Synthesis and characterization of Ga-modified Ti-HMS oxide materials with varying Ga content

This work reports on the structure and surface characteristics of hexagonal mesoporous silica (HMS) modified with both Ti and Ga. Several techniques were used (low-angle XRD, SBET, TPD-NH3, DRS, FT-IR of framework vibration, FT-IR of adsorbed pyridine, SEM and HRTEM). These systems were then used as catalysts in the o-xylene hydroisomerization carried out in a batch reactor at 300 °C and atmospheric H2 pressure. The catalyst characterization demonstrated that the modification of Ti-HMS substrate with Ga by post-synthesis grafting yields high surface area substrates with good Ga dispersion and bimodal distribution of gallium species. On the basis of lattice expansion observed from XRD data together with the increase of absorption band due to vibration of Si–O–Ga linkages, it is inferred that Ga species are incorporated into the silica framework. Moreover, textural analysis revealed that highly dispersed Ga2O3 species are deposited within the inner pores of the substrate. The largest o-xylene conversion observed for the Ti-HMS-2.5Ga sample containing the largest Ga loading is related to the heterogeneous distribution of its Ga species and its large acidity. Upon reaction conditions employed, the o-xylene hydroisomerization over Ti-HMS-Ga proceeds exclusively via intramolecular mechanism (formation of m- and p-xylenes) and hydrogenation of benzene aromatic ring of o-, p- and m-xylenes did not occur.This study is partially supported by The Spanish Ministry of Science and Innovation (ENE2007-67533-C02-01 project) and The Community of Madrid (S2009ENE-1743 project) with financial aid from the Scientific Cooperation FONCICYT Program (FONCICYT-96194 project). The CONACYT projects 152012, 155388 and 117373 for the financial supports.Peer Reviewe

Competitive HDS and HDN reactions over NiMoS/HMS-Al catalysts: Diminishing of the inhibition of HDS reaction by support modification with P

[EN] The effect of the support (Al-HMS) modification with P between (0.0-2.0 wt.%) was studied in this work. NiMo/Al-HMS-P(x) catalysts were prepared and sulfided in order to be tested in the hydrodesulfurizarion (HDS) reaction of dibenzothiophene (DBT), hydrodenitrogenation (HDN) of carbazole and simultaneous HDS and HDN reactions. The materials were characterized by X-ray diffraction (XRD), FT-IR of framework vibration (FTIR-KBr), Micro-Raman spectroscopy, temperature programmed adsorption of ammonia (TPD-NH3), N2 adsorption–desorption isotherms and X-ray photoelectron spectroscopy. For both, individual HDS and HDN reactions, all P-containing catalysts have shown a higher activity with respect to P-free sample. The catalyst modified with optimized amount of P (1 wt.%) promoted DBT transformation via HYD route of this reaction. Due to the important HYD properties, the NiMo/Al-HMS-P1.0 sample showed the lower inhibition factor during simultaneous HDS and HDN.CONACYT projects 152012, 155388 and 117373 for the financialsupports