Propene catalysts performance

Recently, there have been many new catalysts developed for the hydration of alkenes, although most are more suited for industrial purposes. These catalysts include zeolites such as pentasil,283 mordenite286 and ferrierite,183 as well as those containing heavy metals,287 heteropolyacids288 and sulfonic acid exchange resins.289 It is reported that some of these new catalysts perform as high as 99.6% conversions and 99.4% selectivity, as illustrated in the hydration of propene into 2-propanol (equation 192).290... 

Laboratory scale PQC evaluation studies are usually conducted in fixed bed reactors such as MAT, the results from which can provide a reliable and rapid means of ranking catalyst performance [4]. Depending upon the conditions employed, the effect of added ZSM-5 can also be predicted [5] and can give the same trends as those experienced in commercial reactors. For example, the effect of 2.5 wt% addition of ZSM-5 on gas oil cracking yields with Quantum 2000 is described in Table 1. In this example, a 4% reduction in gasoline yield occurs, predominantly from 105°C+ material. The L.P.G. composition indicates an enhancement of propene, butenes, and iso-butane, in agreement with commercial results and, furthermore, the relative increase in the individual butenes are similar to those reported by Schipper et al [1]. 

During induction, catalyst activity and selectivities to aromatics and propene increase steadily. Improvement of catalyst performance is due to increase in Ga dispersion and formation of dispersed Ga species (Gao) which are efficient for the heterolytic recombinative release of hydrogen [18,191. The Ga/H-MFI catalyst then reaches its optimal aromatisation performance (stabilisation). Ci to C3 hydrocarbons productions are at their lowest. The gallium dispersion and the chemical distribution of Ga are optimum and balance the acid function of the zeolite. Reversible deactivation during induction and stabilisation of the catalyst is due to site coverage and limited pore blockage by coke deposition. 

Prior to each reaction test and spectroscopic measurement, the sample was treated with 100 Torr oxygen (1 Torr = 133.3 N m ) at 673 K for 1 h, followed by evacuation at 673 K for 1 h. The photooxidation of propene was performed with a conventional closed system (123 cm ). The sample (200 mg) was spread on the flat bottom (12.6 cm ) of the quartz vessel. Propene (100 pmol, 15 Torr) and oxygen (200 pmol, 30 Torr) were introduced into the vessel, and the sample was irradiated by a 200 W Xe lamp. After collecting the products in gas phase, the catalyst bed was heated at 573 K in vacuo to collect the products adsorbed on the catalyst by a liquid nitrogen trap. These products were separately analyzed by GC. The results presented here are the sum of each product yield. 

In the final example, we will continue with the subject of selective oxidation of propene to PO, but this time using advanced CaCOs supported Ag catalysts. The focus is directed towards a novel synthesis procedure, in which La incorporation is shown to have a significant effect on the alkali content of the catalyst and thus on the resulting catalyst performance. 

Catalyst Performance. [Rh(77 -C3Hs)(CO)(PPh3)2] adsorbed on 7-AI2O3 has been shown to be an active catalyst for the hydroformylation of ethene and propene. A selectivity of two was obtained for propene at atmospheric pressure and 60-90 C. Catalyst deactivation took place, resulting in an 80% drop in activity over 150h. 

Another SLPC study on the hydroformylation of propene using a Rh/silica system has considered the effect of phosphine loading and phosphine Rh ratio on catalyst performance/ The incorporation of excess of triphenyl-phosphine into the catalyst results in an increase in selectivity and a decrease in activity. Thus the behaviour of this system parallels that of homogeneous systems. 

The first studies on the dependence of catalyst performance on propene concentration with zir-conocene catalysts have been reported by Ewen, for the syndiospecific catalyst and by Rieger, for... 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Figures 1 shows the catalytic performance of the Fe-BEA catalysts in the temperature range of 250-550 °C. It is clear from the figure that propylene yield depends on particle size of the parent BEA zeolite. Effect of the N20 concentration has been analyzed under reaction regimes RS-1 and RS-2. Increase in N20 concentration resulted in the same propene yields but increased the N20 conversion and decreased the selectivity toward propylene. At higher temperature has been obtained increases in the formation of the molecular oxygen which further accelerates production of the undesired carbon oxides. Thus, at lower feed concentration of N20, i.e. at 1 1 feed ratio of reactants (RS-1), formation of carbon oxides is suppressed and the selectivity of ODHP reaction is...

In the direct ammoxidation of propane over Fe-zeolite catalysts the product mixture consisted of propene, acrylonitrile (AN), acetonitrile (AcN), and carbon oxides. Traces of methane, ethane, ethene and HCN were also detected with selectivity not exceeding 3%. The catalytic performances of the investigated catalysts are summarized in the Table 1. It must be noted that catalytic activity of MTW and silicalite matrix without iron (Fe concentration is lower than 50 ppm) was negligible. The propane conversion was below 1.5 % and no nitriles were detected. It is clearly seen from the Table 1 that the activity and selectivity of catalysts are influenced not only by the content of iron, but also by the zeolite framework structure. Typically, the Fe-MTW zeolites exhibit higher selectivity to propene (even at higher propane conversion than in the case of Fe-silicalite) and substantially lower selectivity to nitriles (both acrylonitrile and acetonitrile). The Fe-silicalite catalyst exhibits acrylonitrile selectivity 31.5 %, whereas the Fe-MTW catalysts with Fe concentration 1400 and 18900 ppm exhibit, at similar propane conversion, the AN selectivity 19.2 and 15.2 %, respectively. On the other hand, Fe-MTW zeolites exhibit higher AN/AcN ratio in comparison with Fe-silicalite catalyst (see Table 1). Fe-MTW-11500 catalyst reveals rather rare behavior. The concentration of Fe ions in the sample is comparable to Fe-sil-12900 catalyst, as well as... 

Some experiments (entries 3-10, 17, 18, 22-25 Table 1) were performed in liquid propene, which was condensed at -10 °C up to the desired volume in the autoclave. Using liquid propene, the catalyst and cocatalyst solutions were both injected into the autoclave via a pressure burette. 

The CVD catalyst exhibits good catalytic performance for the selective oxidation/ammoxida-tion of propene as shown in Table 8.5. Propene is converted selectively to acrolein (major) and acrylonitrile (minor) in the presence of NH3, whereas cracking to CxHy and complete oxidation to C02 proceeds under the propene+02 reaction conditions without NH3. The difference is obvious. HZ has no catalytic activity for the selective oxidation. A conventional impregnation Re/HZ catalyst and a physically mixed Re/HZ catalyst are not selective for the reaction (Table 8.5). Note that NH3 opened a reaction path to convert propene to acrolein. Catalysts prepared by impregnation and physical mixing methods also catalyzed the reaction but the selectivity was much lower than that for the CVD catalyst. Other zeolites are much less effective as supports for ReOx species in the selective oxidation because active Re clusters cannot be produced effectively in the pores of those zeolites, probably owing to its inappropriate pore structure and acidity. 

Table 8.5 Performance of ReOx/Zeolite Catalysts in Selective Oxidation/Ammoxidation of Propene on a CVD HZcvd Catalyst, an Impregnated HZimp Catalyst, and a Physically Mixed HZphys Catalyst at 673 K...

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