Butane, dehydrogenation and

In order to get better understanding of the role of gallium and acid sites in n-butane transformation over Ga-containing catalysts, we have considered the rate data obtained over H- and Ga-theta-1 catalysts. These catalysts were chosen, since they produced much better results when compared with the ferrierite-based catalysts. Consequently, the activities of the theta-1 catalysts in the initial n-butane dehydrogenation and cracking steps were determined. This was done by the extrapolation of the rate data on formation of the primary reaction products (hydrogen, methane and ethane) to zero n-butane conversions, as shown in Figure 3. 

Dchydrocyclization of /t-hexane Hydrogenation of carbon dioxide Coupling of butane dehydrogenation and hydrogen oxidation Hydrogenation of cij,rra/w-butene-1,4-diol to c/5.rra/i5-butanediol Hydrogenation of 2-butyne-1,4-diol to ci5,/ran -butenediol... 

In order to compare the nature of the carbon deposits on Pc and Pt-Sn catalysts, carbon deposition on three catalysts with different Sn/Pt ratio was carried out in the in situ reaction and TPO system for n-butane dehydrogenation and successive temperature programmed oxidation. The areas of Peaks 1 and 2 of the TPO profiles of the three catalysts after carbon deposition were resolved and detemnined by an integraph. The ratios of areas of Peak 1 to Peak 2 of the TPO profiles were calculated and ploued against the Sn/Pt ratio in Fig. 4. Becanse the addition of Sn can inhibit the cart)on deposition on metallic surfaces, the proportion of Peak 1 to Peak 2 decreases with the increasing of Sn/Pt ratio These results imply that the ratio of carbon deposits on metal surfaces to total carbon deposits decreases with the incorporation of tin. 

Dehydrogenation over Chromia—Alumina. Chromia—alumina catalyst CR-0205 was studied relative to butane dehydrogenation and gave low conversion to butadiene under conditions of appreciable conversion to butenes. In addition, there was an exceptionally small amount of cracked products and essentially no skeletal isomerization. Accordingly, this well-known catalyst was evaluated for n-dodecane dehydrogenation. Conditions of evaluation were temperature of 440°C, atmospheric pressure, hydrogen diluent with a hydrogen to n-dodecane mole ratio of 8 to 1. The results obtained were as follows ... 

Dehydrogenation of /i-Butane. Dehydrogenation of / -butane [106-97-8] via the Houdry process is carried out under partial vacuum, 35—75 kPa (5—11 psi), at about 535—650°C with a fixed-bed catalyst. The catalyst consists of aluminum oxide and chromium oxide as the principal components. The reaction is endothermic and the cycle life of the catalyst is about 10 minutes because of coke buildup. Several parallel reactors are needed in the plant to allow for continuous operation with catalyst regeneration. Thermodynamics limits the conversion to about 30—40% and the ultimate yield is 60—65 wt % (233). 

The term, metal dusting, was first used about this time to describe the phenomenon associated with hydrocarbon processing. Butane dehydrogenation plant personnel noted how iron oxide and coke radiated outward through catalyst particles from a metal contaminant which acted as a nucleating point. The metal had deteriorated and appeared to have turned to dust. The phenomenon has been called catastrophic carburization and metal deterioration in a high temperature carbonaceous environment, but the term most commonly used today is metal dusting. 

Purely parallel reactions are e.g. competitive reactions which are frequently carried out purposefully, with the aim of estimating relative reactivities of reactants these will be discussed elsewhere (Section IV.E). Several kinetic studies have been made of noncompetitive parallel reactions. The examples may be parallel formation of benzene and methylcyclo-pentane by simultaneous dehydrogenation and isomerization of cyclohexane on rhenium-paladium or on platinum catalysts on suitable supports (88, 89), parallel formation of mesityl oxide, acetone, and phorone from diacetone alcohol on an acidic ion exchanger (41), disproportionation of amines on alumina, accompanied by olefin-forming elimination (20), dehydrogenation of butane coupled with hydrogenation of ethylene or propylene on a chromia-alumina catalyst (24), or parallel formation of ethyl-, methylethyl-, and vinylethylbenzene from diethylbenzene on faujasite (89a). 

The oxidation of butane on these orthovanadates were tested at 500°C in a flow reactor using a butane oxygen helium ratio of 4 8 88. The observed products were isomers of butene, butadiene, CO, and CO2. The carbon balance in these experiments were within experimental errors, thus the amount of any undetected product if present should be small. The selectivity for dehydrogenation (butenes and butadiene) was found to depend on the butane conversion and be quite different for different orthovanadates. Fig. 4 shows the selectivity for dehydrogenation at 12.5% conversion of butane [15,18,19]. Its value ranged from a high of over 60% for Mg3(V04)2 to a low of less than 5% for... 

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]. 

Some of the possibilities are illustrated in Figures 17.13 and 17.18. Variations from a single large bed are primarily because of a need for control of temperature by appropriate heat transfer, but also for redistribution of the flow or for control of pressure drop. There are few fixed bed units that do not have some provision for heat transfer. Only when the heat of reaction is small is it possible to regulate the inlet temperature so as to make adiabatic operation feasible butane dehydrogenation, for example, is done this way. 

Figure 24.9 A comparison of catalytic performances of iso-butane dehydrogenation on vanadium and on vanadium carbide catalysts. The reaction was carried out in a circulating batch reactor. The initial partial pressure of isobutane was 13.3 kPa Torr, which was mixed with He for a total pressure of 100 kPa.

Butane dehydrogenation a process for removing hydrogen from butane to produce butenes and, on occasion, butadiene. 

The dehydrogenation of other hydrocarbons has also been studied in CMRs, generally with porous membranes. Conversions of ethane [47], propane [48], butane [49], and ethylbenzene [50] have been reported to be higher when membrane reactors were used. In the case of ethylbenzene dehydrogenation, the undesirable hydrodealkylation side reaction is slowed down due to the removal of H2, i.e. the membrane enables an increase in selectivity as well [50]. 

Thiagarajan, N., U. Ranke and F. Ennenbach, "Propane/butane dehydrogenation by steam active reforming," Achema 2000, Frankfurt, Germany, May 2000. 

A comparison of the UV Raman spectrum measured for coke deposited during the MTH reaction with that deposited during butane dehydrogenation catalyzed by chromia on alumina (66) shows clear differences in the spectral intensity distribution (Fig. 11). In particular, the intensity of the features in the regions 1340-1440cm and 1560 1630 cm are nearly equal for the MTH reaction. 

Catalytic butane dehydrogenation can be successfully carried out in a laboratory scale fluidized bed reactor operating at 310 °C and at atmospheric pressure. The catalytic particles have diameter 310 pm and density 2060 kg/m. Such a reactor is 150 mm in diameter and has a fixed 500 mm long catalytic bed. When the catalyst bed is fluidized with butane blown at a velocity of 0.1 m/s, it becomes 750 mm thick. 

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