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991.
Wioletta Raróg-Pilecka Magdalena Karolewska Elżbieta Truszkiewicz Ewa Iwanek Bogusław Mierzwa 《Catalysis Letters》2011,141(5):678-684
Abstract
Unsupported cobalt catalysts promoted with barium (symbol Co/Ba), cerium (Co/Ce) or both (Co/Ce/Ba) were synthesized and tested in ammonia synthesis at 6.3 MPa. The Ba-free Co and Co/Ce oxide forms of the catalysts were prepared by precipitation/co-precipitation and a subsequent calcination at 500 °C. The Co and Co/Ce powders were impregnated with an aqueous solution of barium nitrite. Nitrogen physisorption and H2 chemisorption measurements revealed that cerium and barium play the role of structural promoters, which hinder the sintering of cobalt oxide during calcination and stabilize the surface of cobalt under reduction conditions. It seems that barium also modifies the surface of the active phase, i.e., cobalt. The kinetic studies of NH3 synthesis have shown that the co-promoted material (Co/Ce/Ba) is about 2–3 times more active than the system doped with barium (Co/Ba) and more than ten times as active as that with Ce. At 400 °C and at low conversion (1% NH3), the ammonia synthesis rate (TOF) over Co/Ce/Ba proved to be almost 60% as high as that obtained for the commercial iron catalyst (KMI, H. Tops?e) commonly used in ammonia plants all over the world. Moreover, at the same temperature and a high ammonia concentration (8%) the co-promoted cobalt catalyst is over two times more active than the fused iron catalyst. Another asset of the cobalt catalyst is its high thermal stability. 相似文献992.
Jacek G. Chęcmanowski Irena Szczygieł Anna Mazur Bogdan Szczygieł 《Ceramics International》2019,45(2):2811-2819
Five layer SiO2 coatings containing SiO2 or Al2O3 nanopowders were deposited on FeCrAl alloy support by sol-gel method. Studies of protective properties of the coatings were carried out during high temperature cyclic oxidation. Changes in surface topography, structure and chemical composition of the surface layer of FeCrAl alloy were investigated. It has been shown that the type of nanofillers present in the SiO2 coating (about 2.5?wt%) affects morphology of Al2O3 growing scale and determines the heat resistance of FeCrAl alloy. The lowest relative mass change (approx. 1.3%) after 10 oxidation cycles in air at 900?°C (one cycle = 12?h) was measured for the samples with coatings containing hydrophilic nanosilica (Aerosil 380) as filler. The protective efficiency of the coatings in the process of high-temperature oxidation is from 66% to 85%. The thickness of the formed scale and the value of the parabolic rate constant depend on the type of nanopowder in the coating. 相似文献
993.
Joanna Mystkowska Magdalena Mazurek-Budzyńska Ewelina Piktel Katarzyna Niemirowicz Wojciech Karalus Piotr Deptuła Katarzyna Pogoda Dawid Łysik Jan Ryszard Dąbrowski Gabriel Rokicki Robert Bucki 《Journal of Polymer Research》2017,24(9):144
Selected mechanical and biological properties of biodegradable elastomeric poly(ester-carbonate-urea-urethane)s (PECUUs) point towards their potential to be applied as scaffolds in tissue engineering. Here we explore their medical applicability taking into account their hemocompatibility and cytotoxicity. The influence of the ester monomer (derivatives of adipic and succinic acids), as well as diisocyanate type (IPDI and HDI) on the investigated PECUUs properties is presented. The presence of aliphatic diisocyanates, cyclic IPDI or linear HDI, governs the adhesion of Candida cells to these polymers offering the possibility to control the biofilm formation on their surface. In comparison to the linear form, cyclic diisocyanates with pentamethylene succinate or adipate fragments had two to three times lower biofilm mass formation on their surface. Reduced hemoglobin release from red blood cells observed during incubation of tested polymers with human erythrocytes suspension indicates their potential biocompatibility with human tissues. PECUUs were also able to support the growth of human keratinocytes HaCaT on their surface when coated with collagen. In effect, IPDI derivatives might possess a high potential for use in biomedical applications. 相似文献
994.
Marzena?Joanna?KurasEmail author Karolina?Perz Wac?aw?Lechos?aw?Ko?odziejski 《Polymer Bulletin》2017,74(12):5029-5048
In our study, a Zn(II) ion-imprinted polymer (ZnIP) and non-imprinted polymer (NIP) were synthesized via free-radical polymerization. 1-Vinylimidazole, ethylene glycol dimethacrylate, 2-hydroxyethylmethacrylate and 2,2′-azobisisobutyronitrile were used as functional, cross-linking monomers and free-radical initiator, respectively. The obtained polymer was characterized by various analytical methods (Fourier Transform Infrared Spectroscopy, Transmission Electron Microscopy, Wavelength Dispersive X-ray Fluorescence, UV VIS, thermal analysis). The sorption properties of ZnIP and NIP were evaluated after removal of Zn(II) ions from the polymer network. The optimum pH for adsorption was 7.0. The maximum adsorption capacity at the pH was 5.2 and 0.22 mg/g for ZnIP and NIP, respectively. To determine the selectivity, the polymer was equilibrated with the binary mixture of Zn(II) ions and the interfering ions [Cu(II), Ni(II) or Co(II)]. The relative selectivity of ZnIP was 22.57, 5.44 and 46.17 for Cu(II), Ni(II) and Co(II) ions, respectively. The proposed ZnIP sorbent was applied to determine the zinc ions in urine samples by Wavelength Dispersive X-ray Fluorescence. 相似文献
995.
This work reports the experimental results of kinetics study of n-butylparaben (BP) degradation in H2O2/UV systems. A pseudo–steady-state and competition kinetic approaches were used to determine the reaction rate constants between the BP and ?OH. In competition kinetics atrazine (2.30?×?109 M?1?s?1) was used as a reference compound. The measured rate constants for ?OH reaction with BP ranged from (3.84 ± 0.12)?×?109 M?1?s?1 to (8.56 ± 0.90)?×?109 M?1?s?1 depending on solution pH and temperature. Values of the rate constant obtained using different methods were in good agreement. The calculated activation energy was equal to 19.01 ± 1.02 kJ mol?1. 相似文献
996.
AB diblock copolymers were prepared by use of poly(tert‐butyl (meth)acrylate) (PtBA/PtBMA) as monofunctional macroinitiator in atom transfer radical polymerization of various (meth)acrylates (methyl, butyl) in the presence of the CuBr/N, N, N′, N′, N″‐pentamethyldiethylenetriamine catalyst system. Then using the diblock copolymer as macroinitiator with a bromine atom at the chain end, ABC and ABA triblock copolymers containing at least one PtBA or PtBMA segment were synthesized via polymerization of the selected (meth)acrylic monomer. Gel permeation chromatography was applied to determine molecular weights and polydispersity indices. The latter, for block copolymers prepared without deactivator addition, were in the range 1.2‐1.6 with a high degree of polymerization (150‐500). The chemical compositions of the block copolymers were characterized with 1H nuclear magnetic resonance. The kind of combined segments and their lengths influenced the glass transition temperature (Tg) determined by differential scanning calorimetry. Copyright © 2012 Society of Chemical Industry 相似文献
997.
Electrical conductivity and transparency of polymer hybrid nanocomposites based on poly(trimethylene terephthalate) containing single walled carbon nanotubes and expanded graphite 下载免费PDF全文
S. Paszkiewicz A. Szymczyk X. M. Sui H. D. Wagner A. Linares A. Cirera A. Varea T. A. Ezquerra Z. Rosłaniec 《应用聚合物科学杂志》2017,134(1)
Single‐walled carbon nanotubes (SWCNT)/expanded graphite (EG)/poly(trimethylene terephthalate) (PTT) hybrid nanocomposites were prepared via in situ polymerization. Raman spectroscopy and scanning electron microscopy (SEM) were employed to determine both, purity and morphology of the nanofillers and the dispersion of nanotubes and nanosheets. The electrical and optical properties of thin polymer films based on both “single” nanocomposites and hybrid nanocomposites were studied. For PTT/SWCNT nanocomposites, results confirmed that films optical transmittance decreases as the concentration of SWCNT increases, attaining almost no optical transmittance for 0.3 wt % of nanofiller. Conversely, the electrical conductivity of nanocomposites was found to increase by increasing the nanofiller amount and the σdc values indicate that percolation occurs at a very low SWCNT content (around 0.05 wt %). In the case of PTT/SWCNT + EG nanocomposites, when the content of SWCNT is 0.05%, the hybrid system presents lower conductivity than that corresponding to the “single” nanocomposite. The incorporation of additional EG to the PTT/SWCNT nanocomposite has a small effect on the electrical conductivity but inhibits the transparency of the system. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44370. 相似文献
998.
Maria Wojciechowska Bogdan Czajka Mariusz Pietrowski Michał Zieliński 《Catalysis Letters》2000,66(3):147-153
The paper presents results of studies on the structure of MgF2 support, performed using various experimental methods such as XRD, IR, temperature‐programmed techniques and low‐temperature
nitrogen adsorption. MgF2 is characterized by an XRD spectrum with over 40 patterns, which enabled us to follow the changes in crystallite size and
internal tension caused by the thermal treatment. TPE‐H2O and TG allowed an estimation of the surface OH groups concentration as ∼3–4 nm-2.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
999.
The addition of Fe(CO)5 to the systems with [Rh(acac)(CO)L] complexes (L = PPh3, P(OPh)3, P(NC4H4)3) as catalyst precursors caused the increase of aldehydes yield in 1-hexene hydroformylation reaction (80°C, 10 atm) up to
71%. The IR and 1H NMR measurements confirm the formation of an unstable bimetallic intermediate, [(H)(PPh3)3Rh(μ-CO)2Fe(CO)4], characterized with νCO at 1749 cm−1 and hydrido signal at δ ™15.8 ppm.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
1000.
Andrzej Kotarba Andrzej Barański Stanisław Hodorowicz Jerzy Sokołowski Andrzej Szytuła Leif Holmlid 《Catalysis Letters》2000,64(2-4):129-134
The kinetics of the NO SCR with propane has been studied on a low‐exchanged Cu‐ZSM‐5 catalyst. The study of the kinetics of
individual reaction stages (2‐nitrosopropane isomerization to acetone oxime and reaction of adsorbed acetone oxime with gaseous
NO) has shown that the NO reaction with acetone oxime is the rate‐determining stage in the whole chain of transformations
leading to the formation of molecular nitrogen in the low‐temperature region below 300 °C. The kinetic analysis of the reaction
has revealed that at the temperatures above 300 °C propane plays a more important role.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献