Chromatographic recovery of chemicals from acidic biomass hydrolysates
Heinonen, Jari (2013-12-13)
Väitöskirja
Heinonen, Jari
13.12.2013
Lappeenranta University of Technology
Acta Universitatis Lappeenrantaensis
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-265-527-1
https://urn.fi/URN:ISBN:978-952-265-527-1
Tiivistelmä
Lignocellulosic biomasses (e.g., wood and straws) are a potential renewable source for the
production of a wide variety of chemicals that could be used to replace those currently
produced by petrochemical industry. This would lead to lower greenhouse gas emissions and
waste amounts, and to economical savings.
There are many possible pathways available for the manufacturing of chemicals from
lignocellulosic biomasses. One option is to hydrolyze the cellulose and hemicelluloses of
these biomasses into monosaccharides using concentrated sulfuric acid as catalyst. This
process is an efficient method for producing monosaccharides which are valuable platforn
chemicals. Also other valuable products are formed in the hydrolysis. Unfortunately, the
concentrated acid hydrolysis has been deemed unfeasible mainly due to high chemical
consumption resulting from the need to remove sulfuric acid from the obtained hydrolysates
prior to the downstream processing of the monosaccharides. Traditionally, this has been done
by neutralization with lime. This, however, results in high chemical consumption. In addition,
the by-products formed in the hydrolysis are not removed and may, thus, hinder the
monosaccharide processing. In order to improve the feasibility of the concentrated acid
hydrolysis, the chemical consumption should be decreased by recycling of sulfuric acid
without neutralization. Furthermore, the monosaccharides and the other products formed in
the hydrolysis should be recovered selectively for efficient downstream processing. The
selective recovery of the hydrolysis by-products would have additional economical benefits
on the process due to their high value.
In this work, the use of chromatographic fractionation for the recycling of sulfuric acid and
the selective recovery of the main components from the hydrolysates formed in the
concentrated acid hydrolysis was investigated. Chromatographic fractionation based on the
electrolyte exclusion with gel type strong acid cation exchange resins in acid (H+) form as a
stationary phase was studied.
A systematic experimental and model-based study regarding the separation task at hand was
conducted. The phenomena affecting the separation were determined and their effects
elucidated. Mathematical models that take accurately into account these phenomena were
derived and used in the simulation of the fractionation process. The main components of the
concentrated acid hydrolysates (sulfuric acid, monosaccharides, and acetic acid) were
included into this model. Performance of the fractionation process was investigated
experimentally and by simulations. Use of different process options was also studied. Sulfuric acid was found to have a significant co-operative effect on the sorption of the other
components. This brings about interesting and beneficial effects in the column operations. It
is especially beneficial for the separation of sulfuric acid and the monosaccharides.
Two different approaches for the modelling of the sorption equilibria were investigated in this
work: a simple empirical approach and a thermodynamically consistent approach (the
Adsorbed Solution theory). Accurate modelling of the phenomena observed in this work was
found to be possible using the simple empirical models. The use of the Adsorbed Solution
theory is complicated by the nature of the theory and the complexity of the studied system. In
addition to the sorption models, a dynamic column model that takes into account the volume
changes of the gel type resins as changing resin bed porosity was also derived.
Using the chromatography, all the main components of the hydrolysates can be recovered
selectively, and the sulfuric acid consumption of the hydrolysis process can be lowered
considerably. Investigation of the performance of the chromatographic fractionation showed
that the highest separation efficiency in this separation task is obtained with a gel type resin
with a high crosslinking degree (8 wt. %); especially when the hydrolysates contain high
amounts of acetic acid. In addition, the concentrated acid hydrolysis should be done with as
low sulfuric acid concentration as possible to obtain good separation performance. The
column loading and flow rate also have large effects on the performance.
In this work, it was demonstrated that when recycling of the fractions obtained in the
chromatographic fractionation are recycled to preceding unit operations these unit operations
should included in the performance evaluation of the fractionation. When this was done, the
separation performance and the feasibility of the concentrated acid hydrolysis process were
found to improve considerably.
Use of multi-column chromatographic fractionation processes, the Japan Organo process and
the Multi-Column Recycling Chromatography process, was also investigated. In the studied
case, neither of these processes could compete with the single-column batch process in the
productivity. However, due to internal recycling steps, the Multi-Column Recycling
Chromatography was found to be superior to the batch process when the product yield and the
eluent consumption were taken into account.
production of a wide variety of chemicals that could be used to replace those currently
produced by petrochemical industry. This would lead to lower greenhouse gas emissions and
waste amounts, and to economical savings.
There are many possible pathways available for the manufacturing of chemicals from
lignocellulosic biomasses. One option is to hydrolyze the cellulose and hemicelluloses of
these biomasses into monosaccharides using concentrated sulfuric acid as catalyst. This
process is an efficient method for producing monosaccharides which are valuable platforn
chemicals. Also other valuable products are formed in the hydrolysis. Unfortunately, the
concentrated acid hydrolysis has been deemed unfeasible mainly due to high chemical
consumption resulting from the need to remove sulfuric acid from the obtained hydrolysates
prior to the downstream processing of the monosaccharides. Traditionally, this has been done
by neutralization with lime. This, however, results in high chemical consumption. In addition,
the by-products formed in the hydrolysis are not removed and may, thus, hinder the
monosaccharide processing. In order to improve the feasibility of the concentrated acid
hydrolysis, the chemical consumption should be decreased by recycling of sulfuric acid
without neutralization. Furthermore, the monosaccharides and the other products formed in
the hydrolysis should be recovered selectively for efficient downstream processing. The
selective recovery of the hydrolysis by-products would have additional economical benefits
on the process due to their high value.
In this work, the use of chromatographic fractionation for the recycling of sulfuric acid and
the selective recovery of the main components from the hydrolysates formed in the
concentrated acid hydrolysis was investigated. Chromatographic fractionation based on the
electrolyte exclusion with gel type strong acid cation exchange resins in acid (H+) form as a
stationary phase was studied.
A systematic experimental and model-based study regarding the separation task at hand was
conducted. The phenomena affecting the separation were determined and their effects
elucidated. Mathematical models that take accurately into account these phenomena were
derived and used in the simulation of the fractionation process. The main components of the
concentrated acid hydrolysates (sulfuric acid, monosaccharides, and acetic acid) were
included into this model. Performance of the fractionation process was investigated
experimentally and by simulations. Use of different process options was also studied. Sulfuric acid was found to have a significant co-operative effect on the sorption of the other
components. This brings about interesting and beneficial effects in the column operations. It
is especially beneficial for the separation of sulfuric acid and the monosaccharides.
Two different approaches for the modelling of the sorption equilibria were investigated in this
work: a simple empirical approach and a thermodynamically consistent approach (the
Adsorbed Solution theory). Accurate modelling of the phenomena observed in this work was
found to be possible using the simple empirical models. The use of the Adsorbed Solution
theory is complicated by the nature of the theory and the complexity of the studied system. In
addition to the sorption models, a dynamic column model that takes into account the volume
changes of the gel type resins as changing resin bed porosity was also derived.
Using the chromatography, all the main components of the hydrolysates can be recovered
selectively, and the sulfuric acid consumption of the hydrolysis process can be lowered
considerably. Investigation of the performance of the chromatographic fractionation showed
that the highest separation efficiency in this separation task is obtained with a gel type resin
with a high crosslinking degree (8 wt. %); especially when the hydrolysates contain high
amounts of acetic acid. In addition, the concentrated acid hydrolysis should be done with as
low sulfuric acid concentration as possible to obtain good separation performance. The
column loading and flow rate also have large effects on the performance.
In this work, it was demonstrated that when recycling of the fractions obtained in the
chromatographic fractionation are recycled to preceding unit operations these unit operations
should included in the performance evaluation of the fractionation. When this was done, the
separation performance and the feasibility of the concentrated acid hydrolysis process were
found to improve considerably.
Use of multi-column chromatographic fractionation processes, the Japan Organo process and
the Multi-Column Recycling Chromatography process, was also investigated. In the studied
case, neither of these processes could compete with the single-column batch process in the
productivity. However, due to internal recycling steps, the Multi-Column Recycling
Chromatography was found to be superior to the batch process when the product yield and the
eluent consumption were taken into account.
Kokoelmat
- Väitöskirjat [1036]