One-step MIBK synthesis:: A new process from 2-propanol

The one-step MIBK synthesis from 2-propanol was investigated as an alternative process to current conventional technology that produces MIBK from acetone. The reaction was studied at 473 K and atmospheric pressure using bifunctional Cu-base catalysts. Single MIOx, binary MIMIIOx, and Cu-containing CuMI(M-II)O-x mixed oxides, where M-I, and M-II, are metal cations such as Mg2+, Al3+, or Ce3+, were obtained by thermal decomposition of precipitated precursors. The density and strength of surface basic sites were obtained by CO2 chemisorption and by temperature-programmed desorption (TPD) of CO2, whereas the acid site densities were measured by TPD of NH3. The MIBK synthesis reaction network involves consecutively the initial 2-propanol dehydrogenation to acetone, the aldol condensation of acetone to mesityl oxide, and the final hydrogenation of this compound to MIBK. Cu/SiO2 promoted 2-propanol dehydrogenation to acetone but did not form any C-6 condensation products. When copper was supported on protonic HY zeolite, 2-propanol was essentially dehydrated to propylene and the formation of acetone was negligible. Bifunctional Cu-base catalysts were active and selective for MIBK synthesis. The highest MIBK formation rates were obtained on Cu-base solids containing a high density of medium-strength Bronsted base-weak Lewis acid pair sites for promoting the acetone aldol condensation step. CuMg10Al7Ox was the best catalyst because it contained in intimate contact highly dispersed Cu-0 crystallites with proper Al3+ Lewis sites and Mg+2-O2- basic pairs and efficiently combines the active sites required for consecutive reactions leading to MIBK. Catalysts containing strongly basic O2- sites, such as CuMg10Ox and CuMg10Ce2Ox, presented lower condensation rates because isolated O2- hindered stabilization of anionic intermediates for acetone condensation. The effect that the reacting atmosphere (N-2 or H-2) has on catalyst activity and selectivity was investigated on CuMg(10)Al(7)Ox. It was found that the catalyst activity is enhanced in N-2, but for a given 2-propanol conversion the selectivity for C-6 aldol condensation products is higher in. hydrogen. MIBK yields as high as 25% were achieved in comparison to the 30% typically obtained in current commercial high-pressure processes from acetone. (C) 2002 Elsevier Science (USA).