Methanol steam reforming for hydrogen production over NiTiO3 nanocatalyst with hierarchical porous structure

Steam reforming for hydrogen production is one of the important research directions for clean energy. NiTiO₃ catalysts with a hierarchical porous structure are prepared and applied to methanol steam reforming for hydrogen production. The results show that the optimum catalyst (10% Ni-Ti-O_x) not only has a hierarchical porous structure, but it also involves the coexistence of NiTiO₃, anatase TiO₂ and rutile TiO₂. The formation of NiTiO₃ is beneficial to the adsorption and activation of methanol molecules on the surface of the Ni-Ti-O_x catalyst, and the main intermediate species of the methanol molecular reaction are hydroxyl groups, methoxy species and formic acid species. Furthermore, the methanol steam reforming reaction is mainly dominated by methanol decomposition at low temperature (350-500 °C), while it is mainly dominated by methanol and water molecular reactions at high temperature (500-600 °C).

Elimination of PCDD/Fs over Commercial Honeycomb-Like Catalyst of V2O5-MoO3/TiO2 at Low Temperature: From Laboratory Experiments to Field Study

With the need for ultra-low emissions and the strict regulation of PCDD/Fs from MSWI plants, traditional SCR catalysts have been applied to remove PCDD/Fs. In this study, we compared one typical commercial V2O5-MoO3/TiO2 catalyst’s performance in removing PCDD/Fs under laboratory and industrial conditions. Various characterization methods like XRF, XPS, BET, and H2-TPR were applied to analyze the catalyst’s properties. The laboratory results showed that the adsorption could significantly affect the removal at low temperatures. The RE on PCDD/Fs was 59.4% (55.0% for toxicity RE), 88.5% (90.3%), and 78.0% (76.0%) at 160 °C, 180 °C, and 200 °C, respectively, showing that 180 °C is the most suitable operation temperature for this V2O5-MoO3/TiO2 catalyst. The field study was conducted at 180 °C, and the results revealed that the competition between water vapor and the interaction of SO2 could lower the RE. However, comparisons between laboratory and field conditions showed that this V2O5-MoO3/TiO2 catalyst still showed good stability, with only a 6.8% drop.

The Synergistic Catalysis of Chloroaromatic Organics and NOx over Monolithic Vanadium-Based Catalysts at Low Temperature

In this study, four monolithic, vanadium-based catalysts in granular (Vox/TiO2), honeycomb-type (Vox-Wox/TiO2 and Vox-MoOx/TiO2), and corrugated forms (Vox-Wox/TiO2) were investigated by multiple characterization methods (BET, XRF, XPS, XRD, H2-TPR, and NH3-TPD). Their catalytic performances were evaluated by the oxidation-reduction performance of ortho-dichlorobenzene (o-DCB) and NO/NH3. The modification of Wox and MoOx could promote catalytic activity by accelerating the transformation of V5+/V4+ and enriching the strong acid sites. The introduction of NO/NH3 significantly impaired the o-DCB oxidation, ascribed to the competitive adsorption of reactants on acid sites. The performance of Vox/TiO2 and Vox-MoOx/TiO2 catalysts indicated that strong acidity could enhance catalytic abilities over o-DCB and Nox. Nevertheless, the CE (conversion efficiency) of o-DCB was more related to a large BET surface area and a high amount of V5+ species, while the CE of Nox was more associated with redox ability and Vox surface density. The V4+/V5+ and OS-A/OS-L ratio increased prominently after the oxidation of o-DCB, indicating that it was the reoxidation of V4+ species, rather than the supplement of oxygen, that limited the reaction rate. This work revealed catalytic activity was positively affiliated with the surface area, amount of V5+ species, transformation rate of V4+/V5+, redox ability, and abundance of strong acid sites. Additionally, the results could guide the selectivity and improvement of industrial low-temperature catalysts for synergistic elimination of chloroaromatic organics and Nox.

Insights of Selective Catalytic Reduction Technology for Nitrogen Oxides Control in Marine Engine Applications

The international shipping industry is facing increasingly stringent limitations on nitrogen oxide (NOx) emissions. New solutions for reducing NOx emitted by marine engines need to be investigated to find the best technology. Selective Catalytic Reduction (SCR) is an advanced active emissions control technology successfully used in automotive diesel engines; it could be applied to marine engines with ad-hoc solutions to integrate it in the exhaust of large engines. In this study, a commercial SCR was tested at the exhaust of a diesel engine in inlet gas conditions typical of a marine engine. The SCR system consisted of a custom monolith (provided by Hug-Engineering AG) that enabled seamless integration for a broad range of engine sizes; the active phases were V2O5 (3 wt%)-WO3 (7 wt%)-TiO2 (75 wt%). The monolith was studied at the laboratory scale for its in-depth chemical/physical characterization and by means of an intermediate-scale engine, reproducing the exhaust gas conditions of a full-scale marine engine. The system’s effectiveness in terms of NOx removal for the selected engine operating conditions was evaluated in a wide range of temperature and NOx emissions values and for different quantities of the reduction agent (AdBlue or ammonia) added to exhaust gases. The investigated technological solution resulted in efficient NOx emission control from a marine engine.

The Promoting Effect of Ti on the Catalytic Performance of V-Ti-HMS Catalysts in the Selective Oxidation of Methanol

The effects of Ti modification on the structural properties and catalytic performance of vanadia on hexagonal mesoporous silica (V-HMS) catalysts are studied for selective methanol-to-dimethoxymethane oxidation. Characterizations including N2 adsorption–desorption (SBET), X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS UV-Vis), Micro-Raman spectroscopy, FTIR spectroscopy, and H2 temperature-programmed reduction (H2-TPR) were carried out to investigate the property and structure of the catalysts. The results show that Ti can be successfully incorporated into the HMS framework in a wide range of Si/Ti ratios from 50 to 10. Ti modification can effectively improve the distribution of vanadium species and thus enhance the overall redox properties and catalytic performance of the catalysts. The catalytic activity of the V-Ti-HMS catalysts with the Si/Ti ratio of 30 is approximately two times higher than that of V-HMS catalysts with comparable selectivity. The enhanced activity exhibited by the V-Ti-HMS catalyst is attributed to the improved dispersion and reducibility of vanadium oxides.

Resource utilization of waste V2O5-based deNOx catalysts for hydrogen production from formaldehyde and water via steam reforming

The harmless disposal of abandoned and toxic V₂O₅(WO₃)/TiO₂ (VWT) deNO_x catalysts has become a worldwide great demand, a new resource path for hydrogen production from steam reforming of formaldehyde and water using the waste VWT deNOx catalysts as catalyst carriers was proposed. The waste V₂O₅-based catalysts supported NiO (N/VWT) catalysts prepared by impregnation method were comparatively studied for hydrogen production. The H₂ and CO selectivity of the optimum N/VWT separately reached 100% and 72.5%, and the formaldehyde conversion of the N/VWT reached 86.3% at 400 ℃ and higher than 93.0% at 450-600 ℃. Analysis showed that the hydroxyl species played the most important role, and its richness determined the catalytic performance directly. The high acid sites and excellent redox properties were beneficial to enhance the catalytic performance. The in situ DRIFT study verified that the hydrogen bonds between formate species and hydroxyl groups reduced reaction steps, which accelerated the progress of the reaction. The adsorbed formaldehyde transformed to formate species firstly, and then produced H₂ and CO₂ (or CO) by dehydrogenation. Ultimately, the resource utilization path not only completely solved the harmless problems of the waste V₂O₅-based deNO_x catalysts and formaldehyde, but also contributed to the hydrogen production.

A relationship between the V4+/V5+ ratio and the surface dispersion, surface acidity, and redox performance of V2O5–WO3/TiO2 SCR catalysts

The electron transfer process between vanadium species is omitted and the activated transition state is formed directly.

Vapor-phase dehydrogenation of ethylbenzene to styrene over a V2O5/TiO2–Al2O3 catalyst with CO2

A stable V₂O₅/TiO₂–Al₂O₃ catalyst was synthesized for the oxidative dehydrogenation of ethylbenzene to styrene using CO₂ as a mild oxidant.

Highly selective oxidation of methanol to dimethoxymethane over SO42−/V2O5–ZrO2

SO₄²⁻/V₂O₅–ZrO₂was an effective catalyst for the oxidation of methanol to dimethoxymethane, being mainly ascribed to the V₂O₅crystalline species.

Role of vanadium oxide and palladium multiple loading on the sensitivity and recovery kinetics of tin dioxide based gas sensors

Improving the gas sensing properties by Pd and V₂O₅ co-loading on the SnO₂ attributed to the role of each additive.

Enhancement of performance and sulfur resistance of ceria-doped V/Sb/Ti by sulfation for selective catalytic reduction of NOx with ammonia

A ceria-doped V/Sb/Ti catalyst prepared by sulfation was investigated for the selective catalytic reduction of NO_x by NH₃.

Gas phase dehydration of glycerol catalyzed by gamma Al2O3 supported V2O5: a statistical approach for simultaneous optimization

Selective gas-phase dehydration of glycerol to acrolein over V₂O₅/γ-Al₂O₃ catalysts was investigated.

NH3-SCR denitration catalyst performance over vanadium-titanium with the addition of Ce and Sb

Selective catalytic reduction technology using NH3 as a reducing agent (NH3-SCR) is an effective control method to remove nitrogen oxides. TiO2-supported vanadium oxide catalysts with different levels of Ce and Sb modification were prepared by an impregnation method and were characterized by X-ray diffractometer (XRD), Brunauer-Emmett-Teller (BET), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), Raman and Hydrogen temperature-programmed reduction (H2-TPR). The catalytic activities of V5CexSby/TiO2 catalysts for denitration were investigated in a fixed bed flow microreactor. The results showed that cerium, vanadium and antimony oxide as the active components were well dispersed on TiO2, and the catalysts exhibited a large number of d-d electronic transitions, which were helpful to strengthen SCR reactivity. The V5CexSby/TiO2 catalysts exhibited a good low temperature NH3-SCR catalytic activity. In the temperature range of 210 to 400°C, the V5CexSby/TiO2 catalysts gave NO conversion rates above 90%. For the best V5Ce35Sb2/TiO2 catalyst, at a reaction temperature of 210°C, the NO conversion rate had already reached 90%. The catalysts had different catalytic activity with different Ce loadings. With the increase of Ce loading, the NO conversion rate also increased.

Efficient V2O5/TiO2 composite catalysts for dimethoxymethane synthesis from methanol selective oxidation

The figure presented the catalytic performances of composite supported V₂O₅–TiO₂–SiO₂ catalyst prepared by improved sol–gel method. V₂O₅–TiO₂–SiO₂ catalyst showed efficient activity of 51% methanol conversion and 99% DMM selectivity at 413 K.

New insight into the promotion effect of Cu doped V2O5/WO3–TiO2 for low temperature NH3-SCR performance

The promotion effect of Cu on the V/WTi catalyst for the selective catalytic reduction of NO_x by NH₃ was investigated in the temperature range of 150–400 °C.

Removal of gaseous HxCBz by gliding arc plasma in combination with a catalyst

Hexachlorobenzene (HxCBz) owns the chemical structure of one benzene ring and six H atoms substituted by Cl atoms and it is a persistent organic pollutant present in flue gas from municipal solid waste incineration as an important precursor of dioxins. Its removal was studied using gliding arc plasma treatment, coupled downstream with a V2O5–WO3–TiO2 catalyst. Several parameters (input voltage, O2 concentration, catalytic temperature and catalyst position) all influenced its removal efficiency (RE). Optimal parameter settings were tentatively determined, i.e., an input voltage of 15 kV, the temperature of the catalyst (250 °C), and the O2 concentration (30 vol% O2) tested at a single, fixed concentration of gaseous HxCBz (71.6 ng Nm−3). A maximum RE of 76 ± 3% HxCBz was attained, with the plasma and coupled catalyst combined. Two destruction pathways, incorporating dechlorination and oxidation reactions, were recognised, both based on the detection of end- and intermediate products as well as of active species produced by the plasma. These end- and intermediate products included: low chlorinated polychlorobenzenes (mainly 1,2,4-Trichlorobenzene) as well as hydrocarbons (mainly C2H6), HCOOH, CH4, CO, CO2, etc.

Comparison of a VO x -TiO2 and a VO x /SbO y -TiO2 Industrial Catalyst in the Oxidative Scission of Methyl Ethyl Ketone and 2-Butanol to Acetic Acid

The oxidative scission of methyl ethyl ketone and 2-butanol on a VO x -TiO2 and a VO x /SbO y -TiO2 catalyst was studied in the temperature range of 120 to 280°C in the presence of water vapour. The catalytic performance of the two catalysts was investigated by variation of reaction temperature and contact time, and the catalysts were characterized by BET, XRD, XPS, TPR-H2, TPD-NH3, and temperature programmed desorption of lattice oxygen (TPD-O2). The investigations indicate that the addition of Sb2O3 to VO x -TiO2 favours the selective formation of acetic acid and depresses total oxidation to CO x in the catalytic oxidation of methyl ethyl ketone and 2-butanol due to changes in the redox properties of the VO x -TiO2 system. Moreover, the higher acidity of the VO x -TiO2 catalyst favours the dehydration of 2-butanol to n-butenes.