(178b) Catalytic Cracking of Dodecane in Supercritical Water

 

Azadeh Zaker, Patricia Guerra, Geoffrey Tompsett, Michael T. Timko

 

Department of Chemical Engineering

Worcester Polytechnic Institute

Worcester MA 10609

An abstract to be submitted to the National Meeting of the AIChE (2016)

Technical Session: Reaction Engineering of Biomass and Hydrocarbons in Supercritical Water

Sponsored by: Catalysis and Reaction Engineering Division

In this work, we investigated dodecane cracking in supercritical water (SCW) using ZSM-5 as an acid catalyst. We studied the reaction in the presence and absence of water by tracking reaction progress in a batch reactor held at 400 Ì?C and 24.1 MPa. For the same catalyst loading (5 wt. % oil-based), addition of water reduced formation rates of gas, liquid, and solid products. We identified and quantified liquid products using GC/MS and GC×GC chromatography. GC/MS was used primarily to track production of specific compounds, including toluene, xylenes, and ethylbenzene. GC×GC was used to monitor both individual compounds as well as classes of compounds: aliphatics, 1-ring aromatics, 2-ring aromatics, and 3-ring aromatics. SCW changes the observed product distribution of dodecane cracking, with increased production of aliphatics observed in the presence of water compared to increased production of aromatic compounds in its absence. Furthermore, in the absence of water, GC×GC analysis indicates increased yields of 2-ring and 3-ring products, including molecules such as naphthalene and alkyl-naphthalene. In addition to liquid phase analysis, we characterized the coke deposited on the catalyst using Temperature Programmed Oxidation (TPO) technique. Water reduces coke formation by an order of magnitude and alters its chemical characteristics. Coke deposited in the presence of water is mostly soft coke while coke formed in the absence of water is mostly graphitic hard coke. Finally, we developed a reaction network model to interpret our results. The reaction network consisted of aliphatic, aromatic, gas, and coke products. Future work will investigate catalysts other than ZSM-5 and more sophisticated molecular reaction networks.