Effects Of Catalyst Content Research Articles

Enhancing photocatalytic degradation of rhodamine B with visible-light-driven HCl-assisted Bi2O3 photocatalysts: Activity, mechanism, and pathways

This study utilized X-diffraction, BET, photoluminescence, UV–vis DRS, FTIR, SEM, XPS, TOC analysis, EPR, electrochemical measurements, and LC-MS to characterize the structural characteristics, morphology, optical properties, photocatalytic activity, surface electronic states, active compounds, and potential photodegradation pathways of rhodamine B (RhB) over as-prepared Bi2O3. The as-prepared Bi2O3 photocatalyst exhibited a narrow bandgap, which enabled efficient absorption of visible light, thereby contributing to its enhanced photocatalytic activity. Additionally, Bi2O3 exhibited a high degradation efficiency for RhB. with up to 96.8 % of RhB removed within 120 min at pH 3.0. The excellent photocatalytic performance of Bi2O3 can be attributed to the formation of the heterogeneous Bi2O3/BiOCl structure on the Bi2O3 surface in the presence of HCl. Moreover, the TOC analysis revealed that over 58.1 % of the carbon in the RhB solution was mineralized into CO2 after 120 min of irradiation. The effect of catalyst content, RhB concentration, initial pH, and inorganic anions on the photocatalytic degradation of RhB over Bi2O3 was examined. Furthermore, the active compounds and potential photocatalytic mechanism of the Bi2O3/BiOCl heterogeneous structure toward RhB were evaluated. The intermediates formed during RhB degradation were identified, and the corresponding degradation pathway was deduced via LC-MS.

Catalytic carbon-bed sintering of CNTs/calcium aluminate cement and its effects on thermal mechanical properties of refractory castables

To improve the dispersion of carbon nanotubes in refractory castables and exert the strengthening effect of carbon nanotubes on castables, the core-shell CNTs/CAC (carbon nanotubes/calcium aluminate cement) was synthesized by the catalytic carbon-bed sintering method. The effects of catalyst content on the microstructure of CNTs/CAC powders were evaluated by Raman spectroscopy, SEM, and HRTEM. The results suggested that the optimal addition amount of catalyst was 0.75 wt%. The diameter of the bamboo-like carbon nanotubes was ∼50 nm and the length of the carbon nanotubes was ∼120 μm. Carbon nanotubes and small calcium aluminate particles were interspersed with each other and wrapped in a compact calcium aluminate shell with a thickness of 3∼5 μm. Moreover, the DFT calculation was employed to investigate the growth mechanism of carbon nanotubes. Electrons were transferred from Ni to H, O, and C atoms, increasing bond length and weakening the strength of C–H and CO bonds which was conducive to the growth of carbon nanotubes. The formation of the core-shell structure was in direct connection with the liquid-phase eutectic phase. Calcium carbonate and alumina reacted preferentially to form C12A7, and then C12A7 continued to react with alumina to form CA and CA2. With the increase of sintering temperature, a large amount of liquid phase was formed. Carbon nanotubes were wrapped by the liquid phase of calcium aluminate to form a core-shell structure. The CNTs/CAC cement bonded Al2O3–SiC castables had great mechanical properties and thermal shock resistance. Compared with Al2O3–SiC castables bonded with Secar71, the HMOR and thermal shock residual strength ratio of Al2O3–SiC castables bonded with CNTs/CAC cement were increased by 24.7% and 22.1%, respectively.

CaMoO4/CaWO4 heterojunction micro/nanocomposites with interface defects for enhanced photocatalytic activity

The polyacrylamide gel method combined with low temperature calcination technology (PGMCLCT) have been applied to prepare the CaMoO4/CaWO4 heterojunction micro/nanocomposites with novel light emission and high photocatalytic activity for the degradation of methylene blue (MB) dye. A variety of characterization methods confirmed the formation of heterojunctions between CaMoO4 and CaWO4 in a special interface contact way. The CaMoO4/CaWO4 heterojunction micro/nanocomposites exhibits a novel emission peak at 400 nm with the excitation wavelength of 240 nm and high photocatalytic activity for the degradation of MB dye. With the increase of the mass percentage of CaWO4, the fluorescence emission intensity of CaMoO4/CaWO4 heterojunction micro/nano composites decreases, while the photocatalytic activity increases gradually. The effects of catalyst content, initial dye concentration and cycle index on the photocatalytic activity of CaMoO4/CaWO4 heterojunction micro/nanocomposites were systematically studied. The optimal catalyst content, initial dye concentration, irradiation time and cycle index are 1 g/L, 20 mg/L, 180 min and 5, respectively. The CaMoO4/ wt 20% CaWO4 heterojunction micro/nanocomposites exhibits highest degradation percentage of about 91.44% due to the carbon skeleton or adsorbed oxygen accelerates the separation of photogenerated electrons and hole pairs. This method provides a technical reference for the synthesis of other types of heterojunction micro/nanocomposites.

Catalytic combustion synthesis of CNTs/MgO composite powders and the influences on the thermal shock resistance of low-carbon Al2O3–C refractories

Using MgC2O4, Mg powders as raw materials and Ni(NO3)2∙6H2O as a catalyst, CNTs/MgO composite powders were prepared by a catalytic combustion synthesis method. The CNTs/MgO composite powders were characterized by XRD, Raman spectroscopy, FESEM/EDS and HRTEM. The effects of catalyst content on the degree of graphitization and aspect ratio of the CNTs in composite powders were investigated. Moreover, the thermal shock resistance of low-carbon Al2O3–C refractories after adding the composite powder was investigated. The results indicated that the CNTs prepared with 1 wt% Ni(NO3)2∙6H2O addition had a higher degree of graphitization and aspect ratio. In particular, the aspect ratio could reach approximately 200. The growth mechanism of hollow bamboo-like CNTs in the composite powders was proven to be a V-L-S mechanism. The thermal shock resistance of Al2O3–C samples could be improved significantly after adding CNTs/MgO composite powders. In particular, compared with CM0, the residual strength ratio of Al2O3–C samples with added 2.5 wt% composite powders could be increased 63.9%.

Growth mechanism of in situ MgSiN2 and its synergistic effect on the properties of MgO–C refractories

To improve the thermal shock resistance of MgO–C refractories, a novel MgO–C refractory, based on high-temperature nitriding, was prepared by introducing Si powder/phenolic resin loaded with catalyst into MgO–C refractories to form silicon-containing ceramic bonding phases in situ. The effects of catalyst content and nitriding temperature on the phase evolution, microstructure, mechanical properties, and corrosion resistance of refractories were investigated. The addition of catalyst accelerated the in-situ formation of more ceramic bonding phases as compared to the catalyst-free refractory, especially the influence on the morphology and quantity of MgSiN2, which determined the properties of MgO–C refractories. Here, the formation mechanism and morphological evolution of MgSiN2 in refractories were explored. In addition, the addition of 1 wt% ferric nitrate greatly optimized the microstructure of MgO–C refractories, and the sample showed excellent mechanical properties, thermal shock resistance, and corrosion resistance after nitriding at 1400°C.

Treatment of Emulsion Bitumen Plant Effluent by Advanced Photocatalyst and Fenton Oxidation Methods Using Adsorption and Coagulation Method as Pretreatment

Background Increasing industrial production has led to the presence of resistant and no biodegradable compounds in the effluents of various industries, many of which cannot be treated with conventional processes in the effluent. Advanced photocatalyst and Fenton oxidation methods were investigated using adsorption and coagulation methods as pretreatments for emulsion bitumen plant effluents. Methods The effluent was prepared from an emulsion bitumen production plant in South Khorasan province located in Iran. Adsorption method (sawdust, activated carbon, human hair, Nano titanium dioxide, and titanium dioxide) and coagulation method (bentonite, aluminum sulfate, and iron sulfate) were performed as pretreatment methods. Then, as complete purification, advanced oxidation methods of photocatalyst and Fenton were performed. The effect of different radiation sources on the rate of effluent decomposition, the effect of reaction time, the effect of catalyst content, the effect of pH changes was investigated. The combination of pretreatment and treatment methods increased the treatment performance. Significant findings In this study, the coagulation method as pretreatment and advanced photocatalytic oxidation process as complete purification at pH = 10 could reduce the effluent pollution load by about 99.5%. The optimum amount of titanium dioxide in this process was 0.5 g / l. The process of reducing pollutants stopped after about 3 hours and reached its final level. In addition, the advanced oxidation process of Fenton after the chemical coagulation method at pH = 2 and under optimal conditions, is able to reduce 99.4% of the effluent pollution load. The time required to complete the process was half an hour, and the minimum concentration of iron ions for the process progress was 0.114 M.

Controllable synthesis of Si@SiC plate@Si3N4 whisker with core-shell structure and their electrochemical performances

The Si@SiC@Si3N4 composites with core-shell structure were synthesized by a catalytic nitridation method, Si powder and phenolic resin were used as the raw materials, ferric nitrate was used as the catalyst. The effect of catalyst content on synthetic powders was investigated. The results indicated that when no catalyst was added, a small amount of whiskers were formed on the surface of the Si powder. The addition of the catalyst could effectively promote the formation of SiC and Si3N4, and a double-layer core-shell structure was formed in which the inner shell is a SiC plate and the outer shell is a Si3N4 whisker. However, excessive addition of the catalyst caused the resulting Si3N4 whiskers to distorted and intertwined. The prepared composite materials (5 wt% catalyst) exhibited good rate capability and a specific capacitance of approximately 200 F/g at 0.5–3 A/g. Finally, the possible formation mechanism of this core-shell structure was proposed.

One step synthesis and characterization of high aspect ratio network-like carbon nanotubes containing calcium aluminate cement composite powders

The poor water dispersion and oxidation resistance of carbon has restricted the widely industrial application of carbon containing castables. High aspect ratio network-like carbon nanotubes containing calcium aluminate cement composite powders were synthesized by carbon-bed sintering method using calcium acrylate and activated alumina as raw materials, and nickel nitrate as catalyst. Meanwhile the effects of catalyst content on the structure and morphology of carbon nanotubes were also studied. The synthesized products were characterized by X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The results indicated that the phase compositions of composite powders were similar to that of commercial Secar71. The length of carbon nanotubes was ca. 25 μm, and the diameter of carbon nanotubes was 55 nm. The aspect ratio of carbon nanotubes is ca. 450. The formation process and mechanism of carbon nanotubes was studied by thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The growth temperature of carbon nanotubes was 700 °C, and the growth of carbon nanotubes agrees with vapour–solid (V–S) model. In addition, the thickness of floating layer, floating ratio and oxidation ratios of the synthesized product were lower than those of the same carbon containing Secar71 cement (S71CB) composite powders, implying that the water dispersion and oxidation resistance of carbon nanotubes were improved because the high aspect ratio network-like carbon nanotubes were not easily separated from calcium aluminate cement and the carbon nanotubes were encased in calcium aluminate cement.

Role of Sn-based and Ti-based catalysts on melt copolymerization of PLA-Polyols

Aiming at improving the ductility of PLA, two polyols: polyethylene glycol (PEG), and polypropylene glycol (PPG) were introduced individually to the PLA structure as a soft component. Copolymerization of PLA and polyols was performed in a melt-mixer via transesterification in the presence of a catalyst. 1H-NMR and GPC results revealed that PLAPEG and PLA-PPG copolymers with different molecular weights were successfully formed. The copolymer formation and characteristics depended strongly on the structure of polyol and type of catalyst. Titanium butoxide (TBT) was found to be a more effective catalyst than dibutyltin dilaurate (DBTL). The effects of catalyst content and reaction time on the characteristics of the copolymers are also reported.

Fabrication of amorphous Co–Cr–B and catalytic sodium borohydride hydrolysis for hydrogen generation

Abstract

The effect of NiO catalyst on reduction, synthesis and binder content of TiC-Ni nanocomposite

In the present study, synthesis of TiC-Ni nanocomposite via magnesiothermic method was investigated. The effects of catalyst content on the mechanisms of TiO2 reduction and synthesis of TiC-Ni nanocomposite were evaluated. For this purpose, the powder mixture was milled at different NiO content. By adding 0.1–0.3 at.% NiO to the mixture and milling after combustion, it was found that the synthesis did not completely occur. In 0.4 at.% NiO to the mixture, the synthesis was completed and after leaching pure TiC was synthesis. Additionally, the effect of NiO on the binder content composite synthesis was examined. It was observed by increasing NiO content, combustion time decreased and Ni content in nanocomposite increased. TEM observations confirmed for 0.4 at.% NiO at initial powder pour TiC with spherical morphology and for >0.5 at.% NiO at initial powder TiC-Ni nanocomposite with semi- spherical morphology was synthesis.

PROMOTING EFFECT OF CERIA ON THE CATALYTIC ACTIVITY OF CeO2-ZnO POLYCRYSTALLINE MATERIALS

A polycrystalline CeO2-ZnO catalyst was prepared by using a hydrothermal procedure in order to improve the structural properties. This polycrystalline material was then used to remove organic pollutants from aqueous solutions by the means of photocatalysis. The structural, morphological and optical properties of as-prepared materials were characterized by several techniques, such as UV-visible spectroscopy, SEM, FTIR, XRD. The SEM analysis shows that the crystallite size sample varies in the range of 0.32.m. The photocatalytic activity under UV irradiation was estimated by measuring the degradation rate of aqueous solutions of methylene blue (MB, 0.01mM/L) and 4 -(1-methyl-benzimidazoyl-2)-phenylazo-2 -(8 -amino-1 -hydroxy-3 , 6 -disulphonic)naphthalene acid (PMBH, 0.05mM/L). The effect of catalyst content on the photocatalytic activity was also studied. The results confirm that this material can be potentially applied for the treatment of water contaminated by organic pollutants.

In-situ catalytic preparation and characterization of SiC nanofiber coated graphite flake with improved water-wettability

Abstract SiC nanofiber coated graphite flake was fabricated at a relatively low temperature via a novel in-situ catalytic reaction route using Fe(NO 3 ) 3 ·9H 2 O as a catalyst precursor. The effects of catalyst content, firing temperature, and graphite/Si ratio on the formation of SiC nanofiber and water wettability of modified graphite were investigated. The in-situ formed Fe catalyst facilitated the formation of SiC nanofiber, and its optimal content was found to be 0.6–0.8 wt%. Single-crystalline SiC nanofibers with diameter in-situ Fe catalyst could be attributed to the increased bond length and weakened bond strength in CO (g) and SiO (g) molecules upon their adsorption onto the Fe catalyst. The water contact angle of SiC nanofiber-coated graphite could be reduced to as low as 6° within just 2.3 s contact time, indicating its substantially improved water wettability.

Effects of Catalyst Content, Anhydride Blending, and Nanofiller Addition on Anhydride-Cured Epoxidized Linseed Oil-Based Thermosets

A series of formulations based on epoxidized linseed oil, ELO cured with various anhydride hardeners, were investigated to assess the potential for enhanced elastic properties and thermal transitions through variations in catalyst concentration (1,8-diazabicyclo[5.4.0]undec-7-ene, DBU), hardener type (nadic methyl anhydride, NMA, methyltetrahydrophthalic anhydride, MTHPA, and their blends with phthalic anhydride, PA), and nanofiller (organically modified hydrotalcite, Perkalite F100S) content. To facilitate rapid screening, Shore D hardness was used as a proxy for Young’s modulus, and the limits of this approach were tested via comparisons with modulus measurements made via dynamic mechanical analysis (DMA). ELO cured with MTHPA at a 1:1 epoxy/anhydride molar ratio with 4.5 phr DBU gave a particularly attractive combination of rigidity, homogeneity, and alpha transition temperature rarely seen in thermosets composed of a 100% biobased epoxy component. Nanocomposite formation provided a modest increase in ...

The Effect of Catalyst Content on Supercritical Water Gasification Process with Shochu (Japanese Popular Distilled Liquor) Residue and the Result of Long-time Continuous Operation

The Effect of Catalyst Content on Supercritical Water Gasification Process with Shochu (Japanese Popular Distilled Liquor) Residue and the Result of Long-time Continuous Operation

Preparation and properties of continuous glass fiber reinforced anionic polyamide-6 thermoplastic composites

Continuous glass fiber (GF) reinforced anionic polyamide-6 (APA6) composites were prepared via in situ ring-opening polymerization of caprolactam monomers. The effects of catalyst content, polymerization temperature and time on the viscosity average molar mass (Mv) and degree of crystallinity (Xc) were investigated in detail. The final mechanical properties of GF/APA6 composites were also studied. The results indicated that both high molecular weight and the high degree of crystallinity of resin matrix lead to the high mechanical properties of composites. Furthermore, the mechanical test results showed that the composites of plain woven fabric had tensile strength of 434MPa and flexural strength of 407MPa. The morphologies of tensile fracture surfaces of the composites specimens were observed through Scanning Electron Microscope (SEM). The SEM analysis showed that many disorganized nano-fiber crystals appear in the tensile fracture surfaces, which improve the mechanical properties of the matrix resin. The mechanical properties of the composites with different post-heat treatments were further investigated. The mechanical properties of the composites are significantly reduced after quenching treatment, but hardly improved after annealing.

Random copolymers based on trimethylene carbonate and ε‐caprolactone for implant applications: Synthesis and properties

AbstractRandom copolymers of trimethylene carbonate (TMC) and ε‐caprolactone (CL) have been synthesized by ring‐opening polymerization of TMC and CL in the presence of stannous octoate. The effects of feeding dose, reaction temperature and polymerization time, and effect of catalyst content on the copolymerization were investigated. The results showed that the composition of the copolymers was in good agreement with the feeding dose, and the molecular weight of the copolymers decreased firstly with increasing CL content and then increased. The decrease in the reaction temperature, polymerization time and catalyst content would increase the molecular weight of the copolymers. Furthermore, the feeding dose affected the thermal and mechanical properties of the copolymer largely, and the possessing different properties of random copolymers could be obtained by adjusting the copolymer compositions. This work could optimize the polymerization conditions to achieve the copolymers with controlled properties for implant applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Growth of Carbon Nanotubes from Supported Metal Catalysts

The growth of carbon nanotubes (CNTs) from supported metal catalysts is under investigation using the chemical vapour deposition (CVD) method with CH4 as the carbon feedstock. Studies include the effects of the structure of the support media, metal catalyst content and other experimental parameters on the CNTs produced. The effects of the surface structure on the catalyst particles and the CNTs produced are being investigated using various alumina-based supported iron catalysts. Supported catalysts have been prepared from ferric sulphate and either aluminium nitrate or deltaalumina nanoparticles in order to produce different substrate morphologies. Preliminary TEM studies indicate that under the same experimental conditions Fe supported on alumina nanoparticles produces mostly bundles of DWCNTs, whereas Fe supported on alumina derived from aluminium nitrate produces predominantly SWNCT bundles with some MWCNTs. The effects of catalyst content on the CNT production is also being investigated with Fe content varying between 5% and 30%. Preliminary TEM results show the presence of bundles of SWCNTs for all the Fe contents except 5% Fe; no CNTs have been observed in this sample.

Influence of Catalyst Content on the Thermal and Mechanical Properties of Epoxy Resins Initiated by a Cationic Latent Thermal Catalyst at Elevated Temperatures

AbstractThe effect of catalyst content on the thermal and mechanical properties of diglycidyl ethers of bisphenol A (DGEBA)/BPH system was investigated at elevated temperatures. The contents of the catalyst, N‐benzylpyrazinium hexafluoroantimonate (BPH), examined were 0.5, 1, and 3 wt.‐% and the elapsed heating time was varied from 0 to 1 024 h. As a result, the thermal‐oxidative resistance and mechanical properties, including flexural strength, elastic modulus in flexure, and impact strength showed a maximum value at 1 wt.‐% BPH. By increasing the elapsed time to 4 h, the thermal and mechanical properties of the specimens were also improved. These results showed that the internal structure of the epoxy system was stabilized and post‐cured as the elapsed time increased, resulting in an improvement of the thermal and mechanical properties of the specimens.Impact strength of the DGEBA/BPH system as a function of BPH content and elapsed heating time.magnified imageImpact strength of the DGEBA/BPH system as a function of BPH content and elapsed heating time.

Kinetic and rheological studies of an unsaturated polyester cured with different catalyst amounts

An unsaturated polyester resin was cured with different catalyst contents. The crosslinking process was followed by static and dynamic viscosimetry and by differential scanning calorimetry (d.s.c.). Activation energies were determined from the gel times obtained by viscosimetry and from the variation in the maximum exotherm temperature obtained by d.s.c. at different heating rates. The existence of a threshold in the amount of catalyst to use is shown by analysis of the gel times. The effect of catalyst content on the glass transition temperatures of the different mixtures has been analysed taking into account the crosslink density, measured by means of the rubber modulus obtained by dynamic mechanical tests.