Cement Kiln Dust Catalyzed Transesterification Of Palm And Waste Cooking Oils To Biodiesel And Glycerol: Process Optimization And Characterization Studies
Hefney Diab, Mahmoud Sayed
MetadataShow full item record
Conventional fossil fuels such as natural gas, oil, and coal have been the main sources of energy utilized to satisfy the unceasing growth of energy needs of the world. However, the environmental issues of fossil fuels and the depletion of their reserves have directed many researchers to search for sustainable alternatives that can compete with conventional fuels economically and technically while conserving the environment. Liquid biofuels such as biodiesel have been of interest to many researchers due to the associated benefits. Availability and sustainability of feedstock, as well as catalyst cost-effectiveness and activity, are the top research interests in the research area of biodiesel for improving its mass production. In this regard, designing a transesterification process to valorize waste, used materials and materials of low value could be one of the best solutions not only to overcome the energy and environmental problems mentioned above but also to ensure better management of used materials and waste reuse. This research introduces a study of different input variables influencing the designed single step transesterification process through which biodiesel is produced from a characteristically enhanced vegetable oil blend of 60 wt % waste cooking oil and 40 wt % low to moderate grade palm oil (which is not suitable for cooking) using cement kiln dust (CKD), as a heterogeneous catalyst. In addition, it aims at determining the optimum reaction conditions in the range of the study to achieve the highest oil to biodiesel conversions (complete conversion). This was done through following the statistical and the experimental procedures of factorial design concept and response surface methodology (RSM). The studied reaction conditions were reaction time 1, 3.5, 6 hours, methanol to oil molar ratio (12:1, 15:1, 18:1), reaction temperature (45, 55, 65 °C) and lastly, catalyst loading (1, 2, 3 % of blend weight). 850 rpm was the stirring speed used in all the CKD catalyzed transesterification reactions of the study. Both quadratic and linear models were developed based on the experimental results obtained. The quadratic model was preferred to the linear one as the optimum conditions can be more accurately obtained from its response surfaces and it proved more validity in explaining the range of experimentally obtained results. The optimum conditions obtained statistically from the quadratic model based response surfaces were catalyst loading of 2.7% of feedstock weight, 4.5 hours reaction time, 17:1 methanol to oil molar ratio and 59-60 °C. Whereas correlating the data from the quadratic model regression equation and the response surfaces plots, plus checking experimentally the validity of conversion values obtained have led to identifying the following conditions at which complete conversion can be achieved: 3 % catalyst loading, 65 oC, 15:1 methanol to oil molar ratio and 3.5 hours reaction time. These conditions were considered to be optimum as they include lower methanol to oil molar ratio and shorter time which can better enhance biodiesel production process economically. Characterization of the produced biodiesel showed that its properties meet the ASTM standards. A suggested model of a lab to industry scaling-up and design of an agitated batch reactor for biodiesel and glycerol production was introduced. An amount of 30 tons of 60 wt % waste cooking oil and 40 wt % palm oil blend per day is the daily rate proposed to feed in the industrial scale biodiesel and glycerol production plant demonstrated. Transesterification reaction conditions of the suggested process are adjusted in order to give a 100 % conversion which means production of about 30 tons biodiesel and 3 tons glycerol per day.