Lignosulfonates

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Lignosulfonates

Lignosulfonates, or sulfonated lignin, (CAS number

CAS registry number

CAS registry numbers are unique numerical identifiers for chemical elements, chemical compound, polymers, biological sequences, mixtures and alloys....
8062-15-5) are water-soluble anionic polyelectrolyte

Polyelectrolyte

Polyelectrolytes are polymers whose repeating units bear an electrolyte group. These groups will dissociation in aqueous solutions , making the polymers charge ....
polymer

Polymer

A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a variety of properties....
s: they are byproducts from the production of wood pulp

Wood pulp

Pulp is a dry fibrous material prepared by chemically or mechanically separating fibers from wood or fiber crops.Pulp can be either fluffy or formed into thick sheets....
using sulfite pulping

Sulfite process

The sulfite process produces wood pulp which is almost pure cellulose fibers by using various salts of sulfurous acid to extract the lignin from wood chips in large pressure vessels called digesters....
.

Most delignification in sulfite pulping involves acidic cleavage of ether

Ether

Ether is a class of organic compounds which contain an ether functional group ? an oxygen atom connected to two alkyl or aryl groups ? of general formula R?O?R....
bonds, which connect many of the constituents of lignin

Lignin

Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae....
. The electrophilic carbocations produced during ether cleavage react with bisulfite ions (HSO₃^-) to give sulfonates.

R-O-R' + H⁺ ? R⁺ + R'OH

R⁺ + HSO₃^- ? R-SO₃H

The primary site for ether cleavage is the a-carbon (carbon atom attached to the aromatic ring) of the propyl

Propyl

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Encyclopedia

Lignosulfonates, or sulfonated lignin, (CAS number

CAS registry number

Polyelectrolyte

Polyelectrolytes are polymers whose repeating units bear an electrolyte group. These groups will dissociation in aqueous solutions , making the polymers charge ....
polymer

Polymer

Wood pulp

Pulp is a dry fibrous material prepared by chemically or mechanically separating fibers from wood or fiber crops.Pulp can be either fluffy or formed into thick sheets....
using sulfite pulping

Sulfite process

Ether

Lignin

R-O-R' + H⁺ ? R⁺ + R'OH

R⁺ + HSO₃^- ? R-SO₃H

The primary site for ether cleavage is the a-carbon (carbon atom attached to the aromatic ring) of the propyl

Propyl

In organic chemistry, propyl is a three-carbon alkyl substituent with chemical formula -Carbon3Hydrogen7. It is the substituent form of the alkane propane....
(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

P-Toluenesulfonic acid

p-Toluenesulfonic acid is an organic compound with the formula methyl groupbenzeneSulfonic acid. TsOH, as it is abbreviated, is a white solid that is soluble in water, alcohols, and other Chemical polarity organic solvents....
. Lignosulfonate have very broad ranges of molecular mass

Molecular mass

The molecular mass of a chemical compound, frequently referred by the older term molecular weight and abbreviated as MW, is the mass of one molecule of that substance, relative to the unified atomic mass unit u ....
(they are very polydisperse

Polydispersity index

In organic chemistry, the polydispersity index , is a measure of the distribution of molecular mass in a given polymer sample. The PDI calculated is the weight average molecular weight divided by the number average molecular weight....
). A range of from 1000–140,000 da

Atomic mass unit

The unified atomic mass unit , or dalton or, sometimes, universal mass unit, is a Units of measurement of mass used to express atomic weight and molecular masses....
has been reported for softwood lignosulfonates with lower values reported for hardwoods.

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

Calcium hydroxide

Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a chemical compound with the chemical formula Calcium2....
. Ultrafiltration and ion-exchange can also be used to separate lignosulfonates from the spent pulping liquid. A list of CAS numbers for the various metal salts of lignosulfonate is available.

Uses

Lignosulfonates have a wide variety of applications.

The single largest use for lignosulfonates is as plasticizers in making concrete

Concrete

Concrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, construction aggregate , water , and Chemistry admixtures....
, 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

Cement

In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together....
, where they act as grinding aids in the cement mill

Cement mill

A cement mill is the equipment used to grind the hard, nodular clinker from the cement kiln into the fine grey powder that is cement. Most cement is currently ground in ball mills....
and as a rawmix

Rawmill

A rawmill is the equipment used to grind raw materials into "rawmix" during the manufacture of cement. Rawmix is then fed to a cement kiln, which transforms it into clinker , which is then ground to make cement in the cement mill....
slurry deflocculant

Deflocculant

A deflocculant is an agent for thinning suspensions or slurries. It is used to reduce viscosity or prevent flocculation and is sometimes incorrectly called a "dispersant." Most deflocculants are low-molecular weight anionic polymers that neutralize positive charges on suspended particles, particularly clays and aryl-alkyl derivative of sul...
(that reduces the viscosity

Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
of the slurry).

Lignosulfonates are also used for the production of plasterboard to reduce the amount of water required to make the stucco

Stucco

Stucco or render is a material made of an Construction aggregate, a binder , and water. Stucco is applied wet and hardens to a very dense solid....
flow and form the layer between two sheets of paper. The reduction in water content allows lower kiln temperatures to dry the plasterboard, saving energy.

The ability of lignosulfonates to reduce the viscosity of mineral slurries is used to advantage in oil drilling mud

Drilling mud

In geotechnical engineering, drilling mud, also known as spud mud , is a drilling fluid used to drill boreholes into the earth. Often used while drilling oil well and natural gas wells and on exploration drilling rigs but can also be used for much simpler boreholes, such as water wells....
, where it replaced tannic acid

Tannic acid

Tannic acid , a commercial form of tannin, is a polyphenol. Its weak acidity is due to these phenol groups in the structure. Tannic acid is a basic ingredient in the chemical staining of wood....
s from quebracho

Quebracho

Quebracho is one of the common names, in Spanish language, of at least three similar species of trees that grow in the Gran Chaco region of South America:...
(a tropical tree).

Lignosulfonates are used to disperse pesticides, dyes, carbon black

Carbon black

Carbon black is a material produced by the incomplete combustion of heavy petroleum products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil....
, and other insoluble solids and liquids into water. They are used in tanning

Tanning

Tanning is the process of making leather, which does not easily Decomposition, from the skins of animals, which do. Often this uses tannin, an acidic chemical compound....
leather

Leather

Leather is a material created through the tanning of rawhides and skins of animals, primarily cattlehide. The tanning process converts the putrescible skin into a durable, long-lasting and versatile natural material for various uses....
. They are also used to suppress dust on unpaved roads.

Oxidation

Redox

Redox describes all chemical reactions in which atoms have their oxidation number changed.This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide or the reduction of carbon by hydrogen to yield methane , or it can be a complex process such as the oxidation of sugar in the human body through a ser...
of lignosulfonates from softwood

Softwood

Softwood is timber obtained from coniferous trees . With the exception of bald cypress, tamarack, and larch, softwood trees are evergreens. Softwood is mostly obtained from the Baltic, Scandinavia, and North America and is the source of about 80% of the world's production of timber....
trees produced vanillin

Vanillin

Vanillin, methyl vanillin, or 4-hydroxy-3-methoxybenzaldehyde, is an organic compound with the molecular formula C8H8O3....
(artificial vanilla flavor), but this is not a current use.

Dimethyl sulfide

Dimethyl sulfide

Dimethyl sulfide or methylthiomethane is an Organosulfur compounds compound with the formula 2S. Dimethyl sulfide is a water-insoluble flammable liquid that boils at 37?C and has a characteristic disagreeable odor....
and dimethyl sulfoxide

Dimethyl sulfoxide

Dimethyl sulfoxide is the chemical compound with the chemical formula 2SO. It was first synthesized in 1866 by the Russian scientist Alexander Saytzeff, who reported his findings in a German chemistry journal in 1867....
(an important organic solvent

Solvent

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseous solute, resulting in a solution.The most common solvent in everyday life is water....
) are produced from lignosulfonates. The first step involves heating lignosulfonates with sulfides or elemental sulfur

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
to produce dimethyl sulfide. The methyl groups come from methyl ethers present in the lignin. Oxidation of dimethyl sulfide with nitrogen dioxide

Nitrogen dioxide

Nitrogen dioxide is the chemical compound with the chemical formula NitrogenOxygen2. One of several nitrogen oxides, NO2 is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year....
produces dimethyl sulfoxide (DMSO).