Superheated Steam Regeneration of a Desiccant Wheel—Experimental Results and Comparison with Air Regeneration

A commercial zeolite desiccant wheel is tested with atmospheric pressure superheated steam regeneration over a range of air inlet conditions, steam inlet temperatures, and wheel rotation speeds. Results are compared with those from high-temperature air regeneration experiments on the same wheel obtained from the literature. For both cases the air stream to be dried was relatively hot and moist with inlet temperature and absolute humidity values of 50°C and 25 g · kg^?1 chosen to reduce heat carryover. Using steam at 160°C to regenerate the wheel leads to the same dehumidification as using hot air at approximately 90°C. The benefit of superheated steam drying is that a nearly closed-loop regeneration process can be used with potential energy savings on the order of 30%.     

小晶粒NaY型分子筛的合成与表征

采用添加晶种和表面活性剂,通过水热晶化的方法合成了小晶粒NaY型分子筛,考察了铝源、硅源、表面活性剂、水等用量对NaY型分子筛合成的影响。采用XRD、N2吸附-脱附、SEM、XRF等手段对合成的分子筛进行了表征。结果表明:在合成体系中各组成的摩尔比n(Na2O):n(Al2O3):n(SiO2):n(H2O)=2.5:0.3:6.7:192.4的条件下,制备出的NaY型分子筛与常规NaY型分子筛的XRD谱图基本一致,且比表面积高达858m2/g;SEM结果显示,NaY型分子筛呈小晶粒聚集态,粒径在100~300nm。     

Preparation,characterization and anticorrosive properties of a novel polyaniline/clinoptilolite nanocomposite

Nanocomposite of polyaniline (PANI) with natural clinoptilolite (Clino) was prepared. Formation of nanocomposite and incorporation of polyaniline in the clinoptilolite channels was confirmed and characterized using FTIR spectroscopy studies, X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM) and cyclic voltammetry techniques. The anticorrosive properties of a 20 μm thickness coating of PANI/Clino nanocomposite with various weight ratios (1, 3 and 5%, w/w) of clinoptilolite content on iron coupons was evaluated and compared with pure polyaniline coating. According to the results in acidic environments PANI/Clino nanocomposite has enhanced corrosion protection effect in comparison to pure polyaniline coating. Comparative experiments revealed that PANI/Clino nanocomposite with 3% (w/w) clinoptilolite content has the best protective properties. Further experiments showed that the PANI/Clino nanocomposite has considerably different corrosion protection efficiencies in various corrosive environments.     

Adsorption of 2,4,6‐Trinitrotoluene on MFI Zeolite

2,4,6‐Trinitrotoluene (TNT) was adsorbed onto all silica MFI zeolite. These TNT doped zeolite samples were examined using Fourier Transform Infrared Spectroscopy (FTIR) and X‐ray Diffraction (XRD). Results indicate that, using FTIR with an Attenuated Total Reflection (ATR) accessory, mass loading percentages as low as 2.5 mass percent TNT in zeolite are detectable. It was also observed that adsorption of TNT onto MFI did not suppress the IR absorbing vibrations of TNT. TNT doped zeolite samples were washed, using vacuum aspiration, with water and acetone, both of which stripped the TNT from the zeolite samples, indicating that the adsorption of TNT onto MFI zeolite is a physisorption, rather than chemisorption, phenomenon. Finally, a lack of strain‐induced peak broadening from XRD studies indicate that TNT does not enter the zeolitic pore structure, rather, it is adsorbed onto the zeolite surface.     

Study of the structure directing effect of the chiral cation (1S,2S)-2-hydroxymethyl-1-benzyl-1-methylpyrrolidinium in aluminosilicate preparations in the presence of co-structure directing agents

We explore the structure directing role of the chiral cation (1S,2S)-2-hydroxymethyl-1-benzyl-1-methylpyrrolidinium (SS-bmpm) in the synthesis of Al-containing zeolite materials in the presence of co-structure directing agents (co-SDAs). Three different co-SDAs are studied: tetramethylammonium (TMA), quinuclidine and sodium. Synthesis with TMA as co-SDA yields a ferrierite related phase and a material from the MWW family, where the SS-bmpm and the TMA cations are incorporated intact within the samples. Quinuclidine produces instead amorphous solids, while the use of Na⁺ leads to crystalline phases that crystallized as a result of the degradation of the SS-bmpm cation. A subsequent computational study based on molecular mechanics was performed in an attempt to unravel the location of TMA and SS-bmpm cations within the void space of the complex MWW structure. The results suggest that the sinusoidal channels are exclusively filled by TMA, while the bulky SS-bmpm cations can only be accommodated within the MWW super-cages, thus providing a new example of cooperative structure-directing effects of small and bulky cations in the synthesis of complex zeolite structures.     

Generation of H2O2 from H2 and O2 over zeolite beta containing Pd and heterogenized organic compounds

The catalytic generation of H₂O₂ from H₂ and O₂ has been studied over zeolite beta-supported Pd and zeolite beta-adsorbed organic compounds such as 1,4-benzoquinone (BQ), hydroquinone (HQ), azobenzene (AB) and hydrazobenzene (HAB). According to catalytic results, zeolite beta-supported Pd catalysts display effective performance relative to those prepared from other types of zeolites reported and Pd-loaded zeolite beta-adsorbed HQ catalysts show enhanced activity compared to zeolite beta-supported Pd catalysts. In situ UV–Vis spectroscopic study indicates that HQ can readily be converted to BQ reversibly under H₂ and air inside zeolite beta only in the presence of Pd. The results suggest that HQ acts as a strong hydrogen transfer agent to promote the production of H₂O₂ from H₂ and O₂ in cooperation with a Pd catalyst. By contrast, adsorption of BQ, AB and HAB induces suppression of the catalytic properties of Pd/zeolite beta.     

A study of various zeolites and CuFe2O4 spinel composite catalysts in steam reforming and hydrolysis of dimethyl ether

The catalytic performance of the composite catalysts of CuFe₂O₄ spinel and various zeolites for steam reforming and hydrolysis of dimethyl ether (DME SR and DME HYD) was investigated. The catalytic activity for DME SR and DME HYD was affected by the type of zeolites and the durability of the CuFe₂O₄ spinel catalysts composed of various zeolites was lower than those composed of alumina as solid acids. Based on several characterizations, the difference of types of zeolite led to the formation of various carbonaceous species on the catalysts during DME SR and DME HYD. The deactivation due to the coke formation was suppressed by the pre-heat treatments in air as a result of the decreasing acid strength. This high durability with heat treatment was obvious for the composite catalyst of CuFe₂O₄ and ZSM-5 (MFI) type zeolite in DME SR. In contrast, the heat treatment did not enhance the durability of the ferrierite (FER) type zeolite composite catalyst.     

Use of NaX porous materials in the recovery of iron ions

Nowadays, the porous materials have an economic impact in certain industrial fields and particularly that of the environment. NaX materials economically prove very interesting; small quantities of these last are enough to treat great toxic volumes of effluent. This work aims at the use of NaX solid materials in the recovery of the ions iron poisons and vermin to the environment. We used a treatment process based on ions exchange reactions. Several parameters related to these operations of treatment were studied and the used materials are types of NaX faujasites. The obtained results show that NaX faujasite and its hydrogenated form NaHX can be used like ion exchangers in the recovery of the ions iron Fe³⁺. NaX and NaHX materials preserve their crystalline structures during the treatment process until 0.2 mol/l Fe³⁺ concentrations.     

Gas sorption in H2-selective mixed matrix membranes: Experimental and neural network modeling

Robust artificial neural network (ANN) was developed to forecast sorption of gases in membranes comprised of porous nanoparticles dispersed homogenously within polymer matrix. The main purpose of this study was to predict sorption of light gases (H₂, CH₄, CO₂) within mixed matrix membranes (MMMs) as function of critical temperature, nanoparticles loading and upstream pressure. Collected data were distributed into three portions of training (70%), validation (19%), and testing (11%). The optimum network structure was determined by trial-error method (4:6:2:1) and was applied for modeling the gas sorption. The prediction results were remarkably agreed with the experimental data with MSE of 0.00005 and correlation coefficient of 0.9994.