ISSN:0008-4034    

DOI:10.1002/cjce.5450690501

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

年代:1991

数据来源: WILEY

摘要:

AbstractProcesses are being developed for the direct catalytic oxidative conversion of methane to higher hydrocarbons and oxygenates. The role of the catalyst in generating methyl radicals is established, and subsequent gas‐phase reactions are well understood. However, the role of several catalyst surface species remains a subject of interest. Application of present process technology using the most promising catalysts shows that direct methane conversion is not yet competitive with conventional processes. Increased yields of desirable products using new process configurations are required to obtain an economically viable proces

ISSN:0008-4034    

DOI:10.1002/cjce.5450690502

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper is an extensive review of the literature dealing with the class of catalytic membrane reactors which involves hydrogen permeable membranes made of palladium and palladium alloys. The fundamental factors which affect hydrogen permeability are first discussed. A classification of the many reactions which have been conducted in such reactors at both laboratory and commercial scales is then presented. The various techniques for the preparation of palladium‐ based membranes are described and the literature on modeling and design of these reactors is also reviewe

ISSN:0008-4034    

DOI:10.1002/cjce.5450690503

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

年代:1991

数据来源: WILEY

摘要:

AbstractIn the present investigation a realistic two‐phase model accounting for the change in the total number of moles accompanying the reaction is utilized to explore a novel reactor configuration suggested for the methane steam reforming process. The suggested design is basically a fluidized bed reactor equipped with a bundle of membrane tubes. These tubes remove the main product, hydrogen, from the reacting gas mixture and drive the reaction beyond its thermodynamic equilibrium. The proposed novel design is also equipped with sodium heat pipes which act as a thermal flux transformer to provide the large amount of heat needed by the endothermic reaction through a relatively small heat transfer surface, assuring better reactor compactness. Two options for fluid routing through the membrane tubes are proposed; each is suitable for a certain industrial application. The performance of this novel configuration is compared with that of an industrial fixed bed steam reformer and the comparison shows the potential advantages of the suggested configuratio

ISSN:0008-4034    

DOI:10.1002/cjce.5450690504

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

年代:1991

数据来源: WILEY

摘要:

AbstractThis paper provides a review of the catalytic upgrading of biomass‐derived oils such as wood pyrolytic oils, plant/vegetable oils and tall oil to transportation fuels and useful chemicals. Both zeolite and hydrotreating type catalysts have been found suitable for upgrading which was usually done in fixed bed reactors. The hydrotreatment of pyrolytic oils at 250‐450°C and 15‐20 MPa H2pressures has been reported to yield up to 55 wt. % of liquid product containing 40‐50 wt. % of gasoline range hydrocarbons. In the case of HZSM‐5, the upgrading has been carried out at atmospheric pressure and 350‐500°C and over 85 wt. % conversions of plant oils and tall oil have been achieved under optimum conditions. Liquid product yields from these oils were up to 70 wt. % of feed which contained 40‐50 wt. % aromatic hydrocarbons. With the high pressure pyrolytic oil, pitch conversions of over 75 wt. % have been observed with HZSM‐5 using co‐feeds such as tetralin. However, there is only scant information available on the kinetic and mechanistic aspects of upgr

ISSN:0008-4034    

DOI:10.1002/cjce.5450690505

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe upgrading of crude tall oil (CTO) to fuels and chemicals was studied at atmospheric pressure and in the temperature range 370 to 440°C in a fixed bed microreactor containing HZSM‐5. The oil was co‐fed with diluents such as tetralin, methanol and steam. High oil conversions of the order of 80–90 wt. % were obtained using tetralin and methanol as diluents but with steam the conversion only ranged between 36 to 70 wt. %. The maximum concentration of gasoline range aromatic hydrocarbons in the liquid product was 52 and 57 wt. % with tetralin and steam but only 39 wt. % with methanol. The amount of gas product in most of the runs was 1–4 wt.%. A reaction scheme is postulated based on the

ISSN:0008-4034    

DOI:10.1002/cjce.5450690506

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

年代:1991

数据来源: WILEY

摘要:

AbstractUsing pilot scale trickle‐bed reactors with commercial NiMo/Al2O3catalysts, hydrotreating of five bitumen‐derived gas oils was conducted. Aromatic carbon was determined byl3C NMR spectra. A simple power law kinetic model of aromatics hydrogenation was developed, assuming a first order reversible reaction which accounts for both forward and reverse rate constants. The model includes power terms for space velocity and hydrogen partial pressure, and the ratio of naphthenes and aromatics in the feed. The model was tested with our experimental results and kinetic parameters were determined. Aromatic carbon calculated with these parameters is in good agreement with observed resu

ISSN:0008-4034    

DOI:10.1002/cjce.5450690507

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe vapor phase Beckmann rearrangement of cyclohexanone oxime has been carried out over zeolites and boria modified HZSM‐5 zeolites to elucidate the effects of acidity and acid strength distribution on the conversion and ε‐caprolactam selectivity. Although ε‐caprolactam selectivity was increased with the SiO2Al2O3ratio in a HZSM‐5 zeolite, the highest selectivity in the study was accomplished over a boria modified HZSM‐5. The selectivity was dependent on the ratio of weak acid sites to strong acid sites. The boria played an important role in controlling the acid strength distribution of the zeolites.It was found that the production of a polymer over strong acid sites caused a decrease in ε‐caprolactam selectivity durin

ISSN:0008-4034    

DOI:10.1002/cjce.5450690508

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe Chemical events involved in cracking and catalyst decay are examined in order to ascertain the possible course of catalyst decay. We find that, regardless of whether site activity is lost by “sudden death” or by gradual “inhibition”, the time course of catalyst decay under a wide variety of assumptions is described by the functionā(t) = (1 +Gt)–N′. Under certain conditions, however, sites on their way to complete deactivation may undergo reactivation by the desorption of an inhibiting species. In such cases, our models predict the existence of a lower activity condition which can be time invariant or, after being established by an initial rapid decay, the intermediate less‐active condition evolves to a final, inactive state. Furthermore, if some of the intermediate steps on the way to complete deactivation lead to site activities higher than those of the pristine sites, a sigmoidal curve of conversion versus time on str

ISSN:0008-4034    

DOI:10.1002/cjce.5450690509

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

年代:1991

数据来源: WILEY

摘要:

AbstractA growing literature demonstrates resonance of the rate of CO oxidation with frequency of composition switching and that a global increase in rate under composition modulation is possible. Differences are found for the various metal catalysts used: CO oxidation is stimulated at frequencies between 0.1 and 1.0 Hz over noble metals, whereas stimulation occurs at frequencies below 0.05 Hz with oxide catalysts. Multiple resonances with an apparent harmonic relationship, “wrong‐way” response, or very slow relaxation to reproducible cycles have been observed. These differences suggest mechanisms through which rate improvements arise are not the same for all cata

ISSN:0008-4034    

DOI:10.1002/cjce.5450690510

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

年代:1991

数据来源: WILEY