Enhanced BTEX formation via catalytic fast pyrolysis of styrene-butadiene rubber: Comparison of different catalysts

Catalytic degradation of styrene-butadiene rubber (SBR) to produce value-added BTEXs (i.e., benzene, toluene, ethylbenzene, and xylenes) is a promising approach to dispose of solid wastes. In this work, the effects of catalyst contact mode (in-situ or ex-situ), catalyst type, and reaction conditions on desirable BTEXs production were investigated. Experimental results indicated that a limited amount of BTEXs with selectivity of 11.1% was obtained in the non-catalytic run, while a ~6-fold content increase was attained upon employing ultrastable Y (USY) zeolite as a catalyst in the in-situ catalytic trial. The USY catalyzed run also produced more C₄ olefin, C_5-6 linear alkanes and alkenes, and C₉₊ aromatic hydrocarbons. A comparison between in-situ and ex-situ catalytic pyrolysis suggesting that the former was more beneficial to the generation of BTEXs as the enhanced factor was 11.5% higher than that of the ex-situ catalytic pyrolysis. Catalyst type played a critical role in the catalytic degradation of SBR, and the BTEXs formation was highly dependent on the acidic property of the employed catalyst. The Y type zeolites with a higher content of acid sites, larger surface area, and moderate pore size, generated more targeted BTEXs than Hβ, HZSM-5, and SAPO-34. The optimized reaction conditions to promote the formation of BETXs in the catalytic degradation of SBR over USY, including heating rate, pyrolysis temperature, and catalyst to feedstock mass ratio, were determined to be at 10 °C/ms, 700 °C, and 3:1, respectively.