Isobutane of technical quality was pyrolyzed in nitrogen as a diluent under standardized conditions (820 "C, 0.4 s, Ndisobutane = 0.4 g/g) in a specially developed, vertically positioned tubular flow reactor coupled with a micro electrobalance. After cooling the dry cracked gases to temperatures thought to be representative for the innertube surface temperatures of a TLE (transfer-line exchanger), the growth of carbon-rich deposits (known as TLE fouling) was measured continuously at the surfaces of material coupons in dependence on (i) the prehistory and (ii) the sort of materials as well as (iii) the temperatures. The results show clearly that on low alloyed steels catalytic reactions can play an important role in TLE fouling if dry cracked gases are used.

No abstract

No abstract

This review considers and evaluates alternative process concepts for the production of ethene on an industrial scale. A fundamental perspective is chosen, focusing on the ability to create a near-optimum conversion path from hydrocarbon (C2+) feed to ethene. The critical conversion aspects are quickly achieving a high temperature at a low hydrocarbon pressure and, after a short reaction time, arresting the composition with a high ethene content by rapid cooling. The features of an ideal process involve a maximum olefin yield, no remains of energy carriers or auxiliary chemicals in the product, minimal ecological impact, minimum energy input per unit product, high availability, and a low degree of complexity of the reaction section. The majority of the current ethene production processes are an evolutionary redesign from earlier existing processes that is able to add a large amount of thermal energy in a short period of time and at elevated temperature levels in the range of 600−1200 °C, enabled by better high-temperature-resistant materials. The process concepts reviewed in this paper are examined from a different point of viewnamely, how well they meet the criteria of the ideal process. The specific energy requirements of the processes are limited in the available literature; therefore, these requirements are systematically determined with Aspen Plus software and the aid of SPYRO for an ethene plant with a fixed ethane feed. A wide variety of process concepts is covered:  dehydrogenation, direct heating, and indirect heating. Although none of the reported processes fulfils all ideals, the new combination of the adapted firing furnace with ceramic reactors internals and the shock wave reactor come close to it.

No abstract