PNNL

Abstract

This paper reports the co-hydrotreatment of the water insoluble (WIS) phase of a commercial pyrolysis oil (also known as pyrolytic lignin) from BTG and yellow greases (waste cooking oil), aiming the production of sustainable aviation fuels. The first paper published by our group on this subject (Han et al, 2020) using a CoMo/Al2O3 catalyst reported our best kerosene yield as 14.6 wt. % and our best coke yield as 6.8 wt. %. In this paper, we use a sulfided NiMo/Al2O3, blends with 20 wt. % WSI and a central composite experimental design to identify processing conditions increasing kerosene yield and reducing coke formation. The input variables were: (1) reaction temperature (320°C, 350°C, and 380°C), (2) initial hydrogen pressure (5 MPa, 6 MPa, and 7 MPa), and (3) amount of catalyst (0.7, 1.0, and 1.3 g). The hydrotreated liquids were distilled to obtain gasoline (350°C). The yield of gaseous, solid, and liquid were mainly affected by the reaction temperature. Meanwhile, higher initial hydrogen pressure and catalyst loading increased the yield of kerosene and other distillates and decreased the coke formation. High temperature correlated with lower content of oxygenates in kerosene cuts. Based on our experimental results, we propose to conduct hydrotreatment studies at 380°C, initial H2 pressure of 7 MPa, and 1.3 g of catalyst. Compared to our first paper, under the conditions herein identified, it was possible to improve the kerosene yield to more than 20 wt. % and reduce the yield of coke to close to 2.0 wt. %. The chemical composition and fuel properties of the gasoline, kerosene and diesel cuts were thoroughly analyzed. The content of aromatics and phenols in the kerosene fraction produced at the conditions identified in this project exceeded the recommended values for sustainable aviation fuels. New strategies (such as blending, more intense hydrotreatment or removal of oxygenated compounds) need to be implemented to reduce the content of these products in our final product.