Synthesis of [¹⁴C]propane

Abstract

[14C]propane of high chemical and radiochemical purity has been prepared from [14C]acetone via [1,3‐14C]acetone semicarbazone.

Mechanism of the Catalytic Conversion of Methanol to Hydrocarbons

“…82 Studies in which n-hexane and n-heptane were converted over H-ZSM-5 at 683 K resulted in the production of C 1 −C 5 aliphatics as well as a significant yield of C 7 and C 8 aromatics (over 25 wt % for both reactants). 83 The presence of aliphatics smaller than the reactant indicates that alkane cracking is occurring simultaneously with cyclization reactions. The formation of aromatics larger than the reactant show that side reactions of cyclization, such as olefin oligomerization and alkylation of aromatics, also occur.…”

Brønsted Acid Catalyzed Cyclization of C7 and C8 Dienes in HZSM-5: A Hybrid QM/MM Study and Comparison with C6 Diene Cyclization

“…Considering strong acidity of the Brønsted acid sites in the zeolite, a mechanism based on carbenium ion chemistry has been suggested. Experimental investigations involving model reactants ,– have concluded that (i) dienes or trienes are the precursor for cyclization, (ii) napthenes like cyclohexane are unlikely to be the intermediates for cyclization on monofunctional Brønsted acid zeolites, and (iii) ring closure to cyclic olefins is irreversible. These studies concluded that ring closure is less activated than other important reactions like dehydrogenation and cracking.…”

DFT-Based Reaction Pathway Analysis of Hexadiene Cyclization via Carbenium Ion Intermediates: Mechanistic Study of Light Alkane Aromatization Catalysis

“…Monofunctional acid catalysts exhibit relatively low aromatics yields which is due to preferentially high cracking, isomerization, and β-scission reactivity. [6][7][8][9][10] Bifunctional metal/ H-ZSM-5 catalysts using Ga, [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Zn, [27][28][29][30][31][32][33][34] and Pt 10,7,[35][36][37][38][39][40] dramatically improve aromatics yields but are prone to deactivation via coking 31 and, although better than purely acidic catalysts, are nevertheless limited in both aromatics yield and selectivity toward H 2 versus CH 4 byproducts.…”

“…Aromatization of even single component feedstocks is complex, involving a large number reaction steps, many of which are not well understood or are only postulated. However, it is generally agreed that the relevant reactions for conversion of light alkanes to aromatics consists of (1) alkane C-H activation to alkoxide/carbenium complexes, (2) dehydrogenation to olefins, (3) oligomerization to higher olefins, (4) rapid isomerization, (5) β-scission, (6) cyclization, and (7) dehydrogenative aromatization. 10,41 Cyclizations involving C(6+) olefins are believed to occur via carbocation/alkoxide-based pathways relatively independent of oligomerization.…”