Ethanol, dehydrogenative dimerization

Table 8.4 Catalytic Performances of the Nb Monomer, Dimer, and Monolayer Supported on Si02, and an Impregnation Nb Catalyst for Dehydrogenation and Dehydration (Intra and Inter) of Ethanol...

Catalytic performances of Mb monomeric, dimeric or monolayered species NbOx on Si02 support for dehydrogenation AA) and dehydration (intra E, inter —> DE) of ethanol... 

Ethylene for polymerization to the most widely used polymer can be made by the dehydration of ethanol from fermentation (12.1).6 The ethanol used need not be anhydrous. Dehydration of 20% aqueous ethanol over HZSM-5 zeolite gave 76-83% ethylene, 2% ethane, 6.6% propylene, 2% propane, 4% butenes, and 3% /3-butane.7 Presumably, the paraffins could be dehydrogenated catalyti-cally after separation from the olefins.8 Ethylene can be dimerized to 1-butene with a nickel catalyst.9 It can be trimerized to 1-hexene with a chromium catalyst with 95% selectivity at 70% conversion.10 Ethylene is often copolymerized with 1-hexene to produce linear low-density polyethylene. Brookhart and co-workers have developed iron, cobalt, nickel, and palladium dimine catalysts that produce similar branched polyethylene from ethylene alone.11 Mixed higher olefins can be made by reaction of ethylene with triethylaluminum or by the Shell higher olefins process, which employs a nickel phosphine catalyst. 

If a vacant site is occupied by another Nb atom, such that it is a dimer, new catalysis, may be designed. A dimeric Nb structure on Si02 (2) was prepared by using a dimeric Nb precursor and characterized by EXAFS, which shows Nb-Nb and Nb-Si interatomic distances at 0.307 nm and 0.335nm, respectively, besides Nb-0 bonds. The Nb dimer catalyst (2) shows high selectivity for the dehydration of ethanol. The dehydrogenation observed on the... 

In the Absence of Oxygen Methanol, Ethanol, 2-Propanol, and t-Butyl Alcohol Alcohols such as methanol, ethanol, and 2-propanol are converted with Pt/Ti02 to the corresponding dehydrogenation products such as formaldehyde, acetaldehyde, and acetone, respectively, with the formation of equimolar H2. t-Butyl alcohol is converted into 2,5-dimethyl-2,5-hexanediol with the formation of H2 through intermolecular dimerization since t-butyl alcohol has no alpha-hydrogen. In these oxidative reactions, alcohols are oxidized by photoformed holes, while photoexcited electrons reduce water (or H" ) to form H2 [4]. 

---