Catalysis of Organic..

64Isobutene TrimerizationFigure 4 Reaction pathways for the isobutene oligomerizationExperimental SectionCatalysts preparation. The NiY catalyst was prepared with the followingprocedure: 300 ml of a warm 0.33 M solution of Ni (NO 3 ) 2 , (Aldrich, 99.9%) wasmixed with 10 g of a commercial Y zeolite (CRITERION). The mixture wasmaintained under reflux at 70°C for 5 hours; then, the sample was filtered andwashed three times with water at 50°C. The washed sample was dried at 110°C andthen annealed at 400ºC for 12 h..The in situ sulfated TiO 2 was synthesized according to the following procedure:200 ml of bidistilled water and 200 ml of ter-butanol were mixed in a glass flaskunder reflux and stirring, then sulfuric acid (Baker 99%) was added to this solutionuntil adjust at pH=3. Then 84.5 ml of titanium n-butoxide (Aldrich 98%) wereslowly added, maintaining the solution under reflux for 24h. After gelling the samplewas dried at 70°C for 24h and annealing at 400°C in air for 12 h.Catalytic test. The catalytic behavior was evaluated for the gas phase isobutenetrimerization reaction using a fixed bed reactor, with dimensions of 2 cm of diameterand 55 cm of length respectively. The operation conditions and evaluation procedurewere as follows: the catalyst was activated at 400°C in flowing air (1 ml/s) during 8hours. After the activation treatment, temperature was lowered to 40°C and a mixtureof isobutane/isobutene 72:28 w/w was feed. The GHSV value was varied to 8, 16, 32and 64 h -1 respectively. The average time of reaction was 11 h. The time of reactorstabilization after the beginning of the catalytic evaluation was 2 h.The analysis of products was made in all the cases by FID-gas chromatography(Varian Mod. CX3400) equipped with a PONA column of 50 m and coupled to aworkstation.AcknowledgementsThanks Gabriel Pineda Velázquez for the technical support in the chromatographicanalysis.