AIChE Paper 219c

Catalytic Routes to Olefins

Michael J. Tallman Manager, Catalytic Olefins Technology

Kellogg Brown & Root (KBR) LLC Houston, Texas

Curtis N. Eng Director, Olefins Technology Kellogg Brown & Root (KBR) LLC

Houston, Texas

Prepared for Presentation at the 2008 Spring National Meeting

New Orleans, Louisiana

April 7-10, 2008

AIChE and EPC shall not be responsible for statements or opinions contained in papers or printed in its publications

KBR Internal Reference Paper 2084

Catalytic Routes to Olefins

Michael J. Tallman Manager, Catalytic Olefins Technology

Kellogg Brown & Root (KBR) LLC Houston, Texas

Curtis N. Eng Director, Olefins Technology Kellogg Brown & Root (KBR) LLC

Houston, Texas

Abstract: Propylene is most commonly produced as a byproduct from conventional steam cracking and from refinery conversion processes such as gas oil fluid catalytic crackers. Because the growth in demand of propylene is higher than either ethylene or refinery fuels products and due to the preponderance of light gas crackers with relatively low propylene yields, there could be gaps in meeting future propylene demands. As such, many producers are considering alternative methods to meet future propylene needs. KBR offers a suite of propylene technologies that can help meet the propylene demand, depending on the feed type and the required ethylene co-production, as follows. Technology Feed Total Ultimate Ethylene + Propylene

Yield Advanced Catalytic Olefins (ACOTM)

Paraffinic naphtha & light distillates

55-65 wt%

SuperflexTM Olefinic C4-C10 hydrocarbons 40-65 wt% MaxofinTM Gas oil and resids 30-40 wt% The features and status of each of these technologies will be discussed.

Catalytic Routes to Olefins

Michael J. Tallman, KBR Curtis N. Eng, KBR

Annual worldwide growth in propylene demand is expected to exceed 5% over the next several years. Steam crackers currently produce approximately 60% of the world's propylene, as a byproduct to ethylene production. This propylene is produced in a typical weight ratio of approximately 0.4 to 0.6 parts of propylene per part of ethylene, and only when cracking heavier feeds such as naphtha and gas oil. The balance of propylene is primarily supplied from refinery sources, mostly as byproduct from FCC units producing fuels (gasoline and diesel).

Since the ethylene market is expected to grow at a slower pace than that of propylene,

and since many of the new steam crackers being built utilize ethane as a feedstock which does not produce any propylene, propylene supply from ethylene expansion is not expected to meet demand. Similarly, FCC operations are driven by fuel demands and new FCC units will not fill the demand either, although some refiners will gravitate toward higher severity operations to increase production and fill a portion of the need. Therefore, new sources of propylene will be necessary to meet the expected future demand.

KBR offers a suite of technologies which target propylene as a primary target, and are

available depending on the type of feed available. These technologies include SuperflexTM technology, a process for increasing propylene production from olefinic byproduct streams from steam crackers or refinery processes, the Advanced Catalytic Olefins (ACOTM) process, a process for enabling increased propylene production from paraffinic feeds and MaxofinTM, a high severity FCC process for increased propylene production from traditional refinery sources such as gas oils and resids.

Propylene-On-Purpose Technologies – An Overview Alternative Sources for Propylene

Currently, steam cracking and refinery operations constitute approximately 94% of the propylene produced today. An alternative technology to steam cracking which can convert paraffinic streams such as straight run naphtha to high quantities of propylene is the Advanced Catalytic Olefins (ACOTM) process; this process will be discussed in more detail later in this paper. Refinery FCC units can boost propylene production through the use of catalyst additives and by higher severity operations; to this end MaxofinTM technology can be used to increase propylene production from the traditional refinery sources and this technology will also be discussed further.

However, as the demand for propylene continues to grow alternative technologies will be come more prominent. There are several of these “on-purpose” routes to propylene, and these are summarized below:

• Methane to Olefins (MTO) – There are currently no economic direct routes for converting methane to propylene despite a significant amount of research and development expended on the subject. Methane must first be converted to methanol (or DME), then it can be converted to propylene. The methanol/DME routes to propylene are not yet commercially proven, although designs have been announced. Due to the high capital intensity for such Methane (or Methanol) To Olefins (MTO) processes the economics are dependent on the value for the natural gas feed (methane), which needs to be priced at values much less than world fuel prices. This alone makes MTO a niche opportunity in most cases.

• Metathesis – Metathesis is the reaction of ethylene with 2-butene to form propylene and

there are a number of commercial units in operation. Traditionally ethylene prices have exceeded those of propylene (typical historical value for the P/E price ratio has ranged from 0.7-0.8) and so economics did not favor the metathesis process for propylene production. However, with recent demand growth propylene prices have equaled and in some areas exceeded those of ethylene and this is necessary to make the economics for metathesis attractive. There also may be cases when ethylene is in excess supply (because of the market or idle units) and metathesis could make economic sense. Grass roots plants which incorporate metathesis as a method to increase propylene production must over-produce ethylene to feed to unit, increasing the overall capital expenditure.

• Propane Dehydrogenation – Propane dehydrogenation produces propylene with rather

high selectivity. However the economics of dehydrogenation of propane to propylene depends heavily on the price of propane and its differential to that of propylene. Most of today’s activity in dehydrogenation is centered in the Middle East where propane is priced extremely favorably compared to world-wide market prices. However, for the most part long term availability of low price propane precludes this technology as an attractive option.

• Olefins Cracking Technologies – Newer catalytic routes using ZSM5 type catalysts have

shown promise recently, by converting C4-C8 olefinic feeds into as much as 40% propylene. A summary of these is given in the table below:

Table 1 Comparison of Olefins Cracking Technologies

SRIPT Note 1 OCC

Lurgi PropylurTM

UOP Olefins Conversion

KBR Note 2 SuperflexTM

Reactor Fixed bed Cyclic

Fixed bed Cyclic

Fixed bed Cyclic

Fluid bed Continuous

Catalyst Sole source Sole source Sole source More than 1

Conversion Low Low Low Low-High

Steam Yes High Low? Minimal

Paraffins Conversion

None to Low None to Low None to Low Low-High

Recycle to Extinction

No No No Yes

Commercial No No No 2006 start up (Sasol)

Note 1: Shanghai Research Institute of Petrochemical of Technology, China

An example of this technology is SuperflexTM technology, originally developed and owned

by LyondellBasell and licensed by KBR, to be discussed in more detail later in this paper.

For the most part, the “propylene-on-purpose” technologies with substantial propylene yields are MTO (discounting the water in the effluent product slate), metathesis and propane dehydrogenation, all of which require a niche feedstock (methanol, ethylene or propane, respectively) that may be difficult to procure regionally or too expensive to be economically viable as a propylene producer.

KBR’s catalytic olefins processes are FCC-type processes which produce propylene from

readily available feed sources. These include olefinic byproduct streams, which can be converted to propylene using Superflex technology; paraffic streams, which already are the feed source for more than half of the world’s ethylene and which can be converted to propylene using ACO technology; and gas oil and resids, which already are the feed source for most FCC’s and which can be converted to propylene using Maxofin technology.

KBR FCC: The OrthoflowTM Converter What is FCC?

All of these technologies produce olefins using process hardware similar to refinery FCC units. KBR is a leader in FCC technology from its participation of the world’s very first FCC unit built for ExxonMobil in Baton Rouge, Louisiana in 1942. Today there are 122 KBR-licensed FCC units in operation world-wide. KBR’s catalytic olefins offerings build on this extensive design experience to provide processes which produce large quantities of propylene using proven FCC hardware.

Refinery FCC units catalytically crack heavy feeds such as gas oil and resids in a riser to lower molecular weight products such as gasoline, diesel and kerosene. A schematic of a typical FCC unit is shown in Figure 1:

Figure 1

Fluidized Catalytic Cracking (FCC) Unit

The reactor (converter) is comprised of four sections: riser/reactor, disengager, stripper and regenerator. The feed is introduced at the bottom of the riser and mixed with hot regenerated catalyst. The feed is vaporized and the reactions take place as the feed gas and catalyst flow upward in the riser. At the end of the riser the product gas and catalyst are separated in cyclones, housed in the disengager. The catalyst is then routed to the stripper, where product gases still entrained in the catalyst pores are stripped with steam or nitrogen and routed with the reactor effluent. Stripped catalyst is then routed to the regenerator, where air is introduced and coke which has formed on the catalyst during the cracking operation is burned, regenerating the catalyst for re-use in the riser and supplying the heat of vaporization and heat of reaction in the riser. Accessory systems for the FCC unit include air supply, flue gas handling and heat recovery and catalyst storage. Reactor overheads are typically routed to the primary fractionator and subsequent product separation and recovery.

What is OrthoflowTM?

Many FCC designers use a “side-by-side” configuration, in which the disengager vessel is adjacent to the regenerator vessel. In KBR’s OrthoflowTM configuration, the disengager vessel is mounted directly above the regenerator vessel (see below).

Side by Side KBR Orthoflow

The advantages of the Orthoflow configuration are several: first of all, the plot space required is much smaller for this configuration compared to the side-by-side type of unit. Foundation and structural costs are also reduced. The Orthoflow configuration allow the unit to be fabricated and dressed off-site and set into place with one lift, saving on construction costs and with less welding required in the field. The stripper is submerged within the regenerator which reduces the vertical height of the unit and thus the cost.

Other Features of KBR FCC

There are several other features of KBR’s FCC reactor system which can be used in the catalytic olefins processes also, including the dual riser, closed cyclones and third stage separator. These features are described briefly below.

• Dual Risers – The use dual risers in FCC units was

quite common during the early stages of FCC development. The first KBR FCC unit in 1942 had dual risers, and KBR has built 14 additional dual riser units since 1950. The primary reason for dual risers at that time was one of scale-up, that is, design commercial risers that had similar flow characteristics as tested in the pilot plant. For several advantageous process reasons dual risers can be used in ACO and Maxofin applications.

The KBR Orthoflow converter, a stacked, inline reactor and regenerator, with two risers.

• Closed Cyclones – Closed cyclones minimize the residence time of hydrocarbon vapor and catalyst in the disengager, thereby eliminating post-riser thermal and catalytic cracking. Less valuable products are destroyed, leading to more valuable products.

KBR’s proprietary closed cyclones enhances yields.

• Third Stage Separator – In regions where there is a stringent particulates emissions requirement, the KBR proprietary third stage separator has proven to be quite effective.

The Third Stage Separator reduces catalyst fines emissions.

For KBR’s light olefins FCC processes (Superflex and ACO) there are other unique and innovative design aspects which address the fact that the feeds are so much lighter than refinery FCC’s which are commercially demonstrated:

• Heat Balance – Both the ACO and the Superflex process are endothermic. As such, to maintain heat balance, fuel must be imported into the reaction system. KBR’s patented

(US#7,153,479) catalyst well design with continuous fuel firing has now been commercially proven.

• Catalyst/Hydrocarbon Separation – Although the cyclones are quite efficient, invariably

some catalyst fines will carry over with the reactor effluent cracked gas. KBR’s patented (US#7,011,740) catalyst fines removal system has now been commercially demonstrated and applicable to both ACO and Superflex technology.

The Advanced Catalytic Olefins (ACOTM) Process

Why Naphtha Feed?

Naphtha is the predominate feed for steam crackers, as more than half of the ethylene currently produced world-wide is derived from cracking naphtha feed. However, propylene production from steam cracking these feeds is limited to 0.4-0.6 parts by weight per part of ethylene. ACO produces nearly the same quantities of propylene and ethylene, still with significant ethylene produced, and uses the most common feedstock available, straight run naphtha. Thus ACO should be of interest to many producers who already use naphtha feeds to produce ethylene. The ACO Reactor

The ACO process combines the KBR OrthoflowTM fluidized catalytic cracking reactor system with a proprietary catalyst developed by SKenergy in Korea which selectively converts naphtha feed to large quantities of propylene and ethylene. The ACO reactor system includes the Orthoflow configuration, the dual riser, closed cyclones, third stage separator, patented catalyst well for continuous fuel firing, and patented catalyst removal system. The reactor section is shown in Figure 2:

Figure 2 ACOTM Reactor System

One significant advantage of the ACO converter is economy of scale regarding olefins

capacity. The maximum commercially demonstrated capacity in a single cell liquid-feed pyrolysis furnace is approximately 200 kta ethylene, or approximately 300 kta of total olefins. By contrast, the world’s largest ACO reactor (if similarly sized to the world’s largest commercial FCC unit today) can make about 4-5 times more olefins, or up to 1,500 kta ethylene + propylene in a single reactor. The ACO Recovery Scheme

The ACO process produces both polymer grade ethylene and propylene. Much of the process flow scheme is similar to typical olefins plant recovery sections; however, there are some unique features. For example, there are trace impurities such as nitrogen oxides, oxygen, and other trace impurities by virtue of the FCC-type reactor that must be removed. These and other issues are addressed in the ACO process flow scheme, which features a front end depropanizer as shown below:

Fresh Feed

To Flue Gas System Reactor

Effluent To Recovery

FuelOil

Steam BFW

CW

Catalyst StorageAnd Handling

Regeneration Air

Oil Wash Tower ACO

Orthoflow Reactor / Regenerator

Catalyst Fines

Recycle

Figure 3 Typical ACO Flow Scheme

ACO Performance Figure 4 below shows a comparison of the yields obtained from steam cracking and from ACO:

Figure 4 Comparison of Naphtha Cracking Yields

Drying

Deprop-anizer

Demeth-anizer

Deeth-anizer

C2 Splitter

C3Splitter

Light gas

Ethylene

Propylene

Depent-anizer

BTX+

Ethane/Propane

QuenchedGas

Coldbox

C2Ref

1-2 3

Dehex-anizer

Non-aromaticC6+Mix C4/C5Recycle to Reactor

C3Ref

Treating

0

25

50

75

100

SteamCracker

ACO

OtherGasolinePropyleneEthylene

Wt%

The ACO process makes about 15-25% more ethylene plus propylene on a relative

basis, depending on the operating conditions. In the example above, the total ethylene plus propylene product yield is about 17% higher than the steam cracker. Further, the ACO process has a higher concentration of BTX in the gasoline fraction, resulting in about 20-25% higher absolute aromatics yield from the ACO process.

One means of comparing the ACO process to a steam cracker is to compare the Cost of Production (COP) of ethylene. In this type of analysis, the feed and operating costs are offset the byproduct costs. Other costs include indirect and overhead costs and depreciation (10%) and profit is added (10%) to arrive at an overall COP. Based upon a constant feed to either a steam cracker or an ACO unit, the ACO process is favored by lower COP of about $90/MT of ethylene. ACO Commercialization SKenergy is a Korean-based conglomerate with 2006 sales over US$24 billion. SK owns and operates two naphtha crackers in Ulsan with a total ethylene capacity of about 800,000 MTY and also operates several refinery units including FCC’s. Studies and plans are currently underway to integrate the ACO converter system with SK’s existing facilities in Ulsan, with anticipated implementation by the end by 2010. Thus, SKenergy will be the first commercial adopter of the ACO process.

Superflex What is Superflex?

Superflex is a catalytic cracking process that produces propylene from C4-C8 olefinic feeds. The reaction area and recovery section flow schemes are nearly identical to those described above for the ACO process and include the same features in the FCC reactor section.

Feeds for Superflex can be sourced from nearly any cracking process, steam cracking or various refinery cracking processes. Such streams include for instance C4 byproduct from a steam cracker (hydrogenated C4’s, raffinate-1 or raffinate-2) and C5 byproduct from a steam cracker, light FCC naphtha and light coker naphtha from refineries. Typical ultimate yields on a recycle-to-extinction basis (i.e., including recycle to extinction of the C4 and C5 products from the Superflex reactor) are shown in Table 2:

Table 2 Superflex Yields

Feedstock Pyrolysis C4's

Pyrolysis C5's FCC LCN Coker LN

Ultimate Yield, wt% Fuel Gas 7.2 12.0 13.6 11.6 Ethylene 22.5 22.1 20.0 19.8 Propylene 48.2 43.8 40.1 38.7 Propane 5.3 6.5 6.6 7.0 C6+ Gasoline 16.8 15.6 19.7 22.9

Superflex Commercialization The first commercial Superflex unit was recently started up at Sasol in South Africa. This unit converts a highly olefinic C6/C7 stream and converts it to propylene and ethylene, with a propylene capacity of approximately 250 kta. The feed also contains a high concentration of oxygenates, but is processed directly in the Superflex converter with no pretreatment. The recovery section is designed to also process various olefins-rich streams from the complex, with final polymer-grade production rates of 525 kta of propylene and 200 kta of ethylene.

JiHua is the second licensee, located in Jilin City, China. The capacity of that unit will be 200 kta of propylene from C4/C5 feed. KBR has completed basic engineering for that plant.

Maxofin What is Maxofin?

It is possible to maximize propylene yields from refinery FCC sources using KBR’s Maxofin technology. Maxofin uses traditional FCC feeds such as gas oils and resids. However, through the use of higher severity cracking, MAXOFIN-3TM catalyst additive and high severity recycle cracking to a second riser, it produces higher propylene yields. The process is flexible, however, to operate also at typical, maximum gasoline production mode, during periods as dictated by prevailing economic conditions.

This operating flexibility can be seen in the following table in which pilot plant test results demonstrate the range of yields that can be expected from a Hydrocracked Gas Oil feedstock with variations in operating conditions and catalyst formulation:

Table 3 Maxofin FCC Pilot Plant Yields

Hydrocracked Gas Oil

Yields, wt% Run A Run B Run C Run D

Ethylene 3.2 3.9 6.4 8.2 Propylene 16.0 18.7 19.1 21.5 C5+ Gasoline 37.9 28.8 26.2 25.0

P/E (wt/wt) 5.0 4.8 3.0 2.6

Maxofin technology builds upon KBR’s extensive FCC design experience and uses proven hardware. The recycle riser can be designed to not only recycle excess light hydrocarbons from the FCC operation (C4’s and light FCC naphtha) but also other olefinic streams from the refinery such as light coker naphtha or straight run naphthas.

Summary

Steam cracking and refinery sources will not keep pace with future propylene demand and so “on-purpose” technologies will become more prevalent. KBR offers several such technologies, with the use dependent on the type of feed available. The ACO process uses straight run paraffinic feeds and cracks them to produce more total olefins than pyrolysis with P/E ratios up to 1/1. Superflex uses olefinic feeds and produces 50-60% total olefins with typical P/E ratios of about 2/1. Maxofin uses typical FCC feeds and increases propylene yield from about 5 wt% in typical refinery operation to up to roughly 20 wt%.