Catalytic reforming

(1)

CATALYTIC REFORMING

Process,Catalysts and Reactors

CATALYTIC REFORMING

Process,Catalysts and Reactors

Mohan Lal

Axens India Private Limited

(Private Limited Company formed under the Companies Act, 1956)

on

Petroleum Federation of India

Indian Oil Corporation Ltd. (Haldia Refinery),

&

(2)

World context:

High octane gasoline requirement

(3)

World context:

Low sulfur content,

Low benzene content,

Limited aromatics content,

Limited olefins content,

No lead

(4)

European Gasoline specifications trends

2000

2005

Soon

*

Ultimate

Severity**

Sulfur, ppm max

150

50

10

5 Aromatics, vol% max

42

35

30

25 Olefins, vol% max

18

14

10 Benzene, vol% max

1

1 Oxygen, wt% max

-

2.7

2.7 Vapor pressure, kPa

max

90

60

50 C5+ ethers, vol%***

15

15 Lead, ppb max

5

5 RON/MON, min

95/85

* Assumed ** Projected final limits ≥ 2015 ***banned in several states of USA

(5)

Gasoline Pool specifications

Bharat

III

Sulfur, ppm max

150 Aromatics, vol% max

42 Olefins, vol% max

21 Benzene, vol% max

1 Oxygen, wt% max

-Vapor pressure, kPa max

60 RON/MON, min

91/81

(6)

New gasoline specifications require:

Maintaining a

high octane level

Meeting

reduced sulfur

specifications

Meeting

reduced Aromatics and Benzene

specifications

(7)

Constraints from straight run gasoline: Initial fractionation

of crude oils gives gasoline cuts with a low octane number

¾

Light gasoline (C5-C6) :

RON between 60 and 70

¾

Heavy gasoline (C7-C10) :

RON between 30 and 50

Refiners have to considerably improve the

quality of gasoline cuts to meet RON/MON

specifications

(8)

RON/MON is increased by chemical transformation

•

Light gasoline : Isomerization process

n-paraffins Æ i-paraffins

Ex: n-Hexane (RON= 24.8) Æ 2,2-DM Butane (RON=

91.8)

•

Heavy gasoline: Catalytic Reforming process

n-paraffins, naphtens Æ aromatics

Ex: Cyclohexane (RON = 83) Æ Benzene (RON = 108)

(9)

Outline

• Fundamentals of Catalytic Reforming

• Objective

• Reactions – desirable and undesirable

• Process

• Semi Regenerative Reforming

• Dualforming

• Continuous Catalytic Regenerative Reforming

• Process Variables

• Reforming Catalyst

• Types

• Poisons

• Some Recent Advances in Reforming

• Update on CCR Technology / Catalyst

• Update on SR Technology/ Catalyst / Debottle-necking

(10)

Fundamentals

(11)

Purpose of reformer

•

The purpose of Reforming process is to produce :The purpose of Reforming process is to produce :

-- high octane number reformate, which is a main component for mhigh octane number reformate, which is a main component for motor otor fuel, aviation gasoline blending or aromatic rich feedstock.

fuel, aviation gasoline blending or aromatic rich feedstock.

-- hydrogen rich gashydrogen rich gas

-- Due to the nature of the reactions, reforming process produces aDue to the nature of the reactions, reforming process produces also:lso:

LPG

(12)

Purpose of reformer

•

• Reformer feed pretreatment

Reformer feed

pretreatment

Due to the presence of contaminants in all cases and to

the specific characteristics of cracked naphtha,

Naphtha

Naphtha Pretreating

Pretreating unit(s

unit(s)

) is(are

is(are

) always necessary.

• Reformer feed

is either:

- Low quality straight run naphtha

- or cracked naphtha, generally mixed with

straight run naphtha.

(13)

(14)

Chemical reactions

•

• Two types of reactions

Two types of reactions

involved in the

Octanizing

process:

–

– Desirable reactionsDesirable reactions, which , which lead to a higher octane

lead to a higher octane

number and to high purity

hydrogen production. They

are the reactions to

promote

–

– Adverse reactionsAdverse reactions, which , which lead to a decrease of

lead to a decrease of

octane number and a

decrease in hydrogen

purity. They are the

reactions to minimize

RON

RON MONMON • • CyclohexaneCyclohexane == 8383 77.277.2 • • MethylcyclohexaneMethylcyclohexane == 74.874.8 71.171.1 • • 1.3 1.3 dimethylcyclohexanedimethylcyclohexane == 71.771.7 71.71. • • BenzeneBenzene == 114.8114.8 > 100> 100 • • TolueneToluene == 120120 103.5103.5 • • mm--XyleneXylene == 117.5117.5 115.115.

RON: Research Octane Number MON: Motor Octane Number

(15)

•

• Naphthenes

Naphthenes

dehydrogenation

–

– Naphthenic compounds dehydrogenated into aromatics with productiNaphthenic compounds dehydrogenated into aromatics with production on of 3 moles of H2 per mole of

of 3 moles of H2 per mole of naphthenenaphthene –

– Promoted by the metallic functionPromoted by the metallic function –

– Highly endothermicHighly endothermic –

– Thermodynamically Thermodynamically favored by high temperature, low pressure favored by high temperature, low pressure and high and high number of carbons

number of carbons –

– Kinetically favored by high temperature, high number of carbon; Kinetically favored by high temperature, high number of carbon; not not affected by the hydrogen partial pressure

affected by the hydrogen partial pressure –

– At the selected operating conditions, reaction is very fast and At the selected operating conditions, reaction is very fast and almost almost total total CH CH CH CH HC HC CH 2 CH 2 CH H C 2 H C 2 + 3H 2 CH 2

(16)

•

Paraffin's Paraffin's dehydrocyclizationdehydrocyclization

–

– Multiple step reactionMultiple step reaction –

– Promoted by both acidic Promoted by both acidic and metallic functions and metallic functions –

– Kinetically favored by Kinetically favored by high high temperature

temperature, and , and low low pressure

pressure

–

– Dehydrogenation step Dehydrogenation step

becomes easier as paraffin becomes easier as paraffin molecular weight increases, molecular weight increases, but is competed

but is competed by hydro cracking by hydro cracking –

– At the selected operating At the selected operating conditions, much

conditions, much lower lower rate than that of

rate than that of

dehydrogenation dehydrogenation Methylcyclohexane CH 2 CH2 CH CH 2 CH3 CH 3 CH CH 2 CH2 CH 2 CH2 CH CH 3 H C 2 C H 7 16 + H 2 C H 7 14 CH 2 CH2 CH2 CH 2 CH2 CH3 CH 3 CH CH 3 CH 3 CH 2 CH2 CH 2 CH H C 2 CH 2 CH₂ CH 2 CH2 CH _CH 3 CH₃ CH CH CH CH HC C + 3H 2

(17)

Desirable reactions with hydrogen production

•

• Linear paraffin's

Linear paraffin's

isomerization

–

– Promoted by the acidic functionPromoted by the acidic function –

– Slightly exothermicSlightly exothermic –

– FastFast –

– Thermodynamically dependant on temperature; pressure has no Thermodynamically dependant on temperature; pressure has no effect

effect

–

– Kinetically favored by Kinetically favored by high temperature; high temperature; not affected by the not affected by the hydrogen partial pressure

hydrogen partial pressure

C H

7 16 C H

7 16

Carbon atom

(18)

•

• Naphthenes

Naphthenes

isomerization

–

– Desirable reaction because of the subsequent dehydrogenation of Desirable reaction because of the subsequent dehydrogenation of the the alkylcyclohexane

alkylcyclohexane into an aromaticinto an aromatic –

– Difficulty of ring rearrangement and high risk of ring opening (Difficulty of ring rearrangement and high risk of ring opening (paraffin paraffin formation)

formation) –

– At the selected operating conditions, theoretically At the selected operating conditions, theoretically low rate but low rate but subsequent dehydrogenation shifts the reaction towards the desir

subsequent dehydrogenation shifts the reaction towards the desired ed direction

direction

–

– Slightly endothermicSlightly endothermic –

– Easier reaction for higher carbon numberEasier reaction for higher carbon number

RON

RON MONMON

• • EthylcyclopentaneEthylcyclopentane == 67.267.2 61.261.2 • • MethylcyclohexaneMethylcyclohexane == 74.874.8 71.171.1 • • TolueneToluene == 120120 103.5103.5

(19)

Adverse reactions

•

• Hydrocraking

Hydrocraking

–

– Hydrocracking Hydrocracking affects either affects either paraffins

paraffins or olefinsor olefins –

– Promoted by both acidic Promoted by both acidic and metallic functions and metallic functions –

– Favored by Favored by high temperature high temperature and high pressure

and high pressure

–

– Exothermic Exothermic (

(risk of runaway risk of runaway reactions)reactions) –

– At the selected operating At the selected operating conditions, hydro cracking conditions, hydro cracking reaction could be complete, reaction could be complete, but is limited by kinetics

but is limited by kinetics

+ H 2 C H 7 14 C H 7 16 (m) + H 2 C H 7 14 (a) + C H 4 8 C H 3 8 + H 2 C H 4 10 C H 4 8 (m)

(20)

•

• Consequences of cracking:

Consequences of cracking:

–

Decrease of

paraffins

and increase of aromatics

proportion (i.e. increase in octane) in the reformate

and a

loss of reformate yield

–

Decrease in hydrogen production

(cracking reactions

consume hydrogen)

–

Increase of light ends

production and low molecular

weight

paraffins

(21)

+ H 2 C H 7 16 CH 4 C H 6 14 + H 2 C H 7 16 C H 2 6 C H 5 12 or + +

•

• Hydrogenolysis

Hydrogenolysis

–

Promoted by metallic function

–

Favored by

high temperature and high pressure

–

Exothermic (risk of runaway reactions)

Adverse reactions

(22)

•

• Hydrodealkylation

Hydrodealkylation

–

– Breakage of the branched radical of an aromatic ringBreakage of the branched radical of an aromatic ring –

– Promoted by metallic functionPromoted by metallic function –

– Favored by Favored by high temperature and high pressurehigh temperature and high pressure –

– Consumes hydrogen and produces methaneConsumes hydrogen and produces methane –

– But at the selected operating conditions, and with the selected But at the selected operating conditions, and with the selected catalyst, catalyst, this reaction is not significant

this reaction is not significant

+ H 2 Xylene Toluene + CH 4 + H 2 Toluene Benzene + CH 4

Adverse reactions

(23)

•

• Alkylation

Alkylation

–

Addition of an olefin molecule on an aromatic ring

–

Promoted by metallic function

–

leads to heavier molecules which may

increase the

end point

of the product

–

High tendency to

form coke

; must be avoided

Benzene Propylene Isopropylbenzene

HC CH 3 + CH = CH – CH 3 2 CH 3

Adverse reactions

(24)

•

• Transalkylation

Transalkylation

(alkyl

disproportionation

)

–

– Dismutation Dismutation of 2 toluene rings to produce benzene and of 2 toluene rings to produce benzene and xylenexylene –

– Promoted by metallic functionPromoted by metallic function –

– Favored by Favored by very severe conditions of temperature and pressurevery severe conditions of temperature and pressure –

– At the selected operating conditions, and with the selected At the selected operating conditions, and with the selected catalyst, this reaction is negligible

catalyst, this reaction is negligible

+ Xylene Benzene + Toluene Toluene

Adverse reactions

(25)

•

• Coking

Coking

–

Results from a complex group of reactions. Detailed

mechanism not fully known yet

–

Linked to heavy unsaturated

products (

polynuclear

aromatics)

and heavy olefins traces or

diolefins

present in the feed or in

CCR reactions

–

Coke deposit

reduces active contact area

and reduces

catalyst activity

–

Favored by low pressure

In

Octanizing

operating conditions, necessity of a

continuous regeneration to maintain a low level of

coke

(26)

–

– All these reactions occur in series and parallel to each other pAll these reactions occur in series and parallel to each other producing a roducing a complicated reaction scheme

complicated reaction scheme. .IIn an effort to simplify the scheme n an effort to simplify the scheme according to the reaction rates the main reactions take place in

according to the reaction rates the main reactions take place in the the following order:

following order:

•

• 1st reactor 1st reactor DehydrogenationDehydrogenation

Isomerization

•

• 2nd and 3rd reactors 2nd and 3rd reactors DehydrogenationDehydrogenation

Isomerization Isomerization Cracking Cracking Dehydrocyclization Dehydrocyclization •

• 4th reactor 4th reactor CrackingCracking

Dehydrocyclization

(27)

Catalyst Distribution

• Highly

endothermic transformation

• Reaction rates vary widely

The overall amount of catalyst

needed for the transformation is distributed –

not equally – among several adiabatic reactors

in series with intermediary heaters providing

the required heat energy input

(28)

Temperatures and Compositions

inside Reactors

T

₀

T

₀

- 25

T

₀

- 50

R

₁

R

₂

R

₃

Aromatics

Paraffins

Naphthenes

P

₀

= 60

N

₀

= 30

A

₀

= 10

H1

R

1 H2

R

2 H3

R

3

Composition, Vol%

Reactor Temperature, °C

(29)

–

– The catalyst distribution is:The catalyst distribution is:

•

R1 R1 = = 10%10%

•

R2 R2 = = 15%15%

•

R3 R3 = = 25%25%

•

R4 R4 = = 50%50% REACTIONS

REACTIONS HEAT OF HEAT OF

REACTION REACTION (1) KCAL/MOLE (1) KCAL/MOLE RELATIVE RATE RELATIVE RATE (2) APPROX. (2) APPROX. Naphthenes

Naphthenes dehydrogenationdehydrogenation - -5050 3030

Paraffin

Paraffin dehydrocyclizationdehydrocyclization - -6060 1 (base)1 (base) Isomerization

Isomerization: : ParaffinsParaffins + 2+ 2

3 3 Naphthenes Naphthenes + 4+ 4 Cracking Cracking + 10+ 10 0.50.5

Chemical reactions

(30)

Reforming Processes

(31)

Fixed bed reformer

Feed Separator Stabilized 1 2 3 Fuel Gas LPG A B Interheater 1 Interheater 2

• The most frequent type of unit

• Current licensors

• Axens, UOP

• In the old days (Chevron, Amoco, Exxon,

(32)

Feed Separator Recycle Compressor Booster Compressor Hydrogen-Rich Gas Unstabilized Reformate Recontacting Drum

1

2

3 Conventional Unit

(33)

Dualforming

Feed Recycle Compressor Hydrogen Rich Gas Unstabilized Reformate 1 2 3 R e g e n C 2 C C R R X Booster Compressor Recontacting Drum Packinox 12b Texicap™+ RG682

• Last Reactor Catalyst Continuously Regenerated

(34)

Continuous Catalytic Regenerative

Reforming

Continuous Catalytic Regenerative

Reforming

(35)

Continuous Catalytic Regenerative

Reforming

Continuous Catalytic Regenerative

Reforming

Elutriator Upper Hoppers Reduction Chamber H₂ Lower Hopper Lift Pot Regenerator Lock Hopper Upper Surge Drum Reactors R1 R2 R3 R4 N₂ FC

Coke

H₂ H₂ N₂ FC LC FC LC FC LC LC FC

(36)

Objectives of Regeneration Section

Recover initial catalyst activity

• Coke removal

2 Burning zones

• Metal redistribution &

chloride adjustment

Oxychlorination

• Catalyst drying

Calcination

(37)

RegenC

Prim ary Burn Finishing Burn C alcination O xychlor-ination C om bustion G as from D ry Loop Additional Air C hloriding A gent + water O xychlorination C alcination G as Spent C atalyst T o D ry Burn Loop T o Effluent T reatm ent

B urning with

dry gas

control:

% O

₂

, tem perature

C atalyst’s specific

area is m aintained

O xychlorination control:

% O

₂

, tem perature

and m oisture

O ptim um P t dispersion

(38)

RegenC Catalyst Regenerator

Com bustion Gas Inlet Air Inlet Com bustion Gas O utlet Oxychlorination Outlet Calcination Gas Inlet

Prim ary Burning

Finishing Burning Oxychlorination Calcination Chloriding Agent Inlet «Coked» Catalyst Regenerated Catalyst

(39)

Processes Variables

(40)

• Pressure

• Temperature

• Space velocity

• Hydrogen partial pressure (H2/HC)

• Quality of the feed

(41)

•

• Each of them

Each of them

can be fixed by the operator

-

within

the operating range of the equipment

-

-independently from the others

independently from the others

•

• For one set

For one set

of independent variables, for same feed

characteristics, there is only

one performance of the

unit

i.e. one set of values for:

–

Product yields

–

Product quality (Octane)

–

Catalyst stability (coke make)

(42)

(43)

Pressure

•

• Pressure is the basic variable because of its

Pressure is the basic variable because of its

inherent

effect on reaction rates

•

• Effect of pressure on reactions

Effect of pressure on reactions

–

Low pressures enhance

hydrogen producing

reactions:

dehydrogenation,

dehydrocyclisation

, coking

–

Cracking

rate is reduced

The lower the pressure, the higher the yields of

reformate and hydrogen for a given octane number.

But high coking rate (compensated by continuous

regeneration)

(44)

Pressure

•

• Average catalyst pressure used, close to

Average catalyst pressure used, close to

last

reactor inlet pressure

•

• During transient conditions (start up,

During transient conditions (start up,

shutdown, upsets) it is recommended to

increase the pressure to lower coke

formation

•

• Limits of operators action

Limits of operators action

–

Pressure rise limited by

equipments design pressure

–

Pressure lowering limited by

recycle compressor

design power and intake volume

(45)

(46)

Temperature

•

• Most important and

Most important and

most used

operating parameter with

space velocity

•

• Catalyst activity

Catalyst activity

is directly related to reactor temperature. By

simply raising or lowering reactor inlet temperatures,

operators

can raise or lower product quality and yields

•

• It is commonly accepted to consider the weight average inlet

It is commonly accepted to consider the weight average inlet

temperature (WAIT)

Where

Where Ti1, Ti2, Ti1, Ti2, …… are inlet temperature of reactorsare inlet temperature of reactors (wt of catalyst R1)

(wt of catalyst R1)… …are weight of catalyst in reactorsare weight of catalyst in reactors

(

)

(

)

(

)

catalyst of wt Total 4 Ti x 4 R Catalyst wt + .... 2 Ti x 2 R Catalyst wt + 1 Ti x 1 R catalyst of wt = WAIT

(47)

•

• An

An

increase of temperature

(i.e. WAIT) has the following

effects:

–

– Increases octaneIncreases octane –

– Decreases the yield (of C5+ fraction)Decreases the yield (of C5+ fraction) –

– Decreases the H2 purity.Decreases the H2 purity. –

– Increases the coke depositIncreases the coke deposit

•

• A

A

slight increase

of temperature (WAIT) through the

life of

the catalyst makes up

for this activity loss

•

• Larger and temporary changes in temperature are required:

Larger and temporary changes in temperature are required:

–

– To change octane To change octane - - at constant feed quality and quantityat constant feed quality and quantity –

– To change feed quantity To change feed quantity and still maintain octaneand still maintain octane –

– To change feed quality To change feed quality and still maintain octaneand still maintain octane

(48)

(49)

Space velocity

•

• Weight hourly space velocity:

Weight hourly space velocity:

•

• Liquid hourly space velocity:

Liquid hourly space velocity:

•

• Linked to residence time of feed in the reactor and

Linked to residence time of feed in the reactor and

affects the kinetics of the Reforming reactions

reactors in catalyst of Weight hour) (per feed of Weight WHSV = reactors in catalyst of Volume hour) (per C 15 at feed of Volume LHSV = ° Space velocity residence time higher severity Octane increased

Lower reformate yield Higher coke deposit

(50)

•

• Operators must bear in mind that

Operators must bear in mind that

each time

liquid feed rate is changed, a temperature

correction must be applied

if octane is to be

maintained.

•

• Important recommendation

Important recommendation

–

Always decrease reactor inlet temperature first and

decrease feed

flowrate

afterwards

–

Always increase feed

flowrate

first and increase

reactor inlet temperature afterwards

(51)

(52)

Hydrogen to hydrocarbon ratio

•

• H2/HC ratio

H2/HC ratio

:

=

Where

Where R R is the recycle flow in Kg/h (or lb/h)is the recycle flow in Kg/h (or lb/h)

M

M is the recycle gas molecular weightis the recycle gas molecular weight

F

F is the feed rate in Kg/h (or lb/h)is the feed rate in Kg/h (or lb/h)

m

m is the feed molecular weightis the feed molecular weight

Y

Y vol. fraction of H2 in the recycle gasvol. fraction of H2 in the recycle gas

•

• The recycle gas MW is obtained by chromatographic

The recycle gas MW is obtained by chromatographic

analysis, as well as the H2 vol. fraction (Y)

•

• The feed MW is obtained by chromatographic analysis

The feed MW is obtained by chromatographic analysis

or by correlation from its distillation range and specific

gravity

) (mole/hour rate flow Naphtha recycle in ) (mole/hour hydrogen Pure = HC H₂ H₂ HC = R M x Y F m

(53)

•

• Operators can change the H2/HC ratio by lowering

Operators can change the H2/HC ratio by lowering

or increasing the

recycle compressor flow

•

• For a given unit, the amount of recycle is

For a given unit, the amount of recycle is

limited by

the recycle compressor

characteristics (power,

suction flow)

•

• The H2/HC ratio has

The H2/HC ratio has

no obvious impact

on the

product quality or yield

•

• But a high H2/HC ratio

But a high H2/HC ratio

reduces the coke build up

•

• It is strictly recommended to operate with a H2/HC

It is strictly recommended to operate with a H2/HC

(54)

(55)

Feed quality Chemical composition

•

• Characterization of the

Characterization of the

feedstocks

by:

•

• With a higher 0.85 N + A

With a higher 0.85 N + A

–

– The same Octane content will be obtained at a lower severity The same Octane content will be obtained at a lower severity (temperature) and the

(temperature) and the product yield will be higherproduct yield will be higher –

– Or for the same severity (temperature), Or for the same severity (temperature), the Octane content will be the Octane content will be higher

higher

–

– Higher Higher naphtenic naphtenic content. Tcontent. The endothermic reaction heat is he endothermic reaction heat is increased and the feed flow rate will be

increased and the feed flow rate will be limited by the heater design limited by the heater design duty

duty

•

• With lower

With lower

0.85 N + A

–

– Higher paraffin content. Higher paraffin content. The hydrogen purity of the recycle gas The hydrogen purity of the recycle gas decreases and operation will be

decreases and operation will be limited by the recycle compressor limited by the recycle compressor capacity

capacity

•

• Impurities

Impurities

–

– Temporary or permanent reduction of catalyst activity by poisons

(56)

•

• The feed distillation range is generally as follows:

The feed distillation range is generally as follows:

•

• IBP (Initial Boiling Point)

IBP (Initial Boiling Point)

70

70 -

-

100

100 °

°

C

•

• EP (End Boiling Point)

EP (End Boiling Point)

150

150 -

-

180

180 °

°

C

•

• Light fractions:

Light fractions:

Cyclization

of C6 more difficult than that of C7

-

C8

The lighter the feed, the

higher the required

severity

for a given Octane

•

• Heavy fractions:

Heavy fractions:

high naphthenic and aromatics content

Lower severity

to obtain good yields

But polycyclic compounds which favor

coke deposit

Feed quality Distillation range

(57)

Operating Parameters Summary

•

• Hereafter the theoretical effect on the unit performance of

Hereafter the theoretical effect on the unit performance of

each independent process variable taken separately

:

Increased

Increased RONCRONC Reformate yieldReformate yield Coke depositCoke deposit Pressure Pressure Temperature Temperature Space velocity Space velocity H2/HC ratio H2/HC ratio Naphtha Naphtha Quality Quality A + 0.85 N A + 0.85 N

End boiling point

Initial boiling point

(58)

Catalysts

(59)

The main characteristics of a catalyst other than its physical and mechanical properties are :

• The activity

o catalyst ability to increase the rate of desired reactions

o Is measured in terms of temperature

• The selectivity

o Catalyst ability to favor desirable reactions

o Practically measured by the C5+ Reformate and Hydrogen

yields

• The stability

o Change of catalyst performance ( activity, selectivity )with

time

o Caused chiefly by coke deposit and by traces of metals in feed

o Measured by the amount of feed treated per unit weight of

catalyst. C5+ wt reformate yield is also an indirect measure of

Catalyst

(60)

Catalyst

• Catalyst

• Chlorinated gamma alumina with nanao

particle of Pt

• The chlorinated gamma alumina has too

strong acid sites

• The Pt promotes hydrogenolysis of

Pt

(61)

Catalyst

• In the 90’s Procatalyse (now Axens)

launched promoted Pt/Re catalyst

• RG 582

• Then RG 682 in 2000

• The promoter provides two benefits

• Reduced hydrogenolysis by a modification

of the metallic cluster

• Lower the number of the strongest acid

(62)

Catalyst

• The stability of Pt has been improved by

addition of promoters (Re, Ir)

• The hydrogenolysis of Pt has been

reduced by addition of promoters

• The acidity of the chlorinated gamma

alumina has been tuned by addition of

promoters

(63)

Catalyst

•

To improve the catalyst stability the Pt sintering has to be hindered

•

Addition of promoters

• Rhenium or Iridium

•

Explanation

• Re and Ir is alloyed with Pt Î the “boiling point” of Pt is increased

Î Sintering reduced

Pt accessible

Pt Total

0.75

0.50

0.25

Pt + Re Pt

1.00

•

Operating conditions

•

T = 650°C

•

H2 = 2 000 L/kg/h

(64)

• Reforming catalysts are bimetallic catalyst consisting of

platinum plus promoters on an alumina support, Rhenium and Tin being essentially one of the promoter besides the others.

• The main features of these catalysts are :

o High purity alumina support - High mechanical resistance

o Platinum associated with Rhenium - high stability &

selectivity

o Platinum associated with Tin – high selectivity

o High Regenerability

• The combination of these qualities give the following

advantages:

o High Reformate yield

o High hydrogen yield

o High on - stream factor

o Low catalyst inventory

Catalyst

(65)

Catalyst

¾Platinum (Pt) plus other promoter(s) impregnated on to

gamma alumina containing around 1% wt chloride to provide acidity.

¾Since 1967, bimetallic catalysts have been widely used.

¾The second metal comes from the group

Rhenium (Re)

Tin (Sn)

Iridium (Ir)

(66)

WHICH METAL COMBINATION TO CHOOSE

¾Depends on what you want from the catalyst - "THE

OBJECTIVES"

¾Stability / cycle life

¾Selectivity towards

hydrogen (H₂)

liquid reformate (C₅+ reformate)

(67)

Stability

•

• Normal causes for catalyst ageing/deactivation

Normal causes for catalyst ageing/deactivation

–

metal sintering

–

temperature

–

metallic phase

–

presence of chloride

–

deposition of coke on metal and acid sites

Coking effect can be split

–

1. Degree of poisoning of deposited coke

–

(68)

•

Desired yields are:Desired yields are: –

– hydrogenhydrogen

–

– CC₅₅+ reformate+ reformate

–

– low benzenelow benzene

•

Benzene Benzene –

– yield can be minimised by preyield can be minimised by pre--fractionating the fractionating the

precursors (MCP, CH, nC6P) which are present in the

fraction boiling between 70 to 85

fraction boiling between 70 to 85°°CC

–

– benzene is also produced by the hydrodealkylation of benzene is also produced by the hydrodealkylation of alkyl benzenes

alkyl benzenes

•

Loss of desired yields is caused by crackingLoss of desired yields is caused by cracking –

– hydrocracking involving the metal plus acid siteshydrocracking involving the metal plus acid sites

–

– hydrogenolysis involving the metal in the presence of hydrogenolysis involving the metal in the presence of hydrogen

hydrogen

(69)

•

Tin and GermaniumTin and Germanium –

– increases selectivity towards desired productsincreases selectivity towards desired products –

– no stability benefitno stability benefit

•

Rhenium and IridiumRhenium and Iridium –

– increase stabilityincrease stability –

– no major effect on yield selectivityno major effect on yield selectivity

•

Other effects such as regenerability and tolerance to feedstock Other effects such as regenerability and tolerance to feedstock impurities has led to the PtRe combination being preferred catal

impurities has led to the PtRe combination being preferred catalyst yst

(70)

•

RG 582 introduced 1994RG 582 introduced 1994

•

Third metal moderates hydrogenolysis activity to Third metal moderates hydrogenolysis activity to between that of balanced PtRe and PtSn

between that of balanced PtRe and PtSn

•

Desired yields increasedDesired yields increased –

– Hydrogen by 0.1 to 0.15wt%Hydrogen by 0.1 to 0.15wt% –

– C C₅₅+ by around 1 wt%+ by around 1 wt%

•

Stability studies in pilot plant show 93 Stability studies in pilot plant show 93 - - 100% of 100% of balanced bimetallic catalyst, but in commercial units

balanced bimetallic catalyst, but in commercial units

>100% is commonly seen.

(71)

Pilot test results

Low pressure pilot test

Previous Generation - Bi-promoted catalyst - High Pt content

Selectivity & stability improvement

Axens New series

- Multi Promoted Catalyst

- Reduced Pt content - Tri-promoted catalyst - Reduced Pt content Selectivity C5+ yield Stability (time)

(72)

• The catalyst affects reaction rates through its two different functions/type of sites:

o Metallic, and

o Acidic

Different types of reactions are promoted by these sites as:

o Dehydrogenation Metallic

o Dehydrocyclisation Metallic + Acidic

o Isomerisation Metallic + Acidic

o Hydrogenolysis Metallic

o Hydrocracking Metallic + Acidic

Catalysis Mechanism

(73)

Catalysts Poisons

(74)

Temporary poisons

• Which can be removed and the proper Activity and Selectivity

of catalyst is restored.

• The most common temporary poisons ( inhibitors ) are:

o Sulphur o Organic nitrogen o Water o Oxygenated organics o Halogens

Catalyst Contaminants

(75)

Permanent poisons

–

Which induce a loss of activity which can not be restored.

Catalyst Contaminants (Contd…)

Main permanent poisons are

• Arsenic • Lead • Copper • Iron • Nickel • Chromium • Mercury • Sodium • Potassium

(76)

Reactor Types

(77)

Typical Axial Fixed-Bed

Reactors

Typical Axial Fixed-Bed

Reactors

(78)

Typical Radial Fixed-Bed

Reactor

Typical Radial Fixed-Bed

Reactor

The design of the upper part of

the reactor was made to take

into account

- density change (settling)

- possible by-passing of catalyst

- space for mechanical assembly

Bolted metal shroud and cover

Catalyst

(79)

Typical Radial CCR Reactor

Catalyst

Feed

(80)

A New Concept of Radial Reactor

Internals

A Flexible Flow-guide that

molds to the shape of the top of the bed

Texicap

TM

(81)

Typical Radial Fixed-Bed

Reactors

Typical Radial Fixed-Bed

Reactors

The design of the upper part of

the reactor was made to take

into account

- density change (settling)

- possible by-passing of catalyst

- space for mechanical assembly

BEFORE

Bolted metal shroud and cover

Catalyst

(82)

Modifying Radial Fixed-Bed

Reactors with Texicap

Modifying Radial Fixed-Bed

Reactors with Texicap

Gained

with

Texicap

BEFORE

AFTER

Catalyst

Dead Space

(83)

Catalyst Sampler N₂ ATM FL Refilling Sampling Box Draining Handling Head Receiving Pot

(84)