Oil and Gas
Crude oil is a mixture of many types of organic molecules with small amounts of nitrogen and sulfur. The composition of crude oil changes with location. It is thought that crude oil was produced over millions of years from the remains of animals and plants.
Direct distillation of crude oil yields the following fractions:
LPG
Gasoline,Naphtha and solvents
Kerosine and jet fuels
Light fuel oil (Soler) and Diesel fuel
Heavy fuel oil (Mazut)
Lubrication oils, asphalt and paraffin.
Upgrading of these fractions is by: Thermal and catalytic cracking
Catalytic reforming
Alkylation
Isomerization
Polymerization
Sulfur recovery
Generally, refineries optimize the mix of products according to market demand.
In Israel the refineries use ,monthly, weekly and daily production plans.
In the last few years the market demand in Israel for petroleum products has changed considerably: More stringent environmental laws led to considerable reduction of the sulfur in the products. The demand for heavy fuel oil decreased and the demand for gasoline increased.
Catalytic cracking is the main process used to control the product mix, by breaking large molecules into smaller molecules and by isomerizaion to more higher value molecules.
The most common cracking process is by a fast fluidized bed (Riser reactor) with very low residence time.
Catalytic reforming results in higher concentrations of non-linear isomers and cyclic and aromatic compounds.
Desulfurization is nowadays done by catalytically reducing sulfur compounds with hydrogen to H2S, oxidation of a third of the H2S to SO2 and the reaction of these two compounds to form sulfur:
2H2S + SO2 = 3S + 2H2O
Naphtha is the most important primary distillation product. It is used as raw material for the production of gasoline, ethylene, propylene and aromatics.
Aromatics are separated from other components by extraction.
The major pure hydrocarbons produced from crude oil in order to serve as the building blocks of the petrochemical industry are:
Ethylene
Propylene
Butenes
Benzene
Toluene
Xylenes
Natural substances have been proposed as raw materials for the petrochemical industry. The most important one is sugar which has been used to derive many petrochemicals, but not in reasonable prices. Acetylene which can be made from coal was the main raw material for petrochemicals in Germany during the second world war.
Synthesis gas: mixtures of CO and hydrogen is an important raw material. It is produced today by the partial oxidation of methane or naphtha for the production of methanol, acetic acid and ammonia. It can be produced by the reactions of coal with oxygen and steam. It can be used to produce petrochemicals or gasoline. Many processes have been developed for these puposes, but only a few are in current use, due to the low crude price (till recently).
Process nameActionMethodPurposeFeedstock(s)Product(s)
| Process name | Action | Method | Purpose | Feedstock(s) | Product(s) |
|---|---|---|---|---|---|
| CONVERSION PROCESSES–ALTERATION OR REARRANGEMENT | |||||
| Catalytic reforming | Alteration/ dehydration |
Catalytic | Upgrade low-octane naphtha | Coker/ hydro-cracker naphtha | High oct. Reformate/ aromatic |
| Isomerization | Rearrange | Catalytic | Convert straight chain to branch | Butane, pentane, hexane | Isobutane/ pentane/ hexane |
| TREATMENT PROCESSES | |||||
| *Amine treating | Treatment | Absorption | Remove acidic contaminants | Sour gas, HCs w/CO2 & H2S | Acid free gases & liquid HCs |
| Desalting | Dehydration | Absorption | Remove contaminants | Crude oil | Desalted crude oil |
| Drying & sweetening | Treatment | Abspt/ therm | Remove H2O & sulfur | Liq Hcs, LPG, alky feedstk | Sweet & dry hydrocarbons |
| *Furfural extraction | Solvent extr. | Absorption | Upgrade mid distillate & lubes | Cycle oils & lube feed-stocks | High quality diesel & lube oil |
| Hydrodesulfurization | Treatment | Catalytic | Remove sulfur, contaminants | High-sulfur residual/ gas oil | Desulfurized olefins |
| Hydrotreating | Hydrogenation | Catalytic | Remove impurities, saturate HC’s | Residuals, cracked HC’s | Cracker feed, distillate, lube |
| *Phenol extraction | Solvent extr. | Abspt/ therm | Improve visc. index, color | Lube oil base stocks | High quality lube oils |
| Solvent deasphalting | Treatment | Absorption | Remove asphalt | Vac. tower residual, propane | Heavy lube oil, asphalt |
| Solvent dewaxing | Treatment | Cool/ filter | Remove wax from lube stocks | Vac. tower lube oils | Dewaxed lube basestock |
| Solvent extraction | Solvent extr. | Abspt/ precip. | Separate unsat. oils | Gas oil, reformate, distillate | High-octane gasoline |
| Sweetening | Treatment | Catalytic | Remv H2S, convert mercaptan | Untreated distillate/gasoline | High-quality distillate/gasoline |