Embedding co-management: community-based fisheries resource management regime in Lake Victoria, Tanzania

This paper discusses fisheries management reforms through involving local level institutions (LLFI). It is based on studies which were undertaken on TanzaniaÆs Lake Victoria fishery where LLFIs were established through the formation of Local enforcement Units, later named Beach Management Units (BMU), between 1998 and 2002. The paper takes the view that the overfishing problems that confront TanzaniaÆs fisheries management authorities are best understood from a social science perspective. The argument is that most communitiesÆ values and institutions are embedded in their societies. The same is however, not true for externally originated management tools and systems as is the case with BMUs. This paper shows that the BMUs established between 1998 and 2002, were not sufficiently grounded in their socio-cultural environment and this led them to be unsustainable and ineffective. The paper demonstrates that this mismatch by examining the different historical and social contexts in which livelihoods such as fishing emerged and was carried out. These social contexts generated social values that explain the individual behaviour of community members. It is such values that communities always strive to maintain in any activity including fishing. Thus, when confronted with situations that threaten these values, communities strategize or negotiate ways to cope. The coping strategies of two communities riparian to the lake are discussed. The paper therefore proposes a framework for making these units æfitÆ local conditions in order to make them effective and sustainable so as to reform fisheries management.Fishery management

Do national resources have to be centrally managed? Vested interests and institutional reform in Norwegian fisheries governance

Corporatism -with its privileged access, restricted participation and centralized structures - has a long history in Norwegian fisheries governance. Co-management – understood as a decentralized, bottom-up and more inclusive form of fisheries governance - has not been considered a relevant alternative.. Why does corporatism still prevail in a context where stakeholder status in fisheries governance globally – both in principle and practice - has been awarded environmental organizations, municipal authorities and even consumer advocacy groups? Why then have alternatives to the corporatist system of centralized consultation and state governance never been seriously considered in Norway, in spite of the growing emphasis on fish as a public resource and fisheries management as human intervention in geographically confined and complex ecosystems? We suggest that thismay have to do with the fundamental assumptions behind Norwegian fisheries governance that since fish is a national resource, it must be centrally managed. We argue that this is an assumption that may be contested

Sol-Gel Prepared Nanoscopic Metal Fluorides - a New Class of Tunable Acid-Base Catalysts

In this article, the high potential of the fluorolytic sol-gel process to synthesise nanoscopic metal fluorides with different acid-base properties is shown. These nanoscopic materials exhibit high potential to be used as heterogeneous catalysts due to their high surface areas and their tunable surface properties. Thus, for each specific reaction the required surface properties of the catalysts can be ”adjusted” to achieve a high yield and selectivity of the desired product. As a consequence, a greener method of chemical production can be accomplished. Moreover the cheap and easy synthesis of the catalysts using basic chemicals makes them not only interesting for fundamental research but provides an easy transformation to industrial applications

Adsorption of Alkanes on Isomerisation Catalysts

Zirconia modified with sulfate is a potential catalyst for the isomerization of n-butane to i-butane. The number of adsorption sites for small alkanes and the respective differential heats of adsorption on zirconia samples are thus of interest. In order to study the adsorption of propane, n-butane, and i-butane on a series of zirconia catalysts including partially deactivated samples, SETARAM MS-70 calorimeters were coupled with a volumetric system. At 313 K and an equilibrium pressure of 5 mbar, typically 10 to 100 µmol alkane per g catalyst were adsorbed. The majority of the sites on the materials were similar, with heats of adsorption between 40-60 kJ mol-1, only a small number of sites at coverages Methods: BET, GC, Microcalorimetry Elements: Fe, O, S, Z

Structural and Active Site Characterization of Sulfated Zirconia Catalysts for Light Alkane Isomerization

Sulfated zirconia (SZ) is active for light alkane isomerization at temperatures as low as 373 K [1]. The material has been investigated extensively in the past 2 decades [2] but so far no convincing structure-activity relationship has been established. Here, we report on the investigation of two different SZ materials with an interesting combination of properties. Both materials have a sulfate content of 9 wt.%; however, the material with lower specific surface area (SZ-1, 90 m2og-1) displays a maximum n-butane isomerization rate (373-423 K, 1-5 kPa n-butane at 101.3 kPa total pressure) that is about one order of magnitude higher than that of the material with higher specific surface area (SZ-2, 140 m2og-1). Both materials were produced through precipitation from zirconyl nitrate solution, followed by aging of the precipitate either at 298 K for 1 h (SZ-1) or 373 K for 24 h (SZ-2). After drying, the samples were sulfated with ammonium sulfate and calcined for 3 h at 873 K. Scanning electron microscopy showed typical particle sizes of 5 to 20 µm for SZ-1, and of 1 to 5 µm for SZ-2. X-ray diffraction and Zr K-edge X-ray absorption spectra identified both materials as predominantly tetragonal ZrO2, but SZ-2 exhibited smaller crystalline domains than SZ-1 (7.5 vs. 10 nm). Diffuse reflectance IR spectra taken during catalyst activation (523 K, inert gas) suggest that the sulfate structures on the two materials rearrange in a slightly different way during dehydration. This is tentatively attributed to different sulfate group densities that result from the ratios of sulfate content to surface area. By ammonia adsorption/desorption, the concentration of acid sites was determined to be 0.52 and 0.48 mmolog-1 for SZ-1 and SZ-2, respectively; this result is not reflected by the catalytic activities. Temporal analysis of products measurements indicated that the residence times for n-butane were shorter than for i-butane, and SZ-1 retained both these molecules longer than SZ-2. The activation energy for n-butane desorption was equivalent for both samples, i.e., 40-41 kJomol-1. Calorimetric measurements of the adsorption of reactant and product at 313 K produced the following results. At 0.3 kPa alkane pressure, SZ-1 and SZ-2 adsorbed similar amounts of n-butane (20 and 25 µmol), but very different amounts of i-butane (80 and 25 µmol). At coverages below 2 µmol the differential heats of adsorption of n-butane were much higher on SZ-2 than on SZ-1, while at higher coverages the heats were nearly identical for both samples and decreased from 60 to 40 kJomol-1. The samples did not differ with respect to the strength of interaction with i-butane, the heats decreased with increasing coverage from 60 to 40 kJomol-1. The results demonstrate that (i) typical SZ catalysts have fewer than 100 µmolog-1 sites, rendering identification by spectroscopic techniques difficult, and (ii) product desorption is a critical factor for the catalytic performance. References: [1] M. Hino, K. Arata, J. Chem. Soc. Chem. Comm. (1980) 851. [2] X. Song, A. Sayari, Catal. Rev. Sci. Eng., 38 (1996) 32

Structural and Active Site Characterization of Sulfated Zirconia Catalysts for Light Alkane Isomerization

Two different sulfated zirconia catalysts were produced through precipitation from zirconyl nitrate solutions, followed by aging of the precipitate either at 298 K for 1 h (SZ-1) or 373 K for 24 h (SZ-2). After drying, the samples were sulfated with ammonium sulfate and calcined for 3 h at 873 K. SZ-1 had a smaller surface area (90 m2 g-1) than SZ-2 (140 m2 g-1) but displayed a one order of magnitude higher maximum n-butane isomerization rate (373–423 K, 1–5 kPa n-butane at 101.3 kPa total pressure). Both materials consisted predominantly of tetragonal ZrO2, contained 9 wt% of sulfate, and adsorbed about 0.5 mmol g-1 NH3. Measurements of adsorption isotherms and differential heats for propane and iso-butane at 313 K reveal a larger number of adsorption sites on SZ-1 than on SZ-2, extrapolated to 1 kPa, 42 vs. 20 µmol g-1 (propane) and 120 vs. 44 µmol g-1 (iso-butane). At coverages > 2 µmol g-1 the heats were similar for both samples with both probes and decreased from 60 to 40 kJ mol-1. Temporal analysis of products measurements indicated shorter residence times for n-butane than for iso-butane, and SZ-1 retained both of these molecules longer than SZ-2. The activation energy for n-butane desorption was 45 kJ mol-1 for both samples. Interaction with pulses of CO2 suggested that non-sulfated, basic ZrO2 surface is exposed on SZ-2, consistent with the larger surface area at the same sulfate content as SZ-1. The results suggest that only a fraction of the sulfate groups participates in adsorption and that product desorption may be of importance

Quasi in-situ Adsorptive Microcalorimetric Characterization of Sulfated Zirconia Catalyst for n-Butane Isomerization with n-Butane and Isobutane as Probe Molecules

Sulfated zirconia (SZ with 0.94 mmol/g sulfur and 100 m2/g) is an active catalyst for the industrially important low temperature (373 K) isomerization of light alkanes, e.g. of n-butane [1]. The catalytic activity exhibits a multicomponent profile along time-on-stream (TOS) including an activation period and a maximum followed by rapid deactivation. This observation suggests a continuous change of the catalyst under reaction conditions, especially, of the sites that gain activity during the induction period. It has been found that a freshly prepared catalyst shows some characteristics that are far from those of the catalyst during reaction. Also it is known that probe molecules such as NH3 and pyridine, which are often used for catalyst characterization by adsorptive microcalorimetry, interact with the active sites much stronger than the reactant. It is hence compulsory to do characterization in-situ using probe molecules with the same characteristics as the reactant. Therefore, we developed a quasi in-situ adsorptive microcalorimetric method in order to characterize the active sites on SZ. The calorimeter cell was used as a fixed bed flow reactor, in which the catalytic reaction of n-butane isomerisation was carried out (0.5 g SZ pellets, 378 K, 1 kPa n-butane in N2). The feed was introduced through a capillary. Conversion was monitored on-line by GC. The reaction was stopped after various TOS, the cell was evacuated at 378 K, and placed in a SETARAM MS 70 calorimeter equipped with a volumetric system that allows dosages of 2 mmol/g show that the majority of sites produce 40 – 50 kJ/mol. These stable sites are probably related to the steady state activity of SZ beyond the activity maximum. Differential heats at < 20 mmol/g show that only a minority (< 2% of sulfur species) of sites change their character during the induction period. It seems that only these sites determine the induction process. The state of highest activity is characterized by a strong interaction of n-butane with the active sites (75 kJ/mol at < 2 mmol/g). However, the weak interaction of isobutane (50 kJ/mol at < 2 mmol/g) indicates an increasing easiness of product-desorption from the surface sites. The adsorbed amount of n-butane and isobutane is comparable (ca. 20 mmol/g at 6 mbar). In the state of highest activity the catalyst reacted with n-butane in the calorimeter cell (additional heat evolution, gas phase products). [1] M. Hino, S. Kobayashi, K. Arata, J. Am. Chem. Soc., 101 (1979) 6439. [2] L.C. Jozefowicz, H.G. Karge, E.N. Coker, J. Phys. Chem. 98 (1994) 8053. [3] S. Wrabetz, X. Yang, F.C. Jentoft, R. Schlögl, in preparation. [4] I. Langmuir, J. Am. Chem. Soc. 38 (1916) 2221

Characterization of catalysts in their active state by adsorption microcalorimetry: Experimental design and application to sulfated zirconia

A method to characterize the surface sites of catalysts in their active state by adsorption microcalorimetry was developed. A calorimeter cell was used as a flow-type reactor, and the skeletal isomerization of n-butane (1 kPa) at 378 K and atmospheric pressure proceeded at comparable rates and with the same states of induction period, maximum and deactivation phase as in a tubular reactor. The reaction was run for selected times on stream and after removal of weakly adsorbed species, n-butane or isobutane were adsorbed at 313 K. The surface of activated sulfated zirconia was characterized by at least two different sites for n-butane adsorption, a small group of sites (about 20 µmol g-1) that yielded heats of 5060 kJ mol-1 and sites that were populated at higher pressures (above about 5 hPa n-butane) and yielded heats of about 40 kJ mol-1. The strongly interacting sites disappear during the induction period and are proposed to be the sites where the isomerization reaction is initiated