<b>The Hydrogen-Graphite Reaction between 360 and 800°</b>

Breisacher, Peter; Marx, Paul C.

doi:10.1021/ja00904a060

Cited by 24 publications

(7 citation statements)

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“…Similarly, although for the opposite reason, the production of CH 4 through the hydrogenation of carbon (reaction ) is always a very minor pathway, because at the temperatures at which gasification reactions are typically run, the equilibrium lies to the left. In addition, the primary step in the reaction, which is the hydrogenation of the graphite, is known to be extremely slow …”

Section: Resultsmentioning

confidence: 99%

Microwave-Specific Effects on the Equilibrium Constants and Thermodynamics of the Steam–Carbon and Related Reactions

et al. 2014

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The steam−carbon reaction, which is the essential reaction of the gasification processes of carbon-based feed stocks (e.g., coal and biomass), produces synthesis gas (H 2 + CO), a synthetically flexible, environmentally benign energy source. The reaction is very endothermic, which mandates high temperatures and a large expenditure of energy to drive the reaction. We have found that using microwave irradiation to selectively heat the carbon leads to dramatically different observed thermodynamics for the reaction. From measurement of the equilibrium constants as a function of temperature, the enthalpy of the reaction under microwave radiation was found to become significantly more exothermic, dropping from 144.2 kJ/mol at the median reaction temperature of 880 K to 15.2 kJ/mol under microwave irradiation. The reaction conditions under which the steam− carbon reaction was run, and under which the equilibrium measurements were determined, consisted of three other reactions that came to equilibrium. These reactions were the Boudouard reaction, which is the reaction of CO 2 with carbon to form CO; the water−gas shift reaction, where CO and water react to form H 2 and CO 2 ; and the carbon−hydrogen reaction, which generates methane from the reaction of H 2 with carbon. We determined the equilibrium constants and thermodynamic parameters for all of these reactions. The Boudouard reaction, which is also strongly endothermic, was found to be more exothermic under microwave radiation (180.2 kJ/mol (thermal) and 27.0 kJ/mol (MW)). The water−gas shift reaction became more endothermic (−36.0 kJ/mol (thermal) and −11.4 kJ/mol (MW)). The carbon−hydrogen reaction also underwent an endothermic shift, from −79.7 to −9.1 kJ/mol. From the associated equilibrium expressions and the equilibrium constants for the steam−carbon reaction system, the mole fractions of the system components under thermal and microwave conditions were estimated. The effect of the microwave radiation was to change the position of the equilibrium so that the temperature at which H 2 was at a maximum dropped from 643 °C in the conventional thermal reaction to 213 °C in the microwave. Notwithstanding the predicted temperature shift, there was an observable threshold below which microwaves could not produce products. In our system, the minimum energy at which H 2 appeared was 373 °C (30 W), while the temperature at which equilibrium could be established in a reasonable period of time (100 min) was 491 °C (100 W).

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Section: Resultsmentioning

confidence: 99%

Microwave-Specific Effects on the Equilibrium Constants and Thermodynamics of the Steam–Carbon and Related Reactions

et al. 2014

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“…Previous studies reported that gaseous H 2 was able to react with graphite at temperatures below 1000 °C to generate hydrocarbons. 29,30 Therefore, we suspect that the carbon source that ultimately yields graphene is a gaseous hydrocarbon by reaction of H 2 (g) with the a-C film.…”

Section: Resultsmentioning

confidence: 99%

Graphene Growth Using a Solid Carbon Feedstock and Hydrogen

Hao

Ren

et al. 2011

ACS Nano

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Graphene has been grown on Cu at elevated temperatures with different carbon sources (gaseous hydrocarbons and solids such as polymers); however the detailed chemistry occurring at the Cu surface is not yet known. Here, we explored the possibility of obtaining graphene using amorphous-carbon thin films, without and with hydrogen gas added. Graphene is formed only in the presence of H(2)(g), which strongly suggests that gaseous hydrocarbons and/or their intermediates are what yield graphene on Cu through the reaction of H(2)(g) and the amorphous carbon. The large area, uniform monolayer graphene obtained had electron and hole mobilities of 2520 and 2050 cm(2) V(-1) s(-1), respectively.

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“…These bonds rupture to liberate an acetylene molecule. (A five bond cleavage sequence has been previously proposed to account for butane formation in the hydrogen-graphite reaction 40 ). It is important to note that there is a reactivity difference between two surface orientations: the zigzag and armchair (basal) forms of carbon.…”

Section: ؒ Oh ⇔ O Ads ϩ H Adsmentioning

confidence: 99%

The formation of olefins and alkynes from the reaction of hydroxyl radical and carbonaceous material

Khachatryan

Dellinger

2002

J. Chem. Soc., Perkin Trans. 2

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Using model systems and laser photolysis techniques, we have examined the mechanism of interaction of hydroxyl radicals with carbonaceous materials. The formation of ppb-level concentrations of methane, ethylene, acetylene, and propylene (prop-1-ene) was observed from interaction of ArF laser-generated hydroxyl radicals with activated carbon pellets in the temperature range of 200-500 ЊC. A maximum in the formation of olefins and acetylene is observed at 430-450 ЊC. A mechanism involving surface epoxide formation is postulated. These results support earlier hypotheses regarding the role of combustion generated hydroxyl radicals and light hydrocarbons in the catalytic formation of polychlorinated dibenzo-p-dioxins and -furans (PCDD/F) by the so-called "fast"de novo and extended precursor mechanisms.

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The Hydrogen-Graphite Reaction between 360 and 800°

Abstract: Fig. 2.-Methylene p.m.r. signals in hexane solutions. Upper center curve is the same, with lower curve is the same, with 5.3 mmoles of curve from 1.6 mmoles of BuLi; 0.76 mmole of EtsO; ether and lower spectrum amplitude in 200-C.P.S. region.

Cited by 24 publications

References 0 publications

Microwave-Specific Effects on the Equilibrium Constants and Thermodynamics of the Steam–Carbon and Related Reactions

Microwave-Specific Effects on the Equilibrium Constants and Thermodynamics of the Steam–Carbon and Related Reactions

Graphene Growth Using a Solid Carbon Feedstock and Hydrogen

The formation of olefins and alkynes from the reaction of hydroxyl radical and carbonaceous material

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