Ru on N‐doped Carbon for the Selective Hydrogenolysis of Sugars and Sugar Alcohols

Glycols are accessible via metal‐catalyzed hydrogenolysis of sugar alcohols such as xylitol obtained from hemicellulose. Ru‐based catalysts are highly active but also catalyze side‐reactions such as decarbonylation and deoxygenation. To achieve high selectivity, these reactions need to be suppressed. In our study, we introduce heteroatom doped carbon materials as catalyst supports providing high selectivity. Heteroatom doping with nitrogen and oxygen was achieved by treating activated carbon with HNO₃, NH₃ and H₂ or carbonization of organic precursors. For all N‐doped materials a high glycol selectivity of ∼ 80 % for sorbitol and xylitol and 44 % for xylose and glucose was reached. XPS analysis confirms the presence of different nitrogen species at the carbon surface and varying ligand effects for oxygen and nitrogen. Oxygen has an electron withdrawing effect on ruthenium and leads to a decreased activity. Nitrogen has weaker electron withdrawing properties, resulting in an enhanced selectivity

Ru on N‐doped Carbon for the Selective Hydrogenolysis of Sugars and Sugar Alcohols

Glycols are accessible via metal‐catalyzed hydrogenolysis of sugar alcohols such as xylitol obtained from hemicellulose. Ru‐based catalysts are highly active but also catalyze side‐reactions such as decarbonylation and deoxygenation. To achieve high selectivity, these reactions need to be suppressed. In our study, we introduce heteroatom doped carbon materials as catalyst supports providing high selectivity. Heteroatom doping with nitrogen and oxygen was achieved by treating activated carbon with HNO₃, NH₃ and H₂ or carbonization of organic precursors. For all N‐doped materials a high glycol selectivity of ∼ 80 % for sorbitol and xylitol and 44 % for xylose and glucose was reached. XPS analysis confirms the presence of different nitrogen species at the carbon surface and varying ligand effects for oxygen and nitrogen. Oxygen has an electron withdrawing effect on ruthenium and leads to a decreased activity. Nitrogen has weaker electron withdrawing properties, resulting in an enhanced selectivity

Hydrogen-efficient non-oxidative transformation of methanol into dimethoxymethane over a tailored bifunctional Cu catalyst

Dimethoxymethane (DMM), a promising synthetic fuel enabling clean combustion, is usually produced by condensation of methanol and formaldehyde, where the latter stems from methanol oxidation. Here, we report the hydrogen efficient non-oxidative DMM synthesis over a bifunctional Cu/zeolite catalyst in a continuous gas-phase fixed bed reactor. Methanol dehydrogenation to formaldehyde (FA) is coupled with FA condensation with methanol to yield DMM, hydrogen and water. Thermodynamic analysis confirms the general feasibility of this route and also manifests the vital importance of catalyst selectivity. Therein, close proximity of the catalyst's metallic Cu species and acidic sites is crucial. Noticeably, DMM selectivity of the catalyst only evolves within the first 13 hours of operation rising from 5.8 to 77.2%. A maximum DMM selectivity of 89.2 or 80.3% could be reached for 0.4 and 0.7 wt% Cu on Hβ(836) zeolite with 1.9 or 3.6% methanol conversion, respectively. Comprehensive characterizations emphasize adaptation of Cu species and Hβ zeolite under reaction conditions resulting in the decisive weakened dehydrogenation and condensation ability for high DMM selectivity. Process simulations confirm superior exergy efficiency compared to state-of-the-art technologies for DMM production already with the herein developed catalyst and highlights the high potential of further innovations for technical implementation

The Palladium‐Catalyzed Carboxytelomerization of Butadiene with Agrobased Alcohols and Polyols

International audienceThe palladium catalyzed carboxytelomerization reaction of alcohols with butadiene allows for efficient and atom-economical access to unsaturated alkyl nona-3,8-dienoate esters. The study focused on the nature of the catalyst (phosphine and acid) with ethanol. Commercially available triarylphosphines and carboxylic acids associated with a simple palladium precursor appear to be the best combination for in situ generation of the catalyst. The reaction conditions were further optimized and the carboxytelomerization reaction was efficiently applied to the full transformation of several industrially relevant agro-based monoalcohols and polyols