Effect of porous and nonporous carbonaceous substrates on polystyrene thermal degradation during past CO2 laser heating

To investigate the effect of porosity on elution of volatiles from a devola tilizing 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 Ca rbon) particles. Particles of approximately 80 mu m (+/- 10 mu m) diameter were then individually handpicked. These 80 mu m diameter particles were he ated to a temperature in the range of 1200-2000 K in 32 ms by means of two converging CO2 laser beams. The eluted products were analyzed by combined g as chromatography/mass spectrometry (GC/MS). The evolved product informatio n 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 sty rene yield profile was predicted satisfactorily in the case of nonporous Gl assy Carbon, styrene evolution rates were approximately four times slower t han predicted in the case of porous Spherocarb. Also, the ratio of secondar y pyrolysis products of polystyrene (benzene, toluene, etc.) to a primary p yrolysis product (styrene) was approximately four times higher in the case of Spherocarb than in the Glassy Carbon case. Both findings strongly sugges t the presence of transport limitations in porous Spherocarb under PCC-type heating rate conditions.