Dehydration of 3-methyl-1,3-butanediol over Al2O3 modified with carbon

• Dehydration of 3-methyl-1,3-butanediol into 3-methyl-3-buten-1-ol was investigated.
• Carbon-modified alumina showed high selectivity to 3-methyl-3-buten-1-ol at 200 °C.
• The C-modified alumina was prepared by depositing coke using 3-methyl-3-buten-1-ol.
• The selectivity to 3-methyl-3-buten-1-ol was increased by the coke content over Al2O3.
• Formation of by-products such as isobutylene decreased by the coke deposition.

Vapor-phase dehydration of 3-methyl-1,3-butanediol to 3-methyl-3-buten-1-ol was investigated over carbon-modified alumina, C/Al2O3, which was prepared by depositing carbonaceous species, i.e. coke, on Al2O3 with contacting Al2O3 surface with 3-methyl-1,3-butanediol vapor at 250 °C. Temperature-programmed desorption of adsorbed NH3 revealed that the strength of acid sites of fresh Al2O3 was weakened by the coke deposition. It was found that the selectivity to 3-methyl-3-buten-1-ol was increased by the coke deposition over Al2O3 catalysts in the dehydration of 3-methyl-1,3-butanediol at 200 °C. Generation of the main by-products such as isobutylene and 4,4-dimethyl-1,3-dioxane were prohibited by the acid sites weakened by the coke deposition. The 13C NMR and IR measurement elucidated that the deposited coke had CC, CO, COO, CH2, CH3, and OH groups, which indicates that the coke consisted of polymeric unsaturated alcohol. The coke content that is effective in inhibiting the decomposition of 3-methyl-1,3-butanediol into isobutylene was ca. 15 wt.% of C/Al2O3.

Figure optionsDownload high-quality image (121 K)Download as PowerPoint slide