Production of x Tonnes

8/3/2019 Production of x Tonnes

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CHAPTER ONE

1.0 INTRODUCTION

Detergents and their ingredients have recently been the subject of public environmental interest.

Individual chemicals have attracted various levels of attention because of their high level of

environmental pollution. This has led to the industry making efforts towards ecological

optimization of detergents. Several research projects have been undertaken with this in mind, and

have produced reliable basic information.

Linear alkylbenzene sulfonate is the worlds largest-volume synthetic surfactant and is widely

used in household detergents as well as in numerous industrial applications. It was developed as

a biodegradable replacement for nonlinear alkylbenzene sulfonate and has largely replaced

branched alkyl benzene sulfonate in household detergents throughout the developed countries.

1.1 WHAT IS SODIUM ALKYLBENZENE SULFONATE?

Sodium dodecylbenzenesulfonate is a series of organic compounds with the formula

C12H25C6H4SO3Na. It is a colourless salt with useful properties as a surfactant. It is usually

produced as a mixture of related sulfonates. It is a major component of laundry detergent

Fig 1.0 Structural formula of sodium dodecylbenzene sulfonate


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Table 1.0 Table showing formula and various names of sodium dodecylbenzene sulfonate

1.1.1 PROPERTIES OF SODIUM DODECYLBENZENE SULFONATE.

The following are properties of sodium dodecylbenzene sulfonate include the following:

1) It has the physical appearance of a white or light yellow flake2) It is soluble in water with a solubility of 5-10mg/ml at 66 o F3) It has a molecular weight of 348.49g/mol and melting point of 572 o F4) It has a flash point of over 200 o F

1.2 USES OF SODIUM DODECYLBENZENE SULFONATE

Sodium dodecylbenzene sulfonate can be used as raw material to produce kinds of detergent,

emulsion. Such as laundry powder, dish wash cleaner in daily chemical industrial; cleaner,

dyeing assistant in textile industrial; degrease agent in electroplate, leather; de-inking agent in

papering.


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1.3 METHODS FOR PRODUCING SODIUM DODECYL BENZENE SULFONATE

Sodium dodecylbenzene sulfonate is prepared commercially by sulfonating dodecylbenzene with

either oleum (10-25% sulfur trioxide [SO3] in sulfuric acid) or an SO3-air mixture and then

neutralizing with sodium hydroxide solution. In both processes, sulfur trioxide is the sulfonating

agent and the major product is the sodium dodecylbenzene sulfonic acid. Both batch and

continuous processes are used.

1.3.1 Sulfonation of dodecylbenzene with oleumIn a typical batch oleum sulfonation process, oleum is added to the dodecylbenzene reaction

mixture. Under normal conditions, 1.0-1.2 pounds of oleum are required per pound of

dodecylbenzene. The reaction temperature is carefully controlled while the acid is added, and the

reaction goes on to completion during a 30 to 45 minute digestion period. Excessive time or

temperature produces undesirable dark-colored products.

In a typical continuous oleum sulfonation process, oleum and dodecylbenzene are proportioned

to a reactor mixing head exchanger. The reaction is generally completed in eight to fifteen

minutes. Whether batch or continuous, the reaction is carried out until sulfonation is 98-99%

complete.

Sulfonation with oleum produces dodecylbenzene sulfonic acid containing considerable excess

sulfuric acid. If this material is neutralized with aqueous sodium hydroxide, the resulting low-

active detergent slurry contains about four parts of sodium sulfate for every six parts of the active

dodecylbenzene. These low-active detergent slurries are somewhat restricted in their application

because of the high sodium sulfate content. This shortcoming of the oleum-derived products may

be partially overcome by adding enough water to the final sulfonation reaction mixture to dilute

the sulfuric acid present from about 98% to 71-72%. At this concentration, the sulfuric acid is

insoluble in the dodecylbenzene sulfonic acid and seperates as a second layer. Decanting of this

sulfuric acid layer leaves an upper phase containing 87-90% dodecyl sulfonic acid and also 7-9%

sulfuric acid. When this product is neutralized with caustic soda, a high-active detergent slurry

results.


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1.3.2 Sulfonation of dodecylbenzene with oleumIn a typical batch SO3

-air process, liquid sulfur trioxide is vaporized in a stream of dry air and

the resulting 5-15% SO3 stream is then reacted with the dodecylbenzene. As in the oleum

processes, good mixing and heat removal are necessary to avoid oxidation and charring, which

result in dark-colored products. The reaction mixture is digested to complete the reaction. Air

and the small remaining excess of sulfur trioxide (only a 3-5% molar excess is used) are

removed. The reaction mixture is then hydrated with a small amount of water to hydrolyze and

dodecylbenzene sulfonic acid anhydrides present in the reaction mixture. In continuous SO3- air

processes, the color of the sulfonic acid products is improved by careful control and maintenance

of reaction temperatures. Variations in the method of temperature control include recycling the

reaction mixture through heat exchangers and the use of two or more reactors connected in

series. When the mixture is neutralized with sodium hydroxide, a 96-97% sulfonate product is

obtained.

1.4 PROCESS ROUTE CHOSEN AND JUSTIFICATION

The process route which will be used for the purpose of this design is the method of sulfonation

of dodecylbenzene with oleumand the oleum used in the sulfonation process is produced from

the raw material sulfur.

Justification of Selected Process

This process of manufacturing sodium dodecyl benzene sulfonate (C12H25C6H4SO3Na) is from

the available raw material of benzene, dodecene and sulfur. This process allows the

maximazation of the available raw material through the presence of distillation columns which

allows for the recycle of benzene and dodecene.

Also the process also gives room for purity which enhances the quality of product. The presence

of seperators to remove impurities such as spent acid (H2S04) from the Deodecylbenzenesulfonic

acid generated from the sulfornator and this in turn can be used in the contact process to produce

oleum.

The method involving sulfur trioxide has not been selected for the following reasons:

1. It is highly exothermic thus requiring extra expense on cooling equipment.


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2. It cannot be added directly to the alkyl hydrocarbon because extensive charring anddealkylation of the alkylaromatic will take place.

3. It is a very difficult process to control.The Oleum method is the more acceptable method of production when the the desired end

product is expected in powder form. Its principal disadvantage is the formation of sodium

sulphate but this can be remedied by the addition of water which reduces the concentration of the

acid produced. The inability of the acid produced to dissolve in LAS acid results in a separate

layer formation. Decanting of this layer gives a highly concentrated alkyl sulphonic acid whose

neutralization will give highly-active detergent slurry.

But it must be noted that a benefit of the above mentioned method is that it requires

lower-cost reagents and the product formed has lower sodium sulphate content. Also this method

is suitable for the production of liquid- based detergents. This method gives quality product at a

very good overall economic analysis.

1.5 PROCESS DESCRIPTION

1.5.1 ALKYLATION

The alkylation process chosen is the FriedelCrafts alkylation which involves the

alkylation of an aromatic ring with an alkyl halide using a strong Lewis acid catalyst. With

anhydrous ferric chloride as the catalyst, the alkyl group attaches at the former site of the

chloride ion. For the purpose of this design, the alkylation process is the reaction of dodecene

with benzene in the presence of ferric chloride catalyst (AlCl3).

C6H6 + C12H24 AlCl3 C6H5C12H25

The alkylation process is in a reaction vessel (alkylator) and the reaction maintained at 45 0C

maximum.

The intermediate product at this stage is dodecylbenzene. An excess of benzene is used to

suppress the formation of by-products. Aluminum chloride requirement is 10 wt% of dodecene.


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After removal of aluminum chloride sludge, the reaction mixture is fractionated to recover

excess benzene (which is recycled to the reaction vessel), a light alkyl aryl hydrocarbon,

dodecylbenzene, and a heavy alkyl aryl hydrocarbon.

1.5.2SULFONATION.

A continuous sulfonation of the dodecylbenzene is chosen using 20 percent oleum as

opposed to sulfuric acid and anhydrous sulfur trioxide and a batch process. The process is very

exothermic but to be maintained (cooled) at a temperature of 38-600C with 55

0C chosen.

C6H5C12H25 + H2SO4 C12H25C6H4SO3H + H2O

Removal of the spent sulfuric acid from the sulfonic acid is facilitated by adding water to

reduce the sulfuric acidstrength to about 78 percent. This dilution prior to neutralization results

in a finalneutralized slurry having approximately 85 percent active agent based on the solids.

Due to the fact that the available material is sulfur and not oleum , a by-process of producing

oleum(25% SO3) from sulfur is designed as well. Oleum is gotten as a by-product from the

contact process. Sulfur is burnt in excess air allowing for the oxidation of sulfur to SO2 and

subsequently to SO3. Purification of air and SO2 is necessary before conversion to SO3 as a

process condition. Hydrochloric acid is used to absorb SO3 to give the needed oleum.

1.5.3 NEUTRALIZATION

The sulfonic acid is neutralized with 40 percent caustic soda solution to a pH of

8 and at a temperature of about 500C. Chemical builders are added to enhance the detersive,

wetting, and other desired properties in the finished product.

C12H25C6H4SO3H + NaOH C12H25C6H4SO3Na + H2O

A bead product is obtained by spray drying.

The Block Flow Diagram of the process showing the manufacture of sodium dodecylbenzene

sulfonate with the key points is shown below:


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1.6 PROPERTIES OF RAW MATERIALS

1.6.1 DODECENE

Physical propertiesDodecene is a clear water-white, mobile liquid with a molecular formula of C12H24 and

molecular weight of 168.319, a boiling point of 2130C, freezing point of -350C and a flash point

temperature of 770C(explosive vapor/air mixtures are formed at this temperature). It is insoluble

in water but soluble in hydrocarbon solvents.

Chemical propertiesDodecene reacts with strong oxidants, halogens (such as chlorates and nitrates) and inorganic

acids. Attacks rubber, paints and lining materials.

Storage


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Dodecene is stored under a nitrogen blanket. It is not corrosive to steel or aluminum. Contact

with air, water or oxygen should be avoided because alpha olefins are sensitive to moisture and

auto-oxidation which form impurities that can interface with subsequent reactions.

1.6.2 BENZENE

Physical propertiesBenzene is a clear, colorless to light yellow aromatic hydrocarbon with a sweet odour but highly

inflammable, has a molecular formula of C6H6 and a molecular weight of 78.11. Benzene's

solubility in water is 1750 mg/L at 25 degrees C. It readily mixes with ethanol, ethyl ether,

acetone and chloroform. Its melting point is 5.50C and the boiling point is 80.1

0C. It has a flash

point of -110C.

Chemical propertiesBenzene is incompatible with strong oxidizing agents, many fluorides, many perchlorates and

nitric acid. Benzene is an excellent ligand in the organometallic chemistry of low-valent metals

1.6.3 ALUMINIUM CHLORIDE

Physical PropertiesAluminium chloride (AlCl3) is the main compound of aluminium and chlorine. It is white, but

samples are often contaminated with iron trichloride, giving it a yellow colour. The solid has a

low melting and boiling point.

Chemical propertiesThe compound is often cited as a Lewis acid. It is an example of an inorganic compound that

"cracks" at mild temperature, reversibly changing from a polymer to a molecule.

Anhydrous aluminium chloride is a powerful Lewis acid, capable of forming Lewis acid-base

adducts with even weak Lewis bases such as benzophenone and mesitylen

Aluminium chloride is hygroscopic, having a very high affinity for water. It fumes in moist air

and hisses when mixed with liquid water as the Cl-ions are displaced with H2O molecules in the

lattice to form the hexahydrate AlCl36H2O (also white to yellowish in color). The anhydrous


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phase cannot be regained on heating as HCl is lost leaving aluminum hydroxide or alumina

(aluminum oxide):

Al(H2O)6Cl3 Al(OH)3 + 3 HCl + 3 H2O

On strong heating (~400C), the aluminum oxide is formed from the aluminum hydroxide via:

Al(OH)3 Al2O3 + 3 H2O

1.6.4 SULFUR

Physical propertiesIn nature, sulfur can be found as the pure element and as sulfide and sulfate minerals. Elemental

sulfur is a bright yellow crystalline solid. Sulfur forms polyatomic molecules with different

chemical formulae, with the best-known allotrope being octasulfur, cyclo-S8.Octasulfur is a soft,

bright-yellow solid with only a faint odor, similar to that of matches It melts at 115.21 C, boils

at 444.6 C and sublimes easily.

Chemical propertiesSulfur burns with a blue flame concomitant with formation of sulfur dioxide, notable for its

peculiar suffocating odor. Sulfur is insoluble in water but soluble in carbon disulfide and, to a

lesser extent, in other nonpolar organic solvents, such as benzene and toluene. sulfur can react as

either an oxidant or reducing agent. It oxidizes most metals and several nonmetals, includingcarbon, which leads to its negatives charge in most organosulfur compounds, but it reduces

several strong oxidants, such as oxygen and fluorine.


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1.7 PLANT LOCATION

The geographical location of the plant can have strong influence on the success of an industrial

venture,therefore considerable care has been exercised in selecting the plant site, and many

different factors have been considered. Primarily, the plant should be located where the

minimum cost of production and distribution can be obtained, but other factors, such as room for

expansion and safe living conditions for plant operation as well as the surrounding community,

are also important.

The choice of the final site is based on a complete survey of the advantages and disadvantages of

various geographical areas and, ultimately, on the advantages and disadvantages of available real

estate.

After several considerations of the major factors which may affect production as well as

profitability, Atan in Ogun State has been chosen as the suitable site. The principal factors which

led to this decision include:

Suitable large expanse of land

Sufficient suitable land must be available for the proposed plant and for future expansion. Wide

expanse of land for various production facilities and utilities required for plant which cannot be

easily obtained in densely populated Lagos or other industrialized cities like Port-Harcourt, can

be obtained in Atan located in Ogun state which even though its not an industrial city in itself, is

gradually developing and at the same time still close enough to places like Lagos to enjoy fringe

benefits of industrial concentration.

Labor Supply

The type and supply of labor available in the vicinity of a proposed plant site was examined and

consideration was given to prevailing pay scales, restrictions on number of hours worked per

week, and variations in the skill and productivity of the workers. The type of labor that will be

required to run the plant varies from skilled labor to unskilled labor. Both of these kinds of labor

are available in Atan. The skilled labors available are provided by the unemployed university

graduates that are present in Atan. While the unskilled labor available is provided by the locals

that live in Atan.


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1.8 ENVIRONMENTAL ISSUES

Linear alkyl benzene sulfonate has been safely consumed in large volumes throughout the

developed world for over 20yrs. Although its use was once questioned in Western Europe

because of its lack of biodegradability under anaerobic conditions, it is disposed under aerobic

conditions (i.e. sewage treatment plants), where it does fully biodegrade. In any case, no

legislation adversely affecting the use of LAS is expected and it is expected to remain the

worlds largest surfactant used in detergents for many years.

According to a recent comprehensive risk assessment study carried out by the Netherlands

government, the use of LAS in laundry detergent powders does not involve any significant

environmental risk. LAS, as well as other large-volume surfactants are efficiently removed in the

sewage treatment systems. A report recently submitted by Britains Department of the

environment states that LAS is readily biodegradable and its use in consumer products poses

no hazard to human health or the environment."

1.9 STORAGE

Keep container dry. Keep in a cool place. Ground all equipment containing material.

Keep container tightly closed. Keep in a

cool, well-ventilated place. Combustible materials should be stored away from extreme heat and

away from strong oxidizing

Sodium dodecyl benzene sulphonate is produced in the most common route of alkylation,

sulfonation and neutralization. However there are different conditions and routes for each of

these three processes.

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