Preparation and characterization of promoted alumina-supported MoS2 catalysts for hydrodenitrogenation
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Kemian tekniikan korkeakoulu |
Master's thesis
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Authors
Date
2022-06-14
Department
Major/Subject
Chemistry
Mcode
CHEM3023
Degree programme
Master's Programme in Chemical, Biochemical and Materials Engineering
Language
en
Pages
155+29
Series
Abstract
This thesis studied the preparation of MoS2 hydrodenitrogenation catalysts supported on gamma-Al2O3 and promoted by different metals. First, literature on the preparation of promoted supported MoS2 catalysts was reviewed. Based on the findings of the literature review, a co-impregnation method using citric acid additive was developed for the preparation of Ni-promoted MoS2/đŸ-Al2O3 catalysts. After impregnation, the precursors were calcined at 500 °C and sulfided in 10% H2S/H2. This method was then used to prepare four catalysts: one promoted by an alkali metal (Na), one by a transition metal (Cr) and two by noble metals (Pt and Ru). The catalysts were characterized by inductively coupled plasma optimal emission spectroscopy (ICP-OES), X-ray diffraction (XRD), X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and laser Raman spectroscopy (LSR). Citric acid reduced the formation of crystalline MoO3 and improved the metal loadings of the unpromoted and Ni-promoted oxidic precursors. Mixed Ni-Mo, Cr-Mo and Na-Mo oxides were formed during calcination, this prevented the formation of crystalline MoO3 and Al2(MoO4)3. In the sulfided state, TEM indicated that the promoters decreased the stacking number of the active MoS2 phase. Ni reduced the edge dispersion of MoS2, while no such effect was found for the other promoters. XPS showed that Na was present as Na2O after sulfidation, while Cr was a mixture of metallic Cr and likely Cr(III) and Cr(IV). The noble metals Ru and Pt were mostly metallic. The metallic Cr and Ru was likely poisoned by H2S, Pt appeared more resistant to poisoning. The results thus indicate that the sulfidation atmosphere (10% H2S/H2) was too reducing for effective formation of Cr, Ru and Pt sulfides. Thus, the work demonstrates that a sulfidation treatment appropriate for the sulfidation of Ni is not necessarily suitable for the use with other promoters, if sulfidation of the promoter is desired.FramstĂ€llning av katalysatorer för hydrodenitrogenering baserade pĂ„ MoS2 pĂ„ gamma-Al2O3-bĂ€rare med olika promotorer undersöktes. Först granskades litteratur gĂ€llande framstĂ€llning av burna MoS2-katalysatorer för hydrodenitrogenering. Baserat pĂ„ resultaten för litteraturgranskningen utvecklades en koimpregneringsmetod för framstĂ€llningen av nickel-promoterade MoS2/đŸ-Al2O3 katalysatorer. Citronsyra anvĂ€ndes som additiv. Efter impregnering kalcinerades prekursorerna vid 500 °C, dĂ€refter sulfideras de i 10% H2S/H2. Denna metod anvĂ€ndes för att framstĂ€lla fyra katalysatorer: en med en alkalimetall (Na) som promotor, en med en övergĂ„ngsmetall (Cr) och tvĂ„ med Ă€delmetaller (Pt och Ru). Katalysatorerna undersöktes med Induktivt kopplad plasma-optisk emissionsspektrometri (ICP-OES), röntgendiffraktion (XRD), röntgenfluoresens (XRF), röntgenfotoelektronspektrometri (XPS), transmissionelektronspektroskopi (TEM) och laser-Raman-spektroskopi (LSR). Citronsyra minskade mĂ€ngden kristallin MoO3 och ökade mĂ€ngden metall i de opromoterade och Ni-promoterade oxid-prekursorerna. Blandade Ni-Mo-, Cr-Mo-, och Na-Mo-faser bildades vid kalcinering, vilket förhindrade kristallin MoO3 och Al2(MoO4)3 frĂ„n att bildas. I de sulfiderade katalyterna visade TEM att promotorerna minskade höjden av MoS2-staplarna. Ni minskade dispersionen av MoS2-kanterna, medan ingen liknande effekt kunde hittas för de andra promotorerna. XPS antydde att Na fanns i form av Na2O efter sulfidering, medan Cr var en blandning av metallisk Cr och sannolikt Cr(III) och Cr(IV). Största delen av Ă€delmetallerna Ru och Pt var metalliskt. Cr- och Ru-metallerna var sannolikt förgiftade av H2S, medan Pt verkade mer resistant mot förgiftning. Resultaten indikerar dĂ€rmed att gasblandningen som anvĂ€ndes vid sulfidering (10% H2S/H2) var för reducerande för effektiv bildning av Cr-, Ru- och Pt-sulfider. DĂ€rmed visar detta diplomarbete att en sulfideringsbehandling lĂ€mplig för sulfidering av Ni inte nödvĂ€ndigtvis Ă€r lĂ€mplig för andra promotorer, om sulfidering av promotorn önskas.Description
Supervisor
Puurunen, RiikkaThesis advisor
Albersberger, SylviaAuvinen, Paavo
Keywords
hydrodenitrogenation, promoted catalysts, oxide-supported MoS2