Lesson Progress
0% Complete
// Non-Hydrocarbon
- 1. Non HC
- High level of organic sulfur and organic nitrogen can cause pollution
- Oxidation product of sulfur and nitrogen are corrosive in nature
- 2. Sulfur
- Two groups of sulfur:
- Organosulfur
- Inorganic sulfur- hydrogen sulfide; H2S harmful and corrosive
- Two class of organosulfur:
- acidic – thiols (mercaptans)
- Non-acidic:
- thiophene
- sulfides
- disulfides
- Sour crude:
- Contain high % of H2S
- Many organic sulfur compounds are not thermally stable, hydrogen sulfide
- is often produced during crude processing.
- High-sulfur crudes are less desirable because treating the different refinery streams for acidic hydrogen sulfide increases production costs.
- Q: How can these sulfur compounds be removed from petroleum streams?
- Two groups of sulfur:
- 3. Nitrogen
- Simple heterocyclic form
- pyridine ; C5H5N
- pyrrole; C4H5N
- Complex stucture – porphyrin
- Nitrogen content in most crudes is very low and does not exceed 0.1 wt%.
- In some heavy crudes, however, the nitrogen content may reach up to 0.9 wt %.
- more thermally stable than sulfur compounds
- Concentrated in heavier petroleum fractions and residues.
- Light petroleum streams may contain trace amounts of nitrogen compounds, which should be removed because they poison many processing catalysts.
- Classified into two groups:
- Basic nitrogen compounds -mainly those having a pyridine ring,
- Non-basic nitrogen compounds – have a pyrrole structure.
- Both pyridine and pyrrole are stable compounds due to their aromatic nature.
- Simple heterocyclic form
- 4. Oxygen
- more complex than the sulfur types.
- However, their presence in petroleum streams is not poisonous to processing catalysts.
- Two groups of oxygen compound in CO;
- Weakly acidic
- Non acidic – Many of the oxygen compounds found in crude oils are weakly acidic.
- Acidic oxygen compound
- They are carboxylic acids, cresylic acid, phenol, and naphthenic acid.
- Naphthenic acids are mainly cyclopentane and cyclohexane derivatives having a carboxyalkyl side chain.
- Naphthenic acids in the naphtha fraction have a special commercial importance and can be extracted by using dilute caustic solutions.
- The total acid content of most crudes is generally low, but may reach as much as 3%, as in some California crudes
- Non-acidic oxygen compound
- less abundant compared to acidic compound
- e.g. esters, ketones, and amides
- no commercial value.