From thermal cracking

Ethyleneamines are used in certain petroleum refining operations as well. Eor example, an EDA solution of sodium 2-aminoethoxide is used to extract thiols from straight-mn petroleum distillates (314) a combination of substituted phenol and AEP are used as an antioxidant to control fouling during processing of a hydrocarbon (315) AEP is used to separate alkenes from thermally cracked petroleum products (316) and TEPA is used to separate carbon disulfide from a pyrolysis fraction from ethylene production (317). EDA and DETA are used in the preparation and reprocessing of certain... 

An isopropyl carbocation cannot experience a beta fission (no C-C bond beta to the carbon with the positive charge).It may either abstract a hydride ion from another hydrocarbon, yielding propane, or revert back to propene by eliminating a proton. This could explain the relatively higher yield of propene from catalytic cracking units than from thermal cracking units. 

The product distribution from thermal cracking is different from catalytic cracking, as shown in Table 4-2. The shift in product distribution confirms the fact that these two processes proceed via different mechanisms. 

Thermal cracking of wax. From thermal cracking a thermodynamic mixture might have been expected, but the wax-cracker product contains a high proportion of 1-alkenes, the kinetically controlled product. Still, the mixture contains some internal alkenes as well. For several applications this mixture is not suitable. In polymerisation reactions only the 1-alkenes react and in most cases the internal alkenes are inert and remain unreacted. For the cobalt catalysed hydroformylation the nature of the alkene mixture is not relevant, but for other derivatisations the isomer composition is pivotal to the quality of the product. 

Prior to 1938, gasoline was obtained from thermal-cracking plants then the Houdry fixed-bed catalytic cracking process led to the development of a fluidized-bed process by Standard Oil for the catalytic production of motor fuels (4-8). Acid-treated clays of the montmorilIonite type were the first fluid-cracking catalysts widely employed by the industry. However, the ever greater demand for aviation fuels during the 1939-1945 period prompted the search for more active and selective catalysts. Research on novel catalyst... 

Heavy fractions of Wilmington crude contained more aromatics and polars compared with a conventional HVGO. The conversion of the Wilmington fractions increased with boiling point range. The zeolitic contribution to the conversion decreased while the matrix contribution remained constant and the contribution from thermal cracking increased. 

Commercial catalysts. Two commercial catalysts made by Katalistiks b.v. were used. The first, EKZ-, was steam aged at 750 C for 18 hrs prior to use and the second, an EKZ-2 equilibrium catalyst from a European refinery, was heated at 300°C in air for 3 hrs prior to use. Alpha alumina, heated at 300 0 in air for 3 hrs, was used in order to estimate the contribution to conversion from thermal cracking. 

In little more than half of the 25 years covered by this symposium, catalytic cracking has been developed from its first acceptance to a major industrial process. It has served to increase the amount and octane rating of gasoline and the amounts of valuable C3 and C gas components obtainable from petroleum feed stocks over those from thermal cracking alone. It is therefore of interest to seek an explanation of the nature of the products obtained in catalytic cracking in terms of the hydrocarbon and catalyst chemistry which has been developed within the past 25 years. 

C2H2 -> C2H6 (selective hydrogenation of C2H2 impurity in C2H4 from thermal-cracking plant)... 

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. 

The original source of feed stock for the production of aviation gasoline was the butylene-isobutane portion of products from thermal cracking. Later, the thermal cracking units were replaced by catalytic cracking units, and most of the feed stocks are now derived from this source. To a... 

The first commercial unit employing Solid Phosphoric Acid was built to polymerize catalytically propylene and butylenes from thermal cracking into motor gasoline. The product has a research method (F-l) octane... 

Gravimetric Results of Catalytic Cracking. Experiments were conducted to assess the effects of temperature, cat-to-oil ratio, and feedstock composition. In addition to the effect of variables on product yields, it was also important to identify the relative influence of thermal reactions, since free-radical reactions may adversely affect product quality. A series of experiments was conducted in the temperature range of 412°-415°C because this is the temperature of maximum increase in production from thermal cracking and catalytic vs. thermal effects are more easily discernible at this temperature. 

Bp 42 44°, obtained from thermal crack ing of cyclopen tadiene dimer at ca. 150, as described in Synthesis 30. 

Reactions of organic compounds, especially hydrocarbons, with oxygen in the gas or liquid phase at moderate temperatures (below 150° C), are important both as industrial processes and as natural decomposition phenomena that are to be suppressed if possible. They are chain reactions, but differ from thermal cracking in that they usually requires initiation. An initiator may have been added intentionally or be present as an impurity or early minor product, possibly a hydroperoxide that had accumulated upon prolonged standing in contact with air. 

Formation of hydrocarbon gases principally results from thermal cracking although tin catalyzes the formation of methane at temperatures >425 C. Weller (16) has also shown that tln(II)... 

The liquid product obtained from thermal cracking can be either catalytically cracked/ hydrocracked or co-processed with a refinery feed. Since the catalytic cracking of oil derived from MWP is more or less problematic, any cracking catalyst can be applied to oil derived from pyrolysis of plastics. But the yield and the quality of gasohne obtained from cracking step vary with the type of catalyst and the properties of the pyrolytic oil derivated from waste plastics. 

As an example, the results from catalytic cracking of three types of waxes from thermal cracking of PE are given in Table 8.2 [22], The catalyst used, the equilibrium FCC catalyst. 

The components of products from thermal and catalytic cracking of HDPE, LDPE, LP, PP, PS were analyzed [48], and the results are shown in Table 28.2 and Table 28.3. The products from thermal cracking of HDPE, LDPE and LP (linear polyethylene) are mainly wax-like substances at normal temperamre. The fraction under 200°C recovered from HDPE accounts for 16% of the total cracking products, while that from LP accounts for 23%. Compared with tlie products of PE, PP produces less solid residue, but more liquid components, and PS produces the highest proportion of liquid fraction, which is 99.17% by thermal cracking and 99.56% by catalytic cracking. 

Figure 4. Ethylene and pyrolysis fuel oil yields from thermal, cracked hydroconverter residue (S).

Catalytic reactions of hydrocarbons over zeolites are reviewed. The historical development of various mechanistic proposals, particularly of the carbonium ion type, is traced. In spite of numerous catalytic, spectroscopic, and structural studies which have been reported concerning the possible roles of Bronsted acid, Lewis acid, and cationic sites, it still is not possible to formulate a comprehensive mechanistic picture. New activity and product data for cumene cracking and isotope redistribution in deuterated benzenes over Ca-and La-exchanged Y zeolites is presented. Cracking of the isomeric hexanes over alkali metal-exchanged Y and L zeolites has been studied. This cracking is clearly radical rather than carbonium-ion in nature but certain distinct differences from thermal cracking are described. 

It is the p-fission reaction that produces much of the ethylene obtained from thermal cracking. 

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