Economic and agronomic impact assessment of wheat straw based alkyl polyglucoside produced using green chemical approaches

Results from a previous environmental impact assessment highlight the potential for the proposed process, that converts low-value agricultural residue (wheat straw) into a high-value biosurfactant, to result in significant (>75%) GHG savings, relative to the commercial candidate derived from palm kernel and wheat grain. This was achieved via the use of low-energy techniques like supercritical CO2 extraction, low-temperature microwave and in-situ fractionation of platform chemicals. Despite the environmental benefits, process commercialization relies on the economic feasibility of the production. Adopting a ‘cradle-to-gate’ life cycle costing approach, this paper has quantified the economic feasibility and resource efficiency characteristics of producing wheat-straw based APG, via the previously suggested green low-waste generating processes. Here, we undertook economic analysis of a wheat straw-derived APG production pathway, in comparison to palm-kernel and wheat-grain APG. Total processing costs were determined to range between $0.92-$1.87 per kg of wheat straw-APG demonstrating relatively better output service quality and energy efficiency, while conventional APG costs $1.95-$2.87 per kg, highlighting the significant potential of the residue-derived pathway to be scaled to commercial-level. In addition, a semi-quantitative assessment of the demand-based implications of adopting and scaling-up the green process, in the current context and practices of wheat cultivation was also undertaken. Potential agronomic impact that might be result from such scale-up scenarios, focusing on the effect of conventional residue incorporation practiced by farmers was assessed in detail to encourage farmers opt for informed choices and also to encourage both environmentally and economically sustainable systems-thinking

Desilicated ZSM-5 Zeolites for the Production of Renewable p-Xylene via Diels-Alder Cycloaddition of Dimethylfuran and Ethylene

The selective production of p-xylene and other aromatics starting from sugars and bioderived ethylene offers great promise and can eliminate the need for separation of xylene isomers, as well as decreasing dependency on fossil resources and CO2 emissions. Although the reaction is known, the microporosity of traditional commercial zeolites appears to be a limiting factor. In this work, we demonstrate for the first time that simply desilication of microporous commercial zeolites by a simple NaOH treatment can greatly enhance conversion and selectivity. The [4 + 2] Diels–Alder cycloaddition of 2,5-dimethylfuran with ethylene in a pressurised reactor was investigated using a series of H-ZSM-5 catalysts with SiO2/Al2O3 ratios 30 and 80 with increasing pore size induced by desilication. X-ray diffraction, scanning electron microscopy, 27Al magic-angle spinning nuclear magnetic resonance, temperature programmed desorption of ammonia, and nitrogen physisorption measurements were used to characterise the catalysts. The enhancement of conversion was observed for all desilicated samples compared to the untreated zeolite, and increases in temperature and ethylene pressure significantly improved both dimethylfuran conversion and selectivity to p-xylene due to the easier desorption from the zeolite’s surface and the augmented cycloaddition rate, respectively. A compromise between acidity and mesoporosity was found to be the key to enhancing the activity and maximising the selectivity in the production of p-xylene from 2,5-dimethylfuran

Environmental impact assessment of wheat straw based alkyl polyglucosides produced using novel chemical approaches

This paper evaluates and quantifies the environmental performance of alkyl polyglucosides sourced from wheat straw (WS-APG), a low-cost and low-ecological impact agricultural residue, compared to that of their commercial counterpart, which is sourced from palm kernel oil and wheat grain (PW-APG). Escalating pressure to consider the environmental sustainability of fossil derived surfactant consumption has driven biosurfactants to become the product of choice within the surfactant market, and a class of ‘plant’ based non-ionic surfactants called alkyl polyglucosides (APG) are particularly prevalent. However, the existing food based feedstock of APG such as coconut oil, palm oil, wheat and corn (in addition to being expensive) will potentially undermine the claimed ‘sustainability’ of the APG products (i.e. the ‘food vs. chemical’ issue). Here, we present the “cradle-to-gate” life cycle impact assessment of a suggested alternative, hybridised APG synthesis technique where the Fisher glycosidation method is supplemented by novel, green chemistry based techniques. This evaluation provides a quantitative insight into direct GHG intensity and other ecological impact indicators, including land use, waste generation and energy consumption. Upon evaluation, the wheat straw-derived pathway delivered GHG-emission savings in the range of 84–98%, compared to that of the palm kernel–wheat grain pathway. Waste generated from the production of unit mass of the product amounted to 0.43 kg and 10.73 kg per kg of WS-APG and PW-APG, respectively. In addition to the above mentioned facts, the ‘cradle–gate’ stages of WS-APG production were also found to consume relatively lower amounts of water and fossil-derived energy. In conclusion, of the two APG production pathways, the suggested ‘hybrid’ pathway using an agricultural residue, wheat straw, was found to be sustainable and to demonstrate better environmental performance

Gold nanomaterials as key suppliers in biological and chemical sensing, catalysis, and medicine

peer reviewe

Gold nanomaterials as key suppliers in biological and chemical sensing, catalysis, and medicine

peer reviewe

Microwave-assisted hydrothermal treatments for biomass valorisation : a critical review

The sustainable conversion of biomass into biofuels, chemicals and biomaterials has gained increasing attention to ensure the well-being of present and future generations. Among the different technologies available to date for the valorisation of biomass, microwave-assisted hydrothermal conversion has recently appeared as a state-of-the-art technology, capable of furnishing a wide range of reaction products for the energy, pharmaceutical and chemistry sectors. This emerging technology combines the inherent benefits of microwave heating and the sustainable features of biomass hydrothermal valorisation. Herein, for the first time, this critical review summarises and analyses all the work conducted to date on the use of microwave-assisted hydrothermal processes (including microwave-assisted carbonisation, liquefaction and treatment/hydrolysis) for the conversion of biomass into hydrochar, bio-crude (bio-oil) and valuable chemicals. In particular, this work has put together vital information addressing the influences of the reaction conditions (temperature, time, amount and type of catalyst, biomass loading and type, and microwave power) on the yields and key properties of the reaction products. The relationships between these processing parameters and the chemical transformations involved in the processes (hydrolysis, dehydration, decarboxylation, condensation and re-polymerisation) have been described in detail, and reliable comparisons have also been established between microwave-assisted and conventional hydrothermal technologies when data were available. As a result, this critical review collects essential information on the use of this cutting-edge, recently appeared microwave-assisted hydrothermal technology, and paves the way for its expansion and future development and commercialisation

Application of heterogeneous catalysts in processing of vegetable oils to valuable hydrocarbon products

Tato práca je zameraná na NiMo-alumina katalyzátory pre (i) deoxygenáciu repkového oleja ako vhodný spôsob obnoviteľnej výroby nafte podobného paliva a (ii) odsírenie modelovej zlúčeniny 4,6-dimethyldibenzotiofénu na odstraňovanie síry z motorových palív. Hlavným cieľom práce bolo zistiť štruktúrne parametre NiMo-alumina katalyzátorov a prepojiť ich s katalytickou aktivitou. To by malo pomôcť prehĺbiť znalosti o hydrorafinačných katalyzátoroch a urýchliť ich optimalizáciu pre jednotlivé žiadané procesy. Táto práca je zložená z jedného prehľadu tematiky (kapitola v knihe), troch výskumných publikácií a doposiaľ nepublikovaných dát. Úvod do problematiky je nasledovaný diskusiou výsledkov. Hlavným cieľom nášho výskumu bolo zistenie štruktúrnych zmien v NiMo-alumina katalyzátoroch. Vplyvy podporujúceho prvku (Ni) a nosiča boli skúmané pomocou Röntgenovej difrakcie, adsorpcie dusíku, teplotne programovanej redukcie pomocou vodíku, Röntgenovej fotoelektrónovej spektroskopie, skenovacej elektrónovej mikroskopie, UV-vis difúznej reflektančnej spektroskopie. Spojenie výsledkov charakterizácií a merania katalytickej aktivity pomohlo odhaliť, že Ni v oktaedrálnej koordinácii je pravdepodobne východiskovou látkou pre aktívnu sírnu fázu. Na druhú stranu, vysoká teplota predúpravy katalyzátoru vedie na neaktívne častice, ktoré sú pevne viazané k nosiču. Ďalej bolo zistené, že textúrne vlastnosti nosiča majú zásadný vplyv na charakter aktívnych materiálov. Meso/makroporézna štruktúra aluminy spolu s jej vysokým špecifickým povrchom, vhodnou kryštalickosťou a povrchovou kyslosťou vedie na katalyzátor s optimálnou disperziou aktívnej fáze. Ďalšie bádania boli zamerané na vplyv východiskových a prídavných látok na impregnáciu katalyzátorov. Bolo objavené, že použitie organických východiskových látok napomáha zlepšeniu disperzie aktívnej fázy a tiež katalytickej aktivity v odstraňovaní heteroatómov (O, S). Taktiež bolo ukázané, že nízky obsah fosforu a opatrná úprava pH impregnačného roztoku NiMo-alumina katalyzátorov môžu pozitívne ovplyvniť štruktúru a katalytickú aktivitu týchto sírnych materiálov s hydrorafinačným určením.This thesis is focused on NiMo-alumina catalysts for application in (i) hydrodeoxygenation of rapeseed oil as a feasible way to produce diesel-like fuels from renewable feedstocks and (ii) for hydrodesulfurization of 4,6-dimethyldibenzothiophene as a model compound for sulfur removal from vehicular fuels. The main aim was to elucidate structural parameters of these catalysts and to connect these properties with their catalytic performance. This should reveal structure-activity relationships, which could deepen the knowledge about hydrotreating catalysts and improve their optimization for particular applications. The thesis consists of 1 review on the topic (book chapter), 3 original research papers and results of so far unpublished work, which are presented as an introduction to hydrotreating and deoxygenation catalysis and discussion of the results. The main point of our investigation was the determination of structural changes in NiMo-alumina catalysts. Promoter and support effects were evaluated by X-ray diffraction, nitrogen adsorption measurements, temperature programmed reduction by hydrogen, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-vis diffuse reflectance spectroscopy. Coupling of characterization results and catalytic measurements revealed that Ni in octahedral environment could be the precursor of active species in sulfide phase, while high-temperature treatment of as-prepared catalysts leads to inactive compounds, generally strongly bound to support. Furthermore, textural properties of alumina were found to play important role in the preparation of active deoxygenation catalysts. It was found that meso/macroporous structure coupled with high specific surface area and suitable crystallinity and acidity of the support leads to the optimum surface dispersion of active phase. Further investigations were aimed at the influence of precursor type and modifiers used during the impregnation of catalysts. It was found that the use of organic precursors helps to improve the dispersion of active phase and catalytic activity in hydrogen-assisted heteroatom (O, S) removal. Moreover, it was shown that low amount of phosphorus and careful pH adjustment during impregnation of NiMo-alumina catalysts can positively influence structure and catalytic performance of these sulfide catalysts for hydrotreating applications.Katedra fyzikální chemie1) Předseda komise seznámil členy komise s průběhem studia disertanta, a s tématem disertační práce a posudky školitele a vedoucího školícího pracoviště. 2) Disertant seznámil komisi se základními tezemi své práce. Prezentace byla jasná a srozumitelná. 3) Předseda komise seznámil ostatní členy s posudkem nepřítomného oponenta a jeho reakcí na písemně odeslané odpovědi na jeho otázky. Ostatní oponenti přednesli své otázky a dizertant na ně adekvátně reagoval. 4) Proběhla obecná diskuze k předložené disertaci. 5) Proběhlo tajné hlasování