Even though there are new petroleum refinery processes being used everyday and new applications for adsorption systems in this market, the majority will be in the following:
CATALYTIC REFORMING - Catalytic reforming refers to the octane improvement of straight run gasoline and cracked refinery naphthas. C5 and C6 naphthenes are isomerized and dehydrogenated to aromatics; paraffins are hydrocracked or cyclized and hydrogenated to aromatics.
The reactions are carried out in a series of three or four fixed bed reactors; and, since the reactions are endothermic, heating furnaces are placed at the inlet to each reactor. Hydrogen is recycled to prevent carbon lay down.
Catalytic reforming is also a source of benzene, toluene, and xylene. The feed for this production is naphtha.
All catalytic reforming reactions produce large quantities of hydrogen. Since many of these reformers are regenerated, an inert and recycled gas is used. Applications for an adsorption system then are: (1) dry and purify recycled hydrogen, (2) dry and desulfurize naphtha feed stock, (3) dry regeneration gas from inert gas generation, (4) dry recycled regeneration gas, and (5) purify the hydrogen produced during reforming for sale and other refinery use.
ALKYLATION - Alkylation is the union of an olefinic with a paraffinic hydrocarbon to obtain high octane gasoline. Alkylation is favored over polymerization since only one mole of olefin is reacted per mole of alkylate produced, thus conserving valuable olefinic stock.
The reaction is catalyzed by hydrofluoric or sulfuric acid. In most processes, the reactive olefin is injected into the stable paraffinic feed stock and the combined streams contacted with the acid. The paraffin concentration is kept in large excess to prevent copolymerization of the olefin. This acid alkylation, however, is limited to isobutane with propylene, butylene, and pentylene. Other alkylations: phosphoric acid is used as a catalyst to unite propylene and benzene to form isopropyl benzene; alumina chloride and HCl catalyzes ethylene and benzene to ethylbenzene. An application for an adsorption system would be to dry and purify these streams to rid them of water, mercaptans, and other impurities in the olefin and paraffin feeds that will increase acid consumption and decrease product quality.
ISOMERIZATION - Isomerization is the conversion of normal butane, pentane, and hexane into their respective iso-isomers. It is a fixed bed, vapor phase process which is carried out under a dry hydrogen atmosphere. The catalyst is usually AlCl3 or HCl loaded on silica-alumina.
The reaction is carried out in this hydrogen atmosphere to prevent coke deposition and saturate any cracking products. Applications for adsorption systems then are: (1) dry and purify the paraffin feed, and (2) dry and purify the hydrogen feed.
CATALYTIC CRACKING - Catalytic cracking consists of breaking saturated C12+ molecules into C1-C4 olefins and paraffins, gasoline, light oil, and coke. The majority of the reactions are endothermic, and heat must be supplied to induce a reaction. Cracking can be either thermal or catalytic. There are two types of catalytic cracking systems, the moving bed system and the fluidized system. An application for an adsorption system would be purification of the light ends (C4 and lighter paraffins and olefins) which are sent to the gas recovery plants for later use in alkylation units.
HYDROCRACKING - Hydrocracking can supply the refinery with the entire range of petroleum fuels from propane to desulfurized residual oil with feed stocks ranging from very heavy sulfur laden distillate to light gas oils. The reactions are similar to catalytic cracking reactions, but with hydrogenation superimposed. Polyaromatics are hydrogenated, naphthene rings are opened, olefins are hydrogenated, paraffins are cracked and isomerized. The reaction occurs in a hydrogen atmosphere in the presence of a catalyst. Most hydrocracking units are fixed bed reactors that are regenerated. Regeneration gas is used to reactivate the catalyst. Applications for adsorption systems include: (1) dry the makeup hydrogen, (2) dry and purify the recycle hydrogen, (3) dry and purify the regeneration gas, and (4) purify the hydrocracking products.
GAS PLANT -The C4 and lighter gases from various refinery operations are sent to this section of the refinery. All of these gases require dehydration.