(313b) Experimental Analysis of Catalytic Gasification of Waste Polymers

Experimental Analysis of Catalytic Gasification of Waste Polymers

 (2) [Undergraduate] Student Researchers:

• Samuel O. Sanya
• UC Obiako
• Aliandra Barbutti
• Stephen Reeves
• Eric M. Lange

(3) Faculty Mentor:

• Dr. Jorge Gatica

 (4) Abstract

Catalytic gasification, or “gasification”, is one effective method which can be applied to promote low-temperature conversion of solid waste to energy. This research focuses on advancing the knowledge of a catalytic gasification process as a potential in-situ resource utilization and waste management alternative. This research has significance in a variety of engineering applications, but it is of particular relevance towards reducing landfill waste or as an in-situ resource generation system for space exploration beyond LEO.

This process evolves through a reaction mechanism consisting of two liquid-phase oxidation reactions of long-chain polymers, complemented by two gas-phase reactions. Using a laboratory grade reactor, the gasification of two model substrates, polyethylene and cellulose, was examined in the presence of ruthenium and platinum catalysts.

Gaseous products consisting of hydrogen, methane, carbon monoxide, carbon dioxide, were quantified by Gas Chromatography (GC). Calibration of the GC using chromatographic standards enabled the formulation of an equation to calculate the composition of the gaseous products for different reaction times. Fundamental reactor design equations along with stoichiometry calculations were then used for determinations of percent polymer gasified as well as selectivity of the gasification process.

Additional characterization of the solid and liquid residuals was performed using Differential Scanning Calorimetry (DSC), Thermo-Gravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM). Quantification of the DSC spectra was used to correlate the thermal characterization of the residues with the unconverted (or non-gasified) substrate after the reaction was quenched. The SEM provided information on the microstructure of the residues, their atomic composition, and preliminary assessment of the possibility of catalyst recovery.

Preliminary results suggest that catalytic gasification provides potential control for the liquid-phase oxidations. Under appropriate conditions, oxidation was found to follow the incomplete oxidation pathway which resulted in significant yields of hydrogen and methane, which are potentially high value products as they can be used for energy recovery.

Comparisons between the gasification rates for the two substrates are drawn. Similarly, comparative studies of different catalysts are also presented. The results are used in conjunction with a kinetic model for the gas-phase to formulate a methodological model for the gasification of solid waste. The results will be presented along with a preliminary extension for a continuous gasification process.