No abstract

&kromatic hydrocarbons have been lcnoivn to be byproducts of cracking processes; from a study of the mechanism of their formation by cracking, it was hoped to develop a method for their industrial production from petroleum or petroleum fractions. The present four papers show that the high temperature aromatization of hydrocarbons proceeds largely through degradation to small unsaturated units, outstanding among them butadiene, and through subsequent "diene reactions" leading to hydroaromatic hydrocarbons which are eventually dehydrogenated to the aromatics. For naphthenic charging atocks, direct thermal dehydrogenation represents a second source of aromatic hydrocarbons.A process is described which converts a nonaromatic (or only partly aromatic) charging stock intoliquidand gaseous products. The gases are predominantly unsaturated (ethyl-HE cyclization of paraffinic hydrocarbons into aromatics, T discovered over a decade ago (10, 21, 24-27) has been described (16, 68, 36, 36, 39) as a three-step process: dehydrogenation of the paraffin hydrocarbon t o a corresponding olefin, cycloisomerization of this olefin to a hexahydrobenzene, and simultaneous removal of the supernumerary hydrogen atoms from the latter to form the aromatic hydrocarbon. This process is catalyzed by various oxides which are used either in the pure state or supported on carriers such as alumina.This reaction mechanism, however, cannot account for the formation of aromatics by thermal cracking in empty or packed tubes (9, 31). Two alternative mechanisms have been proposed. Both suggest that in the first stage of the reaction the starting material undergoes considerable breakdown, followed by resynthesis. Groll (9) assumes that the intermediate is acetylene or, rather, a diradical form of that hydrocarbon, whereas other workers (1.2, 30, 47) believe this intermediate is butadiene. The latter is known to combine with other unsaturated hydrocarbons-for example, with ethylene to form cyclohexene (19), or with a second butadiene molecule to form vinylcyclohexene (2). This reaction is an extension of the classical Diels-Alder synthesis.The present paper describes the second type of aromatization The distinction between them is that in the first type the starting material and the end product have the same number of carbon atoms. In the present work any hydrocarbonaceous starting material will result in the complete series of aromatics, from benzene to the most complicated polycyclic system (53, 46, 46, 46).Under the following conditions a pure, or almost pure, aromatic liquid product can be obtained from a given petroleum fraction or other hydrocarbonaceous raw material: temperature, 630 ' to 680" C.; pressure, 1 to 3 atmospheres; space velocity, 0.05 to 0.5 (litera of liquid charging stock per liter catalyst volume per ene, propylene, butylene, isobu tylene, and some butadiene), and the liquid product is more than 90%, and up to 98%, of aromatic nature and largely free of sulfur and nitrogen, even in cases in which the charging stock contained organic...

THE aromatizing cracking of hydrocarbon oils is, at least to a certain extent, due to a breakdown into small units, particularly olefins and diolefins, and a subsequent resynthesis by a Diels-Alder mechanism, one would expect that the results reflect the proneness of the various types of hydrocarbons to such breakdown-i.e., will depend on the chemical nature of the charging stock. In Table I, a number of charging stocks of roughly similar boiling range but varying nature are compared as to the yield in liquid aromatized product.

The source of the surprisingly large quantity of chrysene will be discussed in the following paper (43). acknowledgment The authors wish to express their gratitude to . E. Charlton, Chief Engineer of Petrocarbon Ltd., who collaborated in all questions of engineering and who was responsible for the design and construction of the pilot plant on which many of the results recorded in this and the following papers were obtained.

This case study considers how a minority stakeholder group of Israeli settlers blocked Prime Minister Yitzhak Rabin’s peace initiatives. Drawing on interviews with those who served in Rabin’s administration and with the settlers’ leaders, this article contends that the prime minister’s use of adversarial public rhetoric against the settlers denied the legitimacy of an influential stakeholder group, triggering a backlash of intense militancy from the right‐wing minority. This, coupled with Rabin’s failure to deal with opposing coalitions, diminished his capacity to implement “land for peace” initiatives. The case illustrates a leader’s failure to maintain adequate forms of engagement with key stakeholders. The accompanying analysis demonstrates that stakeholder theories, though incomplete in their existing forms, can still illuminate the high risk and ineffectiveness of denying the legitimacy of stakeholder groups and the strategic importance of maintaining channels of flexible negotiation and cooperation with seemingly marginal groups when high‐stakes rivalries are likely to ensue.