November 2019

Catalyst

Unlocking FCC potential with an innovative catalyst solution

In 2010, a JV embarked on the deployment of a MHY zeolite technologyb developed at the Massachusetts Institute of Technology. This novel zeolite technology improves traditional zeolite catalysts through the introduction of highly interconnected channels of medium pore size, which enhance diffusion of feed molecules inside zeolite crystals, leading to higher-value product yields, improved process efficiency and increased refinery profitability.

Tavares, T., W. R. Grace

In 2010, a JVa embarked on the deployment of a MHY zeolite technologyb developed at the Massachusetts Institute of Technology. This novel zeolite technology improves traditional zeolite catalysts through the introduction of highly interconnected channels of medium pore size, which enhance diffusion of feed molecules inside zeolite crystals, leading to higher-value product yields, improved process efficiency and increased refinery profitability. The JV co-developed and commercialized this groundbreaking new fluid catalytic cracking (FCC) catalystc in 2012.

Introducing ordered mesoporosity

The MHY-zeolite catalyst technology is a surfactant-templated, post-synthesis zeolite, meso-structuring process that introduces ordered, well-controlled and hydrothermally stable mesoporosity into zeolite crystals (FIG. 1). The MHY-zeolite manufacturing process is engineered to allow a high degree of control in the size and the amount of ordered mesopores created inside the zeolite crystal, resulting in homogeneously distributed and interconnected pores.

FIG. 1. Controlled and ordered mesopores formation.
FIG. 1. Controlled and ordered mesopores formation.

The MHY-zeolite catalyst technology enhances feed molecules’ access to and from active catalytic sites in the zeolite. As a result, the MHY-zeolite catalyst’s zeolites crack larger FCC feed molecules more selectively than conventional active matrix materials. This allows refiners to make more primary cracking products, including LPG olefins and less coke per unit of conversion, both of which are highly valued by many refiners.

In FIG. 2, the image on the left shows a scanning electron microscope (SEM) photomicrograph of a conventional Y-zeolite. Each crystal face contains millions of 7.5-angstrom diameter micropores, which are too small to see even at 100,000 times magnification. The image on the right shows a photomicrograph of the MHY-zeolite at similar magnification. While the micropores still cannot be seen at this magnification, the extensive network of MHY-zeolite’s mesopores is clearly visible.

FIG. 2. Photomicrographs of conventional zeolite (left) and the MHY-zeolite technologyc (right). At similar magnifications, micropores in conventional zeolite are not viewable, while the 40-angstrom network of mesopores within the MHY-zeolite technology are viewable.
FIG. 2. Photomicrographs of conventional zeolite (left) and the MHY-zeolite technologyc (right). At similar magnifications, micropores in conventional zeolite are not viewable, while the 40-angstrom network of mesopores within the MHY-zeolite technology are viewable.

SEM, HR-TEM, electron tomography and rotational electron diffraction all show co-existence of mesoporosity and crystallinity/microporosity within the same zeolite crystal.1 It is this proximity of micro and mesoporosity within the same zeolite crystal that provides the MHY-zeolite catalyst technology its enhanced catalytic performance characteristics (FIG. 3).

FIG. 3. Mesopores are integral to the MHY-zeolite technology crystal.
FIG. 3. Mesopores are integral to the MHY-zeolite technology crystal.

The MHY-zeolite catalyst advantage

With conventional Y-zeolites, molecules with kinetic diameters up to approximately 1 nm (10 Å) can directly enter the Y-zeolite structure. This corresponds to hydrocarbons that boil up to 510°C (950°F). Larger hydrocarbons boiling above this temperature are traditionally cracked in the FCCU by mesoporous aluminas. These materials have somewhat less selective acid sites, and the goal is to cleave off hydrogen-rich side chains, which can subsequently enter the zeolite cage.

FIG. 4. Advantages of utilizing the new MHY-zeolite catalyst in FCC operations.
FIG. 4. Advantages of utilizing the new MHY-zeolite catalyst in FCC operations.

With the vast network of ordered mesopores (3 nm–5 nm; 30 Å–50 Å) in the MHY-zeolite catalyst, larger feed molecules—which boil at temperatures in the range of 510°C–593°C (950°F–1,100°F)—are now able to directly access the strong acid sites in the zeolite (FIG. 4). The MHY-zeolite catalyst can crack these larger feed molecules more selectively than conventional active matrix materials. This translates commercially into coke-selective bottoms cracking. In addition, the MHY-zeolite catalyst technology rapidly channels the valuable cracked products out of the zeolite before they succumb to potentially undesirable reactions, such as over-cracking, hydrogen transfer or condensation reactions, to form coke within the catalyst pores.

Among the primary and secondary “cracked products,” LPG olefins are very reactive, particularly at the high temperatures present within the FCCU riser and reactor. If these valuable, reactive molecules spend too much time inside the catalyst, they can become saturated through hydrogen transfer reactions into less valuable LPG paraffins. The MHY-zeolite catalyst’s ordered mesopores allow rapid transport of valuable LPG olefins out of the zeolite. Preservation of primary products, in conjunction with reduced hydrogen transfer, also leads to a boost in research octane number (RON).

This new catalyst represents the first and only use of ordered mesoporosity in FCC zeolites or catalysts and can provide a step change in value for many FCC operations. The result: enhanced diffusion of hydrocarbons both into and out of the catalyst particle. This adds options to process heavier feeds, reduce feedstock costs, circulate more catalyst and preserve valuable products, increasing operating flexibility for the refiner.

Performance signatures of the MHY-zeolite catalyst include:

  • Increased LPG olefinicity
  • Increase gasoline octane
  • Decreased delta coke
  • Improved bottoms upgrading
  • Increased operational flexibility to the refiner.

Refiners around the world have used these signature benefits to increase FCCU profitability in several different objective/constraint scenarios. These benefits improve operational flexibility, allowing refineries to pursue heavier feedstocks via delta coke reduction, reduce FCC dry gas without loss in LPG, increase volume swell in delta coke limited operations and alleviate existing unit constraints, such as main air blower rate, wet gas compressor rate and regenerator temperature.

Commercial success

The MHY-zeolite catalysts have been used successfully in numerous commercial operations. No increase in catalyst losses or stack opacity have been noted at any of these locations, confirming the excellent physical properties of the catalyst supplied. Several sets of commercial results (including stack opacity comments) have been published.

Case Study 1. A previously published article2 detailed the ongoing operations at a former Motiva refinery (now Shell) along the U.S. Gulf Coast. This FCCU processes a mix of vacuum gasoil, heavy coker gasoils and resid. The feedrate of 10,000 bpd–15,000 bpd is typically pushed to a maximum air blower/supplemental oxygen limit. The catalyst circulation rate could be increased by approximately 10% over base levels before meeting the maximum allowable circulation rate. The catalyst addition was 50% fresh catalyst and 50% purchased equilibrium catalyst (Ecat), mainly to assist with metals management. API and continuous catalytic reforming (CCR) generally remained in similar ranges as before the trial. The MHY-zeolite catalyst demonstrated notable improvements in coke selectivity, dry gas selectivity, LPG olefinicity, bottoms reduction and C3+ total liquid volume (FIG. 5). The result was an uplift in the range of $0.40/bblFF–$1.20/bblFF depending on the market economics.

FIG. 5. Case study 1: Operational data on the new MHY-zeolite catalyst.
FIG. 5. Case study 1: Operational data on the new MHY-zeolite catalyst.

Case Study 2. A commercial trial—in a “high added-iron (Fe)” (e.g., +0.4 wt% added Fe) operation—had the primary objective of reducing the regenerator temperature for a given amount of vacuum tower bottoms in the feed. Over the course of the trial, the delta coke and regenerator temperatures both steadily decreased, as desired (FIG. 6). The MHY-zeolite catalyst provided the refinery with increased operating flexibility to process lower-cost feeds, while not exceeding unit constraints.

FIG. 6. Case study 2: Over the course of the trial, the delta coke and regenerator temperatures both steadily decreased while using the new MHY-zeolite catalyst.
FIG. 6. Case study 2: Over the course of the trial, the delta coke and regenerator temperatures both steadily decreased while using the new MHY-zeolite catalyst.

Overcoming constraints

The MHY-zeolite catalyst provides improved bottoms upgrading, increased olefinicity and octane, decreased delta coke and decreased dry gas production. Refiners have used these trademark benefits to increase FCC feed throughput by alleviating existing unit constraints, such as:

  • Main air blower rate—Increased feed preheat temperature or decreased riser outlet temperature, producing less coke and alleviating the air blower constraint. These actions decrease catalyst circulation and bottoms conversion, but the new catalyst’s improved coke selectivity counteracts them. The feedrate can be increased until a new constraint is met.
  • Wet gas compressor rate—Enhanced diffusion reduces over-cracking of valuable hydrocarbon products to dry gas. This allows the feedrate—or operating severity—to be increased until a new constraint is met.
  • Regenerator temperature—Improved coke selectivity increases the catalyst circulation rate, lowering the regenerator temperature. This allows the feedrate—or feed residue content—to be increased until a new constraint is met.

This improved operating flexibility allows for increased catalyst circulation via lower delta coke, or the introduction of heavier opportunistic feeds, if increased circulation is not possible.

What’s next?

This technology has broad applicability to different types of zeolites. Demand for transportation fuels is projected to peak in the next decade, as competing influences of population growth and higher living standards are offset by fuel efficiency trends. Many refiners are considering shifting FCC objectives to produce light olefins for petrochemical feedstocks to best utilize existing FCC assets. It is estimated that the demand for petrochemical feedstocks will increase by more than 7 MMbpd over the next 20 yr, surpassing oil demand from the transport sector.

As demand for petrochemicals increases, the addition of the MHY-zeolite technology will allow additional solutions and greater flexibility in converting crude oil to petrochemical feedstocks and other chemical applications. HP

NOTES

  a Refers to the JV consisting of Rive Technology Inc. and W.R. Grace Co.

  b Refers to Molecular Highway® zeolite technology developed by Dr. Javier Garcia-Martinez

  c Refers to Rive® FCC catalyst powered by Molecular Highway™ Y-zeolite (also branded as MHY™)

LITERATURE CITED

  1 Garcia-Martinez, J., et. al, “Evidence of intracrystalline mesostructured porosity in zeolites by advanced gas sorption, electron tomography and rotation electron diffraction,” ChemCatChem, 2014

  2 Rakasekaran, K, R. Adarme, C. Cooper C and N. Faulkenberry, “Motiva unlocks value in FCCU through an innovative catalyst solution from Rive and Grace,” AFPM Meeting, 2017

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