Catalytic Conversion of Lignin for the Production of Aromatics

244 Pages·2013·12.92 MB·English

Catalytic Conversion of Lignin for the
Production of Aromatics
ISBN: 978-90-393-6001-9
Printed by: Gildeprint Drukkerijen - www.gildeprint.nl
Catalytic Conversion of Lignin for the
Production of Aromatics
De Katalytische Omzetting van Lignine voor de Productie van
(met eeAnr soammaetnivsacthtein Cg hine mheitc Naleidëenrlands)
Proefschrift
ter verkrijging van de graad van doctor aan de Universiteit Utrecht op gezag
van de rector magnificus, prof.dr. G.J. van der Zwaan, ingevolge het besluit
van het college voor promoties in het openbaar te verdedigen op woensdag 11
september 2013 des ochtends te 10.30 uur
door
Anna Louise Jongerius
geboren op 1 oktober 1985 te Zaandam
Promotor: Prof.dr.ir. B.M. Weckhuysen
Co-promotor: Dr. P.C.A. Bruijnincx
This research was funded by the Smart Mix Program of the Netherlands Ministry
of Economic Affairs and the Netherlands Ministry of Education, Culture and Science
within the framework of the CatchBio Program.
Contents
Chapter 1:
Chapter 2: General Introduction 7
Lignin: Structure, Chemistry and Catalysis 21
Part I: Lignin Depolymerization
Chapter 3:
Lignin Solubilization and Aromatics Production by Liquid- 79
Chapter 4: Phase Reforming and Hydrogenation
Stability of a Pt/γ-Al2O3 Catalyst in Lignin Liquid-Phase 99
Chapter 5: Reforming Reactions
Lignin Depolymerization by Alkaline Hydrogen Peroxide 123
Treatment
Part II: Hydrodeoxygenation of Lignin Model Compounds
Chapter 6:
CoMo Sulfide-Catalyzed Hydrodeoxygenation of Lignin Model 149
Chapter 7: Compounds
W2C and Mo2C-Catalyzed Hydrodeoxygenation of the Lignin 173
Model Compounds Guaiacol
Part III: Combined Depolymerization and Hydrodeoxygenation of Lignin
Chapter 8:
Liquid-Phase Reforming and Hydrodeoxygenation as a Two- 195
Step Route to Aromatics from Lignin
Chapter 9a:
Chapter 9b:
Summary and Concluding Remarks 213
List of Publi catiNonedserlandse Samenvatting 225
Dankwoord
Curriculum Vitae 237
239
243

Chapter 1
General Introduction
Chapter 1
1.1 Introduction
With the depletion of fossil fuels as a source for fuels, chemicals, and energy, the
fraction of energy and chemicals supplied by renewable resources such as biomass can
be expected to increase in the foreseeable future. Furthermore, in an effort to limit the
greenhouse effect by reducing the CO2 that is released into the environment, several
governments have passed legislation mandating increases in energy and chemical
production from renewable resources, especially biomass. The U.S. Department of
Agriculture and U.S. Department of Energy have, for instance, set ambitious goals
to derive 20% of transportation fuels and 25% of U.S. chemical commodities from
biomass by 2030. [1] The European Union has set a mandatory target of 20% for the
renewable energy’s share of energy consumption by 2020 and a mandatory minimum
target of 10% for biofuels for all member states. [2] These goals have contributed to
the current, intensified interest in the development of technology and processes for
biomass valorization. Such processing of biomass to value-added products and energy
is envisaged to take place in so-called biorefineries. In direct analogy to current
petroleum refineries, which produce fuels and chemicals from crude oil, a biorefinery
is a facility that produces multiple products including fuel, power, and bulk or fine
chemicals from biomass. It is important to note that the economic necessity for a
biorefinery to produce chemicals in addition to biofuels has been strongly advocated.
[3] Indeed, the integrated production of fuels and commodity chemicals is deemed
necessary to justify construction of the biorefinery and allow a high energy impact as
well as proper return on investment. [4]
The recent ‘shale gas revolution’ that is currently predominantly taking place in the
US but might soon be followed by other countries, is impacting the implementation of
renewable alternative feedstocks. The production of this new source of fossil fuels
increased from only 1% of the total US natural gas production in 2000 to 20% in 2009.
[5] With shale gas production expected to expand over the coming years, the prices
of fossil fuel-based energy will not increase as dramatically as predicted and as a
result the urgency to find alternatives to replace fossil fuels as an energy feedstock
is decreasing, at least from an economic perspective. This shift in feedstock will
also have important ramifications for commodity chemicals production. Currently,
the commodity chemicals that form the basis of the chemical industry, i.e. ethylene,
propylene, butadiene, benzene, toluene and xylenes (BTX), are produced via cracking
crude oil and further conversion of the naphtha fraction. The shift to lighter feeds
for the crackers will affect the product composition after cracking and as a result
8
General Introduction
the availability of bulk chemicals. Although ethylene and propylene can be obtained
via steam cracking of natural gas, the production of in particular butadiene and BTX
from lighter feeds such as (shale) gas is very limited. [6] Indeed, the increased use
of natural gas in the US has already resulted in an increase in butadiene prices. [7]
To address the expected shortages of these important chemicals, new, dedicated
routes for the on-purpose production of butadiene or BTX, preferably from renewable
resources, are highly desired. The development of routes for the production of liquid
fuels and chemicals from renewable resources therefore has lost none of its urgency
and demands even more attention.
Although all kinds of biomass can in principle be converted into fuels and chemicals,
the use of edible crops for these purposes cannot be justified in a world with our
current population density. To prevent competition with the use of land and resources
used for the production of food, it is recommended to use so-called second-generation
biomass for the production of fuels and chemicals. Lignocellulosic biomass, a typical
example of such a second-generation feedstock, consists mainly of non-edible
cellulose, hemicellulose and lignin. It can be harvested as a waste product from food-
producing crops such as sugarcane and cornstalks, or can be obtained from wood and
purpose-grown crops such as switch grass and wild perennial vegetation able to grow
on non-arable land. [8] Separation of lignocellulosic biomass into its components and
processing the components to value-added products and energy will take place in
biorefinery operations, as discussed above. Again in analogy with the petrochemical
refineries, efficient use of the renewable resource demands that all components of
lignocellulosic biomass are valorized for the biorefinery to be economically viable.
The carbohydrate fraction of lignocellulose can be used for commercial production of
fuels (e.g. bioethanol) and chemicals (e.g. 1,3-propanediol or succinic acid) by means of
fermentation or chemocatalytic conversion. The development of commercial processes
for the conversion of lignin lags behind, however. Currently operating biorefineries
such as the commercial pilot plant of POET-DSM [9] and the integrated biorefining
process of Roquette [10] receive and process enormous quantities of biomass,
generating large amounts of lignin; valorization of also this component, for instance
by converting it into fuels and chemicals, is imperative for economic profitability.
The Borregaard biorefining process provides a successful example of the integration
of lignin valorization in the biorefinery. Borregaard already produces lignin-based
products such as binding and dispersing agents and is the main supplier of synthetic
vanillin (3-methoxy-4-hydroxybenzaldehyde). [11] Vanillin is used extensively in
foods and perfumes because of its flavor but also finds use in medicinal applications
9
Chapter 1
or as a platform chemical for pharmaceuticals production. [12, 13] Nevertheless, the
market for vanillin is very small compared to the total amount of available lignin. To
achieve complete integration of lignin in the biobased economy, more focus on the
development of processes for lignin valorization to bulk chemicals and fuels is clearly
desired.
Lignin is a natural, polyaromatic and amorphous polymer that acts as the
essential glue that gives plants their structural integrity. It is a main constituent
of lignocellulosic biomass (15-30% by weight, up to 40% by energy). [1] A detailed
overview of lignin chemistry, structure and pretreatment methods is given in Chapter
2, in addition to an overview of catalytic lignin conversion processes. As of 2004, the
pulp and paper industry alone produced 50 million tons of extracted lignin, yet the
existing markets for lignin products remain limited and are concerned with low value
products such as dispersing or binder applications in asphalt, cement or polymers.
High value products such as vanillin can only be obtained in relatively low yields
with high process costs and serve markets of limited volume. [14] As a result, only
approximately 2% of the lignins that are available from the pulp and paper industry
are currently used commercially with the remainder simply being burned as a low
value fuel. [15] Nevertheless, lignin holds considerable potential as a renewable
resource for the sustainable production of fuels and bulk chemicals. [1, 16] With its
unique aromatic structure and chemical properties, liquid fuels and a wide variety
of bulk and fine chemicals, particularly aromatic compounds, which will become less
available with the increased use of shale gas, can potentially be obtained from lignin.
Although routes have been reported for the transformation of sugars into aromatics,
p
for example via a Diels-Alder reaction of sugar-derived furanics, [17] and commercial
processes are being developed for the production of -xylene from isobutanol [18]
or biomass-derived alcohols and aldehydes, [19] lignin is the most obvious candidate
to become the major aromatic resource of a future bio-based economy. Utilisation of
the full potential of this large resource is hampered, however, by the current lack of
efficient technologies that both depolymerize and lower the oxygen content of lignin,
but leave the aromaticity intact.
The realization of biorefinery schemes with fully integrated lignin valorization
processes requires the development of catalytic technology to perform the desired
depolymerization of lignin. New approaches and strategies will have to be developed
to achieve this. Cleavage of the primary linkages of lignin will ultimately result in
formation of monomeric aromatic compounds, which depending on the cleavage
10