scholarly journals The Influence of the Support on the Activity of Mn–Fe Catalysts Used for the Selective Catalytic Reduction of NOx with Ammonia

Catalysts ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 63 ◽  
Author(s):  
Irene López-Hernández ◽  
Jesús Mengual ◽  
Antonio Eduardo Palomares
Keyword(s):  
Surface Area ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Catalyst Activity ◽  
High Surface ◽  
High Surface Area ◽  
Acid Sites ◽  
Beta Zeolite ◽  
Ammonia Adsorption ◽  
Fe Catalysts

Mono and bimetallic Mn–Fe catalysts supported on different materials were prepared and their catalytic performance in the NH3–SCR of NOx was investigated. It was shown that Mn and Fe have a synergic effect that enhances the activity at low temperature. Nevertheless, the activity of the bimetallic catalysts depends very much on the support selected. The influence of the support on the catalyst activity has been studied using materials with different textural and acid–base properties. Microporous (BEA-zeolite), mesoporous (SBA15 and MCM41) and bulk (metallic oxides) materials with different acidity have been used as supports for the Mn–Fe catalysts. It has been shown that the activity depends on the acidity of the support and on the surface area. Acid sites are necessary for ammonia adsorption and high surface area produces a better dispersion of the active sites resulting in improved redox properties. The best results have been obtained with the catalysts supported on alumina and on beta zeolite. The first one is the most active at low temperatures but it presents some reversible deactivation in the presence of water. The Mn–Fe catalyst supported on beta zeolite is the most active at temperatures higher than 350 °C, without any deactivation in the presence of water and with a 100% selectivity towards nitrogen.

Spidery catalyst for the synthesis of quinazoline-2,4(1H,3H)-diones

2016 ◽  
Vol 6 (5) ◽  
pp. 1435-1441 ◽  
Author(s):  
Seyed Mohsen Sadeghzadeh
Keyword(s):  
Surface Area ◽  
Active Sites ◽  
High Surface ◽  
High Surface Area

In this study, a novel fibrous nanosilica (KCC-1) based nanocatalyst (Au, Pd, and Cu) with a high surface area and easy accessibility of active sites was successfully developed by a facile approach.

scholarly journals Catalytic Cracking of n-Hexadecane Using Carbon Nanostructures/Nano-Zeolite-Y Composite Catalyst

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1385
Author(s):  
Botagoz Zhuman ◽  
Shaheen Fatima Anis ◽  
Saepurahman ◽  
Gnanapragasam Singravel ◽  
Raed Hashaikeh
Keyword(s):  
Surface Area ◽  
Catalytic Cracking ◽  
Carbon Nanostructures ◽  
Active Sites ◽  
Zeolite Y ◽  
High Surface ◽  
High Surface Area ◽  
Composite Catalyst ◽  
Homogeneous Distribution ◽  
Binding Material

Zeolite-based catalysts are usually utilized in the form of a composite with binders, such as alumina, silica, clay, and others. However, these binders are usually known to block the accessibility of the active sites in zeolites, leading to a decreased effective surface area and agglomeration of zeolite particles. The aim of this work is to utilize carbon nanostructures (CNS) as a binding material for nano-zeolite-Y particles. The unique properties of CNS, such as its high surface area, thermal stability, and flexibility of its fibrous structure, makes it a promising material to hold and bind the nano-zeolite particles, yet with a contemporaneous accessibility of the reactants to the porous zeolite structure. In the current study, a nano-zeolite-Y/CNS composite catalyst was fabricated through a ball milling approach. The catalyst possesses a high surface area of 834 m2/g, which is significantly higher than the conventional commercial cracking catalysts. Using CNS as a binding material provided homogeneous distribution of the zeolite nanoparticles with high accessibility to the active sites and good mechanical stability. In addition, CNS was found to be an effective binding material for nano-zeolite particles, solving their major drawback of agglomeration. The nano-zeolite-Y/CNS composite showed 80% conversion for hexadecane catalytic cracking into valuable olefins and hydrogen gas, which was 14% higher compared to that of pure nano-zeolite-Y particles.

scholarly journals Impact of Thermal Treatment of Nb2O5 on Its Performance in Glucose Dehydration to 5-Hydroxymethylfurfural in Water

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1685
Author(s):  
Katarzyna Morawa Eblagon ◽  
Anna Malaika ◽  
Karolina Ptaszynska ◽  
Manuel Fernando R. Pereira ◽  
José Luís Figueiredo
Keyword(s):  
Thermal Treatment ◽  
Surface Area ◽  
Pure Water ◽  
High Surface ◽  
High Surface Area ◽  
Acid Sites ◽  
High Ratio ◽  
Total Acidity ◽  
One Pot ◽  
Niobic Acid

The cascade dehydration of glucose to 5-hydroxymethylfurfural (HMF) was carried out in water over a series of Nb2O5 catalysts, which were derived from the thermal treatment of niobic acid at 300 and 550 °C, under air or inert atmosphere. Amorphous niobic acid showed high surface area (366 m2/g) and large acidity (2.35 mmol/g). With increasing the temperature of the thermal treatment up to 550 °C, the amorphous Nb2O5 was gradually transformed into a pseudohexagonal phase, resulting in a decrease in surface area (27–39 m2/g) and total acidity (0.05–0.19 mmol/g). The catalysts’ performance in cascade dehydration of glucose realized in pure water was strongly influenced by the total acidity of these materials. A remarkable yield of 37% HMF in one-pot reaction in water was achieved using mesoporous amorphous niobium oxide prepared by thermal treatment of niobic acid at 300 °C in air. The best-performing catalyst displayed a total acidity lower than niobic acid (1.69 mmol/g) which afforded a correct balance between a high glucose conversion and limited further conversion of the target product to numerous polymers and humins. On the other hand, the treatment of niobic acid at 550 °C, independently of the atmosphere used during the sample preparation (i.e., air or N2), resulted in Nb2O5 catalysts with a high ratio of Lewis to Brønsted acid sites and poor total acidity. These materials excelled at catalyzing the isomerization step in the tandem process.

scholarly journals Ultrasonic-assisted preparation of highly active Co3O4/MCM-41 adsorbent and its desulfurization performance for low H2S concentration gas

RSC Advances ◽  
2020 ◽  
Vol 10 (50) ◽  
pp. 30214-30222
Author(s):  
Bolong Jiang ◽  
Jiaojing Zhang ◽  
Yanguang Chen ◽  
Hua Song ◽  
Tianzhen Hao ◽  
...  
Keyword(s):  
Surface Area ◽  
Active Sites ◽  
High Surface ◽  
High Surface Area ◽  
Highly Active ◽  
Ultrasonic Assisted ◽  
Sulfur Capacity ◽  
Mcm 41

Co3O4/MCM-41 adsorbent with high surface area and more active sites was successfully prepared by ultrasonic assisted impregnation (UAI) technology and it has been found that the sulfur capacity was improved by 33.2% because of ultrasonication.

scholarly journals Bifunctional Materials for CO₂ Adsorption: Short Review

2021 ◽  
Vol 7 (2) ◽  
pp. 15-19
Author(s):  
S. M. Yusof ◽  
L. P. Teh
Keyword(s):  
Surface Area ◽  
Active Sites ◽  
Co2 Adsorption ◽  
High Surface ◽  
Co Adsorption ◽  
High Surface Area ◽  
Short Review ◽  
High Dispersion ◽  
High Porosity ◽  
Adsorption Performance

In recent years, there has been growing interest in adsorbents with high surface area, high porosity, high stability and high selectivity for CO2 adsorption. By the incorporation of the additive on the supports such as zeolite, silica, and carbon, the physicochemical properties of the adsorbent and CO2 adsorption performance can be enhanced. In this review, we focus on the overview of bifunctional materials (BFMs) for CO2 adsorption. The findings of this study suggests that the high surface area and high porosity of the support provide a good medium for high dispersion and accessibility of additives (amine or metal oxide), enhancing the CO2 adsorption efficiency. The excessive additive however may lead to a decrease of CO2 adsorption performance due to pore blockage and the decrease of active sites for CO2 interactions. The synergistic relationship of the supporting material and additive is significant towards the enhancement of CO2 adsorption.

scholarly journals Comparison of physicochemical properties and selective catalytic reduction activities of CeMn/TiO2 catalysts with and without phosphorus additives

2021 ◽  
Author(s):  
Zeycan KESKİN
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Catalyst Activity ◽  
High Surface ◽  
High Surface Area ◽  
Phosphorus Loading ◽  
X Ray Diffraction ◽  
Reduction Activity ◽  
Highly Active ◽  
Loading Amount

Abstract Lubricant additives contain phosphorus, which has a fly ash effect. Phosphorus negatively affects catalyst activity. Determining the effects of phosphorus loading amount on the catalytic activity is important for the development of catalysts with high NOx reduction. This study focuses on the control of NOx emissions, one of the air pollutants released from the diesel engine. The catalysts used in the reduction of NOx emissions were synthesized by washcoating method. Ce and Mn contents of all catalysts were adjusted as 3%, while the phosphorus contents of poisoned catalysts were adjusted as 0.5% and 1%. For this purpose, cordierite with high surface area was used. The catalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET), X-Ray diffraction (XRD) and ultraviolet visible spectroscopy (UV-Vis) analyzes. The NOx reduction activity of with and without phosphorus doped CeMn/TiO2 catalysts was investigated with the designed selective catalytic reduction system (SCR). NOx conversion ratios of the CeMn/TiO2 catalyst reached the high values of 84.6% at 280°C. After the phosphorus loading, the structure of the CeMn/TiO2 catalyst deteriorated, and the NOx conversion ratios decreased. 0.5P-CeMn/TiO2 and 1P-CeMn/TiO2 catalysts showed lower NOx conversion ratios compared to CeMn/TiO2 catalyst. CeMn-TiO2 catalyst was found highly active for SCR at all tests. Phosphorus loading caused deactivation of the catalyst and deactivation increased due to the increase in phosphorus loading amount.

Selective catalytic reduction of NO by NH3 over high surface area vanadia-silica catalysts

2001 ◽  
Vol 34 (3) ◽  
pp. 191-200 ◽  
Author(s):  
R.M Caraba ◽  
S.G Masters ◽  
K.M Eriksen ◽  
V.I Pârvulescu ◽  
R Fehrmann
Keyword(s):  
Selective Catalytic Reduction ◽  
Surface Area ◽  
Catalytic Reduction ◽  
High Surface ◽  
High Surface Area ◽  
Reduction Of No

scholarly journals Catalysis of Methanol-Air Mixture Using Platinum Nanoparticles for Microscale Combustion

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
James R. Applegate ◽  
Howard Pearlman ◽  
Smitesh D. Bakrania
Keyword(s):  
Surface Area ◽  
Platinum Nanoparticles ◽  
Flow Reactor ◽  
Catalyst Activity ◽  
High Surface ◽  
High Surface Area ◽  
Catalyst Loading ◽  
Bulk Temperature ◽  
Flow Parameters ◽  
The Stability

High surface area, active catalysts containing dispersed catalytic platinum nanoparticles (dp∼11.6 nm) on a cordierite substrate were fabricated and characterized using TEM, XRD, and SEM. The catalyst activity was evaluated for methanol oxidation. Experimental results were obtained in a miniature-scale continuous flow reactor. Subsequent studies on the effect of catalyst loading and reactor flow parameters are reported. Repeat tests were performed to assess the stability of the catalyst and the extent of deactivation, if any, that occurred due to restructuring and sintering of the particles. SEM characterization studies performed on the postreaction catalysts following repeat tests at reasonably high operating temperatures (∼500°C corresponding to ∼0.3Tmfor bulk platinum) showed evidence of sintering, yet the associated loss of surface area had minimal effect on the overall catalyst activity, as determined from bulk temperature measurements. The potential application of this work for improving catalytic devices including microscale reactors is also briefly discussed.

A porous Brønsted superacid as an efficient and durable solid catalyst

2018 ◽  
Vol 6 (38) ◽  
pp. 18712-18719 ◽  
Author(s):  
Qi Sun ◽  
Kewei Hu ◽  
Kunyue Leng ◽  
Xianfeng Yi ◽  
Briana Aguila ◽  
...  
Keyword(s):  
Surface Area ◽  
Active Sites ◽  
High Surface ◽  
High Surface Area ◽  
Solid Catalyst ◽  
Chemical Transformations ◽  
Catalytic Activities ◽  
Industrial Chemical

A porous superacid material with a high surface area and abundant accessible active sites is rationally designed, showing outstanding catalytic activities and durability in industrial chemical transformations.

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