In situ esterification of rice bran oil with methanol and ethanol

In situ esterifications of high-acidity rice bran oil with methanol and ethanol and with sulfuric acid as catalyst were investigated. In the esterification with methanol, all free fatty acids (FFA) dissolved in methanol were interesterified within 15 min, and it was possible to obtain nearly pure methyl esters. The amount of methyl esters obtained from a given rice bran was dependent on the FFA content of the rice bran oil. In the esterification with ethanol, it was not possible to obtain pure esters as in methanol esterification, because the solubilities of oil components in ethanol were much higher than those in methanol.     

Initiation system effects in the cationic copolymerization of tetrahydrofuran (THF)

Summary Macromonomeric peroxy initiator, poly tetrahydrofuran (poly-THF=inimer) were synthesized via cationic polymerization of THF by the mono- (t-BuBP) and tetra-bromo methyl benzoyl peroxides (BDBP)/ZnCl₂ initiating system. The macromonomers were characterized by ¹H-NMR, IR, and GPC techniques. Methyl methacrylate (MMA) polymerization initiated by poly-THF inimers at 80°C and different times in bulk gave crosslinked poly-THF-b-polymethyl methacrylate block copolymers. Swelling ratios of the crosslinked block copolymers obtained by taking in same amounts of poly-THF inimer and MMA monomer in CHCl₃ were decreased versus time. It was compared the results obtained from t-BuBP-, BDBP-ZnCl₂ initiating systems with t-BuBP-, BDBP-AgSbF₆ initiating systems for THF monomer. Poly(THF-b-MMA) crosslinked block copolymers containing undecomposed peroxide groups initiated the thermal polymerization of styrene, S, were used to obtain poly(THF-b-MM_A-b-S) crosslinked multicomponent copolymers at 90°C. The crosslinked multi component copolymers were investigated sol-gel analysis and swelling ratios in CHCl₃. "Active" poly(THF-b-MM_A) having peroxygen group were used in the free radical coupling reaction of poly butadien (Poly Bd). Poly(THF-b-MM_A)-polybutadien crosslinked blend soluble graft copolymers were obtained. Received: 31 July 2001/Revised version: 16 June 2002/ Accepted: 5 July 2002     

Application of economical models for dye removal from aqueous solutions: cash flow,cost–benefit,and alternative selection methods

Although there are numerous adsorption studies performed by using various adsorbents, there is no deterministic knowledge about selection of appropriate adsorbent type from present alternatives. In order to evaluate the advantages of the selected adsorbent species mathematically, researchers may use economical models such as cash flow diagrams, cost–benefit analyses, and alternative selection methods. In spite of the fact that these models have been used in many other engineering branches they are rarely applied in environmental research. In this study we have aimed to investigate usability of the mentioned economical models in adsorption of reactive azo dyes from aqueous solutions. Activated ash, a waste material, and commercial granular activated carbon were decided to be adsorbent alternatives. By applying economical models appropriate adsorbent type was selected considering both adsorption efficiencies and economical conditions. Although similar tendencies were monitored in cash flow diagrams; considering the amount of expenses activated ash exhibited remarkable advantages compared to granular activated carbon. Furthermore, results of cost–benefit analyses showed that activated ash has been advantageous when total costs and profits were evaluated together. Results of this study suggest usage of these economical models even in adsorption studies in order to provide accurate information on the selection of appropriate adsorbent type. These methods enable evaluation of economical conditions, which is generally neglected, together with the obtained removal efficiencies.     

Variables affecting the yields of methyl esters derived from in situ esterification of rice bran oil

The influence of specific factors on in situ methanolic esterification of rice bran oil (RBO) using sulfuric acid catalyst was investigated. using high-FFA rice bran was found to be the most effective means to increase methyl ester yields. The ester content of the extract increased about 67% when the FFA content of oil was increased from 16.6 to 84.5%. Increasing the reaction time beyond 30 min did not affect yields. Increasing the temperature from 20 to 65°C elevated the FAME yield by about 30%, but increasing the amount of acid catalyst above 5 mL did not enhance yield, and increasing the methanol dose from 200 to 250 mL had a negligible effect.     

Capturing Preservice Chemistry Teachers’ Visual Representations of Redox Reactions through Storyboards

This study aimed to identify preservice chemistry teachers’ understanding of redox reactions at the submicroscopic level and how they make connections to macroscopic level. Twenty‐five preservice chemistry teachers first viewed a video of a redox reaction happening between a zinc wire and a copper(II) sulfate solution, then they reflected on their macroscopic observations, and generated storyboards (a sequence of drawings) representing this reaction at the submicroscopic level. Both the reflections and the storyboards were coded, and the categories reflecting the participants’ levels of understanding were determined. Results showed that the participants usually identified the macroscopic evidences, but they had conceptual difficulties in interpreting and representing evidences at the submicroscopic level. Few participants indicated a scientific or a moderate understanding of redox reactions, whereas the majority exhibited either weak or alternative understanding of redox reactions.     

Modeling and visualization of lifecycle building performance assessment

Lifecycle building performance assessment (LBPA) ensures that buildings perform and operate as intended during building lifecycle. Such assessment activities are typically multi-phase and multi-disciplinary, and generate large amounts of information that need efficient management. During the lifecycle of one building, multiple assessment methods are employed semi-concurrently and with a great deal of information overlap between successive phases. This information is semantically rich and context-dependent, reflecting the local perspective that it exists within. Usage of separate and disconnected tools for each method results in information fragmentation and redundancy, posing problems for well-informed decision making. The objective of this research is to develop an integral reference model, CLIP (Computational support for Lifecycle Integral Performance assessment), that aims to improve the efficiency and quality of existing performance assessment practices. The model provides flexible, modular, and extensible data structures and algorithms for the representation, transformation, integration, and visualization of performance information. The initial results support the CLIP model’s ability to deal with the local volatility and variation in the processes and information content that is being managed, while requiring further refinement and extension work to achieve a customized solution to fit in different contextual settings.     

Physical characterization of low-calorie chocolate formulations

Development of a high-quality low-calorie chocolate needs the use of the most appropriate ingredients that could substitute sugar without negatively affecting several product properties. In this study, sucrose-reduced chocolates sweetened with sucralose and stevia by using bulking agents were investigated in relation to their rheological, textural and sensory attributes. Dark, milk and white chocolates with different amounts of sweeteners were formulated. The Casson model best fitted to the rheological data. In dark chocolates, partial substitution of sucrose with stevia (DCSSt) gave similar plastic viscosity and yield stress values with control samples (DCS). Hardness measurements also supported these results. DCSSt sample was again found to be very similar to control in tested sensory attributes when assessed by a consumer panel. The data indicated that it was possible to manufacture chocolate by partial replacement of sucrose with stevia without adversely affecting its important rheological, textural properties and sensory acceptance.