Bismuth Molybdate Catalysts Research Articles

Efficient degradation of 2,4-DCP by activated molecular oxygen with the introduction of oxygen vacancies in bismuth molybdate catalysts

In this study, the tunability of oxygen vacancies in bismuth molybdate was achieved using a simple solvothermal method assisted by iodine doping. Various characterizations were conducted to investigate the relationship between oxygen vacancy concentrations in bismuth molybdate and iodine doping. The introduction of ample oxygen vacancies through the doping of iodine significantly enhanced molecular oxygen activation, granting Bi2MoO6 high activity for the photocatalytic degradation of 2,4-DCP. Furthermore, the degradation of 2,4-DCP under visible light irradiation reached 78% completion within 180 min. The removal of 2,4-DCP by the I-BMO/PMS system was improved to 87% because of the crucial role of PMS in generating SO42- and inducing photogenerated electron synergism. The results of free radical trapping experiments were combined with these findings to propose a possible degradation mechanism for 2,4-DCP. This study provides a novel perspective on the photocatalytic degradation of organochlorine pesticides using Bi2MoO6.

Microwave-assisted rapid synthesis of bismuth molybdate with enhanced oxidative desulfurization activity

In this work, six different bismuth molybdate catalysts were synthesized by a fast microwave-assisted hydrothermal method. By adjusting the pH in the preparation process, the morphology and structure of the synthesized catalysts can be modified, and the transition of Bi2MoO6 crystals to Bi3.2Mo0.8O7.5 crystals can be selectively achieved. The sample prepared at pH 1, BMO-1, exhibited excellent activity for oxidizing sulfur compounds in fuel oil at 60 °C with a molar hydrogen peroxide to sulfur ratio of four, achieving removal rates of dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene of 99.71%, 99.68%, and 77.95%, respectively. When recycling the catalyst seven times, the removal rate of dibenzothiophene still reached 98.07%. A probable mechanism for the oxidative desulfurization process was proposed. This work not only offers a high-efficiency, method for the rapid preparation of bismuth molybdate catalysts but also extends the application of this catalyst in the field of deep oxidative desulfurization.

Selective oxidation of biomass‐based 5‐hydroxymethylfurfural to 2,5‐diformylfuran catalyzed by multicomponent molybdenum‐based catalyst

AbstractBACKGROUNDOn the way to convert biomass‐derived products as a renewable and environment‐friendly source to high‐value added chemicals, one great challenge is the effective control of selectivity in the reaction. Here, we contribute a heterogeneous catalysis method for selective transformation of biomass‐based 5‐hydroxymethylfurfural (HMF) into 2,5‐diformylfuran (DFF) via multicomponent bismuth molybdate catalyst. The influence of the different pH value on the catalytic activity of the catalyst were investigated. In addition, to evaluate the catalytic performance of the catalyst in the selective oxidation of HMF, a variety of important reaction parameters such as the reaction temperature, catalyst amount, atmosphere, and solvent were examined.RESULTSThe catalyst prepared with pH value in the range of 1–2 exhibits the optimal catalytic activity in the selective aerobic oxidation of the hydroxy group of HMF. As a result, the target compound of DFF could be obtained with excellent yield (99%) and high selectivity (> 99%) in the presence of 0.25 mg Co9Fe3BiMo12O51 (pH = 1–2) in DMSO at 130 °C under O2 atmosphere. In addition, the catalyst Co9Fe3BiMo12O51 could be reused several times without a significant loss of its catalytic activity.CONCLUSIONIn this work, a heterogeneous catalytic approach to oxidizing HMF to DFF using Co9Fe3BiMo12O51 as catalyst and molecular oxygen as oxidant was established. The O2 temperature‐programmed desorption (O2‐TPD) characterization indicated that the pH value of co‐precipitation obviously affected the oxygen mobility and storage capacities in the catalysts, which is related to the catalytic performance in the selective aerobic oxidation. © 2022 Society of Chemical Industry (SCI).

Insights into the mechanism and kinetics of propene oxidation and ammoxidation over bismuth molybdate catalysts derived from experiments and theory

Robert K. Grasselli was a pioneer in the development and commercialization of catalysts for propene oxidation to acrolein and ammoxidation to acrylonitrile, products that today are produced at the level of over 10 billion pounds per year. The catalysts used for both processes are contain bismuth molybdates augmented by up to seven additional elements used to attain high activity, selectivity, and stability. The importance of propene oxidation and ammoxidation has stimulated considerable interest in understanding the mechanism and kinetics of these processes and the particular role of catalyst composition and structure in defining catalyst activity and selectivity. Virtually all of this work has been carried out using bismuth molybdates, primarily α-Bi2Mo3O12. The objective of this paper is to review the findings of experimental studies and illustrate how theoretical studies based on density functional theory provide additional insights that support deductions drawn from experiments and, more importantly, provide information that cannot be accessed experimentally.

The Synergy Effect in Tio2 Supported Bi-Mo Catalysts for Facile and Environmentally-Friendly Synthesis of Pyridylaldehydes from Oxidation of Picolines

The oxidation of picolines to pyridlaldehydes was studied over bismuth molybdate catalysts supported on TiO2. The research results showed that α-Bi2Mo3O12 was superior to β-Bi2Mo2O9 and γ-Bi2MoO6 in terms of reactivity. Further doping MoO3 to α-Bi2Mo3O12/TiO2 gave rise to increased catalytic performance, which was due to the synergy effect of α-Bi2Mo3O12 and MoO3. The effect was on one hand manifested in the intimate relationship between α-Bi2Mo3O12 and MoO3 in stabilizing the crystallographic structure of catalysts and thereafter maintaining the surface area of the catalyst, as indicated by the BET surface area and XRD analysis. Moreover, NH3-TPD analysis demonstrated the effect in modifying the surface acidity of the catalysts, and thus facilitating the substrate adsorption as the picolines are alkaline substances. Additionally, the effect between α-Bi2Mo3O12 and MoO3 rendered the modification of the electronic properties and thereafter the oxygen desorption properties and reducible properties of the catalysts, as evidenced in the H2-TPR and O2-TPD analysis.

Sol–Gel Synthesis of Bismuth Molybdate Catalysts for the Selective Oxidation of Propylene to Acrolein: Influence of pH Value and Theoretical Molar Atomic Ratio

Different bismuth molybdate catalysts for the selective oxidation of propylene to acrolein were prepared by the sol–gel method, starting from bismuth nitrate, ammonium molybdate, and citric acid. The influence of pH value and theoretical molar Bi/Mo atomic ratio on the complexation and gelation is surveyed using IR spectroscopy, X‐ray diffraction, and BET. Their catalytic activities for the conversion propylene to acrolein are examined.

Synergy Effects of the Mixture of Bismuth Molybdate Catalysts with SnO2/ZrO2/MgO in Selective Propene Oxidation and the Connection between Conductivity and Catalytic Activity

Bismuth molybdate catalysts have been used for partial oxidation and ammoxidation of light hydrocarbons since the 1950s. In particular, there is the synergy effect (the enhancement of the catalytic activity in the catalysts mixed from different components) in different phases of bismuth molybdate catalysts which has been observed and studied since the 1980s; however, despite it being interpreted differently by different research groups, there is still no decisive conclusion on the origin of the synergy effect that has been obtained. The starting idea of this work is to find an answer for the question: does the electrical conductivity influence the catalytic activity (which has been previously proposed by some authors). In this work, highly conductive materials (SnO2, ZrO2) and nonconductive materials (MgO) are added to beta bismuth molybdates (β-Bi2Mo2O9) using mechanical mixing, impregnation, and sol–gel methods. The mixtures were characterized by XRD, BET, XPS, and EDX techniques to determine the phase ...

Ammoxidation of acrolein to acrylonitrile over bismuth molybdate catalysts

The present work deals with the potentially significant process converting acrolein of green origin to acrylonitrile using mesoporous bismuth molybdate catalysts. The ammoxidation catalysts were characterized by N2 physisorption, X-ray diffraction, and catalytic tests under various conditions at different temperatures, contact times, and reactant molar ratios. The results indicated a catalytic activity proportional to specific surface area, which depends on bismuth molybdate phases, and concentration of oxygen in the gas feed. The selectivity of the catalysts only depends on reaction temperature. ACN selectivity obtained at 350–400°C was 100% and reduced to 97% at 450°C.

Redox Behavior Analysis of Multicomponent Bismuth Molybdate Catalyst by Using In-situ XAFS

Redox Behavior Analysis of Multicomponent Bismuth Molybdate Catalyst by Using In-situ XAFS

Bismuth Molybdate Catalysts Prepared by Mild Hydrothermal Synthesis: Influence of pH on the Selective Oxidation of Propylene

A series of bismuth molybdate catalysts with relatively high surface area was prepared via mild hydrothermal synthesis. Variation of the pH value and Bi/Mo ratio during the synthesis allowed tuning of the crystalline Bi-Mo oxide phases, as determined by X-ray diffraction (XRD) and Raman spectroscopy. The pH value during synthesis had a strong influence on the catalytic performance. Synthesis using a Bi/Mo ratio of 1/1 at pH ≥ 6 resulted in γ-Bi2MoO6, which exhibited a better catalytic performance than phase mixtures obtained at lower pH values. However, a significantly lower catalytic activity was observed at pH = 9 due to the low specific surface area. γ-Bi2MoO6 synthesized with Bi/Mo = 1/1 at pH = 6 and 7 exhibited relatively high surface areas and the best catalytic performance. All samples prepared with Bi/Mo = 1/1, except samples synthesized at pH = 1 and 9, showed better catalytic performance than samples synthesized with Bi/Mo = 2/3 at pH = 4 and 9 and γ-Bi2MoO6 synthesized by co-precipitation at pH = 7. At temperatures above 440 °C, the catalytic activity of the hydrothermally synthesized bismuth molybdates started to decrease due to sintering and loss of surface area. These results support that a combination of the required bismuth molybdate phase and a high specific surface area is crucial for a good performance in the selective oxidation of propylene.

Oxidative dehydrogenation of 1-butene over vanadium modified bismuth molybdate catalyst: an insight into mechanism

The effect of vanadium addition on the performance of bismuth molybdate catalysts has been discussed. The mechanism of oxygen mobility on the prepared catalysts is proposed.

Selective oxidation of propylene to acrolein by hydrothermally synthesized bismuth molybdates

Hydrothermal synthesis has been used as a soft chemical method to prepare bismuth molybdate catalysts for the selective oxidation of propylene to acrolein. All obtained samples displayed a plate-like morphology, but their individual aspect ratios varied with the hydrothermal synthesis conditions. Application of a high Bi/Mo ratio during hydrothermal synthesis afforded γ-Bi2MoO6 as the main phase, whereas lower initial bismuth contents promoted the formation of α-Bi2Mo3O12. Synthesis with a Bi/Mo ratio of 1:1 led to a phase mixture of α- and γ-bismuth molybdate showing high catalytic activity. The use of nitric acid during hydrothermal synthesis enhanced both propylene conversion and acrolein yield, possibly due to a change in morphology. Formation of β-Bi2Mo2O9 was not observed under the applied conditions. In general, the catalytic performance of all samples decreased notably after calcination at 550°C due to sintering.

One-step synthesis of bismuth molybdate catalysts via flame spray pyrolysis for the selective oxidation of propylene to acrolein.

Flame spray pyrolysis (FSP) of Bi(III)- and Mo(VI)-2-ethylhexanoate dissolved in xylene resulted in various nanocrystalline bismuth molybdate phases depending on the Bi/Mo ratio. Besides α-Bi2Mo3O12 and γ-Bi2MoO6, FSP gave direct access to the metastable β-Bi2Mo2O9 phase with high surface area (19 m(2) g(-1)). This phase is normally only obtained at high calcination temperatures (>560 °C) resulting in lower surface areas. The β-phase was stable up to 400 °C and showed superior catalytic performance compared to α- and γ-phases in selective oxidation of propylene to acrolein at temperatures relevant for industrial applications (360 °C).

Influence of Graphite as a Shaping Agent of Bi Molybdate Powders on Their Mechanical, Physicochemical, and Catalytic Properties

The influence of using graphite (G) as a shaping agent for bismuth molybdate (BiMo) catalysts was analyzed. Shaping was done by tableting, with addition of different loadings of graphite (0, 0.5, 1, 3, 5, 7, and 10 wt %). The use of graphite during the pressing of bismuth molybdate powders eases tableting because of the lubricating properties of the former. Furthermore, the compressive strength of BiMo-G tablets is higher than that of pure BiMo. Concerning the physicochemical properties of BiMo-G, XRD and XPS showed that graphite changes neither the relative distribution of the crystallographic phases of bismuth molybdate nor the oxidation state of bismuth and molybdenum in the tableted powders. Consequently, the shaped BiMo-G catalysts displayed similar, or slightly better, performances in the selective oxidation of propylene to acrolein. TGA analysis of samples of BiMo-G confirmed the thermal stability of the catalysts under oxidative conditions. Graphite was observed to experience crystallization into the hexagonal 2H phase during the catalytic tests. The results reported herein demonstrate that graphite is an effective shaping agent for bismuth molybdate powders.

Selective oxidation of propylene to acrolein by silica-supported bismuth molybdate catalysts

Silica-supported bismuth molybdate catalysts have been prepared by impregnation, structurally characterized and examined as improved catalysts for the selective oxidation of propylene to acrolein. Catalysts with a wide range of loadings (from 10 to 90 wt%) of beta bismuth molybdate (β-Bi2Mo2O9) were studied to provide a better understanding about the distribution of active sites, and to elucidate the role of lattice oxygen in the reaction. The catalyst containing 50 wt% of beta bismuth molybdate on SiO2 was found to possess good distribution of active sites and sufficiently high lattice oxygen, which resulted in an extraordinary increase of the catalytic activity.

THE EFFECT OF PHOSPHORUS ADDITION ON THE ACTIVITY OF BISMUTH MOLYBDATE CATALYST FOR PARTIAL OXIDATION OF PROPYLENE TO ACROLEIN

In order to examine the effect of phosphorus addition on the activity and selectivity of bismuth molybdate catalysts for partial oxidation of propylene to acrolein, three modes of phosphorus addition were performed. The three modes of Preparation were performed by (1) adding phosphorus into a-Bi2Mo3O12 to obtain Bi2PxMo3Oy, (2) inserting phosphorus on bismuth sites to obtain Bi2-xPxMo3Oy, and (3) inserting phosphorus on molybdenum sites to obtain Bi2PxMo3-xOy. Four major phases of bismuth phosphomolybdate were detected as the result of the phosphorus addition, namely a-Bi2Mo3O12, Bi9PMo12O52, MoO3, and BiPO4. Experimental results showed that the catalysts solely containing BiPO4 and/or MoO3 have very low activities for partial oxidation of propylene to acrolein. Meanwhile, catalysts containing a-Bi2Mo3O12 and Bi9PMo12O52, together with either MoO3 or BiPO4 showed on average the same activities as a-Bi2Mo3O12 and one of them (combination of a-Bi2Mo3O12, Bi9PMo12O52 and MoO3) has better performance than a-Bi2Mo3O12 at lower temperatures. The presence of the oxygen donor phase, i.e. BiPO4 and MoO3, are believed to play a key role for the high activities of bismuth-phosphomolybdate catalysts. However, at higher temperatures, the presence of oxygen donor reduces the catalyst selectivity to acrolein.

Production of 1,3-Butadiene From C4 Raffinate-3 Through Oxidative Dehydrogenation of n-Butene Over Bismuth Molybdate Catalysts

Recent progress on the bismuth molybdate catalysts for oxidative dehydrogenation of n-butene to 1,3-butadiene was reported in this review. A number of bismuth molybdate catalysts, including pure bismuth molybdates (α-Bi2Mo3O12, β-Bi2Mo2O9, and γ-Bi2MoO6) and multicomponent bismuth molybdates, were prepared by a co-precipitation method for use in the production of 1,3-butadiene from C4 raffinate-3 through oxidative dehydrogenation of n-butene. It was observed that multicomponent bismuth molybdate catalyst was more efficient than pure bismuth molybdate catalyst in the oxidative dehydrogenation of n-butene. Various experimental measurements such as temperature-programmed reoxidation, X-ray photoelectron spectroscopy, and O2-temperature-programmed desorption analyses were carried out to elucidate the different catalytic activity of bismuth molybdate catalysts. It was revealed that a bismuth molybdate catalyst with a higher oxygen mobility showed a better catalytic performance in terms of conversion of n-butene and yield for 1,3-butadiene. We have successfully demonstrated from experimental findings that oxygen mobility of bismuth molybdate catalyst played a key role in determining the catalytic performance in the oxidative dehydrogenation of n-butene to 1,3-butadiene.

Preparation, characterization and catalytic activity of Bi−Mo-based catalysts for the oxidative dehydrogenation ofn-butene to 1,3-butadiene

Multicomponent bismuth molybdates were prepared by a co-precipitation method for use in the oxidative dehydrogenation ofn-butene to 1,3-butadiene. The effect of divalent and trivalent metals on the catalytic performance of multicomponent bismuth molybdate catalysts was investigated. It was found that the metal ratio of Fe/Bi/Mo=3∶1∶12 was favorable for the reaction. The successful formation of Ni X Co8−X Fe3Bi1Mo12O50 (X=0−8) catalysts was well confirmed by XRD and ICP-AES measurements. The multicomponent bismuth molybdate catalysts showed a better catalytic performance than the pure γ-Bi2MoO6 catalyst. Among the Ni X Co8−X Fe3Bi1Mo12O50 (X=0−8) catalysts, Ni3Co5Fe3Bi1Mo12O50 showed the highest yield of 1,3-butadiene.

Oxidative dehydrogenation of n-butene to 1,3-butadiene over multicomponent bismuth molybdate (M II9Fe 3Bi 1Mo 12O 51) catalysts: Effect of divalent metal (M II)

Multicomponent bismuth molybdate (M II 9Fe 3Bi 1Mo 12O 51) catalysts with different divalent metal (M II = Mg, Mn, Co, Ni, and Zn) were prepared by a co-precipitation method, and were applied to the oxidative dehydrogenation of n-butene to 1,3-butadiene. Effect of divalent metal (M II) on the catalytic performance of M II 9Fe 3Bi 1Mo 12O 51 catalysts was investigated. X-ray photoelectron spectroscopy (XPS) measurements were conducted to determine the oxygen mobility of M II 9Fe 3Bi 1Mo 12O 51 catalysts. It was found that the catalytic performance of M II 9Fe 3Bi 1Mo 12O 51 catalysts was closely related to the oxygen mobility of the catalysts. The yield for 1,3-butadiene was monotonically increased with increasing oxygen mobility of the catalysts. Among the catalysts tested, the Co 9Fe 3Bi 1Mo 12O 51 catalyst with the highest oxygen mobility showed the best catalytic performance in the oxidative dehydrogenation of n-butene.

Structures, Mechanisms, and Kinetics of Selective Ammoxidation and Oxidation of Propane over Multi-metal Oxide Catalysts

In order to determine the chemical mechanism for the (amm)oxidation of propane and propene on multi-metal oxide (MMO) catalysts, we have carried out quantum mechanical (QM) calculations for model reactions on small clusters that we have used to train the parameters for the ReaxFF reactive force field, which enables molecular dynamics (MD) simulations for reactions on the complex reconstructed surfaces of MMO. We report here insights from the QM on the reaction mechanisms of selective (amm)oxidation of propene on bismuth molybdate catalysts and the oxidative dehydrogenation of propane on vanadium oxide catalysts. We also report the application of ReaxFF to predict the stable surfaces of the M1 phases of the MoVTeNbO catalysts.