Synthesis of renewable surfactants using hydroxycarboxylic acids : valorisation of pulping black liquor
Crigna, Giorgia (2024)
Diplomityö
2024
School of Engineering Science, Kemiantekniikka
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe202401092044
https://urn.fi/URN:NBN:fi-fe202401092044
Tiivistelmä
Surfactants are amphiphiles, i.e., they have a hydrophobic and a hydrophilic moiety that confer these molecules peculiar properties, in fact they collect at interfaces between two phases and affect the surface tension. For this reason, they are used for solubilisation, stabilisation, emulsifications and so on. As a result, they are widely applied in several industries.
Surfactants, nowadays, are mostly produced from non-renewables and/or non-sustainable raw materials, in addition to that they end up in water streams and can affect the ecosystems if not biodegradable.
The most sustainable way to produce surfactants is to use waste or side streams to valorise them. In countries where the forestry industry is well developed, such as Finland, side streams resulting from pulping of cellulose-rich materials is very abundant, this stream is called black liquor (BL) and contains among others, hydroxycarboxylic acids. However, BL is mostly burned for energy. Among the hydroxycarboxylic acids, there are the so called GISAs (glucoiosaccharinic acids) which have attracted a lot of attention due to their many -OH groups which makes them perfect as hydrophilic head of surfactants.
Here BL was produced from microcrystalline cellulose at 180°C and 160°C, with the latter having the highest GISAs content. After liberating the hydroxy acids, they were applied in the synthesis of surfactants by combining them with fatty acids and amines. Different reaction conditions, catalysts and solvents were tried to find the most suitable conditions.
Difficulties were encountered in identifying the products due to the high presence of impurities and underdeveloped analysis methods. The most successful reaction was the mechanic synthesis of GISA-dodecanamide, which was detected in sufficient amount to perform contact angle experiment to visualise its effect when present in a mixture.
After these experiments, one step purification was done on the raw acid mixture to remove part of the impurities. This mixture was then used to perform other reactions. The compounds forming/consuming were monitored however the identification of products and byproducts was not possible with the available analysis.
As many reaction conditions and methods were attempted, this research served as a tool to gather experience and put good bases for further work on this topic.
Surfactants, nowadays, are mostly produced from non-renewables and/or non-sustainable raw materials, in addition to that they end up in water streams and can affect the ecosystems if not biodegradable.
The most sustainable way to produce surfactants is to use waste or side streams to valorise them. In countries where the forestry industry is well developed, such as Finland, side streams resulting from pulping of cellulose-rich materials is very abundant, this stream is called black liquor (BL) and contains among others, hydroxycarboxylic acids. However, BL is mostly burned for energy. Among the hydroxycarboxylic acids, there are the so called GISAs (glucoiosaccharinic acids) which have attracted a lot of attention due to their many -OH groups which makes them perfect as hydrophilic head of surfactants.
Here BL was produced from microcrystalline cellulose at 180°C and 160°C, with the latter having the highest GISAs content. After liberating the hydroxy acids, they were applied in the synthesis of surfactants by combining them with fatty acids and amines. Different reaction conditions, catalysts and solvents were tried to find the most suitable conditions.
Difficulties were encountered in identifying the products due to the high presence of impurities and underdeveloped analysis methods. The most successful reaction was the mechanic synthesis of GISA-dodecanamide, which was detected in sufficient amount to perform contact angle experiment to visualise its effect when present in a mixture.
After these experiments, one step purification was done on the raw acid mixture to remove part of the impurities. This mixture was then used to perform other reactions. The compounds forming/consuming were monitored however the identification of products and byproducts was not possible with the available analysis.
As many reaction conditions and methods were attempted, this research served as a tool to gather experience and put good bases for further work on this topic.