Mn-Mo-O Catalysts for Methanol Oxidation. I. Preparation and Characterization of the Catalysts

1992 ◽  
Vol 57 (12) ◽  
pp. 2529-2538 ◽  
Author(s):  
Krasimir Ivanov ◽  
Penka Litcheva ◽  
Dimitar Klissurski
Keyword(s):  
Methanol Oxidation ◽  
Solution Concentration ◽  
Alkaline Media ◽  
Acidic Media ◽  
Chemical Methods ◽  
X Ray ◽  
Ph Values ◽  
Precipitate Composition

Mn-Mo-O catalysts with a different Mo/Mn ratio have been prepared by precipitation. The precipitate composition as a function of solution concentration and pH was studied by X-ray, IR, thermal and chemical methods. Formation of manganese molybdates with MnMoO4.1.5H2O, Mn3Mo3O12.2.5H2O, and Mn3Mo4O15.4H2O composition has been supposed. It is concluded that pure MnMoO4 may be obtained in both acid and alkaline media, the pH values depending on the concentration of the initial solutions. The maximum Mo/Mn ratio in the precipitates is 1.33. The formation of pure Mn3Mo4O15.4H2O is possible in weakly acidic media. This process is favoured by increasing the concentration of initial solutions.

Preparation of Carbon Nanofibers from Polyacrylonitrile Nanofibers by Electrospinning

2011 ◽  
Vol 415-417 ◽  
pp. 642-647
Author(s):  
En Zhong Li ◽  
Da Xiang Yang ◽  
Wei Ling Guo ◽  
Hai Dou Wang ◽  
Bin Shi Xu
Keyword(s):  
Electron Microscope ◽  
Carbon Nanofibers ◽  
Photoelectron Spectroscopy ◽  
Solution Concentration ◽  
Dimethyl Formamide ◽  
Ultrafine Fibers ◽  
X Ray ◽  
Scanning Electron ◽  
Pan Fibers

Ultrafine fibers were electrospun from polyacrylonitrile (PAN)/N,N-dimethyl formamide (DMF) solution as a precursor of carbon nanofibers. The effects of solution concentration, applied voltage and flow rate on preparation and morphologies of electrospun PAN fibers were investigated. Morphologies of the green fibers, stabilized fibers and carbonized fibers were compared by scanning electron microscope (SEM). The diameter of PAN nanofibers is about 450nm and the distribution of diameter is well-proportioned. Characterization of the elements changes of fibers were performed by X-ray photoelectron spectroscopy (XPS).

Synthesis and Characterization of Nano-Calcium Titanate-Based Coated Aluminum Oxide and its Application in Water Analysis of Cr(III) and Cr(VI) Concentration

2010 ◽  
Vol 44-47 ◽  
pp. 2136-2139
Author(s):  
Dong Zhang
Keyword(s):  
Aluminum Oxide ◽  
Sol Gel ◽  
Calcium Titanate ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
Composite Adsorbent ◽  
X Ray ◽  
Ph Values ◽  
Adsorption Capability

Nano-calcium titanate-based coated aluminum oxide (ACCTO) was successfully prepared by the citrate acid sol-gel method and characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Its application in speciation of Cr(III) and Cr(VI) from water was studied. The conditions of adsorption and elution were investigated. The results show that nanometer calcium titanate could be immobilized on the aluminum oxide firmly, becoming a composite adsorbent. Two forms of chromium showed different adsorption capability at different pH values, Cr (III) selectively retained at pH 8-14, whereas Cr (VI) retained at pH≤2. So separation of the Cr(III) and Cr(VI) is possible. Retained species were eluted with 5mL of 1 mol•L-1 HCl and NaOH. The Cr(III) and Cr(VI) concentration was measured by atomic absorption spectroscopy. The adsorption agent has a promising prospect in removal or enriching and separation of Cr(III) and Cr(VI) in water.

Preparation and Characterization of Nanosized Barium-Strontium Titanate Immobilized on Aluminum Oxide and its Application in Separation of Cr(III) and Cr(VI)

2010 ◽  
Vol 152-153 ◽  
pp. 1013-1016
Author(s):  
Hong Wang ◽  
Jing Yang
Keyword(s):  
Aluminum Oxide ◽  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Sol Gel ◽  
Complete Separation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ph Values ◽  
Barium Strontium

Nanometer barium-strontium titanate based coated aluminum oxide (ABST) was prepared by the sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectrophotometry (FTIR). Its application in speciation of Cr(III) and Cr(VI) from water were studied. The results showed that the nanometer barium-strontium titanate was immobilized on aluminum oxide firmly, becoming a new adsorbent. Two forms of chromium showed different exchange capacities at different pH values, viz. Cr (III) selectively retained at pH 10–13, whereas Cr (VI) retained at pH 1. Hence complete separation of the two forms of chromium is possible. Retained species were eluted with 5mL of 1 mol•L−1 HCl and 1 mol•L−1 NaOH. The Cr(III) and Cr(VI) concentration was measured by atomic absorption spectroscopy. The adsorbent had a promising prospect in the separation of Cr(III) and Cr(VI) in environment water.

Preparation and Characterization of Cellulose Carbamate Regeneration Membrane by Supercritical Carbon Dioxide

2013 ◽  
Vol 821-822 ◽  
pp. 1031-1034
Author(s):  
Xu Wang ◽  
Hai Yan Wu ◽  
Cui Yu Yin
Keyword(s):  
Phase Inversion ◽  
Solution Concentration ◽  
Coagulation Bath ◽  
Regenerated Cellulose ◽  
Structure And Properties ◽  
Inversion Process ◽  
X Ray ◽  
Cellulose Carbamate ◽  
Phase Inversion Process

The regenerated cellulose carbamate membranes were prepared by the phase inversion process. The structure and properties of the regenerated cellulose carbamate membranes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Besides, the effects of the casting solution concentration and the coagulation bath concentration on the mechanical property of regenerated cellulose carbamate membrane were discussed.

Electrochemical Preparation and Characterization of a Pt � Polytyramine Composite Material with Electrocatalytic Properties

2009 ◽  
Vol 59 (12) ◽  
Author(s):  
Tanta Spataru ◽  
Maria Marcu ◽  
Alexandra Banu ◽  
Eugen Roman ◽  
Nicolae Spataru
Keyword(s):  
Cyclic Voltammetry ◽  
Composite Material ◽  
Methanol Oxidation ◽  
Electrochemical Deposition ◽  
Electrocatalytic Activity ◽  
Polymer Coatings ◽  
High Porosity ◽  
Acidic Media ◽  
Electrochemical Preparation

Electrochemical deposition of polytyramine (PTy) was performed by cyclic voltammetry and it was observed that, in acidic media, 20 to 50 consecutive deposition cycles allowed us to obtain polymer coatings with good conductivity and high porosity. The polytyramine layers were used as a matrix for electrochemical deposition of platinum and the electrocatalytic activity for methanol oxidation of the composite material thus obtained was put in evidence.

scholarly journals Condensation reaction and crystallization of urea-formaldehyde resin during the curing process

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2924-2936
Author(s):  
Zhongjian Ding ◽  
Zhongqiang Ding ◽  
Tianlin Ma ◽  
Hua Zhang
Keyword(s):  
Condensation Reaction ◽  
Urea Formaldehyde ◽  
Formaldehyde Resin ◽  
Curing Process ◽  
Chemical Methods ◽  
X Ray ◽  
Molar Ratios ◽  
Ph Values ◽  
Uf Resin ◽  
Resin Curing

Urea-formaldehyde (UF) resins were synthesized with different molar ratios and solid contents, and simultaneously they were cured under conditions of different pH values. The curing behaviors of cured UF resins were examined by synchronous thermal analysis (TG-DSC). The crystallinity of cured UF resin was analyzed by X-ray diffractometry. The gel time of cured UF resin was recorded by chemical methods. The results indicate that condensation reactivity leads condensation reaction and crystallization to play various roles during the curing process of UF resin. The condensation reaction and crystallization in the curing process interact to result in different structures of cured resin. A new mechanism for UF resin curing (reaction-crystallization) is thus proposed.

scholarly journals Preparation of cathepsins B and H by covalent chromatography and characterization of their catalytic sites by reaction with a thiol-specific two-protonic-state reactivity probe. Kinetic study of cathepsins B and H extending into alkaline media and a rapid spectroscopic titration of cathepsin H at pH 3-4

1985 ◽  
Vol 227 (2) ◽  
pp. 511-519 ◽  
Author(s):  
F Willenbrock ◽  
K Brocklehurst
Keyword(s):  
Cathepsin B ◽  
Thiol Group ◽  
Catalytic Site ◽  
Alkaline Media ◽  
Cysteine Proteinases ◽  
Acidic Media ◽  
Active Centre ◽  
Ph Values ◽  
Cathepsin H ◽  
Covalent Chromatography

A procedure for the isolation of cathepsin B (EC 3.4.22.1) and of cathepsin H from bovine spleen involving covalent chromatography by thiol-disulphide interchange and ion-exchange chromatography was devised. The stabilities of both cathepsins in alkaline media are markedly temperature-dependent, and reliable kinetic data can be obtained at pH values up to 8 by working at 25 degrees C with a continuous spectrophotometric assay. Both enzyme preparations contain only one type of thiol group as judged by reactivity characteristics towards 2,2′-dipyridyl disulphide at pH values up to 8; in each case this thiol group is essential for catalytic activity. Cathepsin H was characterized by kinetic analysis of the reactions of its thiol group with 2,2′-dipyridyl disulphide in the pH range approx. 2-8 and the analogous study on cathepsin B [Willenbrock & Brocklehurst (1984) Biochem. J. 222, 805-814] was extended to include reaction at pH values up to approx. 8. Cathepsin H, like the other cysteine proteinases, was shown to contain an interactive catalytic-site system in which the nucleophilic character of the sulphur atom is maintained in acidic media. The considerable differences in catalytic site characteristics detected by this two-protonic-state reactivity probe between cathepsin B, cathepsin H, papain (EC 3.4.22.2) and actinidin (EC 3.4.22.14) are discussed. Reaction with 2,2′-dipyridyl disulphide in acidic media, which is known to provide a rapid spectrophotometric active centre titration for many cysteine proteinases, is applicable to cathepsin H. This is useful because other active-centre titrations have proved unsuitable in view of the relatively low reactivity of the thiol group in cathepsin H.

Synthesis and Characterization of Biphasic Calcium Phosphate/ Poly-(DL-Lactide-Co-Glycolide) Biocomposite

2005 ◽  
Vol 494 ◽  
pp. 537-542 ◽  
Author(s):  
M. Radić ◽  
N. Ignjatović ◽  
Zoran Nedić ◽  
M. Mitrić ◽  
Dejan Miličević ◽  
...  
Keyword(s):  
Composite Material ◽  
Calcium Phosphate ◽  
Biphasic Calcium Phosphate ◽  
Synthesis Method ◽  
Synthesis And Characterization ◽  
Chemical Methods ◽  
X Ray ◽  
Precipitation Technique ◽  
New Synthesis

In this paper we report the results on synthesis of a composite biomaterial based on biphasic calcium phosphate (BCP) and poly-(DL-lactide-co-glycolide) (DLPLG). Besides, we have investigated the influence of new synthesis method on the structure and characteristics of the composite. The synthesis of biphasic calcium phosphate from Ca(NO3)2 x 4H2O and (NH4)3 PO4 in alkali environment was performed by means of precipitation technique. Composite material BCP/DLPLG was first prepared from commercial granules using chemical methods. Powdered polymer DLPLG was then homogenized at appropriate ratio with addition of biphasic calcium phosphate into the suspension. All samples were characterized by DSC, IR, X-Ray and SEM techniques.

scholarly journals X-ray Characterization of Conformational Changes of Human Apo- and Holo-Transferrin

2021 ◽  
Vol 22 (24) ◽  
pp. 13392
Author(s):  
Camila Campos-Escamilla ◽  
Dritan Siliqi ◽  
Luis A. Gonzalez-Ramirez ◽  
Carmen Lopez-Sanchez ◽  
Jose Antonio Gavira ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Biomedical Applications ◽  
Iron Release ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ph Values ◽  
X Ray Scattering ◽  
Physiological Relevance ◽  
Ph Conditions

Human serum transferrin (Tf) is a bilobed glycoprotein whose function is to transport iron through receptor-mediated endocytosis. The mechanism for iron release is pH-dependent and involves conformational changes in the protein, thus making it an attractive system for possible biomedical applications. In this contribution, two powerful X-ray techniques, namely Macromolecular X-ray Crystallography (MX) and Small Angle X-ray Scattering (SAXS), were used to study the conformational changes of iron-free (apo) and iron-loaded (holo) transferrin in crystal and solution states, respectively, at three different pH values of physiological relevance. A crystallographic model of glycosylated apo-Tf was obtained at 3.0 Å resolution, which did not resolve further despite many efforts to improve crystal quality. In the solution, apo-Tf remained mostly globular in all the pH conditions tested; however, the co-existence of closed, partially open, and open conformations was observed for holo-Tf, which showed a more elongated and flexible shape overall.

scholarly journals Folic Acid-Conjugated Silica-Modified TbPO4·H2O Nanorods for Biomedical Applications

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Le Thi Vinh ◽  
Tran Thu Huong ◽  
Ha Thi Phuong ◽  
Hoang Thi Khuyen ◽  
Nguyen Manh Hung ◽  
...  
Keyword(s):  
Folic Acid ◽  
Biomedical Applications ◽  
Breast Cancer Cells ◽  
Hexagonal Phase ◽  
X Ray Diffraction ◽  
Chemical Methods ◽  
X Ray ◽  
Wet Chemical ◽  
The Fourier Transform

We report on the synthesis and characterization of folic acid-conjugated silica-modified TbPO4·H2O nanorods for biomedical applications. The uniform shape TbPO4·H2O nanorods with a hexagonal phase were successfully synthesized by wet chemical methods. A novel TbPO4·H2O@silica-NH2 nanocomplex was then formed by functionalizing these nanorods with silica and conjugating with biological agents. The field emission scanning electron microscopy, energy-dispersive X-ray, and X-ray diffraction reveal the morphology and structure of the nanorods, with their controllable sizes (500-800 nm in length and 50-80 nm in diameter). The Fourier transform infrared spectroscopy was employed to identify chemical substances or functional groups of the TbPO4·H2O@silica-NH2 nanocomplex. The photoluminescence spectra show the four emission lines of TbPO4·H2O@silica-NH2 in folic acid at 488, 540, 585, and 621 nm under 355 nm laser excitation, which could be attributed to the 5D4-7 F j ( J = 6 , 5 , 4 , 3 ) transitions of Tb3+. The TbPO4·H2O@silica-NH2 nanorods were conjugated with folic acid for the detection of MCF7 breast cancer cells. The obtained results show a promising possibility for the recognition of living cells that is of crucial importance in biolabeling.

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