Molecular Sieve 13X Research Articles

An experimental investigation to assess the potential of using MgSO4 impregnation and Mg2+ ion exchange to enhance the performance of 13X molecular sieves for interseasonal domestic thermochemical energy storage

The need to develop renewable heat sources for domestic space heating is a well known problem, for solar thermal systems mismatch between generation and load is a major issue, and thermochemical interseasonal heat storage offers a solution to this problem. Recent research has shown that using an absorbent material as a host for salt hydrates can be advantageous in achieving a high energy density material while alleviating the problematic practical characteristics, such as agglomeration, which salt hydrates typically possess. In this paper results are presented for a 13X molecular sieve which was tested to determine its potential for interseasonal domestic thermochemical energy storage alone and as a host material for Magnesium Sulfate (MgSO4). Two different impregnation preparation methods have been utilised in our experiments, (i) a wetness impregnation method and (ii) a new method in which 13X molecular sieve powders and MgSO4 are formed into pellets with use of a binder. The materials produced by each method were tested against each other and compared to a zeolite-Y material to assess which is the best candidate material for thermal energy storage. The impact of ion exchange on the energy storage potential of the 13X materials was also investigated. Analysis of the materials characteristics and thermal performance was conducted using a Differential Scanning Calorimeter (DSC), Thermogravimetric Analyser (TGA) coupled with a Residual Gas Analyser (RGA), Scanning Electron Microscope (SEM) with Energy Dispersive X-ray (EDX) spectroscopy and a custom built fixed bed 200g in-situ hydration and dehydration chamber to assess the materials performance on a larger scale. The results demonstrate that the thermochemical storage potential of the 13X molecular sieve was enhanced following a Mg2+ ion exchange process, resulting in a maximum increased energy storage of approximately 14% (65J/g) compared to standard non treated 13X pellets.

Equilibrium adsorption of ethyl mercaptan and thiophene using molecular sieve 13X

In the present study, adsorption of the sulfur compound onto two types of molecular sieve (HYD10B and LQ-MS-13X) in a batch system was investigated. It has been illustrated that HYD10B type has more adsorption capacity than LQ-MS-13X type to separate ethyl mercaptan from simulated liquid mixture. Selected as the better adsorbent, the isotherm equilibrium adsorptions of ethyl mercaptan and thiophene in liquid phase had been carried out by using this type of molecular sieve in the temperature range of 25–65 °C. HYD10B-MS-13X brought out the highest adsorption capacity for adsorption of ethyl mercaptan component. Diminution of adsorption capacity with temperature increment has been found and it was shown that adsorption of ethyl mercaptan is less affected by temperature changes. Using four more common isotherm models (Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich), Freundlich isotherm was found to be the best representative model for describing ethyl mercaptan and thiophene equilibrium data.

Fluidised bed drying of powdered materials: Effects of operating conditions

The fluidized bed drying of powdered materials was studied with a focus on the modifications of the agglomerate population as a result of abrasion and fragmentation. A number of test were carried out in a Lexan® lab-scale fluidised bed with different granular materials, namely a pharmaceutical powder supplied by Novartis-Farma S.p.A., wheat bran, and a molecular sieve 13X, selected to effectively surrogate powders of interest in various industrial applications such as pharmaceuticals pills and adsorption pellets manufacture. The process was monitored to correlate the temperature and the flow rate of the fluidising gas, the temperature and the moisture level in the bed, the qualitative fluidisation patterns. Experimental results were further worked out to highlight the effects of inlet air temperature and gas velocity on process thermal efficiency. Bed material was characterized to assess the modifications of the population of agglomerates as a function of the operating conditions.

Combination of adsorption followed by ozone oxidation with pressure swing adsorption technology for the removal of VOCs from contaminated air streams

This paper reports the application of adsorption followed by ozone oxidation in the pressure swing adsorption (PSA) process for the removal of VOCs from contaminated air streams. For that 13X molecular sieves and o-xylene selected as adsorbent and contaminant (one of the VOCs), respectively. The adsorption capacity of 13X molecular sieves for o-xylene is significantly increased from 0.6 to 2.8mmol/g with pressure from 0.5 to 5.0kg/cm2 and these values are relatively good compatible with the Freundlich isotherm model. The 13X molecular sieves are efficiently regenerated in 70min by ozone oxidation process at 25°C and the adsorbed o-xylene is significantly oxidized to the CO2. In four successive cycles of adsorption followed by ozone oxidation process, the adsorption efficiency of 13X molecular sieves is not affected (±5%). Further, the adsorption-ozone oxidation process embedded PSA system is operated continuously for 50h and there is no breakthrough observed in the fresh air. So that, the combination of adsorption followed by ozone oxidation with PSA process seems to be the better technology for the removal of VOCs from the contaminated air streams.

Breakthrough Studies of Methyl Salicylate and DMMP Mixed in Methyl Salicylate with Pressure Swing Adsorption Composed of 13X Molecular Sieves

A test procedure for pressure swing adsorption (PSA) was established and elucidated for the air purification using methyl salicylate (MeS) and 5% (v/v) dimethyl methyl phosphonate (DMMP) in MeS containing air stream as feed. The effect of feed flow rate was studied by varying the flow from 5 lpm to 20 lpm, for both the molecules at 25 oC and 4 kg/cm2. The results revealed that the flow rate had a significant influence on the breakthrough time. A method was developed for the determination of feed, purge, and dry air composition, by the solvent extraction method using the XAD-2 and the average concentrations reported. The 13X molecular sieves were characterised for its structural and textural properties such as BET- SA, XRD, and FT-IR. The temperature programmed desorption of DMMP and MeS on 13X clearly demonstrated that it was easily regenerated at ~320 °C after prolonged field operation of PSA. The PSA results obtained with PSA composed molecular sieves appeared to give promising technology for air purification and specifically to the chemical warfare agents simulants.

Preparation and characterization of TiO2 incorporated 13X molecular sieves for photocatalytic removal of acetaminophen from aqueous solutions

Although stabilizing of nano-particles on porous media is a suitable methods in harnessing the agglomeration and inactivation of nano-particles, but still release of particles to the environment remains the most serious challenges facing toward photocatalysis process. Attachment of nanoparticles through ion exchange may be a promising method to solving these defects. In this study TiO2 was incorporated into the 13X molecular sieves by addition of the titanyl ion through an ion-exchange of ammonium-titanyl-oxalate as well as the decomposition of titanyl oxalate salt, which remained on the zeolite through the impregnation and calcination process. A part of TiO2 on the zeolite was also bound through a TiOSi bond. The investigation of TiO2-HX catalytic potential showed that neutral pH and 500mg/L catalyst were the optimal conditions for acetaminophen removal (1mg/L) in the UV/TiO2-HX process. The maximum removal efficiency of 95.45%±0.8 was attained after 75min contact time. The acetaminophen degradation during the UV/TiO2-HX process was followed a pseudo first order kinetic model with rate constants (Kapp) of 0.8676h−1. Under the optimum conditions, maximum synergistic efficiency of 60.07% was acquired. The experimental data showed that the UV/TiO2-HX process is effective in acetaminophen removal from aqueous solutions.

Granular core phenomenon induced by convection in a vertically vibrated cylindrical container.

A mixture of 13X molecular sieve (13XMS) particles and glass particles with identical diameters is placed in a cylindrical container. Under vertical vibration, heavier glass particles tend to cluster and are wrapped inside the convection of 13XMS particles, resulting in the granular core phenomenon. The vibration frequency f strongly influences particle convection and particle cluster modes. By contrast, the effect of the dimensionless acceleration amplitude Γ can be neglected. For different f ranges, the granular core is classified as center-type and ring-type cores. For the center-type core, heavy particles are distributed as an approximate zeroth-order Bessel function of the first kind in the radial direction and an exponential function in the height direction. For the ring-type core, the concentration of heavy particles follows the power-series function in the radial direction. A granular transport model is then established based on heavy-particle movements under steady state to analyze the effect of vibration parameters and granular convection on density segregation.

Polymer Electrolyte Composite Membrane Based on Molecular Sieve 13X Mixed with Sulfonated Poly(ether ketone ether sulfone)/Poly(phenylene ether ether sulfone) Blended Membrane for Use in Direct Methanol Fuel Cell

AbstractBlend membranes between sulfonated poly(ether ketone ether sulfone) (S‐PEKES) and poly(phenylene ether ether sulfone) (PPEES) were fabricated at various mole ratios. Interestingly, increasing the hydrophobic PPEES in S‐PEKES/PPEES blend membranes led to the decreases in water uptake (%) when compared to S‐PEKES. Incorporation of molecular sieve 13X drastically improved proton conductivity. Methanol permeability slightly decreased with molecular sieve 13X. The composite membrane with the 15% v/v molecular sieve 13X content showed the highest proton conductivity of 1.44 × 10−2 S/cm which is four times higher than Nafion 117. Thus, the blending between S‐PEKES and PPEES can help to decrease methanol permeability, and incorporating molecular sieve 13X can enhance proton conductivity.

Vapor Phase Selective Catalytic Oxidation of Cyclohexane over 13X Supported Metal Oxides in the Presence of Ozone

ABSTRACTThis article reports the application of ozone for the selective oxidation of cyclohexane over 13X molecular sieve supported various metal oxides at ambient temperatures. From the SEM, XRD and HR-TEM results, the impregnated metal oxides are highly dispersed on the support. The activity results reveal that Co/MS, Mo/MS, Cu/MS, and Ag/MS catalysts produce cyclohexanone/cyclohexanol as selective oxidation products, whereas Ce/MS, Mn/MS, and V/MS catalysts yield, predominantly, CO and CO2. Among them, Co/MS catalyst exhibits better conversion of 12.2% with selectively of 58% to cyclohexanone/cyclohexanol, which is attributed to the simultaneous activation of ozone and cyclohexane (-C-H bond) at ambient conditions.

Adsorption Behavior and Removal Mechanism of Arsenic from Water by Fe(III)-Modified 13X Molecular Sieves

Presented are the synthesis and characterization of Fe(III)-modified 13X molecular sieves and their application as a novel adsorbent for removing arsenic from aqueous solutions. Batch experimental results showed that Fe(III) adsorption by 13X molecular sieves matched well with the Langmuir adsorption isotherm. The adsorption kinetics of arsenic on the Fe(III)-modified molecular sieves fit well with a pseudo-second-order model. The Langmuir adsorption isotherms of arsenic adsorption indicated the highest adsorption capacities of 1167.79 for As(V) at pH 4 and 731.56 mg/kg for As(III) at pH 9. The Fe(III)-modified 13X molecular sieves removed much more As(V) than As(III) at equivalent arsenic concentrations, regardless of the pH conditions. After As(V) removal, the Fe(III)-modified 13X molecular sieves were characterized by PXRD, SEM-EDX, and ATR-FTIR to analyze the morphology and arsenic speciation. The results of PXRD and SEM-EDX spectroscopy indicated that the material was physically stable after As(V) adsorption. ATR-FTIR spectroscopy showed that the formation of inner-sphere surface complexations between Fe hydroxide on the surface of the molecular sieves and As(V) could be a plausible mechanism for the uptake of arsenic by the Fe(III)-modified 13X molecular sieves. Therefore, the relatively low cost and remarkable arsenic-adsorption performance make the title material a promising absorbent for the treatment of arsenic in wastewater.

Atmospheric Pressure Ammonia Synthesis Using Non-thermal Plasma Assisted Catalysis

This paper described a novel and green approach on catalytic ammonia synthesis using non-thermal plasma (NTP). The process studied in this paper involves the synthesis and absorption of ammonia under atmospheric pressure and low temperature. The effects of operational parameters including applied voltage, frequency, gas component and flow rate on ammonia synthesis under NTP conditions are studied in this paper. In addition, different selected catalysts and absorbents were investigated under different conditions of NTP treatment and the ammonia efficiency was reported and analyzed. Ru catalyst with carbon nanotube support, along with Cs promoter and micro porous absorbents including Molecular Sieve 13X and Amberlyst 15 yield the highest ammonia efficiency in this process. Results further indicated that frequency and applied voltage of 10,000 Hz and 6000 V, with N2:H2 feed ratio of 3:1 provided the optimized efficiency of ammonia synthesis of 2.3 gNH3/kWh.

Synthesis, Characterization and Application of N-Ti/13X/MCM-41 Mesoporous Molecular Sieves.

Di-n-butyl phthalate (DBP) is a type of phthalate ester. In recent years, an increasing number of studies have examined the removal of DBP. In this study we use a composite material of N-Ti/13X/MCM-41, synthesized by nitrogen, molecular sieve 13X, tetrabutyl orthotitanate and tetraethyl orthosilicate as raw materials, CTAB as a structural template and tetrabutyl titanate and urea under hydrothermal conditions. The optimized experimental conditions, such as the amount of material, reaction time, pH value and initial concentration were tested. The surface areas of N-Ti/13X/MCM-41 were found to be 664 m2g(-1). TEM micrographs revealed N-Ti/13X/MCM-41 is consisting of aggregates of spherical particles, similar with standard synthesized MCM-41 (Mobil Composition of Matter No. 41). Through photocatalytic degradation experiments, the optimum degradation efficiency of DBP was more than 90% at a pH 6.0 with catalyst dosing of 0.15 g L(-1).

Preparation of cylindrical extrudates of mesoporous silica-alumina without use of binder and their activity in cracking of cumene

A series of mesoporous silica–aluminas (MSA) containing 24–59 wt% Al2O3 was synthesized from sodium metasilicate and aluminum nitrate and extruded in 1/16″ cylinders without use of a binder. This was followed by slow hydrogel drying, extraction by water and calcination at 500 °C. This procedure gave stable hard extrudates and the absence of binder allowed to keep the surface area, mesoporosity and cracking activity of MSA at the original high values. The resistance to crushing was much better as compared to commercial molecular sieve 13X. The extrudates have average pore size around 3.5 nm. Their properties were affected by the contents of Al2O3 and residual sodium. The MSA containing 50 wt% Al2O3 possessed the maximum values of surface area, pore volume and activity in cumene cracking. The calcined extrudates showed good water sorption capacity and were stable in aqueous environment. This predestinates the MSA extrudates as the shaped mesoporous acidic carriers for preparation of different supported catalysts.

Adsorption equilibrium of methane and carbon dioxide on zeolite 13X: Experimental and thermodynamic modeling

A static, volumetric method has been used to determine the adsorption equilibrium of CH4 and CO2 and their binary mixtures on 13X molecular sieves at various temperatures between 273 and 343K. Pressures for the pure component data extend up to 10bar, while all binary data were obtained at 4bar and 6bar. The measured pure isotherms were regressed using different isotherm equations and the regressed parameters were applied to different thermodynamic models such as ideal adsorbed solution theory (IAST), vacancy solution theory (VST) and real adsorbed solution theory (RAST). CH4/CO2 system that deviate from ideality is not well represented by IAST and VST, whereas RAST which include activity coefficient in the adsorbed phase as characterizing parameter for non-ideality, show a much better representation of the binary equilibria. Experimental selectivities CO2/CH4 range from 26 to 2 at different pressure and temperatures. It is concluded that zeolite 13X suitable for natural gas industrial separation with yCO2<0.2 at 303K and 4bar. For landfill gas upgrading, where yCO2<0.45, zeolite 13X can be successfully applied at 303K, 4bar and 303K, 6bar and 323K, 4bar.

A portable molecular-sieve-based CO2 sampling system for radiocarbon measurements.

We have developed a field-capable sampling system for the collection of CO2 samples for radiocarbon-concentration measurements. Most target systems in environmental research are limited in volume and CO2 concentration, making conventional flask sampling hard or impossible for radiocarbon studies. The present system captures the CO2 selectively to cartridges containing 13X molecular sieve material. The sampling does not introduce significant under-pressures or significant losses of moisture to the target system, making it suitable for most environmental targets. The system also incorporates a significantly larger sieve container for the removal of CO2 from chambers prior to the CO2 build-up phase and sampling. In addition, both the CO2 and H2O content of the sample gas are measured continuously. This enables in situ estimation of the amount of collected CO2 and the determination of CO2 flux to a chamber. The portable sampling system is described in detail and tests for the reliability of the method are presented.

Conventional hydrothermal synthesis of nanoporous molecular sieve 13X for selective adsorption of trace amount of hydrogen sulfide from mixture with propane

Nanoporous molecular sieve 13X was successfully synthesized through the conventional hydrothermal method by using sodium aluminates as Al source and water-glass solution as an economic reagent for Si source. The hydrothermal reaction was performed under a static condition in an air oven maintained at 90 ± 5 °C for 24 h. Nano molecular sieve was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and nitrogen adsorption desorption tests. The adsorption capacity of molecular sieve 13X for trace amount of hydrogen sulfide (72 ppm) mixed with propane was investigated using the volumetric method by two different detectors. After adsorption process the amount of H2S in output gas was about 27 ppm and this confirms approximately more than 62% adsorption at 25 bar and 298 K. As compare CO2 adsorption capacity was measured by the same method. The high adsorption capacity of CO2 is attributed to the high micropore volume on 13X sample. Therefore a cost-effective adsorbent was synthesized successfully to separate the small amounts of acidic and corrosive gas (H2S) from propane.

Synthesis of [11C]palmitic acid for PET imaging using a single molecular sieve 13X cartridge for reagent trapping, radiolabeling and selective purification

IntroductionRadiolabeled fatty acids are valuable metabolic tracers for PET imaging. Carbon-11 is widely used in clinical PET studies due to the prevalence of facile techniques enabling the incorporation of [11C]CO2 and [11C]CH3 into molecules and a short half-life (20.4min) that translates into low patient dose. However, the short half-life considerably limits the time for radiosynthesis. Furthermore, the majority of the syntheses of [11C]palmitic acid in common use employ high starting [11C]CO2 activities and/or expensive equipment. Methods[11C]CO2 was trapped with greater than 99.99% efficiency by a three stage cartridge packed with molecular sieve 13X, 100–120mesh. The labeling of n-pentadecylmagnesium bromide took place in 5min in the cartridge, and the [11C]palmitic acid product was selectively eluted in ethanol following alkaline and acidic washes of the column. ResultsThe system reliably produced more than 925MBq (25mCi) of [11C]palmitic acid suitable for human use from 7.4GBq (200mCi) of [11C]CO2 in 8min from end-of-bombardment. ConclusionsWe have exploited the properties of the inexpensive molecular sieve 13X to develop a miniature, disposable and leak tight “gas capture” system for the rapid labeling and purification of [11C]fatty acids in good yield and >99% radiochemical purity. The rapidity of the synthesis and purification allows small [11C]CO2 starting activities to be used, and with no requirement for expensive synthesis equipment or facilities, the system can be implemented in any radiopharmaceutical center.

Novel One-Pot Synthetic Method for Propargyl Alcohol Derivatives from Allyl Alcohol Derivatives

An efficient one-pot procedure for the synthesis of propargyl alcohol derivatives from allyl alcohol derivatives has been developed. The key to this transformation from a C–C double bond to a C–C triple bond is that hydrogen bromide elimination from 1,2-dibromoalkanes that contain a neighboring oxygen functional group is promoted by the inductive electron-withdrawing effect of the oxygen functional group. In the one-pot reaction, tetrabutylammonium hydroxide was the best base, and the addition of molecular sieves 13X also promoted the reaction.

Assessment of the energy consumption of the biogas upgrading process with pressure swing adsorption using novel adsorbents

Biogas consisting mainly of methane and carbon dioxide can be utilized as renewable energy source in combined heat and power plant, vehicle fuel, or substitute for natural gas after upgrading process. In this work, biogas upgrading with pressure swing adsorption is studied with dynamic process simulation method using the modified Skarstrom cycle, which gives the variation of the pressure and stream concentration with cycle time in the column, while the variation of these variables with cycle time are difficult to be observed by experiments. Thus the simulation results would supply more dynamic information of the process. The pressure swing adsorption performance of the novel adsorbent metal-organic framework 508b is simulated and compared with the processes using traditional adsorbents such as zeolite 13X and carbon molecular sieve 3 K. A two-column six-step pressure swing adsorption simulation model involving parametric sensitivity analysis is established. The Langmuir adsorption isotherm models of the three adsorbents are built by fitting experiment data. The energy consumption of the pressure swing adsorption process with different adsorbents is calculated by fixing a 98% purity and 85% recovery ratio of methane product after investigating the key parameters, i.e., adsorption pressure, desorption pressure and purge to feed ratio. Simulation results reveal that the order of the energy consumption in the process is zeolite 13X > carbon molecular sieve 3 K > metal-organic framework 508b. For metal-organic framework 508b has linear carbon dioxide isotherm compared with zeolite 13X, which makes the desorption of the carbon dioxide easier, and its adsorption capacity is higher than with carbon molecular sieve 3 K under the same partial pressure. In conclusion, the energy consumption of pressure swing adsorption process using metal-organic framework 508b adsorbent is 56% lower than that using zeolite 13X, and the column packed with metal-organic framework 508b is estimated to be 13% smaller in diameter than that with zeolite 13X. The simulation results can help to provide guidelines for development of new adsorbents to meet higher product purity and recovery ratio along with lower process energy consumption.

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.