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FCCPT stacked catalyst systems (TIA)

The pretreatment of feed for FCC units offers significant performance advantages for FCC operation including overall conversion, improved yields, FCC products that meet clean fuels specifications, and reduced catalyst usage.

K Chua, Criterion Catalysts & Technologies
Guosq Zhlh, Sinopec Zhenhai Refinery and Chemical Company
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Article Summary
Many refiners have leveraged the advantages offered by FCCPT units to increase profitability and flexibility. In light of the critical role that this technology plays in modern refining, Criterion has continued to develop and apply new advanced catalysts for FCCPT applications, of which Centera DN-3651 and DC-2651 are the latest high activity NiMo and CoMo catalysts. DN-3651 has demonstrated market leading hydrogenation performance, while both DN-3651 and DC-2651 provide exceptional HDS and HDN activity. Use of each of these products alone provides solid hydrotreating performance, but a key feature of these products is their synergistic behaviour when applied in a stacked system.

The combination of targeted NiMo catalyst layers and CoMo catalyst layers provides an enhanced overall system performance as the hydrogenation power of the NiMo layer removes nitrogen and saturates aromatics in feed, allowing the CoMo catalyst to operate at peak performance. The saturation of aromatics enables improved product upgrade for increased FCC yields while also increasing the rate of deep desulphurisation via direct desulphurisation routes. In addition, the high hydrogenation activity enables increased HDN, improving FCC feed quality as well as improving hydrotreater performance as nitrogen inhibits the removal of sulphur from feed streams. The hydrogenation of FCC feed streams is necessary for deep desulphurisation especially when operating at higher sulphur conversion targets for Tier 3 FCC gasoline production. As such, many refiners have included the application of high severity FCCPT operation in their strategies for Tier 3 fuels production since FCC gasoline is a major blend component for typical refinery product gasoline streams.

The commercial example shown in Tables 1 and 2 illustrates the performance achieved by a refiner operating an FCCPT unit to produce a Tier 3 quality gasoline blend component as well as increase conversion and yields on their FCC unit. This unit is currently operating with Criterion’s latest Centera technology in a stacked catalyst system at custom operating targets for maximum performance. The tables highlight the performance benefits achieved post application of Criterion’s Centera technology compared to a competitive catalyst system. One can observe a clear increase in FCC performance and improved yields while the catalyst system in use remains on target to provide an extended life cycle.

In addition to FCC feed quality, the use of stacked catalyst systems also improves unit stability and cycle longevity. The application of high performance catalysts offers expanded catalyst life cycles by reducing operating temperatures required to meet product specifications at the start of run as well as reducing the rate of deactivation as the cycle progresses. In general, hydroprocessing catalysts suffer from deactivation due to two primary mechanisms; the poisoning of active sites due to feed contaminants such as metals, and the formation of coke on the surface of the catalyst inhibiting access to the active sites. Criterion’s FCCPT portfolio includes performance guard products to protect from poisons and Centera products have advanced substrate geometry and pore structure to enable high tolerance to feed poisons permitting maximum available active volume. In addition to poison control, Centera technology in combination with stacking solutions results in long term catalyst system stability with respect to deactivation as a function of coking. The application of specific catalyst layers throughout the reactor permits the use of the ideal catalyst in targeted temperature zones which reduces the coking potential of each of these regions of the reactor that are susceptible to aromatics equilibrium limitations and the formation of coke.

Coupled with a focus on downstream FCC performance, Criterion has experience with targeted stacked catalyst systems that enable the production of high quality ULSD blend streams produced directly from FCCPT units both in mild hydrocracking operations and distillate co-processing applications. The example shown in Figure 1 features the continued performance gains realised by a refiner over the course of multiple cycles in the FCCPT unit as each system is finely tuned.

This short case study originally appeared in PTQ's Technology In Action feature - Q2 2016 issue.

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