Quantum-chemical study of the nonclassical carbonium ion-like transition states in isobutane cracking on zeolites

The ''ab initio'' quantum chemical calculations at MP2/6- 31++G**//HF/6-31G* level were performed for some elementary steps of isobutane cracking on zeolites. The results demonstrated that adsorbed carbonium ions represent not the observable reaction intermediates, but the high-energy transition states of the corresponding elementary reactions. Calculated activation energies are in reasonable agreement with experimental dat

‘Nudging’ as an architect of more responsible consumer choice in food service provision: The role of restaurant menu design

The sector of food service provision generates substantial environmental and societal impacts. Environmental impacts are particularly pronounced in terms of carbon footprint build-up while societal impacts are reflected in often unhealthy food choice. These impacts should be minimised to facilitate progress of the sector towards sustainability. A significant share of the negative impacts from food service provision is attributed to irresponsible consumer choice which needs to be architected and made more society- and climate-benign. Customer ‘nudging’ is an effective tool of consumer choice architecture and yet little research has examined its application within the context of private food service provision. This study set to better understand the determinants of consumer choice when dining out and how consumer choice could be reinforced to make it more beneficial from the sustainability viewpoint. To this end, the study reported on the outcome of a consumer survey conducted among visitors to a UK casual dining restaurant where menu design was employed as a customer ‘nudging’ tool. The survey demonstrated that, next to price, food provenance and nutritional value determined consumer choice when dining out. This information should therefore be displayed on restaurant menus to enable educated, and more environment- and society-benign, food choice. While presenting the food carbon values on a menu was well perceived, some skepticism attached to their prospective use as a determinant of consumer choice was recorded. Recommendations were made on the design of the industry and policy-making interventions required to enhance the public appeal of this menu item

Rapid Mineral Precipitation During Shear Fracturing of Carbonate‐Rich Shales

Target subsurface reservoirs for emerging low‐carbon energy technologies and geologic carbon sequestration typically have low permeability and thus rely heavily on fluid transport through natural and induced fracture networks. Sustainable development of these systems requires deeper understanding of how geochemically mediated deformation impacts fracture microstructure and permeability evolution, particularly with respect to geochemical reactions between pore fluids and the host rock. In this work, a series of triaxial direct shear experiments was designed to evaluate how fractures generated at subsurface conditions respond to penetration of reactive fluids with a focus on the role of mineral precipitation. Calcite‐rich shale cores were directly sheared under 3.5 MPa confining pressure using BaCl2‐rich solutions as a working fluid. Experiments were conducted within an X‐ray computed tomography (xCT) scanner to capture 4‐D evolution of fracture geometry and precipitate growth. Three shear tests evidenced nonuniform precipitation of barium carbonates (BaCO3) along through‐going fractures, where the extent of precipitation increased with increasing calcite content. Precipitates were strongly localized within fracture networks due to mineral, geochemical, and structural heterogeneities and generally concentrated in smaller apertures where rock:water ratios were highest. The combination of elevated fluid saturation and reactive surface area created in freshly activated fractures drove near‐immediate mineral precipitation that led to an 80% permeability reduction and significant flow obstruction in the most reactive core. While most previous studies have focused on mixing‐induced precipitation, this work demonstrates that fluid–rock interactions can trigger precipitation‐induced permeability alterations that can initiate or mitigate risks associated with subsurface energy systems.Key PointsBarium carbonates precipitate near‐immediately with injection of BaCl2‐rich fluid into freshly sheared calcite‐rich shalesPrecipitation reactions are strongly localized, favoring narrow apertures and zones of extensive fragmentationFluid–rock interactions can promote significant precipitation‐induced permeability alterations that remain challenging to predictPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155917/1/jgrb54184_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155917/2/jgrb54184-sup-0001-2019JB018864-SI.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155917/3/jgrb54184.pd

Sampling and preparation of c.200 mm diameter cylindrical rock samples for geomechanical experiments

Experimental investigation of rock mechanical properties of real and artificial samples often requires much care and attention to detail during sample preparation. This especially applies to high fidelity state of the art complex experimental apparatuses where sample tolerance is low due to the complexity of the measuring and stress control devices as well as the nature of the experiments to be conducted. Although sometimes mundane, the sample preparation methodology is as equally important as the experimental apparatus itself, and can require several new technological developments. The methodology and technical developments required to prepare realistic heterogeneous, fractured and natural reservoir analogue rock samples for coupled thermo-hydro-mechanical-chemical process experimental investigation is described here. We present the sample recovery and preparation procedures for large (c.200 mm diameter), cylindrical samples of 200 mm ± 5 mm length, with variable composition and mechanical properties e.g. rock strength, existing fractures/fracture networks, macro-porosity, or lithic fragments. Although the technology demonstrated is for a specific application, the procedures developed, equipment and methodology are applicable to multiple sizes of sample requirements