Modification of Ni-Substituted Pyrochlore Catalysts for the Steam Reforming of Methane

CATEGORY: METHANE
Modification of Ni-Substituted Pyrochlore Catalysts for the Steam Reforming of Methane
NAM24-24th North American Catalysis Society Meeting, Pittsburgh, PA, June 14-19, 2015
Daniel J. Haynes1, Dushyant Shekhawat 1, David A. Berry 1, Mark Smith 2, Devendra Pakhare 3 and James J. Spivey 4
(1) National Energy Technology Laboratory, USA, (2) URS, USA, (3) Pyrochem Catalyst Co., USA, (4) Louisiana State University, USA.
Introduction
Recent discoveries of natural gas supplies have led to an increasing interest in the reforming of methane to produce hydrogen for use in applications like chemicals and energy production. Although steam reforming of methane (SMR) is a relatively mature process, there are still significant incentives to increase the activity and stability of Ni- based catalysts that are widely used in commercial reforming processes. However, developing a Ni-based catalyst to withstand the rigors of typical reforming conditions is challenging considering the activity of Ni is plagued by numerous deactivation mechanisms;
including carbon formation, thermal sintering, and oxidation from the high steam partial pressure [1]. Previous studies have shown that the substitution of an active metal into the structure of a thermally stable pyrochlore structure can minimize the deactivation by carbon formation and thermal sintering [2]. For this study, Ni will be isomorphically substituted into the structure of the La2Zr2O7 pyrochlore, to create small, well-dispersed, and highly stable Ni sites at the surface which are active for SMR. Further, four different 1st row transition metal (TM) promoters will also be substituted into the pyrochlore structure to minimize the oxidation of Ni sites.
Materials and Methods
The substituted pyrochlore catalysts were synthesized by a variation of the Pechini method [3]. Ni loading was 6wt% for each catalyst, and the amount of TM promoter added was set to 10% of the atomic loading of Ni. SMR experiments were performed in a fixed bed continuous-flow reactor with an S/C=2.0, T= 700 °C, 2 atm, and inert gas composition of 25%. Reforming activity was evaluated as the weight hourly space velocity (WHSV) was increased from 25,000 to 200,000 scc/gcat/h. Carbon formation was quantified by a burnoff after the SMR experiment.
Results and Discussion
Hydrogen concentrations from the SMR studies for the TM promoted Ni catalysts are shown Figure 1. At the lowest WHSV, all catalysts have a product distribution near equilibrium values (~60% H2), with the exception of the Fe promoted catalyst. The activity of the Cr promoted catalyst proved to be the most active as it was able to maintain stable, equilibrium yields through 50,000 WHSV, and showed higher syngas production compared to the other catalysts over each WHSV tested. Activity decline can likely be attributed to the oxidation of Ni metal, as the post run burn off indicated that deactivation by carbon was unlikely by showing an insignificant amount of carbon (ca. 0.0095 gcarbon/gcatalyst).Given similar ionic size of each of the four TM promoters compared to Ni, it is hypothesized that the promoters behave much like Ni during the calcination treatment for the formation of the pyrochlore powder. Therefore, they would occupy a similar coordination and position in proximity to the Ni which likely results in their promotional effects. As observed by the activity test (Figure 1), it could be assumed that the Cr is more dispersed near the active Ni at the surface compared to Fe, however this will need to be confirmed by further characterization with XPS and EDX.
Significance
The addition of Cr to a Ni-substituted pyrochlore improved the activity for SMR at high space velocities by reducing the rate of deactivation, which was likely attributable to the oxidation of active Ni sites.
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Production of oxygenates from a methane conversion process (UOP)

CATEGORY: METHANE 
Production of oxygenates from a methane conversion process (UOP)

Type	Patent
Inventor	Jeffery C. Bricker
Inventor	John Q. Chen
URL	Free Full Text Source:  http://www.google.com/patents/US8933275
Assignee	Uop Llc
Patent Number	US8933275 B2
Issue Date	Jan 13, 2015
Abstract	Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes processing acetylene as an intermediate stream to form a stream having oxygenates. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to oxygenates through subsequent reactors.

Acids removal and methane conversion process using a supersonic flow reactor (UOP)

CATEGORY: METHANE 
Acids removal and methane conversion process using a supersonic flow reactor (UOP)

Type	Patent
Inventor	Dean E. Rende
Inventor	Jayant K. Gorawara
URL	Free Full Text Source:  http://www.google.com/patents/US8937186
Assignee	Uop Llc
Patent Number	US8937186 B2
Issue Date	Jan 20, 2015
Abstract	Methods and systems are provided for converting methane in a feed stream to acetylene. The method includes removing at least a portion of acids from a hydrocarbon stream. The hydrocarbon stream is introduced into a supersonic reactor and pyrolyzed to convert at least a portion of the methane to acetylene. The reactor effluent stream may be treated to convert acetylene to another hydrocarbon process. The method according to certain aspects includes controlling the level of acids in the hydrocarbon stream by use of adsorbents or basic solutions.

Methane Decomposition and Carbon Growth on Y2O3, Yttria-Stabilized Zirconia, and ZrO2

CATEGORY: METHANE 
Methane Decomposition and Carbon Growth on Y2O3, Yttria-Stabilized Zirconia, and ZrO2

Type	Journal Article
Author	Michaela Kogler
Author	Eva-Maria Köck
URL	http://dx.doi.org/10.1021/cm404062r
Volume	26
Issue	4
Pages	1690-1701
Publication	Chemistry of Materials
Date	February 25, 2014
Abstract	Researchers examined carbon deposition following thermal methane decomposition under dry and steam reforming conditions has been studied on yttria-stabilized zirconia (YSZ), Y2O3, and ZrO2 using a variety of chemical, structural, and spectroscopic characterization techniques. All experimental techniques revealed the formation of a conducting layer of disordered nanocrystalline graphite covering the individual grains of the respective pure oxides after treatment in dry methane at temperatures T ≥ 1000 K. Treatment under moist methane conditions results in formation of carbon-nanotube-like architectures by partial detachment of the graphite layers. Experimental results revealed that during carbon growth, no substantial reduction of any of the oxides takes place. Results suggest that these pure oxides can act as efficient nonmetallic substrates for methane-induced growth of different carbon species with potentially important implications regarding their use in solid oxide fuel cells.

Methane combustion by moving bed fuel reactor with Fe2O3/Al2O3 oxygen carriers

CATEGORY: METHANE 
Methane combustion by moving bed fuel reactor with Fe2O3/Al2O3 oxygen carriers

Type	Journal Article
Author	Young Ku
Author	Hsuan-Chih Wu
URL	http://www.sciencedirect.com/science/article/pii/S0306261913005217
Volume	113
Pages	1909-1915
Publication	Applied Energy
Date	January 2014
Abstract	Using a lab-scale moving bed fuel reactor provided with reasonable crush strength, researchers prepared reactivity and recyclability Fe2O3/Al2O3 composite oxygen carriers for chemical looping combustion (CLC) with methane. They noted carbon formation during the combustion process in the empty bed at 900 °C through methane decomposition reaction. Carbon formation was reduced for experiments conducted in the moving bed fuel reactor with oxygen carrier-to-fuel ratio (ϕ) higher than 1.14. The oxygen carriers that exited the moving bed reactor were composed of mainly FeO and FeAl2O4, characterized by X-ray diffraction (XRD) analysis. The formation of FeO and FeAl2O4 indicated that further utilization of oxygen in iron-based oxygen carriers can be achieved by moving bed operation.

Influence of the operating parameters over dry reforming of methane to syngas

CATEGORY: METHANE 
Influence of the operating parameters over dry reforming of methane to syngas

Type	Journal Article
Author	A. Serrano-Lotina
Author	L. Daza
URL	http://www.sciencedirect.com/science/article/pii/S0360319913013670
Volume	39
Issue	8
Pages	4089-4094
Publication	International Journal of Hydrogen Energy
Date	March 6, 2014
Abstract	Describes results of a study of the influence of operating parameters over dry reforming of methane reaction using a Ni-based catalyst obtained after calcination of a hydrotalcite-like precursor. Researchers examined mass to flow ratio (W/F), reaction temperature and CO2/CH4 ratio. They obtained maximum methane and carbon dioxide conversions at W/F ratios above 0.21 g h L−1. The higher the W/F ratio, the lower amount of water was formed, leading to a higher H2/CO ratio. The increase in reaction temperature produced an increase in conversions. Water concentration in the outlet stream exhibited a maximum at 600 °C. At this temperature, reverse water–gas-shift reaction (RWGS) was favored because it is endothermic. However, steam reforming and carbon gasification were also favored and they consumed great part of the water produced. CO2/CH4 ratios above 1 led to a higher CH4 conversion but selectivity to hydrogen decreased because RWGS reaction was favored. When CO2/CH4 was below unity, CH4 conversion decreased but a smaller amount of water was produced, resulting in a higher H2 selectivity. The catalyst exhibited good stability over dry reforming of methane under all the tested conditions, which researchers attribute to its high basicity. This property improved CO2 adsorption and then RWGS reaction and carbon gasification.

Catalytic thermal decomposition of methane to COx-free hydrogen and carbon nanotubes over MgO supported bimetallic group VIII catalysts

CATEGORY: METHANE 
Catalytic thermal decomposition of methane to COx-free hydrogen and carbon nanotubes over MgO supported bimetallic group VIII catalysts

Type	Journal Article
Author	A. E. Awadallah
Author	A. A. Aboul-Enein
Affiliation	Egyptian Petroleum Research Institute, Cairo, Egypt
URL	http://www.sciencedirect.com/science/article/pii/S016943321400083X
Volume	296
Pages	100-107
Publication	Applied Surface Science
Date	March 30, 2014
Abstract	Researchers studied bimetallic Ni–Fe, Ni–Co and Fe–Co supported on MgO catalysts with a total metals content of 50 wt.% for decomposition of methane to CO/CO2 free hydrogen and carbon nanomaterials. They conducted catalytic runs at 700 °C under atmospheric pressure using fixed bed horizontal flow reactor. Characterization results revealed that the bimetallic 25% Fe–25%Co/MgO catalyst exhibited remarkable higher activity and stability up to ∼10 h time-on-stream with respect to H2 production. However, the catalytic activity and durability declined significantly after incorporating 25%Ni to either 25%Fe or 25%Co/MgO catalysts at all time on stream. The main cause of the catalytic inhibition of Ni containing catalysts is consuming NiO during the formation of rock-salt MgxNi(1−x)O solid solution. However, the almost complete segregation of Fe2O3 and Co3O4 oxides played an important role for the high activity of the Fe–Co based catalyst. The TG data showed that a higher yield of MWCNTs was achieved over bimetallic Fe–Co catalyst compared to the Ni–Fe or Ni–Co containing catalysts.

Process for the production of methane (Shell)

CATEGORY: METHANE 
Process for the production of methane (Shell)

Type	Patent
Inventor	Lloyd Anthony CLOMBURG JR
Inventor	Anand Nilekar
URL	Free Full Text Source:  http://www.google.com/patents/US8927610
Assignee	Shell Oil Company
Patent Number	US8927610 B2
Issue Date	Jan 6, 2015
Abstract	A process for the production of methane comprising reacting at least part of a feed gas containing carbon monoxide and hydrogen in an internally cooled methanation reactor containing a nickel comprising methanation catalyst to produce a product gas containing methane, cooling the internally cooled methanation reactor with water, wherein the water enters the internally cooled methanation reactor at a temperature in the range from 20-120° C. below its boiling temperature.

Direct, Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen

CATEGORY: METHANE 
Direct, Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen

Type	Journal Article
Author	Xiaoguang Guo
Author	Guangzong Fang
URL	http://www.sciencemag.org/content/344/6184/616
Volume	344
Issue	6184
Pages	616-619
Publication	Science
Date	05/09/2014
Abstract	Efficient use of natural gas requires catalysts that can activate the first C–H bond of methane, while suppressing complete dehydrogenation and avoiding overoxidation. Authors report that single iron sites embedded in a silica matrix enable direct, nonoxidative conversion of methane, exclusively to ethylene and aromatics. The reaction is initiated by catalytic generation of methyl radicals, followed by a series of gas-phase reactions. The absence of adjacent iron sites prevents catalytic C-C coupling, further oligomerization, and hence, coke deposition. Upgrading Methane Sans Oxygen Direct routes to converting methane to higher hydrocarbons can allow natural gas to be used to provide chemical feedstocks. However, the reaction conditions required to activate the strong C-H bond tend to overoxidize the products. Guo et al. report a high-temperature nonoxidative route that exposes methane to isolated iron sites on a silica catalyst. Methyl radicals were generated and coupled in the gas phase to form ethylene and aromatics along with hydrogen. The isolation of the active sites avoided surface reactions between the radicals that would deposit solid carbon.

Combined steam and CO2 reforming of methane using catalytic nickel membrane for gas to liquid (GTL) process

CATEGORY: METHANE 
Combined steam and CO2 reforming of methane using catalytic nickel membrane for gas to liquid (GTL) process

Type	Journal Article
Author	Shin-Kun Ryi
Author	Sung-Wook Lee
URL	http://www.sciencedirect.com/science/article/pii/S0920586113005750
Series	Proceedings of the 11th International Conference on Catalysis in Membrane Reactors
Volume	236, Part A
Pages	49-56
Publication	Catalysis Today
Date	November 1, 2014
Abstract	Reports a study in which tests on the combined steam and dry reforming of methane were conducted over a catalytic nickel membrane within a short residence time of 120 ms under various process conditions. Researchers examined the effect of the molar ratio of CO2/H2O in the reactants on the H2/CO ratio in the products at 923–1023 K. They noted that in the reaction of the combined steam and dry reforming of methane, CH4 conversion was strongly influenced by the CO2/H2O feed ratio and decreased with the increase in the CO2/H2O feed ratio at 923 K. The influence of the CO2/H2O feed ratio on CH4 conversion was not significant at temperatures ≥973 K. The conversion of CO2 increased with the increase in the CO2/H2O feed ratio over the temperature range of 923–1023 K. The conversion of CH4 and that of CO2 both increased with increasing temperature, due to the fact that the corresponding reactions are endothermic and remained nearly constant at temperatures ≥973 K. The H2/CO molar ratio could be adjusted by the CO2/H2O feed ratio for downstream applications. No carbon deposition on the catalytic nickel membrane was observed after the combined steam and dry reforming of methane tests under all process conditions.