Petrochemicals Notes

Paraffin-Based Petrochemicals

• Paraffin is used in the production of olefins.
• Paraffin is used in the production of substituted derivatives such as chloroparaffin and sulfonated paraffin.
• Paraffin is used in the production of BTX.

Methane-Based Petrochemicals

• Syn Gas (CO/xH2)
• HCN
• CS2
• Chlorinated methane
• Single Cell Protein
• Fuel Cell

Syn Gas (CO/xH2)

CS2

• Produced by the action of vaporized sulfur on methane:
  $CH4 (g) + 2S8 (g) \rightarrow CS2 + H2S$ $\Delta H_o = 150 kJ/mole$

  • Conditions:
    • Alumina/clay
    • 675 °C
    • 2 atm
  • % Conversion = 85-90%

• Process:

  • Vaporize pure S8, then allow it to mix with CH4.
  • The mixture is passed over activated alumina/clay.

• Sulfur in the produced H2S can be recovered using the Claus Process:
  $H2S + O2 \rightarrow SO2 + H2O + S8$
  $H2S \rightarrow S8 + H2O$

• Alternate Route to obtain CS2:
  $Charcoal + S (l) \rightarrow CS2$

• Major Uses:

  1. In the production of CCl4 (solvent, extinguisher) and S2Cl2 (vulcanization):
     $CS2 + 3 Cl2 \rightarrow CCl4 + S2Cl2$ (Fe powder, 30 °C)
  2. In the production of xanthates: $R-(CH2)x -ONa + CS2 \rightarrow R-(CH2)x -OCS2Na$
     • Similarly, the reaction of cellulose with CS2 in the presence of NaOH gives Sodium Cellulose xanthate, which upon neutralization with H2SO4 gives Viscose Rayon or Cellophane paper (Sellotape = Scotch Tape).

HCN

• Production:
  • Andrussaw Process:
    $CH4 + NH3 + O2 \rightarrow HCN + H2O$ (Pt-Rh Alloy, 1100 °C)
  • Degussa Process:
    $CH4 + NH3 \rightarrow HCN + H2$ (Pt-Al-Ru Alloy, 1200 °C)
  • 
    $CH3OH + NH3 + O2 \rightarrow HCN + H2O$
• Major Uses:
  1. NaCN
  2. Oxamide Fertilizer:
     $HCN + H2O + O2 \rightarrow H2NCO-CONH2$ (Conditions: Cu(NO3)2, 70 °C)
  3. In the production of:
     • Acrylonitrile, $CH2=CHCN$
     • Adiponitrile, $NC-(CH2)4 -CN$
     • Methyl methacrylates $CH2=C(CH3)COOCH3$
       $CH3COCH3 + HCN \rightarrow CH3C(OH)(CN)CH3$
       $\downarrow H2SO4$
       $CH2=C(CH3)CN$
       $\downarrow NaOH + H2O$
       $CH2=C(CH3)COOH + NH3$
       $\downarrow CH3OH$
       $CH2=C(CH3)COOCH3$

Chloromethanes

• Production: $CH4 + Cl2 \rightarrow CH3Cl + CH2Cl2 + CHCl3 + CCl4$
  • ~ 59% ~29% ~10% ~2-3%
  • The product distribution depends upon the CH4/Cl2 ratio and conditions.
  • Conditions: 350-370 °C, CH4 / Cl2 = 1.7:1
• Uses:
  • CH3Cl is used in the production of:
    • Silicon polymers
    • Tetramethyllead
    • Methylating agent in methylcellulose
    • Refrigerant
  • CHCl3 is used in the production of freon and Teflon:
    $CHCl3 + 2HF \rightarrow CHClF2 + 2HCl$
    $\downarrow$
    $CF2=CF2$

Single Cell Proteins (SCP)

• Single Cell Proteins refers to a group of microbial cells such as algae and yeast that have a high protein content.
• SCP also contain carbohydrates, lipids, vitamins, and minerals.
• Algae, fungi, and yeast are grown/nourished on different HC substrates such as n-paraffin, methane, methanol, and others.
• These microbes are terminated, and the constituting proteins are extracted.
• One of the problems in SCP is the presence of residual HC in the final protein product.
• This technique is often used to clean seawater from petroleum spills. The resulting proteins are consumed by different marine animals.

Ethane-Based Petrochemicals

• Ethane is generally obtained from liquefied natural gas (LNG).
• Ethane-based petrochemical - Cu oxychloride = CuCl(OH) or ClCu-O-CuCl
  • Oxychlorination
  • Chlorination followed by Dehydrochlorination

Propane-Based Petrochemicals

• Propane is obtained from LNG
• Propane is more reactive than ethane due to the presence of 2° H $CH3 -CH2 -CH3$
• Important Propane-Based Petrochemicals:
  1. Oxygenated hydrocarbons
  2. Trichlor and perchlor
  3. Propene
  4. Nitroalkanes
  5. Cyclar Process

Oxygenated hydrocarbons

• Vapor Phase $CH3 -CH2 -CH3 + O2 \rightarrow CH3CHO + HCHO + C2H5OH + CH3OH$ (~ 400 °C)
  • The process is not selective.

Trichlor and perchlor

• $CH3 -CH2 -CH3 + 8 Cl2 \rightarrow CCl2=CHCl + CCl4 + CCl2=CCl2 + HCl$ (Cu oxychloride, 480-640 °C)
  • Perchlor and trichlor are used as:
    • Metal degreasing agents
    • Solvents for dry cleaning
    • Fumigant
    • Cleaning and drying agent for electronic equipment

Dehydrogenation

• $CH3 -CH2 -CH3 \rightarrow CH2=CHCH3$ (540-680 °C, 5-20 atm)
  • Conversion = 55-65%
  • Selectivity = 95%

Nitration

• $CH3 -CH2 -CH3 + HNO3 \rightarrow CH3CH(NO2)CH3 + CH3CH2CH2NO2 + C2H5NO2 + CH3NO2$ (390-440 °C, 100-125 atm)
  • Conversion = 55-65% of $CH3CH(NO2)CH3 + CH3CH2CH2NO2$
  • 20-25% of $C2H5NO2$
  • 10-30% of $CH3NO2$
  • Nitropropanes are good solvents for vinyl and epoxy resins. They are also used to manufacture rocket propellants.
  • Nitromethane is a fuel additive for racing cars.

Cyclar Process

• The Cyclar process is the most well-known catalytic process that converts propane and butanes to BTX (benzene, toluene, xylenes) with Ga/ZSM-5 bifunctional catalyst.
• Propane (100% feed):
  • Aromatic: 63%
  • H2: 6%
  • Fuel gas: 31%
• Butane (100% feed):
  • Aromatic: 66%
  • H2: 5%
  • Fuel gas: 29%

Butane-Based Petrochemicals

• The major use of n-butane is to control the vapor pressure of gasoline.
• Isobutane is a precursor for producing octane number boosters, such as MTBE (methyl-t-butyl ether) and ETBE (ethyl-t-butyl ether).
  • Isomerization: C-C-C-C ⎯⎯→ isobutane ⎯⎯→ isobutene
• Partial Oxidation:
  • Partial Oxidation: C-C-C-C ⎯⎯→ Maleic anhydride (Conditions: 490 °C, CeCl3/Co-Mo oxides or 500 °C, Fe/V2O5 -P2O5/silica)
• Hydrogenation:
  • Maleic anhydride ⎯⎯→ THF (Tetrahydrofuran)
• Co-polymerization:
  • Maleic anhydride ⎯⎯→ Polyester Resin with unsaturated backbone
• Light Naphtha-Based Petrochemicals (C5 -C7):
  • $C5 -C7 + O2 \rightarrow CH3COOH + H2O + byproducts$ (Mn acetate, 170-200 °C, 50 atm, 40%)
  • The product mixture contains essentially oxygenated compounds (acids, alcohols, esters, aldehydes, ketones, etc.).
  • As many as 13 distillation columns are used to separate the complex mixture.

Paraffin-Based Petrochemicals (C18-C30)

A. Oxidation (two methods):

1. Using Mn salts:
   $R(CH2)nCH2CH2R' + O2 \rightarrow R(CH2)nCOOH + R'COOH + H2O$ (Mn salts, 105-120 °C, 16-60 atm)
   $\downarrow NaOH$
   $R(CH2)nCOONa (soap) + R'COONa (soap)$

   • This method is used to prepare fatty acids from petroleum products and hence soaps.

2. Using Boron oxide/peroxide:
   $C12-C14 + O2 \rightarrow C12H25OH$ ($B2O3 /B2O5$, 120-130 °C, 1 atm)

   • 0.5% t-butylhydroperoxide ($CH3C(CH3)2OOH$) is used to initiate the reaction.
     $RCH2CH2R' + O2 \rightarrow RCH2CH(OH)R'$ (fatty alcohol)

$RCH2CHR'-(OCH2CH2)nOH$
* Ethyoxylated non-ionic detergents.

B. Chloroparaffin

$C10-C14 + Cl2 \rightarrow RCHClCH2R' + HCl$ (80-120 °C)

• Mono-substituted products predominate at low Cl2/paraffin ratio.
• Substitution occurs at the 2nd H.

$RCH2CHClR' \rightarrow RCH=CHR' + HCl$
$\downarrow C6H6 + H+ , AlCl3$
* Alkylated benzene

$\downarrow Sulfonation$
*   Surfactant

• Another Route (Friedel-Craft Alkylation Rxn.):

$C6H6 + RCH2CHClR' \rightarrow \text{Alkylated benzene}$ (AlCl3)

$\downarrow Sulfonation$

• Surfactant

C. Sulfonated Paraffins

$C15-C17 + SO2 + O2 + H2O \rightarrow RSO3H + H2SO4$

• The reaction is catalyzed by ultraviolet light with a wavelength between 3,300–3,600Å.

• The sulfonates are nearly 100% biodegradable, soft, and stable in hard water, and have good washing properties.

• Another Route: $RCH=CH2 + NaHSO3 \rightarrow RCH2CH2SO3Na$