Removal of Nitrogen Compounds before Deep Hydrotreatment of Synthetic Crude Oils

Abstract

Synthetic crude oils (SCOs) derived from oil shale, coal, and oil sands contain relatively large amounts of heteroatoms such as nitrogen and sulfur, and severe hydrorefining conditions are necessary to convert SCOs into substitute transport fuels. In this study, extraction of nitrogen compounds from SCOs by complex formation with CuCl2.2H2O was carried out and the denitrogenated oils were hydrotreated to explore the effect of nitrogen pre-removal on hydrodenitrogenation (HDN) and hydrodesulfurization (HDS). Light gas oil fractions derived from shale oil, coal-derived liquid, and pyrolysis product of Athabasca bitumen were used as feedstocks. Hydrotreatment tests were carried out using a batch-type autoclave and commercial NiMo/Al2O3 catalyst at 350℃ for 2-4 h under H2 initial pressure of 5 MPa. The results showed that basic and heterocyclic nitrogen compounds could be separated efficiently from SCO by complex formation. The pre-removal of nitrogen compounds greatly enhanced the HDN reaction rates and greatly reduced the residual nitrogen content. The recovery of CuCl2.2H2O was also possible by simply washing CH2Cl2 solution containing the complex with water. The proposed method is another option for the conversion of SCO to a high quality feedstock suitable for production of clean diesel fuels.

Deep Hydrotreatment of Middle Distillates Obtained by Pyrolysis of Oil Shale and Oil Sands Bitumen

“…The rate constant of DNOS at 350 could not be measured accurately because the residual nitrogen content was below 1 wtppm even at LHSV 2 h -1 . The batch-type experiments in the previous work showed that the HDN rate of denitrogenated SO at 350 was 2.0-4.4 times larger than that of SO depending on the degree of nitrogen pre-removal 5) . The effect of nitrogen pre-removal on the HDN rate of the continuous flow reaction was much larger than that of the batch-type reaction.…”

“…The enhancement of HDS rates was caused by the reduced amount of nitrogen and the rapid conversion to ammonia which causes less inhibition. The previous study showed that HDS rates obtained by batch-type experiments at 350 were increased by factors of 1.0-1.8 for SO and 1.8 for OS 5) . The enhanced effect of nitrogen pre-removal on HDS rates in the continuous flow reaction system was attributed to the great increase in the HDN rates.…”

“…Shale oils also contain n-alkyl nitriles, amides, and diazaaromatics 8) which could not be extracted by complex formation with CuCl2 ・2H2O 5) . n-Alkylnitriles are abundant in DNSO 5) and reactive in catalytic hydrotreatment 1) , which would lead to the great increase in HDN rate of DNSO. Figure 2 shows the sulfur contents of the feeds and products obtained at LHSV 1 h -1…”

“…Therefore, nitrogen removal before hydrotreatment is a promising way to produce ultra-clean fuels from nitrogenrich feedstocks. Pre-removal of nitrogen by complex formation with CuCl2 ・2H2O is efficient for synthetic crude oils such as shale oil 4) , and HDN and HDS of the denitrogenated oils in a batch-type autoclave are greatly accelerated 5) .…”

Insights into the integrated effects of polymeric pretreatment and catalytic hydrotreatment of light gas oil

“…Ahmed et al impregnated phosphotungstic acid on metal–organic framework for the adsorption of nitrogen containing compounds from a model fuel. Transition metal salts were used by Narangerel and Sugimoto for the removal of basic nitrogen and other heterocyclic compounds. Almarri et al used activated carbon and activated alumina for the adsorption of quinoline and dibenzothiophene.…”