Biodiesel from Hydrolyzed Waste Cooking Oil Using a S-ZrO2/SBA-15 Super Acid Catalyst under Sub-Critical Conditions

Abstract

Due to rapid changes in food habits, a substantial amount of waste fat and used oils are generated each year. Due to strong policies, the disposal of this material into nearby sewers causes ecological and environmental problems in many parts of the world. For efficient management, waste cooking oil, a less expensive, alternative and promising feedstock, can be used as a raw material for producing biofuel. In the present study, we produced a biodiesel from hydrolyzed waste cooking oil with a subcritical methanol process using a synthesized solid super acid catalyst, a sulfated zirconium oxide supported on Santa Barbara Amorphous silica (S-ZrO 2 /SBA-15). The characterization of the synthesized catalyst was carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), and the Brunauer-Emmett-Teller (BET) method. The catalytic effect on biodiesel production was examined by varying the parameters: temperatures of 120 to 200 • C, 5-20 min times, oil-to-methanol mole ratios between 1:5 to 1:20, and catalyst loadings of 1-2.5%. The maximum biodiesel yield was 96.383%, obtained under optimum reaction conditions of 140 • C, 10 min, and a 1:10 oil-to-methanol molar ratio with a 2.0% catalyst loading. We successfully reused the catalyst five times without regeneration with a 90% efficiency. The fuel properties were found to be within the limits set by the biodiesel standard.

Optimization of Biodiesel Production from Waste Cooking Oil Using S–TiO2/SBA-15 Heterogeneous Acid Catalyst

“…The SBA-15 support and the S-TiO2/SBA-15 catalyst both exhibited XRD diffraction patterns with one very intense diffraction peak and two small peaks. The intense peak was indexed as d100, and the smaller peaks were indexed as d110 and d200, which are characteristic of the 2-D hexagonal (p6 mm) ordered mesoporous structure of the SBA-15 with excellent textural uniformity [2]. From this finding, it can be concluded that the S-TiO2/SBA-15 catalyst retains the mesoporous structure of the SBA-15 support.…”

“…The decrease in the surface area, pore volume, and pore size are due to the gradual accumulation of the metal oxide species blocking some of the pores of the support during preparation. However, the decrease in the surface area is very small, suggesting that the active sulfated metal oxide species are highly dispersed on the surface of the support [2,4]. Figure 3 shows the XRD patterns of the support and catalyst as measured using an X-ray diffractometer system (D/MAX-2500V).…”

“…Recently, biodiesel has become the most promising alternative energy source to address the energy and global warming crises because of its cost effectiveness, eco-friendliness, and renewability [1]. Biodiesel is composed of fatty acid mono alkyl esters and is synthesized by esterification or transesterification of vegetable oils [2], animal fats [3,4], or waste oils with methanol in the presence or absence of acid, base, or enzyme catalyst [5][6][7].…”

“…However, more work is still needed in the search for new solid acid catalysts for sustainable biodiesel production [15,19,20]. In recent years, mesoporous silica-supported catalysts have been used in the esterification process because of their high surface area, uniformity, nonporous channel, stability, and large pore size, which make them helpful to reactions involving large molecules [2,20].…”

“…Biodiesel production by noncatalytic transesterification at supercritical conditions can resolve the difficulties resulting from homogeneous catalytic transesterification as it can handle impurities in the oil sample, such as high FFA or moisture content. However, it involves high production cost and requires high reaction conditions (high temperature and pressure) and a special alloyed reactor [2,16]. Therefore, to overcome these drawbacks, the focus of the current advancements in heterogeneous catalysis research is to develop a reusable heterogeneous solid acid catalyst.…”