Coking deactivation and regeneration of Cs2O–P2O5/SiO2 for aziridine synthesis

Hydroisomerization of <i>n</i>-Pentane over Zn-Fe-S<sub>2</sub>O<sub>8</sub><sup style="margin-left:-6px;">-2</sup>/ZrO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Superacid Catalyst: Activity, Surface Analysis and the Investigation of Deactivation and Regeneration

“…Compared with the Zn-Fe-SZA-F catalyst, the surface area of the Zn-Fe-SZA-D catalyst decreased significantly to 45.5 m 2 •g −1 , accompanied by a decrease in the pore volume from 0.101 to 0.06 cm 3 •g −1 Apparently, the pores of catalyst blocked dramatically by deposition of carbon on surface of the catalyst during isomerization. The increased pore diameter for the spent sample confirms that deposited carbon blocked the smaller pores on surface of catalyst [18] [19]. In addition, the deposition of carbon would cover This shows that after calcining the spent catalyst, BET surface area and pore volume were basically recovered.…”

Understanding the Catalytic Stability of Cs2O–P2O5 over Acid-Activated Montmorillonite for the Gas-Phase Dehydration of Monoethanolamine to Ethylenimine

“…Noteworthy, this conclusion is drawn based on the reaction results with a relatively lower MEA conversion of about 45% although the catalyst is operated for a time on stream (TOS) as long as of 4000 h. 16 Under mild reaction conditions, i.e., 40 mL of the catalyst loaded in the reactor with flow rates of the N 2 diluent (1200 mL/min) and the MEA liquid (0.1 mL/min), coking is also considered to be the main reason for the deactivation of the (Cs 2 O) 5.5 -(P 2 O 5 ) 1.8 /SiO 2 catalyst since the online air-flow treatment of the deactivated catalyst at a slightly higher temperature of 450 °C for 5 h can fully restore both the MEA conversion and EI selectivity. 7,8 Thus, the correlation between properties of solid acid/base catalysts and the catalytic stability of the MTE reaction is still far behind unambiguous, which is worthy to be investigated. Montmorillonite (MMT) is an effective support or catalyst for the cooperative acid−base heterogeneous catalysis since its acidity, basicity, and porosity can be facilely tailored by different methods such as the simple acid activation.…”

“…Ethylenimine (EI) is widely used as a fine chemical and a starting ingredient for synthesizing value-added chemicals such as dyes and pharmaceuticals. Gas-phase dehydration of monoethanolamine (MEA) over solid acid/base catalysts has been identified as an important approach for the industrial production of EI. − Contrary to the traditionally homogeneous processes by using liquid acid and/or base as catalysts, the gas-phase route characterizes by a higher efficiency and environmentally benign mode. However, as discussed in our previous work, the simultaneous presence of the highly reactive hydroxyl and amine groups in the MEA molecule makes the reaction network very complex over solid acid/base catalysts.…”

“…Thus, the EI selectivity is a key index in determining the process efficiency of the gas-phase dehydration of MEA to EI (MTE) reaction. To date, a few investigations are reported for the MTE reaction by screening different types of solid acids and bases as potential catalysts, e.g., acidic oxides such as WO 3 , Ta 2 O 5 , − Nb 2 O 5 , − Al 2 O 3 , and protonated zeolites, basic oxides including MgO and CaO, and bifunctional acid–base oxides. ,, It is revealed that the synergy between weaker acidic and basic sites is an important factor in determining the selectivity of EI. , Moreover, the presence of stronger acidic or basic sites over solid acids/bases always favors side reactions such as the deamination and the intermolecular dehydration of MEA …”

“…On the other hand, fewer studies are conducted on the catalytic stability of the MTE reaction. To date, there are only four open reports on the deactivation/regeneration of solid acids/bases for the MTE reaction. ,,, The earlier work reveals that coke deposition dominates the deactivation of SiO 2 -X m -P n -O p catalysts (X stands for alkali and alkaline-earth metals), which can be regenerated after burning the deposited coke at high temperatures . However, in the later work from the same research group, the deactivation of the Si 5 Cs 1 P 0.8 O x catalyst can be divided into two stages with different deactivation mechanisms, i.e., coking at the early stage of the reaction while structural changes of the catalyst including loss of phosphorus and sintering for the long-term catalyst deactivation.…”