Zeolite catalysts increased yields

The presence of zeolite catalysts increases the amount of gaseous hydrocarbons produced during pyrolysis but decreases the amount of pyrolysis oil. Further, significant quantities of coke were formed on the surface of the catalysts in the course of pyrolysis. The catalysts reduced the yield of e.g., as styrene and cumene, in favor of naphthalene. The zeolite catalysts, especially Y-Zeolite, were found to be very effective in removing volatile organo bromine compounds. However, they were less effective in removing antimony bromide from the highly volatile products of pyrolysis (133). 

The process which was developed hy DOW involves cyclodimerization of hutadiene over a proprietary copper-loaded zeolite catalyst at moderate temperature and pressure (100°C and 250 psig). To increase the yield, the cyclodimerization step takes place in a liquid phase process over the catalyst. Selectivity for vinylcyclohexene (VCH) was over 99%. In the second step VCH is oxidized with oxygen over a proprietary oxide catalyst in presence of steam. Conversion over 90% and selectivity to styrene of 92% could he achieved. ... 

These metals, when deposited on the E-cat catalyst, increase coke and gas-making tendencies of the catalyst. They cause dehydrogenation reactions, which increase hydrogen production and decrease gasoline yields. Vanadium can also destroy the zeolite activity and thus lead to lower conversion. The deleterious effects of these metals also depend on the regenerator temperature the rate of deactivation of a metal-laden catalyst increases as the regenerator temperature increases. 

Alumina, silica, clays, and zeolites are increasingly used as acidic or basic supports [26], Cycloaddition reactions often require Lewis-acid catalysts if good yields are to be obtained. Clay and doped silica gel catalysts have emerged as useful alternatives to the use of Lewis acids. Cycloaddition offuran (5) under solvent-free conditions, catalyzed by K10 montmorillonite, results in a decrease in the reaction time the endo-exo relationship is no different that obtained by use of classical heating (Scheme 9.2) [27]. 

Unlike to zeolite catalysts acidic sites hardly play any role in the C-methylation of 2-Et-A on oC-Fe Oj or GeOg-FegO since germanium promotion induces a considerable increases in the 2-Et-6-Me-A yield and selectivity while acidity remains practically unchanged. Regarding that the yield of the N-alkyl derivatives is only slightly influenced by germanium the participation of the weak basic or acidic sites in the N-methylation can not be ruled out. 

To increase the overall yield, the DIPB is reconverted to cumene in a transalkylation reactor in the presence of a large excess of benzene. The same zeolite catalyst may be used. Practical data for the design are temperatures of140-150 °C, benzene/ DIPB ratios between 20-30 and a WHSV of 2 to 3. 

Another important parameter is the catalyst concentration. Thermocatalytic cracking of HDPE and MDPE over HZSM-5 and Y-zeolite catalysts was carried out in a cycled-spheres reactor. It was found that the required temperature of cracking could be decreased by 2% using a low concentration of catalysts, and by 16-20% in the case of greater catalyst concentration because the reaction rate increased with increasing catalyst concentration [51]. Not only the catalyst concentration, but also the temperature is a parameter that determines properties. Increasing temperature increases the yields of volatile products. At higher temperature more C-C bonds are cracked in consequence of their lower... 

The oxidation of benzene to phenol can also be achieved using nitrous oxide as an oxidant in the presence of a catalytic system such as vanadium, molybdenum or tungsten oxides at 550 °C, and after addition of 30% of water to afford phenol in 10% yield . More effective catalytic systems have been investigated and zeolites show promise to be good catalysts for the oxidation of benzene to phenol with nitrous oxide . The use of zeolite catalysts has led to a reduction in the reaction temperature to 300-400°C, to the exclusion of water addition to the reaction mixture and to an increase in the yields up to 25-30% . Recently, direct oxidation of benzene to phenol by nitrous oxide has been commercialized . 

With the old amorphous catalyst, the cat cracker was getting about 16 gallons of gasoline from each barrel of feed. But with the new zeolite catalyst, the same cracker squeezed out another 8 gallons of gasoline from the same barrel of feed. That s a fifty percent increase in gasoline yield — an almost unbelievable result. 

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