103272-52-2Relevant academic research and scientific papers
Hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and their hydrogenated intermediates over Ni-MoS2/γ-Al2O3
Wang, Huamin,Prins, Roel
, p. 31 - 43 (2009)
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
Preparation of unsupported NiMoP catalysts for 4,6-dimethyldibenzothiophene hydrodesulfurization
Wang, Rui,Smith, Kevin J.
, p. 1594 - 1601,8 (2014)
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.]
Regioselective addition of atomic hydrogen to olefins. Reversible 1-methyl-5-hexenyl radical cyclization in the solution-phase hydrogenation
Tanner, Dennis D.,Zhang, Liying
, p. 6683 - 6689 (1994)
The solution-phase reactions of microwave-generated hydrogen atoms with terminal olefins is regioselective. Since addition is to the terminal end of the olefin, the reaction yields a secondary radical which undergoes either reaction with molecular or atomic hydrogen, disproportionation, combination, or addition to another olefin, and in the case of hydrogen atom addition to 1,6-heptadiene, cyclization. The cyclized radicals are formed reversibly, and the final product mixture contains only minor amounts of cis-1,2-dimethylcyclopentane (the product of kinetic control) while the major cyclized product is methylcyclohexane. Although an equilibrium mixture could not be obtained, the dimethylcyclopentyl and 3-methylcyclohexyl radicals were shown to be formed reversibly.
Mo and NiMo catalysts supported on SBA-15 modified by grafted ZrO2 species: Synthesis, characterization and evaluation in 4,6-dimethyldibenzothiophene hydrodesulfurization
Gutierrez, Oliver Y.,Valencia, Diego,Fuentes, Gustavo A.,Klimova, Tatiana
, p. 140 - 153 (2007)
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.
Hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene over sulfided NiMo/γ-Al2O3, CoMo/γ-Al 2O3, and Mo/γ-Al2O3 catalysts
Egorova, Marina,Prins, Roel
, p. 417 - 427 (2004)
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.
Behavior of NiMo/SBA-15 catalysts prepared with citric acid in simultaneous hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene
Klimova, Tatiana E.,Valencia, Diego,Mendoza-Nieto, Juan Arturo,Hernandez-Hipolito, Patricia
, p. 29 - 46 (2013)
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.
Palladium islands on iron oxide nanoparticles for hydrodesulfurization catalysis
Mansouri, Ali,Semagina, Natalia
, p. 2323 - 2332 (2018)
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.
Palladium Nanoparticle Size Effect in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT)
Shen, Jing,Semagina, Natalia
, p. 2565 - 2571 (2016)
Pd nanoparticle size sensitivity of 4,6-dimethyldibenzothiophene (4,6-DMDBT) hydrodesulfurization was investigated by using 4, 8, 13, and 87 nm particles and was compared with the sulfur-free and sulfur-inhibited hydrogenation of 3,3-dimethylbiphenyl, which is a product of direct desulfurization of 4,6-DMDBT. The smallest 4 nm particles provided unprecedented (for Pd at 5 MPa and 300 °C) direct desulfurization selectivity of 20 % at 40 % conversion because of the reduced contribution of the hydrogenation path. The 4 nm particles were poisoned by the adsorbed sulfur to the greatest extent. The optimal size, providing the highest Pd mass-based yield of the desulfurized products, was found to be 8 nm. The catalyst with 87 nm particles was based on Pd nanocubes with the lowest edge/terrace surface atom ratio and large terraces and this showed the lowest sulfur extraction from both 4,6-DMDBT and sulfurous intermediates as a result of the low availability of edge atoms for a perpendicular sigma-mode adsorption through the lone pair of the sulfur atom.
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
Zhang, Lei,Fu, Wenqian,Yu, Quanyong,Tang, Tiandi,Zhao, Yicheng,Li, Yongdan
, p. 295 - 307 (2017)
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.
Design and synthesis of metal sulfide catalysts supported on zeolite nanofiber bundles with unprecedented hydrodesulfurization activities
Tang, Tiandi,Zhang, Lei,Fu, Wenqian,Ma, Yuli,Xu, Jin,Jiang, Jun,Fang, Guoyong,Xiao, Feng-Shou
, p. 11437 - 11440 (2013)
Developing highly active hydrodesulfurization (HDS) catalysts is of great importance for producing ultraclean fuel. Herein we report on crystalline mordenite nanofibers (NB-MOR) with a bundle structure containing parallel mesopore channels. After the introduction of cobalt and molybdenum (CoMo) species into the mesopores and micropores of NB-MOR, the NB-MOR-supported CoMo catalyst (CoMo/NB-MOR) exhibited an unprecedented high activity (99.1%) as well as very good catalyst life in the HDS of 4,6-dimethyldibenzothiophene compared with a conventional γ-alumina-supported CoMo catalyst (61.5%). The spillover hydrogen formed in the micropores migrates onto nearby active CoMo sites in the mesopores, which could be responsible for the great enhancement of the HDS activity.
