scholarly journals Effect of Mesostructured Zirconia Support on the Activity and Selectivity of 4,6-Dimethydibenzothiophene Hydrodesulfurization

Catalysts ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1162
Author(s):  
Sylvette Brunet ◽  
Bénédicte Lebeau ◽  
Issam Naboulsi ◽  
Laure Michelin ◽  
Jean Dominique Comparot ◽  
...  
Keyword(s):  
Active Phase ◽  
Alumina Catalyst ◽  
Zirconia Support ◽  
Deep Hydrodesulfurization ◽  
Promotion Rate ◽  
Cobalt Species

In contrast with the conventional CoMoS/alumina catalyst, the use of amorphous mesostructured ZrO2 as support for the dispersion of the CoMoS active phase in deep hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene led to a higher promotion rate and a better sulfidation of the cobalt species. The CoMoS, dispersed over mesostructured amorphous ZrO2 as catalyst, also induced a modification of the main desulfurization way; in this case, a shift towards direct desulfurization selectivity was observed. This result was unexpected regarding the literature. Indeed, the hydrogenated route was observed for commercial zirconia. The designed catalysts are therefore more eco-friendly, since they consume less hydrogen. This implies a better use of the fossil resources.

scholarly journals Ultrathin Washcoat and Very Low Loading Monolithic Catalyst with Outstanding Activity and Stability in Dry Reforming of Methane

Nanomaterials ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 445 ◽  
Author(s):  
Fazia Agueniou ◽  
Hilario Vidal ◽  
María Pilar Yeste ◽  
Juan C. Hernández-Garrido ◽  
Miguel A. Cauqui ◽  
...  
Keyword(s):  
Thermodynamic Limit ◽  
Catalyst Layer ◽  
Active Phase ◽  
Dry Reforming ◽  
Redox Properties ◽  
Dry Reforming Of Methane ◽  
Alumina Catalyst ◽  
Monolithic Catalyst ◽  
Prolonged Time ◽  
Zro2 Catalyst

A Ni/CeO2/ZrO2 catalyst with improved redox properties has been washcoated onto a honeycomb cordierite monolith in the form of a nonconventional alumina-catalyst layer, just a few nanometers thick. In spite of the very low active phase loading, the monolith depicts outstanding performance in dry reforming of methane, both in terms of activity, with values reaching the thermodynamic limit already at 750 °C, even under extreme Weight Hourly Space Velocities (WHSV 115–346 L·g−1·h−1), as well as in terms of stability during prolonged Time on Stream (TOS 24–48 h).

scholarly journals Alloying Effect of Silver on Zirconia Support Manipulated Palladium Catalyst for Methane Combustion

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 863
Author(s):  
Mengmeng Chu ◽  
Fan Cai ◽  
Xiaohong Cao ◽  
Li Xing ◽  
Lefu Yang ◽  
...  
Keyword(s):  
Oxidation Reaction ◽  
Methane Combustion ◽  
Active Phase ◽  
Alloying Effect ◽  
Redox Cycles ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Zirconia Support ◽  
Effect Of Support ◽  
Alloy Catalysts

PdAg/ZrO2 alloy catalysts calcined at different temperatures were employed to elucidate the effect of support-metal interaction (SMI) on methane combustion. Combustion activity was depressed when the sample was calcined at an elevated temperature from 500 °C to 700 °C. However, calcination at 850 °C enhanced the beneficial SMI, which facilitated a more active phase for the oxidation reaction. The high-resolution transmission electron microscopy experiments show that a special micro-domain structure at the interface is formed during the reduction pretreatment. H2-TPR and O2-TPD measurements illustrate that the active phase would undergo reconstruction upon redox cycles. The active phase manipulated by the support is more suitable for combustion reaction in the course of temperature altering.

In situ XAFS analysis of catalytically active cobalt species in porous clays for deep hydrodesulfurization

2003 ◽  
Vol 87 (1-4) ◽  
pp. 117-121 ◽  
Author(s):  
Masayuki Shirai ◽  
Nobuhiro Iwasa ◽  
Kyoko K Bando ◽  
Takeshi Kubota
Keyword(s):  
In Situ Xafs ◽  
Catalytically Active ◽  
Deep Hydrodesulfurization ◽  
Cobalt Species

Nanostructured SBA-15 Materials as Appropriate Supports for Active Hydrodesulfurization Catalysts Prepared from HSiW Heteropolyacid

2012 ◽  
Vol 1479 ◽  
pp. 77-82 ◽  
Author(s):  
J.A. Mendoza-Nieto ◽  
K.D. Tejeda-Espinosa ◽  
I. Puente-Lee ◽  
C. Salcedo-Luna ◽  
T. Klimova
Keyword(s):  
Active Phase ◽  
Catalytic Performance ◽  
Nominal Composition ◽  
Incipient Wetness Impregnation ◽  
Model Compounds ◽  
Characteristic Structure ◽  
Pure Silica ◽  
Sulfided Catalysts ◽  
Phase Precursor ◽  
Deep Hydrodesulfurization

ABSTRACTA series of NiW catalysts supported on SBA-15-type materials modified with Al, Ti or Zr were prepared and tested in simultaneous hydrodesulfurization (HDS) of two model compounds: dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Catalysts were prepared by incipient wetness impregnation of SBA-type materials (pure silica SBA-15, Al-SBA-15, Ti-SBA-15 or Zr-SBA-15) using Keggin-type heteropolyacid H4SiW12O40 as active phase precursor and nickel nitrate. Nominal composition of the catalysts was 19 wt.% of WO3 and 3 wt.% of NiO. The supports and catalysts were characterized by SEM-EDX, N2physisorption, small-angle and powder XRD, UV-Vis DRS, TPR and HRTEM. It was shown that a good dispersion of Al, Ti and Zr species on the SBA-15 surface was reached. The characteristic structure of the SBA-15 support was preserved in all supports and NiW catalysts. Addition of metal atoms (Al, Ti, Zr) on the SBA-15 surface prior to catalysts’ preparation improved dispersion of Ni and W oxide species in calcined catalysts. HRTEM characterization of sulfided catalysts showed that the dispersion of NiW active phase was also better on metal-containing SBA-15 supports than on the pure silica one. All NiW catalysts supported on metal-containing SBA-15 materials showed an outstanding catalytic performance in HDS of both model compounds used (DBT and 4,6-DMDBT). A good correlation was found between the dispersion of sulfided NiW active phase and catalytic activity results. The highest HDS activity was obtained with the NiW catalyst supported on Zr-containing SBA-15 molecular sieve, which makes it a promising catalytic system for ultra-deep hydrodesulfurization of diesel fuel.

What catalysis needs from the electron microscopist

1988 ◽  
Vol 46 ◽  
pp. 694-695
Author(s):  
Alexis T. Bell
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
Surface Composition ◽  
Internal Surface ◽  
Active Phase ◽  
Atomic Scale ◽  
Metal Catalyst ◽  
Internal Surface Area ◽  
Porous Support

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.

CHANGES IN THE METABOLISM OF CALCIUM AND PHOSPHORUS IN THE VARIOUS PHASES OF ACROMEGALY AND FOLLOWING THE IMPLANTATION OF THE PITUITARY GLAND WITH 90Y

1961 ◽  
Vol 36 (2) ◽  
pp. 161-179 ◽  
Author(s):  
G. M. Molinatti ◽  
F. Camanni ◽  
O. Losana ◽  
M. Olivetti
Keyword(s):  
Pituitary Gland ◽  
Marked Decrease ◽  
Active Phase ◽  
Tolerance Test ◽  
Urinary Calcium ◽  
Phosphorus Metabolism ◽  
Blood Calcium ◽  
X Ray ◽  
Calcium Retention ◽  
Calcium And Phosphorus

ABSTRACT A study of calcium and phosphorus metabolism has been carried out on 13 acromegalic patients, in various stages of the disease. This study was repeated in nine patients following implantation of the pituitary gland with 90Y and in another two patients after deep X-ray therapy and suction removal of a pituitary adenoma respectively. Increased urinary calcium and phosphorus excretion was found in all the patients in whom the disease was in an active phase of evolution. The calcium tolerance test revealed a marked decrease of calcium retention in certain subjects, while in others, calcium retention was found to be increased. Such changes were not found in patients in whom the disease was in a quiescent phase. The blood calcium, phosphorus and alkaline phosphatase were found to be either normal or slightly increased. The implantation of the pituitary gland with 90Y and deep X-ray therapy induced a marked decrease of hypercalciuria, both spontaneous and induced, and of hyperphosphaturia, together with a definite improvement, of the clinical picture and glucose metabolism. It is concluded that the changes in calcium and phosphorus metabolism described above depend either directly or indirectly on a pituitary factor. They may therefore prove a reliable index for assessing pituitary growth hormone activity.

Sign in / Sign up

Export Citation Format

Share Document