Carbon and Fossil Fuels

When substances of vegetable origin, e.g. coal, oil shale, peat or wood, are heated in the absence of air (dry distillation), they decompose into gas, liquid products and solid residue coke/charcoal.

Coal tar is the destructive distillation of bituminous coal. Coal tar is distilled into many fractions to yield a number of useful organic products like benzene, toluene, xylene, naphthalene, anthracene, etc.

Coke can be used both as a fuel and a reducing agent. The combustion of coke (carbon) is highly exothermic and releases a huge amount of energy. Hence, coke is a fuel. Carbon itself is easily oxidized to $CO$ and $CO _2$. $C$ can easily reduce several metal oxides to metal.

Syngas or synthesis gas is a fuel gas mixture consisting primarily of H, CO and very small carbon dioxide. The reaction between coke and steam is highly endothermic and when the coke bed is cooled to a normal temperature the steam is replaced by a blast of air.

Coal tars are complex and variable mixtures of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds. Hence have unpleasant smell.

Coking is the process used industrially to produce coke. They produce many compounds which are very useful industrially.

Synthesis gas is made by passing steam over a red-hot carbon fuel such as coke, Water gas is a mixture of carbon monoxide and hydrogen produced from synthesis gas
$ H _2O + C\rightarrow  CO + H _2(\delta H = +131KJ/mol)$
Synthesis gas is a useful product, but requires careful handling due to its flammability and the risk of carbon monoxide poisoning.

Synthesis gas is made by passing steam over a red-hot carbon fuel such as coke:
$H _2O + C \rightarrow  H _2  + CO ( \delta H =+131KJ/mol) $
Synthesis gas is a useful product, but requires careful handling due to its flammability and the risk of carbon monoxide poisoning

Coal tar is to make plastics, paints, dyes, naphthalene balls and explosives, Pharmaceutical Industry.

Coal gas, gaseous mixture—mainly hydrogen ($H _2$), methane ($CH _4$), and carbon monoxide  ($CO$) — formed by the destructive distillation (i.e., heating in the absence of air) of bituminous coal and used as a fuel. Sometimes steam is added to react with the hot coke, thus increasing the yield of gas. Coal tar and coke are obtained as by-products.

A solid fuel formed by heating coal in the absence of air is coke. Coke is black colored, tough porous substance. It is pure carbon. It has applications in steel manufacture and in the metallurgy.

Coke is a better fuel because coke  produces more heat on burning as compared to coal. Coke has higher calorific value than coal. When equal masses of coke and coal are bunt, coke produces more heat. Also when coke is burnt, smoke is not obtained whereas coal produces smoke on coal.

Coke is used in the preparation of producer gas which is a mixture of carbon monoxide and nitrogen. Producer gas is produced by passing air over red-hot coke. Coke is also used to manufacture water gas.

Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities.

Natural coke is also called as carbonite coke. It is formed by metamorphism from bituminous coal when intrusive igneous rock cuts across vein of coal.