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Production of fuels and chemicals from renewable biomass resources is an attractive way to alleviate the shortage of fossil fuels and reduce CO2 emission. Glycerol is an important biomass derivative currently produced as a by-product in the manufacture of biodiesel in a huge amount close to 10 wt% of the overall biodiesel production. The application of glycerol as a renewable raw material has attracted much attention in the last decade, and some catalytic technologies for the conversion of glycerol into useful chemicals such as methanol, epichlorohydrin, and 1,2-propanediol have been established. Acrylic acid is an important bulk chemical widely used in the manufacture of polymeric products and is currently produced in the petrochemical industry via two-step gas-phase oxidation of propylene. The depletion of fossil resources motivates developments in the production of acrylic acid from renewable raw materials. Glycerol has potential for use as a raw material for the production of acrylic acid, and the variety of glycerol derivatives provides opportunities for producing acrylic acid from glycerol through different ways. In this review, possible routes and the corresponding catalytic technologies for the conversion of glycerol to acrylic acid are primarily summarized, and the advantages as well as the challenges in each route are discussed. [ABSTRACT FROM AUTHOR]

The role of the crystalline phase of Mo3VO x in the catalytic oxidation of allyl alcohol over four kinds of crystalline (orthorhombic, trigonal, tetragonal, amorphous) Mo3VO x catalysts was investigated to determine the active sites for the reactions. Tetragonal Mo3VO x was found less active for the formation of acrylic acid from allyl alcohol, although acrolein was obtained selectively at higher temperature. For orthorhombic and trigonal Mo3VO x catalyst, allyl alcohol converted to acrolein and propanal competitively at the mouth of the heptagonal channel over the a- b plane of the rod-type crystalline particles, and these aldehydes were oxidized consecutively to acrylic acid. Acrylic acid was formed effectively at increased reaction temperature over orthorhombic, trigonal and amorphous Mo3VO x catalysts, and the maximum yields of acrylic acid were 73 % for the orthorhombic Mo3VO x catalyst and 72 % for the trigonal Mo3VO x catalyst at 350 °C. [ABSTRACT FROM AUTHOR]

Being single (crystalline): Four single‐crystalline‐phase Mo3VOx materials are utilized as catalysts for the partial oxidation of acrolein to acrylic acid. The crystalline structure has a clear effect on catalytic performance. Mo3VOx with a trigonal crystalline structure is the most efficient catalyst: 99.8 % conversion with 93.9 % selectivity for acrylic acid is obtained at a temperature (217.3 °C) much lower than that previously reported. [ABSTRACT FROM AUTHOR]

Mo-V-O-based complex metal oxide catalysts were synthesized hydrothermally for the first time, characterized structurally and tested in the selective oxidation of propane to acrylic acid, and the results obtained were compared on the basis of catalyst crystal structures in order to clarify key aspects of alkane selective oxidation over multifunctional metal oxide catalysts. The catalysts tested were black solids of rod-shaped crystals, which had a layer structure in the direction of fiber axis and various high dimensional arrangements of metal octahedra in the cross-section plane. A strong dependency on the octahedra arrangements and a facet dependency were observed, and the roles of metal elements in the course of selective oxidation of propane were clarified by comparing the catalytic performance of various Mo-V-O-based catalysts. We discuss the multi-functional character derived from high dimensional structures of the catalysts and mechanism of the selective oxidation of propane. [ABSTRACT FROM AUTHOR]

Abstract: Three single crystalline Moh name="sbnd" />O based oxides, Moh name="sbnd" />O, Moh name="sbnd" />Tece:glyph name="sbnd" />Vph name="sbnd" />Nb which have the same orthorhombic layer-type structure with the particular arrangement of MO6 (M = Mo, V, Nb) octahedra forming slabs with pentagonal, hexagonal, and heptagonal rings in (100) plane, were synthesized by hydrothermal method and their catalytic performance in the selective oxidation of propane to acrylic acid were compared in order to elucidate the roles of constituent elements and crystal structure in the course of the propane oxidation. It was observed that the rate of propane oxidation was almost the same over all three catalysts, revealing that Mo and V, which were indispensable elements for the structure formation, were responsible for the catalytic activity for propane oxidation. The Te-containing catalysts showed much higher selectivity to acrylic acid than the Moh name="sbnd" />O catalyst. Since propene was formed as a main product at low conversion levels over every catalyst, it can be concluded that Te located in the central position of the hexagonal ring promoted the conversion of intermediate propene effectively to acrylic acid. The catalyst with Nb occupying the same structural position of V clearly showed the improved selectively to acrylic acid particularly at high conversion region, because the further oxidation of acrylic acid to CO x was greatly suppressed. These conclusions were further supported by the additional studies of the determination of activation energy and catalytic oxidations of intermediate products of the propane oxidation. [Copyright &y& Elsevier]

Several single phasic MoVO-based mixed oxides, all of which have a layer structure in the direction of c-axis and a high dimensional arrangement of metal octahedra in a–b plane, were synthesized by hydrothermal method and their catalytic performance in the selective oxidation of propane to acrylic acid were compared in order to elucidate structure effects on catalytic property and roles of constituent elements. It was clearly demonstrated that the catalyst with the particular arrangement of MO6 (M = Mo, V) octahedra forming slabs with pentagonal, hexagonal and heptagonal rings in (001) plane of orthorhombic structure was exclusively superior both in the propane oxidation activity and in the selectivity to acrylic acid to the other related Mo- and V-based layer oxide catalysts consisting of either pentagonal or hexagonal ring unit. The role of constituent elements was clarified by the comparison of catalytic performance of MoVO, MoVTeO and MoVTeNbO, all of which have the same orthorhombic structure. Mo and V, which were indispensable elements for the structure formation, were found to be responsible for the catalytic activity for propane oxidation. Te located in the central position of the hexagonal ring promoted the conversion of intermediate propene effectively, resulting in a high selectivity to acrylic acid. The introduced Nb occupied the same structural position of V and the resulting catalyst clearly showed the improved selectively to acrylic acid particularly at high conversion region, because the further oxidation of acrylic acid to COx was suppressed. [Copyright &y& Elsevier]

Preparation of a new orthorhombic Mo--V--O catalyst was succeeded by hydrothermal synthesis for the first time. This orthorhombic structure showed high activity for propane oxidation. Selectivity to acrylic acid dramatically increased by the introduction of Te into the orthorhombic Mo--V--O catalyst. [ABSTRACT FROM AUTHOR]

W–V–Nb–O complex metal oxides having a structure like that of orthorhombic Mo 3 VO x were found to be an efficient catalyst for the gas-phase direct oxidative transformation of glycerol to acrylic acid. The catalysts with various compositions were facilely synthesized by hydrothermal method. The W–Nb–O catalyst without V component, mainly promoted the glycerol dehydration, giving acrolein selectively. Since Nb–O catalyst showed poor activity for the reaction, the introduction of W into the Nb–O catalysts was found effective for improving the activity for the dehydration of glycerol to acrolein. This is mainly due to the increase of Brönsted acidity by the combination of W and Nb. When V was incorporated into the framework of W–Nb–O, the resulting catalyst was found to prominently promote the formation of acrylic acid in the glycerol transformation in the presence of O 2 , while showed no effect on the dehydration of glycerol to acrolein. It was also found that V acts as an oxidation site only when glycerol is completely reacted. The optimum elemental composition for the reaction was W 2.2 V 0.4 Nb 2.4 O 14 giving ca. 46% one path yield of acrylic acid and this catalytic performance was further improved by the surface modification with phosphoric acid, achieving ca. 60% one path yield of acrylic acid. [ABSTRACT FROM AUTHOR]

• Additional elements were introduced into crystalline trigonal Mo 3 VO x catalysts. • Local catalyst structure of the catalysts was strongly influenced the catalytic activity for selective oxidation of ethane, acrolein and allyl alcohol. • Trigonal Mo 3 VO x containing Fe in the crystal structure showed excellent acrylic acid yield by the one pot selective oxidation of allyl alcohol. • Partial location of metals in the micropore affected the catalytic properties. Crystalline "MoVO", "MoVCuO", "MoVFeO" and "MoVWO" catalysts with a trigonal symmetry were successfully synthesized and characterized. The influence of the as-obtained structures on catalytic performances in selective oxidation reactions was investigated. MoVFeO and MoVCuO accomodated Fe and Cu species inside heptagonal channels, while W in MoVWO was incorporated in pentagonal {Mo 6 O 21 }6− units. Whereas MoVO and MoVWO showed catalytic activity in the selective oxidation of ethane and acrolein, MoVFeO and MoVCuO performed very poorly in the same reaction, suggesting that the presence of empty heptagonal channels is related to ethane and acrolein activations. In the selective oxidation of allyl alcohol, substantial amounts of acrolein (formed by oxidative dehydrogenation) and propanal (formed by isomerization) were formed as primary products over MoVO and MoVWO, whereas MoVFeO and MoVCuO preferentially promoted the formation of acrolein. It was found that the local crystal structure around the heptagonal channel was related with a modification of the reaction pathway for the selective oxidation of allyl alcohol. Due to the prevention of isomerization over MoVFeO, a high acrylic acid yield of 83.1% from allyl alcohol was achieved at 350 °C over this sample. [ABSTRACT FROM AUTHOR]