Large-scale prodn. of microstructured carbon by benzene pyrolysis at 900 °C has been investigated using a quartz plug flow reactor. It was found that a significant increase in carbon yield was achieved by filling the quartz reactor with porcelain tiles. Contrary to what is normally reported in the literature, both lamellar and spherical carbon, characterized by different morphologies and interlayer spacings, was obtained. Considerations about the carbon growth mechanism indicated that the formation of different carbon structures mainly depends on the environment in which the carbon spheres are nucleated. [on SciFinder(R)]