Is a catalyst required in pyrolysis plant?

There is no need catalyst in pyrolysis plant when we pyrolysis waste tyres,plastic or rubber. But, we have another machine need catalyst name distillation plant, this plant can refining waste oil(waste engine oil,motor oil,tyre oil,plastic oil etc to clean diesel) When we refining waste oils,there need some additives in the reactor to romove bad color,bad smell,sulphur and ash etc.

Waste oil distillation plant