Ethylene yield

Ethylene. Under the influence of pressure and a catalyst, ethylene yields a white, tough but flexible waxy sohd, known as Polythene. Polyethylene possesses excellent electric insulation properties and high water resistance it has a low specific gravity and a low softening point (about 110°). The chemical inertness oi Polythene has found application in the manufacture of many items of apparatus for the laboratory. It is a useful lubricant for ground glass connexions, particularly at relatively high temperatures. 

Hoechst HTP Process. The two-stage HTP (high temperature pyrolysis) process was operated by Farbwerke Hoechst ia Germany. The cracking stock for the HTP process can be any suitable hydrocarbon. With hydrocarbons higher than methane, the ratio of acetylene to ethylene can be varied over a range of 70 30 to 30 70. Total acetylene and ethylene yields, as wt % of the feed, are noted ia Table 11. 

Thermal Cracking. Thermal chlorination of ethylene yields the two isomers of tetrachloroethane, 1,1,1,2 and 1,1,2,2. Introduction of these tetrachloroethane derivatives into a tubular-type furnace at temperatures of 425—455°C gives good yields of trichloroethylene (33). In the cracking of the tetrachloroethane stream, introduction of ferric chloride into the 460°C vapor-phase reaction zone improves the yield of trichloroethylene product. 

A fluidi2ed-bed catalytic reactor system developed by C. E. Lummus (323) offers several advantages over fixed-bed systems ia temperature control, heat and mass transfer, and continuity of operation. Higher catalyst activity levels and higher ethylene yields (99% compared to 94—96% with fixed-bed systems) are accompHshed by continuous circulation of catalyst between reactor and regenerator for carbon bum-off and continuous replacement of catalyst through attrition. 

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. 

Activated alumina and phosphoric acid on a suitable support have become the choices for an iadustrial process. Ziac oxide with alumina has also been claimed to be a good catalyst. The actual mechanism of dehydration is not known. In iadustrial production, the ethylene yield is 94 to 99% of the theoretical value depending on the processiag scheme. Traces of aldehyde, acids, higher hydrocarbons, and carbon oxides, as well as water, have to be removed. Fixed-bed processes developed at the beginning of this century have been commercialized in many countries, and small-scale industries are still in operation in Brazil and India. New fluid-bed processes have been developed to reduce the plant investment and operating costs (102,103). Commercially available processes include the Lummus processes (fixed and fluidized-bed processes), Halcon/Scientific Design process, NIKK/JGC process, and the Petrobras process. In all these processes, typical ethylene yield is between 94 and 99%. 

Copolymentation of CTFE and ethylene yields linear, semicrystalhne polymers known as ECTFE resins. They have a highly altemahng structure... 

Deep catalytic cracking (DCC) is a catalytic cracking process which selectively cracks a wide variety of feedstocks into light olefins. The reactor and the regenerator systems are similar to FCC. However, innovation in the catalyst development, severity, and process variable selection enables DCC to produce more olefins than FCC. In this mode of operation, propylene plus ethylene yields could reach over 25%. In addition, a high yield of amylenes (C5 olefins) is possible. Figure 3-7 shows the DCC process and Table 3-10 compares olefins produced from DCC and FCC processes. ... 

A fairly new development in cracking liquid feeds that improves ethylene yield is the Millisecond furnace, which operates between 0.03-0.1 sec with an outlet temperature range of 870-925°C. The Millisecond furnace probably represents the last step that can be taken with respect to this critical variable because contact times below the. 01 sec range lead to production of acetylenes in large quantities. 

Propane cracking is similar to ethane except for the furnace temperature, which is relatively lower (longer chain hydrocarbons crack easier). However, more by-products are formed than with ethane, and the separation section is more complex. Propane gives lower ethylene yield, higher propylene and butadiene yields, and significantly more aromatic pyrolysis gasoline. Residual gas (mainly H2 and methane) is about two and half times that produced when ethane is used. Increasing the severity... 

The ethylene selectivity (Fig. 5) and thus the ethylene yield depend strongly on the adsorbent mass (Fig. 5). For fixed catalyst mass, oxygen supply I/2F and methane conversion there is an optimal amount of adsorbent for maximizing ethylene selectivity and yield (Fig. 5). Excessive amounts of adsorbent cause quantitative trapping of ethane and thus a decrease in ethylene yield according to the above reaction network. This shows the important synergy between the catalytic and adsorbent units which significantly affects the product distribution and yield. 

Figure 6a shows the effect of F02 on the C2 selectivity and yield. The C2 yield is up to 53%. Figure 6b refers to the same experiments and shows the corresponding elBfect of CH4 conversion on the selectivity and yield of ethylene and ethane. The ethylene yield is up to 50% (65% ethylene selectivity at 76% methane conversion). To the best of our knowledge this is the maximum ethylene yield obtained for the OCM reaction under continuous-flow steady-state conditions. 

Methane can be oxidatively coupled to ethylene with very high yield using the novel gas recycle electrocatalytic or catalytic reactor separator. The ethylene yield is up to 85% for batch operation and up to 50% for continuous flow operation. These promising results, which stem from the novel reactor design and from the adsorptive properties of the molecular sieve material, can be rationalized in terms of a simple macroscopic kinetic model. Such simplified models may be useful for scale up purposes. For practical applications it would be desirable to reduce the recycle ratio p to lower values (e.g. 5-8). This requires a single-pass C2 yield of the order of 15-20%. The Sr-doped La203... 

Since deuterium addition to ethylene yields C2H4D2, both of the last steps are irreversible and (13) can be taken as the rate-determining step. Accordingly, if all prior steps are at equilibrium, we can write for the rate R of ethane formation ... 

This reaction decreases the ethylene yield while increasing the G of ethane. 

Nitric Acid.—In the presence of concentrated sulphuric acid ethylene yields the nitric ester of nitroethyl alcohol. 

Reactions of amines with alkenes have been reviewed298,299. Alkali metal amides are active homogeneous catalysts for the amination of olefins. Thus diethylamine and ethylene yield triethylamine when heated at 70-90 °C at 6-10 atm in the presence of lithium diethylamide and /V./V./V. /V -tetrarncthylcthylcncdiaminc. Solutions of caesium amide promote the addition of ammonia to ethylene at 100 °C and 110 atm to give mixtures of mono-, di- and triethylamines300. The iridium(I)-catalysed addition of aniline to norbomene affords the anilinonorbomane 274301. Treatment of norbomene with aniline... 

Mechanistic and theoretical studies of the Diels-Alder reaction have resulted in the characterization of this reaction as a concerted, although not necessarily synchronous, single-step process28-31 45. The parent reaction, the addition of 1,3-butadiene to ethylene yielding cyclohexene, has been the subject of an ongoing mechanistic debate. Experimental results supported a concerted mechanism, whereas results from calculations seemed to be dependent on the method used. Semi-empirical calculations predicted a stepwise mechanism, whereas ab initio calculations were in favor of a concerted pathway. At the end of the 80s experimental and theoretical evidence converged on the synchronous mechanism29-31. 

When naphtha or gas oil is cracked, imagine the limitless combinations possible. Naphthas are made up of molecules in the C5 to Cio range gas oils from Cio to perhaps C30 or C40. The structures include everything from simple paraffins (aliphacics) to complex polynuclear aromatics, so a-much wider range of possible molecules can form. Ethylene yields.froin..cracking naphtha or gas oil are much smaller than those from ethane or propane, as you can see from Table 5-1- But to compensate the plant operator, a full range of other hydrocarbons is produced as by-products also. 

In 1965, a gas-phase chemiluminescent reaction between ozone and ethylene was reported by Nederbragt et and the sensitivity of this technique was later improved by Warren and Babcock.The reaction between ozone and ethylene yields chemiluminescent emission in the 300- to 600-nm region, with maximal intensity at 435 nm. The intensity of this emission is directly proportional to the ozone concentration. 

The alkylation product of benzene (W) and ferf-butylbenzene (S4) with ethylene yields predominantly sec-butyl alkylates. This is the case because the ethylbenzene alkylate formed reacts very rapidly in the normal side-chain alkylation reaction. The sec-butyl aromatic alkylates much less readily. The much greater ease of side-chain alkylation over nuclear alkylation also accounts for the exclusive formation of side-chain alkylates from compounds, such as cumene, that are predominantly metalated on the ring by alkylalkali metal compounds. 

Propylene is a coproduct of steam cracking, the yield of which accounts for nearly half of the ethylene yield. Currently, propylene demand exceeds ethylene demand and steam cracking cannot keep up with the required propylene/ethylene balance. To close the gap, an increase in propylene production from the FCC process is needed. 

But certain compounds of ethylene yield paralactic acid,... 

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