206
1 Introduction
Hydrogenation processes of poly-unsaturated hydrocarbons to selectively produce
alkenes have attracted significant interest since 1990s, due to the high demand of
alkenes from the petrochemical and polymer industries. Initial work on the catalytic
hydrogenation was developed considerably during early 1960s, particularly with the
boom of olefin production by steam cracking. Majority of the catalytic hydrogenation
processes are used in refining and petrochemical sector, specifically the downstream
units of the mother plant, the cracker, e.g. selective hydrogenations of acetylenes,
methyl acetylenes, propadienes, 1,3-butadienes, selective hydrogenations of C5
unsaturates, etc. All of these molecules are produced in large scale due to their use
as fuels, fuel precursors, polymerization precursors, etc. In particular, C4-rich
streams consisting of 1-butene are currently used as precursors for the production of
polybutene and co-monomer of low-density polyethylene. However, the presence of
1,3-butadiene in the C4 stream blocks the active sites of the polymerization catalyst,
which inhibit the polymerization kinetics. Thus, there is a wide scope for
understanding and developing newer and improved active, selective and stable
catalysts of industrial importance, which can convert 1,3-butadiene into 1-butene
selectively. In addition, this specific hydrogenation reaction is considered as a model
reaction to investigate the catalytic, structural and electronic properties of the
catalyst. Due to these advantages, a continued research activity on hydrogenation of
1,3-butadiene is significant from both fundamental and applied aspects, to achieve
a better insight in the catalyst, process, and mechanism—key factors which control
the catalyst performance as well as selectivity. Owing to the practical and theoretical
importance, it is very important to collate the different aspects of this process from
the existing literature to understand the reaction mechanism of hydrogenation
reaction. Thus, this book chapter provides a detailed information of the selective
catalytic hydrogenation of 1,3-butadiene, and summarizes the knowledge,
significance and future scope of this heterogeneous catalytic process. Specifically,
product selectivity and kinetics of this reaction, which were correlated to factors
such as the effect of the support, the structure sensitivity, size of the active sites,
metal dispersion, promoters and additives, are discussed in detail.
1.1 Significance and Background
To realize the potential of a model reaction to probe the catalyst structure, it is
important to understand the hydrogenation reaction of 1,3-butadiene, physical
properties of both 1,3-butadiene as well as the expected hydrogenated products
from 1,3-butadiene (Table 1). Their chemical structures including the reactants and
the products in this reaction sequence are also presented in Fig. 1, which clearly
shows how the reaction kinetics on different catalyst can affect the product
selectivity. From the data listed, the density of butane (2.480 g/cm
3
) is higher than
P. R. Selvakannan et al.
1 Introduction
Hydrogenation processes of poly-unsaturated hydrocarbons to selectively produce
alkenes have attracted significant interest since 1990s, due to the high demand of
alkenes from the petrochemical and polymer industries. Initial work on the catalytic
hydrogenation was developed considerably during early 1960s, particularly with the
boom of olefin production by steam cracking. Majority of the catalytic hydrogenation
processes are used in refining and petrochemical sector, specifically the downstream
units of the mother plant, the cracker, e.g. selective hydrogenations of acetylenes,
methyl acetylenes, propadienes, 1,3-butadienes, selective hydrogenations of C5
unsaturates, etc. All of these molecules are produced in large scale due to their use
as fuels, fuel precursors, polymerization precursors, etc. In particular, C4-rich
streams consisting of 1-butene are currently used as precursors for the production of
polybutene and co-monomer of low-density polyethylene. However, the presence of
1,3-butadiene in the C4 stream blocks the active sites of the polymerization catalyst,
which inhibit the polymerization kinetics. Thus, there is a wide scope for
understanding and developing newer and improved active, selective and stable
catalysts of industrial importance, which can convert 1,3-butadiene into 1-butene
selectively. In addition, this specific hydrogenation reaction is considered as a model
reaction to investigate the catalytic, structural and electronic properties of the
catalyst. Due to these advantages, a continued research activity on hydrogenation of
1,3-butadiene is significant from both fundamental and applied aspects, to achieve
a better insight in the catalyst, process, and mechanism—key factors which control
the catalyst performance as well as selectivity. Owing to the practical and theoretical
importance, it is very important to collate the different aspects of this process from
the existing literature to understand the reaction mechanism of hydrogenation
reaction. Thus, this book chapter provides a detailed information of the selective
catalytic hydrogenation of 1,3-butadiene, and summarizes the knowledge,
significance and future scope of this heterogeneous catalytic process. Specifically,
product selectivity and kinetics of this reaction, which were correlated to factors
such as the effect of the support, the structure sensitivity, size of the active sites,
metal dispersion, promoters and additives, are discussed in detail.
1.1 Significance and Background
To realize the potential of a model reaction to probe the catalyst structure, it is
important to understand the hydrogenation reaction of 1,3-butadiene, physical
properties of both 1,3-butadiene as well as the expected hydrogenated products
from 1,3-butadiene (Table 1). Their chemical structures including the reactants and
the products in this reaction sequence are also presented in Fig. 1, which clearly
shows how the reaction kinetics on different catalyst can affect the product
selectivity. From the data listed, the density of butane (2.480 g/cm
3
) is higher than
P. R. Selvakannan et al.