Ethylene/Propylene Yield

Improved overall ethylene/propylene yield by recycle cracking of DCC—... 

In a single stage, without liquid recycle, the conversion can be optimized between 60 and 90%. The very paraffinic residue is used to make lubricant oil bases of high viscosity index in the range of 150 N to 350 N the residue can also be used as feedstock to steam cracking plants providing ethylene and propylene yields equal to those from paraffinic naphthas, or as additional feedstock to catalytic cracking units. 

Furthermore, treatment of the aminopalladation product with bromine affords aziridines[176]. The aziridine 160 was obtained stereoselectively from methylamine and 1-decene in 43% yield. The aminopalladation of PdCl2 complexes of ethylene, propylene, and 1-butene with diethylamine affords the unstable ir-alkylpalladium complex 161, which is converted into the stable chelated acylpalladium complex 162 by treatment with CO[177],... 

Low density polyethylene has been pyrolyzed at 800°C to produce ethylene, propylene, and other light olefins ia 75% yield (43). 

Significant products from a typical steam cracker are ethylene, propylene, butadiene, and pyrolysis gasoline. Typical wt % yields for butylenes from a steam cracker for different feedstocks are ethane, 0.3 propane, 1.2 50% ethane/50% propane mixture, 0.8 butane, 2.8 hill-range naphtha, 7.3 light gas oil, 4.3. A typical steam cracking plant cracks a mixture of feedstocks that results in butylenes yields of about 1% to 4%. These yields can be increased by almost 50% if cracking severity is lowered to maximize propylene production instead of ethylene. 

Elastomers. Ethylene—propylene terpolymer (diene monomer) elastomers (EPDM) use a variety of third monomers during polymerization (see Elastomers, ethyiene-propylene-diene rubber). Ethyhdenenorbomene (ENB) is the most important of these monomers and requires dicyclopentadiene as a precursor. ENB is synthesized in a two step preparation, ie, a Diels-Alder reaction of CPD (via cracking of DCPD) with butadiene to yield 5-vinylbicyclo[2.2.1]-hept-2-ene [3048-64-4] (7) where the external double bond is then isomerized catalyticaHy toward the ring yielding 5-ethyhdenebicyclo[2.2.1]-hept-2-ene [16219-75-3] (ENB) (8) (60). 

Table 6 shows the effect of varying coil oudet pressure and steam-to-oil ratio for a typical naphtha feed on the product distribution. Although in these tables, the severity is defined as maximum, in a reaUstic sense they are not maximum. It is theoretically possible that one can further increase the severity and thus increase the ethylene yield. Based on experience, however, increasing the severity above these practical values produces significantly more fuel oil and methane with a severe reduction in propylene yield. The mn length of the heater is also significantly reduced. Therefore, this is an arbitrary maximum, and if economic conditions justify, one can operate the commercial coils above the so-called maximum severity. However, after a certain severity level, the ethylene yield drops further, and it is not advisable to operate near or beyond this point because of extremely severe coking. 

Methanol to Ethylene. Methanol to ethylene economics track the economics of methane to ethylene. Methanol to gasoline has been flilly developed and, during this development, specific catalysts to produce ethylene were discovered. The economics of this process have been discussed, and a catalyst (Ni/SAPO 34) with almost 95% selectivity to ethylene has been claimed (99). Methanol is converted to dimethyl ether, which decomposes to ethylene and water the method of preparation of the catalyst rather than the active ingredient of the catalyst has made the significant improvement in yield (100). By optimizing the catalyst and process conditions, it is claimed that yields of ethylene, propylene, or both are maximized. This is still in the bench-scale stage. 

The addition of various Kolbe radicals generated from acetic acid, monochloro-acetic acid, trichloroacetic acid, oxalic acid, methyl adipate and methyl glutarate to acceptors such as ethylene, propylene, fluoroolefins and dimethyl maleate is reported in ref. [213]. Also the influence of reaction conditions (current density, olefin-type, olefin concentration) on the product yield and product ratios is individually discussed therein. The mechanism of the addition to ethylene is deduced from the results of adsorption and rotating ring disc studies. The findings demonstrate that the Kolbe radicals react in the surface layer with adsorbed ethylene [229]. In the oxidation of acetate in the presence of 1-octene at platinum and graphite anodes, products that originate from intermediate radicals and cations are observed [230]. 

Anh, T.H. and Vu-Khanh, T. Fracture and Yielding Behaviors of Polystyrene/Ethylene-Propylene Rubber Blends Effects of Interfacial Agents, Polym. Eng. Set 41(12), 2073-2081, December 2001. 

Stereochemistry Coordination Polymerization. Stereoisomerism is possible in the polymerization of alkenes and 1,3-dienes. Polymerization of a monosubstituted ethylene, such as propylene, yields polymers in which every other carbon in the polymer chain is a chiral center. The substituent on each chiral center can have either of two configurations. Two ordered polymer structures are possible — isotactic (XII and syndiotactic (XIII) — where the substituent R groups on... 

Xenon difluoride labelled with positron-emitting F has been prepared by reaction of cyclotron produced [ F]p2 with xenon [88]. This low-yielding method requires high pressure. [ F]Xep2 was also obtained by treating sulfuryl chloride fluoride solutions of Xep2 in fluorinated ethylene propylene vessels with Bronst-... 

Figure 5.3 shows light olefin yields of DCC process in four refineries with different feedstocks at reaction temperatures of 545-565°C. The propylene yield can reach 23 wt% with paraffinic feed, and about 18-19 wt% with intermediate-based feed. The propylene/ethylene ratio is about 3.5-6.2, much higher than that of steam cracking. The DCC operation can be modified to further increase the yield of propylene. For example, recycling a part of DCC cracked naphtha to the reactor resulted in a propylene yield increment of 3.5 wt % in Jinan Refinery [16]. 

Selective modification of polyols such as ethylene glycol, 1,3-propylene glycol, or glycerol with butadiene (1) has been studied [7-10]. The monosubstituted compounds are preferred due to their potential applications as surfactants, PVC plasticizers, or even in cosmetics. The telomerization of 1 with ethylene glycol yields a complex mixture including linear and branched mono- and ditelomers, as well as 1,3,7-octatriene and vinyl cyclohexene (Fig. 2) [11]. 

Cycloalkanes may be pyrolized in a manner similar to that for alicyclic alkanes. Cyclopentane, for instance, yields methane, ethane, propane, ethylene, propylene, cyclopentadiene, and hydrogen at 575°C. Analogous to cracking of alicyclic alkanes, the reaction proceeds by abstraction of a hydrogen atom followed by p scission. The cyclopentyl radical may undergo successive hydrogen abstractions to form cyclopentadiene. 

Technologies for the reverse process to produce propylene from ethylene and 2-butenes were also developed.138 139 The Arco process139 dimerizes ethylene to 2-butenes, which, in turn, are metathesized with ethylene to yield propylene. The process is not practiced at present, but it is a potential technology in case of a propylene shortage. 

The Gas Phase. The gas-phase analysis is only qualitative since the volatile products remain partially adsorbed, and the transformation into gaseous products is always rather small. As expected, ethylene is by far the most abundant component. The next component in abundance is CH4 but in an approximate ratio of 1/10 with respect to ethylene. The yield in hydrocarbons is the highest after the thermal treatment of the TEA sample and the lowest for the DEA sample. In the gaseous phase obtained from the heated TEA sample, C2H5OH and C2H5-O-CH3 were found at the beginning of the reaction. Also traces of methanol were recorded. Among the minor components, propylene, m-2-butene, ethane, and butane were observed. 

Ethylene, propylene, and cyclohexene are converted in low yields into the corresponding epUnlfides by reacting the olefin with ethyl tefrasulfide at approximately 150c.6C> The ethyl tetraeulfide serves as a source of free sulfur. 

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