Hydrotreating of middle distillates with addition of pyrolysis oil from depolymerisation of waste plastics

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The research work deals with the influence of the addition of alternative pyrolysis fractions as a component of feedstock processed in the hydrogenation of middle distillates. The alternative feedstocks are middle boiling fractions of oils derived from pyrolysis of sorted waste plastics, namely polystyrene (PyOil-PS) and mixture of polypropylene and polyethylene (PyOil-PP/PE). The down-flow testing reactor was used for simulation of hydrogenation process. The effects of the addition of alternative pyrolysis fractions on the quality of products as well as on the activity of the desulphurisation catalyst were studied. The testing was divided into three steps. The reaction temperature was subsequently changed to achieve the level of sulphur content of 10 mg.kg-1. In the first step, the feedstock was changed to the standard feedstock used in the hydrogenation unit. When the required level of sulphur content has been achieved, the feedstock was changed in the second step. The feedstock was changed to a standard feedstock with addition of 5 wt% of the mentioned alternative feedstock. The addition of alterna-tive pyrolysis fractions were compensated by an increase in reaction temperature by 6 °C to achieve the level of sulphur content of 10 mg.kg-1. In the third step, the feed-stock was changed to the standard feedstock. The addi-tions of recycled alternative materials resulted in higher deactivation of the catalyst, which had to be compensated by an increase in reaction temperature of 3 °C for PyOil-PS oil and 6 °C for PyOil-PP/PE. Pyrolysis oils used showed to be potential raw material for co-processing with conventional feedstock. The overall effect on activity of catalyst should be verified during long-term testing. Products meet requirements of standard ČSN 590.