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Topic: Methane to hydrogen and gasoline?  (Read 3212 times)

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Offline Enthalpy

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Methane to hydrogen and gasoline?
« on: September 04, 2018, 08:04:42 AM »
Hello everyone and everybody!

Commercial hydrogen is presently made from methane and water vapour, which outputs hydrogen and carbon monoxide, possibly dioxide in a second step
https://en.wikipedia.org/wiki/Steam_reforming
which all sorts of naysayers take as an argument against hydrogen-based transports: "releases dioxide too". It's not even so wrong.

Could it be done better?

By some sort of pyrolysis maybe, obtain H2 and a spectrum of CnH2n as a feed for valuable fuel components, for instance for alkylates to blend gasoline?

Cars would still emit dioxide when burning gasoline obtained from natural gas, as much as when gasoline derives from oil, but we would have run in addition planes, trains and cars on hydrogen
http://www.scienceforums.net/topic/73798-quick-electric-machines/?do=findComment&comment=738806
with no more dioxide emissions, and bought natural gas cheaper than oil.

Or do the same with C3 and C4 fractions. These are commonly torched at the well as they are too cheap to transport, but if a refinery transforms them, it would pay the tanker.

My understanding is that as long as crude oil is affordable, CO2 emissions are for free, and hydrogen is a marginal commodity, steam reforming is the economic answer. But time may change this situation.

So: could you imagine such a process? Ideas, suggestions, proposals, guidelines, fantasy?

Offline Enthalpy

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Re: Methane to hydrogen and gasoline?
« Reply #1 on: September 07, 2018, 04:48:07 AM »
How easy or difficult do you suppose it is?

Like: heat methane over some catalyst, freeze everything, sort out H2 and C2H4 from remaining CH4, process C2H4 further?

Offline Enthalpy

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Re: Methane to hydrogen and gasoline?
« Reply #2 on: September 07, 2018, 11:03:05 AM »
The desire I expressed is long identified and routes investigated. Keywords:
nonoxidative conversion of methane
Yes, I could have begun with that.

The oxidative routes couple carbons but results in some carbon oxides as well, while nonoxidative conversion seeks the higher hydrocarbons without oxides. The usual goal is "valuable chemicals", understand less cheap than natural gas, especially C2Hn, rather than hydrogen and additives for gasoline.

For instance Xiaoguang Guo et al used a catalyst of iron in silica
http://science.sciencemag.org/content/344/6184/616.full
to obtain ethylene, benzene and naphthalene without coke. Aromatics are presently an additive to gasoline but are unhealthy; more hydrogen in the feed squeezes the proportion of acetylene and aromatics, so ethylene and ethane would make most of the output.

Or Yang Xiao and Arvind Varma used Pt-Bi on zeolite (how expensive?)
https://pubs.acs.org/doi/abs/10.1021/acscatal.8b00156?src=recsys&journalCode=accacs
to convert >90% of carbon atoms to C2Hn.

Heat being so cheap, maybe the conversion can live without a catalyst, if enough hydrogen is present and the products are separated early to stop the reaction at C2Hn? If the reaction and the separation are quick enough, a low conversion per pass is acceptable.

Offline zarhym

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Re: Methane to hydrogen and gasoline?
« Reply #3 on: December 08, 2018, 02:57:17 AM »
My boss once talked about another way to convert methane into liquid form. He was talking about methanol. He suggested that by photolysis of ozone the triplet oxygen atom can be used as the oxidizing reagent to convert methane into methanol. I guess this can be done with flow chemistry.

However, mixing methane and oxygen is not a safe idea. A single spark could be devastating.

Offline BobfromNC

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Re: Methane to hydrogen and gasoline?
« Reply #4 on: December 18, 2018, 02:11:11 PM »
There are ways to do what you describe, but the challenge is all in economics.    It is possible to burn natural gas as it comes from the ground, without any complex factories or much technology.   In order to reform it to H2 and other alkanes, it would require an expensive plant, likely some precious metals and strong acids, and then you have to purify, store and sell the multiple products to different groups.  That all costs a lot of money, but the laws of thermodynamics show that you will get less energy out of the final products than went in, so you have to make products that have a high value.  With coal, natural gas, and oil being cheap, there is almost no one willing to invest billions in building facilities to reform one fuel into another, when it is already plentiful.   

I have seen companies spend billions on projects like that, biofuels, nuclear power, coal liquification, MTBE, and a host of other technologies in the last few years, but only a few have survived and every made any money, mostly the ones that either got government money, tax breaks, or some requirement that they have to be used.   So unless you have a few billion dollars to spend, or a lobbyist working for you, I doubt that this type of plant will happen in a large scale.    It might one day make sense to just cleave water into oxygen and hydrogen on a larger scale, but that does not compare favorably to just using the same source of power directly, such as solar thermal or PV systems, which don't require hydrogen storage or transport.

The simpler the system, often, the more efficient and less expensive.   The best way to "do things better" to me is to just not waste as much power as we tend to in the first place.  No source of power is as cheap and efficient as not using as much in the first place.   Use LED lights, higher efficiency devices, and insulate your house, and we can cut power use in the US by 50% easily.   I have seen it done, but so few are willing to spend the little up front money to do it, even though most efficiency projects pay off within a few years.

Offline Enthalpy

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Re: Methane to hydrogen and gasoline?
« Reply #5 on: December 19, 2018, 04:41:24 PM »
BobfromNC, I widely agree with you, but we may have surprises in the near future, coming from aeroplanes, yessir, and even more from helicopters.

Cleanliness is just one aspect, highly debatable depending on how the hydrogen is produced (which is my attempt here). But range and flight duration is a huge incentive too, and for that, hydrogen with fuel cells beat all other fuels by a huge margin, at least where the plane speed makes volume less important than mass.

Presently helicopters fly for 1h, simplifying. This is too short for rescue operations at sea or in the mountains, bad also to resupply offshore platforms, visit ships, monitor pollution. Their turbine takes >1min to start, undesirable for rescue operations on the land. With (my) tank of liquid hydrogen, they can start immediately and fly for many hours. Batteries, kerosene, methane can't. Huge improvement.
http://www.scienceforums.net/topic/75102-electric-helicopter/?do=findComment&comment=745535
Design examples
http://www.scienceforums.net/topic/75102-electric-helicopter/?do=findComment&comment=748087 and previous
http://www.scienceforums.net/topic/75102-electric-helicopter/?do=findComment&comment=770514 and previous

Some fixed-wing aeroplanes would benefit from longer flight. This water bomber design would lift off in the morning from a populated area, rotate all the day between a lake and a fire (Canada, Russia, USA...), come back to land in the evening
http://www.scienceforums.net/topic/79265-water-bomber/?do=findComment&comment=772040 (last one in that message)

Then you have governments who want electric airliners, and batteries can't do the job, but hydrogen can already
https://www.scienceforums.net/topic/73798-quick-electric-machines/?do=findComment&comment=1069208 and next

Fun, and instructive too, the risks of liquid hydrogen were experimented in the 60's (that's no computer simulation!)
https://www.youtube.com/watch?v=7bFJK5kU_UQ part 1
https://www.youtube.com/watch?v=RNzjksIImb8 part 2

Offline billnotgatez

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Re: Methane to hydrogen and gasoline?
« Reply #6 on: January 04, 2019, 09:28:08 PM »
...
Presently helicopters fly for 1h, simplifying. This is too short for rescue operations at sea or in the mountains, bad also to resupply offshore platforms, visit ships, monitor pollution. Their turbine takes >1min to start, undesirable for rescue operations on the land.
...

Just a side note
not meant to refute your thoughts
not meant to hijack the thread
Just pointing out more than one way to solve a problem
Bell Boeing V-22 Osprey
https://en.wikipedia.org/wiki/Bell_Boeing_V-22_Osprey


Offline Enthalpy

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Re: Methane to hydrogen and gasoline?
« Reply #7 on: January 07, 2019, 10:09:56 AM »
Yes!

I'd love to see the V22 used, for instance, in sea rescue operations. Faster than a helicopter, more range, can stop over the victims too.

The 70M$ price tag must be barrier. Twice as expensive as a big helicopter, which is already more difficult to build than a quad or hexacopter whose rotors have fixed blades.

So if the cost prevented the use of tiltrotors in civil and rescue operations, maybe hexacopters have a market, with hydrogen for the range.

Offline BobfromNC

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Re: Methane to hydrogen and gasoline?
« Reply #8 on: January 08, 2019, 05:08:06 PM »
My point is that ALL forms of energy are originally derived from the sun (or radioactivity, which was originally from a star...).   Solar power is current, but coal, oil, gas, biomass, etc are all just stored forms of solar produced biomass.   Even hydroelectric is indirect solar energy.   But hydrogen is not able to be mined, gathered, extracted, etc in any form that does not use more energy than is produced in the form of the hydrogen.  It is either electrolyzed from water, which wastes about 1/2 of the electricity in real life, or generated from steam-water-gas reactions, which involved burning fossil fuels.   So hydrogen is one of many ways to STORE energy, but it is not a source of energy, since it does not exist free in nature. 

If you can find a great way to make hydrogen from solar power, that would be a huge help, but for now, it is not a practical fuel for many tasks.   A new way to bioengineer algae, soybeans, or other crops to make more fuel per acre would be incredibly useful, as that could create a fuel more directly from the sun.  Or a better PV cell, but it is hard to compete with energy that was created and stored and concentrated in the ground for millions of years into a useful fuel. 

Offline Enthalpy

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Re: Methane to hydrogen and gasoline?
« Reply #9 on: January 09, 2019, 12:40:01 PM »
It's widely recognized that hydrogen is only a means to store energy - on a chemistry forum even more so.

For helicopters and quadcopters, the better energy per mass unit, even if including the tank as I propose it, changes the game. In some uses, where the hydrogen comes from and how much energy was wasted to obtain it is of secondary importance.

By the way, efficient hydrogen from sunlight runs already. It uses metal and metal oxide as intermediate steps. My gut feeling is that upscaling and reasonable engineering would make it competitive.

If you re-read my first post in this thread, the first aim was to obtain hydrogen from methane or C3-C4 fractions and not waste the rest of the molecule. That is, make a more meaningful production. And as it looks, many people had already success at this.

Offline Enthalpy

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Re: Methane to hydrogen and gasoline?
« Reply #10 on: April 15, 2019, 12:06:48 PM »
The desire I expressed is long identified and routes investigated [...]

Not only did researchers observe the pyrolysis of hydrocarbons, they also found ways to separate the hydrogen from the mix.

Several teams let hydrogen diffuse through palladium, possibly as a thin film deposited on a porous metal, including at the pyrolysis temperature directly. Poisoning by adsorption of other gases is a worry.

Pressure swing adsorption (PSA) seems advantageous, rather near ambient temperature. It separates H2 from the rest, but also C2H4 from CH4 for instance. Mature industrial process.

So there is presently no reason to emit CO2 when producing H2.

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