- Ultradeep hydrodesulfurization of fuel over superior NiMoS phases constructed by a novel Ni(MoS4)2(C13H30N)2precursor
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This article presents novel decyltrimethylammonium bromide-dispersed Ni-Mo sulfide (DTMA-NiMo) as a precursor for preparing an efficient NiMoS/γ-Al2O3hydrodesulfurization (HDS) catalyst. The as-synthesized DTMA-NiMo is a sulfide containing both long-chain quaternary ammonium and Ni-Mo-S elements. The proposed method not only significantly improves the dispersion of Mo species but also greatly promotes the incorporation of Ni into MoS2slabs, leading to an increase in the number of NiMoS phases. As a result, the DTMA-NiMo-based NiMoS/γ-Al2O3catalyst exhibits much higher activity for the HDS of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and fluid catalytic cracking (FCC) diesel than NiMoS/γ-Al2O3catalysts prepared by the co-impregnation and tetrapropylammonium bromide (TPAB)-assisted methods. This novel strategy sheds a light on the facile and low-cost preparation of superior NiMoS phases without sulfidation treatment.
- Fan, Yu,He, Shuisen,Wen, Chenglong,Xu, Jundong
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p. 6065 - 6075
(2020/09/23)
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- Hydroconversion of Thiophene Derivatives over Dispersed Ni–Mo Sulfide Catalysts
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Abstract: The activity of unsupported Ni–Mo sulfide catalysts is studied in the hydroconversion of benzothiophene and dibenzothiophenes in the temperature range of 340–380°С and at an increased H2 pressure and in the СО/H2О system. The structure of dispersed catalysts formed by the in situ high-temperature decomposition of oil-soluble precursors (molybdenum hexacarbonyl, nickel naphthenate) is investigated by TEM. Effects of СО/H2О molar ratio, water mass content in the system, and CO pressure on the activity of the catalysts and yields of the products are explored. It is shown that, in the СО/H2О system, the highest conversion of benzothiophene and dibenzothiophene is attained at a temperature of 380°С, a СО pressure of 5?MPa, and a СО/H2О molar ratio of 2. The introduction of alkyl substituents into a dibenzothiophene molecule causes a reduction in the rate of reaction that predominantly occurs via the hydrogenation of aromatic rings. The catalyst activities in hydrogenation under H2 pressure and in the СО/H2О system are comparable.
- Vutolkina,Makhmutov,Zanina,Maximov,Kopitsin,Glotov,Egazar’yants,Karakhanov
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p. 1227 - 1232
(2019/02/05)
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- Palladium islands on iron oxide nanoparticles for hydrodesulfurization catalysis
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A four-fold increase in palladium (Pd) mass-based hydrodesulfurization (HDS) activity was achieved by depositing Pd species as nanosized islands on 12 nm colloidal iron oxide (FeOx) nanoparticles via the galvanic exchange reaction. The highest palladium dispersion was obtained at an optimal Pd/Fe molar ratio of 0.2, which decreased when the ratio increased. The improved dispersion was responsible for the enhanced catalytic activity per the total Pd amount in the HDS of 4,6-dimethyldibenzothiophene at 623 K and 3 MPa as compared to the iron-free Pd/Al2O3 catalyst. The lattice strain and modified electronic properties of the Pd islands suppressed deep hydrogenation to dimethylbicyclohexyl and changed the hydrocracking product distribution. Pd nanoparticles deposited on commercial Fe2O3 did not provide such an activity enhancement and catalyzed significant cracking. This study demonstrates that FeOx@Pd structures are a possible alternative to monometallic Pd catalysts with enhanced noble metal atom efficiency for ultra-deep HDS catalysis and points to their great potential to reduce the catalyst cost and move towards more earth-abundant catalytic materials.
- Mansouri, Ali,Semagina, Natalia
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p. 2323 - 2332
(2018/05/23)
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- Effect of citric acid addition on the morphology and activity of Ni2P supported on mesoporous zeolite ZSM-5 for the hydrogenation of 4,6-DMDBT and phenanthrene
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Preparing small, highly dispersed Ni2P particles is important for improving the hydrogenation ability of Ni2P. Here, Ni2P nanoparticles (approximately 4.3 nm) on mesoporous zeolite ZSM-5 (Ni2P/MZSM-5-CA) were prepared using citric acid (CA) as an assistant agent. The formation mechanism of small Ni2P particles when CA was added was investigated by combining UV–vis diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and temperature-programmed reduction with a transmission electron microscope and CO chemisorption. The results indicated that the formed CA–Ni complex with high viscosity favors the Ni precursor dispersed on the dried catalyst. After calcination, the released Ni species strongly interacted with surface acidic hydroxyl groups on MZSM-5, leading to the formation of Ni2P particles with small sizes and good dispersion under a reducing atmosphere. The reaction rate constants and TOFs over Ni2P/MZSM-5-CA (16.2 × 10?2μmol g?1s?1and 9.7 × 10?4s?1) are much higher than over Ni2P/MZSM-5 (8.2 × 10?2μmol g?1s?1and 8.3 × 10?4s?1) in 4,6-dimethyldibenzothiophene hydrodesulfurization. In addition, Ni2P/MZSM-5-CA catalyst shows higher activity than Ni2P catalyst without CA in phenanthrene hydrogenation.
- Zhang, Lei,Fu, Wenqian,Yu, Quanyong,Tang, Tiandi,Zhao, Yicheng,Li, Yongdan
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p. 295 - 307
(2016/12/26)
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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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- 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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- Preparation of unsupported NiMoP catalysts for 4,6-dimethyldibenzothiophene hydrodesulfurization
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The preparation of unsupported NiMoP catalysts in the presence of citric acid (CA) is reported. Phase pure NiMoP with a surface area ~60 m 2/g was synthesized in the presence of CA at low reduction temperature (550 °C), with a Ni/Mo/P molar ratio of 1/1/1 and a 1.5 CA/Me ratio (Me = Ni + Mo). Depending on the synthesis conditions, small amounts of MoP and NiMoP2 were also present in the catalysts. The catalyst precursors appeared similar to those identified for MoP and Ni2P catalysts, also synthesized in the presence of CA. For the phase pure NiMoP catalysts, the TOFs for the HDS of 4,6-dimethyldibenzothiophene were almost identical, despite large differences in NiMoP surface area and crystallite size. Graphical Abstract: [Figure not available: see fulltext.]
- Wang, Rui,Smith, Kevin J.
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p. 1594 - 1601,8
(2014/12/09)
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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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- Ga and Al containing MCM-41 mesoporous molecular sieves: Structure and catalytic performance for the 4,6 dimethyldibenzothiophene hydrodesulfurization
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MCM-41 type materials containing Al and Ga (Al-Ga-MCM-41) were prepared by a synthesis gel using cethyltrimethylammonium chloride as surfactant. In the preparation, Si/(Al + Ga) ratios were 21, 27 and 32 in the gel, maintaining the concentration of Al constant. The structures of the materials were characterized by X-ray diffraction (XRD), nitrogen physisorption, Fourier transform infrared spectroscopy (FTIR) of adsorbed pyridine, 27Al MAS NMR, 29Si MAS NMR and energy dispersive analysis of X-ray (EDX). Al-Ga-MCM-41 exhibited prominent characteristics as supports for the Ni-Mo-S type catalysts used in the hydrodesulfurization of 4,6-dimethyldibenzothiphene (4,6 DMDBT). The presence of Ga was detected by TEM with a resolution of 1.9 ? point to point; therefore the Ga is in the lattice. The amount of Ga in the support enhanced the activity of the catalysts and modified the products distribution. The maximum catalytic activity and direct desulfurization capability was achieved on the catalyst NiMo/Al-Ga-MCM-41 with Si/(Al + Ga) = 32 molar ratio.
- Martínez-Belmonte,Aguilar,Gutierrez,Montoya,De Los Reyes,Torres,Chen
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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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- Synthesis of 4,6-dimethyldibenzothiophene and 1,2,3,4-tetrahydro-4,6- dimethyldibenzothiophene via Tilak annulation
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1,2,3,4-Tetrahydro-4,6-dimethyldibenzothiophene was prepared by coupling 2-bromo-3-methylcyclohexanone with 2-methylbenzenethiol and annulating the product with the aid of polyphosphoric acid. A mixture of 1,2,3,4-tetrahydro-4, 6-dimethyldibenzothiophene and 4,6-dimethyldibenzothiophene was prepared by coupling 2-bromo-3-methylcyclohex-2-en-1-one with 2-methylbenzenethiol and annulating the product with the aid of polyphosphoric acid. 2-Bromo-3- methylcyclohexanone was synthesized by conjugate addition of Me3Al to 2-bromocyclohex-2-en-1-one with CuBr as catalyst and 2-bromo-3-methylcyclohex- 2-en-1-one by bromination-elimination of 3-methylcyclohex-2-en-1-one. 1,2,3,4,4a,9b-Hexahydro-4,6-dimethyldibenzothiophene was prepared by reduction of 1,2,3,4-tetrahydro-4,6-dimethyldibenzothiophene with Zn and CF 3COOH. Copyright
- Xu, Xiaoying,Li, Xiang,Wang, Anjie,Sun, Yinyong,Schweizer, W. Bernd,Prins, Roel
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experimental part
p. 1754 - 1763
(2011/12/03)
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- Simultaneous promotion of hydrogenation and direct desulfurization routes in hydrodesulfurization of 4,6-dimethyldibenzothiophene over NiW catalyst by use of SiO2-Al2O3 support in combination with trans-1,2-diaminocyclohex
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Effect of novel SiO2-Al2O3 support on surface structure and hydrodesulfurization (HDS) activity of the NiW catalyst prepared using trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CyDTA) was investigated by combina
- Koizumi, Naoto,Hamabe, Yusuke,Yoshida, Shohei,Yamada, Muneyoshi
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scheme or table
p. 79 - 88
(2010/11/05)
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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 4,6-dimethyldibenzothiophene over noble metals supported on mesoporous zeolites
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(Figure Presented) Pores for thought: Noble-metal catalysts supported on mesoporous zeolites have been found to be much more efficient than on microporous zeolites and γ-Al2O3 for the hydrodesulfurization of 4,6-dimethyldibenzothioph
- Sun, Yinyong,Prins, Roel
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supporting information; experimental part
p. 8478 - 8481
(2009/04/12)
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- Good sulfur tolerance of a mesoporous Beta zeolite-supported palladium catalyst in the deep hydrogenation of aromatics
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The activities of a Pd catalyst supported on mesoporous Beta zeolite (Beta-H) were evaluated for the hydrogenation of naphthalene and pyrene in the absence and presence of 200-ppm sulfur and for the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). Compared with Pd/Al-MCM-41, the Pd/Beta-H catalyst exhibited better sulfur tolerance for hydrogenation of naphthalene and pyrene and higher activity for HDS of 4,6-DMDBT. The ratio of the hydrogenation of the second ring naphthalene in the absence and presence of 200-ppm sulfur for Pd/Beta-H was larger than that for Pd/Al-MCM-41 (0.47 vs 0.19). The desulfurization effect of Pd/Beta-H was greater than that of Pd/Al-MCM-41 (51 vs 35%). The difference in sulfur tolerance and HDS ability of the 2 catalysts is attributed to the difference in support acidity. Beta-H exhibited more acidic sites and a higher percentage of strong acidic sites than Al-MCM-41 (552 μmol/g and 43% vs 291 μmol/g and 18%).
- Tang, Tiandi,Yin, Chengyang,Wang, Lifeng,Ji, Yanyan,Xiao, Feng-Shou
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scheme or table
p. 125 - 133
(2009/02/08)
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- Kinetics of the HDS of 4,6-dimethyldibenzothiophene and its hydrogenated intermediates over sulfided Mo and NiMo on γ-Al2O3
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To study the hydrodesulfurization (HDS) reaction network of 4,6-dimethyldibenzothiophene (DMDBT), three hydrogenated intermediates-tetrahydro-, hexahydro-, and dodecahydro-DMDBT-were synthesized, and their HDS was investigated over sulfided Mo and NiMo on γ-Al2O3 catalysts at 300 °C and 5 MPa. Tetrahydro-DMDBT reacted by hydrogenation to hexahydro-DMDBT, which in turn reacted to dodecahydro-DMDBT by hydrogenation and to 3,3′-dimethylcyclohexylbenzene by desulfurization. All four diastereoisomers of hexahydro-DMDBT were observed, all of which interconverted rapidly during HDS. Dodecahydro-DMDBT reacted by desulfurization to 3,3′-dimethylbicyclohexyl. The rate constants of all steps in the kinetic network of the HDS of DMDBT could be measured over Mo/γ-Al2O3, and those of some steps could be measured over NiMo/γ-Al2O3. The first step-hydrogenation of DMDBT to tetrahydro-DMDBT-is the slowest, rate-determining step, but the hydrogenation of and the sulfur removal from hexahydro-DMDBT are also slow. Opening of the sulfur-containing ring in DMDBT and its hydrogenated intermediates occurs by C{single bond}S hydrogenolysis rather than by elimination.
- Li, Xiang,Wang, Anjie,Egorova, Marina,Prins, Roel
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p. 283 - 293
(2008/04/12)
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- Mo and NiMo catalysts supported on SBA-15 modified by grafted ZrO2 species: Synthesis, characterization and evaluation in 4,6-dimethyldibenzothiophene hydrodesulfurization
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A series of ZrO2-containing mesoporous SBA-15 supports and their respective Mo and NiMo catalysts were prepared to study the effect of zirconia loading on the characteristics of Ni and Mo species and their catalytic activity in 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS). ZrO2-containing SBA-15 solids with different metal loadings (up to 23 wt% of ZrO2) were prepared by chemical grafting at room temperature. Supports and catalysts were characterized by N2 physisorption, XRD, UV-vis DRS, TPR, chemical analysis, and HRTEM. The incorporation of zirconia into the SBA-15 support provides better dispersion to the deposited molybdenum species, increasing the effective surface of the MoS2 phase. Mo and NiMo catalysts supported on SBA-15 materials showed an increase in catalytic activity in 4,6-dimethyldibenzothiophene HDS with zirconia loading in the support. Unpromoted Mo catalysts were active in the formation of hydrogenated intermediates of 4,6-DMDBT, namely tetrahydro- and hexahydrodimethyldibenzothiophenes; however, they were not able to realize efficient sulfur elimination from these intermediates with the formation of desulfurized products. Addition of the Ni promoter resulted in a further increase in Mo dispersion, as well as in the acceleration of C-S bond cleavage in hydrogenated intermediates of 4,6-DMDBT, improving the overall kinetics of the HYD pathway of HDS.
- Gutierrez, Oliver Y.,Valencia, Diego,Fuentes, Gustavo A.,Klimova, Tatiana
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p. 140 - 153
(2008/03/13)
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- Preparation of partially hydrogenated 4,6-dimethyldibenzothiophenes
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The synthesis of three key intermediates of the hydrogenation pathway in the hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DM-DBT; 1) is described. The hydrogenated derivatives 1,2,3,4-tetrahydro-4,6- dimethyldibenzothiophene (=4,6-dimethyl-1,2,3,4-tetrahydrodibenzothiophene; 4,6-DM-TH-DBT; 2), 1,2,3,4,4a,9b-hexahydro-4,6-dimethyldibenzothiophene (=4,6-dimethyl-1,2,3,4,4a,9b-hexahydrodibenzothiophene; 4,6-DM-HH-DBT; 3), and dodecahydro-4,6-dimethyldibenzothiophene (=4,6-dimethylperhydrodibenzothiophene; 4,6-DM-PH-DBT; 4) were prepared by direct hydrogenation of 1. The reactions were carried out in continuous and batch reactors by using metal sulfide as well as noble-metal catalysts. The influence of the reaction conditions on the formation of the products and the distribution of their stereoisomers was studied in detail. The isomers of the main products were isolated and characterized by NMR, GC/MS/MS, and X-ray crystal-structure diffractometry.
- Kukula, Pavel,Gramlich, Volker,Prins, Roel
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p. 1623 - 1640
(2007/10/03)
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- Investigation of 4,6-dimethyldibenzothiophene hydrodesulfurization over a highly active bulk MoS2 catalyst
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The hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene was investigated in a batch-stirred microautoclave reactor over a laboratory-synthesized MoS2 catalyst. The reaction was found to proceed through two main parallel pathways: direct desulfurization (DDS) and hydrogenation (HYD). The effect of a wide range of H2S concentrations on the HDS activity and selectivity was studied. Contrary to the well-known inhibition of HDS caused by H2S, the global catalytic activity of HDS was enhanced more than two times with inclusion of H2S in the reaction zone. The increase in the activity is attributed to a significant enhancement in the hydrogenation reaction route, while the direct desulfurization products were only slightly affected. It is suggested that H2S modifies the active sites so that they can be exploited more efficiently in the hydrogenation reaction.
- Farag, Hamdy,Sakanishi, Kinya
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p. 531 - 535
(2007/10/03)
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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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