Production of 1,6-Hexanediol from Tetrahydropyran-2-Methanol
Burt, Samuel P., et al. Green Chemistry, 2017, 19(5), 1390-1398.
Tetrahydropyran-2-methanol (THP2M), a biomass-derived feedstock, can be converted with high selectivity into 1,6-hexanediol (1,6-HDO), an important basic chemical. However, the high cost and low productivity of catalysts limit their industrial applicability. A three-step method is proposed for the synthesis of 1,6-HDO from THP2M via 2,3,4,5-tetrahydrooxepine (THO), avoiding the use of expensive catalysts.
Synthetic route from THP2M to 1,6-HDO
· In the first step, THP2M is dehydrated to 2,3,4,5-tetrahydrooxepine (THO) in a continuous flow, gas-phase reactor over a silicoaluminate catalyst. Various zeolite frameworks, as well as various alkali metals as exchange ions were tested in this dehydration reaction.
· In the second step, THO was hydrated to 2-oxepanol (OXL) and 6-hydroxyhexanal (6HDHX) in the absence of catalyst in an overall yield of 85%.
· Finally, 6HDHX and OXL (likely through 6HDHX) were then hydrogenated to 1,6-HDO with Ru/C or Ni/C nearly quantitatively.
· This pathway affords an overall yield of 34% to 1,6-HDO from THP2M, higher than previously reported 1,6-HDO yields from THP2M without using toxic metals.
Selective Hydrogenolysis of Tetrahydropyran-2-Methanol with Different Catalyst Carbon Supports
Karanjkar, Pranav U., et al. Catalysis Science & Technology, 2016, 6(21), 7841-7851.
Tetrahydropyran-2-methanol (THP2M) can undergo selective C-O-C hydrogenolysis under the action of a bifunctional RhRe catalyst to generate 1,6-hexanediol. The catalytic performance of bifunctional RhRe catalysts supported on two distinct carbon supports (NDC and VXC) towards THP2M was compared. The results show that the hydrogenolysis rate of the VXC-supported catalyst is two orders of magnitude higher than that of the NDC-supported catalyst.
Research on hydrogenolysis and catalyst activity of THP2M
· Continuous Flow Fixed Bed Reactor: Hydrogenolysis of THP-2M was conducted in a stainless-steel tubular flow reactor at elevated temperatures and pressure. Liquid products were analyzed by HPLC and GC, while gaseous products were analyzed using a gas chromatograph.
· Batch Reactor: Reactions using a 25 mL reaction mixture volume were performed in a 50 mL pressure vessel, and temporal concentration profiles over the course of reaction were obtained. Product mixtures were analyzed by HPLC and GC for quantitative analysis.
Download
