Sieve Type Research Articles

High-performance carbon molecular sieve membranes for ethylene/ethane separation derived from an intrinsically microporous polyimide

An intrinsically microporous polymer with hydroxyl functionalities, PIM-6FDA-OH, was used as a precursor for various types of carbon molecular sieve (CMS) membranes for ethylene/ethane separation. The pristine polyimide films were heated under controlled N2 atmosphere at different stages from 500 to 800°C. All CMS samples carbonized above 600°C surpassed the polymeric ethylene/ethane upper bound. Pure-gas selectivity reached 17.5 for the CMS carbonized at 800°C with an ethylene permeability of about 10Barrer at 2bar and 35°C, becoming the most selective CMS for ethylene/ethane separation reported to date. As expected, gravimetric sorption experiments showed that all CMS membranes had ethylene/ethane solubility selectivities close to one. The permselectivity increased with increasing pyrolysis temperature due to densification of the micropores in the CMS membranes, leading to enhanced diffusivity selectivity. Mixed-gas tests with a binary 50:50 v/v ethylene/ethane feed showed a decrease in selectivity from 14 to 8.3 as the total feed pressure was increased from 4 to 20bar. The selectivity drop under mixed-gas conditions was attributed to non-ideal effects: (i) competitive sorption that reduced the permeability of ethylene and (ii) dilation of the CMS that resulted in an increase in the ethane permeability.

Synthesis and Characterization of Bio-based Nanomaterials from Jabon (Anthocephalus cadamba (Roxb.) Miq) Wood Bark: an Organic Waste Material from Community Forest

The application of nanotechnology to produce nanomaterials from renewable bio-based materials, like wood bark, has great potential to benefit the wood processing industry. To support this issue, we investigated the production of bio-based nanomaterials using conventional balls milling. Jabon ( Anthocephalus cadamba (Roxb.) Miq) wood bark (JWB), an organic waste material from a community forest was subjected to conventional balls milling for 96 h and was converted into bio-based nanomaterial. The morphology and particle size, chemical components, functional groups and crystallinity of the bio-based nanomaterial were evaluated using scanning electron microscopy (SEM), scanning electron microscopy extended with energy dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The particle-sizes obtained for the JWB bio-based nanomaterial were between 43 nm to 469 nm and the functional groups were detected as cellulose. The chemical components found were carbon, oxygen, chloride, potassium and calcium, except for the sample produced from sieve type T14, which did not contain chloride. The crystalline structure was calcium oxalate hydrate (C 2 CaO 4 .H 2 O) with crystalline sizes 21 nm and 15 nm, produced from sieve types T14 and T200 respectively.

A method to engineer phase-encoded photon sieve for intensity pattern generations

We propose a novel type of photon sieve where phases of its sieved waves are encoded as radial positions of the pinholes and use such phase-encoded sieves for generating designed intensity patterns in Fresnel domain. The sieve pinholes are arranged around Fresnel-rings to eliminate the quadratic Fresnel phase factor of diffraction of the sieved waves, leading the wave propagation to be equivalent to Fraunhofer diffraction. The pinholes take constant size in this paper and realize equal amplitude in the multiple sieved waves. Their positions are adjusted radially from corresponding rings to encode wave phases, taking effect by resulting in different optical paths from them to the observation plane origin. Then along with wave propagation, the encoded phases are decoded and the required phase differences are obtained in the discrete waves. We first conduct numerical simulations to show satisfactory performance of such phase-encoded photon sieves in generating arbitrarily designed intensity patterns and describe the quality of the reconstructed patterns. Then for qualitatively verifying the phase-encoding method, we experimentally fabricate three such sieves with relatively small pinhole number and obtain the designed patterns.

Development length of steel reinforcement with corrosion protection cementitious coatings

The bond strength and development length of steel reinforcing bars coated with cementitious capillary crystalline waterproofing materials were evaluated using a modified pull-out test method. The coatings possess self-healing capabilities and are characterized by a novel eka-molecular sieve type structure to prevent moisture penetration. Following a study on corrosion protection, in which the coating showed a great promise, it was decided to investigate the effect of the coating on bond strength. A self-reacting inverted T-shaped beam was designed to simulate the stress conditions of flexural structural members. Six T-beams were fabricated, each of which contained eight rebar test samples. Tests were conducted at approximately seven days and at three months after casting to investigate curing effect on bond. Although the bond strength of the coated samples were reduced compared with the uncoated bars, theoretical development lengths obtained from current concrete design code equations were sufficient to reach the yield strength of the bars.

Cryogenic separation of an oxygen-argon mixture in natural air samples for the determination of isotope and molecular ratios.

The separation and purification of oxygen-argon mixtures are critical in the high-precision analysis of Δ(17) O and δ(O2 /Ar) for geochemical applications. At present, chromatographic methods are used for the separation and purification of oxygen-argon mixtures or pure oxygen, but these methods require the use of high-purity helium as a carrier gas. Considerable interest has been expressed in the development of a helium-free cryogenic separation of oxygen-argon mixtures in natural air samples. The precise and simplified cryogenic separation of oxygen-argon mixtures from natural air samples presented here was made possible using a single 5A (30/60 mesh) molecular sieve column. The method involves the trapping of eluted gases using molecular sieves at liquid nitrogen temperature, which is associated with isotopic fractionation. We tested the proposed method for the determination of isotopic fractionations during the gas exchange between water and atmospheric air at equilibrium. The dependency of fractionation was studied at different water temperatures and for different methods of equilibration (bubbling and stirring). Isotopic and molecular fractionations during gas desorption from molecular sieves were studied for different amounts and types of molecular sieves. Repeated measurements of atmospheric air yielded a reproducibility (±SD) of 0.021 ‰, 0.044 ‰, 15 per meg and 1.9 ‰ for δ(17) O, δ(18) O, Δ(17) O and δ(O2 /Ar) values, respectively. We applied the method to determine equilibrium isotope fractionation during gas exchange between air and water. Consistent δ(18) O and Δ(17) O results were obtained with the latest two studies, whereas there was a significant difference in δ(18) O values between seawater and deionized water. We have revised a helium-free, cryogenic separation of oxygen-argon mixtures in natural air samples for isotopic and molecular ratio analysis. The use of a single 13X (1/8" pellet) molecular sieve yielded the smallest isotopic and molecular fractionations, and this fractionation by molecular sieves can be corrected by the amount of molecular sieve used in the experiment. The reproducibility of the method was tested by the measurement of the oxygen isotope ratios of dissolved oxygen at equilibrium with atmospheric air. We confirmed that the choice of methods for making air-equilibrated water was not related to the magnitude of isotope fractionation, whereas there was a difference between seawater and deionized water.

Aminopropyl-modified mesoporous molecular sieves as efficient adsorbents for removal of auxins

In the present study, mesoporous siliceous materials grafted with 3-aminopropyltriethoxysilane (APTES) were examined as sorbents for removal of chosen plant growth factors (auxins) such as 1-naphthaleneacetic acid (NAA), indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA). Four different types of mesoporous molecular sieves including SBA-15, PHTS, SBA-16 and MCF have been prepared via non-ionic surfactant-assisted soft templating method. Silica molecular sieves were thoroughly characterized by nitrogen adsorption–desorption analysis, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The maximum adsorption capacity (Qmax) for NAA, IAA and IBA was in the range from 51.0 to 140.8mg/g and from 4.3 to 7.3mg/g for aminopropyl-modified adsorbents and pure silicas, respectively. The best adsorption performance was observed for IAA entrapment using both APTES-functionalized SBA-15 and MCF matrices (Qmax of 140.8 and 137.0mg/g, respectively) which can be ascribed to their larger pore volumes and pore diameters. Moreover, these silicas were characterized by the highest adsorption efficiency exceeding 90% at low pollutant concentration. The experimental points for adsorption of plant growth factors onto aminopropyl-modified mesoporous molecular sieves fitted well to the Langmuir equation.

Carbonylation of Methanol with CO in Presence Potassium Methoxide Catalyst

Catalysts prepared from potassium hydroxide and methanol were tested for methanol carbonylation with CO in the range of 70-90oC and 20-25kg/cm2(g). Methyl formate was produced selectively under the studied conditions. Lower temperatures and higher pressures enhanced the conversion of CO. Water in the catalyst solution did not completion removed by molecular sieve type 3A, thus the catalyst activity becomes decreased. The influence of inert gases in the gas mixture will cause the partial pressure of CO decreased and also conversion of CO. The reaction rate was first order with respect to the concentration of CO in the gas phase. The activation energy was found to be 14.95kJ/mol and frequency collision factor is 0.59 min-1.

N-methyldiethanolamine: A multifunctional structure-directing agent for the synthesis of SAPO and AlPO molecular sieves

In the present study, N-methyldiethanolamine (MDEA) is demonstrated to be a multifunctional structure-directing agent for the synthesis of aluminophosphate-based molecular sieves. Four types of molecular sieves, including SAPO-34, -35, AlPO-9 and -22, are for the first time acquired with MDEA as a novel template. The phase selectivity of the present synthesis is found to be condition-dependent. SAPO-34 (CHA) crystallizes from a conventional hydrothermal system with a higher MDEA concentration. When using MDEA as both the template and solvent, pure SAPO-35 (LEV) is obtained from the synthetic gel with a high P2O5/Al2O3 ratio of (2–3), in which the concentration of MDEA could be varied in a wide range. AlPO-9 and AlPO-22 (AWW) are synthesized under the similar conditions to SAPO-35, except without the addition of Si source. The physicochemical properties of the obtained samples are investigated by XRD, XRF, SEM, N2 physisorption, TG-DSC, and various NMR spectra (13C, 29Si, 27Al and 31P). Both SAPO-34 and SAPO-35 show good thermal stability, large surface area, and high pore volume. The catalytic performance of SAPO-34 is evaluated by the methanol-to-olefins (MTO) reaction and a good (C2H4+C3H6) selectivity of 82.7% has been achieved.

Determination of Milling Module for Different Categories of Concentrates Feeds (Grain: Wheat and Corn)

The study was made in order to establishing qualitative indexes of concentrate feeds made by hummer mill MB-7,5 equipped with 3 type of sieves and 2 type of hummers on mill rotor. Granularity tests were made by Sieving Machine AS-300 with 4 sieve-plates. Concentrate feeds were wheat and corn at 2 different humidity levels, from each milling product were tacked 3 samples for Sieving Machine, were made averages to estimate milling module. Results show us the major influence of grain type (wheat or corn) in granularity determination, humidity of grain modify also our expected results.

회사장 혼합석탄재의 압축강도 특성

The various recycling methods of mixed coal ash have been developed considerably and it`s recycling quantity has been increased. However, the more relatively finer grain content of coal ash in ash pond is increased the more it`s quantity is increased in recycling as products for drainage in soft ground etc. Accordingly, the geotechnical properties of mixed coal ash in ash pond would be inferior and it`s recycling rate should reach the limitations in increase. In this study, to recycle mixed coal ash contained fine grain in considerably amount as products for strength, etc. By adding binder to it and manifesting, it`s compressive strength is stronger than the criteria, these are suggested; 1) the variety of compressive strength test performed on mixed coal ash of various grain distributions as main material, 2) the kind of binder, it`s mixing quantity and the optimum content rate range of fine grain coal ash that the compressive strength stronger than a certain compressive strength is manifested. Cement is more excellent than quicklime as binder in manifesting stronger compressive strength and the sieve type to sort it is #40 sieve in order to recycle all mixed coal ash in ash pond efficiently as products for drainage as well as products for strength, etc. And, it could increase insufficient compressive strength remarkably that content of pure sand is more in the rate as pure sand and the part of mixed coal ash in ash pond to pass through #40 sieve is mixed in the ratio of 2 to 8.

Verifying the mechanism of the ethene-to-propene conversion on zeolite H-SSZ-13

Several types of microporous molecular sieves with similar nSi/nAl ratios (except for SAPO-34) and different pore structures were prepared and applied as ethene-to-propene (ETP) catalysts. H-SSZ-13 zeolite consisting of chabazite cages connected via 8-ring windows possessed the highest adsorption capacity for ethene and exhibited the best activity in the ETP conversion. The decreasing amount of Brønsted acid sites after dealumination of H-SSZ-13 caused a prolonged lifetime of the catalyst in the ETP reaction. The reaction mechanism and deactivation behavior of H-SSZ-13 catalysts during the ETP process were investigated by in situ FT-IR, UV/Vis, GC–MS, TGA and 1H MAS NMR methods. Ethene was rapidly oligomerized and converted into naphthalene-based carbenium ions, playing a significant role in the ETP reaction. The accumulation of these species lead to the formation of polycyclic aromatics, which are responsible for a total blocking of H-SSZ-13 pores, and cause the deactivation of the catalyst.

Composite Proton Exchange Membranes of Sulfonated Poly(ether ketone ether sulfone) (S-PEKES) and Molecular Sieve With High Mechanical Strength for Direct Methanol Fuel Cell

Composite proton exchange membranes are prepared by solvent casting via the incorporation of molecular sieves 3A, 4A, and 5A into the sulfonated poly(ether ketone ether sulfone) (S-PEKES) at the sulfonation degree of 0.66, with varying the ratio at of 3%, 6%, 9%, and 12% v/v. The influences of type and amount of the molecular sieves on the proton conductivity, methanol permeability, structural, thermal, and mechanical stabilities of the membranes are investigated. The composite membranes are characterized by FTIR, TGA, LCR meter, and GC techniques. All properties of the composite membrane are compared with the pristine S-PEKES and Nafion 117 membrane.

A local large sieve inequality for cusp forms

We prove a large sieve type inequality for Maass forms and holomorphic cusp forms with level greater or equal to one and of integral or half-integral weight in short interval.

Influence of Sieve Openings Size for Hammer Mills on the Degree of Shredding and Grinding Energy Consumption for Wheat

Hammer mills are machines used in agriculture to obtain concentrated fodder mix. The hammer mills grinding materials is produced upon impact of the hammer material and crushing plate located inside the grinding chamber. Depending on the hammers rotor assembly mode, the following types of mills can be used: hammer mills articulated and fixed hammer mills. The finesse of the flour obtained is directly influenced by the type of hammer and sieve used.

Microwave radiation hydrothermal synthesis and characterization of micro- and mesoporous composite molecular sieve Y/SBA-15

A microwave radiation hydrothermal method to control synthesis of micro- and mesoporous Y/SBA-15 composite molecular sieves was reported. The synthesized SBA-15 and Y/SBA-15 were characterized by scanning electron microscopy (SEM) and N2 adsorption–desorption. The three kinds of different concentrations of hydrochloric acid (0.75M, 2M and 3.25M) were used to investigate the effect on Y/SBA-15. The analysis results of the composite products indicated that the optimization synthesis condition employed zeolite type Y and TEOS as silicon sources under 0.75M hydrochloric acid by the microwave radiation hydrothermal synthesis method. The N2 adsorption–desorption test results of micro–mesoporous composite molecular sieve type Y/SBA-15 in mesoporous extent indicated that SBET is 355.529m2/g, D‾BET is 4.050nm, and mesoporous aperture focuses on the distribution region of 5.3nm. It was found that the received composite product has an appropriate proportion of smaller size, larger size pore structure and the thicker pore wall. In addition, its internal channels have a high degree of order and smooth flow in long-range channels.

Evaluation of Iron-Containing Aluminophosphate Molecular Sieve Catalysts Prepared by Different Methods for Phenol Hydroxylation

Three iron-containing AlPO4-5 molecular sieve catalysts (i.e. FeAlPO-5-Iono, FeAlPO-5-Hydro and FeAlPO-5-Imp) were prepared by ionothermal synthesis, direct hydrothermal synthesis and impregnation method, and characterized by various techniques. N2 adsorption/desorption measurements, together with the results of SEM and TEM, showed that FeAlPO-5-Iono was a new type of aluminophosphate molecular sieve with hierarchical micro- and meso-porous structure, whereas both FeAlPO-5-Hydro and FeAlPO-5-Imp were typical microporous materials. DR UV–Vis analysis suggested that the order of the amounts of isolated Fe3+ species in these three samples was as follows: FeAlPO-5-Hydro > FeAlPO-5-Iono > FeAlPO-5-Imp. However, the order of their catalytic performances towards phenol hydroxylation was in opposition to that of the amounts of isolated Fe3+ species. Detailed analysis revealed that it was textural properties of these catalysts that determined phenol conversion and dihydroxylbenzene selectivity. The catalyst-recycling tests suggested that extra-framework iron clusters were readily leached into the reaction system and had great influence on the hydroxylation of phenol. Due to the sole presence of isolated Fe3+ species and enhanced mass transport of reactants and products to/from these active sites, FeAlPO-5-Hydro was found to have the best reusability among these catalysts. .

Continuous Membrane Emulsification with Pulsed (Oscillatory) Flow

Tubular micrometer pore sized sieve type membranes with internal diameter of 14 mm and length of 60 mm containing uniform pores of diameter 10 and 20 μm were used to generate emulsions of sunflower oil dispersed in water and stabilized by Tween 20 using oscillatory flow of the continuous phase. Drop diameters between 30 and 300 μm could be produced, in a controllable way and with span values of down to 0.4. By using pulsed flow it was possible to provide dispersed phase concentrations of up to 45% v/v in a single pass over the membrane, that is, without the need to recirculate the continuous phase through the membrane tube. It was possible to correlate the drop size produced with the shear conditions at the membrane surface using the wave shear stress equation. The oscillatory Reynolds number indicated flow varying from laminar to substantially turbulent, but the change in flow conditions did not show a notable influence on the drop diameters produced, over what is predicted by the varying wall shear stress applied to the wave equation. However, the 20 μm pore sized sieve type membrane appeared to allow the passage of the pressure pulse through the membrane pores, under certain operating conditions, which did lead to finer drop sizes produced than would be predicted. These through-membrane pulsations could be suppressed by changes in operating conditions: a higher dispersed phase injection rate or more viscous continuous phase, and they did not occur under similar operating conditions used with the 10 μm pore sized sieve type of membrane. Generating emulsions of this size using pulsed continuous phase flow provides opportunities for combining drop generation at high dispersed phase concentration, by membrane emulsification, with downstream processing such as reaction in plug flow reactors.

Carboxylesterase from Spodoptera Litura: Immobilization and use for the Degradation of Pesticides

The immobilization of carboxylesterase from Spodoptera Litura in mesoporus molecular sieves was studied in this paper. Two different types of mesoporous sieves (MCM-41, SBA-15) were initially used as enzyme support to compare the efficiency of immobilization. The outcome showed the maximum enzyme loadings, twice as many in MCM-41, are 0.0267 L/g in SBA-15 support. The most efficient pH value for immobilization was at 6.5 for both types of the support and the optimal immobilizing time was 2h for SBA-15 and 4h for MCM-41. Hence, the SBA-15 mesoporous support was determined as the enzyme immobilization matrix to continue the investigation because of its superior properties for enzyme immobilization. Then a series of characters of the free and immobilized Carboxylesterase were compared. As a result, the immobilized enzyme was substantiated to be obviously more stable than the free enzyme under the variant conditions. The experiments of pesticides degradation show that, relative to degradation in natural environment, immobilization enzyme had a higher ability to reduce the organic compounds with ester bonds.

Deconvolution estimation of mixture distributions with boundaries

In this paper, motivated by an important problem in evolutionary biology, we develop two sieve type estimators for distributions that are mixtures of a finite number of discrete atoms and continuous distributions under the framework of measurement error models. While there is a large literature on deconvolution problems, only two articles have previously addressed the problem taken up in our article, and they use relatively standard Fourier deconvolution. As a result the estimators suggested in those two articles are degraded seriously by boundary effects and negativity. A major contribution of our article is correct handling of boundary effects; our method is asymptotically unbiased at the boundaries, and also is guaranteed to be nonnegative. We use roughness penalization to improve the smoothness of the resulting estimator and reduce the estimation variance. We illustrate the performance of the proposed estimators via our real driving application in evolutionary biology and two simulation studies. Furthermore, we establish asymptotic properties of the proposed estimators.

On some lower bounds of some symmetry integrals

We study the “symmetry integral”, say \(I_f\), of some arithmetic functions \(f:\mathbb{N }\rightarrow \mathbb{R }\); we obtain from lower bounds of \(I_f\) (for a large class of arithmetic functions \(f\)) lower bounds for the “Selberg integral” of \(f\), say \(J_f\) (both these integrals give informations about \(f\) in almost all the short intervals \([x-h,x+h]\), when \(N\le x\le 2N\)). In particular, when \(f=d_k\), the divisor function (having Dirichlet series \(\zeta ^k\), with \(\zeta \) the Riemann zeta function), where \(k\ge 3\) is integer, we give lower bounds for the Selberg integrals, say \(J_k=J_{d_k}\), of the \(d_k\). We apply elementary methods (Cauchy inequality to get Large Sieve type bounds) in order to give \(I_f\) lower bounds.