Chemical Engineer Article

Nuclear Reactor,how its work?

2011-03-30T00:09:00.000-07:00

Nuclear Reactor

Just as conventional power stations generate electricity by harnessing the thermal energy released from burning fossil fuels, nuclear reactors convert the thermal energy released from nuclear fission.

Fission

When a large fissile atomic nucleus such as uranium-235 or plutonium-239 absorbs a neutron, it may undergo nuclear fission. The heavy nucleus splits into two or more lighter nuclei, releasing kinetic energy, gamma radiation and free neutrons; collectively known as fission products. A portion of these neutrons may later be absorbed by other fissile atoms and trigger further fission events, which release more neutrons, and so on. This is known as a nuclear chain reaction.

The reaction can be controlled by using neutron poisons, which absorb excess neutrons, and neutron moderators, which reduce the velocity of fast neutrons, thereby turning them into thermal neutrons, which are more likely to be absorbed by other nuclei. Increasing or decreasing the rate of fission has a corresponding effect on the energy output of the reactor.

Commonly used moderators include regular (light) water (75% of the world's reactors), solid graphite (20% of reactors) and heavy water (5% of reactors). Beryllium has also been used in some experimental types, and hydrocarbons have been suggested as another possibility.

Heat generation

The reactor core generates heat in a number of ways:

The kinetic energy of fission products is converted to thermal energy when these nuclei collide with nearby atoms. Some of the gamma rays produced during fission are absorbed by the reactor, their energy being converted to heat. Heat produced by the radioactive decay of fission products and materials that have been activated by neutron absorption. This decay heat source will remain for some time even after the reactor is shut down.

A kilogram of uranium-235 (U-235) converted via nuclear processes releases approximately three million times more energy than a kilogram of coal burned conventionally (7.2 × 1013 joules per kilogram of uranium-235 versus 2.4 × 107 joules per kilogram of coal).[3][4]

Cooling

A nuclear reactor coolant — usually water but sometimes a gas or a liquid metal or molten salt — is circulated past the reactor core to absorb the heat that it generates. The heat is carried away from the reactor and is then used to generate steam. Most reactor systems employ a cooling system that is physically separated from the water that will be boiled to produce pressurized steam for the turbines, like the pressurized water reactor. But in some reactors the water for the steam turbines is boiled directly by the reactor core, for example the boiling water reactor.

Reactivity control

Main articles: Nuclear reactor control, Passive nuclear safety, Delayed neutron, Iodine pit, SCRAM, and Decay heat. The power output of the reactor is adjusted by controlling how many neutrons are able to create more fissions. Control rods that are made of a neutron poison are used to absorb neutrons. Absorbing more neutrons in a control rod means that there are fewer neutrons available to cause fission, so pushing the control rod deeper into the reactor will reduce its power output, and extracting the control rod will increase it. At the first level of control in all nuclear reactors, a process of delayed neutron emission by a number of neutron-rich fission isotopes is an important physical process. These delayed neutrons account for about 0.65% of the total neutrons produced in fission, with the remainder (termed "prompt neutrons") released immediately upon fission. The fission products which produce delayed neutrons have half lives for their decay by neutron emission that range from milliseconds to as long as several minutes. Keeping the reactor in the zone of chain-reactivity where delayed neutrons are necessary to achieve a critical mass state, allows time for mechanical devices or human operatures to have time to control a chain reaction in "real time"; otherwise the time between achievement of criticality and nuclear meltdown as a result of an exponential power surge from the normal nuclear chain reaction, would be too short to allow for intervention.

In some reactors, the coolant also acts as a neutron moderator. A moderator increases the power of the reactor by causing the fast neutrons that are released from fission to lose energy and become thermal neutrons. Thermal neutrons are more likely than fast neutrons to cause fission, so more neutron moderation means more power output from the reactors. If the coolant is a moderator, then temperature changes can affect the density of the coolant/moderator and therefore change power output. A higher temperature coolant would be less dense, and therefore a less effective moderator.

In other reactors the coolant acts as a poison by absorbing neutrons in the same way that the control rods do. In these reactors power output can be increased by heating the coolant, which makes it a less dense poison.[citation needed] Nuclear reactors generally have automatic and manual systems to Scram the reactor in an emergency shut down. These systems insert large amounts of poison (often boron in the form of boric acid) into the reactor to shut the fission reaction down if unsafe conditions are detected or anticipated.

Most types of reactors are sensitive to a process variously known as xenon poisoning, or the iodine pit. Xenon-135 is normally produced in the fission process, and acts as a neutron absorbing "neutron poison", which acts to shut the reactor down, but can be controlled in turn within the reactor by keeping neutron and power levels high enough to destroy it as fast as it is produced. The normal fission process also produces iodine-135, which in turn decays with a half life of under seven hours, to new xenon-135. Thus, if the reactor is shut down, iodine-135 in the reactor continues to decay to xenon-135, to the point that the new xenon-135 from this source ("xenon poisoning") makes re-starting the reactor more difficult, for a day or two, than when first shut down (this temporary state is the "iodine pit.") If the reactor has sufficient extra capacity, it can still be re-started before the iodine-135 and xenon-135 decay, but as the extra xenon-135 is "burned off" by transmuting it to xenon-136 (not a neutron poison), within a few hours the reactor may become unstable as a result of such a "xenon burnoff (power) transient," and then rapidly become overheated, unless control rods are reinserted in order to replace the neutron absorption of the lost xenon-135. Failure to properly follow such a procedure, was a key step in the Chernobyl disaster.

Reactors used in nuclear marine propulsion (especially nuclear submarines) often cannot be run at continuous power around the clock in the same way that land-based power reactors are normally run, and in addition often need to have a very long core life without refueling. For this reason many designs use highly enriched uranium but incorporate burnable neutron poison directly into the fuel rods. This allows the reactor to be construced with a high excess of fissionable material, which is nevertheless made relatively more safe early in the reactor's fuel burn-cycle by the presense of the neutron-absorbing material which is later replaced by naturally prodused long-lived neutron poisons (far longer-lived than xenon-135) which gradually accumulate over the fuel load's operating life.

Nuclear Energy

2011-03-29T23:59:00.000-07:00

Nuclear Explotions

Nuclear potential energy is the potential energy of the particles inside an atomic nucleus. The nuclear particles are bound together by the strong nuclear force. Weak nuclear forces provide the potential energy for certain kinds of radioactive decay, such as beta decay.

Nuclear particles like protons and neutrons are not destroyed in fission and fusion processes, but collections of them have less mass than if they were individually free, and this mass difference is liberated as heat and radiation in nuclear reactions (the heat and radiation have the missing mass, but it often escapes from the system, where it is not measured). The energy from the Sun is an example of this form of energy conversion. In the Sun, the process of hydrogen fusion converts about 4 million tonnes of solar matter per second into electromagnetic energy, which is radiated into space.

n-butyraldehyde

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n-butyraldehyde (boiling point: 74.8oC, density: 0.8016) is made by the reaction of propylene (propene-1, CH3CH=CH2), carbon monoxide, and hydrogen (synthesis gas) at 130 to 175oC and 3675 psi (25.3 MPa) over a rhodium carbonyl, cobalt carbonyl, or ruthenium carbonyl catalyst (Fig. 1).

CH3CH=CH2 + CO + H2 → CH3CH2CH2CH=O

The reaction is referred to as the oxo process, and a second product of the reaction is iso-butyraldehyde (boiling point: 64.1oC, density: 0.7891).

CH3CH=CH2 + CO + H2 → CH3CH(CH3)CH=O

The ratio of the normal to the iso product is approximately 4:1. Other catalysts produce different normal-to-iso product ratios under different conditions. For example, a rhodium catalyst can be used at lower temperatures and pressures and gives a normal-to-iso product ratio of approximately 16:1.

Butyraldehyde is used for the production of n-butyl alcohol.

CH3CH2CH2CH=O + H2 → CH3CH2CH2CH2OH

t-Butyl alcohol

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t-Butyl alcohol (melting point: 25.8oC, boiling point: 82.4oC, density: 0.7866, flash point: 11.1oC) is a low-melting solid that, after melting,exists as a colorless liquid. t-Butyl alcohol is produced by the hydration of iso-butene. The favored tertiary carbocation intermediate limits the possible alcohols produced to only this one.

(CH3)2C=CH2 → (CH3)3COH

Anion exchanger resin

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Ion exchange resins can be used in the separation method or concentration by using redemption equality. Ion exchange resin is an organic high polymer containing ionic functional group, resin, there is generally a polymer granules with various sizes. These pellets are placed in a glass tube long enough to produce the ion exchange column in which ions will happen leveling process.

resin manufacture is a way to enter that in the ionisation cluster into the organic polymer matrix, the most common is polystyrene which acts as adsorbent.

solution through a column called influent, while the solution is out of the column is called effluent. The process is the exchange resin absorption and returns that have been used to shape called regeneration. While spending the ions from the column with the appropriate reagent called elusi. total exchange capacity is the number of cluster-cluster that can be exchanged within the column is expressed in milleknalen, breakthrough capacity is defined as the number of ions that can be taken by the column on the separation conditions.

Elusi analysis has many benefits, for example all the ions are separated leaving the column as factions separate. Elusi process consists of two, the first is the fraction with some eluen and the second is still mengelusi active ions.

anionik resin is a substance that can replace menukaratau anions existing in the surrounding medium. Resin-resin (synthetic) can be derived from solid polymers that bind tightly in a cross with a large molecular weight can come from certain organic substances such as phenol and sterina associated with a particular group can be ionized and alkaline, such as amine or phenol groups or kuartener aluminum is added to the resin polifeniletana stable.

The basic principle is the anion exchange resin can trade for other anion anion hidroksiloleh happened to the ion exchange resin. There are two types of anion exchange resin having strongly basic groups (kuartener ammonium groups) and the resin which has a weak base group (cluster anions).

Surface of a strong base can be used over a pH range of 0 to 12, while the weak base resin exchanger only above a pH range of 0 to 9. Weak base exchanger groups will not let go of a very weak acid, but is preferred for strong acids that may be restrained by a strong base resin like sulfanol.

Ion exchange process is a process of competition between solut ions contained in ion phase with opponent cars are attached to the functional group on the matrix of opposite charge. This means that the solut ion should be able to replace one or more ions are bound by the opponent stationer phase (matrix). When we have exchange positively charged ions or cation exchanger that has bound ions in the phase opposite the car present in the solut ion ion exchange process can act.

Liquid propellants?

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All the fuel that can drive called propellant rockets. Propellant is generally classified into 3 types, namely:

Solid propellant
Liquid propellant
Propellant hybrid

Each type of propellant on the advantages and disadvantages of each. However, for the current development, liquid propellant is more commonly used in the field of space.

Examples of liquid propellant please see here

So how rockets can fly into space?

Just like a conventional engine, a rocket of energy use arising from the oxidation reaction of fuel with the oxidant. Only the pressure of fuel in a rocket engine could reach more than 300 psi. Meanwhile, the air pressure outside the engine about 1 atm, sometimes even a vacuum.

Because there is this pressure difference results of the combustion gas velocity changes from slow to very fast. Changes in velocity than occurs because the pressure difference, as well as the results of the combustion gases flowing through the throat of diameter 4 times smaller than the diameter of the engine.

In accordance with the continuity equation, because the flow remains, while the narrower area, then the velocity changes.

Change in velocity per unit of time equal to the acceleration. After the laws of classical physics of Newton, the acceleration will result in the emergence of force (force). The force that drives this arise so that the rocket could be launched.

The Nitration of Benzene

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Benzene reacts slowly with hot concentrated nitric acid in an electrophilic aromatic substitution reaction to form nitrobenzene. This reaction is potentially dangerous, however, because nitric acid is a strong oxidizing agent that often explodes in the presence of any material that readily oxidizes. A safer, faster, and more convenient synthesis employs a mixture of concentrated nitric acid and concentrated sulfuric acid. The concentrated sulfuric acid acts as a catalyst allowing nitration to take place more readily at more moderate temperatures.

The nitronium ion (⊕NO2) is the electrophile in the nitration of benzene to form nitrobenzene. Although concentrated nitric acid produces the nitronium ion by itself, the equilibrium is so far to the left that the process is slow. Adding concentrated sulfuric acid to the reaction mixture increases the concentration of the nitronium ion, thereby increasing the rate of the nitration reaction. The nitronium ion forms via a pathway similar to the first step in the dehydration of an alcohol.

After the nitronium ion forms, it reacts with benzene to form the σ complex, the first step of the electrophilic aromatic substitution reaction. This step is slow because the σ complex is not aromatic. Additionally, the σ complex is higher in energy than the benzene and the nitronium ion.

In the next step of the mechanism, the σ complex loses a proton to form nitrobenzene. This step is rapid because the loss of a proton allows the molecule to become aromatic again.

Chemists tested whether the loss of a proton is the fast step or the slow step of an electrophilic aromatic substitution by replacing the hydrogens in benzene with deuterium and then running the reaction. Deuterium (2H abbreviated as D) is an isotope of hydrogen (1H) that contains not only one proton in its nucleus but also one neutron. Thus, deuterium has twice the mass of hydrogen. Because the bond energy between a pair of atoms changes in proportion to the masses of the isotopes involved in that bond, the C—D bond is higher in energy than the C—H bond. This isotope effect is observable in the IR spectrum. The IR absorption of the C—H bond in benzene is approximately 3050 cm–1; whereas the C—D bond of deuteriobenzene is about 2150 cm–1.

Because breaking a C—D bond requires more energy than breaking a C—H bond, a reaction whose rate-determining step involves breaking a C—H bond proceeds more slowly when deuterium is present. Thus, replacing C6H6 with C6D6 results in a reduction of the nitration rate if the breaking of a C—H bond is the rate-determining step. With the electrophilic aromatic substitution reaction, chemists measured no difference in the rate of reaction between C6D6 and C6H6. This shows that the rate-determining step is the formation of the σ complex, not the step that breaks the C—H bond.

Batch Pan

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Next to natural solar evaporation, the batch pan (Figure 1) is one of the oldest methods of concentration. It is somewhat outdated in today's technology, but is still used in a few limited applications, such as the concentration of jams and jellies where whole fruit is present and in processing some pharmaceutical products. Up until the early 1960's, batch pan also enjoyed wide use in the concentration of corn syrups. With a batch pan evaporator, product residence time normally is many hours. Therefore, it is essential to boil at low temperatures and high vacuum when a heat sensitive or thermodegradable product is involved. The batch pan is either jacketed or has internal coils or heaters. Heat transfer areas normally are quite small due to vessel shapes, and heat transfer coefficients (HTC’s) tend to be low under natural convection conditions. Low surface areas together with low HTC's generally limit the evaporation capacity of such a system. Heat transfer is improved by agitation within the vessel. In many cases, large temperature differences cannot be used for fear of rapid fouling of the heat transfer surface. Relatively low evaporation capacities, therefore, limit its use.

Titanium Dioxide

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The production of titanium dioxide pigments involves reaction between sulfuric acid and the ore which contains iron, titanium sulfate and other compounds. After pretreatment, which includes the crystallization of iron as ferrous sulfate, the liquor is heated and hydrolyzed to precipitate Titanium dioxide. Prior to this operation, the concentration of liquor has to be adjusted by the evaporation of water. It is essential that this process takes place in an evaporator with short heat contact times in order to avoid the premature hydrolysis that occurs with prolonged heating, which subsequently causes fouling of the heat surface and blockage of the tubes. Although the liquor contains a high proportion of sulfuric acid, the presence of other ions in solution may inhibit corrosion, so that copper often can be used for heat transfer surfaces. Titanium is another material used for this application. Generally, single or multiple effect rising film evaporators are used for this duty, the number of effects being determined by throughput and by assessing the cost of operation against the increase in capital required for additional equipment. In some cases, it is economically attractive to operate the evaporator as a single effect unit at atmospheric pressure using the vapor given off for preheating. The liquor is discharged at a temperature in excess of 212°F (100°C), reducing the subsequent thermal load at the hydrolysis stage.

Acetaminophen

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Acetaminophen, sold under the trade name Tylenol, is a widely used anal- gesic and antipyretic that is an over-the-counter drug. Combined with codeine it is one of the top five prescription drugs. Acetaminophen is pre- pared by treating p-aminophenol with a mixture of glacial acetic acid and acetic anhydride.

Chemical reaction engineering By Levenspiel O. (3ed., Wiley, 1998).pdf

2010-03-10T22:06:00.000-08:00

Chemical Reaction Engineering Book Description

Publisher: John Wiley & Sons
Author: Octave Levenspiel, Cctave Levenspiel
Edition Number: 3
Language: English
ISBN:
047125424X
EAN:
9780471254249
No. of Pages: 688
Publish Date: 1998-08-31

Chemical Process and Design Handbook

2010-03-10T22:00:00.000-08:00

Introduction to Chemical Reaction Engineering and Kinetics - RW Missen

2010-03-10T21:21:00.000-08:00

Heat Transfer Handbook - Wiley Bejan 2003

2010-03-10T21:14:00.000-08:00

Book: Heat Transfer (in SI Units) (SIE)
This hallmark text on Heat Transfer presents an elementary and classical treatment of principles of heat transfer With emphasis on physical understanding while relying on meaningful experimental data.
Key Features:

Analytical and Numerical treatment of Conduction-to gain insight into important tools of numerical analysis used in practice. (Chapter 2-4) Integral analysis of both free and forced convection boundary layers is used to present a physical picture of convection process. (Chapters 5-7) Heat Exchangers: Log mean temperature difference and effectiveness approaches are discussed. (Chapter 10) Important analogies between heat, mass and momentum transfer are discussed through a brief introduction to diffusion and mass transfer in chapter 11. Design is highlighted with over 100 open ended, design oriented homework problems. Emphasis on resistance capacity formulation in computer numerical methods. Large number of numerical examples on heat sources, radiation boundary conditions, non uniform mesh size and 3D nodal systems.

Table of Content:

Chapter 1. Introduction
Chapter 2. Steady-State Conduction-One Dimension
Chapter 3. Steady-State Conduction-Multiple Dimension
Chapter 4. Unsteady-State Conduction
Chapter 5. Principles of Convection
Chapter 6. Empirical and Practical Relation for Forced-Convection Heat Transfer
Chapter 7. Natural Convection Systems
Chapter 8. Radiation Heat Transfer
Chapter 9. Condensation and Boiling Heat Transfer
Chapter 10. Heat Exchange
Chapter 11. Mass Transfer
A. Tables
B. Exact Solutions of Laminar-Boundary-Layer Equations
C. Analytical Relations for the Heisler Charts
D. Use of Microsoft Excel for Solution of Heat- Transfer Problems

Process Heat Transfer - DQ Kern

2010-03-10T21:00:00.000-08:00

This book is designed to provide fundamental instruction in heat transfer while employing the methods and language of industry.

Key Features:

Provides the rounded group of heat-transfer tools required in process engineering it has been necessary to present a number of empirical calculation methods which have not previously appeared in the engineering literature.

Considerable throught has been given to these methods, and the author has discussed them with numerious engineers before accepting and including them in the text.

About the Author:

DONALD KERN
DONALD Q.KERAN D.Q. Kern Associate and He is a Professorial Lecturer in Chemical Engineering Case Insitiue of Technology.

Table of Content:

Preface
Index to the Principal Apparatus Calculations
Chapter 1 Process Heat Transfer
Chapter 2 Conduction
Chapter 3 Convection
Chapter 4 Radiation
Chapter 5 Temperature
Chapter 6 Counterflow: Double-pipe Exchangers
Chapter 7 1-2 Parallel-Counterflow: Shell-And-Tube Exchangers
Chapter 8 Flow Arrangeements for Increased Heat Recovery
Chapter 9 Gases
Chapter 10 Streamline Flow and Free Convection
Chapter 11 Calculations for Process Condition
Chapter 12 Condensation of Single Vapors
Chapter 13 Condensation of Mixed Vapors
Chapter 14 Evaporation
Chapter 15 Vaporizers, Evaporators, and Reboilers
Chapter 16 Extended Surfaces
Chapter 17 Direct-Contact Transfer: Cooling Towers
Chapter 18 Batch and Unsteady State Processes
Chapter 19 Furnace Calculations
Chapter 20 Additional Applications
Chapter 21 The Control of Temperature and Related Process Variables
Appendix of Calculation Data
Author Index
Subject Index

Design of Distillation Column Control Systems

2010-03-10T20:52:00.000-08:00

Design of Distillation Column Control Systems

By: Buckley, Page S.; Luyben, William L.; Shunta, Joseph P. © 1985 Elsevier

Description: It is the purpose of this book to indicate the range of technology, which has been developed for distillation control, to the point where it can be economically and reliably used for design.

Perry Chemical Engineering Handbooks

2010-03-10T18:49:00.000-08:00

Perry's Chemical Engineers' Handbook (also known as Perry's Handbook or Perry's)[1] was first published in 1934 and the most current eighth edition was published in October 2007. It has been a source of chemical engineering knowledge for chemical engineers, and a wide variety of other engineers and scientists, through seven previous editions spanning more than seventy years.

The subjects covered in the book include: physical properties of chemicals and other materials; mathematics; thermodynamics; heat transfer; mass transfer; fluid dynamics; chemical reactors and chemical reaction kinetics; transport and storage of fluid; heat transfer equipment; psychrometry and evaporative cooling; distillation; gas absorption; liquid-liquid extraction; adsorption and ion exchange; gas-solid, liquid-solid and solid-solid operations; biochemical engineering; waste management, materials of construction, process economics and cost estimation; process safety and many others. An electronic version of this reference book is provided by Knovel.

KirkOthmer Encyclopedia of Chemical Technology

2010-03-10T18:47:00.000-08:00

Kirk, Othmer: KirkOthmer Encyclopedia of Chemical Technology (Kirk-Othmer Encyclopedia of Chemical Technology) 5th Edition

The fifth edition of the Kirk-Othmer Encyclopedia of Chemical Technology builds upon the solid foundation of the previous editions, which have proven to be a mainstay for chemists, biochemists, and engineers at academic, industrial, and government institutions since publication of the first edition in 1949.

The new edition includes necessary adjustments and modernisation of the content to reflect changes and developments in chemical technology. Presenting a wide scope of articles on chemical substances, properties, manufacturing, and uses; on industrial processes, unit operations in chemical engineering; and on fundamentals and scientific subjects related to the field.

The Encyclopedia describes established technology along with cutting edge topics of interest in the wide field of chemical technology, whilst uniquely providing the necessary perspective and insight into pertinent aspects, rather than merely presenting information.

* Set began publication in January 2004
* Over 1000 articles
* More than 600 new or updated articles
* 27 volumes

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Sulfonation

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Sulfonation is the introduction of a sulfonic acid group (–SO3H) into an organic compound as, for example, in the production of an aromatic sulfonic acid from the corresponding aromatic hydrocarbon.

ArH + H2SO4 → ArSO3H + H2O

The usual sulfonating agent is concentrated sulfuric acid, but sulfur trioxide, chlorosulfonic acid, metallic sulfates, and sulfamic acid are also occasionally used. However, because of the nature and properties of sulfuric acid, it is desirable to use it for nucleophilic substitution wherever possible. For each substance being sulfonated, there is a critical concentration of acid below which sulfonation ceases. The removal of the water formed in the reaction is therefore essential. The use of a very large excess of acid, while expensive, can maintain an essentially constant concentration as the reaction progresses. It is not easy to volatilize water from concen- trated solutions of sulfuric acid, but azeotropic distillation can some- times help.

The sulfonation reaction is exothermic, but not highly corrosive, so sulfonation can be conducted in steel, stainless-steel, or cast-iron sulfona- tors. A jacket heated with hot oil or steam can serve to heat the contents sufficiently to get the reaction started, then carry away the heat of reaction. A good agitator, a condenser, and a fume control system are usually also provided.

1- and 2-naphthalenesulfonic acids are formed simultaneously when naphthalene is sulfonated with concentrated sulfuric acid. The isomers must be separated if pure α- or β-naphthol are to be prepared from the product mix. Variations in time, temperature, sulfuric acid concentration, and acid/hydrocarbon ratio alter the yields to favor one particular isomer, but a pure single substance is never formed. Using similar acid/hydrocar- bon ratios, sulfonation at 40oC yields 96% alpha isomer, 4% beta, while at 1600C the proportions are 15% α-naphthol, 8.5% β-naphthol.

The α-sulfonic acid can be hydrolyzed to naphthalene by passing steam at 160o C into the sulfonation mass. The naphthalene so formed passes out with the steam and can be recovered. The pure β-sulfonic acid left behind can be hydrolyzed by caustic fusion to yield relatively pure β- naphthol.

In general, separations are based on some of the following consideration:

1. Variations in the rate of hydrolysis of two isomers
2. Variations in the solubility of various salts in water
3. Differences in solubility in solvents other than water
4. Differences in solubility accentuated by common-ion effect (salt additions)
5. Differences in properties of derivatives
6. Differences based on molecular size, such as using molecular sieves or absorption.

Sulfonation reactions may be carried out in batch reactors or in continuous reactors. Continuous sulfonation reactions are feasible only when the organic compounds possess certain chemical and physical properties, and are practical in only a relatively few industrial processes. Most commercial sulfonation reactions are batch operations.

Continuous operations are feasible and practical (1) where the organic compound (benzene or naphthalene) can be volatilized, (2) when reaction rates are high (as in the chlorosulfonation of paraffins and the sulfonation of alcohols), and (3) where production is large (as in the manufacture of detergents, such as alkylaryl sulfonates). Water of reaction forms during most sulfonation reactions, and unless a method is devised to prevent excessive dilution because of water formed during the reaction, the rate of sulfonation will be reduced. In the interests of economy in sulfuric acid consumption, it is advantageous to remove or chemically combine this water of reaction. For example, the use of reduced pressure for removing the water of reaction has some technical advantages in the sulfonation of phenol and of benzene. The use of the partial-pressure distillation is predicated upon the ability of the diluent, or an excess of volatile reactant, to remove the water of reaction as it is formed and, hence, to maintain a high concentration of sulfuric acid. If this concentration is maintained, the necessity for using excess sulfuric acid is eliminated, since its only function is to maintain the acid concentration above the desired value. Azeotropic removal of the water of reaction in the sulfonation of benzene can be achieved by using an excess of vaporized benzene. The use of oleum (H2SO4 SO3) for maintaining the necessary sulfur trioxide concentration of a sulfonation mixture is a practical procedure. Preferably the oleum and organic compound should be added gradually and concurrently to a large volume of cycle acid so as to take up the water as rapidly as it is formed by the reaction. Sulfur trioxide may be added intermittently to the sulfonation reactor to maintain the sulfur trioxide concentration above the value for the desired degree of sulfonation.

Vinylation

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Unlike ethynylation, in which acetylene adds across a carbonyl group and the triple bond is retained, in vinylation a labile hydrogen compound adds to acetylene, forming a double bond.

XH + HC≡CH → CH2=CHX

Catalytic vinylation has been applied to the manufacture of a wide range of alcohols, phenols, thiols, carboxylic acids, and certain amines and amides. Vinyl acetate is no longer prepared this way in many countries, although some minor vinyl esters such as vinyl stearate may still be man- ufactured by this route. However, the manufacture of vinyl-pyrrolidinone and vinyl ethers still depends on acetylene as the starting material.

Polymerization

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Polymerization is a process in which similar molecules (usually olefins) are linked to form a high-molecular-weight product; such as the formation of polyethylene from ethylene

nCH2CH2 → H–( CH2CH2)n–H

The molecular weight of the polyethylene can range from a few thousand to several hundred thousand. Polymerization of the monomer in bulk may be carried out in the liquid or vapor state. The monomers and activator are mixed in a reactor and heated or cooled as needed. As most polymerization reactions are exothermic, pro- vision must be made to remove the excess heat. In some cases, the polymers are soluble in their liquid monomers, causing the viscosity of the solution to increase greatly. In other cases, the polymer is not soluble in the monomer and it precipitates out after a small amount of polymerization occurs. In the petroleum industry, the term polymerization takes on a different meaning since the polymerization processes convert by-product hydrocarbon gases produced in cracking into liquid hydrocarbons suitable (of limited or specific molecular weight) for use as high-octane motor and aviation fuels and for petrochemicals. To combine olefinic gases by polymerization to form heavier fractions, the combining fractions must be unsaturated. Hydrocarbon gases, particularly olefins, from cracking reactors are the major feedstock of polymerization.

(CH3)2C=CH2 → (CH3)3CH2C(CH3)=CH2
(CH3)3CH2C(CH3)=CH2 → C12H24

Vapor-phase cracking produces considerable quantities of unsaturated gases suitable as feedstocks for polymerization units. Catalytic polymerization is practical on both large and small scales and is adaptable to combination with reforming to increase the quality of the gasoline. Gasoline produced by polymerization contains a smog-producing olefinic bond. Polymer oligomers are widely used to make detergents.

Oxo reaction

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The oxo reaction is the general or generic name for a process in which an unsaturated hydrocarbon is reacted with carbon monoxide and hydrogen to form oxygen function compounds, such as aldehydes and alcohols. In a typical process for the production of oxo alcohols, the feedstock comprises an olefin stream, carbon monoxide, and hydrogen. In a first step, the olefin reacts with CO and H2 in the presence of a catalyst (often cobalt) to produce an aldehyde that has one more carbon atom than the originat- ing olefin:

RCH=CH2 + CO + H2 → RCH2CH2CH=O

This step is exothermic and requires an ancillary cooling operation.

The raw aldehyde exiting from the oxo reactor then is subjected to a higher temperature to convert the catalyst to a form for easy separation from the reaction products. The subsequent treatment also decomposes unwanted by-products. The raw aldehyde then is hydrogenated in the pres- ence of a catalyst (usually nickel) to form the desired alcohol:

RCH2CH2CH=O + H2 → RCH2CH2CH2OH

The raw alcohol then is purified in a fractionating column. In addition to the purified alcohol, by-products include a light hydrocarbon stream and a heavy oil. The hydrogenation step takes place at about 150°C under a pressure of about 1470 psi (10.13 MPa). The olefin conversion usually is about 95 percent.

Among important products manufactured in this manner are substituted propionaldehyde from corresponding substituted ethylene, normal and iso-butyraldehyde from propylene, iso-octyl alcohol from heptene, and trimethylhexyl alcohol from di-isobutylene.

Fermentation

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Fermentation processes produce a wide range of chemicals that complement the various chemicals produced by nonfermentation routes. For example, alcohol, acetone, butyl alcohol, and acetic acid are produced by fermentation as well as by synthetic routes. Almost all the major antibiotics are obtained from fermentation processes.

Fermentation under controlled conditions involves chemical conversions, and some of the more important processes are:

Oxidation, e.g., ethyl alcohol to acetic acid, sucrose to citric acid, and dextrose to gluconic acid
Reduction, e.g., aldehydes to alcohols (acetaldehyde to ethyl alcohol) and sulfur to hydrogen sulfide
Hydrolysis, e.g., starch to glucose and sucrose to glucose and fructose and on to alcohol
Esterification, e.g., hexose phosphate from hexose and phosphoric acid

Esterification

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A variety of solvents, monomers, medicines, perfumes, and explosives are made from esters of nitric acid. Ethyl acetate, n-butyl acetate, iso-butyl acetate, glycerol trinitrate, pentaerythritol tetranitrate (PETN), glycol dini- trate, and cellulose nitrate are examples of such reactions.

Ester manufacture is a relatively simple process in which the alcohol and an acid are heated together in the presence of a sulfuric acid catalyst, and the reaction is driven to completion by removing the products as formed (usually by distillation) and employing an excess of one of the reagents. In the case of ethyl acetate, esterification takes place in a column that takes a ternary azeotrope. Alcohol can be added to the condensed over- head liquid to wash out the alcohol, which is then purified by distillation and returned to the column to react.

Amyl, butyl, and iso-propyl acetates are all made from acetic acid and the appropriate alcohols. All are useful lacquer solvents and their slow rate of evaporation (compared to acetone or ethyl acetate) prevents the surface of the drying lacquer from falling below the dew point, which would cause con- densation on the film and a mottled surface appearance (blushing). Other esters of importance are used in perfumery and in plasticizers and include methyl salicylate, methyl anthranilate, diethyl-phthalate, dibutyl-phthalate, and di-2-ethylhexyl-phthalate.

Unsaturated vinyl esters for use in polymerization reactions are made by the esterification of olefins. The most important ones are vinyl esters: vinyl acetate, vinyl chloride, acrylonitrile, and vinyl fluoride. The addition reac- tion may be carried out in either the liquid, vapor, or mixed phases, depending on the properties of the acid. Care must be taken to reduce the polymerization of the vinyl ester produced.

Esters of allyl alcohol, e.g., diallyl phthalate, are used as bifunctional polymerization monomers and can be prepared by simple esterification of phthalic anhydride with allyl alcohol. Several acrylic esters, such as ethyl or methyl acrylates, are also widely used and can be made from acrylic acid and the appropriate alcohol. The esters are more volatile than the cor- responding acids.

Condensation and Addition (Friedel-Crafts) reactions

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There are only a few products manufactured in any considerable tonnage by condensation and addition (Friedel-Crafts) reactions, but those that are find use in several different intermediates and particularly in making high- quality vat dyes. The agent employed in this reaction is usually an acid chloride or anhy- dride, catalyzed with aluminum chloride. Phthalic anhydride reacts with chlorobenzene to give p-chlorobenzoylbenzoic acid and, in a continuing action, the p-chlorobenzoylbenzoic acid forms β-chloroanthraquinone. Since anthraquinone is a relatively rare and expensive component of coal tar and petroleum, this type of reaction has been the basis for making relatively inexpensive anthraquinone derivatives for use in making many fast dyes for cotton. Friedel-Crafts reactions are highly corrosive, and the aluminum-con- taining residues are difficult to dispose.