Diesel fluid catalytic cracking

Cracking reactions are carried out in order to reduce the molecular size and to produce more valuable transport fuel fractions (gasoline and diesel). Fluid catalytic cracking is acid catalyzed (zeolites) and a complex network of carbe-nium ion reactions occur leading to size reduction and isomerization (see Chapter 4, Section 4.4). Hydrogenation also takes place in hydrocracking, as well as cracking. 

Fluid catalytic cracking over an acid catalyst converts residual hydrocarbons from the vacuum gas oil fraction into valuable olefins, gasoline, and diesel products. The catalytic cracking proceeds... 

Gas oils Utilized as straight-run distillate after desulfurization. Lighter atmospheric and vacuum gas oils are often hydrocracked or catalytically cracked to produce gasoline, jet, and diesel fuel fractions heavy vacuum gas oils can be used to produce lubestocks or as fluid catalytic cracking (FCC) feedstock... 

Fluid catalytic cracking, fluid cat-cracking or FCC, is a common oil refinery process. The duty of an FCC unit is to take a heavy low value gas oil or fuel oil and convert this to higher valued liquid products, particularly gasoline blend-stock. The process also produces diesel fuel blend-stock and a gas by-product stream. The gaseous by-products are rich in olefins and in particular propylene and isobutene. Ethylene is a minor component. 

The use of CeOs-based materials in catalysis has attracted considerable attention in recent years, particularly in applications like environmental catalysis, where ceria has shown great potential. This book critically reviews the most recent advances in the field, with the focus on both fundamental and applied issues. The first few chapters cover structural and chemical properties of ceria and related materials, i.e. phase stability, reduction behaviour, synthesis, interaction with probe molecules (CO. O2, NO), and metal-support interaction — all presented from the viewpoint of catalytic applications. The use of computational techniques and ceria surfaces and films for model catalytic studies are also reviewed. The second part of the book provides a critical evaluation of the role of ceria in the most important catalytic processes three-way catalysis, catalytic wet oxidation and fluid catalytic cracking. Other topics include oxidation-combustion catalysts, electrocatalysis and the use of cerium catalysts/additives in diesel soot abatement technology. 

Although gas oils obtained from the atmospheric distillate still remain the main source of diesel fuels, in order to cope with the increased consumption of naphtha and middle distillates almost all refineries in Romania use conversion processes such as fluid catalytic cracking on vacuum distillates and coking or visbreaking on residue. These processes generate middle distillates with higher olefins, diolefins, sulphur, nitrogen and aromatics content compared to gas oil obtained from an atmospheric distillation unit... 

Application The worldwide demand for gasoline, diesel and petrochemicals is shifting toward a greater emphasis on diesel and propylene, and flexibility to meet changing demands will be vital for refinery profitability. Axens has developed the new FlexEne technology to expand the capabilities of the fluid catalytic cracking (FCC) process, which is the main refinery conversion unit traditionally oriented to maximize gasoline and at times propylene. 

As catalysts, zeolites have found their most important application in petroleum refining processes. Their acid function is used in Fluid Catalytic Cracking (FCC), in hydroisomerisation of light alkane fraction as well as in ohgomerisation and isomerisation steps to upgrade the hquid fuels into gasohne and diesel. The combination of two different zeolites in the same industrial process is illustrated in the Shell-UOP TIP process an acidic zeolite, MOR, is used for isomerisation and the neutral LTA is used as molecular sieve for separation as shown in the scheme below (Figure 5.3). 

An important example are alumina-supported Co—Mo and Ni—Mo sulfides, which constitute the active phases in catalysts for hydrotreating of middle distillates (403). It appears that in such catalysts, mostly pseudoboehmite-derived Y-AI2O3 is used as the support. According to fiter-ature data, catalysts for fluid catalytic cracking (FCC) gasoline desulfurization, which is performed at 260—340 °C and 5—30 atm, may contain 5—11 wt% molybdenum and 2-3 wt% cobalt supported on AI2O3 with a surface area of220—240 w (405). Catalysts for diesel fuel desulfurization to low-sulfur... 

Fluid catalytic cracking is one of the key processes for the production of gasoline and diesel oil in present-day refineries. Worldwide, about 400 units are in operation with a total annual capacity of about 600 million tonnes. Commercial catalytic crackers operate at about 550 °C. Since after a contact time in the cracking section (upflow pipe, entrained bed) of only a few seconds the catalyst is largely deactivated by coke at a level of about 1 wt%, the catalyst is routed to a regenerator (fluidized bed), where the coke is burned off at temperatures of 700 °C with air to a level of less than 0.1%. The catalyst is returned pneumatically to the catalytic cracking section. 

The process of fluid catalytic cracking (FCC) is undoubtedly at the heart of the refinery and may be considered one of the most important processes of the chemical industry. This process converts heavy atmospheric residues and vacuum distillates into value-added fractions such as gasoline, diesel, kerosene, and LPG. 

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