scholarly journals Hollow MFI Zeolite Supported Pt Catalysts for Highly Selective and Stable Hydrodeoxygenation of Guaiacol to Cycloalkanes

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 362 ◽  
Author(s):  
Xiaopo Niu ◽  
Fuxiang Feng ◽  
Gang Yuan ◽  
Xiangwen Zhang ◽  
Qingfa Wang
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Acid Sites ◽  
Pt Catalyst ◽  
Pt Catalysts ◽  
Mfi Zeolite ◽  
Long Term Stability ◽  
Supported Pt Catalysts ◽  
Hierarchical Porous ◽  
Ft Ir

Hollow Silicalite-1 and ZSM-5 zeolites with hierarchical porous shells have been synthesized by using a dissolution-recrystallization method. The morphology, structure, and acidity of these zeolites supported Pt catalysts were characterized by XRD, FT-IR, MAS-SSNMR, FE-SEM, FE-TEM, N2-BET, XPS, NH3-TPD, and CO pulse chemisorption. Compared to the conventional ZSM-5 supported Pt catalyst, the special structure in hollow ZSM-5 zeolite significantly promotes the dispersion of metallic Pt and the synergistic effect between metal active sites and acid sites. These boost the catalytic activity, selectivity of guaiacol hydrodeoxygenation toward cycloalkanes and long-term stability over the Pt/hollow ZSM-5 catalyst combined with improved mass transfer of products and reactants derived from the hierarchical hollow porous structure. Moreover, the Pt/hollow ZSM-5 catalyst exhibits excellent low temperature catalytic activity to completely transform guaiacol into cycloalkanes with the cyclohexane selectivity of more than 93% at 220 °C, suggesting that hollow ZSM-5 zeolite is a promising support for upgrading of bio-oils.

A Single Turnover (STO) Characterization of Supported Palladium Catalysts

1987 ◽  
Vol 111 ◽  
Author(s):  
Robert L. Augustine ◽  
David R. Baum
Keyword(s):  
Palladium Catalysts ◽  
Active Sites ◽  
Pt Catalyst ◽  
Catalyst Characterization ◽  
Pt Catalysts ◽  
Ambient Conditions ◽  
Reaction Conditions ◽  
Pd Catalysts ◽  
Supported Pt Catalysts

AbstractWhile the STO catalyst characterization procedure has been applied to a variety of supported Pt catalysts, application of this technique to the characterization of supported Pd catalysts showed that there were several significant differences between the Pt and the Pd catalysts. Under STO reaction conditions each surface site on a Pt catalyst reacts only once so there is a 1:1 relationship between the product composition and the densities of the various types of active sites present. With Pd catalysts under these same conditions, alkene isomerization takes place so readily that the amount of isomerized product formed depends on the contact time of the reactant pulse with the catalyst so there is no direct relationship between the amount of isomerization and the number of isomerization sites present. On Pt there are some direct saturation sites present on which H2 is rather weakly held. Such sites are not present on Pd catalysts. The reactive surface of supported Pt catalysts remains constant on long exposure to air. With Pd catalysts exposure to air results in a decrease in saturation site densities which can be reversed by re-reduction of the surface with H2 under ambient conditions but not completely under what can be termed “reaction conditions” where the extent of surface re-reduction decreases with catalyst age.

scholarly journals Structure-Catalytic Properties Relationship in Friedel Crafts Alkylation Reaction for MCM-36-Type Zeolites Obtained by Isopropanol-Assisted Pillaring

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 299
Author(s):  
Karolina Ogorzały ◽  
Agnieszka Węgrzyn ◽  
Aleksandra Korzeniowska ◽  
Andrzej Sławek ◽  
Andrzej Kowalczyk ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Acid Sites ◽  
Alkylation Reaction ◽  
High Catalytic Activity ◽  
Large Molecules ◽  
External Acid Sites ◽  
Hierarchical Porous ◽  
Acid Centers ◽  
Ir Study

MWW type zeolites are characterized by the presence of zeolitic layers of 2.5 nm thickness, containing 10-member ring sinusoidal channels inside and supercavities with 12-member ring openings located on their surfaces. Expansion and pillaring of layered zeolites increase the access to active sites and can enable or facilitate catalytic activity towards larger reactant molecules. This goal is explored in this work reporting the pillaring of layered zeolite MCM-56 with MWW topology by tetraethylorthosilicate (TEOS) treatment with the assistance of isopropanol, aimed at obtaining hierarchical micro-mesoporous systems. MCM-56 (Si/Al = 12) was synthesized with hexamethyleneimine as a structure-directing and aniline as a structure-promoting agent. Hierarchical porous systems were obtained using two different pillaring methods: (1) with TEOS only and (2) with TEOS mixed with isopropanol. The MWW framework was preserved during swelling/pillaring in both methods. Pillared zeolites obtained via alcohol-assisted pillaring possessed unique intermediate micro-mesopores with the size of about 2 nm. IR study revealed a decrease in the concentration of accessible acid centers upon pillaring. However, the fraction of acid sites on the external surface, accessible for adsorption of large molecules, increased by up to 90%. Catalytic activity was evaluated in the Friedel-Crafts alkylation of mesitylene with benzyl alcohol. Pillaring resulted in reduction of the acid site concentrations, but the materials retained high catalytic activity. Pillaring in the presence of alcohol produced increased turnover frequency values based on the concentrations of the external acid sites.

scholarly journals Influence of the Reduction Temperature and the Nature of the Support on the Performance of Zirconia and Alumina-Supported Pt Catalysts for n-Dodecane Hydroisomerization

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 88
Author(s):  
Diana García-Pérez ◽  
Maria Consuelo Alvarez-Galvan ◽  
Jose M. Campos-Martin ◽  
Jose L. G. Fierro
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Catalytic Properties ◽  
Catalytic Performance ◽  
Major Influence ◽  
Pt Catalysts ◽  
Reduction Temperature ◽  
Metal Dispersion ◽  
Tungsten Oxides ◽  
Supported Pt Catalysts

Catalysts based on zirconia- and alumina-supported tungsten oxides (15 wt % W) with a small loading of platinum (0.3 wt % Pt) were selected to study the influence of the reduction temperature and the nature of the support on the hydroisomerization of n-dodecane. The reduction temperature has a major influence on metal dispersion, which impacts the catalytic activity. In addition, alumina and zirconia supports show different catalytic properties (mainly acid site strength and surface area), which play an important role in the conversion. The NH3-TPD profiles indicate that the acidity in alumina-based catalysts is clearly higher than that in their zirconia counterparts; this acidity can be attributed to a stronger interaction of the WOx species with alumina. The PtW/Al catalyst was found to exhibit the best catalytic performance for the hydroisomerization of n-dodecane based on its higher acidity, which was ascribed to its larger surface area relative to that of its zirconia counterparts. The selectivity for different hydrocarbons (C7–10, C11 and i-C12) was very similar for all the catalysts studied, with branched C12 hydrocarbons being the main products obtained (~80%). The temperature of 350 °C was clearly the best reduction temperature for all the catalysts studied in a trickled-bed-mode reactor.

scholarly journals Warped graphitic layers generated by oxidation of fullerene extraction residue and its oxygen reduction catalytic activity

2019 ◽  
Vol 10 ◽  
pp. 1391-1400 ◽  
Author(s):  
Machiko Takigami ◽  
Rieko Kobayashi ◽  
Takafumi Ishii ◽  
Yasuo Imashiro ◽  
Jun-ichi Ozaki
Keyword(s):  
Catalytic Activity ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Oxidation Time ◽  
Pt Catalyst ◽  
Oxidation Treatment ◽  
Orr Activity ◽  
Temperature Programmed ◽  
Carbon Catalysts

Carbon-based oxygen reduction reaction (ORR) catalysts are regarded as a promising candidate to replace the currently used Pt catalyst in polymer electrolyte fuel cells (PEFCs); however, the active sites remain under discussion. We predicted that warped graphitic layers (WGLs) are responsible for the ORR catalytic activity in some carbon catalysts (i.e., carbon alloy catalysts (CACs)). To prove our assumption, we needed to use WGLs consisting of carbon materials, but without any extrinsic catalytic elements, such as nitrogen, iron, or cobalt, which effectively enhance ORR activity. The present study employed a fullerene extraction residue as a starting material to construct WGLs. The oxidation of the material at 600 °C exposed the WGLs by removing the surrounding amorphous moieties. Transmission electron microscopy (TEM) observations revealed the formation of WGLs by oxidation treatment at 600 °C in an O2/N2 stream. Extending the oxidation time increased the purity of the WGL phase, but also simultaneously increased the concentration of oxygen-containing surface functional groups as monitored by temperature programmed desorption (TPD). The specific ORR activity increased with oxidation up to 1 h and then decreased with the intensive oxidation treatment. Correlations between the specific ORR activity and other parameters confirmed that the development of the WGL and the increase in the O/C ratio are the competing factors determining specific ORR activity. These results explain the maximum specific ORR activity after 1 h of oxidation time. WGLs were found to lower the heat of adsorption for O2 and to increase the occurrence of heterogeneous electron transfer.

Effect of Pt Dispersion on the Catalytic Activity of Supported Pt Catalysts for Diesel Hydrocarbon Oxidation

2013 ◽  
Vol 56 (1-8) ◽  
pp. 249-254 ◽  
Author(s):  
Masaaki Haneda ◽  
Motoi Sasaki ◽  
Hideaki Hamada ◽  
Masakuni Ozawa
Keyword(s):  
Catalytic Activity ◽  
Hydrocarbon Oxidation ◽  
Pt Catalysts ◽  
Supported Pt Catalysts

Hydrogenation of xylenes over supported Pt catalysts. Influence of different variables on their catalytic activity

1992 ◽  
Vol 46 (2) ◽  
pp. 305-312 ◽  
Author(s):  
M. A. Aramendía ◽  
V. Borau ◽  
C. Jiménez ◽  
J. M. Marinas ◽  
F. Rodero ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Pt Catalysts ◽  
Supported Pt Catalysts

Hydrogenation of tetralin on silica–alumina-supported Pt catalysts II. Influence of the support on catalytic activity

2007 ◽  
Vol 251 (2) ◽  
pp. 497-506 ◽  
Author(s):  
M WILLIAMS ◽  
B FONFE ◽  
C WOLTZ ◽  
A JENTYS ◽  
J VANVEEN ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Pt Catalysts ◽  
Supported Pt Catalysts ◽  
Silica Alumina

Acid Properties of MCM-36 Molecular Sieve and its Catalytic Behavior in Benzene Alkylation with Propylene

2014 ◽  
Vol 1015 ◽  
pp. 434-437 ◽  
Author(s):  
Fei Zhao ◽  
Yu Zhang ◽  
Wen Jing Jiang
Keyword(s):  
Catalytic Activity ◽  
Molecular Sieve ◽  
Acid Sites ◽  
Velocity Space ◽  
Acidic Properties ◽  
Catalytic Behavior ◽  
Benzene Alkylation ◽  
Acid Properties ◽  
Ft Ir ◽  
Excellent Selectivity

Pillared layered MCM-36 zeolite was synthesized from pure MCM-22 precursor with polymeric silica as pillaring agent. Characterization results of acidic properties from FT-IR indicate a decrease in the amounts of Lewis acidic and Brønsted acidic. The catalytic behavior of pillared layered MCM-36 zeolite in benzene alkylation with propylene was studied. It was found that pillared MCM-36 zeolite shows stable catalytic activity in a 200h time-on-stream measurement under a relatively high propylene velocity space. The excellent selectivity to cumene over MCM-36 should be mainly due to the decrease in the amount of Brønsted acidity, while the improvement of the catalytic activity of MCM-36 can be mainly assigned to the presence of a larger amount of structurally accessible acid sites caused by the increment of mesoporous volume in this material.

Hydrogenation ofp-Nitrophenol top-Aminophenol as a Test Reaction for the Catalytic Activity of Supported Pt Catalysts

2014 ◽  
Vol 37 (3) ◽  
pp. 551-554 ◽  
Author(s):  
Michael Goepel ◽  
Majd Al-Naji ◽  
Patrick With ◽  
Gerald Wagner ◽  
Oliver Oeckler ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Pt Catalysts ◽  
Test Reaction ◽  
Supported Pt Catalysts
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