Dehydrogenation of isobutene

The effect of Ca loading on the acid-base and redox properties of chromia catalysts supported on alumina has been investigated by microcalorimetry of NH3 adsorption and TPR. This alkaline promoter strongly decreases the acidity of the chromia catalyst, particularly suppressing the medium and strong acid sites. No clear correlations were found between the surface acidic properties and the catalytic behavior of the investigated samples in the oxidative dehydrogenation of isobutene, while clear trends were observed between reducibihty and catalytic activity [52]. 

Zaspalis et al. [1991b] and Bitter [1988] utilized alumina membrane reactors containing Pt catalysts to examine dehydrogenation of n-butane to butene and 2-methylbutenes to isoprene, respectively. Both the conversion and selectivity improved by using the membrane reactors. The increase of conversion is about 50% in both cases. Moreover, Suzuki [1987] used stainless steel membranes and Pi or CaA-zeolite layer catalysts to perform dehydrogenation of isobutene and propene to produce propane. 

Scheme 18.17 Summary of the single site concept applied to selective dehydrogenation of isobutene.

Yanglong G., Guanzhong L., Yunsong W., Ren W. 2003. Preparation and characterization of Pd-Ag/ceramic composite membrane and application to enhancement of catalytic dehydrogenation of isobutene. Separation and Purification Technology 32 271-279. 

Sheintuch M, Dessau RM (1996) Observation, modeling and optimization of yield, selectivity and activity during dehydrogenation of isobutene and propane in a Pd membrane reactor. Chem Eng Sci 51 535-547... 

Liang W, Hughes R (2005) The catalytic dehydrogenation of isobutene to isobutene in a palladium/silver eomposite membrane reactor. Catal Today 104 238-243... 

A specific and very useful equipment for coking rate studies is the electrobalance, used by Takeuchi et al. [1966] in their study of the dehydrogenation of isobutene, by Ozawa and Bischoff [1968] in their investigation of coking associated with ethylene cracking, by De Pauw and... 

Bi, Y, Zhen, K., Valenzuela, R., et al. (2000). Oxidative dehydrogenation of isobutene over labasm oxide catalyst Influence of the addition of CO2 in the feed, Catal. Today, 61, pp. 369-375. 

Cavani F, Koutyrev M, Trifiro F, Bartolini A, Ghisletti D, lezzi R, Santucci A, Del Piero G (1996) Chemical and physical characterization of alumina-supported chromia-based catalysts and their activity in dehydrogenation of isobutene. J Catal 158 236-250... 

J.C. Serrano-Ruiz, A. Sepulveda-Escribano, F. Rodriguez-Reinoso, Bimetallic PtSn/C catalysts promoted by ceria application in the nonoxidative dehydrogenation of isobutene. J. Catel. 246, 158-165 (2007)... 

Matsuda T., Koike I., Kubo N. and Kikuchi E., Dehydrogenation of isobutene to isobutene in a palladium membrane reactor, App/. Catal., 96 (1993) 3. 

Methyl /-Butyl Ether. MTBE is produced by reaction of isobutene and methanol on acid ion-exchange resins. The supply of isobutene, obtained from hydrocarbon cracking units or by dehydration of tert-huty alcohol, is limited relative to that of methanol. The cost to produce MTBE from by-product isobutene has been estimated to be between 0.13 to 0.16/L ( 0.50—0.60/gal) (90). Direct production of isobutene by dehydrogenation of isobutane or isomerization of mixed butenes are expensive processes that have seen less commercial use in the United States. 

Methyl tert-Butylluther Methyl /-butyl ether (MTBE) is an increasingly important fuel additive. Platinum—tin and other PGM catalysts are used for the dehydrogenation of isobutane to isobutene, an intermediate step in MTBE manufacture. 

Isoprene is the second important conjugated diene for synthetic rubber production. The main source for isoprene is the dehydrogenation of C5 olefins (tertiary amylenes) obtained by the extraction of a C5 fraction from catalytic cracking units. It can also be produced through several synthetic routes using reactive chemicals such as isobutene, formaldehyde, and propene (Chapter 3). 

Because hydrogen can easily be removed from a reaction stream, many dehydrogenations have been studied. These include dehydrogenation of methane to carbon,326 ethane to ethene,327,328 propane to propene,329 n-butane to butenes,330 isobutane to isobutene,331,332 cyclohexane to benzene,332-334 meth-ylcyclohexane to toluene 335 n-heptane to toluene,336 methanol to formaldehyde,330 and ethanol to acetaldehyde.337... 

Figure 14.3 Different strategies for integration of isobutane (oxi)dehydrogenation to isobutene and isobutene oxidation to methacrolein and to methacrylic acid.

The concept of site isolation is important in catalysis. On metal particles one usually assumes that ensembles of metal atoms are necessary to activate bonds and to accommodate the fragments of molecules that tend to dissociate or to recombine. We present here three examples of such effects the dehydrogenation of decane into 1-decene, the dehydrogenation of isobutane into isobutene and the hydrogenolysis of acids or esters into aldehydes and alcohols. In most cases the effect of tin, present as a surface alloy, wiU be to dilute the active sites, reducing thereby the yield of competitive reactions. 

Figure 3.37 Activity and selectivity in the reaction of isobutane dehydrogenation to isobutene with nanoparticles of Pt/silica (a) and with Pt/Sn bimetallic nanoparticles/silica obtained via the organometallic route (b).

In this paper, we will report the electronic and catalytic reactivities of the model VC/V(110) surface, and our attempt to extend them to VC powder catalysts. By using high-resolution electron energy loss spectroscopy (HREELS) and NEXAFS techniques, we observed that the surface properties of V(110) could be significantly modified by the formation of vanadium carbide some of the experimental results on these model surfaces were published previously.3-5 We will discuss the selective activation of the C-H bond of isobutane and the C=C bond of isobutene on V(110) and on VC/V(110) model systems. These results will be compared to the catalytic performances of vanadium and vanadium carbide powder materials in the dehydrogenation of isobutane. 

Among the different method for manufacturing olefins discussed in Section 2, the dehydrogenation of paraffins and the dehydration of alcohols find a specific application in tte manufacture of isobutene. The following is one of the schemes propos ... 

From now on, butane can be dehydrogenated by a new technique caQed the Star process, already mentioned in the case of propane dehydrogenation (see Section 23.4.2) and also in that of isobutene manufoctnre (see Secticm 63). 

In these conditions, isoamylenes can yield isoprene by dehydrogenation. The production of 1 t of isoprene requires 1.16 t of isobutene and l.l t of n-butene. In addition. 

In order to make isobutene, n-butane (an abundant, cheap C4 hydrocarbon) can be dehydrogenated to 1-butene then isomerized to isobutene. Derive an expression for the concentration of isobutene formed as a function of time by the isomerization of 1-butene ... 

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