Zeopore is in the position to couple these catalytic bene- fits with an economical and tunable zeolite manufactur - ing process. A Chad A Perrott, Business Advisor, Galexia & VGO applications, Albemarle, email@example.com Cold flow properties such as cloud point, pour point, and cold filter plugging point are a function of the diesel paraffin content. Longer carbon chain n-paraffins exhibit poor cold flow properties, and the concentration must be reduced via one or a combination of several solutions to meet desired product specifications. One avenue is to dilute the n-paraffin content with a lower cloud point material, such as blending kerosene into the diesel pool. Although this is a relatively sim - ple solution, it has the disadvantage of downgrading kerosene to diesel and may impact other diesel prop- erties, such as end point. Another solution is to adjust the feedstock quality by reducing the end point and removing the high carbon number n-paraffins. This solution has the benefit of potentially improving the performance of the hydro- treating catalyst; however, it also downgrades diesel feed to vacuum gasoil and lowers the yield of diesel products. Finally, cracking or isomerisation dewaxing catalysts enable improvement of cold flow properties without requiring any feed adjustments or blending of other streams. Cracking dewaxing catalysts work by crack- ing n-paraffins to shorter carbon numbers with lower cold flow properties. Isomerisation dewaxing catalysts isomerise n-paraffins to iso-paraffins, thereby improv - ing cold flow properties while maintaining molecules in the diesel boiling range. When only moderate cold flow improvement is required in trim dewaxing, either catalytic solution can provide comparable per- formance. However, when high severity cold flow improvement is required, such as the production of winter or arctic diesel, an isomerisation catalyst is the preferred route because cracking catalysts result in high yield loss with the production of naphtha and light ends. Regardless of the technology selected for catalytic dewaxing, a reduction in treating catalyst volume to make room for dewaxing catalyst is typical. This change can result in higher space velocities and oper- ating severity to ensure dewaxing activity. Higher severities can lead to unit cycle length constraints. The treating section can be rebalanced by using bulk metal catalysts with increased volumetric activity in HDN/ HDA reactions to mitigate cycle length concerns when initiating dewaxing operations. A Eelko Brevoord, Consultant, Catalyst Intelligence Sarl, Brevoord@catalyst-intelligence.com ULSD cold flow properties are determined by the dis - tillation curve and product composition. Especially normal paraffins create pour cold flow properties. With the co-processing of vegetable oils in mind, con- verted to normal paraffins, cold flow properties are
In catalytic dewaxing, the highest selectivity to an ULSD product with much improved cold flow prop - erties, hence the lowest degree of undesired (over) cracking, is often achieved using isomerisation-selective zeolite-based bi-functional catalysts. The narrow unidi- rectional micropore structure of today’s isomerisation zeolite catalysts forms the highest industry standard of dewaxing improvement based on a stable and tunable CP improvement. Nevertheless, the zeolite’s narrow micropores also provoke undesired access and diffu - sion limitations, resulting in significant losses through overcracking. Mesoporous zeolites add a secondary level of larger mesopores to conventional zeolites, thereby increasing their catalytic efficiency by improving access to the active sites located in the zeolites’ micropores (prin- ciple visualised in related Zeopore article: https://bit. ly/3qIHRsE). The superior performance of mesoporous zeolites in selective isomerisation is firmly established. For example, Zeopore scientists have, together with world-renowned isomerisation expert Prof. Johan Martens (University of Leuven, Belgium), pioneered the superior catalytic performance of mesoporous zeolites almost a decade ago [Refs DOI: 10.1002/ cssc.201200888 and DOI:10.1016/j.cattod.2013.03.041]. However, the big challenge remains to manufacture such superior mesoporous zeolites at an industrially affordable price tag. Recently, to convince the global dewaxing industry, Zeopore has tested a noble-metal-containing unidirec- tional mesoporised dewaxing zeolite on a waxy ULSD in a parallel state-of-the-art 16-fold high-throughput testing unit at hte GmbH in Heidelberg, Germany (related Zeopore article: https://bit.ly/3AaD7jH). The test has been conducted in broad ranges of industrially relevant pressures, temperature, and space velocities. The results (also summarised in related Zeopore article: https://bit.ly/3AaD7jH) demonstrate a breakthrough in catalytic dewaxing: at fixed CP improvement, the mesoporised Zeopore dewaxing zeolite enables a five- fold lower diesel yield loss, reaching below 0.06 wt% loss per degree of CP improvement. This achievement becomes particularly attractive when considering that Figure 1 Catalytic dewaxing routes towards lower could and melting points, hence improved cold flow properties Graph taken from www.digitalrefining.com/article/1000927 (2014).
18 Catalysis 2022
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