Catalysis of Organic..

412“Green” Catalysts for Biodiesel4. Sulfur-free fuel, since SAC do not leach into the product5. No waste streams because no salts are produced (no neutralization step)Experimental SectionThe experimental results are presented for the esterification of dodecanoic acid(C 12 H 24 O 2 ) with 2-ethylhexanol (C 8 H 18 O) and methanol (CH 4 O), in presence of solidacid catalysts (SAC). Reactions were performed using a system of six parallelreactors (Omni-Reacto Station 6100). In a typical reaction 1 eq of dodecanoic acidand 1 eq of 2-ethylhexanol were reacted at 160 °C in the presence of 1 wt% SAC.Reaction progress was monitored by gas chromatography (GC). GC analysis wasperformed using an InterScience GC-8000 with a DB-1 capillary column (30 m ×0.21 mm). GC conditions: isotherm at 40 °C (2 min), ramp at 20 °C min –1 to 200 °C,isotherm at 200 °C (4 min). Injector and detector temperatures were set at 240 °C.Reaction profiles were measured for both non-catalysed and catalysed reactions.Chemicals and catalysts.Double distilled water was used in all experiments. Unless otherwise noted,chemicals were purchased from commercial companies and were used as received.Dodecanoic acid 98 wt% (GC), methanol, propanol and 2-ethylhexanol 99+ wt%were supplied by Aldrich, zirconil chloride octahydrate 98+ wt% by Acros Organics,25 wt% NH 3 solution and H 2 SO 4 97% from Merck. Zeolites beta, Y and H-ZSM-5were provided by Zeolyst, and ion-exchange resins by Alfa.Preparation of mixed metal oxides.The sulfated metal oxides (zirconia, titania and tin oxide) were synthesized using atwo steps method. The first step is the hydroxylation of metal complexes. The secondstep is the sulfonation with H 2 SO 4 followed by calcination in air at varioustemperatures, for 4 h, in a West 2050 oven, at the temperature rate of 240 °C h –1 .Sulfated zirconia: ZrOCl 2 .8H 2 O (50 g) was dissolved in water (500 ml), followedby precipitation of Zr(OH) 4 at pH = 9 using a 25 wt% NH 3 soln. The precipitate waswashed with water (3×500 ml) to remove the chloride salts (Cl – ions weredetermined with 0.5 N AgNO 3 ). Zr(OH) 4 was dried (16 h at 140 °C, impregnatedwith 1N H 2 SO 4 (15 ml H 2 SO 4 per 1 g Zr(OH) 4 ), calcined at 650 °C. Sulfatedtitania: HNO 3 (35 ml) was added to an aqueous solution of Ti[OCH(CH 3 ) 2 ] 4 (Acros,>98%, 42 ml in 500 ml H 2 O). Then 25% aqueous ammonia was added until the pHwas raised to 8. The precipitate was filtered, washed and dried (16 h at 140 o C) .Theproduct was impregnated with 1N H 2 SO 4 (15 ml H 2 SO 4 per 1 g Ti(OH) 4 ). Theprecipitate was filtered, washed, dried and then calcined. Sulfated tin oxide:Sn(OH) 4 was prepared by adding a 25% aqueous NH 3 solution to an aq. sol. of SnCl 4(Aldrich, >99%, 50 g in 500 ml) until pH 9-10. The precipitate was filtered, washed,suspended in a 100 ml aq. sol. of 4% CH 3 COONH 4 , filtered and washed again, thendried for 16 h at 140 o C. Next, 1N H 2 SO 4 (15 ml H 2 SO 4 per 1 g Sn(OH) 4 ) was addedand the precipitate was filtered, washed, dried and calcined.