Titanate Catalyst Research Articles

Highly efficient La/Ni co-doped strontium titanate catalyst for co-production of propylene and hydrogen from propane in protonic ceramic electrochemical cells

A highly efficient La/Ni co-doped strontium titanate (LSNT) perovskite catalyst is developed and integrated in a protonic ceramic electrochemical cell for co-production of propylene and high-purity hydrogen from commercial propane feedstock. Propane conversion and hydrogen production rate can be effectively enhanced under an applied current due to the electrochemical promotion effect and/or shifted reaction equilibrium induced by rapid separation of hydrogen product. Water vapor in the feed gas could significantly improve the catalyst stability by suppressing the coke formation. The propane conversion could reach up to 53% at 600 °C under a current density of 90 mA cm−2. The LSNT catalyst also shows excellent tolerance for the sulfur contaminant in commercial propane gas. The excellent performance of the LSNT catalyst is attributed to the highly active and selective Ni species at the interface with the perovskite substrate, which are formed in situ via reduction-induced exsolution under reaction conditions.

Molecularly rigid porous polyamine host enhances barium titanate catalysed H2O2 generation

Barium titanate catalyst performance in hydrogen peroxide production is improved and the catalyst is re-usable, when embedded into the polymer of intrinsic microporosity PIM-EA-TB.

Glycerol carbonate synthesis over nanostructured titanate catalysts: Effect of morphology and structure of catalyst

The indirect conversion of CO2 into glycerol carbonate using DMC was investigated using pristine sodium titanate nanotubes (NaTNT) and nanostructured titanates (calcined NaTNT at different temperatures) as catalysts. The calcination changes the morphology of the nanostructured titanates, between 200 and 400 °C the nanotubes shape is retained, however above these temperatures (500 and 600 °C) nanoribbons were identified, as well as nanorods obtained at 700 °C. A significant decrease in specific surface area and total pore size in temperatures up 500 °C was also observed. Furthermore, a decrease in the Ti+4/Ti+2 ratio and in the binding energy of Ti 2p3/2 and Ti 2p1/2 were observed, indicating an increase in the electron density and consequently increase in the Lewis acidity character of the titanium atom. All the nanostructured titanates showed good catalytic activity with glycerol conversion and GC selectivity above 90%. The results of the recycling showed that the nanostructured catalysts retained a good catalytic activity with high glycerol conversion (> 90%) although the GC selectivity decreased due the formation of glycidol, a high value-added by-product.

Pseudo-homogeneous kinetic modeling of dioctyl terephthalate (DOTP) production by esterification of terephthalic acid and 2-ethylhexanol over tetrabutyl titanate catalyst

Pseudo-homogeneous kinetic modeling of dioctyl terephthalate (DOTP) production by esterification of terephthalic acid and 2-ethylhexanol over tetrabutyl titanate catalyst

Mechanism of One-Step Hydrothermally Synthesized Titanate Catalysts for Ozonation.

A titanate nanotube catalyst for ozonation was synthesized with a simple one-step NaOH hydrothermal treatment without energy-consuming calcination. The synthesized titania catalysts were characterized by X-ray diffraction (XRD), Raman, porosimetry analysis, high-resolution transmission electron microscopy (HR-TEM), Fourier transformed infrared (FTIR), and electron paramagnetic resonance (EPR) analysis. The catalyst treated with a higher concentration of NaOH was found to be more catalytically active for phenol removal due to its higher titanate content that would facilitate more OH groups on its surface. Furthermore, the main active oxidizing species of the catalytic ozonation process were recognized as singlet oxygen and superoxide radical, while the hydroxyl radical may only play a minor role. This work provides further support for the correlation between the properties of titania and catalytic performance, which is significant for understanding the mechanism of catalytic ozonation with titania-based materials.

Preparation and performance study of V2O5/TiO2 catalysts supported on ceramic filter

As the country pays more and more attention to air pollution, the ceramic filter catalyst that can achieve the effects of dust removal and NO reduction simultaneously has a promising prospect. In this paper, ceramic fiber filter supported catalyst was prepared by impregnation method and tetrabutyl titanate method. The effects of vanadium content, space velocity, temperature, and tetrabutyl titanate concentration on the NO conversion of ceramic fiber catalysts were studied, and various physical and chemical methods were used for characterization. The results show that ceramic fiber had excellent multi-dimensional space and bridging structure. The NO conversion of impregnation catalyst and tetrabutyl titanate catalyst increased with the increase of vanadium content and tetrabutyl titanate concentration; At 6700h−1 and a temperature of 300°C, both catalysts can reached the highest catalytic efficiency, tetrabutyl titanate method catalyst was 93.67%. The tetrabutyl titanate catalyst can be loaded more evenly and the filtration pressure drop of the catalyst was smaller than that of the impregnation catalyst. The filtration pressure drop was increased by about 20% compared with the unsupported ceramic fiber.

Optimization of Melt-mixing Transesterifi cation of Polylactide by Polyethylene Glycol Employing Response Surface Methodology

A process for preparing polylactide-block-polyethylene glycol (PLA-b-PEG) copolymers has been developed and optimized by employing a transesterifi cation reaction in a melt-mixing process. The reaction was carried out in a counter-rotating mixer unit, using polyethylene glycol (PEG) and tetrabutyl titanate (TBT) catalyst. The effects of PEG weight percentage, catalyst contents, temperatures, and rotor speeds on chemical structures of the resulting PLA-b-PEG were examined, in terms of number average molecular weight (Mn), weight average molecular weight (Mw), in-chain PEG contents (wt.% PEG), and specifi c mechanical energy (SME) imparted by the mixer. The process parameters were optimized using a central composite rotatable design (CCRD) response surface methodology (RSM). The CCRD was designed with four variables at three levels of variations (-1, 0, -1), four replicates center point, and a redundancy factor (α) of 2.000. The responses (Mn, Mw, wt.% PEG, and SME) from 28 experimental trials were analyzed by a multiple linear regression fi tting, a second-order equation, and the RSM model. Mn and Mw of the products were determined by gel permeation chromatography (GPC). The in-chain PEG content was examined by nuclear magnetic resonance (1H-NMR) spectroscopy. The results show that the PEG weight percentage and the reaction temperature signifi cantly affect (P< 0.05) Mw and Mn of the products, which are drastically decreased with an increase in the PEG weight percentage and temperature. A quadratic interaction is observed between the PEG weight percentage and temperature, indicating that high reaction temperature leads to lower PEG conversions, due to undesirable competing thermal-oxidative degradations of PEG in the presence of the catalyst. Optimum operating conditions on the PEG weight percentage, catalyst contents, temperatures, and rotor speed for obtaining high Mw with high wt.% PEG was identifi ed. Although the optimal conditions are observed at the boundary level, the model serves as a platform for effective preparation of PLA-b- PEG copolymers with designed molecular weight and chemical structures. Further optimization of the model may be conducted by extending the range of independent factor levels. The resulting fl exible PLA-b-PEG copolymers, with tunable structures and properties, have high potential for use as singlecomponent degradable bioplastics with excellent mechanical properties, plasticizers, or toughening agent for enhancing PLA’s toughness.

Catalytic deoxygenation of fatty acids via ketonization and α-carbon scissions over layered alkali titanate catalysts under N2.

The ketonization of fatty acid with subsequent McLafferty rearrangement of the fatty ketone allows the deoxygenation to hydrocarbons. Here, we report the cascade reaction of palmitic acid (C16) to hydrocarbons (≤C14) over lepidocrocite-type alkali titanate K0.8Zn0.4Ti1.6O4, K0.8Mg0.4Ti1.6O4, and K0.8Li0.27Ti1.73O4 and the reassembled TiO2 catalysts at ≤400 °C under atmospheric N2 in a continuous fixed-bed flow reactor. The C16 acid is coupled to C31 ketone prior to the scissions mostly to a C17 methyl ketone and C14 hydrocarbons (i.e., the McLafferty rearrangement). The hydrocarbons yield increases with temperature and is proportional to partial charge at the O atom, suggesting that basic sites are responsible for C31 ketone scissions. The layered alkali titanate catalysts with two-dimensional (2D) space inhibit diffusion of the ketone primarily formed and promote its scissions to hydrocarbons within the confined space. Otherwise, low hydrocarbons yield (but high ketone yield) is obtained over TiO2 and the Mg/Al mixed oxide catalysts possessing no interlayer space. Meanwhile, the semi-batch experiment with pre-intercalated palmitic acid favors a direct deoxygenation, demonstrating the essential role of reaction mode toward ketone scission reaction pathway. Over K0.8Li0.27Ti1.73O4, the complete palmitic acid conversion leads to ∼47% hydrocarbons yield, equivalent to ∼80% reduction of the oxygen content in the feed under N2.

Selective synthesis of camphene from isomerization of α- and β-pinene over heterogeneous catalysts

The selective synthesis of fine chemicals from wasted derived biomass is one of the main challenges for the industry for valorizing and transforming these products into valuable substances. In this work, several materials based on zeolites, titanium dioxide, titanates and molybdenum were tested in the isomerization reaction of biomass derived α- and β-pinene for obtaining camphene, a very high-added value chemical. Liquid phase reaction of α- and β-pinene revealed that zeolites and titanates materials are capable to isomerize both monoterpenes at benign conditions (1 h, 90 °C, cyclohexane as solvent); nevertheless, the catalyst based on titanates is suitable for obtaining camphene in the highest yield from both terpenes (77% from α-pinene and 67% from β-pinene). Density of acid sites, Brønsted acid sites and the typical architecture of each catalyst gave significant differences in the catalytic activity. An increase of the Brønsted sites with medium strength favored the yield to camphene. An excess of acidity respect to other materials (e.g. zeolites) increases the formation of secondary products (limonene, pinenes, β-phellandrene, among others) over camphene, in comparison with titanate catalyst, which shape and acidity is considerably lower. Catalytic isomerization was also explored in essential oils extracted from crude biomass. Camphene weight composition increased in turpentine and Rosmarinus essential oils from 3% to 61% and from 7% to 31%, respectively, in presence of titanates-based material. In addition, this material was also capable to isomerize camphene and limonene into added value chemicals in good to excellent yields. Finally, titanate-based material was reused until 5 times for the selective synthesis of camphene from α- and β-pinene. • Acid curl sheets titanates capable to isomerize α- and β-pinene into camphene. • Selective production of camphene from Rosmarinus and Turpentine essential oils. • Medium Brönsted acid sites of titanates abled the isomerization. • Strong acid sites in zeolites produce a complex mixture of pinenes isomers. • Titanates also isomerize limonene and camphene into value products.

Oxidative decomposition of chlorobenzene over iron titanate catalysts: The critical roles of oxygen vacancies and adsorption geometries

Iron titanate catalysts with various Fe/(Fe + Ti) ratios were prepared by sol-gel method and investigated in catalytic oxidation of chlorobenzene (CB). The catalysts exhibited good activity and sulfation further promoted the performance in both activity and stability. Ti3+-oxygen vacancy (Vo) was determined with Raman, EPR and O2-TPD, while the generation mechanism of Ti3+-Vo was investigated by XPS and UV–vis. The structure-activity relationship was established between oxygen vacancies (Vo) and CB oxidation. The generation of Ti3+-Vo was attributed from the electron transfer from Fe3+ to Ti4+ in FeOTi structure as well as the incorporation of S4+ into surface lattice (for the sulfated catalyst). Moreover. the adsorption geometries of CB were comparatively studied. CB adsorbed on a pair of adjacent Lewis acid sites over the iron titanate catalysts through the Cl atom and the π cloud. CB of this adsorption type was highly activated and essentially contributed to the high activities.

Oxidative decomposition of dichloromethane over sulfated iron titanate catalysts: Catalytic performance and reaction mechanism

Iron titanate catalysts prepared by sol-gel method and modified by different amounts of SO42− were investigated in catalytic oxidation of dichloromethane (DCM). In situ DRIFT spectra revealed three different pathways for DCM decomposition over the serial catalysts, with active sites of hydroxyls, Lewis pairs and Brønsted acid-sulfate sites, respectively, verified by the designed experiments. Specifically, over sulfate-Brønsted sites, DCM decomposed through reaction intermediate of COHCl, which directly converted to CO and HCl. Sulfation of iron titanate significantly promoted the acidity and reaction activity, with great reaction stability provided by sulfate species and reproducible Brønsted acid sites.

Synthesis of sodium titanate catalysts using a factorial design for biodiesel production

AbstractIn this work, the synthesis of sodium titanate for the biodiesel production was evaluated with emphasis on the synthesis parameters of titanates in the conversion of vegetable oil to biodiesel. Sodium titanate catalysts were synthesized via sol–gel hydrothermal method and tested as heterogeneous catalysts for biodiesel production, using a factorial design 2k. Four experimental factors were considered: NaOH concentration, hydrothermal temperature, TiO2/NaOH ratio, and calcination temperature, using as response variable the catalysts activity in soybean oil conversion to biodiesel. Titanates were characterized by XRD, SEM, and N2 physisorption techniques. The presence of tri and hexatitanate were confirmed. Trititanate was the most efficient in the conversion of soybean oil to biodiesel, achieving around 80% with an alcohol:oil molar ratio of 6:1 at 55°C for 5 hr and 300 rpm. Among the trititanate catalysts, the best performing sample showed a surface area of 217 m2/g with a porous size average of 4.8 nm related to nanotube structure with inter and intra particle mesoporosity. Conditions to prepare the efficient performing catalyst were as follows: NaOH concentration, 7.5 M; hydrothermal temperature, 130°C; TiO2/NaOH ratio, 0.06 g/mL; and calcination temperature, 600°C.

Effect of annealing temperature on structural, optical and visible light photocatalytic performance of CaTiO3 catalysts synthesized by simple sol-gel technique

This work, simple wet chemical route has been adapted to prepare calcium titanate (CaTiO3) catalyst nanopowders. The nature of crystalline structural, morphological, optical and textural properties of the products was monitored through XRD, SEM, TEM, Raman, UV, PL and BET analysis. Orthorhombic crystalline phase with clear spherical are found in the XRD and TEM results. There is no trace in the impurity of the products, which denotes that product purity nature. The optical band gap energies (3.03–2.82 eV) and rapid generation electron-hole with presence of light was identified through UV and PL results. Mesoporous nature (34.2 nm) with huge surface area (97.5 m2/g) was identified through BET analysis. The photocatalytic results exposed that the 900 °C annealed CaTiO3 catalyst shows fabulous degradation efficiency (88%), high apparent constant (0.0578 min−1) and long term stability towards MO dye under visible light illumination. The improved photocatalytic activity of CaTiO3 is due to the narrowing the band gap energy and prevent the recombination process of electron-hole pairs. The improved mechanism of the proposed photocatalyst was also discussed in detail.

Effect of surface morphology on the adhesion of silicone elastomers on AA6061 aluminum alloy

In this study, different primer formulations were used for enhancing the adhesion between a high consistency methyl phenyl vinyl silicone rubber (HCR) and AA6061 aluminum alloy. These formulations were selected on the basis of their different chemical composition. One contains only silanes and a titanate catalyst, a second contains only reactive macromolecular polysiloxane chains and a third contains both silanes and reactive macromolecular polysiloxane chains as the main components. The effect of the metal surface topography on the efficiency of the primers was investigated. The condensation reactions in the primers were followed by Fourier Transform Infrared Reflexion Absorption (FTIR-RA) spectroscopy and rheological measurements. 90° peel test was used to measure the adhesive strength of the silicone on metal and the fracture surfaces after peeling were analysed using SEM-EDS to determine the loci of failure. Cure monitoring of the silane based formulations showed that hydrolysis/condensation of silanes occur rapidly after their application on AA6061 surfaces and lead to a high degree of crosslinking even in the formulations with PDMS additives. The heat cure of the formulation based on a one-component addition curing system (SiH oligomer, vinylated-PDMS with a platinum catalyst) resulted in a film with a high cohesive strength. The primer formulation containing silanes and reactive PDMSs as the main components resulted in the best adhesion of the silicone elastomer with a dominant cohesive failure. However, a weaker adhesion was obtained at a high roughness of the substrate due to a weak adhesive strength at the metal/primer interface. A pretreatment composed of a first layer of activated silanes and a second layer of reactive silicone chains gave a good adhesion both at low and high roughness of the aluminum substrate.Roughening of the metal surface did not improve the adhesion of silicone elastomers on the primed metals in any of the studied treatments, indicating that mechanical interlocking and increase in contact area do not contribute to adhesion. The results were discussed based on the different chemical composition and rheological properties of the primer formulations.

Tailored Alkali Resistance of DeNOx Catalysts by Improving Redox Properties and Activating Adsorbed Reactive Species

SummaryIt is still challenging to develop strongly alkali-resistant catalysts for selective catalytic reduction of NOx with NH3. It is generally believed that the maintenance of acidity is the most important factor because of neutral effects of alkali. This work discovers that the redox properties rather than acidity play decisive roles in improving alkali resistance of some specific catalyst systems. K-poisoned Fe-decorated SO42−-modified CeZr oxide (Fe/SO42−/CeZr) catalysts show decreased acidity but reserve the high redox properties. The higher reactivity of NHx species induced by K poisoning compensates for the decreased amount of adsorbed NHx, leading to a desired reaction efficiency between adsorbed NHx and nitrate species. This study provides a unique perspective in designing an alkali-resistant deNOx catalyst via improving redox properties and activating the reactivities of NHx species rather than routinely increasing acidic sites for NHx adsorption, which is of significance for academic interests and practical applications.

Synthesis of mesoporous calcium titanate catalyst for transesterification of used cooking oil: A review of the synthesized potential

Synthesis of mesoporous calcium titanate catalyst for transesterification of used cooking oil: A review of the synthesized potential

Temperature sensitivity of the selective catalytic reduction (SCR) performance of Ce-TiO2 in the presence of SO2.

Cerium titanate catalyst (Ce-TiO2) is competitive as a substitute for the commercial SCR (selective catalytic reduction) catalysts VO5-WO2/TiO2 due to its high SCR activity and excellent redox performance. The reaction mechanisms of Ce-TiO2 at 180°C, 240°C, and 300°C in the presence of SO2 were systematically studied regarding the evolution of the SCR activity, quantitative analysis of sulfate compounds, and comprehensive identification of the fresh and poisoned catalysts. The results demonstrated that NO conversion at 180°C in the presence of SO2 is highly sensitive to the formation of cerium sulfates/sulfites, limiting the reactivity of NH4+ adsorbed on SO Brønsted acid sites and inhibiting the E-R reaction pathway. At 240°C, the degradation of NO conversion was commenced by the cumulative influence of cerium sulfates/sulfites. With the increase of the reaction temperature to 300°C, the NO conversion is gradually immune to the formation of cerium sulfates in spite of the great amount of cerium sulfates deposited on the deeper interior of CeO2. The high SCR activity of the Ce-TiO2 catalyst in the presence of SO2 at a higher reaction temperature might be ascribed to the synergistic catalysis between surface cerium sulfates and bulk CeO2, where surface cerium sulfates act as acid sites for the adsorption of NH3 and the bulk CeO2 acts as the redox sites. The reaction mechanisms of the Ce-TiO2 catalyst in the presence of SO2 at different temperatures are proposed as the two reaction routes.

Studies on fast and green biodiesel production from an indigenous nonedible Indian feedstock using single phase strontium titanate catalyst

Strontium titanate was synthesized by polymer precursor method and its catalytic activity as heterogeneous basic catalyst was tested in transesterification reaction for high-quality biodiesel production form Madhuca indica oil. The synthesized strontium titanate was characterized by powder X-ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) attached with Energy Dispersive X-ray Spectroscopy (EDS), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR). Surface area and basicity were also determined using Brunauer-Emmett-Teller (BET)surface area analyzer and Hammett indicator method. The structural characterizations of catalyst enunciated the single perovskite phase formation of well-assorted strontium titanate nanospheres. The transesterification reaction was optimized using one variable at a time (OVAT) and Response Surface Methodology (RSM) using Box Behnkehn Design (BBD) to comprehend the linear effect and interactive effect of process variables on biodiesel production. The optimized reaction condition through OVAT was obtained as: catalyst dose (1.3 wt%), methanol to oil molar ratio (18:1), reaction temperature (65 °C), reaction time (120 min), and agitation speed (600 rpm) while RSM predicted the highest methyl ester conversion at optimum catalyst dose (1.19 wt%), methanol to oil molar ratio (21.5:1), reaction temperature (71 °C), and reaction time (97.7 min). The confirmatory experiment noticed the highest 98% FAME conversion at following reaction conditions catalyst dose (1.2 wt%), methanol to oil molar ratio (22:1), reaction temperature (65 °C), and reaction time (100 min). Confirmatory experiment showed its close agreement with the predicted values from RSM instead OVAT. According to RSM, catalyst dose, reaction temperature, reaction time, and methanol to oil molar ratio were influencing process parameters for transesterification in descending order of their strength. Furthermore, a pseudo-first-order kinetic model was established with the activation energy (Ea) of 65.95 kJ mol−1. The Environmental Factor (E-factor) and Turn Over Frequency (TOF) were also determined and demonstrated the prepared catalyst as a sustainable and potential heterogeneous base catalyst. The physicochemical properties of produced biodiesel were evaluated to check its compatibility with conventional diesel fuel.

Application of solid electrolyte cells in ion pump and electrolyzer modes to promote catalytic reactions: An overview

Solid electrolyte cells can be operated in three basic modes: fuel cell, electrolyzer and ion pump. In the fuel cell mode, a fuel such as hydrogen, CO and light hydrocarbons is electrochemically oxidized to generate power. Electrolyzer and ion pump modes, however, need application of power from an external source in order to perform the desired tasks. In this article, we present a brief overview of the studies that use an oxygen ion conducting electrolyte for catalytic applications, with two specific examples from our own studies: use of a solid electrolyte cell in the ion pump mode for alkane oxidative dehydrogenation and in the electrolyzer mode for CO2 reduction. The solid electrolyte cell assembly used in these studies consists of a button cell containing yttria-stabilized zirconia solid oxide electrolyte, a modified strontium titanate (ST) catalyst as the working electrode, i.e., anode for the ODH reaction and cathode for the CO2 reduction reaction, and a lanthanum strontium manganite (LSM) catalyst as the counter electrode.Physical properties of the titanate materials were studied using XRD, conductivity measurement and temperature-programmed oxidation with CO2. Lanthanum doped strontium titanate (La0.2Sr0.8TiO3±δ), with or without Cl, was seen to have a higher electrical conductivity compared to un-doped strontium titanate (SrTiO3). Cl doping, however, was seen to improve the electrocatalytic activity for both ODH and CO2 reduction reactions, giving higher yields of ethylene and CO compared to Cl-free La0.2Sr0.8TiO3±δ. The comparison of the catalytic and electrocatalytic ODH reactions clearly pointed out that oxygen in ionic form was more selective to ethylene than molecular oxygen at similar conversion values.

Effect of Nb Promoter on the Structure and Performance of Iron Titanate Catalysts for the Selective Catalytic Reduction of NO with NH3

Iron titanate catalysts with variable Nb content was synthesized by the homogeneous precipitation method, and they were applied to the NH3-selective catalytic reduction (SCR). The widest performanc...