Mineral Acids Course : ACCE-2221 2nd Year : Even Semester Group-A : Chapter-1
7 December 2015 Course Outline
1. Sources of sulphur
2. Mining of sulphur- Sicilian and Frasch processes
3. Manufacture of sulphuric acid- chamber and contact process
4. Oleum and uses
5. Production of hydrochloric acid and nitric acid- Properties & uses
7 December 2015 Mineral Acid
A Mineral Acid is an acid derived from one or more inorganic compounds. One part of these acid comes from inorganic minerals, that is why these acids are known as mineral acid. Some mineral acids are- • HCl
• HNO3
• H2SO4
• H3PO4
• H3BO3
• HClO4
• H4TiO4
7 December 2015 Sources of Sulfur
• Volcanic deposits in Sicily (Italy) • Iron pyrite • Ammonium sulfate • Calcium sulfate • Fossil fuel • Zinc blend • Gypsum • Epsom salt
7 December 2015 Sources of Sulfur
Sulfur Mining of Sulfur Mining of Sulfur
7 December 2015 Sources of Sulfur
Sulfur can be collected by two major process:
1. Sicilian Process
2. Frasch Process
7 December 2015 Frasch process
In the Frasch process, three concentric tubes are introduced into the sulfur deposit. Superheated water (165 °C, 2.5-3 MPa) is injected into the deposit via the outermost tube. Sulfur (m.p. 115 °C) melts and flows into the middle tube. Water pressure alone is unable to force the sulfur into the surface due to the molten sulfur's greater density, so hot air is introduced via the innermost tube to froth the sulfur, making it less dense, and pushing it to the surface.
The sulfur obtained can be very pure (99.7 - 99.8%). In this form, it is light yellow in color. If contaminated by organic compounds, it can be dark-colored; further purification is not economic, and usually unnecessary. Using this method, the United States produced 3.89 million tons of sulfur in 1989, and Mexico produced 1.02 million tons of sulfur in 1991.
7 December 2015 Frasch process
7 December 2015 Frasch process
7 December 2015 Sulfuric Acid
History Islamic alchemists Jābir ibn Hayyān and Jamal Din al-Watwat included vitriol in their mineral classification lists. Ibn Sina focused on its medical uses and different varieties of vitriol. Sulfuric acid was called "oil of vitriol" by medieval European alchemists because it was prepared by roasting "green vitriol" (iron (II) sulfate) in an iron retort.
Sulfuric acid (alternative spelling sulphuric acid) is a highly corrosive strong mineral acid with the
molecular formula H2SO4. It is a pungent-ethereal, colorless to slightly yellow viscous liquid which is soluble in water at all concentrations. Sometimes, it is dyed dark brown during production to alert people to its hazards.The historical name of this acid is oil of vitriol.
7 December 2015 Sulfuric Acid
Production Process
1. Contact Process
2. Chamber Process
7 December 2015 Sulfuric Acid
1. Contact Process
The contact process is the current method of producing sulfuric acid in the high concentrations needed for industrial processes. Platinum was formerly employed as a catalyst for the reaction, but as it is
susceptible to poisoning by arsenic impurities in the sulfur feedstock, vanadium(V) oxide (V2O5) is now preferred.
This process was patented in 1831 by British vinegar merchant Peregrine Phillips.In addition to being a far more economical process for producing concentrated sulfuric acid than the previous lead chamber process, the contact process also produces sulfur trioxide and oleum.
7 December 2015 Sulfuric Acid
1. Contact Process
The process can be divided into five stages:
1. combining of sulfur and oxygen 2. purifying sulfur dioxide in the purification unit; 3. adding excess of oxygen to sulfur dioxide in presence of catalyst vanadium pentoxide, with temperatures of 450 degrees Celsius and pressure of 1-2 atm.; 4. sulfur trioxide formed is added to sulfuric acid which gives rise to oleum (disulfuric acid); 5. the oleum then is added to water to form sulfuric acid which is very concentrated.
7 December 2015 Sulfuric Acid 1. Contact Process
H2S407
7 December 2015 Sulfuric Acid-Reaction
-1 Sulfur dioxide and oxygen then react as follows: 2 SO2(g) + O2(g) ⇌ 2 SO3(g) : ΔH = -197 kJ mol
According to the Le Chatelier's principle, a lower temperature should be used to shift the chemical equilibrium towards the right, hence increasing the percentage yield. However too low of a temperature will lower the formation rate to an uneconomical level. Hence to increase the reaction rate, high temperatures (450 °C), medium pressures (1-2 atm), and vanadium(V) oxide (V2O5) are used to ensure a 96% conversion. Platinum would be a more effective catalyst, but it is very costly and easily poisoned.The catalyst only serves to increase the rate of reaction as it does not change the position of the thermodynamic equilibrium. The mechanism for the action of the catalyst comprises two steps:
5+ 5+ 2- 4+ 1. Oxidation of SO2 into SO3 by V : 2 SO2 + 4V + 2 O → 2 SO3 + 4V
4+ 5+ 4+ 5+ 2- 2. Oxidation of V back into V by oxygen (catalyst regeneration): 4 V + O2 → 4 V + 2 O
7 December 2015 Sulfuric Acid
Condition for maximum yield of SO3
1. Purification of gas 2. Oxygen supply 3. Temperature (450˚C) 4. Condition of catalyst 5. Pressure (1.5-1.7 atm.)
7 December 2015 Sulfuric Acid
2. Chamber Process
Sulfur dioxide is introduced with steam and oxides of nitrogen into large chambers lined with sheet lead where the gases are sprayed down with water and chamber acid. The sulfur dioxide and nitrogen dioxide dissolve and over a period of approximately 30 minutes the sulfur dioxide is oxidized to sulfuric acid. The presence of nitrogen dioxide is necessary for the reaction to proceed. The process is highly exothermic, and a major consideration of the design of the chambers was to provide a way to dissipate the heat formed in the reactions.
7 December 2015 Sulfuric Acid
2. Chamber Process
7 December 2015 Sulfuric Acid 2. Chamber Process
7 December 2015 Sulfuric Acid
2. Chamber Process (Chemistry)
Sulfur dioxide is generated by burning elemental sulfur or by roasting pyritic ore in a current of air:
S8 + 8 O2 → 8 SO2
4 FeS2 + 11 O2 → 2 Fe2O3 + 8 SO2
Nitrogen oxides are produced by decomposition of niter in the presence of sulfuric acid or hydrolysis of nitrosylsulfuric acid:
2 NaNO3 + H2SO4 → Na2SO4 + H2O + NO + NO2 + O2
2 NOHSO4 + H2O → 2 H2SO4 + NO + NO2
7 December 2015 Sulfuric Acid
2. Chamber Process
In the reaction chambers, sulfur dioxide and nitrogen dioxide dissolve in the reaction liquor. Nitrogen dioxide is hydrated to produce nitrous acid which then oxidizes the sulfur dioxide to sulfuric acid and nitric oxide. The reactions are not well characterized but it is known that nitrosylsulfuric acid is an intermediate in at least one pathway. The major overall reactions are:
2 NO2 + H2O → HNO2 + HNO3
SO2 (aq) + HNO3 → NOHSO4
NOHSO4 + HNO2 → H2SO4 + NO2 + NO
SO2 (aq) + 2 HNO2 → H2SO4 + 2 NO
7 December 2015 Sulfuric Acid
2. Chamber Process
Nitric oxide escapes from the reaction liquor and is subsequently reoxidized by molecular oxygen to nitrogen dioxide. This is the overall rate determining step in the process:
2 NO + O2 → 2 NO2
Nitrogen oxides are absorbed and regenerated in the process, and thus serve as a catalyst for the overall reaction:
2 SO2 + 2 H2O + O2 → 2 H2SO4
7 December 2015 Sulfuric Acid
Comparison between Chamber process & Contact process
Chamber Process Contact Process Dilute acid is produced (65-70%) Conc. Acid is produced Impure acid is produced Pure acid is produced
SO2 is not use fully SO2 is used fully
Purification of SO2 is not so necessary Purification of SO2 is necessary Purification of acid is costly No need purification process Production process less costly Costly It is very critical to make conc. acid Conc. Acid is produced
7 December 2015 Sulfuric Acid Physical Properties :
MP : 10°C BP : ~338 °C Density : 1.840 g/mL at 25 °C(lit.) Vapor density : <0.3 (25 °C, vs air) Vapor pressure : 1 mm Hg ( 146 °C) Storage temp. : Store at RT.
Solubility : H2O: soluble Water Solubility : miscible Sensitive : Hygroscopic
7 December 2015 Sulfuric Acid
Chemical Properties :
1. Reaction With Water
2. Reaction With Metals
3. Reaction With Salt
4. Reaction With Alkali
5. As oxidizing agent
6. Action of Heat
7 December 2015 Uses - Sulfuric Acid
1. Production of acid (HCl, HNO3, HF), Washing soda, salt, explosive, dying industry, petroleum purification industry etc. 2. Drying of wet gas 3. Medicine industry 4. Storage cells, plastic industry 5. As a reagent in laboratory.
7 December 2015 Uses - Sulfuric Acid
7 December 2015 Sulfuric Acid
7 December 2015 Oleum Oleum or fuming sulfuric acid, is a solution of various compositions of sulfur trioxide in sulfuric acid, or sometimes more specifically to disulfuric acid (also known as pyrosulfuric acid).
Oleums can be described by the formula ySO3.H2O where y is the total molar sulfur trioxide content. The value of y can be varied, to include different oleums. They can also be described by the formula
H2SO4.xSO3 where x is now defined as the molar free sulfur trioxide content. Oleum is generally assayed according to the free SO3 content by weight. It can also be expressed as a percentage of sulfuric acid strength
Oleum is produced in the contact process, where sulfur is oxidized to sulfur trioxide which is subsequently dissolved in concentrated sulfuric acid. Sulfuric acid itself is regenerated by dilution of part of the oleum. Oleum is the term used to describe fuming sulfuric acids. Oleum is made in various strengths and
consists of SO3 dissolved in 100% H2SO4. Thus, for example, 20% oleum contains 20% SO3 and 80% H2SO4 by weight.
7 December 2015 Uses of Oleum
Oleum is a harsh reagent, and is highly corrosive.
1. As an intermediate for transportation 2. Organic chemistry 3. Explosives manufacture 4. chemical-technical industry
7 December 2015 Hydrochloric Acid History
Hydrochloric acid was first discovered by Jabir ibn Hayyan (Geber), by mixing common salt with vitriol
(sulfuric acid). Jabir discovered many important chemicals, and recorded his findings in over 20 books,
which carried his chemical knowledge of hydrochloric acid and other basic chemicals for hundreds of
years.
7 December 2015 Hydrochloric Acid
The large scale production of HCl as a desired primary finished product is almost always integrated in a large scale chlor-alkali facility. In the chlor-alkali industry, salt solution is electrolyzed producing chlorine gas, sodium hydroxide and hydrogen gas. The pure chlorine gas can be re-combined with the hydrogen gas forming hydrogen chloride gas.
The resulting hydrogen chloride gas is absorbed in de-mineralized water to form hydrochloric acid.
7 December 2015 Hydrochloric Acid
Fig: Chlor-Alkali process for producing HCl acid
7 December 2015 Hydrochloric Acid
7 December 2015 Hydrochloric Acid
Concentrated hydrochloric acid when kept in open air sometimes produces a cloud of white fumes. The explanation for it is that ,
(a) Concentrated hydrochloric acid emits strongly smelling HCl gas all the time
(b) Oxygen in air reacts with the emitted HCl gas to form a cloud of chlorine gas
(c) Strong affinity of HCl gas for moisture in air results in forming of droplets of liquid solution which appears like a cloudy smoke
(d) Due to strong affinity for water, concentrated hydrochloric acid pulls moisture of air towards itself. This moisture forms droplets of water and hence the cloud is formed.
7 December 2015 What is the maximum purity of HCl acid and why?
7 December 2015 Properties of Hydrochloric Acid
Physical Properties of Hydrochloric Acid:
1. It is a colorless acid.
2. It has sharp irritating smell.
3. It has sour taste.
4. It is heavier than air.
5. It gives white fumes in open air.
7 December 2015 Properties of Hydrochloric Acid
Chemical Properties of Hydrochloric Acid:
1. Reaction With Water
2. Reaction With Metals
3. Reaction With Ammonia
4. Reaction With Bases
5. Reaction With Carbonates and Bi-charbonates
6. Reaction With Silver Nitrate
7 December 2015 Uses of Hydrochloric Acid
1. It is used in the manufacturing of plastics, dyes, textile, rubber and medicines.
2. It is used in the preparation of aqua regia.
3. It is used as a reagent in laboratory.
4. It is used for the extraction of glue from animal tissue and bones.
5. It is used for the cleaning of iron sheets during electroplating.
6. It is used to clean calcium carbonate deposits from sanitary and floors.
7 December 2015 Uses of Hydrochloric Acid
7 December 2015 Nitric Acid
Nitric acid (HNO3), also known as aqua forties and spirit of niter, is a highly corrosive mineral acid.
The pure compound is colorless, but older samples tend to acquire a yellow cast due to decomposition
into oxides of nitrogen and water. Most commercially available nitric acid has a concentration of 68%.
7 December 2015 History of Nitric Acid
Throughout History, Nitric Acid has been called Aqua Regina, which is Latin meaning "royal water", by ancient scientists and chemists who first discovered it. Nitric Acid has the name Aqua Regina due to the fact that because to its corrosive behavior, it is one of few "reagents" that can dissolve metals such as gold and platinum.
The first known person to write a decription and discuss their method of sythesizing nitric acid was named Jabir ibn Hayyan (born in Persia c. 721 and died in Iraq c. 815).
Jabir ibn Hayyan
7 December 2015 Nitric Acid
Production process of Nitric acid
1. Distillation process
2. Arc process
3. Ostwald’s process
7 December 2015 Nitric Acid
Distillation process
7 December 2015 Nitric Acid Arc process
7 December 2015 Nitric Acid Ostwald process
Originally Nitric acid was produced via several routes, but in 1906 the first large scale production of
Nitric acid using the Ostwald process came on stream and since then almost all nitric acid is
manufactured by this route. The Ostwald process takes place in 3 main steps, as follows:
1. Oxidation of ammonia to produce nitrogen monoxide,
2. Oxidation of the nitrogen monoxide to produce nitrogen dioxide
3. Absorption of the nitrogen oxides in water to produce nitric acid.
7 December 2015 Nitric Acid Industrial Preparation On a commercial scale, nitric acid is manufactured through the Ostwald's process - the process of catalytic oxidation of ammonia. Ostwald's process The conversion of ammonia into nitric acid in this process is done through the following steps:
Step1 Oxidation of ammonia to nitric oxide Ammonia is oxidized by air in the presence of Pt catalyst at 800°C to give nitric oxide.
7 December 2015 Nitric Acid Step 2
Oxidation of NO to NO2 The nitric oxide is oxidised by air at temperature below 100°C, to give nitrogen dioxide (NO2)
Step 3 Formation of nitric acid
Nitrogen dioxide is then converted to nitric acid by absorbing NO2 in water, in the presence of air.
7 December 2015 Nitric Acid
Flow diagram: Ostwald's process for the manufacture of nitric acid
7 December 2015 Nitric Acid
Fig: Ostwald's process for the manufacture of nitric acid
7 December 2015 Ostwald Process
Converter The converter is made of aluminium and fitted with platinum - rhodium gauze cylinder (23 cm x 34 cm). The cylinder is closed at the bottom with a silica lid. The gauze is initially heated to 800°C electrically. Thereafter no external heating is required as oxidation of ammonia is an exothermic reaction. A mixture of ammonia and clear air (volume ratio = (1:8) is then passed through the gauze from the top, and the products leave from the bottom. Every 1000 cm2 area of the gauze produces about 500 kg of nitric oxide, every 24 hours.
7 December 2015 Ostwald Process
Oxidation tower When nitric oxide, containing nitrogen and some water vapors, come out of the converter, they are cooled to about 100°C by passing them through coolers. In the oxidation tower, nitric oxide
is mixed with more air and it gets converted to NO2.
Absorption tower
NO2 is allowed to enter the absorption tower from the lower end. The tower is packed with quartz pieces and water is sprinkled from the top. Here, NO2 is absorbed into water in the presence of air to yield nitric acid.
7 December 2015 Nitric Acid
7 December 2015 Properties of Nitric Acid
Physical Properties Molecular Weight 63.02 Colour Colorless In liquid state Transparent to yellow As gaseous oxides Transparent to yellow or brown Odour Sweet to pungent Hazards Corrosive In liquid state Rapidly attacks flesh and most organic matter As gaseous oxides Anaesthetic to dangerously toxic Melting Point -41.6°C
Boiling Point of constant – (68% HNO3 at 78mmHg) 120.5°C Density (68% HNO3 at 20°C) 1.41g/l
7 December 2015 Properties of Nitric Acid
Chemical Properties
1. Reaction with water
2. Reaction with basic oxide
3. Reaction with hydroxide
4. Reaction with carbonates
5. Reaction with metals
6. Reaction with metallic sulphites
7 December 2015 Properties of Nitric Acid
Chemical Properties
7 December 2015 Properties of Nitric Acid
Chemical Properties
7 December 2015 Properties of Nitric Acid
Chemical Properties
7 December 2015 Properties of Nitric Acid
Chemical Properties
7 December 2015 Uses of Nitric Acid
Nitric acid is an oxidising mineral acid with physical and chemical properties that make it one of the most useful inorganic minerals. Nitric acid is used in a wide range of industries the most common of which are the production of - Explosives, Nitrogen fertilizers Dyestuffs Nylon precursors Specialty organic compounds. Analytical reagent
7 December 2015 Thank you all
7 December 2015