Isopropanol Decomposition Research Articles

Gold and gold–iron modified zeolites—Towards the adsorptive deodourisation

Zeolites exhibiting different structures (Y, Beta, and ZSM-5) were modified with gold and iron and applied for odour adsorption from the air containing dibutyl sulphide (Bu 2S) used as a representative odour producing compound. The structure of the zeolites used determines the rate of adsorption (higher on Y type zeolites and smaller on two other zeolites), whereas hydrophilicity affects the selectivity towards Bu 2S adsorption increasing in the order: Y < Beta < ZSM-5. For the same zeolite structure, Bu 2S adsorption selectivity depends on the total acidity of zeolites which increases after iron modification. The texture and surface properties of the modified zeolites were studied by XRD, XPS, UV–vis, TEM, pyridine adsorption and FTIR, test reactions (acetonylacetone cyclisation, isopropanol decomposition).

Nb-doped hematites for decomposition of isopropanol: Evidence of surface reactivity by in situ CO adsorption

A series of Nb-containing hematites, Fe 2− x Nb x O 3 (%Nb = 0.00, 1.49, 5.00 and 9.24) were prepared using a conventional co-precipitation method. Room-temperature Mössbauer spectroscopy and powder X-ray diffraction measurements suggested the formation of a crystalline phase with partial substitution of Fe 3+ by Nb 5+. The reactivity of these Fe 2− x Nb x O 3 materials as catalysts was investigated using the decomposition of isopropanol as a model reaction. Theoretical calculations and CO adsorption monitored by in situ infrared absorption spectroscopy showed that the presence and the position of substituting niobium atoms in the structure of hematite modify its surface properties. The results from this study also show that the presence of Nb changes the catalytic properties toward a preferential formation of propene, presumably because of the addition of oxygen vacancies. All catalysts show high catalytic activity, and reach total isopropanol conversion above 375 °C. Moreover, the material with high Nb content reaches total conversion at lower temperatures, at approximately 290 °C with conversion to propene of 92%.

Photocatalytic Properties of TiO2 Nanostructures Fabricated by Means of Glancing Angle Deposition and Anodization

Structural, optical, and photocatalytic properties of various nanostructures prepared by glancing angle deposition (GLAD) and by electrochemical anodic oxidation of Ti have been studied. The nanorods were prepared on unheated glass substrates by using reactive sputtering of Ti in the GLAD regime. nanotubes and brush-type nanostructures were fabricated by anodic oxidation of flat Ti films and Ti nanorods prepared by GLAD, respectively. The optical studies revealed that the nanotubes and brush-type nanostructures possess antireflection properties. The photocatalytic activity of nanostructures was characterized by following decomposition of isopropanol under visible and UV light irradiation and found to be significantly higher in nanostructured samples than in their flat counterparts. Also, nanotubes and brush-type nanostructures showed superior photocatalytic activity in comparison with nanorods due to a significantly higher specific surface area.

Applying spray pyrolysis to synthesize MnO x for decomposing isopropyl alcohol in ozone- and thermal-catalytic oxidation

Manganese oxides (MnOx) were prepared by spray pyrolysis methods (MnS) and calcination at 600 and 1,000 o C (Mn600 and Mn1000) in this study. Further, the efficiencies of oxidizing isopropanol (IPA) by these MnOx utilizing ozone (OZCO) and thermal catalytic oxidation (TCO) were compared. The results indicated that MnS, which are char- acterized by larger surface areas, processed gas hourly space velocity of 42,000 h −1 and inlet IPA concentration of 400 ppm performing IPA decomposition efficiencies approaching 100%, and the reaction temperature was operated at only 85 o C for OZCO. The reaction temperature of TCO operated above 270 o C decomposed IPA at the same efficiency.

Anomalous diffusion during isopropanol decomposition on (ZrO 2) 1− x (CeO 2) x catalysts

In this work the effect of composition of (ZrO 2) 1− x (CeO 2) x catalysts on the ratio γ = E c/ E d between the activation energies for the isopropanol decomposition, estimated in the chemical reaction ( E c) and the diffusion ( E d) controlled regimes, was studied. The solid catalysts with x = 0.0; 0.2; 0.5; 0.8 and 1.0 were prepared by heating the precursors at 400, 600 and 800 °C and characterized by N 2 porosimetry, X-ray diffraction, SEM/EDS analysis and NH 3/TPD. Their catalytic activity for the decomposition of isopropanol in the temperature range 200–400 °C was probed in a tubular flow reactor. The estimated Arrhenius plots showed a distinct and well-defined change of slopes corresponding to alternation from the chemical to the internal diffusion-controlled regime of the process. The ratio γ = E c/ E d of the corresponding activation energies was found equal to γ ≈ 1 for x = 0.0, meaning total lack of diffusion limitations, and converges to γ ≈ 2 for x = 1.0, corresponding to classical internal diffusion control. For 0 < x < 1 the values of 1 < γ < 2 signify anomalous diffusion related linearly to some compositional property of the (ZrO 2) 1− x (CeO 2) x catalysts. The origin of this phenomenon is discussed in relation to the variable binding strength and friction of movement of the isopropanol species on the more active ZrO 2 and the less active CeO 2 nanoparticles of the solid catalysts.

Effects of Silver on the Photocatalytic Degradation of Gaseous Isopropanol

The decomposition of gaseous isopropanol (IPA) by UV/TiO2 process in an annular photoreactor was studied under various conditions such as UV light intensity and inlet IPA concentrations. In order to impede the rapid electron/hole recombination during photoreaction, the Ag deposited on TiO2 photocatalysts were prepared by a photodeposition process. This study was aimed at applying the photocatalytic oxidation using the Ag/TiO2 and pure TiO2 catalysts to remove gaseous IPA. The PL analyses indicated that the silver on the surface of TiO2 could inhibit the electron/holes recombination. For experiments conducted with gaseous IPA under UV light irradiation, the photocatalytic activity of Ag deposited TiO2 surface was significantly superior to that of TiO2 only ones.

Catalytic performance of porous carbons obtained by chemical activation

Porous carbons were prepared by the pyrolysis of pinewood in nitrogen at 773 K, followed by chemical activation using different concentrations of KOH in nitrogen at 973 K. Both water-washed and acid-washed samples exhibited much higher specific surface areas than unactivated carbon. The water-washed sample showed strong basicity and a high catalytic performance in the decomposition of isopropanol, even higher than superbase 26%KNO 3/γ-Al 2O 3. Moreover, these porous carbons can act as water-resistant solid bases. The formation of the insoluble basic sites is most possibly related to the intercalation of potassium in the carbon during the chemical activation.

Activated Carbon Modified with Different Chemical Agents as a Catalyst in the Dehydration and Dehydrogenation of Isopropanol

Activated carbons modified with different chemical agents such as HNO3, H2SO4, peroxyacetic acid (PAA), air, NH3 and Cl2 have been tested as catalysts in decomposition (dehydration and dehydrogenation) of isopropanol. The majority of the samples obtained have been characterised by well-developed microporous surface with a small contribution of mesopores (8–18%). The influence of the surface area of the samples on their catalytic performance has been insignificant. The carbon oxidation with oxidants in the liquid or gas phase leads to an increased catalytic activity and the dominant process is dehydration of the alcohol studied. Carbon modification by contact with gas ammonia or chlorine results in a decrease in the catalytic activity and a significant increase in the contribution of dehydrogenation of isopropanol. It has been shown that such behaviour of the catalysts has been a consequence of changes in the acid-base character of the carbons induced by their modification.

A visible light-sensitive tungsten carbide/tungsten trioxde composite photocatalyst

A photocatalyst composed of tungsten carbide (WC) and tungsten oxide (WO3) has been prepared by the mechanical mixing of each powder. Its photocatalytic activity was evaluated by the gaseous isopropyl alcohol decomposition process. The photocatalyst showed high visible light photocatalytic activity with a quantum efficiency of 3.2% for 400–530nm light. The photocatalytic mechanism was explained by means of enhanced oxygen reduction reaction due to WC, which may serve as a multielectron reduction catalyst, as well as the photogeneration of holes in the valence band of WO3.

The oxidation study of 2-propanol using ozone-based advanced oxidation processes

In the present study, advanced oxidation processes (AOPs) have been successfully used to decompose isopropyl alcohol (IPA). IPA degradation and its major degradation intermediate, acetone formation and total organic carbon (TOC) removal efficiency were studied using O 3, O 3/UV, H 2O 2/UV, H 2O 2/O 3, and H 2O 2/O 3/UV processes at various physico-chemical conditions. Complete degradation of IPA was noted in AOPs whereas complete acetone decomposition was not observed under the experimental conditions. Ozonation process was strongly enhanced in the presence of UV light, H 2O 2 or in the presence of both oxidants. Ozonation process in the presence of UV light enhancement about 11%, 15%, 28% of IPA decomposition and 20%, 23%, 0% of TOC removal was observed at pH 3, 7, and 10. Similarly, in the presence of H 2O 2 (0.25 g/g) further enhancement of 31%, 50%, 18% of IPA degradation and 26%, 30%, 27% of TOC removal at 180 min was noted at pH 3, 7, and 10, respectively. UV/H 2O 2 process was found to be the least efficient and UV/H 2O 2/O 3 was the most efficient process compared to all other selected AOPs. Acetone was identified as a primary degradation intermediate and subsequently acetic acid, formic acid, and oxalic acid were identified as secondary intermediates. It was concluded that ozone-based AOPs were efficient for IPA degradation in wastewater.

Ozone Transfer and Decomposition of Isopropyl Alcohol by H2O2/Ozone Process in a Rotating Packed Contactor

AbstractOzone transfer and decomposition of isopropyl alcohol in aqueous solution by H

Síntese, caracterização e avaliação catalítica de Vo x/Mg yAlo x na reação de decomposição do isopropanol

Vanadium oxide supported on hydrotalcite-type precursors was studied in the decomposition of isopropanol. Hydrotalcite-type compounds with different y = Mg+2/Al+3 ratios were synthesized by the method of coprecipitating nitrates of Mg+2 and Al+3 cations with K2CO3 as precipitant. The X-ray diffraction patterns of Al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. It was shown that chemical composition, texture, acid-base properties of the active sites and also Mg/Al ratio strongly affect the formation of the products in the oxidation of isopropanol. The Al-rich catalysts were much more active than the Mg-rich ones, converting isopropanol mainly to propylene.

Multiple Functionalization of Mesoporous Silica in One‐Pot: Direct Synthesis of Aluminum‐Containing Plugged SBA‐15 from Aqueous Nitrate Solutions

AbstractAluminum‐containing plugged mesoporous silica has been successfully prepared in an aqueous solution that contains triblock copolymer templates, nitrates, and silica sources but without using mineral acid. The acidity of the solution can be finely tuned from pH 1.4 to 2.8 according to the amount of the introduced aluminum species which ranged from an Al/Si molar ratio of 0.25/1 to 4.0/1. The aluminum nitrate additive in the starting mixture, along with the weak acidity produced by the nitrates, contributes to the formation of plugged hexagonal structures and the introduction of different amounts of aluminum species into the mesostructure. Characterization by X‐ray diffraction, transmission electron microscopy, and N2 sorption measurements show that the Al‐containing plugged silicas possess well‐ordered hexagonal mesostructures with high surface areas (700–860 m2 g–1), large pore volume (0.77–1.05 cm3 g–1) and, more importantly, combined micropores and/or small mesopores in the cylindrical channels. Inductively coupled plasma–atomic emission spectrometry results show that 0.7–3.0 wt % aluminum can be introduced into the final samples. 27Al MAS NMR results display that about 43–60% aluminum species are incorporated into the skeleton of the Al‐containing silicas and the amount of the framework aluminum increases as the initial added nitrates rises. Scanning electron microscopy images reveal that the directly synthesized Al‐containing plugged silica has a similar morphology to that of traditional SBA‐15. Furthermore, the Al‐containing plugged samples have excellent performances in the adsorption and the catalytic decomposition of isopropyl alcohol and nitrosamine. Finally, the direct synthesis method is used to produce plugged mesoporous silicas that contain other metals such as chromium and copper, and the resultant samples also show good catalytic activities.

Synthesizing nanocrystal-assembled mesoporous magnesium oxide using cotton fibres as exotemplate

A novel biomorphic nanocrystal-assembled mesoporous (NAM) magnesium oxides have been synthesized via an exotemplating pathway using cotton fibres as template and magnesium acetate as MgO precursor. These mesoporous MgO materials replicate the microtubular or zonal structure of the cotton morphology, and their frameworks are constructed by plenty of uniform MgO nanocrystals, which are different from those of the cotton template and reference MgO prepared by directly thermal-decomposition of MgO precursor. The mesoporous structure with narrow slit-like pores can be formed, if suitably chosen amounts of precursor magnesium acetate are used. These biomorphic NAM MgO materials have high surface areas, exhibit high selectivity in the catalytic decomposition of isopropanol, and display their potential for an effective basic catalyst or support.

Photocatalytic Oxidation of Isopropanol in Aqueous Solution Using Perovskite‐Structured La2Ti2O7

AbstractThis study is focused on the application of a highly‐doped layered perovskite, La2Ti2O7, as the photocatalyst for the photocatalytic decomposition of isopropanol (IPA). The La2Ti2O7 powder prepared by solid state reaction was characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), UV‐Vis diffuse reflectance spectrophotometry (UV‐DRS), X‐ray photoelectron spectroscopy (XPS), and zeta potential. The temporal behavior of the photocatalytic decomposition of IPA in aqueous solution by the UV/La2Ti2O7, with a photoreactor operated in a recirculation mode, was studied under various conditions including solution pH, light intensity, and La2Ti2O7 loading. The decomposition of IPA in aqueous solution by La2Ti2O7 photocatalytic processes was found to be technically feasible. A kinetic equation was developed for modeling the photocatalytic decomposition of IPA by the UV/La2Ti2O7 photocatalytic processes.

Phosphated Alumina Catalysts: Surface Properties and Reactivity towards 2-PrOH Decomposition

Summary. The influence of the type of precursor, the phosphate content, as well as the source of phosphate ions on the surface texture, acidity, and catalytic activity of phosphated aluminas has been described. Phosphated alumina catalysts were prepared by impregnating two different precursors with two different sources of phosphate in different loading levels w ¼ 3, 6, and 10% PO4 3� . The characterisation of the catalyst was performed using X-ray powder diffraction (XRD), thermal analysis (TG), and nitrogen adsorption–desorption methods at 77 K. The surface acidity of the catalysts has been studied by FT-IR spectroscopy of adsorbed pyridine at different temperatures. Moreover, the activity in the catalytic decomposition of isopropanol (2-PrOH) has been investigated at 520 K. Investigation of the surface properties shows that the addition of phosphate ions does not change the crystal phase (� -phase) and the samples prepared from gel and phosphoric acid have the highest surface area. An FT-IR study of pyridine adsorption shows both Lewis and Bronsted acid sites on the surface of the samples prepared from gel, while only Lewis acid sites are detected on the samples prepared from crystalline oxide. The catalytic activity by 2-PrOH conversion shows that the conversion of 2-PrOH as well as the selectivity towards propene formation increases from w ¼ 3t o 6% followed by a decline for w ¼ 10%. Moreover, the strongest activity was detected in case of phosphated alumina gel with w ¼ 6% which gives 97.3% propene and 96.1% conversion of 2-PrOH.

Epoxidation of propylene with nitrous oxide on Rb 2SO 4-modified iron oxide on silica catalysts

The catalytic activity of alkaline and earth alkaline-modified silica-supported metal oxide was investigated for epoxidizing propylene with nitrous oxide. Iron oxide gave the best results, and surprisingly chromium oxide also produced propylene oxide (PO). Unmodified iron oxide catalyst showed low oxidation activity and produced propanal (57% selectivity) in concert with small amounts of acrolein, allyl alcohol, and acetone. After modification, the oxidation rate increased significantly, with PO the principal product. PO selectivities up to 85–90% and space–time yields of 0.25–0.53 mmol PO g −1 h −1 were obtained over supported iron oxide modified with Rb 2SO 4. A high throughput composition study revealed that other alkali and earth alkali salts were less effective modifiers. Isopropanol decomposition demonstrated that Rb 2SO 4 severely reduced the acidity of the catalyst. As a result of the neutralization, PO isomerization was drastically reduced. Accordingly, when feeding PO instead of propylene with N 2O over the catalyst, a similar reduction of consecutive PO reactions was observed on Rb 2SO 4 modification. Despite the excellent epoxidation results, a catalytic process remains infeasible due to the restricted service time of the catalyst. Thermogravimetric analyses of a spent catalyst showed carbonaceous residues, suggesting that cokes deactivate the catalyst. Feeding PO indicates that PO itself is a source of cokes. Catalyst regeneration is possible without significant loss of performance. UV–vis DRS and EPR were used to determine the local environment of Fe 3+ in the (un)promoted iron oxide catalyst; the findings suggest well-dispersed distorted tetrahedral Fe 3+ sites for epoxidation activity. Fe dispersion is ruled by the promoter salts, with both anions and cations being essential. Along with the structural influences, inspection of the catalytic data in concert with XPS and Raman analyses provides evidence of a direct (electronic) promoter effect on the catalytic activity.

Synthesis of mixed silica–titania by the sol–gel method using polyethylenimine: porosity and catalytic properties

By means of the sol–gel method, hybrid xerogels of silica, titania and silica–titania mixed networks of different composition with polyethylenimine (PEI) were formed. After removal of PEI followed by calcination, mesoporous oxides of high surface area with monomodal and narrow porosity distribution were obtained. The surface area of the mixed oxides decreases with increasing titania content, but pore size remains almost constant when a PEI:(SiO2 + TiO2) ratio of 1 is kept constant in the xerogel precursor. By doubling and tripling the proportion of PEI, the surface area increases by 15% and 30%, respectively, but pore size remains constant, indicating the formation of a larger number of PEI domains of similar size in the hybrid. Isopropanol decomposition reactions were carried out using the mixed oxides as catalysts, and it was found that the networks contain Lewis acid sites but lack Bronsted acid sites.

Effect of Platinum on the Decomposition Efficiency and Apparent Quantum Yield of Photocatalysis of Isopropanol in an Annular Photoreactor

AbstractPhotocatalytic decomposition of isopropanol (IPA) in air stream in a continuous TiO

An FT-IR study of the adsorption of isopropanol on calcined layered double hydroxides containing isopolymolybdate

The acid–base and red–ox properties of amorphous magnesium and zinc molybdates obtained through calcination at 400 °C of Mg 2Al- and Zn 2Al-heptamolybdate layered double hydroxides, which had been prepared by anionic exchange from the corresponding nitrate-hydrotalcite precursors, have been studied. Lewis-type acid and basic sites have been detected in both systems, in addition to Brönsted-type acid sites in magnesium molybdate; however, as studied by FT-IR spectroscopy, none of them is strong enough to yield propene through isopropanol decomposition. The higher reducibility of Mo 6+ cations in zinc-containing samples than the magnesium containing ones makes them more selective for acetone production. Moreover, a small amount of products formed on basic sites through acetone aldol reaction have been identified at high reaction temperatures.