Introduction To Zeolite Molecular Sieves - UOP

 

An Introduction to

Zeolite Molecular Sieves

ry Purify Separate Dry Purify Separate Dry Purify Sep

 

What are zeolite molecular sieves? undreds of systems for the

H

Unlike other adsorbents, zeolit zeolite e

 Why they are used

drying and purification of 

molecular sieves have precisely 

Use of zeolite molecular sieves to dry,

liquids and gases rely on the

uniform pore sizes and molecular 

purify and separate liquids and gases

high adsorption efficiency of zeolite

dimensions. dimensio ns. This translat translates es into a

prevents unwanted side reactions,

molecularr sieves. molecula sieves. These unique unique

sieve-like selectivity where molecules

helps meet product specifications,

adsorbents are a result of synthetically  produced crystalline metal alumino-

of varying size and polarity may be readily adsorbed, slowly adsorbed or 

and avoids costly complications from equipment corrosion and freeze-up.

silicates that have been activated for 

completely excluded. This selectivity selectivity,,

adsorption by removing their water of 

combined with a high capacity over

hydration. hydr ation. Since little little or no change change

a wide range of operating conditions,

in structure occurs during this

gives each zeolite molecular sieve a

dehydration, highly porous adsorbents

high level of adsorption efficacy.

are formed that have a strong affinity  for water and specific molecules.

Used successfully in hundreds of commercial systems for drying and purifying liquids and gases, zeolite molecular   sieves are the most universally applicable adsorbents in the  process industries.

Other beneficial performance characteristics include: • Dehy Dehydrati dration on to water content content less than 0.1ppm • High capacity capacity for for water above above 200°F (93°C)

 

Table of Contents Purification tion and dehydrat dehydration ion • Purifica in one operation • Dehy Dehydrati dration on without adsorbing adsorbing  valuable product or altering the composition • High produ product ct recovery  recovery  • Numer Numerous ous purificati purification on and dehydration cycles are possible due to the reversible adsorption process

Specific, unif Specific, uniform orm pore size is the key to adsorbentt efficiency  adsorben and selectivity… Based on size and charge distribution in a molecule, zeolite molecular sieves can adsorb individual molecules readily,slowly readily, slowly or not at all.

Page Pa ge 2 What What are are zeolite zeolite molecular sieves? Page Pa ge 4 Zeolite Zeoli te resea researc rchh and synthetic production Pag agee 6 Crysta Crystall structur structuree and molecular sievee types siev ty pes

• High cyclic cyclic capacity with with sufficient sufficient thermal or pressure swing purging

Page Pa ge 8 Adsorp dsorption tion base basedd on molecular size, polarity and degree of unsa unsatura turation tion Page Pa ge 12 Zeolite Zeolite mole molecula cularr sieves and adsorption efficiency  Pag agee 13 Zeolit Zeolitee molecu molecular lar siev sieves es and co-adsorption Pag agee 15 15 Re Rege gener nerati ation on cyc cycle less Pag agee 17 17 Appl plic icat atio ions ns Pag agee 18 Put Put UOP’ UOP’s experi experienc encee and technology to work for you TM

MOLSIVTM Adsorbents

 

Salt Steam

Ion Exchange Tank Ion-Substituted Zeolite Sodium Silicate Sodium Aluminate

Wash Water

Clay Binder

Steam Makeup Tank

Zeolite Crystals

Crystal Slurry

Filter

Crystallization Tank

Weigh Hopper

Naturally occurring crystalline

molecular dimensions were

had for commercial commercial use, they began to

zeolites, a subset of molecular sieves,

synthesized synth esized and and patented. patented. The

delve into adsorption technology and

 were first noted two centuries c enturies ago.

synthetic zeolites’ sieve-like selectivity 

design processes that could rely on

Their ability to release water when

offered the consistent performance

these new materials.

heated and readsorb upon cooling

necessary necessa ry for for commercia commerciall use. use. By 

 was known at that time, but their 

1953, more than 30 pure zeolite

capacity to selectively adsorb

species had had been prepared. prepared. Their 

molecules other than water was not

crystal structures and adsorption

recorded record ed until until the 1920s. 1920s. In the early  early 

properties had been characterized,

1930s, X-ray diffraction studies

and researchers had learned how to

revealed the zeolites as crystalline

regenerate them for repeated use in

materials with precisely arrayed

commercial applications. Extensive QC testing insures superior 

cavities and pores within each crystal. Since zeolites found in nature have a high degree of chemical and physical  variability,, these products were not  variability  viable for commercial separation processes. proces ses. In the the early early 1950s, a division of Union Carbide Corporation, that is now part of UOP, UOP,  was searching for an adsorbent to separate atmospheric gases and to be used in other industrial applications.  As a result of this research, structures of silicon and aluminum oxides with uniform pore sizes and precise

 product quality and consistency 

Zeolite research and synthetic production Zeolite research spawns commercial adsorption  technology  technol ogy nce engineers recognized

O

the incredible potential zeolite molecular sieves

4

 As a consequence of their research, zeolite molecular sieves were substituted into existing dryer and simple adsorber systems with amazing results. resul ts. The use of zeolite zeolite molecular  molecular  sieves improved the drying and purifying of various gas and liquid process streams with minimal changes in technology technology.. For more more advanced advanced uses, howev however er,, additio additional nal proces processs engineering knowledge was required. To address this problem, problem, Union

 

Wash Water

Filter

Manufacturing process for the production of activated  zeolite molecular sieves.

Activated Molecular Sieve Product Mixer

Particle Forming

Dryer

Kiln Screen

Carbide formed a large, large, process engineering group to develop new and

Forming final product

comprehensiv compr ehensive e adsorption technology technology and design guidelines. guidelines. Starti Starting ng with

Once separated and washed, the filter

fundamental adsorbent data, the researchers studied adsorption equilibria,

cake is conveyed conveyed to hoppers. To form

adsorption kinetics, deactivation phenomena, cyclic life and scale-up factors.

commercial 1/16-in and 1/8-in (about

 After much research, the group discovered how to economically economic ally manufacture

1.6-mm and 3.2-mm) pellets (extrudates) or 

the zeolites in commercially useful forms without adversely affecting their 

beads (spheres), crystals from the filter are

adsorption properties.

mixed with specially formulated clay 

In November of 1954, Union Carbide announced the availability of the first

binders. The crystals crystals are then fed through through

limited commercial quantities. The pure zeolites were then then used within the

forming equipment to produce pellets

chemical, manufacturing and petroleum refining industries to solve difficult gas

or beads. The various various product forms forms are

purification and dehydration dehydration problems. Today oday,, by altering existing crystalline

then dried,screene dried, screened d and fired in a rotary 

structures for improved functionality, functionality, UOP continues to manufacture many 

kiln to drive out the water and activate the

types of zeolites for a myriad of industries.

zeolite molecular molecular sieves. The adsorbents adsorbents are

How zeolite products are manufactured

then immediately packaged to prevent any  moisture pick up.

Sodium silicate, alumina trihydrate and sodium hydroxide hydroxide are batch-weighed into mix tanks and stirred stirred until homogenous. The mixture forms forms a gel that is pumped into a crystallization tank where it is monitored under closely 

Many tests are used to determine product quality from crystallization to final firing. Examples include x-ray diffraction, McBain-

controlled conditions.

Bakr adsorption,loss adsorption,loss on ignition, crush

Filter, wash and exchange

strength, streng th,densit densityy and particle particle size. Quali Quality  ty 

 After crystallization is complete, a rotary filter separates and washes the

control techniques including Statistical

zeolite zeolit e crystal slurry. slurry. For cationic cationic exchange exchange to take place (calcium, (calcium, potas potassium sium

Process Control and adherence to ISO 9000

or other cations substituted for sodium in the crystal), the filter cake is

standards ensure that crystallization and

transferred to a heated tank where it will be mixed with a solution of the appropriate metal salt. The exchanged exchanged forms will then be washed and

other manufacturing processes achieve exact specifications.

filtered in the same manner as the original crystal slurry. 5

 

Structural model of a zeolite.

Crystal structure and molecular sieve types

T

he basic formula for zeolite molecular sieves is M 2/nO • Al2O3 • xSiO2 • yH2O

 where  whe re M is a cat cation ion of of n valen valence. ce. The fun fundam dament ental al buil building ding blo block ck of of the the molecular sieve crystal structure is a tetrahedra with four oxygen anions

surrounding surrou nding a smaller silicon or aluminum aluminum cation. Sodium ions or other cations cations make up the positive charge deficit in the alumina tetrahedra,and each of the four oxygen anions is shared, in turn, with another silica or alumina tetrahedron tetrahedron to extend the the crystal lattice in three dimensions. dimensions. In all molecular sieve types, types,the the sodium ion can be exchanged exchanged to form other functional products. The crystal structure of zeolite molecular sieves is honeycombed with relatively large cavities. cavitie s. Each cavity cavity is connected through through apertures apertures or pores. pores. The water of hydrat hydration ion is contained contain ed within these cavities. cavities. Befo Before re product is used,the water of hydration is removed by heating.

Skeletal Tetrahedron

Packed Spheres

Solid Tetrahedron

Illustrations of the rigid, three-dimensional  framework of SiO4 and Al04 tetrahedra

1

2

The crystallization of molecular sieve Type A from a hydrous gel as seen through the electron microscope. microscope. Photo 1 shows shows development of crystallization after two hours at 100º C. Photo 2 shows completely crystallized A.

6

 

Commercially useful zeolite species In general, the elasticity and kinetic

• The Type A molecular sieve sieve

Type 3A

energy of incoming molecules allows

has a framework composed of

Type 3A crystals are produced when

for easy passage of molecules of up

truncated octahedra joined in

some of the sodium ions are replaced

to 0.5 angstroms larger than the

a cubic array array. The result result is

by potassium potassium ions. Since potass potassium ium

free diamete diameterr of the the aperture. aperture. In

a central truncated

ions are larger than than sodium ions, the

addition, the size and position of the

cube-octahedron with an

pore size is effectively reduced to

exchangeable cations may affect the

internal cavity 11 angstroms

about 3.2 angstroms.

free aperture size in any type of 

in diameter (alpha cage).

molecular molecu lar sieve. The zeolite zeolite molecular  molecular 

• Each centr central al cavity cavity,, or alpha alpha

sieves that are most commonly used

cage, is entered through six

include Ty include Types pes A and X. Unit cell formulas and structural details for 

circular apertures formed by a nearly regular ring of eight

each type are outlined o utlined below.

oxygen atoms with a free

Type A Na12 [(AlO2 )12 (SiO2 )12] • 27H2O Note: Not e: Na+ (sodium) can be replaced

diameter of 4.2 angstroms. • The cavities cavities are arrange arranged d in a continuous three-dimensional pattern forming a system of

by other cations.

Type 4A

Type 4A sodium-bearing crystals have a free aperture size of 3.5 angstroms in diameter. diameter. At typical typical operating temperatures, molecules with an effective diameter of up to four  angstroms may be passed through this aperture. °

4.2 A

unduloid-like channels with a Type A contains roughly spherical

maximum diameter of 11

cavities that are approximately 11

angstroms and a minimum

°

2.6 A °

11.4 A

angstroms in diameter and about 925 of 4.2 angstroms. • The truncated truncated octahed octahedra ra encl enclose ose

cubic angstrom angstromss in volume. volume. They  account for nearly half of the total

°

6.6 A

a second set of smaller cavities

crystalline volume that is available

6.6 angstroms in internal

for adsorption.

diameter diamet er (beta (beta cages). cages). The smaller cavities are connected to 2

1

°

4A

the larger cavities via a distorted

 Above: Two adjacent unit cells of

ring of six oxygen atoms of

Type 4A — light circles represent

2.2 angstroms free diameter d iameter..

(1) Truncated Truncated octahedron. (2) Face Face of cubic  cubic  array of truncated octahedra.

7

oxygen ions and dark circles represent sodium cations.

 

Type 5A

High silica molecular sieves

 When some of the sodium sodi um ions in

Like Types A and X, high silica zeolites selectively adsorb molecules based

Type 4A are replaced with calcium

on their size. Howev However er,, they differ from Ty Types pes A and X in that they have

ions,Type ions,T ype 5A is is produced. produced. It features features the largest pore opening of the A 

a significantly higher proportion of SiO 2 to AlO2 in their molecular structure. struct ure. With the reduced reduced amount of AlO AlO2 and the corresponding

types, with a free aperture aperture size of

reduction in cation density, density, the high silica zeolites are hydrophobic and

4.2 angstroms.

organophilic adsorbents. The high silica silica zeolites are also stable at low

Type X Na86 [(AlO2 )86 (SiO2 )106] • 264H2O Note: Not e: Na+ (sodium) can be replaced

pH ranges and high temperatures up to 1,292ºF (700ºC).

by other cations.  Although Type X is based on the same building blocks as Type Type A, the beta cages are linked tetrahedrally  instead of in a cubic arrangement. The Type X crystal has a larger larger,,

Adsorption based on molecular size, polarity and degree of unsaturation

N

umerous zeolite species that differ in chemical composition,crystal composition, crystal structure and adsorption adsorption properties are known. By selecting selecting the appropriate adsorbent — one that allows entry of those molecules small

elliptical-shaped internal cavity of 13 angstroms in diameter with a pore diameter of approximately 8 angstroms for the sodium form.

enough to pass into the pore system — and by choosing the proper operating conditions, zeolite molecular sieves can be adapted to suit specific applications.  While the external surface area of the molecular sieve crystal cr ystal is available for  adsorption of molecules of all sizes, the internal area is available only to those

Zeolite molecular sieve characteristics and applications  Type†

Nominal Pore Diameter  Angstroms

Common Form

Bulk Density lb/cu-ft (gm/cc)

Heat of Adsorption (max) btu/lb H2O (kcal/kg H2O)

Equilibrium H2O Capacity* wt-%

Molecules Adsorbed**

3A 

3

Powder 1/16-inch Pellets

35 (0.56) 40(0.64)

1800 (1,000)

26 21

Molecules with an effective diameter 5 >5 an angstroms (iso (i so co comp mpou ound ndss and and al alll 4-c 4-car arbo bonn rin rings gs))

• Sep Sepaara rate tess nor norma mall pa para raff ffiins fr from om br braanc nche hedd-ccha hain in and cy cyccli licc hydrocarbons th through a selective ad adsorption pr process • Pre Press ssur uree swi swing ng pu puri rifi fica cati tion on of hy hydr drog ogen en

 value typically corresponds to a complete filling of the internal void  volume with the adsorbate. When adsorbed molecules are desorbed

Molecu Mol ecules lesangstroms withh an wit an effec ef(C fectiv tive diamete F e)diam N eterr >8 493

• (Used Ussed commer genera gas dryin gas dr g, and air plan air pliquid lantt feed feed pur purifi ificat cation ion imucom ltanemercia ouscially relly mofor val gen of Heral Ol and COying, ), 2 2 hydrocarbon and natural gas sweetening (H2S and mercaptans removal)

 via heat or by b y displacement with another material, material, the crystal’s chemical state remains unchanged.

 

2. The relative relative size size of molecules molecules

Water Vapor Adsorption at 25  C °

(Equilibrium Data)

25

20

and molecular sieve pores

Molecular Sieve Type A

15

  y    t     i   c    %      a    t    p    a   w     C

Silica Gel

20

forces between molecular

requires less than six hours for the

sieves and adsorbate

adsorption step, additional beds can

30

be added to permit continuous

Fundamental adsorption systems

Alumina

5

cooled. When the the process process design design

4. Adsorp Adsorption tion tempera temperature ture Activated

10

bed is being heated, purg purged ed and

3. The strength strength of adsorpt adsorptive ive

10

0

to purify the fluid while the other

40

50

Relative Humidity Percent

 Adsorption on zeolite molecular sieves  produces a Langmuir-type isotherm.

processing of the feed.

Depending on the type of operation,

Single-bed adsorption

zeolite molecular sieves may be used

Single-bed adsorption can be used

in one of three basic types of 

 when interrupted product flow can

adsorption systems:

be tolerated. tolerated. When the adsorpt adsorption ion

• Multi Multiple-be ple-bed d adsorp adsorption tion

capacity of the bed is reached, it can

• Sin Singlegle-bed bed adsorpti adsorption on

be regenerated for further use either 

• Sta Static tic adsorp adsorption tion

in place or at another location.

 With zeolite molecular sieve

 Alternatively,, it can be discarded  Alternatively di scarded

powders,, no hysteresis powders hysteresis occurs

Multiple-bed adsorption

during desorpti desorption. on. Adsorp Adsorption tion and

Multiple bed adsorption is ideal for 

desorption are completely reversible

most commercial, commercial, large large-scale -scale fluid

Static adsorption

 with their respective isothermal

purification purific ation operat operations. ions. Conve Conventiona ntionall

 When manufactured into various

curves coinciding coincidi ng completely. completely.

fixed-bed, heat-regenerated adsorption

physical forms, zeolite molecular 

However,, with zeolite molecular sieve However

systems syste ms are commonly commonly used. A typical

sieves can be used as static desiccants

pellets or beads, further adsorption

dual-bed installation places one bed

in closed gas or liquid systems.

may occur at pressures near the

on-stream

if economically feasible.

saturation satur ation vapor pressur pressure. e. This can occur as a result of condensation in the pellet or bead voids external to Out

the zeolit zeolite e crystals. crystals. In addition, addition, hysteresis may take place during desorption of the adsorbate in the macro-pore region of the binder.

A brief review of adsorption principles and systems

Heater Out Liquid Stream

   n    o     i    t    p    r    o   s     d     A

   n    o     i    t    p    r    o   s   e     D

Cooling Gas In

In

In

Purge Gas

The rate at which molecules are

Out

adsorbed into formed zeolite molecular sieves depends on the

Cooler Condenser

following four variables: 1. The rate rate at which which molecules molecules

General flow chart for liquid drying.

being adsorbed can diffuse to activated crystals within the pellet or bead

Multiple bed adsorption for H  20 and C0 2 removal from natural gas before methane liquification.

10

 

11

 

Zeolite molecular sieves and adsorption efficiency

Z

eolite molecular sieves are

The isobars plotted below illustrate zeolite molecular sieve performance

employed in numerous

over a spectrum of operating temperatures. The solid lines assume the the

installations and operations

use of completely regenerated adsorbents. The capacity is lowered lowered by any 

due to their exceptional adsorption

residual water left on the adsorbent, a factor of particular importance in

efficiency efficien cy.. The following following details

high temperatur temperature e drying operations. operations. As an example, example, the dotted dotted line isobars

typical conditions where they

show the effect of two percent residual water at the start of adsorption

are effectively used.

on silica gel, gel, zeolit zeolite e molecular molecular sieves and and activated activated alumina. alumina. In some

 When very dry streams are required In industry, industry, drying by adsorption is favored due to its ability to produce a much drier liquid or gas than other commerc commercial ial methods. methods. When extremely dry streams are required,

applications, this residual water can completely consume the the adsorption capacityy of silica and alumina capacit alumina type adsorbents adsorbents.. For this reason, reason, it is best to use silica and alumina type adsorbents for the bulk separation of water. They are very effective for this purpose and offer the additional benefit of extending the life of zeolite molecular sieves. After bulk separation processes have taken place, zeolite molecular sieves can then then be used to achieve very low dew point levels.

zeolite molecular sieves are selected

Water Vapor Adsorption Isobars at 10mm Hg Partial Pressure

because they can reduce water  concentrations to less than 0.1 ppm.

(Equilibrium Data) 25

In addition, they are effective over a

Silica Gel

 wide range of operating conditions. co nditions.

 When operating at high temperatures Zeolite molecular sieves are also a good choice when drying streams at high temper temperature atures. s. In fact, fact, they are the only adsorbents that remain effective under very hot conditions. For example, at 200ºF (93ºC) and

20  Zeolite

    d   e     b 15    r    o   s     d   %       A   t    r   w    t   e 10    a     W

Molecular Sieves

 Activated  Alumina

5

above, zeolite molecular sieves have more than 13 weight-percent capacity  while other adsorbents have none.

0

0 (-18)

100 (38)

200 (93)

300 (149)

400 (204)

500 (260)

Temperature F ( C) °

°

Drying power of silica gel, zeolite molecular sieves and activated alumina under various operating temperatures.

12

 

 When purifying acidic streams s treams

T

he chemical stability of 

hydrocarbo hydr ocarbons, ns, alcoho alcohols, ls, esters, ethers,

of 5 to 12, 12, and a few few are stable stable in

zeolite molecular sieves

amines, amides, ketones and and others.

solutions having a pH as low as 3.

allows them to dry, dry, purify

and separate numerous types of  materials including inorganic gases, hyd hydrocarb rocarbons, ons, halog halogenated enated

Zeolite molecular sieves are alkaline in nature with a pH range in water  slurry of 9 to 11. Most types are stable in solutions within a pH range

They are stable in most organic streams, strea ms, howev however er in vapor phase phase processes, gases that will hydrolize to form strong acids will readily react  with the adsorbents.

Zeolite molecular sieves and co-adsorption

I

n some drying applications, components other than water may may be adsorbed. In many chemical process streams,this altering of stream composition, or co-adsorption,can co-adso rption,can cause serious problems. problems. When product composition composition is

critical, zeolite molecular sieves can be used to solve these co-adsorption difficulties.

Co-adsorption and pore size Co-adsorption can be avoided through

adsorbed. adsorb ed. To further enhance enhance this

proper selection of zeolite molecular 

selectivity for water, water, the temperature

sieve type. type. The zeolite molecular molecular sieve

of the adsorbent bed can be raised.

should have a critical pore diameter small

 Although the rate of adsorption will wil l

enough to prevent all stream components

be somewhat reduced if the water

except water from being admitted to the

has to displace another material

active inner surfaces of the adsorption

before it can be adsorbed, zeolite

cavities. In this this way way, co-adsorp co-adsorption tion of 

molecular sieves still offer better 

molecules other than water (including polar and unsaturated components), components),is is

performance when compared to other adsorbents.

eliminated.. By eliminating eliminated eliminating co-adsorp co-adsorptions tions

Due to the ability of zeolite molecular

the molecular sieve will provide

 sieves  siev es to produc produce e a drier drier liquid liquid or gas, gas,

maximum capacity for water and reduce outlet water concentrations

industry operations typically favor drying by adsorption over other commercial methods.

to less than 10 ppm.

Co-adsorption and affinity for water Zeolite molecular sieves feature an

Zeolite molecular sieves’strong attraction for water prevents co-adsorption problems in chemical process streams.

extremely high adsorptive attraction for water water. This affinity affinity is so strong that water will normally displace any  other material that is already  13

 

Carbon Dioxide Capacity at 25  C °

Molecular Sieve Type A (Equilibrium Data) One-step drying and purifying

20

In addition to water,impurities water, impurities in a process stream can be removed via proper operating conditions and appropriate zeolite

15   y    t     i   c      a    % 10    p   t   w    a     C 5

molecular sieve sieve selection. Since zeolite molecular sieves sieves adsorb

15

 water more strongly strongly than other material, the adsorbed water 

10

concentrates at the inlet end of the bed. Here, it displaces other 5 0 0

impurities that have have been previously previously adsorbed. These desorbed 2

4

6

8

10

impurities are then then re-adsorbed farther farther down the column. column. The desorbed impurities will begin to appear in the eff luent stream

0

0

100 200 300 400 500 600 700 Carbon Dioxide Pressure, mm Hg

Hydrogen Hyd rogen Sulfide Capacity at 25 2 5  C °

Molecular Sieve Type A (Equilibrium Data)

continue until little adsorbate, adsorbate, other than water, water, is left on the bed. However,, it is possible to design and operate a zeolite molecular However sieve adsorption system so that impurities are retained on the adsorbent rather than re-entering the purified stream. To accomplish this, sufficient bed must be provided to contain

20

the impurities impurities in addition addition to the water. water. See the figure figure below for an example of a co-adsorption system.

15   y    t     i   c      a    % 10    p   t   w    a     C 5

8 6

2

0

Pad Gas

Sweet LPG Product

4

0

0

as displacement continues. continues. This displacement can be allowed to

Heater 0

0.5

1.0

1.5

2.0

3.0

2.5

Adsorption

50 100 150 200 250 300 350 Hydrogen Sulfide Pressure, mm Hg

Ammonia Capacity at 25  C Sulfur Dioxide Capacity at 25  C °

°

    )    p   e    t     S    n   n    o    i     i Adsorption    t    o    t    p    a (Desulfurization    r    i    z    o    r   s Step)   u     d    f     l     A  e   u   s     D     (

Regeneration   e    n     i     L    g    n     i     l    o    o

    C

Molecular Sieve Type A (Equilibrium Data)

Sulfur Dioxide

    )    n   p   e    o   t     i    t Regeneration     S    a    r (Heating   e    g    n     i    n    t   e Step)    a    g   e   e     R     H     (

Fuel

Separator Cooler

40 30

Regeneration Gas In

Sour LPG Feed

Liquids

Typical co-adsorption system. Since zeolite molecular molecular sieves have the ability to adsorb hydrogen sulfide, mercaptans and water, the propane

  y    t     i   c      a    % 20    p   t   w    a     C 10

feed is simultaneously purified (sweetened) and dried.

Ammonia These three graphs depict the equilibrium capacity of zeolite molecular sieves for various various gas impurities. Through co-adsorption, co-adsorption, zeolite molecular molecular sieves

0

will remove these materials in addition to water.

0

100 200 300 400 500 600 700 Pressure, mm Hg

14

 

Regeneration cycles  yclic regeneration,

surface. reactivation vation surface. Once the reacti

Purge gas stripping

or desorption,

temperature is reached, the bed is

This method uses non-adsorbing

can be classified into

flushed with a dry purge gas or 

purge purg e gas. The purge purge gas desorbs the

four types.Used types. Used separately or in combination, the major adsorption-

reduced in pressu reduced pressure. re. It is then returned to adsorption conditions.

bed by reducing the partial pressure

desorption cycles are:

 As a result, high loadings of water

higher the operating temperature and

and impurities on the adsorbent

the lower the operating pressure, the

can be obtain obtained, ed, foll following owing

more efficient efficient the stripping stripping.. The use

a cooling step.

of a condensable purge gas offers

C

• The Thermal rmal sw swing ing • Pre Pressu ssure re swin swing g • Pur Purge ge gas gas stripping stripping • Dis Displa placeme cement nt

Pressure swing

of the adsorbed adsorbed compone component. nt. The

the following advantages: • Reduc Reduced ed power power requirem requirements ents

Pressure swing swing cycles, operating at

Thermal swing Thermal swing cycles reactivate the sieve by elevating the temperature.

nearly isothermal conditions, use

gained by using a liquid pump

either a lower pressure or a vacuum

instead of a blower 

to desorb the the bed. Advan Advantages tages of this this

Typically,, the operating temperature Typically

• An effluent strea stream m that that may

technique include fast cycling with

is increased to 400 - 600ºF (204 –

be condensed to separate the

reduced adsorber dimensions and

316ºC). 316ºC ). The bed is heated heated either by 

desorbed material by simple

adsorbent inventory, inventory, direct production

direct heat transfer via hot fluid in

distillation

of a high purity product and the

contact with the bed or by use of indirect heat transfer through a

ability to use gas compression as

Displacement cycles

the main source of energy.

Displacement cycles use an adsorbable purge to displace the

Residual Loading After Regeneration Minimum Obtainable Dew Point

previously previo usly adsorbed adsorbed material. material. The stronger the adsorption of the purge

(Dynamic Data) 120 (+49) +80 (+27)

    )     C+40             °     (     F

(+4)

 ,   0 (-18)    t    n-40 (-40)     i             °

media, the more completely the bed is desorbe desorbed. d. In this this case, case, less lesser  er 

4.0 WT–% 3.2 WT–% 2.3 WT–% 1.7 WT–% 1.0 WT–% 0 WT–%

amounts of purge purge can be used, but it is consequently more difficult to remove the adsorbed purge.

   o     P -80 (-62)   w   e     D-120 (-84)

-160 (-107)

This graph is used to find the minimum obtainable dew point as a function of 

-200 (-129)

0 100 200 300 400 500 600 700 (-18) (38) (93) (149) (204) (260) (316) (371) Bed Temperature, F ( C) °

°

residual loading and effluent gas temperature temperature during adsorption. Also shown is residual loading after regeneration as a function of regeneration temperature and purge gas dew point.

15

 

 Air dryers with a desiccant-type in-line filtration system supplies clean, dry air to truck air brake systems aiding in the prevention of air line freezeups.

 Zeolite molecular sieves keep

 Zeolite molecular molecular sieves are

dual pane windows free of 

used to purify industrial gases

moisture and vapors.

and for the bulk separation of  oxygen from air.

16

 

The chart below provides a brief review of how and where zeolite molecular sieves are used in industry today.  Application  Air dryers

Oxygenn concentr Oxyge concentrators ators for respir respiratory atory patien patients ts  Air brakes

Insula Ins ulated ted gla glass ss (du (dualal-pan panee wind windows ows))

Poly Po lyme merr fo form rmuula lati tion onss

Rad adio ioac acti tivve cle cleaanu nupp Refrigeratio Refrig erationn and air-con air-condition ditioning ing (A/C) (A/C) systems systems

Deodorization

Role of zeolite molecular molecular sieves • Dehydration of plastic pellets before they are molded • Dehydration for instrument air • Dehydration of room air with molecular sieve impregnated dessicant wheels • Adsorption Adsorption of nitrog nitrogen en from from compress compressed ed air air using using a press pressure ure or or vacuum vacuum swing swing system system to to obtain oxygen purity up to 95% • Dehydration of compressed air on brake systems of heavy- and medium-duty trucks, buses and trains • Pressure swing dryers are used to reduce the dew point of air in the brake reservoir below ambient temperature to prevent freeze-up and corrosion • Remo Removal val of ini initial tial tra trappe ppedd mois moistur turee insi inside de the dua dual-p l-pane ane win window dow and the moi moistu sture re tha thatt will will permeate during the life of the unit to prevent fogging • Removal of vapors from organic sealing materials, paint and cleaning solvents introduced during window manufacture • De Dehhyd ydrrat atio ionn of mo mois istu turree-se sennsi siti tivve fo form rmul ulat atio ions ns — ad adde dedd to po poly ly coa oati ting ngss, epo epoxxie iess and urethanes to control the curing process and coatings, adhesives, sealants, elastomers, metal-rich paints and vinyl foams to eliminate unwanted water reactions • Remo Removval of of rad radio ioaacti tivve nu nucle leooti tide dess by by io ion ex excha hang ngee — ces esiu ium m an and str stroont ntiu ium m ar are exc exchhan angged preferentially into the zeolite molecular sieves to greatly reduce the volume of liquid waste • Dehydratio Dehydrationn of automotive automotive A/C, A/C, transport transport refrigera refrigeration, tion, home refrig refrigerato erators, rs, freezers freezers,, residential residential  A/C, heat pumps and commercial refrigerants to prevent freeze-up and corrosion • Dehydration to protect system materials from adverse adverse chemical reactions reactions • Re Rem moval of of od odor or or ta taste fr from pe personal-care pr products an and pl plastics wi with hi high si silica (hydrophobic) zeolite molecular sieves. Odors are adsorbed, not masked

Pac ackkag agee deh dehyd ydrrat atio ionn

• De Dehhyd ydrrat atio ionn wit withh ze zeol olit itee mol molec ecul ular ar sie ieve vess whe whenn ve very lo low w hum humid idit ityy co cond ndit itio ionns ar are req requuir ired ed.. Small desiccant packets or tablets protect products such as pharmaceuticals, medical diagnostic reagent kits, vitamins, food, candy, batteries, dry fuel propellants, machine parts, film and instruments

 Air separation

• Removal of water and carbon dioxide from air before liquefaction and cryogenic separation of nitrogen, oxygen and other atmospheric gases • Separation of oxygen and nitrogen with pressure swing or vacuum swing adsorption systems

Natural gas

• De Dehydration before cryogenic recovery of hydrocarbon products and helium • Dehydration of high acid gas content content (CO2 and H2S) natural gas and natural gas condensate streams • Removal of sulfur compounds from ethane, propane and butane • Removal of water and CO 2 before methane liquefaction • Removal of water and sulfur compounds to protect gas transmission pipelines • Dehydration of natural gas liquids • Desulfurization of feed streams for ammonia and other chemical plants • Removal of mercury, preventing damage to aluminum heat exchangers

Petr Pe trol oleu eum m re refi fini ning ng

• De Dehhyd ydrrat atio ionn of of alk alkyyla lati tion on fe feed ed,, re refi fine nery ry ga gass st stre ream amss pri prior or to cry ryog ogeeni nicc se sepa parrat atio ion, n, na nappht htha ha and diesel oil • Purification of feedstocks to protect isomerization catalysts • Removal of water, HCl and H 2S from reformer streams • Removal of oxygenates from etherification raffinate streams and alkylation feed • Removal of nitriles from etherification feed • Dehydration of ethanol • Dehydration and desulfurization of LPG streams • Separation of normal paraffins from branched chain and cyclic compounds • Purification by pressure pressure swing adsorption for upgrading hydrocarbon hydrocarbon streams

Petrochemicals

• Dehydration and purification of NGL/ethane/propane feed • Dehydration of cracked cracked gas, gas, C2 and C3 splitter feed and hydrogen • Dehydration and purification of salt-dome-stored ethylene, propylene and various other feedstocks • Removal of water, carbon dioxide, methyl alchohol and other oxygenates, hydrogen hydrogen sulfide and

 Volatile organic compound removal

sulfuruscompounds, and mercury from ethylene, propylene, butylenes, amylenes and  vario  various solvents and solvents andammonia co-monomers co-monomer s • Removal of trace volatile organic compounds from air streams • Removal of volatile organic compounds from moisture-laden process streams 17

 

Put UOP's experience and technology to work for you OP's expertise and innovation extends from

technical support staff, and manufacturing facilities facilities

research and development to manufacturing

located around the globe, UOP continues to lead the the

and from application product selection to

industry through our commitment to our customers.

U

technical tech nical services. services. To meet customer needs, UOP offers

 Whether you are looking to dr y, purify or separate,

the broadest portfolio of molecular sieve and activated

 you'll find the adsorbent solution with UOP. UOP.

urify

alumina products products in the world. world. With sales, 18

 

UOP Adsorbent Sales Offices UOP LLC Adsorbents 307 Fellowship Fellowship Road, Road, Suite 207 Mt. Laur Laurel, el, NJ 0805 08054 4 (856) 727-9400

UOP Canada Inc. 444 5th Avenue S.W. Suite 1860 Calgary Calg ary,, Albe Alberta rta T2P 2T8, Cana Canada da (403) 777-3750

UOP GmbH. Steinhof 39 D-40699 Erkrath, Germany 49-211-24903-25

UOP LLC Adsorbents PO Box 163 Riverside, IL 60546-0163 60546-0163 (708) 442-4092

UOP Ltd. 5th Floor Marine House Rakhman Rakh manov ovsky sky pe perr. 4, bld bld.. 1 127051 Moscow Moscow,, Russia 7-095-258-2893

UOP S.r.l. S.r .l. Viale M.S., MilanoFiori Strada 1, 1, Palazzo E1 I-20090 ASSAGO MI Milan, Mil an, Ital Italyy 39-02-89224200

UOP Middle East Co. Dubai World Trade Center, 25th Fl. P.O. Box 9428 Dubai, United Arab Arab Emirates Emirates (971-4) 3313-841

Union Showa KK Sanwa San wa Bui Buildi lding ng,, 4F 27-17, 27-1 7, Hamam Hamamatsu-c atsu-cho, ho, 1 chome Minato-ku,T Minato-ku, Tokyo 105-0013 Japan 81-3-3432-7553

UOP LLC Adsorbents 25111 Country Club Blvd., Suite 265 N. Olmste Olmsted, d, OH 4407 44070 0 (440) 734-0086 UOP LLC Adsorbents 13105 Northwest Freeway Suite 600 Houston,TX 77040 (713) 744-2840 UOP LLC Adsorbents Danville Business Center 4115 Blackhawk Plaza Circle, Suite 100 Danville,, CA 94506 Danville (925) 648-2060

UOP Ltd. “Liongate”” Ladymead “Liongate Guildford Surrey GU1 1AT United Kingdom 44-1-483-466139

Shanghai UOP UOP Ltd. Ltd. (Sales) Suite 1203, 1203, Huiy Huiyin in Plaza, Plaza, South 2088 Hua Shan Road Shanghai 200030 People’s Republic of China 86-21-54070555

UOP France s.a.r.l. 24 Rue Saarinen Silic 252 94568 Rungis Rungis Cedex, France

Universal Oil Products Asia Pacific Pte. Ltd. 101 Thomson Road #16-03/04 United Square

33 (1) 41-80-1660

Singapore,, 307591 Singapore 65-6-253-1652

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