Abhishek Burri

Synthesis and catalytic behavior of tetrakis(4-carboxyphenyl) porphyrin-periodic mesoporous organosilica

The periodic mesoporous organosilica having the tetrakis(4-carboxyphenyl)porphyrin (TCPP) unit was successfully synthesized by the direct co-condensation method using microwave with the corresponding tetra-silane. The tetra-silane precursor, TCPP-silsesquioxane was prepared through the reaction of TCPP with the APTES(3-Aminopropyltrietoxysilane). And TCPP-PMOs were synthesized with sodium metasilicate as a silica source and P123 (EO20PO70EO20) as a supramolecular template at 100 °C. The TCPP-PMO-n (n = 2.5 and 5.0, n refers to the molar percentage of TCPP precursor per silica) materials had >400 m2 g−1 of specific surface areas with ∼8.7 nm of pore diameter. TCPP-PMOs were illustrated to give superiority in the organocatalytic hydrogen transfer reactions of various ketones such as acetophenone, cyclohexanone and pinacolone as well as good activity in the photocatalytic degradation of methylene blue (MB) without metal incorporation. Fe-TCPP-PMO prepared by ion-exchange method gave also good activity and selectivity in the oxidation of cyclohexene.

High surface area TiO2–ZrO2 prepared by caustic solution treatment, and its catalytic efficiency in the oxidehydrogenation of para-ethyltoluene by CO2

High surface area TiO2–ZrO2 (1 : 1) has been synthesized by co-precipitation—digestion method using KOH solution as a hydrolyzing agent as well as a digestion medium. The quenching of the mother liquor solution at elevated temperatures resulted in the amorphization of the TiO2–ZrO2 mixed oxide. The highest surface area obtained for TiO2–ZrO2 by the co-precipitation–digestion method is 256 m2 g−1 calcined at 600 °C with complete amorphous nature and having a particle size of less than 5 nm. Herein, we discuss the concept of amorphization of metal oxides based on the digestion times, supported by the characterization of the catalysts and its application in dehydrogenation of substituted benzene, mainly para-ethyltoluene to para-methylstyrene by CO2 as soft oxidant which showed high conversion and selectivities of 69% and 96%, respectively.

Oxidative Dehydrogenation of Ethylbenzene to Styrene with CO 2 Over V 2 O 5 –Sb 2 O 5 –CeO 2 /TiO 2 –ZrO 2 Catalysts

Utilization of CO2 as a soft oxidant in the oxidative dehydrogenation of ethylbenzene to styrene, a remarkable V2O5–Sb2O5–CeO2/TiO2–ZrO2 catalyst has been accomplished. Preparation of TiO2–ZrO2 support by co-precipitation followed by a single step deposition of V and Ce and Sb as stabilizers yielded a highly active and selective catalyst. Acid–base and redox properties including sustained stability of active species (V5+) are responsible for high activity of V2O5–Sb2O5–CeO2/TiO2–ZrO2 catalyst. The redox cycle is related to the dispersed V5+ and lattice reduced vanadium site in the VSbO4 phase. The antimony oxide inhibits the easy redox cycle between different vanadia species.

Ethylbenzene to styrene over ZrO2-based mixed metal oxide catalysts with CO2 as soft oxidant

Abstract ZrO2-based mixed metal oxide catalysts for the industrially important dehydrogenation process of ethylbenzene to styrene monomer have been explored by our group for the past 20 years. These efforts were subjected to the activation of CO2 over mixed metal oxide catalysts and resulted in several promising benefits to the dehydrogenation processes, such as stabilized conversion and selectivity, suppressed coke formation and commercially-acceptable longevity. In this review, we summarize the most recent developments on ZrO2-based mixed metal oxide catalysts, including the further optimization of sol-gel process in the synthesis of catalysts, rationalizing acid-base properties by doping, co-operative properties between redox and acid-base active sites and additional promoters towards the effective improvement of the longevity of catalysts.