Selective Catalytic Hydrogenolysis of Carbon–Carbon σ Bonds in Primary Aliphatic Alcohols over Supported Metals

Abstract

The selective scission of chemical bonds is always of great significance in organic chemistry. The cleavage of strong carbon−carbon σ bonds in the unstrained systems remains challenging. Here, we report the selective hydrogenolysis of carbon−carbon σ bonds in primary aliphatic alcohols catalyzed by supported metals under relatively mild conditions. In the case of 1-hexadecanol hydrogenolysis over Ru/TiO 2 as a model reaction system, the selective scission of carbon−carbon bonds over carbon−oxygen bonds is observed, resulting in n-pentadecane as the dominant product with a small quantity of n-hexadecane. Theoretical calculations reveal that the 1hexadecanol hydrogenolysis on flat Ru (0001) undergoes two parallel pathways: i.e. carbon−carbon bond scission to produce n-pentadecane and carbon−oxygen bond scission to produce n-hexadecane. The removal of adsorbed CO on a flat Ru (0001) surface is a crucial step for the 1hexadecanol hydrogenolysis. It contributes to the largest energy barrier in n-pentadecane production and also retards the rate for n-hexadecane production by covering the active Ru (0001) surface. The knowledge presented in this work has significance not just for a fundamental understanding of strong carbon−carbon σ bond scission but also for practical biomass conversion to fuels and chemical feedstocks.

Size Effects of Ni Particles on the Cleavage of C–H and C–C Bonds toward Hydrogen Production from Cellulose

“…Cu/La 2 O 2 CO 3 , with more basic sites, efficiently catalyzes transfer dehydrogenation of primary aliphatic alcohols and provides an aldehyde yield visibly higher than Cu/La 2 O 3. Decreasing the particle size of the supported metal increases less-coordinated metal sites located at the interface between the metal and support, thus clearly improving the cleavage of C–H bond in the generated alkoxide. , The combined thermochemical and kinetic analysis has addressed that dehydrogenation is the prerequisite for the scission of C–C bonds in oxygenates. − The C–C breaking occurs at the three-fold or two-fold metal sites. − In the hydrogenolysis of 1-hexadecanol, for example, increasing the Ru particle size by increasing Ru loading in Ru/TiO 2 leads to a gradual increase in n-pentadecane selectivity from 83.6 to 93.1% . Great efforts have also been devoted to revealing the intrinsic active sites and reaction mechanism of WGS. − So far, it has been generally accepted that the reaction involves the metal-oxide interface, even though there are still many controversies about the nature of active sites and the mechanism is also ambiguous. ,− To produce H 2 from cellulose or cellulose-derived platform compounds more efficiently, previous studies have focused predominantly on the boosting of WGS ability to improve H 2 yield by the incorporation of WGS promoter − or the addition of sacrificial basic reagents. , Much higher H 2 production rates have been achieved from ethylene glycol on Pd/Fe 2 O 3 than on Pd/Al 2 O 3 owing to the boosting of WGS reaction .…”

“…21−23 In the hydrogenolysis of 1-hexadecanol, for example, increasing the Ru particle size by increasing Ru loading in Ru/TiO 2 leads to a gradual increase in n-pentadecane selectivity from 83.6 to 93.1%. 24 Great efforts have also been devoted to revealing the intrinsic active sites and reaction mechanism of WGS. 25−29 So far, it has been generally accepted that the reaction involves the metal-oxide interface, even though there are still many controversies about the nature of active sites and the mechanism is also ambiguous.…”

Direct Catalytic Conversion of Ethanol to C5+ Ketones: Role of Pd–Zn Alloy on Catalytic Activity and Stability

“…Combined with the lack of redox sites for ethanol dehydrogenation, this results in the preferential generation of dehydration products over ZrO 2 .N ext, ZrO 2 was promoted with 0.1 %P dt o provide the necessary redox sites,w ith the results showing am inor increase in ketone formation and mild decrease in dehydration products such as ether,aswell as hydrogenation of most alkenes to alkanes.Atthe same time,the introduction of Pd led to additional formation of carbon monoxide (CO) and methane from ethanol decomposition, presumably through sequential dehydrogenation and metal-catalyzed decarbonylation reactions. [10] Rapid deactivation of the Pd, likely due to CO poisoning as commonly reported, [11] was marked by the disappearance of these decomposition products,t rending towards unpromoted ZrO 2 .…”

Direct Catalytic Conversion of Ethanol to C5+ Ketones: Role of Pd–Zn Alloy on Catalytic Activity and Stability

“…Next, ZrO 2 was promoted with 0.1 % Pd to provide the necessary redox sites, with the results showing a minor increase in ketone formation and mild decrease in dehydration products such as ether, as well as hydrogenation of most alkenes to alkanes. At the same time, the introduction of Pd led to additional formation of carbon monoxide (CO) and methane from ethanol decomposition, presumably through sequential dehydrogenation and metal‐catalyzed decarbonylation reactions . Rapid deactivation of the Pd, likely due to CO poisoning as commonly reported, was marked by the disappearance of these decomposition products, trending towards unpromoted ZrO 2 .…”