14411-56-4Relevant articles and documents
Effects of crystallinity of ZSM-5 zeolite on para-selective tert-butylation of ethylbenzene
Pushparaj, Hemalatha,Mani, Ganesh,Muthiahpillai, Palanichamy,Velayutham, Murugesan,Park, Yong-Ki,Choi, Won Choon,Jang, Hyun Tae
, p. 294 - 304 (2013/04/10)
Highly crystalline ZSM-5 zeolites are important for para-selective alkylation of alkyl aromatics, because they carry few external acid sites for isomerization of p-dialkyl products. Such zeolites (Si/Al = 25, 50, and 75) were synthesized in a fluoride medium between pH 4 and 6. Their crystallinities, crystal sizes, and surface areas were higher than those of a commercial ZSM-5 zeolite. Their para selectivities in alkylation were tested for vapor-phase tert-butylation of ethylbenzene between 200 and 400 °C. As expected, all the catalysts showed more than 90% para selectivity. At 300 °C, ethylbenzene conversion decreased in the order ZSM-5(25, commercial) > ZSM-5(25) > ZSM-5(50) > ZSM-5(75). The catalysts had weak, medium, and strong acid sites, but all the acid sites of ZSM-5(75) were weaker than those of ZSM-5(25) and ZSM-5(50). The high activity of commercial ZSM-5 was caused by its strong acid sites being stronger than those of the synthesized zeolites. Although the activity of the commercial catalyst was higher than those of the present catalysts, the selectivity for 4-t-butylethylbenzene (4-t-BEB) was low. The optimum feed ratio (ethylbenzene:t-butyl alcohol) was 2:1 and the feed rate was 1.65 h-1 for high ethylbenzene conversion and 4-t-BEB selectivity. Time-on-stream studies showed slow catalyst deactivation. Highly crystalline ZSM-5 zeolites are therefore better than a commercial zeolite for para-selective alkylation of alkyl aromatics. They do not require much post-modification for high para selectivity. A fluoride medium is therefore better than an alkaline medium for obtaining highly crystalline para-selective ZSM-5 zeolites.
Arene-Metal Complexes. 12. Reaction of Substituted (Benzene)tricarbonylchromium Complexes with n-Butyllithium
Card, Roger J.,Trahanovsky, Walter S.
, p. 2560 - 2566 (2007/10/02)
Reaction of a series of substituted (benzene)tricarbonylchromium complexes with n-butyllithium has been examined.The reaction appears to proceed via proton abstraction to yield an (aryllithium)tricarbonylchromium intermediate which may then be quenched by the addition of primary alkyl halides,usually methyl iodide.New alkylated complexes may be obtained,or the material may be decomplexed to yield alkylated benzene derivatives.In this manner,(monoalkylbenzene)tricarbonylchromium complexes yield mainly m-dialkylbenzenes;(fluorobenzene)tricarbonylchromium yields o-fluorotoluene;(anisole)tricarbonylchromium yields mainly 2,6-dimethylanisole;and (N,N-dimethylaniline)tricarbonylchromium yields several isomeric N,N-dimethyltoluidines.(Iodobenzene)tricarbonylchromium undergoes metal-halogen exchange with n-butyllithium and may be converted to either toluene or n-butylbenzene depending on the reaction conditions.Comparison with known chemistry of the uncomplexed analogues demonstrates the strongly activating effect of the tricarbonylchromium moiety on these reactions.It is especially interesting that under these conditions reaction of (fluorobenzene)tricarbonylchromium with n-butyllithium results in proton abstraction rather than net nucleophilic displacement,as observed when less basic nucleophiles are used.
