In silico designed microporous carbons

AbstractThis work presents a computational study on the packing of three-dimensional carbon nanostructures and their effect on gas adsorption properties. We show that it is possible to obtain intrinsically microporous materials without specifying structural properties such as surface area or pore size distribution by packing individual graphene platelets connected at a contortion site. The resulting structures can potentially represent disordered carbons and provide understanding of the relationship between pore structure and adsorption performance. The calculated CO2/CH4 selectivity of these materials at the zero coverage selectivity can be as high as 25, whilst at low finite pressures (0.05bar) is between 6 and 10, which is comparable with what is expected for most carbons. We compare the results to the ones obtained from a simple slit pore model and highlight the importance of pore morphological complexity to adsorption of industrially important gases

Controlling mass loss from RTM6 epoxy resin under simulated vacuum infusion conditions

A certified aerospace resin (RTM 6) normally utilised for resin transfer moulding is considered for vacuum infusion. The resin was subjected to simulated vacuum infusion conditions by using a specialised thermogravimetric analysis that enables control of pressure as well as temperature. By varying conditions, it was possible to investigate the expected occurrence of volatile loses during infusion that could cause mechanical or cosmetic defects in a part. With particular reference to RTM6, it was determined that full vacuum could be used for infusion provided that the temperature was kept below ∼130 °C. Higher temperatures could be used, but the applied vacuum should be significantly reduced. Of note is that the manufacturers datasheet recommends processing parameters that could result in volatile loss. As such, the pressure enhanced TGA method may be considered more widely for providing processing conditions supplemental to the manufacturers recommendation for any liquid resin used under vacuum conditions

Kerogen nanoscale structure and CO2 adsorption in shale micropores

Gas storage and recovery processes in shales critically depend on nano-scale porosity and chemical composition, but information about the nanoscale pore geometry and connectivity of kerogen, insoluble organic shale matter, is largely unavailable. Using adsorption microcalorimetry, we show that once strong adsorption sites within nanoscale network are taken, gas adsorption even at very low pressure is governed by pore width rather than chemical composition. A combination of focused ion beam with scanning electron microscopy and transmission electron microscopy reveal the nanoscale structure of kerogen includes not only the ubiquitous amorphous phase but also highly graphitized sheets, fiber- and onion-like structures creating nanoscale voids accessible for gas sorption. Nanoscale structures bridge the current gap between molecular size and macropore scale in existing models for kerogen, thus allowing accurate prediction of gas sorption, storage and diffusion properties in shales

Polymers of Intrinsic Microporosity Containing Tröger Base for CO₂ Capture

Properties of four polymers of intrinsic microporosity containing Tröger’s base units were assessed for CO₂ capture experimentally and computationally. Structural properties included average pore size, pore size distribution, surface area, and accessible pore volume, whereas thermodynamic properties focused on density, CO₂ sorption isotherms, and enthalpies of adsorption. It was found that the shape of the contortion site plays a more important role than the polymer density when assessing the capacity of the material, and that the presence of a Tröger base unit only slightly affects the amount adsorbed at low pressures, but it does not have any significant influence on the enthalpy of adsorption fingerprint. A comparison of the materials studied with those reported in the literature allowed us to propose a set of guidelines for the design of polymers for CO₂ capture applications

PIM-1/graphene composite: A combined experimental and molecular simulation study

This work presents a combined molecular simulation and experimental study to understand the effect of graphene on the packing and gas adsorption performance of a new class of polymers, known as polymers of intrinsic microporosity (PIMs). PIMs can be processed to membranes or other useful forms and their chemistry can be tailored for specific applications. Their rigid and contorted macromolecular structures give rise to a large amount of microvoids attractive for small molecule adsorption. We show that the presence of graphene in the composite affects the structure of the membrane as evidenced by the change in colour and SEM micrographs, but it does not reduce significantly the adsorption capacity of the material. (C) 2014 The Authors. Published by Elsevier Inc