Chemistry Reference
In-Depth Information
Potential for metal-carbide, -nitride, and
-phosphide as future hydrotreating (HT)
catalysts for processing of bio-oils
Sara Boullosa-Eiras,
a
Rune Lødeng,
b
Håkon Bergem,
b
Michael St
¨
cker,
c
Lenka Hannevold
c
and Edd A. Blekkan*
a
DOI: 10.1039/9781782620037-00029
E
cient thermochemical conversion of ligno-cellulosic biomass towards compatible
liquid fuels like diesel and gasoline, potentially alcohols and ethers, is a story about new
opportunities and challenging chemistry. Innovations of enabling materials (catalysts,
adsorbents, membranes), e
cient processing schemes, robust products portfolios and
smart business strategies are needed to close the priority gap between fossil and the more
complex renewable resources. Co-production of (platform) chemicals and bio-products
can improve the economical basis. Options for thermochemical processing towards fuels
include the pyrolysis route, which is proceeding via bio-oil (BO) upgrading, and the al-
ternative gasification route, which is proceeding via syngas followed by catalytic synthesis,
e.g. Fischer-Tropsch. The number of conditioning and conversion steps that can be
envisaged along both routes needs to be minimized. Basic pretreatment of raw BO is
chemical stabilization, which enables its storage or transport. More advanced upgrading is
required to reach oil qualities suitable for heat and power, and even more advanced for
transport applications (including aviation fuel). Catalysts and hydrogen can provide the
required processing flexibility and product quality. Catalytic hydrodeoxygenation (HDO) is
one of the most attractive upgrading options, enabling removal of heteroatoms, adding
energy, and chemical transformations for tuning of properties. This review focuses on
HDO and the catalytic properties of metal carbides, nitrides and phosphides, the potential
of mesoporous-based catalytic materials, and also of noble metals. An overview of
matured hydrotreating (HT) technology and conventional catalysts for HDS is provided as
the benchmarking technology for developments towards increased biomass utilization.
1 Introduction
The first review dedicated to research on hydrodeoxygenation (HDO) was
published by Furimsky in 1983.
1
Since then, the increased interest in the
field of hydroprocessing of non-conventional feeds has led to significant
research, which has been summarized in several review papers, often
with complementary focus. An overview is given in Table 1.
The thermal removal of chemically bound oxygen from biomass or bio-
oils is by nature a relatively slow process at moderate temperatures. Re-
action rates can be increased by orders of magnitude by using a suitable
catalyst. However, the feedstock is of a nature that introduces severe
challenges to the catalyst, particularly in terms of stability and selectivity,
due to the chemical composition and variability of the feedstock. Still,
