Acid‐, Water‐ and High‐Temperature‐Stable Ruthenium Complexes for the Total Catalytic Deoxygenation of Glycerol to Propane

Abstract

The ruthenium aqua complexes [Ru(H(2)O)(2)(bipy)(2)](OTf)(2), [cis-Ru(6,6'-Cl(2)-bipy)(2)(OH(2))(2)](OTf)(2), [Ru(H(2)O)(2)(phen)(2)](OTf)(2), [Ru(H(2)O)(3)(2,2':6',2''-terpy)](OTf)(2) and [Ru(H(2)O)(3)(Phterpy)](OTf)(2) (bipy = 2,2'-bipyridine; OTf(-) = triflate; phen = phenanthroline; terpy = terpyridine; Phterpy = 4'-phenyl-2,2':6',2''-terpyridine) are water- and acid-stable catalysts for the hydrogenation of aldehydes and ketones in sulfolane solution. In the presence of HOS(O)(2)CF(3) (triflic acid) as a dehydration co-catalyst they directly convert 1,2-hexanediol to n-hexanol and hexane. The terpyridine complexes are stable and active as catalysts at temperatures > or = 250 degrees C and in either aqueous sulfolane solution or pure water convert glycerol into n-propanol and ultimately propane as the final reaction product in up to quantitative yield. For the terpy complexes the active catalyst is postulated to be a carbonyl species [(4'-R-2,2':6',2''-terpy)Ru(CO)(H(2)O)(2)](OTf)(2) (R = H, Ph) formed by the decarbonylation of aldehydes (hexanal for 1,2-hexanediol and 3-hydroxypropanal for glycerol) generated in the reaction mixture through acid-catalyzed dehydration. The structure of the dimeric complex [{(4'-phenyl-2,2':6',2''-terpy)Ru(CO)}(2)(mu-OCH(3))(2)](OTf)(2) has been determined by single crystal X-ray crystallography (Space group P1 (a = 8.2532(17); b = 12.858(3); c = 14.363(3) A; alpha = 64.38(3); beta = 77.26(3); gamma = 87.12(3) degrees, R = 4.36 %).

Hydrogenation and hydrogenolysis of furfural and furfuryl alcohol catalyzed by ruthenium(II) bis(diimine) complexes

“…Given that hydrogenolysis of FFR (a trace of 2-MF) was observed in the reaction of FFR with H 2 (51 atm) catalyzed by cis-[Ru (6, (1) has been reported to be 135˚C), [44] as well as in solvents that would preclude formation of acetal and/or ether by-product(s). Reaction of FFR with H 2 (51 atm) in the presence of 1 mol% of 1 at 130 C in ethanol for 4 h proceeded to 100% FFR conversion and furnished a mixture of products (Table 3, entry 8), including FFA (17% yield), 2-MF (20% yield), and 2-(diethoxymethyl) furan (furfural diethyl acetal, 14% yield).…”

From 5-Hydroxymethylfurfural (HMF) to Polymer Precursors: Catalyst Screening Studies on the Conversion of 1,2,6-hexanetriol to 1,6-hexanediol

“…sulfuric acid) were added to improve catalytic conversions. There are also reports [46][47][48][49][50][51][52] on the use of homogeneous ruthenium catalysts in combination with triflic acid (HOTf) and sulfolane as the solvent for the selective hydrodeoxygenation of a secondary alcohol in the presence of a primary alcohol. For example, Schlaf et al [51] reported the production of 1-propanol from 6 using [{Cp*Ru(CO) 2 While preparing this manuscript, Dumesic et al [44] reported hydrodeoxygenation reactions of various diols and triols using bimetallic Rh-ReO x catalysts on carbon supports.…”

Selective Hydrogenolysis of C–O Bonds Using the Interaction of the Catalyst Surface and OH Groups

“…Therefore over-hydrogenolysis to propanols and even propane can proceed over the catalysts that can work by the dehydration + hydrogenation route. Homogeneous Ru and Ir complexes combined with external acid are typical catalysts for production of propanols or propane from glycerol [10,11] and 1,2-PrD [12][13][14]. In contrast, under more basic conditions over heterogeneous metal catalysts, the dehydrogenation + dehydration + hydrogenation route is preferred to the dehydration + hydrogenation route.…”