16587-33-0Relevant academic research and scientific papers
Highly Active Low Cobalt Content-Based Bulk MoS2 Hydrodesulfurization Catalysts with a Unique Impact of H2S
Farag, Hamdy,Embaby, Abd-Alrahman,Kishida, Masahiro,El-Hendawy, Abdel-Nasser A.,Nasef, Mohamed Mahmoud
, (2018)
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.
Conformational Effects in the Alkali Metal Reduction of Diaryl Sulfides and Dibenzothiophene
Francisco, Manuel A.,Kurs, Argo,Katritzky, Alan R.,Rasala, Danuta
, p. 596 - 600 (1988)
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.
Highly Active Bulk Mo(W)S2 Hydrotreating Catalysts Synthesized by Etching out of the Carrier from Supported Mono- and Bimetallic Sulfides
Kokliukhin,Mozhaev,Nikulshina,Lancelot,Blanchard,Lamonier,Nikulshin
, p. S53 - S59 (2020/01/23)
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.
Trimetallic Hydrotreating Catalysts CoMoW/Al2O3 and NiMoW/Al2O3 Prepared on the Basis of Mixed Mo-W Heteropolyacid: Difference in Synergistic Effects
Mozhaev,Nikul’shina,Lancelot,Blanchard,Lamonier,Nikul’shin
, p. 1198 - 1205 (2019/02/05)
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.
Hydroconversion of Oxidation Products of Sulfur-Containing Aromatic Compounds
Vutolkina,Akopyan,Glotov,Kotelev,Maksimov,Karakhanov
, p. 981 - 989 (2018/08/31)
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.
Synthesis of Ni-Mo binary transition metal complex and application in hydrodesulfurization
Liang, Jilei,Wu, Mengmeng,Cai, Hongmei,Cao, Yiyang,Lu, Xiaorong,Wang, Yuhang,Zhu, Min
, p. 1075 - 1079 (2018/02/22)
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.
Preparation of Ni-Mo2C/carbon catalysts and their stability in the HDS of dibenzothiophene
Wang, Haiyan,Liu, Shida,Govindarajan, Rubenthran,Smith, Kevin J.
, p. 114 - 127 (2017/04/27)
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
Influence of nanoscale distribution of Pd particles in the mesopores of MCM-41 on the catalytic performance of Pd/MCM-41
Dong, Chao,Li, Xiang,Wang, Anjie,Chen, Yongying,Liu, Haiou
, p. 219 - 222 (2017/07/24)
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.
The preparation of Mo/γ-Al2O3 catalysts with controllable size and morphology via adjusting the metal-support interaction and their hydrodesulfurization performance
Yuan, Pei,Cui, Chunsheng,Han, Wei,Bao, Xiaojun
, p. 115 - 125 (2016/07/12)
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.
Hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and their hydrogenated intermediates over bulk tungsten phosphide
Yang, Lei,Li, Xiang,Wang, Anjie,Prins, Roel,Chen, Yongying,Duan, Xinping
, p. 330 - 343 (2015/09/01)
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.
