# Tag Info

53

Probably the biggest drivers behind using methane as a fuel is that it is abundant in natural gas and is (currently) mostly useless as a chemical feedstock. Ethane makes up a few percent of natural gas and can also be obtained as byproducts of petroleum refining, but the big difference from methane is that ethane is extremely useful in chemical synthesis (...

43

As is usual with rocket fuels, the problems of ozone are practicality not performance Almost every answer for why a specific rocket fuel component is used or not will end up referring to John D Clarke's magnificent and sparklingly written book: Ignition: An informal history of liquid rocket propellants (a rare technical book worth reading for the brilliant ...

39

In both cases, there appears to be a confusion of terminology between common and technical uses. We commonly use methane and propane for cooking (and home heating), but not ethane. I would expect ethane to be suitable for this, being in between the two, but I've never heard of anyone using it for this purpose. Why is that? In reality, anyone using ...

18

Higher $\mathrm{RON}$ seems possible. Yet the boiling point rises accordingly while heat of combustion remains roughly the same. Here are two compounds that fit all posed criteria. \begin{array}{|c|c|c|c|c|} \hline \mathbf{Molecule} & \mathrm{mp\ \mathrm{(^\circ C)}} & \mathrm{bp\ \mathrm{(^\circ C)}} & \Delta_\mathrm cH_\mathrm m^\circ\ (\...

18

The answer is NO. The article you quote makes a completely unwarranted generalisation that "all flames are hollow". This is true of some flames but only because the fuel that is burning is only able to burn when mixed with oxygen from the air. In those flames, the flame is "hollow" because only in regions where air can mix with the fuel ...

17

There's a NASA report that looks into this: "ON THE SOLUBILITIES AND RATES OF SOLUTION OF GASES IN LIQUID METHANE", Hibbard and Evans, 1968 and concludes that such mixtures are possible. Starting on page 8: Figure 5(a) presents the curves for oxygen, argon, carbon monoxide, and nitrogen. Also shown are the two experimental values for nitrogen. ...

15

Liquid ozone is rather stable (as in "can be stored") as an up to 70% solution in LOx, if you add some stabilisers. That would give quite a bit of additional boost in a rocket, but it's surely going to explode already in the rocket's fuel pumps and tubing, instead of burning in the engine's nozzle. Rocket engines are tricky enough to build, you don'...

14

Diesel engines vs. gasoline engines Diesel engines don't rely on spark plugs, but they still work by igniting the fuel to generate a force that moves a cylinder in the engine. The air/fuel mixture in a diesel engine is ignited by the compression of the same cylinder during the "compression" stroke. That is, like most gasoline engines in cars, diesel ...

12

Usually when we say something "burns", it's being oxidized. In the case of carbon dioxide only the oxygen can be oxidized, by displacing it as the element; that requires fluorine or a sufficiently powerful fluorinating agent. Carbon dioxide supports combustion, acting as the oxidizer instead of being oxidized, with some active metals such as magnesium. ...

12

To add to the Bob's excellent answer (and expand a bit on my comment there), I've found two other potentially interesting papers to peruse. The first is R.J. Hodges and R.J. Burch, Cryogenics 7 112-113 (1967), titled "The equilibrium distribution of methane between the liquid and vapour phases of oxygen". They note a "very high solubility of methane in ...

11

No: trying to catch up with 100+ years of technological optimizations in your kitchen won't be an economical enterprise. Store-brought batteries are standardized and relatively inexpensive. Power from an outlet is even less expensive (by one or two orders of magnitude). On the other hand, in many places you can save on electricity by going solar. Even if ...

10

The answer depends on what do you mean for ancient people. There are a lot of reactions that could produce gas for ejecting projectiles. The most common was the mixture of sulphur, potassium nitrate $\ce{KNO3}$ and carbon that is known as gun powder and has been reported to be used since the IX century in China. If you want some less efficient and not used ...

9

Ethanol clearly can be used as a fuel. But there are several reasons why it isn't. First is simple economics. Ethanol costs more to produce than gasoline: oversimplifying only slightly, fermentation is more complicated than simple distillation. Those countries that do use mixtures of ethanol in gasoline do so for "environmental" reasons (which are not ...

9

I recommend the @Stanley Yu own answer, as I admit I was not particular familiar with the shape of the ON number curve. It is done by an extrapolation of the critical compression ratios of mixtures 0-100% of isooctane and 100-0% of n-heptane for ON values <0 and >100. If, just illustratively, 100% isooctane had the critical compression ratio 1:20, 90% ...

8

Vegetable oils are mainly made of glycerol esters of oleic acid, linoleic acid and palmitic acid. For example, the fatty acids extracted from olive oil are a mixture of $74$% oleic acid, $11$% palmitic acid, and $10$% linoleum acid, plus 5% other acids. These proportions are average values that may change from one sample to the next one. The mass proportion ...

7

Diesel fuel The difference between gasoline and diesel fuel lies in the length of carbon chains. Gasoline and diesel fuel are examples of hydrocarbons, molecules made up purely of hydrogen ($\ce{H}$) and carbon ($\ce{C}$) atoms. Simple examples include $\ce{C_3H_8}$ (propane) and $\ce{C_8H_18}$ (octane). Gasoline contains compounds with carbon chains ...

7

Historically, this sort of process has been done with the Fischer–Tropsch process. The core of this process is to use "syngas" (a mixture of $\ce{CO}$ and $\ce{H2}$) in the presence of a catalyst to make higher molecular weight hydrocarbons: $$\ce{(2n + 1) H2 + n CO → C_{n}H_{2+2n} + n H2O}$$ Under normal conditions, this will actually make mostly ...

7

During WWII many cars were powered by a gasogene engine, which transformed wood or charcoal into a synthetic gas composed by $\ce{CO}$, $\ce{N2}$, $\ce{H2}$ and $\ce{CO2}$. Thus the use of $\ce{CO}$ (albeit not as a pure gas) as a fuel is not something new (the former use of piped coal gas for house heating and cooking has already been mentioned above). I am ...

7

Gas to liquid technology is known, but propane isn't a good choice of end product The idea of converting natural gas (which is mostly methane) into liquids is widely used not least because the earth has, inconveniently, located the best natural gas fields some way from the places that most want to use natural gas. Right now (in 2016), though, it seems it ...

7

I'll address you questions in order: 1) Yes, that is basically the correct reaction, although not quite balanced; here is how I would write it: $$\ce{2H2(l) + O2(l) -> 2H_2O(g)}$$ 2) Ideally, if there were no side reactions, then yes, this particular reaction is "polution free", and the only product is water. 3) You are correct in your ...

6

... are homemade batteries ... a practical alternative for powering your appliances ...? No, those type of batteries don't have enough energy to power more than a small light bulb or a transistor radio. If fact the light bulb probably won't stay lit for more than 10 minutes. An LED would be much better. You need at least 30 car batteries to power your home ...

6

Techron is a detergent based on PEA, polyeter amine. It is a complex synthetic molecule that will basically 'loosen' and 'solve' deposits in your fuel system. They then become part of the fuel-air mixture and burn in the combustion chamber with it. Be it in the carburettor, the injectors, the valves (for indirect injection vehicles) or the combustion chamber....

6

Carbon monoxide has been used as a fuel but not usually by itself. The reason why we don't use it much now is that there are better, safer alternatives. Before the widespread use of natural gas as a fuel (which consists mostly of methane) many cities piped coal gas (sometimes called town gas) to consumers as a fuel. Coal gas is made (obviously) from coal ...

5

What you have is classified as a Mg-air battery. You can read more about it here : https://en.wikipedia.org/wiki/Category:Metal-air_batteries These are a class of primary(i.e. not rechargeable) batteries, where the anodic reaction is a metal being oxidised and the cathodic reaction is oxygen reduction. The reactions are: $\ce{Mg → Mg^{2+} + 2 e^{-}}$ on ...

5

"Energy gained needs to be greater than the sum of lost energy in all steps" http://www.lhup.edu/~dsimanek/museum/unwork.htm Perpetual motion machines http://news.sciencemag.org/chemistry/2014/01/rhubarb-battery-could-store-energy-future Flow battery, which works. 1) You cannot win (First Law of thermodynamics from Noether's theorems and the isotropy ...

5

$\mathrm{KNO_3(s)}$ can oxidize charcoal without sulfur. It needs a "hot" primer through to get the reaction started. Sulfur's role is to lessen the ignition temperature. See section in Wikipedia article. Since the reaction isn't complete and has a number of possible products bthere isn't an exact chemical formula for black gunpowder burning. The ...

5

One of the earliest use of Black Powder was crude large-bore handheld guns (early China). And, actually much more, to quote a source: Other Song military applications of gunpowder included primitive hand grenades, poisonous gas shells, flamethrowers and landmines. The first artillery pieces were rocket tubes made from hollow bamboo shoots, but these were ...

5

The main reason for the high quantity of iso-octane is to prevent Engine Knocking. The Wikipedia page for Octane explains this quite well: The octane rating was originally determined by mixing fuels from only heptane and 2,2,4-trimethylpentane (a highly branched octane), and assigning anti-knock ratings of zero for pure heptane and 100 for pure 2,2,4-...

5

Because petrol engines work differently to diesel engines and the property differences matter more than the absolute energy of combustion Your basic assumption is wrong: diesel engines use mainly straight chain hydrocarbons and it is petrol engines that prefer the unsaturated or branched hydrocarbons. The absolute amount of energy produced in engines is not ...

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