Dependence of tacticity distribution in thermal oxidative degradation of polypropylene

Summary Thermal oxidative degradation behavior of two kinds of polypropylene (PP) with different tacticity distribution was investigated based on the data obtained by NMR, temperature rising elution fractionation (TREF) and thermogravimetric analysis (TGA). Although these PPs have similar molecular weights and tacticity, the behavior of degradation was considerably different. The differences were found to be due to the tacticity distribution by TREF measurement. In order to investigate the effect of tacticity distribution on the degradation in more detail, the more stable PP having a broad tacticity distribution was divided into four kinds of tacticity fraction by TREF, and each of degradation behavior was investigated by TGA. The results indicated that the rate of degradation systematically depended on the tacticity. The higher stability of PP with the broader tacticity distribution would be originated from the abstraction reaction of tertiary hydrogen, which was the rate-determining step in PP degradation reaction.     

Transformation of methanol to gasoline range hydrocarbons using HZSM-5 catalysts impregnated with copper oxide

Various CuO/HZSM-5 catalysts were studied in a fixed bed reactor for the conversion of methanol to gasoline range hydrocarbons at 673 K and at one atmospheric pressure. The catalysts were prepared by wet impregnation technique. Copper oxide loading over HZSM-5 (Si/Al=45) catalyst was studied in the range of 0 to 9 wt%. XRD, BET surface area, metal oxide content, scanning electron microscopy (SEM) and thermogravimetric (TGA) techniques were used to characterize the catalysts. Higher yield of gasoline range hydrocarbons (C₅-C₁₂) was obtained with increased weight % of CuO over HZSM. Effect of run time on the hydrocarbon yields and methanol conversion was also investigated. The activity of the catalyst decreased progressively with time on-stream. Hydrocarbon products’ yield also decreased with the increase in wt% of CuO. Relatively lower coke deposition over HZSM-5 catalysts was observed compared to CuO impregnated HZSM-5 catalyst.     

Mechanical properties of directionally solidified lead-antimony alloys

The Pb-17wt％ Sb alloy was directionally solidified under two solidification conditions:with different temperature gradients (G=0.93-3.67 K/mm)at a constant growth rate(V=17.50 μm/s)and with different growth rates(V=8.3-497 μm/s)at a constant temperature gradient(G=3.67 K/mm)in a Bridgman furnace.Microstructure parameters,such as primary dendrite arm spacing(λ1),secondary dendrite arm spacing(λ2),and dendrite tip radius(R),were measured.The microhardness(Hv)and ultimate tensile strength(σ)of the directional solidification samples were also measured.The influences of solidification and microstructure parameters on Hv and σrwere investigated.The results obtained in this work were compared with similar experimental researches in literatures.It is shown that the Hv and σrvalues increase with the increase of G and V,but decrease with the increase of λ1,λ2,and R.     

Uptake of anionic and cationic dyes by highly effective porous carbon adsorber based on industrial processing residues

In this work, we investigated the performance of porous carbon prepared from carob (Ceratonia siliqua L.) processing residues at optimized conditions for the removal of the Basic Green 4 (BG4) and Direct Red 28 (DR28) dyes from aqueous solutions. The influence of several parameters such as adsorbent dose, initial dye concentration, contact time and temperature was evaluated in batch adsorption experiments. Maximum adsorption capacities were observed as 769 mg g^?1 and 323 mg g^?1 for BG4 and DR28, respectively. These results suggest that BG4 and DR28 could be removed using a novel porous carbon from carob processing residues.     

High‐Selectivity Y2O3‐Doped SiO2 Nanocomposite Membranes for Gas Separation in Steam at High Temperatures

Asymmetric structures were fabricated by depositing Y₂O₃‐doped SiO₂ (Si/Y) membranes onto γ‐Al₂O₃ supported by tubular α‐Al₂O₃. The thickness of the Y₂O₃‐doped SiO₂ deposits was approximately 100 nm. The deposits/membranes have micropores with a pore diameter ~ <0.40–0.55 nm. Pore size distribution measurements were conducted directly on the membranes before and after hydrothermal treatment with a nano‐permporometer. The gas permeance properties of the membranes were measured in the temperature range 100°C–500°C. The Y‐doped SiO₂ membrane (Si/Y = 3/1) was found to exhibit asymptotically stable permeances of 2.39 × 10^?7 mol/m²/s/Pa for He and 6.19 × 10^?10 mol/m²/s/Pa for CO₂, with a high selectivity of 386 (He/CO₂) at 500°C for 20 h in the presence of steam. The Y‐doped silica membranes exhibit very high gas permeances for molecules with smaller kinetic diameters. The apparent activation energies of the H₂ permeance at 400°C were 24.2 ± 0.2 and 21.3 ± 0.7 kJ/mol for SiO₂ and Si/Y, respectively.     

Computer-aided process intensification of natural gas to methanol process

The recent revolution in shale gas has presented opportunities for distributed manufacturing of key commodity chemicals, such as methanol, from methane. However, the conventional methane-to-methanol process is energy intensive which negatively affects the profitability and sustainability. We report an intensified process configuration that is both economically attractive and environmentally sustainable. This flowsheet is systematically discovered using the building block-based representation and optimization methodology. The new process configuration utilizes membrane-assisted reactive separations and can have as much as 190% higher total annual profit compared to a conventional configuration. Additionally, it has 57% less CO₂-equivalent greenhouse gas emission. Such drastic improvement highlights the advantages of building block-based computer-aided process intensification method.     

Data-driven approximation of thermodynamic phase equilibria

We present a new data-driven approach for both accurate and computationally efficient approximation of vapor liquid equilibria (VLE) models. Our method is able to provide guaranteed enclosure to limit the approximation errors over the entire domain of interest, all just by sampling only at select points. The approximation relies on a mixed-integer linear programming (MILP) formulation that exploits vertex polyhedral properties of theoretically guaranteed lower and upper bounds to enclose nonlinear and nonconvex equations of state (EOS) and empirical models. Another advantage is that, unlike traditional full simulation-based data-driven approaches, we do not solve nonlinear system of equations ( f ( x ) = 0) for sampling. Instead of looking for only feasible samples, we evaluate f ( x ) over x -domain. This functional evaluation eliminates the need for computationally-demanding full-scale simulations and the associated convergence issues. We demonstrate excellent performance of the proposed MILP formulation in predicting the solubility of hydrofluorocarbon (HFC) refrigerants in ionic liquids (IL).     

Combination of lignin polyol–tannin adhesives and polyethylenimine for the preparation of green water‐resistant adhesives

In this study, a green adhesive from renewable lignin and tannin was developed with polyethylenimine (PEI) with a method to improve the water resistance of the lignin/tannin adhesive. Lignin polyols were prepared through the liquefaction of oil‐palm empty fruit bunches. The characteristics of the adhesive samples were compared with those of a commercial phenol–formaldehyde resin. Three plywood specimens bonded with the new adhesive showed a very high tensile strength (63.04 MPa) and were very water resistant. The effect of the solid content of the adhesives on the tensile strength and gel time and various weight ratios of PEI on the tensile strength and water resistance of the plywood specimens were evaluated. Thermal stability tests revealed that the lignin polyol–tannin/PEI adhesives had a high heat resistance (360 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43437.     

Determination of economic upper limit of drying processes in coal-fired power plants

In this study, the economic assessment of coal drying prior to ga rinding mill process in coal-fired thermal power plants was carried out. In the literature, despite the fact that there are studies regarding drying systems, the advantages and disadvantages of these systems in comparison to each other and the benefits that drying will provide, and the economic factors that are the most important determinants in the practice of the drying system, were not adequately analyzed. In this study, on the other hand, a model was developed to determine the necessary critical cost point in order to identify the appropriate drying system. Through the use of this model, the benefits to be gained from the planned drying system and the financial upper limit required for this investment can be specified. As a model application, eight of the thermal power plants in Turkey were examined. The economic upper limit of a drying system to enable coal to be dried at a rate of 10% was determined through a model study carried out for Catalagzi Power Plant.