Distillation

 

Distillation is one of the most very process for separation the components of a solution. The solution is heated to form a vapor of the more volatile components in the system, and vapor is then cooled, condensed, and collected as pure liquid. By repeating vaporization and condensation, individual components in the solution can be recovered in a pure state. Essences and many pure products from the oil refinery industry are processed via distillation.

Principles

Distillation is a technique by which a liquid mixture is separated into fractions with higher concentrations of certain components by using differences in relative volatility. The mechanism involved in distillation is the differences in volatility between individual components. With sufficient heat applied, vapours are formed from the liquid solution. The liquid product is subsequently condensed from the vapour phase by removal of the heat. Therefore, heat is used as the separating agent during distillation. In general, distillation can be carried out either with or without reflux involved. For the case of single-stage differential distillation, the liquid mixture is heated to form a vapour that is in equilibrium with the residual liquid. The vapour is then condensed and removed from the system without any liquid allowed to return to the still pot. This vapour is richer in the more volatile component than the liquid removed as the bottom product at the end of the process. However, when products of much higher purity are desired, part of the condensate has to be brought into contact with the vapour on its way to the condenser and recycled to the still pot. This procedure can be repeated many times to increase the efficiency of separation of mixture. This  process is called as rectification.

 Objectives

Distillation is used to separate the liquid mixture into two or more separated components. In a basic distillation column, a feed stream enters in the middle of the column and two fractions leave, one at the top and other at the bottom. Component with lower boiling points will be concentrated in the fraction leaving the top while component with higher boiling point will be concentrated in the stream at the bottom. Separation is achieved by controlling the column temperature and pressure to take advantage of differences in the relative volatility of the components of mixture and therefore has tendency to change phase. The lighter and lower boiling point components evaporate and travel up the column to form the top product and the heavier, higher boiling point components condense and travel down the column to form the bottom product.

Principle of Separation

Distillation takes advantage of the difference in relative volatility of the feed mixture components. Generally for two or more compounds at a given pressure and temperature, there will be a difference in the vapour and liquid compositions at equilibrium due to component partial pressure. Distillation exploits this by bringing liquid and gas phases into contact at temperatures and pressures that promote the desired separation. During this contact, the components with the lower volatility (typically lower boiling point) preferentially move into the liquid phase while more volatile components move into the vapour phase. A distillation column may use either trays or a packed bed to bring the gas and liquid into contact. For a column using trays, we can consider the changes to gas and liquid phase compositions as they both enter and exit a single tray. The liquid entering the tray will contact the gas exiting the tray, Fig.2. The hotter vapour phase heats the incoming liquid phase as it bubbles through the tray, evaporating the light components which then leaves the tray with the vapour phase. Conversely, the cooling of the vapour phase by the liquid phase will cause the heavier components of the vapour phase to condense and exit the tray with the liquid phase.

1.     Applications

Distillation has been used widely to separate volatile components from non-volatile compounds. In industrial settings such as oil refineries and natural gas processing plants, this separation process is undertaken using a distillation column. 

Di  Distillation is used in industries to proceed many commercial processes; Production of gasoline,  , xylene, alcohol, paraffin, kerosene,  distilled water and many other liquids. Distillation is used for purification of solvents and liquid products from there reaction mixture.

3.      It is used in the manufacturing of distilled water, double distilled water used in laboratories and pharmaceutical industries. toxic and expensive organic solvents that are extensively used in the extraction, synthesis and analysis can be recovered by distillation for economic benefits as well as for  protection of environmental.

5.      Distillation is used in the separation of volatile oils such as clove oil, cardamom oil, anise oil,  eucalyptus oil etc. from the plant extracts.

6.      It can also be used in the isolation of volatile components from a mixture of two or more volatile liquids. It can be used as a quality control method for alcohol content in liquid formulations. The alcohol is separated from formulations by distillation and alcohol content is determined.

8.      It can be used to liquefy and separate gases from the air. For example: nitrogen, oxygen, and argon are distilled from the air.

9.      Distillation is used in crude fermentation broths to separate alcoholic spirits.

10.  It can also be used in the fractionation of crude oil into gasoline and heating oil.

7.    

 

Column Chromatography

Adsorption chromatography in biochemical applications usually consists of a solid stationary phase and a liquid mobile phase. The most useful technique is column chromatography, in which the stationary phase is confined to a glass or plastic tube and the mobile phase (a solvent or buffer) is allowed to flow through the solid adsorbent. A small amount of the sample to be analyzed is layered on top of the column. The sample mixture enters the column of adsorbing material and the molecules present are distributed between the mobile phase and the stationary phase. The various components in the sample have different affinities for the two phases and move through the column at different rates. Collection of the liquid phase emerging from the column yields separate fractions containing the individual components in the sample.

Specific terminology is used to describe various aspects of column chromatography. Poured or packed: When the actual adsorbing material is made into a column, it is said to be poured or packed.  Loading is Application of the sample to the top of the column. Developing or eluting: Movement of mobile phase through the loaded column is called developing or eluting the column. The bed volume is the total volume of solvent and adsorbing material taken up by the column. The void volume: is the volume taken up by the liquid phase in the column is the void volume. The elution volume is the amount of solvent required to remove a particular analyte from the column. This is analogous to Rf values in planar chromatography. In adsorption chromatography, solute molecules take part in specific interactions with the stationary phase. Herein lies the great versatility of adsorption chromatography.

Adsorbing material: A specific sorbent can be chosen that will effectively separate a mixture. from a large variety of available sorbing materials,  There is still an element of trial and error in the selection of an effective stationary phase. However, experiences of many investigators are recorded in the literature and are of great help in choosing the proper system.  Adsorbing materials come in various forms and sizes. The most suitable forms are dry powders or a slurry form of the material in an aqueous buffer or organic solvent. Alumina, silica gel, and fluorisil do not normally need special pretreatment. The size of particles in an adsorbing material is defined by mesh size. This refers to a standard sieve through which the particles can pass. A 100-mesh sieve has 100 small openings per square inch. Adsorbing material with high mesh size (400 and greater) is extremely fine and is most useful for very high resolution chromatography. For most biochemical applications, 100 to 200 mesh size is suitable.

Operation of A Chromatographic Column

A typical column setup is shown in Figure 5.4. The heart of the system is, of course, the column of adsorbent. In general, the longer the column, the better the resolution of components. However, a compromise must be made because flow rate decreases with increasing column length. The actual size of a column depends on the nature of the adsorbing material and the amount of chemical sample to be separated. For preparative purposes, column heights of 20 to 50 cm are usually sufficient to achieve acceptable resolution. Column inside diameters may vary from 0.5 to 5 cm.

Packing of Column

Once the adsorbing material and column size have been selected, the column is poured. If the tube does not have a fritted disc in the bottom, a small piece of glass wool or cotton should be used to support the column. Most columns are packed by pouring a slurry of the sorbent into the tube and allowing it to settle by gravity into a tight bed. The slurry is prepared with the solvent or buffer that will be used as the initial developing solvent. Pouring of the slurry must be continuous to avoid formation of sorbent layers. Excess solvent is eluted from the bottom of the column while the sorbent is settling. The column must never run dry. Additional slurry is added until the column bed reaches the desired height. The top of the settled adsorbent is then covered with a small circle of filter paper or glass wool to protect the surface while the column is loaded with sample or the eluting solvent is changed. Sometimes it is necessary to pack a column under pressure (5 to 10 psi). This leads to a tightly packed bed that yields more reproducible results, especially with gradient elutions sections).

Loading Of Column

The sample to be analyzed by chromatography should be applied to the top of the column in a concentrated form. If the sample is solid, it is dissolved in a minimum amount of solvent; p. 74. After the sample is loaded onto the column with a graduated or disposable pipet, it is allowed to percolate into the adsorbent. A few milliliters of solvent are then carefully added to wash the sample into the column material. The column is then filled with eluting solvent.

Eluting The Column

The chromatography column is developed by continuous flow of a solvent. Maintaining the appropriate flow rate is important for effective separation. If the flow rate is set too high, there is not sufficient time for complete equilibration of the analytes with the two phases. Too low a flow rate allows diffusion of analytes, which leads to poor resolution and broad elution peaks. It is difficult to give guidelines for the proper flow rate of a column, but, in general, a column should be adjusted to a rate slightly less than “free flow.” Sometimes it is necessary to find the proper flow rate by trial and error. One problem encountered during column development is a changing flow rate. As the solvent height above the column bed is reduced, there is less of a “pressure head” on the column, so the flow rate decreases. This can be avoided by storing the developing solvent in a large reservoir and allowing it to enter the column at the same rate as it is emerging from the column.

Adsorption columns are eluted in one of three ways. All components may be eluted by a single solvent or buffer. This is referred to as continual elution. In contrast, stepwise elution refers to an incremental change of solvent to aid development. The column is first eluted with a volume of one solvent and then with a second solvent. This may continue with as many solvents or solvent mixtures as desired. In general, the first solvent should be the least polar of any used in the analysis, and each additional solvent should be of greater polarity or ionic strength. Finally, adsorption columns may be developed by gradient elution brought about by a gradual change in solvent composition. The composition of the eluting solvent can be changed by mixing two different solvents to gradually change the ratio of two solvents.

Alternatively, the concen tration of a component in the solvent can be gradually increased. This is most often done by addition of a salt (KCl, NaCl, etc.). Devices are commercially avail able to prepare predetermined, reproducible gradients.

Collecting the Eluent

The separated components emerging from the column in the eluent are usually collected as discrete fractions. This may be done manually by collecting specified volumes of eluent in Erlenmeyer flasks or test tubes. Alternatively, if many fractions are to be collected, a mechanical fraction collector is convenient and even essential. An automatic fraction collector  directs the eluent into a single tube until a predetermined volume has been collected or until a preselected time period has elapsed; then the collector advances another tube for collection. Specified volumes are collected by a drop counter activated by a photocell, or a timer can be set to collect a fraction over a specific period.

Detection of Components

The completion of a chromatographic experiment calls for a means to detect the presence of analytes in the collected fractions. The detection method used will depend on the nature of the analytes. Smaller molecules such as lipids, amino acids, and carbohydrates can be detected by spotting fractions on a thin-layer plate or a piece of filter paper and treating them with a chemical reagent that pro duces a color. The same reagents that are used to visualize spots on a thin-layer or paper chromatogram are useful for this. Proteins and nucleic acids are conveniently detected by spectroscopic absorption measurements at 280 and 260 nm, respectively. Enzymes can be detected by measurements of catalytic activity asso ciated with each fraction. Research-grade chromatographic systems are equipped with detectors that continuously monitor some physical property of the eluent and display the separation results on a computer screen . The newest advance in detectors is the diode array . Most often the eluent is directed through a flow cell where absorbance or fluorescence characteristics can be measured. The detector is connected to a recorder or com puter for a permanent record of spectroscopic changes. When the location of the various analytes is determined, adjacent fractions containing identical components are pooled and stored for later use.

Liquification of gases

https://docs.google.com/presentation/d/1dciKSI9iGj5l4hQjxAjaTPAgxqbQS9Fh/edit?usp=drive_link&ouid=103038410916064935907&rtpof=true&sd=true

 

Nano Chemistry Contents

 

Course Title:              Nano Chemistry

Course Code:             CHM-421                                                      

Credit Hours:            3(2-1)

 

COURSE OBJECTIVES:

The main goal of this course is to give students an in-depth/up-to-date acquaintance with the emerging interdisciplinary research field of nanochemistry. The course will offer a comprehensive overview of special topics, such as nanomedicine, molecular imaging, drug delivery, and nano-bio devices and systems, which all represent major applications in the field of Nano chemistry.

 

COURSE CONTENTS:

Nano Materials

Introduction of nanochemistry and nanomaterials. Properties of material at nanoscale. Carbon nanotubes. Metal nanoconfiguration, nanoparticles, wires, rods, discs, thin films and bulk.

Application of nano materials in industries

Use in textile. Opto electronics. Polymers. Food and cosmetic industries.

Application in medical sciences

Nano biotic. Drug delivery. Photo dynamic therapy. Anticancer therapies.

nano robots                     

Mechanical, physical and electrical functions of Nano robots.

 

PRACTICALS:

Synthesis of semiconductor nano particles through, Precipitation, Co precipitation, Microwave and Internal Combustion methods

 

RECOMMENDED BOOKS:

1.      G.B. Sergeev. 2006. Nanchemistry.  Elsevier. 1^st Ed. Netherland.

2.      I. Kirkland. and J. I. Hutchison, 2007. Nanocharacterisation. The Royal Society of Chemistry. U.K.

3.      R. E. Hester and R. M. Harrison, 2007. Nanotechnology: Consequences for Human Health and the Environment. The Royal Society of Chemistry. U.K

Nanomaterials

 

https://docs.google.com/presentation/d/1780SISZ4l9JOhzAjpvq4Mt5xwFrkhwKE/edit?usp=drive_link&ouid=103038410916064935907&rtpof=true&sd=true

Deviation of gases from ideal behavior

 

Physical Chemistry I CHM-170Physical Chemistry I CHM-170Physical Chemistry I CHM-1

https://docs.google.com/presentation/d/1gnqrpnjxgGS0R4-sPmSPjWfytmmJJE7y/edit?usp=drive_link&ouid=103038410916064935907&rtpof=true&sd=true

Physical Chemistry I

 

Semester III

 

Course Title:              Physical Chemistry-I  

Course Code:             CHM-270

Credit Hours: 4 (3-1)

 

Course Objectives:

• Understanding of fundamental to slight advanced principles of Physical Chemistry.
• Understanding of the behaviour of matter in its different states.
• This course also highlights the basics of chemical reactions and their kinetic behaviour.
• Thermodynamic study will also help out the students to know about the prediction of reaction feasibility.

 

Course Contents:

Physical States of Matter:

Critical phenomenon and critical constants, Equation of state, Physical properties of liquids: surface tension, viscosity, refractive index etc. and their applications, Unit cells and crystal systems, Method of crystal structure analysis (X-Ray Diffraction, Electron diffraction), The Bragg Equation, Introduction to plasma.

Chemical Equilibrium and Chemical Kinetics

Concepts of chemical equilibrium, Rate of reaction, Rate law, order and molecularity of the reactions. Integrated rate laws: Zero, pseudo first, second order reactions with same and different initial concentrations of reactants, third order reactions, Determination of reaction order and its rate constant, Effect of temperature on the reaction rate

Solution Chemistry

Ideal and non-ideal solutions, Raoult’s and Henery’s laws and their applications, Molecular interactions in solutions, Colligative properties, Distillation and concept of azeotropic mixture, Catalysis, Colloids, emulsion and industrial applications of colloids.

Thermodynamics

State functions, Laws of thermochemistry and thermodynamics, Thermodynamic processes.

 

Practicals:

Investigate the kinetics of hydrolysis of ethyl acetate in the presence of HCl at room temperature. Determine the viscosity and parachor values of liquids. Determination of percent composition of liquid solution viscometrically. Determine the molecular mass of a given compound by lowering of freezing point (Cryoscopic method). Determine the molecular mass of a given compound by elevation of boiling point (Ebullioscopic method). Determine the molecular mass of a given polymer viscometrically. Determination of heat of solution by solubility method

 

Recommended Books:

        1.            G.M. Barrow. 2007. Physical Chemistry. 5^th Ed. Tata McGraw-Hill New Delhi.

        2.            H.N. Bhatti and Z.H. Farooqi. 2014. Modern Physical Chemistry. The Caravan Book House

        3.            I .N. Levine. 2008. Physical Chemistry. 6^th Ed. McGraw-Hill Education.

        4.            K.J. Laidler. 2001. The world of Physical Chemistry. 1^st Ed. Oxford University Press.

        5.            K.J. Laidler; H.M. John; C.S. Bryan. 2003. Physical Chemistry. 4^th Ed. Houghton Mifflin Publishing Company Inc.

        6.            P. Atkins and J. D. Paula. 2010. Atkin’s Physical Chemistry. 9^th Ed. Oxford University Press.

        7.            R. J. Silbey, R. A. Alberty and M. G. Bawendi. 2005. Physical Chemistry. 4^th Ed. John Wiley & Sons.

        8.            D.Shoemaker.2003. Experiments in Physical Chemistry. 8^th Ed. McGraw-Hill Publishing Company Limited

        9.            P. Atkins; L. Jones. 2010. Chemical Principles. 5^th Ed. W.H. Freeman and Company, New York

    10.            H.N. Bhatti. 2005. Experimental Physical Chemistry. 1^st Ed. Caravan Press

    11.            B.D. Khosla; V.C. Garg; A. Gulati. 2008. Senior Practical Physical Chemistry. R. Chand & Co, New Delhi

    12.            A.M. Hepern and G.C. McBane. 2006. Experimental Physical Chemistry. 3^rd Ed. W. H. Freeman and Co, New York