Light alkanes butane

The butane-containing streams in petroleum refineries come from a variety of different process units consequently, varying amounts of butanes in mixtures containing other light alkanes and alkenes are obtained. The most common recovery techniques for these streams are lean oil absorption and fractionation. A typical scheme involves feeding the light hydrocarbon stream to an absorber-stripper where methane is separated from the other hydrocarbons. The heavier fraction is then debutanized, depropanized, and de-ethanized by distillation to produce C, C, and C2 streams, respectively. Most often the stream contains butylenes and other unsaturates which must be removed by additional separation techniques if pure butanes are desired. 

With propene, n-butene, and n-pentene, the alkanes formed are propane, n-butane, and n-pentane (plus isopentane), respectively. The production of considerable amounts of light -alkanes is a disadvantage of this reaction route. Furthermore, the yield of the desired alkylate is reduced relative to isobutane and alkene consumption (8). For example, propene alkylation with HF can give more than 15 vol% yield of propane (21). Aluminum chloride-ether complexes also catalyze self-alkylation. However, when acidity is moderated with metal chlorides, the self-alkylation activity is drastically reduced. Intuitively, the formation of isobutylene via proton transfer from an isobutyl cation should be more pronounced at a weaker acidity, but the opposite has been found (92). Other properties besides acidity may contribute to the self-alkylation activity. Earlier publications concerned with zeolites claimed this mechanism to be a source of hydrogen for saturating cracking products or dimerization products (69,93). However, as shown in reaction (10), only the feed alkene will be saturated, and dehydrogenation does not take place. 

The dehydroaromatization of light alkane feeds (methane to butanes) into aromatics has come into prominence as a method of converting the unreactive light paraffins into useful chemical precursors. In many of the world s markets, light alkanes are very undesired off-gasses which can not be used other than as fuel. To accomplish this difficult transformation, catalysts typically are bifunctional, containing a dehydrogenating component such as Pt, Ga, Zn or Mo with an acidic zeolite. 

Aromatic hydrocarbon anomalies are evident in soils over both fields (Fig. 2). The anomalous 4-, 5-, and 6-ring aromatic hydrocarbons, which correspond with the 395 nm, 431 nm and 470 nm fluorescence peaks suggest the presence of heavy oil seeps at surface. Light alkanes (ethane and n-butane) are the most important... 

A similar conclusion applies to a Mg-V-O catalyst in which Mg3(V04)2 is the active component. The relative rates of reaction for different alkanes on this catalyst follow the order ethane < propane < butane 2-methylpropane < cyclohexane (Table I) [12-14]. This order parallels the order of the strength of C-H bonds present in the molecule, which is primary C-H > secondary C-H > tertiary C-H. Ethane, which contains only primary C-H bonds, reacts the slowest, whereas propane, butane, and cyclohexane react faster with rates related to the number of secondary carbon atoms in the molecule, and 2-methylpropane, with only one tertiary carbon and the rest primary carbons, reacts faster than propane which contains only one secondary carbon. Similar to a Mg-V-O catalyst, the relative rates of oxidation of light alkanes on a Mg2V207 catalyst follow the same order (Table I). 

Catalytic hydrogenolysis of light alkanes (propane, butanes, pentanes) with the exception of ethane has been accomplished under very mild conditions over silica-supported hydride complexes.502 The hydrogenolysis proceeds over (=SiO)3 ZrH,503 (=SiO)3HfH,504 and (=SiO)3TiH505 by stepwise cleavage of carbon-carbon bonds by P-alkyl elimination from surface metal-alkyl intermediates. 

The low cost of light alkanes and the fact that they are generally environmentally acceptable because of their low chemical reactivity have provided incentives to use them as feedstock for chemical production. A notable example of the successful use of alkane is the production of maleic anhydride by the selective oxidation of butane instead of benzene (7). However, except for this example, no other successful processes have been reported in recent years. A potential area for alkane utilization is the conversion to unsaturated hydrocarbons. Since the current chemical industry depends heavily on the use of unsaturated hydrocarbons as starting material, if alkanes can be dehydrogenated with high yields, they could become alternate feedstock. 

After this paper was accepted for publication in November, 1992, a number of reports have appeared that deal with the subject of oxidative dehydrogenation of light alkanes. The effect of the structure of vanadia on a support has been investigated for the oxidation of butane [87J and propane [88-90], The evidence supports the concepts that the bridging oxygen in V — O — V plays an important role in the oxidation reaction [87, 90], The data also show that vanadia species of different structures on these supports have different catalytic properties, and that isolated V04 units are the most selective [91]. 

The abundance and low cost of light alkanes have generated in recent years considerable interest in their oxidative catalytic conversion to olefins, oxygenates and nitriles in the petroleum and petrochemical industries [1-4]. Rough estimates place the annual worth of products that have undergone a catalytic oxidation step at 20-40 billion worldwide [4]. Among these, the 14-electron selective oxidation of -butane to maleic anhydride (2,5-furandione) on vanadium-phosphorus-oxide (VPO) catalysts is one of the most fascinating and unique catalytic processes [4,5] ... 

This paper is an attempt to summarize the situation with respect to the selective catalytic oxidation of light alkanes using heterogeneous catalysts. Methane oxidation reactions and the oxidation of butane to maleic anhydride will only be alluded to occasionally, because they have been reviewed in detail in a large number of papers. 

A very large amount of work has been devoted in the past to the oxidation of olefins ("allylic" oxidation to unsaturated aldehydes) and butane (to maleic anhydride). This has led to the development of ideas and concepts which are quite naturally used in the new investigations concerning light alkanes. It is necessary to examine these ideas and concepts and to evaluate in a critical way their potential for discovering or improving catalysts in the new field that oxidation of light alkanes constitutes. This will be done here shortly on the basis of classical books or articles [53,58-62]. 

The hydrate forming gases include light alkanes (methane to n-butane), carbon dioxide, hydrogen sulfide, nitrogen, and oxygen. 

Because of the global abundance of liquefied petroleum gas (LPG), interest in the potential use of ethane, propane, and butanes as sources of the corresponding alkenes or their derivatives is increasing [1]. In the last decade much progress has been made, particularly in the selective partial oxidation of light alkanes with molecular oxygen in gas phase [1,2]. For economic reasons, molecular oxygen is usually used as the primary oxidant[3]. 

The INS spectra of the normal (unbranched) n-alkanes (n = 5—25)) are discussed in 10.1.2 and [6,7]. The light alkanes, ethane, propane and butane have also been investigated [8,9]. Methane has been extensively studied by tunnelling spectroscopy both in the solid [10] and as an adsorbate e.g. [11-13]. 

One oxidation reaction that is of large industrial relevance is the oxidative dehydrogenation of light alkanes to the corresponding alkene (Scheme 3.20). This reaction has been reported to be promoted by r-GO as catalyst [29]. The importance of this reaction type is particularly high for the industrial preparation of propene from propane and butenes from butanes. Both reactions are carried out industrially in very large scale, because propene is the monomer of polypropene and also the starting material of propylene oxide, acrylonitrile, and other base chemicals. Butenes are mainly used for the preparation of 1,3-butadiene that is one of the major components of rubbers and elastomers. 

Light alkanes, mainly propane and -butane, are an overplus from LPG fractions. On the other hand, liquefied natural gas (LNG), mainly composed of methane, also contains other hydrocarbons such as ethane (3-10%) or propane (0.5-2%). However, to date, LPG and LNG fractions (except in the case of ethane) have mainly been employed as domestic/industrial fuel to generate heat. The ready availabihty of LPG fractions, as an overplus in refineries, and the existence of huge natural gas deposits imply the low merit of their components, which has increased interest in profiting from them by their employment as raw materials in the petrochemical industry. 

At the moment, selective oxidation of -butane to MA is the only catalytic oxidation process employing a light alkane as the feedstock which has been fully established at an industrial level. It must be indicated that surprisingly the results from the -butane process (MA yield around 80%, with selectivity of 60%) are better than those obtained from butenes. This fact has encouraged the scientific community to study similar catalytic reactions with other alkanes. Thus, other successful processes could be developed by using the appropriate catalyst, optimal reaction conditions, and an improved reactor technology. 

Natural gas and LPG are interesting feedstocks for petrochemical processes since their components (light alkanes as methane, ethane, propane, and butanes) could be alternative raw materials in well-known industrial processes. 

This paper presents experimental results for the equilibrium adsorption of the shorter unbranched hydrocarbons, ethane, ethene, propane, and propene and of the linear and branched C4 alkanes n-butane and isobutane on Kureha activated carbon, a purely microporous material. The aim of the present study is to investigate comparative packing efficiencies of these light alkanes and alkenes and of the linear and branched C4 alkanes inside the adsorbent pores. An interpretation of the difference in the adsorption behaviour for these six adsorptives is given. In addition, thermodynamic properties like isosteric heat associated with adsorption are presented to characterize interactions between adsorptive and adsorbent and an outlook on mixture adsorption is discussed for this carbon. 

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