Chemical Reactivity of Methane with Water

Water and methane gas interact at temperatures below 10 degrees Celsius and pressures more than 30 bar, or 30 times normal atmospheric pressure, to form methane hydrate. The meth-ane is encased in a molecular cage and surrounded by water molecules. As a result, chemists refer to this type of molecular structure as a clathrate (lat. clathratus = imprisoned with bars). Permafrost zones on land or beneath the seafloor are where methane hydrates form. Usually, a layer of silt covers them. Their creation requires a suitably high pressure and low temperature environment beneath the seafloor. The higher the water pressure, the warmer the water must be.

Thus, methane hydrates can be found below sea depths of around 300 metres in the Arctic, but only below 600 metres in the tropics. The majority of methane hydrate occurrences on the planet are found at depths of 500 to 3000 metres. The hydrates are solid and white in appearance, resembling regular water ice.

Chemical Reactivity between Methane with Water

In the region of the second explosion limit, the effect of methane on the hydrogen oxygen reaction was investigated. The results reveal that there is a critical concentration of methane below which both methane and water vapour reduce the explosive limit in the same way. Observations of the sluggish reaction demonstrate that the accelerating effects of these additions on the rate of hydrogen and oxygen combination are proportional to one another. On the basis of the explosion and sluggish reaction rate data, it is hypothesised that methane and water vapour influence the kinetics of the hydrogen oxygen reaction through similar mechanisms.

Chemical reactivity of methane with water

Chemists have been looking for efficient catalysts to convert methane, a significant component of abundant natural gas, into methanol, a liquid fuel that can be conveniently transported and used to make other useful compounds. While adding water to the reaction solves some problems, it also complicates the process. Now, a team from the US Department of Energy’s Brookhaven National Laboratory has discovered a new method that uses a common industrial catalyst to effectively complete the conversion both with and without water. The discoveries, which were published in the Journal of the American Chemical Society, indicate ways to improve water-free conversion catalysts.

Characteristics of methane and water

• Water samples were taken from 15 domestic water wells in 12 counties across Ohio that were known to emit methane.

• Dissolved inorganic components, dissolved organic carbon, methane and other dissolved gases, stable isotopes (carbon, hydrogen, and oxygen) of methane, water, and dissolved inorganic carbon, and methane carbon-14 were all tested in the wells.

• Water types ranged from NaCl, while total dissolved solids concentrations ranged from 318 to 2,940 milligrammes per litre (mg/L) in the 15 wells. The quantities of methane in the water ranged from 1.2 to 120 mg/L.

• Twelve of the 15 samples contained chemical and isotopic “signatures” that were consistent with microbial methane produced by CO₂ reduction. Microbial decomposition of organic materials in anaerobic aquifers and the generation of microbial shale gas and coalbed methane along sedimentary basin borders are usually linked to CO₂ reduction.

• The ¹³C of methane in the 12 samples interpreted as microbial methane generated by CO₂ reduction ranged from 75 to –56 per mil. A general pattern of rising ¹³C  of methane with depth was seen in multiple samples from the same aquifer. The isotopic signature of the water was compatible with current or postglacial groundwater recharge, and samples with lighter ¹³C  of methane (75 to 62 per mil) came from shallow wells (or wells with shallow open intervals).

Methane and water

At temperatures ranging from 274 to 285 K and pressures ranging from 35 to 65 bar, the amount of methane dissolved in the aqueous phase in the presence of CH₄ gas hydrate has been observed. The solubility of methane in the presence of hydrate is shown to decrease as the temperature in the hydrate forming zone falls. The solubility of methane gas in water increases with decreasing temperature in the absence of gas hydrate, as expected. The findings reveal that the hydrate formation process reverses the solubility trend between gas and liquid. Theoretical calculations are confirmed. It was also discovered that in the presence of hydrates, pressure had little effect on solubility.

Conclusion

Water and methane gas interact at temperatures below 10 degrees Celsius and pressures more than 30 bar, or 30 times normal atmospheric pressure, to form methane hydrate. The higher the water pressure, the warmer the water must be. Methane with Water In the region of the second explosion limit, the effect of methane on the hydrogen oxygen reaction was investigated. The results reveal that there is a critical concentration of methane below which both methane and water vapour reduce the explosive limit in the same way. Observations of the sluggish reaction demonstrate that the accelerating effects of these additions on the rate of hydrogen and oxygen combination are proportional to one another. On the basis of the explosion and sluggish reaction rate data, it is hypothesised that methane and water vapour influence the kinetics of the hydrogen oxygen reaction through similar mechanisms.