Difference between revisions of "Hydrolysis"

Hydrolysis (view source)

Revision as of 09:46, 17 December 2021

1,756 bytes added , 09:46, 17 December 2021

→‎Pre-treatment

Margaux Lambrecht

Autochecked users, Editors

20

edits

@@ Line 8: / Line 8: @@
 ==== Cellulose ====
-Explain structure of cellulose
+''Explain structure of cellulose''
 ==== Hemi-cellulose ====
-Explain structure of hemi-cellulose
+''Explain structure of hemi-cellulose''
 ==== Lignin ====
-Explain structure of Lignin
+''Explain structure of Lignin''
-=== Pre-treatment ===
+== Process and technologies ==
+=== Chemical processing ===
+Chemical pretreatments have been used extensively for removal of lignin surrounding cellulose and for destroying its crystalline structure. Even though chemical pretreatments are usually effective, they have disadvantages which should not be ignored [10]. These include use of specialized corrosion resistant equipment, need for extensive washing, and disposal of chemical wastes. Various chemical methods are discussed under several headings, namely, alkalis, acids, gases, oxidizing agents, cellulose solvents, extraction, and swelling agents.
+==== Acid ====
+'''Acid hydrolysis''' is a hydrolysis process in which a protic acid is used to catalyze the hydrolysis reaction. Acids are used mainly for hydrolysis of cellulose [10]. A strong acid, such as formic, hydrochloric, nitric, phosphoric, or sulphuric acid can be used in concentrated or diluted form. '''Concentrated acid''' (10-30 %) can penetrate the lignin structure and break down the cellulose and hemicellulose to individual sugars at low temperature and with high yield. Downsides are the high acid consumption and high corrosion potential. These downsides are circumvented with the use of '''diluted acid''' (2-5 %). However, in the latter case, higher temperature is required, which can lead to side product formation such as furfural and 5-hydroxymethyl-furfural.<ref name=":1">{{Cite book|author=Alessandra Verardi, Isabella De Bari, Emanuele Ricca and Vincenza Calabrò|year=2012|section_title=Hydrolysis of Lignocellulosic Biomass: Current Status of Processes and Technologies and Future Perspectives|editor=Marco Aurelio Pinheiro Lima and Alexandra Pardo Policastro Natalense|book_title=Bioethanol|publisher=IntechOpen}}</ref>
+===== Sulfuric acid =====
+''Elaborate more the reactions conditions and give some examples from literature.''
-* [[Sizing]]
+===== '''Hydrochloric acid''' =====
-*....
+''Elaborate more the reactions conditions and give some examples from literature.''
-== Process and technologies ==
+===== Phosphoric acid =====
+''Elaborate more the reactions conditions and give some examples from literature.''
+==== Alkali ====
+'''Alkaline hydrolysis''' refers to hydrolysis reactions using hydroxide, commonly from sodium hydroxide or calcium hydroxide. The hydroxide breaks down the lignin bonds to make the cellulose more accessible. The reaction proceeds at lower temperature and pressure and residual alkali can be recycled. However, the pretreatment does result in irrecoverable salts in the product.<ref>{{Cite journal|title=Pretreatment of lignocellulosic sugarcane leaves and tops for bioethanol production|year=2020-01-01|journal=Lignocellulosic Biomass to Liquid Biofuels|page=301–324|doi=10.1016/B978-0-12-815936-1.00010-1|author=S. Niju, M. Swathika, M. Balajii|volume=}}</ref>
+===== Sodium hydroxide =====
+Dilute sodium hydroxide (NaOH) treatment of lignocellulosic material causes swelling, leading to an increase in internal surface area, decrease in the degree of polymerization, decrease in crystallinity, separation of structural linkages between lignin and carbohydrates, and disruption of the lignin structure [10].
+''Elaborate more the reactions conditions and give some examples from literature.''
+===== '''Ammonia''' =====
+Liquid or gaseous ammonia acts as a strong swelling agent for cellulose [1].
+''Elaborate more the reactions conditions and give some examples from literature.''
+===== Ammonium sulfite =====
+Ammonium sulfite is used mainly in a conventional pulping process.
-=== Acid ===
+''Elaborate more the reactions conditions and give some examples from literature.''
-'''Acid hydrolysis''' is a hydrolysis process in which a protic acid is used to catalyze the hydrolysis reaction. A strong acid, such as formic, hydrochloric, nitric, phosphoric, or sulphuric acid can be used in concentrated or diluted form. '''Concentrated acid''' (10-30 %) can penetrate the lignin structure and break down the cellulose and hemicellulose to individual sugars at low temperature and with high yield. Downsides are the high acid consumption and high corrosion potential. These downsides are circumvented with the use of '''diluted acid''' (2-5 %). However, in the latter case, higher temperature is required, which can lead to side product formation such as furfural and 5-hydroxymethyl-furfural.<ref name=":1">{{Cite book|author=Alessandra Verardi, Isabella De Bari, Emanuele Ricca and Vincenza Calabrò|year=2012|section_title=Hydrolysis of Lignocellulosic Biomass: Current Status of Processes and Technologies and Future Perspectives|editor=Marco Aurelio Pinheiro Lima and Alexandra Pardo Policastro Natalense|book_title=Bioethanol|publisher=IntechOpen}}</ref>
-=== Alkali ===
-'''Alkaline hydrolysis''' refers to hydrolysis reactions using hydroxide, commonly from sodium hydroxide or calcium hydroxide. The hydroxide breaks down the lignin bonds to make the cellulose more accessible. The reaction proceeds at lower temperature and pressure and residual alkali can be recycled. However, the pretreatment does result in irrecoverable salts in the product.<ref>{{Cite journal|title=Pretreatment of lignocellulosic sugarcane leaves and tops for bioethanol production|year=2020-01-01|journal=Lignocellulosic Biomass to Liquid Biofuels|page=301–324|doi=10.1016/B978-0-12-815936-1.00010-1|author=S. Niju, M. Swathika, M. Balajii|volume=}}</ref>
 === Salt ===