CHM 585/490 Chapter 2

Petroleum Cracking C 4 Methanol derivatives –MTBE –Formaldehyde –Acetic Acid Ethylene, Chloroalkali and derivatives

Major Petroleum Fractions FractionBoiling Range (ºC) Use Gases< 20Methane(65-90%), ethane, propane, butane Naptha Base for gasoline; used for chemicals Gas Oil Jet, diesel and heating fuel Heavy Fraction > 370Lubrication, boiler fuel, paving

Thermal Cracking Radical cleavage of hydrocarbons 400 – 500 ºC under pressure

Example of Products from Naptha Cracking ProductWeight % Residual Gas ( CH 4, H 2 )16 Ethylene35 Propene15 C 4 Fraction8.5 C 5 Fraction and higher boiling fractions 25.5

Typical C 4 Composition ComponentsVolume % Isobutene Butene Butene ( cis and trans)19-21 N-Butane6-8 Isobutane2-3

MTBE Synthesis C 4 raffinate is reacted with methanol at ºC 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)

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.

MTBE U.S.Production 282,000 barrels per day (2001) 42 gallons per barrel => 12 million gallons per day Density = 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

Formaldehyde Uses 40%: urea- and phenol-formaldehyde resins used in particleboard and plywood, respectively 13%: polyacetal resins 11%: 1,4-butanediol

Acetic Acid CH 3 OH + CO CH 3 CO 2 H Catalyst developed by Monsanto is Rhodium (Rh) in the presence of I 2 The reaction involves CO insertion into a CH 3 -Rh bond Co and iridium based catalysts also known

Acetic Acid 6 Billion pounds per year produced in the U.S. Celanese is the major producer 42% used to make vinyl acetate monomer

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 Cl 2 / 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.

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 Cell Anode2Cl - Cl e - Cathode2H 2 O + 2 e - H 2 + 2OH - Overall2Na + + 2Cl - + 2H 2 O 2Na + + 2OH - + Cl 2 + H 2 2 Mole NaOH produced for each mole of Cl 2 80 grams NaOH produced for each 71 grams of Cl 2 80 tons NaOH produced for each 71 tons of Cl 2

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 C 2 H 4 + Cl 2  C 2 H 4 Cl 2 liquid phase; FeCl 3 or CuCl 2 catalysts Oxychlorination C 2 H 4 + 2HCl + ½O 2  C 2 H 4 Cl 2 + H 2 O Gas phase; CuCl 2 catalyst

VCM Synthesis

Balanced VCM Process Chlorination of ethylene C 2 H 4 + Cl 2  C 2 H 4 Cl 2 Cracking to make vinyl chloride 2C 2 H 4 Cl 2  2C 2 H 3 Cl + 2HCl OxyChlorination C 2 H 4 + 2HCl + ½O 2  C 2 H 4 Cl 2 + H 2 O Overall 2C 2 H 4 + Cl 2 + ½O 2  2C 2 H 3 Cl + H 2 O

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 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 Friedel-Crafts catalysts or zeolites(Al 2 O 3. SiO 2 )

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

12 Billion pounds Same producers as ethylbenzene Used for polystyrene production