Gas oil catalytically cracked

However, in many industrial processes a large number of chemical reactions occurs simultaneously. In petroleum refining operations dealing with feeds containing hundreds of components (i.e. gas oil catalytic cracking, n htha catalytic reforming, middle distillate hydrodesulfurization), where the complete analysis is a problem, the number of reactions becomes formidable and the reaction network may also become very complicated, so that components of the feed can be lumped into a small number of groups. 

Figure 4 Catalytic cracking (fluid catalytic cracking). Heavy fraction gas oils are cracked (broken down) into lower molecular weight fractions in the presence of finely powdered catalyst, handled as a fluid. (From Ref. 5.)...

Feed stock for the first sulfuric acid alkylation units consisted mainly of butylenes and isobutane obtained originally from thermal cracking and later from catalytic cracking processes. Isobutane was derived from refinery sources and from natural gasoline processing. Isomerization of normal butane to make isobutane was also quite prevalent. Later the olefinic part of the feed stock was expanded to include propylene and amylenes in some cases. When ethylene was required in large quantities for the production of ethylbenzene, propane and butanes were cracked, and later naphtha and gas oils were cracked. This was especially practiced in European countries where the cracking of propane has not been economic. 

Catalytic Cracking Test. A standard microactivity test (MAT) was used to evaluate the conversion and selectivity of catalyst samples. The tests were done at the University of Pittsburgh s Applied Research Center (former Gulf Research Laboratory), a qualified laboratory for MAT evaluations. A standard method, developed by Gulf, was used without modification. A Cincinnati gas oil was cracked under the following conditions cat/oil=3, 16 h 1 WHSV, and 516°C. Prior to charging the reactor, all samples underwent a standard thermal pretreatment. Solids were first heat shocked for 1 h at 593°C. Next, selected materials were impregnated with 3000 ppm Ni and 6000 ppm V, as naphthenates. Then all samples were calcined for 10 h at 538°C. Finally, each material was steamed at 732°C for 14 h in a fluidized bed to produce a catalyst in a simulated equilibrium state. 

Catalytic cracking is the process of upgrading gas oil or even residual oil (heavy oil) to produce gasoline, distillates, light olefines, etc. Commercialized processes include fluid catalytic cracking (FCC), residual oil catalytic cracking (RFCC), and catalytic pyrolysis, etc. 

Refinery ethylene is usually made by the catalytic cracking of ethane, propane, or a mixed hydrocarbon stream, such as recovered natural gas liquids, naphthas, or gas oil [11]. Cracking conditions are quite severe 750-900°C and 0.1-0.6 second residence time for a low partial pressure hydrocarbon stream. A number of metal oxide catalysts have recently been evaluated for this purpose [12]. The usual diluent is steam, used at a weight ratio of steam to hydrocarbon of 0.2 1 for ethane feed, to progressively higher ratios with the higher molecular weight hydrocarbons of up to 2.0 1 for gas oil. 

Low-value distillates, including heavy-cycle oils from FCC units, thermal and coker gas oils, and other heavy-vacuum gas oils, are cracked to produce naphtha, jet fuel, and diesel oils. The reaction mechanism is the same as in catalytic cracking and some aromatic products are also hydrogenated. 

Cracking (thermal) and gas recovery 16-40 cents per bbl reduced crude (1956) Cracking (catalytic) and gas recovery 28-50 cents per bbl gas oil (1956) Cracked (pressure) distillate rerun-... 

The gas oil cut from catalytic cracking called Light Cycle Oil (LCO), is characterized by a very low cetane number (about 20), high contents in aromatics, sulfur and nitrogen, all of which strongly limit its addition to the diesel fuel pool to a maximum of 5 to 10%. 

For gas oil from catalytic cracking (LCO), reducing the aromatics content to 20 wt. % results in a chemical hydrogen consumption of 3.4 wt % and a cetane number of 40. 

Catalytic Processes. A second group of refining operations which contribute to gas production are the catalytic cracking processes, such as fluid-bed catalytic cracking, and other variants, in which heavy gas oils are converted into gas, naphthas, fuel oil, and coke (5). 

Gas oil is a product hoiling slightly higher (235—425°C, or sometimes wider) than kerosene. The main feedstock to the catalytic cracking units (see Feedstocks), it received its name from use as an enriching agent in the production of city or manufactured gas. It is often used as diesel fuel. 

Cycle stock (recycle stock) denotes any product that is recycled, that is, taken back to an earlier stage in the process. The term cycle stock is also used for the gas oil-like product of catalytic cracking. 

As is indicated in Figure 4, saturates contribute less to the vacuum gas oil (VGO) than the aromatics, but more than the polars present at percentage, rather than trace, levels. VGO itself is occasionally used as a heating oil but most commonly it is processed by catalytic cracking to produce naphtha or by extraction to yield lubricant oils. 

Refinery Production. Refinery propylene is formed as a by-product of fluid catalytic cracking of gas oils and, to a far lesser extent, of thermal processes, eg, coking. The total amount of propylene produced depends on the mix of these processes and the specific refinery product slate. For example, in the United States, refiners have maximized gasoline production. This results in a higher level of propylene production than in Europe, where proportionally more heating oil is produced. 

In fluid catalytic cracking, a partially vaporized gas oil is contacted with zeoflte catalyst (see Fluidization). Contact time varies from 5 s—2 min pressure usually is in the range of 250—400 kPa (2.5—4 atm), depending on the design of the unit reaction temperatures are 720—850 K (see BuTYLENEs). 

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