Disclosed are a ferrite catalyst and preparation methods thereof. The catalyst is provided with a formula below, wherein A is Mg atom, Zn atom or a mixture of both atoms at any ratio; D is one or more atoms selected from the group consisting of Ni, Co, W, Mn, Ca, Mo or V atom; Z is a catalyst carrier, which is one or more selected from the group consisting of calcium phosphate, calcium dihydrogen phosphate, aluminum phosphate, aluminum dihydrogen phosphate, ferric phosphate, magnesium phosphate, zinc phosphate, Mg—Al hydrotalcite, calcium carbonate, magnesium carbonate; a=0.01-0.6; b=0-0.30; c is a number balancing each valence; x, y represent the amounts of principal catalyst and carrier Z respectively, wherein the weight ratio y/x=0.5:1-7:1.
x(FeA.sub.aD.sub.bO.sub.c)/yZ

The present invention relates to a catalyst system comprising a transition metal compound on a solid carrier which is a surface-reacted calcium carbonate. The invention further relates to a method for manufacturing said catalyst system and to its use in heterogeneous catalysis.

The present invention relates to a catalyst system comprising a transition metal compound on a solid carrier which is a surface-reacted calcium carbonate. The invention further relates to a method for manufacturing said catalyst system and to its use in heterogeneous catalysis.

The present disclosure relates to a method for recovering styrene monomers from waste polystyrene, and more specifically, to a method for recovering styrene monomers from waste polystyrene, in which the waste polystyrene is depolymerized using an eco-friendly solvent and a potassium-containing carbonate depolymerization catalyst to suppress the generation of ethylbenzene, etc. generated as by-products in a styrene monomer recovery step, and thus the styrene monomers can be recovered in high yield.