Continuous Hydrogen Generation from Formic Acid: Highly Active and Stable Ruthenium Catalysts

Abstract

The ruthenium-catalyzed decomposition of formic acid was investigated with respect to continuous hydrogen generation and long-term stability of the catalytic systems. A highly active and stable system is presented, which was studied in batch and continuous modes for up to two months. The optimized catalyst system containing N,N-dimethyl-nhexylamine with an in situ generated catalyst from (benzene)ruthenium dichloride dimer [RuCl 2 A C H T U N G T R E N N U N G (benzene)] 2 and 6 equivalents of 1,2-bis(diphenylphosphino)ethane (dppe) reached at room temperature a total turnover number (TON) of approximatly 260,000 with average turnover frequency (TOF) of about 900 h À1. Only hydrogen and carbon dioxide were detected in the produced gas mixture which makes this system applicable for direct use in fuel cells.

Improved hydrogen generation from formic acid

“…Noteworthy, applying a catalyst system containing [RuCl2(benzene)]2 and dppe with triethylamine (3:4; amine to HCO2H) or N,N-dimethyl-nhexylamine (4:5) a fast hydrogen generation is possible with full conversion within 2 hours. [4] Applying 20 mL of 5HCO2H/4HexNMe2 as substrate a TON of 5716 within 3 hours at 40 °C was reached, which constituted the highest activity for our approach to hydrogen generation so far. After gas evolution had ceased, the catalyst was reactivated ten times by addition of formic acid.…”

Liquid‐Phase Chemical Hydrogen Storage: Catalytic Hydrogen Generation under Ambient Conditions

“…. [97] They also found that visible light significantly accelerated and controlled the ruthenium-catalyzed generation from formic acid in the presence of amines. [98] Almost at the same time, Laurenczy et al reported the reaction of [Ru(H 2 O) 6 ] 2 + or commercial RuCl 3 ·xH 2 O with meta-trisulfonated triphenylphosphine (TPPTS) to yield a hydrophilic ruthenium-based catalyst, which was catalytically active for the decomposition of formic acid.…”

Catalytic Generation of Hydrogen from Formic acid and its Derivatives: Useful Hydrogen Storage Materials

“…Using ruthenium in combination with the dppe ligand, the system was further developed towards practical applications [101]. Applying 20 mL of 5HCO 2 H/4HexNMe 2 as substrate a TON of 5,716 within 3 h at 40°C was reached, which constituted the highest activity for our approach to hydrogen generation so far.…”