Abstract
Commercial use of H2 production catalysts requires a repeated use/stop/store and reuse of the catalyst. Ideally, this cycle should be possible under ambient O2. Herein we exemplify the concept of Use-Store-Reuse (USR) of a (Ru-phosphine) catalyst in a biphasic catalytic system, for H2 production via dehydrogenation of HCOOH. The catalytic system can operate uninterrupted for at least four weeks, including storage and reuse cycles, with negligible loss of its catalytic efficiency. The catalytic system consisted of a RuP(CH2CH2PPh2)3 (i.e. RuPP3) in (tri-glyme/water) system, using KOH as a cocatalyst, to promote HCOOH deprotonation. In a USR cycle of 1 week, followed by storage for three weeks under ambient air and reuse, the system achieved in total TONs > 90,000 and TOFs > 4000 h−1. Thus, for the first time, a USR concept with a readily available stable ruthenium catalyst is presented, operating without any protection from O2 or light, and able to retain its catalytic performance.
Highlights
Nowadays, fossil fuels & natural gas constitute the main sources of energy production [1]
The most promising methods for chemical-storage of H2 include liquid organic hydrogencarriers (LOHCs) [7], under the condition that they would allow for a cost-efficient release of H2, i.e., via an efficient catalytic reaction
The set-up of the optimum functional catalytic system used in this work includes the in situ formation of the (Ru-PP3) pre-catalyst with a molar ratio of (Ru):(PP3) = 1:2 and its addition in a water/tri-glyme (v/v = 1:8) solution, containing 2 mL of Formic Acid (FA) and 10 mmol of KOH which were added to promote deprotonation of a fraction of HCOOH
Summary
Fossil fuels & natural gas constitute the main sources of energy production [1]. Given that most of the catalytic systems suffer from a rather rapid deactivation of the catalyst and poor long-term stability performance, the development of stable catalysts under long-term applications, i.e., at a commercial level, is an appealing challenge Within this context, so far, some efforts have been realized towards the development of continuous operating systems. Huang et al [24] used a water-soluble (Ru/N,N0 diamine) complex, operating under a continuous FA/HCOONa feed This system required high-pressure conditions achieving TOFs = 12,000 h−1 after 30 h [24]. In all the reported previous works, the uninterrupted long-term operation of the catalyst required operation under a strictly non-ambient atmosphere, i.e., exclusion of O2 by an inert gas, to avoid the decomposition of the catalytic complexes [22,23,24].
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