Propane catalytic dehydrogenation

Figure 7.5 Scheme of the two-zone FBMR for propane catalytic dehydrogenation. Reproduced from [11], With permission from Elsevier. 

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

Catalytic testings have been performed using the same rig and a conventional fixed-bed placed in the inner volume of the tubular membrane. The catalyst for isobutane dehydrogenation [9] was a Pt-based solid and sweep gas was used as indicated in Fig. 2. For propane oxidative dehydrogenation a V-Mg-0 mixed oxide [10] was used and the membrane separates oxygen and propane (the hydrocarbon being introduced in the inner part of the reactor). 

Comparison of promoted alkaline-earth oxide catalysts prepared through evaporation and sol-gel methods by their catalytic performance in propane oxidative dehydrogenation... 

Alkaline earth oxides (AEO = MgO, CaO, and SrO) doped with 5 mol% Nd203 have been synthesised either by evaporation of nitrate solutions and decomposition, or by sol-gel method. The samples have been characterised by chemical analysis, specific surface area measurement, XRD, CO2-TPD, and FTIR spectroscopy. Their catalytic properties in propane oxidative dehydrogenation have been studied. According to detailed XRD analyses, solid solution formation took place, leading to structural defects which were agglomerated or dispersed, their relative amounts depending on the preparation procedure and on the alkaline-earth ion size match with Nd3+. Relationships between catalyst synthesis conditions, lattice defects, basicity of the solids and catalytic performance are discussed. 

As chemical companies rely more heavily on ethane and propane feeds to their olefins plants to generate their ethylene and propylene supplies, the coproduction of butadiene in olefins plants has not kept up with demand. Industry has resorted to building plants that make on-purpose or swing supply butadiene. The processes involve catalytically dehydrogenating (removing hydrogen from) butane or butylene. 

Figure 1 is the catalytic behavior of VSU545 in propane oxidative dehydrogenation to propylene. Selectivities to propylene in the range of60-80% are obtained up to propane conversions of about 20-25% and reaction temperatures up to around 450- 500 C. For higher reaction temperatures and conversions the selectivity decreases due both to the formation of carbon oxides and of aromatics. As compared to pure silicalite, a significant increase in both the selectivity to propylene and the activity in propane conversion is observed. 

Figure 2. Comparison of the catalytic behavior of VSil samples in propane oxidative dehydrogenation to propylene. Conversion of propane and selectivity to propylene at 470 C. Exp. conditions as in Fig. 1.

The good catalytic behavior of V-containing silicalite may be associated with the presence of the tetrahedral V species stabilized by the interaction with the zeolite framework as regards both redox and coordination changes. In fact, ESR and TPR data indicate the lower rate of reduction of this species as compared to that of supported vanadium-oxide, and V-NMR data indicate the stability against changes in the coordination environment. Catalytic data (Fig.s 2 and 3) indicate the better catalytic performances of this species in propane oxidative dehydrogenation as compared to supported polynuclear vanadium-oxide which can be removed by treatment with an ammonium acetate solution. 

Natural gas liquids represent a significant source of feedstocks for the production of important chemical building blocks that form the basis for many commercial and industrial products. Ethylene (qv) is produced by steam-cracking the ethane and propane fractions obtained from natural gas, and the butane fraction can be catalytically dehydrogenated to yield 1,3-butadiene, a compound used in the preparation of many polymers (see Butadiene). The -butane fraction can also be used as a feedstock in the manufacture of MTBE. 

UOP Propylene Propane Converts propane into propylene by catalytic dehydrogenation 5 1999... 

Molecular strucmre and reactivity of vanadia-based catalysts for propane oxidative dehydrogenation smdied by in sim Raman spectroscopy and catalytic activity measurments. Journal of Catalysis, 111 (2), 293-306. 

There has been a large volume of data showing the benefit of having thin dense membranes (mostly Pd-based) on the hydrogen permeation rate and therefore the reaction conversion. An example is catalytic dehydrogenation of propane using a ZSM-5 based zeolite as the catalyst and a Pd-based membrane. Clayson et al. [1987] selected a membrane thickness of 100 m and achieved a yield of aromatics of 38% compared to approximately 80% when a 8.6 pm thick membrane is used [Uemiya et al., 1990]. 

The catalytic dehydrogenation of propane is carried out in a continuous packed-bed reactor. One thousand kilograms per hour of pure propane is preheated to a temperature of67(TC before it passes into the reactor. The reactor effluent gas. which includes propane, propylene, methane, and hydrogen, is cooled from 80(fC to lllfC and fed to an absorption tower, where the propane and propylene are dissolved in oil. 

Propylene is usually produced as a byproduct of ethylene manufacture. An alternative process is catalytic dehydrogenation of propane, as described in U.S. 4,381,417 (to UOP). What is the cost of production of propylene by this route for a world-scale plant ... 

The TPD/XPS results indicated that CO, propane and propene bind stronger to a reduced V-terminated 203(000 ) surface than to an oxidized V = 0 terminated surface. Nevertheless, vanadyl groups are probably required in the course of catalytic reactions. However, rates of propane oxidative dehydrogenation (ODH) to propene at atmospheric pressure are rather low and no reaction products were observed by gas chromatography, both for oxidized and reduced V Oj model surfaces at temperatures up to 500 K [12]. 

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 ... 

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. 

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

The world propylene production capacity based on the use of catalytic dehydrogenation of propane has increased steadily over the past lOyr and is expected to grow even further under the right economic conditions relative to the availability and pricing of pro-pane. On the other hand, environmental concerns on the use of methyl-/ r/-butyl ether (MTBE), an oxygenated gasoline additive, are expected to adversely impact the future expansion of isobutane dehydrogenation applications. 

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.

Hydrolytic and non-hydrolytic sol-gel routes are implemented to prepare various pure and silica-dispersed vanadium- or niobium-based oxide catalysts corresponding to the compositions Nb-V, Sb-V and Nb-V-M (M = Sb, Mo, Si). Starting reagents in the hydrolytic procedure are isopropanol solutions of the metal alkoxides. The non-hydrolytic route is based on reactions between metal and Si alkoxides and hexane suspensions of niobium(V) chloride. The catalysts are tested in propane oxidative dehydrogenation. NbVOs, SbV04 and Nb2Mo30n are the major crystalline phases detected in the fresh catalysts, but structural modifications are in some cases observed after the use in the catalytic tests. At 500 C, propane conversions of 30 % and selectivities to propene between 20 and 40 % are attained. When the space velocity is decreased, acrolein is in some cases found as by-product. 

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