Conversion of flaxseed oil into biodiesel using KOH catalyst: Optimization and characterization dataset

The dataset presented here are part of the data planned to produce biodiesel from flaxseed. Biodiesel production from flaxseed oil through transesterification process using KOH as catalyst, and the operating parameters were optimized with the help of face-centered central composite design (FCCD) of response surface methodology (RSM). The operating independent variables selected such as, methanol oil ratio (4:1 to 6:1), catalyst (KOH) weight (0.40–1.0%), temperature (35 °C–65 °C), and reaction time (30 min–60 min) were optimized against biodiesel yield as response. The maximum yield (98.6%) of biodiesel from flaxseed can achieved at optimum methanol oil ratio (5.9:1), catalyst (KOH) weight (0.51%), reaction temperature (59.2 °C), and reaction time (33 min). The statistical significance of the data set was tested through the analysis of variance (ANOVA). These data were the part of the results reported in “Optimization of process variables for biodiesel production by transesterification of flaxseed oil and produced biodiesel characterizations” Renewable Energy [1].

of the data set was tested through the analysis of variance (ANOVA). These data were the part of the results reported in "Optimization of process variables for biodiesel production by transesterification of flaxseed oil and produced biodiesel characterizations" Renewable Energy [1]. © 2020 The Author(s  Table   Subject Energy Specific subject area Renewable energy, sustainability and the Environment Type of data Table  Graph Figure How data were acquired Titration method was used for biodiesel yield estimation and the yield data were set in face centered cubic design of response surface methodology approach using Design-Expert 6.0.6 (Stat-Ease, Inc.

Data
The exponential growth of world population and its consequence on energy demand consumes the limited source of conventional non-renewable fossil fuel at much faster rate than expected. The rise of energy demand and fast depletion in fossil fuel triggered the research for finding the alternate source of energy. Biodiesel is one of the solutions to fulfil the energy demand as well as safety of the environment, because it is free from Sulphur, biodegradable, non-toxic, and renewable [2e4]. The fatty acid content of the flaxseed oil is reported elsewhere [5]. The data reported here is for the optimum production of the biodiesel from flaxseed oil. Table 1 shows the data obtained from the face-centered composite design (FCCD) approach of response surface methodology for the independent factors (methanol to oil ratio, catalyst (KOH) weight, temperature, and reaction time) and dependent factor (actual percentage yield of biodiesel) based on design of experiments. The levels

Value of the Data
The data set reported in this article will provide researchers with better understanding of the effects of operating parameters on the yield of biodiesel production. The four operating parameters such as, volume ratio of methanol/oil, KOH weight percent to oil, reaction temperature, and reaction time, were selected to optimize for maximum production of biodiesel. The face-centered central composite design (FCCD) of RSM was used to obtain the optimum value of each parameters for maximum biodiesel yield. The data describes the optimum conditions under which flaxseed oils can be converted into biodiesel with cost effective and energy saving approach. and ranges of independent factors and their effect on standard deviation with measures derived from the (X'X) À1 matrix are elaborated in Tables 2 and 3. The parameters for prediction design and the correlation matrix of regression coefficients with correlation matrix of factors are described in Table  4. The 3D interactive effects of the process variables for the percent yield of the flaxseed biodiesel is shown in Fig. 1 while deviation of input values of different parameter from reference point depicted in Fig. 2. The sequential model sum of squares and lack of fit test and model summary statistics are discussed in Tables 5 and 6. Analysis of variance (ANOVA) table for response surface reduced quadratic model was reported elsewhere [1]. The adjustment of R-squared value parameters and coefficient estimation for final model equation along with diagnostics case statistics are illustrated in Tables 7e9. Fig. 3 shows contour plot for maximum biodiesel yield within the selected independent variables (methanol to oil ratio, catalyst (KOH) weight, temperature, and reaction time) ranges. In addition, cubic graph for the maximum percent yield of the flaxseed biodiesel against independent  78.500 Scaled D-optimality Criterion 2.510 Determinant (X'X)À 1 1.148x10À 16 Trace of (X'X)À 1 2.251   variables and residual variation plots for normal and predicted value along with run and reaction time are shown in Fig. 4 and Fig. 5, respectively. The Residual variation plots with different process variables and variation in run number for the diagnostics case statistics are elaborated in Figs. 6 and 7. The criteria for desirability for constraints is shown in Fig. 8. The point prediction and optimization of independent variables for maximum biodiesel yield from the flaxseed oil are tabulated in Tables 10  and 11 respectively.

Materials
The flaxseed oil was collected from the local market of Bale-Robe, Ethiopia. Methanol (CH 3 OH, 99.8% purity), sulfuric acid (H 2 SO 4 , 98%), and KOH were bought from Sigma Aldrich and were of analytical grade. During experiment 0.1 N sulfuric acid solution was used. All chemicals consumed during the biodiesel synthesis were of analytical grade.

Methods
Biodiesel from flaxseed oil was produced in a batch experiment. The biodiesel produced in the laboratory from flaxseed oil involved a two-step transesterification reaction accompanied with product separation, washing, and drying. The process flow chart for the biodiesel production from flaxseed oil shown in Fig. 9. A fixed quantity (50 g) of the oil was measured and poured into a conical flask. The    flaxseed oil was pre-heated at 110 C for 30 min to remove the moisture content in oil. The process involves the catalyst KOH in different weight percentage of oil (0.40, 0.70, and 1.0%), methanol at various molar ratios of methanol/oil (4:1, 5:1, and 6:1) under different temperature (35, 50, and 65 C) and reaction time (30, 45, and 60 min). The water washing method was used for further purification of FAME (biodiesel). The mixture was stirred gently to avoid foam formation. The mixture was left overnight to settle into two phases: a water-impurity phase and a biodiesel phase. Separating funnel was used to separate the FAME (biodiesel) from the water-impurity phase. This process was repeated three times to ensure the removal of most impurities from the biodiesel fraction. The washed biodiesel fraction was then reheated at 100 C for 1 h to evaporate the residual water. The titration of biodiesel fraction with sulfuric acid (0.1 N) was used for the quantification of the FAME [6]. The percentage yield of flaxseed biodiesel was determined by comparing biodiesel weight with flaxseed oil weight used initially.

Design of experiment
The face-centered central composite design (FCCD) was applied to optimize the biodiesel yield. This design is most suitable approach to optimize such processed which have a quantitative independent variable, and its response can also be observed quantitatively experimental matrix. The FCCD have sufficient tool to find the optimum values of independent variables within the selected range. Two levels and four factors with five center point values were considered for this experiment, the total number of experiments suggested through this method was (2 4 þ 2 x 4 þ 5) 29 batch experiments. The independent variables selected for optimization were methanol/oil molar ratio (A), catalyst weight percent (B), reaction temperature (D) and reaction time (E). The response chosen was the biodiesel yields produced through KOH catalyzed transesterification reaction of flaxseed oil. The actual values of   the independent variables are listed in Table 1. The biodiesel synthesis was conducted in batch, and each set of experimental conditions were selected randomly to minimize systematic error. All statistical parameters including analysis of variance (ANOVA) and figures were plotted with the help of Design-Expert 6.0.6 (Stat-Ease, Inc., Minneapolis, USA) [7].

Acknowledgments
The author sincerely acknowledges Universiti Teknologi PETRONAS and YUTP grant (015CLO-144) for providing financial support to completion of this research work.  . 9. Flow chart for biodiesel production from flaxseed oil.