Chloromethanes are manufactured by two different routes:
1. All four chlorinated derivatives are manufactured together via thermal chlorination or catalytic oxychlorination of methane.
2. Special processes and other raw materials are used for specific manufacture of CCl₄, the most commercially important product, and CH₃Cl, used as an intermediate for further chlorination or in other reactions.

To 1:

The first industrial gas-phase chlorination of methane was performed by Hoechst in 1923. Today, their manufacturing capacity for chlorinated C₁ compounds is about 180000 tonnes per year. The strongly exothermic free radical reaction is conducted without external heat and usually in the absence of a catalyst (i. e., without addition of radical forming substances) at 400- 450 °C and slightly raised pressure. The chlorination is thermally initiated via the homolysis of chlorine molecules; it can, however, also be initiated photochemically.

If methyl chloride is to be preferentially produced then a large excess of methane (about tenfold) must be used in order to obtain a satisfactory yield, as methyl chloride is more rapidly chlorinated than methane. On the other hand, when an equimolar Cl₂/CH₄ ratio is employed, all possible chlorinated methanes are formed together in the mole percents given:



Desired higher degrees of chlorination can be obtained by recycling the lower chlorinated products. During the treatment of the reaction mixture in the majority of the industrial processes, the resulting HCl is first scrubbed with water or with azeotropic hydrochloric acid. The chlorinated products are then condensed using a system of low temperature condensers, separated from CH₄, and isolated in pure form by distilling under pressure.

The byproducts are hexachloroethane and small quantities of trichloroethylene.

The selectivity to chlorinated C₁ products is more than 97%. Asahi Glass, Dow, Hüls, Montecatini, and Scientific Design have all developed various modifications for industrial operation. These differ in the technological solutions to problems characteristic of the strongly exothermic chlorination of CH₄, which is first initiated at 250-270°C and can proceed explosively in the industrially important temperature range of 350-550 °C.

Solutions include reactor construction with backmixing characteristics and heat removal (loop-type bubble column, Hoechst; fluidized-bed reactor, Asahi Glass; tubular reactor, C.F. Braun), high CH₄/Cl₂ ratio or addition of an inert gas (N₂, Montecatini), reaction temperature (thermal initiation of radical chains with most manufacturers, photochemical initiation via UV irradiation at Dow), and the workup of the reaction products (1. HCl removal, then 2. pressurized distillation, Hoechst and Huls; or 1. CH₃Cl/CCl₄ extraction of the reaction gases, then 2. HCl removal by scrubbing, Dow).

The oxychlorination of methane is a second route to the manufacture of a mixture of all the chlorinated methane products. Direct oxychlorination has not yet been used commercially; however, a process which can be viewed as an indirect oxychlorination was developed by Lummus and put on stream in a 30000 tonne-per-year unit by Shinetsu in Japan in 1975. A modified version is also suitable for the manufacture of vinyl chloride.

The process operates with a melt consisting of CuCl₂ and KCl, which acts simultaneously as catalyst and as chlorine source. The melt first chlorinates methane to the four chloromethanes and is subsequently fed into an oxidation reactor, where it is rechlorinated in an oxychlorination - also known as oxyhydro-chlorination - reaction with hydrogen chloride or hydrochloric acid and air. More detailed process conditions are not known to date. This process enables the utilization of the waste product (hydrochloric acid) in accordance with the following equation:

To 2:

There are four methods available for a direct synthesis of tetrachloride. They can be readily characterized by the very different precursors required:
1. Carbon disulfide
2. -propene mixtures
3. Organic residues containing chlorine
4. Elemental carbon, e.g., low temperature coke

To 2.1:

In several countries such as the USA, Italy, United Kingdom, and Mexico, carbon disulfide is chlorinated to CCl₄ in the liquid phase at 30°C and atmospheric pressure in the presence of metallic iron, FeCl₃, or without catalyst. CS₂ was the only carbon source used for CCl₄ until the 1950s, when chlorination of methane and chlorinolysis of hydrocarbons were introduced as new sources of CCl₄. Today, about 25% of the production worldwide and 30% in the USA (1990) is still based on CS₂. When stoichiometric amounts of chlorine are used, the byproduct is , which can be recycled and used for the manufacture of CS₂. Sulfur monochloride, which is obtained with excess hlorine, is also of interest industrially; it can also be reacted with CS₂ to give CCl₄ and sulfur:

To 2.2:

Propane-propene mixtures can be converted into the C₁ and C₂ fragements and perchloroethylene via crackingcoupled withchlorination (chlorinolysis) at 600-700 °C and 2-5 bar :



The ratio of CCl₄ to perchloroethylene can be varied between 65 : 35 and 35 : 65 depending on reaction conditions and the ratio of the starting materials. The selectivities for both products are about 90%(C₃H₆ and Cl₂ Industrially operated processes were developed by Progil-Electrochimie and Scientific Design.

Many plants are in operation in Western Europe.

To 2.3:

The most economically interesting feedstocks for the manufacture of carbon tetrachloride via chlorinolysis are chlorine-containing organic residues. Particularly suitable residues (due to their high chlorine content) result, for example, from the chlorination of methane, manufacture of vinyl chloride, ally1 chloride, and chlorobenzene, and from propylene oxide via chlorohydrin.

The chlorine required for the chlorinolysis can be introduced into the process either as HCl/air, e. g., as in the PPG oxychlorination process, or preferably directly as elemental chlorine. Numerous companies (Diamond Shamrock, Stauffer Chemical, Hoechst, etc.) have developed processes of the latter type.

Important process variables such as pressure, temperature, residence time, and the Cl2/hydrocarbon ratio determine the selectivity of the chlorinolysis, i.e., whether carbon cetrachloride is formed exclusively or, instead, mixtures of CCl₄, Cl₂C=CCl₄, and Cl₂C=CHCl are produced.

Almost 100% selectivity to CCl₄ is obtained with the chlorinolysis process at 120-200 bar and 600°C developed by Hoechst. Short residence times and high pressure prevent the formation of an equilibrium between CCl₄ and perchloroethylene which would otherwise occur. With aromatic residues as feedstock, hexachlorobenzene is formed as an isolable intermediate, and with aliphatic residues the corresponding intermediate is hexachloroethane. Hoechst brought one plant on stream in West Germany in early 1976, and another in the CIS in 1984.

To 2.4:

Coal, with its low H content, would be an interesting feedstock for the manufacture of carbon tetrachloride as very little chlorine would be lost by the simultaneous formation of HCl. However, the principal disadvantage lies with the low reactivity of the coal which necessitates temperatures of about 800 °C. Processes for the direct chlorination of carbon have been frequently described, but have not been developed beyond the pilot plant stage.

Besides the chlorination of methane, methyl chloride can also be prepared by esterification of methanol with hydrogen chloride. This reaction is performed either in the liquid phase at 100-150°C with a slight excess pressure, either uncatalytically or in the presence of e.g, ZnCl₂ or FeCl₃, or, preferentially, in the gas phase at 300-380°C and 3-6 bar, with a catalyst like ZnCl₂, CuCl₂, or H₃PO₄ on a support such as SiO₂, or with Al₂O₃, in a fixed or fluidized bed:

This reaction has a high selectivity, almost 98% relative to CH₃OH. Only a small amount of is formed as byproduct.

Today, with low-cost methanol and the growing surplus of HCl from numerous chlorination processes, hydrochlorination of methanol has become the most important commercial route to methyl chloride.