SBA-catalyzed synthesis of ethers from alcohols

A highly defective SBA with proton concentration of 1.35 meq/g has been synthesized, and this material exhibited approximately a 2-fold increase in activity over highly ordered SBA-15 for coupling methanol/isobutanol (MeOH/i-BuOH) to form methylisobutylether (MIBE). In addition, this material is active in dehydrocondensation of isopropanol (i-PrOH) to form diisopropylether (DIPE), dehydration of i-PrOH to propene (PE), and coupling of i-PrOH with MeOH to form methylisopropylether (MIPE). A strong reaction pressure dependence on the product selectivities was observed. The effective activation barriers have been determined, and DFT calculations located all of the transition states (TS) involved. The theory includes the determination of imaginary vibrational frequencies associated with the passage of the reacting groups through the TS and assessment of kinetic isotope effects (KIE) due to labeling of critical parts or the molecule or catalyst by deuterium. The predicted KIE provides further evidence for a dual site TS in both ether-forming and dehydration reactions.