Decomposition Of Acetic Acid Research Articles

Synthesis and Photocatalytic Activity of Titania Pillared Clays

TiO2-pillared clays such as montmorillonite, saponite and mica were prepared with an intercalation of polynuclear titanium complex formed by the reaction of Ti(i-C3H7O)4 and acetic acid. Characterization of the products was performed by XRD, XPS, IR, UV-V spectra, the measurement of surface area and pore size distribution. The photocatalytic decomposition of carboxylic acids has been studied on TiO2-pillared montmorillonite, saponite and mica. TiO2-pillared mica showed higher catalytic activity than TiO2 for the photocatalytic decomposition of acetic acid and adipic acid. On the contrarily, TiO2 was the most active catalyst and TiO2-pillared mica showed low activity for the photocatalytic decomposition of capric acid. The results show that the molecular size of carboxylic acid contributes to the catalytic activity of TiO2-pillared clays.

Ultrafast photodissociation studies of acetyl cyanide and acetic acid and unimolecular decomposition rates of the acetyl radical products

Unimolecular decomposition rates for acetyl radical following the photodissociation of acetyl cyanide and acetic acid near 193 nm have been studied using ultrafast mass-resolved photoionization spectroscopy. In both cases, the parent decays with an instrumentally limited lifetime, while the acetyl radical behaves in a manner consistent with an RRKM mechanism, in contrast to our previous results on acetone. It is necessary to convolute the population distribution with the microcanonical RRKM rates in order to achieve this agreement. We have also undertaken an ab initio study of the excited states of acetyl cyanide to clarify the assignments of these states. The state excited at 193 nm arises from a π→π* transition with a calculated transition velocity dipole moment oriented at an angle of 57° with respect to the C–C≡N bond, resulting in an anisotropy parameter of −0.22. This is in reasonable agreement with the previous data of North et al. [J. Phys. Chem. A 101, 9224 (1997)]. The apparent RRKM behavior of the acetyl radical formed by the photodissociation of acetic acid and acetyl cyanide indicates that acetyl radical produced by the photodissociation of acetone at 193 nm may exhibit “extrinsic non-RRKM” effects, i.e., dynamic bottlenecks or mode specific effects.

Parallel Pathways for Photocatalytic Decomposition of Acetic Acid on TiO2

Acetic acid decomposes photocatalytically on TiO2 at room temperature in an inert atmosphere through two parallel pathways. In one pathway, acetic acid decomposes to gas-phase CO2 and apparently forms hydrogen and methyl groups, which combine on the surface to form CH4. In the other pathway, acetic acid extracts oxygen from the TiO2 lattice to form adsorbed H2O and gas-phase CO2 and C2H6. The extracted oxygen is replenished by diffusion from the bulk in an inert atmosphere or by gas-phase O2. The formation of CH4 and CO2 in the first pathway does not consume lattice oxygen. The first step in photocatalytic decomposition (PCD) of acetic acid appears to be dissociation of the O–H bond, producing surface acetates. However, molecularly adsorbed acetic acid reacts at the same rate and with the same selectivity as surface acetates. Only the α-carbon forms CO2 during PCD. When gas-phase O2 is present, adsorbed methyl groups oxidize before they are hydrogenated to CH4. The oxidizing agent during photocatalytic oxidation (PCO) is different from that during PCD and is most likely adsorbed oxygen. Adsorbed oxygen reacts with acetic acid in a different pathway from the two reactions observed for PCD, so a Mars Van Krevlen mechanism for PCO appears unlikely. The TiO2 surface is not homogeneous and some surface sites are more active during both PCD and PCO. Co-adsorbed water increases the rate of CH4 formation, apparently by reacting with CH3(ads) to form CH4, but in contrast to adsorbed O2, water does not react with acetic acid in a separate pathway that is different from those observed for PCD without water.

Performance of simplified G2 model chemistry approaches in the study of unimolecular mechanisms: thermal decomposition of acetic acid in gas phase

Ab initio calculations of equilibrium structures and transition states for decarboxylation and dehydration mechanisms of gas phase pyrolysis of acetic acid are put forward. The accuracy and efficiency of different G2-based methods are compared, namely G2(MP2), G2(MP2,SVP)/B3-LYP and G2/CASSCF10-in-10 of Duan and Page. The theoretical activation energies obtained using these three methods are very close to the experimental ones and the optimized equilibrium structures at B3-LYP, MP2 and CASSCF/6-31G(d) levels are very similar. However, the computational effort is reduced for the G2 (MP2,SVP)/B3-LYP calculation without any accuracy loss.

Synthesis of Ti-containing Porous Silica with High Photocatalytic Activity

Abstract Ti-containing mesoporous silica with high photocatalytic activity has been synthesized by a simple reaction system at ambient temperature; one of these products shows photocatalytic activity in the decomposition of acetic acid as high as 39 times than that of one of most photocatalytic commercial anatase.

Low-temperature formation of photocatalytic Pt-anatase film by magnetron sputtering

Films of TiO2 dispersed or coated with platinum were deposited on glass and Pt-buffered polyamide substrates respectively by magnetron sputtering. The photocatalytic activity of the films was evaluated through the decomposition of acetic acid under UV irradiation. The Pt-dispersed TiO2 film of approximately 1.5 wt % platinum shows a maximum activity due to for the formation of anatase phase with a fine grain size. Platinum particles ∼20A in thickness coated on anatase film greatly improves activity. The activity shows a steplike dependence of film thickness where the critical thickness varies between 150 and 200 nm depending on the deposition temperatures. The correlation between defects and activity was verified by measuring either the temperature dependence of electric resistance or the shift of binding energy from XPS.

Preparation and photocatalysis evaluation of anatase film on Pt-buffered polyimide

Films of TiO 2 (anatase) with platinum particles on the surface was deposited on the Pt-buffered polyimide substrates by dc magnetron sputtering. The photocatalytic activities of the films were evaluated through decomposition of acetic acid under UV irradiation. Platinum particles approximately 20 Å in thickness coated on the anatase film greatly improves the activities. The activity shows a steplike dependence of film thickness, i.e., the photocatalytic reaction degrades rapidly when film thickness is less than a threshold value, typically around 150∼300 nm. This behavior was thought to be related to the surface state formed on TiO 2-to-solution contact, based on the fact that the measurement of Mott–Schottky plots gives rise to a depletion width around 380 nm, which is comparable to the effective threshold thickness for photocatalysis.

Factors Governing the Initial Process of TiO2 Photocatalysis Studied by Means of in-Situ Electron Spin Resonance Measurements

The ratio of the amount of carboxymethyl radicals to that of methyl radicals was measured in situ for the photocatalytic decomposition of acetic acid over platinized TiO2 powder in deoxygenated aqueous solution at room temperature and discussed in connection with the contribution of ·OH radicals in the oxidation process. Since carboxymethyl radicals are formed only by indirect oxidation, the radical ratio was used to measure the indirect oxidation via ·OH radicals. Thus, ratios of the indirect oxidation were estimated for five commercially available TiO2 photocatalysts, in addition to the several properties of the powders. The ratios were found to be sensitive to the characteristics of the TiO2 catalysts. The larger the amount of surface OH group, the more likely the indirect oxidation via ·OH radicals occurs. This could be attributed to the difference in the structures of the surface trapped holes elucidated by the ESR measurements of the corresponding TiO2 powder at 77 K.

Chemical adsorption of acetic acid and deuterated acetic acid on Ru(0001), by RAIRS

The adsorption and thermal decomposition of acetic acid and deuterated acetic acid on clean Ru(0001) were studied by reflection absorption infrared spectroscopy. Acetic acid adsorbs molecularly, with dimer formation, at 100 K. At 113 K, the molecular form is still predominant, although some dissociative adsorption already occurs. Dehydrogenation is complete at 123 K, leaving adsorbed acetate as a symmetric bidentate species. Depending on coverage, two bonding configurations are proposed: a bidentate bridging [ μ 2- η 2(O,O)-CH 3COO], with each oxygen bonded to a neighbour Ru atom, at low coverages, and a bidentate chelating [ η 2(O,O)-CH 3COO], with the two oxygen atoms bonded to the same Ru, at higher coverages. The decomposition temperature increases with coverage, giving evidence in favour of a stabilizing effect of acetate ions and decomposition products on neighbour adsorbed acetates. For high enough coverages, adsorbed acetate was still detected at 500 K, proving the high stability of this surface species on Ru(0001). The adsorption of deuterated acetic acid gave consistent results, although dissociative adsorption starts occurring at 123 K and complete dehydrogenation occurs at 133 K, ∼10 K above the respective temperatures for acetic acid.

Thermal reactions of acetic acid: 13C/ 12C partitioning between CO 2 and CH 4

Analysis of the gaseous products from the thermal decomposition of acetic acid in the temperature range of 290 to 650°C shows CO 2 contents to decrease from 94 to 2% and CH 4 and CO contents to increase from 4 to 87% and 1 to 11% respectively. Ethane contents maximise at 1.6% at 500°C. Δ 13C(CO 2 CH 4)‰ values at all reaction temperatures closely approximate those theoretically predicted at isotopic equilibrium and, by extrapolation, those commonly observed in natural gases of biogenic origin. The bulk isotopic composition of these product gases at all reaction temperatures reflects that of the acetic acid starting material, thus supporting the concept of isotope partitioning in a transition stage.

Photocatalytic decomposition of acetic acid on TiO2

During room‐temperature transient experiments, acetic acid decomposes photocatalytically on TiO2 in an inert atmosphere by two parallel pathways. One pathway forms CO2 and C2H6 in a 2:1 ratio, and H2O forms with lattice oxygen that was extracted from the surface. The other pathway forms CO2 and CH4 in a 1:1 ratio.

Transient oxidation of volatile organic compounds on aCuO/Al 2O 3 catalyst

Temperature-programmed desorption (TPD) and oxidation (TPO) were used to study decomposition and oxidation of methanol, ethanol, acetaldehyde, formic acid, and acetic acid on aCuO/Al 2O 3 catalyst. The volatile organic compounds (VOCs) were adsorbed on the alumina surface and diffused to the CuO to react. Lattice oxygen in CuO is active for deep oxidation, and as lattice oxygen is depleted, diffusion of lattice oxygen to the surface limits the rate of oxidation. Supported CuO dehydrogenates and oxidizes VOCs and the order of reactivity is: HCOOH > CH 3OH > CH 3COOH > C 2H 5OH > C 2H 4O. Nearly all the oxygen in CuO can be extracted by VOCs. In the absence of gas-phase O 2, extraction of lattice oxygen limits the oxidation rates of acetaldehyde and acetic acid, but gas-phase O 2 rapidly replenishes the lattice oxygen. No less-reactive, partial oxidation products were detected.

Photocatalytic effect in platinum doped titanium dioxide films

The photocatalytic effect has a major role in the purification of water, air and solar energy conversion in modern technology. Platinum dispersed titanium dioxide films were prepared on silica and Corning glass 7059 substrates at 200 °C substrate temperature for various compositions. The photocatalytic activity of the films was studied by the decomposition of acetic acid under UV irradiation. X-ray analysis revealed that the formation of the anatasa phase in the films contributed to their increase in activity; this activity increase was observed with a platinum content of 1.3%. The film morphology showed that reduction of the platinum content enhanced the photocatalytic effect and reduced the grain size in the film.

Oxidation of volatile organic compounds on a Ag/Al 2O 3 catalyst

Temperature-programmed desorption (TPD) and oxidation (TPO) were used to study decomposition and oxidation of methanol, ethanol, acetaldehyde, formic acid, and acetic acid on an Ag/Al 2O 3 catalyst. The volatile organic compounds (VOCs) were adsorbed on the alumina support. Silver was inactive for decomposition of adsorbed VOCs; all dehydration and dehydrogenation products evolved from reaction on the Al 2O 3 support during TPD. Silver was active for oxidation of VOCs during TPO, however, and a portion of the VOCs reacted on Al 2O 3 sites in parallel. Adsorbed VOCs reacted at silver sites with adsorbed oxygen; oxygen was supplied to silver sites from the gas phase, and surface diffusion on Al 2O 3 transported adsorbed VOCs to the silver sites. Adsorbed oxygen also activated neighboring silver sites for alcohol dehydrogenation in parallel with oxidation. Dehydrogenation was not observed for the aldehyde and acids.

Oxidation of Volatile Organic Compounds on Al2O3, Pd/Al2O3, and PdO/Al2O3Catalysts

Temperature-programmed desorption (TPD) and oxidation (TPO) were used to study the decomposition and oxidation of methanol, ethanol, acetaldehyde, formic acid, and acetic acid on Al2O3, Pd/Al2O3, and PdO/Al2O3catalysts. The oxidation and decomposition rates were much higher on Pd/Al2O3than on Al2O3, even though the volatile organic compounds (VOCs) were adsorbed on the Al2O3support in both cases. The VOCs surface-diffused to Pd and mostly dehydrogenated during TPD whereas they oxidized to CO2and H2O in the presence of oxygen. Partial oxidation products also apparently formed on the surface during TPO and they oxidized completely above 550 K. Above 600 K, VOCs oxidation was consistent with the Mars–van Krevelen mechanism, involving the oxidation and reduction of Pd and PdO. On PdO/Al2O3adsorbed VOCs were oxidized by lattice oxygen from PdO, but PdO was less active than Pd metal for VOC decomposition. Oxidation began at the same temperatures on PdO/Al2O3whether or not O2was present, indicating that extraction of lattice oxygen from PdO was the limiting factor initially. After lattice oxygen was removed, metallic Pd decomposed VOCs and also adsorbed O2, which was incorporated into the Pd lattice above 600 K. The reduction of PdO during TPD resulted in an autocatalytic oxidation since metallic Pd was more active than PdO. A portion of the VOCs reacted in parallel on Al2O3since these sites are active for dehydration and dehydrogenation at moderate to high temperatures.

TiO2 coating photocatalysts with nanostructure and preferred orientation showing excellent activity for decomposition of aqueous acetic acid

TiO2 coatings are attractive materials for use as photocatalysts, photoelectrodes and solar cells. Structural modification, quantum size effects, and large surface-to-volume make the coatings interesting. We have described the effects of crystal strucmre [1], crystallinity [2] and morphology [3] of TiO2 coatings on photocatalytic properties, and shown that a TiO2 coating prepared from a chemically-modified alkoxide solution had characteristic structur.es [4]. Here we report the photocatalytic properties of TiO2 coatings prepared by the chemically modified alkoxide method, which have nanostructure and show preferred orientation along the c axis. We also report the effect of oxygen vacancies in the TiO2 coatings on the photocatalytic properties. Decomposition of acetic acid is a very important reaction because during decomposition acetic acid usually generates organic compounds containing more than two carbons. Decomposition of aqueous acetic acid by use of oxygen and photocatalysts is lcnown to proceed differently from the photo-Kolbe reaction [5] with a product of ethane. During the photocatalytic decomposition of aqueous acetic acid with oxygen, formaldehyde is generated as an intermediate compound and this oxidizes readily to carbon dioxide. Chemical oxygen demand (COD) decreases to zero characteristically in the process. Therefore, the photocatalytic decomposition of aqueous acetic acid with oxygen is a key reaction for purification and treatment of water. T iQ coatings were prepared by the chemically modified alkoxide method. The method has been described in detail elsewhere [4]. The precursor solution for the coatings was prepared from titanium tetraisopropoxide, anhydrous el:hanol, diethanol amine, water and polyethylene glycol (molecular weight; Mw = 2000). The concentration of titanium tetraisopropoxide in ethanol was 0.5 mol dm -3. The molar ratios of water and diethanolamine to titanium tetraisopropoxide were 1 and 2, respectively. The concentration of polyethylene glycol to titanium tetraisopropoxide was 20 wt%. Gel coating, which was prepared on a quartz glass plate by a dip-coating method, crystallized to anatase during elevation on

Reaction Mechanism of the Decomposition of Acetic Acid on Illuminated TiO2 Powder Studied by Means of in Situ Electron Spin Resonance Measurements

The existence of methyl radicals in the photo-Kolbe reaction was confirmed by means of in situ measurements with flow electron spin resonance for deuterated acetic acid. From the dependence of the flow rate, two reaction paths were deduced for methyl radical formation. These were assigned to those caused by trapped holes and •OH radicals. It is suggested that the former path is dominant when platinum has not been loaded onto TiO2 powder.

Self-acceleration in the decomposition of acetic acid on Rh{111}: a combined TPD and laser induced desorption study

Adsorption of acetic acid at 130 K on Rh{111} produces the following phases: multilayers (130–200 K); a mixed acetate/hydrogen monolayer (220–280 K); an acetate monolayer after desorption of hydrogen (> 300 K); and decomposition of acetate into hydrogen and carbon dioxide (∼ 400 K). Room temperature saturation of the clean surface and 200 K saturation of the surface with preadsorbed oxygen and/or potassium leads to sharp H 2 and CO 2 temperature-programmed-desorption (TPD) peaks, which are characteristic of self-accelerating processes. Oxygen is found to stabilize the acetate, causing it to decompose at a higher temperature; potassium destabilizes the acetate, and O K mixtures have an intermediate effect. The results in the absence of co-adsorbed species are discussed in terms of a simple two-step empty-site-creation autocatalytic mechanism for systems in which most of the surface is initially fully saturated with adsorbate species. This mechanism is verified by laser-induced thermal decomposition and desorption. In the presence of co-adsorbates (O and/or K), mixed acetate-coadsorbate dense phases formed on the surface cause the acetate to decompose in an autocatalytic manner, and both electronic interactions as well as site blocking influence the desorption temperature.

Theoretical Investigation of Competing Mechanisms in the Thermal Unimolecular Decomposition of Acetic Acid and the Hydration Reaction of Ketene

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheoretical Investigation of Competing Mechanisms in the Thermal Unimolecular Decomposition of Acetic Acid and the Hydration Reaction of KeteneXiaofeng Duan and Michael PageCite this: J. Am. Chem. Soc. 1995, 117, 18, 5114–5119Publication Date (Print):May 1, 1995Publication History Published online1 May 2002Published inissue 1 May 1995https://doi.org/10.1021/ja00123a013RIGHTS & PERMISSIONSArticle Views441Altmetric-Citations56LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (636 KB) Get e-Alerts Get e-Alerts

Mechanisms of decomposition of acetic acid by methane-producing bacteria in submerged paddy soil

Abstract During most of the rice season in Japan, paddy fields are usually flooded with irrigation water. Although fresh organic materials such as rice straw are important elements for rice cultivation, their incorporation into flooded paddy fields sometimes inhibits the growth of rice plant. Especially in cool areas, the accumulation of acetic acid (AA), which is generated as intermediate product of the decomposition of organic matter, is considered to be responsible for this inhibition (Takijima 1963). The AA produced in submerged paddy soil is decomposed by anaerobic bacteria such as methane-producing bacteria (MPBs) (Hori et al. 1990). To control the accumulation of AA in paddy soil, therefore, the role of MPBs in the decomposition of AA needs to be analyzed.