CHM 585/490

Chapter 2

Chapter 2

• Petroleum Cracking

• C4

• Methanol derivatives– MTBE– Formaldehyde– Acetic Acid

• Ethylene, Chloroalkali and derivatives

Major Petroleum Fractions

Fraction Boiling Range (ºC)

Use

Gases < 20 Methane(65-90%), ethane, propane, butane

Naptha 70 - 200 Base for gasoline; used for chemicals

Gas Oil 175-370 Jet, diesel and heating fuel

Heavy Fraction

> 370 Lubrication, boiler fuel, paving

Thermal Cracking

• Radical cleavage of hydrocarbons

• 400 – 500 ºC under pressure

CH3(CH2)6CH3 CH3(CH2)3CH2 CH2CH2CH3. .+

CH3CH2CH2CH2CH2. CH3(CH2)6CH3

CH3(CH2)3CH3 CH3(CH2)5CHCH3

+

+ .CH3CH2CH2CH2CH2

. CH3CH2CH2. H2C CH2

CH3(CH2)5CHCH3. CH3CH2CH2CH2CH2.

+

+

Example of Products from Naptha Cracking

Product Weight %

Residual Gas ( CH4, H2) 16

Ethylene 35

Propene 15

C4 Fraction 8.5

C5 Fraction and higher boiling fractions

25.5

Typical C4 Composition

Components Volume %

Isobutene 44-49

1- Butene 24-28

2-Butene ( cis and trans) 19-21

N-Butane 6-8

Isobutane 2-3

MTBE Synthesis

• C4 raffinate is reacted with methanol at 30 - 100ºC with an acid ion exchange resin

• Isobutene selectively reacts

• Methanol and MTBE form a pressure dependent azeotrope. Methanol removed either by a pressurized distillation or by pervaporation (membrane)

OCH3+ CH3OH

MTBE

Since 1995, the Clean Air Act requires reformulated gasoline (RFG) year-round in cities with the worst ground-level ozone (smog).

RFG is oxygenated gasoline (minimum of 2 percent oxygen by weight) that is specially blended to have fewer polluting compounds than conventional gasoline.

About 30 percent of this country’s gasoline is reformulated gasoline, of which 87% contains MTBE. 

Refiners have chosen MTBE as the main oxygenate in RFG in cities outside of the Midwest primarily for economic reasons and its blending characteristics. Unlike ethanol, MTBE can be shipped through existing pipelines, and its volatility is lower, making it easier to meet the emission standards.

The majority of the human health-related research conducted to date on MTBE has focused on effects associated with the inhalation of the chemical.

When research animals inhaled high concentrations of MTBE, some developed cancers or experienced other non-cancerous health effects EPA's Office of Water has concluded that available data are not adequate to estimate potential health risks of MTBE at low exposure levels in drinking water but that the data support the conclusion that MTBE is a potential human carcinogen at high doses.

EPA reviewed available health effects information on MTBE in its 1997 Drinking Water Advisory. The drinking water advisory document indicates that there is little likelihood that MTBE in drinking water will cause adverse health effects at concentrations between 20 and 40 ppb or below.

EPA estimates that smog-forming pollutants are being reduced annually by at least 105 thousand tons, and toxics by at least 24 thousand tons.

http://www.epa.gov/mtbe

MTBE U.S.Production

• 282,000 barrels per day (2001)

• 42 gallons per barrel => 12 million gallons per day

• Density = 0.74 1 gallon of water = 8.3 lbs.

• 6.1 lb. MTBE per gallon

• 72 million pounds per day

• At 365 days => 26 billion pounds per year

• December 1998 – underground storage tanks for gasoline were required to be double walled with a detection system between the inner and outer tanks.

• Cost penalty to the use of ethanol in place of MTBE about 5 cents per gallon even with government subsidies for ethanol.

Formaldehyde

• 12.5 Billion Pounds per year U.S. capacity on a 37 percent basis. ( Demand about 10 billion pounds)

• Commercial production is from methanol either by silver catalyst or metal oxide catalyst processes.

• Seventy to 80 percent of formaldehyde output is used captively.

Formaldehyde Producers

• Borden, Georgia Pacific and Hoechst Celanese are major U.S. producers

• Wright Chemical has capacity of 160 million pounds ( Chem Expo report)

Formaldehyde HCHO 3 Commercial Forms

• Aqueous solution ( 35-55%)• Cyclic trimer (trioxane)

– from the acid catalyzed reaction of formaldehyde

• Paraformaldehyde can be reversibly converted to the monomer by heat or acid

O

O

O

O O O

Formaldehyde Uses

• 40%: urea- and phenol-formaldehyde resins used in particleboard and plywood, respectively

• 13%: polyacetal resins

• 11%: 1,4-butanediol

Acetic Acid

• CH3OH + CO CH3CO2H

• Catalyst developed by Monsanto is Rhodium (Rh) in the presence of I2

• The reaction involves CO insertion into a CH3-Rh bond

• Co and iridium based catalysts also known

catalyst

Acetic Acid

• 6 Billion pounds per year produced in the U.S.

• Celanese is the major producer

• 42% used to make vinyl acetate monomer

O

O

Vinyl Acetate

• The dominant method of commercial production is by reaction of ethylene with acetic acid and oxygen in the presence of a palladium catalyst.

• About 2 billion pounds produced in North America

• Main use is for polymer manufacture

Ethylene

• In terms of quantity produced, ethylene is the most important organic chemical

• Ranked # 4 among all chemicals after– 1. Sulfuric acid– 2. Nitrogen– 3. Oxygen

Ethylene U.S. Production

• About 60 billion pounds made per year (2002)

• Major U.S. manufacturers (capacity lb.) – Equistar ( 10B)– Exxon Mobil ( 9B)– Dow (8B)– Chevron Phillips (8B)– Shell(7B)

Ethylene

• Steam cracking of hydrocarbons accounts for virtually all of the ethylene produced throughout the world. Hydrocarbons used as feedstocks range from natural gas liquids (ethane, propane and butane) to petroleum liquids (gas oils and naphtha).

• Roughly 70 percent of the US ethylene industry's production is used captively for downstream derivatives.

Ethylene Uses

• Polyethylene 54%

• Ethylene dichloride, 18%

• Ethylene oxide 12%

• Ethylbenzene, 6 %

Chloralkali

• Chlorine / Caustic

• Cl2 / NaOH

• 13 million tons of chlorine

• 15 million tons of NaOH

Coproduced by the electrolysis of NaCl

U.S. Chlorine Producers

• Dow 4 billion tons per year

• OxyChem 3 billion tons per year

• PPG 2 billion tons per year

• These three are also the top caustic producers

• Manufacture The process of manufacture uses electricity and salt. In manufacture, for every 80 tonnes of caustic soda, 71 tonnes of chlorine and 2 tonnes of hydrogen are co-produced. Each tonne of caustic soda requires around 2200 kWh of electricity and 1.55 tonnes of salt.

2NaCl + 2H2O 2NaOH + Cl2 + H2

80g 71g 2g

Chlorine / Caustic

• Three processes of manufacture. • Mercury cell - the oldest technology

employed which has been largely closed down around the world being less efficient and polluting. (HoltraChem)

• Diaphragm cell - the dominant technology.

• Membrane cell - preferred technology for new plants

Diaphragm CellAnode 2Cl- Cl2 + 2 e-

Cathode 2H2O + 2 e- H2 + 2OH-

Overall 2Na+ + 2Cl- + 2H2O

2Na+ + 2OH- + Cl2 + H2

2 Mole NaOH produced for each mole of Cl2

80 grams NaOH produced for each 71 grams of Cl2

80 tons NaOH produced for each 71 tons of Cl2

Chlorine / Caustic

• Diaphragm acts to separate the anode and cathode to prevent mixing of chlorine with NaOH or hydrogen

• The effluent cell liquor contains about 14% NaCl and 12% NaOH. This is passed though an evaporation train where NaCl is removed by crystallization and returned as a feed material

NaOH Use

• 54%: direct application (pulp and paper, soaps and detergents, alumina, petroleum, textiles, water treatment)

• 35% organic chemicals (propylene oxide, polycarbonate,ethyleneamines, epoxy resins,

• 11%: inorganic chemicals (sodium/calcium hypochlorite, sulfur-containing compounds, sodium cyanide).

Chlorine Use

• 36% Polyvinyl chloride (ethylene dichloride and vinyl chloride monomer)

• 41% Other organic chemicals

• 15% inorganic chemicals

• 4% water treatment

• 1% pulp and paper

• 3% miscellaneous

Ethylene Dichloride

• About 16 billion pounds produced in U.S.

• 94% goes to PVC manufacture

• OxyVinyls (JV between OxyChem and Geon) number 1 manufacturer

• Dow # 2

• Formosa #3

EDC Synthesis

Direct Chlorination

C2H4 + Cl2 C2H4Cl2

liquid phase; FeCl3 or CuCl2 catalysts

Oxychlorination

C2H4 + 2HCl + ½O2 C2H4Cl2 + H2O

Gas phase; CuCl2 catalyst

VCM Synthesis

ClCl

HH

HH

500 C

radical mechanism

EDC

Cl

VCM

+ HCl

Balanced VCM Process

Chlorination of ethylene C2H4 + Cl2 C2H4Cl2

Cracking to make vinyl chloride

2C2H4Cl2 2C2H3Cl + 2HClOxyChlorination

C2H4 + 2HCl + ½O2 C2H4Cl2 + H2OOverall

2C2H4 + Cl2 + ½O2 2C2H3Cl + H2O

Ethylene Oxide

+ 0.5 O2

O

EO

Ag catalyst

Ethylene Oxide

• 9 Billion lbs in U.S.

• Dow/Union Carbide, Shell, Huntsman and Equistar are some of the major producers

• 57% used for ethylene glycol

• Source for various ethers and alcohols

Ethylene glycol

O

EOOHHO

large excess of water

Ethylene glycol

Typically uses a ten fold excess of water; if lower water ratio is used, di, tri, and polyethylene glycols are formed

Product ethylene glycol is concentrated by evaporation and then fractionally vacuum distilled

Ethylene Glycol Uses

• 58% for Polyester (PET)

• 26% for antifreeze

Ethylbenzene

+

Ethylbenzene

Friedel-Crafts catalysts or zeolites(Al2O3.SiO2)

Ethylbenzene – U.S. Production

• 14 billion pounds annually

• Lyondell, Sterling, Cos-Mar (Ato-Fina & GE), Dow and Chevron are among the major producers

• Used for styrene production

Styrene

Ethylbenzene Styrene

FeO3 catalyst

600 Cdehydrogenation

Styrene

• 12 Billion pounds

• Same producers as ethylbenzene

• Used for polystyrene production