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A model has been developed and implemented in the software package BoilFAST that allows for reliable calculations of the self-pressurization and boil-off losses for liquid hydrogen in different tank geometries and thermal insulation systems. The model accounts for the heat transfer from the vapor to the liquid phase, incorporates realistic heat transfer mechanisms, and uses reference equations of state to calculate thermodynamic properties. The model is validated by testing against a variety of scenarios using multiple sets of industrially relevant data for liquid hydrogen (LH2), including self-pressurization and densification data obtained from an LH2 storage tank at NASA’s Kennedy Space Centre. The model exhibits excellent agreement with experimental and industrial data across a range of simulated conditions, including zero boil-off in microgravity environments, self-pressurization of a stored mass of LH2, and boil-off from a previously pressurized tank as it is being relieved of vapor.

While it has long been known that some highly adsorbing microporous materials suddenly become inaccessible to guest molecules below certain temperatures, previous attempts to explain this phenomenon have failed. Here we show that this anomalous sorption behaviour is a temperature-regulated guest admission process, where the pore-keeping group’s thermal fluctuations are influenced by interactions with guest molecules. A physical model is presented to explain the atomic-level chemistry and structure of these thermally regulated micropores, which is crucial to systematic engineering of new functional materials such as tunable molecular sieves, gated membranes and controlled-release nanocontainers. The model was validated experimentally with H 2 , N 2 , Ar and CH 4 on three classes of microporous materials: trapdoor zeolites, supramolecular host calixarenes and metal-organic frameworks. We demonstrate how temperature can be exploited to achieve appreciable hydrogen and methane storage in such materials without sustained pressure. These findings also open new avenues for gas sensing and isotope separation. Regulating guest access and release in porous materials remains an important goal. Here, May and colleagues elucidate the mechanism by which guest admission can be temperature-regulated in typical microporous materials, and experimentally exploit this process to achieve appreciable and reversible hydrogen storage.

Adsorption equilibria and kinetics are two sets of properties crucial to the design and simulation of adsorption based gas separation processes. The adsorption equilibria and kinetics of N2 and CH4 on commercial activated carbon Norit RB3, zeolite 13X, zeolite 4A and molecular sieving carbon MSC-3K 172 were studied experimentally at temperatures of (273 and 303) K in the pressure range of (5–120) kPa. These measurements were in part motivated by the lack of consistent adsorption kinetic data available in the literature for these systems, which forces the use of empirical estimates with large uncertainties in process designs. The adsorption measurements were carried out on a commercial volumetric apparatus. To obtain reliable kinetic data, the apparatus was operated in its rate of adsorption mode with calibration experiments conducted using helium to correct for the impact of gas expansion on the observed uptake dynamics. Analysis of the corrected rate of adsorption data for N2 and CH4 using the non-isothermal Fickian diffusion (FD) model was also found to be essential; the FD model was able to describe the dynamic uptake observed to better that 1% in all cases, while the more commonly applied isothermal linear driving force model was found to have a relative root mean square deviation of around 10%. The measured sorption kinetics had no dependence on gas pressure but their temperature dependence was consistent with an Arrhenius-type relation. The effective sorption rates extracted using the FD model were able to resolve inconsistencies in the literature for similar measurements.

Hydrate risk management is critically important for an energy industry that continues to see increasing demand. Hydrate formation in production lines is a potential threat under low temperature and high-pressure conditions where water and light gas molecules are present. Here, we introduce a 1-inch OD single-pass flow loop and demonstrate the Joule-Thomson (JT) expansion of a methane-ethane mixture. Initially, dry gas flowed through the apparatus at a variable pressure-differential. Larger pressure differentials resulted in more cooling, as predicted by standard thermodynamic models. A systematic deviation noted at higher pressure differentials was partially rectified through corrections incorporating heat transfer, thermal mass and kinetic energy effects. A wet gas system was then investigated with varying degrees of water injection. At the lowest rate, hydrate plugging occurred close to the expansion point and faster than for higher injection rates. This immediate and severe hydrate plugging has important implications for the design of safety relief systems in particular. Furthermore, this rate of plugging could not be predicted by existing software tools, suggesting that the atomization of liquids over an expansion valve is a critical missing component that must be incorporated for accurate predictions of hydrate plug formation severity.

Knowledge of thermodynamic properties of aqueous solutions of CO 2 is crucial for various applications including climate science, carbon capture, utilisation and storage (CCUS), and seawater desalination. However, there is a lack of reliable experimental data, and the equation of state (EOS) predictions are not reliable, particularly for sound speeds in low CO 2 concentrations typical of water resources. For this reason, we have measured speeds of sound in three different aqueous solutions containing CO 2 . We report speeds of sound in the single-phase liquid region for binary mixtures of water and CO 2 for mole fractions of CO 2 of 0.0118, 0.0066 and 0.0015 at temperatures from 273.15 K to 313.15 K and at pressures up to 50 MPa, measured using a dual-path pulse-echo apparatus. The relative standard uncertainties of the sound speeds are 0.05 %, 0.03 % and 0.01 % at 0.0118, 0.0066 and 0.0015 CO 2 mole fractions, respectively. The change in sound speeds as functions of composition, pressure and temperature are analysed in this study. We find that dissolution of CO 2 in water increases its sound speeds at all conditions, with the greatest increase occurring at the highest mole fractions of CO 2 . Our sound speed data agree well with the limited available experimental data in the literature but deviate from the EOS-CG of Gernert and Span by up to 7 % at the lowest temperatures, highest pressures, and highest CO 2 mole fraction. The new low-uncertainty sound speed data presented in this work could provide a basis for development of an improved EOS and in establishing reliable predictions of the change in thermodynamic properties of seawater-like mixtures due to absorption of CO 2 gas.

Functionalized porous materials could play a key role in improving the efficiency of gas separation processes as required by applications such as carbon capture and storage (CCS) and across the hydrogen value chain. Due to the large number of different functionalizations, new experimental approaches are needed to determine if an adsorbent is suitable for a specific separation task. Here, it is shown for the first time that Raman spectroscopy is an efficient tool to characterize the adsorption capacity and selectivity of translucent functionalized porous materials at high pressures, whereby translucence is the precondition to study mass transport inside of a material. As a proof of function, the performance of three silica ionogels to separate an equimolar (hydrogen + carbon dioxide) gas mixture is determined by both accurate gravimetric sorption measurements and Raman spectroscopy, with the observed consistency establishing the latter as a novel measurement technique for the determination of adsorption capacity. These results encourage the use of the spectroscopic approach as a rapid screening method for translucent porous materials, particularly since only very small amounts of sample are required. For the first time, Raman spectroscopy is applied to characterize the adsorption capacity and selectivity of translucent functionalized porous materials. Results for the adsorption of an equimolar (hydrogen + carbon dioxide) gas mixture on three silica ionogels are presented. Validation is carried out by comparison with accurate gravimetric adsorption measurements.

“Breathing” and “gating” are striking phenomena exhibited by flexible metal-organic frameworks (MOFs) in which their pore structures transform upon external stimuli. These effects are often associated with eminent steps and hysteresis in sorption isotherms. Despite significant mechanistic studies, the accurate description of stepped isotherms and hysteresis remains a barrier to the promised applications of flexible MOFs in molecular sieving, storage and sensing. Here, we investigate the temperature dependence of structural transformations in three flexible MOFs and present a new isotherm model to consistently analyse the transition pressures and step widths. The transition pressure reduces exponentially with decreasing temperature as does the degree of hysteresis (c.f. capillary condensation). The MOF structural transition enthalpies range from +6 to +31 kJ·mol −1 revealing that the adsorption-triggered transition is entropically driven. Pressure swing adsorption process simulations based on flexible MOFs that utilise the model reveal how isotherm hysteresis can affect separation performance. Flexible metal–organic frameworks that undergo structural transformations upon gas sorption show great promise for applications in gas storage and separation, but accurately describing their stepped isotherms and hysteresis remains a challenge. Here, the authors introduce an empirical model to describe hysteretic MOF sorption isotherms and determine their temperature dependence, which is asymptotic at low temperatures.

The formation and the blockage of plant equipment such as heat exchangers by heavy hydrocarbon (HHC) solids is an inherent risk in cryogenic natural gas processing. The accuracy of the gas mixture’s compositional characterization significantly impacts the reliability of solid formaiton temperature predictions. Recently, we showed that complete characterization of the mixture is necessary to obtain accurate predictions of the melting temperature, as current methods based on pseudocomponent characterizations of HHCs are inadequate. Here, we present an improved method of characterizing HHCs that represents each pseudocomponent up to C14+ by a paraffinic, isoparaffinic, naphthenic and aromatic (PINA) composition and allocates an associated defined component to represent these sub-fractions. This new, extended PINA-based characterization of HHC pseudocomponents is derived from 46 different pipeline natural gas samples, and the method is validated against three representative gas samples that were fully characterized. The melting temperatures of the three gas samples based on their full characterizations are 263.2 K (14.1 °F), 260.1 K (8.5 °F) and 248.3 K (−12.8 °F), respectively. Predictions made with the new method match these within (1 to 2) K, while previous correlation methods under-predict them by (10 to 20) K. The improved performance arises from (1) the selection of suitable discrete components to represent each PINA fraction within a pseudocomponent, (2) the more representative distribution of PINA fractions as a function of carbon number, and (3) the use of discrete components to represent the pseudocomponent’s thermodynamic properties in both the fluid and solid phases. These results show how the new characterization method can reliably predict HHC freeze-out conditions, particularly when a full compositional analysis is unavailable. Future research should aim to test the new method on natural gas samples from regions other than the US Gulf Coast.

Lessons from launching a spin-off company: invest in collaborations and engineering, and protect intellectual property to speed up tech development. Lessons from launching a spin-off company: invest in collaborations and engineering, and protect intellectual property to speed up tech development.