Effect of Porous and Nonporous Carbonaceous Substrates on Polystyrene Thermal Degradation during Fast CO 2 Laser Heating Ashish Tripathi, † Chris L. Vaughn, † Waleed Maswadeh, ‡ and Henk L. C. Meuzelaar* ,† Center for Microanalysis and Reaction Chemistry, The University of Utah, Salt Lake City, Utah 84112, and 2-Geo-Centers, E3220 Aberdeen Proving Grounds, Maryland 21010 Received November 17, 1998 To investigate the effect of porosity on elution of volatiles from a devolatilizing coal particle under pulverized coal combustion (PCC) type heating rate conditions, polystyrene was doped into porous model char (Spherocarb) particles and also coated on the surface of nonporous model char (Glassy Carbon) particles. Particles of approximately 80 μm(( 10 μm) diameter were then individually handpicked. These 80 μm diameter particles were heated to a temperature in the range of 1200-2000 K in 32 ms by means of two converging CO 2 laser beams. The eluted products were analyzed by combined gas chromatography/mass spectrometry (GC/MS). The evolved product information was used to construct yield curves. These yield curves were compared to a simple first-order rate law prediction. It was observed that while the styrene yield profile was predicted satisfactorily in the case of nonporous Glassy Carbon, styrene evolution rates were approximately four times slower than predicted in the case of porous Spherocarb. Also, the ratio of secondary pyrolysis products of polystyrene (benzene, toluene, etc.) to a primary pyrolysis product (styrene) was approximately four times higher in the case of Spherocarb than in the Glassy Carbon case. Both findings strongly suggest the presence of transport limitations in porous Spherocarb under PCC-type heating rate conditions. Introduction The focus of this study is to investigate the effect of porosity on the release of products from small carbon- aceous particles (40-100 μm diameter) at the very high heating rates (approximately 10 5 K/s) characteristic of PCC conditions. 1 To achieve these conditions, we con- structed and tested the CO 2 laser pyrolysis system (shown in Figure 1). 2-5 Porous (Spherocarb) and non- porous (Glassy Carbon) spherical particles were selected as the carbonaceous substrates, and polystyrene was chosen as the model polymer for these studies. 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Fuel 1984, 63, 640. 984 Energy & Fuels 1999, 13, 984-991 10.1021/ef980254u CCC: $18.00 © 1999 American Chemical Society Published on Web 07/01/1999