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Hydroprocessing of low temperature coal tar for the production of clean fuel over fluorinated NiW/Al2O3-SiO2 catalyst Wengang Cui, Wenhong Li, Rong Gao, Haixia Ma, Dong Li, Menglong Niu, and Xiong Lei Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.6b03390 • Publication Date (Web): 10 Mar 2017 Downloaded from http://pubs.acs.org on March 19, 2017
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Energy & Fuels
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Hydroprocessing of low temperature coal tar for the production of clean fuel over fluorinated NiW/Al2O3-SiO2 catalyst
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Wengang Cui
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a
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Supporting Information
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ABSTRACT: Hydroprocessing of low temperature coal tar (LTCT) for the production of clean fuel was investigated over
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fluorinated NiW/Al2O3-SiO2 catalyst in a fixed bed reactor. A series of NiW/Al2O3-SiO2 catalysts with different F-loading
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were prepared by incipient wetness co-impregnation and characterized by various techniques such as nitrogen
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adsorption, FT-IR, XRD, SEM TPD-NH3 and XPS. The effects on the yield, properties of liquid products and gas
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components from using fluorinated NiW/Al2O3-SiO2 catalysts were discussed. In addition, coke formation was also
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evaluated by TG-DTG. The result showed that the introduction of F influenced both acidity and active phase while have
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little effect on crystalline structure of NiW/Al2O3-SiO2 catalysts. Lower F-loading in the NiW/Al2O3-SiO2 catalysts not only
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improved catalytic performance but also was helpful to improve some of the physicochemical properties of liquid
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product including dynamic viscosity, density, distillation range and hydrocarbon content and so on. The optimal F
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concentration to NiW/Al2O3-SiO2 is 1.0 wt.%, at which the highest naphtha and diesel yield was obtained due to its
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appropriate acid distribution and more active phase. Meanwhile, liquid product produced displayed the lowest N
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content (78.6 ug/g) and density (0.8507 g/mL). Furthermore, compared with feedstock, phenols almost disappeared
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and phenyl cycloalkanes (PCA) and cycloalkanes (CA) are rich in hydrogenated product.
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Keywords: Hydroprocessing; Low temperature coal tar; clean fuel; NiW/Al2O3-SiO2 catalyst
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1 Introduction
[a,b]
, Wenhong Li
[a,b*]
[c]
[a]
, Rong Gao , Haixia Ma , Dong Li
[a,b]
[a]
, Menglong Niu , Xiong Lei
[a,b]
School of Chemical Engineering, Northwest University, Xi’an 710069, PR China Shaanxi Research Center of Chemical Engineering Technology for Resource Utilization, Xi’an 710069, PR China c The 451st Hospital of People’s Liberation Army. Xi’an 710054, PR China b
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The increase in transportation fuel demands and depletion of finite oil reserves have focused recent attention to
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the development of alternative energy sources to ensure energy security. In this respect, utilization of biofuel, oil shale
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and coal-derived liquid fuel have emerged as an important option. Low heat value and high water content of biofuel
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restrict its industrial utilization. As comparison, coal will be the chief energy source in China over the next few decades,
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coal tar is obtained mainly from the process of coal gasification and carbonization, its output accounts for 2.5-10.0
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mass % of coal feed, and over 10 million tons of coal tar is produced within the country in 2015 . Nonetheless, due to its
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high aromatics and asphaltenes contents, especially, it is rich in heteroatomic compounds (such as S, N and O), which
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limit its application as an energy fuel for direct combustion. Considering this, a highly efficient process and better active
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catalysts for the conversion of coal tar to clean fuel was in an urgent demand.
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There are several common methods for converting coal tar into light clean fuel, such as hydroprocessing,
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hydrocracking, catalytic cracking and thermal-cracking. Among these above methods, the thermal cracking process used
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for coal tar conversion without the addition of catalyst and at temperatures up to 500 °C, which make it has a higher
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coking rate of 80% and shows a low selectivity for light fuel production . In general, hydrocracking (HC) and catalytic
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cracking process employs a catalyst and a small amount of hydrogen to crack coal tar at operating pressures of 12-20
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MPa and temperatures of 350-450 °C, however the coking rate is also rather high and can produce a lot of C1-C4 light
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hydrocarbon gases . Hydroprocessing has been considered as one of the most effective methods to convert coal tar
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into light clean fuel even if hydrogen's introduction contributes a share of the processing cost
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capital investment the can be reduced by using the existing infrastructure of petroleum refineries during the production
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. Besides, the initial
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of clean fuel though a hydroprocessing method.
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Types of catalysts, reactor, feed properties and hydrotreating parameters have a significant impact on the quality
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and composition of the liquid product. There are considerable efforts have been expended to investigate the
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hydroprocessing of coal tar about these aspects
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fraction were studied employing NiW/Al2O3 and CoMo/Al2O3 catalysts by Kan, et al. , raw coal tar was considerably
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upgraded and high-quality fuels were obtained. However, there are only about 20 wt.% of the gasoline yield was
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produced. Tang, et al.11 have probed the reaction mechanisms of the main aromatic compounds in a distillate of LTCT (a
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boiling point
