Science Buddies: "Ask an Expert"

My project that I plan to submit next year in my regional science fair is titled "From Garbage to Ga-Sol-line: A Synthesis of Fuel Oils from Biomass." It is an engineering project dealing with the construction of a working apparatus to produce motor fuel from carboneous trash materials such as grass clippings, leaves, and paper. The main route will be through the industrialized Fischer-Trospch process, where the materials are vaporized into carbon monoxide and hydrogen gas using a high temperature source (in this instance, a 1 meter by 1 meter Fresnel lens will be used to concentrate sunlight to a single point of light, so the apparatus is essentialy solar powered). The gaseous mixture is then reacted under a catalyst to form gasoline/diesel components, such as pentane, heptane, octane, and decane. These would be condensed using coiled piping and calculated for its yield.

I'm currently finishing up the research stage, and am beginning the experimentation phase. My main question is calculating the percent yield. The process produces several hydrocarbon alkanes, anywhere from methane (CH4) to triacontane (C30H62). Most of the chains will be somewhere around C5 chains to C20 chains; temperature varies the yields. But the process also generates water. So the problem concerning the percent yield is this: how can I calculate the amount of products formed if they are jumbled to such the extent explained above, and would it be possible to differentiate the mass of the products formed from the mass of the water formed? Whatever comes out of as products will be a mixture of water and hydrocarbons, which would prevent me from just simply weighing the mass of the products to find the amount of hydrocarbons formed.

Hi bereal511!

You might want to consult the Fischer-Tropsch Archive, http://www.fischer-tropsch.org.

There are a wealth of resources on this site including, a "Physical Chemistry of the Fischer-Tropsch Synthesis."

Yes, I have done quite a bit of research there, but I suppose my question is more specific to the practical yields of my own experimentation. I don't have access to much financial support, so I can't buy a spectrometer to identify the different hydrocarbons that I would be creating. I want to at least ballpark the product yield amount. My hypothesis would be to seperate the water from the product mixture using a dessicant of some sort, remove the dessicant, distill the water from the dessicant and collect it, then measure the mass of the water. Then that could at least give me somewhat of a yield, and I could perhaps calculate the amount of hydrocarbons produced using the water as a reference point. From the reactions that I have researched, for every mole of water formed, a mole of carbon monoxide is chained into a hydrocarbon. I am currently debating whether this will give me at least a close estimate to the percent yield.

Oh, and is there an edit option? I'd like to thank you for your reply.

Hi bereal511!

Thank you for your response.

I should have prefaced my comments with a note that you might already be familiar with this site.

And no, beyond the referenced site, I am not familiar with a low-cost way to measure the Fischer-Trospch Process.

Maybe a fellow expert can help? To gain visibility, you may want to post a new topic with subject "Low-cost Fischer-Trospch." I'll leave that to your discretion.