摘要:

AbstractA simple design of an adiabatic reactor for the production of hydrogen from methanol without external heating has been explored. Heat and steam are generated by oxidising part of the methanol and are removed in the process of reforming methanol to hydrogen. The reactor design emphasises the degree of control that can be achieved in a two‐bed system by controlling the air to methanol and water to methanol ratios in the feed. Predictions of the model are compared with experimental testing to allow optimisation of the process. Up to 75% of methanol can be converted to hydroge

ISSN:0930-7516    

DOI:10.1002/ceat.270180102

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe basic sites of various oxide catalysts for the oxidative dimerisation of methane were studied by FTIR spectroscopy of adsorbed molecular probes (chloroform and CO2). The methods used are compared and the advantage of CO2as probe for specifying the basic sites is demonstrated. The strengths of the basic sites were seen to correlate with the spectral parameters of the surface carbonates. Differences in spectral responses of carbonates are attributed to the different states of oxygen participating in their formation. The concentration of the strongest sites was estimated. A study of the catalytic activity of this system indicates that the system's activity in oxidative methane coupling depends on the presence and concentration of strong basic sites on the catalyst surface.

ISSN:0930-7516    

DOI:10.1002/ceat.270180103

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe feasibility of methane coupling as an add‐on unit to a naphtha cracker was studied. The existing cold box was used for separation of ethylene and unconverted methane, but arrangements were made for separation of the coupling by‐products. The cracker's methane was used as a feedstock. The concept is technically and economically feasible at spring 1992 prices, provided the catalyst meets the assumed 30% conversion and 80% C2selectiv

ISSN:0930-7516    

DOI:10.1002/ceat.270180104

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractTwo vanadia/titania catalysts, containing 1 and 8 wt% vanadia on anatase, have been investigated for the selective oxidation ofo‐xylene to phthalic anhydride. In a comparative study, activity and selectivity ino‐xylene oxidation were measured using an integral reactor and a reactor with external product recirculation, with the objective of studying the influence of backmixing in the latter on the reaction behaviour. Adsorbed surface species were investigated by means ofin‐situdiffuse reflectance FT‐IR spectroscopy, using an environmental chamber which corresponds to an integral reactor. No difference in activity and selectivity ino‐xylene oxidation was observed between the two catalysts. FT‐IR studies showed adsorbedo‐xylene, benzoate and a high concentration of phthalic anhydride on the surface of both catalysts.o‐Xylene oxidation follows a sequential reaction path, witho‐tolualdehyde as the first intermediate and phthalide, phthalic anhydride and maleic anhydride as sequential products. No evidence was found for a direct oxidation‐path ofo‐xylene to phthalic anhydride. Total oxidation products CO and CO2are formed by direct oxidation of theo‐xylene and by oxidation of the reaction products. Due to greatly reduced concentration and temperature gradients, the recycle reactor proved to be highly suitable for studying the extremely exotherm

ISSN:0930-7516    

DOI:10.1002/ceat.270180105

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractCO hydrogenation over Mn‐promoted Rh/NaY catalysts was studied at 1 MPa and 250°C. Significant selectivity to ethanol and ethyl acetate was obtained only after neutralising the protons formed on reduction of Rh ions. Layered bed experiments show that protons act as Brønsted acid sites catalysing secondary reactions that convert the oxygenates to hydrocarbons and c

ISSN:0930-7516    

DOI:10.1002/ceat.270180106

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe influence of altervalent cation doping of TiO2carriers on the chemisorptive and catalytic properties of supported Pt and Rh crystallites has been investigated. It was observed that doping of the carrier with higher valence cations leads to suppression of the H2and CO chemisorption capacity of Pt catalysts, while their activity in hydrogenation and oxidation reactions is significantly reduced. The opposite effects were observed in the case of Rh catalysts supported on higher valence doped TiO2. These catalysts were found to possess higher activity in CO and CO2hydrogenation, in aromatics hydrogenation and in CO and C2H4oxidation. Their stability characteristics were also found to be superior to those of the undoped Rh/TiO2catalyst. These effects are believed to originate from an electronic type interaction at the metal‐support interface, induced by doping, which results in electron transfer from the support to the metal crystallite

ISSN:0930-7516    

DOI:10.1002/ceat.270180107

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSingle liquid drop velocities in structured packings have been measured to aid calculation of throughput of liquid extraction columns using characteristic (single drop) velocities. Solvent drops were passed through two types of glass and two types of steel structured packing and further work was done using sloping glass tubes. Existing wall‐effect equations for drop velocity reduction in vertical tubes were considered and that given by Clift et al. [1] was used as a basis for correlation of structured packing data. Drop breakage was studied in order to improve understanding of drop size distribution development in packed columns. Drops broke only rarely within the structured packing; most of the breakage occurred as a drop hit the exposed edges on entry to a piece of packing. An energy balance equation was used to correlate critical conditions for breakage of drops hitting glass blades at various angles. Under the conditions used all those drops moving at terminal velocity had enough energy to break but a condition exists when drops may be small enough to have insufficient energy to brea

ISSN:0930-7516    

DOI:10.1002/ceat.270180108

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractStudies have been made on the extent and mechanism of breakage of single liquid drops of organic liquids immiscible in water rising through short sections of Kühni liquid‐liquid extraction columns. Information on drop breakage probabilities is required for calculation of drop size distributions developed under counter‐current column operating conditions. The breakage probability data from two small diameter Kühni columns containing one, three or five stages have been correlated as a function of a modified Weber number based on the shearing forces on drops. The critical condition for breakage, giving a maximum stable drop size, is based on an impeller Weber number. Characteristic velocities of drops were measured relative to terminal velocity and the ratio was tentatively correlated with a function of an impeller Reynolds number together with the fractional free area of the perforated plates used to separate compartments. The drops were found to break predominantly at the holes in the plates, not at the turbine, in the region of transitional Reynolds number used in this work. The results apply only to non‐turbulent conditions so further work on larger diameter equipment is cal

ISSN:0930-7516    

DOI:10.1002/ceat.270180109

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThis paper describes the design principles of multistage molecular evaporators with a wiped film which are used for gentle distillation of low‐volatility blends of thermolabile materials. The conditions of distillation in an evaporator with a convex evaporation surface are discussed, along with problems relating to the function of the segmented wiper in the formation of the retarded liquid film and the functional principles of closing elements in a multistage evaporator with a single evaporating cylinder and of the built‐in entrainment separator in the distillation space, which is designed to retain splashing spray. A TMO 65 three‐stage molecular evaporator is described, with an evaporating cylinder having a diameter of 65 mm and a total evaporating area of 0.19 m2. This pilot‐plant evaporator can be used in the small‐capacity production of specialty chemicals or in technological research as a verification unit for establishing data necessary for the operation of large evaporators. These possible applications are documented by the results obtained on fractionation of various important materials. Fractional distillation of crude monoacylglycerols (M) containing 35 to 55% M afforded concentrates containing over 90% M, at yields of 78 – 95% M in the product fraction. Fractionation of oligomers of higher α‐olefins gave distillate cuts with high contents of the respective n‐mer, suitable for use as synthetic lubricating oils. Fractionation of polyalkylaromatic residue from the production of monoalkylbenzenes produced a distillate fraction with excellent electrical insulation properties. Finally, purification of technical diane‐bis‐glycidyl ether yielded over 75% of a product fraction which was found suitable for production of insulating material for electrical equipment operating at vo

ISSN:0930-7516    

DOI:10.1002/ceat.270180110

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractAn experimental study on the gas dispersion behaviour of a cocurrent downflow gas‐solids suspension in a 140 mm i.d. circulating fluidised bed (CDCFB) using the steady‐state tracer method is presented. The influence of gas velocity, solids circulating rate and particle density on radial gas dispersion has been examined. Gas dispersion can well be described by an eddy diffusion mechanism and a proposed two dimensional dispersed plug‐flow model can fit the experimental data very well. Correlations of the radial diffusion coefficient were obtained. It is found that the axial diffusion coefficient obtained in the CDCFB is much lower than that in conventional circulating fluidised

ISSN:0930-7516    

DOI:10.1002/ceat.270180111

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY