The use of a natural Mexican zeolite as support of NiMoW sulphide hydrotreating catalysts

In order to examine the influence of type of metal precursor on the hydrodesulfurization (HDS) activity of synthetized samples, a series of ternary Ni–Mo–W catalysts supported on a natural Mexican zeolite (clinoptilolite) were prepared by sequential wet impregnation of the zeolite support with different thiosalts of W and Mo, and Ni(NO3)2·6H2O. The synthetized samples were characterized by N2 adsorption–desorption isotherms at −196 °C, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX/SEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) techniques. The catalysts activity was evaluated in the HDS of dibenzothiophene (DBT) reaction performed in a batch reactor at 350 °C and 3.1 MPa of total hydrogen pressure. The activity tests demonstrated that the best catalyst was the NiMoW-H/zeo sample synthesized from ammonium thiosalts. The use of tetraalkylammonium thiometalates as metal precursors led to the decrease in the HDS activity. The most active catalyst in the HDS of DBT reaction showed the largest density of active phases on the support surface determined from HRTEM measurements.Dr. R. Huirache-Acuña wants to thank the support of CONACYT CIENCIA BASICA 182191 and CIC-UMSNH 2012-2013 Projects (Mexico) and the valuable assistance of Dr. Eric M. Rivera Muñoz (CFATAUNAM) and financial support of Project DGAPA – UNAM PAPIIT IN107311–3. The authors are grateful to Prof. J.L.G. Fierro (ICP-CSIC, Spain) for stimulating discussion and providing laboratory facilities for the catalyst characterization. This study was partially supported by The Spanish Ministry of Science and Innovation (ENE2010-21198-C04-01) and The Community of Madrid (S2009ENE-1743 project) with financial aid from the Scientific Cooperation FONCICYT Program (FONCICYT-96194 project).Peer Reviewe

Synthesis of Ni-Mo-W sulphide unsupported HDS catalysts from ex-situ activation of trimetallic precursors: effect of preparation method

Trabajo presentado en el International Mexican Congress on Chemical Reaction Engineering, celebrado en Acapulco (México) del 07 al 13 de junio de 2014.Unsupported Ni-Mo-W sulphide hydrodesulphurization (HDS) catalysts were prepared by ex-situ decomposition of trimetallic Ni-Mo-W precursors. The effect of the catalyst preparation method was investigated. Firstly, the trimetallic precursors were treated in a stainless steel vessel of 45 mL volume at 523 K for 2 h under argon atmosphere. Subsequently, the respective thiosalt was decomposed under a reductive atmosphere of H2S/H2 (15 vol.% H2S) from room temperature to 673 K. A series of four catalysts was tested in HDS of dibenzothiophene (DBT). The catalysts were labeled as Ni0.5, Ni1 and Ni2 according with the molar ratio of Ni in the sample. In addition, a precursor with a molar ratio Ni-Mo-W of 2:1:2 was prepared varying the concentration of tungsten, named as W2. The catalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and BET speci¿c surface area measurements. The ex-situ activation method leads to catalysts with a distribution of speci¿c surface areas from 8 to 34 m2/g, showing type IV adsorption¿desorption isotherms of nitrogen typical for mesoporous materials, and poorly crystalline structures with different morphology, and varying phase composition. The Ni:Mo:W atomic ratios for the trimetallic catalysts show variations and are slightly smaller than those expected. The sample labeled as Ni-Mo-W2 showed the highest catalytic activity in the HDS of DBT (k = 12 x 10-7 mol/g s).Peer Reviewe

Catalytic performance of CoMoW Sulfide catalysts supported on hierarchically structured porous silicas for HDS reactions

In this work, monolithic silica materials with hierarchical porosity were synthesized by the sol-gel method combined with a dual hard-soft templating route. Silica materials were used for the synthesis of hydrodesulfurization CoMoW-S catalysts by the immersion technique using transition metal salts as precursors, followed by oxidation and sulfidation in H2S/H2 mixture. Styrene-HEMA copolymer hard template presented homogeneous well-defined spherical shape with an average diameter of about 800 nm. Samples prepared over the hard template presented similar morphology. The surface areas of all supports prepared resulted in around 800 m2.g−1 and decreased to 220 m2.g−1 on average after the sulfidation process. Small-angle X-ray diffraction confirmed the presence of the 2D hexagonal or Im3m array of mesopores in all samples. The CoMoW oxide state catalysts presented low intensity peaks assigned to the b-CoMo(W)O4 phase and minor peaks related to MoO3 and polyoxides with the general formula MoxW1-xO3. The high conversion was obtained for catalysts supported on hierarchically structured porous silicas, even greater than that of the commercial catalyst used as reference (>30–50%). XPS results revealed that the degree of sulfidation and CoMoWS active species resulted higher in the CoMoW-HOPSCM catalyst compared to the CoMoW-MoNoSBA-15 sample, which in turn coincides with the catalytic activity results

Synergetic effect in RuxMo(1-x)S2/SBA-15 hydrodesulfurization catalysts: Comparative experimental and DFT studies

The effect of introducing Ru impurities into the MoS2crystalline structure of the sulfided RuxMo(1-x)S2/SBA-15catalysts have been investigated using density functional theory (DFT) calculations and the catalyst character-ization by different techniques (chemical analysis (ICP-AES), temperature-programmed reduction (TPR), X-raydiffraction (XRD), N2physisorption, DRIFTS of adsorbed pyridine (DRIFTS-Py) and X-ray photoelectron spec-troscopy (XPS)). The catalyst activity was tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT)reaction carried out in a batch reactor,T= 320 °C and total H2pressure of 5.5 MPa. From electronic structureDFT calculations is was concluded that the 4d orbitals of both Mo and Ru played an important role in the catalystoptimization being the processes of transport and charge transference the most important ones. It was found thatthe enrichment with Ru, promotes a greater electronic participation (DOS at the Fermi level) of the differentatoms in the RuxMo(1-x)S2phase leading to metallization of the Mo ions. The catalyst activity in HDS of DBTreaction demonstrated a similar behavior to that of theoretical density of states (DOS) calculated via DFT. Allbimetallic systems presented the synergetic effect between Ru and Mo in the HDS of DBT reaction overRuxMo(1-x)S2/SBA-15 catalysts. The highest activity observed for Ru content ofx= 0.4 was consistent with theoretical results predicting that the optimum DOS contributions should be aroundx= 0.44. The most activeRu0.4Mo0.6S2/SBA-15 exhibit the best hydrogenation properties linked with the Ru-induced metallization of Moions in the Ru0.4Mo0.6S2phase. This catalyst showed two-fold higher hydrogenation properties than CoMoS/γ-Al2O3reference catalyst. The linear dependencies of initial activity on Brønsted-to-Lewis acidities ratio (fromDRIFT-Py) and total metal surface exposure (from XPS) were observed.The authors acknowledge the Consejo Nacional de Ciencia yTecnología (CONACyT) for the financial support of CONACYT (Projects117373 and 152012). D.H. Galvan and B. Pawelec acknowledges Supercómputo UNAM through project No. LANCAD-UNAM-DGTIC-041and CTQ2016-76505-C3-1 project supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO), respectively