Lignosulfonates 3049349 201431652 2008-03-27T22:20:33Z Beetstra 855858 moved [[My files]] to [[Lignosulfonates]] over redirect: Move back after vandalism '''Lignosulfonates''', or '''sulfonated lignin''', ([[CAS registry number|CAS number]] 8062-15-5) are water-soluble anionic [[polyelectrolyte]] [[polymer]]s: they are byproducts from the production of [[wood pulp]] using [[sulfite process|sulfite pulping]].<ref name="kirk">{{cite encyclopedia |last=Lebo |first=Stuart E. Jr. |author= |authorlink= |coauthors=Gargulak, Jerry D. and McNally, Timothy J. |editor= |encyclopedia=Kirk‑Othmer Encyclopedia of Chemical Technology |title=Lignin |url=http://www.mrw.interscience.wiley.com/emrw/9780471238966/kirk/article/lignlin.a01/current/pdf |accessdate=2007-10-14 |year=2001 |publisher= John Wiley & Sons, Inc |location= |doi=10.1002/0471238961.12090714120914.a01.pub2 }}</ref> Most delignification in sulfite pulping involves acidic cleavage of [[ether]] bonds, which connect many of the constituents of [[lignin]].<ref name="eero">{{cite book |author= E. Sjöström |title= Wood Chemistry: Fundamentals and Applications |publisher= [[Academic Press]]|year= 1993}}</ref> The [[electrophilic]] [[carbocations]] produced during ether cleavage react with bisulfite ions (HSO<sub>3</sub><sup>-</sup>) to give sulfonates. :R-O-R' + H<sup>+</sup> → R<sup>+</sup> + R'OH :R<sup>+</sup> + HSO<sub>3</sub><sup>-</sup> → R-SO<sub>3</sub>H The primary site for ether cleavage is the α-carbon (carbon atom attached to the aromatic ring) of the [[propyl]] (linear three carbon) side chain. The following structures do not specify the structure since lignin and its derivatives are complex mixtures: the purpose is to give a general idea of the structure of lignosulfonates. The groups labeled "Q" can be a wide variety of groups found in the structure of lignin. Sulfonation occurs on the side chains, not on the aromatic rings, like in [[p-toluenesulfonic acid]]. [[Image:Lignosulfonate.png|450px|center|Generalized structure of lignosulfonates]] Lignosulfonate have very broad ranges of [[molecular mass]] (they are very [[Polydispersity index|polydisperse]]). A range of from 1000–140,000 [[Atomic mass unit|da]] has been reported for softwood lignosulfonates with lower values reported for hardwoods.<ref name="kirk"/> ==Preparation== Lignosulfonates are recovered from the spent pulping liquids (red or brown liquor) from sulfite pulping. The most widely used industrial process is the Howard process, in which 90–95% yields of calcium lignosulfonates (CAS number 904-76-3), are precipitated by adding of excess [[calcium hydroxide]]. Ultrafiltration and ion-exchange can also be used to separate lignosulfonates from the spent pulping liquid.<ref name="kirk"/> A list of CAS numbers for the various metal salts of lignosulfonate is available.<ref>{{cite web|url=http://www.lignin.org/rln.html|title=List of lignosulfonate CAS numbers|accessdate=2007-10-15}}</ref> ==Uses== Lignosulfonates have a wide variety of applications.<ref name="ligno">{{cite web|url=http://www.lignin.org/whatis.html|title=Uses of lignosulfonates|accessdate=2007-10-15}}</ref> The single largest use for lignosulfonates is as [[Plasticizers#Plasticizers for concrete production|plasticizers]] in making [[concrete]],<ref name="kirk"/> where they allow concrete to be made with less water (giving stronger concrete) while maintaining the ability of the concrete to flow. Lignosulfonates are also used during the production of [[cement]], where they act as grinding aids in the [[cement mill]] and as a [[rawmill|rawmix]] slurry [[deflocculant]] (that reduces the [[viscosity]] of the slurry). Lignosulfonates are also used for the production of [[plasterboard]] to reduce the amount of water to, make the [[stucco]] flow, and form the layer between to sheets of paper. This allows lower kiln temperatures to dry the plasterboard and to save energy. The ability of lignosulfonates to reduce the viscosity of mineral slurries is used to advantage in [[oilwell#Life of a well|oil drilling]] [[drilling mud|mud]], where it replaced [[tannic acid]]s from [[quebracho]] (a tropical tree). Lignosulfonates are used to disperse [[pesticides]], [[dyes]],<ref>{{cite web |url=http://www.lignin.org/02marchdialogue.html |title=Dyes (lignosulfonates as dispersants)|accessdate=2007-10-16 |last= |first= |coauthors= |date=March 2002 |work=Dialogue/Newsletters , Vol. 11 No. 1 |publisher=Lignin Institute}}</ref> [[carbon black]],<ref>{{cite web |url=http://www.lignin.org/03marchdialogue.html |title=Carbon Black Dispersion |accessdate=2007-10-16 |last= |first= |coauthors= |date=March 2003 |work=Dialogue/Newsletters Vol. 12 No. 1 |publisher=Lignin Institute}}</ref> and other insoluble solids and liquids into water. They are used in [[tanning]] [[leather]]. They are also used to suppress dust on unpaved roads.<ref>{{cite web |url=http://www.lignin.org/roads.htm |title=Lignins: A Safe Solution for Roads |accessdate=2007-10-16 |last= |first= |coauthors= |date=July 1992 |work=Dialogue/Newsletters Vol.1 No. 3 |publisher=Lignin Institute}}</ref> [[Redox|Oxidation]] of lignosulfonates from [[softwood]] trees produced [[vanillin]] (artificial vanilla flavor), but this is not a current use.<ref>{{cite journal | last = Hocking| first = Martin B.| year = 1997| month = September | title = Vanillin: Synthetic Flavoring from Spent Sulfite Liquor | journal = Journal of Chemical Education| volume = 74| issue = 9| pages = 1055| url = http://jchemed.chem.wisc.edu/hs/Journal/Issues/1997/Sep/abs1055.html | format = PDF| accessdate = 2006-09-09}}</ref> [[Dimethyl sulfide]] and [[dimethyl sulfoxide]] (an important organic [[solvent]]) are produced from lignosulfonates. The first step involves heating lignosulfonates with [[sulfides]] or elemental [[sulfur]] to produce dimethyl sulfide. The [[methyl]] groups come from methyl [[ethers]] present in the lignin. Oxidation of dimethyl sulfide with [[nitrogen dioxide]] produces dimethyl sulfoxide (DMSO). <ref name="kirk"/> ==References== {{reflist}} [[Category:Pulp and paper industry]] [[Category:Petroleum production]] [[Category:Organic polymers]] [[Category:Polyelectrolytes]]