KATALIS - nuristianah.lecture.ub.ac.idnuristianah.lecture.ub.ac.id/files/2019/04/TRK-8-KATALIS.pdf · Outline Definisi, Jenis-jenis, Klasifikasi katalis Katalis homogen Reaksi katalisis

NUR ISTIANAH,ST,MT,M.Eng

KATALIS

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Outline

Definisi, Jenis-jenis, Klasifikasi katalis

Katalis homogen

Reaksi katalisis

Katalis Heterogen

Deaktivasi katalis

Katalis dalam Industri, dan bidang lainnya

Pengenalan reaktor dan bioreaktor

Definition

• Catalyst is a foreign material that hinder or accelerate the reaction process by a factor of a million or much more. It need not be present in large amounts.

• The man-made catalysts, mostly solids, usually aim to cause the high-temperature rupture or synthesis of materials. These reactions play an important role in many industrial processes, such as the production of petrochemicals, polymers, and plastics.

• It is estimated that well over 50% of all the chemical products produced today are made with the use of catalysts.

Definition

Catalyst types:

• Porous(the slolid contains many fine pores, and the surface of these pores suppIies the area needed for the high rate of reaction)

• Monolithic/honeycomb/supported (continuous unitary structures containing many narrow, parallel and usually straight passages)

• Molucular sieve(Sometimes pores are so small that they will admit small molecules but prevent large ones from entering)

• Coated surface

• Living cell or enzyme(biocatalyst)

1

Role of catalyst

Catalytic reaction

Homogenious

Heterogenious

Example

Catalytic reaction

• Some reaction need to use catalyst such as Halogenation-dehalogenation, Hydration-dehydration, Hydrogenation-dehydrogenation, Oxidation, Isomerization, Alkylation-dealkylation

(Foggler)

Catalyst

Heterogeneous catalyst

• Since more than one phase is present, the mass transfer of material from phase to phase must be considered in the rate equation

• Example: burning reaction

• C + O2 CO2

Heterogeneous catalyst

• So do with aerobic fermentation

Mecanism of catalytic reaction

1. Mass transfer (diffusion) of the reactant(s) from the bulk fluid to the external surface of the catalyst pellet

2. Diffusion of the reactant from the pore mouth through the catalyst pores to the immediate vicinity of the internal catalytic surface

3. Adsorption of reactant A onto the catalyst surface

4. Reaction on the surface of the catalyst

5. Desorption of the products from the surface

6. Diffusion of the products from the interior of the pellet to the pore mouth at the external surface

7. Mass transfer of the products from the external pellet surface to the bulk fluid

Mecanism of catalytic reaction

Catalytic reaction

• However, each type has different reaction control (that are dominant in influencing reaction)

• Surface reaction, mass transfer, and alsotemperature may affect the rate of catalytic reaction

Homogeneous catalyst

• A homogeneous reaction is one that involves only one phase.

• Contribution of homogeneous catalytic process in chemical industry is significantly smaller compared to heterogeneous catalytic process, it is only about 17-20

%.

• The significance of homogeneous catalysis is growing rapidly particularly in the area of pharmaceutical and polymer industry.

• Some of the important industrial processes include: 1. Oxidations of alkenes such as production of acetaldehyde, propylene oxide etc. 2. Polymerization such as production of polyethylene, polypropylene or polyesters

Homogeneous catalyst

• In homogeneous catalysis, all the reactants and catalysts are present in a single fluid phase and usually in the liquid phase.

• Homogeneous catalysts are the simple molecules or ions such as HF, H2SO4, Mn+2 as well as complex molecules such as organometallic complexes, macrocyclic compounds and large enzyme molecules

• During one catalytic cycle, the catalyst may pass through several intermediate forms and finally produce the products. After end of each catalytic cycle, the catalyst itself should be regenerated without any change

Catalysis by Organometallic complexes

HOMOGENEOUS CATALYST

- general acid and base catalysis (ester hydrolysis),

- Lewis acids as catalysts (Diels-Alder reactions). B6,

- organic catalysts (thiazolium ions in

Cannizzarro reactions of polyols(sweetener)

- porphyrin complexes (epoxidations,

hydroxylations), acid production,

- enzymatic processes, (polyester condensations).PET

NUR ISTIANAH,ST,MT,M.Eng

KATALIS(II)

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Catalyst Deactivation

Costs to industry for catalyst replacement and process shutdown

total billions of dollars per year.

catalyst deactivation id inavitable(can not be avoided) for most

processes

The loss over time of catalytic activity and/or selectivity, is a

problem.

Slow down the deactivation please!

Mechanisms of Deactivation

• Sulfur, arsenic, phosphorous, and selenium Poisoning

• crystallite growth, support and pore collapse Thermal degradation

• Atomic or polymeris Carbon, coke Fouling

• Volatile metal carbonyl Vapor formation

• Cause sintering and others Solid reaction

• Mechanical failure crushing

Mechanisms of Deactivation

Poisoning

Fouling

Fouling

Sintering

Chemical reaction

• (1) reactions of the vapor phase with the catalyst surface to produce (a) inactive bulk and surface phases (rather than strongly adsorbed species), (b) volatile compounds that exit the catalyst and reactor in the vapor phase, or (c) sintering due to adsorbate interactions, that we call chemical-assisted sintering to distinguish it from thermal sintering previously discussed;

• (2) catalytic solid-support or catalytic solid-promoter reactions, and

• (3) solid-state transformations of the catalytic phases during reaction.

Vapor formation

volatile

Vapor formation

Crushing

• (1) crushing of granular, pellet, or monolithic catalyst forms due to a load in fixed beds;

• (2) attrition, the size reduction, and/or breakup of catalyst granules or pellets to produce fines, especially in fluid or slurry beds; and

• (3) erosion of catalyst particles or monolith coatings at high fluid velocities in any reactor design.

Effects of deactivation

Prevention

Regeneration

• Despite our best efforts to prevent it, the loss of catalytic activity in most processes is inevitable. When the activity has declined to a critical level, a choice must be made among four alternatives:

• (1) restore the activity of the catalyst(regeneration)

• (2) use it for another application,

• (3) reclaim and recycle the important and/or expensive catalytic components, or

• (4) discard the catalyst.

Regeneration

• The ability to reactivate a catalyst depends upon the reversibility of the deactivation process.

• carbon and coke formation is relatively easily reversed through gasification with hydrogen, water, or oxygen.

• Sintering is generally irreversible and hard to be regenerated

• Some poisons or foulants can be selectively removed by chemical washing, mechanical treatments, heat treatments, or oxidation

Catalytic reactor

Fixed

bed

Fluidized bed

Moving

bed

Need more catalyst, efficient contacting

Effective temperature control, good product distribution

Catalytic reactor

Catalytic reactor

Catalytic

reactor

NUR ISTIANAH,ST,MT,M.Eng

THANK YOU

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