the amount of methane exiting all divided by the methane fed. The product selectivities are calculated based on the amount of product exiting the reactor divided by the amount of all carbon containing species in the case of carbon monoxide and by the amount of all hydrogen containing species in the case of molecular hydrogen. The back face temperature that is reported is measured by the thermocouple that is placed between the downstream heat shield and the catalyst.

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To start the reactor, methane and air are fed at an appropriate stoichiometry for partial oxidation. The flame of a Bunsen burner is placed so that it impinges on the outside of the reactor at the catalyst. The back face temperature of the catalyst will slowly heat up. At ~250°C, the back face temperature will begin to rise rapidly indicating lightoff. At that time, the Bunsen burner is removed from the reactor and insulation is wrapped around the reactor at the catalyst. To shut down the reactor, the air flow rate is turned off, while simultaneously turning on a stream of pure nitrogen. By turning the air off first, the normally fuel rich mixture stays fuel rich avoiding the possibility of the reactant mixture entering the flammable regime. Turning the methane off first or turning the air and methane off simultaneously may cause the reactor to explode. After thirty seconds of nitrogen and methane flow, the methane is turned off. The nitrogen is allowed to flow to cool the reactor down to a safe temperature.

2.3 Catalyst Synthesis Catalyst supports were supplied by Robocasting Enterprises LLC. The supports were made using their Robocasting method. A slurry of ceramic powder is 3-D printed into a monolith shape, allowed to dry, then sintered at 1500°C. The supports are cylinders that are 1.7 cm in diameter and 1 cm in length. The void fraction of the supports is 58%. Figure 1 shows a top view (left) and side view (right) of the supports. The support is printed by depositing one layer of struts then building each successive layer until the support is of the desired length. Each successive layer is rotated 90°C and each odd layer (or even) layer is offset from the previous odd (or even layer). In figure 1, the top layer is a vertical strut, the second layer is a horizontal strut, and the third layer is a vertical strut that is visible because it is not underneath the first strut. Instead it is offset from the first layer. This has been described as the fcc configuration 19. In this configuration, there is no line of sight from one end of the support to the other. For all supports used in this work, the strut thickness is 1.11 mm and the spacing between struts is 1.79 mm. To deposit the catalyst, a 14% rhodium nitrate solution (Alfa Aesar) in water is diluted and added drop wise to each support. When the support becomes saturated, they are allowed to dry overnight at room temperature. The addition of solution continues until all of the solution is gone. Once all of the solution has been added and the catalyst has been dried in air for the final time, it is placed in a furnace at 600°C for 4 hours. Four different catalysts were examined in this work. The first consisted of an alumina monolith denoted as Al2O3. The second consisted of an alumina monolith that had ceria deposited on the surface with rhodium (CeO2 on Al2O3). The third consisted of a ceria monolith (CeO2). The fourth and final catalyst consisted of a support composed of 50% alumina and 50% ceria by weight (CeO2/Al2O3). The final total mass of Rh, Rh loading, and mass of rhodium per void volume on each support are presented in Table 1. Each support had nearly the same mass of rhodium and nearly the same mass of rhodium per void volume. Due to differences in support density, the weight percent loadings differed from 1.08 to 1.76%.


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Table 1: Composition of Rhodium Catalyst on 3-D Printed Supports CATALYST Mass of Rh (g) Wt% Rh Catalyst mass per support void volume (gRh/mLsupport)

Rh/Al2O3 0.060 1.42 0.143

Rh/Ce on Al2O3 0.059 1.38 0.141

Rh/CeO2 0.061 1.08 0.146

Rh/CeO2/Al2O3 0.058 1.76 0.138

2.4 Thermogravimetric Analysis (TGA) Thermogravimetric analyses were conducted in a Shimadzu TGA-50 instrument. After calibrating the scale, a sample of used catalysts was placed in an alumina sample dish. The sample was heated from room temperature to 900°C at a rate of 10°C per minute in air flowing at 20 mL/min.

3. Results 3.1 Feed Ratio Figure 2 presents reactor data for the 4 catalysts as a function of the methane to oxygen feed ratio. The methane to oxygen ratios varied from 1.4-2.2. In figure 2a, the methane conversion for the CeO2/Al2O3 supported catalyst is clearly higher than the other catalysts going from 0.94 at the low feed ratio to 0.68 at the higher feed ratio. For the most part the other three catalysts are clustered decreasing from 0.90 to 0.64 as the feed ratio increases. For all catalysts, a steady decline in methane conversion was observed as the feed ratio increased. In figure 2b, the hydrogen selectivity is also higher for the CeO2/Al2O3 supported catalyst. The other three supports have values that are much closer though CeO2 is a little bit higher than the others while Al2O3 is a little bit lower than the others. As the feed ratio increases, a slight increase in the hydrogen selectivity can be observed. In Figure 2c, the carbon monoxide selectivity of the CeO2/Al2O3 and the Al2O3 support have selectivities of 0.85 to 0.86 over the entire range of feed ratios. The CeO2 and CeO2 on Al2O3 supported catalysts have lower selectivities in the range of 0.83 to 0.84. The carbon monoxide selectivity does not change significantly as the feed ratio changes. Figure 2d shows the back face temperature for all 4 catalysts and clearly the CeO2/Al2O3 catalyst has the lowest back face temperature of the four catalysts. The temperature decreases from 910°C to 725°C over the range of feed ratios. The other catalysts are 25-40°C higher than the CeO2/Al2O3 catalyst except for Al2O3 which goes lower at times. Finally, figure 2e shows the H2:CO ratio for all 4 catalysts. The CeO2/Al2O3 supported catalyst demonstrated the highest ratio especially over the higher range of feed ratios. The Al2O3 support 5 ACS Paragon Plus Environment


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showed the lowest H2:CO ratio over the entire range. All catalysts showed a H2:CO ratio close to 2 over the entire range of feed ratios presented. Additionally, the ceria containing catalysts show a clear yet slight trend of increasing H2:CO ratio as the feed ratio increases. 3.2 Gas Hourly Space Velocity Figure 3 presents reactor data for the 4 catalysts as a function of gas hourly space velocity. The GHSVs ranged from ~110,000 h-1 to ~470,000 h-1. Figures 3 a & b show clear trends for the different supports. The CeO2/Al2O3 supported catalyst shows higher methane conversion and hydrogen selectivity than the other catalysts over the entire range of GHSVs. The CeO2 and CeO2 on Al2O3 supports show similar conversion and selectivity to each other over the entire range. The Al2O3 support shows the lowest methane conversion and hydrogen selectivity over the entire range of GHSVs. All catalysts show a slight downward trend of 0.04-0.05 in methane conversion and 0.04-0.08 in hydrogen selectivity as the GHSV increases from the bottom of the range to the top of the range. Figure 3c shows carbon monoxide selectivity for all 4 supports. The CeO2/Al2O3 and Al2O3 supports show a higher CO selectivity than the other two supports by 0.02-0.03 over the entire range. All catalysts demonstrate a slight increase in carbon monoxide selectivity over the range of GHSVs investigated. The back face temperatures, figure 3d, show that the CeO2/Al2O3 support has a lower back face temperature at the higher GHSVs while the others tend to be clustered close to one another. The difference for the CeO2/Al2O3 support is nearly 50°C at the higher GHSVs. All catalysts show an increasing trend in back face temperature as the GHSV increases. The CeO2/Al2O3 catalyst increases from 655°C to 810°C. Finally, figure 3e shows the H2:CO ratio for all 4 catalysts. The Al2O3 support had the lowest ratio over the entire range of GHSVs ranging from 2.1 at the lowest GHSV to 1.8 at the highest GHSV. The three ceria containing catalysts have similar H2:CO ratios ranging from 2.25 at the lowest GHSV to 2 at the highest space velocity. All four catalysts show a clear decreasing trend in H2:CO ratio as the GHSV increases. 3.3 Thermogravimetric Analysis The TGA results (not shown) for all 4 catalysts show a negligible change in mass when heating in air from room temperature to 900°C. No losses in mass corresponding to carbon burn off were detected for any of the 4 different supported catalysts.

4. Discussion 4.1 Promotion of Methane Conversion All supports containing ceria displayed higher methane conversions than the alumina support. Whether the support was made of ceria or had ceria precipitated on the surface, the conversion improved. The mixture of alumina and ceria in the support showed superior performance than either single material by itself. Clearly, the presence of ceria does increase the conversion of methane. 6 ACS Paragon Plus Environment

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4.2 Promotion of Water Gas Shift Activity Pure ceria or ceria precipitated on alumina supports showed enhanced water gas shift activity as demonstrated by higher hydrogen selectivities and lower carbon monoxide selectivities than the alumina support. The H2:CO ratio in the product stream was higher for these two catalysts as compared to alumina. The mixture of alumina and ceria showed higher hydrogen selectivity but similar carbon monoxide selectivity, so it is not clear that the water gas shift activity was enhanced in this case. 4.3 Promotion of Carbon Burnoff Based on TGA results, no carbon was detected on the surface of any of the used catalysts making it impossible to determine if ceria in fact enhances carbon burnoff. Accumulation of carbon has not been reported to be a problem for rhodium catalysts in short contact time catalytic partial oxidation of methane, so this may not be an appropriate system to test the carbon burnoff abilities. For example, a system utilizing hexadecane, as a surrogate for diesel, would be more likely to experience carbon build up or perhaps using a different catalyst as well. 4.4 Promotion of Carbon Monoxide Oxidation The ceria support and the ceria deposited on the alumina support led to catalysts with lower carbon monoxide selectivity. However, as previously stated, these catalysts also had higher hydrogen selectivities. The combination of higher hydrogen selectivity and lower carbon monoxide selectivity could be a result of the water gas shift reaction and not carbon monoxide oxidation. 4.5 Different Support Materials Clearly, the 50:50 mixture of ceria and alumina showed the highest activity in terms of hydrogen yield. Two other interesting results present themselves from this work. In terms of a ceria monolith versus a ceria deposited on alumina monolith as supports, there was little difference in terms of catalytic activity between the two. The interaction between rhodium and ceria should be very different in the two catalysts. In the former, rhodium is guaranteed to be in contact with ceria as it would in a powder catalyst. In the latter, there is no guarantee that rhodium and ceria interact. Despite that, they appear to have similar activities. The second other result is that a physical mixture of alumina and ceria actually performs better than the other catalysts. This scenario could easily be tested in a powder bed and determined if still true in that case. Though outside the scope of this paper, further characterization could shed some light on the nature of the rhodium/ceria and ceria/alumina interactions. Due to the intense temperature and concentration gradients down the length of the monolith 20, this will require an extensive investigation. Since the structure of the 3-D printed support is such that the support can be deconstructed in layers, it may actually be possible to obtain axial profiles of different characterization results. 5. Conclusions This work seeks to confirm the findings that ceria promotes methane conversion, water gas shift activity, carbon burnoff, and carbon monoxide oxidation when used as a support material in the short contact time catalytic partial oxidation of methane. We have demonstrated that ceria does promote methane conversion. It was not possible to determine if ceria promotes carbon burnoff and/or water gas shift activity. In some but not all cases, it was true. Finally, no conclusions could be made about carbon 7 ACS Paragon Plus Environment


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burnoff except for the fact that none of the catalysts showed evidence of carbon accumulation. A different fuel or catalyst that is known to undergo coking would be a better candidate for that study. Since the 3-D printed supports can easily be deconstructed such that axial position can be monitored, an extensive study of composition, reduction, etc. can now be undertaken to see how the large gradients in temperature and composition affect the catalyst.

Acknowledgements The authors thank John Stuecker of Robocasting LLC for custom making the catalyst supports used in this paper.

References 1. Hickman, D. A.; Schmidt, L. D., Production of syngas by direct catalytic oxidation of methane. Science 1993, 259, 343-346. 2. Salge, J. R.; Deluga, G. A.; Schmidt, L. D., Catalytic partial oxidation of ethanol over noble metal catalysts. Journal of Catalysis 2005, 235, 69-78. 3. Traxel, B. E.; Hohn, K. L., Partial oxidation of methanol at millisecond contact times. Applied Catalysis A: General 2003, 244, 129-140. 4. O'Connor, R. P.; Klein, E. J.; Schmidt, L. D., High yields of synthesis gas by millisecond partial oxidation of higher hydrocarbons. Catalysis Letters 2000, 70, 99-107. 5. Krummenacher, J. J.; West, K. N.; Schmidt, L. D., Catalytic partial oxidation of higher hydrocarbons at millisecond contact times: decane, hexadecane, and diesel fuel. Journal of Catalysis 2003, 215, 332-343. 6. Nguyen, B. N. T.; Leclerc, C. A., Catalytic partial oxidation of methyl acetate as a model to investigate the conversion of methyl esters to hydrogen. International Journal of Hydrogen Energy 2008, 33, 1295-1303. 7. Leclerc, C. A., Short contact time catalytic partial oxidation of biogas - A comprehensive study on CO2 and N2 dilution. Biomass and Bioenergy 2014, 63, 58-63. 8. Huff, M.; Torniainen, P.; Schmidt, L. D., Partial oxidation of alkanes over noble metal coated monoliths. Catalysis Today 1994, 21, 113-128. 9. Bodke, A.; Bharadwaj, S.; Schmidt, L. D., The effect of ceramic supports on partial oxidation of hydrocarbons over noble metal coated monoliths. Journal of Catalysis 1998, 179, 138-149. 10. Pantaleo, G.; La Parola, V.; Deganello, F.; Singha, R. K.; Bal, R.; Venezia, A. M., Ni/CeO2 catalysts for methane partial oxidation: Synthesis driven structural and catalytic effects. Applied Catalysis B: Environmental 2016, 189, 233-241. 11. Costa, L. O. O.; Silva, A. M.; Borges, L. E. P.; Mattos, L. V.; Noronha, F. B., Partial oxidation of ethanol over Pd/CeO2 and Pd/Y2O3 catalysts. Catalysis Today 2008, 138, 147-151. 12. Dadyburjor, D. B.; Das, T. K.; Kugler, E. L., Reactions for the partial oxidation of propane over Pton-Ceria. Applied Catalysis A: General 2011, 392, 127-135. 13. Moral, A.; Reyero, I.; Alfaro, C.; Bimbela, F.; Gandia, L. M., Syngas production by means of biogas catalytic partial oxidation and dry reforming using Rh-based catalysts. Catalysis Today 2018, 299, 280288. 8 ACS Paragon Plus Environment

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14. Scarabello, A.; Dalle Nogare, D.; Canu, P.; Lanza, R., Partial oxidation of methane on Rh/ZrO2 and Rh/Ce-ZrO2 on monoliths: Catalyst restructuring at reaction conditions. Applied Catalysis B: Environmental 2015, 174-175, 308-322. 15. Vita, A.; Italiano, C.; Ashraf, M. A.; Pino, L.; Specchia, S., Syngas production by steam and oxysteam reforming of biogas on monolith-supported CeO2-based catalysts. International Journal of Hydrogen Energy 2018, 43, 11731-11744. 16. Vita, A.; Cristiano, G.; Italiano, C.; Pino, L.; Specchia, S., Syngas production by methane oxysteam reforming on Me/CeO2 (Me = Rh, Pt, Ni) catalyst lined on cordierite monoliths. Applied Catalysis B: Environmental 2015, 162, 551-563. 17. Moraes, T. S.; Borges, L. E. P.; Farrauto, R.; Noronha, F. B., Steam reforming of ethanol on Rh/SiCeO2 washcoated monolith catalyst: Stable catalyst performance. International Journal of Hydrogen Energy 2018, 43, 115-126. 18. Ferrizz, R. M.; Stuecker, J. N.; Cesarano, I., Joseph; Miller, J. E., Monolithic supports with unique geometries and enhanced mass transfer. Industrial & Engineering Chemistry Research 2005, 44, 302308. 19. Stuecker, J. N.; Miller, J. E.; Ferrizz, R. E.; Mudd, J. E.; Cesarano, I., Joseph, Advanced support structures for enhanced catalytic activity. Industrial & Engineering Chemistry Research 2004, 43, 51-55. 20. Horn, R.; Williams, K. A.; Degenstein, N. J.; Schmidt, L. D., Syngas by catalytic partial oxidation of methane on rhodium: Mechanistic conclusions from spatially resolved measurements and numerical simulations. Journal of Catalysis 2006, 242, 92-102.



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FIGURE CAPTIONS Figure 1: A photo of the 3-D printed supports showing the top (left) and side (right).

Figure 2: The methane conversion (a), hydrogen selectivity (b), carbon monoxide selectivity (c), back face temperature (d), and H2:CO ratio (e) for experiments run at a GHSV of 290,000 h-1 with varying methane to oxygen ratios ranging from 1.4 to 2.2 for the following supports: Al2O3 (), CeO2 (), CeO2/Al2O3 (), and CeO2 on Al2O3 ().

Figure 3: The methane conversion (a), hydrogen selectivity (b), carbon monoxide selectivity (c), back face temperature (d), and H2:CO ratio (e) for experiments run at a CH4/O2 feed ratio of 1.7 with varying GHSVs varying from 115,000 to 480,000 h-1 for the following supports: Al2O3 (), CeO2 (), CeO2/Al2O3 (), and CeO2 on Al2O3 ().


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FIGURE 1



1

1

0.9

Al2O3

CeO2

CeO2/Al2O3

CeO2 on Al2O3

0.95

Hydrogen Selectivity

Methane Conversion

0.95

0.85 0.8 0.75 0.7 0.65

0.9 0.85 0.8 0.75 0.7

b

0.65

0.6 1.4

1.5

1.6

1.7

1.8

1.9

2

2.1

1.4

0.95

950

Back Face Temperature

Carbon Monoxide Selectivity

1000

0.9 0.85

0.75

c

CeO2

CeO2/Al2O3

CeO2 on Al2O3

1.5

1.6

1.7

1.8

1.9

2

2.1

2.2

CH4/O2

1

0.8

Al2O3

0.6

2.2

CH4/O2

Al2O3

CeO2

CeO2/Al2O3

CeO2 on Al2O3

900

Al2O3

CeO2

CeO2/Al2O3

CeO2 on Al2O3

850 800

d

750 700

0.7 1.4

1.5

1.6

1.7

1.8

1.9

2

2.1

2.2

1.4

1.5

1.6

1.7

1.8

1.9

2

2.1

2.2

CH4/O2

CH4/O2 2.5 2.4

Al2O3

CeO2

2.3

CeO2/Al2O3

CeO2 on Al2O3

2.2 2.1

H2:CO

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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2 1.9 1.8 1.7

e

1.6 1.5 1.4

1.5

1.6

1.7

1.8

1.9

2

2.1

2.2

CH4/O2

FIGURE 2


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1

0.9

0.95

Hydrogen Selectivity

Methane Conversion

0.85 0.8 0.75 0.7 0.65

Al2O3

a

CeO2

CeO2/Al2O3

CeO2 on Al2O3

0.9 0.85 0.8 0.75

b

CeO2/Al2O3

CeO2 on Al2O3

GHSV (hr-1)

0.9

1000 950

0.85

Back Face Temperature

Carbon Monoxide Selectivity

CeO2

0.6 100000 150000 200000 250000 300000 350000 400000 450000 500000

GHSV (hr-1)

0.8 0.75 0.7 0.65

Al2O3

0.7 0.65

0.6 100000 150000 200000 250000 300000 350000 400000 450000 500000

c

Al2O3

CeO2

CeO2/Al2O3

CeO2 on Al2O3

0.6 100000 150000 200000 250000 300000 350000 400000 450000 500000

d

900 850 800 750 700

Al2O3

CeO2

650

CeO2/Al2O3

CeO2 on Al2O3

600 100000 150000 200000 250000 300000 350000 400000 450000 500000

GHSV (hr-1)

GHSV (hr-1)

2.5 2.4 2.3 2.2

H2/CO

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.1 2 1.9 1.8 1.7 1.6

e

Al2O3

CeO2

CeO2/Al2O3

CeO2 on Al2O3

1.5 100000 150000 200000 250000 300000 350000 400000 450000 500000

GHSV (hr-1)

FIGURE 3



Page 14 of 14

CH4 + O2

Rhodium on 3-D Printed Cerium Oxide

Rh/CeO2

Rh/CeO2

Rh/CeO2

Rh/CeO2

Rh/CeO2

Rh/CeO2

Rh/CeO2

CO + H2 Table of Contents Graphic


Short Contact Time Catalytic Partial Oxidation of Methane over

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