Intelligent Gravimetric Analyzer Research Articles

Rational design of a novel Silica-Based material with abundant open micropores for efficient VOC removal

Porous materials with high adsorption capacity for volatile organic compounds (VOCs) have been a hot topic in the zeolite field, and preparing a silica-based material suitable for the removal of VOCs with different molecular sizes is still challenging. Here, a novel microporous silica-based material (MIS) having abundant micropores (∼0.278 cm3/g) and wide range of pore sizes (0.5–2.0 nm) was successfully obtained via a room-temperature synthesis route by using tetrabutylammonium hydroxide (TBAOH). The pore structure and accessibility could be finely modulated by tuning the interaction between TBAOH and silica precursors based on intelligent gravimetric analyzer and hyperpolarized 129Xe NMR spectra results. The optimized MIS with open micropores exhibited a much higher m-xylene adsorption capacity (114 mg/g) than conventional adsorbents and no decrease of adsorption capacity in the fourth adsorption–desorption test. Similarly, good adsorption performance was also observed for acetone, isopropanol, toluene, styrene, and mesitylene, demonstrating its wide applicability. In adsorption–desorption tests for the whole VOCs, the maximum desorption temperature of MIS was below 115 °C. Therefore, the proposed MIS is a promising efficient adsorbent for VOC removal.

Selective adsorption of water vapor in the presence of carbon dioxide on hydrophilic zeolites at high temperatures

• H 2 O v /CO 2 adsorption selectivity for FAU-13X and LTA-4A zeolites up to 250 °C and different flow configurations. • The presence of H 2 O v promotes a significant fall in the CO 2 uptake. • FAU-13X zeolite is more selective for H 2 O v /CO 2 removal than LTA-4A. • DSE model applies successfully for adsorption data of CO 2 , H 2 O v , and H 2 O v +CO 2 on both zeolites. CO 2 valorization by chemical recycling into useful chemicals and alternative fuels is often accompanied by the production of water as by-product, which limits thermodynamically the CO 2 conversion and has a negative effect on catalyst activity. Water removal from the reaction medium through the intensified sorption enhanced reaction process (SERP) is an effective way to significantly increase the conversion of reactants and the selectivity of desired products. We have previously revealed that FAU-13X and LTA-4A zeolites have adequate water adsorption capacity in the temperature range of 100–250 °C. To study the competitive adsorption of water in the presence of CO 2 and the corresponding adsorption kinetics, essential for SERP, experiments using combinations of water vapor and CO 2 were carried out in the range of 100–250 °C by using an Intelligent Gravimetric Analyzer (IGA) integrated with an infrared (IR) CO 2 analyzer. The results showed that FAU-13X zeolite presents a significant adsorption selectivity for water vapor over CO 2 , which is 1.2 times higher compared to LTA-4A. In addition, water vapor is adsorbed on FAU-13X 46 and 20 times (on average) more than CO 2 at 100 °C and 250 °C, respectively. The double stretched exponential model was applied to determine the kinetic parameters, which represent key data in modeling, design, and simulation of sorption enhanced reaction processes involving CO 2 catalytic conversion.

Investigation uncovered the impact of anions on CO2 absorption by low viscous ether functionalized pyridinium ionic liquids

Ionic liquids, which are designable and nonvolatile, have become a hot topic in the field of CO2 separation from industrial gases. In order to utilize the nonvolatile and low heat capacity of ionic liquids, it is necessary to solve the problem of high viscosity of pure ionic liquids. In the present study, ether functionalized pyridinium ion [E1Py]+ with good biodegradability and low viscosity was selected as cation. Ions containing cyano groups were used as anions, such as thiocyanate ion [SCN]-, dicyanamide ion [N(CN)2]-, tricyanomethanide ion [C(CN)3]-. Three ionic liquids with low viscosity were synthesized and characterized by 1HNMR, 13CNMR and FTIR. The physiochemical properties of ionic liquids such thermal decomposition temperature, density and viscosity were tested. The CO2 absorption capacity was systematically studied by using intelligent gravimetric analyzer at the pressure range between 0 and 15 bars and the temperature range from 303.15 to 333.15 K. The results showed that the order of CO2 absorption capacity of these three ionic liquids is [E1Py][C(CN)3] > [E1Py] [N(CN)2] > [E1Py][SCN], which showed that the solubility increased by increasing more cyano groups in ionic liquids. Thermodynamic properties such as enthalpy, entropy, and Gibbs free energy were also calculated for CO2 absorption.

Synthesis of composite zeolites composed of SAPO-5 and SAPO-34 and its application in methanol dehydration to light olefins

In present work, bi-phases composite zeolites consisting of SAPO-5 and SAPO-34 (named as SSC) are prepared by a traditional hydrothermal way, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption, intelligent gravimetric analyzer (IGA), intrusive mercury technology, and NH3-TPD techniques. The results display that the crystals in the as-synthesized composites have a hierarchical pore system with a size of about 3–130 nm, which displays a butterfly-like pattern on the crystal faces and runs throughout the whole crystal. Catalytic performances of the as-synthesized SSC catalysts are tested during methanol to olefin (MTO). As compared with a microporous composite catalyst, the hierarchical SSC composite catalyst displays excellent catalytic performances with a prolonged catalytic life and an elevated selectivity for light olefins.

Synthesis optimization of metal-organic frameworks MIL-125 and its adsorption separation on C8 aromatics measured by pulse test and simulation calculation

The metal-organic frameworks (MIL-125) were synthesized by the solvothermal method and the experimental parameters of preparation, purification and activation were optimized and the physicochemical properties were characterized. The adsorption capacity of MIL-125 on C8 aromatics was tested by the intelligent gravimetric analyzer (IGA) and the toluene vapor static adsorption device. The adsorption selectivity was studied by liquid static adsorption equilibrium experiment and large-scale pulse test. The C8 aromatics adsorption conformation and adsorption heat in MIL-125 was simulated by Materials Studio software. The characterization results show that the synthesized sample has excellent crystallinity, regular morphology with a grain size of about 1 ​μm, surface area of 1315 ​m2/g, micropore volume of 0.601 ​mL/g and a bulk density of 0.45 ​g/mL. Moreover, the vapor static adsorption results show that the synthesized sample has almost three times of adsorption capacity as large as BaX zeolite and the liquid dynamic adsorption results indicate the synthesized sample is preferentially selective to pare-xylene with the alkane desorbent. The simulation results show that the adsorption heat of pare-xylene in the synthesized sample and the binding energy of pare-xylene in the tetrahedral cage are the largest among these four isomers.

Measurement of solubility and diffusion coefficients of ethylene in solid and molten low‐density polyethylene with different melt indices

AbstractThe diffusion behavior of ethylene in polyethylene is of great importance for the polymerization and degassing of polyethylene (PE) industry. Based on the gravimetric sorption and desorption measurement approach, an intelligent gravimetric analyzer is applied to obtain the solubility and diffusion coefficients of ethylene in solid low‐density PE (LDPE) with different melt indices at 30°C to 70°C, 0 to 4 atm and in molten LDPE at 160°C to 230°C, 0 to 4 atm, respectively. Results indicate that both the solubility and diffusion coefficients of ethylene in solid LDPE are smaller than those in molten LDPE, while the dissolution enthalpy and diffusion activation energy of ethylene in solid LDPE are higher. In addition, one‐ and two‐dimensional diffusion models are built and the effects of particle size, polymer properties, and operation conditions are systematically investigated on the diffusion behaviors of ethylene in solid and molten LDPE.

Preparation of Porous Liquid Based on Silicalite-1.

Solid porous materials, like zeolites, have been widely used in a variety of fields such as size-and-shape-selective absorption/separation and catalysis because of their porosity. However, there are few liquid materials that exhibit permanent porosity. Porous liquids are a novel material that combine the properties of fluidity and permanent porosity. They have potential applications in many fields such as gas separation, storage and transport. Herein, we report a novel Type 1 porous liquid prepared based on silicalite-1. The pore size of this porous liquid was determined by positron annihilation lifetime spectroscopy (PALS), and the CO2 capacities were determined by the intelligent gravimetric analyzer (IGA). The unique properties of this porous liquid can promote its application in many fields such as gas storage and transport.

Mass Transfer Behavior of Benzene in Hierarchically Structured ZSM-5.

A series of ZSM-5 zeolites with hierarchical porous structure were synthesized using NaOH solutions treatment method. The structural and acidity properties of hierarchical ZSM-5 zeolites as-synthesized were characterized by X-ray diffraction (XRD), N2 adsorption, scanning electron microscope (SEM), NH3-temperature programmed desorption (TPD), and pyridine Fourier transform infrared spectroscopy (Py-FTIR). The adsorption and diffusion performances of benzene in hierarchical ZSM-5 zeolites were studied by an intelligent gravimetric analyzer (IGA). It was found that mass transfer (adsorption and diffusion) performance of benzene was significantly affected by synergetic effect of hierarchical structure, acid amount, acidity, adsorption sites of ZSM-5 zeolites. After suitable alkali treatment, the crystal structure of ZSM-5 was retained and finely tailored. Hierarchical ZSM-5 was obtained with a uniform size of mesoporous and microporous structure. Acidity of hierarchical ZSM-5 zeolites was improved, which produced more adsorption sites and thus increased the adsorption performance of benzene in hierarchical ZSM-5. As a result, connectivity in hierarchical ZSM-5 was improved with increasing of mesopores in hierarchical ZSM-5. Hierarchical ZSM-5 well-contributed to the adsorption performance of benzene on active sites and improved catalytic performance of hierarchical ZSM-5.

Facile fabrication of effective Cerium(III) hydroxylated species as adsorption active sites in CeY zeolite adsorbents towards ultra-deep desulfurization

Ce-containing materials attracted much attention in adsorption desulfurization due to their excellent adsorption selectivity. Identification and fabrication of specific Ce species as effective adsorption active sites, however, still remained ambiguous which had impeded the development of a potential desulfurization adsorbent. In this paper, series of CeY zeolites were synthesized via liquid phase ion exchange method. The implication of Ce loadings and calcination temperatures on the nature of Ce species active sites that can be present in the Y zeolite was a major focus of this work. Specially, the chemical speciation and location of Ce species in the CeY adsorbents were analyzed by the intelligent gravimetric analyser (IGA), XRD, in situ FTIR spectroscopy, and XPS techniques. The prepared CeY adsorbents were tested in terms of their sulfur breakthrough adsorption capacities using a fixed-bed column and model fuels. The experimental results indicate that more effective Ce(III) hydroxylated species as adsorption active sites, located in the supercages of CeY0.075C150 zeolite, are facilely fabricated as low as the calcination temperature (ca. 150 °C) and the suitable Ce loading (ca. 12.31 wt%). Remarkable sulfur breakthrough adsorption capacity can be achieved by using the new CeY0.075C150 adsorbent, which is no less ca. 5 folds than that of the reported CeY adsorbents to the best of our knowledge, especially for the 2-methylthiophene capture (ca. 18 folds). After regenerated with two cycles, the adsorbent still remains high sulfur breakthrough adsorption capacity. Importantly, this controllable method to construct specific Ce species as active sites in the CeY zeolites should play an instructive role for the development of the directional design of effective adsorption active sites in other excellent desulfurization adsorbents.

Synthesis of novel regenerable 13X zeolite-polyimide adsorbent foams

A new generic synthesis method is presented for the production of a polyimide (PI)/adsorbent (80 wt% 13X zeolite) regenerable foam filter. The method uses a dual parallel reaction foaming process comprising CO2 generation (blowing) and polymerisation reactions. The paper describes the development of the foam structure and its characterisation in the context of removing CO2 from air. Polyvinylpyrrolidone (PVP) of different molecular weights (10k, 40k and 58k) was used as a pore former to allow more adsorption sites to be exposed to CO2. In dynamic adsorption breakthrough experiments at 101.325 kPa and 293 K, 10k PVP foams demonstrated an equilibrium loading of 0.039 g g−1 for CO2 (at 40,000 ppmv in air), showing the best equilibrium time and adsorption capacity. The foams and equivalent commercial 13X beads were able to achieve loadings of 0.094 g g−1 and 0.097 g g−1 (at 40 mbar), respectively, when tested using pure CO2 in an Intelligent Gravimetric Analyser. At pressures beyond 100 mbar, a weighted average isotherm shows only a 1.3 wt% reduction in adsorption capacity due to the polymer binder. The foams showed superior CO2/N2 selectivity compared to other adsorbents in literature. The thermal analysis of pure PI and 13X powder showed that the foams can be regenerated at 300 °C. Computational Fluid Dynamics simulation was successfully implemented in order to understand the CO2 adsorption behaviour on the new foam filter. Such modelling proved to be invaluable in understanding adsorptive behaviour through the complex foam structures as this is difficult to achieve experimentally.

Adsorption Equilibrium and Kinetics of Methanol Vapor on Zeolites NaX, KA, and CaA and Activated Alumina

Methanol vapor as a contaminant presented in industrial streams leads to catalysts deactivation. Therefore, it needs deep removal with adsorption technique. The isotherms and effective diffusion coefficients of methanol vapor are essential to design the purification process. The equilibrium sorption of methanol steam on commercial zeolites NaX, KA, and CaA and activated alumina were tested using an intelligent gravimetric analyzer, respectively. The equilibrium experiments were carried out at 303.2 K and pressures of up to 19.6 kPa, and the results obtained were fitted with the Dubinin–Astakhov (D-A) model. Moreover, the diffusion of methanol vapor in the adsorbents was investigated, and the effective diffusion coefficients were obtained with fitting the Fick diffusion model. The adsorbents are compared on the basis of adsorption capacities for methanol steam, and the descending order of zeolites is NaX > CaA > KA > Al2O3. The sorption equilibrium experimental results of methanol steam on NaX, KA, and CaA...

Adsorption/desorption of 2,2,4-trimethylpentane on MCM-36 zeolite functionalized by acidic ionic liquid

The facile desorption of products from the reaction sites is crucial to the reaction selectively and catalyst life. In the alkylation process of isobutane and olefine, the product is need to remove from the reaction sites timely so as to inhibit the sequential side reactions and improve the catalyst life. MCM-36 was modified by immobilizing ionic liquid [BTPIm][HSO4] (1-buty-3-(3-triethoxysilane)-propyl imidazolium hydrosulfate) so as to provide an effective way to improve the desorption of product 2,2,4-trimethylpentane from the reaction sites. The adsorption/desorption behaviors of 2,2,4-trimethylpentane on MCM-36 or ionic liquid immobilized MCM-36 were studied systematically by an intelligent gravimetric analyzer. The results showed that a decease adsorption capacity of 2,2,4-trimethylpentane was obtained after grafting [BTPIm][HSO4]. Langmuir–Freundlich model described the adsorption isotherms well. The ionic liquid immobilization led to a low isosteric adsorption heat. It indicated that a weaken interaction between adsorbate and adsorbent was obtained by the grafting of ionic liquid. The kinetics research results showed that the adsorption/desorption process was limited by the surface adsorption step. An increase of desorption rate constant and a decrease of adsorption sites were observed after the IL immobilization. It suggested that the ionic liquid loading was helpful to improve the desorption of 2,2,4-trimethylpentane from the reaction surface.

Isobutanol Vapor Adsorption on Activated Carbons: Equilibrium and Kinetic Studies

Activated carbon (AC) is commonly used to remove volatile organic compounds (VOCs) from the air. The purification efficiency depends on adsorbent characteristics (surface area, pore size, surface chemistry), adsorbate properties (size, functional groups, polarity), and process conditions. In the present study, the affinity of the Sorbonorit 4 (S4), Sorbonorit B4 (SB4), and BPL 4 × 6 (BPL) activated carbons toward the isobutanol (i-BuOH) vapor adsorption was investigated. The impact of vapor pressure and temperature on the process efficiency was examined. Adsorption equilibrium and kinetic measurements were conducted at 293.15, 313.15, 348.15, 373.15, and 393.15 K using an intelligent gravimetric analyzer (IGA). Experimental isotherm data were analyzed using the multitemperature Toth, Sips, and hybrid Langmuir–Sips models. Results indicated that the Sips model gave somewhat better fit than the others. The adsorption capacities of ACs at the same vapor pressure followed the order: S4 > BPL > SB4. Adsorption...

The Repeatability of Sorption Processes Occurring in the Coal-Methane System during Multiple Measurement Series

The aim of this paper was to investigate the repeatability of sorption processes occurring in the coal-methane system during multiple measurement series. For research purposes, three granular samples of coal sorbent were used. The samples were subjected to a series of three measurements, each time performed under the same conditions. During each series of measurements, the following stages took place: outgassing the sample in a vacuum, and then saturating it with methane under the pressure of 1, 3, and 10 bar. Sorption capacities and the values of effective diffusion coefficients were compared. The studies into the repeatability of measurements of sorption capacities, conducted by means of the IGA-001 (Intelligent Gravimetric Analyzer) gravimetric instrument for three measurement cycles, showed that the obtained measurement discrepancies in relation to the mean value did not exceed 1.23%. The discrepancies in question approximated the measurement uncertainty of the IGA-001 device. The evaluation of the recurrence of determining the values of effective diffusion coefficients showed that the obtained discrepancies were no larger than 10%, which might have resulted from problems with fulfilling most of the assumptions of the applied unipore diffusion model. The authors did not observe any changes of the sorption parameters of hard coal during consecutive cycles of methane saturation.

Comparative investigation of the MTH induction reaction over HZSM-5 and HSAPO-34 catalysts

Methanol to hydrocarbons (MTH) induction reaction was comparatively investigated over HZSM-5 and HSAPO-34 catalysts combined with on line thermogravimetry analysis of catalyst weight increment by intelligent gravimetric analyzer (IGA) studies. The influence of catalyst topology and acidity and reaction temperature on the reaction performance were correlated with the confined organics formation and evolution over the catalysts. For the latter stage of the MTH induction period, methanol conversion over HZSM-5 catalyst was proved a well-defined autocatalysis process, while over HSAPO-34, the increasing rate of methanol conversion was retarded due to accumulation of methyladamantanes. There existed a similar deactivation behaviour for HZSM-5 catalysts with low Si/Al ratios and HSAPO-34 catalysts during the temperature-programmed MTH (TP-MTH) reaction. But the IGA studies showed that the change of the retained species amount was quite different: for TP-MTH reaction over HZSM-5, the amount firstly increased and then decreased to a stable value; while for HSAPO-34, the amount kept increasing until reached a constant value. MTH induction reaction over HZSM-5 catalyst with different Si/Al ratios and HSAPO-34 catalysts with different Si contents were also investigated. All these findings revealed the influence of catalyst topologies on the formation of retained species and then on the catalyst activity during the MTH induction reaction.

Investigation on the mechanism of adsorption and desorption behavior in cerium ions modified Y-type zeolite and improved hydrocarbons conversion

AbstractDifferent types of Y zeolites (HY, USY and NaY) containing various amounts of cerium (Ce) were prepared with the method of liquid ion exchange and characterized by X-ray diffraction (XRD), intelligent gravimetric analyzer (IGA), and a molecular simulation technology (grand canonical Monte Carlo simulation, GCMC). A novel calculation method of desorption index (DI) was proposed and the influence of cerium cationic species on the processes of adsorption-desorption of hydrocarbon molecules (n-octane) on the cerium modified Y zeolites (CeY) was studied. The results indicated that Ce ion species played a key role in reducing desorption activation energy of n-octane on Y type zeolites, leading to an improvement of the desorption ability of the CeY and the regulation of the adsorption state of n-octane from aggregation to decentralization. These findings are essential factors for enhancing the product selectivity of light hydrocarbon component and the catalytic activity of rare earth modified Y zeolites (REY) catalysts in fluid catalytic cracking (FCC) process.

Solubility measurement of hydrogen, ethylene, and 1‐hexene in polyethylene films through an intelligent gravimetric analyzer

ABSTRACTThe solubility of hydrogen (H2), ethylene (C2H4), 1‐hexene (C6H12), and the mixture of C2H4/1‐C6H12 in semicrystalline polyethylene (PE) films is measured using an intelligent gravimetric analyzer (IGA) in combination with prediction equations. For the pure‐component sorption in PE, the solubility of C2H4 and 1‐C6H12 decreases with the temperature, while that of H2 exhibits an opposite variation tendency in the temperature range under test. For the C2H4/1‐C6H12 mixture, the co‐solubility is almost 10% smaller than the sum of the pure‐component solubility. 1‐C6H12 acts as a co‐solvent and C2H4 an antisolvent. Moreover, good consistency has been achieved between the measured data and the prediction results from the Sanchez‐Lacombe EOS model, demonstrating the reliability of the measurement approach employed in this work. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44507.

Synthesis of Wool-Ball-Like ZSM-5 with Enlarged External Surfaces and Improved Diffusion: A Potential Highly-Efficient FCC Catalyst Component for Elevating Pre-cracking of Large Molecules and Catalytic Longevity

A hierarchical ZSM-5 zeolite composed of nano-sized MFI zeolite crystals was synthesized without using secondary template by a traditional hydrothermal procedure. The as-synthesized hierarchical ZSM-5 and a reference catalyst were both characterized by XRD, SEM, FT-IR, in situ infrared (IR) spectrometry of pyridine, NH3-TPD, N2 adsorption–desorption, intelligent gravimetric analyzer, and by thermogravimetry analyses. After examining and comparing the results, it is discovered that the hierarchical ZSM-5 catalyst displays excellent catalytic performance with an improved conversion of isopropylbenzene and a longer catalytic life because of its dramatically enlarged external surfaces. The results also display that the shortened diffusion path length contributes to enhancing the stability of the hierarchical catalyst by depressing the coking deposit during the catalytic cracking of n-octane. A wool-ball-like zeolite composed of nano-sized MFI crystals was synthesized without a secondary template by the traditional hydrothermal procedure. Nanocrystallization of crystal particles in the hierarchical ZSM-5 zeolite gives the catalyst an improved diffusion and a dramatically enhanced external surface which contributes to elevating pre-cracking of large molecules and catalytic longevity, and to offering a potential and high-efficiency FCC catalyst component.

Synthesis of palladium incorporated MCM-41 via microwave irradiation and investigation of its hydrogen storage properties

MCM-41 is a mesoporous silica material with high surface area and uniform pore size, which makes it a good candidate for gas adsorption applications. To improve the hydrogen storage capacity of the pure MCM-41, the samples were loaded with Pd that is known with its affinity to hydrogen. MCM-41 samples were synthesized by microwave irradiation and Pd was loaded before the samples were calcined. In this study, the effect of loading Pd and microwave power (90 & 120 W) to the structure of MCM-41 was investigated. The surface areas and density functional theory (DFT) pore diameters of the samples were in the range of 1073–1515 m2/g and 3.54–3.78 nm, respectively. The hydrogen storage capacities of the samples were measured by Intelligent Gravimetric Analyzer (IGA) at 298 K and up to 10 bar pressure. The hydrogen uptake of the samples were affected by the microwave power used for the synthesis and the Pd content. The highest hydrogen uptake was 1.74 wt% for 10:100 Pd: MCM-41 (120 W).

Morphology-controllable synthesis and characterization of carbon nanotube/polypyrrole composites and their hydrogen storage capacities

Sphere-like and layer-by-layer growth mechanisms of polypyrrole are controlled by changing pyrrole monomer concentration and using carbon nanotubes (CNT) as template. Pristine polypyrrole has sphere-like structures but remarkable change in types of polypyrrole growth is observed from spherical-like to layer-by-layer structures in the presence of CNT. Acid treatment enhances polypyrrole coverage on CNT surface by preventing agglomeration of polypyrrole due to an increase in surface oxygen groups and sp2 bonds in CNT structure. The crystallinity of powders comparably decreases after polypyrrole coating due to the amorphous structure of polypyrrole and a sharp decrease in the intensity of 002 peak. The influence of surface functionalization and polymer coating on the structural parameters of multi-walled CNT and their composites is investigated by tailoring the feeding ratio of polypyrrole. The hydrogen sorption measurements at ambient conditions by Intelligent Gravimetric Analyzer demonstrate that hydrogen uptake of CNT/polypyrrole composite is 1.66 wt.% which is almost 3 times higher than that of pristine CNT. Higher hydrogen uptake values are obtained by keeping the mass ratio of pyrrole monomer and CNT equal by using non-functionalized CNT in composite production. Hydrogen adsorption/desorption kinetics of polypyrrole/CNT composites is improved by increasing adsorption sites after polymer coating and acid treatment. The desorption curves of these modified surfaces are higher than their adsorption curves at lower pressures and hysteresis loop is observed in their isotherms since hydrogen is chemically bonded to the modified surfaces by the conversion of carbon atoms from sp2 to sp3 hybridization.