### Publication / Presented: NPRA Annual Meeting

**Date:** 1998 

# MAXOFINTM: A NOVEL FCC PROCESS **FOR MAXIMIZING LIGHT OLEFINS USING A NEW GENERATION ZSM-5 ADDITIVE** 

**Authors:** Rik B. Miller - KBR Phillip K. Niccum - KBR Alan Claude - KBR Michael A. Silverman - KBR Nazeer A. Bhore - Mobil Technology Company Girish K. Chitnis - Mobil Technology Company Stephen J. McCarthy - Mobil Technology Company Ke Liu - Mobil Technology Company

# MAXOFINTM: A Novel FCC Process

for Maximizing Light Olefins Using a New Generation ZSM-5 Additive

by 

### Rik B. Miller, Phillip K. Niccum, Alan Claude, and Michael A. Silverman Kellogg Brown & Root, Inc. Houston, Texas USA
and 

### Nazeer A. Bhore, Girish K. Chitnis, Stephen J. McCarthy, and Ke Liu Mobil Technology Company Paulsboro, New Jersey USA

Presented at: 1998 NPRA Annual Meeting San Francisco, California USA 16 March 1998MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 1 

### ABSTRACT
TheMobil-Kellogg FCC Alliance announces MAXOFINTM -- a remarkably flexible FCC process that produces maximum light olefins from traditional feedstocks without resorting to severe operating conditions. MAXOFINTM is based on commercially proven technology and is now available for grassroots or revamp FCC application.
A new generation, higher ZSM-5 content additive and proprietary FCC hardware provide the flexibility to produce either maximum olefins or conventional fuels based on market demands. This paper shows an example where MAXOFINTM can produce between 6 and 18 wt% propylene from Minas vacuum gas oil. The key features of the MAXOFINTM FCC process are: # A new generation, high ZSM-5 content MAXOFIN-3TM additive that produces maximum light olefins without catalyst dilution # No requirement for large amounts of riser steam or severe operating conditions # A cost-effective ZSM-5 additive that is only now being offered to the industry # Proprietary Mobil-Kellogg Hardware: T New ATOMAX-2TM feed nozzles to provide superior atomization and greater riser coverage T Second Riser or lift zone for re-cracking of Naphtha T Closed Cyclones for olefin generation with minimum associated dry gas production



### BACKGROUND

a. Demand for propylene increasing Light olefins, propylene and butylenes, have long been basic building blocks for the manufacture

of a variety of petrochemical products and fuels. Today, light olefins are used for the production of gasoline, polymers, antifreezes, petrochemicals, explosives, solvents, me dicinals, fumigants, resins, synthetic rubber, and many other products. Propylene is second in importance to ethylene as a raw material for petrochemical manufacture. The largest source

of petrochemical propylene on a worldwide basis is that produced as the primary byproduct of ethylene manufacture by thermal cracking. Ethylene plants charging liquid feedstocks typically produce about 15 wt% propylene and provide about 70 percent of the propylene consumed by the petrochemical industry. Petroleum refining, nearly all from FCC, is by far the next largest supplier of worldwide propylene production, supplying about 30 percent of the petrochemical requirement. In the U.S., FCCU's supply about one-half of the petrochemical propylene demand.MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 2 The demand for propylene is expected to more than double, primarily driven by the rapidly increasing market for polypropylene. Propylene demand by the petrochemical industry is projected to increase more rapidly than the demand for ethylene. Since ethylene plants produce more ethylene than propylene, and furthermore, since many of the new ethylene plants in construction are based on ethane feed with no propylene co-produced, significant increases

in propylene from FCC will be required to meet the increased demand. This will beaccomplished by increasing FCC propylene selectivity, and by increasing the percentage of FCC propylene sent to petrochemical manufacture. Dehydrogenation of propane is expected to supply a much smaller proportion of the increased propylene demand, due to its higher production costs. Although propylene demand is high, refiners are still cautious about committing large capital investments for propylene production alone because of the large swings in propylene-fuels margins. To mitigate these risks, the MAXOFINTM process can switch from a maximum propylene mode to a fuels mode to meet the marketplace demands. The key to the flexibility of MAXOFINTM process is the high ZSM-5 content additive that was previously unavailable to the FCC industry.
b. ZSM-5 additive evolution
Mobil invented ZSM-5 zeolite in 19721

. Since its invention, ZSM-5 has been commercially used in a wide variety of catalytic applications including petrochemicals (ethylbenzene, xyleneisomerization, etc.), synthetic fuels (Methanol to Gasoline), and petroleum upgrading (lube and distillate dewaxing, gasoline octane enhancement, etc.).
In 1983, Mobil demonstrated that ZSM-5 increased gasoline octane in a moving bed Thermofor

Catalytic Cracking (TCC) Unit 2

. In 1986, GRACE-Davison, working with Mobil, developed the first ZSM-5 additive for use in FCC. Mobil licensed GRACE and other catalyst manufacturers to market and sell ZSM-5 additives containing 25 wt% or less ZSM-5 crystal for use in fluid and moving bed cracking processes. Within a few years, the industry embraced ZSM-5 additives for octane enhancement and maximizing alkylate.
More recently the industry has looked to ZSM-5 additives for incremental production of propylene from FCC. However, current ZSM-5 additives are best suited for increasing FCC propylene yield by 50-100%. Extensive pilot plant studies by Mobil, GRACE, and others show that further increases in propylene (up to 300%) require an additive with more than 25 wt% ZSM-5 crystal content to minimize dilution of the base catalyst activity 3 . Mobil conducted commercial trials of its own proprietary high ZSM-5 additive as early as 1992, validating this approach.
With propylene demand increasing, Mobil will now allow catalyst manufacturers to produce high ZSM-5 content additives pursuant to Mobil’s patent position. The MAXOFINTM FCC process couples these new additives with proprietary hardware to produce either maximum olefins or conventional fuels, as the market demands, from traditional FCC feedstocks without resorting to severe operating conditions.MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 3 

### DESCRIPTION OF KEY MAXOFINTM FEATURES
TheMAXOFINTM process brings together a new generation high ZSM-5 content additive and proprietary

FCC hardware to economically produce high yields of light olefins from traditional FCC feedstocks such as gas oils, deasphalted oil, and residual oil feedstocks. All thesefeatures are commercially proven and provide flexibility to alternate between light olefin maximization and traditional maximum gasoline operations. The next few sections provide details of the MAXOFINTM technology.

a. MAXOFIN-3TM Additive
TheMAXOFINTM process is built around a family of proprietary additive formulations containing higher levels of ZSM-5 than previously available. The formulation can be tailored to the refiner’s needs based on the extensive data base compiled by Mobil during ZSM-5 development. The result is a new generation of additives that exhibit superior activity, high propylene selectivity, and excellent attrition resistance. Furthermore, these additives exploit the synergies with the Mobil-Kellogg hardware to produce maximum propylene from FCCU’s.
Table 2 shows a comparison between conventional ZSM-5 additives and MAXOFIN-3TM additive at the same crystal level in the inventory. The large amount of conventional additive would dilute the base catalyst activity and produce lower conversion, higher bottoms yield, and fewer C 6 + gasoline olefins. It is the C 6 + gasoline olefins that subsequently react over ZSM-5 to produce propylene and butylenes. 

### TABLE 2: MAXOFIN-3TM Additive Achieves High Propylene Yield

Without Significant Conversion Penalty Additive D Propylene yield, wt% D Catalyst MAT Activity MAXOFIN-3TM Additive Base Base Conventional Additive -1.2 -4.0

b. ATOMAX-2TM Feed Injection System
Thefeed injection system plays a key role in the yield performance of the MAXOFINTM process becausea large fraction of the ZSM-5 cracking precursors, C 6 -C 12 olefins, is formed in the feed-catalyst mixing zone. By minimizing bacmixing in the riser, an efficient feed injection system protects the C 6 -C 12 olefins from deleterious bimolecular hydrogen transfer and makes them available for ZSM-5 to crack into light olefins.MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 4 -20 -10 0 10 20 0.4 0.6 0.8 1.0 1.2

Distance from Center of Spray, inchesRelative Sauter Mean Diameter

ATOMAX-1 Avg. SMD = 1.0
ATOMAX-2 Avg. SMD= 0.57 Wider Spray Angle and More Uniform Atomization DROPLET SIZE ACROSS SPRAY ATOMAX-2 vs. ATOMAX-1

Figure 3 In 1992, Mobil and Kellogg commercialized the ATOMAXTM feed nozzle, which provided a significant advancement in FCC feed injection technology. Although the original ATOMAXTM nozzle quickly became the market leader, Mobil and Kellogg were not

willing to rest on this accomplishment.
In 1996, we began work to develop the nextgeneration feed nozzle. A custom feed nozzle test rig was built

at the Kello gg Technology Devel opment Center to evaluatenozzle prototypes. This rig incorporatesa state-of-theartLaser Dopplerimeter that can measure droplet size, velocity, and liquid flux atany point in the spray pattern. Each of these parameters is key to developing a wellintegrated feed injection system

. Our successful development efforts have led to the commercialization of the ATOMAX-2TM nozzle, representing a significant step forward in feed nozzle technology. As shown in Figure 3, ATOMAX-2TM produces a significantly smaller Sauter mean droplet size than the industry-leading ATOMAXTM nozzle at all points in the fan-shaped spray

. ATOMAX-2TM produces a “spray-averaged” Sauter mean droplet size that is about 43% smaller than ATOMAXTM. For a given volume of spray, the new nozzle produces about six times more droplets than its predecessor!MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 5 Closed

Cyclone System

ATOMAX-2 Fresh Feed Injection Primary Feed Riser 2nd Riser for Naphtha Recycle

Recycle Naphtha InjectionCounterCurrent Regenerator Two-Stage Stripper 

### MAXOFINTM FCC with Dual Risers

Figure 4 c. Second Riser for Naphtha Cracking FCC naphtha, preferably light cat naphtha, can be re-cracked in the presence of ZSM-5, high cat-to-oil ratios, and high riser outlet temperaturesto produce olefins. For clients requiring maximum olefin yields, a second riser can be installed that processes recycled naphtha and operates at a riser outlet temperature of approximately 1100°F. A dual riser MAXOFINTM FCC configuration is depicted in Figure 4
Thecombination of high temperature and high levels of ZSM-5 allow the gasolinerange light olefins and light paraffins to crack. The high riser outlet temperature and the high heat of reaction produce a cat-to-oil ratio close to 25-to-1, thus maximizing the effectiveness of MAXOFIN-3TM additive.
At lower cost than a second riser, naphtha can also be recycled to the "lift zone" at the base of the riser and below the fresh feed nozzles. This location produces the highest temp erature possible in a unit with only one riser. However, in this scenario gasoline cracking is less than with a separate riser due to reduced residence time and inefficient gas-solid contacting. As a result, olefin yields are slightly lower and selectivity is better for lift-zone naphtha cracking than for separate-riser naphtha cracking. However, the second riser gives more operating flexibility, especially when it is desirable to maximize the distillate and light olefins with minimum gasoline produced. Thus, the choice between a lift-zone and a second riser depends on the need for operating flexibility and capital availability.
d. Choice of base catalyst and feedstock
In addition to the MAXOFIN-3TM additive, the propylene yield from a given feedstock can be optimized by proper choice of the base catalyst. The base FCC catalyst is optimized to minimize

hydrogen transfer and produce maximum C 6 -C 12 olefins, which will convert to light olefins in the presence of ZSM-5. Reaction pathways 4-8 for cracking over base catalystand ZSM-5 are depicted in Figure 5.MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 6 FCC REACTION PATHWAYS for production of C3-C4 olefins with base catalyst & ZSM-5
Feed Component Intermediate Product
Paraffin & Side Chains

Naphthene

Aromatic C6 - C12 Olefins Paraffin

Coke C3 - C4 Olefins ZSM-5 Cracking

Condensation Cracking Cracking Cracking H Transfer H Transfer Polymerization

Figure 5

FEATURES OF CLOSED CYCLONES

Closed Cyclones Excellent catalyst / vapor separation 97+% of riser product vapors flow directly to overhead line Very brief vapor residence time Very little thermal cracking No dilute phase catalytic cracking Yield benefits: less dry gas higher propylene yield less bottoms yield improved coke selectivity

Figure 6 Thefeedstock can be optimized among the available feed components. As mentioned earlier, recycle of naphtha to a second riser or lift zone can be used to produce incremental propylene.
Mobil and Kellogg have pilot plant and commercial test data on cracking streams of various unfinished gasoline streams. These include virgin naphtha, coker gasoline, visbreaker gasoline, and hydro treated naphtha. The optim um feedstock and catalyst are identified by using a propr ietary compositional FCC yield model that tracks more than 3000 components in the FCC feed and products.
Unlike competing processes, the MAXOFIN-3TM additive and base catalyst combination obviates the need for low riser hydrocarbon partial pressure and high amounts of riser steam.

e. Riser Termination (Closed Cyclones)
The MAXOFINTMprocess uses relatively high riser outlet temperaturesto optimize the yield ofpropylene. In this environ ment, modern riser termination technology is essential.
Closed Cyclones minimize the residence

time of hydrocarbon vapor and catalyst in the disengager vessel. By eliminating post

riser thermal and catalytic cracking, Closed Cyclones reduce the yield of dry gas, reduce coke formation on the catalyst, and increase the yield of more valuable products, as depicted in Figure 6.MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 7 Slide

Valve Catalyst Return Fluidization Air Catalyst In Tubesheet

Tubesheet Inner Tube

Scabbard -- Outer Tube Water In

Water & Steam Out

Figure 7- Dense Phase Catalyst Cooler Closed Cyclones have been in commercial service since 1985 and have proven to minimize thermal cracking in the disengager while being both operationally and mechanically reliable.
f. Dense Phase Catalyst Cooler
For processing heavyresid-containing feedstocks the MAXOFINTM process offers a Dense PhaseCatalyst Cooler to control regenerator temperature and optimize catalyst-to-oil ratio.
Theunique design of the system allows complete turndown by adjustment of the catalyst circulation rate through the cooler. Byplacing the tube bundle on top of the cooler shell as shown in Figure 7, the fluidization air distributors within the cooler shell are located well below the tubes, eliminating the possibility of tube erosion and failure due to impingement of air jets. Since 1989, eleven Kellogg dense phase catalyst coolers have been licensed and three are now in operation.



### MAXOFINTM PROCESS EXAMPLE

a. Basis and Yields
As a case study, we have illustrated the flexibility of the MAXOFINTM process by studying three different modes of operation:
T Maximum propylene T Maximum fuels T An intermediate case
While this technology can be easily applied to revamp cases, the illustrations below cover a grassroot FCC processing 600-1000°F TBP boiling range gas oil feed derived from Minas crude oil. The unit is designed to process 30 MBPSD of gas oil in the maximum propylene mode at 1000°F riser top temperature and 400°F combined feed temperature.MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 8 Table 3 shows that the propylene yield / fuels yield tradeoffs can be selected to suit the current market needs. For example, the propylene yield can be changed from 6.2 wt% in the fuels mode to 18.4 wt% in the maximum propylene mode. The maximum propylene case producesabout 300,000 tons of propylene per year for a downstream world scale polypropylene facility. 

### TABLE 3: MAXOFINTM Process Yields and Operating Conditions

DESCRIPTION OPERATING MODE Maximum Propylene Case Intermediate Case Fuels Mode

Case Propylene Yield, wt.% 18.4 14.4 6.2 Feed VGO & Light Naphtha Recycle VGO VGO Catalyst RE-USY + ZSM-5 RE-USY + ZSM-5 RE-USY Only Reactor Configuration Dual Riser Single Riser Single Riser Riser Top Temp, °F 1000 / 1100 1000 1000 Catalyst / Oil 8.9 / 25 8.9 8.9 Feed Rate, MBPSD 30.0 30.0 44.1
YIELDS, wt% Hydrogen Sulfide 0.03 0.02 0.01 Hydrogen 0.91 0.18 0.12 Methane & Ethane 6.61 2.07 2.08 Ethylene 4.30 1.96 0.91 Propane 5.23 3.90 3.22 Propylene 18.37 14.38 6.22 n-Butane 2.25 2.16 2.17 i-Butane 8.59 8.52 7.62 Butylenes 12.92 12.33 7.33 Gasoline 18.81 35.53 49.78 Light Cycle Oil 8.44 7.33 9.36 Decant Oil 5.19 5.24 5.26 Coke 8.34 6.38 5.91
Theextraordinary propylene yield is accomplished with a combination of high ZSM-5 content additive and re-cracking of gasoline in a second riser. The optimal top temperature, gasoline recycle ratio, and residence time in the second riser depends on gasoline composition, incremental propylene and gasoline prices, metals on equilibrium catalyst, andMAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 9 FCCU constraints such as air rate, main fractionator, wet gas compressor, and gas concentration section bottlenecks.
Thesecond riser converts essentially all the gasoline range olefins and naphthenes in the recycled gasoline. Both the fresh feed riser and the gasoline re-cracking riser are operated at conventional steam rates (2-5 wt%). For purposes of the example, and to more clearly show the effects of the ZSM-5 additive and the effects of the second riser, a 1000°F primary riser temperature is used for all three cases. In a commercial application, depending on unit constraints

and other operating objectives, the primary riser temperature would be optimized in each case.
Also listed in Table 3 is an intermediate case that provides up to 14.4 wt% propylene yield without the use of the second gasoline re-cracking riser. In this intermediate case, the increased coke yield relative to the fuels case is due to the heat requirement for C 6 + olefin re-cracking and lack of hydrogen transfer.
An additional 5-7 wt% propylene yield can be obtained by secondary processing of ethylene and butylenes through olefin interconversion processes, thereby producing a net propylene yield of up to 25 wt% on a fresh feed basis.
b. Fuels Mode
Theuse of MAXOFIN-3TM additive can be discontinued if market conditions change and the production of fuels becomes more economic than the productioni of propylene. The third column of Table 3 outlines a maximum fuels operating mode, which uses a conventional FCC catalyst (without ZSM-5 additive) and employs the second riser for gas oil feed. The fresh feed rate is increased to take full advantage of the available capacity of the air blower required for producing maximum propylene. For simplicity we show the incremental feed quality to be the same as the base feed. However, depending on the refiner's configuration, this incremental feed could be light gas oil, vacuum tower overflash, or vacuum tower bottoms.
Detailed investigations indicate that all the equipment can be designed to operate at the extremes

of both cases (high vapor loads at the top of the main fractionator for the maximum propylene case and high liquid loads for the debutanizer in the fuels operation). Although these examples show a maximum conversion FCC operation, the MAXOFINTMprocess can also be used for providing maximum propylene in a low-conversion, highdistillate mode of operation. Distillate mode consists of low riser temperature, high feed preheat temperature, and high recycle of bottoms.

c. Utilities Mobil/Kellogg can assist in evaluations of propylene production costs for the various catalyst and hardware options. The production costs should always include the visible catalyst andMAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 10 additive expenses as well as thelife cycle effect of the less visible utility costs. The life cycle costs can be significant, especially if a large amount of steam is necessary to maintain low hydrocarbon partial pressures. Surprisingly, the cost of steam may actually exceed the cost of the ZSM-5 additive!
To allow a quick comparison of utilities requirements, Table 4 outlines the estimated utilities require ments for three different operating modes: 1) MAXOFINTM maximum propylene case, 2) MAXOFINTM fuels case, and 3) A process using 20 wt% dispersion steam.
TheMAXOFINTM process provides high yields of propylene with only 4 wt% dispersion steam on a fresh feed basis. The cost of this steam is estimated to be approximately 7 cents per barrel of fresh feed when main fractionator condensing costs and sour water treating costs are included along with the cost of producing the steam. The cost per barrel of fresh feed would be approximately 5 times higher if 20 wt% dispersion steam were required. The difference in steam costs, approximately 28 cents per barrel, is typically more than the cost of ZSM-5 additive.
Table 4 shows that consuming large amounts of dispersion and stripping steam in the converter can also lead to significant costs for condensing the steam and for treating the subsequent

sour water. In addition to the increased steam consumption and production of sour water, the high dispersion steam case requires an increase in air blower capacity to burn the extra coke required to heat the dispersion steam to riser outlet temperature. The extra coke production must come at the expense of liquid product yield, a factor that has not been considered in this analysis.



### CONCLUSIONS
As worldwide demand for polypropylene has increased, refiners have looked to FCC to produce incremental propylene for petrochemical feedstock. The Mobil-Kellogg MAXOFINTM FC C process, based on a new MAXOFIN-3TM ZSM-5 additive and proprietary hardware technology features, is available for maximizing the production of light olefins from FCC feedstocks.
Thekey feature of this technology is its flexibility to respond to market demands by effectively operating in maximum olefin mode, maximum fuels mode, or anywhere between. TheMAXOFINTM FCC process can produce propylene yields approaching 20 wt% of feed while retaining the ability to operate as a conventional fuels FCC. This flexibility is provided by using the highly active MAXOFIN-3TM additive and FCC hardware components designed for maximum operating flexibility. Mobil’s extensive database can be used to optimally match the selection of FCC feedstock components, base FCC catalyst, and MAXOFIN-3TM additive.MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 11 1. R.J. Argauer and G.R. Landolt; US Patent 3,702,886; Nov 14, 1972 to Mobil.
2. C.D. Andersen, F.G. Dwyer, G. Koch, P. Niiranen; 9th Ibero American Symp. Catal.; Lisbon, Portugal; 1984.
3. Y.G. Adewuyi, J. Klocke, J.S. Buchanan; Appl. Catal. A,131 (1995), 121. 

### REFERENCES

4. J. S. Buchanan and Y. G. Adweyi, Applied Catalysis, 134 (1996) 237.
5. D. A. Pappal and P. H. Schipper, ACS Symposium Series 452, 1990.
6. R. J. Madon, J. Catal. 73 (1991) 275.
7. J. S. Buchanan, Appl. Catal. 74 (1991), 83.
8. P.H. Schipper, F.A. Dwyer, P.T. Sparrell, S. Mizrahi, S.P. Donnelly, J.A. Herbst; ACS Symp. Series 375 (1982) 364.MAXOFINTM: A Novel FCC Process for Maximizing Light Olefins

AM-98-18 Page 12 

### TABLE 4: Estimated Utilities OPERATING MODEMax Propylene Case Fuels Mode

Case High Dispersion Steam Case Feed Rate, BPSD 30,000 42,350 30,000 Dispersion Steam, wt% Fresh Fd 4.0 3.0 20.0 High Pressure Stm (600 psig) Production, lb/hr Flue Gas Cooling 98,000 104,600 102,300 Consumption, lb/hr Air Blower Turbine (99,300) (99,300) (103,600) Wet Gas Comp. Turbine (91,700) (50,500) (91,700) C3 Drier (11,700) (6,600) (11,700) Med Pressure Stm (250 psig) Production, lb/hr Main Frac P/A’s 30,000 34,400 45,700 Consumption, lb/hr Converter (28,800) (26,000) (89,000) Main Frac Stripping (1,600) (2,400) (1,600) Amine Stripper (600) (300) (600) Low Pressure Stm (50 psig) Consumption, lb/hr VRU Reboilers (244,000) (152,800) (244,000) Condensate Return , gpm 894 619 903 Boiler Feedwater , gpm 264 286 305 Cooling Water , gpm (20E F rise) 54,500 42,100 55,700 Main Frac Wash Water , gpm 60 85 60 Sour Water Produced , gpm 121 141 241 Electric Power , kW 2,300 2,100 2,500 Main Frac Ovhd Duty , MMBtu/hr 126 138 192