3 ms·

Thanks. Can I read this as there's no way this process could run any other way than as a massive energy sink? Or are the graphene bindings sufficiently low ener

by usrusr 3y ago

Thanks. Can I read this as there's no way this process could run any other way than as a massive energy sink? Or are the graphene bindings sufficiently low energy that the hydrogens will happily hop away to their "higher" bindings in h2? (that's my mental model of chemistry: stuff "wants" to go down but there are plenty of local minima where certain combinations can rest until "shaken out", never made it to the point where I could reason about why certain combinations are local minima)

adrian_b 3y ago
Any hydrocarbon derivative can be converted by pyrolysis into hydrogen and carbon (and small amounts of other substances, if it is not a pure hydrocarbon), where the carbon may be graphite or other forms, e.g. graphene. This requires a great amount of energy. By burning the obtained hydrogen, depending on the amount of hydrogen in the original hydrocarbon, there are good chances to obtain more energy than used for pyrolysis, if all the processes are done carefully, to avoid losses (the reason why energy can be gained is that every new hydrogen-oxygen bond corresponds to an old hydrogen-carbon bond replaced by a half of a hydrogen-hydrogen bond and a half of a carbon-carbon bond, and even when ignoring the other bonds and ignoring the weak old oxygen-oxygen bond, a hydrogen-oxygen bond is strong enough in comparison to a hydrogen-carbon bond to ensure a positive energy balance). Nevertheless, the amount of energy obtained in this way would be much less than the energy obtained by burning the hydrocarbon derivative at the beginning, so this would be a waste that could be justified only if the graphene could be sold at a high price. If it is desired to not release carbon dioxide, then the original hydrocarbon derivative should be left alone and hydrogen should be obtained from water. If the hydrocarbon derivative needs to be destroyed, it is easier to ensure a clean process for burning followed by carbon dioxide capture, than for pyrolysis, which can produce many dangerous substances.

by usrusr 3y ago

adrian_b 3y ago

Any hydrocarbon derivative can be converted by pyrolysis into hydrogen and carbon (and small amounts of other substances, if it is not a pure hydrocarbon), where the carbon may be graphite or other forms, e.g. graphene. This requires a great amount of energy. By burning the obtained hydrogen, depending on the amount of hydrogen in the original hydrocarbon, there are good chances to obtain more energy than used for pyrolysis, if all the processes are done carefully, to avoid losses (the reason why energy can be gained is that every new hydrogen-oxygen bond corresponds to an old hydrogen-carbon bond replaced by a half of a hydrogen-hydrogen bond and a half of a carbon-carbon bond, and even when ignoring the other bonds and ignoring the weak old oxygen-oxygen bond, a hydrogen-oxygen bond is strong enough in comparison to a hydrogen-carbon bond to ensure a positive energy balance). Nevertheless, the amount of energy obtained in this way would be much less than the energy obtained by burning the hydrocarbon derivative at the beginning, so this would be a waste that could be justified only if the graphene could be sold at a high price. If it is desired to not release carbon dioxide, then the original hydrocarbon derivative should be left alone and hydrogen should be obtained from water. If the hydrocarbon derivative needs to be destroyed, it is easier to ensure a clean process for burning followed by carbon dioxide capture, than for pyrolysis, which can produce many dangerous substances.