scholarly journals Catalytic Conversion of Lignin in an Isopropanol/formic Acid Medium With Nimo Catalyst Promoted by W Species

2021 ◽  
Author(s):  
Xinyu Lu ◽  
Hossain Mahmud Robin ◽  
Haoquan Guo ◽  
Dandan Wang ◽  
Pengcheng Xiu ◽  
...  
Keyword(s):  
Formic Acid ◽  
Active Sites ◽  
Chemical Properties ◽  
Acid Sites ◽  
Hydrolysis Lignin ◽  
Remarkable Effect ◽  
Product Evolution ◽  
Stable Chemical ◽  
Nimo Catalysts

Abstract Background: Large amounts of enzymatic hydrolysis lignin (EHL) are generated with the production of cellulosic bioethanol. Efficient degradation and upgrading of EHL is significant for the sustainable and stable development of energy supply.Results: In this study, hydrodeoxygenation (HDO) of EHL to biofuels was carried out promoted by the in situ hydrogen donor produced from the decomposition of formic acid over NiMo catalysts. Results showed that active sites (derived from the support SiO2, W, and NiMo species) had remarkable effect on lignin conversion, and the highest oil yield (57.2 wt%) was gained over NiMo/W-SiO2 catalyst. Conclusions: The product evolution demonstrated that active metal sites (derived from NiMo species) favored hydrogenolysis and deoxygenation via leading in situ hydrogen to attack C-O-C bonds, while acid sites (derived from the support) adsorbed and activated chemical bonds in lignin, resulting in the linkage cleavage caused by the heating program. The obtained bio-oil was rich in alkyl guaiacols (6.7 wt%), containing stable chemical properties and high quality.

scholarly journals Influence of the ZrO2 Crystalline Phases on the Nature of Active Sites in PdCu/ZrO2 Catalysts for the Methanol Steam Reforming Reaction—An In Situ Spectroscopic Study

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1005
Author(s):  
Daniel Ruano ◽  
Beatriz M. Pabón ◽  
Càtia Azenha ◽  
Cecilia Mateos-Pedrero ◽  
Adélio Mendes ◽  
...  
Keyword(s):  
Steam Reforming ◽  
Active Sites ◽  
Surface Composition ◽  
Ambient Pressure ◽  
Chemical Properties ◽  
Spectroscopic Studies ◽  
Metal Species ◽  
Methanol Steam Reforming ◽  
Reaction Products

In this work, the electronic properties of the metal sites in cubic and monoclinic ZrO2 supported Pd and PdCu catalysts have been investigated using CO as probe molecule in in-situ IR studies, and the surface composition of the outermost layers has been studied by APXPS (Ambient Pressure X-ray Photoemission Spectroscopy). The reaction products were followed by mass spectrometry, making it possible to relate the chemical properties of the catalysts under reaction conditions with their selectivity. Combining these techniques, it has been shown that the structure of the support (monoclinic or cubic ZrO2) affects the metal dispersion, mobility, and reorganization of metal sites under methanol steam reforming (MSR) conditions, influencing the oxidation state of surface metal species, with important consequences in the catalytic activity. Correlating the mass spectra of the reaction products with these spectroscopic studies, it was possible to conclude that electropositive metal species play an imperative role for high CO2 and H2 selectivity in the MSR reaction (less CO formation).

scholarly journals Influence of Biomass Inorganics on the Functionality of H+ZSM-5 Catalyst during In-Situ Catalytic Fast Pyrolysis

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 124
Author(s):  
Ravishankar Mahadevan ◽  
Sushil Adhikari ◽  
Rajdeep Shakya ◽  
Oladiran Fasina
Keyword(s):  
Aromatic Hydrocarbons ◽  
Active Sites ◽  
Acid Sites ◽  
Diffusion Resistance ◽  
Progressive Reduction ◽  
Fresh Catalyst ◽  
Oxygenated Compounds ◽  
Benzene Toluene ◽  
And Diffusion

In this study, the contamination of H+ZSM-5 catalyst by calcium, potassium and sodium was investigated by deactivating the catalyst with various concentrations of these inorganics, and the subsequent changes in the properties of the catalyst are reported. Specific surface area analysis of the catalysts revealed a progressive reduction with increasing concentrations of the inorganics, which could be attributed to pore blocking and diffusion resistance. Chemisorption studies (NH3-TPD) showed that the Bronsted acid sites on the catalyst had reacted with potassium and sodium, resulting in a clear loss of active sites, whereas the presence of calcium did not appear to cause extensive chemical deactivation. Pyrolysis experiments revealed the progressive loss in catalytic activity, evident due the shift in selectivity from producing only aromatic hydrocarbons (benzene, toluene, xylene, naphthalenes and others) with the fresh catalyst to oxygenated compounds such as phenols, guaiacols, furans and ketones with increasing contamination by the inorganics. The carbon yield of aromatic hydrocarbons decreased from 22.3% with the fresh catalyst to 1.4% and 2.1% when deactivated by potassium and sodium at 2 wt %, respectively. However, calcium appears to only cause physical deactivation.

scholarly journals Multifunctional Coatings of Titanium Implants Toward Promoting Osseointegration and Preventing Infection: Recent Developments

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaoxuan Lu ◽  
Zichen Wu ◽  
Kehui Xu ◽  
Xiaowei Wang ◽  
Shuang Wang ◽  
...  
Keyword(s):  
Antibacterial Properties ◽  
Chemical Properties ◽  
Inflammatory Cells ◽  
Titanium Implants ◽  
Stable Chemical ◽  
Recent Developments ◽  
Good Biocompatibility ◽  
Biological Environment ◽  
Insight Into

Titanium and its alloys are dominant material for orthopedic/dental implants due to their stable chemical properties and good biocompatibility. However, aseptic loosening and peri-implant infection remain problems that may lead to implant removal eventually. The ideal orthopedic implant should possess both osteogenic and antibacterial properties and do proper assistance to in situ inflammatory cells for anti-microbe and tissue repair. Recent advances in surface modification have provided various strategies to procure the harmonious relationship between implant and its microenvironment. In this review, we provide an overview of the latest strategies to endow titanium implants with bio-function and anti-infection properties. We state the methods they use to preparing these efficient surfaces and offer further insight into the interaction between these devices and the local biological environment. Finally, we discuss the unmet needs and current challenges in the development of ideal materials for bone implantation.

scholarly journals Synthesis of Ni-Modified ZSM-5 Zeolites and Their Catalytic Performance in n-Octane Hydroconversion

2020 ◽  
Vol 8 ◽  
Author(s):  
Qiang Wei ◽  
Pengfei Zhang ◽  
Xiaodong Liu ◽  
Wenbin Huang ◽  
Xiayun Fan ◽  
...  
Keyword(s):  
Supported Catalysts ◽  
Synthesis Method ◽  
Textural Properties ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Impregnation Method ◽  
Isomerization Selectivity ◽  
Nimo Catalysts ◽  
Adsorption Desorption

Ni-modified ZSM-5 zeolites with different nickel contents were successfully prepared by the in situ synthesis method and the impregnation method. The synthesized samples were characterized by XRD, SEM, N2 adsorption–desorption isothermals, and Py-FTIR. The characterization results show that both the textural properties and crystallization of Ni-modified ZSM-5 zeolites were preserved well, and their acidic properties can be modulated after nickel modification. The corresponding NiMo catalysts supported on Ni-modified ZSM-5 zeolites were prepared by the incipient wetness co-impregnation method, and their catalytic performances were evaluated in n-octane hydroconversion. Compared to the those modified by the in situ synthesis method, ZSM-5 zeolite-supported catalysts modified by the impregnation method exhibit higher stability and higher isomerization selectivity. This is due to the synergistic effect between Brønsted acid sites and Lewis acid sites on the Ni-modified ZSM-5 zeolites, especially for the NiMo/1Ni-Z5 catalyst.

scholarly journals Promoting Effect of Mn on In Situ Synthesized Cu-SSZ-13 for NH3-SCR

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1375
Author(s):  
Jinpeng Du ◽  
Jingyi Wang ◽  
Xiaoyan Shi ◽  
Yulong Shan ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Acid Sites ◽  
Promoting Effect ◽  
Nh3 Scr ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared ◽  
Redox Ability

The effect of Mn impregnation on the NH3-SCR (selective catalytic reduction of NOx by NH3) activity of in situ synthesized Cu-SSZ-13 was investigated in this work. It was found that Mn addition could efficiently improve the low-temperature activity of Cu-SSZ-13. The optimal amount of Mn was 5 wt.%, and NOx conversion was improved by more than 20% over a temperature range of 120 °C to 150 °C. SEM (scanning electron microscopy), XRD (X-ray diffraction), N2 adsorption-desorption, H2-TPR (temperature programmed reduction of H2), NH3-TPD (temperature programmed desorption of NH3) and in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) experiments were conducted to investigate the changes in the zeolite structure, active sites, acid sites and reaction mechanism. The impregnated MnOx species caused a decline in the crystallinity of Cu-SSZ-13 but markedly improved the redox ability. Nitrate and nitrite species were observed in the Mn-modified Cu-SSZ-13, and the formation of these species was thought to cause the observed increase in low-temperature NH3-SCR activity. The results show that the addition of Mn is a promising method for promoting the low-temperature catalytic activity of Cu-SSZ-13.

Thermocatalytic conversion of lignin in an ethanol/formic acid medium with NiMo catalysts: Role of the metal and acid sites

2017 ◽  
Vol 217 ◽  
pp. 353-364 ◽  
Author(s):  
Mikel Oregui-Bengoechea ◽  
Inaki Gandarias ◽  
Nemanja Miletić ◽  
Sveinung F. Simonsen ◽  
Audun Kronstad ◽  
...  
Keyword(s):  
Formic Acid ◽  
Acid Medium ◽  
Acid Sites ◽  
Nimo Catalysts ◽  
Thermocatalytic Conversion

Cathodoluminescence of Catalyst Crystallites

1982 ◽  
Vol 40 ◽  
pp. 664-665
Author(s):  
E.D. Boyes ◽  
P.L. Gai ◽  
D.B. Darby ◽  
C. Warwick
Keyword(s):  
Defect Density ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Semiconductor Materials ◽  
Environmental Cell ◽  
High Resolution Structure ◽  
Commercially Important ◽  
Crystallographic Defects ◽  
Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

scholarly journals Electrokinetic and in situ spectroscopic investigations of CO electrochemical reduction on copper

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jing Li ◽  
Xiaoxia Chang ◽  
Haochen Zhang ◽  
Arnav S. Malkani ◽  
Mu-jeng Cheng ◽  
...  
Keyword(s):  
Mass Transport ◽  
Active Sites ◽  
Gas Diffusion ◽  
Reduction Reaction ◽  
Adsorbed Hydrogen ◽  
Diffusion Type ◽  
Proton Coupled Electron Transfer ◽  
Alkaline Electrolytes ◽  
Reaction Orders

AbstractRigorous electrokinetic results are key to understanding the reaction mechanisms in the electrochemical CO reduction reaction (CORR), however, most reported results are compromised by the CO mass transport limitation. In this work, we determined mass transport-free CORR kinetics by employing a gas-diffusion type electrode and identified dependence of catalyst surface speciation on the electrolyte pH using in-situ surface enhanced vibrational spectroscopies. Based on the measured Tafel slopes and reaction orders, we demonstrate that the formation rates of C2+ products are most likely limited by the dimerization of CO adsorbate. CH4 production is limited by the CO hydrogenation step via a proton coupled electron transfer and a chemical hydrogenation step of CO by adsorbed hydrogen atom in weakly (7 < pH < 11) and strongly (pH > 11) alkaline electrolytes, respectively. Further, CH4 and C2+ products are likely formed on distinct types of active sites.

scholarly journals Enhanced Tensile Strength of Monolithic Epoxy with Highly Dispersed TiO2-Graphene Nanocomposites

2021 ◽  
Vol 5 (7) ◽  
pp. 191
Author(s):  
Yanshuai Wang ◽  
Siyao Guo ◽  
Biqin Dong ◽  
Feng Xing
Keyword(s):  
Tensile Strength ◽  
Epoxy Resin ◽  
Mechanical Performance ◽  
Chemical Properties ◽  
High Mechanical Property ◽  
Graphene Nanocomposites ◽  
Highly Dispersed ◽  
Dispersion State ◽  
Physical And Chemical

The functionalization of graphene has been reported widely, showing special physical and chemical properties. However, due to the lack of surface functional groups, the poor dispersibility of graphene in solvents strongly limits its engineering applications. This paper develops a novel green “in-situ titania intercalation” method to prepare a highly dispersed graphene, which is enabled by the generation of the titania precursor between the layer of graphene at room temperature to yield titania-graphene nanocomposites (TiO2-RGO). The precursor of titania will produce amounts of nano titania between the graphene interlayers, which can effectively resist the interfacial van der Waals force of the interlamination in graphene for improved dispersion state. Such highly dispersed TiO2-RGO nanocomposites were used to modify epoxy resin. Surprisingly, significant enhancement of the mechanical performance of epoxy resin was observed when incorporating the titania-graphene nanocomposites, especially the improvements in tensile strength and elongation at break, with 75.54% and 176.61% increases at optimal usage compared to the pure epoxy, respectively. The approach presented herein is easy and economical for industry production, which can be potentially applied to the research of high mechanical property graphene/epoxy composite system.

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