scholarly journals The Role of Cations in Resorcinol–Formaldehyde Gel Textural Characteristics

Gels ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 60
Author(s):  
Stewart J. Taylor ◽  
Liu Yang ◽  
Ashleigh J. Fletcher

The production of resorcinol–formaldehyde xerogels has yielded insight into the gelation processes underpinning their structures. In this work, the role of the cation species from the catalyst is probed by studying the simultaneous addition of sodium carbonate and calcium carbonate to a resorcinol–formaldehyde mixture. Twenty-eight xerogels were prepared by varying the solids content, catalyst concentration, and catalyst composition, and each was analysed for its textural properties, including the surface area and average pore diameter. The results indicate that the role of the cation is linked to the stabilisation of the clusters formed within the system, and that the Group II catalyst causes the salting out of the oligomers, resulting in fewer, larger clusters, hence, an increase in pore size and a broadening of the pore size distribution. The results provide insight into how these systems can be further controlled to create tailored porous materials for a range of applications.

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.


2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Zhilin Liu ◽  
Yang Teng ◽  
Kai Zhang

An array of new MCM-41 with substantially larger average pore diameters was synthesized through adding 1,3,5-trimethylbenzene (TMB) as the swelling agent to explore the effect of pore size on final adsorbent properties. The pore expanded MCM-41 was also grafted with (3-Aminopropyl)triethoxysilane (APTES) to determine the optimal pore size for CO2adsorption. The pore-expanded mesoporous MCM-41s showed relatively less structural regularity but significant increments of pore diameter (4.64 to 7.50 nm); the fraction of mesopore volume also illustrated an increase. The adsorption heat values were correlated with the order of the adsorption capacities for pore expanded MCM-41s. After amine functionalization, the adsorption capacities and heat values showed a significant increase. APTES-grafted pore-expanded MCM-41s depicted a high potential for CO2capture regardless of the major drawback of the high energy required for regeneration.


1996 ◽  
Vol 11 (2) ◽  
pp. 518-528 ◽  
Author(s):  
V. Vendange ◽  
Ph. Colomban

Optically clear monolithic (OCM) gels of mesoporous aluminosilicates (average pore diameter 3.6 nm) and alumina (6 nm) have been prepared by slow hydrolysis-polycondensation of alkoxides and converted into OCM mesoporous glasses by heating. In order to change the properties, different ways of modifying the pore size and structure are proposed. We show that addition of boron oxide reduces the average pore diameter. A higher effect can be obtained by addition of a surfactant. In this case the mesoporous matrix becomes microporous (d < 2 nm). Another way of modifying the pore structure consists of introducing nanoprecipitates inside the porosity by an impregnation process. Modifications of the porous structure are different in alumina and aluminosilicates.


2014 ◽  
Vol 700 ◽  
pp. 125-131
Author(s):  
Jie Cheng ◽  
Han Min Liu ◽  
Dong Chen ◽  
Yue Hua Wen ◽  
Gao Ping Cao

Porous carbon monoliths are prepared by carbonization of a simple polymer blend, in which phenolic resin (PF) as carbon precursor, polyvinyl butyral as pore former and activated carbon as conducting additive and contraction inhibitor are used to make polymer blend. The results show that the carbon monoliths, with a narrow pore size distribution with mean controlled diameters in the sub-micron/micron range, can be easily produced by controlling the stabilization temperature of the PF, the carbonization temperature, and particle diameters of the precursor powders. The pore size decrease as the stabilization temperature of the PF increases or the particle diameters of the precursor powders decreases. The electrical resistance of the carbon monoliths decreases as the carbonization temperature increases, but the average pore diameter and volume of the carbon monoliths are almost constant as the carbonization temperature increases.


2013 ◽  
Vol 753-755 ◽  
pp. 792-797 ◽  
Author(s):  
Bing Xuan Ni ◽  
Peng Zhang

The hydraulic permeability performance of geosynthetics is an important functional technical index in the field of engineering application. In this paper, the pore size characteristics of a series different specifications of spunbond and needlepunched nonwoven geotextile has tested through capillary flow aperture measuring instrument, including average pore diameter, maximum pore size and pore size distribution. The permeability characteristics of nonwoven geotextile has measured by vertical permeability measuring instrument, including flow index and vertical permeability coefficient. We study on the compressive properties of nonwoven geotextile under the different pressure, through the relationship between the average pore diameter and flow index to fit curve, and built the regression equation, so we can calculate and predict the water permeability performance through pore size Characteristics.


Author(s):  
Jason Mandela ◽  
Wega Trisunaryanti ◽  
Triyono Triyono ◽  
Mamoru Koketsu ◽  
Dyah Ayu Fatmawati

The zeolite Y had been successfully modified by HCl and/or NaOH treatment. The modification of zeolite Y was performed by leaching the protonated zeolite Y (HY) in HCl solution (0.1 and 0.5 M) at 70 °C for 3 h resulting in DY0.1 and DY0.5. Subsequently, HY, DY0.1, and DY0.5 zeolites were immersed in 0.1 M NaOH for 15 min at room temperature resulting in AHY, ADY0.1, and ADY0.5. All samples were analyzed for acidity, crystallinity, Si/Al ratio, morphology, and textural properties. The catalytic performance of all samples was investigated in hydrotreating of α-cellulose bio-oil with a catalyst/feed weight ratio of 1/30. The HCl and NaOH treatment led to the decrease of the zeolite Y crystallinity and the increase of the zeolite Y average pore diameter (i.e., the mesopore distribution). The ADY0.5 gave the highest mesopore distribution, which was 43.7%, with an average pore diameter of 4.59 nm. Moreover, both of the treatments were found to increase the Si/Al ratio that caused the decrease of zeolites Y acidity. All the zeolite Y samples gave better catalytic activity to produce liquid products after being treated by NaOH. The sample ADY0.5 managed to produce 6.12% of 1-isopropyl-2,4-dimethylbenzene that has good potential to be processed into fuel.


2002 ◽  
pp. 27-34 ◽  
Author(s):  
Erne Kis ◽  
Jonjana Ranogajec ◽  
Radmila Marinkovic-Neducin ◽  
Etelka Dimic ◽  
Tatjana Vulic

AI-pillared montmorillonite was synthesized from raw clay, mined at Sipovo Srpska Republic. Its textural properties and bleaching capacity were compared with some commercial adsorbents and filtration aid materials commonly used in domestic oil industry. The bleaching capacity of AI-pillared montmorillonite is lower than that of commercial Super Celite L748 (Johns Manville, USA) or Perfit PF-3 (Termika dd., Zrenjanin Yugoslavia), but somewhat is higher than the bleaching capacity of pure montmorillonite. The results suggest that the bleaching capacity of the investigated samples is primarily determined by average pore diameter and not by specific surface area.


Author(s):  
Helen M. Kerch ◽  
Rosario Gerhardt

The pore size distribution of an unsintered colloidal gel has been determined by stereological analysis of ultramicrotomed thin sections (70 nm) of the gel. This is a novel use of the ultramicrotomy technique as the epoxy represents the porous phase of the microstructure rather than just the medium used to maintain a coherent structure during thinning. In order to obtain statistically significant pore size information a nested sampling scheme was carried out, and a total of 36 two-dimensional fields taken at 19,000 X were examined. Pore diameters were measured with a digital image analyzer which measured 15 projected diameters every 12° from the center of the feature. Stereological quantities obtained were average pore diameter (Davg), number of pores per unit area (NA), and number of pores per unit volume (NV).


Gels ◽  
2020 ◽  
Vol 6 (3) ◽  
pp. 23
Author(s):  
Elisha Martin ◽  
Martin Prostredny ◽  
Ashleigh Fletcher ◽  
Paul Mulheran

Tailoring the properties of porous organic materials, such as resorcinol–formaldehyde gels, for use in various applications has been a central focus for many studies in recent years. In order to achieve effective optimisation for each application, this work aims to assess the impact of the various synthesis parameters on the final textural properties of the gel. Here, the formation of porous organic gels is modelled using a three-dimensional lattice-based Monte Carlo simulation. We model growth from monomer species into the interconnected primary clusters of a gel, and account for varying catalyst concentration and solids content, two parameters proven to control gel properties in experimental work. In addition to analysing the textural properties of the simulated materials, we also explore their fractal properties through correlation dimension and Hurst exponent calculations. The correlation dimension shows that while fractal properties are not typically observed in scattering experiments, they are possible to achieve with sufficiently low solids content and catalyst concentration. Furthermore, fractal properties are also apparent from the analysis of the diffusion path of guest species through the gel’s porous network. This model, therefore, provides insight into how porous organic gels can be manufactured with their textural and fractal properties computationally tailored according to the intended application.


2016 ◽  
Vol 119 (suppl_1) ◽  
Author(s):  
Maureen Wanjare ◽  
Joseph Jung-Woong Kim ◽  
Ngan Huang

Since the heart is effectively an anisotropic organ in which the cardiomyocytes (CM) are locally aligned in series, it is important to engineer cardiac tissues that promote CM alignment in order to closely mimic the architecture of the native tissue, as well as better mimic the cellular composition of the heart. The objective of this study was to define the role of anisotropic extracellular matrix cues on the organization and survival of human induced pluripotent stem cell-derived CMs (hiPSC-CMs) by co-culturing hiPSC-CMs and primary endothelial cells (ECs) on parallel-aligned microfibrillar scaffolds. The hiPSC-CMs were generated from hiPSCs using small molecule Wnt pathway agonists and antagonists. Subsequently, the hiPSC-CMs were sequentially seeded on day 15 after EC attachment. We cultured monocultures and cocultures on electrospun three-dimensional (3D) scaffolds of polycaprolactone (PCL) and polyethylene oxide (PEO) polymer blends with an average fiber diameter of 14 μm. Aligned scaffolds were fabricated by stretching the randomly oriented scaffolds by 300% of the original scaffold length. Randomly oriented fibrillar scaffolds had an average pore diameter of 17 μm when compared to the 36 μm pore diameter of aligned scaffolds. Our results indicate that alignment of co-cultured cells at a 5:1 hiPSC-CMs : EC ratio was promoted by anistropic 3D electrospun scaffolds when compared to similar random 3D electrospun scaffolds. Additionally, cocultured cells on aligned fibrillar scaffolds had a mean angle of orientation of 30.8°, relative to the direction of fibrils, which was similar to that of hiPSC-CM monocultures on aligned scaffolds (32.8°). In contrast, the degree of alignment of hiPSC-CMs on randomly oriented fibrillary scaffolds was 43.4°, which suggests a non-oriented population of cells. Aligned scaffolds also produced more synchronized cardiomyocyte contraction than random scaffold orientations, although both induced spontaneous contraction frequency of ~1Hz. This study highlights the importance of nanotopographical cues and intercellular interactions in mediating the morphology and contractility of hiPSC-CMs for treatment of cardiovascular diseases such as myocardial infarction.


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