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Öğe Decision tree analysis for efficient CO2 utilization in electrochemical systems(Elsevier Sci Ltd, 2018) Gunay, M. Erdem; Turker, Lemi; Tapan, N. AlperIn this work, a database of 471 experimental data points excerpted from 34 different publications on electro-catalytic reduction of CO2 was formed. Firstly, the database was examined by exploratory data analysis using box and whiskers plots. Then, decision tree analysis was applied to determine the significance of the variables and to reveal the conditions leading to higher faradaic efficiency, production rate and product selectivity. It was found that Cu content smaller than 71% resulted high faradaic efficiencies depending on the amount of Sn, catholyte type, applied potential and pH of electrolyte. In this case, applied potential and Cu content were found to have the highest significance among all the input variables. On the other hand, the most generalizable combination of variables leading to high level of rate occurred when the Cu content being less than 13%, using a membrane other than Selemion AMV, employing a backing layer such as TGP-H-60 and keeping the applied potential between -1.5 and -2.6 V; for which the applied potential and CO2 flow rate were determined as the highest significant variables. Finally, the most generalizable path for the case of selectivity was obtained with Sn content higher than 15% and Cu content less than 52%, which leaded to formic acid production having the highest production rates. It was then concluded that, exploratory data analysis and decision trees can provide useful information to determine the conditions leading to higher CO2-electroreduction performance that may guide the future studies in this area.Öğe Significant parameters and technological advancements in biodiesel production systems(Elsevier Sci Ltd, 2019) Gunay, M. Erdem; Turker, Lemi; Tapan, N. AlperBiodiesel is a mixture of fatty acid esters formed by transesterification of vegetable oil, animal fat, algae oil or waste oil with an alcohol like methanol (CH3OH), ethanol (C2H5OH) or higher alcohols. There are many important catalytic variables like catalyst type and composition, support type and pretreatment conditions (i.e. calcination temperature and time) which are utilized to achieve high yields for the transesterification reaction. In addition, operational conditions such as reaction temperature, alcohol type, alcohol to oil molar ratio and stirring speed have also quite high significance. Moreover, all these variables can be optimized under supercritical conditions by novel techniques like ultrasonic and microwave irradiation or hydrodynamic cavitation. In this work, significant catalytic and operational variables for biodiesel production are reviewed. In addition, dominant parameters together with their limitations during the application of advanced technologies are investigated in detail. Then, it has been concluded that, for better control and higher yields of biodiesel production, future research works should focus on addition of co-solvents, use of longer chain alcohols, bulky structures or ionic liquids, adjustment of mode of irradiation and modification of the instrumentation or the equipment.