Effect Of γ-Al2O3 Research Articles

Microwave-assisted catalytic rapid pyrolysis of soybean straw for the preparation of high-value indole-rich bio-oils

Microwave-assisted catalysed rapid pyrolysis of soybean straw to prepare high-value bio-oils rich in indoles achieved value-added use of biomass. The effects of different urea doping ratios, two typical Al-based catalysts (γ-Al2O3, HZSM-5), and different HZSM-5 doping ratios on the preparation of N-rich bio-oils (NCBs) from soybean straw by microwave-assisted pyrolysis were investigated. It was shown that the yield of the liquid product at 40 % urea addition was 39.63 %, in which pyridine compounds were enriched to the extent of 20.86 %. On this basis, the effects of γ-Al2O3 and HZSM-5 on N-containing compounds (NCCs) in bio-oil were analyzed in detail. The yield of NCCs increased significantly with the addition of HZSM-5. The best parameter combinations were obtained through orthogonal experiments: urea addition of 50 %, HZSM-5 catalyst type, and catalyst doping ratio of 200 %. At this point, the bio-oil yield reached 29.575 wt%. Among them, indole yield reached 41.66 wt% and exhibited high selectivity of 68.92 % in NCCs. The formation mechanism of indoles during microwave-assisted N-rich pyrolysis was further investigated on the basis of experimental studies. In addition, the inhibitory effect of the HZSM-5 catalyst on the formation of pyridine compounds during pyrolysis process and the enhancement mechanism of the formation of indole compounds were deeply investigated. This provided a green pathway for the preparation of indoles by microwave-assisted fast pyrolysis directional catalytic conversion of biomass.

Investigation of the Lubrication Performance of γ-Al2O3/ZnO Hybrid Nanofluids for Titanium Alloy

Titanium alloys are difficult to machine and have poor tribological properties. This paper investigates the lubricating performance of γ-Al2O3/ZnO hybrid nanofluids for Ti-6Al-4V. Pure and hybrid nanofluids are compared, and the effects of γ-Al2O3/ZnO ratios are studied. The results show that γ-Al2O3/ZnO hybrid nanofluids outperform pure nanofluids in terms of lower friction coefficients and better surface quality. Moreover, the hybrid nanofluid with a mass ratio of Al2O3 to ZnO of 2:1 demonstrates the best lubrication performance with a reduced friction coefficient of up to 22.1% compared to the base solution, resulting in improved surface quality. Al2O3 nanoparticles can adhere to the surface of ZnO nanoparticles and work as a coating, which further enhances the lubrication performance of the water-based nanofluid.

Effects of oxides nanoparticles on the microstructure and properties of Mo composites prepared via SPS sintering

Simultaneous achieving the second-phase particle strengthening, high density, and fine grain is a great difficulty for designing and preparing Mo alloys. In this study, the effects of γ-Al2O3 and Y2O3 nanoparticles on the microstructures and properties of Mo composites prepared via spark plasma sintering (SPS) were systematically investigated. It was found that for pure Mo and Mo–Y2O3 powders, Mo compact with both high density and fine grain size can't be achieved. However, Mo-Al2O3 composite with both a relatively high density (98%) and a fine grain size (1.67 μm) was synthesized successfully. The small γ-Al2O3 particles transformed into larger κ-Al2O3 particles by obvious grain boundary migration and grain growth in the sintering process, which effectively pinned the migration of Mo grain boundary with few effects on the surface atom diffusion of Mo. Moreover, there was a crystallographic orientation relationship between the κ-Al2O3 particles and Mo matrix (Mo (110)//Al2O3 (134‾1)). Ultrafine Mo composite containing dispersed Al2O3 particles with stable boundary adhesion can efficiently hinder dislocation movement and crack propagation, resulting in the obvious enhancements of bending strength, hardness and compressive yield strength.

Probing the Interaction of Plasma with Nano-Catalysts for CO₂ Conversion Using In-Situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy.

The effect of γ-Al₂O₃ and Ce/Al₂O₃ nano-catalysts under plasma on CO₂ conversion was investigated via In-Situ DRIFTS. The adsorption of CO₂ on the nanoparticle of γ-Al₂O₃ surface caused to produce the carbonate species, of which the amount was dependent on temperature. In addition, we confirmed that the formation of carbonate could be more activated by plasma. The Ce nano-catalyst played a role to inhibit the production of carbonate on the surface of Al₂O₃ under the plasma. Indeed, when the Ce/Al₂O₃ catalyst was exposed to plasma-excited CO₂, the carbonate was almost eliminated at over 300 °C, resulting in the improved CO₂ conversion. Notably, the Ce-promoted catalyst was able to enhance the formation of intermediate formate species by the plasma-excited CO₂. Consequently, the formed intermediate species facilitated the generation of CO by the reaction of formate and bicarbonate.

Effect of γ-Al2O3/Water Nanofluid on Natural Convection Heat Transfer of Corrugated ┐ Shaped Cavity: Study the Different Aspect Ratio of Grooves

In this paper, the effect of γ-Al2O3/water nanofluid on the flow pattern and natural convection heat transfer of corrugated ⅂ shaped cavity is investigated numerically by the Lattice Boltzmann Method (LBM). The effects of nanoparticles solid volume fraction (ϕ=0-0.006), Rayleigh number (Ra=103-106) and the aspect ratio of grooves cavity (h/H=0.05-0.15) on the streamlines, isotherms and averaged Nusselt number have been examined. In addition, a comparison between γ-Al2O3/water nanofluid and MWCNT-Fe3O4/Water Hybrid Nanofluid on the average Nusselt number are studied. The results showed that the heat transfer rate of γ-Al2O3/water nanofluid is higher than water. For all Rayleigh numbers and solid volume fraction of nanoparticles, increasing the height of grooves leads to an increment in average Nusselt number. Moreover, when the Rayleigh number reaches to 106, the average Nusselt number increases, which the domain mechanism of heat transfer, in this case, becomes convection. As to be expected, the influence of MWCNT-Fe3O4/Water Hybrid Nanofluid on heat transfer rate is higher than the γ-Al2O3/water nanofluid.

Fabrication of Porous Mullite Ceramics with Different Phase of Alumina for Insulation Materials

This paper reports the effects of γ-Al2O3 and α-Al2O3 on the properties of lightweight insulation materials. The phase compositions, microstructure and mechanical properties of lightweight insulation materials are separately investigated by XRD, SEM and tabulate thermal conductivity apparatus methods. The results indicate that the increasing of the amount of γ-Al2O3 is beneficial to improving the bulk density, compressive strength and acid resistance of the fired specimens. The fact negatively impacts on the increasing of the apparent porosity; however, it has no significant effect on the thermal conductivity of specimens. Meanwhile, the studies highlight that when the content of γ-Al2O3 increases, the nucleation and growth of mullite is accelerated at high calcination temperature, which has positive effect on improving the physicochemical properties of lightweight insulation materials. And the γ-Al2O3-free SiO2 glass phase system is guided by theoretical analysis of reaction conditions for non-catalytic system with Factsage modelling.

Subcooled flow boiling heat transfer of γ-Al2O3/water nanofluids in horizontal microtubes and the effect of surface characteristics and nanoparticle deposition

In this study, subcooled flow boiling heat transfer characteristics of nanofluids were investigated at micro scale. For this purpose, the effect of γ-Al2O3 (gamma-alumina) nanoparticles with an average solid diameter of 20nm was considered. In the experiments, various mass fractions were considered in horizontal smooth stainless steel microtubes with inner and outer diameters of ∼502µm and ∼717µm, respectively, at mass fluxes of 1200 and 3400kgm−2s−1. Nanoparticles were added to distilled water (base fluid) at five mass fractions (low mass fractions 0.05wt% and 0.2wt%; high mass fractions 0.5wt%, 1wt% and 1.5wt%). According to our results, subcooled flow boiling heat transfer coefficients for nanofluids with low mass fractions were nearly the same as those of the pure water. However, heat transfer deteriorated for nanofluids with high mass fractions. Observations of dynamic light scattering measurements for low and high mass fractions before and after the experiments revealed that agglomeration of nanoparticles is an important parameter in deterioration of heat transfer at higher concentrations. Besides, Scanning Electron Microscopy images of microtube inner surfaces showed that deposition of nanoparticles and agglomerated nanoparticles on the inner surface of the microtubes also contributed to the heat transfer deterioration at high mass fractions. Generally, the deterioration in heat transfer beyond a specific mass fraction value was linked to the disturbance in the stability of suspended nanoparticles and deposition of nanoparticles upon boiling.

Characterization and activity of CuMnOx/γ-Al2O3 catalyst for oxidation of carbon monoxide

The addition of γ-Al2O3 support into the CuMnOx catalyst enhances the dispersion capacity as compared to unsupported CuMnOx catalysts. There exist strong interactions between the copper, manganese oxide and γ-Al2O3 support. The effect of γ-Al2O3 on the dispersion, active states and reduction behavior of surface supported CuMnOx catalysts have been investigated by X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), Scanning electron microscopy with energy-dispersed X-ray (SEM-EDX) and Brunauer Emmett Teller (BET) analysis. The characterization results confirm that Cu+, Mn2+ and Al mostly existed on the effective surface sites of the CuMnOx/γ-Al2O3 catalysts. These results indicate that there is a synergistic interaction between the copper, manganese and aluminum oxide, which is responsible for the high catalytic activity of CO oxidation reactions. In the CuMnOx/γ-Al2O3 catalysts, the 40%CuMnOx/γ-Al2O3 catalyst shows the highest catalytic activity for complete oxidation of CO at 130°C temperature. The main aim of this paper is to find the optimum percentage of γ-Al2O3 support into the CuMnOx catalyst for total oxidation of CO at a low temperatures. Using γ-Al2O3 support in the CuMnOx catalyst lowers the cost without sacrificing the performance.

Effect of γ-Al2O3/water nanofluid on the thermal performance of shell and coil heat exchanger with different coil torsions

This work investigated experimentally the thermal performance of shell and coil heat exchanger with different coil torsions (λ) for γ-Al2O3/water nanofluid flow. Five helically coiled tube (HCT) with 0.0442 ≤ λ ≤ 0.1348 were tested within turbulent flow regime. The average size of γ-Al2O3 particles is 40 nm and volume concentration (φ) is varied from 0 to 2%. Results showed that reducing coil torsion enhances the heat transfer rate and increases HCT-friction factor (fc). Also, it is noticed that HCT average Nusselt number (Nut) and fc of nanofluids increase with increasing γ-Al2O3 volume concentration. The thermal performance index, TPI = (ht,nf/ht,bf)/(ΔPc,nf/ΔPc,bf). increases with increasing nanoparticles concentration, coil torsion, HCT-side inlet temperature and nanofluid flow rate. Over the studied range of HCT-Reynolds number, the average value of TPI is of 1.34 and 2.24 at φ = 0.5% and φ = 2%, respectively. The average value of TPI is of 1.64 at λ = 0.0442 while its average value at λ = 0.1348 is of 2.01. One of the main contributions is to provide heat equipments designers with Nut and fc correlations for practical configurations shell and coil heat exchangers with a wide range of nanofluid concentration.

Experimental and theoretical investigation on Nano-fluid surface tension

Effect of γ-Al2O3 and MgO nanoparticle on surface tension of Tri Ethylene Glycol (TEG) was studied for different nanoparticle concentrations. Furthermore, the effect of nanoparticle size on the Nano-fluid surface tension was investigated. Results showed that surface tension increases for some particle concentrations and decreases for some others; in other words, a certain particle concentration could not be determined as the boundary for the increase or decrease of surface tension. Moreover, Sorbitan oleate was added to TEG solution to investigate the changes in surface tension that may occur due to the addition of surfactants. It is shown that by increasing surfactant concentration, Nano-fluid surface tension would decrease. The effect of nanoparticle size on surface tension was analyzed as well. Using experimental data, five empirical and thermodynamic-based models; i.e., Redlich–Kister (RK), Malanovsky-Marsh (MM), Jufu et al. (JBZ), Chunxi et al. (CWZ) and Santos et al. (SFF) were evaluated for surface tension estimation, and it was found that SFF method is the best method to correlate nano fluid surface tension in this study.

Effect of γ-Al2O3/Water Nanofluid on Heat Transfer and Pressure Drop Characteristics of Shell and Coil Heat Exchanger With Different Coil Curvatures

This study presents an experimental investigation of the characteristics of convective heat transfer in horizontal shell and coil heat exchangers in addition to the friction factor for fully developed flow through their helically coiled tube (HCT). Five heat exchangers of counterflow configuration were constructed with different HCT-curvature ratios (δ) and tested at different mass flow rates and inlet temperatures of γ-Al2O3/water nanofluid in the HCT. The tests were performed for γ-Al2O3 with average size of 40 nm and particles volume concentration (ϕ) from 0% to 2% for 0.0392≤δ≤0.1194. Totally, 750 test runs were performed from which the HCT-average Nusselt number (Nu¯t) and fanning friction factor (fc) were calculated. Results illustrated that Nu¯t and fc of nanofluids are higher than those of the pure water at same flow condition, and this increase goes up with the increase in ϕ. When ϕ increases from 0% to 2%, the average increase in Nu¯t is of 59.4–81% at lower and higher HCT-Reynolds number, respectively, and the average increase in fc is of 25.7% and 27.4% at lower and higher HCT-Reynolds number, respectively, when ϕ increases from 0% to 2% for δ=0.1194. In addition, results showed that Nu¯t and fc increase by increasing coil curvature ratio. When δ increases from 0.0392 to 0.1194 for ϕ=2%, the average increase in Nu¯t is of 130.2% and 87.2% at lower and higher HCT-Reynolds number, respectively, and a significant increase of 18.2–7.5% is obtained in the HCT-fanning friction factor at lower and higher HCT-Reynolds number, respectively. Correlations for Nu¯t and fc as a function of the investigated parameters are obtained.

Effect of Volume Fraction of γ‐Al2O3 Nanofluid on Heat Transfer Enhancement in a Concentric Tube Heat Exchanger

In this work, γ-Al2O3 nanoparticles with mean diameter of 10 nm are dispersed in deionized water with four nanoparticle volume concentrations of 0.25, 0.5, 0.75, and 1%. The effect of γ-Al2O3/water nanofluids on the heat transfer enhancement of heat exchangers is investigated under turbulent regime for four different volumetric flow rates of 150, 200, 250, and 300 L/h. The experimental results showed that the convective heat transfer is increased by increasing particles volume fraction as well as flow rate. The maximum enhancement obtained in Nusselt number and heat transfer coefficient was 20 and 22.8%, respectively, at Reynolds number of 6026 and particle volume fraction of 1%. The experimental Nusselt numbers of nanofluids showed good agreement with the available empirical correlation at particle volume fractions of 0.25 and 0.5%. An empirical correlation is obtained to estimate the Nusselt number of nanofluid under the conditions of this work.

Catalytic formation of carbonyl sulfide during warm gas clean-up of simulated coal-derived fuel gas with Pd/γ-Al2O3 sorbents

Coal gasification processes, such as the Integrated Gasification Combined Cycle (IGCC), will increase in importance due to the expanding concern over CO2 emissions and global climate change. During the development of a Pd/γ-Al2O3 sorbent for warm (200°C) fuel gas cleanup, the catalytic formation of carbonyl sulfide (COS), was observed. This is attributed to a heterogeneous reaction involving fuel gas components (CO/CO2/H2/H2S/H2O) and Pd/γ-Al2O3. The concentration of COS increases 200-fold when exposed to the Pd/γ-Al2O3 sorbent. A Langmuir–Hinshelwood reaction mechanism is proposed and a kinetic model is developed based on experimental results. The effect of γ-Al2O3, a common catalyst for hydrolysis of COS, and H2O on the COS concentration is discussed.

In situ time-resolved X-ray diffraction of tobermorite synthesis process under hydrothermal condition

Hydrothermal synthesis process of tobermorite (5CaO.6SiO2.5H2O) has been investigated by in situ X-ray diffraction (XRD) using high-energy X-rays from a synchrotron radiation source in combination with a laboratory-made autoclave cell and a photon-counting pixel array detector. Three types of quartz sand having different particle size distributions were used. Not only the dissolution rate of quartz but also that of portlandite (Ca(OH)2) were largely affected by particle size distribution of quartz in starting mixtures. The effect of γ-Al2O3 on quartz dissolution and tobermorite formation was also investigated. In all cases, portlandite dissolved completely before the tobermorite formation, while a certain amount of quartz remained undissolved at the timing for tobermorite to start to be detected (denoted as T0). However, the composition (Ca/Si) of non-crystalline C-S-H at T0 was identical regardless of the quartz dissolution rate. Possible reaction mechanism for tobermorite formation has been discussed in terms of distribution of Ca/Si in non-crystalline C-S-H.

The Effect of γ-Al2O3, TiO2 and ZrO2 Supports on Hydrodesulfurization Activity of Transition-Metal Sulfides

The transition metals V, Cr, Mn, Fe, Co, Ni, Mo, Ru, Rh, Pd, W, Re, Os, Ir and Pt were deposited from aqueous solutions of their salts onto conventional γ-Al2O3 and unconventional TiO2 and ZrO2 supports by vacuum impregnation and characterized in their sulfided form by a model reaction of benzothiophene hydrodesulfurization. It was found that the TiO2 and ZrO2 supports influenced predominantly positively the resulting activity of relatively low-active metals (V, Cr, Mn, Fe, Co, Ni, Mo, Ru, W and Os), whereas the highly active metals (Rh, Pd, Ir, Pt and Re) were influenced slightly negatively or not at all by those supports compared with the γ-Al2O3-supported system. A significant effect of the supports on the hydrodesulfurization-activity ranking of the transition-metal sulfides studied was ascertained.

Vapour-liquid equilibria and surface tensions for the nitrogen-argon-methane system at 90·67° K

Effect of γ-Al2O3 and MgO nanoparticle on surface tension of Tri Ethylene Glycol (TEG) was studied for different nanoparticle concentrations. Furthermore, the effect of nanoparticle size on the Nano-fluid surface tension was investigated. Results showed that surface tension increases for some particle concentrations and decreases for some others; in other words, a certain particle concentration could not be determined as the boundary for the increase or decrease of surface tension. Moreover, Sorbitan oleate was added to TEG solution to investigate the changes in surface tension that may occur due to the addition of surfactants. It is shown that by increasing surfactant concentration, Nano-fluid surface tension would decrease. The effect of nanoparticle size on surface tension was analyzed as well. Using experimental data, five empirical and thermodynamic-based models; i.e., Redlich–Kister (RK), Malanovsky-Marsh (MM), Jufu et al. (JBZ), Chunxi et al. (CWZ) and Santos et al. (SFF) were evaluated for surface tension estimation, and it was found that SFF method is the best method to correlate nano fluid surface tension in this study.