Brorson, Michael

Grunwaldt, Jan-Dierk

Høj, Martin

Jensen, Anker Degn

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 19, 2017CoMo/Al2O3 hydrotreating catalysts prepared by flame synthesisHøj, Martin; Brorson, Michael; Jensen, Anker Degn; Grunwaldt, Jan-DierkPublication date:2011Link back to DTU OrbitCitation (APA):Høj, M., Brorson, M., Jensen, A. D., & Grunwaldt, J-D. (2011). CoMo/Al2O3 hydrotreating catalysts prepared byflame synthesis. Abstract from 10th EuropaCat Congress , Glasgow, United Kingdom.CoMo/Al2O3 hydrotreating catalysts prepared by flame synthesis  Martin Høj1 DTU Chemical Engineering, Technical University of Denmark, Lyngby, DK-2800, Denmark 1,*, Michael Brorson2, Anker D. Jensen1 and Jan-Dierk Grunwaldt1,3 2Haldor Topsøe A/S, Nymøllevej 55, Lyngby, DK-2800, Denmark 3Institute for Chemical Technology and Polymer Chemistry (ICTP), Karlsruhe Institute of Technology (KIT), Karlsruhe, D-76131, Germany *mh@kt.dtu.dk Introduction Liquid fed flame spray pyrolysis (FSP) is a novel one-step synthesis method for nano-sized particles [1]. Typically, organo metallic compounds are dissolved in an organic solvent and the precursor solution is sprayed with high velocity oxygen and ignited with a small premixed methane-oxygen flame [2]. The solvent and metal organic precursors evaporate and combust to form atomically dispersed vapours, which nucleate to form clusters when reaching cooler parts of the flame. The formed clusters grow by surface growth and coalescence, accompanied by sintering [3]. This result in non-porous nanoparticles which coagulate and sinter to form agglomerates and aggregates with high inter particle porosity [1].  Hydrotreating is performed at oil refineries in order to remove sulphur and nitrogen from the heterocyclic compounds in which these elements typically occur in crude oil [4]. Industrial hydrotreating catalysts contain cobalt or nickel promoted molybdenum(IV)sulphide as active phase, on an alumina support [4]. The transition metal sulphide phase is obtained after sulfiding an oxide precursor, which can be prepared by FSP [5]. Experimental Cobalt 2-ethylhexanoate, molybdenum 2-ethylhexanoate and aluminium acetylacetonate dissolved in toluene to metal concentration of 0.4 M were used as FSP precursors. The solutions were sprayed at 3 ml/min with 7 Nl/min oxygen dispersion gas at 2 bar. The specific surface areas were measured by 6 point BET (p/p0 = 0.05 – 0.25), UV-vis reflectance using an integration sphere and Kubelka-Munk analysis and XRD using Ni filtered Cu Kα radiation. Bright field TEM images were recorded on a Technei T20 microscope. Catalytic activity was measured using liquid feed 0.5 ml/min of 3.0 wt.% dibenzothiophene, 0.5 wt.% indole, 1.0 wt.% naphthalene, 2.5 wt.% DMDS and 0.5 wt.% n-nonane dissolved in n-heptane. The catalyst activity was measured at: Temperature 350 °C, pressure p(total) = 50 atm and p(H2) = 38 atm, H2 flow rate 250 Nml/min and 300 mg catalyst. Results/Discussion Seven CoMo/Al2O3 samples were synthesized by one flame FSP. Four samples contained 8, 16, 24 and 32 wt.% Mo with a Co/Mo atomic ratio of 1/3 (alumina balance), and two samples 16 wt.% Mo with Co/Mo atomic ratio 2/3 and 1/1 and finally one unsupported reference sample with Co/Mo atomic ratio 1/3. The catalysts had specific surface areas between 221 and 90 m2/g, with decreasing surface area with increasing transition metal content. This corresponds to average primary particle sizes of 7 to 13 nm, showing that nanoparticles were the product of the flame synthesis. The activities of the catalysts for removal of heterocyclic sulphur and nitrogen were measured after sulfidation. The best catalysts contained 16 wt.% Mo (atomic ratio Co/Mo = 1/3). With approximately 75% of the activity of a commercial alumina supported CoMo catalyst this is strikingly good. Increasing the Co content in the FSP material caused a small drop in activity, while increasing or decreasing the Mo content resulted in significantly lower activity. TEM images of the FSP made oxides confirmed that the primary particles were nano-sized and images of the sulfided catalysts showed a significant increase in MoS2 particles size with increasing Mo content, explaining the lower activity of the high Mo loaded catalysts (Fig. 1). X-ray diffraction (XRD) and UV-vis reflectance spectroscopy revealed that the oxide precursor contained γ-Al2O3 with some CoAl2O4 spinel, while MoO3 was XRD amorphous. The CoAl2O4 spinel is unwanted since the cobalt does not promote the MoS2 active phase. Experiments of suppressing this phase are under way.   Figure 1: TEM images of 16 wt.% Mo (Co/Mo = 1/3) oxide (a) and sufide (b). References 1.  R. Strobel, and S.E. Pratsinis, J. Mater. Chem., 17, 4743 (2007) 2.  L. Mädler, H.K. Kammler, R. Mueller and S.E. Pratsinis, J. Aerosol Sci., 33, 369 (2002) 3.  H.K. Kammler, L. Mädler and S.E. Pratsinis, Chem. Eng. Technol., 24, 583 (2001) 4.  H. Topsøe, B.S. Clausen and F.E. Massoth, “Hydrotreating” (J.R. Anderson, M. Boudart, Eds.), Springer-Verlag, Berlin, 1996. 5. M. Høj, K. Linde, T. K. Hansen, M. Brorson, A. D. Jensen and J.-D. Grunwaldt, Appl. Catal. A: Gen., accepted for publication. (a) (b) 

CoMo/Al2O3 hydrotreating catalysts prepared by flame synthesis

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CoMo/Al2O3 hydrotreating catalysts prepared by flame synthesis

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