Production of diesel range hydrocarbons from crude oil sludge via microwave-assisted pyrolysis and catalytic upgradation

Crude oil sludge is one of the key waste streams of the refinery, and it contains valuable hydrocarbons that can be potentially converted to fuels and petrochemicals. This study is unique in evaluating the effects of activated carbon susceptor (ACS) and catalysts to selectively recover hydrocarbons from crude sludge via microwave-assisted pyrolysis (MAP). Two different sludge samples received from the refinery, viz., sludge from storage tank bottoms (sludge 1) and mixed sludge (sludge 2), were characterized. Sludge 1 was rich in volatile matter and hydrocarbons, while sludge 2 contained a significant amount of ash, nitrogen, sulfur and iron. At 600 W microwave power with 10 % ACS loading, maximum oil yield of 87.3 wt.% was obtained from sludge 1, while it was 41.2 wt.% from sludge 2. An increase in yield of gaseous products with a concomitant decrease in oil yield was observed when the sample heating rates were increased by using high microwave power or high loading of ACS. MAP of crude sludge at 600 W with 10 % ACS produced char and oil with higher heating values (HHV) of 26 and 42.4 MJ kg(-1), respectively. For the first time, ex situ catalytic upgradation with H-ZSM-5 and regenerated fluid catalytic cracking (FCC) catalyst was employed to produce refinery blendstocks from crude sludge through MAP. Catalytic upgradation resulted in significant deoxygenation of pyrolysates with low oxygen content (<5%), and high carbon (80-85 wt.%) and hydrogen (12-14 wt.%) content in the oil fraction. The HHV of the upgraded oil was 44-45 MJ kg(-1). Importantly, the selectivity to hydrocarbons in the diesel range (C8 to C20) increased by more than 10 % in the oil fraction containing paraffins, iso-paraffins, and aromatic hydrocarbons. This study proves that a liquid fuel, resembling refinery blendstock, can be generated from crude oil sludge by adopting this process. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.