Effects of H2O and CO2 addition in catalytic partial oxidation of methane on Rh

Michael, Brian C.; Donazzi, Alessandro; Schmidt, L.D.

doi:10.1016/j.jcat.2009.04.015

Cited by 87 publications

(70 citation statements)

References 23 publications

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“…[8,9] This suggests that the more active sphere catalysts would yield less pyrolysis oil than monoliths; opposite to what was observed. Michael et al found that increased catalytic activity did not affect the length of the oxidation zone within a catalytic monolith, indicating that the system is mass-transfer-limited, which has also been discussed by Horn et al [10,11] Higher mass transfer rates can allow complete oxygen consumption early in the catalyst bed, yielding high front face temperatures and abundance of heat for pyrolysis. The experiments by Michael et al showed that oxygen is consumed within 2 mm of an 80 ppi, 5 wt % Rh monolithic catalyst.…”

Section: à2mentioning

confidence: 81%

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Rapid Ablative Pyrolysis of Cellulose in an Autothermal Fixed‐Bed Catalytic Reactor

et al. 2010

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Many biological, chemical, and thermal pathways have been investigated as potentially efficient processing methods to utilize biomass as a renewable feedstock. Pyrolysis of biomass has been investigated as a process to produce gas and liquid products by using, amongst others, fluidized-bed, rotary kiln, and plate-ablative reactors. [1,2] However, many pyrolysis reactors are hindered by char production, resulting from limited heat transfer rates to the reactor. As a result, reactors are difficult to scale up due to the large heat inputs required to maintain operation, causing lower pyrolysis oil yields.Heat transfer rates to feed particles should be sufficiently high to prohibit char formation within pyrolysis reactors. Previous research has demonstrated the volatilization of cellulose particles on the front face of a Rh-Ce/a-Al 2 O 3 catalyst bed.[3]High-speed photography was used to image 300 mm cellulose particles impacting the 700 8C catalyst, pyrolyzing to liquid intermediate compounds that were then volatilized and convected into the catalyst bed and further reacted to synthesis gas. High heat transfer rates to the particles (3.4 MW m À2) resulted in the complete conversion of cellulose particles without char formation.An ideal pyrolysis reactor should operate continuously, efficiently, and char-free to maximize the yield of pyrolysis. Graham et al. demonstrated an ultrafast pyrolysis process that converted cellulose to more than 80 wt % gases at temperatures between 750 and 900 8C on millisecond timescales.[4] Wei et al. examined the fast pyrolysis of different biomass feedstocks by using a free-fall reactor with a residence time < 2 s. [5] Particles (300-450 mm) pyrolyzed at 700-800 8C yielded up to 80 wt % gases and 20 wt % char. Similar to these pyrolysis processes, the reactor presented here operates at millisecond residence times and high temperatures (700-900 8C); however, it is able to select for larger hydrocarbon liquid products, rather than gas products. A fraction of the cellulose pyrolysis vapors (10-40 %, Table 1) are sacrificially oxidized to CO 2 and H 2 O to provide heat to the front face for pyrolysis allowing for autothermal and char-free operation.Reactions were carried out in a quartz reactor tube (internal diameter 19 mm) over a fixed catalyst bed (1 cm), as shown in Figure 1. Two types of supports were used: a cylindrical monolith [16 mm diameter, 10 mm long, 65 ppi (pores per linear inch) a-Al 2 O 3 , 5 wt% g-Al 2 O 3 washcoat] and spheres (1 cm bed, 1.3 mm diameter a-Al 2 O 3 ). Metals were impregnated onto the supports by using the incipient wetness technique, described previously.[6] Rh-Ce catalysts contained 2.5 wt % of each metal, Pt was applied to the support at 2.5 wt %. Mass flow controllers fed N 2 , O 2 , CH 4 , and H 2 into the reactor. Methane (0

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Section: à2mentioning

confidence: 81%

“…This is expected as Rh is widely regarded as an excellent partial oxidation catalyst with high reforming activity. [10] Support geometry also plays an important role in pyrolysis oil yield. The fixed bed of spheres consistently gave higher yields of desired products than the monolithic catalyst bed.…”

Section: à2mentioning

confidence: 99%

Rapid Ablative Pyrolysis of Cellulose in an Autothermal Fixed‐Bed Catalytic Reactor

et al. 2010

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“…C n H 2n+2 + n H 2 O (g) = n CO + (2n + 1) H 2 (4) C n H 2n+2 + n CO 2 = 2n CO + (n + 1) H 2 (5) with n = 1, 3, or 4 for methane, propane, or butane, respectively. Several other reactions can also take place, e.g., the water gas shift reaction, Equation (2), which is mildly exothermal, whereas the reforming reactions, Equations (8) and (9), are highly endothermal (see Table 1).…”

Section: Basic Reactionsmentioning

confidence: 99%

“…This makes the selection of an appropriate catalyst and its configuration difficult in order to provide high performance of the reactor with respect to the hydrogen production [4]. Conventional steam reformers deliver relatively high concentrations of hydrogen at a high fuel conversion rate [5]. The excess steam supports the completion of the reaction and inhibits coke and soot formation; however, additional heat has to be added to the system.…”

Section: Introductionmentioning

confidence: 99%

On the Deposition Equilibrium of Carbon Nanotubes or Graphite in the Reforming Processes of Lower Hydrocarbon Fuels

Jaworski

Pianko‐Oprych

2017

Entropy

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Abstract:The modeling of carbon deposition from C-H-O reformates has usually employed thermodynamic data for graphite, but has rarely employed such data for impure filamentous carbon. Therefore, electrochemical data for the literature on the chemical potential of two types of purified carbon nanotubes (CNTs) are included in the study. Parameter values determining the thermodynamic equilibrium of the deposition of either graphite or CNTs are computed for dry and wet reformates from natural gas and liquefied petroleum gas. The calculation results are presented as the atomic oxygen-to-carbon ratio (O/C) against temperature (200 to 100 • C) for various pressures (1 to 30 bar). Areas of O/C for either carbon deposition or deposition-free are computed, and indicate the critical O/C values below which the deposition can occur. Only three types of deposited carbon were found in the studied equilibrium conditions: Graphite, multi-walled CNTs, and single-walled CNTs in bundles. The temperature regions of the appearance of the thermodynamically stable forms of solid carbon are numerically determined as being independent of pressure and the analyzed reactants. The modeling indicates a significant increase in the critical O/C for the deposition of CNTs against that for graphite. The highest rise in the critical O/C, of up to 290% at 30 bar, was found for the wet reforming process.

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“…Michael et al [30] studied the effect of steam introduction in a CPO mixture with Rh-based catalyst by testing steam-tocarbon ratio equal to 0.5, 1, and 2. They observed that the rate of CH 4 reforming is independent of H 2 O content, while differences in product distribution were ascribed to water-gas shift chemistry causing an increase of H 2 and CO 2 production at the expense of CO and H 2 O.…”

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confidence: 99%

Catalytic Partial Oxidation Coupled with Membrane Purification to Improve Resource and Energy Efficiency in Syngas Production

Iaquaniello¹,

Salladini

Palo³

et al. 2015

ChemSusChem

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Catalytic partial oxidation coupled with membrane purification is a new process scheme to improve resource and energy efficiency in a well-established and large scale-process like syngas production. Experimentation in a semi industrial-scale unit (20 Nm(3) h(-1) production) shows that a novel syngas production scheme based on a pre-reforming stage followed by a membrane for hydrogen separation, a catalytic partial oxidation step, and a further step of syngas purification by membrane allows the oxygen-to-carbon ratio to be decreased while maintaining levels of feed conversion. For a total feed conversion of 40 %, for example, the integrated novel architecture reduces oxygen consumption by over 50 %, with thus a corresponding improvement in resource efficiency and an improved energy efficiency and economics, these factors largely depending on the air separation stage used to produce pure oxygen.

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Effects of H2O and CO2 addition in catalytic partial oxidation of methane on Rh

Cited by 87 publications

References 23 publications

Rapid Ablative Pyrolysis of Cellulose in an Autothermal Fixed‐Bed Catalytic Reactor

Rapid Ablative Pyrolysis of Cellulose in an Autothermal Fixed‐Bed Catalytic Reactor

On the Deposition Equilibrium of Carbon Nanotubes or Graphite in the Reforming Processes of Lower Hydrocarbon Fuels

Catalytic Partial Oxidation Coupled with Membrane Purification to Improve Resource and Energy Efficiency in Syngas Production

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