Process Intensification in Photocatalytic Decomposition of Formic Acid over a TiO2 Catalyst by Forced Periodic Modulation of Concentration, Temperature, Flowrate and Light Intensity

Abstract

The effect of forced periodic modulation of several input parameters on the rate of photocatalytic decomposition of formic acid over a TiO2 thin film catalyst has been investigated in a continuously stirred tank reactor. The kinetic model was adopted based on the literature and it includes acid adsorption, desorption steps, the formation of photocatalytic active sites and decomposition of the adsorbed species over the active titania sites. A reactor model was developed that describes mass balances of reactive species. The analysis of the reactor was performed with a computer-aided nonlinear frequency response method. Initially, the effect of amplitude and frequency of four input parameters (flowrate, acid concentration, temperature and light intensity) were studied. All single inputs provided only a minor improvement, which did not exceed 4%. However, a modulation of two input parameters, inlet flowrate and the acid molar fraction, considerably improved the acid conversion from 80 to 96%. This is equivalent to a factor of two increase in residence time at steady-state operation at the same temperature and acid concentration.

Catalysis for an electrified chemical production

“…Inducing periodic fast modulations in the catalyst temperature can induce metastable states for the catalysts with enhanced performances. Forced periodic temperature modulations have been shown to enhance the conversion of formic acid over a TiO2 thin film catalyst [51]. In general, however, studies on how to exploit this possibility are missing.…”

Review on recent progress and reactor set-ups for hydrogen production from formic acid decomposition

“…The photocatalytic decomposition of FA over TiO2 thin film catalyst in a CSTR was investigated by Ellwood et al [137]. A non-stationary dynamic model was proposed including the FA adsorption, the desorption steps, the formation of catalytic active sites and the decomposition of the adsorbed species over the catalyst.…”

Catalysis on the move

“…Also, the periodic modulation of temperature, flow rate or other process parameters in chemical reactors leads to significant improvement in reactant conversion and selectivity, thus introducing a further element to improve the catalytic performance over stationary conditions. 2…”