NUR ISTIANAH,ST,MT,M.Eng
KATALIS
ALLPPT.com _ Free PowerPoint Templates, Diagrams and Charts
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 pr esent 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, a nd the surface of these pores suppIies the a rea needed for the high rate of reaction)
• Monolithic/honeycomb/supported (continuo us unitary structures containing many narro w, parallel and usually straight passages)
• Molucular sieve(Sometimes pores are so sm all 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 Ha logenation-dehalogenation, Hydration-dehydrat ion, 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 b e 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 flu id 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 cat alytic 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 surfa ce 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 alsotemperat ure may affect the rate of catalytic reaction
Homogeneous catalyst
• A homogeneous reaction is one that involves only on e phase.
• Contribution of homogeneous catalytic process in c hemical 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 acetalde hyde, propylene oxide etc. 2. Polymerization such as production of polyethylene, polypropylene or polyest ers
Homogeneous catalyst
• In homogeneous catalysis, all the reactants and c atalysts are present in a single fluid phase and us ually in the liquid phase.
• Homogeneous catalysts are the simple molecules or ions such as HF, H2SO4, Mn+2 as well as com plex molecules such as organometallic complex es, macrocyclic compounds and large enzyme molecules
• During one catalytic cycle, the catalyst may pass through several intermediate forms and finally pr oduce the products. After end of each catalytic cycle, the catalyst itself should be regenerated wi thout 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)
ALLPPT.com _ Free PowerPoint Templates, Diagrams and Charts
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 catal yst surface to produce (a) inactive bulk and sur face phases (rather than strongly adsorbed spe cies), (b) volatile compounds that exit the catal yst and reactor in the vapor phase, or (c) sinter ing due to adsorbate interactions, that we call chemical-assisted sintering to distinguish it fro m thermal sintering previously discussed;
• (2) catalytic solid-support or catalytic solid-pro moter reactions, and
• (3) solid-state transformations of the catalytic
phases during reaction.
Vapor formation
volatile
Vapor formation
Crushing
• (1) crushing of granular, pellet, or monolit hic catalyst forms due to a load in fixed b eds;
• (2) attrition, the size reduction, and/or br eakup of catalyst granules or pellets to pr oduce fines, especially in fluid or slurry b eds; and
• (3) erosion of catalyst particles or monolit
h coatings at high fluid velocities in any r
eactor design.
Effects of deactivation
Prevention
Regeneration
• Despite our best efforts to prevent it, the loss of catalytic activity in most processes is inevita ble. When the activity has declined to a critical level, a choice must be made among four alter natives:
• (1) restore the activity of the catalyst
(regeneration)• (2) use it for another application,
• (3) reclaim and recycle the important and/or ex pensive catalytic components, or
• (4) discard the catalyst.
Regeneration
• The ability to reactivate a catalyst depends upo n the reversibility of the deactivation process.
• carbon and coke formation is relatively easily r eversed through gasification with hydrogen, w ater, or oxygen.
• Sintering is generally irreversible and hard to b e regenerated
• Some poisons or foulants can be selectively re
moved by chemical washing, mechanical treat
ments, 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
ALLPPT.com _ Free PowerPoint Templates, Diagrams and Charts
