Heterogeneous Silica‐Supported Ruthenium Phosphine Catalysts for Selective Formic Acid Decomposition

Abstract

The water‐soluble ruthenium(II)–mTPPTS complex (mTPPTS=meta‐trisulfonated triphenylphosphine) efficiently catalyzes the generation of hydrogen from formic acid in aqueous solution. This catalyst has been immobilized in a hydrophilic silica support to facilitate mobile portable applications. It was used in diluted formic acid solutions, in which the recycling of a liquid phase catalyst is problematic. A series of heterogenized catalysts have been prepared by the reaction of the ruthenium(II)–mTPPTS dimer and silica functionalized with diphenylphosphine groups via alkyl chains. The length of the alkylene chain separating the silica from the diphenylphosphine group has been varied in these catalysts—all of them catalyzing the decomposition of formic acid. The catalysts were easily separated from the solution and reused. The optimized catalytic system based on MCM41‐Si‐(CH2)2PPh2/Ru‐mTPPTS demonstrated an activity and stability comparable to those of the homogeneous catalyst: a turnover frequency of 2780 h−1 was obtained at 110 °C, and no ruthenium leaching was detected after turnover numbers of 71 000.

Highly Robust Hydrogen Generation by Bioinspired Ir Complexes for Dehydrogenation of Formic Acid in Water: Experimental and Theoretical Mechanistic Investigations at Different pH

“…However, reports of highly active and stable catalysts in aqueous solution are scarce. 16, [46][47][48] We recently reported that a five-membered azole moiety is an efficient electron donor, and its incorporation into a catalyst complex is effective for FA dehydrogenation in water. 49 This is supposedly due to the high electron donating ability of the azole moieties.…”

Solid Molecular Phosphine Catalysts for Formic Acid Decomposition in the Biorefinery

“…[10] Catalytic FA decomposition is well known and can be achieved using avariety of transition metal complexes and supported metal catalysts.P articularly Ru/PR 3 and Ir/bipyridine complexes are highly active and selective for the synthesis and decomposition of FA. Laurenczy et al [15] tethered Ru/ TPPTS on phosphine-modified MCM41 and reported TOFs up to 2780 h À1 at 110 8 8C. [12] Nevertheless,f or the continuous decomposition of large volume streams of aqueous FA,h eterogeneous catalysts are required.…”

Advances in Ruthenium Catalysed Hydrogen Release from C1 Storage Materials

“…Further work to attach the catalyst to a hydrophilic silica catalyst with varying linker-lengths was therefore conducted. It was reported that the short linker distances in particular could have a positive effect on the turnover frequencies of the catalyst whilst overcoming some of the stability limitations of the homogenous systems [44].…”