Apr-2022

Fibre-based specialty catalyst material maximises surface area and catalyst contact

Customisable high surface area catalyst support material offers enhanced production for specialty chemical and industrial catalytic reactions.

Kevin Siters
Alkegen

Article Summary

Despite a long history of adoption, catalyst media is overdue for step-change innovation.  Additionally, there is great interest in improving the function of catalysts in terms of yield and purity. Improving the conversion rates and yield while preserving purity and reducing side products is crucial for catalysts across all areas of use, from oil refining to petrochemical applications to emission control. As a result, many processes have failed to offer a significant stepwise change in terms of performance. In the context of this study, there is a widening demand for propene for use in the production of various polymers; thus, the discovery of a catalyst technology that allows for the efficient and pure generation of propene from propane would be highly valuable to the market.

Alkegen’s response to these challenges is FlexCat — a high surface area, fiber based, flexible catalyst support solution that maximises surface area and catalyst contact, enhancing cost-effectiveness, increasing yield with reduced catalyst weight in the reactor, and preserving purity.

Boosting yield and throughput
Historically, the catalysis industry has relied on alumina supports to execute chemical reactions. Alumina shapes — like pellets, spheres, and extrudates — typically are used in petrochemical and processing chemical reactions, while cordierite monolithic or foil supports are used primarily in emission control applications. However, the former comes with challenges: inefficient performance, greater expense, and susceptibility to uneven thermal gradients in the reactor bed.

The benefits of increasing yield while reducing catalyst weight are numerous: the overall installation footprint can be smaller and/or additional catalyst units or beds can be installed in an existing unit, thereby increasing yield even further. Currently, the industry’s best way to increase reactor output or yield using traditional catalyst materials and formulations is to build out additional units. However, these require physical space availability and additional infrastructure, and can cost upwards of $200 million.3 Thus, to improve yield, output, and even purity in such installations, the best solutions require a far greater surface area than traditional supports can provide.

Driving solutions
Alkegen set about creating a new option to overcome limitations and expand benefits. With up to 50 times greater surface area, 40% faster regeneration time, and the ability to increase yield while preserving purity, FlexCat:
- Improved mass transfer of feedstock to catalyst surface
- Provides a lightweight fiber mat structure, which allows for smaller reactors and lower investment costs
- Boosts effectiveness (such as higher yield with smaller units, reducing catalyst load, lowering operational costs, protecting purity)
- Increases employee safety across a number of applications

Customising catalysis
Current goals for catalyst support innovation entail moving from static, long-established technology to novel, flexible supports that afford a significant step-change in yield, purity, regeneration time, and coke laydown in existing installations or new builds. Alkegen brings such a fibrous catalyst support solution to the forefront with a fiber mat that can be customised for a myriad of catalysis operations. It is designed to work across several markets to provide enhanced catalyst effectiveness with increased yield for any type of catalytic reaction, including hydrogen production, industrial emission control, and traditional chemical feedstock applications.

Benefits include:
High alumina, highly amorphous fibrous support material: Designed with a high internal surface area and defined surface microstructure, FlexCat can accommodate and directly adhere to active elements including Cu, Pt, Pd, Ni, Fe (see Figure 1).

Strong performance in propane dehydrogenation reaction, tested under rigorous conditions: Alkegen, along with a reputable catalyst development and performance evaluation laboratory, confirmed FlexCat’s overall increase in yield and improved run-to-run stability compared to a conventional pellet support media.

Increased hourly propene yield (g/hr.): In testing at 590°C, 2 barg, 72 ml/min with 8 to 16 hr-1 WHSV, FlexCat demonstrated:
- Greater gravimetric yield of propene (g) compared to incumbent pellet support material, realising the same yield using less catalyst mass and thus a smaller footprint (see Figure 2).
- Higher geometric surface area enables greater mass transfer of the feedstock to the active catalyst (Pt) for increased throughput and yield per hour (> 40%) while fixing all other conditions, such as flow rate.

Fibrous material that allows for dramatically increased selectivity (50%): This translates into fivefold less benzene formation, which is critical to reducing side products in the outlet (for easier downstream purification) and limiting coke laydown (up to 80% reduced coke/carbon laydown after each cycle for greater long-term support efficacy). Limiting coke laydown can lengthen catalyst lifetime by preventing deactivation and blinding of the catalyst. Reducing the amount of coke laydown prior to regeneration also reduces the chances for local hotspots on the catalyst surface and subsequent permanent damage to the catalyst through sintering or reduction of pores.

A proven faster rate of regeneration: Thanks to limited coke build-up and a high surface area, regeneration time is 40% faster than pellets without adjusting jacket/reactor temperatures, thereby allowing plants to get back to producing faster. While the regeneration process requires synthetic air, FlexCat utilises only 5% O2 at most to burn off excess coke, versus pellets which can require up to 20% O2.

Less susceptible to irreversible deactivation: Under the conditions described, FlexCat exhibits greater run-to-run stability and a demonstrated superior resistance to irreversible deactivation.

Stability of microstructure and amorphous alumina: Analysis using common methods like XRD and N2 adsorption — BET surface area demonstrates that the fibrous catalyst support is not damaged after cycling but rather remains highly porous, with a well-defined surface microstructure, as surface area and pore volume remain unchanged. The temperatures required for conversion and the consecutive regenerations did not alter the phase of the alumina, γ-alumina.