Experimental Microkinetic Approach of the Photocatalytic Oxidation of Isopropyl Alcohol on TiO₂. Part 1. Surface Elementary Steps Involving Gaseous and Adsorbed C₃H_xO Species

Abstract

The present study concerns an experimental microkinetic approach of the photocatalytic oxidation (PCO) of isopropyl alcohol (IPA) into acetone on a pure anatase TiO2 solid according to a procedure previously developed. Mainly, the kinetic parameters of each surface elementary step of a plausible kinetic model of PCO of IPA are experimentally determined: natures and amounts of the adsorbed species and rate constants (preexponential factor and activation energy). The kinetics parameters are obtained by using experiments in the transient regime with either a FTIR or a mass spectrometer as a detector. The deep oxidation (CO2 and H2O formation) of low concentrations of organic pollutants in air is one of the interests of the PCO. For IPA, literature data strongly suggest that acetone is the single route to CO2 and H2O and this explains that the present study is dedicated to the elementary steps involving gaseous and adsorbed C3H(x)O species. The microkinetic study shows that strongly adsorbed IPA species (two species denoted nd-IPA(sads) and d-IPA(sads) due to non- and dissociative chemisorption of IPA, respectively) are involved in the PCO of IPA. A strong competitive chemisorption between IPA(sads) and a strongly adsorbed acetone species controls the high selectivity in acetone of the PCO at a high coverage of the surface by IPA(sads). The kinetic parameters of the elementary steps determined in the present study are used in part 2 to provide a modeling of macroscopic kinetic data such as the turnover frequency (TOF in s(-1)) of the PCO using IPA/O2 gas mixtures.

Abatement of VOCs with Alternate Adsorption and Plasma-Assisted Regeneration: A Review

“…The adsorption of IPA on TiO2 surface leads to the formation of three surface species. The formation of monodentate isopropoxy groups and surface hydroxyl species indicates dissociative adsorption of IPA through Equation (2) [54], the authors proposed that acetone, produced from oxidation of adsorbed IPA on S(1) sites, could not remain adsorbed on similar adsorption sites (due to competitive adsorption phenomena between IPA and acetone). Acetone either rapidly desorbed to the gas phase if no surface sites denoted by S(2) were available or diffused toward an available S(2) site.…”

“…Noting that only a small fraction of TiO2 surface sites S(2) are specific to the acetone adsorption (there is no competitive chemisorption with IPA). For IPA, literature data [54][55][56] strongly suggest that acetone is the single route to produce CO2 and H2O. Experiments have revealed that when the TiO2 surface is fully saturated with IPA, small amounts of S(2) sites are accessible for irreversibly adsorbed acetone and its subsequent oxidation into CO2 [51].…”

Surface reaction of 2‐propanol on modified Keggin type polyoxometalates: In situ IR spectroscopic investigation of the surface acid–base properties

“…During the reaction a consecutive reduction of the intensity of the n(O-O) vibration of the peroxo group is observed, which [22,23]. The band at 1734 cm À1 is assigned to the n(CO) vibration of acetone [9,24,25].…”

Enhanced photocatalytic degradation of 2-propanol over macroporous GaN/ZnO solid solution prepared by a novel sol-gel method

“…For GaN/ZnO solid solution, the IPA photodegradation process is much more complex as described in processes (3)- (8): both e − and h + are very active simultaneously. [27][28][29] Figure 6 schematically illustrates the whole reaction mechanisms of IPA photodegradation over ZnO, GaN, and GaN/ZnO solid solution, respectively.…”