Selective oxidation of methanol on mixed oxide catalysts

In the present work selective oxidation of methanol over the model Mo/Fe2O3 and Mo/Co(Zn) Fe2O4 systems has been investigated. It was shown that pure iron oxide and cobalt ferrite combust methanol to carbon dioxide and water. When molybdenum is loaded on the surface of iron oxide and calcined at 500 C, this leads to the formation of iron molybdate surface layer over Fe2C>3 core, which significantly changes selectivity in methanol oxidation towards partial oxidation products. The neighbouring Fe-Mo and Mo-Mo pairs of iron molybdate layer are responsible for the formation of carbon monoxide and formaldehyde respectively. According to XRD, Raman and XPS data, dosing of molybdenum onto the cobalt ferrite surface results in the formation of a mixed layer consisting of cobalt molybdate, iron molybdate and molybdena phases. Oxidation of methanol over Mo/CoFe2O4 results in the formation of a mixture of CO and CO2 with small traces of formaldehyde. CO is produced on mixed Fe-Mo and Co-Mo sites at temperatures above 220 C, whereas CO2 is mainly produced at lower temperatures and low oxygen conversion due to oxidation of CO by highly reactive traces of pure cobalt ferrite or cobalt molybdate present on the surface. Methanol oxidation was used as a model reaction to establish whether there is a relationship between catalytic activity and selectivity, and magnetic properties of catalysts. The catalytic behaviour of the pure and Mo impregnated ZnxCoi-xFe2O4 systems in the vicinity of Curie point was studied. Curie temperature of the material and the nature of Curie transition were adjusted varying Zn content and sample calcination temperature

A critical review of life cycle assessment studies of woody biomass conversion to sugars

Funder: Prince of Wales Global Sustainability Fellowship ProgrammeWoody biomass could potentially become a viable raw material for the future sustainable chemical industry. For this, a suitable regulatory framework must exist, that would create favourable economic conditions for wood biorefineries. Such policies must be developed on the basis of scientific evidence—in this case, data supporting the environmental advantages of the bio-based feedstocks to the chemical industry. The most suitable methodology for comprehensive evaluation of environmental performance of technologies is life cycle assessment (LCA). In this review, the available LCA studies of woody biomass fractionation and conversion to bulk chemical feedstocks are critically evaluated. It has been revealed that the majority of the openly available studies do not contain transparent inventory data and, therefore, cannot be verified or re-used; studies containing inventory data are reported in this review. The lack of inventory data also prevents comparison between studies of the same processes performed with different evaluation methods or using different system boundaries. Recommendations are proposed on how to overcome issues of commercial data sensitivity by using black-box modelling when reporting environmental information. From several comparable LCA studies, it has been concluded that today the most environmentally favourable technology for wood biomass fractionation is organosolv. This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)’

Understanding the environmental impacts of large-scale cellulose nanocrystals production: Case studies in regions dependent on renewable and fossil fuel energy sources

Favorable functional properties of cellulose nanocrystals (CNCs) in several end-use application areas, as well as its ‘green’ credential as a bio-based material stimulate significant interest in scaling up the manufacture of CNCs. As in any other process, there exist several design options for the overall process and decisions on adoption of a specific plant configuration should be based on economic as well as environmental data, preferably from the life cycle assessment perspective. In this study we establish a benchmark LCA study of a conceptual large-scale CNC manufacturing process based on sulfuric acid hydrolysis. We then use the benchmark process model to explore several plant configuration scenarios and sensitivity of optimal plant configurations to energy mix of different regions. Results of LCA study suggest the optimal plant configuration to include partial recycle of sulfuric acid, which allows to attain the minimum cradle-to-gate environmental impacts. This study provides benchmark figures of LCA impacts of CNC manufacture, which could be used for the assessment of carbon footprint and other environmental metrics of final products manufactured from CNCs

Structural and magnetic properties of Zn-substituted cobalt ferrites prepared by co-precipitation method

Zn substituted cobalt ferrite spinels with the general formula ZnxCo1−xFe2O4 (with x varying from 0 to 0.5) were synthesized by a co-precipitation method and calcined at 500 °C and 800 °C. It was found that Zn substitution has a big effect in decreasing the Curie temperature (Tc), from around 440 °C for the undoped sample to 180 °C with x = 0.5. However, these values were also strongly affected by the pre-calcination temperature of the samples, thus TC shifts from 275 °C for the x = 0.3 sample to 296 °C after calcination at 500 °C and 800 °C respectively. These effects are due to facilitation of demagnetisation by substitution of the non-magnetic Zn ions and by production of very small nanoparticles. The latter are removed by higher temperature calcinations and so TC increases

Synthesis of the antimalarial API artemether in a flow reactor

The earlier developed flow protocol for stoichiometric reduction of an important biologically derived pharmaceutical precursor, artemisinin, to dihydroartemisinin was extended to a sequential reaction to produce one of the final APIs, artemether. A highly active heterogeneous catalyst was found for the etherification reaction. The use of QuadraSil catalyst allows to eliminate one step of reaction workup. A comparative Life Cycle Assessment of both reactions has shown advantages of the flow process over the optimized literature batch protocols. Results of LCA highlight the significance of solvents in pharmaceuticals manufacture and the advantage of flow technology, enabling small solvent inventories to be used

Continuous Synthesis of Doped Layered Double Hydroxides in a Meso-Scale Flow Reactor

Detailed characterisation of morphology of doped hydrotalcites as catalysts precursors. Trends of material stability, pore size distribution, particle size as a function of the nature of dopants. Data on the flow synthesis method and reproducibility of materials that can be attained by this method

A Continuous Process for Buchwald-Hartwig Amination at Micro-, Lab-, and Mesoscale Using a Novel Reactor Concept

A continuous Buchwald–Hartwig reaction using the bulky N-heterocyclic carbene (NHC) precatalyst [Pd(IPr*)(cin)Cl] 4 has been developed for the synthesis of a key pharmaceutical intermediate 2. Using microreactor technology, the reaction could be optimized under dilute conditions with low material burden and the kinetic parameters investigated. For larger lab-scale operation (gram scale), process-relevant concentrations could be employed and the conditions developed for continuous workup effectively demonstrated (batch methodology published concurrently). The stability of the NHC catalyst allowed for a continuous acidic extraction of the product and on-stream recycling of the catalyst in the organic phase. At this scale, sonication is employed to prevent clogging in the reactor unit. Finally, a bespoke continuous flow reactor has been developed for carrying out the reaction beyond lab scale. This novel reactor concept for running heterogeneous reactions in flow combines the flexibility of continuously stirred tank reactors (CSTRs) with the smooth operation, low residence time distribution and excellent heat transfer capability of a conventional flow reactor. A LCA (life cycle analysis) study has been carried out on the resulting process in comparison with the existing batch protocol, revealing it to be favorable under the majority of environmental factors considered