A comprehensive birds eye view of catalysis in green chemistry. Includes descriptions of photocatalysis,zeolites and nanoparticles as efficient green catalysts.A simple and crisp presentation with minimum words and alot of figures and colors.

1. GREEN
CATALYSTS

2. ZEOLITES
THE "BOILING STONE"

3. WHAT ARE ZEOLITES
 Zeolites, also called molecular sieves, are traditionally referred to as a family of
aluminosilicate materials consisting of orderly distributed micropores in molecular
dimensions.
 •In simpler words, they're solids with a relatively open, three-dimensional crystal
structure built from the elements aluminum, oxygen, and silicon, with alkali or alkaline-
Earth metals (such as sodium, potassium, and magnesium) plus water molecules
trapped in the gaps between them.
 They have been widely used as highly efficient catalysts, adsorbents, and
ion exchangers in petrochemical industries and in our daily life.

4. ZEOLITES AS GREEN CATALYST
1.BRONSTED ACID
CATALYST
2.LEWIS ACID
CATALYST
3.MULTIFUNCTIONAL
CATALYST
HIGH MELTING
POINT
RESISTANT TO
ENVIRONMENTAL
CONDITIONS
DON'T DISSOVE
IN WATER
DOESN'T OXIDISE

5. BRONSTED
ACID
CATALYSTS
Bronsted acid sites are highly polarized HYDROXYL GROUPS in zeolite frameworks, which are
very active to many catalytic reactions as proton donors
APPLICATIONS
1.the oil-refining and petrochemical industries.
2.Bronsted acidic zeolites are playing an important role in many processes of biomass
conversion
Bronsted acidic zeolites can be used to catalyze the conversion of microbially produced lactic
acid (LA) into lactide, which is the key building block for biodegradable and renewable polylactic
acid.
The traditional method for lactide synthesis from LA requires a time- and energy-intensive two-
stage process involving polycondensation and transesterification at high temperatures in vacuo.
Moreover, different lengths of LA oligomers form as the side products

6. LEWIS ACID CATALYST
Besides Brønsted acid sites, substituting Si atoms in zeolite frameworks
with tetrahedrally coordinated Ti, Sn, or Zr atoms can produce Lewis acid
sites, which can accept electron pairs from guest molecules, facilitating
many biomass conversion processes
Traditional strategies for production of diacids and diesters from biomass-
derived molecules suffered from poor selectivity and inefficient carbon
utilization. With zeolites Sn-, Zr-, and Hf-beta as the
catalysts, ethyl pyruvate was condensed into diethyl 2-methyl-4-oxopent-2-
enedioate and diethyl 2-methylene-4-oxopentanedioate. In particular, Zr-
and Hf-beta exhibited the best catalytic performance, giving the highest
ethyl pyruvate conversions (>80%) with comparable selectivities (>64%)
toward diesters.

7. MULTIFUNCTIONAL CATALYST
 The transformation of biomass into chemicals and fuels often undergoes multistep
reactions, each of which might require a distinct catalyst. Zeolite catalysts can be fine-
tuned with combined active sites to allow multistep reactions occurring in a “one-pot”
way.
 For instance, zeolite Sn-Al-beta contains both Brønsted and Lewis acid sites because
of the presence of both tetrahedral AlIII and SnIV, respectively, which can be used for the
cooperative catalysis of multistep conversion of 1,3-dihydroxyacetone into ethyl lactate
. During this multistep reaction, the Brønsted AlIII acid sites accelerated the dehydration
of dihydroxyacetone to form pyruvic aldehyde, and the Lewis SnIV acid sites catalyzed
the hydride shift of pyruvic aldehyde into ethyl lactate with ethanol.

8. TiO2
Photocatalyst

9.  Environmental pollution and destruction on a global scale have drawn attention to the
vital need for totally new environmentally friendly, clean chemical technologies and
processes, the most important challenge facing chemical scientists in the field of green
chemistry. Strong contenders as environmentally harmonious catalysts are photocatalysts
that operate at room temperature and in a clean manner, while applications of such safe
photocatalytic systems are urgently desired for the purification of polluted water, the
decomposition of offensive atmospheric odors as well as toxins, the fixation of CO2, and
the decomposition of NOx and chlorofluorocarbons on a huge global scale.
 One of the most ideal catalytic processes is the so-called ‘
artificial photosynthesis’which
has the potential to realize safe and clean chemical processes and systems with the use
of limitless solar energy

10. ADVANTAGES
 , TiO2 is the most attractive due to its low cost
 Availability
 high photocatalytic reactivity
 chemical stability
LIMITATION
 TiO2 has a large bandgap with an absorption edge in UV regions shorter than 380 nm
 TiO2 semiconductors absorb only 3–4% of the solar light that reaches the Earth

12. Working
 semiconducting metal oxides such as TiO2, ZnO and Fe2O3 are known to act as sensitizers for light-
induced redox processes due to their unique electronic structure characterized by a filled valence band
and an empty conduction band
 when semiconducting metal oxide absorbs a photon having an energy larger than its bandgap, an
electron is promoted from the valence band to the conduction band, leaving a hole
 The holes in the valence band act as powerful oxidants, while the electrons in the conduction band are
good reductants
 When the TiO2 is irradiated by UV light (l < 380 nm) in water, H+ is reduced to H2 by the photo-formed
electrons, while OH is oxidized to OH radicals by the photo-formed holes to produce O2 through
several reaction steps. In this way, TiO2 can decompose water into H2 and O2
 It should be noted that the irradiation of vacuum UV light (l < 165 nm) is necessary for the direct
photolysis of water molecules into H2 and O2 [1–6].
 On the other hand, when TiO2 is irradiated by UV light in the presence of air and reactant molecules
such as organic compounds in water, the photo-formed electrons react with O2 to form O2 , while OH
is oxidized into OH q radicals. The oxygen radicals formed can easily react with the organic
compounds, decomposing them into CO2 and H2O

13. Direct Photocatalytic Decomposition of
NO into N2 and O2
 When the TiO2 photocatalyst is irradiated by UV light in the presence of NO in
atmospheric conditions, NO is oxidized into NO2 and then further oxidized into NO3 .
This NO3 species on the TiO2 surface can be removed as HNO3 by water in the form
of, for example, raindrops


14. MODIFICATION FOR
TiO2 PHOTOCATALYST
 A modification of the electronic properties of Ti/zeolite photocatalysts by bombarding
them with high-energy metal ions led to the discovery that metal ion implantation with
various transition metal ions such as V and Cr, accelerated by high electric fields, can
produce a large shift in the absorption band toward visible light regions

15. NANOMATERIA
L CATALYSTS

16. WHY DO WE NEED NANO-
CATALYSIS?
Homogeneous
catalysts
Cumbersome
purification process
Difficulty in recovery
and recycling
Expensive
Heterogeneous
catalysts
Reduced contacts
between catalyst
and substrates
Inferior catalytic
performance
compared to
homogeneous
catalysts
Leaching of active
species

17. PROPERTIES OF
NANOCATALYSTS
Nano size ie,high surface area
Contact between reactants and
catalysts increases dramatically
Mimicking homogeneous catalysts
Insoluble in reaction solvent
Tailormade physical and chemical
properties

18. APPLICATIONS OF NANOCATALYSTS
Biomass gasification to produce high syn gas and biomass pyrolysis for production of bio-oil
Process Improvements: • Novel Al2O3 supported NiO catalyst reduces tar yield significantly and
increases tar removal efficiency to 99% • Significant increase in gas yield • Lighter fractions of H2 & CO
are increased in the syn gas composition while heavier fractions of CH4 & CO are reduced, thus
improving syn gas quality
Catalyst: Nano NiO catalyst supported on γ- Al2O3 microspheres of 3 mm size (Johnson Mathey
Company, greater than 99% purity)
Application: Production of biodiesel from waste cooking oil
Process Improvements: • Esterification of fatty acids (FFAs) and transesterification of triglycerides to
biodiesel in one pot • Solid acid nanocatalysis of Al0.9H0.3PW12O40 nanotubes with double acid sites
yield 96% of biodiesel from waste cooking oil as compared to 42.6% with conventional
H3PW12O40 catalyst Catalyst: Aluminium dodeca-tungsto-phosphate (Al0.9H0.3PW12O40) nanotubes
as solid catalysts with surface area of 278 m2/g