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Syngas Production (synga + production)

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Chemistry100%

Selected Abstracts

Theoretical study on the gas-phase reaction mechanism between nickel monoxide and methane for syngas production

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2009
Hua-Qing Yang
Abstract The comprehensive mechanism survey on the gas-phase reaction between nickel monoxide and methane for the formation of syngas, formaldehyde, methanol, water, and methyl radical has been investigated on the triplet and singlet state potential energy surfaces at the B3LYP/6-311++G(3df, 3pd)//B3LYP/6-311+G(2d, 2p) levels. The computation reveals that the singlet intermediate HNiOCH3 is crucial for the syngas formation, whereas two kinds of important reaction intermediates, CH3NiOH and HNiOCH3, locate on the deep well, while CH3NiOH is more energetically favorable than HNiOCH3 on both the triplet and singlet states. The main products shall be syngas once HNiOCH3 is created on the singlet state, whereas the main products shall be methyl radical if CH3NiOH is formed on both singlet and triplet states. For the formation of syngas, the minimal energy reaction pathway (MERP) is more energetically preferable to start on the lowest excited singlet state other than on the ground triplet state. Among the MERP for the formation of syngas, the rate-determining step (RDS) is the reaction step for the singlet intermediate HNiOCH3 formation involving an oxidative addition of NiO molecule into the CH bond of methane, with an energy barrier of 120.3 kJ mol,1. The syngas formation would be more effective under higher temperature and photolysis reaction condition. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009 [source]

Evaporation of pyrolysis oil: Product distribution and residue char analysis

AICHE JOURNAL, Issue 8 2010
Guus van Rossum
Abstract The evaporation of pyrolysis oil was studied at varying heating rates (,1,106°C/min) with surrounding temperatures up to 850°C. A total product distribution (gas, vapor, and char) was measured using two atomizers with different droplet sizes. It was shown that with very high heating rates (,106°C/min) the amount of char was significantly lowered (,8%, carbon basis) compared to the maximum amount, which was produced at low heating rates using a TGA (,30%, carbon basis; heating rate 1°C/min). The char formation takes place in the 100,350°C liquid temperature range due to polymerization reactions of compounds in the pyrolysis oil. All pyrolysis oil fractions (whole oil, pyrolytic lignin, glucose and aqueous rich/lean phase) showed charring behavior. The pyrolysis oil chars age when subjected to elevated temperatures (,700°C), show similar reactivity toward combustion and steam gasification compared with chars produced during fast pyrolysis of solid biomass. However, the structure is totally different where the pyrolysis oil char is very light and fluffy. To use the produced char in conversion processes (energy or syngas production), it will have to be anchored to a carrier. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source]

Rapid lightoff of syngas production from methane: A transient product analysis

AICHE JOURNAL, Issue 1 2005
Kenneth A. Williams
Abstract Steady-state production of syngas (CO and H2) can be attained within 10 s from room-temperature mixtures of methane and air fed to a short-contact-time reactor by initially operating at combustion stoichiometry (CH4/O2 = 0.5) and then quickly switching to syngas stoichiometry (CH4/O2 = 2.0). The methane/air mixture is first ignited, forming a premixed flame upstream of the catalyst that heats the Rh-impregnated ,-alumina foam monolith to catalytic lightoff (T > 500°C) in a few seconds. The methane/oxygen ratio is then increased to partial oxidation stoichiometry, which extinguishes the flame and effects immediate autothermal syngas production. Transient species profiles are measured with a rapid-response mass spectrometer (response time constant , 0.5 s), and catalyst temperature is measured with a thermocouple at the catalyst back face. Because the monolith thermal response time (, 1 s) is several orders of magnitude larger than the reaction timescales (, 10,12 to 10,3 s), chemistry and flow should be mathematically decoupled from local transient variations in catalyst temperature. Using this assumption, a transient temperature profile is combined with detailed surface chemistry for methane on Rh in a numerical plug-flow model. This approach accurately reproduces the transient species profiles measured during experimental lightoff for short combustion time experiments and lends insight into how the monolith temperature develops with time. The combined experimental and numerical efforts supply useful information on the transient reactor behavior for various combustion times and identify a combustion time to avoid undershoot or overshoot in catalyst temperature and minimize start-up time. © 2004 American Institute of Chemical Engineers AIChE J, 51: 247,260, 2005 [source]