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1.
Weixia Wang Shuai Zhou Zhong Xin Yaoqi Shi Shicheng Zhao 《Frontiers of Chemical Science and Engineering》2016,10(3):396
Foamable high melt strength polypropylene (HMSPP) was prepared by grafting styrene (St) onto polypropylene (PP) and simultaneously introducing polydimethylsiloxane (PDMS) through?a?one-step?melt extrusion process. The effect of PDMS viscosity on the foaming behavior of HMSPP was systematically investigated using supercritical CO2 as the foaming agent. The results show that the addition of PDMS has little effect on the grafting reaction of St and HMSPP exhibits enhanced elastic response and obvious strain hardening effect. Though the CO2 solubility of HMSPP with PDMS (PDMS-HMSPP) is lower than that of HMSPP without PDMS, especially for PDMS with low viscosity, the PDMS-HMSPP foams exhibit narrow cell size distribution and high cell density. The fracture morphology of PDMS-HMSPP shows that PDMS with low viscosity disperses more easily and uniformly in HMSPP matrix, leading to form small domains during the extrusion process. These small domains act as bubble nucleation sites and thus may be responsible for the improved foaming performance of HMSPP. 相似文献
2.
Shu-Kai Yeh Ying-Ru Chen Ting-Wei Kang Tzu-Jian Tseng Sheng-Ping Peng Chien-Chia Chu Syang-Peng Rwei Wen-Jeng Guo 《Journal of Polymer Research》2018,25(1):30
In this study, three different approaches were applied to obtain thermoplastic polyurethane (TPU) nanocellular foams. The TPU was synthesized with a 4, 4′-methylenebis (phenyl isocyanate) and 1, 4-butanediol (MDI/BD) hard segment system using a pre-polymer method. The three approaches included increasing the hard segment content, adding a graphene nucleation agent, and replacing the soft segments. Although the synthesized TPUs had a different hardness, it was possible to obtain nanocellular structures with all of the methods. The cell structure is not a function of hardness only. Crystallinity affects the cell structure as well. The addition of graphene and replacement of the soft segments were more effective at yielding nanocellular foams. Our best results showed that after adding 0.1 wt% of graphene, the average cell size of the TPU foam decreased to 715 nm, and the cell density was improved to 4.94 × 1011 cells/cm3. The relative density of the foam could be as low as 0.77. This study first reported elastomer-based nanocellular structures with such low relative density. 相似文献
3.
Angélique Léonard Cedric Calberg Greet Kerckhofs Martine Wevers Robert Jérôme Jean-Paul Pirard Albert Germain Silvia Blacher 《Journal of Porous Materials》2008,15(4):397-403
Poly(ε-caprolactone) foams were prepared, via a batch process, by using supercritical CO2 as foaming agent. Their porous structure was characterized through mercury porosimetry, helium and mercury pycnometry, scanning
electron microscopy (SEM) and X-ray microtomography observations coupled with image analysis. The pore size distributions
obtained by these two latter techniques show that the pore structure is more homogeneous when the foaming process is performed
under a high CO2 saturation pressure (higher than 250 bars). 相似文献
4.
5.
Influences of polypropylene (PP) grafted to SiO2 nanoparticles (7 nm) were studied on the crystallization behavior and the mechanical properties of PP/SiO2 nanocomposites. PP for the matrix and grafting was synthesized in order to have an identical primary structure, aiming at
their co-crystallization and resulting reinforcement of filler-matrix interfaces. The grafted PP chains improved the dispersion
of SiO2, and notably accelerated nucleation in crystallization. It was plausible that the grafted chains whose one chain end was
pinned to SiO2 became nuclei of the crystallization (co-crystallization between the matrix and grafted chains), thus directly bridging between
the matrix and SiO2 nanoparticles. The Young’s modulus and tensile strength were most improved by the grafted PP chains at low filler contents
such as 2.3 wt%, whose origin was attributed to effective load transfer to SiO2 through the co-crystallization-mediated bridging. 相似文献
6.
Fractionation by supercritical carbon dioxide (SC−CO2) might be a way to purify used frying oils, since a selective separation of the oil components based on their polarity and
M.W. can be attained. In this work, we studied the purification of peanut oil used for frying by SC−CO2 continuous fractionation in a packed column. The influence of pressure (15–35 MPa) and temperature (25–55°C) on the yield
and on the composition of products was determined. The composition of the top and bottom products was evaluated by using size-exclusion
chromatography and other accepted chemical methods. Process conditions were selected to separate TG from degraded compounds.
Experimental results indicated that the operating conditions leading to maximal TG recovery in the extract were 35 MPa, 55°C,
and a solvent-to-feed ratio of 53. By operating at these conditions, it was possible to recover 97% of the TG placed on the
column and about 52% by weight of the used frying oil. The composition of the purified top stream was very similar to that
of fresh frying oil. 相似文献
7.
Nanoporous silica membrane without any pinholes and cracks was synthesized by organic templating method. The tetrapropylammoniumbromide
(TPABr)-templating silica sols were coated on tubular alumina composite support ( γ-Al2O3/ α-Al2O3 composite) by dip coating and then heat-treated at 550 °C. By using the prepared TPABr templating silica/alumina composite
membrane, adsorption and membrane transport experiments were performed on the CO2/N2, CO2/H2 and CH4/H2 systems. Adsorption and permeation by using single gas and binary mixtures were measured in order to examine the transport
mechanism in the membrane. In the single gas systems, adsorption characteristics on the α-Al2O3 support and nanoporous unsupport (TPABr templating SiO2/ γ-Al2O3 composite layer without α-Al2O3 support) were investigated at 20–40 °C conditions and 0.0–1.0 atm pressure range. The experimental adsorption equilibrium
was well fitted with Langmuir or/and Langmuir-Freundlich isotherm models. The α-Al2O3 support had a little adsorption capacity compared to the unsupport which had relatively larger adsorption capacity for CO2 and CH4. While the adsorption rates in the unsupport showed in the order of H2> CO2> N2> CH4 at low pressure range, the permeate flux in the membrane was in the order of H2≫N2> CH4> CO2. Separation properties of the unsupport could be confirmed by the separation experiments of adsorbable/non-adsorbable mixed
gases, such as CO2/H2 and CH4/H2 systems. Although light and non-adsorbable molecules, such as H2, showed the highest permeation in the single gas permeate experiments, heavier and strongly adsorbable molecules, such as
CO2 and CH4, showed a higher separation factor (CO2/H2=5-7, CH4/H2=4-9). These results might be caused by the surface diffusion or/and blocking effects of adsorbed molecules in the unsupport.
And these results could be explained by surface diffusion.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
8.
Particle size effects on supercritical CO<Subscript>2</Subscript> extraction of oil-containing seeds
Rosehip seeds were milled, sieved, and extracted with 26.3 g/g substrate/h of supercritical carbon dioxide (CO2) at 40°C and 300 bar. The extraction kinetics were characterized by an initial solubility-controlled period (8.78 g oil/kg
CO2 at 40°C and 300 bar), followed by a transition period to a final mass transfer-controlled process. The integral yield of
oil approached an asymptotic value that was dependent on the particle size of the substrate: 57.1 g oil/kg dry oil-free substrate
(large particles), 171.0 g/kg (medium-size particles), or 391.5 g/kg (small particles). Based on gravimetric determinations
and microscopic analysis, our size-classification process segregated seed parts having different oil contents. Particles ≥0.85
mm were mainly composed of tough, lignified testa fragments devoid of oil, whereas particles ≤0.425 mm contained mostly brittle,
oil-rich germ fragments. The segregation of seed in fractions with different oil contents may be a common occurrence in supercritical
extraction experiments, especially for seeds with thick and/or hard testa and small germ, whose fractions can be separated
by sieving. 相似文献
9.
A series of Mn-promoted 15 wt-% Ni/Al2O3 catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al2O3 catalysts for CO2 methanation and the comethanation of CO and CO2 in a fixed-bed reactor was investigated. The catalysts were characterized by N2 physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and highresolution transmission electron microscopy. The presence of Mn increased the number of CO2 adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al2O3 catalysts had improved CO2 methanation activity especially at low temperatures (250 to 400 °C). The Mn content was varied from 0.86% to 2.54% and the best CO2 conversion was achieved with the 1.71Mn-Ni/Al2O3 catalyst. The co-methanation tests on the 1.71Mn-Ni/Al2O3 catalyst indicated that adding Mn markedly enhanced the CO2 methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO2 methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process. 相似文献
10.
11.
Hydrotalcite was synthesized from hydroxide-form precursors to prepare a novel high-temperature CO2 sorbent, and the effect of Mg/Al ratio on CO2 sorption was studied. To enhance the CO2 sorption capacity of the sorbent, K2CO3 was coprecipitated during the synthetic reaction. X-ray diffraction analysis indicated that the prepared samples had a well-defined crystalline hydrotalcite structure, and confirmed that K2CO3 was successfully coprecipitated in the samples. The morphology of the hydrotalcite was confirmed by scanning electron microscopy, and N2 adsorption analysis was used to estimate its surface area and pore volume. In addition, thermogravimetric analysis was used to measure its CO2 sorption capacity, and the results revealed that the Mg: Al: K2CO3 ratio used in the preparation has an optimum value for maximum CO2 sorption capacity. 相似文献
12.
Investigations were conducted to purify crude Li2CO3 via direct carbonation with CO2-water solutions at atmospheric pressure. The experiments were carried out in a slurry bubble column reactor with 0.05 m inner
diameter and 1.0 m height. Parameters that may affect the dissolution of Li2CO3 in the CO2-water solutions such as CO2-bubble perforation diameter, CO2 partial pressure, CO2 gas flow rate, Li2CO3 particle size, solid concentration in the slurry, reaction temperature, slurry height in the column and so on were investigated.
It was found that the increases of CO2 partial pressure, and CO2 flow rate were favorable to the dissolution of Li2CO3, which had the opposite effects with Li2CO3 particle size, solid concentration, slurry height in the column and temperature. On the other hand, in order to get insight
into the mechanism of the refining process, reaction kinetics was studied. The results showed that the kinetics of the carbonation
process can be properly represented by 1−3(1−X)2/3+2(1–X)=kt+b, and the rate-determining step of this process under the conditions studied was product layer diffusion. Finally,
the apparent activation energy of the carbonation reaction was obtained by calculation. This study will provide theoretical
basis for the reactor design and the optimization of the process operation. 相似文献
13.
Xiaohong Li Jun Ai Wenying Li Dongxiong Li 《Frontiers of Chemical Science and Engineering》2010,4(4):476-480
A co-precipitation method was employed to prepare Ni/Al2O3-ZrO2, Co/Al2 O3-ZrO2 and Ni-Co/Al2O3-ZrO2 catalysts. Their properties were characterized by N2 adsorption (BET), thermogravimetric analysis (TGA), temperature-programmed reduction (TPR), temperature-programmed desorption (CO2-TPD), and temperature-programmed surface reaction (CH4-TPSR and CO2-TPSR). Ni-Co/Al2O3-ZrO2 bimetallic catalyst has good performance in the reduction of active components Ni, Co and CO2 adsorption. Compared with mono-metallic catalyst, bimetallic catalyst could provide more active sites and CO2 adsorption sites (C + CO2 = 2CO) for the methane-reforming reaction, and a more appropriate force formed between active components and composite support (SMSI) for the catalytic reaction. According to the CH4-CO2-TPSR, there were 80.9% and 81.5% higher CH4 and CO2 conversion over Ni-Co/Al2O3-ZrO2 catalyst, and its better resistance to carbon deposition, less than 0.5% of coke after 4 h reaction, was found by TGA. The high activity and excellent anti-coking of the Ni-Co/Al2O3-ZrO2 catalyst were closely related to the synergy between Ni and Co active metal, the strong metal-support interaction and the use of composite support. 相似文献
14.
The rapid expansion of a supercritical solution (RESS) process is an attractive technology for the production of small, uniform
and solvent-free particles of low vapor pressure solutes. The RESS containing a nonvolatile solute leads to loss of solvent
power by the fast expansion of the supercritical solution through an adequate nozzle, which can cause solute precipitation.
A dynamic flow apparatus was used to perform RESS studies for the preparation of fine anthracene particles in pure carbon
dioxide over a pressure range of 150–250 bar, an extraction temperature range of 50–70 °C, and a pre-expansion temperature
range of 70–300 °C. To obtain fine particles, 100, 200 and 300 μm nozzles were used to disperse the solution inside of the
crystallizer. Both average particle size and particle size distribution (PSD) were dependent on the extraction pressure and
the pre-expansion temperature, whereas extractor temperature did not exert any significant effect. Smaller particles were
produced with increasing extraction pressure and preexpansion temperature. In addition, the smaller the nozzle diameter, the
smaller the particles and the narrower the PSD obtained. 相似文献
15.
Bahman Zarenezhad Mona Mottahedin Ali Haghighi Asl 《Korean Journal of Chemical Engineering》2011,28(3):949-953
Accurate prediction of phase equilibria regarding CH4 replacement in hydrate phase with high pressure CO2 is an important issue in modern reservoir engineering. In this work we investigate the possibility of establishing a thermodynamic framework for predicting the hydrate equilibrium conditions for evaluation of CO2 injection scenarios. Different combinations of equations of state and mixing rules are applied and the most accurate thermodynamic models at different CO2 concentration ranges are proposed. 相似文献
16.
Andrzej Wilk Lucyna Więcław-Solny Adam Tatarczuk Aleksander Krótki Tomasz Spietz Tadeusz Chwoła 《Korean Journal of Chemical Engineering》2017,34(8):2275-2283
Amine absorption processes are widely used to purify both refinery and process gases and natural gas. Recently, amine absorption has also been considered for application to CO2 removal from flue gases. It has a number of advantages, but there is one major disadvantage-high energy consumption. This can be solved by using an appropriate solvent. From a group of several dozen solutions, seven amine solvents based on primary amine, tertiary amine and sterically hindered amine were selected. For the selected solutions research was conducted on CO2 absorption capacity, an absorption rate and finally a solvent vapor pressure. Furthermore, tests on an absorber-desorber system were also performed. In this study the most appropriate solvent for capturing CO2 from flue gases with higher carbon dioxide concentrations was selected. 相似文献
17.
18.
Young Eun Kim Jeong Ho Choi Soung Hee Yun Sung Chan Nam Yeo Il Yoon 《Korean Journal of Chemical Engineering》2016,33(12):3465-3472
The specific heat capacity, heat of CCO2 absorption, and CCO2 absorption capacity of aqueous solutions of potassium carbonate (K2CO3)+2-methylpiperazine (2-MPZ) and monoethanolamine (MEA) were measured over various temperatures. An aqueous solution of K2CO3+2-MPZ is a promising absorbent for CCO2 capture because it has high CCO2 absorption capacity with improved absorption rate and degradation stability. Aqueous solution of MEA was used as a reference absorbent for comprison of the thermodynamic characteristics. Specific heat capacity was measured using a differential scanning calorimeter (DSC), and heat of CCO2 absorption and CCO2 absorption capacity were measured using a differential reaction calorimeter (DRC). The CCO2-loaded solutions had lower specific heat capacities than those of fresh solutions. Aqueous solutions of K2CO3+2-MPZ had lower specific heat capacity than those of MEA over the temperature ranges of 303-353 K. Under the typical operating conditions for the process (CCO2 loading=0.23mol-CCO2·mol?1-solute in fresh solution, T=313 K), the heat of absorption (?ΔHabs) of aqueous solutions of K2CO3+2-MPZ and MEA were approximately 49 and 75 kJ·mol-CO2, respectively. The thermodynamic data from this study can be used to design a process for CCO2 capture. 相似文献
19.
TiO2 thin and thick films promoted with platinum and organic sensitizers including novel perylene diimide dyes (PDI) were prepared
and tested for carbon dioxide reduction with water under visible light. TiO2 films were prepared by a dip coating sol–gel technique. Pt was incorporated on TiO2 surface by wet impregnation [Pt(on).TiO2], or in the TiO2 film [Pt(in).TiO2] by adding the precursor in the sol. When tris (2,2′-bipyridyl) ruthenium(II) chloride hexahydrate was used as sensitizer,
in addition to visible light activity towards methane production, H2 evolution was also observed. Perylene diimide derivatives used in this study have shown light harvesting capability similar
to the tris (2,2′-bipyridyl) ruthenium(II) chloride hexahydrate. 相似文献
20.
Junyeong Kim Jeong Yeon Do No-Kuk Park Seung Jong Lee Jin-Pyo Hong Misook Kang 《Korean Journal of Chemical Engineering》2018,35(5):1089-1098
Nano-sized bismuth sulfide (Bi2S3) and titanium dioxide (TiO2) with the orthorhombic and anatase tetragonal structures, respectively, were synthesized for application as catalysts for the reduction of carbon dioxide (CO2) to methane (CH4). Four double-layered dense films were fabricated with different coating sequences—TiO2 (bottom layer)/Bi2S3 (top layer), Bi2S3/TiO2, TiO2/Bi2S3: TiO2 (1 : 1) mix, and Bi2S3: TiO2 (1 : 1) mix/Bi2S3: TiO2 (1 : 1) mix—and applied to the photoreduction of CO2 to CH4; the catalytic activity of the fabricated films was compared to that of the pure TiO2/TiO2 and Bi2S3/Bi2S3 doubled-layered films. The TiO2/Bi2S3 double-layered film exhibited superior photocatalytic behavior, and higher CH4 production was obtained with the TiO2/Bi2S3 double-layered film than with the other films. A model of the mechanism underlying the enhanced photoactivity of the TiO2/Bi2S3 double-layered film was proposed, and it was attributed in effective charge separation. 相似文献