- Highly Active Low Cobalt Content-Based Bulk MoS2 Hydrodesulfurization Catalysts with a Unique Impact of H2S
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A series of unsupported MoS2, Co9S8, and Co-promoted MoS2 catalysts have been synthesized by tuned impregnation and successive thermal annealing methods using a continuous flow of a mixture of H2 and H2S gases. The resulting catalysts were evaluated in terms of their activity and selectivity for the hydrodesulfurization of dibenzothiophene (DBT) both in the absence and the presence of H2S. The inclusion of Co onto MoS2 affected both the hydrogenation and direct desulfurization reactions, with the latter (production of biphenyl) being magnified to a much greater degree than the former. Interestingly, low cobalt/molybdenum ratio of ca. 0.05 of the catalyst exhibited outstanding promotion efficiency in the hydrodesulfurization reaction. However, as cobalt is added, the synergy effect drastically decreased. H2S in the reaction mixture led to a remarkable step up in the product from the direct desulfurization reaction route with the most notable increases occurring for the product from the hydrogenation reaction pathway. The HDS activity of such catalysts was much higher than that of the commercial CoMo/Al2O3. The promotion by H2S was discussed.
- Farag, Hamdy,Embaby, Abd-Alrahman,Kishida, Masahiro,El-Hendawy, Abdel-Nasser A.,Nasef, Mohamed Mahmoud
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- Conformational Effects in the Alkali Metal Reduction of Diaryl Sulfides and Dibenzothiophene
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In alkali metal reductions, the carbon-sulfur bond cleavage that occurs in diaryl sulfides and similar structures such dibenzothiophene is shown to be controlled not by the relative stability of the reactive intermediates but by their degree of conformational freedom.Regardless of the stability of the reactive intermediates, diaryl sulfides suffer carbon-sulfur bond cleavage because the aryl groups are free to assume a configuration that favors cleavage.Dibenzothiophene, although similar in structure to diphenyl sulfide, does not have such freedom and therefore, instead of carbon-sulfur bond cleavage, undergoes ring hydrogenation.The behavior of di-1-naphthyl sulfide and di-4-quinolinyl sulfide support this conclusion and provide further evidence for intramolecular coupling of the aryl moieties at some reactive intermediate stage to form an episulfide type of intermediate.This is then follwed by a double carbon-sulfur bond cleavage to extrude sulfur.
- Francisco, Manuel A.,Kurs, Argo,Katritzky, Alan R.,Rasala, Danuta
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- Highly Active Bulk Mo(W)S2 Hydrotreating Catalysts Synthesized by Etching out of the Carrier from Supported Mono- and Bimetallic Sulfides
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Abstract: A bulk MoWS2 catalyst has been synthesized by acid etching of the carrier from the supported MoWS2/Al2O3 catalyst obtained on the basis of the mixed bimetallic heteropoly acid (HPA) H4[SiMo3W9O40]. As reference samples, monometallic MoS2 and WS2 catalysts have been prepared from the corresponding supported analogues, as well as a Mo + WS2 sample based on a mechanical mixture of monometallic HPA in the atomic ratio of Mo/W = 1/3. The catalytic properties of the synthesized catalysts have been studied in model reactions of hydrodesulfurization (HDS) of dibenzthiophene (DBT) and hydrogenation (HYD) of naphthalene in a flow unit. It has been shown that the catalytic activity of the samples in both the DBT HDS and naphthalene HYD reactions increases in the following order: MoS2 2 2? MoWS2. It has been found that the bulk tungsten-containing catalysts exhibit higher specific catalytic activity than the supported counterparts. Increased values of hydrogen uptake according to the results of hydrogen temperature-programmed reduction for the bulk catalysts indicate an increase in the number of active sites and the formation of a more effective active phase compared to supported catalysts.
- Kokliukhin,Mozhaev,Nikulshina,Lancelot,Blanchard,Lamonier,Nikulshin
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p. S53 - S59
(2020/01/23)
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- Hydroconversion of Oxidation Products of Sulfur-Containing Aromatic Compounds
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Hydroconversion of benzo- and dibenzothiophene sulfone on a Ni–Mo sulfide catalyst based on mesoporous aluminosilicate Al-HMS and on unsupported catalysts prepared in situ in the course of decomposition of poorly soluble precursors (molybdenum hexacarbonyl, nickel naphthenate) was investigated. Hydrogenation of sulfones was performed at 250°С, 340°С, and 380°С and elevated СО pressure in the presence of H2O ensuring in situ generation of H2 via water-gas shift reaction. The products that are formed by oxidation of organic sulfur compounds and remain in the hydrocarbon medium (mainly sulfones) will not significantly affect the subsequent hydrotreatment since under the conditions of hydroprocesses, they transform into the corresponding benzo- and dibenzothiophenes, which undergo the subsequent hydrodesulfurization to form mono- and diaromatic hydrocarbons.
- Vutolkina,Akopyan,Glotov,Kotelev,Maksimov,Karakhanov
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p. 981 - 989
(2018/08/31)
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- Trimetallic Hydrotreating Catalysts CoMoW/Al2O3 and NiMoW/Al2O3 Prepared on the Basis of Mixed Mo-W Heteropolyacid: Difference in Synergistic Effects
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Abstract: Trimetallic CoMo3W9/Al2O3 catalyst is prepared using the Keggin structure mixed heteropolyacid H4SiMo3W9O40 and cobalt citrate. CoMo12/Al2O3 and CoW12/Al2O3 catalysts based on H4SiMo12O40 and H4SiW12O40, respectively, are synthesized as reference samples. Sulfided catalysts are analyzed by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Catalytic properties are investigated in the co-hydrotreatment of dibenzothiophene (DBT) and naphthalene in a flow unit. It is shown that the catalytic activity in both DBT hydrodesulfurization and naphthalene hydrogenation (HYD) decreases in the following sequence: CoMo12/Al2O3 > CoMo3W9/Al2O3 > CoW12/Al2O3, and it correlates with the degree of promotion of active-phase particles by cobalt atoms. A comparison with the published data available for Ni-promoted catalysts makes it possible to reveal the general regularity for bi- and trimetallic Со(Ni)-Mo(W)S catalysts: the use of mixed Mo-W H4SiMo3W9O40 heteropolyacid instead of monometallic H4SiW12O40 causes an increase in the degree of promotion of MoWS2 crystallite edges for the series of catalysts promoted by both cobalt and nickel. The use of nickel as a promoter leads to a higher degree of promotion of edges of active-phase particles in comparison with cobalt; as a result, the NiMo3W9/Al2O3 catalyst is much more active than the CoMo3W9/Al2O3 counterpart. Possible reasons behind the found features are discussed.
- Mozhaev,Nikul’shina,Lancelot,Blanchard,Lamonier,Nikul’shin
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p. 1198 - 1205
(2019/02/05)
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- Synthesis of Ni-Mo binary transition metal complex and application in hydrodesulfurization
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The study showed the synthesis of nickel-molybdenum binary metal complex Ni(en)3MoO4 with high purity from the impregnating solution. The complex was characterized and confirmed by single-crystal XRD, FT-IR and TGA. The binary transition metal complex was impregnated to γ-Al2O3 to prepare hydrodesulfurization catalyst. The catalyst was characterized by low temperature N2 adsorption-desorption isotherms, XRD and HRTEM. No molybdenum and nickel species were observed over the hydrodesulfurization catalyst surface, and the average slab length and layer number of the MoS2 crystallites in the catalyst are 2.6 nm and 2.3, respectively. The results indicated the high dispersion of active metal species over support. The DBT conversion of the catalyst can reach 91.4%, and the overall pseudo-first order rate constant kDBT is 3.1×10-4 gcat -1 s-1. The result showed the catalyst possessed good catalytic activity and Ni(en)3MoO4 can make efficient precursor to produce hydrotreating catalyst.
- Liang, Jilei,Wu, Mengmeng,Cai, Hongmei,Cao, Yiyang,Lu, Xiaorong,Wang, Yuhang,Zhu, Min
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p. 1075 - 1079
(2018/02/22)
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- Influence of nanoscale distribution of Pd particles in the mesopores of MCM-41 on the catalytic performance of Pd/MCM-41
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Two different nanoscale Pd particle distributions in MCM-41, i.e. in the mesopores and on the external surface, were obtained by using a siliceous MCM-41 and a silylated MCM-41 (S-MCM-41) as the starting support materials, respectively. The electron density of Pd in Pd/S-MCM-41 was lower than that in Pd/MCM-41. Pd/S-MCM-41 exhibited much better selective hydrogenation performance but a lower hydrogenolysis activity than Pd/MCM-41. These differences are related to the different Pd particle distributions in MCM-41 and S-MCM-41, demonstrating that the performance of noble metal catalysts is tunable by simply controlling the nanoscale metal particle distribution in the pores.
- Dong, Chao,Li, Xiang,Wang, Anjie,Chen, Yongying,Liu, Haiou
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p. 219 - 222
(2017/07/24)
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- Preparation of Ni-Mo2C/carbon catalysts and their stability in the HDS of dibenzothiophene
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The HDS activity and stability of Ni-Mo2C/AC catalysts, prepared by carbothermal hydrogen reduction (CHR) at different temperatures and with different Ni:Mo ratios, is reported. The highest HDS activity occurred for catalysts with Ni:Mo ratios
- Wang, Haiyan,Liu, Shida,Govindarajan, Rubenthran,Smith, Kevin J.
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p. 114 - 127
(2017/04/27)
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- The preparation of Mo/γ-Al2O3 catalysts with controllable size and morphology via adjusting the metal-support interaction and their hydrodesulfurization performance
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In this work, a series of Mo/γ-Al2O3 catalysts have been prepared by using Mo species enwrapping with dodecyltrimethylammonium bromide (DTAB) as the novel precursors for the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The objective of this work is to get a deep insight into the effect of the Mo precursors on the size and morphology of the active phases and HDS activity. DTAB as the organic additive for the preparation of Mo precursors can dominate the nature of precursor solution and adjust the metal-support interaction so as to control the dispersion and morphology of the active phases. It is clearly shown that the addition of DTAB can effectively decrease the strong interaction between the Mo species and γ-Al2O3 support and favor to tune the size and morphology of MoS2 nanoparticles. The optimum molar ratio of DTAB/Mo is 3/5 and the corresponding catalyst shows the highest sulfidation degree with the most suitable stacking layer numbers and the shortest length of MoS2 and thus exhibits the best HDS performance. Our work explores the important roles of organic additive to adjust the metal-support interaction and control the morphology of active phases and provides an effective precursor which can be used widely to prepare supported catalysts.
- Yuan, Pei,Cui, Chunsheng,Han, Wei,Bao, Xiaojun
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p. 115 - 125
(2016/07/12)
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- Hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and their hydrogenated intermediates over bulk tungsten phosphide
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The kinetics of the hydrodesulfurization (HDS) of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and their hydrogenated intermediates over bulk tungsten phosphide (WP) was studied. WP possessed high hydrogenation/dehydrogenation activity but was highly sensitive to piperidine inhibition. 4,6-DMDBT reacted faster than DBT, and both DBT and 4,6-DMDBT reacted mainly through the hydrogenation pathway. The methyl groups suppressed the direct desulfurization of 4,6-DMDBT but significantly promoted the hydrogenation of 4,6-DMDBT and the dehydrogenation of 1,2,3,4-tetrahydro-4,6-dimethyldibenzothiophene (TH-4,6-DMDBT) and 1,2,3,4,4a,9b-hexahydro-4,6-dimethyldibenzothiophene, but decreased the rate of hydrogenation of TH-4,6-DMDBT. Piperidine inhibited the HDS of 4,6-DMDBT much more strongly than that of DBT. Substantial dehydrogenation of TH-4,6-DMDBT to 4,6-DMDBT and two of its isomers occurred. The formation of these 4,6-DMDBT isomers in the dehydrogenation of TH-4,6-DMDBT and the hydrocracking of 1-methyl-4-(3-methylcyclohexyl)-benzene, as well as the formation of cyclopentylphenylmethane and (cyclopentylmethyl)cyclohexane, is ascribed to the metallic character of WP.
- Yang, Lei,Li, Xiang,Wang, Anjie,Prins, Roel,Chen, Yongying,Duan, Xinping
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p. 330 - 343
(2015/09/01)
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- Hierarchization of Mordenite as NiW Sulfide Catalysts Support: Towards Efficient Hydrodesulfurization
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NiW-based catalysts were supported on Al2O3, commercial mordenite (HM), and hierarchical mordenite prepared by acid-base-acid treatment (HM-M). Their catalytic performance was evaluated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) at 613K under 4MPa as total pressure. In the HDS of DBT, NiW/Al2O3 exhibited better catalytic activity than NiW/HM and NiW/HM-M. On the contrary, NiW/HM-M exhibited the highest catalytic performance in the HDS of 4,6-DMDBT, attributed to different factors: an improved dispersion of the active phase, a better accessibility to the active sites owing to the creation of mesoporosity, and an additional reaction route (isomerization) owing to the acidic properties of the zeolitic support. These results show the potential interest of hierarchical mordenite as support for HDS catalysts, with the presence of mesoporosity beneficial to the HDS of large and refractory molecules. Hierarchy rules: In the hydrodesulfurization of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), NiW on mesoporous mordenite shows higher activity than mordenite-based catalysts, and, in the latter case, also higher activity than on alumina, attributed to an improved dispersion of the active phase, a better accessibility to the active sites, and the additional isomerization route owing to the acidic properties of the zeolitic support.
- Wang, Yi,Lancelot, Christine,Lamonier, Carole,Richard, Frdric,Leng, Kunyue,Sun, Yinyong,Rives, Alain
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p. 3936 - 3944
(2016/01/26)
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- Development of a Magnetically Recyclable Molybdenum Disulfide Catalyst for Direct Hydrodesulfurization
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Superparamagnetic MoS2/SiO2/Fe3O4 catalysts that consist of magnetite as the core, silica as the covering layer, and molybdenum sulfide as the top layer were prepared in easy steps. Two different surfactants (anionic and cationic) were used to assist with the synthesis of two of the samples, and one sample was prepared without surfactant. The surfactant was found to have a significant effect on the properties and activity of the final catalysts. Hydrodesulfurization (HDS) tests of the catalysts show higher activity for the cationic-surfactant-assisted catalyst. Between the direct desulfurization (DDS) and hydrogenation pathways for the prepared catalysts, the DDS pathway was found to be dominant for the HDS of dibenzothiophene. As a result of the magnetic properties of this catalyst, it can be separated easily from the reaction media by a magnetic field applied externally and reused, which makes it an ideal choice for slurry reactors that process heavy and extra-heavy crude oil.
- Sharifvaghefi, Seyyedmajid,Zheng, Ying
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p. 3397 - 3403
(2015/10/28)
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- Distribution of Metal Cations in Ni-Mo-W Sulfide Catalysts
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The distribution of metal cations and the morphology of unsupported NiMo, NiW, and NiMoW sulfide catalysts were explored qualitatively and quantitatively. In the bi- and trimetallic catalysts, Mo(W)S2 nanoparticles are deposited on Ni sulfide particles of varying stoichiometry and sizes (crystalline Ni9S8, and Ni3S4 were identified). These nanoparticles are stacks of Mo(W)S2 slabs with varying size, degrees of bending and mismatch between the slabs. High resolution electron microscopy and X-ray absorption spectroscopy based on particle modeling revealed a statistical distribution of Mo and W within individual layers in sulfide NiMoW, forming intralayer mixed Mo1-xWxS2. Ni is associated with MoS2, WS2, and Mo1-xWxS2 creating Ni-promoted phases. The incorporation of Ni at the edges of the slabs was the highest for sulfide NiMoW. This high concentration of Ni in sulfide NiMoW, as well as its long bent Mo1-xWxS2 slabs, were paralleled by the highest activity for nitrogen and sulfur removal from model hydrocarbons such as o-propylaniline and dibenzothiophene.
- Hein, Jennifer,Gutiérrez, Oliver Y.,Schachtl, Eva,Xu, Pinghong,Browning, Nigel D.,Jentys, Andreas,Lercher, Johannes A.
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p. 3692 - 3704
(2015/12/05)
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- Effect of the amount of citric acid used in the preparation of NiMo/SBA-15 catalysts on their performance in HDS of dibenzothiophene-type compounds
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In the present work, NiMo catalysts supported on SBA-15 were prepared with the addition of different amounts of citric acid (CA) in the impregnation solutions. The aim of this study was to inquire into the effect of the amount of citric acid on the activity and selectivity of the NiMo/SBA-15 catalysts in deep hydrodesulfurization (HDS). Catalysts were prepared by coimpregnation of Ni and Mo species from acidic aqueous solutions containing citric acid without further adjusting the solution's pH. The amount of citric acid used in the catalyst preparation was varied from CA:Mo molar ratio 0.5 to 2.0. In addition, a reference NiMo/SBA-15 catalyst was prepared without citric acid. After the impregnation, catalysts were dried (100 C, 6 h) and calcined (500 C, 4 h). The prepared catalysts were characterized by nitrogen physisorption, small-angle and powder X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR), high resolution transmission electron microscopy (HRTEM) and tested in simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in a batch reactor at 300 C for 8 h. XRD, DRS and TPR characterizations showed that Ni and Mo oxide species were well dispersed in all catalysts prepared with CA. In contrast, a NiMoO4 crystalline phase was detected by XRD in the reference NiMo/SBA-15 catalyst prepared without citric acid. Addition of citric acid to the impregnation solutions used for the catalyst preparation also resulted in an increase in the degree of sulfidation and in the dispersion of catalytically active MoS 2 phase (elemental analysis, HRTEM). In accordance with this, HDS activity of the NiMo catalysts prepared with the addition of citric acid resulted to be significantly higher than that of the reference NiMo/SBA-15 sample for both sulfur-containing compounds tested (DBT and 4,6-DMDBT). It was found that the optimum amount of citric acid, which allows achieving the highest catalytic activity, corresponds to CA:Mo molar ratio equal to 1. Further increase in the amount of citric acid resulted in a slight decrease in the HDS activity. Regarding selectivity, addition of small amounts of CA, in general, resulted in an increase of the hydrogenation ability of the NiMo/SBA-15 catalysts. However, some differences in the selectivity of the catalysts were observed with different amounts of citric acid used.
- Calderón-Magdaleno, Miguel ángel,Mendoza-Nieto, Juan Arturo,Klimova, Tatiana E.
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- Desulfurization of diesel fuel with nickel boride in situ generated in an ionic liquid
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In order to improve the desulfurization efficiency, an ionic liquid (IL) was used as the solvent for the desulfurization of diesel fuel with nickel boride. The nickel boride prepared in IL-H2O showed high specific surface area. The desulfurization efficiency of model organosulfur compounds in this work was higher than that in the previous studies. The desulfurization reactivity of model organosulfur compounds followed the order of BT (DBT) > 3-MBT > 4,6-DMDBT. Furthermore, the products of model organosulfur compounds after desulfurization were analyzed by GC/MS and their corresponding reaction routes were proposed. The effectiveness of nickel salts followed the order of NiCl2 (Ni(OAc)2) > NiSO4 > Ni(NO 3)2. The desulfurization efficiency of model diesel fuels reached 90.6% under the conditions of B/S molar ratio = 9, Ni(OAc)2/S molar ratio = 3, oil/IL volume ratio = 3, water content in IL = 5%, and reaction time = 50 min. ILs maintained their original structures after regeneration. Finally, the desulfurization of real diesel fuel was carried out and a desulfurization efficiency of 88.6% was obtained in 50 min. This journal is the Partner Organisations 2014.
- Shu, Chenhua,Sun, Tonghua,Guo, Qingbin,Jia, Jinping,Lou, Ziyang
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p. 3881 - 3889
(2014/08/05)
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- Behavior of NiMo/SBA-15 catalysts prepared with citric acid in simultaneous hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene
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In the present work, NiMo catalysts supported on SBA-15 were prepared using citric acid (CA) during the synthesis. The objective of this work was to realize a comparative study of NiMoCA/SBA-15 catalysts prepared under different conditions in order to get a deeper insight into the effect of the thermal treatment and pH of the impregnation solution used on the catalytic behavior in deep hydrodesulfurization (HDS). Catalysts were prepared by simultaneous impregnation of Ni and Mo species and CA, using impregnation solutions of acidic or basic pH values (pH = 1 or 9, respectively). The speciation diagrams of Ni(II) and Mo(VI) species in aqueous solution as a function of pH were established. Nicit24- complex was formed in aqueous solution at pH = 9. After the impregnation, NiMoCA/SBA-15 catalysts were dried at 100 C and some of them were calcined at 500 C in air atmosphere. Prepared catalysts were characterized by thermogravimetric analysis (TGA/DTG), nitrogen physisorption, powder X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), temperature-programmed reduction (TPR), and high-resolution transmission electron microscopy (HRTEM) and tested in simultaneous HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) in a batch reactor at 300 C for 8 h. XRD characterization showed that Ni and Mo oxide species were well dispersed in all catalysts prepared with CA. In contrast, reference NiMo/SBA-15 catalysts prepared by co-impregnation of Ni and Mo species, without the addition of CA, showed signals of crystalline phases: (NH4) 4[Ni(OH)6Mo6O18] 4H2O after drying at 100 C and NiMoO4 after calcination at 500 C. HDS of DBT showed differences in activity and selectivity of the catalysts depending on the pH of the impregnation solutions and the temperature at which the catalysts were treated: NiMoCA/SBA-15 catalysts prepared from acidic impregnation solutions were more active for HDS of DBT than those prepared using basic ones. Both dried and calcined catalysts prepared at pH = 1 were selective toward the hydrogenation (HYD) route of hydrodesulfurization. However, the selectivity of the catalysts prepared from basic solutions (pH = 9) was strongly affected by the thermal treatment: dried catalyst was highly selective for the direct desulfurization (DDS) of DBT, whereas the calcined one for the HYD route. NiMoCA/SBA-15 catalysts with high hydrogenation ability showed high activity in hydrodesulfurization of 4,6-DMDBT.
- Klimova, Tatiana E.,Valencia, Diego,Mendoza-Nieto, Juan Arturo,Hernandez-Hipolito, Patricia
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- Kinetic study of NiMo/SBA-15 catalysts prepared with citric acid in hydrodesulfurization of dibenzothiophene
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We performed a kinetic study of the effect of citric acid (CA) during the synthesis of NiMo catalysts supported on SBA-15 in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The aim of this work is to get a deeper insight with respect to the thermal treatment and the pH of the impregnation solutions on the kinetic behavior of NiMoCA/ SBA-15 catalysts. NiMoCA/SBA-15 catalysts were characterized by N2 physisorption, powder XRD, HRTEM and elemental analysis and tested in HDS of DBT in a Batch reactor at 300 °C for 8 h. The kinetic study of these catalysts showed changes by CA addition on hydrogenation and direct desulfurization reaction routes depending on catalyst preparation conditions.
- Valencia, Diego,Klimova, Tatiana
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experimental part
p. 77 - 81
(2012/06/01)
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- Effects of preparation conditions in hydrothermal synthesis of highly active unsupported NiMo sulfide catalysts for simultaneous hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene
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Unsupported NiMo sulfide catalysts were prepared from ammonium tetrathiomolybdate (ATTM) and nickel nitrate by using a hydrothermal synthesis method involving water, organic solvent and hydrogen. The activity of these catalysts in the simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was much higher than that of the commercial NiMo/Al2O3 sulfide catalysts. Interestingly, the unsupported NiMo sulfide catalysts showed higher activity for hydrogenation (HYD) pathway than the direct desulfurization (DDS) pathway in the HDS of DBT. The same trends were observed for the HDS of 4,6-DMDBT. Morphology, surface area, pore volume and the HDS activity of unsupported NiMo sulfide catalyst depended on the catalyst preparation conditions. Higher temperature and higher H2 pressure and addition of an organic solvent were found to increase the HDS activity of unsupported NiMo sulfide catalysts for both DBT and 4,6-DMDBT HDS. Higher preparation temperature increased HYD selectivity but decreased DDS selectivity. High-resolution TEM images revealed that unsupported NiMo sulfide prepared at 375 °C shows lower number of layers in the stacks of catalyst with more curvature and shorter length of slabs compared to that prepared at 300 °C. On the other hand, higher preparation pressure increased DDS selectivity but decreased HYD selectivity for HDS of 4,6-DMDBT. HRTEM images showed higher number of layers in the stack for the NiMo sulfide prepared under an initial H2 pressure of 3.4 MPa compared to that under 2.1 MPa. The optimal Ni/(Mo + Ni) ratio for the NiMo sulfide catalyst was 0.5, higher than that for the conventional Al2O3-supported NiMo sulfide catalysts. This was attributed to the high dispersion of the active species and more active NiMoS generated. The present study also provides new insight for controlling the catalyst selectivity as well as activity by tailoring the hydrothermal preparation conditions.
- Yoosuk, Boonyawan,Song, Chunshan,Kim, Jae Hyung,Ngamcharussrivichai, Chawalit,Prasassarakich, Pattarapan
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scheme or table
p. 52 - 61
(2010/11/16)
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- Hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and their hydrogenated intermediates over Ni-MoS2/γ-Al2O3
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The rate constants of all reaction steps in the hydrodesulfurization (HDS) of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (DMDBT), and their tetra- and hexahydro intermediates TH(DM)DBT and HH(DM)DBT over Ni-MoS2/γ-Al2O
- Wang, Huamin,Prins, Roel
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experimental part
p. 31 - 43
(2009/09/30)
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- Hydrodesulfurization of dibenzothiophene and its hydrogenated intermediates over sulfided Mo/γ-Al2O3
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Two intermediates of dibenzothiophene (DBT)-tetrahydro-DBT (THDBT) and hexahydro-DBT (HHDBT)-were synthesized, and their hydrodesulfurization (HDS) mechanism was investigated over Mo/γ-Al2O3 at 300-340 °C and 5 MPa in the absence and presence of H2S and 2-methylpiperidine. The rate constants of all steps in the kinetic network of the HDS of DBT were measured. THDBT underwent desulfurization by hydrogenolysis to 1-phenylcyclohexene, followed by hydrogenation to phenylcyclohexane. The desulfurization of HHDBT occurred by hydrogenolysis of the aryl C{single bond}S bond and then cleavage of the cycloalkyl C{single bond}S bond of the resulting thiol by elimination to 1-phenylcyclohexene and by hydrogenolysis to phenylcyclohexane. H2S strongly inhibited the desulfurization of all three molecules but did not inhibit (de)hydrogenation. 2-Methylpiperidine also had a strong inhibitory effect, especially on (de)hydrogenation and, to a lesser extent, on desulfurization. The order of the inhibition of DBT, THDBT, and HHDBT was explained by the adsorption constants of these three molecules.
- Wang, Huamin,Prins, Roel
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experimental part
p. 153 - 164
(2009/02/08)
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- Molecular rearrangement in the Birch reduction of dibenzothiophenes
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A molecular rearrangement observed during the Birch reduction of dibenzothiophene and 4,6-dimethyl-dibenzothiophene was explored and a mechanism for the rearrangement has been proposed.
- Kukula, Pavel,Dutly, Andreas,Rüegger, Heinz,Prins, Roel
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p. 5657 - 5659
(2008/02/10)
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- Palladium-catalysed intramolecular enolate O-arylation and thio-enolate S-arylation: synthesis of benzo[b]furans and benzo[b]thiophenes
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Enolates derived from α-(ortho-haloaryl)-substituted ketones undergo palladium-catalysed C-O bond formation to deliver benzofuran products in good yield. A catalyst generated from Pd2(dba)3 and the ligand DPEphos effects the key bond
- Willis, Michael C.,Taylor, Dawn,Gillmore, Adam T.
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p. 11513 - 11520
(2007/10/03)
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- Palladium-catalyzed intramolecular O-arylation of enolates: Application to benzo[6]furan synthesis
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(Chemical Equation Presented) A catalyst generated from Pd 2(dba)3 and the ligand DPEphos effects intramolecular C-O bond formation between enolates and aryl halides in the conversion of 1-(2-haloaryl)ketones directly into the corres
- Willis, Michael C.,Taylor, Dawn,Gillmore, Adam T.
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p. 4755 - 4757
(2007/10/03)
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- Mutual influence of the HDS of dibenzothiophene and HDN of 2-methylpyridine
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The influence of 2-methylpyridine and 2-methylpiperidine on the hydrodesulfurization of dibenzothiophene (DBT) and the effect of DBT on the hydrodenitrogenation of 2-methylpyridine and 2-methylpiperidine were studied over a sulfided NiMo/Al2O3 catalyst at 5 MPa, 35 kPa H2S, and 300 and 340°C. Both N-containing molecules strongly suppressed the hydrogenation pathway of the hydrodesulfurization of DBT and inhibited the direct desulfurization route at both reaction temperatures. The inhibitory effect on the direct desulfurization was stronger for 2-methylpyridine than for 2-methylpiperidine. H2S promoted the hydrogenation of 2-methylpyridine up to 10 kPa and inhibited it at higher partial pressures. H2S had a positive influence on the hydrodenitrogenation conversions of 2-methylpiperidine and 2-methylpyridine. DBT had a negative effect on the hydrogenation of 2-methylpyridine, but did not influence the C-N bond cleavage of 2-methylpiperidine. Therefore, C-N and C-S bond breaking takes place at different active sites, whereas the hydrogenation sites for N- and S-containing molecules may be the same.
- Egorova, Marina,Prins, Roel
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- Hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene over sulfided NiMo/γ-Al2O3, CoMo/γ-Al 2O3, and Mo/γ-Al2O3 catalysts
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The hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was studied over sulfided NiMo/γ-Al2O3, CoMo/γ-Al2O 3, and Mo/γ-Al2O3 catalysts. The Ni and Co promoters strongly enhanced the activity of the Mo catalyst in the direct desulfurization pathway of the HDS of DBT and 4,6-DMDBT and in the final sulfur-removal step in the hydrogenation pathway, while the hydrogenation was moderately promoted. H2S had a negative effect on the HDS of DBT and 4,6-DMDBT, which was strongest for the NiMo catalyst and stronger for the direct desulfurization pathway than for the hydrogenation pathway. Because the direct desulfurization pathway is less important for the HDS of 4,6-DMDBT than the hydrogenation pathway, the conversion of 4,6-DMDBT was less affected by H 2S than the conversion of DBT. The sulfur removal via the direct desulfurization pathway and the ultimate sulfur removal in the hydrogenation pathway were affected by H2S to the same extent over all the catalysts. This suggests that the removal of sulfur from tetrahydrodibenzothiophenes takes place by hydrogenolysis, like the direct desulfurization of DBT to biphenyl. The CoMo catalyst performed better than the NiMo catalyst in the final desulfurization via the hydrogenation pathway in the HDS of 4,6-DMDBT at all partial pressures of H2S.
- Egorova, Marina,Prins, Roel
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p. 417 - 427
(2007/10/03)
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- XPS study of the deactivation and sulfiding of nitrided molybdena-alumina catalyst during the hydrodesulfurization of dibenzothiophene
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The deactivation and sulfidation processes of nitrided 12.5% Mo/Al2O3 catalysts at the initial stage were studied on the basis of the behavior of sulfur and nitrogen using XPS spectroscopy. The hydrodesulfurization (HDS) of dibenzothiophene was carried out in a fixed-bed microreactor at 573 K and 10.1 MPa of total pressure. The Mo/Al2O3 catalyst was nitrided by a temperature-programmed reaction with pure ammonia at 4 L h-1 at various temperatures. From XPS measurement, the sulfur atoms removed from dibenzothiophene were not exchanged with nitrogen atoms in the nitride catalyst during the first hour but molybdenum was sulfided by 71% of the total sulfur accumulated during the 14-h run. The sulfur deposition followed the Elovich equation. The decreased HDS activity and increased hydrogenation selectivity of the nitride Mo/ Al2O3 catalyst were caused by the accumulation of sulfur on the nitride catalyst. At steady state achieved after 14 h, however, the nitrogen achieved after the Mo/Al2O3 catalysts were nitrided at high temperatures was difficult to exchange by deposition of sulfur and the release of nitrogen from the nitride catalyst was hampered. The regeneration of the aged nitride catalysts with NH3 after the 14 h-run increased the activity and decreased the hydrogenation selectivity. The mechanism of the regeneration of the aged nitride catalyst by NH3 retreatment and the exchange of oxygen or nitrogen atoms with sulfur atoms in the HDS of dibenzothiophene on the nitrided Mo/Al2O3 catalyst are also discussed.
- Nagai, Masatoshi,Irisawa, Atsushi,Omi, Shinzo
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p. 7619 - 7626
(2007/10/03)
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- Hydrodesulfurization of Alkyldibenzothiophenes over a NiMo/Al2O3 Catalyst: Kinetics and Mechanism
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The transformation mechanism of dibenzothiophene, 4-methyldibenzothiophene, 4,6-dimethyldibenzothiophene, and 2,8-dimethyldibenzothiophene has been studied in a batch reactor over an industrial NiMo/Al2O3 hydrotreating catalyst at 573 K under 5 MPa of hydrogen pressure. A detailed mechanistic study including competitive catalytic experiments proved that the adsorption of the most refractory molecules at the catalyst surface was not the rate-determining step for their transformation. Our results imply that the hydrodesulfurization of these compounds occurs on one single type of sites by a flat adsorption, leading to a preliminary partial hydrogenation of one aromatic ring. Variations in reactivities of the dibenzothiophene derivatives were thus explained by different reaction rates for the C-S bond scission due to steric hindrance generated by the methyl substitution near the sulfur atom.
- Meille, Valerie,Schulz, Emmanuelle,Lemaire, Marc,Vrinat, Michel
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- CATALYTIC FUNCTIONALITIES OF MOLYBDENUM CATALYSTS SUPPORTED ON BRAZILIAN BENTONITES.
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Two kinds of Brazilian bentonites were applied to suports of molybdenum catalysts to improve the catalytic selectivities of the hydrotreating catalysts. Separate model tests reactions showed that bentonite-supported molybdenum catalysts have higher activities for hydrocracking and hydrodesulfurization as compared to a standard Al//2O//3 supported catalyst, while the Al//2O//3 was superior to the bentonites for hydrogenation activity.
- Schultz,Shimada,Yoshimura,Sato,Nishijima
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p. 1077 - 1078
(2007/10/02)
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