scholarly journals Enhancing Methane Aromatization Performance by Reducing the Particle Size of Molybdenum Oxide

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1991
Author(s):  
Jing Hu ◽  
Jinghai Liu ◽  
Jinglin Liu ◽  
Yangyang Li ◽  
Peihe Li ◽  
...  
Keyword(s):  
Molybdenum Oxide ◽  
Type Species ◽  
Active Sites ◽  
High Performance ◽  
Acid Sites ◽  
Reaction Conditions ◽  
Methane Aromatization ◽  
Synthetic Strategy ◽  
Aromatization Reaction ◽  
Molybdenum Oxide Nanoparticles

Efficient use of natural gas to produce aromatics is an attractive subject; the process requires catalysts that possess high-performance active sites to activate stable C–H bonds. Here, we report a facile synthetic strategy to modify HMCM-49 with small molybdenum oxide nanoparticles. Due to the higher sublimability of nano-MoO3 particles than commercial MoO3, they more easily enter into the channels of HMCM-49 and associate with Brønsted acid sites to form active MoCx-type species under calcination and reaction conditions. Compared with commercial MoO3 modified MCM-49, nano-MoO3 modified MCM-49 exhibits higher methane conversion (13.2%), higher aromatics yield (9.1%), and better stability for the methane aromatization reaction.

scholarly journals The Effect of Preparation Method of Ni-Supported SiO2 Catalysts for Carbon Dioxide Reforming of Methane

Catalysts ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1221
Author(s):  
Hua-Ping Ren ◽  
Si-Yi Ding ◽  
Qiang Ma ◽  
Wen-Qi Song ◽  
Yu-Zhen Zhao ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Particle Size ◽  
Active Sites ◽  
High Performance ◽  
Preparation Method ◽  
Complexing Agent ◽  
Preparation Process ◽  
Carbon Dioxide Reforming ◽  
Preparation Methods ◽  
Synthetic Strategy

Reforming methane to produce syngas is a subject that generates considerable interest. The process requires catalysts that possess high-performance active sites to activate stable C–H bonds. Herein, we report a facile synthetic strategy to prepare Ni-based catalysts by complexation–impregnation (Ni-G/SiO2-C) and precipitation–impregnation (Ni-G/SiO2-P) methods using glycine as a complexing agent. The particle size of Ni in both types of catalysts is decreased by adding glycine in the preparation process. Nevertheless, the preparation methods and amount of glycine play a significant role in the particle size and distribution of Ni over the Ni-based catalysts. The smaller particle size and narrower distribution of Ni were obtained in the Ni-G/SiO2-P catalyst. The catalysts were comparatively tested for carbon-dioxide reforming of methane (CDR). Ni-G/SiO2-P showed better CDR performance than Ni-G/SiO2-C and Ni/SiO2 and increased stability because of the smaller particle size and narrower distribution of Ni. Moreover, a high-performance Ni-based catalyst was prepared by optimizing the amount of glycine added. An unobservable deactivation was obtained over Ni-G-2/SiO2-P and Ni-G-3/SiO2-P for CDR during TOS = 20 h. Thus, a new promising method is described for the preparation of Ni-based catalysts for CDR.

scholarly journals Synthesis of SAPO-34 Nanoplates with High Si/Al Ratio and Improved Acid Site Density

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3198
Author(s):  
Syed Fakhar Alam ◽  
Min-Zy Kim ◽  
Aafaq ur Rehman ◽  
Devipriyanka Arepalli ◽  
Pankaj Sharma ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Molecular Sieves ◽  
Active Sites ◽  
High Performance ◽  
Hydrothermal Process ◽  
Acid Sites ◽  
High Density ◽  
Structure Directing Agent ◽  
Transfer Resistance ◽  
Low Mass

Two-dimensional SAPO-34 molecular sieves were synthesized by microwave hydrothermal process. The concentrations of structure directing agent (SDA), phosphoric acid, and silicon in the gel solution were varied and their effect on phase, shape, and composition of synthesized particles was studied. The synthesized particles were characterized by various techniques using SEM, XRD, BET, EDX, and NH3-TPD. Various morphologies of particles including isotropic, hyper rectangle, and nanoplates were obtained. It was found that the Si/Al ratio of the SAPO-34 particles was in a direct relationship with the density of acid sites. Moreover, the gel composition and preparation affected the chemistry of the synthesized particles. The slow addition of phosphoric acid improved the homogeneity of synthesis gel and resulted in SAPO-34 nanoplates with high density of acid sites, 3.482 mmol/g. The SAPO-34 nanoplates are expected to serve as a high performance catalyst due to the low mass transfer resistance and the high density of active sites.

scholarly journals Vapor-Phase Furfural Decarbonylation over a High-Performance Catalyst of 1%Pt/SBA-15

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1304
Author(s):  
Qiang Yuan ◽  
Jifeng Pang ◽  
Wenguang Yu ◽  
Mingyuan Zheng
Keyword(s):  
High Performance ◽  
Catalyst Support ◽  
Pt Nanoparticles ◽  
Space Velocity ◽  
Acid Sites ◽  
Pt Catalyst ◽  
Reaction Conditions ◽  
Weight Hourly Space Velocity ◽  
Wide Range ◽  
Superior Property

A high-performance Pt catalyst supported on SBA-15 was developed for furfural decarbonylation. Compared to Pt catalysts loaded on microporous DeAl-Hbeta zeolite and hierarchical micro-mesoporous MFI nanosheet (NS) materials, the 1%Pt/SBA-15 catalyst afforded notably higher activity, furan selectivity and stability owing to the negligible acid sites and proper mesopores on the SBA-15 support. Among a set of 1%Pt/SBA-15 catalysts bearing Pt nanoparticles (NPs) with sizes of 2.4–4.3 nm, the catalyst with 3.7 nm Pt NPs afforded the highest furan selectivity. Over the optimal catalyst, 88.6% furan selectivity and ca. 90% furfural conversion were obtained at 573 K and a high weight hourly space velocity (WHSV) of 16.5 h−1. Moreover, the reaction temperatures at 440–573 K and the ratios of H2 to furfural at 0.79–9.44 did not affect the reaction selectivity notably, showing that the reaction over 1%Pt/SBA-15 can be conducted over a wide range of conditions. The catalyst was stable under the harsh reaction conditions and lasted for 90 h without significant deactivation, demonstrating the superior property of SBA-15 as a catalyst support for furfural decarbonylation.

scholarly journals Highly Efficient Synthesis of Glucose Fatty Acid Esters Catalyzed by High Performance Lipase Preparations

2021 ◽  
Vol 33 (10) ◽  
pp. 2489-2497
Author(s):  
Benu Arora
Keyword(s):  
Fatty Acid ◽  
High Performance ◽  
Acyl Chain ◽  
Solvent System ◽  
Fatty Acid Esters ◽  
Acyl Donor ◽  
Reaction Conditions ◽  
Acyl Chain Length ◽  
Synthetic Strategy ◽  
Acid Esters

Glucose fatty acid esters were synthesized using cross-linked enzyme aggregates (CLEAs), protein coated microcrystals (PCMCs) and cross-linked protein coated microcrystals (CLPCMCs) of Candida antarctica lipase B (CALB) as biocatalyst designs in single and mixed solvent systems. Up to 90% conversion and more than 99% regioselectivity were obtained using vinyl acetate as the acyl donor in a solvent system composed of 2-methyl-2-butanol (2M2B) and 30% (v/v) DMSO, with CALB CLEAs within 45 min. Similar results were obtained with CALB CLPCMCs as the biocatalyst under the same reaction conditions. This approach was then extended to the synthesis of glucose esters with higher acyl chain length. The synthetic strategy used in this work can potentially be extended for the fast and regioselective esterification/transesterification of other sugars as well.

scholarly journals Delocalized electron effect on single metal sites in ultrathin conjugated microporous polymer nanosheets for boosting CO2 cycloaddition

2020 ◽  
Vol 6 (17) ◽  
pp. eaaz4824 ◽  
Author(s):  
Xiaofei Zhang ◽  
Haitao Liu ◽  
Pengfei An ◽  
Yanan Shi ◽  
Jianyu Han ◽  
...  
Keyword(s):  
Oxidation State ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Acid Sites ◽  
Molecular Engineering ◽  
Reaction Conditions ◽  
Tert Butyl ◽  
Conjugated Microporous Polymer ◽  
Microporous Polymer ◽  
Delocalized Electron

CO2 cycloaddition with epoxides at low temperature and pressure has been broadly recognized as an ambitious but challenging goal, which requires the catalysts to have precisely controlled Lewis acid sites. Here, we demonstrate that both stereochemical environment and oxidation state of single cobalt active sites in cobalt tetraaminophthalocyanine [CoPc(NH2)4] are finely tuned via molecular engineering with 2,5-di-tert-butyl-1,4-benzoquinone (DTBBQ). Notably, DTBBQ incorporation not only enables formation of 5-nm-thick conjugated microporous polymer (CMP) nanosheets due to the steric hindrance effect of tert-butyl groups but also makes isolated cobalt sites with high oxidation state due to the presence of delocalized electron-withdrawing effect of alkene groups in DTBBQ via conjugated skeleton. Notably, when used as heterogeneous catalysts for CO2 cycloaddition with different epoxides, single cobalt active sites on the ultrathin CMP nanosheets exhibit unprecedentedly high activity and excellent stability under mild reaction conditions.

scholarly journals High-Performance Chlorine-Doped Cu2O Catalysts for the Ethynylation of Formaldehyde

Processes ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 198
Author(s):  
Jie Gao ◽  
Guofeng Yang ◽  
Haitao Li ◽  
Mei Dong ◽  
Zhipeng Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Bond Strength ◽  
Reaction Temperature ◽  
Active Sites ◽  
High Performance ◽  
Lattice Structure ◽  
Reaction Conditions ◽  
Simple Strategy ◽  
Co Precipitation

The in situ formed Cu+ species serve as active sites in the ethynylation of formaldehyde. The key problem that needs to be solved in this process is how to avoid excessive reduction of Cu2+ to inactive metallic Cu, which tends to decrease the catalytic activity. In this work, Cl−-modified Cu2O catalysts with different Cl content were prepared by co-precipitation. The characterization results demonstrated that Cl− remained in the lattice structure of Cu2O, inducing the expansion of the Cu2O lattice and the enhancement of the Cu–O bond strength. Consequently, the reduction of Cu+ to Cu0 was effectively prevented in reductive media. Moreover, the activity and stability of Cu2O were significantly improved. The Cl− modification increased the yield of 1,4-butynediol (BD) from 73% to 94% at a reaction temperature of 90 °C. More importantly, the BD yield of Cl− modified Cu2O was still as high as 86% during the ten-cycle experiment, whereas the BD yield of Cu2O in the absence of Cl− decreased sharply to 17% at the same reaction conditions. This work provides a simple strategy to stabilize Cu+ in reductive media.

Core-shell nanostructured Zn-Co-O@CoS arrays for high-performance hybrid supercapacitors

2021 ◽  
Author(s):  
Yi He ◽  
Lei Xie ◽  
Shixiang Ding ◽  
Yujia Long ◽  
Xinyi Zhou ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Energy Storage ◽  
Active Sites ◽  
High Performance ◽  
Electronic Conductivity ◽  
Wide Distribution ◽  
Energy Storage Materials ◽  
Core Shell ◽  
Storage Materials ◽  
Hybrid Supercapacitors

Although the zinc oxide (ZnO) with wide distribution is one of the most attractive energy storage materials, the low electronic conductivity and insufficient active sites of bulk ZnO increase the...

scholarly journals Efficient Catalytic Conversion of Polysulfides by Biomimetic Design of “Branch-Leaf” Electrode for High-Energy Sodium–Sulfur Batteries

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Wenyan Du ◽  
Kangqi Shen ◽  
Yuruo Qi ◽  
Wei Gao ◽  
Mengli Tao ◽  
...  
Keyword(s):  
Active Sites ◽  
High Performance ◽  
Electrochemical Reaction ◽  
Molecular Layer ◽  
Specific Capacity ◽  
High Energy ◽  
Reduction Reaction ◽  
Biomimetic Design ◽  
Co Nanoparticles ◽  
Sodium Sulfur

AbstractRechargeable room temperature sodium–sulfur (RT Na–S) batteries are seriously limited by low sulfur utilization and sluggish electrochemical reaction activity of polysulfide intermediates. Herein, a 3D “branch-leaf” biomimetic design proposed for high performance Na–S batteries, where the leaves constructed from Co nanoparticles on carbon nanofibers (CNF) are fully to expose the active sites of Co. The CNF network acts as conductive “branches” to ensure adequate electron and electrolyte supply for the Co leaves. As an effective electrocatalytic battery system, the 3D “branch-leaf” conductive network with abundant active sites and voids can effectively trap polysulfides and provide plentiful electron/ions pathways for electrochemical reaction. DFT calculation reveals that the Co nanoparticles can induce the formation of a unique Co–S–Na molecular layer on the Co surface, which can enable a fast reduction reaction of the polysulfides. Therefore, the prepared “branch-leaf” CNF-L@Co/S electrode exhibits a high initial specific capacity of 1201 mAh g−1 at 0.1 C and superior rate performance.

scholarly journals N, S and Transition-Metal Co-Doped Graphene Nanocomposites as High-Performance Catalyst for Glucose Oxidation in a Direct Glucose Alkaline Fuel Cell

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 202
Author(s):  
Yexin Dai ◽  
Jie Ding ◽  
Jingyu Li ◽  
Yang Li ◽  
Yanping Zong ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Active Sites ◽  
High Performance ◽  
Glucose Oxidation ◽  
Alkaline Fuel Cell ◽  
Blank Group ◽  
Graphene Nanocomposites ◽  
Doped Graphene ◽  
One Step ◽  
Hydrothermal Approach

In this work, reduced graphene oxide (rGO) nanocomposites doped with nitrogen (N), sulfur (S) and transitional metal (Ni, Co, Fe) were synthesized by using a simple one-step in-situ hydrothermal approach. Electrochemical characterization showed that rGO-NS-Ni was the most prominent catalyst for glucose oxidation. The current density of the direct glucose alkaline fuel cell (DGAFC) with rGO-NS-Ni as the anode catalyst reached 148.0 mA/cm2, which was 40.82% higher than the blank group. The DGAFC exhibited a maximum power density of 48 W/m2, which was more than 2.08 folds than that of blank group. The catalyst was further characterized by SEM, XPS and Raman. It was speculated that the boosted performance was due to the synergistic effect of N, S-doped rGO and the metallic redox couples, (Ni2+/Ni3+, Co2+/Co3+ and Fe2+/Fe3+), which created more active sites and accelerated electron transfer. This research can provide insights for the development of environmental benign catalysts and promote the application of the DGAFCs.

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