Yield Of Formaldehyde Research Articles

Oxidation of organic pollutants by peroxymonosulfate activated with low-temperature-modified nanodiamonds: Understanding the reaction kinetics and mechanism

Changes in surface carbon hybridization through high-temperature annealing (>1000 °C) of nanodiamond (ND), i.e., surface graphitization, enable peroxymonosulfate (PMS) activation by ND. Alternatively, this study suggests low-temperature surface modification (500 °C) of ND as an effective strategy for allowing ND to activate PMS. ND calcination in the presence of poly(diallydimethylammonium chloride) (PDDA) and graphene oxide (GO) in an NH3 atmosphere produced binary and ternary nitrogen-doped ND composites (i.e., N-ND/PDDA and N-ND/PDDA/GO). Compared with bare ND, theses surface-modified NDs markedly enhanced organic oxidation associated with PMS activation. In particular, N-ND/PDDA/GO outperformed graphitized ND in terms of PMS activation capacity. Spectroscopic characterization implied that the content of pyridinic N and the N doping level increased with further modification of ND. Oxidation by PMS activated with ND-based materials did not involve radical attack, as methanol did not exhibit a quenching effect, formaldehyde yield was insignificant, conversion of bromide into bromate was negligible, the substrate specificity contradicted sulfate radical (SO4−) reactivity, and no electron paramagnetic resonance spectral features were assignable to SO4− adducts. Impedance spectroscopic analysis indicated a high correlation between PMS activation efficacy and electrical conductivity. Chronoamperometric measurements showed that sequential injection of PMS and 4-chlorophenol caused current generation at electrodes coated with ND-based activators, and the increase in current intensity correlated well with PMS activation capacity. These findings suggest that ND-derived materials facilitated the electron transfer from organics to PMS, resulting in a degradative reaction route not reliant on radical species.

Catalytic Activity Studies of Vanadia/Silica–Titania Catalysts in SVOC Partial Oxidation to Formaldehyde: Focus on the Catalyst Composition

In this work, silica–titania supported catalysts were prepared by a sol–gel method with various compositions. Vanadia was impregnated on SiO2-TiO2 with different loadings, and materials were investigated in the partial oxidation of methanol and methyl mercaptan to formaldehyde. The materials were characterized by using N2 physisorption, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), Scanning transmission electron microscope (STEM), NH3-TPD, and Raman techniques. The activity results show the high importance of an optimized SiO2-TiO2 ratio to reach a high reactant conversion and formaldehyde yield. The characteristics of mixed oxides ensure a better dispersion of the active phase on the support and in this way increase the activity of the catalysts. The addition of vanadium pentoxide on the support lowered the optimal temperature of the reaction significantly. Increasing the vanadia loading from 1.5% to 2.5% did not result in higher formaldehyde concentration. Over the 1.5%V2O5/SiO2 + 30%TiO2 catalyst, the optimal selectivity was reached at 415 °C when the maximum formaldehyde concentration was ~1000 ppm.

The production of formaldehyde and hydroxyacetone in methacrolein photooxidation: New insights into mechanism and effects of water vapor

Methacrolein (MACR) is an abundant multifunctional carbonyl compound with high reactivity in the atmosphere. In this study, we investigated the hydroxyl radical initiated oxidation of MACR at various NO/MACR ratios (0 to 4.04) and relative humidities (<3% to 80%) using a flow tube. Meanwhile, a box model based on the Master Chemical Mechanism was performed to test our current understanding of the mechanism. In contrast to the reasonable predictions for hydroxyacetone production, the modeled yields of formaldehyde (HCHO) were twice higher than the experimental results. The discrepancy was ascribed to the existence of unconsidered non-HCHO forming channels in the chemistry of CH3C(CH2)OO, which account for approx. 50%. In addition, the production of hydroxyacetone and HCHO were affected by water vapor as well as the initial NO/MACR ratio. The yields of HCHO were higher under humid conditions than that under dry condition. The yields of hydroxyacetone were higher under humid conditions at low-NOx level, while lower at high-NOx level. The reasonable explanation for the lower hydroxyacetone yield under humid conditions at high-NOx level is that water vapor promotes the production of methacrolein nitrate in the reaction of HOCH2C(CH3)(OO)CHO with NO due to the peroxy radical-water complex formation, which was evidenced by calculational results. And the minimum equilibrium constant of this water complex formation was estimated to be 1.89×10−18cm3/molecule. These results provide new insights into the MACR oxidation mechanism and the effects of water vapor.

On-line gaseous formaldehyde detection by a microfluidic analytical method based on simultaneous uptake and derivatization in a temperature controlled annular flow

This paper is focused on the improvement of a microfluidic analytical method for the detection of low airborne formaldehyde concentrations, based on only two distinct steps permitting to reduce the response time and to improve the compactness of the device. First, gaseous formaldehyde is trapped into an acetylacetone solution at 65°C through an annular liquid/gas flow and reacts immediately to form 3,5-Diacetyl-1,4-dihydrolutidine which is then quantified by colorimetry using a liquid core waveguide (LCW).To obtain an annular flow, 3 different hydrophilic silica capillaries of 320, 450 and 530µm ID were tested and the corresponding phase diagrams were obtained in the ranges of liquid and gas flows of 5–35µLmin−1 and 5–35mLmin−1 respectively.Finally, the analytical performances were determined using the lowest flow values of 5µLmin−1 and 5NmLmin−1, ensuring an annular flow and increasing the microdevice autonomy. If the uptake yield of gaseous formaldehyde into the solution was close to 100%, only the 530µm ID capillary permits to obtain a reaction time long enough for a full conversion of formaldehyde into 3,5-Diacetyl-1,4-dihydrolutidine. With a LCW pathlength of 5cm, the microdevice response was perfectly linear in the range 0–154µgm−3 with a detection limit of 1.8µgm−3.

Structure and Reactivity of sol–gel V/SiO2 Catalysts for the Direct Conversion of Methane to Formaldehyde

Vanadium oxide-silica catalysts prepared by the sol–gel method were characterized by different techniques (nitrogen adsorption–desorption isotherms, scanning electron microscopy, X-ray diffraction, temperature-programmed reduction, Raman spectroscopy and X-ray photoelectron spectroscopy) and applied in the direct conversion of methane to C1 oxygenates. The addition of a small amount of nitric oxide to the reaction mixture reduced the energy barrier for H-abstraction, increasing the methane conversion and formaldehyde yield. Correlations between the characterization and activity results indicate that the reaction occurs on tetrahedrally coordinated vanadium sites, as the maximum formaldehyde yield was found for the catalyst with a vanadium content of 1.5 wt%, which has a high surface density of well-dispersed tetrahedrally coordinated monomeric or slightly oligomerized VO4 species. On the other hand, a high space velocity and CH4:O2 ratio decrease the subsequent oxidation to carbon oxides, increasing oxygenate formation.

Photocatalytic behavior of metal-decorated TiO2 and their catalytic activity for transformation of glycerol to value added compounds

In this work, TiO2 was decorated with one of four different metals (Bi, Pd, Pt and Au) by sol immobilization at ambient condition. The individual addition of each metals on the TiO2 did not affect the crystallite size or band gap energy of TiO2, but increased its visible light absorption ability due to the localized surface plasmon resonance effect of the doped metals, except for Bi, as well as the mechanism of the charge transfer. Among all the prepared metal-decorated TiO2 photocatalysts, Au/TiO2 exhibited the highest visible light absorption ability and an appropriate mechanism of charge transfer, which consequently alleviated the e−–h+ recombination. It also provided the highest photocatalytic activity for glycerol conversion (92.8% at 14h) and yield of dihydroxyacetone, glyceraldehyde, glycolic acid, hydroxypyruvic acid and formaldehyde of 12.0, 23.1, 10.7, 13.6 and 15.3%, respectively.

Kinetic and Mechanistic Study of the Thermal Decomposition of Ethyl Nitrate

Thermal decomposition of ethyl nitrate (ENT; CH3CH2ONO2) has been studied in a low-pressure flow reactor combined with a quadrupole mass spectrometer. The rate constant of the nitrate decomposition was measured as a function of pressure (1–12.5 Torr of helium) and temperature in the range 464–673 K using two different approaches: from kinetics of ENT loss and those of the formation of the reaction product (CH3 radical). The fit of the observed falloff curves with two-parameter expression provided the following low- and high-pressure limits for the rate constant of ENT decomposition: k0 = 1.0 × 10−4 exp(−16,400/T) cm3 molecule−1 s−1 and k∞ = 1.08 × 1016 exp(−19,860/T) s−1, respectively, which allow to reproduce (via above expression and with 20% uncertainty) all the experimental data obtained for k1 in the temperature and pressure range of the study. It was observed that the initial step of the thermal decomposition of ethyl nitrate is O–NO2 bond cleavage leading to formation of NO2 and CH3CH2O radical, which rapidly decomposes to form CH3 and formaldehyde as final products. The yields of NO2, CH3, and formaldehyde upon decomposition of ethyl nitrate were measured to be near unity. In addition, the kinetic data were used to determine the O–NO2 bond dissociation energy in ENT: 38.3 ± 2.0 kcal mol−1.

Direct dehydrogenation of methanol to anhydrous formaldehyde over Ag2O/γ-Al2O3 nanocatalysts at relatively low temperature

A series of Ag2O/γ-Al2O3 nanocatalysts for direct dehydrogenation of methanol with various extents of Ag2O loading (0.5–15 wt%) were prepared by the wet impregnation method. The catalysts were characterized by XRD, TEM and N2 sorption. The catalysts were tested for direct dehydrogenation of methanol in a fixed-bed reactor at a relatively low temperature, 330 °C, using N2 as a carrier gas. The obtained results revealed that pure γ-Al2O3 exhibits quite poor selectivity toward formaldehyde (FA) formation (≈28%). On the other hand, the addition of Ag2O improves the catalytic activity of γ-Al2O3 where the catalyst with 10 wt% Ag2O exhibits 100% conversion of methanol with 100% yield of FA. Moreover, the catalyst with 1 wt% Ag2O achieved similar results at the reaction temperature of 370 °C.

Development of microfluidic analytical method for on-line gaseous Formaldehyde detection

This paper reports on the development of a novel colorimetric analytical method based on microfluidic technologies for the detection of low airborne Formaldehyde concentrations, representative of those found in indoor air, i.e. 10–100μgm−3. The new analytical technique operates according to 4 distinct steps: 1) gas sampling, 2) gaseous Formaldehyde uptake into the aqueous solution using an annular gas/liquid flow at room temperature, 3) derivatization reaction with acetylacetone solution at 65°C producing 3,5-Diacetyl-1,4-dihydrolutidine (DDL) and 4) colorimetric DDL detection with a liquid-core-waveguide.Laboratory experiments were performed to determine the experimental conditions permitting to obtain a stable annular flow, i.e. a liquid flow rate above 5μLmin−1 and gas to liquid flow rate ratios greater than 1000. Effects of liquid-core-waveguide of internal diameter and length were also investigated.Using liquid and gas flow rates of 35μLmin−1 and 35mLmin−1 respectively, the resulting uptake yield of gaseous Formaldehyde in aqueous solution was around 90% and the detection limit of gaseous Formaldehyde was 0.7μgm−3, which is consistent with the guideline values for indoor air. In addition, the low reagent consumption increases significantly the device autonomy up to 20days with 1L of acetylacetone solution.

Hydrogenation of Carbon Monoxide into Formaldehyde in Liquid Media

Formaldehyde is a bulk chemical which is produced in excess of 30 million tons per annum and is growing in demand. However, the current production process requires methanol production, which is oxidized in air to produce formaldehyde, which must then be absorbed into water. Our recent work introduced a novel method to produce formaldehyde through CO hydrogenation in the aqueous phase. However, the aqueous phase has certain limitations which must be overcome to make it commercially viable. By applying a deuterium labeling technique and investigating the potential intermediates, the reaction mechanism was established which showed that solvents play a vital role in determining the yield. Various solvents were used for formaldehyde production, and the highest formaldehyde yield was achieved by using pure methanol followed by methanol–water mixtures. Formaldehyde reacts with methanol and water to produce hemiacetal and methylene glycol, respectively, thereby shifting the equilibrium of CO hydrogenation toward ...

ReaxFF MDSs-based studies on gasification of glucose in supercritical water under microwave heating

It is shown that ReaxFF molecular dynamics simulations (MDSs) can be used to study the high temperature gasification of glucose in supercritical water under microwave heating. At the early stage of gasification, yields of gas products have great difference under microwave and conventional heating models. It is considered that the difference results from the non-thermal effect of microwave. Therefore, simplified pathway model of free radical reactions is further constructed to study the influences of external electric fields on the yields of hydrogen gas, carbon monoxide and intermediate formaldehyde. Rotation characteristics of water and carbon monoxide electric dipoles are also studied at a high temperature. To analyze the impacts of external electric fields on the water-gas shift reactions, collision theory is introduced and several simplified collision models are constructed and detailed. Based on our studies, for the first time, it is concluded that using microwaves as heating source is feasible to the gasification of glucose in supercritical water, where no obvious thermal runaway is found. Moreover, the external microwave can increase the production of hydrogen gas through promoting the yields of glucose decomposed into formaldehyde and hydrogen free radical.

Sensitivity to grid resolution in the ability of a chemical transport model to simulate observed oxidant chemistry under high-isoprene conditions

Abstract. Formation of ozone and organic aerosol in continental atmospheres depends on whether isoprene emitted by vegetation is oxidized by the high-NOx pathway (where peroxy radicals react with NO) or by low-NOx pathways (where peroxy radicals react by alternate channels, mostly with HO2). We used mixed layer observations from the SEAC4RS aircraft campaign over the Southeast US to test the ability of the GEOS-Chem chemical transport model at different grid resolutions (0.25° × 0.3125°, 2° × 2.5°, 4° × 5°) to simulate this chemistry under high-isoprene, variable-NOx conditions. Observations of isoprene and NOx over the Southeast US show a negative correlation, reflecting the spatial segregation of emissions; this negative correlation is captured in the model at 0.25° × 0.3125° resolution but not at coarser resolutions. As a result, less isoprene oxidation takes place by the high-NOx pathway in the model at 0.25° × 0.3125° resolution (54 %) than at coarser resolution (59 %). The cumulative probability distribution functions (CDFs) of NOx, isoprene, and ozone concentrations show little difference across model resolutions and good agreement with observations, while formaldehyde is overestimated at coarse resolution because excessive isoprene oxidation takes place by the high-NOx pathway with high formaldehyde yield. The good agreement of simulated and observed concentration variances implies that smaller-scale non-linearities (urban and power plant plumes) are not important on the regional scale. Correlations of simulated vs. observed concentrations do not improve with grid resolution because finer modes of variability are intrinsically more difficult to capture. Higher model resolution leads to decreased conversion of NOx to organic nitrates and increased conversion to nitric acid, with total reactive nitrogen oxides (NOy) changing little across model resolutions. Model concentrations in the lower free troposphere are also insensitive to grid resolution. The overall low sensitivity of modeled concentrations to grid resolution implies that coarse resolution is adequate when modeling continental boundary layer chemistry for global applications.

Temperature- and Coverage-Dependent Kinetics of Photocatalytic Reaction of Methanol on TiO2 (110)-(1 × 1) Surface

We systematically investigated the photocatalytic reaction of methanol on the TiO2 (110)-(1 × 1) surface under irradiation with ultraviolet (UV) light performed at various conditions, using scanning tunneling microscopy (STM) jointed with temperature-programmed desorption (TPD) techniques. Our STM and TPD results show that the photocatalytic reaction is indeed initiated from the molecular methanol at the 5-fold coordinated Ti sites, as commonly ascribed to the methanol oxidation by the photogenerated holes, reflecting the highly photoactive nature of methanol. The formaldehyde yield from the TPD results is much smaller by a factor of 2/3 than the amount of dissociated methanol from the STM results at 80 K. This observation can be assigned to the reverse reaction during the TPD measurement, and may explain the lower yield of formaldehyde using molecular methanol than using methoxy. From the fractal-like reaction kinetics of methanol, we can associate the coverage-dependence of the spectral dimensions with ...

Water co-catalyzed selective dehydrogenation of methanol to formaldehyde and hydrogen

The non-oxidative dehydrogenation of methanol to formaldehyde is considered a promising method to produce formaldehyde and clean hydrogen gas. Although Cu-based catalysts have an excellent catalytic activity in the oxidative dehydrogenation of methanol, metallic Cu is commonly believed to be unreactive for the dehydrogenation of methanol in the absence of oxygen adatoms or oxidized copper. Herein we show that metallic Cu can catalyze the dehydrogenation of methanol in the absence of oxygen adatoms by using water as a co-catalyst both under realistic reaction conditions using silica-supported PtCu nanoparticles in a flow reactor system at temperatures below 250°C, and in ultra-high vacuum using model PtCu(111) catalysts. Adding small amounts of isolated Pt atoms into the Cu surface to form PtCu single atom alloys (SAAs) greatly enhances the dehydrogenation activity of Cu. Under the same reaction conditions, the yields of formaldehyde from PtCu SAA nanoparticles are more than one order of magnitude higher than on the Cu nanoparticles, indicating a significant promotional effect of individual, isolated Pt atoms. Moreover, this study also shows the unexpected role of water in the activation of methanol. Water, a catalyst for methanol dehydrogenation at low temperatures, becomes a reactant in the methanol steam reforming reactions only at higher temperatures over the same metal catalyst.

Selective Oxidation of Methanol to Formaldehyde Over Active Molybdenum Oxide Supported on Hydroxyapatite Catalysts

Hydroxyapatite (HAP) was synthesized by sol–gel method. Different ratios of molybdenum oxide (1–15 % w/w) supported on HAP were prepared by the impregnation method and calcined at 400 °C in a static air atmosphere. The catalysts were characterized by thermogravimetry, differential thermal analysis, X-ray diffraction, FTIR spectroscopy and nitrogen sorption measurements. The surface acidity of the catalysts was investigated by the dehydration of isopropyl alcohol and the adsorption of pyridine (PY) and 2,6-dimethyl pyridine (DMPY). The gas–phase oxidation of methanol to formaldehyde was carried out in a conventional fixed-bed flow type reactor using N2 as a carrier gas. The obtained results clearly revealed that HAP–MoO3 systems were active and selective towards the formation of formaldehyde. The maximum yield of formaldehyde (97 %) was achieved on the catalyst containing 5 wt% MoO3/HAP. The generation of Mo6+as Lewis together with Bronsted acid sites play the main role in the formation of formaldehyde. Catalytic oxidation of methanol over MoO3/HAP calcined at 400 °C for 4 h.

Reassessing the ratio of glyoxal to formaldehyde as an indicator of hydrocarbon precursor speciation

Abstract. The yield of formaldehyde (HCHO) and glyoxal (CHOCHO) from oxidation of volatile organic compounds (VOCs) depends on precursor VOC structure and the concentration of NOx (NOx = NO + NO2). Previous work has proposed that the ratio of CHOCHO to HCHO (RGF) can be used as an indicator of precursor VOC speciation, and absolute concentrations of the CHOCHO and HCHO as indicators of NOx. Because this metric is measurable by satellite, it is potentially useful on a global scale; however, absolute values and trends in RGF have differed between satellite and ground-based observations. To investigate potential causes of previous discrepancies and the usefulness of this ratio, we present measurements of CHOCHO and HCHO over the southeastern United States (SE US) from the 2013 SENEX (Southeast Nexus) flight campaign, and compare these measurements with OMI (Ozone Monitoring Instrument) satellite retrievals. High time-resolution flight measurements show that high RGF is associated with monoterpene emissions, low RGF is associated with isoprene oxidation, and emissions associated with oil and gas production can lead to small-scale variation in regional RGF. During the summertime in the SE US, RGF is not a reliable diagnostic of anthropogenic VOC emissions, as HCHO and CHOCHO production are dominated by isoprene oxidation. Our results show that the new CHOCHO retrieval algorithm reduces the previous disagreement between satellite and in situ RGF observations. As the absolute values and trends in RGF observed during SENEX are largely reproduced by OMI observations, we conclude that satellite-based observations of RGF can be used alongside knowledge of land use as a global diagnostic of dominant hydrocarbon speciation.

The role of the suprastoichiometric molybdenum during methanol to formaldehyde oxidation over Mo–Fe mixed oxides

Iron molybdates are common industrial catalysts for methanol oxidation. The role of Mo excess, usually present in the catalyst formulation still doubtful. Some authors claim a stability effect whereas others claim that surface MoO3, segregated from bulk, is the active phase.In order to clarify the role of Mo excess on the catalytic performances, catalysts were prepared by Mo surface loading of stoichiometric Fe2(MoO4)3. No crystalline MoO3 was detected even for the sample prepared with five monolayers (maximum number) of MoO3. XPS data reveals a Mo surface enrichment even for the stoichiometric mixed oxide sample. All the samples presented Mo/Fe atomic ratio higher than the stoichiometric value (1.5). Adding of MoO3 monolayers seems to promote surface aggregation of Mo species.Catalytic data showed that Mo surface enrichment of the stoichiometric phase leads to an increase of formaldehyde yield for loadings higher than 0.5 monolayers. The observed behavior seems to result from a compromise between the higher catalytic activity of the Fe2(MoO4)3 phase and the lower activity but higher selectivity of the MoO3 phase. A cooperative effect between the MoO3 and the molybdate phase seems to dictate the catalytic performances.

New approach on the catalytic oxidation of methanol to formaldehyde over MoO3 supported on nano hydroxyapatite catalysts

Molybdenum oxide (20 wt. %) supported on nano hydroxyapatite mixed was prepared by impregnation method and calcinated at 400° 500° 600° and 700°C in static air atmosphere. The catalysts were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and nitrogen sorption measurements. The gas-phase oxidation of methanol to formaldehyde was carried out in a conventional fixed flow bed reactor. The obtained results clearly revealed that the formation of CaMoO4 spinel nano particles was active and selective catalyst towards the formation of formaldehyde. The maximum yield of formaldehyde was 97% on the catalyst calcined at 400 ° C. Moreover, the yield of formaldehyde was found unaffected by increasing the calcination temperature up to 700° C.

Approaches for the design of reduced toxicant emission cigarettes.

Cigarette smoking causes serious diseases through frequent and prolonged exposure to toxicants. Technologies are being developed to reduce smokers’ toxicant exposure, including filter adsorbents, tobacco treatments and substitutes. This study examined the effect of modifications to filter ventilation, variations in cigarette circumference and active charcoal filter length and loading, as well as combinations of these features in a reduced-toxicant prototype (RTP) cigarette, on the yields of toxicants in cigarette smoke. An air-dilution mechanism, called split-tipping, was developed in which a band of porous paper in the centre of the filter tipping functions to minimise the loss of effective filter ventilation that occurs at the high flow rates encountered during human-smoking, and to facilitate the diffusional loss of volatile toxicants. As compared with conventional filter ventilation cigarettes, split-tipping reduced tar and volatile smoke constituent emissions under high flow rate machine-smoking conditions, most notably for products with a 1-mg ISO tar yield. Furthermore, mouth level exposure (MLE) to tar and nicotine was reduced among smokers of 1-mg ISO tar cigarettes in comparison to smokers of cigarettes with traditional filter ventilation. For higher ISO tar level cigarettes, however, there were no significant reductions in MLE. Smaller cigarette circumferences reduced sidestream toxicant yields and modified the balance of mainstream smoke chemistry with reduced levels of aromatic amines and benzo[a]pyrene but increased yields of formaldehyde. Smaller circumference cigarettes also had lower mainstream yields of volatile toxicants. Longer cigarette filters containing increased levels of high-activity carbon (HAC) showed reduced machine-smoking yields of volatile toxicants: with up to 97% removal for some volatile toxicants at higher HAC loadings. Split-tipping was combined with optimal filter length and cigarette circumference in an RTP cigarette that gave significantly lower mainstream (up to ~90%) and sidestream (predominately 20%–60%) smoke yields of numerous toxicants as compared with a commercial comparator cigarette under machine-smoking conditions. Significantly lower mainstream and sidestream smoke toxicant yields were observed for an RTP cigarette comprising several toxicant reducing technologies; these observations warrant further evaluation in clinical studies where real-world relevance can be tested using biomarkers of exposure and physiological effect.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-374) contains supplementary material, which is available to authorized users.

Evaluation of the O2 and pH Effects on Probes for Surface Bound Hydroxyl Radicals

Interfacial reactions between H2O2 and metal oxides are important in several fields but are yet not fully understood. Recently, tris(hydroxymethyl)aminomethane (Tris) was used as a probe in detecting the intermediate hydroxyl radical (HO•) during such process via the formation of formaldehyde (CH2O). In this work, we evaluate two probes (methanol and Tris) for detection of surface bound HO• by investigating the O2 and pH effects on the production of formaldehyde. Moreover, we also examine the pH effect on the production of formaldehyde from Tris in the catalytic decomposition of H2O2 on ZrO2. The influence of O2 and pH on the yield of formaldehyde under homogeneous conditions was studied via γ-radiolysis of water. The solution was either deoxygenated or saturated with gas containing 20% O2, and the pH was ranging from 7.0 to 9.0. In the γ-radiolysis experiment, O2 shows a strong impact on the yield of formaldehyde: 14–68% for methanol and 16–29% for Tris. However, during the catalytic decomposition of H2O2, O2 only enables a 30% enhancement of the production of CH2O when using Tris as the scavenger. While for methanol, the O2 effect is almost negligible, and the production of CH2O from Tris is much higher than that from methanol. For practical reasons, only Tris was studied when evaluating the pH effect. A significant increase in the production of formaldehyde is observed by increasing pH during γ-radiolysis of water while an even more pronounced pH-dependent increase is observed in the catalytic decomposition of H2O2 on ZrO2. The former indicates that the scavenging yield is base-catalyzed while the latter indicates that the formation of HO• is also base-catalyzed. On the basis of the observed effects of O2 and pH, we propose a mechanism for the production of formaldehyde from Tris. The mechanism accounts for the observed impacts of O2 and pH on the yield of formaldehyde.