Hydrotreatment Followed by Oxidative Desulfurization and Denitrogenation to Attain Low Sulphur and Nitrogen Bitumen Derived Gas Oils

Sandeep Badoga,Prachee Misra,Ying Zheng,Girish Kamath,Ajay Dalai

doi:10.3390/catal8120645

Sandeep Badoga, Prachee Misra + Show 3 more

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https://doi.org/10.3390/catal8120645

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Abstract

To lower the sulphur content below 500 ppm and to increase the quality of bitumen derived heavy oil, a combination of hydrotreating followed by oxidative desulfurization (ODS) and oxidative denitrogenation (ODN) is proposed in this work. NiMo/γ-Al2O3 catalyst was synthesized and used to hydrotreat heavy gas oil (HGO) and light gas oil (LGO) at typical operating conditions of 370–390 °C, 9 MPa, 1–1.5 h−1 space velocity and 600:1 H2 to oil ratio. γ-Alumina and alumina-titania supported Mo, P, Mn and W catalysts were synthesized and characterized using X-ray diffractions, N2 adsorption-desorption using Brunauer–Emmett–Teller (BET) method, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). All catalysts were tested for the oxidation of sulphur and nitrogen aromatic compounds present in LGO and HGO using tert-butyl hydroperoxide (TBHP) as oxidant. The oxidized sulphur and nitrogen compounds were extracted using adsorption on activated carbon and liquid-liquid extraction using methanol. The determination of oxidation states of each metal using XPS confirmed the structure of metal oxides in the catalyst. Thus, the catalytic activity determined in terms of sulphur and nitrogen removal is related to their physico-chemical properties. In agreement with literature, a simplistic mechanism for the oxidative desulfurization is also presented. Mo was found to be more active in comparison to W. Presence of Ti in the support has shown 8–12% increase in ODS and ODN. The MnPMo/γ-Al2O3-TiO2 catalyst showed the best activity for sulphur and nitrogen removal. The role of Mn and P as promoters to molybdenum was also discussed. Further three-stage ODS and ODN was performed to achieve less than 500 ppm in HGO and LGO. The combination of hydrotreatment, ODS and ODN has resulted in removal of 98.8 wt.% sulphur and 94.7 wt.% nitrogen from HGO and removal of 98.5 wt.% sulphur and 97.8 wt.% nitrogen from LGO.

Highlights

Worldwide increase in industrialization has led to an increase in consumption of petroleum oil and coal [1]
Mo/γ-Al2 O3 catalysed oxidation followed by of oxygenates with activated carbon removed 32% and 44.9% sulphur from single stage oxidative adsorptive removal of oxygenates with activated carbon removed 32% and 44.9% sulphur from single desulfurization of HDT-heavy gas oil (HGO) and HDT-light gas oil (LGO) respectively, as against to less than 10% removal by ion stage oxidative desulfurization of HDT-HGO and HDT-LGO respectively, as against to less than 10%
The nitrogen removal was higher with activated single stage oxidative denitrogenation

Summary

Introduction

Worldwide increase in industrialization has led to an increase in consumption of petroleum oil and coal [1]. It has raised serious environmental concerns due to the rise in sulphur oxide (SOx) levels in air. The gas oil extracted from unconventional sources such as, oil sands and shale oil contain high amount of sulphur and nitrogen impurities. For instance the oil sands bitumen derived heavy gas oil (HGO). The bitumen derived gas oils (HGO, light gas oil (LGO) and naphtha) are upgraded onsite via hydrotreating to lower the sulphur and nitrogen content before sending them to further processing in existing refineries. Hydrotreating is a catalytic process operating in the presence of hydrogen at high pressure (8–12 MPa) and temperatures (350–400 ◦ C) to remove sulphur and nitrogen via processes known as hydrodesulfurization (HDS)

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Conclusion