Author Keywords: trimethylaluminium hydrolysate; stereoregular; poly(propylene oxide); fractionation; end-group analysis; cyclic oligomers 相似文献
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1.
Burcu Selen alayan Ahmet K. Avc Z. lsen
nsan A. Erhan Aksoylu 《Applied Catalysis A: General》2005,280(2):181-188
Indirect partial oxidation (IPOX) of propane was studied over bimetallic 0.2 wt.% Pt–15 wt.% Ni/δ-Al2O3 catalyst in the 623–743 K temperature range. The unreduced and reduced forms of the catalyst were characterized by ESEM–EDAX and X-ray diffraction (XRD). In the IPOX tests, the effects of steam to carbon ratio (S/C), carbon to oxygen ratio (C/O2) and residence time (W/F (gcat h/mol HC)) on the hydrogen production activity, selectivity and product distribution were studied in detail. The effect of temperature program applied (increasing from 623 to 743 K, ITP; decreasing from 743 to 623 K, DTP) during reaction was also tested. The results showed that the Pt–Ni bimetallic system has superior performance characteristics compared to the monometallic catalysts reported in literature. The reason is thought to be the utilization of the catalyst particles as micro heat exchangers during IPOX; the heat generated by Pt sites during exothermic total oxidation (TOX) being readily transferred through the catalyst particles acting as micro heat exchangers to the Ni sites, which promote endothermic steam reforming (SR). The optimal conditions were found as S/C = 3, C/O2 = 2.70 and W/F = 0.51 gcat h/mol HC for IPOX of propane on the basis of high hydrogen productivity and selectivity between 623 and 748 K for the experimental conditions tested. The thermo-neutral points obtained showed the sustainability of reaction in terms of energy. 相似文献
2.
A dual-series-based solution is obtained for the scattering of an H-polarized plane wave from a slitted infinite circular cylinder coated with absorbing material from inside or outside. For both cases, numerical results are presented for the radar cross section and comparisons are given for two different realistic absorbing materials. The radar cross-section dependencies are also given for the aspect angle of the scatterer and the thickness of the absorbing layer 相似文献
3.
Partially stereoregular poly(propylene oxide) samples were synthesized via reactions catalysed by a preformed analytically defined trimethylaluminium hydrolysate. These samples were fractionated into two contrastingly different fractions.
1. (i) D-polymers: This fraction constituted the major part (up to 90%). It mainly contained cyclic low molecular weight oligomers (MW < 1000). The linear chains found in D-polymers had hydroxyl end groups. No double bonds could be detected spectroscopically.
2. (ii) K-polymers: This fraction was high molecular weight stereoregular polymer. Stepwise thermal precipitation from dilute isooctane solution of K-polymers yielded a succession of fractions which differed in melting point. It appears that the phase equilibria during the thermal precipitations were not controlled by the molecular weights of species.
4.
Mohammadreza Nofar Beril Saadet Yenigul Burcu Ozdemir Ceren Yargici Kovanci Abbas Ghanbari Amirjalal Jalali 《应用聚合物科学杂志》2021,138(32):50793
In this study, recycled polyethylene (rPE) based microfibrillated composites (MFCs) were developed while incorporating recycled poly(ethylene terephthalate) (rPET) and recycled polyamide 6 (rPA) as the reinforcing fibrillar phases at a given weight ratio of 80 wt% (rPE)/20 wt% (rPET or rPA). The blends were first melt processed using a twin-screw extruder. The extrudates were then cold stretched at a drawing ratio of 2.5 to form rPET and rPA fibrillar structures. Next, the pelletized drawn samples were injection molded at the barrel temperatures below the melting temperatures of rPET and rPA. The tensile, three-point bending, impact strength, dynamic thermomechanical, and rheological properties of the fabricated MFCs were analyzed. The effects of injection molding barrel temperature (i.e., 150°C and 190°C) and extrusion melt processing temperature (i.e., 250°C and 275°C) on the generated fibrillar structure and the resultant properties were explored. A strong correlation between the fibrillar morphology and the mechanical properties with the extrusion and injection molding temperatures was observed. Moreover, the ethylene/n-butyl acrylate/glycidyl methacrylate (EnBAGMA) terpolymer and maleic anhydride grafted PE (MAH-g-PE) were, respectively, melt processed with rPE/rPET and rPE/rPA6 blends as compatibilizers. The compatibilizers refined the fibrillar structure and remarkably influenced mechanical properties, specifically the impact strength. 相似文献
5.
The uniaxial tension (loading and unloading), creep and relaxation experiments on high density polyethylene (HDPE) have been
carried out at room temperature. The stress–strain behavior of HDPE under different strain rates, creep (relaxation) behavior
at different stress (strain) levels have been investigated. These experimental results are used to compare the simulation
results of a unified state variable theory, viscoplasticity theory based on overstress (VBO) and a macro-mechanical constitutive
model for elasto-viscoplastic deformation of polymeric materials developed by Boyce et al. (Polymer 41:2183–2201, 2000). It is observed that elasto-viscoplasticity model by Boyce et al. (Polymer 41:2183–2201, 2000) is not good enough to simulate stress–strain, creep and relaxation behaviors of HDPE. However, the aforementioned behaviors
can be modeled quantitatively by using VBO model. 相似文献
6.
Xuesong Liu Burcu Akinci Mario Bergés James H. Garrett 《Advanced Engineering Informatics》2013,27(4):496-505
Heating, Ventilation and Air-Conditioning (HVAC) systems account for more than 15% of the total energy consumption in the US. In order to improve the energy efficiency of HVAC systems, researchers have developed hundreds of algorithms to automatically analyze their performance. However, the complex information, such as configurations of HVAC systems, layouts and materials of building elements and dynamic data from the control systems, required by these algorithms inhibits the process of deploying them in real-world facilities. To address this challenge, we envision a framework that automatically integrates the required information items and provides them to the performance analysis algorithms for HVAC systems. This paper presents an approach to identify and document the information requirements from the publications that describe these algorithms. We extend the Information Delivery Manual (IDM) approach so that the identified information requirements can be mapped to multiple information sources that use various formats and schemas. This paper presents the extensions to the IDM approach and the results of using it to identify information requirements for performance analysis algorithms of HVAC systems. 相似文献
7.
Aydogan Sakir Kocyigit Adem Cirak Burcu Bozkurt Erdogan Erman Yilmaz Mehmet 《Journal of Materials Science: Materials in Electronics》2022,33(9):6059-6069
Journal of Materials Science: Materials in Electronics - Zinc oxide (ZnO) rods film was fabricated by homemade and simple spray pyrolysis technique on a p-type silicon (Si) substrate, and the film... 相似文献
8.
Burcu Okutucu Figen Zihnioglu 《Materials science & engineering. C, Materials for biological applications》2012,32(5):1174-1178
Selective recognition of proteins by synthetic molecularly imprinted polymers is one of the interesting topics in biosciences. Carnosine (β-alanyl-l-histidine) and related histidine containing peptides are distributed in a wide range of tissues in vertebrate organisms. These peptides have been extensively studied because of their important physiological properties besides their metal chelation property. In this study, preparation of carnosine specific imprinted polymers (MIPs) for the recognition of imidazole containing peptides with and without copper ion is reported. Carnosine and copper–carnosine complex were employed as template molecules where 4-vinylpyridine and ethylenglycol dimethacrylate were chosen as monomer and crosslinker, respectively. The selectivity and binding studies of copper–carnosine imprinted polymer showed high selectivity toward both carnosine (template peptide) and the cupric ion. The selectivity of copper–carnosine imprinted polymer was 65% and carnosine imprinted polymer was approximately 40%. These results indicate that specific recognition of carnosine is depending on the basis of metal coordination 相似文献
9.
H. Erdem Çamurlu Ahmet Gençer Burcu Becer Şükrü Özdoğan 《Ceramics International》2013,39(8):8589-8595
Effect of potassium carbonate addition on the carbothermic formation of hexagonal boron nitride (hBN) was investigated by keeping the K2CO3 added B2O3+C mixtures in nitrogen atmosphere at 1400 °C for 40–160 min. K2CO3 amount was varied in the range of 10–60 wt% of the B2O3+C mixture. Products were subjected to XRD and quantitative analyses, SEM and TEM observations, and particle size measurement. Amount of hBN increased considerably with K2CO3 addition; also particle size and crystallinity improved. Catalytic role of K2CO3 was suggested as forming a potassium borate melt in which hBN particles form, in addition to carbothermic formation reaction. Effect of K2CO3 on increasing the hBN amount decreased when it was used over 40%. This was attributed to the rapid evaporation of the formed potassium borate liquid. 相似文献
10.