Zeolite butane yields

With propene, n-butene, and n-pentene, the alkanes formed are propane, n-butane, and n-pentane (plus isopentane), respectively. The production of considerable amounts of light -alkanes is a disadvantage of this reaction route. Furthermore, the yield of the desired alkylate is reduced relative to isobutane and alkene consumption (8). For example, propene alkylation with HF can give more than 15 vol% yield of propane (21). Aluminum chloride-ether complexes also catalyze self-alkylation. However, when acidity is moderated with metal chlorides, the self-alkylation activity is drastically reduced. Intuitively, the formation of isobutylene via proton transfer from an isobutyl cation should be more pronounced at a weaker acidity, but the opposite has been found (92). Other properties besides acidity may contribute to the self-alkylation activity. Earlier publications concerned with zeolites claimed this mechanism to be a source of hydrogen for saturating cracking products or dimerization products (69,93). However, as shown in reaction (10), only the feed alkene will be saturated, and dehydrogenation does not take place. 

Methanol can be converted to hydrocarbons over acidic catalysts. However, with the exception of some zeolites, most catalysts deactivate rapidly. The first observation of hydrocarbon formation from methanol in molten ZnCl2 was reported in 1880, when decomposition of methanol was described to yield hexamethylbenzene and methane.414 Significant amounts of light hydrocarbons, mostly isobutane, were formed when methanol or dimethyl ether reacted over ZnCl2 under superatmo-spheric pressure.415 More recently, bulk zinc bromide and zinc iodide were found to convert methanol to gasoline range (C4-C13) fraction (mainly 2,2,3-trimethyl-butane) at 200°C with excellent yield (>99%).416... 

Gavalas et al. [7] prepared ZSM-5 membranes onto porous a-alumina disks by in-situ hydrothermal synthesis at 175°C. The zeolite layers were formed on the bottom face of disks placed horizontally near the air-liquid interface of clear synthesis solutions. The films grown at the optimized conditions were about 10 pm thick and consisted of well-intergrown crystals of about 2 pm in size Pure gas permeation measurements of the best preparations yielded hydrogen isobutane and butane isobutane ratios of 151 and 18 at room temperature and of 54 and 31 at 185°C, respectively. 

The test run used commercially-produced zeolite catalyst, and the unit was a modified, commercial wax hydrofinisher. Charge stock was an LPG mixture of propane/propene/butanes/butenes (62% olefins) from an FCC unit. The test run lasted 70 days and product yields and selectivities were the same as in our smaller pilot plants. 

Figure 2 presents ethylene conversion at 250 C as a function of thermal pretreatment given to a sample at different temperatures. In case of both the ZSM-5 (Si/Al=40,80) samples used in this study, the ethylene conversion was affected only marginally when the san )le pretreatment temperature was in range 300-700 C (curves a,b. Fig. 2). On the contrary, the catalytic activity of HZSM-5 sample showed an increase with the rise in pretreatment temperature from 300 to 700°C (Fig. 2c). Further rise in the pretreatment temperature to 900°C resulted in the reduced activity of all the three zeolite samples. The product distribution showed a significant change as a function of pretreatment in the case of HZSM-5 zeolite while the effect was only marginal for the improtonated ZSM-5 sample. These data are shown in Fig.3. As seen in Fig.3, the rise in the pretreatment temperature to 700°C resulted in the progressively reduced yields of C3-C5 hydrocarbons (particularly propene, butane, butene, pentene, hexene and benzene) whereas the selectivity for C7-C8 hydrocarbons (methyl cyclohexene, toluene, octane and octene) increased significantly. No such change in the selectivity was observed in the case of improtonated ZSM-5 samples(Fig. 3b).

Friedel-Craft s alkylation of phenol with 4-hydroxybutan-2-one was investigated over HP, HY and Zr and Fe ion exchanged p and Y zeolites. The expected para-alkylated product raspberry ketone [4-(4-hydroxyphenyl)butan-2-one] was obtained regioselectively over Hp (SiO2/Al2O3=10) catalyst in 77% yield. The para product is formed not only by direct alkylation but also by the facile rearrangement of 0-alkylated product. HY and cation exchanged catalysts yielded 0-alkylated, para-alkylated and small amount of orz/io-alkylated products. 

Figure 8.13 Plots of product distributions from the reaction of n-butene over zeolites H-ZSM-5 and H-Theta-1 as a function of temperature C1-C5 hydrocarbon A all butenes isobutene (the desired product). The maximum possible thermodynamic yield of the desired product, isobutene, is shown by a dashed line. GC traces (below) illustrate the differences in selectivity to butanes between ZSM-5 and Theta-1 (1, n-butene 2, trans-2-butene 3, cis-2-butene 4, isobutene). All measurements made with a continuous stream of 10% 1-butene in He, WHSV = 3h over the activated catalysts.

The conversion of n-butane and methanol (methanol/ -butane molar ratio of 3) on HZSM-5 zeolites with different SiO/Al Oj ratios and doped with Ni and SAPO-18 affords the yield of C -C olefins 24.4% (11.5% of propene), with a selectivity of 43% at 575°C (Fig. 13) [114]. The catalyst survives at least 10 reaction-regeneration cycles. 

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