Thermochemical Recycling of Oily Sludge by Catalytic Pyrolysis: A Review

Table 1

The advantages and disadvantages of different types of catalysts and suggestions [26].

Catalyst type	Advantage	Shortcoming	Suggest
Metal	Good effect	Expensive, causing secondary pollution	Use according to actual conditions, and use metal waste when appropriate
Metal compound	Variety and easy access	Different metal oxides have different effects on the pyrolysis of oily sludge; so, it is necessary to find a suitable metal oxide	Exploring the metal compounds required by the corresponding oily sludge
Molecular sieve	Not only can be used as a catalyst, but also other catalysts can be supported, so that the catalytic effect is better, and the reaction system is not required.	High price, prone to coking, high pyrolysis temperature	Explore suitable process conditions and carry out catalyst regeneration treatment to extend catalyst life
Biomass	It is not easy to cause secondary pollution, the price is cheap, and the two sides have a coordinated reaction, which promotes a more comprehensive pyrolysis	It is necessary to find suitable biomass for synergistic reaction. Some biomass not only does not promote the reaction but also inhibits the reaction from proceeding.	Explore the biomass that is conducive to the pyrolysis of different oily sludges