Comparison of citric acid and glycol effects on the state of active phase species and catalytic properties of CoPMo/Al2O3 hydrotreating catalysts

Pimerzin, Aleksey A.; Можаев, А. В.; Varakin, A.N.; Maslakov, K. I.; Nikulshin, P.A.

doi:10.1016/j.apcatb.2016.12.022

Cited by 62 publications

(34 citation statements)

References 73 publications

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“…Depending on the reaction conditions, phosphoric acid reacts with the molybdenum precursor (ammonium heptamolybdate or MoO 3 ) and gives a variety of phosphomolybdate anions, such as diphosphopentamolybdate (P 2 Mo 5 O 23 6− ), Keggin (PMo 12 O 40 3− ), and Dawson (P 2 Mo 18 O 62 6− ) heteropolyanions (HPAs). Further, the use of various types of organic modifiers during catalyst preparation has resulted in materials of enhanced HDS activity; both chelating agents and glycol-type additives are used for this purpose [1, 3,4,[6][7][8][9][10][11][12]. In contrast with ligand-type modifiers, such as α-hydroxycarboxylic, thioglycolic, or aminopolycarboxylic acid, only a limited number of publications have been found concerning the effect of glycol-type additives on catalytic properties of sulfide CoMo or NiMo catalysts [3,13].…”

Section: Introductionmentioning

confidence: 99%

“…Most articles describe the effect of glycols on the activity of CoMo systems, using post-treatment of CoMo(P)/Al 2 O 3 systems with triethylene glycol (TEG) or polyethylene glycol (PEG) [14][15][16], or co-impregnation with the solution of active metals and glycols [6][7][8][9]17]. Just a few reports are found concerning the effect of addition of glycols to the impregnation solution on the activity of NiMo/Al 2 O 3 catalysts [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

“…Just a few reports are found concerning the effect of addition of glycols to the impregnation solution on the activity of NiMo/Al 2 O 3 catalysts [10][11][12]. It was shown that the glycol-modified catalysts displayed higher activity in the HDS of model compounds [6][7][8][9][10][11][12]16,17] and gasoil fractions [10,12,16,17], as well as in toluene hydrogenation [14,15]. Moreover, a synergetic effect of glycol-type additives and phosphate was disclosed [6,7,12].…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, a synergetic effect of glycol-type additives and phosphate was disclosed [6,7,12]. It was proposed that glycols hinder the interaction between the active phase precursors and alumina, promoting the formation of sulfide phase with the improved activity [6,7,[9][10][11]. However, the results concerning the effect of glycol addition on the dispersion of sulfide phase and surface distribution of promoter (Co, Ni) and Mo species (expressed as metal/alumina ratio) are rather contradictory.…”

Section: Introductionmentioning

confidence: 99%

“…However, the results concerning the effect of glycol addition on the dispersion of sulfide phase and surface distribution of promoter (Co, Ni) and Mo species (expressed as metal/alumina ratio) are rather contradictory. According to [9], dispersions of both Co and Mo are increased in the sulfide CoMo(P)/Al 2 O 3 catalysts when ethylene glycol (EG), diethylene glycol (DEG), and TEG are added to impregnation solution. Using the results of the XPS study, the authors [12] came to the conclusion that the addition of PEG to the solution leads to the increase of Ni dispersion in the dried NiMo(P)/Al 2 O 3 system, but has no effect on Mo distribution.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Mono-, Di-, and Triethylene Glycol on the Activity of Phosphate-Doped NiMo/Al2O3 Hydrotreating Catalysts

et al. 2019

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The effect of glycols on the catalytic properties of phosphate-doped NiMo/Al2O3 catalysts in the hydrotreating of straight-run gas oil (SRGO) was studied. The NiMo(P)/Al2O3 catalysts were prepared using ethylene glycol (EG), diethylene glycol (DEG), and triethylene glycol (TEG) as additives. The organic agent was introduced into the aqueous impregnation solution obtained by the dissolving of MoO3 in H3PO4 solution, followed by Ni(OH)2 addition. The Raman and UV–Vis studies show that the impregnation solution contains diphosphopentamolybdate HxP2Mo5O23(6−x)− and Ni(H2O)62+, and that these ions are not affected by the presence of glycols. When the impregnation solution comes in contact with the γ-Al2O3 surface, HxP2Mo5O23(6−x)− is decomposed completely. The catalysts were characterized by Raman spectroscopy, low-temperature N2 adsorption, X-ray photoelectron spectroscopy, and transmission electron microscopy. It is shown that the sulfide catalysts prepared with glycols display higher activity in the hydrotreating of straight-run gas oil than the NiMoP/Al2O3 catalyst prepared without the additive. The hydrodesulfurization and hydrodenitrogenation activities depend on the glycol type and are decreased in the following order: NiMoP-DEG/Al2O3 > NiMoP-EG/Al2O3 > NiMoP-TEG/Al2O3 > NiMoP/Al2O3. The higher activity of NiMoP-DEG/Al2O3 can be explained with the higher dispersion of molybdenum on the surface of the catalyst in the sulfide state.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Mono-, Di-, and Triethylene Glycol on the Activity of Phosphate-Doped NiMo/Al2O3 Hydrotreating Catalysts

et al. 2019

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Role of Phosphorus and Triethylene Glycol Incorporation on the Activity of Model Alumina‐Supported CoMoS Hydrotreating Catalysts

et al. 2022

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Environmental regulations concerning fuel‐related sulfur emissions are currently experiencing worldwide expansion. This is motivating the research and development of improved hydrotreating (HDT) catalysts with carefully engineered synthesis methods that maximize activity as ultimate goal. In this contribution, the effect of phosphorus doping and triethylene glycol (TEG) incorporation on the genesis of the CoMoS phase of model HDT catalysts is assessed. Following a surface‐science approach, α‐Al2O3 single crystals with four orientations: C(0001), A(11true2‾ 0), M(10true1‾ 0), and R(1true1‾ 02) are used as model supports of the traditional γ‐Al2O3 support for the study of active phase‐support interactions at the molecular scale. The model catalysts are prepared by traditional impregnation of a solution containing metal and phosphorus precursors and TEG. The catalysts are characterized in the sulfide phase by XPS, XAS, TEM, and AFM, revealing that the calcination step is key in the emergence of distinctive metal‐support interactions, which are directly related to the nature of alumina surface sorption sites. In addition, TEG incorporation on dried catalysts increases metal sulfidation and enhances promotion with respect to non‐additivated systems, especially at mild sulfidation temperatures. The catalytic activity of the model catalysts is tested in a thiophene hydrodesulfurization reaction, revealing the following activity trend with respect to alumina surface orientations: A()112‾0 ≫ M()101‾0 >R()11‾02 , C(0001). This trend is identical to the one observed for non‐phosphorus doped non‐TEG additivated model systems, confirming the predominance of surface effects on the catalytic activity over those exerted by P and TEG. By transposing these results to the industrial γ‐Al2O3 support, the (100) facet would provide surface sites that lead to better performing catalysts. This could result in the development of novel supports, engineered to expose surface sites that maximize hydrotreating activity.

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Speciation of the Oxide Phase of Molybdenum‐Based HDS Catalysts Enhanced with Organic Additives Using an EXAFS/Raman Coupling Methodology

Lesage,

Devers,

Legens

et al. 2024

ChemCatChem

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The ability to gain access to the speciation of hydrodesulfurization catalysts used for removing sulfur from transportation fuels is becoming a key feature in the understanding and improvement of their catalytic activity with the aim of reducing greenhouse gas emissions of fossil fuels. A novel coupling methodology between Raman spectroscopy and X‐ray absorption spectroscopy (XAS) was developed, which allows for precise qualitative and quantitative analysis of the oxide phase of Mo‐based catalysts. This enabled the detailed study of various impregnation parameters and the characterisation of hydrodesulfurization (HDS) catalysts before sulfidation. To illustrate this methodology, the effects of two additives (triethylene glycol and citric acid) were studied. The results demonstrated that organic additives exert a profound influence on the speciation of oxide precursors of molybdenum‐based catalysts. The presence of these additives enhances the dispersion of Keggin or Dawson heteropolyanions on the support by maintaining a high phosphorus‐to‐molybdenum ratio in solution. This is achieved by two strategies: triethylene glycol (TEG) exhibits a pronounced affinity for alumina hydroxyls, while citric acid compensates for phosphate adsorption through the formation of a stable Mo‐citrate complex.

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Comparison of citric acid and glycol effects on the state of active phase species and catalytic properties of CoPMo/Al2O3 hydrotreating catalysts

Cited by 62 publications

References 73 publications

Effect of Mono-, Di-, and Triethylene Glycol on the Activity of Phosphate-Doped NiMo/Al2O3 Hydrotreating Catalysts

Effect of Mono-, Di-, and Triethylene Glycol on the Activity of Phosphate-Doped NiMo/Al2O3 Hydrotreating Catalysts

Role of Phosphorus and Triethylene Glycol Incorporation on the Activity of Model Alumina‐Supported CoMoS Hydrotreating Catalysts

Speciation of the Oxide Phase of Molybdenum‐Based HDS Catalysts Enhanced with Organic Additives Using an EXAFS/Raman Coupling Methodology

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