Aromatic hydrocarbons, dehydrogenative

The dehydrogenation reaction produces crude styrene which consists of approximately 37.0% styrene, 61% ethylbenzene and about 2% of aromatic hydrocarbon such as benzene and toluene with some tarry matter. The purification of the styrene is made rather difficult by the fact that the boiling point of styrene (145.2°C) is only 9°C higher than that of ethylbenzene and because of the strong tendency of styrene to polymerise at elevated temperatures. To achieve a successful distillation it is therefore necessary to provide suitable inhibitors for the styrene, to distil under a partial vacuum and to make use of specially designed distillation columns. 

A key feature of our polyphenylene dendrimers is that they can be planarized and thus reduced in dimensionality by intramolecular dehydrogenation [29,35]. This results in large, fused polycyclic aromatic hydrocarbons (PAHs). PAHs serve as structurally distinct, two-dimensional subunits of graphite and show attractive properties such as high charge carrier mobility, liquid crystallinity, and a high thermal stability, which qualifies these materials as vectorial charge transport layers [81]. 

The ability of a catalyst to promote isomerization plays two roles in reforming it increases the amount of branched chain paraffins in the product and it converts naphthene hydrocarbons with cyclopentane rings into cyclohexane ring naphthenes which are necessary for the formation of aromatics by dehydrogenation. 

Catalytic reforming. Catalytic reforming is a process for increasing the octane number of naphthas. It involves isomerisation of alkanes, dehydrogenation of cyclohexanes to aromatic hydrocarbons, isomerisation and dehydrogenation of alkylcyclopentanes, and dehydrocyclisation of alkanes. 

Aromatization the conversion of nonaromatic hydrocarbons to aromatic hydrocarbons by (1) rearrangement of aliphatic (noncyclic) hydrocarbons (q.v.) into aromatic ring structures and (2) dehydrogenation of alicyclic hydrocarbons (naphthenes). 

Probably the same reaction, the dehydrogenation, condensation, and irreversible adsorption of highly condensed aromatic hydrocarbons, causes the loss of activity of the WS2 catalyst when used at pressures well below 200 atm. As an example (20), in experiments with a paraffin-base petroleum-oil fraction boiling between 200° and 325°C. the results in the accompanying tabulation were obtained ... 

Tertiary amines have also been employed in electron transfer reactions with a variety of different acceptors, including enones, aromatic hydrocarbons, cyanoaro-matics, and stilbene derivatives. These reactions also provide convincing evidence for the intermediacy of aminoalkyl radicals. For example, the photoinduced electron transfer reactions of aromatic hydrocarbons, viz. naphthalene, with tertiary amines result in the reduction of the hydrocarbon as well as reductive coupling [183, 184]. Vinyl-dialkylamines can be envisaged as the complementary dehydrogenation products their formation was confirmed by CIDNP experiments [185]. 

The catalytic activity of various semiconducting oxides and mixtures of oxides for the dehydrogenation of aromatic hydrocarbons is increased by ultraviolet irradiation 65>. The carbon monoxide oxidation photosensitized by ZnO has been studied by several authors (see below) 66 70>. 

They include aromatic hydroxylation, hydrocarbon and alcohol oxidation, alkene epoxidation, nitro-aromatic reduction, dehydrogenation, carbonylation, cyclization, heterocycle functionalization, etc. 

The source of all carbon relevant to the present context is the feedstock of hydrocarbon molecules (aliphatic, aromatic, with and without heteroatoms). Figure 10 summarizes the possibilities for their conversion into black carbon. The chemical route comprises polymerization into aromatic hydrocarbons with final thermal dehydrogenation. This process often includes a liquid crystalline phase immediately before final solidification. In this phase large aromatic molecules can sclf-organizc into parallel stacks and form well-ordered precursors for graphitic structures with large planar graphene layers. This phase is referred to... 

SiH-functional poly(silylated) aromatic hydrocarbons are important starting materials for the preparation of arene-bridged polysilanes through thermal or catalytic dehydrogenative coupling reactions. 

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