PREPARATION, CHARACTERIZATION AND UTILIZATION OF CARBON BASED SOLID ACID MATERIALS IN BIODIESEL PRODUCTION

ABSTRACT

Biodiesel is a promising alternative renewable fuel. It is composed of mono-alkyl ester of fatty acid derived from either the transesterification of triglycerides or the esterification of free fatty acids (FFA) with short chain alcohols using a basic or acidic catalyst.
In this study, sulphonated carbon based solid acid materials were prepared from bamboo and coconut shell by carbonization and sulphonation with concentrated sulphuric acid. Carbon based solid material (coconut shell and bamboo) was carbonized using muffle furnance at temperature of 4000C for 4 hr and the biochars were ground into powder and sieved using a sieve of mesh size, 600nm. A known amount of biochar (20±0.01g) was treated with 100ml concentrated sulphuric acid at 100oC under N2 for 12hr. The transesterification reaction was performed in a 250 ml capacity three-necked round bottom flask using the oil feedstock (rubber seed oil,, waste cooking oil and palm kernel oil), methanol and the prepared catalyst under three different reaction conditions(Temperature, time and catalyst dosage). Characterization of the synthesized carbon based solid acid materials was carried out using scanning electron microscopy (SEM),FT-IR,TGA, BET, Bulk density determination and total acid determination. The biodiesel yield was determined; GC-MS was used to analyzed the biodiesel produced and physiochemical properties of the biodiesel such as viscosity, iodine value, and acid values were determined using standard methods.
The SEM result shows that bamboo based sulphonated materials (BBSMs) and coconut based sulphonated materials (CBSMs) have rough surfaces, irregular shapes and are porous. The peaks in the FT-IR spectra at 1163 cm-3and 1154 cm-3 confirms the (O=S=O) stretching vibrations for BBSMs and CBSMs respectively. The TGA curve shows that both BBSMs and CBSMs were thermally stable below 3000C . The BBSMs and CBSMs were found to have a surface area of 869.8 m2/g and 636.3 m2/g respectively; a pore volume of 0.287 and 0.260 cm3/g respectively and the same pore size of 2.694 nm. The biodiesel yield for Rubber seed oil (BRSO) was 81.8 and 79.2% for BBSMs and CBSMs respectively using 1g of the sulphonated solid materials at a temperature of 60oC for 5hr. The biodiesel yield for palm kernel oil (BPKO) were found to be 82.3% and 81.5% for BBSMs and CBSMs; while for waste cooking oil (BWCO) it was 87.6 and 86.9% for BBSMs and CBSMs respectively. The GC-MS show that fatty acids methyl esters such as 9,12-octadecadienoic acid, methyl esters; pentadecanoic acid,14-methyl ester were present in the biodiesels prepared. The viscosity of BRSO and BWCO satisfied the ASTMD6751 viscosity specification, while that of BPKO was slightly above the ASTMD6751 limit. The acid values of the three biodiesel were above the ASTMD6751 and EN14214 standards.The iodine value of BRSO and BWO were below the ASTMD6751 and EN14214 standards while the iodine value of BWCO is just slightly above the limit of 120mgI2/100g. The biodiesel yield and the physiochemical properties of the carbon based sulphonated acid materials determined in this study, showed both BBSMs and CBSMs to be alternatives solid acid and can find use in other acid catalyzed reactions.