Are TiO2-based exterior paints useful catalysts for gas-phase photooxidation processes? A case study on n-decane abatement for air detoxification

Abstract

26n-Decane is a saturated long-chain hydrocarbon, belonging to the family of the 27 volatile organic compounds (VOCs), which is persistently present in indoor air of several 28 industrial closed facilities. Due to the VOCs environmental impact, all efforts that have 29 been made during the last decades to degrade this kind of air pollutants are extremely 30 important. Accordingly, the present paper reports n-decane photooxidation studies carried 31 out in an annular photoreactor under simulated solar irradiation and employing a catalytic 32 bed made of cellulose acetate monoliths coated with a photocatalytic paint. The influence 33 of the feed flow rate, n-decane concentration, relative humidity, and incident irradiance 34 on the n-decane degradation kinetics was assessed. Within this work, n-decane 35 photodegradations higher than 90% were achieved, depending on the experimental 36 conditions. Additionally, a phenomenological reaction rate model of the n-decane 37 photocatalytic oxidation was proposed and assessed. The proposed model assumes that 38 n-decane and water molecules compete for different active sites on the catalyst surface. 39Finally, despite the high n-decane photodegradation achieved, reaction by-products were 40 identified and, based on these compounds, a reaction mechanism was formulated. 41 42

Gas phase oxidation of n-decane and PCE by photocatalysis using an annular photoreactor packed with a monolithic catalytic bed coated with P25 and PC500

“…It should be pointed out that after more than 50 h under simulated solar radiation and continuous feed (humid air contaminated with n-decane or PCE), similar n-decane and PCE conversions (less than 1% of variation) were obtained under the same operating conditions and for both photocatalytic films (data not shown). Considering the results and our previous works where cellulose acetate monolithic structures were used as substrates [32,36,37], it is suggested that deterioration of the support and/or the photocatalytic film was negligible.…”

Improvement of photocatalytic activity of silicate paints by removal of K2SO4

“…However for high yield of photocatalytic reactions some conditions have to be realized, such as low concentration of pollutant, low relative humidity and relative long residence time of pollutant on the active photocatalyst surface. It was reported in many papers that water vapor could compete with organic molecules in adsorption on the active sites of photocatalyst (Monteiro et al, 2014;Chen and Poon, 2009;Maggos et al, 2007b). Degradation rate of pollutants is decreasing at high pollutant concentration levels due to the deposition of by-products on the photocatalyst surface.…”

“…The photocatalytic building materials contained nanosized TiO 2 have been recently extensively developed on the market and applied (Fujishima et al, 2007;Laufs et al, 2010;Monteiro et al, 2014;Hodgson et al, 2007). The versatile function of TiO 2 , which can both serve as photocatalytic and structural materials, has facilitated its application in exterior construction materials and interior furnishing materials, such as cement, mortar, exterior tiles, paving blocks, glass and PVC fabric.…”

Impact of paint matrix composition and thickness of paint layer on the activity of photocatalytic paints

“…, volatile organic compounds (VOC) 15 , polycyclic aromatic compounds (PAC) 5, 16 and can also lead to deactivation of bacteria 17 . Mineral photocatalytic paints usually exhibit lower photocatalytic activity than the acrylic ones, but they have better stability during exposure to solar radiation 18 .…”