C2PT Catalyst Process Technology

By Gerard B Hawkins Managing Director

FCC Off Gas Treatment

Refinery off gas sourced from a number of units FCC / Coker / HDT / etc

FCC off gas contains valuable olefins which can be recovered by stand-alone cryogenic unit

Gas stream typically contains many contaminants which affect either final product specs or processing options

H2S Catalyst poison COS Impacts on C3= product spec RSH Impacts on C2= / C3= product spec Acetylene Impacts on C2= / C3= product spec Oxygen Impacts on C2= / C3= product spec Chlorides Corrosive to aluminium Ammonia Potential reactant to form NH4NO3 Nitric oxides Can react to form explosive nitroso gums Mercury Attacks aluminium in cold section Arsine Impacts C3= product spec HCN Impacts C2= / C3= product spec H2O Freezes in cold section

H2S Amine/caustic wash + absorbent guard bed COS Hydrolysis or solid bed absorption RSH Caustic and/or solid bed absorption Acetylene Hydrogenation to ethylene across catalyst Oxygen Hydrogenation to water across catalyst Chlorides Solid bed absorbent Nitric oxides Hydrogenation to NH3 across catalyst Mercury Solid bed absorbent Arsine Solid bed absorbent HCN Solid bed absorbent or hydrogenation across

catalyst H2O Regenerable mol sieve

Products for sale as polymer feeds

and LPG

Feed Gas Compression

Acetylene conversion

Acid Gas Removal

Contaminant Absorption

Steps Drying

Cryogenic Recovery

Unit

Product Fractionation

Off gas to fuel or hydrogen recovery

Refinery off gas streams

Typical Off Gas Processing Scheme

Supply of the full range of catalysts / absorbents

for off gas processing

and / or treatment of fractionated product streams Commercial references for both duties under the product brand name VULCAN VGP Series

Input to the flow sheet and reactor design

All spent catalysts / absorbents can be reprocessed

Amine and caustic systems most cost effective route

for bulk H2S removal

For specifications of < 3 ppmv H2S then a fixed bed absorbent

bed on polishing duty most cost effective

Polishing guard bed also provides insurance for amine or caustic

unit upsets

VULCAN VGP Series H2S absorbents market leader in gas processing industry and wide-spread use in refineries to protect catalysts from sulfur poisoning

Amine & caustic systems not effective at COS removal

COS can be hydrolysed across a catalyst COS + H2O -----> H2S + CO2 or absorbed directly by reaction with a non-regenerable absorbent bed

Performance of the catalyst dependant on component partial pressures and temperature

VULCAN Absorbent references on reducing off-gas streams and polymer grade propylene streams

Amine systems not effective at RSH removal

Caustic will remove RSH but struggles to meet tight exit specifications

VULCAN Series absorbents remove RSH onto a non-regenerable absorbent at ambient temperature

VULCAN Series RSH absorbents in use on refineries to protect catalysts from sulfur poisoning and meet product specifications

Sulfided metal catalyst removes all

acetylene hydrogenated to ethylene

oxygen hydrogenated to water

arsine, phosphine and cyanides absorbed

nitriles converted to amines

cyanides converted to ammonia

Key to activity is proprietary catalyst sulfiding procedure

VULCAN Series catalyst proven for selective hydrogenation duties on both refineries & petrochemical plants

HCl removed by chemical reaction onto a non-

regenerable absorbent bed

Care needed if Aluminas specified because of danger of synthesis of organic chlorides which are difficult to remove R= + HCl ------> RCl This does not occur with VULCAN Series absorbents

VULCAN Series absorbents market leader in refineries for catalytic reformer off gas dechlorination

NO and NO2 hydrogenated across a catalyst NOx + H2 -----> NH3 + H2O

Key is to ensure no co-hydrogenation of olefins

Proven on side-stream reactor unit on commercial FCC unit

Mercury reacts with absorbent to form mercuric sulfide which remains as part of absorbent structure

Exit mercury specification determined by equilibrium

Typical exit specs < 0.001 ppb

VULCAN VGP Series mercury absorbents proven in many gas processing plants to meet transmission specifications and protect aluminium equipment

The primary objective of the oxygen converter

is to reduce the Oxygen content of the treated gas to less than 0.1 ppm (V)

Acetylene < 1 ppm (wt)

Arsine < 5 ppb (wt) Phosphines < 5 ppb (wt)

Cost effectiveness: VULCAN VGP Series catalyst must meet several criteria. Meet Oxygen specification of less than 0.1 vppm Meet Acetylene specification of less than 0.1 wppm Meet Arsine specification of less than 5 vppb Meet Phosphine specification of less than 5 vppb Provide a 18 month cycle length.

Client minimum guarantee levels for the following performance metrics at SOR:

Oxygen content of treated gas to be less than 0.1

ppmv at maximum treat gas rate. Acetylene specification of less than 0.1 wppm at

maximum treat gas rate. Arsine specification of less than 5 vppb at

maximum treat gas rate. Phosphine specification of less than 5 vppb

at maximum treat gas rate.

Catalysts promote chemical reactions and accelerate the rate at which a chemical reaction approaches equilibrium.

The catalyst provides a suitable surface for reactants to

adsorb and for products to desorbed. Primary Function - to lower the activation energy of the

reaction by providing a suitable reaction pathway.

GBHE offers VULCAN VGP Series catalyst for the treatment of fluidized catalytic cracker unit (FCCU) off gas to remove a variety of impurities, which are unacceptable for downstream processing in which useful olefins are recovered in a cold train.

Acetylene and higher acetylenes are hydrogenated selectively by

VULCAN VGP Series catalyst using the large excess of hydrogen in the process stream without significant onward hydrogenation of the olefins, which are to be recovered.

Oxygen is removed by hydrogenation to H2O.

Traces of Phosphine and arsine are removed by chemisorption.

CATALYST DESCRIPTION Form Spheres Size nominal 8 mm TYPICAL CHEMICAL COMPOSITION Component Wt. % dry Ni 0.5% Co 0.15% Cr 0.05% Al2O3 84 89% PHYSICAL DESCRIPTION Crush Strength > 50 Kgs Bulk Density 1 1.1 Kg/L

VULCAN VGP Series: Catalyst of the sulfided Ni type.

The catalyst is principally designed to hydrogenate

acetylene to ethylene by the reaction: C2H2 + H2 C2H4

Typical Feed Impurity Levels

Inlet acetylene 1000 - 3000 ppm mol Outlet acetylene < 1 ppm mol

The VULCAN VGP hydrogenates other acetylene and diene

compounds in FCCU off gas. (MA/PD) Removal efficiency 60 - 80 % (BD) Removal efficiency 20 - 30 %

O2 Oxygen is removed by the reaction: O2 + 2 H2 2 H2O

Typical oxygen Levels:

Inlet oxygen 300 - 1000 ppm mol Outlet oxygen < 1 ppm mol can be achieved

Optimum Inlet temperature range: 190 200 oC.

Operating temperature range: 150 260 oC (300 500 oF).

Delta T: The temperature rise is typically 30 50 oC Dependent on the amount of acetylenes, dienes and oxygen in the feed The catalyst selectivity

Activity for the desired hydrogenation reactions and selectivity for olefin hydrogenation is controlled by; Continuous sulfur doping with H2S Operating temperature

Both of which must be varied as the catalyst ages.

A new charge of catalyst requires sulfiding prior to being brought on line, and after periodic steam/air regenerations.

The reactions take place in the presence of a large excess of

hydrogen over acetylene

Typically 5 - 10 mol % and 2000 ppm mol (respectively)

High selectivity and minimizes undesirable hydrogenation ethylene and propylene products.

The catalyst performance slowly deteriorates

over time online due to the build up of foulants on the catalyst surface.

Once the selectivity and activity of VULCAN VGP become

unacceptable, the catalyst requires regeneration.

The regeneration frequency depends on the operating conditions, the catalyst age, vessel sizing and the level of acetylene slip or ethylene loss that the operator can tolerate.

Regenerations are usually required every few months but may be more or less frequent.

Regeneration conditions require heating of the catalyst in

air/steam at approximately 500 oC for approximately one week until the fouling species are removed.

Re-sulfiding before the catalyst is ready for re-use VULCAN VGP operates in a sulfided form, which has activity

for the absorption of various species

Phosphine Arsine.

NiO is a known catalyst for the reduction of NOx with both CO and H2, at temperatures below 392 0F (200 0C), with the principal product of reaction

being N20. NO and NO2 hydrogenated across a catalyst

NOx + H2 -----> NH3 + H2O

References: E Echigoya et al, Bull. Japan. Petr. Inst, 1975, 17, 232 G V Glazneva et al., Dokl. Akad. Nauk. SSR, 1973, 213, 971 T P Kobylinski et al., J. Catal, 1973, 31, 450 F Nozaki et al, Bull. Chem. Soc. Japan. 1975, 48, 2764

Control parameters: A combination of rate of sulfur injection and inlet temperature

optimization Higher temperature increases activity but diminishes

selectivity so that the acetylene conversion is increased but also the level of ethylene hydrogenation increases

Oxygen conversion can be affected also Conversely, higher sulphur decreases activity but augments

selectivity

There are numerous factors which affect the catalyst performance:

- Hydrogen partial pressure: Increases hydrogenation activity and therefore lower

selectivity Sulfur (ppm): Any sulfur injection must be adjusted to

compensate for varying levels of feed sulfur

- Moisture: Increasing H2O diminishes activity

- CO level: Increasing CO decreases activity and helps selectivity

but large changes are needed for the effect to be significant;

- Space velocity: Faster gas flow results in less apparent activity but more selectivity; - Olefin partial pressure: In theory the selectivity will decrease with increasing

olefin levels but the effect is small.

Typically inlet temperature 200 oC (392 oF) Reaction may be substantial at 190 oC (374 oF) or may require an increase in temperature to 220 oC (428 oF) Typical Sulfur levels: 2 - 50 ppmv (total sulphur) Over the lifecycle, temperatures should be increased and

sulfur injection rates reduced, in order to maintain catalyst activity. - Decreased selectivity

Under certain conditions, the catalyst will desulfide to give Ni

rather than NiS and this is an effective ethylene hydrogenation catalyst so selectivity may collapse.

Permanent Poisons Arsenic, lead, mercury, cadmium

Silica, Iron Oxide. Temporary Poisons Sulfur, carbon

- Heavy metals in FCC feedstocks Nickel Vanadium

- Tramp iron contamination, formed as corrosion products within the pipe work

- Scale and carbon deposits from heaters and exchangers

- Polymerization caused by reactive molecules within the feedstock

- Particulates contained within the feedstock or caused by upstream attrition of catalysts.

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0.001 0.01 0.1 1 10 100 1000

Pore size (microns)

Cum

ulat

ive

vol (

mls

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Catalyst ACatalyst B

The contaminants may vary in size from sub micron to several hundred microns and be deposited in the interstitial voids between the catalyst spheres.

Result: Flow restriction, channeling, and a reduction in catalyst

activity by; - Deposition and encapsulation of the catalyst

surface - Pore mouth narrowing mechanism leading to eventual total pore plugging

During operation, carbonaceous polymer builds up on the catalyst surface for side reactions of unsaturated hydrocarbons in the process gas. As a result, catalyst selectivity and activity declines.

VULCAN VGP can be regenerated using a steam/air oxidation

at high temperature to remove the carbonaceous polymer deposits.

The regeneration frequency depends on the operating

conditions, the catalyst age, vessel sizing and the level of acetylene slip or ethylene loss that the operator can tolerate.

V5

V2

V4

Feed GAS

V1

B A

V6 V3

PRODUCT GAS

Regeneration conditions require heating of the

catalyst in air/steam at approximately 500 oC for until the fouling species are removed.

VULCAN VGP is formulated to hydrogenate acetylene to ethylene. Other diene compounds can also be hydrogenated with relatively high efficiency, and impurities removed by chemisorption

The amount of temperature rise will vary depending on the inlet impurity content and catalyst selectivity

Continuous sulfur injection is required to maintain catalyst selectivity

VULCAN VGP is regenerable

GBH ENTERPRISES, LTDBack Ground Typical Impurities & Their Effect Typical Impurities & Their RemovalSlide Number 5GBH Enterprises / Haiso Technology H2S AbsorptionCOS Removal RSH RemovalAcetylene / Oxygen / Arsine / Phosphine / Nitriles / Cyanides RemovalChlorides Removal Nitrogen Oxides Removal Mercury RemovalFCC Offgas Oxygen Converter Process ObjectivesFCC Offgas Oxygen ConverterProcess RequirementsFCC Offgas Oxygen ConverterPerformance GuaranteesFCC Offgas Oxygen Converter Catalyst: Classical DefinitionFCC Offgas Oxygen ConverterVulcan VGP IntroductionFCC Offgas Oxygen Converter Vulcan VGP Series Catalyst Chemical & Physical PropertiesFCC Offgas Oxygen Converter Vulcan VGP Series: Reaction ChemistryFCC Offgas Oxygen Converter Vulcan VGP Reaction ChemistryFCC Offgas Oxygen Converter Vulcan VGP Reaction ChemistryFCC Offgas Oxygen Converter Vulcan VGP Reaction ChemistryFCC Offgas Oxygen Converter Vulcan VGP Reaction ChemistryFCC Offgas Oxygen Converter Vulcan VGP Reaction ChemistryFCC Offgas Oxygen Converter Vulcan VGP Reaction ChemistryFCC Offgas Oxygen ConverterNOx RemovalFCC Offgas Oxygen Converter Control During Normal OperationFCC Offgas Oxygen Converter Control During Normal OperationFCC Offgas Oxygen Converter Control During Normal OperationFCC Offgas Oxygen Converter Control During Normal OperationFCC Offgas Oxygen ConverterCatalyst PoisonsFCC Offgas Oxygen ConverterCatalyst FoulantsFCC Offgas Oxygen ConverterCatalyst FoulantsFCC Offgas Oxygen Converter Catalyst RegenerationFCC Offgas Oxygen Converter Catalyst RegenerationSummarySlide Number 38