Search

A vapor-phase dehydration of acetaldoxime to acetonitrile was investigated over various solid catalysts. Among the tested catalysts, ZrO2, Al2O3 and SiO2 showed high catalytic activity for the formation of acetonitrile from acetaldoxime, while the correlation between catalytic activity and the acid property of the catalysts was not observed. Weak acidic sites such as silanols sufficiently work as catalytic sites for the dehydration, which does not require strong acids such as zeolites. Several SiO2 catalysts with different physical properties were tested, and the SiO2 with the smallest pore size and the highest specific surface area showed the highest catalytic activity for the formation of acetonitrile. Because the dehydration of acetaldoxime to acetonitrile is exothermic, a large amount of reaction heat was generated during the reaction, and the reaction temperature was found to be significantly affected by the feed rate of the reactant and the flow rate of the carrier gas. In order to effectively utilize the in situ generated reaction heat, the dehydration of acetaldoxime to acetonitrile without using the external heat supply was conducted. The temperature was controllable even in the absence of the external heat, and the acetonitrile yield higher than 90% could be achieved in such a green operation under the environment-friendly adiabatic conditions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Adsorption structure of 1,4-butanediol on Er2O3 was elucidated by DFT calculation. [•] Interaction of 1,4-butanediol with Er2O3 was calculated by PIO theory. [•] Tridentate adsorption of 1,4-butanediol on Er2O3 accelerated the dehydration into 3-buten-1-ol. [•] Reaction mechanism in the dehydration of 1,4-butanediol over Er2O3 was elucidated. [•] The reaction proceeds via acid–base concerted mechanism over Er2O3. [Copyright &y& Elsevier]

Abstract: Vapor-phase dehydration of 1,4- and 1,5-alkanediols was investigated over three scandium ytterbium mixed oxides, Sc2-xYbxO3 (x=0.5, 1.0, and 1.5), to produce the corresponding unsaturated alcohols. In the dehydration of 1,5-pentanediol, Sc0.5Yb1.5O3 was more active than simple rare earth oxides such as Sc2O3, Lu2O3, Yb2O3, and Tm2O3. The selectivity to 4-penten-1-ol surpassed 80mol% over the Sc2-xYbxO3 catalysts. The highest formation rate of 4-penten-1-ol was obtained at x=1.5 and affected by lattice parameter of cubic bixbyite Sc2-xYbxO3. In the dehydration of 1,4-butanediol, however, Tm2O3 was the most active among the catalysts. [Copyright &y& Elsevier]

Applications of renewable biomass provide facile routes to alleviate the shortage of fossil fuels as well as to reduce the emission of CO 2 . Glycerol, which is currently produced as a waste in the biodiesel production, is one of the most attractive biomass resources. In the past decade, the conversion of glycerol into useful chemicals has attracted much attention, and glycerol is mainly converted by steam reforming, hydrogenolysis, oxidation, dehydration, esterification, carboxylation, acetalization, and chlorination. In this review, we focused on the catalytic hydrogenolysis of glycerol into C3 chemicals, which contain many industrially important products such as 1,2-propanediol, 1,3-propanediol, allyl alcohol, 1-propanol and propylene. In the hydrogenolysis of glycerol into propanediols, advantages and disadvantages of liquid- and vapor-phase reactions are compared. In addition, recent studies on catalysts, reaction conditions, and proposed pathways are primarily summarized and discussed. Furthermore, new research trends are introduced in connection with the hydrogenolysis of glycerol into allyl alcohol, propanols and propylene. [ABSTRACT FROM AUTHOR]

Vapor-phase catalytic dehydration of 5-amino-1-pentanol was investigated over various oxide catalysts including rare earth oxides (REOs). Over ordinary acidic oxides such as Al 2 O 3 , SiO 2 , SiO 2 -Al 2 O 3 , TiO 2, and ZrO 2 , a cyclic amine such as piperidine was mainly produced at temperatures of 300 °C and higher. In contrast, basic REOs with a cubic bixbyite structure showed the catalytic activity in the conversion of 5-amino-1-pentanol to produce 4-penten-1-amine at 425 °C. In REO catalysts, Tm 2 O 3 , Yb 2 O 3 , and Lu 2 O 3 showed the high conversion of 5-amino-1-pentanol and the high selectivity to 4-penten-1-amine. Especially, Yb 2 O 3 calcined at 800 °C showed a high formation rate of 4-penten-1-amine with the selectivity of ca. 90% at 425 °C. In comparing the reactivity of several amino alcohols to form the corresponding unsaturated amines, Yb 2 O 3 effectively catalyzed the dehydration of 6-amino-1-hexanol into 5-hexen-1-amine, whereas 3-amino-1-propanol and 4-amino-1-butanol were not effectively dehydrated due to the decomposition of the reactant. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dehydration of 3-methyl-1,3-butanediol into 3-methyl-3-buten-1-ol was investigated. [•] Carbon-modified alumina showed high selectivity to 3-methyl-3-buten-1-ol at 200°C. [•] The C-modified alumina was prepared by depositing coke using 3-methyl-3-buten-1-ol. [•] The selectivity to 3-methyl-3-buten-1-ol was increased by the coke content over Al2O3. [•] Formation of by-products such as isobutylene decreased by the coke deposition. [ABSTRACT FROM AUTHOR]

Abstract: Vapor-phase catalytic dehydration of 1,5-pentanediol was investigated over rare earth oxides (REOs) at 325–450°C. The conversion of 1,5-pentanediol over REOs calcined at 700 and 800°C was higher than that calcined at 500°C. Sc2O3, Yb2O3, and Lu2O3 with cubic bixbyite structure showed the selectivity to 4-penten-1-ol with higher than 74mol%, while REOs with hexagonal and monoclinic structures showed the selectivity with less than 50mol%. Especially, Yb2O3 and Lu2O3 calcined at 1000°C showed high formation rate of 4-penten-1-ol per specific surface area over 1mmolh−1 m−2 at 400°C. In the Yb2O3 catalyst calcined at 800°C, the conversion of 1,5-pentanediol was increased up to 74.4mol% with increasing contact time, together with stable selectivity to 4-penten-1-ol of 71.8mol%. In comparing the reactivity of alkanediols to form the corresponding unsaturated alcohols over Yb2O3, we found the reactivity of alkanediols into the corresponding unsaturated alcohols was the following order: 1,4-butanediol>1,3-diols≫1,5-pentanediol≫1,6-hexanediol. [Copyright &y& Elsevier]

Vapor-phase dehydration of 1,4-butanediol and 3-buten-1-ol to produce 1,3-butadiene was investigated over rare earth oxides such as Lu 2 O 3 , Yb 2 O 3 , Tm 2 O 3 , Er 2 O 3 , and Sc 1.0 Yb 1.0 O 3 . In the dehydration of 3-buten-1-ol, heavy rare earth oxides such as Lu 2 O 3 , Yb 2 O 3 , and Er 2 O 3 showed high catalytic performance for the selective formation of 1,3-butadiene with producing small amount of propylene whereas acidic catalysts such as alumina decomposed 3-buten-1-ol into propylene. In particular, over Yb 2 O 3 calcined at 800 °C, 3-buten-1-ol was converted with a yield of 1,3-butadiene higher than 95% at 340 °C. In the dehydration of 1,4-butanediol, furthermore, we developed an efficient catalytic system: 1,3-butadiene was produced via an intermediate, 3-buten-1-ol, over Yb 2 O 3 with an excellent yield of 96% at 360 °C and a high contact time of 2.26 h. Yb 2 O 3 successfully inhibited the major side reaction such as decomposition of 3-buten-1-ol to propylene and provided the selective production of 1,3-butadiene from 1,4-butanediol. [ABSTRACT FROM AUTHOR]

Vapor-phase catalytic dehydration of 1,5-pentanediol (1,5-PDO) was investigated over monoclinic ZrO 2 catalysts modified with basic oxides. An unsaturated alcohol, 4-penten-1-ol (4P1OL), was produced together with the formation of tetrahydropyran, δ-valerolactone, 1,4-pentadiene, pentanal, 1-pentanol, and 5-hydroxypentanal, etc. Among the modified ZrO 2 catalysts, only ZrO 2 modified with MgO enhanced the selectivity to 4P1OL efficiently. The most active modified catalyst was found to have 20 mol% MgO and a calcination at 800 °C (MgO/ZrO 2 ), and the selectivity of 4P1OL exceeded 83% at 400 °C. A pulse adsorption measurement of several chemicals clarified adsorptive interaction between a reactant and a catalyst at 220 °C: the interaction between 1,5-PDO and MgO/ZrO 2 was stronger than the other adsorbates and catalysts. Another strong adsorptive interaction between 1,4-butanediol and CaO/ZrO 2 , which was effective in the dehydration of 1,4-butanediol to produce 3-buten-1-ol, was also observed. [ABSTRACT FROM AUTHOR]

Vapor-phase catalytic dehydration of 1,4-butanediol (1,4-BDO) was investigated over modified ZrO 2 catalysts. In the dehydration of 1,4-BDO over monoclinic ZrO 2 (m-ZrO 2 ), an unsaturated alcohol, 3-buten-1-ol (3B1OL), was produced together with tetrahydrofuranand γ-butyrolactone. Among alkaline earth metal oxide modifiers, CaO with an appropriate content significantly enhanced the 3B1OL selectivity of m-ZrO 2 . The modification of CaO was more efficient over m-ZrO 2 than tetragonal ZrO 2 . CO 2 -TPD measurements reveal that CaO supported on m-ZrO 2 calcined at 800 °C or higher generated new basic sites, which are attributed from Ca-O-Zr hetero-linkages, for the effective formation of 3B1OL from 1,4-BDO. In order to create more Ca-O-Zr hetero-linkages on the m-ZrO 2 surface efficiently, additional ZrO 2 was loaded on m-ZrO 2 together with CaO via a co-impregnation method. At an appropriate weight ratio of CaO/ZrO 2 = 7/2 loaded on m-ZrO 2 , both the 1,4-BDO conversion and the 3B1OL selectivity were enhanced greatly. Especially, the 3B1OL selectivity exceeded 90% at 350 °C. [ABSTRACT FROM AUTHOR]

Vapor-phase dehydration of C4 unsaturated alcohols such as 3-buten-1-ol, 2-buten-1-ol and 3-buten-2-ol were performed to produce 1,3-butadiene over various solid catalysts including ordinary solid acid catalysts such as Al 2 O 3 , SiO 2 -Al 2 O 3 , and TiO 2 and basic rare earth metal oxides such as Yb 2 O 3 and CeO 2 . In the reaction of 3-buten-1-ol, 1,3-butadiene could not be selectively produced because the acid catalysts decomposed 3-buten-1-ol into propylene. In contrast to the acid catalysts, CeO 2 inhibited the decomposition of 3-buten-1-ol and showed a relatively high performance for the formation of 1,3-butadiene. In the dehydration of 2-buten-1-ol and 3-buten-2-ol, however, acid catalysts were effective for the formation of 1,3-butadiene. Among the tested catalysts, commercial SiO 2 -Al 2 O 3 showed a relatively high catalytic performance, although it deactivated rapidly. We prepared a series of SiO 2 /Al 2 O 3 catalysts by depositing SiO 2 species onto Al 2 O 3 support, and the SiO 2 /Al 2 O 3 with a SiO 2 content of 10 wt.% showed more stable catalytic activity than the commercial SiO 2 -Al 2 O 3 . Furthermore, modification of SiO 2 /Al 2 O 3 with Ag at a loading of 3–5 wt.% was found to be efficient for inhibiting the coke formation and improving the catalytic stability of SiO 2 /Al 2 O 3 in the dehydration of both 2-buten-1-ol and 3-buten-2-ol under hydrogen flow conditions. [ABSTRACT FROM AUTHOR]

Vapor-phase catalytic dehydration of 2,3-butanediol (2,3-BDO) to produce 3-buten-2-ol (3B2OL) was investigated over several monoclinic ZrO 2 (m-ZrO 2 ) catalysts modified with alkaline earth metal oxides (MOs), such as SrO, BaO, and MgO, to compare with the previously reported CaO/m-ZrO 2 . It was found that these modifiers enhanced the 3B2OL formation to the same level as CaO did by loading an appropriate MO content. Among all the tested catalysts, the BaO/m-ZrO 2 calcined at 800 °C with a low BaO content (molar ratio of BaO/ZrO 2 = 0.0452) shows the highest 2,3-BDO conversion (72.4%) and 3B2OL selectivity (74.4%) in the initial stage of 5 h at 350 °C. In order to characterize those catalysts, their catalytic activities, crystal structures, and basic properties were studied in detail. In X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) experiment, it was elucidated that highly dispersed M-O-Zr (M = Ca, Sr, and Ba) hetero-linkages were formed on the surface by loading these MOs onto m-ZrO 2 with an appropriate content and then calcining at 800 °C. It can be concluded that the M-O-Zr hetero-linkages generate the proper base-acid balance for the efficient formation of 3B2OL from 2,3-BDO. [ABSTRACT FROM AUTHOR]

• Dehydration of crotyl alcohol to 1,3-butadiene over silica-supported V, Al, and W oxides was investigated. • 1,3-Butadiene formation was initialized by isomerization to 3-butene-2-ol over Lewis acid sites of V 2 O 5 /SiO 2 catalyst. • Brønsted acid sites of Al 2 O 3 /SiO 2 catalyzed both stepwise reaction and direct dehydration of crotyl alcohol to 1,3-butadiene. • Dehydration route of crotyl alcohol to 1,3-butadiene over WO 3 /SiO 2 was influenced by W loading. • Density functional theory calculation and poisoning experiment clarified the dehydration mechanism. Catalytic dehydration of crotyl alcohol (2B1OL) to 1,3-butadiene (BD) over silica-supported metal oxides such as V 2 O 5 /SiO 2 , Al 2 O 3 /SiO 2 , and WO 3 /SiO 2 was investigated by kinetic analysis, acid-base titration including poisoning experiments, and theoretical calculations. The BD production over V 2 O 5 /SiO 2 catalyst proceeded via stepwise reaction, in which isomerization of 2B1OL into 3-butene-2-ol (3B2OL) occurred before consecutive dehydration of 3B2OL proceeded to give BD. Both direct dehydration of 2B1OL into BD and stepwise reaction via 3B2OL proceeded over Al 2 O 3 /SiO 2 catalyst. Meanwhile, the mechanism for the BD production over WO 3 /SiO 2 catalyst was affected by the W loading. The poisoning experiment by use of 2,6- and 3,5-dimethylpyridine clarified the role of Brønsted and Lewis acid sites in the transformation of 2B1OL into BD over these catalysts. The density functional theory calculations show that the activation energies of elemental reactions and desorption energy of 3B2OL dominate the reaction selectivity, which clarifies the behaviors of different metal oxide catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

Vapor-phase cyclodehydration of diethylene glycol (DEG) into 1,4-dioxane (DOX) were performed over several solid acid catalysts, such as Al 2 O 3 , SiO 2 Al 2 O 3 , Beta and MFI zeolites. All the catalytic activity gradually decreased with time on stream, especially Beta and MFI zeolites with strong acidic property. The catalysts were modified with silver metal for stabilizing the catalytic activity: Al 2 O 3 modified with 1 wt.% Ag 2 O showed the best catalytic performance. Characterizations such as XRD, TPD and FTIR were performed for analyzing the carbonaceous compound deposited on the catalysts after reaction and investigating the effect of the addition of Ag 2 O onto Al 2 O 3 . Polyethylene glycol was proposed as the carbonaceous compound by FTIR analysis. The modification of Ag was found to decrease the averaged acid strength of Al 2 O 3 , which is supposed to be effective for inhibiting carbon deposition and stabilizing the catalytic activity. It was also found that H 2 , as a carrier gas, was indispensable for stabilizing the conversion of DEG into DOX. Silver metal would work as a remover of the product on the catalyst surface together with H 2 to prevent carbon deposition. Over Al 2 O 3 modified with 1 wt.% Ag 2 O, a stable DOX selectivity of 90% with a complete conversion was achieved at 250 °C and a contact time of 156.8 g h mol −1 . [ABSTRACT FROM AUTHOR]

Vapor-phase catalytic dehydration of 2,3-butanediol was investigated over metal oxides such as CeO2, La2O3, Yb2O3, ZrO2, Al2O3, TiO2, ZnO, Fe2O3, NiO, and Cr2O3. In the dehydration of 2,3-butanediol, 3-buten-2-ol was preferentially produced over monoclinic ZrO2 along with major by-products such as butanone and 3-hydroxy-2-butanone. Over ZrO2 calcined at 900°C, 3-buten-2-ol was produced with a maximum selectivity of 59.0% at 300°C without producing 1,3-butadiene. [ABSTRACT FROM AUTHOR]

[Display omitted] • Vapor-phase dehydration of 1,3-butanediol was investigated over oxygen-defected Yb 2 Zr 2 O 7 catalysts. • An efficient oxygen-defected Yb 2 Zr 2 O 7 catalyst was prepared through a hydrothermal treatment at 200 °C. • Catalytic activity was significantly affected by calcination temperature of Yb 2 Zr 2 O 7 catalysts. • Unsaturated alcohols such as 3-buten-2-ol and 2-buten-1-ol were preferentially produced in the dehydration. • Stable conversion of 1,3-butanediol with high unsaturated alcohols selectivity of 96.0% was obtained at 325 °C. Vapor-phase dehydration of 1,3-butanediol was performed over Yb 2 O 3 -ZrO 2 catalysts in an ambient nitrogen atmosphere. Catalysts were prepared by a hydrothermal (HT) method as well as a coprecipitation method. The Yb 2 O 3 -ZrO 2 sample prepared by HT was confirmed to be crystallites of oxygen-defected type cubic Yb 2 Zr 2 O 7 , while the as-prepared coprecipitation sample was amorphous. The HT samples had high specific surface areas as ca. 40 m2 g−1 even after calcined at temperatures higher than 800 °C, whereas the coprecipitation samples without HT was readily sintered at the high temperatures. The best catalytic performance was obtained over HT Yb 2 O 3 -ZrO 2 catalyst calcined at 900 °C: the total selectivity to unsaturated alcohols was higher than 95% at a 1,3-butanediol conversion of 82% at 325 °C. The structure of active sites and the reaction mechanism of the dehydration of 1,3-butanediol were discussed. We proposed that an oxygen defect site on the stable (111) face of cubic Yb 2 Zr 2 O 7 would provide an active site, and that Zr4+, Yb3+, and O2- exposed on the defect could coordinate with a 1,3-butanediol molecule to form a tridentate coordination structure, which possibly initiate the dehydration to produce unsaturated alcohols through a base-acid concerted mechanism. [ABSTRACT FROM AUTHOR]