A grinder was used to crush a total of 1600gm of Citrus maxima seeds, in each batch varying from 380-410gm. The average particle size of 0.7 mm, was observed after milling which would maximise the particle contact surface area. The ground seeds were then extracted using n-hexane as a solvent for 8h in a Soxhlet extractor (for each batch). A rotary evaporator (EYELA, CCA-1110) was used to remove the excess solvent under reduced pressure using at 46°C and the resulting fixed oil (CM-FO) was recovered.
The acid value of CM-FO was found to be 3.99 mg KOH g−1, which indicated that an acid pretreatment step was necessary. It was performed as described by Rashid et al. To carry out the base-catalyzed transesterification process, the acid value of the substance was measured until it was less than 1%.
The physical, chemical and fuel-related properties of CM-FO which includes colour, odour, appearance, taste, density, kinematic viscosity, specific gravity, refractive index, acid value, saponification value, cloud point, pour point, and the flashpoint was determined as per the ASTM standard procedures .
To the measured volume of methanol, sodium methoxide (catalyst) was added and stirred until it was entirely dissolved. The solution was poured into 100g of pre-heated citrus oil and stirred for 2 hours at 750 revolutions per minute (rpm) and 70°C with a 6:1 molar ratio of methanol to citrus oil. The resulting mixture after the reaction was then placed into a separating funnel and was cooled down to room temperature, allowing the two phases to separate. The upper layer was comprised of methyl esters, while the lower layer was comprised of glycerol and other materials including excess methanol, catalyst, soaps produced during the reaction, and entrained methyl esters and partial glycerides. By distilling off any remaining methanol, the methyl esters were purified. Using purified water, traces of residual catalyst, methanol, and glycerol were washed away. After that, the esters were dried with Na2SO4 and purified.
Attenuated total reflectance (ATR) Fourier transform infrared spectroscopy (FT-IR) (Alpha II, Bruker Optik) was used to compare the main functional groups that were present in CM-FO and CM-FANE. The IR spectrum was scanned through a wavelength range of 4000–700 cm−1. The FT-IR technique was used for qualitative analysis of the product, before moving on to the quantitative analysis by GC-MS.
The GC-MS analysis of the CM-FAME was performed using an Agilent 6890 Gas Chromatograph (Agilent Technologies, Palo Alto, CA, USA) equipped with a model 5973 N mass selective detector using Chemstation software. HP-5MS capillary column, composed of (5%-phenyl)-methylpolysiloxane, with dimensions, 30m in length, 250µm internal diameter, and 0.25µm film thickness was used. The temperature of the column oven was programmed to increase steadily from 50°C to 280°C, with a 2 minute hold-up period and a 10°C min-1 ramp. The temperature hold-up time was 5 minutes in the end (total run time: 30 min). In continuous flow mode, helium was used as the carrier gas at a flow rate of 1.0ml min-1. The temperatures of the inlet and GC-MS interfaces were held at 250°C and 280°C, respectively. A split (10:1) injection model was used to insert the samples. The EI source and quadrupole analyzer were kept at temperatures of 230°C and 150°C, respectively.
Each of the compounds was analyzed using the same GC-MS process. Fatty acids were identified by three MS libraries which includes NIST14.L, NIST02.L, and W9N11.L programmeOrder Now