A Comparative Analysis of Data-Driven Models (SVR,ANFIS, and ANNs) for Daily Karst Spring Discharge Prediction

Water Resources Management - Spring discharge always illustrates the groundwater-flux and aquifer storage oscillations. Because of inherent heterogeneity in karst environments, it is essential to...     

Hydrogen adsorption in metal- organic frameworks (MOFs): Effects of adsorbent architecture

In this work, the effect of metal-organic framework (MOF) structure of MOF-5 was investigated in hydrogen adsorption based on the degree of solvent exploitation and/or sample preparation procedures. In this regard, the characterization analyses of FT-IR, BET and PXRD pattern of MOF-5 samples were used to compare their architectures with different specific surface area and porosity in hydrogen adsorption. The results show that the pore size distribution of samples is related to the main peaks in the micropores, mesopores and macropores regions. One can found that the adsorption of hydrogen at room temperature (296 K) is controlled by diffusion of adsorbed hydrogen inside the pores of the crystals. Larger diffusivities at a given pressure are expected due to diffusion in macroporous. The values of heats of adsorption on prepared sample are calculated as 3.68 and 12.45 kJ mol^?1 for meso and macroporous regions, respectively. These results are suggesting that weak interactions between the adsorbed hydrogen molecules and MOF crystals is occur in mesoporous regions and the adsorption into macroprous which are filling in high temperature shows strong interaction.     

Fischer-Tropsch synthesis by reduced graphene oxide nanosheets supported cobalt catalysts: role of support and metal nanoparticle size on catalyst activity and products selectivity

In this paper,a series of cobalt catalysts supported on reduced graphene oxide(rGO)nanosheets with the loading of 5,15 and 30 wt-%were provided by the impregnation method.The activity of the prepared catalysts is evaluated in the Fischer-Tropsch synthesis(FTS).The prepared catalysts were carefully characterized by nitrogen adsorption-desorption,hydrogen chemisorption,X-ray diffraction,Fourier transform infrared spectroscopy,Raman spectroscopy,temperature programmed reduction,transmission electron microscopy,and field emission scanning electron microscopy techniques to confirm that cobalt particles were greatly dispersed on the rGO nanosheets.The results showed that with increasing the cobalt loading on the rGO support,the carbon defects are increased and as a consequence,the reduction of cobalt is decreased.The FTS activity results showed that the cobalt-time yield and turnover frequency passed from a maximum for catalyst with the Co0 average particle size of 15 nm due to the synergetic effect of cobalt reducibility and particle size.The products selectivity results indicated that the methane selectivity decreases,whereas the C5+selectivity raises with the increasing of the cobalt particle size,which can be explained by chain propagation in the primary chain growth reactions.     

Structural Effects of HZSM-5 Zeolite on Methanol-to-Propylene Reaction

ZSM-5 zeolite was synthesized using n-butylamine as a template under hydrothermal conditions. The morphology of the prepared zeolites was changed with the initial gel composition. The influences of OH⁻/template and H₂O/template ratios on the morphology, mesoporosity, acid properties, and crystal size of the synthesized zeolites were evaluated, also the structural effects of the prepared zeolites on the catalytic performances of the methanol-to-propylene process. Increasing the external surface area and mesopore volume of the catalysts improved the propylene selectivity. A direct relationship between the deactivation of catalysts and their acidic properties was found. The results were derived from laboratory data and need to be re-examined on a larger scale to ensure their accuracy on an industrial scale.     

Intrinsic Hydrodynamic Investigation of Three-Phase Bubble Column: Comparative Experimental Study on Gas Holdup

Theoretical Foundations of Chemical Engineering - A comprehensive experimental study of the hydrodynamic behaviors for the specific system of air/paraffin oil/silica particles in a slurry bubble...     

Evaluation of rutting resistance of asphalt binders and asphalt mixtures modified with polyphosphoric acid

In this research, a polyphosphoric acid (PPA) additive was used to modify a performance graded binder (PG 58-22). Experimental program included use of three PPA contents (0.5%, 1%, and 1.5%) by weight of bitumen and use of antistripping limestone aggregates. High-temperature rheological properties of asphalt binders were evaluated through the frequency sweep test. Complex modulus test was also used to evaluate rutting characteristics of asphalt mixtures. Results showed that PPA significantly improved rutting resistance of both unmodified asphalt binder and unmodified asphalt mixture, especially for the asphalt binder.     

CFD modeling of hydrogen production using steam reforming of methane in monolith reactors: Surface or volume-base reaction model?

In the present work, two approaches for reaction modeling in monolith reactors were taken into account and compared to each other. In the first approach, the reactions are assumed to take place on the wall surfaces, while penetration and reaction of chemical species inside a thin layer near the walls are of essential concern in the second approach. Experiments of Steam Methane Reforming (SMR) were carried out in a Bench-scale monolith reactor. A single-channel was considered and two axi-symmetric CFD models were developed for modeling. General kinetic models for SMR and Water-Gas-Shift (WGS) reaction rates based on Langmuir-Hinshelwood type were employed. Comparisons between modeling results and experimental data showed that despite its ease of implementation, the first approach (surface reactions) exhibits better results both in generality and accuracy. It was realized that uncertainties in obtaining the effective diffusion coefficients in the volumetric approach may cause a variation up to 16% in the prediction of reaction conversion.     

Predictive Dynamic Model of Air Separation by Pressure Swing Adsorption

A general dynamic model is developed for separation of air over a carbon molecular sieve and a zeolite adsorbent for production of nitrogen and oxygen. The proposed model is validated using experimental data from working laboratory scale N₂–PSA and laboratory scale O₂–PSA systems. Simulations studies are performed to investigate the effect of changing various process variables, such as the duration of PSA steps, bed length and feed inlet velocity.     

Experimental study on optimization of CO2 laser welding parameters for polypropylene-clay nanocomposite welds

In this paper, polypropylene-clay nanocomposite sheets of 2 mm thickness with 0 wt%, 3 wt% and 5 wt% nanoclay are butt welded using a CO₂ laser to determine the effect of clay content and laser process parameters on weld tensile strength. For this purpose, Taguchi parametric design and optimization method was used to design experiments and develop a model to predict weld tensile strength as a function of clay content and laser process parameters such as laser power, welding speed and focal position. The adequacy of the model was checked using analysis of variance and by conducting extra confirmation tests. Using Taguchi optimization approach, the optimum levels of parameters were determined. The results indicated that an increase in clay content and welding speed decreased the weld strength, whereas increasing laser power increased weld strength. Furthermore, increase in focal position showed an increasing and then a decreasing effect on weld strength.