Scielo RSS <![CDATA[Journal of applied research and technology]]> vol. 16 num. 6 lang. es <![CDATA[SciELO Logo]]> <![CDATA[Kinetic modeling of canola oil transesterification catalyzed by quicklime]]> Abstract This work aimed to study and model the kinetics of transesterification of canola oil with methanol catalyzed by calcined quicklime (CaO + MgO). The influence of three main variables was studied at 328 K: reagents order addition (has a negligible effect on the reaction), methanol-oil molar ratio (has minor effect on reaction rate after 1.5 h of reaction) and catalyst loading (high effect on reaction rate) to achieve at least a triglycerides conversion of 96.5% in concordance with norm EN 14103. A kinetic model based on an Eley-Rideal mechanism was found to well fit (R2 = 0.9886) the experimental data. Thus, it was concluded that for the quicklime catalyzed transesterification of canola oil with methanol to occur, first the methanol must be chemisorbed and the resulting methoxy species react with triglycerides in the interface liquid-solid. The whole process is limited by this step since methanol readily adsorbs onto the catalytic surface. <![CDATA[Tungsten based catalysts for oxidative desulfurization: surface species and partially reduced systems as key features to improve the activity]]> Abstract Tungsten oxide based catalysts for the oxidative desulfurization (ODS) process of dibenzothiophene compounds using H2O2 as oxidizing agent were studied. Catalysts were characterized by TPR-H2, SEM-EDS, XRD, N2-physisorption and Raman spectroscopy. Different surface tungsten oxide species were detected and related to the ODS activity, furthermore, the predominance of the surface tungsten oxide species was associated with the tungsten loading. Moreover, in some catalysts, WO3 crystals were detected and their role in the performance of the catalysts was studied too. Finally, the catalysts were partially reduced and tested in the ODS reaction, the reduced catalysts exhibited high activity and an improvement of H2O2 to sulfones yield. <![CDATA[Firefly optimization technique based test scenario generation and prioritization]]> Abstract Model-based testing shows a significant role-play in the area of software testing. This paper presents a new automatic test scenarios generation technique using UML state machine diagram having composite states. The intention of this research is to generate test scenarios for concurrent and composite states in state machines using the proposed algorithm SMToTSG (State Machine To Test Scenarios Generation). We have prioritized the test scenarios using Firefly optimization algorithm. We have used state-based coverage criteria such as state, transition, transition pair coverage to evaluate the efficiency of the proposed algorithm. The proposed approach is useful for feasible test scenario generation. Generating exhaustive test scenarios for all concurrent interdependent sequences is very difficult. In this paper, we generate the important test scenarios in the presence of concurrency in composite models. After prioritization, we apply Average Percentage Fault Detection (APFD) metric to calculate the efficiency of the prioritized test scenarios. <![CDATA[Influence of incorporating a small amount of silica on the catalytic performance of a MoO<sub>3</sub>/Al<sub>2</sub>O<sub>3</sub> catalyst in ethanol oxidative dehydrogenation]]> Abstract The influence of incorporating a small amount of silica on the catalytic performance of MoO3/Al2O3 catalyst was studied. Molybdenum supported on pure alumina and 5% SiO2-Al2O3 supports were synthesized. The catalysts were characterized by XRD, Raman, UV-Vis and IR spectroscopies, FE-SEM microscopy, and their activity was evaluated in the oxidative dehydrogenation of ethanol to acetaldehyde. Molybdenum supported on pure alumina gives a 74% yield to acetaldehyde (at 573 K) due to the generation of oxy-dehydrogenation active sites by molybdenum and to the decrement of the alumina dehydration sites. For the molybdenum catalyst supported on silica-containing alumina, the molybdenum species were displaced from the strongest alumina’s acid-base couples, located on nanoparticles edges, corners and defects, to weaker ones located on plane faces causing the rise of weakly bonded species with less active redox behavior. <![CDATA[Synthesis of hybrid materials, immobilization of lipase in SBA-15 modified with CaO]]> Abstract Mesoporous silica materials (SBA-15) doped with calcium (Ca) at 1, 3 and 5% w/w were synthesized in order to immobilize candida rugosa lipase (CRL), through the adsorption method. It was found that calcium (Ca) is present as CaO, highly dispersed on the surface of SBA-15, the specific area of SBA-15 decreases on incrementing CaO content. The environmental pH influences the adsorption of CRL due to the polarization of positive charges below the isoelectric point (IEP) whereas the Ca-SBA-15 materials present negative charges. The adsorption model proposed for CRL is about the accessible surface of the material, as this has a size of 7 nm and the Ca-SBA-15 present pores at an interval of 3 nm. <![CDATA[Synthesis and characterization of a mesoporous cerium oxide catalyst for the conversion of glycerol]]> Abstract CeO2 mesoporous materials were synthesized employing the “hard and soft template” technique. Ceria catalysts have been prepared by a nanocasting procedure using SBA-15 and KIT-6 silica-based templates and Pluronic P123 and F127 for the “soft template” technique. The mesoporous CeO2 was characterized by techniques such as N2 physisorption, which confirmed a mesoporous size pore system and transmission electron microscopy, TEM, which confirmed the material ordered pore structure. TGA/DTA analysis was used to determine the loss of weight compared to the temperature before and after the elimination of the template. On the other hand, by means of IR spectroscopy of the Ce-KIT-6 material, the partial elimination of the Si template after the NaOH treatment was confirmed by decreasing the peaks corresponding to the vibration bands of the Si-O-Si linkages. Finally, by temperature-programmed desorption (TPD) of NH3 and CO2, the acid and basic strength of the catalysts were determined, respectively. All samples exhibited much higher total basicity relative to total acidity. The analysis of TPR-H2 showed regions of low temperature (350-400ºC) where the reduction of the bulk is plausible to be initiated and of high temperature (550ºC) of superficial reduction of the ceria.The performance of the catalysts was evaluated in the dehydration reaction of glycerol in gas phase at 320 ºC. The mesoporous CeO2 material was selective to acetol and reached a 100% conversion of glycerol. The catalyst prepared by the “soft template” technique (CeO2-P123) was the most selective to acetol (76%) with a 12% selectivity to acrolein. With the catalyst prepared by the “hard template” technique (Ce-KIT-6), the selectivity towards acetol was 48% and 22% towards acrolein. The acid properties of CeO2 were found to be a determining factor for the selectivity to acetol and acrolein. <![CDATA[Lifetime enhancement in wireless sensor networks using binary search tree based data aggregation]]> Abstract Energy efficient data aggregation is a key solution to enhance the lifetime of wireless sensor networks since sensor nodes are battery-powered and deployed in remote environments. This article explore a two-hop data aggregation tree construction algorithm using binary search tree to reduce the total energy consumption of sensor nodes in wireless sensor networks. An adaptive and hybrid routing algorithm for simultaneous data aggregation and exploit the data correlation between nodes using the two-hop data aggregation tree framework is proposed. Routes are chosen based on the shortest response time for the broadcasting request to minimize the total energy expended by the network. This paper also proposes a high secure asymmetric key cryptography algorithm to provide the secure data communication among the network. The data aggregation function that is used in the proposed routing algorithm enhances the lifetime of sensor network by resolving the delay, collision and security issues. Simulations results show that the binary tree based data aggregation can appreciably reduces the total energy consumption and resolves the maximum data aggregation issues in wireless sensor network.