Catalysis 2025 Issue

0.3 0.2 Strong acidity/mmol/g

0.4

200

300

400

500

600

>150 100-120 120-150 60-80 80-100 Acid strength/KJ/mol

Acid strength/˚C

Figure 1 Academic works showing that mesoporous USY zeolites (Mx) display substantially reduced acid strength as com- pared to the parent zeolites (Px) they were derived from. Reproduced with permission from the publishers. (Left) derived from [6], (middle) derived from [7], and (right) derived from [8]

These species are used to scavenge dissolved silicon spe- cies, direct mesopore formation, and/or protect the fragile faujasite framework during the mesoporisation process (typically executed in alkaline media).¹ Illustratively, the state-of-the-art suggests that mesoporous USY zeolites of high crystallinity can only be made using organics (see Type D in Figure 2 ). Such organic species are undesired as they not only com- plicate the wastewater treatment but also attach tightly to the zeolite. Accordingly, the removal of organics needs to be executed via combustion. This is a dangerous operation due to the release of explosive volatiles. It requires signif- icant energy consumption and gives rise to carbon and nitrous oxide emissions. Another undesired aspect is the unit operations asso- ciated with the manufacture of mesoporous zeolites. For example, the use of hydrothermal stages for extended peri- ods is commonly reported. Moreover, using alkali cations to make alkaline media implies the need for complementary

ion exchange treatments to restore the catalytically active protonic form. Furthermore, the use of organics carries the risk of foaming and separation difficulties. As a result, a ‘rel - atively simple’ mesoporisation treatment simply does not appear to exist. Finally, it is crucial to highlight that one of the most over- looked expensive ingredients is the USY zeolite itself. As a precious zeolite, solid losses during mesoporisation should be minimised. The lack of coverage in the top right corner of Figure 2 is significant: not only will high-quality zeolites be unattainable without using organics, but achieving them also appears impossible without losing a sizable mass of the pristine parent USY zeolite. Thus, the underwhelm- ing industrial adaptation may very well be attributed to the sub-optimal quality of the zeolite and a plethora of manufacturing challenges, complications, and costs (see Figure 3 ). Limitations of conventional descriptors In order to improve the understanding of mesoporous USY in hydrocracking, Zeopore has executed several hydroc- racking campaigns. In each, industrial catalytic testing of a strategic variation of USY samples was applied. Zeolite powders were shaped into extrudates, impregnated with non-noble metals, and evaluated in the hydrocracking of vacuum gasoil in a fixed-bed reactor under both sweet and sour conditions. In the quest for improved hydrocracking performance,

High-quality USY zeolite

Scalable and low-cost manufacture

Retain intrinsic properties

Optimal production process

Access via mesopores

Economical ingredients

Low

Medium

High

Crystallinity

Figure 2 Overview of material yield (y-axis), crystallinity (x-axis), and the need for organics (colour) for four different types of mesoporisation approaches Adapted from [1] with permission from the publisher

Figure 3 Challenges in the commercialisation of accessible USY zeolites range from attaining high-quality zeolites to ensuring a scalable and low-cost manufacture

Catalysis 2025