Catalytic Combustion Of Toluene Research Articles

Catalytic oxidation of dichloromethane and toluene over platinum alumite catalyst

Catalytic oxidation technology is one of the most promising technologies for the reduction of volatile organic compound (VOC) emissions. It is very necessary to study the catalytic oxidation of mixture of VOCs and volatile organic compounds (CVOCs), because VOCs are always emitted accompanying with CVOCs. Hence, the catalytic oxidation reaction of toluene and CH 2Cl 2 is explored on a platinum alumite catalyst in this work. The results show that the addition of toluene has no effect on the decomposition of CH 2Cl 2, although it can suppress CH 3Cl formation because the steam generated from the catalytic combustion of toluene suppresses the formation of CH 3Cl from CH 2Cl 2. High concentrations of CH 2Cl 2 have a negative effect on the catalytic combustion of toluene.

Influence of physicochemical treatments on iron-based spent catalyst for catalytic oxidation of toluene

The catalytic oxidation of toluene was studied over an iron-based spent and regenerated catalysts. Air, hydrogen, or four different acid solutions (oxalic acid (C 2H 2O 4), citric acid (C 6H 8O 7), acetic acid (CH 3COOH), and nitric acid (HNO 3)) were employed to regenerate the spent catalyst. The properties of pretreated spent catalyst were characterized by the Brunauer Emmett Teller (BET), inductively coupled plasma (ICP), temperature programmed reduction (TPR), and X-ray diffraction (XRD) analyses. The air pretreatment significantly enhanced the catalytic activity of the spent catalyst in the pretreatment temperature range of 200–400 °C, but its catalytic activity diminished at the pretreatment temperature of 600 °C. The catalytic activity sequence with respect to the air pretreatment temperatures was 400 °C > 200 °C > parent > 600 °C. The TPR results indicated that the catalytic activity was correlated with both the oxygen mobility and the amount of available oxygen on the catalyst. In contrast, the hydrogen pretreatment had a negative effect on the catalytic activity, and toluene conversion decreased with increasing pretreatment temperatures (200–600 °C). The XRD and TPR results confirmed the formation of metallic iron which had a negative effect on the catalytic activity with increasing pretreatment temperature. The acid pretreatment improved the catalytic activity of the spent catalyst. The catalytic activity sequence with respect to different acids pretreatment was found to be oxalic acid > citric acid > acetic acid ≥ nitric acid > parent. The TPR results of acid pretreated samples showed an increased amount of available oxygen which gave a positive effect on the catalytic activity. Accordingly, air or acid pretreatments were more promising methods of regenerating the iron-based spent catalyst. In particular, the oxalic acid pretreatment was found to be most effective in the formation of FeC 2O 4 species which contributed highly to the catalytic combustion of toluene.

Toluene combustion on γ-Al 2O 3–CeO 2 catalysts prepared from boehmite and cerium nitrate

γ-Al 2O 3–Ce catalysts were obtained by the impregnation of boehmite with cerium nitrate at different Ce contents (1, 5, 10, 20 wt%) and tested in the catalytic combustion of toluene. The catalysts annealed at 650 °C showed a diminution of the BET specific surface areas as a function of the cerium content. At low cerium content, the XRD spectra showed the γ-Al 2O 3 phase, whereas at high cerium content, the γ-Al 2O 3 phase and cerium oxide were observed. A diminution of the Lewis acidity was shown by the FTIR-pyridine absorption spectra. Both Ce 3+ and Ce 4+in variable proportions were observed by XPS. It has been found that the activity for the toluene combustion can be related to the C 4+/Ce 3+ ratio obtained in the various catalysts. The higher the C 4+/Ce 3+ ratio is the higher the toluene combustion activity.

Catalytic combustion of toluene over platinum supported on Ce–Zr–O solid solution modified by Y and Mn

A series of CeO 2–ZrO 2 mixed oxides were prepared using coprecipitation method and characterized by BET, oxygen storage capacity (OSC), X-ray diffraction (XRD) and H 2-temperature-programmed reduction (H 2-TPR). The catalytic activities toward toluene combustion were investigated in a micro-reactor. The results demonstrate that the catalytic activity of Pt/γ-Al 2O 3/Ce 0.50Zr 0.50O 2 monolithic catalyst can be greatly improved by doping metal into Ce 0.50Zr 0.50O 2. When doping Y and Mn into Ce 0.50Zr 0.50O 2 simultaneously, the catalyst Pt/γ-Al 2O 3/Ce 0.40Zr 0.40Y 0.10Mn 0.10O X shows the highest activity. The T 10 (the temperature of 10% toluene conversion) and the complete conversion temperature (the temperature of 90% toluene conversion) of toluene are 443 and 489 K, respectively. Gas hourly space velocity (GHSV) results show that the prepared catalyst can be applied in a wide range of GHSV (from 12,000 to 20,000 h −1). The catalyst prepared shows great potential for practical application.

Preparation and Catalytic Performance of Pd Monolithic Catalysts Supported by Y2O3 Washcoat

Abstract A novel Y 2 O 3 washcoat adhered to the cordierite honeycomb was prepared using Y(NO 3 ) 3 as the precursor. The Y 2 O 3 washcoat is suitable for supported Pd catalysts. Catalytic combustion of toluene and ethyl acetate was conducted as model reactions to evaluate the performance of Pd/Y 2 O 3 catalysts. The catalysts exhibit fairly good catalytic activity and thermal stability. For the catalysts calcined at 500°C, the T 99 of toluene is 210°C. The Y 2 O 3 washcoat and the Pd/Y 2 O 3 catalysts were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, and H 2 -temperature-programmed reduction. The results show that the washcoat has sufficient adhesion and high adsorption efficiency for active species. For the catalysts calcined at higher temperatures (700 and 900°C), the crystallite size of the active species (PdO) increases, which possibly results in a decline in the catalytic activity.

Catalytic combustion of toluene over mixed Cu–Mn oxides

The influence of the synthesis pH and of the Zn and/or Al additives on the Cu–Mn precursors, obtained by co-precipitation at a constant pH from aqueous solutions of appropriate nitrates at (Cu + Zn)/(Mn + Al) ratio equal 2, was investigated. The relative content of Mn increased with the pH of precipitation. Depending on the sample composition the identified crystalline phases included layered hydroxy double salt, hydrotalcite-like structure, CuO and ZnO. Some precursors had strongly amorphous character. Calcination of the precursors at 673 K resulted in mixed oxides, in which CuO of various degrees of crystallinity could be identified. The Mn-containing phases remained amorphous. All calcined materials proved extremely active in catalytic combustion of toluene. Some catalysts reached 100% conversion already at 403 K. High conversions observed in the low temperature regime were partially due to the strong sorption of toluene. In the catalysts containing Al additive this effect was suppressed.

Improvement of toluene catalytic combustion by addition of cesium in copper exchanged zeolites

HY and HMFI zeolites exchanged with copper and cesium have been studied for the catalytic combustion of toluene (800ppm) with air. The catalysts activity has been analyzed by comparison of light-off curves and in both Cu zeolites, the addition of Cs leads to a decrease of the light-off temperature by 50°C. Temperature-programmed reduction (H2-TPR) and EPR studies have evidenced clear differences in the characteristics of the copper species both in the presence and absence of Cs co-cations. These differences account for the nature of the active centers in the Cu zeolites for the toluene oxidation. The position and geometry of the copper ions in the zeolite matrix are of great significance for the redox behavior and activity for toluene oxidation. In both MFI and FAU structures, the bulky Cs co-cations are located in the more accessible main zeolite pores, forcing the copper ions to occupy the most stable, but less accessible positions within each structure. In the case of the MFI zeolite, the EPR study revealed that the Cs exchange resulted in an increased abundance in the number of square pyramidal Cu2+ ions relative to the other Cu environments. Cs co-cations also lead to an increase in the reducibility of the copper ions mainly due the reduction of protons in Cu, Cs-containing samples.

톨루엔 산화에 의한 CuOx/SnO2-ZrO2촉매의 특성고찰

Catalytic combustion of toluene was investigated on <TEX>$CuOx/SnO_2-ZrO_2\;CuOx/SnO_2\;CuOx/ZrO_2$</TEX> catalysts prepared by impregnation. Characteristics of catalysts loaded on binary support and single support were observed by TPR, TPO, XRD, XPS techniques. The results on catalytic combustion showed that binary supports improve the activity of copper in the combustion of toluene. The reason for high catalytic activity on toluene combustion of <TEX>$CuOx/SnO_2-ZrO_2$</TEX> catalyst was ascribed to oxidation<TEX>$\cdot$</TEX>reduction activity at low temperatures and stability of oxidation state after reduction.

Kinetics of catalytic combustion in air over Pt/Al2O3/Al catalyst

Catalytic combustion of toluene, propylene and CO over Pt/Al2O3 /Al catalyst was investigated. Strong inhibition effects are observed when the mixture of toluene, propylene and CO is oxidized. A reaction mechanism of catalytic combustion over Pt/Al2O/Al is proposed. The results from kinetic models are in good agreement with the experimental data.

Catalytic combustion of toluene on platinum-containing monolithic carbon aerogels

Monolithic organic aerogels were prepared by the sol–gel procedure from the polymerisation reaction of resorcinol and formaldehyde in water. The organic aerogels were heat treated in inert atmosphere at either 500 or 1000°C to obtain the carbon aerogels. The catalysts were prepared by impregnation with an aqueous solution of [Pt(NH3)4]Cl2 or by dissolving this salt in the initial aerogel mixture. Supported catalysts were pretreated in He at 400°C or H2 at 300°C before their characterization by H2 chemisorption, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy or before testing their catalytic activity. Catalyst activities in toluene combustion were evaluated by conversion versus temperature (light-off curves) and conversion versus time catalytic tests. In the case of catalysts prepared by impregnation, the light-off curves for the total combustion of toluene were shifted to lower temperatures with increasing Pt particle size. This suggests that the reaction was sensitive to the Pt structure within the dispersion range of these catalysts. However, the reverse occurred with catalysts prepared by mixing the precursor in the initial aerogel mixture. Results found could be due to the different surface Pt content of these catalysts as revealed by X-ray photoelectron spectroscopy. This difference was related to the growth of large three-dimensional Pt particles on the surface of the less dispersed catalyst. This means that there is a critical Pt particle size above which the toluene combustion activity decreases with increasing Pt particle size, due to the reduction in active surface sites available for the combustion reaction. Other effect that might influence the activity of these last catalysts is the encapsulation of some Pt particles by the carbon matrix.

Activated carbon and tungsten oxide supported on activated carbon catalysts for toluene catalytic combustion.

We have used activated carbon (AC) prepared from almond shells as a support for tungsten oxide to develop a series of WOx/AC catalysts for the catalytic combustion of toluene. We conducted the reaction between 300 and 350 degrees C, using a flow of 500 ppm of toluene in air and space velocity (GHSV) in the range 4000-7000 h(-1). Results show that AC used as a support is an appropriate material for removing toluene from dilute streams. By decreasing the GHSV and increasing the reaction temperature AC becomes a specific catalyst for the total toluene oxidation (SCO2 = 100%), but in less favorable conditions CO appears as reaction product and toluene-derivative compounds are retained inside the pores. WOx/AC catalysts are more selective to CO2 than AC due to the strong acidity of this oxide; this behavior improves with increased metal loading and reaction temperature and contact time. The catalytic performance depends on the nonstoichiometric tungsten oxide obtained during the pretreatment. In comparison with other supports the WOx/AC catalysts present, at low reaction temperatures, higher activity and selectivity than WO, supported on SiO2, TiO2, Al2O3, or Y zeolite. This is due to the hydrophobic character of the AC surface which prevents the adsorption of water produced from toluene combustion thus avoiding the deactivation of the active centers. However, the use of WOx/AC system is always restricted by its gasification temperature (around 400 degrees C), which limits the ability to increase the conversion values by increasing reaction temperatures.

Catalytic oxidation of toluene on Mn–containing mixed oxides prepared in reverse microemulsions

Catalytic combustion of toluene over Mn–containing mixed oxides has been investigated. The catalysts have been prepared by reverse microemulsion method and characterized by XRD, SEM and TPR. It is found that catalytic conversion of toluene on the Mn–Zr mixed oxides prepared by reverse microemulsion method is much higher than that on the Mn–Zr mixed oxides prepared by conventional coprecipitation with the same chemical compositions. The catalytic activity gradually increases with an increase of Mn loading on ZrO 2 prepared by reverse microemulsion method. When Mn loading reaches 50 mol%, the total conversion temperature is lowered to 260 °C. Heat treatment of the catalysts leads to the decrease in the activity of toluene conversion, however the toluene conversion remains still high, i.e., 99% at 320 °C after calcination up to 750 °C, which implies the catalyst is highly thermally stable. In addition, Fe–Mn, Co–Mn and Cu–Mn mixed oxides have also been synthesized by reverse microemulsion method, and tested for catalytic oxidation of toluene. Among these metal oxides, the Cu–Mn catalyst is found to give the highest activity for complete oxidation of toluene. Mn 0.67–Cu 0.33 (Cu loading 33 mol%) shows the total oxidation of toluene at about 220 °C, which is very close to the activity of the widely investigated Pd catalyst for the reaction.

Toluene combustion over palladium supported on various metal oxide supports

Metal–support interaction in the catalytic combustion of toluene was studied using metal oxides with different acid–base properties as supports for Pd. The catalytic performance was correlated with XPS data and the reaction order for oxygen. These studies revealed that the affinity for oxygen of Pd surface changed according to the acid–base character of metal oxide over MgO, Al2O3, SiO2, SnO2, Nb2O5, and WO3. However, ZrO2 exhibited exceptional character in that metal Pd was unusually stabilized, which was derived from the weak interaction between Pd and support surface. The reason for high toluene combustion activity of Pd/ZrO2 was ascribed to the stabilization of metal Pd on ZrO2.

Influence of acid–base property of support on the toluene combustion activity of palladium

Metal–support interaction in the catalytic combustion of toluene was studied, using metal oxides with different acid–base properties as supports. The combustion activity over Pd loaded on strong acidic or basic support was lower than over Pd on weak acidic or basic metal oxides. The study of Pd surface with X-ray photoelectron spectroscopy and reaction order measurement showed that the affinity for oxygen changed according to the acid–base property of support. It was considered that the combustion activity of Pd was controlled by the acid–base property of support through an electronic interaction.

Direct post-thaw dilution of mouse embryos frozen in a solution containing glycerol

Pt/CeO2–ZrO2–Bi2O3/γ-Al2O3 (Pt/CZB/Al2O3) catalysts for the catalytic combustion of toluene, which is one of the volatile organic compounds (VOCs), were prepared by the wet impregnation method in the presence of polyvinyl pyrrolidone (PVP). X-ray powder diffraction, transmission electron microscopy, and BET specific surface area measurement using N2 adsorption have been used to characterize the catalysts. The catalytic test was conducted from room temperature in a flow of 900 ppm of toluene in air and gas hourly space velocity (GHSV) of 8000 h−1. The catalytic activity was evaluated in terms of C7H8 conversion and the gas composition after the reaction was analyzed using two gas chromatographs with a flame ionization detector (FID) and a thermal conductivity detector (TCD). The Pt/CZB/Al2O3 catalysts are specific for the total toluene oxidation and CO and any toluene-derivative compounds were not detected as by-products. The specific surface area of the catalysts was increased by the addition of PVP in the preparation process. By the optimization of the amount of platinum, complete oxidation of toluene was realized at a temperature as low as 120 °C on a 7 wt%Pt/16 wt%Ce0.64Zr0.15Bi0.21O1.895/γ-Al2O3 catalyst.