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J I Di Cosimo - One of the best experts on this subject based on the ideXlab platform.
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Kinetic and mechanistic study of the synthesis of ionone isomers from Pseudoionone on Brønsted acid solids
Catalysis Today, 2017Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Abstract The kinetics of the liquid-phase synthesis of α-, β- and γ-ionones from Pseudoionone was studied on Bronsted acid solids. Four silica-supported tungstophosphoric acid catalysts containing different heteropolyacid loadings, as well as a silica-supported triflic acid sample and a commercial resin (Amberlyst 35W) were tested in a batch reactor at 343–383 K under autogenous pressure. The final composition of the ionone isomer mixture depended on the catalyst acidic properties and operational conditions. The reaction pathways leading to the three ionone isomers were elucidated by postulating a heterogeneous Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic model. First order rate expressions, participation of a single Bronsted acid site in each reaction step and a cationic cyclic intermediate shared by the three ionone isomers were the main model assumptions. It was found that α-, β- and γ-ionones form directly from Pseudoionone by cyclization. However, the final concentration of α- and β-ionones is enhanced in consecutive pathways involving the isomerization of γ-ionone. The relative importance of the isomerization steps and the selective formation of α- or β-ionone depend on the Bronsted acid site strength and reaction temperature.
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synthesis of ionones on solid bronsted acid catalysts effect of acid site strength on ionone isomer selectivity
Catalysis Today, 2010Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Abstract The effect of Bronsted acid site strength on the liquid-phase conversion of Pseudoionone to ionone isomers (α-, β- and γ-ionone) was studied on resin Amberlyst 35W, silica-supported heteropolyacid (HPAS) and silica-supported triflic acid (TFAS). Catalyst acidity was probed by temperature-programmed desorption of NH3 coupled with infrared spectra of adsorbed pyridine. The initial Pseudoionone conversion rate followed the order: TFAS > Amberlyst 35W ≈ HPAS. Synthesis of the three ionone isomers occurred via a common cyclic carbocation intermediate formed from the activation of the Pseudoionone molecule on Bronsted acid sites. Initial ionone mixtures containing a α:β:γ isomer distribution of about 40:20:40 were formed, irrespective of the acid site strength. But the ionone mixture composition changed with the progress of the reaction because γ-ionone was consecutively converted to α-ionone on HPAS and Amberlyst 35W, whereas the stronger acid sites of TFAS converted γ-ionone to β-ionone.
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Synthesis of ionones on solid Brønsted acid catalysts: Effect of acid site strength on ionone isomer selectivity
Catalysis Today, 2010Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:The effect of Brønsted acid site strength on the liquid-phase conversion of Pseudoionone to ionone isomers (α-, β- and γ-ionone) was studied on resin Amberlyst 35W, silica-supported heteropolyacid (HPAS) and silica-supported triflic acid (TFAS). Catalyst acidity was probed by temperature-programmed desorption of NH3 coupled with infrared spectra of adsorbed pyridine. The initial Pseudoionone conversion rate followed the order: TFAS > Amberlyst 35W ≈ HPAS. Synthesis of the three ionone isomers occurred via a common cyclic carbocation intermediate formed from the activation of the Pseudoionone molecule on Brønsted acid sites. Initial ionone mixtures containing a α:β:γ isomer distribution of about 40:20:40 were formed, irrespective of the acid site strength. But the ionone mixture composition changed with the progress of the reaction because γ-ionone was consecutively converted to α-ionone on HPAS and Amberlyst 35W, whereas the stronger acid sites of TFAS converted γ-ionone to β-ionone.Fil: Diez, Veronica Karina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Apesteguia, Carlos Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Di Cosimo, Juana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin
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ionone synthesis by cyclization of Pseudoionone on silica supported heteropolyacid catalysts
Applied Catalysis A-general, 2009Co-Authors: V K Diez, B J Marcos, C R Apesteguia, J I Di CosimoAbstract:Abstract The liquid-phase cyclization of Pseudoionone to ionones (α, β and γ isomers) was studied on silica-supported heteropolyacid (HPA) catalysts containing between 18.8 and 58.5% HPA. The HPA used was tungstophosphoric acid (H3PW12O40). The catalyst surface and structural properties were thoroughly characterized by several techniques. The density, chemical nature and strength distribution of the surface acid sites were determined by adsorbing and monitoring by temperature-programmed desorption and infrared spectroscopy probe molecules such as NH3 and pyridine. The Pseudoionone conversion to ionones increased linearly with the Bronsted acid site density until the HPA loading approached to the monolayer saturation coverage. For higher HPA contents, the Pseudoionone adsorption and conversion were hampered because of spatial constraints that diminished the reactant accessibility to the proton active sites. The highest ionone yield, 79%, was obtained on a 58.5 wt% HPA/SiO2 catalyst at 383 K and is comparable to the best values reported in literature for the homogeneously catalyzed reaction using sulfuric acid. The ionone isomer distribution was modified by varying both the temperature and the reaction time. A reaction mechanism was postulated in which ionone isomers (α, β and γ) are primary products, but γ-ionone is isomerized to α-ionone while β-ionone is not converted in the other isomers.
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Synthesis of Ionones by Cyclization of Pseudoionone on Solid Acid Catalysts
Catalysis Letters, 2008Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Ionone synthesis ( α , β and γ isomers) by Pseudoionone cyclization was studied on zeolite HBEA, Amberlyst 35W, SiO_2–Al_2O_3, and unsupported and silica-supported heteropolyacids (HPA/SiO_2). Ionone formation was preferentially promoted on strong Brønsted acid sites. A 79% ionone yield was obtained on 58.5 wt.% HPA/SiO_2 after 1.5 h of reaction at 383 K and 250 kPa. This value is similar to the best yields reported for the homogeneously-catalyzed reaction using sulfuric acid.
V K Diez - One of the best experts on this subject based on the ideXlab platform.
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Kinetic and mechanistic study of the synthesis of ionone isomers from Pseudoionone on Brønsted acid solids
Catalysis Today, 2017Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Abstract The kinetics of the liquid-phase synthesis of α-, β- and γ-ionones from Pseudoionone was studied on Bronsted acid solids. Four silica-supported tungstophosphoric acid catalysts containing different heteropolyacid loadings, as well as a silica-supported triflic acid sample and a commercial resin (Amberlyst 35W) were tested in a batch reactor at 343–383 K under autogenous pressure. The final composition of the ionone isomer mixture depended on the catalyst acidic properties and operational conditions. The reaction pathways leading to the three ionone isomers were elucidated by postulating a heterogeneous Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic model. First order rate expressions, participation of a single Bronsted acid site in each reaction step and a cationic cyclic intermediate shared by the three ionone isomers were the main model assumptions. It was found that α-, β- and γ-ionones form directly from Pseudoionone by cyclization. However, the final concentration of α- and β-ionones is enhanced in consecutive pathways involving the isomerization of γ-ionone. The relative importance of the isomerization steps and the selective formation of α- or β-ionone depend on the Bronsted acid site strength and reaction temperature.
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synthesis of ionones on solid bronsted acid catalysts effect of acid site strength on ionone isomer selectivity
Catalysis Today, 2010Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Abstract The effect of Bronsted acid site strength on the liquid-phase conversion of Pseudoionone to ionone isomers (α-, β- and γ-ionone) was studied on resin Amberlyst 35W, silica-supported heteropolyacid (HPAS) and silica-supported triflic acid (TFAS). Catalyst acidity was probed by temperature-programmed desorption of NH3 coupled with infrared spectra of adsorbed pyridine. The initial Pseudoionone conversion rate followed the order: TFAS > Amberlyst 35W ≈ HPAS. Synthesis of the three ionone isomers occurred via a common cyclic carbocation intermediate formed from the activation of the Pseudoionone molecule on Bronsted acid sites. Initial ionone mixtures containing a α:β:γ isomer distribution of about 40:20:40 were formed, irrespective of the acid site strength. But the ionone mixture composition changed with the progress of the reaction because γ-ionone was consecutively converted to α-ionone on HPAS and Amberlyst 35W, whereas the stronger acid sites of TFAS converted γ-ionone to β-ionone.
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Synthesis of ionones on solid Brønsted acid catalysts: Effect of acid site strength on ionone isomer selectivity
Catalysis Today, 2010Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:The effect of Brønsted acid site strength on the liquid-phase conversion of Pseudoionone to ionone isomers (α-, β- and γ-ionone) was studied on resin Amberlyst 35W, silica-supported heteropolyacid (HPAS) and silica-supported triflic acid (TFAS). Catalyst acidity was probed by temperature-programmed desorption of NH3 coupled with infrared spectra of adsorbed pyridine. The initial Pseudoionone conversion rate followed the order: TFAS > Amberlyst 35W ≈ HPAS. Synthesis of the three ionone isomers occurred via a common cyclic carbocation intermediate formed from the activation of the Pseudoionone molecule on Brønsted acid sites. Initial ionone mixtures containing a α:β:γ isomer distribution of about 40:20:40 were formed, irrespective of the acid site strength. But the ionone mixture composition changed with the progress of the reaction because γ-ionone was consecutively converted to α-ionone on HPAS and Amberlyst 35W, whereas the stronger acid sites of TFAS converted γ-ionone to β-ionone.Fil: Diez, Veronica Karina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Apesteguia, Carlos Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Di Cosimo, Juana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin
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ionone synthesis by cyclization of Pseudoionone on silica supported heteropolyacid catalysts
Applied Catalysis A-general, 2009Co-Authors: V K Diez, B J Marcos, C R Apesteguia, J I Di CosimoAbstract:Abstract The liquid-phase cyclization of Pseudoionone to ionones (α, β and γ isomers) was studied on silica-supported heteropolyacid (HPA) catalysts containing between 18.8 and 58.5% HPA. The HPA used was tungstophosphoric acid (H3PW12O40). The catalyst surface and structural properties were thoroughly characterized by several techniques. The density, chemical nature and strength distribution of the surface acid sites were determined by adsorbing and monitoring by temperature-programmed desorption and infrared spectroscopy probe molecules such as NH3 and pyridine. The Pseudoionone conversion to ionones increased linearly with the Bronsted acid site density until the HPA loading approached to the monolayer saturation coverage. For higher HPA contents, the Pseudoionone adsorption and conversion were hampered because of spatial constraints that diminished the reactant accessibility to the proton active sites. The highest ionone yield, 79%, was obtained on a 58.5 wt% HPA/SiO2 catalyst at 383 K and is comparable to the best values reported in literature for the homogeneously catalyzed reaction using sulfuric acid. The ionone isomer distribution was modified by varying both the temperature and the reaction time. A reaction mechanism was postulated in which ionone isomers (α, β and γ) are primary products, but γ-ionone is isomerized to α-ionone while β-ionone is not converted in the other isomers.
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Synthesis of Ionones by Cyclization of Pseudoionone on Solid Acid Catalysts
Catalysis Letters, 2008Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Ionone synthesis ( α , β and γ isomers) by Pseudoionone cyclization was studied on zeolite HBEA, Amberlyst 35W, SiO_2–Al_2O_3, and unsupported and silica-supported heteropolyacids (HPA/SiO_2). Ionone formation was preferentially promoted on strong Brønsted acid sites. A 79% ionone yield was obtained on 58.5 wt.% HPA/SiO_2 after 1.5 h of reaction at 383 K and 250 kPa. This value is similar to the best yields reported for the homogeneously-catalyzed reaction using sulfuric acid.
C R Apesteguia - One of the best experts on this subject based on the ideXlab platform.
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Kinetic and mechanistic study of the synthesis of ionone isomers from Pseudoionone on Brønsted acid solids
Catalysis Today, 2017Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Abstract The kinetics of the liquid-phase synthesis of α-, β- and γ-ionones from Pseudoionone was studied on Bronsted acid solids. Four silica-supported tungstophosphoric acid catalysts containing different heteropolyacid loadings, as well as a silica-supported triflic acid sample and a commercial resin (Amberlyst 35W) were tested in a batch reactor at 343–383 K under autogenous pressure. The final composition of the ionone isomer mixture depended on the catalyst acidic properties and operational conditions. The reaction pathways leading to the three ionone isomers were elucidated by postulating a heterogeneous Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetic model. First order rate expressions, participation of a single Bronsted acid site in each reaction step and a cationic cyclic intermediate shared by the three ionone isomers were the main model assumptions. It was found that α-, β- and γ-ionones form directly from Pseudoionone by cyclization. However, the final concentration of α- and β-ionones is enhanced in consecutive pathways involving the isomerization of γ-ionone. The relative importance of the isomerization steps and the selective formation of α- or β-ionone depend on the Bronsted acid site strength and reaction temperature.
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synthesis of ionones on solid bronsted acid catalysts effect of acid site strength on ionone isomer selectivity
Catalysis Today, 2010Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Abstract The effect of Bronsted acid site strength on the liquid-phase conversion of Pseudoionone to ionone isomers (α-, β- and γ-ionone) was studied on resin Amberlyst 35W, silica-supported heteropolyacid (HPAS) and silica-supported triflic acid (TFAS). Catalyst acidity was probed by temperature-programmed desorption of NH3 coupled with infrared spectra of adsorbed pyridine. The initial Pseudoionone conversion rate followed the order: TFAS > Amberlyst 35W ≈ HPAS. Synthesis of the three ionone isomers occurred via a common cyclic carbocation intermediate formed from the activation of the Pseudoionone molecule on Bronsted acid sites. Initial ionone mixtures containing a α:β:γ isomer distribution of about 40:20:40 were formed, irrespective of the acid site strength. But the ionone mixture composition changed with the progress of the reaction because γ-ionone was consecutively converted to α-ionone on HPAS and Amberlyst 35W, whereas the stronger acid sites of TFAS converted γ-ionone to β-ionone.
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Synthesis of ionones on solid Brønsted acid catalysts: Effect of acid site strength on ionone isomer selectivity
Catalysis Today, 2010Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:The effect of Brønsted acid site strength on the liquid-phase conversion of Pseudoionone to ionone isomers (α-, β- and γ-ionone) was studied on resin Amberlyst 35W, silica-supported heteropolyacid (HPAS) and silica-supported triflic acid (TFAS). Catalyst acidity was probed by temperature-programmed desorption of NH3 coupled with infrared spectra of adsorbed pyridine. The initial Pseudoionone conversion rate followed the order: TFAS > Amberlyst 35W ≈ HPAS. Synthesis of the three ionone isomers occurred via a common cyclic carbocation intermediate formed from the activation of the Pseudoionone molecule on Brønsted acid sites. Initial ionone mixtures containing a α:β:γ isomer distribution of about 40:20:40 were formed, irrespective of the acid site strength. But the ionone mixture composition changed with the progress of the reaction because γ-ionone was consecutively converted to α-ionone on HPAS and Amberlyst 35W, whereas the stronger acid sites of TFAS converted γ-ionone to β-ionone.Fil: Diez, Veronica Karina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Apesteguia, Carlos Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; ArgentinaFil: Di Cosimo, Juana Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera". Universidad Nacional del Litoral. Instituto de Investigaciones en Catálisis y Petroquímica "Ing. José Miguel Parera"; Argentin
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ionone synthesis by cyclization of Pseudoionone on silica supported heteropolyacid catalysts
Applied Catalysis A-general, 2009Co-Authors: V K Diez, B J Marcos, C R Apesteguia, J I Di CosimoAbstract:Abstract The liquid-phase cyclization of Pseudoionone to ionones (α, β and γ isomers) was studied on silica-supported heteropolyacid (HPA) catalysts containing between 18.8 and 58.5% HPA. The HPA used was tungstophosphoric acid (H3PW12O40). The catalyst surface and structural properties were thoroughly characterized by several techniques. The density, chemical nature and strength distribution of the surface acid sites were determined by adsorbing and monitoring by temperature-programmed desorption and infrared spectroscopy probe molecules such as NH3 and pyridine. The Pseudoionone conversion to ionones increased linearly with the Bronsted acid site density until the HPA loading approached to the monolayer saturation coverage. For higher HPA contents, the Pseudoionone adsorption and conversion were hampered because of spatial constraints that diminished the reactant accessibility to the proton active sites. The highest ionone yield, 79%, was obtained on a 58.5 wt% HPA/SiO2 catalyst at 383 K and is comparable to the best values reported in literature for the homogeneously catalyzed reaction using sulfuric acid. The ionone isomer distribution was modified by varying both the temperature and the reaction time. A reaction mechanism was postulated in which ionone isomers (α, β and γ) are primary products, but γ-ionone is isomerized to α-ionone while β-ionone is not converted in the other isomers.
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Synthesis of Ionones by Cyclization of Pseudoionone on Solid Acid Catalysts
Catalysis Letters, 2008Co-Authors: V K Diez, C R Apesteguia, J I Di CosimoAbstract:Ionone synthesis ( α , β and γ isomers) by Pseudoionone cyclization was studied on zeolite HBEA, Amberlyst 35W, SiO_2–Al_2O_3, and unsupported and silica-supported heteropolyacids (HPA/SiO_2). Ionone formation was preferentially promoted on strong Brønsted acid sites. A 79% ionone yield was obtained on 58.5 wt.% HPA/SiO_2 after 1.5 h of reaction at 383 K and 250 kPa. This value is similar to the best yields reported for the homogeneously-catalyzed reaction using sulfuric acid.
Qi-zhong Jiang - One of the best experts on this subject based on the ideXlab platform.
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Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment
Chinese Journal of Chemical Physics, 2008Co-Authors: Dai-shi Guo, Chun-sheng Yin, Qi-zhong JiangAbstract:TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of Pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Bronsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of Pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.
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Sulfated and Persulfated TiO2/MCM-41 Prepared by Grafting Method and their Acid-catalytic Activities for Cyclization of Pseudoionone
Catalysis Letters, 2006Co-Authors: Dai-shi Guo, Qi-zhong JiangAbstract:Solid acid catalysts of SO 4 2− /TiO2/MCM-41 and S2O 8 2− /TiO2/MCM-41 were prepared via grafting method and sulfate/persulfate promotion. The catalysts exhibited desirable activity and better selectivity for cyclization reaction of Pseudoionone compared to traditional SO 4 2− /TiO2. A combination of XRD, N2 adsorption–desorption and FTIR spectroscopy indicated that the catalysts possess well-ordered mesostructure, and the grafted TiO2 are in highly dispersed amorphous form rather than crystalline phase. For S2O 8 2− /TiO2/MCM-41 higher S content and more Bronsted acid sites can be achieved by persulfation, which is favorable for the protons participated cyclization reaction. The similar Si–O–Ti–O–S=O structure of all acid sites on pore surface of the catalysts is attributed to the improvement of selectivity in comparison with SO 4 2− /TiO2.
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sulfated and persulfated tio2 mcm 41 prepared by grafting method and their acid catalytic activities for cyclization of Pseudoionone
Catalysis Letters, 2006Co-Authors: Dai-shi Guo, Qi-zhong JiangAbstract:Solid acid catalysts of SO 4 2− /TiO2/MCM-41 and S2O 8 2− /TiO2/MCM-41 were prepared via grafting method and sulfate/persulfate promotion. The catalysts exhibited desirable activity and better selectivity for cyclization reaction of Pseudoionone compared to traditional SO 4 2− /TiO2. A combination of XRD, N2 adsorption–desorption and FTIR spectroscopy indicated that the catalysts possess well-ordered mesostructure, and the grafted TiO2 are in highly dispersed amorphous form rather than crystalline phase. For S2O 8 2− /TiO2/MCM-41 higher S content and more Bronsted acid sites can be achieved by persulfation, which is favorable for the protons participated cyclization reaction. The similar Si–O–Ti–O–S=O structure of all acid sites on pore surface of the catalysts is attributed to the improvement of selectivity in comparison with SO 4 2− /TiO2.
Dai-shi Guo - One of the best experts on this subject based on the ideXlab platform.
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Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment
Chinese Journal of Chemical Physics, 2008Co-Authors: Dai-shi Guo, Chun-sheng Yin, Qi-zhong JiangAbstract:TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of Pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Bronsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of Pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.
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Sulfated and Persulfated TiO2/MCM-41 Prepared by Grafting Method and their Acid-catalytic Activities for Cyclization of Pseudoionone
Catalysis Letters, 2006Co-Authors: Dai-shi Guo, Qi-zhong JiangAbstract:Solid acid catalysts of SO 4 2− /TiO2/MCM-41 and S2O 8 2− /TiO2/MCM-41 were prepared via grafting method and sulfate/persulfate promotion. The catalysts exhibited desirable activity and better selectivity for cyclization reaction of Pseudoionone compared to traditional SO 4 2− /TiO2. A combination of XRD, N2 adsorption–desorption and FTIR spectroscopy indicated that the catalysts possess well-ordered mesostructure, and the grafted TiO2 are in highly dispersed amorphous form rather than crystalline phase. For S2O 8 2− /TiO2/MCM-41 higher S content and more Bronsted acid sites can be achieved by persulfation, which is favorable for the protons participated cyclization reaction. The similar Si–O–Ti–O–S=O structure of all acid sites on pore surface of the catalysts is attributed to the improvement of selectivity in comparison with SO 4 2− /TiO2.
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sulfated and persulfated tio2 mcm 41 prepared by grafting method and their acid catalytic activities for cyclization of Pseudoionone
Catalysis Letters, 2006Co-Authors: Dai-shi Guo, Qi-zhong JiangAbstract:Solid acid catalysts of SO 4 2− /TiO2/MCM-41 and S2O 8 2− /TiO2/MCM-41 were prepared via grafting method and sulfate/persulfate promotion. The catalysts exhibited desirable activity and better selectivity for cyclization reaction of Pseudoionone compared to traditional SO 4 2− /TiO2. A combination of XRD, N2 adsorption–desorption and FTIR spectroscopy indicated that the catalysts possess well-ordered mesostructure, and the grafted TiO2 are in highly dispersed amorphous form rather than crystalline phase. For S2O 8 2− /TiO2/MCM-41 higher S content and more Bronsted acid sites can be achieved by persulfation, which is favorable for the protons participated cyclization reaction. The similar Si–O–Ti–O–S=O structure of all acid sites on pore surface of the catalysts is attributed to the improvement of selectivity in comparison with SO 4 2− /TiO2.
