M. Azhar Uddin

Catalytic degradation of polyethylene into fuel oil over mesoporous silica (KFS-16) catalyst

Abstract The thermal degradation of plastic polymers into fuel oil over mesoporous silica (KFS-16) catalyst has been investigated. The product yields, composition and degradation rate of polyethylene over KFS-16 were compared with those over solid acid catalyst (silica–alumina and zeolite) and non-catalytic thermal degradation. The initial rate of degradation of PE over KFS-16, which possesses no acid sites was as fast as that over silica–alumina (SA-1) and the yield of liquid products was higher. The composition of the liquid products of degradation over KFS-16 was different from that over SA-1 and similar to that of non-catalytic thermal degradation. SA-1 catalyst deactivated very rapidly due to coke deposition, whereas KFS-16 deactivated much more slowly. These findings over mesoporous silica suggest that the mesopores surrounded by the silica sheet may act as a flask for storing radical species for a long time and then long-lived radicals accelerate the degradation of plastics.

Catalytic degradation of polyethylene and polypropylene into liquid hydrocarbons with mesoporous silica

Abstract The catalytic degradation of polyolefinic polymers such as polyethylene (PE) and polypropylene (PP) was carried out at atmospheric pressure by batch operation at 430 °C and 380 °C using non-acidic mesoporous silica catalyst (FSM). A comparison with non-catalytic thermal degradation and catalytic degradation using solid acid catalysis (silica-alumina, zeolite ZSM-5), silicalite, and silica-gel was made. Compared with thermal degradation, non-acidic FSM catalyst accelerated the initial rate of degradation, increased the liquid product yield and promoted degradation into lower molecular weight products. Silicalite and silica-gel had very negligible effects on polymer degradation. When the batch reaction was repeated four times using the same FSM catalyst, the extent of the decline in the degradation rate was lower for PE than PP. Compared with the solid acid catalyst, which turned completely black in the cases of both PE and PP, the deposition of coke on the used FSM catalyst was extremely slight. It seems likely that the catalytic effect of FSM for polyolefinic polymer degradation is related more to the hexagonal pore structure system of FSM.

The role of temperature program and catalytic system on the quality of acrylonitrile-butadiene-styrene degradation oil

Abstract Thermal and catalytic degradation of acrylonitrile-butadien-styrene copolymer (ABS) was performed at 450°C by semi-batch operation. Four different temperature programs were used for thermal degradation. SA4 silica alumina and three SA4/iron oxide combinations (γ-Fe2O3, a Fe3O4-C composite and α-FeOOH) were used for catalytic degradation. The heating rate affects the quality of the degradation oil, the following heating program giving the lowest amount of heavy nitrogen-containing compounds: room temperature→400°C (heating rate β=10°C min−1)→450°C (β=1°C min−1; then isothermally hold at 450°C for 210 min). SA4 catalyst used in liquid phase contact mode has a cracking effect on ABS degradation. The SA4/iron oxide catalytic systems give better results than the separate use of the catalysts, converting the heavy nitrogen (N)-containing compounds into light aliphatic nitriles that can be easily removed from the degradation oil by distillation. With SA4/α-FeOOH system the amount of 4-phenylbutyronitrile, the main N-containing compound from ABS thermal degradation, was strongly decreased in oil, from 17.5 to 1.7 wt.%.