Adsorption properties of palladium particles supported on aluminum oxides with varied acidity in hydrogenation of butadiene-1,3

© 2017, Pleiades Publishing, Ltd.Influence exerted by acid-base modifiers of aluminum hydroxide on the texture and acid characteristics of the aluminum oxide support was studied. The effect of the modified aluminum oxides on the charge state of the active component of aluminum-palladium catalysts was determined. It was found that catalysts based on a support with high concentration of strong acid centers are characterized by low conversion of butadiene-1,3 due to the firm chemisorption of the diene on electron-deficient palladium particles. Their formation is due to the strong metal-support interaction. By contrast, catalysts synthesized with supports having a small number of acid centers provide a high conversion of butadiene-1,3

Modification of a phase-inhomogeneous alumina support of a palladium catalyst. Part II: the effect of palladium dispersion on the formation of hydride forms, electronic state, and catalytic performance in the reaction of partial hydrogenation of unsaturated hydrocarbons

It was shown for the first time that amorphous phase in an alumina support promotes the formation of palladium particles in a wide size range. This catalyst has a low selectivity to butenes in the 1,3-butadiene hydrogenation. It was suggested that surface palladium aluminates contribute to an increase in butene selectivity up to 99.5% at a hydrogenation temperature of not more than 65 °C. At higher reaction temperatures, the catalyst based on phase-homogeneous γ-Al2O3 has the highest activity and butene selectivity. This catalyst was obtained by the traditional impregnation method and contains highly dispersed palladium particles with a sufficiently high electron density. It was shown that the formation of hydride forms on palladium particles with a size of less than 1 nm was detected by temperature-programmed reduction with hydrogen

Adsorption properties of palladium particles supported on aluminum oxides with varied acidity in hydrogenation of butadiene-1,3

© 2017, Pleiades Publishing, Ltd.Influence exerted by acid-base modifiers of aluminum hydroxide on the texture and acid characteristics of the aluminum oxide support was studied. The effect of the modified aluminum oxides on the charge state of the active component of aluminum-palladium catalysts was determined. It was found that catalysts based on a support with high concentration of strong acid centers are characterized by low conversion of butadiene-1,3 due to the firm chemisorption of the diene on electron-deficient palladium particles. Their formation is due to the strong metal-support interaction. By contrast, catalysts synthesized with supports having a small number of acid centers provide a high conversion of butadiene-1,3

Adsorption properties of palladium particles supported on aluminum oxides with varied acidity in hydrogenation of butadiene-1,3

© 2017, Pleiades Publishing, Ltd.Influence exerted by acid-base modifiers of aluminum hydroxide on the texture and acid characteristics of the aluminum oxide support was studied. The effect of the modified aluminum oxides on the charge state of the active component of aluminum-palladium catalysts was determined. It was found that catalysts based on a support with high concentration of strong acid centers are characterized by low conversion of butadiene-1,3 due to the firm chemisorption of the diene on electron-deficient palladium particles. Their formation is due to the strong metal-support interaction. By contrast, catalysts synthesized with supports having a small number of acid centers provide a high conversion of butadiene-1,3

Adsorption properties of palladium particles supported on aluminum oxides with varied acidity in hydrogenation of butadiene-1,3

© 2017, Pleiades Publishing, Ltd.Influence exerted by acid-base modifiers of aluminum hydroxide on the texture and acid characteristics of the aluminum oxide support was studied. The effect of the modified aluminum oxides on the charge state of the active component of aluminum-palladium catalysts was determined. It was found that catalysts based on a support with high concentration of strong acid centers are characterized by low conversion of butadiene-1,3 due to the firm chemisorption of the diene on electron-deficient palladium particles. Their formation is due to the strong metal-support interaction. By contrast, catalysts synthesized with supports having a small number of acid centers provide a high conversion of butadiene-1,3

Identification of amorphous and crystalline phases in alumina entity and their contribution to the properties of the palladium catalyst

© 2019 Elsevier B.V. The purpose of this paper is to identify the phase inhomogeneity, undetectable by X-ray method, and the reason for its occurrence in the composition of aluminum oxide. It is shown that even a trace amount of carbon (0.23 wt%) in the precursor of aluminum oxide can cause a high content of amorphous phase (38%). Carbon is present due to the products of incomplete hydrolysis of the aluminum alkoxides (alumoxanes) in the commercial sample of boehmite. The fact that the amorphous and crystalline phases in the composition of aluminum oxide differ in reactivity under hydrothermal treatment is first described. It is shown in a split endothermic peak on the differential scanning calorimetry curve. It is investigated that the brief hydrothermal treatment of the phase-inhomogeneous aluminum oxide and its subsequent calcination lead to formation of a defective structure with greater acidity in the composition of the aluminum oxide. This aluminum oxide was used as a support of the palladium catalyst in the 1,3-butadiene hydrogenation. This catalyst showed higher selectivity to 1-butene and low selectivity to butane, compared to the catalyst on alumina with amorphous phase

Identification of amorphous and crystalline phases in alumina entity and their contribution to the properties of the palladium catalyst

© 2019 Elsevier B.V. The purpose of this paper is to identify the phase inhomogeneity, undetectable by X-ray method, and the reason for its occurrence in the composition of aluminum oxide. It is shown that even a trace amount of carbon (0.23 wt%) in the precursor of aluminum oxide can cause a high content of amorphous phase (38%). Carbon is present due to the products of incomplete hydrolysis of the aluminum alkoxides (alumoxanes) in the commercial sample of boehmite. The fact that the amorphous and crystalline phases in the composition of aluminum oxide differ in reactivity under hydrothermal treatment is first described. It is shown in a split endothermic peak on the differential scanning calorimetry curve. It is investigated that the brief hydrothermal treatment of the phase-inhomogeneous aluminum oxide and its subsequent calcination lead to formation of a defective structure with greater acidity in the composition of the aluminum oxide. This aluminum oxide was used as a support of the palladium catalyst in the 1,3-butadiene hydrogenation. This catalyst showed higher selectivity to 1-butene and low selectivity to butane, compared to the catalyst on alumina with amorphous phase

Modification of a phase-inhomogeneous alumina support of a palladium catalyst. Part I: effect of the amorphous phase on the textural and acidic characteristics of alumina and methods for controlling its phase homogeneity

© 2020 Elsevier Ltd The contribution of the amorphous phase in aluminum hydroxide and alumina to their properties was investigated in this work. It was shown that the amorphous phase in aluminum hydroxide is stabilized by alumoxanes, and it is a source of a finely porous component and capable of increasing the surface area by ~78%. In γ-Al2O3, amorphous alumina raises the surface area and the acidity. It was established that the method of chemical modification does not change the phase inhomogeneity but allows adjusting the acid properties while maintaining the high specific surface area. It was shown that the amorphous phase is more reactive when processing phase-inhomogeneous aluminum hydroxide with acetic acid. Crystallization of amorphous alumina as a result of high-temperature treatment of phase-inhomogeneous aluminum hydroxide is accompanied by significant decrease in specific surface area and acidity

Influence of the obtaining method on the properties of amorphous aluminum compounds

© 2019 by the authors. Amorphous aluminum compounds are formed during the synthesis of the γ -Al2O3 catalyst precursor. Amorphous compounds influence on the alumina catalyst variously due to different physicochemical properties, which depend on the method of their preparation. In this research, the comparative analysis of physicochemical properties of amorphous aluminum compounds that were obtained by the precipitation method, the thermal decomposition of aluminum nitrate, and alcoxide hydrolysis product were studied. It is the first time that a new method for calculating of quantitative phase composition of amorphous aluminum compounds using the X-ray powder diffraction, thermogravimetric and differential scanning calorimetry analysis, mass-spectrometry, and CHN-analysis was described. Properties of obtaining samples were studied using scanning electron microscopy, low-temperature nitrogen adsorption, and temperature programmed desorption of ammonium analyses. The methods of precipitation and thermal decomposition of aluminum nitrate allows for obtaining non-porous samples consisting of a mixture of amorphous phases (hydroxide and basic salt) that contain the metals impurities and have low acidity of the oxides obtained from them. The highly porous amorphous alumina formed by the thermal decomposition of the alcoxide hydrolysis product with the least amount of impurities and a high acidity of the surface was observed

Influence of the obtaining method on the properties of amorphous aluminum compounds

© 2019 by the authors. Amorphous aluminum compounds are formed during the synthesis of the γ -Al2O3 catalyst precursor. Amorphous compounds influence on the alumina catalyst variously due to different physicochemical properties, which depend on the method of their preparation. In this research, the comparative analysis of physicochemical properties of amorphous aluminum compounds that were obtained by the precipitation method, the thermal decomposition of aluminum nitrate, and alcoxide hydrolysis product were studied. It is the first time that a new method for calculating of quantitative phase composition of amorphous aluminum compounds using the X-ray powder diffraction, thermogravimetric and differential scanning calorimetry analysis, mass-spectrometry, and CHN-analysis was described. Properties of obtaining samples were studied using scanning electron microscopy, low-temperature nitrogen adsorption, and temperature programmed desorption of ammonium analyses. The methods of precipitation and thermal decomposition of aluminum nitrate allows for obtaining non-porous samples consisting of a mixture of amorphous phases (hydroxide and basic salt) that contain the metals impurities and have low acidity of the oxides obtained from them. The highly porous amorphous alumina formed by the thermal decomposition of the alcoxide hydrolysis product with the least amount of impurities and a high acidity of the surface was observed