Direct preparation of biodiesel using high acid value oils is a difficult and hot topic.
Sulfonated activated carbon can be used for esterification and transesterification to catalyze the preparation of biodiesel from high-acid-value oils. Because activated carbon has properties similar to surface oxides, reducing agents, and stable acid base groups, and its structure is similar to that of graphite, fullerenes, and carbon nanotubes, and it can construct -SO3H acid groups. At present, magnetic carbon-based solid acids have been successfully developed and used for magnetic field recovery, such as catalysts for cellulose hydrolysis, fructose degradation, and polysaccharide hydrolysis, respectively, but the above catalysts have a lower acid amount (eg, 1.3, 1.95 and 0.38 mmol). /g) or weaker magneticity is not suitable for biodiesel production.
Zhang Fan, a doctoral student in the bio-energy group of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, under the guidance of the researcher, has prepared a cheap and highly active magnetic solid acid catalyst for the preparation of biodiesel from high-acid-value oils. The preparation method of the catalyst is as follows: first, a carbon-based magnetic core is prepared under high-temperature hydrothermal conditions through a mixed solution of glucose and ferric chloride, and then the heat-treated carbon-based magnetic core is embedded again with hydrothermal carbonized glucose, and finally the sulfur is passed through the high-temperature heat treatment. The carbon-based magnetic solid acid is prepared.
The study found that the prepared solid acid was re-sulphonated at a temperature of 600° C., while having a high acid amount (2.79 mmol/g) and magnetic saturation (14.4 Am 2 /kg). The catalyst has high activity, stability and recyclability. Sex, cycle 3 times for Jatropha biodiesel production (biodiesel yield: 90.5%, 91.8%, 90.3%; Jatropha oil acid value 17.2mgKOH/g), catalyst acid amount slightly decreased (2.43vs.2.79mmol /g) And with 96.3% recovery. At the same time, it was also found that the ultrasonic energy is resistant to free fatty acids: using Na2SiO3 as a catalyst, the biodiesel yield of high-acid Jatropha oil (4.8 mg KOH/g) can still be achieved at a lower ultrasonic energy density (0.1 W/mL). 90.7%.
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