scholarly journals Co-blending modification of activated coke using pyrolusite and titanium ore for low-temperature NOx removal

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Lin Yang ◽  
Lu Yao ◽  
Yuguo Lai ◽  
Xia Jiang ◽  
Wenju Jiang
Keyword(s):  
Mass Transfer ◽  
Electron Transfer ◽  
Low Temperature ◽  
Active Sites ◽  
Surface Acidity ◽  
Catalytic Performance ◽  
Bridge Structure ◽  
Nox Removal ◽  
No Removal ◽  
Activated Coke

Abstract Activated coke (AC) has great potential in the field of low-temperature NO removal (DeNOx), especially the branch prepared by blending modification. In this study, the AC-based pyrolusite and/or titanium ore blended catalysts were prepared and applied for DeNOx. The results show blending pyrolusite and titanium ore promoted the catalytic performance of AC (Px@AC, Tix@AC) clearly, and the co-blending of two of them showed a synergistic effect. The (P/Ti-1/2)15@AC performed the highest NO conversion of 66.4%, improved 16.9% and 16.0% respectively compared with P15@AC and Ti15@AC. For the (P/Ti-1/2)15@AC DeNOx, its relative better porous structure (SBET = 364 m2/g, Vmic = 0.156 cm3/g) makes better mass transfer and more active sites exposure, stronger surface acidity (C–O, 19.43%; C=O, 4.16%) is more favorable to the NH3 adsorption, and Ti, Mn and Fe formed bridge structure fasted the lactic oxygen recovery and electron transfer. The DeNOx of (P/Ti-1/2)15@AC followed both the E–R and L–H mechanism, both the gaseous and adsorbed NO reacted with the activated NH3 due to the active sites provided by both the carbon and titanium.

scholarly journals Designing a Mesoporous Zeolite Catalyst for Products Optimizing in n-Decane Hydrocraking

Catalysts ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 766 ◽  
Author(s):  
Li Tan ◽  
Xiaoyu Guo ◽  
Xinhua Gao ◽  
Noritatsu Tsubaki
Keyword(s):  
Mass Transfer ◽  
Active Sites ◽  
Zeolite Catalyst ◽  
Catalytic Performance ◽  
Hydrogen Spillover ◽  
Mesoporous Zeolite ◽  
Mesoporous Catalyst ◽  
Hydrogen Atoms ◽  
Effect Factors ◽  
And Diffusion

Mesoporous ZSM-5 zeolite is developed to enhance the catalytic performance in a hydrocracking reaction. The generated mesopores and mesoporous channels in the new catalyst supply more opportunities for reactant accessing the active sites according to the better mass transfer and diffusion. Meanwhile, the acidity of the mesoporous catalyst is also weakened because of the removal of Si and Al species from its MFI structure, which makes the products distribution drift to more valued chemicals such as olefins. In the modified mesoporous ZSM-5 zeolites via different metallic promoters, the olefins’ selectivity increases as the alkalinity of the catalyst increases. The reason for this is that the formed olefins will be further hydrogenated into corresponding alkanes immediately over the extremely acidic zeolite catalyst. Hence, the moderate alkalinity will limit this process, while at the same time the remaining olefins products will too. Furthermore, the Pd-based mesoporous ZSM-5 zeolite shows an excellent n-decane conversion and high propane selectivity due to the occurrence of hydrogen spillover via the Pd promoter. The phenomenon of hydrogen spillover supplies more chemisorbed sites of hydrogen atoms for hydrocracking and hydrogenating in this reaction. In short, this study explores the important effect factors in n-decane hydrocracking reaction activity and products distribution. It also shows a potential for the further industrial application of petroleum-derived fuel hydrocracking according to the optimized products distribution under metallic promoted mesoporous zeolite.

Catalytic Oxidation of Formaldehyde Over Mesoporous MnOx-CeO2 Catalysts

2015 ◽  
Vol 14 (01n02) ◽  
pp. 1460028 ◽  
Author(s):  
Yanlei Zhao ◽  
Hua Tian ◽  
Junhui He ◽  
Qiaowen Yang
Keyword(s):  
Low Temperature ◽  
Indoor Air ◽  
Active Sites ◽  
Harmful Effect ◽  
Practical Interest ◽  
Catalytic Performance ◽  
Air Pollutant ◽  
Ordered Mesoporous ◽  
Formaldehyde Oxidation ◽  
Catalytic Performances

Formaldehyde is regarded as the major indoor air pollutant. Because of harmful effect on human health, its emission abatement is of significant practical interest. We report here excellent low-temperature catalytic performances of mesoporous MnO x - CeO 2 catalysts in the process of formaldehyde oxidation. These MnO x - CeO 2 catalysts were synthesized by a "nanocasting" method using SBA-15 as hard template. TEM images showed that the as-fabricated MnO x - CeO 2 composites possess well-ordered mesoporous architectures. Results of catalytic tests revealed that mesoporous MnO x - CeO 2 nanocomposites have excellent low-temperature catalytic activity for formaldehyde oxidation, the temperature for 100% formaldehyde conversion can be as low as 65°C over these noble-metal-free mesoporous catalysts. The excellent catalytic performance is attributed to their ordered mesoporous structures that expose abundant active sites to formaldehyde molecules.

Suitability of pyrolusite as additive to activated coke for low‐temperature NO removal

2017 ◽  
Vol 93 (3) ◽  
pp. 690-697 ◽  
Author(s):  
Lin Yang ◽  
Wenju Jiang ◽  
Lu Yao ◽  
Xia Jiang ◽  
Jianjun Li
Keyword(s):  
Low Temperature ◽  
No Removal ◽  
Activated Coke

scholarly journals Co-Promoted Ni Nanocatalysts Derived from NiCoAl-LDHs for Low Temperature CO2 Methanation

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 121
Author(s):  
Fanying Zhang ◽  
Bin Lu ◽  
Peiqin Sun
Keyword(s):  
Low Temperature ◽  
Active Sites ◽  
High Performance ◽  
Carbon Deposition ◽  
Catalytic Performance ◽  
Ni Nanoparticles ◽  
Co2 Methanation ◽  
Test Conditions ◽  
Challenging Research ◽  
Continuous Reaction

Ni-based catalysts are prone to agglomeration and carbon deposition at high temperatures. Therefore, the development of Ni-based catalysts with high activities at low temperatures is a very urgent and challenging research topic. Herein, Ni-based nanocatalysts containing Co promoter with mosaic structure were prepared by reduction of NiCoAl-LDHs, and used for CO2 methanation. When the reaction temperature is 250 °C (0.1 MPa, GHSV = 30,000 mL·g−1·h−1), the conversion of CO2 on the NiCo0.5Al-R catalyst reaches 81%. However, under the same test conditions, the conversion of CO2 on the NiAl-R catalyst is only 26%. The low-temperature activity is significantly improved due to Co which can effectively control the size of the Ni particles, so that the catalyst contains more active sites. The CO2-TPD results show that the Co can also regulate the number of moderately basic sites in the catalyst, which is beneficial to increase the amount of CO2 adsorbed. More importantly, the NiCo0.5Al-R catalyst still maintains high catalytic performance after 92 h of continuous reaction. This is due to the confinement effect of the AlOx substrate inhibiting the agglomeration of Ni nanoparticles. The Ni-based catalysts with high performance at low temperature and high stability prepared by the method used have broad industrial application prospects.

scholarly journals Bridging Adsorption Analytics and Catalytic Kinetics for Metal-Exchanged Zeolites

2020 ◽  
Author(s):  
Pengfei Xie ◽  
Tiancheng Pu ◽  
Gregory Aranovich ◽  
Jiawei Guo ◽  
Marc Donohue ◽  
...  
Keyword(s):  
Low Temperature ◽  
Active Sites ◽  
Molecular Spectroscopy ◽  
Catalytic Performance ◽  
Quantitative Information ◽  
Adsorption Properties ◽  
Structure Property ◽  
Atomic Structures ◽  
Structure Property Relationships ◽  
High Temperature Reaction

Abstract Metal-exchanged zeolites have been widely used in industrial catalysis and separation, but fundamental understanding of their structure-property relationships has remained challenging, largely due to the lack of quantitative information concerning the atomic structures and reaction-relevant adsorption properties of the embedded metal active sites. We report on the use of low-temperature chemisorption to titrate Cu-exchanged ZSM5. Quantitative descriptors of the atomic structures and adsorption properties of Cu-ZSM5 are established by combining atomistic simulation, DFT calculations, operando molecular spectroscopy, chemisorption and titration measurements. These descriptors are then applied to interpret the catalytic performance of Cu-ZSM5 for NO decomposition. Linear correlations are established to bridge the low-temperature adsorption analytics and high-temperature reaction kinetics, which are demonstrated to be generally applicable for understanding the structure-property relationships of metal exchanged zeolites and foregrounded for guiding the development of advanced catalytic materials.

scholarly journals NO Removal by Plasma-Enhanced NH3-SCR Using Methane as an Assistant Reduction Agent at Low Temperature

2019 ◽  
Vol 9 (13) ◽  
pp. 2751 ◽  
Author(s):  
Weixuan Zhao ◽  
Yanghaichao Liu ◽  
Heng Wei ◽  
Renxi Zhang ◽  
Gang Luo ◽  
...  
Keyword(s):  
Low Temperature ◽  
Reaction System ◽  
Excess Oxygen ◽  
Nox Removal ◽  
No Removal ◽  
Promotion Effect ◽  
Nh3 Scr ◽  
O2 Concentration ◽  
New Process ◽  
Better Than

The effects of using CH4 as an assistant reduction agent in plasma-assisted NH3–SCR were investigated. The new hybrid reaction system performed better than DBD–NH3–SCR when the O2 concentration varied from 2% to 12%. Compared with DBD–NH3–SCR, DBD–NH3–CH4–SCR (NH3:CH4 = 1:1) showed a more significant promotion effect on the performance and N2 selectivity for NOX abatement. When the O2 concentration was 6% and the SIE was 512 J/L, the NO removal efficiency of the new hybrid system reached 84.5%. The outlet gas components were observed via FTIR to reveal the decomposition process and its mechanism. This work indicated that CH4, as an assistant agent, enhances DBD–NH3–SCR in excess oxygen to achieve a new process with significantly higher activity at a low temperature (≤348 K) for NOX removal.

Promoting effects of ceria on the catalytic performance of gold supported on TiO2 for low-temperature CO oxidation

RSC Advances ◽  
2014 ◽  
Vol 4 (33) ◽  
pp. 16985-16991 ◽  
Author(s):  
Jun Yu ◽  
Guisheng Wu ◽  
Guanzhong Lu ◽  
Dongsen Mao ◽  
Yun Guo
Keyword(s):  
Low Temperature ◽  
Co Oxidation ◽  
Active Sites ◽  
High Stability ◽  
Oxygen Vacancies ◽  
Catalytic Performance ◽  
Quick Recovery ◽  
Low Temperature Co Oxidation

Doping with Ce enhanced the Au–support synergy and modified the active sites. The effortless decomposition of carbonates and quick recovery of oxygen vacancies on the Au/CeO2–TiO2 surface may be responsible for its high stability.

scholarly journals Selective Catalytic Reduction of NO by NH3 Using a Combination of Non-Thermal Plasma and Mn-Cu/ZSM5 Catalyst

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1044
Author(s):  
Tao Zhu ◽  
Xing Zhang ◽  
Wenfeng Niu ◽  
Yatao Liu ◽  
Bo Yuan ◽  
...  
Keyword(s):  
Energy Density ◽  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Removal Efficiency ◽  
Thermal Plasma ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
High Energy ◽  
No Removal ◽  
Non Thermal Plasma

Dielectric barrier discharge (DBD) could generate non-thermal plasma (NTP) with the advantage of fast reactivity and high energy under atmosphere pressure and low-temperature. The presented work investigated the selective catalytic reduction (SCR) of nitric oxide (NO) using a combination of NTP and an Mn-Cu/ZSM5 catalyst with ammonia (NH3) as a reductant. The experimental results illustrate that the plasma-assisted SCR process enhances the low-temperature catalytic performance of the Mn-Cu/ZSM5 catalyst significantly, and it exhibits an obvious improvement in the NO removal efficiency. The reaction temperature is maintained at 200 °C in order to simulate the exhaust temperature of diesel engine, and the 10% Mn-8% Cu/ZSM5 catalyst shows the highest NO removal performance with about 93.89% at an energy density of 500 J L−1 and the selectivity to N2 is almost 99%. The voltage, frequency and energy density have a positive correlation to NO removal efficiency, which is positively correlated with the power of NTP system. In contrast, the O2 concentration has a negative correlation to the NO removal, and the NO removal efficiency cannot be improved when the NO removal process reaches reaction equilibrium in the NTP system.

scholarly journals Proposal of a Facile Method to Fabricate a Multi-Dope Multiwall Carbon Nanotube as a Metal-Free Electrocatalyst for the Oxygen Reduction Reaction

2022 ◽  
Vol 14 (2) ◽  
pp. 965
Author(s):  
Sara Bakhtavar ◽  
Mehdi Mehrpooya ◽  
Mahboobeh Manoochehri ◽  
Mehrnoosh Karimkhani
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Electron Transfer ◽  
Low Temperature ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Multiwall Carbon Nanotube ◽  
Multiwall Carbon

In this study, a one-pot, low-temperature synthesis method is considered for the fabrication of heteroatom dope multiwall carbon nanotubes (MWCNT). Doped MWCNT is utilized as an effective electrocatalyst for oxygen reduction reaction (ORR). Single, double, and triple doping of boron, nitrogen and sulfur elements are utilized as the dopants. A reflux system with temperature of 180 °C is implemented in the doping procedure. Actually, unlike the previous studies in which doping on the carbon structures was performed using a furnace at temperatures above 700 °C, in this green and sustainable method, the triple doping on MWCNT is conducted at atmospheric pressure and low temperature. The morphology and structure of the fabricated catalysts were evaluated by Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Raman spectroscopy. According to the results, the nanoparticles were encapsulated in the carbon nanotubes. Aggregated clusters of the sulfur in the case of S-MWCNT are considerable. Cyclic voltammetry (CV), rotating disk electrode, linear sweep voltammetry (LSV), and chronoamperometry electrochemical tests are employed for assessing the oxygen reduction activity of the catalysts. The results illustrate that by using this doping method, the onset potential shifts to positive values towards the oxidized MWCNT. It can be deduced that by doping the N, B, and S atoms on MWCNTs, the defects in the CNT structure, which serve as active sites for ORR application, increase. The N/S/B-doped graphitic layers have a more rapid electron transfer rate at the electrode/electrolyte interface. Thus, this can improve the electrochemistry performance and electron transfer of the MWCNTs. The best performance and electrochemical activity belonged to the NB-MWCNT catalyst (−0.122 V vs. Ag/AgCl). Also, based on the results gained from the Koutecky–Levich (KL) plot, it can be said that the ORR takes place through the 4 e− pathway.

Oxygen defect engineering in cobalt iron oxide nanosheets for promoted overall water splitting

2019 ◽  
Vol 7 (38) ◽  
pp. 21704-21710 ◽  
Author(s):  
Chengying Guo ◽  
Xuejing Liu ◽  
Lingfeng Gao ◽  
Xiaojing Ma ◽  
Mingzhu Zhao ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Water Splitting ◽  
Active Sites ◽  
Oxygen Vacancies ◽  
Catalytic Performance ◽  
Oxygen Defect ◽  
Defect Engineering ◽  
Transfer Property ◽  
Cobalt Iron Oxide ◽  
Cobalt Iron

Benefited from the optimized activity of active sites, adsorption energy and the proposed electron transfer property, the CoFe2O4 nanosheet with oxygen vacancies exhibited significantly enhanced water splitting catalytic performance.

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