Glycerol

In Situ Spectroscopic Investigation of the Rhenium‐Catalyzed Deoxydehydration of Vicinal Diols

“…go condensation to a rhenium(VII) diolate that is subsequently reduced to a rhenium(V) diolate, has been suggested in computational studies by Lin and co-workers, [12] who investigated the CH 3 ReO 3 -catalyzed DODH of 1-phenyl-1,2-ethanediol using hydrogen as the reductant. The pathway shown on the righthand side of Scheme 2, in which CH 3 ReO 3 is reduced to CH 3 ReO 2 that subsequently undergoes condensation with the diol to a rhenium(V) diolate, has been suggested by Shiramizu and Toste [11] who concluded that methyldioxorhenium(V) is the catalytically relevant species. However, they added an alkyne to capture the in situ-generated rhenium(V) center, and an investigation of the unmodified reaction would, therefore, be desirable.…”

“…The two bands of CH 3 O is 1:8). Although the scrambling hindered a more certain confirmation of the assignment of the bands, it is noteworthy that, on this time scale, scrambling only occurs for the presumed dimeric rhenium(VI) diolate and not for the monomeric rhenium(VII) diolate.…”

“…One such waste product is glycerol-the inevitable byproduct from the production of biodiesel (i.e., fatty acid methyl esters) from triglycerides-the production of which is estimated to become six times larger than its demand by 2020. [3] The already low value of glycerol could decrease even further, and most chemical transformations-oxidation, reduction, dehydration, and others-will, therefore, make it more valuable. [4] Petroleum, the primary feedstock for the chemical industry today, contains very little oxygen, and the C/O ratio of 1:1 for glycerol and other biomass-derived polyols (sugar alcohols) means that reactions that are able to reduce the oxygen content are relevant.…”

“…The two fundamentally different pathways that can be envisioned for the CH 3 ReO 3 -catalyzed DODH of 1,2-tetradecanediol driven by the oxidation of 3-octanol (Scheme 1) are shown in Scheme 2. A pathway similar to that shown on the left-hand side of Scheme 2, in which the rhenium(VII) center and the diol underThe mechanism of the CH 3 ReO 3 -catalyzed deoxydehydration of a vicinal diol to an alkene driven by oxidation of a secondary alcohol was investigated by time-resolved, in situ IR spectroscopy and was found to occur in three steps: 1) reduction of the catalytically active methyltrioxorhenium(VII) to a rhenium(V) complex (the rate-limiting step), 2) condensation of the diol and the rhenium(V) complex to a rhenium(V) diolate, and 3) extrusion of the alkene accompanied by oxidation of the Re center and thus regeneration of CH 3 ReO 3 . The reaction follows zero-order kinetics initially but, unexpectedly, accelerates towards the end, which is explained in terms of a deactivating pre-equilibrium, in which the catalytically active CH 3 ReO 3 condenses reversibly with the diol to form an inactive rhenium(VII) diolate.…”

Microbial Conversion of Waste Glycerol from Biodiesel Production into Value-Added Products

“…Trace amounts of soap formed in an undesirable saponification reaction can also be found in waste glycerol [4]. Previously, commercial glycerol synthesis was primarily performed by propylene chlorine hydrolyzation in caustic environments [5]. Nowadays, the chemical synthesis of glycerol only accounts for about 10% of the current market because of the increasing cost of petrochemical precursors and decreasing price of pure glycerol [6].…”