The Uhde STAR process®

Oxydehydrogenation oflight paraffins to olefins

ThyssenKrupp Uhde

Our new name is

ThyssenKrupp Industrial Solutions

www.thyssenkrupp-industrial-solutions.com

1. Company profile 3

2. Introduction 42.1 Steam reforming and olefin production plants by Uhde 7 3. Oxydehydrogenation – basic principles 8

4. STAR process® technology 94.1 STAR catalyst® 9 4.2 Process pressure 9 4.3 Operation cycle 9 4.4 Oxidant 104.5 Space-Time-Yield 104.6 STAR process® reaction section 104.7 Heat recovery 104.8 Gas separation and fractionation 11

5. Proprietary equipment 135.1 STAR process® reformer 135.2 STAR process® oxyreactor 14

6. Comparison of dehydrogenation technologies 166.1 General remarks 166.2 Adiabatic reactors connected in series 166.3 Parallel adiabatic reactors 176.4 STAR process® with oxydehydrogenation step 17

7. Application of the STAR process® 187.1 Oxydehydrogenation of propane to propylene 187.2 Oxydehydrogenation of butanes 197.2.1 Oxydehydrogenation for the production of alkylate 197.2.2 Oxydehydrogenation for the production of dimers 21

8. Services for our customers 23

Table of contents

2

Company profile

With its highly specialised workforce of more than 4,500 employees and its international network of subsidiaries and branch offices, Uhde, a Dortmund-based engineering contractor, has, to date, successfully completed over 2,000 projects throughout the world. Uhde’s inter- national reputation has been built on the successful application of its motto Engineering with ideas to yield cost-effective high-tech solutions for its customers. The ever-increasing demands placed upon process and application technology in the fields of chemical processing, energy and environmental protection are met through a combination of specialist know-how, comprehensive service packages, topquality engineering and impeccable punctuality. The extensive international experience in the design and construction of chemical plants makes Uhde the ideal licensor and engineering contractor for dehydrogenation plants using the advanced STAR process®.

Uhde’s head office

Dortmund, Germany

3

2. Introduction

STAR, which is the acronym for STeam Active Reform-ing, is a commercially established dehydrogenation tech- nology that was initially developed by Phillips Petroleum Company, Bartlesville, OK, USA.

Uhde acquired the technology including process know-how and all patents related to process and catalyst from Phillips in December 1999.

Medium and long-term forecasts expect to see a growing demand for on-purpose technologies for olefin pro duction (e.g. propylene, butylenes) such as dehy-drogenation of light paraffins.

Today most propylene is produced as co-product in steam crackers (approx. 57%) and as by-product in FCC units (approx. 35%). Only approx. 6 - 8% is produced by on-purpose technologies like propane dehydrogen-ation (PDH) or metathesis.

However, higher annual growth rates for propylene than for ethylene are expected. Additionally, steam cracking increasingly shiftsto ethane feedstocks due to more favourable economics compared to naphtha or LPG feedstocks. Because ethane cracking yields consider-ably less propylene than LPG or naphtha cracking this will result in a gap for supply of propylene. This gap can very economically be closed by propane dehydro-genation applying the STAR process®.

Rapid further growth is expected for on-purpose pro-pylene and butylene production to yield the following derivatives:

Derivates of Propylene Derivates of Isobutylene

Polypropylene* MTBE/ETBE

Propylene Oxide** Alkylate

Cumene Dimers

Acrylonitrile MMA

Acrylic Acid Alcohols/MEK

Oxo-Alcohols Butyl Rubber

*Authorized Contractor **Own technology with Evonik

Coastal Chemical Inc. in Cheyenne, Wy, USA,

Capacity: 100,000 t/y isobutene

4

Two commercial units applying the STAR process® tech- nology have been commissioned for the dehydrogen- ation of isobutane integrated with the production of MTBE:

• Coastal Chemical Inc., Cheyenne, Wy, USA was commissioned in 1992 and produces 100,000 tonnes per annum of isobutene.

• Polybutenos, Argentina, was designed for a capacity of 40,000 tonnes per annum of isobutene and was commissioned in 1994.

The successful operation of those plants demonstrated the high stability of the STAR catalyst®.

In the period from 2000 to 2004 Uhde significantly increased the performance of the STAR process® by adding an oxydehydrogenation step.

Uhde has a long and broad experience in design and commissioning of equipment used in STAR process® technology as well as plants for production of olefins and olefin derivatives.

In 2006 Uhde was awarded a lump sum turnkey con-tract to build a 350,000 tonne-per-annum PDH/PP com- plex by Egyptian Propylene & Poly-propylene Company (EPP) in Port Said, Egypt.

In 2009 and 2010 two other clients have awarded Uhde contracts for 450,000 tonnes per annum PDH plants.

3-D model of PDH/PP complex for Egyptian Propylene

and Polypropylene Company (EPP)

5

2.1 Steam reforming and olefin production plants supplied by Uhde

SINCOR C.A. in Jose, Venezuela,

Capacity: 2 x 97,770 Nm3/h of hydrogen

6

7

Uhde and steam reformingThe references on steam reforming attached hereto re-flect Uhde’s experience in connection with the reaction section and steam generation equipment applied in the STAR process®. Today the total count is as follows:

• Steam reformer: more than 65 units (basis for STAR process® reformer)

• Secondary reformer: more than 40 units (basis for STAR process® oxyreactor)

Uhde and olefinsUhde has also designed and successfully commis-sioned plants for a wide range of applications for production of olefins and olefin derivatives using the technologies described in Table 1. In combination with the STAR process® Uhde is in the position to offer complete process routes:

• Production of polypropylene (PP) or propylene oxide (PO) from propane.

• Production of MTBE or other high octane blend- stocks (e.g. alkylate or dimers) from butane.

Another advantage of the STAR process® is the fact that Uhde combines the functions of technology owner/licensor and overall turnkey contractor and is therefore able to provide process performance guaran-tees as well as total plant completion and mechanical guaranties within the framework of a single-point responsibility (turnkey) contract.

Product Process Licensor

Ethylene dichloride Vinnolit

Ethylene oxide Shell Chemicals

Ethylene glycol Shell Chemicals

Propylene oxide Evonik-Uhde

High density polyethylene LyondellBasell

Low density polyethylene LyondellBasell

Polypropylene LyondellBasell

Alkylate UOP, ConocoPhillips, Stratco

MTBE/ETBE Uhde

Dimers Axens, UOP

Olefins Uhde

Table 1:

Uhde’s portfolio for

the production of olefins

and olefin derivatives

7

3. Oxydehydrogenation – basic principles

Dehydrogenation is an endothermic equilibrium reaction. The conversion of paraffins increases with decreasing pressure and increasing temperature. In general pro-cess temperature will increase with decreasing carbon number to maintain conversion at a given pressure. As shown below for propane and butane, respectively, the major reaction is the conversion of paraffin to olefin.

Propane dehydrogenation (PDH):

C3H

8 C3H

6 + H

2

Butane dehydrogenation (BDH):

C4H

10 C4H

8 + H

2

Lower hydrocarbons (i.e. lower in carbon number than that of the feedstock) are also formed. Minor reactions that occur are cracking, which is primarily thermal and results in the formation of small amounts of coke.

Obviously conversion is limited by the thermodynamic equilibrium for a given pressure and temperature. As conversion approaches equilibrium, reaction velocity decreases and catalyst activity is not efficiently utilised. However, if oxygen is admitted to the system this will form H

2O with part of the hydrogen, which in turn will

shift the equilibrium of the dehydrogenation reaction to increased conversion. Figure 1 shows the influence of oxygen addition as it shifts the equilibrium towards in-creased conversion of propane to propylene. Formation of H

2O is exothermic and hence provides the heat of

reaction for further endothermic conversion of paraffin to olefin.

Major requirements to achieve this objective are as follows:

• The catalyst continues to maintain its activity for dehydrogenation and does not convert the hydrocarbons to carbon oxides and hydrogen (’Steam reforming’).

• The catalyst is stable in the presence of steam and oxygen.

• The STAR catalyst® fully satisfies those requirements.

Above mentioned advantages are utilised in the STAR process® which connects conventional de-hydrogenation (i.e. the STAR reformer) in series with an oxydehydro-genation step (i.e. oxyreactor).

In principle, the concept of oxydehydrogenation has already been commercially proven for the conversion of butene-1 to butadiene (’Oxo-D’ process developed by Petro-Tex Corp.). Seven units were installed (five of them in the USA) between the years 1965 to 1983, with plant capacities ranging from 65,000 to 350,000 tonnes per annum of butadiene. The total installed capacity was over a million tonnes per annum. Oxidant was air.

60

55

50

45

40

25

30

35

540

20

550 560 570 580 590 600

Temperature [°C]

Con

vers

ion

Prop

ane

[%]

without OxygenO2 / HC Ratio = 0.05O2 / HC Ratio = 0.1

Figure 1:

Thermodynamic equilibrium data

(Partial pressure 1 bar, molar oxygen

to propane ratios)

8

Process steam

Process condensate

Olefinproduct

Fuel gas

Hydrogen

Boiler feed water

Hydrocarbon feed

O2

Oxyreactor

STARreformer

Fuel gas

Air

HP steam

Heatrecovery

Feedpreheater

Raw gascompression

Gasseparation Fractionation

Hydrocarbon recycle

PSA

4. STAR process® technology

4.1 STAR catalyst®

The STAR catalyst® is based on a zinc and calcium alu-minate support that, impregnated with various metals, demonstrates excellent dehydrogenation properties with very high selectivities at near equilibrium conversion. Due to its basic nature it is also extremely stable in the presence of steam and oxygen at high temperatures. This commercially proven noble metal promoted catalyst in solid particulate form is utilised in the STAR process®.

4.2 Process pressureThe reaction takes place in the presence of steam, which reduces the partial pressure of the reactants. This is favourable, as the endothermic conversion of paraffin to olefin increases with decreasing partial pressures of hydrocarbons. Competing dehydrogenation technologies operate at reactor pressures slightly above atmospheric pressure or even under vacuum. In the STAR process®, however, reactor exit pressure is approximately 5 bar. This allows sufficient pressure drop to utilise the heat

available in the reactor effluent efficiently and also allows to design the raw gas compressor with a suction pres-sure of min. 3.0 bar thus saving investment and operat- ing costs.

4.3 Operation cycleDuring normal operation a minor amount of coke is deposited on the catalyst which requires frequent re-generation of the catalyst. Steam present in the system converts most of the deposited coke to carbon dioxide. This leaves very little coke to be burnt off during the oxidative regeneration, thus allowing longer operation cycles and making the regeneration quick and simple. Also no additional treatment for coke suppression or catalyst reactivation (e.g. sulfiding or chlorinating) is required. The cycle length is seven hours of normal operation followed by a regeneration period of one hour. Therefore only 14.7% additional reactor capacity is needed to account for regeneration requirements, which is the lowest of all commercial technologies.

Figure 2:

The overall block flow scheme

of the STAR process® for propane

oxydehydrogenation

9

Feed Propane Isobutane

Inlet temperature - STAR process® reformer (°C) 510 510

Exit temperature - STAR process® reformer (°C) 580 550

Exit temperature - Oxyreactor (°C) 580 575

Exit pressure - Oxyreactor (bar) 5.3 5.2

Steam-to-hydrocarbon ratio (St/HC) - Overall 4.2 4.2

4.5 Space-Time-YieldSTAR process® oxydehydrogenation operates at a high Liquid Hourly Space Velocity (LHSV) of 6 compared to 4 in conventional STAR process® dehydrogenation. LHSV represents the ratio of total hydrocarbon feed liquid volume flow at 15.6°C (60°F) per volume of catalyst.

In spite of increased space velocity oxydehydrogenation substantially increases the olefin yield in the reaction section. The result is a high space-time-yield, the impact of which (in comparison with conventional dehydro-genation) is summarised below:

• Reformer tubes are shorter in oxydehydrogenation due to increased space velocity.

• The required amount of catalyst for oxydehydro- genation is reduced by more than 30%.

• The externally heated reactor (i.e. top-fired STAR process® reformer) contains approx. 75% of the catalyst required. The oxyreactors are filled with the remainder of the catalyst. In other words, the size of the STAR process® reformer in oxydehydrogenation is considerably smaller. The amount of catalyst in the reformer tubes is reduced by more than 50% and number of tubes is reduced by approx. 30%.

• The higher yield reduces the dry gas flow to the raw gas compressor and to the down-stream units handling the product work up.

• As a consequence of these advantages, the invest- ment as well as the utility consumption are less.

4.4 OxidantOxidant is either air or oxygen enriched air. Use of 90% oxygen is the more economic option as it reduces the amount of nitrogen in the reactor effluent. This minim-ises gas volume flow to raw gas compression and gas separation which results in an appreciable reduction in operating costs.

4.6 STAR process® reaction sectionThe reaction section comprises an externally heated reactor (STAR process® reformer) connected in series with an adiabatic reactor (oxyreactor).

This configuration, as shown in figure 3, represents the scheme for all applications described in Section 7.

Table 2 summarises process parameters for the STAR process® reaction section.

Main features of the reaction section are:

• The tubes of the reformer and the oxyreactors are filled with the STAR catalyst®, where the conversion of paraffin takes place.

• Oxidant is > 90% oxygen.

• Feed to the oxyreactor is cooled by condensate and steam injection, which also adjusts the steam-to- hydrocarbon (St/HC) ratio required in the oxyreactor. Cooling of feed to the oxyreactors is adjusted to set the amount of oxygen that matches the requirement for conversion and that required to provide the heat of reaction for further dehydrogenation of paraffin.

4.7 Heat recoveryHeat from the process gas is efficiently recovered and utilised for:

• Production of steam

• Feed preheating

• Feed vaporisation and superheating

• Direct heating of fractionation column reboilers

Table 2:

Process

Parameters

10

4.8 Gas separation and fractionationA steady continuous feed to the fractionation at a con-stant composition is important to ensure the product quality. The gas separation is designed to meet these requirements.

The major features of this design are as follows:

• The cold box virtually removes all the hydrogen and nitrogen from the reactor product. About 70% of methane and minor amounts of ethane are also removed.

• Only approx. 10% of the propane/propylene mixture enters the cold box. Thus, in case of a coldbox failure still approx. 90% of production can be achieved which is a unique feature of the STAR process®.n

• Olefin losses are very low. Olefin recovery in the pro- duct is 99.5% of the olefin produced in the reactor.

• No gas phase is admitted to the fractionation. The entire fractionation feed is liquid, which is collected in an intermediate storage vessel, from where it is continuously fed to the distillation columns. Hence operation of this section is not influenced by the load variations (between the normal and regeneration mode) in the front end.

• Light ends are removed as tail gas in the fraction- ation. The removal of hydrogen, nitrogen and a substantial amount of methane in the cold box reduces the amount of these components in the light ends. This increases the dew point of the tail gas for a given pressure. As a result, the required temperature level of the refrigerant is also relatively higher, which in turn reduces compression costs.

Figure 3:

STAR process® reformer connected

in series with the oxyreactor

11

Feed/steam

Furnace arch

Reformer tube

Fire box

Catalyst grid

Furnace bottom

Bellow

Gas conducting tube

Shop weld

Field weld

Carbon steel

Outlet manifold

Inlet manifold

Burners

Reformer

tubes

Cold outlet

manifold system

Figure 4:

Reformer tube-to-manifold connection

Figure 5:

Furnace box of top-fi red

Uhde STAR process® reformer

1212

5.1 STAR process® reformerSTAR process® reformer is an industrially well known and commercially established top fi red „Steam Reformer”, which is a tubular fi xed bed type and hence will not suff er catalyst losses due to attrition. The arrangement of this equipment is shown in fi gure 5.

Main features of the reformer are:

• Top fi ring for optimum uniformity of tube skin temperature profi le.

• Small number of burners required.

• Internally insulated cold outlet manifold system (Figure 4) made from carbon steel and located externally under the reformer bottom.

• Internally insulated reformer tube to manifold connection operating at moderate temperatures.

• Each tube row connected to separate cold outlet manifold.

Uhde has installed more than 60 reformers of this type since 1966 in various parts of the world, to generate synthesis gas for the production of ammonia, methanol, oxo alcohols and hydrogen. The largest unit designed by Uhde has 960 tubes.

As shown in table 3 the operating conditions for the above mentioned applications are far more stringent than those required for the dehydrogenation.

Figure 6 shows, that the top fi red reformer ensures a uniform temperature profi le with a steady increase of temperature in the catalyst bed, thus effi ciently utilising the activity of the catalyst.

Uhde reformers demonstrate a very high availability of fi ve years of operation between maintenance shut downs.

Table 3:

Industrial applications of steam reformers

Figure 6:

Temperature profi le of the reformer tubes

Application Pressure [bar abs] Temperature [°C]

Ammonia 40 780 - 820

Methanol 20 - 25 850 - 880

Hydrogen 20 - 25 880

Oxogas 9 - 12 900

Olefins (STAR process®) 5 - 6 550 - 590

450 500 550 600 650 700 7500

20

40

60

80

100

Catalyst bedtemperature

Tube walltemperature

Temperature [°C]

Hea

ted

Leng

th [

%]

1313

5.2 STAR process® oxyreactorThe adiabatic oxyreactor is a refractory lined vessel, which means that no metallic surfaces are exposed to the reaction zone. The design of this equipment, as shown in figure 7, is virtually the same as the Uhde secondary reformer, which is used in ammonia plants. The only difference is the kind of distribution of the oxi-dant. Air or oxygen-enriched air diluted with steam is distributed so as to allow the oxygen to come into con-tact with the process medium at the top of the catalyst bed.

Compared to ammonia plants, the operating conditions in oxydehydrogenation are a lot milder (refer to table 4).

Uhde’s answer to a safe and reliable design is high-lighted by the following features:

• Reactor effluent from STAR process® reformer enters the STAR process® oxyreactor at the bottom and passes into one centrally arranged tube, which con- ducts the gas to the top. This eliminates trouble- some external hot piping to the head of the reactor.

• Process gas is discharged from the central tube into the dome for reversal of the flow direction.

• Air or oxygen is admitted to the system and uni- formly distributed directly over the catalyst surface via a proprietary oxygen distribution system. In other words, process gas and oxygen are rapidly mixed and directly contacted with the catalyst bed to achieve high selectivities for the conversion of hydrogen with oxygen.

Service Ammonia Olefins (STAR process®)

Operating pressure (bar abs.)

Operatingtemperature (°C)

38 max. 6

970 max. 600

Table 4:

Comparison of operating conditions of the secondary reformer for

production of synthesis gas for ammonia and of the STAR process®

oxyreactor for dehydrogenation

Figure 7:

STAR process® oxyreactor design

14

15

6. Comparison of dehydrogenation technologies

6.1 General remarksDehydrogenation is an endothermic equilibrium reac-tion. As more and more product is formed, the resi-dence time required for production of a certain amount of product will continuously increase due to the fact that the driving force decreases. This means, that the yield per time and catalyst volume (space-time-yield) will decrease as the dehydrogenation reaction pro-gresses.

The following chapters describe the technologies available on the market.

The two most expensive units within a dehydrogenation plant are the reaction section and the raw gas com-pression. Defining the reaction pressure will also define the required compression ratio for the raw gas com-pressor, which directly influences compressor operating and investment costs.

6.2 Adiabatic reactors connected in seriesThe endothermic reaction will cause a temperature drop across the catalyst bed. Reactor feed needs to be preheated so as to contain the heat of reaction. Across the catalyst bed, the temperature profile and conver-sion are counter current.

Hence conversion is limited by the reactor exit tem-perature which is lower than the inlet temperature.

This system, besides a charge heater, also requires preheating of partially reacted gases prior to admit-tance to the next reactor (Figure 9), which results in cracking of already formed olefin. Hence measures are needed to suppress coke formation in the intermediate heaters. Otherwise coke deposit on catalyst will in-crease thereby causing temporary deactivation of the catalyst. Furthermore the space time yield is low.

One of the measures to suppress coke formation is to recycle hydrogen. This is bound to decrease the driving force of the reaction as hydrogen is also a dehydro-genation product.

The reaction section of the STAR process® with oxydehydrogenation step off ers signifi cant advantages compared to competing technologies, which will be explained in the following.

4000 20 806040 100

500

600

700

Tem

pera

ture

[°C

]

Catalyst bed volume [%]

0

70

Con

vers

ion

[%]

Temperatureprofile

Equilibriumconversion

Actualconversion

Intermediate Heaters

Figure 9:

Temperature and conversion profi le

for adiabatic reactors

16

6.3 Parallel adiabatic reactorsSuch systems require multiple parallel beds, particularly for large capacities. Ensuring efficient distribution of feed is bound to limit the diameter of the reactor. Allowable pressure drop will limit the bed height as well. Conversion takes place in one bed which will also limit the space velocity.

Typically, feed preheated does not supply sufficient heat for high conversion. This means that during the regeneration phase heat has to be introduced into the system which is utilised during the following reaction phase. Catalyst is used as a heat source for endother-mic reaction. During reaction phase catalyst bed tem- perature decreases, which in turn leads to short cycle length of only 6 - 10 minutes. Hence several parallel beds at large capacities cannot be avoided. Space-time-yield is even lower compared to adiabatic systems connected in series.

For world scale plants a large number of reactors in parallel is required. Only few of them are used at the same time for de-hydrogenation.

6.4 STAR process® with oxydehydrogenation stepThis configuration of an externally heated tubular reactor (STAR process® reformer) followed by an air or oxygen operated adiabatic reactor (oxyreactor) combines the advantages of both reactor systems:

• STAR process® reformer, as known from the steam reforming process for the production of synthesis gas, monitors the temperature profile to efficiently utilise the activity of the catalyst.

• External heating in the reformer monitors a steady increase of temperature in the catalyst bed (see figure 11). This is in accordance to the thermo- dynamic requirements in terms of increasing con version.

• Admission of oxygen to the oxyreactor shifts the thermodynamic equilibrium and provides the heat of reaction for further dehydrogenation (Figure 11).

• The overall effect is a high space-time-yield at in- creased conversion and selectivity.

• Due to higher operating pressure lower compression costs.

Typical space time yield

(kg product/kg catalyst hour) 0.8 - 1.0

Typical compression ratio 6 - 10

Required number of reactor

systems for world-scale plants

for propylene production

(450,000 tonnes per annum) 2

(650,000 tonnes per annum) 3

4000 20 806040 100

500

600

700

Tem

pera

ture

[°C

]

Catalyst bed volume [%

Reformer Oxyreactor

]

0

70

Con

vers

ion

[%]

Addition ofoxygen

Temperatureprofile

Equilibriumconversion Actual

conversion

5000 20 40 60 80 100

550

600

650

Catalyst bed volume [%]

Tem

pera

ture

[°C

]

t0

t1

t2

t3

t4

Figure 10:

Temperatures in the catalyst bed

for diff erent times (t0-t4)

Figure 11:

Temperature and conversion profi le for an externally

heated tubular reactor followed by an adiabatic oxyreactor

(STAR process® with oxydehydrogenation step)

17

7. Application of the STAR process®

7.1 Oxydehydrogenation of propane to propylenePropylene is a base petrochemical used for the pro-duction of polypropylene (PP), oxo-alcohols, acrylon-itrile, acrylic acid (AA), propylene oxide (PO), cumene and others.

About 60% of the propylene produced today is used as feedstock for the production of PP.

With the STAR process® technology Uhde can supply complete process routes to propylene derivatives, e.g. PP or PO, based on on-purpose propylene production from propane within a single-point responsibility. Pro-cess economics for a production complex, e.g. of PP from propane by PDH (STAR process®) and subsequent polymerisation are very favourable.

Hydrogen produced by dehydrogenation can be pur-ified and used as feedstock for subsequent plants (e.g. for H

2O

2 production in connection with the Evonik-Uhde

HPPO process) minimising raw material costs.

Contaminants regarding the feed to a subsequent plant (CO, CO

2 and sulphur compounds) are efficiently re-

moved in the STAR process®. Thus, a Selective Hydro-genation Unit (SHU) or guard beds for removal of trace components are in most of the cases not required. Additionally, recycle streams from the PP plant can be purified with the existing equipment of the PDH plant. Integration of utilities and offsites units (steam, cooling water, refrigerant, oxygen/nitrogen, etc.) will further increase project economics.

The process configuration for a stand-alone propane oxydehydrogenation plant is outlined in figure 2, page 9.

7.2 Oxydehydrogenation of butanesDehydrogenation of isobutane to isobutene for the production of MTBE is a commercially well established process route. MTBE is phased out in the USA. How-ever, it is not clear, whether this will apply to other regions as well.

Other options for octane boosting are alkylate and dimers. Dehydrogenation of butanes to butenes can also be utilised for the production of alkylate or dimers, which are used as blending stock to enhance the quality of unleaded gasoline to premium grade.

Since 2008 the world’s first commercial scale plant for

the production of propylene oxide based on the innovative

HPPO process has been in successful operation.

18

7.2.1 Oxydehydrogenation for the production of alkylateBoth HF and H

2SO

4 alkylation are mature and efficient

technologies for the production of C7 and C

8 alkylate

from propene and butenes. C8 alkylate has higher octane

numbers than C7 alkylate.

The Research Octane Number (RON) of the alkylate produced will depend on the type of olefin as well as the process applied (refer to table 5). It is worthwhile to limit isobutene when the alkylation process is based on H

2SO

4, whereas preferable feed components for HF

alkylation are butene-2 and isobutene. Plant configur-ation will depend on the alkylation scheme selected. For alkylation based on H

2SO

4 the preferred plant feed

is mixed butanes.

The process steps are as follows:

• STAR process® oxydehydrogenation

• Butenex®

• Selective hydrogenation

• H2SO

4 alkylation

Butenex®, a technology licensed by Uhde, is an extract-ive distillation process. C

4 fraction from STAR is separ-

ated into butenes and butanes. Solvent is a mixture of N-formylmorpholine (NFM) and morpholine. NFM is a commercially well established solvent known from its application in Uhde’s Morphylane® process for the ex-tractive distillation of aromatics. To date two commercial Butenex® units have been successfully designed and commissioned by Uhde.

Table 5:

RON of alkylate depending on

alkylation technology and olefin

Figure 12:

Alkylate from

mixed butanes

Alkylate RON

Alkylate from HF alkylation H2SO

4 alkylation

Butene-1 91 98

Butene-2 97 98

Isobutene 95 91

N-butane recycle

Mixedbutanes

Hydrogen

Fuel gas

Isobutane

C8alkylate

19

Depending on the content of isobutane in the mixed butanes feed, the STAR process® unit could be con-ceived to include a deisobutaniser column so as to separate isobutane from n-butane in the mixed butanes feed. N-butane is recycled from the Butenex® unit to the STAR process® unit. Butadiene in the unsaturated C

4 stream (extract) from Butenex® is selectively hydro-

genated to butene-1. The selectively hydrogenated stream is the olefin feed to alkylation.

It seems to be advantageous to process isobutane (instead of mixed butanes), if the selected scheme is HF alkylation.

The reasons are:

• RON of C8 alkylate derived from isobutene is high (95).

• For a given conversion the selectivity of isobutene (from isobutane) is higher than that of n-butenes (from n-butane). In other words plant feed is less by 6%.

• Selective hydrogenation of butadiene will not be required.

• STAR process® unit can be designed to provide an isobutane/isobutene mixture in the desired stochio- metric ratio for the alkylation. In other words recycle of unconverted paraffin to the STAR process® unit will not be required. This in turn will eliminate the requirement for a Butenex® unit.

ST ® HFalkylation

Isobutane

Fuel gas

C8alkylate

ocessAR pr Figure 13:

Alkylate from isobutane

20

7.2.2 Oxydehydrogenation for the production of dimersAmount and quality (RON) of gasoline produced will depend on the process option whether isobutene is selectively dimerised or whether all butenes present in the feed are dimerised. Furthermore when processing mixed butenes, the concentration of isobutene in mixed butenes will also influence the quality of gasoline.

Dimerisation of mixed butenes will result in a liquid product of which max. 80% is gasoline and 20% is jet fuel. Liquid product yield will be around 95 - 98% of butenes present in feed. Octane rating will increase as the concentration of isobutene in feed increases. Iso-butene concentration of about 50% (in total butenes) will be required to obtain unleaded premium gasoline (RON 95) quality.

Selective dimerisation of isobutene (in the mixed butenes feed) will result in a liquid product which will primarily consist of high octane gasoline (RON 99) and a minor amount (4% of liquid product) of jet fuel.

However, liquid product yield is low. Whereas isobutene is virtually completely dimerised the conversion of n-butenes will be only in the order of 50%. Isobutene will be completely converted to high octane gasoline (RON 99).

The process configuration (Figure 14) consists of the following process steps:

• STAR process® oxydehydrogenation

• Selective hydrogenation of butadiene

• Dimerisation unit (incl. product hydrogenation)

Selective hydrogenation of butadiene is only required if plant feed consists of mixed butanes.

Hydrogen required for selective hydrogenation of feed to dimerisation and for product hydrogenation will be supplied from the STAR process®. The utility system of the dimerisation and hydrogenation units is integrated with the STAR process® unit to enhance process eco-nomy. Unconverted butanes are recycled from the dimerisation unit to the STAR process® unit.

STAR process®Selective

hydrogenation

Butanes recycle

Fresh feed(mixed butanes orisobutane)

Hydrogen

Fuel gas

Gasoline

DimerisationJet fuel

Figure 14:

Dimers from butanes

21

Inside view of the furnace box

of an Uhde steam reformer

22

Uhde is dedicated to providing its customers with a wide range of services and to supportingthem in their efforts to succeed in their line of business.

With our worldwide network of subsidiaries, associated companies and experienced local representatives, as well as first-class backing from our head office, Uhde has the ideal qualifications to achieve this goal.

We at Uhde place particular importance on interacting with our customers at an early stage to combine their ambition and expertise with our experience.

Whenever we can, we give potential customers the opportunity to visit operating plants and to personally evaluate such matters as process operability, main-tenance and on-stream time. We aim to build our future business on the confidence our customers place in us.

Uhde provides the entire spectrum of services asso- ciated with an EPC contractor, from the initial feasibility study, through financing concepts and project manage-ment right up to the commissioning of units and grass-roots plants.

Our impressive portfolio of services includes:

• Feasibility studies/technology selection

• Project management

• Arrangement of financing schemes

• Financial guidance based on an intimate knowledge of local laws, regulations and tax procedures

• Environmental studies

• Licensing incl. basic/detail engineering

• Utilities/offsites/infrastructure

• Procurement/inspection/transportation services

• Civil works and erection

• Commissioning

• Training of operating personnel using operator training simulator

• Plant operation support /plant maintenance

• Remote Performance Management (Teleservice)

The policy of the Uhde group and its subsidiaries is to ensure utmost quality in the implementation of our pro-jects. Our head office and subsidiaries worldwide work to the same quality standard, certified according to:DIN/ISO 9001/EN29001.

We remain in contact with our customers even after project completion. Partnering is our byword.

By organising and supporting technical symposia, we promote active communication between customers, licensors, partners, operators and our specialists. This enables our customers to benefit from the development of new technologies and the exchange of experience as well as troubleshooting information.

We like to cultivate our business relationships and learn more about the future goals of our customers. Our after-sales services include regular consultancy visits which keep the owner informed about the latest deve-lopments or revamping options.

Uhde stands for tailor-made concepts and international competence. For more information contact one of the Uhde offices near you or visit our website:

www.uhde.eu

Further information on this subject can be foundin the following brochures:

• Ammonia

• Organic chemicals and polymers

• Propylene oxide

8. Services for our customers

23

Uhde

Friedrich-Uhde-Strasse 15

44141 Dortmund, Germany

Tel.: +49 231 5 47-0 · Fax: +49 231 5 47-30 32 · www.uhde.eu

GT

617e

/200

0 4/

2011

U/T

K p

rintm

edia

/ Pr

inte

d in

Ger

man

y