Date of Graduation
1997
Document Type
Dissertation/Thesis
Abstract
The formation of aromatics during catalytic cracking was investigated using model compounds. Cracking reactions were carried out in a microactivity test (MAT) unit. Three ASTM standard catalysts, obtained from the National Institute of Standards and Technology (NIST) were used for this work. Representative compounds were chosen to represent the following compound classes: linear and branched paraffin, linear and branched olefin and cycloparaffin. Cracking of a paraffin-olefin mixture was carried out to investigate synergistic effects if any. The dependence of aromatization reactions on cracking temperature was investigated. Characterization, separation and analysis of products was carried out using GC and GC-MS. In general, aromatization increased with increase in catalytic activity. Only traces of benzene (if any) were detected with the cracking of linear and branched compounds. The mono-aromatics produced had short alkyl side chains of up to C{dollar}\\sb2{dollar}. The results indicate a tendency to substitute heavily in the benzene ring rather than to increasing the length of the side chain--i.e. the probability of forming a trimethyl benzene is much higher than forming a propyl benzene. One possible reason may be the self alkylation reactions of the long-chain mono-aromatics to form higher aromatic products. Higher aromatics like naphthalenes and small amounts of triaromatics (phenanthrene or anthracene) were formed using some feeds. Synergistic effects between the paraffin and the olefin were negligible. Aromatization products increased with a decrease in reaction temperature. A possible reason may be that ring opening reactions (hydride abstraction followed by {dollar}\\beta{dollar} scission) increase with increase in temperature. Four possible routes for the formation of aromatics were theorized. The principal mechanism of benzene formation was by the dehydrogenation of the cyclic compounds. Linear compounds preferentially formed toluene on cyclization. This was probably due to the relative ease of cyclizing a C{dollar}\\sb7{dollar} compared to a C{dollar}\\sb6{dollar}. Branched olefins may be the intermediate which lead to xylene formation from non-cyclic components. Complete conversion data (overall and MAT conversions) and the product distributions obtained from these reactions are documented in this work. Further, a complete list of the aromatic products have been tabulated for each model compound.
Recommended Citation
Subramanian, Ramesh B., "Aromatic formation in catalytic cracking: A study using model compounds over ASTM standard catalysts." (1997). Graduate Theses, Dissertations, and Problem Reports. 9856.
https://researchrepository.wvu.edu/etd/9856