For ethane cracking

Do these results also suggest that five-coordinate carbonium ions are not essential to explain alkane cracking The evidence is mixed. Kazansky and van Santen (132) reported low-level calculations and found a metastable carbonium ion (CH3-H-CH1) formed from ethane and a zeolite Brpnsted site, but this species was so high in energy that it did not appear to be thermally accessible. More extensive work by van Santen (133) shows, however, that the transition states leading from this species do not relate to ethane cracking Blaszkowski, Nascimento, and van Santen (134) found other transition states for ethane cracking (Fig. 26) that are similar to carbenium ions albeit with stabilization from the lattice. 

As one progresses from ethane through heavier, lower hydrogen content feedstocks the yield of ethylene decreases and causes feed requirements to increase markedly. For example, cracking heavy gas oil would require slightly over three times the amount of feed (per lb of ethylene) that is needed for ethane cracking. The extra feed required for heavier stocks is, of course, distributed among the various by-products. 

Energy consumption Energy consumptions are 3,300 kcal/kg of ethylene produced for ethane cracking and 5,000 kcal/kg of ethylene for naphtha... 

Commercial plants Technip has been awarded four ethylene plants ranging from 500 kty up to 1,400 kty using either ethane or liquid feedstocks. While over 300 cracking furnaces have been built, and 15 units operate worldwide, numerous expansions over the nominal capacity based on progressive separation techniques are under way, with up to an 80% increase in capacity. For ethane cracking, front-end hydrogenation scheme is also available. 

Both 1-butene and 2-butene can be used as a monomer for specialist polymers. Of interest to integrated cracking and polymer production operations is 1-butene for co-polymerisation with ethylene to produce LLDPE (linear low-density polyethylene/. For ethane cracking operations where the C4 stream maybe insufficient, 1-butene can be made by from ethylene by dimerisation. ... 

This chapter describes the basic process of ethane steam cracking operations to produce ethylene and the integration with downstream operations. The approach to economic analysis for various types of ethane cracking operations is described and the economic analysis for ethane cracking in a standardised approach is developed. The production of olefins from other feed stocks and the economics of production are developed in later chapters ... 

Figure 7.1 Typical flow-sheet for ethane cracking...

Many cracker operations are integrated into the downstream production of polymers and resins. For ethane cracking this usually means integration into the production of various polyethylene grades. 

The cracking of normal butane is very similar to that for propane and is accomplished in plants similar in design to that for ethane cracking. Capital costs are shghtly higher (at 850 million for... 

The analysis follows the method as described previously for ethane cracking and the results are illustrated in Figure 8.8. 

In developing the above concentration-time relationship, we used PSSH. However, we can now utilize the techniques described in Chapter 6 to solve the full set of equations for ethane cracking and then compare these results with the much simpler PSSH solutions. 

The evolution of the H/C ratio of the bulk of deposit is extremely important because it affects the void fraction, specific gravity and thermal conductivity of the solid. For ethane cracking, an asymptotic value for H/C, slightly larger than the one yielded by heavy feeds, is obtained at low and intermediate temperatures (700-900 K). At low temperatures (700 K), the deposit mostly loses methyl... 

Part (b) Tesfiitg ffie PSSH for Ethane Cracking... 

Energy consumption Energy consumptions are 3,300 kcal/kg of ethylene produced for ethane cracking and 5,000 kcal/kg of ethylene for naphtha feedstocks. Energy consumption can be as low as 4,000 kcal/kg of ethylene for naphtha feedstocks with gas turbine integration. As noted above, the new flow scheme reduces energy consumption by 14%. 

The overall order of the reaction depends on the relative importance of the different termination steps and whether the initiation step is first or second order. For ethane cracking, experiments indicate an order of 1 or... 

Ab initio and density functional study of the activation barrier for ethane cracking in cluster models of zeolite H-ZSM-5 ... 

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