Binary Metal Oxide Catalysts Research Articles

Binary metal oxide nanoparticle incorporated composite multilayer thin films for sono-photocatalytic degradation of organic pollutants

We report reduced graphene oxide (rGO) supported binary metal oxide (CuO–TiO2/rGO) nanoparticle (NP) incorporated multilayer thin films based on Layer-by-Layer (LbL) assembly for enhanced sono-photocatalytic degradation of methyl orange under exposure to UV radiation. Multilayer thin films were fabricated on glass and quartz slides, and investigated using scanning electron microscopy and UV–vis spectroscopy. The loading of catalyst NPs on the film resulted in the change of morphology of the film from smooth to rough with uniformly distributed NPs on the surface. The growth of the control and NP incorporated films followed a linear regime as a function of number of layers. The%degradation of methyl orange as a function of time was investigated by UV–vis spectroscopy and total organic carbon (TOC) measurements. Complete degradation of methyl orange was achieved within 13h. The amount of NP loading in the film significantly influenced the%degradation of methyl orange. Catalyst reusability studies revealed that the catalyst thin films could be repeatedly used for up to five times without any change in photocatalytic activity of the films. The findings of the present study support that the binary metal oxide catalyst films reported here are very useful for continuous systems, and thus, making it an option for scale up.

ChemInform Abstract: Advancement in Heterogeneous Base Catalyzed Technology: An Efficient Production of Biodiesel Fuels

AbstractReview: 199 refs.

Advancement in heterogeneous base catalyzed technology: An efficient production of biodiesel fuels

Price fluctuation of petroleum-based diesel, climate change, emerging mandate obligations, availability of new feedstock and the upgrading of conversion technologies are expected to drive biodiesel market to grow robustly in the next coming 10 years. However, the current bottleneck in biodiesel production is the lack of economical sustainable conversion technologies. Generally, industrial production of biodiesel is greatly relied on alkaline homogeneous transesterification reaction. Limitation of the technology, such as multistep process which incur extra pre-step for high acid oil treatment and post-step for biodiesel purification and alkali washing as diminished the economic feasibility and low environmental impact of the entire biodiesel process. Heterogeneous catalysis offers immense potential to develop simple transesterification process, including one step reaction, easy separation, reusability of catalyst, and green reaction. Thus, the aim of this paper is to review the biodiesel production technologies such as blending, micro-emulsion, pyrolysis, and transesterification. Furthermore, recent studies on heterogeneous catalyzed transesterification were presented by discussing the issues such as catalytic performance on different types of biodiesel feedstock, transesterification reaction conditions, limitations encountered by heterogeneous catalysts, and reusability of solid catalysts. The heterogeneous catalysts presented in this review is mainly focused on solid base catalysts, which include single metal oxides, supported metal oxide, binary metal oxide, hydrotalcite, and natural waste shell-based catalyst. Furthermore, current perspectives on application of heterogeneous catalyzed technology in biodiesel industry were discussed herein.

혼합 금속산화물 촉매에서 글리세롤의 수소화 분해반응을 통한 프로필렌 글리콜의 합성

Hydrogenolysis of glycerol to propylene glycol was performed over binary and ternary metal oxide catalysts. The conversion of glycerol and selectivity to propylene glycol were increased on Cu/Zn and Cu/Cr mixed oxides compared to pure CuO and ZnO oxides. The addition of alumina into Cu/Zn mixed oxide very highly increased the conversion of glycerol and selectivity to propylene glycol. The conversion of glycerol was increased with increasing the reaction temperature but the selectivity to propylene glycol was shown to have maximum value at 200 ℃ and then decreased at 250 ℃. The conversion of glycerol and selectivity to propylene glycol were decreased with increasing the glycerol concentration.

Sustainable production of acrolein: Acidic binary metal oxide catalysts for gas-phase dehydration of glycerol

Acidic binary metal oxide catalysts, including SnO 2–TiO 2, SnO 2–ZrO 2, TiO 2–Al 2O 3, SiO 2–TiO 2, ZrO 2–SiO 2, ZnO–TiO 2 and TiO 2–ZrO 2, were prepared and employed to catalyze the dehydration reaction of glycerol (GL) at 315 °C. Correlation of the catalyst acidities with their catalytic performance demonstrated that the strongly acidic sites at −8.2 < H 0 ≤ −3.0 were efficient for the selective production of acrolein (AC) from aqueous GL (10 mol% or 36.2 wt% GL). Micropores in the catalyst textures showed a negative effect on AC selectivity, probably by inducing secondary reactions of AC. The highest AC selectivity obtained over these binary oxide catalysts was in the range between 45 mol% and 52 mol%. A direct use of the anhydrous GL, instead of the aqueous GL, for the dehydration reaction produced much lower AC selectivity but larger amount of heavier products. Among all the catalysts investigated, 10 mol% TiO 2–Al 2O 3 calcined at 600 °C and 50 mol% TiO 2–ZrO 2 calcined at 550 °C exhibited the best catalytic performance for AC production from aqueous GL. The appropriate reaction temperature range for the production of AC was also reported by using this 50 mol% TiO 2–ZrO 2 as a representative catalyst.

The total oxidation of propane over supported Cu and Ce oxides: A comparison of single and binary metal oxides

The total oxidation of propane is studied by means of steady-state experiments over a set of Cu- and Ce-based catalysts at a propane inlet partial pressure of 0.6 kPa, an oxygen partial pressure of 3.5 kPa and temperatures from 595 to 648 K. The catalysts were characterized by inductively coupled plasma (ICP), Brunauer–Emmett–Teller specific surface area (BET), temperature-programmed desorption (TPD), X-ray diffraction (XRD), pulse reduction–reoxidation, and H 2- and C 3H 8-temperature-programmed reduction (TPR). A synergistic effect between cupric oxide, CuO, and ceria, CeO 2, is observed using a Mars–van Krevelen model to describe the kinetic data: the activation energies for reduction and reoxidation, obtained on the binary metal oxide catalyst with both cupric oxide and ceria, are 20 kJ mol −1 lower than those obtained on the single Cu- or Ce-based catalysts. The corresponding turnover frequencies are the highest.

Supported indium oxide as novel efficient catalysts for dehydrogenation of propane with carbon dioxide

In 2O 3–MO x binary mixed metal oxide catalysts (M: Al, Zn, Zr, Ti, Fe, Mg, Si, and Ce) prepared by a coprecipitation or sol–gel method have been tested for the dehydrogenation of propane to propylene in the presence of carbon dioxide. Several techniques including N 2 adsorption/desorption, X-ray diffraction, H 2-temperature-programmed reduction and X-ray photoelectron spectroscopy were applied to characterize the physicochemical properties of the as-synthesized materials. Catalytic tests showed that all In-containing samples were active in the CO 2-promoted dehydrogenation of propane with good propylene selectivity. Among the In 2O 3–MO x catalysts tested, the In 2O 3–Al 2O 3 sample containing a 20 mol% indium content showed the highest dehydrogenation activity with superior long-term stability. The specific interaction between In 2O 3 and Al 2O 3 leading to a high component dispersion is suggested to play a key role in regulating the redox and structural properties of surface indium species, which makes the In 2O 3–Al 2O 3 composite highly active and stable for the reaction.

Novel Y2O3 Doped MnO x Binary Metal Oxides for NO x Storage at Low Temperature in Lean Burn Condition

MnO x -Y2O3 binary metal oxide catalysts are synthesized by a constant-pH co-precipitation method, their ability of NO x storage capacity and absorbing process were investigated. The pure MnO x and Y2O3 calcined at 500 °C for 4 h in static air are both of body-centre structure, while the binary metal oxides containing Mn and Y are mainly of amorphous phase. The adulteration of Y2O3 can remarkably improve the specific surface areas of the catalysts, which probably result of the enhancement on NO storage capacity and catalytic oxidation ability of NO at 100 °C. The XPS results indicate that both Mn and Y have 3+ chemical states in the binary oxides. FT-IR spectra could be beneficial to explain the NO storage process on the binary metal oxide: NO can be adsorbed on the MnO x and Y2O3 sites as nitrates and nitrites, respectively, and then the nitrites on Y2O3 site are shifted to Mn2O3 site and then is oxidized to nitrates. As a result, the NO storage capacity is enhanced due to the adulteration of Y2O3, finally the NO x are adsorbed on the Mn2O3 site as nitrate species.

TiO2-Supported Binary Metal Oxide Catalysts for Low-temperature Selective Catalytic Reduction of NOx with NH3

Abstract Binary metal oxide(MnOx-A/TiO2) catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide(TiO2), where, A indicates Fe2O3, WO3, MoO3, and Cr2O3. Their catalytic activity, N2 selectivity, and SO2 poisonous tolerance were investigated. The catalytic performance at low temperatures decreased in the following order: Mn-W/TiO2>Mn-Fe/TiO2>Mn-Cr/TiO2>Mn-Mo/TiO2, whereas the N2 selectivity decreased in the order: Mn-Fe/TiO2>Mn-W/TiO2>Mn-Mo/TiO2>Mn-Cr/TiO2. In the presence of 0.01% SO2 and 6% H2O, the NOx conversions in the presence of Mn-W/TiO2, Mn-Fe/TiO2, or Mn-Mo/TiO2 maintain 98.5%, 95.8% and 94.2%, respectively, after 8 h at 120 °C at GHSV 12600 h-1. As effective promoters, WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly. The Fourier transform infrared(FTIR) spectra of NH3 over WO3 show the presence of Lewis acid sites. The results suggest that WO3 is the best promoter of MnOx/TiO2, and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.

Effects of Metal Oxide Domain Size, Dispersion, and Interaction in Mixed WOx/MoOx Catalysts Supported on Al2O3 for the Partial Oxidation of Ethanol to Acetaldehyde

UV−visible diffuse reflectance spectroscopy (UV−vis DRS) and the ethanol oxidation probe reaction were used to investigate the structure and function of binary transition metal oxide catalysts containing dispersed WOx and MoOx domains supported together on alumina. The efficacy of UV−vis DRS as a tool to identify segregated MoOx and WOx surface domains along with their growth into larger and interacting binary oxides is demonstrated for the first time. UV−vis absorption edge analysis of physical mixtures of single oxide catalysts indicates that spatially segregated domains of different composition result in multiple edges in the UV−vis absorption spectra. Binary oxide catalysts containing 0.5 Mo atoms/nm2 and 0.5 W atoms/nm2 show two distinct absorption edges at 3.60 and 4.13 eV, corresponding to spatially and compositionally segregated MoOx and WOx domains. At higher surface densities (2−8 total metal atoms/nm2) only one edge is observed, suggesting that MoOx and WOx are molecularly mixing and forming a unique metal oxide nanostructure with a band gap different from WOx or MoOx single metal oxide catalysts of comparable surface densities. The number of absorption edges and the edge energies obtained for MoOx/WOx-Al2O3 catalysts are independent of the sequence of metal oxide deposition during catalyst preparation, indicating that the two metal oxides are compositionally well dispersed at all surface densities. Ethanol partial oxidation reactions over single oxide catalysts confirm the primarily redox nature (acetaldehyde formation) of MoOx domains and acidic character (diethyl ether formation) of WOx domains and alumina. Binary MoOx/WOx-Al2O3 catalysts containing mixed metal atom surface densities of 2−4 Mo atoms/nm2 and 2−6 W atoms/nm2 show higher acetaldehyde selectivities than MoOx-Al2O3 catalysts of the same Mo-atom surface density despite the poor redox character of WOx. The presence of WOx does not affect product selectivity in binary catalysts with MoOx present in excess of monolayer coverage. Comparison of acetaldehyde selectivities over MoOx/WOx-Al2O3 to calculated selectivities based on an ideal noninteracting binary oxide catalyst in which the MoOx and WOx domains react with ethanol independently suggests a synergistic interaction between MoOx and WOx resulting in enhanced acetaldehyde selectivity in MoOx/WOx-Al2O3 catalysts.

Catalytic decomposition of sulfur trioxide on the binary metal oxide catalysts of Fe/Al and Fe/Ti

The iodine–sulfur (IS) cycle has been focused for hydrogen production by water splitting using a very high temperature nuclear reactor (VHTR) which is a high temperature heat source. The nuclear energy was absorbed at the temperature ranges of 750–900 °C by SO 3 decomposition reaction to SO 2 and O 2 in IS cycle. In this work, the activity of Fe/Al and Fe/Ti catalysts prepared by a co-precipitation was studied in an attempt to find some suitable catalysts for the decomposition of sulfur trioxide as the oxygen-generating reaction in the thermo-chemical water splitting process. The SO 3 decomposition was performed in the temperature range of 750–950 °C at a space velocity of 72,000 cm 3/g cat. h in a fixed bed reactor. The catalytic activity of Fe/Al and Fe/Ti catalysts increased with an increase in Fe loadings, indicating that the Fe component should be active. The mechanism for the SO 3 decomposition on metal oxides can be described as follows: the metal sulfate formation (MO + SO 3 → MSO 4) and the decomposition of metal sulfate (MSO 4 → MO 2 + SO 2 and MO 2 → MO + 1/2O 2).

Oxidative dehydrogenation of isobutane on chromium oxide-based catalyst

Isobutane oxidative dehydrogenation offers a prospect of cheaper and environment friendly route to isobutene. The reaction has been studied at 250 °C, 1 atm and feed flow rate of 75 cm 3/min over supported chromium oxide-based catalysts. Effects of various supports (Al 2O 3, MgO, TiO 2 and SiO 2), catalyst precursors (K 2Cr 2O 7, CaCr 2O 7·H 2O, CrO 3, CrK(SO 4) 2·12H 2O and Cr(NO 3) 3·9H 2O) and binary mixed metal oxide catalysts of the form Cr-M-oxide/γ-Al 2O 3 (where M is V, Ni, Co, Mo, W, Ho, La, Li or Bi) were investigated. The supported catalysts are ranked (based on isobutene yields at 250 °C) as; Cr-Mg-O (3.4%) = Cr-Si-O (3.4%) < Cr-Ti-O (4.5%) < Cr-Al-O (6.0%). The performances of the catalysts showed strong dependence on the precursor used. The 10 wt.% Cr-Al-O prepared using K 2Cr 2O 7 and CrK(SO 4) 2·2H 2O exhibited the lowest isobutene yields of 0.14 and 0.3%, respectively. Partial substitution of chromium ions with nickel or tungsten exhibited minor increase in selectivity to isobutene of about 6% at comparable isobutane conversions. Substitution with other metals show similar or inferior performance compared with the base catalyst. Thus, showing that chromium oxide-based catalysts are active for the reaction and their performance could be improved by appropriate choice of active component precursor, support and additives.

Hydrolytic decomposition of CF 4 over alumina-based binary metal oxide catalysts: high catalytic activity of gallia-alumina catalyst

The hydrolytic decomposition of CF 4 has been conducted on gallia promoted alumina (Ga-Al oxide) catalysts at 803–903 K and 0.1 MPa. Steady state activity on 20% Ga-Al oxide was 15 times of that on Ce10%-AlPO 4 catalyst, on which the highest activity has been reported. The catalytic activity was further improved by incorporation of sulfate anion in Ga-Al oxide and by applying sol–gel method in preparation of the catalyst. XRD spectra of Ga-Al oxides showed a shift of diffraction peaks assigned to γ-alumina toward lower angles, indicating the formation of gallia-alumina solid solution. In situ FT-IR of pyridine adsorption spectra of Ga-Al oxides showed peaks solely attributable to Lewis acid (L-acid) sites at 1445–1455, ca. 1495, 1577, ca. 1594, and ca. 1622 cm −1. The steady state catalytic activities increased with increasing peak areas at 1446 or 1622 cm −1 of Ga-Al oxides with various Ga%, suggesting participation of Lewis acid sites into the reaction. It is demonstrate from surface area measurements of Ga-Al oxide catalyst before and after the reaction that not only higher catalytic activity but also higher catalyst stability were observed on Ga-Al oxide, Ga-Al oxide with sulfate, and Ga-Al oxide prepared by sol–gel method than on their parent oxides of alumina, Ga-Al oxide, and Ga-Al oxide prepared by incipient wetness method, respectively.

Hydrolysis of CF4 over alumina-based binary metal oxide catalysts

Carbon tetrafluoride (CF4), which is the most stable compound in perfluorocarbons (PFCs), was catalytically decomposed by the hydrolysis reaction at mild condition as 850–950K on alumina-based binary metal oxide catalysts. The catalytic activities for the hydrolysis reaction of CF4 with water on the selected metal-Al oxide catalysts were optimized in terms of H2O/CF4 ratio, loading amount of metal oxide to alumina and pre-treatment conditions of the catalyst. Then, the decomposition reaction of CF4 in the presence of water was examined at the optimized conditions over a variety of metal oxides supported on Al2O3. The steady state catalytic activities on the binary metal oxide catalysts with 5% metal oxide loading on alumina at the reaction temperatures between 853–953K were found to decrease in the order of Ga≈Zn≈Zr>Ni≈Cr>Sn≈(Al2O3)≈Ce≈In>B≈W>Mg≈Mn≈Cu>Ge≈Pb≈Li>Bi>Cd>Tl. More than 90% of the robust CF4 can be decomposed over alumina-based Ga, Zn, Ni, In, Sn, and Zr oxide catalysts. The catalytic activity maintained for more than 18h.Surface metal fluorides produced on binary metal oxide catalysts by the reaction with HF were hydrolyzed under temperature programmed mode and the products were analyzed by a mass spectrometer. It was clearly demonstrated from the experiments that the amount of released HF was well correlated with the corresponding catalytic activity. Further the amounts of L-acid sites measured by in situ FT-IR studies of adsorbed pyridine on the various binary metal oxides also followed the same order as the catalytic activity. These results suggest that breaking of CF bond in CF4 molecule by L-acid sites is a rate-limiting step in the hydrolysis reaction of CF4 and resulting surface fluoride is easily hydrolyzed with water. Other physical techniques such as XRD, weight and surface area of samples before and after the CF4 hydrolysis reaction were demonstrated that some of binary oxide catalysts were stable under the reaction conditions, especially Ga-Al and Ni-Al binary oxide catalysts.

Hydrocracking of Athabasca bitumen over binary metal oxide (SiO 2MoO 3 and CoO/SiO 2MoO 3) catalysts

The hydrocracking of Athabasca bitumen was studied over SiO 2MoO 3 (80: 20wt%), 2.92 and 5.54 wt% CoO on SiO 2MoO 3, and commercially available CoOMoO 3/Al 2O 3 catalysts at temperatures in the range 648–698 K for 2 h under an initial hydrogen pressure of 7.0 M Pa in a batch reactor. The reaction products were separated into coke, asphaltenes, resins, aromatics, saturates and gases. The severity of cracking increased with increased reaction temperature. At 698 K, asphaltene and resin yields were low (0.59 and 13.22 wt%, respectively) and gas yields high (40.5 wt%). SiO 2MoO 3 and CoO/SiO 2MoO 3 catalysts showed higher activity than commercial CoOMoO 3/Al 2O 3 catalyst in the conversion of heavy fractions (asphaltenes and resins) and in the formation of light fractions (saturates and aromatics).

Surface electronic structure of binary metal oxide catalyst ZrO 2/SiO 2

The surface electronic structure of the binary metal oxide ZrO 2/SiO 2 was studied by means of XPS and the decrete variational (DV) Xα cluster model calculation. The results show that when ZrO 2, was supported on SiO 2, the SiO bond of SiO 2, neighboring ZrO 4, became stronger and that the Brönsted acid site H which is located on the SiO 4 unit exhibits stronger acidity.

Amination of Decyl Alcohol over the Binary Metal Oxide Catalysts

Abstract Catalytic amination of decyl alcohol was examined over binary oxide catalysts containing molybdenum, and the selective formation of decylamine was observed over TiO2-, SnO2-, and Fe2O3–MoO3 catalysts. The reaction was often accompanied by the formation of 1-decene. It was found that catalytic activity for the amination of aliphatic alcohol was associated with the acidic property of metal oxide catalysts.