Chemical Liquid Deposition Research Articles

Catalytic cracking of 1-butene to propylene using modified H-ZSM-5 catalyst: A comparative study of surface modification and core-shell synthesis

Surface modification of ZSM-5 catalyst was carried out by silica deposition using chemical liquid deposition (CLD) method as well as core-shell silicalite composite material by hydrothermal method. The modified ZSM-5 catalyst was characterized using various physiochemical methods such as XRD, TPD, N2 adsorption-desorption and SEM analysis. Catalytic cracking of 1-butene was carried out using modified ZSM-5 catalysts. The propylene yield was higher for core-shell silicalite composite as compared to silica deposition through CLD method. Silica deposited using CLD method showed propylene-to-ethylene (P/E) ratio of 1.7, whereas core-shell silicalite composite resulted in P/E ratio of 3.0. The higher selectivity to light olefins using core-shell silicalite composite to be attributed to weak acid sites and effective control of external acid sites, which reduces the hydrogen transfer reactions that form alkanes and aromatics. The effective external surface passivation was verified using catalytic cracking of triisopropyl benzene. The core-shell silicalite composite showed excellent stability over 50h for the cracking of 1-butene stream.

Preparation of Gold Nanoparticles Using 2-Ethoxyethanol, 2-Methoxyethanol and 1,3-Butyleneglycol Supported in Chitosan

The aim of this work was to prepare and characterize several properties of Au nanoparticles colloids prepared by the “chemical liquid deposition” method, which involves the co-deposition of metallic Au with organic vapors (2-ethoxyethanol, 2-methoxyethanol and 1,3-butylenglycol at 77 K). AuNPs supported on chitosan were performed by solvated metal atom dispersed method. Then, colloids were characterized by transmission electron microscopy (TEM), electron diffraction (ED), UV–Vis spectroscopy, electrophoretic mobility, physical stability, medium–far infrared spectroscopy and thermogravimetric analysis. These studies had demonstrate that Au nanoparticles solvated with 1,3-butylenglycol and 2-ethoxyethanol, shows higher stability, due to their high dielectric constant and a better NPs solvation. TEM analysis showed a size distribution between 4.61 and 48.8 nm. From ED, a face-centered cubic structure was found. UV–Vis analysis showed lower stability of nanoparticles solvated with 2-methoxyethanol. FTIR spectra showed that the solvent was incorporated and surround the Au NPs. The thermograms shows that thermal decomposition of AuNPs–chitosan decreases with the metal presence. Bioassays of acute toxicity on fishes with AuNPs–chitosan with 1,3-butylenglycol were carried out due to the lower toxicity. The bioassay showed that 0.94 mL/L produce mortality of 50 % (LD 50) of fishes exposed 96 h calculated with a confidence interval of 0.810–1.148 mL/L.

Samarium colloids prepared in organic solvents and active solids

Samarium colloids in organic solvents (2-methoxyethanol, 2-propanol, 2-propanone, and 1,2-dimethoxyethane) were obtained by the chemical liquid deposition (CLD) method at 77 K. The colloids were characterized by electron diffraction, energy-dispersive X-ray (EDX), UV-Vis spectroscopy, kinetic stability, and electrophoretic measurements. The colloid stability depends on the solvent used and the metal concentration. The higher stability was obtained in 2-methoxyethanol, which is in agreement with previous results for other lanthanide colloids. The zeta potential (ζ) of the colloids ranges between 0.138 and 1.945 mV. The UV-Vis spectra exhibit bands characteristic of the solvent. The 2-methoxyethanol shows bands at 205 and 234 nm very similar to the 2-propanol which exhibits bands at 202 and 253 nm for 2.5E−4 M concentration. However, bands for 1,2-dimethoxyethane and 2-propanone colloids were impossible to determine due to their highest extinction coefficient values. A dependence of the UV/Vis spectral properties of these new sol materials with Sm(III) is described. In all cases, the EDX analyses confirm the presence of metal in the colloids. The electron diffraction gives the most common (hkl) planes corresponding to Sm and Sm2O3 (211) and (100), respectively. As shown by the particle size distribution determined from transmission electron microscopy (TEM), the Sm-2-methoxyethanol colloids exhibit ranges from 1.6 and 2.9 nm, but the Sm-2-propanol colloids show ranges from 2.3 to 2.5 nm; the medium particle size of Sm-1,2-dimetoxyethane colloid is 0.8 nm, and the Sm-2-propanone colloids have a range from 1.0 and 4.3 nm, exhibiting a solvent polarity dependence. Also, active solids from the evaporation of the colloids which have been fully characterized by several chemical and physical techniques have been obtained.

Coating mechanism and near-infrared reflectance property of hollow fly ash bead/TiO2 composite pigment

Nanometer titanium dioxide was deposited on hollow fly ash beads using a chemical liquid deposition method. Surface modification of hollow fly ash beads with Ca(OH)2 saturated solution resulted in the presence of calcium silicate hydrate. The surface modification had a great influence on the growth and micro-morphology of TiO2 nanoparticles on the surfaces of hollow beads. Electrostatic repulsive forces between the modified hollow bead surfaces and hydrated TiO2 were significantly reduced after the surface modification, favoring the formation of a homogeneous and uniform TiO2 film with high TiO2 loading. A possible growth mechanism of TiO2 coatings was proposed. Moreover, the near-infrared solar reflectance of hollow bead/TiO2 composite pigment reached 0.68, which was approximately 1.8 times as high as that of hollow beads. An approximately 28.1°C decrease in temperature was obtained for the inner surface of a calcium silicate board coated with composite pigments. Therefore, hollow fly ash bead/TiO2 composite pigments are excellent candidates for near-infrared reflective pigments used in solar reflective coatings.

Chemical Liquid Deposition Modified ZSM-5 Zeolite for Adsorption Removal of Dimethyl Disulfide

A series of ZSM-5 zeolites were prepared through a chemical liquid deposition (CLD) method and used for adsorption removal of dimethyl disulfide (DMDS) from methyl tert-butyl ether (MTBE). The structural properties and acidity were characterized, and the proper deposition amount and calcination temperature have been accessed. N2 adsorption test and X-ray photoelectron spectroscopy (XPS) results show that methylsilicone oil is deposited on the external surface and narrows the pore size of the zeolite. NH3-temperature-programmed desorption (NH3-TPD) and modified Hammett indicator titration results indicate that the acid sites on the external surface are eliminated while acid sites in the channel are not influenced significantly. Both the pore structure and acidity play important roles in determining the sulfide adsorption process. The optimal modification condition was found as a deposition amount of 30% and a calcination temperature of 500 °C. Adsorption isotherms were also conducted in both parent and CLD...

Development of surface modified mordenite catalysts and their stability in hot liquid water

Stable zeolites are demanded in heterogeneous catalytic upgrading of water-containing feedstocks such as biomass and heavy oil. Herein, we report hydrophobic mordenite (MOR) via chemical liquid deposition (CLD). Prior to the surface treatment, pure MOR was synthesized with a Si/Al ratio of 15. The Si/Al ratio plays a crucial role in the synthesis of pure MOR phase. Surfaces of MOR crystals were treated with two different silane reagents and multiple-cycle treatments. Improved hydrophobic surface properties were observed for tetraethyl orthosilicate (TEOS) as compared with 3-aminopropyl triethoxysilane (3-APTS). The amount of silane compound deposited on the zeolite surface increased with an increase in the number of cycles. These findings are expected to stimulate the applications of hydrophobic zeolites in biomass and heavy oil conversion.

Enhanced hydrothermal stability of Cu-ZSM-5 catalyst via surface modification in the selective catalytic reduction of NO with NH3

The surface of Cu-ZSM-5 catalyst was modified by chemical liquid deposition (CLD) of tetraethoxysilane (TEOS) for enhancing its hydrothermal stability in the selective catalytic reduction of NO with NH3. After hydrothermal aging at 750°C for 13h, the catalytic performance of Cu-ZSM-5-Aged catalyst was significantly reduced for NO reduction in the entire temperature range, while that of Cu-ZSM-5-CLD-Aged catalyst was affected very little. The characterization results indicated that an inert silica layer was deposited on the surface of Cu-ZSM-5 and formed a protective layer, which prevents the detachment of Cu2+ from ZSM-5 ion-exchange positions and the dealumination of zeolite during the hydrothermal aging process. Based on the data it is hypothesized to be the primary reason for the high hydrothermal stability of Cu-ZSM-5-CLD catalyst.

Preparation of MWCNTs/CuPc/Ag modified conductive polyester fiber with chemical liquid deposition

Novel multi-walled carbon nanotubes (MWCNTs) and copper phthalocyanine (CuPc) modified conductive silver-plated fiber (MCA-fiber) was successfully prepared via chemical liquid deposition method with polyester as soft template. The structures and morphologies were characterized by X-ray photoelectron spectroscopy and field emission scanning electron microscopy. The binding energy of oxygen and carbon are 543, 296 eV respectively and the SEM images show CuPc and MWCNTs are deposited on the surface of silvered fiber continuously. The MCA-fiber is about 75 μm in diameter. The effect of process conditions on the properties of MCA-fiber was investigated. With the increasing of the concentration of AgNO3, the coating amount and electrical conductivity first increase and then decrease. The decrease of MWCNTs can bring down the electrical conductivity, but can improve the coating amount of materials on the surface of fibers. There is a sharp decrease from 7.20 × 10−4 to 1.33 × 10−4 s/cm when the MWCNT-doping content is 20 %. When the doping ratio of MWCNTs and CuPc is 2:8, the coating amount rises to 19.2 %. The mechanism study on the photovoltaic properties of MCA-fiber verifies that it can be used in fiber-shaped solar cells.

Production of Light Olefins Through Catalytic Cracking of C5 Raffinate Over Surface-Modified ZSM-5 Catalyst.

Surface modification of phosphorous-containing porous ZSM-5 catalyst (P/C-ZSM5-Sil.(X)) was carried out by a chemical liquid deposition (CLD) method using tetraethyl orthosilicate (TEOS) as a silylation agent. Different amount of TEOS (X = 5, 10, 20, and 30 wt%) was introduced into P/C-ZSM5il.(X) catalysts for surface modification. The catalysts were used for the production of light olefins (ethylene and propylene) through catalytic cracking of C5 raffinate. It was found that external surface acidity of P/C-ZSM5-Sil.(X) catalysts significantly decreased with increasing TEOS content. In the catalytic reaction, both conversion of C5 raffinate and yield for light olefins showed volcano-shaped curves with respect to TEOS content. Among the catalysts tested, P/C-ZSM5-Sil.(20) catalyst exhibited the best catalytic performance in terms of conversion of C5 raffinate and yield for light olefins. Thus, an optimal TEOS content was required for CLD treatment to maximize light olefin production in the catalytic cracking of C5 raffinate over P/C-ZSM5-Sil.(X) catalysts.

Impact of external surface passivation of nano-ZSM-5 zeolites in the methanol-to-olefins reaction

Surfaces of nano-sized ZSM-5 zeolites have been passivated by a chemical liquid deposition (CLD) technique using tetraethylorthosilicate (TEOS). The impact of this post-synthesis treatment has been evaluated in the methanol-to-olefins (MTO) reaction.A two-step surface passivation led to enhanced selectivity towards C2–C4 light olefins, between 10 and 30% in relative, at nearly complete methanol conversion when compared with pristine zeolites. However, these post-treated zeolites exhibited a significant loss in stability.To rationalize these results and establish structure-activity relationships, zeolite catalysts have been thoroughly characterized by nitrogen adsorption–desorption, SEM, XRF, XRD and FTIR techniques. ZSM-5 zeolite (Si/Al=27) in the form of well-arranged rectangular nanocrystals behave in MTO after silylation as a commercial ZSM-5 zeolite having a Si/Al=52.

Defect-Patching of Zeolite Membranes by Surface Modification Using Siloxane Polymers for CO2 Separation

Grain boundary defects are normally formed in zeolite membranes during membrane preparation and calcination processes. In this work, a siloxane polymer coating with an imidazole group was grafted on the surface of defective SSZ-13 membranes by chemical liquid deposition to seal the defects. The parameters, such as silanization time, polymerization time, monomer type, and concentration, were optimized. Characterizations including Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy showed that siloxane polymers were coated on the surfaces of SSZ-13 crystals and membrane. Six modified membranes showed decreased CO2 permeance by only 21 ± 5% [average CO2 permeance of 1.9 × 10–7 mol/(m2 s Pa)] and increased CO2/CH4 selectivity by a factor of 9 ± 3 (average CO2/CH4 selectivity of 108) for an equimolar CO2/CH4 mixture at 298 K. CO2/CH4 and CO2/N2 selectivities of the modified membrane decreased with pressure and temperature. Membrane stab...

Selective adsorption of p-CNB and o-CNB in silica-coating HZSM-5 zeolite

HZSM-5 zeolite was modified by chemical liquid deposition (CLD) using TEOS as silylation agent. Meanwhile, selective adsorption of p-chloronitrobenzene (p-CNB) was investigated with modified zeolite from an aqueous mixture of p-CNB and o-CNB. Results show that the modification of HZSM-5 zeolite significantly improved p-CNB selectivity compared to that of parent zeolite. As a result, 98.8% p-CNB and 94.3% o-CNB can be recovered from the mixture in modified zeolite at 300 K on the basis of the larger differences in adsorption capacity and diffusivity between p-CNB and o-CNB. The enhanced p-CNB selectivity in modified zeolite can be mainly attributed to the slight regulation in pore size of zeolite channel.

Silica-titania composite aerogel photocatalysts by chemical liquid deposition of titania onto nanoporous silica scaffolds.

Silica-titania composite aerogels were synthesized by chemical liquid deposition of titania onto nanoporous silica scaffolds. This novel deposition process was based on chemisorption of partially hydrolyzed titanium alkoxides from solution onto silica nanoparticle surfaces and subsequent hydrolysis and condensation to afford titania nanoparticles on the silica surface. The titania is homogeneously distributed in the silica-titania composite aerogels, and the titania content can be effectively controlled by regulating the deposition cycles. The resultant composite aerogel with 15 deposition cycles possessed a high specific surface area (SSA) of 425 m(2)/g, a small particle size of 5-14 nm, and a large pore volume and pore size of 2.41 cm(3)/g and 18.1 nm, respectively, after heat treatment at 600 °C and showed high photocatalytic activity in the photodegradation of methylene blue under UV-light irradiation. Its photocatalytic activity highly depends on the deposition cycles and heat treatment. The combination of small particle size, high SSA, and enhanced crystallinity after heat treatment at 600 °C contributes to the excellent photocatalytic property of the silica-titania composite aerogel. The higher SSAs compared to those of the reported titania aerogels (<200 m(2)/g at 600 °C) at high temperatures combined with the simple method makes the silica-titania aerogels promising candidates as photocatalysts.

Thermal and microstructural analysis of doped alumina nanofibers

Gamma-alumina nanofibers of 7nm in diameter and aspect ratio ∼106 were doped with 10% of zirconia or alpha-alumina by in situ chemical liquid deposition (CLD) technique. Thermal behavior and decomposition kinetics of dopant nano-layers were conducted using simultaneous coupled thermal analysis (TG-DSC-FTIR) to optimize the processing conditions and suggest possible reaction mechanisms. SEM and TEM analysis of fine structure of functionalized nanofibers revealed changes in dopants localization at the base nanofibers. The effect of dopants on thermally-treated materials properties treatment was evaluated after consolidation of the samples by HIP at 1200°C and 150MPa. These sintered specimens have shown an increase in microhardness (HV) by 30% and 55% for alumina- and zirconia-doped materials, respectively. The mechanism and kinetics of the dopants precursor reactions are discussed on the basis of the simultaneous thermal analysis.

Robust, Highly Thermally Stable, Core–Shell Nanostructured Metal Oxide Aerogels as High-Temperature Thermal Superinsulators, Adsorbents, and Catalysts

Robust, highly thermally stable, MOx/(MOx–SiO2)/SiO2 core–shell nanostructured metal oxide aerogels with a MOx core and (MOx–SiO2)/SiO2 shell are produced via novel alkoxide chemical liquid deposition techniques. The core–shell nanostructure not only significantly reinforces the nanoparticles but also effectively inhibits the crystal growth and phase transition of metal oxide upon heat treatment, which enhances the heat resistance from approximate 400–800 °C up to 1000–1300 °C. The resultant core–shell nanostructured Al2O3, ZrO2, and TiO2 aerogels can support at least 5800 times their weight and exhibit high surface areas of 139, 186, and 154 m2/g after fired at 1300, 1000, and 1000 °C, respectively, which are the highest surface areas for metal oxide aerogels ever reported. We demonstrate that the core–shell ZrO2 and TiO2 aerogels show enhanced adsorption and photocatalytic performances, respectively, for dye after fired at 1000 °C. The core–shell Al2O3 aerogel/mullite fiber/TiO2 composite possesses ultralow thermal conductivities of 0.058, 0.080, and 0.11 W/mK at 800, 1000, and 1200 °C, respectively, which are the lowest values for inorganic aerogels ever reported. The resulting materials are promising candidates as high-temperature (400–1300 °C) thermal superinsulators, adsorbents, and catalysts.

A Two-Step Method Synthesis and Microwave Absorption Properties of Double-Shell Ni@/BN@BaTiO&lt;sub&gt;3 &lt;/sub&gt;Nanocapsules

BN@BaTiO3 coated Ni nanocapsules were prepared by a two-step method, composed of an arc-discharge and a chemical liquid deposition process. Their microstructure, surface component as well as electromagnetic properties (1-18GHz) were investigated by means of high-resolution transmission electron microscopy, X-ray diffraction, FTIR spectra (FT-IR) and a network analyzer, respectively. The core double-shell Ni@/BN@BaTiO3nanocapsules exhibit stronger EM absorption properties and the position of absorb peaks move to the low frequency direction in GHz range in the same thickness, compared to that of Ni@/BN. The microwave absorptive mechanisms of BN@BaTiO3coated Ni nanocapsule absorbent were discussed.

Effect of surface modification on the stability and thermal conductivity of water-based SiO2-coated graphene nanofluid

SiO2-coated graphene was prepared by chemical liquid deposition method by using tetraethyl orthosilicate (TEOS), and then SiO2 particles were successfully coated on the graphene surface. A new kind of stable water-based graphene nanofluid was further prepared using the functionalized nanomaterial (graphene/SiO2). The effect of SiO2-coated modification on the stability and thermal conductivity of water-based graphene nanofluid was examined. The results showed that SiO2-coated modification significantly improved the hydrophilicity of graphene, as well as the stability and thermal conductivity of water-based graphene nanofluid. SiO2-coating can improve thermal conductivity better than surfactants for preparing water-based graphene nanofluid.

Flexible quantum dot-sensitized solar cells employing CoS nanorod arrays/graphite paper as effective counter electrodes

We present a flexible solar cell which is composed of cobalt sulfide (CoS) nanorod arrays (NRAs) on graphite papers (GPs) (CoS NRAs/GP) as the counter electrode and CdS/CdSe quantum dot sensitized ZnO NRAs (CdS/CdSe@ZnO NRAs) as the photoanode. Orderly ZnO NRAs were directly fabricated on the flexible ITO/PET substrate by a hydrothermal method and CdS and CdSe quantum dots were subsequently deposited on them by chemical liquid deposition. CoS NRA/GP hybrid electrodes showed much higher electrocatalytic activity, higher exchange current density, and lower charge transfer resistance toward the reduction of Sx2− ions compared to Pt and GP electrodes and they exhibited superior performance when functioning as counter electrodes (CEs) in CdS/CdSe quantum dot-sensitized solar cells (QDSSCs), 400–500% better than that with Pt and GP as counter electrodes. An absolute energy conversion efficiency of 2.70% has been demonstrated for the QDSSC employing an optimized CoS NRA/GP hybrid electrode, which was relatively higher than those of the QDSSCs featuring Pt (0.52%) and GP (0.71%) CEs. This work not only provides a hybrid electrode with high catalytic activity for QDSSCs, but also demonstrates a cost-effective way to fabricate flexible electrodes that can be applied in dye-sensitized solar cells or super capacitors.

Selective fabrication of carbon nanowires, carbon nanotubes, and graphene by catalytic chemical liquid deposition

Large quantities of graphene sheets, carbon nanotubes, and ultra-long carbon nanowires can be selectively fabricated at a high rate in ethanol by catalytic chemical liquid deposition under atmospheric pressure at room temperature. Synthesis of the carbon nanostructures can be achieved through the following procedural changes: (a) by manipulating the H2O content, carbon nanostructures can be tailored from carbon nanotubes (CNTs) with various inner diameters to carbon nanowires (CNWs). (b) By adding an organic precursor containing S, graphene can be selectively fabricated. The simplicity and scalability of our method provides a high potential for mass growth, and the inherent cleanliness of the procedure offers a perfect starting point for straightforward, contamination-free synthetic processes without the use of expensive equipment. We also provide clear pictures of the growth process of these materials, where the pressure difference across the graphene surface results in the formation of bubbles that leads to the growth of CNTs, CNWs, or graphene.

Catalytic conversion of biomass pyrolysis-derived compounds with chemical liquid deposition (CLD) modified ZSM-5

Chemical liquid deposition (CLD) with KH550, TEOS and methyl silicone oil as the modifiers was used to modify ZSM-5 and deposit its external acid sites. The characteristics of modified catalysts were tested by catalytic conversion of biomass pyrolysis-derived compounds. The effects of different modifying conditions (deposited amount, temperature, and time) on the product yields and selectivities were investigated. The results show KH550 modified ZSM-5 (deposited amount of 4%, temperature of 20°C and time of 6h) produced the maximum yields of aromatics (24.5%) and olefins (16.5%), which are much higher than that obtained with original ZSM-5 catalyst (18.8% aromatics and 9.8% olefins). The coke yield decreased from 44.1% with original ZSM-5 to 26.7% with KH550 modified ZSM-5. The selectivities of low-molecule-weight hydrocarbons (ethylene and benzene) decreased, while that of higher molecule-weight hydrocarbons (propylene, butylene, toluene, and naphthalene) increased comparing with original ZSM-5.