Dehydrogenation of propane to propylene

The Phillips process is also based on the principle of the operation of two reactors in parallel, one in the reaction phase, and the second in the regeneration phase. It operates 

The Pacol/Olex technique comprises two sections, dehydrogenation and extraction (Fig. Z24). 

Dehydrogenation takes place in a fixed bed reactor in the gas phase, at a temperature of about 400 to 500°C, and low pressure 0.2 to OJ. 10 Pa) and in the presence of hydrogen (H2/feedstock molar ratio = 5/10). 

Conversion is limited to about 10 per cent Selectivity exceeds 90 mole per cent in linear mono-olefms, whose internal double bond is statistically distributed along the chain, with less than 10 per cent in the alpha position. The catalyst is placinnm on alumina promoted by lithium and arsenic. The main co-products are diolefms (2 to 3 per cent), aromatics (3 to 4 per cent), light hydrocarbons and hydrogen, which is more than 96 per cent volume pure. 

This is carried out by selective adsorption of olefins in the liquid phase on a solid. The distribution of the circuits is designed to simulate a countercurrent exchange between the liquid and solid phases, wthout any effective movement of the adsorbenn 

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A two-step process involving conventional nonoxidative dehydrogenation of propane to propylene in the presence of steam, followed by the catalytic ammoxidation to acrylonitrile of the propylene in the effluent stream without separation, is also disclosed (65). 

Dehydrogenation. The dehydrogenation of paraffins is equihbrium-limited and hence requites high temperatures. Using this approach and conventional separation methods, both Houdry and UOP have commercialized the dehydrogenation of propane to propylene (92). A similar concept is possible for ethane dehydrogenation, but an economically attractive commercial reactor has not been built. 

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. ... 

Smits, Seshan and Ross have studied the selective oxidative dehydrogenation of propane to propylene over Nb20s and Nb2C>5 supported on alumina.32 Vanadia supported on MgO has typically been used in these reactions, although reduced surface vanadyl ions can give rise to decreasing selectivity to propylene. Niobia on the other hand, is much more difficult to reduce than vanadyl but there have been few studies with this oxide in such reactions. 

The process shown in Fig. P2.71 is the catalytic dehydrogenation of propane to propylene. The composition and flow rate of the recycle stream are unknown. Certain data are known for the reactor, absorber, and distillation colunrn as follows ... 

In all three, hydrogen separation will take place the dehydrogenation of propane to propylene, the dehydrogenation of ethylbenzene to styrene, and the water-gas shift reaction. 

In recent decades various processes have been developed for catal) ic dehydrogenation of propane to propylene [34-37]. These processes can be divided into two groups ... 

Current commercial processes for catalytic dehydrogenation of propane to propylene are based on adiabatic reactor systems. Typical examples are ... 

Besides several side reactions, the following main endothermic reactions are of importance in the dehydrogenation of propane to propylene ... 

Technical and economic evaluation study for the use of ceramic membrane reactors for the dehydrogenation of propane to propylene. Confidential NOVEM Report No. 33105/0090, by KTl, ECN and HlC, Jan. 1994. 

In the late 1980s, the application of chromia-alumina catalysts was extended by Houdry to the dehydrogenation of propane to propylene and isobutane to isobutylene. The new process application called Catofin operates on the same cyclic principle as in the former Catadiene process. As of late 2000, a total of eight Catofin units existed for the production of isobutylene (including two converted older Catadiene units) with an aggregate capacity of about 2.8 million metric tons per annum (MTA) of isobutylene. In addition, two Catofin units were built for the production of propylene, but it is understood that only... 

Several commercial processes have been developed for the catalytic dehydrogenation of propane to propylene as presented in Table 4. Of the seven commercial propane dehydrogenation plants in operation, six use UOP s Oleflex continuous moving-bed process. The other uses ABB Lummus Catofin cyclic multiple-reactor system. Other processes include Krupp Uhde s STAR process, as well as technologies from Linde and Snamprogetti. ... 

Fig. 2 Flow diagram of catalytic dehydrogenation of propane to propylene.

Dehydrogenation of propane to propylene (Pt/Sn as active metal with K promoter)... 

Over the years, several processes for the catalytic dehydrogenation of propane to propylene have been developed, which can be divided into processes based on an adiabatic or an isothermal reactor concept, respectively. The processes currently apphed on an industrial scale are based on adiabatic systems, such as the Catofin (Lummus/Air Products) and the Oleflex (UOP) process. As the dehydrogenation of propane to propylene comprises an equihbrium reaction (11), selective removal of hydrogen from the reaction mixture can shift the reaction towards the product side. At high temperatures, thermal cracking may occur. 

Kinetic analysis of propane ammoxidation with V-Sb-0 catalysts has shown that the reaction proceeds through propylene as the key intermediate (130). The first step in the propane ammoxidation reaction is the oxidative dehydrogenation of propane to propylene. Essentially, all the products of the reaction derive from conversion of the propylene intermediate. The kinetic results also suggest that there is a lesser direct reaction pathway from propane to acrylonitrile. 

This preparation procedure also creates solid-state phases that are key to the performance of the Mo-V-Nb-Te-0 catalyst for propane ammoxidation. High activity and selectivity result when the x-ray powder diffraction pattern shows the presence of specific diffraction lines attributed to two separate phases denoted as Ml and M2 by Mitsubishi Chemical Corp. The diffraction lines assigned to these two phases are given in Table 7 (146). The coexistence of these two phases is viewed as key to the successful functioning of the catalyst. Specifically, the Ml phase is purportedly responsible for the oxidative dehydrogenation of propane to propylene, the key intermediate in the reaction network. This reaction sequence, in which the first step is the formation of a propylene intermediate, is the same as noted previously with other propane ammoxidation catalysts, most notably with the V-Sb-0 catalyst (see above). The M2 phase of the Mo-V-Nb-Te-0 catalyst is reportedly the center for the selective ammoxidation of the propylene intermediate to acrylonitrile. As the first-formed intermediate, propylene is apparently the source of all the observed reaction products. Although a detailed kinetic analysis has not been presented, a cursory report, published in Japan, summarized the kinetic experiments for the conversion of propane and propylene over a... 

The approach, based on dilution of catalytically active components with inert or low active material, has been employed to improve the performance of VSb-based oxide catalysts in reactions of the selective oxidation of propane. In particular, the incorporation of low active A1 into the body of NiVSb, FeVSb, BiVSb and other mixed-metal oxides significantly improved their selectivity in the oxidative dehydrogenation of propane to propylene. As is seen in Fig. 11.5, the addition of A1 to the Feo,3 Vi.oSbo.eOx catalyst increased selectivity to propylene by 2-3 times. The selectivity of an Al-diluted catalyst was further improved by adding small amounts of alkali and alkaline earth metals. Figure 11.5 illustrates the effect of potassium which, along with increasing catalyst intrinsic selectivity, also decreased propylene over-oxidation. This improvement in selectivity has been related to the lower acidity... 

Liu, Y, Feng, W., Li, T., etal. (2006). Structure and Catalytic Properties of Vanadium Oxide Supported on MesoceUulous SUica Foams (MCF) for the Oxidative Dehydrogenation of Propane to Propylene, J. Catal., 239, pp. 125—136. 

Dury, R, Centeno, M., Gaigneaux, E., et al. (2003). Interaction of N2O (as Gas Dope) with nickel molybdate catalysts during the oxidative dehydrogenation of propane to propylene, Appl. Catal. A Gen., 247, pp. 231-246. 

Liu L, Li H, Zhang Y (2007) Mesoporous silica-supported chromium catalyst characterization and excellent performance in dehydrogenation of propane to propylene with carbon dioxide. Catal Commun 8 565-570... 

The dehydrogenation processes used for the production of butadiene from n-butane and -butenes dirring the development of GR-S rubber were modified in the 1990s for the dehydrogenation of propane to propylene. This compensated for the short supply of steam cracked propylene used to produce polypropylene. The new processes can also be used for the dehydrogenation of other paraflins. 

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