Extending Catalyst Life in Glycerol-to-Acrolein Conversion Using Non-thermal Plasma

Abstract

Booming biodiesel production worldwide demands valorization of its byproduct of glycerol. Acrolein, an important intermediate chemical, can be produced by gas-phase glycerol dehydration catalyzed by solid acids. Because catalysts that lead to high acrolein selectivity usually deactivate rapidly due to the formation of coke that blocks the active sites on their surface, one major challenge of this method is how to extend the service life of the catalyst. Silica-supported silicotungstic acid (HSiW-Si) is a good example of such a catalyst that shows good activity in glycerol dehydration to acrolein initially, but deactivates quickly. In this study, HSiW-Si was selected to probe the potential of using non-thermal plasma with oxygen-containing gas as the discharge gas (NTP-O 2 ) to solve the catalyst deactivation problem. NTP-O 2 was found to be effective in coke removal and catalyst regeneration at low temperatures without damaging the Keggin structure of the HSiW-Si catalyst.

Nonthermal Plasma Induced Fabrication of Solid Acid Catalysts for Glycerol Dehydration to Acrolein

“…In our previous study using a regular catalyst, we found no difference in XRD patterns between the fresh catalyst and spent catalyst in that the deposited coke was amorphous and would not change the crystalline structure of the catalyst on which it was deposited. Importantly, the coke formation significantly decreased the glycerol conversion with only minor impact on the selectivity to acrolein; with periodic regeneration using oxygen-containing NTP at low temperatures, the glycerol conversion could be effectively restored [25].…”

“…The supported HSiW catalysts on Al (denoted as HSiW-Al) and Si (denoted as HSiW-Si) fabricated with different methods were tested and compared in glycerol dehydration reactions carried out in a down-flow packed-bed reactor at 275 • C and atmospheric pressure. Detailed description of the experiment and evaluation of catalyst performance can be found in our previous publication [25]. Briefly, the reactor was made of a quartz tube (length 300 mm, ID 19.35 mm, OD 25.3 mm), which was heated by a heating tape evenly wrapped around the outer wall of the quartz tube.…”

“…Undesirable side reactions also led to the formation of acetol, acetaldehyde, and propionaldehyde [22], which were quantified in the same way using GC-FID. The formation of coke is the most undesirable, as it would deactivate the catalysts [25]. Coke is a distribution of complex carbonaceous species, and it is almost impossible to know the exact chemical content of coke.…”

“…Among the value-added chemicals that can be derived from glycerol, acrylic acid, which produced via the intermediate glycerol dehydration to acrolein, received much attention, because this appears to be one of the most promising ways to valorize glycerol [21,22]. Extensive efforts have been committed in recent years to improve glycerol dehydration to acrolein, including glycerol conversion in sub-and supercritical water [23], as well as selective gas-phase conversions [24][25][26][27][28][29][30]. Although these different processes gave good glycerol conversion and selectivity to acrolein, a continuous process catalyzed by solid acids is desirable for industrial application.…”

Coproduction of Acrylic Acid with a Biodiesel Plant Using CO2 as Reaction Medium: Process Modeling and Production Cost Estimation

“…Among the value-added chemicals that can be derived from glycerol, acrylic acid produced via the intermediate of glycerol dehydration to acrolein received much attention because this appears to be one of the most promising ways to valorize glycerol [4,5]. There have been extensive efforts in recent years to improve glycerol dehydration to acrolein, including glycerol conversion in sub-and supercritical water [6][7][8], as well as selective gas-phase conversions [9][10][11][12][13]. Although these different processes gave adequate glycerol conversion rates and selectivity to acrolein, a continuous process catalyzed by solid acids is desirable for industrial application.…”