Technical Manual - Section 3 (Safety Hazards)
Technical Manual - Section 3 (Safety Hazards) Technical Manual - Section 3 (Safety Hazards)
carbon atoms. The lighter, straight-chain paraffin molecules are found in gases and paraffin waxes. Examples of straight-chain molecules are methane, ethane, propane, and butane (gases containing from one to four carbon atoms), and pentane and hexane (liquids with five to six carbon atoms). The branched-chain (isomer) paraffins are usually found in heavier fractions of crude oil and have higher octane numbers than normal paraffins. These compounds are saturated hydrocarbons, with all carbon bonds satisfied, that is, the hydrocarbon chain carries the full complement of hydrogen atoms. AROMATICS Aromatics are unsaturated ring-type (cyclic) compounds which react readily because they have carbon atoms that are deficient in hydrogen. All aromatics have at least one benzene ring (a single-ring compound characterized by three double bonds alternating with three single bonds between six carbon atoms) as part of their molecular structure. Naphthalenes are fused double-ring aromatic compounds. The most complex aromatics, polynuclears (three or more fused aromatic rings), are found in heavier fractions of crude oil. NAPHTHENES Figure III:2-2 Typical Aromatics Naphthenes are saturated hydrocarbon groupings with the general formula C n H 2n , arranged in the form of closed rings (cyclic) and found in all fractions of crude oil except the very lightest. Single-ring naphthenes (monocycloparaffins) with five and six carbon atoms predominate, with two-ring naphthenes III:2-6
(dicycloparaffins) found in the heavier ends of naphtha. OTHER HYDROCARBONS ALKENES Alkenes are mono-olefins with the general formula C n H 2n and contain only one carbon-carbon double bond in the chain. The simplest alkene is ethylene, with two carbon atoms joined by a double bond and four hydrogen atoms. Olefins are usually formed by thermal and catalytic cracking and rarely occur naturally in unprocessed crude oil. DIENES AND ALKYNES Dienes, also known as diolefins, have two carbon-carbon double bonds. The alkynes, another class of unsaturated hydrocarbons, have a carbon-carbon triple bond within the molecule. Both these series of hydrocarbons have the general formula C n H 2n-2 . Diolefins such as 1,2-butadiene and 1,3-butadiene, and alkynes such as acetylene occur in C 5 and lighter fractions from cracking. The olefins, diolefins, and alkynes are said to be unsaturated because they contain less than the amount of hydrogen necessary to saturate all the valences of the carbon atoms. These compounds are more reactive than paraffins or naphthenes and readily combine with other elements such as hydrogen, chlorine, and bromine. NONHYDROCARBONS SULFUR COMPOUNDS Sulfur may be present in crude oil as hydrogen sulfide (H 2 S), as compounds (e.g., mercaptans, sulfides, disulfides, thiophenes, etc.), or as elemental sulfur. Each crude oil has different amounts and types of sulfur compounds, but as a rule the proportion, stability, and complexity of the compounds are greater in heavier crude-oil fractions. Hydrogen sulfide is a primary contributor to corrosion in refinery processing units. Other corrosive substances are elemental sulfur and mercaptans. Moreover, the corrosive sulfur compounds have an obnoxious odor. Figure III:2-3 Typical Napthenes III:2-7
- Page 1 and 2: OR-OSHA TECHNICAL MANUAL OR-OSHA TE
- Page 3 and 4: SECTION III: CHAPTER 1 OIL WELL DER
- Page 5 and 6: C. STABILITY CONSIDERATIONS FOUNDAT
- Page 7 and 8: D. OBSERVATIONS, DIRECTIONS, AND CO
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- Page 21 and 22: Table III:2-3 OVERVIEW OF PETROLEUM
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- Page 39 and 40: egeneration and changeover. Catalys
- Page 41 and 42: CATALYTIC HYDROTREATING Catalytic h
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- Page 45 and 46: needed to prevent HCl from entering
- Page 47 and 48: ALKYLATION Alkylation combines low-
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- Page 51 and 52: Figure III:2-23 Molecular Sieve Dry
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(dicycloparaffins) found in the heavier ends of naphtha.<br />
OTHER HYDROCARBONS<br />
ALKENES<br />
Alkenes are mono-olefins with the general formula C n H 2n and<br />
contain only one carbon-carbon double bond in the chain.<br />
The simplest alkene is ethylene, with two carbon atoms joined<br />
by a double bond and four hydrogen atoms. Olefins are<br />
usually formed by thermal and catalytic cracking and rarely<br />
occur naturally in unprocessed crude oil.<br />
DIENES AND ALKYNES<br />
Dienes, also known as diolefins, have two carbon-carbon<br />
double bonds. The alkynes, another class of unsaturated<br />
hydrocarbons, have a carbon-carbon triple bond within the<br />
molecule. Both these series of hydrocarbons have the general<br />
formula C n H 2n-2 . Diolefins such as 1,2-butadiene and<br />
1,3-butadiene, and alkynes<br />
such as acetylene occur in C 5 and lighter fractions from<br />
cracking. The olefins, diolefins, and alkynes are said to be<br />
unsaturated because they contain less than the amount of<br />
hydrogen necessary to saturate all the valences of the carbon<br />
atoms. These compounds are more reactive than paraffins or<br />
naphthenes and readily combine with other elements such as<br />
hydrogen, chlorine, and bromine.<br />
NONHYDROCARBONS<br />
SULFUR COMPOUNDS<br />
Sulfur may be present in crude oil as hydrogen sulfide (H 2 S),<br />
as compounds (e.g., mercaptans, sulfides, disulfides,<br />
thiophenes, etc.), or as elemental sulfur. Each crude oil has<br />
different amounts and types of sulfur compounds, but as a<br />
rule the proportion, stability, and complexity of the<br />
compounds are greater in heavier crude-oil fractions.<br />
Hydrogen sulfide is a primary contributor to corrosion in<br />
refinery processing units. Other corrosive substances are<br />
elemental sulfur and mercaptans. Moreover, the corrosive<br />
sulfur compounds have an obnoxious odor.<br />
Figure III:2-3 Typical Napthenes<br />
III:2-7
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