Читать книгу Biodiesel Production - Группа авторов - Страница 40

There exist quite a number of reports by researchers on successful conversion of oil into biodiesel using catalysts that do not fall under the general spectrum of acids, bases, or enzymes. Mostly heterogeneous in nature, they are usually insensitive to the presence of FFAs and can convert them as well into esters (Table 2.2). The preparation strategies for each catalyst, therefore, vary greatly as they can be the source material itself (albeit modified to a certain extent) [32], a chemical compound that exists naturally as a salt [33], or other inert supports (carbonaceous or siliceous) that have been doped with transition metals, which are able to catalyze the transition much more efficiently [15, 26]. The form of doping in the last category is usually by the use of analytical grade salts containing the metal ion, which gets impregnated, leaving the anion to be washed off. Natural waste materials containing such elements can also be processed and used as a cost‐efficient alternative (such as cow bones for calcium doping).