Pyrolysis of plastic wastes - 2. Effect of catalyst on product yield

Thermolysis of plastic waste may have an important role in dealing with the enormous amounts of plastic waste produced all over the world, by decreasing their negative impact on the environment. This waste may be converted into economically valuable hydrocarbons, which can be used both as fuels and as feed stock in the petrochemical industry. End product yields and properties depend on the plastic waste composition. The presence of PE (polyethylene) increases alkane content, whilst PS (polystyrene) leads to higher aromatic content in the end product. The alkene formation benefited from the presence of PP (polypropylene). Although, the desired end products can be obtained by adequate blending of plastic wastes, it is not always technically or economically possible to obtain the quality required. The addition of a catalyst could not only improve the quality of products obtained, but could also enable the selectivity of a certain product to be achieved. To study the influence of several catalysts on product distribution, the average plastic waste composition existing in Portuguese municipal solid wastes (68% PE, 16% PP and 16% PS) was chosen. Unfortunately, the catalysts studied in this work, led to results similar to those obtained in their absence. (C) 1999 Elsevier Science B.V. All rights reserved.