Value-added Chemicals from Biomass by Heterogeneous Catalysis

I den samtidige debat om ressourceudnyttelse har anvendelsen af biomasse været diskuteret som en alternativ carbon-kilde til de fossile reserver med henblik på at reducere CO2-emissionen til atmosfæren. Erstatningen eller supplementet til de oliebaserede transportbrændstoffer gennem konversion af biomasse er allerede etableret. Fremstilling af kemikalier fra biomasse har haft ringere bevågenhed. Denne afhandling beskriver og evaluerer en søgen efter en alternativ konversionsrute, baseret på biomasseføde og under anvendelse af en heterogen katalysator, som er i stand til at omsætte føden til et merværdi-kemikalie. Projektarbejdet i denne forbindelse er udført med en tværfaglig tilgang omfattende fra fundamentale katalysatorundersøgelser, gennem eksperimenter, karakterisering og procesevalueringer til markedsanalyse. Rationalet herfor er søgt gennem aktiverne i den opnåede bæredygtige ressourceudnyttelse for sådan en proces og under hypotesen, at lønsomheden af processen, i sammenligning med de konventionelle teknologier, yderligere kan opnås gennem fordelen ved bevarelsen af kemiske C-C bindinger i biomasse-baserede føder. Med udgangspunkt i ethanol som eksempel på en biomasse-baseret føde, som har beholdt en C-C binding fra det oprindelige biomasse-udgangsstof, bliver aspekterne for at udnytte heterogen katalyse til dets omsætning til merværdi-kemikalier undeersøgt. Gennem en simpel analyse af kendte, men ikke-industraliserede procesruter, bliver ethanol til eddikesyre-ruten identificeret som én, der viser gode perspektiver. Inkorporeringen af en nyttig katalysator i en effektiv proces er afgørende for potentialet af den overordnede procesinnovation. En gruppe Cu baserede katalysatorer, som viser sig aktive i pågældende konversion, bliver identificeret i en forundersøgelseseksperimentrække. Under hensynet til handlefriheden bliver endvidere procesudviklingsmuligheder afdækket, baseret på de opnåede eksperimentelle vidnesbyrd, teori og proceselementer beskrevet i litteraturen (fortrinsvis patent-). Der bliver søgt beskyttelse af de relaterede opfindelser gennem indlevering af tre patentansøgninger. Afhandlingens vigtigste bidrag er afspejlet i den endelige konklusion, at en ethanol til eddikesyreproces og tilhørende katalysator, begge genstande for videreudvikling, er identificeret. Forståelsen af den katalytiske opførsel af udvalgte katalysatorer, Cu spinel (CuAl2O4) og Cu/SiO2, bliver opnået gennem karakterisering heraf såvel som målinger af aktivitet, selektivitet og stabilitet bl.a. i formålsudviklede testopstillinger. Gennem adskillige karakteriseringsanalyser (XAFS, XRPD, SEM, TEM, TPR, carbon analysis etc.) kan det konkluderes, at den hurtige deaktivering af Cu spinel katalysatoren skyldes dannelsen af højmolekylære kulholdige stoffer som dækker katalysatoroverfladen, katalyseret af sure alumina sites, der opstår under katalysatoraktiveringen. Denne forklaring er i overensstemmelse med adskillige observerede fænomener for katalysatoren. Cu/SiO2 - katalysatoren, som har en inert support, viser langt højere robusthed over for procesvariationer, men udviser umiddelbart en for lav katalytisk aktivitet set fra en industriel vinkel. Adskillige måder til forbedring af aktiviteten bliver belyst. F.eks. indikeres en aktivitetsafhængighed af Cu-krystalstørrelsen ved en sammenligning af aktivitet og XRPD analyser for nedknuste og hele katalysatorpiller. Der bliver udledt empiriske kinetiske modeller, i god overensstemmelse med de opnåede eksperimentelle data for Cu/SiO2-katalysatoren, for at understøtte etableringen af en forbedret økonomisk vurdering af den undersøgte proces. Ekstrapolation af de udledte modeller indikerer tilfredsstillende aktivitet i det industrielle trykområde. Cu/SiO2-katalysatoren er endvidere i stand til at klare delvist oxidative dehydrogeneringsbetingelser, som tillader betydelige procesforbedringer. Slutteligt bliver ethanol til eddikesyre processen sat i en større sammenhæng ved i et tilbageblik at revurdere de i arbejdet anvendte metoder, markedets indflydelse på processens chancer, konklusioner og forbedringsmuligheder for processen. Endeligt, i betragtning af nogle fremadrettede alternative procesmuligheder, gives mine konkluderende anbefalinger under hensynet til det oprindelige projektformål. Afhandlingens resultater viser, med udgangspunkt i et enkelt eksempel på biomassekonversion, at udnyttelsen af biomasse i produktionen af kemikalier er lovende fra et teknisk synspunkt. Men risikoen for markedsprisudsving, domineret af fossilt baserede kemikalier, stiller endvidere kriteriet om en pålidelig økonomisk margin. Derfor bør man under markedshensyn undersøge alternativer. I tillæg til de tekniske konklusioner forekommer det, at en tvær-disciplinær tilgang til procesinnovation er fordelagtig.In the contemporary debate on resource utilisation, biomass has been discussed as an alternative carbon source to fossil reserves in order to reduce the emission of CO2 to the atmosphere. The replacement or supplement of oil based transportation fuels through biomass based conversions has already been implemented. The subject on chemical production has received less attention. This thesis describes and evaluates the quest for an alternative conversion route, based on a biomass feedstock and employing a heterogeneous catalyst capable of converting the feedstock, to a value-added chemical. The project work to fulfil the above objective has been conducted with a multi-disciplinary approach ranging from fundamental catalyst research, through experiments, characterisation and process evaluation to market analysis. The motivation herein is sought in the assets of sustainable resource utilisation obtained for such a process and the hypothesis that process feasibility in comparison with the conventional synthesis gas based technologies may further be attainable, taking advantage of the conservation of chemical C-C bonds in biomass based feedstocks. With ethanol as one example of a biomass based feedstock, having retained one C-C bond originating from the biomass precursor, the aspects of utilising heterogeneous catalysis for its conversion to value added chemicals is investigated. Through a simple analysis of known, but not industrialised catalytic routes, the direct conversion of ethanol to acetic acid product is identified to show good perspectives. The nesting of a useful catalyst and an effective process is crucial to the potential of the overall process innovation. In a pre-screening study, a group of Cu based catalysts active in the conversion have been identified. Considering the freedom to operate, the prospects of process development are further identified through process calculations based on the experimental evidence attained, theory and the process elements described in literature (primarily patent-related). The protection of the process inventions made in relation to this is sought through the filing of three patent applications. The most important contributions of this thesis are reflected in the eventual conclusion that an ethanol to acetic acid process and a related catalyst, both subject to further development, are identified. The understanding of the catalytic behaviour of down-selected catalysts, Cu spinel (CuAl2O4) and Cu/SiO2, is obtained through characterisation as well as activity, selectivity and stability studies in appropriately developed experimental set-ups. Through numerous characterisation analyses (XAFS, XRPD, SEM, TEM, TPR, carbon analysis etc.) the rapid deactivation of the Cu spinel catalyst may be concluded to be attributed to the formation of high molecular carbonaceous compounds covering the catalytic surface, being catalysed by acidic alumina sites present during and after catalyst activation. This theory explains several phenomena observed for this catalyst. The Cu/SiO2 catalyst, having an inert support, shows far higher robustness to process variations, but immediately exhibits a too low activity from an industrial angle. Several means of improving its activity are elucidated. For example an activity dependence on the Cu crystal size is indicated by the comparison of the activity and XRPD analyses obtained for crushed and whole catalyst pellets. Empirical kinetic models, in good agreement with the experimental data obtained for the Cu/SiO2 catalyst, are developed in order to support the establishment of an improved economic evaluation of the investigated process. Extrapolation of the derived model to the industrial pressure regime indicates a satisfactory activity. The Cu/SiO2 catalyst is further able to withstand partly oxidative dehydrogenation conditions, allowing for immense process improvements. Finally, the ethanol to acetic acid process is put into a broader context, by reviewing the methods used in this work, the market influence on its fate, the conclusions and suggested improvements listed. Eventually, with an outlook on some alternative process possibilities, my recommendations are given under the consideration of the initial project objective. The results of the thesis, taking one example of biomass conversion, show that the utilisation of biomass in the production of chemicals by heterogeneous catalysis is promising from a technical point of view. But risks of market price excursions dominated by fossil based chemicals further set a criterion of a solid economic margin. Therefore, under market considerations other alternatives are to be investigated. In addition to the technical conclusions it appears that a multi-disciplinary approach to process innovation is advantageous

Introduction: Toward an Engaged Feminist Heritage Praxis

We advocate a feminist approach to archaeological heritage work in order to transform heritage practice and the production of archaeological knowledge. We use an engaged feminist standpoint and situate intersubjectivity and intersectionality as critical components of this practice. An engaged feminist approach to heritage work allows the discipline to consider women’s, men’s, and gender non-conforming persons’ positions in the field, to reveal their contributions, to develop critical pedagogical approaches, and to rethink forms of representation. Throughout, we emphasize the intellectual labor of women of color, queer and gender non-conforming persons, and early white feminists in archaeology

Gonadotropin-releasing hormone analog buserelin causes neuronal loss in rat gastrointestinal tract.

Gonadotropin-releasing hormone (GnRH) analogs are given to women undergoing in vitro fertilization. Case reports describing the development of chronic intestinal pseudo-obstruction and auto-antibodies against GnRH after such treatment suggest a strong association between intestinal dysfunction and GnRH analogs. No experimental model for studying such a relationship is currently at hand. Our main goal was to investigate possible enteric neurodegeneration and titers of GnRH antibodies in response to repeated administration of the GnRH analog buserelin in rat. Rats were treated for 1-4 sessions with daily subcutaneous injections of buserelin or saline for 5 days, followed by 3 weeks of recovery. Buserelin treatment caused significant loss of submucous and myenteric neurons in the fundus, ileum, and colon. The loss of enteric neurons can, at least partly, be explained by increased apoptosis. No GnRH- or GnRH-receptor-immunoreactive (IR) enteric neurons but numerous luteinizing hormone (LH)-receptor-IR neurons were detected. After buserelin treatment, the relative number of enteric LH-receptor-IR neurons decreased, whereas that of nitric-oxide-synthase-IR neurons increased. No intestinal inflammation or increased levels of circulating interleukins/cytokines were noted in response to buserelin treatment. Serum GnRH antibody titers were undetectable or extremely low in all rats. Thus, repeated administrations of buserelin induce neurodegeneration in rat gastrointestinal tract, possibly by way of LH-receptor hyperactivation. The present findings suggest that enteric neurodegenerative effects of GnRH analog treatment in man can be mimicked in rat. However, in contrast to man, no production of GnRH auto-antibodies has been noted in rat