Millisecond catalytic reforming of monoaromatics over noble metals

Balonek, Christine M.; Colby, Joshua L.; Schmidt, L.D.

doi:10.1002/aic.12045

Cited by 10 publications

(6 citation statements)

References 36 publications

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“…This strong nickel activity in the conversion of aromatic hydrocarbons was attributable to the catalytic activity of the Ni 0 NPs. It is, in fact, well established that aromatic compounds are highly chemisorbed at the surface of transition metals such as Ni 0 , through the formation of a covalent combination of π orbitals from the aromatic cycle with the unoccupied d orbitals from the metal. − According to DFT calculations, the benzene molecule generally adopts a flat-lying, or very nearly flat-lying, geometry, binding to the surface through donation of electrons from one or both of its two degenerate highest occupied molecular orbitals (HOMOs) and back-donation into one or both of its two degenerate lowest unoccupied molecular orbitals (LUMOs) . It is worth pointing out that the production of tertiary tars, such as benzene and naphthalene, could be reduced by 60% and 70%, respectively, through the presence of nickel species in the wood inserted by method B (Table ).…”

Section: Resultsmentioning

confidence: 99%

Catalytic Investigation of in Situ Generated Ni Metal Nanoparticles for Tar Conversion during Biomass Pyrolysis

et al. 2013

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In order to promote process intensification in syngas production from biomass gasification, our research team has already considered the integration of transition metal-based nanocatalysts in the biomass feedstock through its impregnation with metal salt aqueous solutions. The purpose of this work is to provide new insights into the complex physicochemical and catalytic mechanisms involved in this catalytic pathway from nickel salt. Applying a primary vacuum during impregnation allowed the rate of nickel insertion to be optimized and the generation of strong interactions between the metal cations and the lignocellulosic matrix. During biomass pyrolysis, Ni0 nanoparticles (NPs) form in situ below 500 °C through carbothermal reduction and provide the active sites for adsorption of aromatic hydrocarbons and subsequent catalytic conversion. In order to test whether it was possible to improve the catalytic efficiency of Ni0 NPs by making them available right from the pyrolysis onset, some preformed Ni0 NPs were inserted into the biomass prior to pyrolysis. The in situ generated Ni0 NPs exhibit higher catalytic efficiency, particularly for aromatic tar conversion, than preformed Ni0 NPs. The high decrease in hard-to-destroy aromatic hydrocarbons formation during pyrolysis is of particular interest in the overall gasification process. The proposed catalytic strategy reveals promising for simplifying the cleaning up of the producer gas.

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Section: Resultsmentioning

confidence: 99%

Catalytic Investigation of in Situ Generated Ni Metal Nanoparticles for Tar Conversion during Biomass Pyrolysis

et al. 2013

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“…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.…”

Section: à2mentioning

confidence: 99%

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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“…This has been little treated in the literature. In fact, the experimental investigations concerning the CPO of C 2+ hydrocarbons have mostly focused on the integral performances of the reactors, in terms of temperature and composition of the syngas. − ,− Some works have also measured the evolution of the temperature profile along the axis of the catalyst by means of sliding thermocouples. , Only a few experimental works have focused on the temperature and concentration profiles within the catalyst, ,, but none, to our knowledge, has addressed the CPO of C 3 H 8 .…”

Section: Introductionmentioning

confidence: 99%

Experimental and Modeling Analysis of the Thermal Behavior of an Autothermal C₃H₈Catalytic Partial Oxidation Reformer

Livio

Donazzi

Beretta

et al. 2012

Ind. Eng. Chem. Res.

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In this work, a spatially resolved sampling technique is applied to characterize the performance of a C3H8 CPO reformer and to compare it with that of a CH4 reformer. The case of Rh-coated honeycomb catalysts is examined. The axial profiles show that higher temperatures are reached in C3H8 CPO, especially at the reactor inlet. Surface hot-spot temperatures around 950 °C lead the catalyst to rapid loss of activity. A detailed model analysis is also applied to better understand the reasons for the observed differences of the thermal behavior. On one hand, the heat release via oxidation reactions is controlled by O2 mass transfer rate and thus proportional to O2 inlet concentration, which is 20% higher in the C3H8/air mixture at equal C/O ratio. On the other hand, while CH4 steam reforming is partly chemically controlled, C3H8 steam reforming is mainly limited by gas–solid diffusion. Thus, a less efficient balance between exo- and endothermic reactions occurs in the case of C3H8 CPO, and this results in much higher hot-spot temperatures. As a consequence, specific strategies for the optimization of the thermal behavior are required depending on the fuel. Modeling of the C3H8 CPO results shows that an increased catalyst load or a suitable aspect ratio of the reactor, combined with a decrease of the flow rate, produces a beneficial moderation of the hot-spot temperature of the catalytic wall

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Millisecond catalytic reforming of monoaromatics over noble metals

Cited by 10 publications

References 36 publications

Catalytic Investigation of in Situ Generated Ni Metal Nanoparticles for Tar Conversion during Biomass Pyrolysis

Catalytic Investigation of in Situ Generated Ni Metal Nanoparticles for Tar Conversion during Biomass Pyrolysis

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

Experimental and Modeling Analysis of the Thermal Behavior of an Autothermal C₃H₈Catalytic Partial Oxidation Reformer

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Millisecond catalytic reforming of monoaromatics over noble metals

Cited by 10 publications

References 36 publications

Catalytic Investigation of in Situ Generated Ni Metal Nanoparticles for Tar Conversion during Biomass Pyrolysis

Catalytic Investigation of in Situ Generated Ni Metal Nanoparticles for Tar Conversion during Biomass Pyrolysis

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

Experimental and Modeling Analysis of the Thermal Behavior of an Autothermal C3H8Catalytic Partial Oxidation Reformer

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Experimental and Modeling Analysis of the Thermal Behavior of an Autothermal C₃H₈Catalytic Partial Oxidation Reformer