Propane aromatics from

Chemicals directly based on propane are few, although as mentioned, propane and LPG are important feedstocks for the production of olefins. Chapter 6 discusses a new process recently developed for the dehydrogenation of propane to propylene for petrochemical use. Propylene has always been obtained as a coproduct with ethylene from steam cracking processes. Chapter 6 also discusses the production of aromatics from LPG through the Cyclar process. ... 

Duo-Sol A process for separating aromatic from aliphatic hydrocaibons by partition between two solvents. The first solvent (Selecto or Selectox) is a mixture of phenol and cresylic acids the second is liquid propane. Developed by the Max B. Miller Company and licensed by Milwhite Company. 

FIGURE 1 Manufacture of aromatics from propane by reforming. 

Dehydrocyclodimerization of liquefied petrol gas (propane and butane) can be performed to yield BTX-aromatics (Table2, entry 21). Modified ZSM-5 based catalysts are used, for example in the UOP cyclar process [33], and the process will become attractive for extraction of aromatics from natural gas fields containing further C3-C4 fractions. 

Several new pathways of zeolite catalysis are offered by ZSM-5 based catalysts [1]. One of their applications is production of aromatics from short-chain alkanes [2]. The presence of metals such as platinum (partly as Pt " ") has been foimd to promote conversion of propane to aromatics [3, 4], although Pt was not the best additive for this purpose. Alkanes with longer carbon chain have also been foimd to form aromatics [5] or skeletal isomers [6] on various Pt-ZSM catalysts. 

This suggests, for these two samples that the balance between the dehydrogenating function (GaxOy) and the acid function (H ) was almost unmodified. For sample 5%Ga A1, for which deactivation is faster, the selectivity for aromatics decreases with time on stream. This change appears to be mainly due to the decrease of the conversion rather than to a change in the balance between dehydrogenating and acid functions. It is Known that during propane aromatization CH4 is formed and that the main source of C-f comes from the first step of the reaction on the acid sites (2) (5). 

Gorlatova, N., M. Tchorzewski, T. Kurihara, K. Soda, and N. Esaki. 1998. Purification, characterization, and mechanism of a flavin mononucleotide-dependent 2-nitro-propane dioxygenase from Neurospora crassa. Appl. Environ. Microbiol. 64 1029-1033. Corny, N., G. Wahl, A. Brune, and B. Schink. 1992. A strictly anaerobic nitrate-reducing bacterium growing with resorcinol and other aromatic compunds. Arch. Microbiol. 158 48-53. 

The rotating disc contactor (B), developed in the Netherlands in 1951, uses the shearing action of a rapidly rotating disc to interdisperse the phases. These have been used in the petrochemical industry for furfural and SOj extraction, propane deasphalting, sulfolane extraction for the separation of aromatics from aliphatics, and caprolactam purification. Columns up to 4.3 m in diameter are in service. 

Modification of H-ZSM-5 zeolites through solid-state reaction with ZnO was described by Yang et al. [32]. On the basis of XPS results they reported that, upon heat-treatment of a ZnO/H-ZSM-5 mixture, Zn ions migrated from the outer surface into the channels of the zeolite. This finding was supported by TPDA, IR (decrease of acidic Brpnsted sites upon solid-state reaction between ZnO and H-ZSM-5) and temperature-programmed reduction (TPR). The latter showed increased uptake and reducibility after thermal treatment of ZnO/H-ZSM-5 compared to ZnO. Zeolites Zn,H-ZSM-5 exhibited, after reduction in H2, pronounced selectivity in propane aromatization. 

HZSM5 zeolites catalyze the transformation of propane aromatic products. This aromatization requires various steps of propene, oligomerization of propene, cyclization of oligomers and hydrogen transfer from naphtenes to olefinic compounds with formation of aromatics. The cracking of Cg-Cg oligomers leads to C2-C5 olefins which, like propene, participate in the formation of aromatics. 

Pathways (I) and (ll) have been respectively postulated in (2) and (5). In order to determine which of the steps (I) or (II) are the most probable we have studied, over Ga-HZSM-5 the rate of benzene (or toluene) formation starting from molecules considered as possible intermediates during the propane aromatization. 

Other reactions that occur over the Cyclar catalyst are isomerization, dealkylation, and transalkylation of the aromatics species formed in the main reaction mechanism. The transalkylation reactions result in a distribution of benzene and alkylbenzenes that depends on the charge stock and process conditions. Slightly more benzene is produced from propane than from butane-rich feedstocks. ... 

Although a lot of effort has been spent in the development of membranes for the separation of mixtures of nonpolar organic components no large-scale application has yet been reached. Of specific interest is the separation of olefins from paraffins, e.g. propene from propane, aromatics like benzene or toluene from aliphatic hydrocarbons or the separation of the xylene isomers. A number of different membranes are reported in the patent literature [27]. The first pilot plants are being operated and results reported for the separation of sulfur-containing aromatics from gasoline [28], or for the separation of benzene from a mixture of saturated hydrocarbons [29]. 

The characteristic bands at 1605, 1513, 1460, and 1425 cm correspond to aromatic ring vibration of the phenyl-propane skeleton from lignin chemical stmcture. The peaks noticed at 1150 and 1105 cm can be assigned to the syringyl C-H in beech wood hgnin (Pandey 1999). 

Potato flavor is greatly influenced by methods of cooking or preparation. Raw potato contains the characteristic earthy aroma component, 2-ixo-propyl-3-methoxypyrazine. A character impact compound common to boiled and baked potatoes is methional (3-[methylthio]propanal). Baked potatoes contain Maillard products such as 2-ethyl-3-methylpyrazine (earthy, nutty) and 2-ethyl-6-vinylpyr-azine (buttery, baked potato) (34). In potato chips and French-fried potatoes, the potato flavor character of methional is modified by volatile aromatics from frying oils, such as ( , )-2,4-decadienal, and thermally generated alkyl oxazoles possessing lactone-like flavors (34,39). The pyrazines 2-ethyl-3,5-dimethyl and 2,3-diethyl-5-methylpyrazine are described as potato chip like (40). 

In industry, the elimination of asphaltenes from oil involves using propane or butane. The utilization of a lighter paraffin results in the heavier paraffins precipitating along with the asphaltenes thereby diminishing their aromatic character. The oil removed from its asphaltene fraction is known as deasphalted oil or DAO. The precipitated portion is called asphalt. 

Reactions other than those of the nucleophilic reactivity of alkyl sulfates iavolve reactions with hydrocarbons, thermal degradation, sulfonation, halogenation of the alkyl groups, and reduction of the sulfate groups. Aromatic hydrocarbons, eg, benzene and naphthalene, react with alkyl sulfates when cataly2ed by aluminum chloride to give Fhedel-Crafts-type alkylation product mixtures (59). Isobutane is readily alkylated by a dipropyl sulfate mixture from the reaction of propylene ia propane with sulfuric acid (60). 

Evaporative emissions from vehicle fuel systems have been found to be a complex mixture of aliphatic, olefinic, and aromatic hydrocarbons [20,24,33]. However, the fuel vapor has been shown to consist primarily of five light paraffins with normal boiling points below 50 °C propane, isobutane, n-butane, isopentane, and n-pentane [33]. These five hydrocarbons represent the more volatile components of gasoline, and they constitute from 70 to 80 per cent mass of the total fuel vapor [24,33]. 

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