FROM MICROSTRUCTURE AND REACTIVITY OF SOLID CARBONS TO FORMATION AND DEPOSITION MECHANISMS
Laboratory for Hydrocarbon Process Chemistry, The Energy Institute
Department of Energy and Geo-Environmental Engineering
The Pennsylvania State University
University Park, PA 16802
Monday, June 7, 1999 3:30 pm
Ben Bandy Conference Center
Center for Applied Energy Research
In three basic allotpropic forms and different degrees of microcrystalline aggregation, solid carbons cross over a wide range of materials with a fascinating diversity in properties and applications - e.g., from graphite to diamond, from carbon fiber to glassy carbon, from carbon black to activated carbon, and from fullerenes to meso carbon microbeads. Solid carbons, or carbonaceous solids, can also constitute many undesirable deposits encountered in petroleum refining and petrochemical processes, and in operation of combustion engines. A good understanding of carbon formation and deposition mechanisms is essential for controlling the production of desirable or undesirable solid carbons. Microscopic examination and characterization of solid carbons in conjunction with reactivity measurements offer important insigths into carbon formation and deposition mechanisms.
At different levels of resolution, from optical microscopy (micrometer scale) to atomic force microscopy (nanometer scale), including SEM and TEM (micrometer-nanometer scale), microscopic examination of solid carbons provides information on:
- structural isotropy/anisotropy of samples
- catalytic/non-catalytic formation
- phase transformations
- possible precursors and reactions
- reaction or deposition conditions
Three different examples, i) characterization of needle coke texture (carbonaceous mesophase formation), ii) solid deposition from heated jet fuels, and iii) undesired globular coke formation in carbon black production, will be discussed to illustrate the use of different microscopic techniques to elucidate carbon formation and deposition mechanisms. Complementary to microscopic characterization, a temperature programmed oxidation (TPO) method was used to determine the reactivity of solid carbon deposits produced from jet fuels heated on different metal surfaces.