Inorganic Commodity Chemicals

HYDROCHLORIC ACID

ChE 313 Industrial Chemistry Lecture

Engr. May V. Tampus

Hydrochloric Acid: interesting facts

Found naturally in the gases evolvedfrom volcanoes

Present in the atmosphere of theplanet Venus

Present in the digestive system ofmost mammals

Listed as one of the prohibitedsubstance

Hydrochloric Acid Production

*Data source: Kirk-Othmer Encyclopedia of Chemical Technology

Today worldwide usage of HCl exceeds 20 M tons annually.

Industrial Uses of HCl

Descaling agent

Catalyst in food processing

Pickling liquor to dissolve mill scales in steel industry

Dissolve pulverized stone during petroleum operation –oil-well acidiIng

CaCl2 manufacture

Oil & gas well acidizing

Production of high-fructose corn syrup (HFCS)

Manufacture of dyes, phenols, & plastics

pH control and neutralization

Regenerant of ion-exchange

resins

Gelatin manufacture

Soy sauce production

Magnesia and metal

production

Manufacture of chemical

intermediates, e.g., FeCl3,

ZnCl2, Al2Cl3, etc.

Ore reduction (Mn, Ra, V, Ta,

Sn, W)

Leather processing

Hydrochloric Acid

Forms of Hydrochloric Acid

Hydrogen chloride: gas at ordinarytemperature

Hydrochloric acid: aqueous solutionof hydrogen chloride

Muriatic acid: commercial grade ofHCl solution; clear colorless to slightlyyellow liquid with a strong pungentand irritating odor; strong and highlycorrosive; soluble in water and alcoholbut insoluble in hydrocarbon

Common Grades of Muriatic Acid

Mass %HCl

Density

Specific gravity O Be

27.92 1.1417 18

31.45 1.1600 20

35.21 1.1789 22

Industrial Grades of HCl

1) Concentrated grade – 38-40%

2) Bulk-industrial grade – 30-34%

(optimized for transport & limit product

loss)

3) Household grade – 10-12% (intended for

cleaning)

Physical Properties of Hydrochloric Acid

Properties Value

Molar mass 36.46 g/mol

Melting point -114.8o C

Boiling point -84.9oC

Specific gravity 1.84

Solubility in water 720 g/L (at 20o C)

Vapor pressure 423 kPa

pKa -7

pKb 21.0

NFPA ratings Health: 3 Flammability: 0 Reactivity: 1 Other: ACID

Stability Stable under ordinary conditions

Thermochemistry of HCl

Thermodynamic Properties

Std enthalpy of formation ΔfH

o298

–92.31 kJ mol-1

Std enthalpy of combustion ΔcH

o298

–95.31 kJ mol-1

Standard molar entropy So

298

186.902 J K-1 mol-1

Specific heat capacity, C 0.7981 J K-1 g-

Chemical Properties of Hydrochloric Acid

• Hydrochloric acid readily ionizes in water:

HCl (g) + H2O(l) Cl-(aq) + H3O+(aq)

• Even in the absence of water it still reacts as an acid to form:

HCl (g) + CH3OH (l) Cl-(aq) +

CH3O+H2(aq)

Industrial Production of Hydrochloric Acid

Direct Synthesis from hydrogen

and chlorine

Decomposition of metal chlorides

by acids

As by-product from chemical

processes

Recovery by incineration of waste

organics

Recovery from hydrochloric acid

solutions

Synthesis from Hydrogen and Chlorine

• Less than 10% of HCl in U.S.is made via this reaction

• Reaction is adiabatic andtakes place in an HCl burneror HCl oven

• Acid produced is calledBURNER ACID

)44(1842 )()(2)(2 kcalkJHClClH ggg

Synthesis from Hydrogen and Chlorine

• PROCESS CONDITIONSTemperature: 2490o CPressure: 14 kPaRapid cooling of free

H2 & Cl2 to 200o CEquilibrium mixture contains 4.2% v/v

free Cl2

Use a stoichiometric amount of feed gas mixture in order to produce 99% HCl 30-32% HCl (burner acid) is produced

by absorption

Decomposition of Metal Chlorides by Acids

1. Salt-Sulfuric Acid (Saltcake) Process

NaCl + H2SO4 HCl + NaHSO4 at 150oC (1)

NaCl + NaHSO4 HCl + Na2SO4 at 550-660o C (2)

Both reactions are endothermic.

Reactions occur in a Mannheim mechanical furnace.

Produces 30-60% HCl

Decomposition of Metal Chlorides by Acids

2. Hargreaves Process & Leblanc Process

2SO2 + O2 + 2H2O + 4NaCl 4HCl + 2Na2SO4

Reaction is at 4000-5500o C Reaction is self-sustaining. Reaction is exothermic. Produces 10-12% HCl

Hydrogen chloride as By-products from

Chemical Processes

1. As a by-product in chlorination of botharomatic and aliphatic hydrocarbons– integration of organic and inorganic chemicals industry

RH + Cl2 RCl + HClRCl + HF RF + HCl

Hydrogen chloride as By-products from Chemical Processes

2. As a by-product of the Leblanc Process

NaCl + H2SO4 NaHSO4 + HCl

NaHSO4 + NaCl Na2SO4 + HCl4HCl + MnO2 2Cl2 + MnCl2 + H2O

Na2SO4 + C + CaCO3 Na2CO3 + CaSO4

Na2CO3 + Ca(OH)2 2NaOH + CaCO3

Hydrogen chloride as By-products from Chemical Processes

3. As a by-product of the Manufacture ofIsocyanate

RNH2 + COCl2 RNCO + 2HCl

But HCl cannot be recycled other than the

regeneration of chlorine!

Group Assignment

1. Enumerate at least five industries which use hydrochloric acid anddescribe how HCl is used or applied in each industry.

2. List down at least seven chemical reactions of HCl with other compounds.Literature source: Kirk-Othmer Encyclopedia.

3. Identify the sources of raw materials for each production methodpresented.

4. Tabulate the operating temperature, operating pressure, enthalpy ofreaction, yield, and other process conditions for the following:

a. Production of HCl via the Saltcake process

b. Productio of HCl via the Hargreaves process

c. Production of HCl as by-product of chlorination of benzene

d. Production of HCl as by-product of the Leblanc process

e. Production of HCl as by-product of the Isocyanate manufacture

INSTRUCTION:S Write your answer on a short bondpaper. Cite references used. Submitassignment on July 13, WED, not later than 5:00 PM. Group members must affix theirsignature.