Processing map for hot working of powder

The constitutive flow behavior of a metal matrix composite (MMC) with 2124 aluminum containing 20 vol pct silicon carbide particulates under hot-working conditions in the temperature range of 300 °C to 550 °C and strain-rate range of 0.001 to 1 s^-1 has been studied using hot compression testing. Processing maps depicting the variation of the efficiency of power dissipation given by [2m/(m + 1)] (wherem is the strain-rate sensitivity of flow stress) with temperature and strain rate have been established for the MMC as well as for the matrix material. The maps have been interpreted on the basis of the Dynamic Materials Model (DMM). [3] The MMC exhibited a domain of superplasticity in the temperature range of 450 °C to 550 °C and at strain rates less than 0.1 s^-1. At 500 °C and 1 s^-1 strain rate, the MMC undergoes dynamic recrystallization (DRX), resulting in a reconstitution of microstructure. In comparison with the map for the matrix material, the DRX domain occurred at a strain rate higher by three orders of magnitude. At temperatures lower than 400 °C, the MMC exhibited dynamic recovery, while at 550 °C and 1 s^-1, cracking occurred at the prior particle boundaries (representing surfaces of the initial powder particles). The optimum temperature and strain-rate combination for billet conditioning of the MMC is 500 °C and 1 s^-1, while secondary metalworking may be done in the super- plasticity domain. The MMC undergoes microstructural instability at temperatures lower than 400 °C and strain rates higher than 0.1 s^-1.     

Ethanol steam reforming study over ZSM-5 supported cobalt versus nickel catalyst for renewable hydrogen generation

The renewable hydrogen generation through ethanol steam reforming is one of the anticipated areas for sustainable hydrogen generation. To elucidate the role of Ni and Co with ZSM-5 support, catalysts were prepared by wet impregnation method and ethanol steam reforming(ESR) was performed. The catalysts were characterized by HR-XRD, ATR–FTIR, HR-SEM, TEM with SAED, EDAX, surface area analyzer and TPR. It had shown complete ethanol conversion at 773 K, but the selectivity in hydrogen generation was found higher for 10% Ni/ZSM-5 catalyst as compared to 10% Co/ZSM-5. The 10% Ni/ZSM-5 catalyst has about 72% hydrogen selectivity at temperature 873 K. It indicates that Ni is a more sustainable catalyst as compared to Co with ZSM-5 support for ESR. The C_2H_4 was found major undesirable products up to 823 K temperature. Nevertheless, the 10% Ni/ZSM-5 catalyst had shown its stability for high temperature(873 K) ESR performance.     

BUBBLE TEMPERATURES OF THE BINARY MIXTURES OF 1,2-DIMETHYLBENZENE WITH 2-PROPANOL, 1-BUTANOL, 2-BUTANOL, 2-METHYLPROPAN-1-OL AND 2-METHYLPROPAN-2-OL AT 95 kPa

Bubble temperatures at 95 kPa over the entire composition range are measured for the five binary systems formed by 1,2-dimethylbenzene with 2-propanol, 1-butanol, 2-butanol, 2- methylpropan-1-ol, and 2-methylpropan- 2-ol. A Swietoslawski - type ebulliometer was used for the measurements. The composition versus temperature measurements are well represented by the Wilson model.     

Morphology of EVA based nanocomposites under shear and extensional flow

Shear and extensional rheological measurements were conducted in conjunction with laser light scattering (LLS) on ethylene‐vinyl acetate copolymer (EVA) nanocomposites. The materials were prepared by melt‐mixing EVA and commercially acquired layered silicates. Wide Angle X‐Ray Scattering (WAXS) was used to ascertain the degree of layer swelling. This could be attributed to the intercalation of polymer chains into the interlayer of the silicates. The nanocomposites prepared were determined to be predominantly intercalated in nature. In shear rheological tests, the nanocomposites exhibited an increase in viscoelastic properties compared to the pure EVA. The extent of this property enhancement was not as pronounced as had been reported in many instances with respect to other polymer nanocomposites. This could be attributed to the absence of a network structure normally observed in an exfoliated system. The extensional rheological tests showed an increase in extensional flow properties. This was confirmed by the LLS, which indicated that the filled systems had higher deformability than the unfilled one. Polym. Eng. Sci. 44:1220–1230, 2004. © 2004 Society of Plastics Engineers.     

Pilot plant study of post-combustion carbon dioxide capture by reactive absorption: Methodology, comparison of different structured packings, and comprehensive results for monoethanolamine

Post-combustion carbon capture (PCC) from fossil fuel power plants by reactive absorption can substantially contribute to reduce emissions of the greenhouse gas CO₂. To test new solvents for this purpose small pilot plants are used. The present paper describes results of comprehensive studies of the standard PCC solvent MEA (0.3 g/g monoethanolamine in water) in a pilot plant in which the closed cycle of absorption/desorption process is continuously operated (column diameters: 0.125 m, absorber/desorber packing height: 4.25/2.55 m, packing type: Sulzer BX 500, flue gas flow: 30-110 kg/h, CO₂ partial pressure: 35-135 mbar). The data establish a base line for comparisons with new solvents tested in the pilot plant and can be used for a validation of models of the PCC process with MEA. The ratio of the solvent to the flue gas mass flow is systematically varied at constant CO₂ removal rate, and CO₂ partial pressure in the flue gas. Optimal operating points are determined. In the present study the structured packing Sulzer BX 500 is used. The experiments with the removal rate variation are carried out so that the results can directly be compared to those from a previous study in the same plant that was carried out using Sulzer Mellapak 250.Y. A strategy for identifying the influence of absorption kinetics on the results is proposed, which is based on a variation of the gas load at a constant L/G ratio and provides valuable insight on the transferability of pilot plant results.     

ZSM-5 Supported Cobalt Catalyst for the Direct Production of Gasoline Range Hydrocarbons by Fischer–Tropsch Synthesis

Abstract  

Fischer–Tropsch synthesis (FTS) reaction for the direct production of gasoline range hydrocarbons (C₅–C₉) from syngas was investigated on cobalt-based FTS catalyst supported on the ZSM-5 possessing a four different Si/Al ratio. The FTS catalysts were prepared by impregnation method using cobalt nitrate precursor in a slurry of ZSM-5, and they were characterized by surface area, XRD, H₂-TPR and NH₃-TPD. Cobalt supported catalyst on ZSM-5 having a low Si/Al ratio of 15 was found to be superior to the other catalysts in terms of better C₅–C₉ selectivity due to the formation of small cobalt particle and the presence of larger number of weak acidic sites. It also exhibited the highest catalytic activity because of the higher reducibility and the small cobalt particle size.     

Fuel grade ethanol by diffusion distillation: an experimental study

BACKGROUND: Fuel grade ethanol (anhydrous ethanol) is considered to be an excellent alternative clean burning fuel to gasoline. It is now used as an additive to gasoline to enhance its octane number and combustibility. Owing to its high energy values, ethanol is the most promising future biofuel. Because of azeotrope formation, anhydrous ethanol cannot be achieved by conventional distillation. Diffusion distillation is one of the several processes that can be used to separate azeotropes. Diffusion distillation takes advantage of differences in relative rates of diffusion using inert gas as selective filter. RESULTS: Effect of vaporization temperature and feed composition on diffusion distillation of an ethanol–water mixture using air as the inert gas has been studied. A new quantity S_az(N₂/N₁) has been suggested to find the optimum vaporization temperature. In the present study this was found to be about 46 °C. The pseudo‐azeotrope has been observed at 0.697 mole fraction of ethanol at a vaporization temperature of 50 °C. Separation is effected by diffusion distillation even at the azeotropic ethanol mole fraction of 0.894. The experimental results were compared with a Stefan–Maxwell equations based mathematical model and found to be in good agreement with theoretical results. CONCLUSIONS: Experimental results demonstrate that fuel grade ethanol can be produced by diffusion distillation. The new quantity S_az(N₂/N₁) is a key variable for vaporization temperature optimization. Copyright © 2011 Society of Chemical Industry     

Preparation and characterization of 4A zeolite‐filled mixed matrix membranes for pervaporation dehydration of isopropyl alcohol

Sodium carboxymethylcellulose/poly (vinyl alcohol) mixed matrix membranes filled with different amounts 4A zeolite (0, 5, 10, 15, and 20 wt %) were prepared by solution casting method. Prepared membranes were crosslinked with GA and used for pervaporation dehydration of isopropyl alcohol of different feed mixtures at 35°C. On increment in zeolite content in the membrane it was found the improvement in the performance of the membrane, due to its hydrophilic nature and molecular sieving effect in addition to its favorable interaction with hydrophilic sodium carboxymethylcellulose and polyvinyl alcohol. The structure and chemical constituents of the MMM's were investigated by attenuated total reflectance Fourier transform infrared spectroscopy. Thermal stability of the membranes was assessed by DSC and TGA techniques. Crystallinity of the membranes was assessed using X‐ray diffraction, and the morphological properties were assessed by scanning electron microscopy. Mechanical properties were also carried out to determine the tensile strength and % of elongation at break using universal testing machine. It was found that the mechanical strength increases with increase in the zeolite content upto 15 wt % of zeolite with an optimum tensile strength of 113.31 N/mm². Pervaporation was carried out to asses the membrane performance, the highest flux and selectivity obtained is 0.584 kg/m²/h and 6945 for NaCMCA20 and NaCMCA15, respectively, for a feed composition containing 17.5 and 10 wt % of water in the feed and further swelling studies also supporting the pervaporation results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Pervaporation separation of IPA‐water mixtures through 4A zeolite‐filled sodium alginate membranes

Incorporation of zeolites into natural polymers has been shown experimentally to enhance both the flux and selectivity in pervaporative dehydration separation of organic compounds. Pervaporation is a promising membrane technique for separation of volatile organic compounds (VOCs)/water mixtures. In this study, hydrophilic sodium alginate (SA) mixed membranes were prepared using solution casting technique by incorporating zeolites into the polymer matrix. The prepared membranes were characterized by ATR‐Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), Thermal Gravimetric Analysis (TGA), and differential scanning calorimetry (DSC) were tested in a laboratory scale pervaporation experimental set‐up. The effect of experimental parameters such as the type and composition of zeolites on permeation flux and selectivity was investigated. When tested on IPA‐water mixtures, the zeolite‐filled membrane was found to give much higher selectivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011