Catalyst formulation for direct conversion of microalgae in growth medium to biofuels

A synthesis method of heterogeneous catalyst formulation with high catalytic activity and selectivity to be used in direct conversion of microalgae into biofuels without harvesting and dewatering and by one-step sol-gel method comprises the following steps,

• i. synthesizing silica sol by mixing 1-5 M hydrochloric acid (HCl, 36.5-38 wt. %) with the precursor of tetraethylorthosilicate (≥98% purity), ethanol (≥99.8% purity), and deionized water at 60-90° C. for 1-4 hours
• ii. synthesizing alumina sol by mixing precursor of aluminum isopropoxide (AIP, ≥98% purity), deionized water at room temperature,
• iii. increasing the temperature to 80-90° C. in 15-30 min with 1000-1500 rpm of stirring rate and adding sulfuric acid (H2SO4, ≥98 purity) or hydrochloric acid or nitric acid (68 wt. %) to obtain the alumina sol,
• iv. mixing silica and alumina sols, and adding nickel (II) acetate hydrate (>99% purity) to the silica-alumina sol mixture,
• v. evaporating the excess solvent at 50-80° C. under vacuum or inert flow for 30-120 min, and obtaining a gel,
• vi, drying the gel at 100-15° C. for 3-24 h, and calcinating the gel at 500-900° C. for 6-24 h with 10° C./min heating rate, obtaining a catalyst which has formulation of Ni—Al2O3—SiO2
• vii. after calcination, ball milling or hand grinding and sieving of the catalyst to mesh size less than 200 for catalytic reactions
• viii. sieved catalysts are pretreated with sodium chloride (1-5 wt. %) containing water at 70-90° C. for 12-48 h, and drying at 100-150° C. for 3-24 h