Suchergebnisse

Nanosized SSZ-13 has been obtained from a one-pot synthesis procedure with the addition of CTAB to the synthesis precursor solution. Nano-SSZ-13 zeolite showed high intracrystalline mesoporosity and compared to standard SSZ-13 presented a much longer lifetime and higher conversion capacity for the reaction of methanol to olefins. The improved properties were attributed to a more efficient utilization of micropores by easier diffusion of reactants and products and slower deactivation by coke. A higher C2/C3 ratio was found for nano-SSZ-13, pointing to a lower deactivation of the aromatics cycle of the hydrocarbon pool. ; Financial support by the Spanish Government-MINECO through "Severo Ochoa" (SEV 2012-0267), CTQ2015-67592-P, CTQ2015-70126-R, CTQ2015-68951-C3-1-R, MAT2015-71842-P, by the European Union ERC-AdG-2014-671093-SynCatMatch and by the Generalitat Valenciana PROMETEOII/2013/011 is acknowledged. Z. Li acknowledges China Scholarship Council (CSC) for a fellowship. J. Yu thanks the Major International Joint Research Project of China for financial support (Grant No. 21320102001). ; Peer Reviewed

Cobalt catalysts supported on Y zeolite and mesoporized Y zeolite (Y-mod) have been studied in steam reforming of ethanol (SRE). Specifically, the eect of the mesoporosity and the acidity of the y zeolite as a support has been explored. Mesoporous were generated on Y zeolite by treatment with NH4F and the acidity was neutralized by Na incorporation. Four cobalt catalysts supported on Y zeolite have been prepared, two using Y zeolite without mesoporous (Co/Y, Co/Y-Na), and two using Y zeolite with mesoporous (Co/Y-mod and Co/Y-mod-Na). All catalysts showed a high activity, with ethanol conversion values close to 100%. The main dierences were found in the distribution of the reaction products. Co/Y and Co/Y-mod catalysts showed high selectivity to ethylene and low hydrogen production, which was explained by their high acidity. On the contrary, neutralization of the acid sites could explain the higher hydrogen selectivity and the lower ethylene yields exhibited by the Co/Y-Na and Co/Y-mod-Na. In addition, the physicochemical characterization of these catalysts by XRD, BET surface area, temperature-programmed reduction (TPR), and TEM allowed to connect the presence of mesoporous with the formation of metallic cobalt particles with small size, high dispersion, and with high interaction with the zeolitic support, explaining the high reforming activity exhibited by the co/y-mod-Na sample as well as its higher hydrogen selectivity. It has been also observed that the formation of coke is aected by the presence of mesoporous and acidity. Both properties seem to have an opposite eect on the reforming catalyst, decreasing and increasing the coke deposition, respectively. ; "This research was funded by Generalitat Valenciana, grant number PROMETEO/2018/006", Spanish Government (Project RTI2018-102161-I00) and RED DE EXCELENCIA EN BIORREFINERIAS SOSTENIBLES (RED2018-102623-T).

Titanosilicate zeolites are catalysts of interest in the field of fine chemicals. However, the generation and accessibility of active sites in titanosilicate materials for catalyzing reactions with large molecules is still a challenge. Herein, we prepared titanosilicate zeolite precursors with open zeolitic structures, tunable pore sizes, and controllable Si/Ti ratios through a hydrothermal crystallization strategy by using quaternary ammonium templates. A series of quaternary ammonium ions are discovered as effective organic templates. The prepared amorphous titanosilicate zeolites with some zeolite framework structural order have extra-large micropores and abundant octahedrally coordinated isolated Ti species, which lead to a superior catalytic performance in the oxidative desulfurization of dibenzothiophene (DBT) and epoxidation of cyclohexene. It is anticipated that the amorphous prezeolitic titanosilicates will benefit the catalytic conversion of bulky molecules in a wide range of reaction processes. ; The authors thank the National Key Research and Development Program of China (Grant 2016YFB0701100), the National Natural Science Foundation of China (Grant 21621001, 21920102005 and 21835002), the 111 Project (B17020), the European Union through the European Research Council (grant ERC-AdG-2014-671093, SynCatMatch), and the Spanish Government through "Severo Ochoa" (SEV-2016-0683, MINECO) for supporting this work. The APS was operated for the U.S. DOE Office of Science by the Argonne National Laboratory, and the CLS@APS facilities (Sector 20) were supported by the U.S. DOE under contract no. DEAC02-06CH11357, and the Canadian Light Source and its funding partners. R. Bai acknowledges the China Scholarship Council for the financial support. ; Peer reviewed

Upgrading of the heavy reformate fraction (HR), containing mainly C aromatics, is usually performed by dealkylation or by transalkylation with added benzene and/or toluene to obtain the more valuable xylenes. However, when the costs related to the use of benzene and toluene are considered, the one-step dealkylation/transalkylation of the C alkylaromatics to xylenes becomes economically attractive. Thus, in a first step, ethylmethylbenzenes (EMB) will have to be dealkylated to toluene, which will then react with the trimethylbenzenes (TMB) present in the HR feed to produce xylenes by transalkylation. Medium pore zeolites will favor dealkylation, whereas large pore zeolites will be more adequate for carrying out the transalkylation reaction. In this work, we present the one-pot synthesis of beta-pentasil aggregates with tunable ratios of the large pore beta to the medium pore component. We show that the close proximity of the beta and pentasil nanocrystals obtained by one-pot co-crystallization synthesis, results in a highly efficient catalyst for the consecutive dealkylation/transalkylation process. The bifunctional catalyst based on the co-crystallized aggregate is more active and selective to xylenes than a catalyst based on a physical mixture of equivalent beta and pentasil nanozeolites synthesized following an analogous procedure. The small crystallite sizes of the co-crystallized zeolites provide the additional advantage of a lower deactivation rate as compared to a reference benchmark catalyst. Results are shown on both, model molecules and industrial HR feed. ; This work has been supported by Saudi Aramco, by the Spanish Government-MICINN through "Severo Ochoa" (SEV 2012-0267) and RTI2018-101033-B-I00, by the European Union through ERC-AdG-2014-671093 (SynCatMatch) and by the Fundación Ramón Areces through a research contract of the "Life and Materials Science" program. We thank Belén Esparcia for technical assistance, and the Electron Microscopy Service of the UPV for their help in sample characterization.