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The conversions and yields of the fractions of gases (C1, C2), LPG (C3, C4), gasoline (C5−C12), and coke and their compositions have been studied in the catalytic cracking of blends made up of polystyrene and polystyrene−butadiene with a LCO (light cycle oil, which is a secondary refinery product) used as the solvent. The catalysts were prepared from HZSM-5 zeolites of different total acidities. The reaction was carried out in the 450−550 °C range and under the standard conditions of FCC units. The important effects both of the total acidity of the zeolite and of the temperature on the conversion and yield of styrene are demonstrated. Total recovery of the monomer styrene is attained at 550 °C. Likewise, the LCO is valorized, as high yields of both the C5−C12 aromatic fraction and LPG (olefinic) are obtained with low yields of gases (C1, C2) and coke.

The effects of a sweeping treatment on the activity recovery, coke content, H/C ratio, and kinetics of coke combustion have been studied in the coke deposited on an HZSM-5 zeolite. The reaction test studied is the transformation of acetone into hydrocarbons at 400 °C, and the gases used in the sweeping are He, H2, and steam. Aside from the partial elimination of coke, which occurs with all these gases, each one has a different effect. Thus, sweeping with H2 causes catalyst rejuvenation. Sweeping with He promotes coke aging and a reduction in the H/C ratio. Steam is efficient for coke elimination but causes dealumination. The combustion of the remaining coke is disfavored (the activation energy is increased, and the kinetic constant is decreased) by the sweeping treatment that decreases the H/C ratio of the coke.

A study has been made of the valorization of polyolefins, PE (polyethylene) and PP (polypropylene), dissolved in LCO [light cycle oil obtained as a product stream in a fluid catalytic cracking (FCC) unit] by their cracking on three catalysts prepared based on HY zeolites of different acidity and different porous structure. The reaction has been studied in the 450−550 °C range and under conditions similar to those of the FCC. The determining factor in the performance of the catalyst is the accessibility of the acid sites by the dissolved macromolecular chains, where a moderate acidity of the zeolite is sufficient. Whereas a feed of dissolved PE contributes to a decrease of the yield of coke with respect to that corresponding to the cracking of LCO, a feed of PP increases the yield of coke. The optimum temperature for maximizing the yield of gasoline, and minimizing that of coke, is 450 °C. The gasoline fraction (C5−C12) is mainly aromatic with C8+ components. The stream of gaseous products is largely made up of propylene and butenes.

The effect of both the Cr/Zn atomic ratio of the Cr2O3−ZnO catalyst and the Si/Al ratio (different surface acidity) of the ZSM-5 catalyst on the activity and selectivity to gasoline is studied, when a physical mixture of both catalysts is used for transformation of syngas into gasoline in a single step. Furthermore, the composition of each catalyst required for a good compromise between activity and selectivity and for a high aromatic content in the gasoline has been determined. The kinetic behavior of these catalysts has been compared with that of others which have been prepared by combining conventional metallic catalysts in methanol synthesis with a ZSM-5 catalyst.