Chlorine and methane gases and their interaction

Reactions between chlorine and methane

[Deposit Photos]

In this ar­ti­cle, we will look at the in­ter­ac­tion of two gas­es, meth­ane and chlo­rine. The his­to­ry of the dis­cov­ery of meth­ane is very in­ter­est­ing. The Ital­ian sci­en­tist Alessan­dro Vol­ta was very in­spired by an ar­ti­cle writ­ten by Ben­jamin Franklin about “flammable air”. In 1776, Vol­ta be­gan col­lect­ing air in the swamps of lake Lago Mag­giore, which is be­tween Italy and Switzer­land. Two years lat­er, the sci­en­tist man­aged to ob­tain pure meth­ane. He proved that he had dis­cov­ered tru­ly flammable air, by light­ing it with a spark in front of an amazed au­di­ence. In or­di­nary con­di­tions, meth­ane is a col­or­less gas, which is much lighter than air and prac­ti­cal­ly in­sol­u­ble in wa­ter. Meth­ane also has no smell, and is one of the safest gas­es for the en­vi­ron­ment and hu­man be­ings, it does not cause short­ness of breath and is not poi­sonous. Sci­en­tists dis­cov­ered that it is only fa­tal to liv­ing crea­tures if the amount of meth­ane sig­nif­i­cant­ly ex­ceeds the amount of oxy­gen. But the prob­a­bil­i­ty of this is ex­treme­ly low, as meth­ane is lighter than air, and so it does not ac­cu­mu­late in­doors.


[Deposit Photos]

Meth­ane is an es­sen­tial source of fuel in large-scale in­dus­tri­al pro­duc­tion, in­clud­ing rock­et pro­duc­tion. Meth­ane is also a pow­er­ful green­house gas, which has a much greater im­pact than car­bon diox­ide.

Ob­tain­ing meth­ane

It is quite easy to ob­tain meth­ane in the lab­o­ra­to­ry. We will look at sev­er­al meth­ods:

  • with alu­minum car­bide and wa­ter:

Al₄C₃ + 12H₂O = 3CH₄↑ + 4Al(OH)₃;

  • by melt­ing sodi­um salt, acetic acid and sodi­um hy­drox­ide:

CH₃­COONa + NaOH = CH₄↑ + Na₂­CO₃;

  • it is also pos­si­ble to ob­tain meth­ane nat­u­ral­ly with a bio­gas unit.
Biogas factory [Deposit Photos]

Chem­i­cal prop­er­ties of meth­ane

Meth­ane has the for­mu­la CH₄ and is in first place in the ho­mol­o­gous se­ries of alka­nes. It has low chem­i­cal ac­tiv­i­ty, and in nor­mal con­di­tions bare­ly re­acts with acids, al­ka­lis and ox­i­diz­ers. Meth­ane does not en­ter into com­bi­na­tion re­ac­tions, but can en­ter into dis­place­ment re­ac­tions. This gas in­ter­acts with chlo­rine (chlo­ri­na­tion of meth­ane), and hy­dro­gen atoms are dis­placed by chlo­rine atoms one af­ter an­oth­er:

CH₄ + Cl₂ = CH₃­Cl + HCl

CH₃­Cl + Cl₂ = CH₂­Cl₂ + HCl

CH₂­Cl₂ + Cl₂ = CHCl₃ + HCl

CHCl₃ + Cl₂ = CCl₄ + HCl.

This re­ac­tion only takes place in dis­persed light, as in di­rect sun­light an ex­plo­sion may take place. In air, meth­ane burns with­out col­or, re­leas­ing a large amount of heat:

CH₄ + 2O₂ = СО₂ + 2Н₂О

There­fore, meth­ane is ex­plo­sive in com­bi­na­tion with air. In an air­less space at a tem­per­a­ture of over 1000 de­grees Cel­sius, the gas breaks down into its com­po­nents: car­bon and hy­dro­gen:

CH₄ = С + 2Н₂.


Chlorine gas in an ampoule [Wikimedia]

This gas is the com­plete op­po­site of meth­ane, as chlo­rine is much heav­ier than air, has a green­ish-yel­low col­or and an un­pleas­ant harsh smell. From the stand­point of tox­i­col­o­gy, in pure form it is haz­ardous to hu­man be­ings and oth­er liv­ing crea­tures. For ex­am­ple, if it en­ters the res­pi­ra­to­ry tract, chlo­rine caus­es burns to the mu­cous mem­branes, and suf­fo­ca­tion. There is a high prob­a­bil­i­ty of fa­tal­i­ty from chlo­rine poi­son­ing.

In in­dus­try, chlo­rine is ob­tained by the elec­trol­y­sis of sodi­um chlo­ride. This is the most ef­fec­tive method. How­ev­er, there are also chem­i­cal meth­ods for ob­tain­ing this sub­stance, for ex­am­ple the re­ac­tion with man­ganese diox­ide:

MnO₂ + 4HCl = Mn­Cl₂ + Cl₂ + 2H₂O

Manganese dioxide [Flickr, Creative commons by five seventh is licensed under CC BY 2.0]

There are around 10 meth­ods for ob­tain­ing chlo­rine chem­i­cal­ly, but it is un­prof­itable to use them in large-scale pro­duc­tion.

Click here to find out how to ob­tain chlo­rine at home.

Chem­i­cal prop­er­ties of chlo­rine

Chlo­rine is very ac­tive, and in­ter­acts with the ma­jor­i­ty of el­e­ments. Chlo­rine dis­plays strong ox­i­diz­ing prop­er­ties, prac­ti­cal­ly on a par with oxy­gen. Chlo­rine takes part in com­bi­na­tion re­ac­tions, as well as dis­place­ment and ox­i­da­tion re­ac­tions. It can re­act with both or­gan­ic and in­or­gan­ic com­pounds.

In­ter­ac­tion of chlo­rine and meth­ane, dis­place­ment re­ac­tion

Chlo­ri­na­tion of alka­nes – dis­place­ment re­ac­tion of hy­dro­gen atoms of an alka­ne by chlo­rine atoms The re­ac­tion of meth­ane and chlo­rine is a dis­place­ment re­ac­tion, which takes place ac­cord­ing to a rad­i­cal mech­a­nism. There is dif­fer­ing in­for­ma­tion about the chlo­ri­na­tion of meth­ane, for ex­am­ple some sci­en­tists state that the in­ter­ac­tion of gas­es takes place in light, while oth­ers state that the sub­stances are heat­ed. How­ev­er, they agree that the re­ac­tion of meth­ane and chlo­rine is high­ly ex­plo­sive, so it must be car­ried out with spe­cial prepa­ra­tion.