# What are the byproducts from converting petroleum into H2? **URL:** \ **Category:** Factual Questions\ **Created:** [May 2, 2014, 6:15pm UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519 "2014-05-02T18:15:58Z")\ **Posts on this page:** 8\ **Page:** 3
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [May 6, 2014, 11:32am UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519/41 "2014-05-06T11:32:32Z")
> [@njtt](#): > > (I also dispute that 30% figure, and I do not recognize [howstuffworks.com](http://howstuffworks.com) as a reliable source that trumps knowledge of basic chemistry.)… > > Burning natural gas as opposed to burning oil (although it may have other advantages) is not going to lead to any very significant improvement in greenhouse gas emissions. I’m sorry your cite must have gotten cut off here. It’s all well and good that you don’t recognize my cite as a reliable source that trumps knowledge of basic chemistry , but I don’t recognize your knowledge of basic chemistry to be qualified to make that call either. 😉 > [@](#): > > Furthermore, the more you try to use natural gas, the more of it will escape into the atmosphere, and natural gas itself is a much worse greenhouse gas than CO2 is. Yes fair to state, it is not without it’s issues. ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [May 6, 2014, 1:09pm UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519/42 "2014-05-06T13:09:54Z")
> [@kanicbird](#): > > IIRC Spacecrafts use liquid cyrogenic H2 which takes care of the volumetric density issue you state. Gasonline’s volumetric energy density is 4x that of liquid hydrogen. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [May 6, 2014, 7:57pm UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519/43 "2014-05-06T19:57:22Z")
> [@Ruken](#): > > Gasonline’s volumetric energy density is 4x that of liquid hydrogen. The use of hydrogen for rocket fuel has to do with the energy density per unit MASS not volume. Consider the following reactions : 1\> Hydrogen reacts with Fluorine H2 + F2 —\> 2HF 537kJ are released per mole of hydrogen or 1x2 + 9x2 = **20** g or 537/20 ~ **27 kJ/g** of propellant 2\> Gasoline reacts with pure Oxygen (gasoline is approximated by Octane - I know it is not octane and is a mixture of C4-C12, but for energy calcs this equation is good) C8H18 + 12.5 O2 —\>8CO2 +9 H2O 5460kJ are released per mole of octane (gasoline) or 12x8+1x18 +12.5x16x2 = **514** g or 5460/514 ~ **11 kJ/g** of propellant So on a mass basis - Hydrogen + Fluorine will contain 2.5 times the energy density of Gasoline + Oxygen. The mass density of energy is important because of the[rocket equation](http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation). The rocket is best propelled by fuel that has a High exit velocity and low mass. So the best propulsion will come from electrons (or even less massive particles) shot out at a speed approaching light. The [Ion thruster](http://en.wikipedia.org/wiki/Ion_thruster) comes close to this. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [May 6, 2014, 8:05pm UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519/44 "2014-05-06T20:05:10Z")
Why use fluorine in one reaction and oxygen in the other when you want to compare hydrogen and hydrocarbons? ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [May 6, 2014, 8:22pm UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519/45 "2014-05-06T20:22:07Z")
> [@njtt](#): > > No we are not. I was correct, as you admit in your final paragraph, and **kanicbird** was wrong, in the statements of his that I was responding to. The rest of what you say, even if true (and I am not at all sure you are right about little oil being used in power production) is completely irrelevant to what I said, … njtt - I was pointing out that the basis was not relevant and my statement still stands. Here is why - Its not just the ratio of Carbon to Hydrogen that is linked to CO2 emissions, it is also the efficiency of the power producing system. Units running on heavy oil have less efficiency than units running on gases like methane or ethane. So CO2 produced per kw-hr of produced electrical energy is a better metric and[here is how they compare](http://www.eia.gov/tools/faqs/faq.cfm?id=74&t=11). As you can see - natural gas leads to the least CO2 emissions per kw-hr of produced electrical energy. ---
**Author:** ![Ruken](https://avatars.discourse-cdn.com/v4/letter/r/f475e1/32.png) [@Ruken](https://boards.straightdope.com/u/Ruken)\ **Post date:** [May 6, 2014, 9:56pm UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519/46 "2014-05-06T21:56:34Z")
> [@am77494](#): > > The use of hydrogen for rocket fuel has to do with the energy density per unit MASS not volume. We weren’t taking about gravimetric energy density. When we were, I wrote: > [@Ruken](#): > > It has a high gravimetric energy density, which matters in a space ship ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [May 6, 2014, 10:13pm UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519/47 "2014-05-06T22:13:38Z")
> [@Ruken](#): > > We weren’t taking about gravimetric energy density. When we were, I wrote: Yes - but you had a number for the volume energy density (4x - based on combustion with air) and it was a “high” for gravimetric energy density. I provided you the number - 2.5x. ---
**Author:** ![am77494](https://avatars.discourse-cdn.com/v4/letter/a/d2c977/32.png) [@am77494](https://boards.straightdope.com/u/am77494)\ **Post date:** [May 6, 2014, 10:22pm UTC](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519/48 "2014-05-06T22:22:16Z")
> [@naita](#): > > Why use fluorine in one reaction and oxygen in the other when you want to compare hydrogen and hydrocarbons? Alkanes react explosively (not very controllable which is needed for propellants) with fluorine and form solid carbon (not desirable - you want to make as much gases as possible). Anyways - if you want the numbers, I calculated them approximately for you C8H18 + 9F2 —\> 8C + 18HF Heat of reaction ~ 4700 kJ/g mol Or 4700 kJ are released per 12x8 + 1x18 + 9x9x2 = 276 g or 4700/276 = 17 kJ/g [Previous page](https://boards.straightdope.com/t/what-are-the-byproducts-from-converting-petroleum-into-h2/687519.md?page=2)