Question

which is the chemical used in the chimney of the industry to reduce the air polution

Answer 1

much of the popllution is caused by phosphates, nitrates and sulphates from the industry, this causes acid rains and greenhouse effect. The chemicals in the filters are depending on what the factory rejects, most often they will bond directly the sulphates and phosphates present in the dirty gas to make it cleaner. A good chemical for such bonding is CaO

Answer 2

If this is for SOX and NOX reduction, I agree with sbhb91's answer. SOx and NOx can be reduced by the Selective Catalytic Reduction.