摘要:

AbstractFour laboratory prepared catalysts (Ni/Al2O3, NiNaY‐uncalcined, NiNaY‐calcined, NiCaY‐calcined) and a commercially available catalyst G‐87 were studied for their deactivation behavior over a period of 24 h at 573 k for various H2/CO ratios (3.1, 3.8, 6.4 and 24.5). The results indicated that the activities did not change much with time at H2/CO ratios of 3.8 and higher. Detailed measurement of catalytic activities, crystallite sizes, metal areas and carbon depositions were made at an H2/CO ratio of 3.1. These measurements indicated that sintering and carbon depositions occurred on all the catalysts thus deactivating the catalysts. An attempt has been made to explain the catalytic behavior in terms of crystallite size changes and carbon depositions. Limited regeneration studies of G‐87 and NiNaY‐calcinated catalysts have als

ISSN:0008-4034    

DOI:10.1002/cjce.5450600102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractProgress in understanding the nature of cracking catalysts has led from the early recognition of the carbonium ion intermediate to the current view which ascribes cracking activity to the acidic nature of active sites. Here we develop the concept of acid catalysis to include the specific effects of Bronsted and Lewis acid sites on gas oil cracking. It is shown that these two types of sites react with specific substrates and that each has a characteristic kinetic behaviour. This leads us to suggest that careful control of the total site density and of the proportion of Bronsted/Lewis sites can result in a catalyst which is optimized for the feedstock, reactor configuration, and product distribution desired.

ISSN:0008-4034    

DOI:10.1002/cjce.5450600103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractTemperature programmed desorption (TPD) and reduction (TPR) studies were carried out on H2S and thiophene adsorbed on Mo/Al2O3and CoMo/Al2O3catalysts. Freshly sulfided and pyridine poisoned catalysts were run. For sulfided catalysts, the major products of desorption of thiophene were thiophene and butene, leaving a carbonaceous residue. Subsequent TPR in H2effected complete removal of the residue with formation of H2S, thiophene and butene. The residue appeared to consist of an easily reactive thiophene polymer and a less‐reactive, sulfur‐containing coke. Runs on poisoned catalysts showed less adsorption but product profiles were similar, showing that the adsorption characteristics of the remaining sites were not significantly alte

ISSN:0008-4034    

DOI:10.1002/cjce.5450600104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractChemisorption behavior of hydrogen, carbon monoxide, nitric oxide and ethylene on three iron and three cobalt moly catalysts has been investigated in an attempt to determine active metal sites. Mode of adsorption for nitric oxide and of ethylene whether of associative or dissociative nature on the metal surface has been discussed in relation to hydrogen and carbon monoxide chemisorption. There appears to be a definite correlation between the amounts of hydrogen and carbon monoxide (VH/VCO= 1), between carbon monoxide and nitric oxide (VNO/VCO= 1.2) as well as between carbon monoxide and ethylene (CCO/V C 2H 4= 2) chemisorb. ed. The data suggest that the selective chemisorption behavior of nitric oxide and of ethylene should provide a suitable method to determine active metal sites in metal oxide cata

ISSN:0008-4034    

DOI:10.1002/cjce.5450600105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractA synthesis of studies on the photocatalytic oxidation of various compounds (isobutane, propene, alkyltoluenes, butanols, ammonia, halide ions in aqueous solution) is presented, TiO2being the main photocatalyst. Comparisons are also made with other n‐type semiconductors: ZrO2, V2O5, Sb2O4, ZnO, SnO2, CeO2, WO3. Information about the mechanism has been obtained by (i) an examination of the photocatalytic isotopic exchange of oxygen in competition with the oxidation of a hydrocarbon, (ii) kinetics and photoconductivity measurements, and (iii) oxidation of butanols by NO. The main conclusions are that these reactions proceed in an adsorbed phase and that dissociated oxygen species play an essential rol

ISSN:0008-4034    

DOI:10.1002/cjce.5450600106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractPorous alumina catalyst supports have been prepared with pore volumes exceeding 1.0 mL/g, with most pores having diameters of the order of 3 μm and with surface areas exceeding 150 m2/g. They were obtained from dilute alumina gels having large concentrations of acid and very large concentrations of fluid. Attempts were made to dry the gel without collapsing the pore structure between the alumina particles. The catalysts were characterized by gravimetrical BET surface area, mercury porosimetry, X‐ray diffraction and scanning electron microscopy. Catalyst supports having these geometric properties should eliminate mass transfer restrictions during hydrocracking of petroleum residua, heavy oils and bitumen derived from oil sand deposi

ISSN:0008-4034    

DOI:10.1002/cjce.5450600107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractMolybdenum dioxide is deposited on the form of an aerogel (in the autoclave) on nickel Mond. The catalytic activity for the hydrogenation of benzene into cyclohexane at 100°C depends on the proportion of MoO2and on the temperature of a pretreatment in hydrogen. When this temperature is 440°C, the catalytic activity exceeds that of pure nickel Mond and exhibits a maximum for about 10% of MoO2. This synergetic effect, which is an exemple of a strong metal‐support interaction (SMSI), is explained by the incorporation into the surface of nickel Mond crystals of molybdenum produced by partial reduction of MoO2, with the formation of an inter‐metallic compound

ISSN:0008-4034    

DOI:10.1002/cjce.5450600108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe use of a two mole percent n‐butane in helium stream in a fixed bed mini‐reactor at a temperature of 500°C over a zeolite bed (20 to 40 mesh and ≤ 5 grams in weight) was found to be a good tool for characterizing zeolitic acidity. In a broad spectrum of various kinds of zeolites tested, the test results are especially useful in differentiating the extremely active materials from the very active ones. Among the zeolites tested, the decreases in the order of HΩ>H‐Zeolon>NH4‐ZSM‐5>NH4Y (thermally modified)>NH4‐erionite (thermally modified)>>HKL>NH4Y>NaY ˜ amorphous silica‐alumina. The calculated first order rate constant covered a range from over 10

ISSN:0008-4034    

DOI:10.1002/cjce.5450600109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractThe influence of the degree of chromium ion exchange on Y zeolites on the catalytic activity for cracking and dehydrocyclization of n‐heptane has been studied at 673, 723 and 748 K and atmospheric pressure in a continuous flow system. The kinetic rate constants and activation energy in absence of decay for the cracking of n‐heptane on the catalysts have been obtained. Measurements of the surface acidity of these catalysts by I.R. spectroscopy of adsorbed pyridine and by titration with n‐butylamine has been carried out. A good correlation between the activity cracking of n‐heptane and the concentration of stronger acid sites (pKa≤ + 1.5) on the chromium‐exchanged Y zeolites has

ISSN:0008-4034    

DOI:10.1002/cjce.5450600110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY

摘要:

AbstractIn this work we have studied the effect of adding Li, Na or K chloride to CuCl2supported on α‐Al2O3, on its catalytic activity for the oxyhydrochlorination of ethylene to dichloroethane in a fixed bed reactor, at 573 K and atmospheric pressure. Both NaCl and KCl show a strong promoting effect. For the case of KCl, this effect has been further examined for a wide range of concentrations and a fixed amount of CuCl2supported on either α‐Al2O3, γ‐Al2O3or SiO2gel. The catalytic and thermogravimetric results obtained indicate that KCl is very effective on the overall rate, even at low concentrations, particularly because it increases considerably the rate of reoxidation of the reduced form of the catalyst. In the case of the γ‐Al2O3series, the promoting effect is only moderate.Ethylene oxyhydrochlorination data for a series of α‐Al2O3supported catalysts containing a constant K+/Cu2+atomic ratio and increasing total amount of KCl + CuCl2are shown. The activity curve shows a maximum for about 18 wt % total active phase.Finally, the influence of Ce, Nd and Pr chlorides on the activity of CuCl2+ KCl supported on α‐Al2O3is also shown. In the case of Pr, the entire range of Pr3+/Cu2+atomic ratios has been examined. The results indicate that the rare earths, especially praseodymium, also have an additional positive e

ISSN:0008-4034    

DOI:10.1002/cjce.5450600111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1982

数据来源: WILEY