Production of renewable diesel from vegetable oil using zeolite based catalyst

Abstract

Straight Vegetable Oil (SVO) can be converted into diesel-like hydrocarbon as renewable diesel. Hydrotreating is the process is used to convert fatty acids of esters into straight-chain hydrocarbons. This catalytic process can produce n-heptadecane (n-C17) and n-octadecane (n-C18) in the product. In this process, the hydrodeoxygenation produces n-C18 and, decarbonylation or decarboxylation produces C17 along with the intermediates such as carbonyl or carboxylic compounds by using CoMo-S or NiMo-S/and#947;-Al2O3. Recently, there has been more interest shown to use zeolites-based material in catalyst to attain the hydrotreatment of SVO because: it can enhance the deoxygenation through sulfur-free process, produce the product in selective shape and structure, can reduce the cold-flow plugging point by producing isomeric fragments and reduce the energy cost by integrating the hydrotreating with isomerisation in a single-stage system. In this attempt, synthesis of mesopores type Silicoaluminophosphate (SAPO) support for the catalyst is executed by using two methods such as hydrothermal and ultrasonic-assisted, where the incorporation of the acidic active sites by selection of appropriate template, ensure with uniform pore diameter, high crystalline material, morphological textural arrangement and moderate acidic strength on surface sites are evaluated from the synthesis, and compared with the product selectivity and yield with commercial catalyst using SVO as a triglycerides model compound. The synthesis of SAPO has focused to obtain similar topology and morphology as SAPO-11. Different Si/Al mol ratio such as 1:1(SAPO(11)), 1:2(SAPO(12)) and 2:1((SAPO(21)) of the SAPO is synthesied with cetyl trimethyl ammonium bromide (surfactant) as a template in both the methods. Detailed morphological and crystalline structure is investigated using XRD, SEM and BET of therespective material properties. The synthesised SAPO showed identical crystalline structure as SAPO-11 that is proposed in literature. Also, surfactant based ultrasonic assisted SAPO(11) support has shown high surface area and crystalline with uniform mesopores structure. The hydrothermal synthesis has average crystal size of 100 to 140 nm diameter, whereas ultrasonic assisted method has 60 to 100 nm. Different templates like npropyl amine, diethyl amine and dimethyl amine are also attempted to synthesize SAPO, which have defective morphology and rejected in operation for the deoxygenation process. The Pyridine-FTIR monitored the acidic level on the surface of SAPO, wherein both the methods show relatively same strength and amount of acidic character newline