Molecular Sieve Type Research Articles

Study on the Adsorption of Trace Water in N-Methyl-pyrrolidone Solvents by A-Type Molecular Sieves.

N-Methyl-pyrrolidone (NMP) is an important coating solvent for the production of lithium batteries, and its water content will greatly affect the coating quality and energy density of lithium batteries, which needs to be reduced to 200 ppm. The current vacuum distillation technology suffers from high operating costs and high energy consumption, whereas the pervaporation technology only achieves solvent dehydration up to 99.5%. Therefore, it is of great significance to carry out the study of trace water removal from NMP solvents. In this paper, the A-type molecular sieve adsorption method was used to remove trace water from the NMP solvent, and the effects of molecular sieve type, particle size, adsorption temperature, feeding amount, and contact time on the dehydration performance of NMP system were first investigated. Adsorbed at 25 °C for 240 min at a feeding amount of 120 g/L, 3A molecular sieves were able to reduce the water content of the NMP solvent from 5000 to 140 ppm. Second, Langmuir and Freundlich equations were used to fit the static isothermal adsorption data, and the results showed a better correlation of the Langmuir equation. Then, the adsorption kinetics and diffusion mechanism were analyzed by the kinetic model and the Crank single-pore diffusion model. The R2 of the pseudo-first-order kinetic model was 0.9993, which was more suitable for describing the process of adsorption of water from the NMP solvent by 3A molecular sieves, and the effective diffusion coefficient De = 2.986 × 10-8 cm2/s was calculated for the Crank single-pore adsorption model, which proved water molecules on the 3A molecular sieve. The diffusion of water molecules on the inner surface of the pores is the controlling step of the adsorption process. Finally, the fixed-bed dynamic penetration curves were investigated to obtain the experimental data of fixed-bed adsorption, and the experimental data were fitted using the Thomas and Yoon-Nelson models, which showed that both models could describe the adsorption behavior of trace water in NMP solvents on 3A molecular sieves. This study provides a new idea for the removal of trace water in NMP systems, and a series of model fitting parameters provide basic data for industrial scale-up.

Molecular sieve vacuum swing adsorption purification and radon reduction system for gaseous dark matter and rare-event detectors

In the field of directional dark matter experiments SF6 has emerged as an ideal target gas. A critical challenge with this gas, and with other proposed gases, is the effective removal of contaminant gases. This includes radon which produce unwanted background events, but also common pollutants such as water, oxygen and nitrogen, which can capture ionisation electrons, resulting in loss of detector gas gain over time. We present here a novel molecular sieve (MS) based gas recycling system for the simultaneous removal of both radon and common pollutants from SF6. The apparatus has the additional benefit of minimising gas required in experiments and utilises a Vacuum Swing Adsorption (VSA) technique for continuous, long-term operation. The gas system's capabilities were tested with a 100 L low-pressure SF6 Time Projection Chamber (TPC) detector. For the first time, we present a newly developed low-radioactive MS type 5 Å. This material was found to emanate radon at 98% less per radon captured compared to commercial counterparts, the lowest known MS emanation at the time of writing. Consequently, the radon activity in the TPC detector was reduced, with an upper limit of less than 7.2 mBq at a 95% confidence level (C.L.). Incorporation of MS types 3 Å and 4 Å to absorb common pollutants was found successfully to mitigate against gain deterioration while recycling the target gas.

Comparison at laboratory scale of different types and configurations of commercial molecular sieves for one-step direct upgrading of biogas produced by anaerobic digestion

In the present study we investigated, at laboratory scale, the possibility of upgrading biogas with a single step, without involving any pre- or post-treatment or multiple stage recirculation. This would allow small-scale AD plants to achieve convenient in-situ biomethane production entirely in accordance with REPowerEU objectives. In this respect, three commercial molecular sieves, i.Honeywell 13X, 4A, and 5A, were tested in two configurations in series (4A/13X and 4A/5A) in 25/75 v/v relative amounts. A control trap containing only the 4A molecular sieve using the same amount as the in series configuration was also used. Real biogas fed directly from the production reactors at atmospheric pressure was used in the experiments. The ability of the sieves to adsorb CO2 in the proposed operational conditions was tested and proved. In particular, sample 4A was highly efficient in biogas upgrading (CO2 retention rate of 42.4 gCO2/kg, equivalent to 0.96 mmolCO2/g) but its activity was limited to 18 days, while increasing the amount of material and combining different types of molecular sieves in series improved the performance. The possibility to regenerate and reuse the sieves was also proven.

Novel construction and synthesis mechanism of b-axis oriented flower-like SAPO-11 molecular sieve in OSC-containing system for efficient hydroisomerization of long-chain n-alkanes

In view of the fact that different kinds of flower-like zeolites and materials have been synthesized for catalysis, but there are few reports on the construction of flower-like SAPO-11 molecular sieve. In this work, we successfully synthesized b-axis oriented flower-like SAPO-11 molecular sieve with multi-layered structure in the organosilicon compounds (OSC)-containing system for the first time. The morphology and b-axis thickness of SAPO-11 flakes were controlled and the tailored synthesis of b-axis oriented flower-like SAPO-11 with multi-layered structure was realized by adding [3-(trimethoxysilyl) propyl] octadecyl dimethyl ammonium chloride (DMC) into the synthesis system. The NiWS supported catalyst for hydroisomerization of n-hexadecane was prepared by using the synthesized flower-like SAPO-11 as support. Through a series of characterization techniques, the effects of morphological changes of SAPO-11 molecular sieve on the textural properties, acidity, element composition and silicon distribution of SAPO-11 molecular sieve were investigated, and the influence mechanism of morphological changes of the support on the active phase properties of the catalyst was studied. The formation mechanism of multi-layered flower-like SAPO-11 was proposed, the influence mechanism of the morphological change of the support on the catalytic performance of the catalyst and the catalytic reaction kinetics was investigated, and the structure–activity relationship between flower-like SAPO-11 and NiWS supported catalyst was systematically expounded. It provides a reference for enriching the morphological types of SAPO-11 molecular sieve and preparing catalyst for high-efficiency hydroisomerization of long-chain n-alkanes.

High-Pressure Gravimetric Measurements for Binary Gas Adsorption Equilibria and Comparisons with Ideal Adsorbed Solution Theory (IAST).

Measurements of gas mixture adsorption equilibria at high pressures are important for assessing actual adsorbent selectivities but are often out of reach, given the challenging nature of the required experiments. Here, we report a high-pressure gravimetric binary gas adsorption equilibrium measurement system based on simultaneous gas density and mixture adsorption measurements in a single gas cell coupled to a magnetic-suspension balance. Compared to traditional techniques which rely on analytical measurements of gas composition, this approach does not require any sampling. Adsorption measurements of two gas mixtures (0.500 N2 + 0.500 CH4 and 0.400 N2 + 0.600 CO2, mole fraction) on a commercially available molecular sieve (NaY, sodium molecular sieve type Y) were carried out in the temperature range 282 to 325 K with a pressure up to 10 MPa. A prediction method for the gas mixture adsorption equilibria in a closed system using the ideal adsorbed solution theory (IAST) model was used to compare the experimental results. For binary mixtures of components with similar adsorption capacities (here N2 and CH4), the system can measure the adsorption equilibria at pressures higher than 1.0 MPa and the result agrees well with the IAST model prediction. For two gases with very different adsorption capacities, the uncertainty in the adsorption equilibrium measurement is much larger. The dominant uncertainty source is the gas density measurement, whose uncertainty could potentially be cut to half if the current titanium sinker is replaced with a sinker made of single-crystal silicon and with a larger volume.

Interlayer spacing in pillared and grafted MCM-22 type silicas: density functional theory analysis versus experiment.

Pillaring of synthetic layered crystalline silicates and aluminosilicates provides a strategy to enhance their adsorption and separation performance, and can facilitate the understanding of such behavior in more complex natural clays. We perform the first-principles density functional theory calculations for the pillaring of the pure silica polymorph of an MCM-22 type molecular sieve. Starting with a precursor material MCM-22P with fully hydroxylated layers, a pillaring agent, (EtO)3SiR, can react with hydroxyl groups (-OH) on adjacent internal surfaces, 2(-OH) + (EtO)3SiR + H2O → (-O)2SiOHR + 3EtOH, to form a pillar bridging these surfaces, or with a single hydroxyl, -OH + (EtO)3SiR + 2H2O → (-O)Si(OH)2R + 3EtOH, grafting to one surface. For computational efficiency, we replace the experimental organic ligand, R, by a methyl group. We find that the interlayer spacing in MCM-22 is reduced by 2.66 Å relative to weakly bound layers in the precursor MCM-22P. Including (-O)2SiR bridges for 50% (100%) of the hydroxyl sites in MCM-22P increases the interlayer spacing relative to MCM-22 by 2.52 Å (2.46 Å). For comparison, we also analyze the system where all -OH groups in MCM-22P are replaced by non-bridging grafted (-O)Si(OH)2R which results in a smaller interlayer spacing expansion of 2.17 Å relative to MCM-22. Our results for the interlayer spacing in the pillared materials are compatible with experimental observations for a similar MCM-22 type material with low Al content (Si : Al = 51 : 1) of an expansion relative to MCM-22 of roughly 2.8 Å and 2.5 Å from our x-ray diffraction and scanning transmission electron microscopy analyses, respectively. The latter analysis reveals significant variation in individual layer spacings.

Rapid synthesis of hierarchical silicoaluminophosphate molecular sieves using carbon-silicon composites from rice husk ash for deoxygenation of stearic acids

To improve the low temperature fluidity of bio-diesel, a Ni/SAPO catalyst is prepared using hierarchical silicoaluminophosphate (i.e., SAPO-11/SAPO-31) molecular sieves as supports. A rapid, cost-effective, and eco-friendly approach is proposed using carbon-silicon composites from rice husk ash (RHA). The carbon-silicon composite is obtained via an anaerobic calcination of RHA, which acts as the silicon source and mesopore filler, simultaneously. As-synthesized SAPO-11/SAPO-31 intergrowth molecular sieve has a high mesopore volume due to the mesopore filler function of carbon in RHA. A lower crystallization temperature and shorter duration are achieved with the assistance of microwave irradiation. Ni/SAPO catalysts exhibit a high conversion of stearic acids (concentration, 0.5–5 wt%) to form n-/isoparaffins. These results are important to develop a potential efficient catalyst for the upgrade of bio-oil and the novel synthesis method provides reference to the synthesis of other types of SAPO molecular sieves.

Energy Saving on Spray Drying Process by Modifying the Hot Air Flow

The drying machine works with the Spray Dryer method to dry particles from a liquid state through continuous spraying in the drying chamber. This Spray Dryer uses an atomizer in the form of a 0.2mm mist nozzle type injector with a spraying capacity of 0.00045 kg/s. Function for atomization during the drying process occurs with a change in the vortex angle of 35°. In this study, the liquid used was pure cow’s milk with a specific heat value of 3930 J/kg K. To increase the total amount of solids, increase the volume, speed up the drying process, and prevent material damage due to high temperatures, the milk was mixed with maltodextrin, water, and salt. In this drying process, the temperatures used are 100°C, 105°C, and 110°C. The humidity of the surrounding air can be reduced by using a dehumidifier containing a zeolite stone type molecular sieve measuring 1.7-2.5mm as an absorbent. The results of this study indicate that the moisture content of dry powdered milk products is 10.01% using a temperature of 105°C with a drying air flow speed of 16 m/sec. In addition, the drying time process was taken a time of 73 minutes which resulted in a drying rate of 0.455gram/second. This dehumidifier affects the temperature in the drying chamber to be constant between 101°C-104°C and lowers the humidity of the air by 7%, resulting in a 222gram milk soak. The efficiency value of the drying machine with a temperature of 105°C is 18.68%.

Adsorption properties of environmentally friendly insulating medium C4F7N and its common decomposition products in NaA, NaZSM‐5, and NaX molecular sieves

AbstractSelecting suitable materials to adsorb the C4F7N mixtures decomposition products could not only keep the stable operation of the environmentally friendly insulating gas switch cabinet, but also ensure the safety of operation and maintenance personnel. It is necessary to study the interaction of three types of molecular sieves with the C4F7N mixture and its decomposition products, which could provide a theoretical basis for the selection of adsorbents in the C4F7N gas switch cabinet. In this research, the molecular dynamics simulation was used to study the C4F7N‐CO2 mixture and its ten kinds of decomposition products CO, CF4, C2F6, C3F6, C3F8, CF3H, CF3CN, C2F5CN, C2N2, and COF2 in three molecular sieves adsorption process (NaA, NaZSM‐5, and NaX). The gas concentration distribution curve and interaction energy parameters were obtained by simulation. The interaction energies of C3F8 in NaA, C4F7N in NaZSM‐5, and C3F6 in NaX molecular sieve are the largest, which are −368.35 kJ/mol, −174.93 kJ/mol, and −340.09 kJ/mol respectively. Then, the theoretical results were verified by the fluorocarbon gases adsorption experiment. The adsorption performance of three molecular sieves for all gases was obtained by combining the experimental results and dynamics parameters. The adsorption rate of the NaA molecular sieve for fluorocarbon gas is less than 35%, and its adsorption performance for all gases is weak. NaZSM‐5 and NaX molecular sieves show excellent adsorption performance for C3F6 and C3F8, and the adsorption rates are over 70%. NaZSM‐5 molecular sieve shows good adsorption capacity for CF3CN, C2F6, C2N2, C3F6, C3F8, C4F7N, and C2F5CN. NaX molecular sieve shows good adsorption capacity for C3F6, C3F8, C4F7N, and C2F5CN. Both of them have the potential to be used as adsorbents in environmental protection insulated gas switch cabinet.

Effect of Activation Methods of Molecular Sieves on Ketimine Synthesis.

Although the use of molecular sieves for imine synthesis is a common protocol, there have been no comprehensive studies on heat-drying methods. This can be crucial for reproducibility. It was found that molecular sieve 5A dried at 160 °C for 5 h under vacuum efficiently promoted the condensation of various ketones and amines to afford even relatively bulky ketimines. Several control experiments and analyses revealed that only a small amount of Brønsted acid sites was important for the activity, rather than dehydration ability. Other types of molecular sieves could be utilized for the reaction after treatment with water followed by heat drying. A continuous-flow acetalization reaction of alcohols using the activated molecular sieve 5A was also demonstrated.

Removal of Elemental Mercury from Simulated Flue Gas by a Copper-Based ZSM-5 Molecular Sieve

A series of Cu-ZSM-5 molecular sieve adsorbents were prepared by the impregnation method. The experimental results revealed that the mercury removal efficiency of the 2.5 wt% CuCl2-ZSM-5 can reach up to 99%. Furthermore, both the crystal type and pore size distribution of the ZSM-5 molecular sieve remain the same after the process of copper-based active materials impregnated modification, and its specific surface area decreases as the load increases. Importantly, the surface of ZSM-5 modified by CuCl2 equips many more Cu-O functional groups, which are beneficial to the catalytic oxidation of mercury and can even oxidize Hg0 to Hg2+. The adsorption process strictly follows the Mars–Maessen reaction mechanism.

Investigation on the influence of modified zeolite molecular sieve on the hydrocarbon adsorbent and adsorption performance during cold-start conditions based on Monte Carlo simulation and grey relational analysis

To discover adsorbents with promising adsorption capability for hydrocarbon catcher, this study numerically investigated the adsorption process of modified MOR, MFI, and CON zeolites utilized in hydrocarbon catcher of hydrocarbon (HC) molecules for hydrocarbon emission control during cold-start. Ethylene (C2H4) and benzene (C6H6) were used as probe molecules in the single-component adsorption simulation. The mixture of methane (CH4), C2H4, propylene (C3H6), propane (C3H8), water (H2O) and C6H6 was used as adsorbate in the multicomponent adsorption simulation. The Grand Canonical Monte Carlo (MC) method was used in the adsorption simulation. Grey Relational Analysis (GRA) method was used to determine the influence degree of zeolite molecular sieve type and environmental conditions on the adsorption capacity of hydrocarbons. The adsorption isotherms of hydrocarbon single component and multicomponent molecules on different silicon-aluminum (Si/Al) ratios and different ion exchange zeolites were studied at various low temperatures and pressures. Results of adsorption simulation present that the best adsorption effect on C2H4 was obtained for the magnesium ion (Mg2+) modified MFI molecular sieve at a Si/Al ratio of 3. The adsorption of C6H6 was better for the Na+ modified molecular sieve at Si/Al ratios of 15 and 7. Mg2+ modified MOR molecular sieve can be given priority when the overall control of hydrocarbon mixture content is required, which has adsorption for all kinds of hydrocarbon molecules and more uniform adsorption performance. The calcium ion (Ca2+) modified MFI molecular sieve is suitable for the condition when exhaust gas contains more C3H6, while Mg2+ modified MFI molecular sieve can be used when there are more C3H8. In GRA, the factors with the greatest influence on the adsorption of the C2H4 component are the type of molecular sieve and the porosity. The most important factors on the adsorption of the C6H6 component are the molecular sieve type and temperature, followed by the porosity. In the adsorption of multicomponent hydrocarbons, porosity has the greatest effect on the adsorption amount, followed by molecular sieve type and Si/Al ratio. In addition, the total adsorption of hydrocarbon molecules will be increased with the Si/Al ratio of the molecular sieve.

Synergistic Antimicrobial Activities of Limonene with Mineral Carriers in LDPE Films for Active Packaging Application

The integration of essential oils (EOs) into polymers to endow antimicrobial properties has received a lot of attention. EOs are remarkable in that they have broad antimicrobial activity from a natural source while also being volatile. Their volatility, on the other hand, makes high-temperature processing techniques difficult to incorporate into polymers. In this study, active films based on low-density polyethylene (LDPE) and limonene essential oil (LEO) were prepared and characterized. Before incorporation of LEO into LDPE, vacuum pulling method was used to load the LEO into five different mineral carriers. All Carrier-LEO complexes were added into LDPE using melt compounding. The goal is to analyze the potential use of these formulations to achieve prolonged antimicrobial film packaging. The halloysite nanotubes (HNTs), kaolinite (Kao), mesoporous silica nanoparticles (MSNs), zinc oxide nanoparticles (ZnONPs), and molecular sieve type 4A (Z4A) were used as mineral carriers for limonene. The functional characterizations including mechanical, thermal, optical, barrier, and antimicrobial properties as well as limonene release behavior from the LDPE composite films were investigated. As expected, free limonene molecules acted as a plasticizer in the LDPE matrix. Thermogravimetric analysis (TGA) showed 20-25% of the initial limonene content was retained against thermal degradation in compounding and film making steps and its release from the films was efficiently delayed. A decrease in optical and oxygen barrier properties, as well as elastic modulus and tensile strength, was obtained for all developed films compared with neat LDPE. Significant antibacterial activities of the films were observed against <i>Escherichia coli DH5-Alpha</i> (<i>E. coli)</i> as a model gram-negative bacterial species. Moreover, the obtained results and the short-term and long-term release studies indicated that both HNTs and the MSNs due to their strong synergistic interactions with limonene exhibited sustained release profiles of limonene from LDPE films. Thus, these new active polymer composites present promising features in controlling microbial contamination, rendering them as excellent candidates in active packaging applications.

Study on the alkylation of aromatic hydrocarbons and propylene

In order to improve the efficiency of the alkylation reaction to aromatic hydrocarbons and propylene, different types of catalysts were screened, including ultra-stable Y molecular sieves (USY), solid phosphoric acid (SPA), ZSM type molecular sieve (HZSM), etc. The effects of reaction temperature, catalyst loading, and reaction time on the conversion rate of aromatic hydrocarbons and the selectivity of target products were investigated using the high-pressure reaction device. The catalysts were characterized by XRD, BET, SEM, FT-IR, NH3-TPD, and other methods. The experimental results show that the USY catalyst exhibits higher catalytic activity for alkylation. This catalyst can be used for the alkylation of different aromatic hydrocarbons. Good conversion and selectivity can be obtained. Futhermore, in a six-cycle experiment, the USY catalyst was reused without loss of efficiency.

Effects of zeolite molecular sieve on the hydrocarbon adsorbent and diffusion performance of gasoline engine during cold start

In this work, adsorption characteristic of the MOR, MFI, and CON zeolites used in hydrocarbon catcher and diffusion properties of hydrocarbon (HC) molecules on them were studied for hydrocarbon emission control during cold start. To find adsorbents with promising adsorption performance for hydrocarbon catcher, the numerical simulation was carried out by using Material studio software with benzene (C6H6) and ethylene (C2H4) as the probes, the Grand Canonical Monte Carlo (MC) method was used in the adsorption simulation, and Molecular Dynamics (MD) method was used to simulate the diffusion of hydrocarbon molecules. The isotherms, adsorption sites, heats of adsorption, and interaction energy distribution of hydrocarbon single-component and multi-component molecules on three different zeolites were studied at various low temperatures and pressures. Based on the simulation results, the most suitable type of molecular sieve was found from the three molecular sieves when the type and quantity of components were different. Results of adsorption simulation show that CON molecular sieve has batter adsorption performance for benzene component. The adsorption amount is 65/unitecell (UC) benzene molecules per cell, which is about twice of MFI molecular sieve. MFI molecular sieve has batter adsorption performance for ethylene component. The adsorption amount is 130/UC ethylene molecules per cell, which is about 2 and 1.5 times of MOR and CON, respectively of MOR molecular sieve. The adsorption simulation results of mixed hydrocarbon components show that the adsorption capacity of each component on the three molecular sieves was ranked as follows: C6H6 > C3H6 > C2H4 > C3H8 > H2O > CH4, collectively. The results of diffusion simulation show that the single component of ethylene molecule has relatively small diffusion coefficient on MFI molecular sieve about 2.2×10−10m/s and good adsorption performance at low temperature, and the largest diffusion coefficient on CON molecular sieve about 3.4×10 −10m/s. The single component of benzene molecules has the smallest diffusion coefficient on the CON molecular sieve 5.9×10−11m/s about and the largest diffusion coefficient on the MOR molecular sieve about 1.76×10−10m/s. In multicomponent diffusion. In multicomponent diffusion. The diffusion degree of each component molecule in the MFI and CON molecular sieve from strong to weak is about: H2O, CH4, C2H4, C3H8, C3H6 and C6H6. The diffusion pattern within the MOR molecular sieve from strong to weak approximately: C3H8, C6H6, C3H6, C2H4, CH4 and H2O. The results show that the high temperature had an obvious effect on the adsorption capacity of zeolite. As temperature rises the molecular diffusion coefficient increases and the molecular motion becomes more intense. After about 500 K, the adsorption capacity is at a very low level.

Insight in the Crystallization Kinetics of AlPO4-11 Molecular Sieve Using Di-Isopropylamine as Template

The hydrothermal synthesis of aluminophosphate molecular sieve type AlPO4-11 was processed from chemicals containing psueudobohemite, 85% phosphoric acid, water, and di-isopropylamine as templating agent. The crystallization of the samples was studied by taking samples in times from 2 to 74 h. The obtained white powder products were characterized by X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and differential scanning calorimetry (DTG) data and pH measurement of the mother liquor. The pore volume, as determined from TG and DTG curves, was ca. 0.17 cm3g−1. The percent relative crystallinity was determined by XRD and FT-IR methods. The crystallization kinetics evidenced that the hydrothermal synthesis of AlPO4-11 exhibited in its initial phase a behavior of first order reaction with a specific velocity constant of ca. 0.25 h−1, as determined from XRD and FT-IR data. The results obtained by both X-ray diffraction and infrared spectroscopy are comparable, and FT-IR is found to be a rapid method for estimating crystallinity and structure of aluminophosphate.

Performance Enhancement of Rotary Desiccant Wheel using Novel Homogenous Composite Desiccant Designs

Rotary solid desiccant wheels are used as sensible and latent heat recovery wheels in the Desiccant-HVAC systems. The two major types of these wheels include enthalpy (total energy recovery) wheels which remove sensible heat and latent heat from process air and transfer them to regeneration air, and dehumidification wheels which transfer a significant amount of moisture (latent heat) at the same time minimizes heat transfer. In this work a set of novel design of hybrid rotary desiccant wheel constructed using a composite homogeneous mixture of solid desiccants (multiple types of silica gel and molecular sieves) are proposed. The transport phenomena taking place in the proposed set of novel design of hybrid rotary desiccant wheel are simulated numerically using an in house finite volume method based CFD code. The performances of these wheels are compared with conventional type of wheels made of molecular sieves and silica gel, respectively. The results show that the performance of these hybrid wheels are enhanced by up to 40 % by using these novel composite wheel designs.

Enrichment of Oxygen-Containing Low-Concentration Coalbed Methane with CMS-3KT as the Adsorbent.

A type of carbon molecular sieve (CMS-3KT) was used as the adsorbent for the CH4 enrichment of a methane/oxygen/nitrogen (CH4/O2/N2) mixture using micro-positive pressure vacuum pressure swing adsorption (∼120 kPa). The adsorption isotherms of individual CH4, O2, and N2 on CMS-3KT were studied and fitted. The results indicated the important influence of the adsorbent surface heterogeneity on the adsorption equilibrium process. In addition, the interaction of adsorbent–adsorbate in this process was studied from the measured adsorption heat. The adsorption uptake curves were fitted linearly with a classical micropore model for evaluating the kinetics-based separation possibility of CH4/O2/N2, and the corresponding diffusion time constants of CH4, O2, and N2 were calculated. Based on the results of adsorption equilibrium and kinetics, breakthrough experiments were employed to explore the upper limit value of methane concentration in feed gas such that methane can be enriched feasibly but difficultly. The breakthrough experiments were performed on the CH4/O2/N2 mixture with CH4 concentration ranging from 1 to 30%. Regarding industrial application, the O2 removal and CH4 enrichment performance of ultra-low-concentration methane (CH4 < 5%) were evaluated according to the results of the breakthrough experiment. The results indicated that the proposed method was promising for enriching O2-containing ultra-low-concentration CBM.

Structure and catalytic activity of highly ordered AlMCM-48 materials with different Si/Al ratios on the degradation of high-density polyethylene

Catalysts of AlMCM-48 with different Si/Al molar rations were synthesized by modified hydrothermal method with respect to previous works. As a consequence, the materials showed different porous structures making them of high adsorption capacities and high efficiency to high-density polyethylene (HDPE). Samples synthesized with various Si/Al molar ratios were characterized by X-ray diffraction (XRD), nitrogen adsorption at – 196 °C, scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared (FTIR) and dispersive energy X-ray spectrometry (EDX). Characterization results suggested the presence of tetrahedral Al species on AlMCM-48(x), giving highly ordered materials that exhibit thermal stability. It is important to highlight that the use pseudoboehmite as a promising Al source for the synthesis of this type of molecular sieves, leading to materials with slight morphological differences due to the formation of interconnected particles spherical. The catalytic performance showed that the high-density polyethylene (HDPE) degradation reaction occurs in complex reaction steps in the heating rates 5, 10 and 20 °C min−1. The pore diameters of the catalysts influence the degradation process under non-isothermal condition. Furthermore, on the conditions studied, the AlMCM-48(x) catalysts exhibited high conversion values and play important roles in the decrease of HDPE degradation temperature, potentially leading to an efficient process in terms of energy expenditure.

Study on the alkylation of aromatic hydrocarbons and propylene.

In order to improve the efficiency of the alkylation reaction to aromatic hydrocarbons and propylene, different types of catalysts were screened, including ultra-stable Y molecular sieves (USY), solid phosphoric acid (SPA), ZSM type molecular sieve (HZSM), etc. The effects of reaction temperature, catalyst loading, and reaction time on the conversion rate of aromatic hydrocarbons and the selectivity of target products were investigated using the high-pressure reaction device. The catalysts were characterized by XRD, BET, SEM, FT-IR, NH3-TPD, and other methods. The experimental results show that the USY catalyst exhibits higher catalytic activity for alkylation. This catalyst can be used for the alkylation of different aromatic hydrocarbons. Good conversion and selectivity can be obtained. Futhermore, in a six-cycle experiment, the USY catalyst was reused without loss of efficiency.