Studies on ethylbenzene dehydrogenation with CO2 as soft oxidant over Co3O4/COK-12 catalysts

Abstract

Oxidative dehydrogenation of ethylbenzene to styrene has been studied over Co 3 O 4 supported on mesoporous silica (COK-12) with CO 2 as soft oxidant in a fixed bed reactor at atmospheric pressure in the temperature range of 723 to 923K. While COK-12 has been prepared by self-assembly method using long chain ionic surfactant i.e., P123 as template, cobalt oxide supported on COK-12 catalysts with variable Co content have been synthesised by simple wet impregnation technique. All the catalysts were characterized by N 2 adsorption -desorption, XRD, FT-IR, TPR, UV-Vis and XPS techniques. XRD and pore size distribution studies indicate the intactness of mesoporous structure of SiO 2 even after incorporation of Co 3 O 4 . Presence of Co 3 O 4 crystallites were observed beyond 5 wt% Co loading. High ethylbenzene conversion and stable styrene yields have been observed over 3% Co 3 O 4 /COK-12 catalyst due to the presence of large number of active Co 3 O 4 catalytic sites. Enhancement in the activity has been observed with CO 2 as soft oxidant than with N 2 as diluent. This is because of the fact that the liberated H 2 reacts with CO 2 in the form of reverse water gas shift reaction.

Selective vapor‐phase oxidation of o‐xylene to phthalic anhydride over Co‐Mn/H3PW12O40@TiO2 using molecular oxygen as a green oxidant

“…No diffraction peaks could be assigned to HPW, cobalt oxide, and manganese oxide which means that these components form too small crystallites or are well dispersed in the mesoporous anatase TiO 2 framework rather than existing as aggregates in the matrix . In authorization of this comment, results obtained from EDX and elemental mapping analysis (Figure d inset) indicate high dispersion of HPW and other components over the TiO 2 network, which could explain why XRD of the catalysts did not show any crystalline phases related to the phosphotungstic acid and others …”

“…However, because of the low quantities of Co and Mn in these catalysts these bands were not seen clearly as distinct peaks . Also, the bands at around 1630 and 3400 cm −1 can be assigned to the deformation modes of OH bonds in TiO 2 and adsorbed H 2 O …”

Hierarchical COK-X Materials for Applications in Catalysis and Adsorptive Separation and Controlled Release

“…Also, in the field of heterogeneous catalysis, some gains have been achieved by using COK-12 as support. For instance, COK-12-supported Co 3 O 4 was found to be an excellent catalyst for oxidative ethylbenzene dehydrogenation to styrene (Pochamoni et al, 2015). In another report, MoO 3 /COK-12 catalyst with 14 wt% MoO 3 loading was found to be very active in this reaction as well (Pochamoni et al, 2014).…”

The Role of CO2 as a Mild Oxidant in Oxidation and Dehydrogenation over Catalysts: A Review

“…However, the use of appropriate dopants' support materials might enhance the activity by promoting re-oxidation of Fe 2+ and preventing coke deposition [57,58]. High product yield stability was observed in a mesoporous silica COK12-assisted CoO 3 catalyst [59]. The performance of several effective catalysts in the oxidative dehydrogenation of ethyl benzene to styrene in the existence of CO 2 is shown in Table 7.…”