Dehydrogenation of propane

The catalytic dehydrogenation of propane is a selective reaction that produces mainly propene  

For a given dehydrogenation system, i.e., operating temperature and pressure, thermodynamic theory provides a limit to the per pass conversion that can he achieved. A general formula is 

Kp = equilibrium constant at a given temperature X = fraction paraffin converted to mono-olefms P = reaction pressure in atmospheres 

This section is written in close cooperation with Kinetics Technology International B. V. in Zoetermeer and Holland Industrial Ceramics in Velsen-Noord, The Netherlands [33]. 

Steam cracker plants based on naphtha and/or gas-oil feedstocks are the major source of locally produced propylene in Europe and the Far East. In the United States approximately 90% of propylene comes from steam crackers and refinery operations. The balance comes from catalytic dehydrogenation units. The growth rate of propylene use is expected to be 3—4% worldwide. With the more conventional sources of propylene such as steam cracker operations and refinery operations, it is not possible to supply sufficient propylene for this growing demand. However, at the price levels of mid 1993 the economics of propane dehydrogenation are not very attractive. 

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  

The potential benefits which can be achieved by using ceramic membranes in comparison to conventional propane dehydrogenation processes such as Oleflex and Catofin will be discussed here. 

---

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). 

About 35% of total U.S. LPG consumption is as chemical feedstock for petrochemicals and polymer iatermediates. The manufacture of polyethylene, polypropylene, and poly(vinyl chloride) requires huge volumes of ethylene (qv) and propylene which, ia the United States, are produced by thermal cracking/dehydrogenation of propane, butane, and ethane (see Olefin polymers Vinyl polymers). 

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. ... 

Like ethylene, propylene (propene) is a reactive alkene that can be obtained from refinery gas streams, especially those from cracking processes. The main source of propylene, however, is steam cracking of hydrocarbons, where it is coproduced with ethylene. There is no special process for propylene production except the dehydrogenation of propane. 

Research is also being conducted in Japan to aromatize propane in presence of carhon dioxide using a Zn-loaded HZSM-5 catalyst/ The effect of CO2 is thought to improve the equilibrium formation of aromatics by the consumption of product hydrogen (from dehydrogenation of propane) through the reverse water gas shift reaction. 

K. Chen, S. Xie, A.T. Bell, and E. Iglesia, Alkali effects of molybdenum oxide catalysts for the oxidative dehydrogenation of propane, J. Catal. 195, 244-252 (2000). 

Oxidative dehydrogenation of propane over carbon nanofibers... 

As a new kind of carbon materials, carbon nanofilaments (tubes and fibers) have been studied in different fields [1]. But, until now far less work has been devoted to the catalytic application of carbon nanofilaments [2] and most researches in this field are focused on using them as catalyst supports. When most of the problems related to the synthesis of large amount of these nanostructures are solved or almost solved, a large field of research is expected to open to these materials [3]. In this paper, CNF is tested as a catalyst for oxidative dehydrogenation of propane (ODP), which is an attractive method to improve propene productivity [4]. The role of surface oxygen annplexes in catalyzing ODP is also addressed. 

Steinfeldt, N., Buyevskaya, O. V, Wole, D., Baerns, M., Comparative studies of the oxidative dehydrogenation of propane in micro-channels reactor module and fixed-bed reactor, in Spivey, J. J., Iglesia, E., Fleisch, T. H. (Eds.), Stud. Surf. Sci. Catal., pp. 185-190, Elsevier Science, Amsterdam (2001). 

Catalytic oxidative dehydrogenation of propane by N20 (ODHP) over Fe-zeolite catalysts represents a potential process for simultaneous functionalization of propane and utilization of N20 waste as an environmentally harmful gas. The assumed structure of highly active Fe-species is presented by iron ions balanced by negative framework charge, mostly populated at low Fe loadings. These isolated Fe sites are able to stabilize the atomic oxygen and prevent its recombination to a molecular form, and facilitate its transfer to a paraffin molecule [1], A major drawback of iron zeolites in ODHP with N20 is their deactivation by accumulated coke, leading to a rapid decrease of the propylene yield. 

The oxidative dehydrogenation of propane to give propene catalyzed by TS-1, Ti-beta, Ti-MCM-41, Ti02-silicalite-l, or others was investigated by Schuster et al (259). TS-1 was the best catalyst, with a selectivity of 82% for propene at a propane conversion of 11% (Fig. 42). Sulfation of TS-1 by H2S04 prior to the reaction increased the conversion to 17%, with a selectivity of about 74%. Although conversion of propane was higher on Ti-beta and Ti-MCM-41, selectivity for propene was much lower C02 was the main product. Lewis acid sites were considered to be the major active sites (259). 

Fig. 42. Catalyst screening for the oxidative dehydrogenation of propane to propene. T = 823 K molar ratios C3H8/02/N2/H20 = 5/25/25/45 GHSV = 1300 h-1 mcat = 1.4 - 8.0 g vcat = 5 ml [from Schuster et al. (259)].

Vanadia catalysts exhibit high activity and selectivity for numerous oxidation reactions. The reactions are partial oxidation of methane and methanol to formaldehyde, and oxidative dehydrogenation of propane to propene and ethane to ethcnc.62 62 The catalytic activity and selectivity of... 

Watling, T.C. Deo, G. Seshan, K. Wachs, I.E. Lercher, J.A. Oxidative dehydrogenation of propane over niobia supported vanadium oxide catalysts. Catal. Today 1996, 28, 139-145. 

Dehydrogenation of Propane to Propene Porous A1203 membranes Bitter (1986)... 

Dehydrogenation of propane to propene Cra03 (20 wt. %)/ AljO catalytic pellets packed on the shell side of the reactor. 

Rives et al. reported the use of Mg/V mixed oxides obtained from V(III)-substituted LDH precursors as catalysts for the oxidative dehydrogenation of propane and -butane [71]. Their results indicated that the relative amounts of Mg3V04 and MgO, which depend on the V(III) content of the starting LDHs, determine the performance of the catalysts. 

The diagram doesn t show the ethylene and propylene made by metathesis of methanol or the propylene made by catalytic reaction of ethylene and butylene or by dehydrogenation of propane. The volumes are small, and besides, it would make the diagram too messy. 

Dehydrogenation of methanol, dehydrogenation of propane, metathesis of ethylene and butylene, and cat crackers. (Other crackers in refineries produce olefins too.)... 

In addition to the epoxidation of olefins, zeolitic materials have been studied for other fine chemical transformations. Table 12.21 indexes the zeolites used for oxidative dehydrogenation of propane, direct hydroxylation of benzene to phenol and e-caprolactam synthesis. A recent review summarizes other reactions for which there is not enough space in the table [138, 139]. 

---