Heat-integrated reactor concepts for catalytic reforming and automotive exhaust purification

Optimal solutions in environmental catalysis require a well-coordinated development of catalysts and of process design. This contribution is devoted to energy integrated design concepts for fuel reforming and for automotive exhaust purification. The examples presented demonstrate the importance of an innovative process design for optimal utilization of existing catalysts and show the potential of future developments.

New concepts for steam reforming through the efficient coupling of the endothermic reforming reaction with an exothermic combustion reaction are discussed in the first part. These concepts have been implemented for methanol steam reforming in a counter-current reactor with distributed side feed of burner gas and for methane steam reforming in a modular reactor with a co-current reaction section for the endothermic and the combustion reaction and attached counter-current heat exchangers. Both applications employ the so-called folded sheet reactor design, which ensures an excellent heat transfer between the reforming and combustion channels and efficient heat recovery.

A similar design solution is introduced for the apparently different case of automotive exhaust purification. The proposed concept aims at decoupling exhaust after-treatment from engine control. Its main component is a counter-current heat exchanger with integrated purification stages for HC-oxidation, NO_X storage and reduction and soot filtering. A small catalytic burner at the hot end of the heat exchanger provides both heat and oxidizing or reducing agents on demand. A new soot filter design allows for safe soot filter regeneration.     

2‐(1‐Ethynylpyrene)‐Adenosine as a Folding Probe for RNA—Pyrene in or out

A series of short RNA duplexes containing one or two 1‐ethynylpyrene‐modified adenine bases was synthesised. The melting behaviour of these duplexes was examined by monitoring temperature‐dependent pyrene fluorescence. In the singly modified RNA duplexes, the bases flanking the ethynylpyrene‐rA were varied to examine the sequence specificity of the fluorescence change of pyrene upon RNA hybridisation. Because an increase in pyrene fluorescence upon melting of the duplex can be correlated with intercalation of pyrene, and a decrease is usually associated with the position of pyrene outside the strand, a relationship between the flanking bases and the tendency of the dye to intercalate has been established. It was found that pyrene intercalation is less likely to take place if the modified base is flanked only by A–U base pairs. Flanking G–C base pairs, even only in the 5′‐direction of the modified base, will favour intercalation. In addition, we examined a doubly modified compound that had a pyrene located on each strand. The spectra indicated that the two pyrenes were close enough for interaction. Upon melting of the strand, a fluorescence blue shift corresponding to the dissociation of the pyrene–pyrene complex could be observed in addition to the intensity effect already known from the singly modified compounds. Two melting curves based on the different properties of the fluorophore could be extracted, leading to different melting points corresponding to the global duplex melting and to the change of local pyrene environment, respectively.     

Adaptability of competitive electricity reforms a modular analysis

Among the competitive electricity reforms that have been implemented in Europe and the US for the last 18 years, none has “survived” over several years without major changes. Their changing nature raises the question of their adaptability. Two characteristics of reforms play a key role on their adaptation properties. Firstly, they are “modular” objects in the sense of [Baldwin, C., 2008. Where do transactions come from? Modularity, transactions, and the boundaries of firms. Industrial and Corporate Change 17 (1), 155–195]. Secondly, they are produced in an institutional process which leads to “incomplete” rules and designs [Pistor, K., Xu, C., 2003. Incomplete law. International Law and Politics 35, 931–1013]. We propose a typology of adaptations based on the framework proposed by [Williamson, O.E., 1991. Comparative economic organization: the analysis of discrete structural alternatives. Administrative Science Quarterly 36 (2), 269–296] for contracts: (1) in case of small disturbances, adaptations are realized quasi-automatically, by autonomous decisions of the institutions governing the implementation of reforms; (2) in case of middle-range disturbances, adaption is made by Coasian bargaining; (3) finally, in case of strong disturbances, or when bargaining is not feasible, the adaptation of reforms is in the hands of legislative and executive institutions [North, D.C., 2005. Le processus du développement économique. Editions d’Organisation]. These institutions can reform the reforms [Joskow, P.L., 2006. Introduction to electricity sector liberalization: lessons learned from cross-country studies. In: Sioshansi, F.P. (Ed.), Electricity Market Reform: An International Perspective. Elsevier, Amsterdam, pp. 1–32; Hogan, W.W., 2002. Electricity market restructuring: reforms of reforms. Journal of Regulatory Economics 21, 103–132]. The role of these types of adaptations in each electricity reform is a consequence of the allocation of rights to the regulator, to stakeholders and to legislative and executive institutions.     

Starch derivatives with high degree of functionalization. III. Influence of reaction conditions and starting materials on molecular structure of carboxymethyl starch

Carboxymethyl starch (CMS) was prepared in a completely heterogeneous procedure in a methanol/water slurry activated with aqueous sodium hydroxide (45%, w/v) using monochloroacetic acid as the etherifying agent. The influence of the reaction conditions and the type of starting starch (amylose content and preactivation) was evaluated in regard to the formation of the main repeating units (i.e., unfunctionalized and mono‐, di‐, tri‐, and tetra‐O‐carboxymethylated) and the pattern of functionalization within the anhydroglucose units (AGU). The reproducible synthesis gave products with a maximal degree of substitution of CM groups (DS_CM) of 0.66, which was reached in a one‐step synthesis. Repeated carboxymethylation led to products with a DS_CM of 0.88. As revealed by means of HPLC analysis after complete acidic depolymerization, in any sample the mono‐O‐carboxymethylated glucose (mono‐O‐CMglc) was preferably present while the di‐O‐CMglc was formed to a very low extent only. The tri‐O‐CMglc was found in some samples while tetra‐O‐CMglc was not detected. The mole fractions determined did not follow the simple Spurlin statistic as shown for CM cellulose synthesized under comparable conditions. Within the carboxymethylated AGUs a preferred functionalization at position 2 was analyzed by means of ¹H‐NMR spectroscopy after hydrolytic chain degradation. Consequently, the CMS samples synthesized contained mainly 2‐mono‐O‐CM‐AGU. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2036–2044, 2001     

Structure,homogeneity ranges,magnetic, and electrical properties of the ordered Laves phases RENi4Mg with MgCu4Sn type structure

New ordered Laves phases RENi₄Mg (RE = Sc, Sm, Tb–Lu) were synthesized from the elements in sealed tantalum ampoules in an induction furnace. Six of the structures were refined on the basis of X-ray single crystal data. The diffraction experiments gave hint for small homogeneity ranges RE_1+xNi₄Mg_1?x. Magnetic susceptibility measurements show Curie–Weiss behavior for RE = Gd, Dy, Ho, Tm, Yb and the resulting effective magnetic moments suggest both stable trivalent states for all RE and a non-magnetic state for Ni. Gd_1+xNi₄Mg_1?x (x ≈ 0.12) orders antiferromagnetically at a Néel temperature of T_N = 4.6(5) K. Resistivity measurements reflect the metallic nature of these compounds.     

Aspects of decision support in water management--example Berlin and Potsdam (Germany) I--spatially differentiated evaluation

Decisions about sustainable development demand spatially differentiated evaluations. As an example, we demonstrate the evaluation of water management strategies in the cities of Berlin and Potsdam (Germany) with respect to their ecological effects in 14 sections of the surface water system. Two decision support systems were compared, namely PROMETHEE, which is designed to obtain a clear decision (linear ranking), and Hasse Diagram Technique (HDT), normally providing more than one favourable solution (partial order). By PROMETHEE, the spatial differentiation had unwanted effects on the result, negating the stakeholders determined weighting of indicators. Therefore, the stakeholder can barely benefit from the convenience of obtaining a clear decision (linear ranking). In contrast, the result obtained by HDT was not influenced by spatial differentiation. Furthermore, HDT provided helpful tools to analyse the evaluation result, such as the concept of antagonistic indicators to discover conflicts in the evaluation process.     

Models for low resolution slit scan measurements based on high resolution laser scanning image analysis: DNA and nuclear dimensions

A laser scanning microscope has been developed and employed to make high precision measurements of cells from clinical cervical samples. These specimens have been stained with the DNA specific fluorochrome mithramycin and the fluorescent images analyzed to give information on nuclear size, DNA content and nuclear shape. This information has been used to develop low resolution parameters as measured with flow cytometers, thus permitting some comparisons between high resolution and low resolution features as measured from the same cells. The results indicate that both low resolution flow slit scan and high resolution pattern recognition techniques yield the same average cellular information. However, low resolution methods are insensitive to shape and the influence of shape on the broadening of low resolution features is now under investigation.