66
6 Hydrogen from Miscellaneous Sources and Nanotechnology
resulting in the leeching of the metal particles; however, they can be loaded again,
and maximum efficiency can be achieved. The catalysts were later on used to reduce
the NaBH 4 in the alkaline environment. Chemical equation for the reaction can be
given as [28].
NaBH 4 + H 2 O → NaBO 2 + 4H 2
Similar studies with same hydrogel matrix containing cobalt and nickel nanoparticles have also been reported for the hydrolysis of alkaline sodium borohydride
solution for the generation of sustainable hydrogen [29, 30].
6.3 Waste Material-Based Hydrogen Generation
Different waste materials that are involved in the generation of hydrogen require
extensive use of nanotechnology. In case of the plastics, nanomaterials are involved
in different ways. In some cases, the nanomaterials are produced simultaneously
from the polymeric waste plastic along with sustainable hydrogen (normally carbon
nanotubes are obtained by the process). However, some studies have reported the
recovery of metallic nanoparticles from the plastics but no hydrogen was obtained
along with them [31]. Some studies have reported the formation of particular nanoparticles from different types of waste plastics which are involved in the generation of
hydrogen. Some of these works will be discussed here.
A study published in 2012 reported the generation of simultaneous generation
of hydrogen-rich synthesis gas and supreme quality multiwalled carbon nanotubes
from the waste plastics. The conversion was achieved through gasification instead
of thermal recycling. The process of the conversion was designed in a manner so
that it can be altered so as to achieve desired end product. In the practice, the waste
polypropylene was used as the waste plastic and the steam gasification of the substrate
was achieved by Ni/Zn–Al and Ni/Ca–Al catalysts in a two-step reaction. The carbon
nanotubes were obtained in the form of deposition on the surface of the catalysts
and were characterized with Raman spectroscopy, SEM, and TEM. The mass of
the obtained nanotubes was determined through temperature-programmed oxidation
(TPO) of the catalyst with product deposition. The percentage yield of sustainable
hydrogen obtained through the steam gasification of the polymer was found to be
34.1 vol. %. The study proposed 16,800 Nm
3 per day generation of the hydrogen by
the process if the plants are installed with 10 tons per day capacity of the plastic [6].
A graphical explanation of plastic conversion into carbon nanotubes and sustainable
hydrogen is given in Fig. 6.1.
In another study, novel waste polyethylene-based nanomaterials were created and
were employed in the generation of hydrogen from electrochemical reactions. These
nanomaterials involve carbon nanotubes decorated with Ni/Pd nanoparticles. In practice, the nanomaterial was prepared by disintegrating the polyethylene waste plastic
in supercritical CO 2 at high temperatures. This led to the formation of a mixture
6 Hydrogen from Miscellaneous Sources and Nanotechnology
resulting in the leeching of the metal particles; however, they can be loaded again,
and maximum efficiency can be achieved. The catalysts were later on used to reduce
the NaBH 4 in the alkaline environment. Chemical equation for the reaction can be
given as [28].
NaBH 4 + H 2 O → NaBO 2 + 4H 2
Similar studies with same hydrogel matrix containing cobalt and nickel nanoparticles have also been reported for the hydrolysis of alkaline sodium borohydride
solution for the generation of sustainable hydrogen [29, 30].
6.3 Waste Material-Based Hydrogen Generation
Different waste materials that are involved in the generation of hydrogen require
extensive use of nanotechnology. In case of the plastics, nanomaterials are involved
in different ways. In some cases, the nanomaterials are produced simultaneously
from the polymeric waste plastic along with sustainable hydrogen (normally carbon
nanotubes are obtained by the process). However, some studies have reported the
recovery of metallic nanoparticles from the plastics but no hydrogen was obtained
along with them [31]. Some studies have reported the formation of particular nanoparticles from different types of waste plastics which are involved in the generation of
hydrogen. Some of these works will be discussed here.
A study published in 2012 reported the generation of simultaneous generation
of hydrogen-rich synthesis gas and supreme quality multiwalled carbon nanotubes
from the waste plastics. The conversion was achieved through gasification instead
of thermal recycling. The process of the conversion was designed in a manner so
that it can be altered so as to achieve desired end product. In the practice, the waste
polypropylene was used as the waste plastic and the steam gasification of the substrate
was achieved by Ni/Zn–Al and Ni/Ca–Al catalysts in a two-step reaction. The carbon
nanotubes were obtained in the form of deposition on the surface of the catalysts
and were characterized with Raman spectroscopy, SEM, and TEM. The mass of
the obtained nanotubes was determined through temperature-programmed oxidation
(TPO) of the catalyst with product deposition. The percentage yield of sustainable
hydrogen obtained through the steam gasification of the polymer was found to be
34.1 vol. %. The study proposed 16,800 Nm
3 per day generation of the hydrogen by
the process if the plants are installed with 10 tons per day capacity of the plastic [6].
A graphical explanation of plastic conversion into carbon nanotubes and sustainable
hydrogen is given in Fig. 6.1.
In another study, novel waste polyethylene-based nanomaterials were created and
were employed in the generation of hydrogen from electrochemical reactions. These
nanomaterials involve carbon nanotubes decorated with Ni/Pd nanoparticles. In practice, the nanomaterial was prepared by disintegrating the polyethylene waste plastic
in supercritical CO 2 at high temperatures. This led to the formation of a mixture