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Papers by Christopher J Pope

Thermochemical Properties of Curved PAH and Fullerenes: A Group Additivity Method Compared with MM3(92) and MOPAC Predictions

The Journal of Physical Chemistry, 1995

A group additivity method for strongly curved polycyclic aromatic hydrocarbons (PAH) containing f... more A group additivity method for strongly curved polycyclic aromatic hydrocarbons (PAH) containing five- and six-membered rings (PAH5/6) has been developed. The existing set of groups, those for PAH containing only six-membered rings (PAH6) and for flat PAH5/6, has been extended by addition of a new group, derived from known properties of the fullerene Cââ. The constituent groups for all the species in a recently-published merchanism for fullerenes Cââ and Cââ formation are given. Thermochemical properties, including standard entropies and heat capacities, for all species in the mechanism are estimated. Properties estimated from group additivity are compared with values obtained from MM3(92) for all ring-only stable species. The group additivity approach is shown to be limited in its treatment of ring strain and H-H repulsion, although the estimated properties gave sufficiently reliable results when used in preliminary kinetic modeling studies of fullerenes Cââ and Cââ formation. Semiempirical (MOPAC) calculations were performed for Cââ and Cââ and for all selected precursors, including those of C{sub 5v} symmetry, such as corannulene. All MM3(92) and MOPAC calculations presented include evaluations of standard entropies and heat capacities. 56 refs., 6 figs., 8 tabs.

FULLERENES SYNTHESIS IN COMBUSTION

The Fullerenes, 1993

Thermodynamic limitations for fullerene formation in flames

Tetrahedron, 1996

Proceedings of the Combustion Institute, 2000

... EXPLORING OLD AND NEW BENZENE FORMATION PATHWAYS IN LOW-PRESSURE PREMIXED FLAMES OF ALIPHATIC... more ... EXPLORING OLD AND NEW BENZENE FORMATION PATHWAYS IN LOW-PRESSURE PREMIXED FLAMES OF ALIPHATIC FUELS CHRISTOPHER J. POPE and ... re-seen in .ames, due to the resonance-enhanced sta cent work have been provided by Westmoreland et bility ...

Further testing of the fullerene formation mechanism with predictions of temperature and pressure trends

Symposium (International) on Combustion, 1994

Journal of Hazardous Materials, 2000

Carbon, 1992

The early suggestion in fullerenes research that fullerenes might be produced in flames was soon ... more The early suggestion in fullerenes research that fullerenes might be produced in flames was soon supported by rhe observation of polyhedral carbon ions in flames, and in 199 I was confirmed by the recovery and identification of fullerenes Cnc and CT0 from benzene/oxygen flames. Recent research has determined the effects of pressure, carbon/oxygen ratio, temperature, and the type and concentration of diluent gas, on the yields of Co and C,O in subatmospheric pressure premixed laminar flames of benzene and oxygen. Similar flames but with acetylene as fuel have also been found to produce fullerenes, but in smaller yields than with benzene fuel. The largest observed yieldsofC60+C70 from benzene/oxygen flames are substantial, being 20% of the soot produced and 0.5% of the carbon fed. The largest rate of production ofGn+C~ was observed at a messure of 69 Torr. a C/O ratio of 0.989 and a dilution of 25% helium.

Aerosol Science and Technology, 1997

Environmental Progress & Sustainable Energy, 2010

The product stream from a biomass gasifier is at a sufficiently high temperature (roughly 11008C)... more The product stream from a biomass gasifier is at a sufficiently high temperature (roughly 11008C) to be able to undergo further chemical reactions if not immediately quenched. If the product stream is allowed to cool at a slower rate, there is the possibility of solid carbon formation, which can foul surfaces in contact with the cooling product gas. The goal of this work is to assess the thermodynamic driving forces for solid carbon formation via global equilibrium calculations, identifying conditions under which carbon formation is favored or disfavored. Global equilibrium calculations are performed using conditions representative of biomass gasifiers. Operating variables explored include the steam/carbon mass ratio, system pressure, and the amount of carbon lost and removed as char after the gasifier (% char). Both by varying the steam/carbon ratio and the % char, the temperature at which solid carbon is predicted to form and deposit on surfaces (T dep ) varies by hundreds of degrees Celsius, because varying both these operating conditions directly affects the atomic carbon/oxygen ratio of the product stream. There is a direct correlation between the atomic C/O ratio and T dep . Varying the steam/carbon ratio and the % char also strongly changes the predicted gas-phase product compositions. The effect of pressure upon T dep and gas-phase compositions is also explored. These results have implications for optimizing the composition of the product stream so as to not only preclude carbon formation but also maximize the yield from further downstream processes such as catalytic reactions to produce liquid fuels.

A kinetic mechanism is constructed for the formation of fullerenes C60 and C70 in flames, based o... more A kinetic mechanism is constructed for the formation of fullerenes C60 and C70 in flames, based on types of reactions used in describing growth of polycyclic aromatic hydrocarbons (PAH) and including additional chemical processes needed to describe evolution of the unique structural features of fullerenes. The mechanism consists of types of reactions, each characterized by an approximate rate coefficient, including processes for ring formation (via H atom abstraction, C2H2 addition, and cyclization leading to ring closing), reactive coagulation of aromatic molecules, and cage closing via H2 elimination and ring closing but also allowing for additional processes such as intramolecular rearrangements. Curved PAH, including benzo[ghi]fluoranthene (C~SHIO) and dibenzo-[ghi,mno]fluoranthene (corannulene, CzoHlo), are likely fullerene precursors. Corannulene is considered a key intermediate in the fullerene formation mechanism. Although alternatives to corannulene as an intermediate are mentioned, the proposed mechanism is based on corannulene and other related PAH of C5, symmetry.