Direct contact pyrolysis of hydrocarbons: A source of hydrogen and interesting carbon formations.

摘要

The work detailed in this document looks at a novel liquid metal supported catalytic system for the generation of hydrogen by decomposition of ethanol through direct contact pyrolysis. The hydrogen is produced at relatively low temperatures (500--600°C) and has carbon and water as co-products. It should be noted that CO is not observed as a product at these low temperatures. This is to be contrasted with the hydrogen produced at higher temperature from ethanol which does contain carbon monoxide. The presence of carbon monoxide in hydrogen complicates fuel cell operation and catalytic chemical processes. Thus, the lack of CO in this process is advantageous.;In theory the process is slightly exothermic, however in actual practice the process will require a small amount of heat to be added to the system for the reaction to occur. This heat could be usefully provided by a solar facility or waste heat generated as a byproduct of an industrial process. Further, if the source of the ethanol is either biological or otherwise uses a carbon dioxide stream (e.g. syn-gas based production), this process can be seen as net carbon sequestering.;The intent of this work was to investigate four major concepts, the first being the design and testing of the liquid metal reactor and feed stock delivery system. This system must produce hydrogen by decomposition of ethanol at temperatures in excess of 700°C, a relatively straight forward thermodynamic process.;Additionally, the system design was intended to test the effects on this process when transitional metals such as iron, nickel, and cobalt are added to the system as a catalyst. Of further interest is the unique way in which the catalyst is delivered and regenerated during the operation of the system.;Finally, we examine the morphology of the carbon co-products produced during the lower temperature catalytic reaction. These carbon products manifested themselves in varied particulate forms depending on the liquid metal medium and catalyst used. One of the more interesting forms observed, was a carbon nano-tube (CNT) structure.;We conclude this work by examining potential changes for the second generation reactor design as well as potential uses and capture techniques for the carbon co-products produced by the process.