On the Performance of Metal Supported Catalysts Prepared by Microemulsion: Sol Gel and Precipitation of the Support Precursor

2005 ◽  
Vol 3 (1) ◽  
Author(s):  
Gustavo Pérez ◽  
J. Luis Suaste ◽  
César Barrales ◽  
J. Antonio De los Reyes ◽  
Juan Pérez-Sea ◽  
...  
Keyword(s):  
Supported Catalysts ◽  
Sol Gel ◽  
Synthesis Method ◽  
Active Phase ◽  
Catalytic Performance ◽  
Ammonium Bromide ◽  
Microemulsion Method ◽  
Structure Sensitive ◽  
Cetyltrimethyl Ammonium

Ni/SiO2, NiMo/Al2O3 and CoMo/Al2O3 were prepared by microemulsion method. Precipitation and sol-gel of the support precursor allowed the synthesis of catalysts with differences in textural, structural and catalytic properties. The main difference between the precipitation and sol-gel microemulsion routes is the role of surfactant (Cetyltrimethyl Ammonium Bromide) in each synthesis method. The aggregation mechanism of support is modified by the synthesis route. There are differences in the catalytic performance of Ni/SiO2 microemulsion catalysts by the precipitation or sol-gel of support precursor. The hydrogenation of benzene, a low structure-sensitive reaction, showed that the precipitation 9%Ni/SiO2 microemulsion catalyst is more active than the sol-gel 9%Ni/SiO2 microemulsion catalyst. On other hand, these catalysts showed opposite result in the hydrogenation of C=C double bond of crotonaldehyde molecule. These results are indicative of the effects of nanostructured support and nanostructured active-phase in the hydrogenation activity. NiMo/Al2O3 and CoMo/Al2O3 catalysts prepared by sol-gel-microemulsion method were used in the hydrodesulphurization (HDS) of dibenzothiophene and 4,6-dimethyldibenzothiophene. The HDS activity was improved as a function of metal content and it motivates the study of NiMo and CoMo microemulsion catalysts with higher contents of metals to enhance the HDS of 4,6-dimethyldibenzothiophene.

Role of cetyltrimethyl ammonium bromide on sol–gel preparation of porous cerium titanate photocatalyst

2018 ◽  
Vol 88 (1) ◽  
pp. 202-210
Author(s):  
Wenjie Zhang ◽  
Yinghao Dong ◽  
Yanwen Zhou ◽  
Jing Li ◽  
Xuan Xiao ◽  
...  
Keyword(s):  
Sol Gel ◽  
Ammonium Bromide ◽  
Cetyltrimethyl Ammonium Bromide ◽  
Gel Preparation ◽  
Cetyltrimethyl Ammonium ◽  
Cerium Titanate

Positive Role of Synthesis Method and Hard Template on the Catalytic Performance of SAPO-34 in Methanol to Olefin Reaction.

2020 ◽  
Vol 23 ◽  
Author(s):  
Sajjad Rimaz ◽  
Reza Katal
Keyword(s):  
Particle Size ◽  
Synthesis Method ◽  
Catalytic Performance ◽  
Hard Template ◽  
Structure Directing Agent ◽  
Positive Role ◽  
Methanol To Olefin ◽  
Dg Method ◽  
Synthesis Procedure

: In the present study, SAPO-34 particles were synthesized using hydrothermal (HT) and dry gel (DG) conversion methods in the presence of diethyl amine (DEA) as an organic structure directing agent (SDA). Carbon nanotubes (CNT) were used as hard template in the synthesis procedure to introduce transport pores into the structures of the synthesized samples. The synthesized samples were characterized with different methods to reveal effects of synthesis method and using hard template on their structure and catalytic performance in methanol to olefin reaction (MTO). DG conversion method results in smaller particle size in comparison with hydrothermal method, resulting in enhancing catalytic performance. On the other side, using CNT in the synthesis procedure with DG method results in more reduction in particle size and formation of hierarchical structure which drastically improves catalytic performance.

How does the Support Influence the Catalytic Activity of the Keggin Ion?

1996 ◽  
Vol 454 ◽  
Author(s):  
Zakiyyah Smith ◽  
Michael Palmieri ◽  
Nancy Buecheler ◽  
Susan A. Jansen
Keyword(s):  
Catalytic Activity ◽  
Carbon Materials ◽  
Solid Acid ◽  
Sol Gel ◽  
Catalytic Performance ◽  
Heteropoly Acids ◽  
Keggin Ion ◽  
Oxide Substrates ◽  
Silica Matrices

AbstractHeteropoly acids, HPA are well known solid acid and oxidation catalysts that find application in hetergeneous and homogeneous reactions. In the former, surface area and stability problems are diminshed by supporting the HPA. Typical supports include oxide substrates and porous carbon materials. The HPA's show some instability on these supports however. In this work, we demonstrate that HPA encapsulated in sol-gel silica matrices show enhanced catalytic performance without compromising the catalytic activity of the HPA. In addition, the specific role of the support in the catalytic process is described as well.

scholarly journals Structural and Oxidative Properties of Manganese Incorporated Mesostructure Silica for Methane Oxidation

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Rihem Dardouri ◽  
Anis Gannouni ◽  
Mongia Saïd Zina
Keyword(s):  
Ion Exchange ◽  
Methane Oxidation ◽  
Crystalline Phase ◽  
Synthesis Method ◽  
Porous Silica ◽  
Chemical Properties ◽  
Active Phase ◽  
Catalytic Performance ◽  
Adsorption Desorption ◽  
Mcm 41

Manganese catalysts containing templated mesostructured porous silica were prepared using different methods of preparation, namely, the direct hydrothermal (DHT), solid-state ion exchange (SSI), template ion exchange (TIE), and impregnation (Imp) methods. The physical-chemical properties of materials were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, FT-IR, TEM, EDX, UV-Vis, EPR, and H2 TPR techniques. The results of this study indicate that the obtained catalysts retained their hexagonal mesopore structure after introducing Mn into MCM-41. On the contrary, the crystalline phase of manganese oxide was stabilized on the external surface and inside the mesoporosity of the MCM-41 and seems to be dependent on the synthesis method used. Catalytic performances of synthesized materials were then investigated in methane oxidation at atmospheric pressure. The results showed that the metal loading and catalysts synthesis procedure influence the catalytic performance of the obtained materials. Moreover, the activity of the catalyst depends on the crystalline phase and particularly on the environment of the active phase.

scholarly journals Vanadium oxides doped porous titania photocatalysts for phenol photodegradation

2016 ◽  
Vol 12 (1) ◽  
Author(s):  
Siew Ling Lee ◽  
Swee Por Khaw ◽  
Yee Khai Ooi
Keyword(s):  
Anatase Phase ◽  
Sol Gel ◽  
Phenol Degradation ◽  
Nitrogen Adsorption ◽  
Band Gap Energy ◽  
Vanadium Oxides ◽  
Ammonium Bromide ◽  
Porous Titania ◽  
Cetyltrimethyl Ammonium ◽  
Adsorption Desorption

Vanadium oxides (1 - 5 wt%) doped porous TiO2 using tetrabutyltitanate and cetyltrimethyl ammonium bromide as Ti precursor and template, respectively was successfully synthesized via sol-gel method. All the samples crystallined in anatase phase as indicated by X-ray diffraction analysis. The results of diffused reflectance UV-visible spectroscopy analysis showed that the band gap energy of TiO2 reduced from 3.02 to 2.72 eV after introduction of 5 wt% V. The nitrogen adsorption-desorption analysis revealed that the surface area of samples increased with the amount of V dopant. These materials contained of disorder mesopores with particle size ranged 5 – 56 nm. Amongst, sample 4V-TBT-p-TiO2 recorded the highest percentage of phenol degradation (62.2%) under visible light irradiation

Effects of Surfactants on the Synthesis of Silica Aerogels Prepared by Ambient Pressure Drying

2012 ◽  
Vol 512-515 ◽  
pp. 1625-1630
Author(s):  
Hua Zheng Sai ◽  
Li Xing ◽  
Jun Hui Xiang ◽  
Fu Shi Zhang ◽  
Li Jie Cui ◽  
...  
Keyword(s):  
Ambient Pressure ◽  
Sol Gel ◽  
Drying Shrinkage ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Ammonium Bromide ◽  
High Porosity ◽  
Free Silica ◽  
Sol Gel Process ◽  
Cetyltrimethyl Ammonium

In this research, aerogels were synthesized by a two-step sol-gel process without supercritical conditions. During the process, tetraethoxysilane (TEOS) was used as precursor, and different surfactants, i.e. cetyltrimethyl ammonium bromide (CTAB) and polyethylene glycol–600 (PEG–600), were used as dopants respectively. In order to minimize the drying shrinkage and preserve the high porosity structure, the surface of the gels was modified by trimethylchlorosilane (TMCS) before the ambient pressure drying (APD). The effect of surfactent on the structure of the resulting aerogels was investigated. The aerogels which involved surfactants exhibited resistance to cracking during the APD of the alcogels. The modification by TMCS has been confirmed using Infrared (IR) spectroscopy. The porous structure of aerogels was investigated by Brunauer-Emmett- Teller (BET) instrument, differential scanning calorimeter (DSC) and scanning electron micrograph (SEM). The results indicated that surfactants as dopants could significantly affect the structure and optical property of aerogels and be beneficial for obtaining crack-free silica aerogels via ambient pressure drying process.

scholarly journals Effect of Metal Loading in Unpromoted and Promoted CoMo/Al2O3–TiO2 Catalysts for the Hydrodeoxygenation of Phenol

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 550 ◽  
Author(s):  
J. Andrés Tavizón-Pozos ◽  
Carlos E. Santolalla-Vargas ◽  
Omar U. Valdés-Martínez ◽  
José Antonio de los Reyes Heredia
Keyword(s):  
Catalytic Activity ◽  
Active Sites ◽  
Mixed Oxides ◽  
Batch Reactor ◽  
Sol Gel ◽  
Active Phase ◽  
Catalytic Performance ◽  
Octahedral Coordination ◽  
Optimum Amount ◽  
Co Concentration

This paper reports the effects of changes in the supported active phase concentration over titania containing mixed oxides catalysts for hydrodeoxygenation (HDO). Mo and CoMo supported on sol–gel Al2O3–TiO2 (Al/Ti = 2) were synthetized and tested for the HDO of phenol in a batch reactor at 5.5 MPa, 593 K, and 100 ppm S. Characterization results showed that the increase in Mo loading led to an increase in the amount of oxide Mo species with octahedral coordination (MoOh), which produced more active sites and augmented the catalytic activity. The study of the change of Co concentration allowed prototypes of the oxide species and their relationship with the CoMo/AT2 activity to be described. Catalysts were tested at four different Co/(Co + Mo) ratios. The results presented a correlation between the available fraction of CoOh and the catalytic performance. At low CoOh fractions (Co/(Co + Mo) = 0.1), Co could not promote all MoS2 slabs and metallic sites from this latter phase performed the reaction. Also, at high Co/(Co + Mo) ratios (0.3 and 0.4), there was a loss of Co species. The Co/(Co + Mo) = 0.2 ratio presented an optimum amount of available CoOh and catalytic activity since the XPS results indicated a higher concentration of the CoMoS phase than at a higher ratio.

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