Chapter 1 Introduction SCP 04-10-13

8/11/2019 Chapter 1 Introduction SCP 04-10-13

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Design and synthesis of nanomaterials for catalytic applications2

that stabilizes a negative charge is going to enhance the dissociation process and results

in stronger acid. Thus electronegative elements can enhance the acid strength through

inductive effects. The closer the substituent to the anion the more pronounced the effect.

Figure 1.1: Nature of succinic acid molecule

Succinic acid is known to be a building block material. The basic chemistry of

succinic acid is similar to the petrochemically derived maleic acid and maleic anhydride

(Corma et al., 2007).The major technical difficulties encountered in the development of

succinic acid as a building block include the development of very low cost fermentation

routes. The only real technical consideration here is the development of heterogeneous

catalysts that would not be affected by impurities in fermentation.

Scheme 1.1 presents the various derivatives of succinic acid which are

commercially important.


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O

O N

H

O

O

O

N

OHOH

NH2

NH2

1,4-diaminaobutane

O

O

NH2

NH2

Succinic Acid1,4-butanediol

NCCN

succinonitrile

O

OH

O

OH

-butyrolactone

Tetrahydrofuran

Pyrrolidin-2-one

1-ethenylpyrrolidin-2-one

Butanediamide

Scheme 1.1: Commercially important derivatives of succinic acid.

1.2 Heterogeneous catalysts:

Heterogeneous catalyst is a composite material characterized by; active species

physical or chemical promoters and supports, shape, size, pore volume and surface area.

(Vaccari et al., 2003). In order to increase the efficacy and economics, active sites are

supported on a suitable support which may be microporous or mesoporous. Good

supports combine relatively high dispersion with a high degree of thermal stability of the

catalytic component.

1.3 Nanocatalysts:

Heterogeneous catalysis engineering involves length scales ranging from atomic

to the catalyst particle or pellet size. The activity and selectivity of catalyst depends on

the atomic structure of its so called active sites. The geometry of these sites determines


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how some species are bound and converted on the surface of the catalyst. The structures

of the active sites govern the conversion rates towards different products and the

probability for the products to detach from the active site. The active sites are of atomic

dimensions or rather a few nanometers in size (Ozkan, 2008). A vast network of

extremely narrow pores inside the catalyst particle is desirable to achieve a high surface

area per unit volume.

1.4Supercritical Fluids:

Fluids at a temperature and pressure near their critical points are called as

supercritical fluids (Savage, 2000). There are many potential advantages for carrying out

chemical reactions under supercritical conditions like providing higher concentration of

reactant gases compared to the conventional gas-liquid systems, eliminating mass transfer

limitations which might exist in multiphase reacting systems, providing easier product

separation and providing higher diffusivities than liquids and better heat transfer than in

gases.

All different kinds of fluids have their respective critical temperature and

pressure. Most commonly considered fluids are supercritical water and supercritical

carbon dioxide. Supercritical water is highly corrosive in comparison to supercritical

carbon dioxide and can be considered to be most relevant and green fluid because of low

critical temperature, non-inflammability and low toxicity. The supercritical carbon

dioxide has dual properties (properties of both gas and liquid) which provide ideal

conditions for extracting compounds with a high degree of recovery in short time period.

Carbon dioxide is in supercritical state when both temperature and pressure equal or

exceed the critical point of 31oC and 73 atm. (Beckman, 2004).

As stated earlier the current research is based on valorization of succinic acid to

-butyrolactone and a strategy was planned accordingly.


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1.5Organization of thesis:

The thesis is covered in eight chapters.

Chapter 1 gives a brief information about biomass derived products,

heterogeneous catalysis and supercritical fluids.

Chapter 2 covers literature survey about the topic. It gives details about prior art

on the topic with regards to catalyst and support preparation, different routes to obtain the

desired product and use of different catalysts and supports to carry out hydrogenation of

succinic acid.

Chapter 3 gives details about hydrogenolysis i.e. hydrogenation and dehydration

reactions.

Chapter 4 deals with support and catalyst preparation and characterization of the

catalysts.

Chapter 5 covers hydrogenation of succinic acid and analysis of the progress of

reaction. It covers the effect of different solvents and bimetallic catalysts. Also the effect

of supports prepared by calcination and by supercritical carbon dioxide on the reaction

progress is studied.

Chapter 6 describes the kinetic model for the reaction with respect to the effects

of different parameters on the progress of reaction.

Chapter 7 discusses the results and conclusions of the work done.

Chapter 8 finally highlights the accomplishments of the present research work and

an insight on the future work.

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Chapter 1 Introduction SCP 04-10-13