Process intensification for heavy oil upgrading using supercritical water

Demand for light hydrocarbons has been steadily increasing in the market with a corresponding decrease in heavy hydrocarbon demand. Therefore, there is a need to develop environmentally friendly and efficient technologies for conversion of heavy molecular weight hydrocarbons. Supercritical fluids (SCF) are attracting increased attention as solvents for green chemistry and among those supercritical water (SCH₂O) is promising for the upgrading of heavy hydrocarbons. Because of a sharp decrease in its dielectric constant, water loses its polarity when brought to the supercritical conditions and its properties starts to resemble the properties of hydrocarbons and becomes an excellent solvent for organic compounds. Moreover, increased ionic product of water leads to an increasing [H₃O⁺] concentration and thus promotes the reactions requiring the addition of an acid. Solvation power enables the extraction of lighter compounds while increased [H₃O⁺] concentration makes the reactive extractions of heavy hydrocarbons possible. As a result of its favorable properties, a wide variety of process intensification studies have been carried out using near critical or SCH₂O such as combined distillation-cracking-fractionation and in some cases even without the utilization of catalysts and/or hydrogen. In this review, recent advances on reactions of hydrocarbons occurring in a SCH₂O environment will be highlighted. Fundamental aspects of these reactions including their thermodynamics and kinetics will be discussed. Experimental and theoretical developments on phase equilibria of relevant water–hydrocarbons systems will be presented.     

Study of the physicochemical and pasting properties of instant corn flour added with calcium and fibers from nopal powder

This work presents a physicochemical and apparent viscosity characterization of commercial nixtamalized corn flours (CNCF) added with nopal powder. The chemical proximate analysis of CNCF and traditional nixtamalized corn flours (TNCF) shows equal amounts of protein and fat, but the calcium content and total dietary fiber is higher in the TNCF. Nopal powder contains a high amount of Ca, soluble and insoluble fiber. The inclusion of 4% of nopal powder increases the calcium and fiber content of the CNCF to the level of traditional nixtamalized products steeped at 7 h. A pasting characteristics analysis based on the profile curves was done in order to study the influence of soluble and insoluble fibers on the pasting conditions of the studied samples added with nopal. At low temperatures the insoluble fiber governs the water absorption and below the gelatinization temperature (T_g) a competition between starch swelling and water absorption was found; for T higher than T_g the system is complex because it includes the interactions between soluble–insoluble fibers and exuding amylose.     

Conducting Composites of Polyurethane Resin and Polypyrrole: Solvent‐Free Preparation,Electrical, and Mechanical Properties

Summary: Three methods were used for solvent‐free preparation of conducting composites of PUR and PPy. In all cases, PUR was prepared from TDI and hydroxol 15‐W as polyol cross‐linker, whereas PPy was obtained upon oxidative coupling of Py using ferric chloride as oxidant. In method 1, PPy powder was dispersed in hydroxol. After addition of TDI the mixture was cured to yield the final product. In method 2, ferric chloride and Py were dissolved in hydroxol and a PPy dispersion was obtained. Then TDI was added and the final product was obtained upon curing. In method 3, Py was dissolved in TDI and ferric chloride dissolved in hydroxol. Then the two solutions were mixed and cured resulting in the simultaneous formation of PPy and PUR. Method 1 led to composites with a specific electrical conductivity σ of 10^?10 S · cm^?1 and a Shore A hardness of 40 to 55. Using methods 2 and 3, composites with σ values of 10^?7 S · cm^?1 and a hardness of 30 to 40 were obtained. Presence of moisture increased the σ values and decreased the hardness. Due to the solvent‐free preparation, the maximum PPy content of the samples was limited to 10 wt.‐%. The studies also demonstrated that the conductivity was mainly dependent on the amount of ferric chloride present in the sample and not on the PPy content, suggesting that the conductivity was ionic.

Flow diagram of different preparation methods for PUR–PPy composites.     

A hybrid simulated annealing-tabu search algorithm for the part selection and machine loading problems in flexible manufacturing systems

Part selection and machine loading are two major problems in the production planning phase of the flexible manufacturing systems. The problems have a combinatorial structure and usually, in practice, it is difficult to deal with this kind of problems using a mathematical programming model. In this paper, the above problems are formulated as a mixed-integer programming model which is handled sequentially and solved by a diversification-strategy-added version of the hybrid tabu search/simulated annealing algorithm of Zhang et al. (Comput Oper Res 35:282–294, 2008) presented in 2008. The performance of the algorithm is tested on eight random-generated problems with different sizes. The results are compared with those of the mathematical programming model, the original version of Zhang et al.’s (Comput Oper Res 35:282–294, 2008) algorithm and also a tabu search algorithm developed earlier by the authors.     

Getriebefedern für einen effizienten und regelbaren Betrieb von Kupplungs- und Bremssystemen in E-Fahrzeugen

Forschung im Ingenieurwesen - Nasslaufende Lamellenkupplungen und Bremsen bieten in elektrischen Antrieben als Schaltelement für ein Mehrganggetriebe oder als Bremse bei radnahen Antrieben...     

Effect of processing parameters on the morphology of hydrothermally synthesized calcium borate powders

The present study aimed to examine the effect of pH and time on the final morphology of calcium borate powders. Primarily, aqueous solutions that mainly consisted of borax and calcium chloride were prepared with five different pH values varying between 2 and 15. Hydrothermal synthesis temperature was determined as 200°C, and four different times from 30 min to 24 h were selected. Phase formation and powder morphology were examined via an X-ray diffractometer and scanning electron microscopy. Fourier transform infrared spectroscopy was used to identify the type of borate groups. Results revealed that pH directly determines the growth mechanism of calcium borate crystals. Lower pH induced nonclassical growth by forming self-assembled nano-plates. Individual, rodlike particles were observed for alkali solution. At weak basic conditions, priceite (4CaO·5B₂O₃·7H₂O) and alkali condition parasibirskite (2CaO·B₂O₃·H₂O) phases were obtained.