Carbon–GO Composites with Preferential Water versus Ethanol Uptake

The elimination of small amounts of water from alcohols is by no means a trivial issue in many practical applications like, for instance, the dehumidification of biocombustibles. The use of carbonaceous materials as sorbents has been far less explored than that of other materials because their hydrophobic character has typically limited their water uptake. Herein, we designed a synthetic process based on the use of eutectic mixtures that allowed the homogeneous dispersion of graphene oxide (GO) in the liquid containing the carbon precursor, e.g., furfuryl alcohol. Thus, after polymerization and a subsequent carbonization process, we were able to obtain porous carbon–GO composites where the combination of pore diameter and surface hydrophilicity provided a remarkable capacity for water uptake but extremely low methanol and ethanol uptake along the entire range of relative pressures evaluated in this work. Both the neat water uptake and the uptake difference between water and either methanol or ethanol of our carbon–GO composites were similar or eventually better than the uptake previously reported for other materials, also exhibiting preferential water-to-alcohol adsorption, e.g., porous coordination polymers, metal–organic frameworks, polyoxometalates, and covalent two-dimensional nanosheets embedded in a polymer matrix. Moreover, water versus alcohol uptake was particularly remarkable at low partial pressures in our carbon–GO composites.This work was supported by MINECO/FEDER (Project Numbers MAT2015-68639-R, MAT2016-80285-P, and RTI2018-097728-B-I00). L.Z.G. acknowledges the Chinese Scholarship Council for a PhD research fellowship (CSC No. 201608330266). C.C.-C. acknowledges UA for a research contract

Metal-Free Modified Boron Nitride for Enhanced CO2 Capture

Porous boron nitride is a new class of solid adsorbent with applications in CO2 capture. In order to further enhance the adsorption capacities of materials, new strategies such as porosity tuning, element doping and surface modification have been taken into account. In this work, metal-free modification of porous boron nitride (BN) has been prepared by a structure directing agent via simple heat treatment under N2 flow. We have demonstrated that textural properties of BN play a pivotal role in CO2 adsorption behavior. Therefore, addition of a triblock copolymer surfactant (P123) has been adopted to improve the pore ordering and textural properties of porous BN and its influence on the morphological and structural properties of pristine BN has been characterized. The obtained BN-P123 exhibits a high surface area of 476 m2/g, a large pore volume of 0.83 cm3/g with an abundance of micropores. More importantly, after modification with P123 copolymer, the capacity of pure CO2 on porous BN has improved by about 34.5% compared to pristine BN (2.69 mmol/g for BN-P123 vs. 2.00 mmol/g for pristine BN under ambient condition). The unique characteristics of boron nitride opens up new routes for designing porous BN, which could be employed for optimizing CO2 adsorption

Measurement of Sorption-Induced Strain

Strain caused by the adsorption of gases was measured in samples of subbituminous coal from the Powder River basin of Wyoming, U.S.A. and high-volatile bituminous coal from east-central Utah, U.S.A. using an apparatus developed jointly at the Idaho National Laboratory (Idaho Falls, Idaho, U.S.A.) and Colorado School of Mines (Golden, Colorado, U.S.A.). The apparatus can be used to measure strain on multiple small coal samples based on the optical detection of the longitudinal strain instead of the more common usage of strain gauges, which require larger samples and longer equilibration times. With this apparatus, we showed that the swelling and shrinkage processes were reversible and that accurate strain data could be obtained in a shortened amount of time. A suite of strain curves was generated for these coals using gases that included carbon dioxide, nitrogen, methane, helium, and various mixtures of these gases. A Langmuir-type equation was applied to satisfactorily model the strain data obtained for pure gases. The sorption-induced strain measured in the subbituminous coal was larger than the high-volatile bituminous coal for all gases tested over the range of pressures used in the experimentation, with the CO2-induced strain for the subbituminous coal over twice as great at the bituminous coal

Activated carbon materials with a rich surface chemistry prepared from L-cysteine amino acid

A series of activated carbon materials have been successfully prepared from a non-essential amino acid, such as L-cysteine. The synthesized carbons combine a widely developed porous structure (BET surface area up to 1000 m2/g) and a rich surface chemistry (mainly oxygen, nitrogen and sulphur functionalities). These surface functional groups are relatively stable even after a high temperature thermal treatment (O>N∼S). Experimental results show that these samples with a rich surface chemistry exhibit a significant improvement in their hydrophilic character. Although the role of the surface functional groups is less pronounced for the adsorption of non-polar molecules such as CO2, CH4 and C2H4, their adsorption at atmospheric pressure is to some extend conditioned by the characteristics of the adsorbent-adsorbate interactions. The synthesized carbons exhibit an excellent adsorption performance for CO2 (up to 3 mmol/g at 0°C). Furthermore, samples with a low activation degree exhibit molecular sieving properties with very promising CO2/CH4 (up to 4.5) and C2H4/CH4 (up to 6) selectivity ratios. These results anticipate that non-essential amino acids are a versatile platform to obtain carbon materials combining a tailored porous structure and rich multifunctional surface chemistry and with potential application for gas adsorption/separation processes.Authors would like to acknowledge financial support from the MINECO (Projects PID2019-108453GB-C21 and PCI2020-111968/ERANET-M/3D-Photocat) and NATO SPS program (Project G5683)

Pyrolyzed chitosan-based materials for CO2/CH4 separation

Chitosan is a biopolymer obtained by deacetylation of chitin extracted from sub-products of the food industry and it is rich in nitrogen content. Pyrolyzed chitosan– and chitosan-periodic mesoporous organosilica (PMO)– based porous materials with different pore structures and chemical features are prepared using different dry methods and ensuing pyrolysis at 800 °C, for application in the CO2/CH4 adsorption/separation. The highest CO2 adsorption capacity (1.37 mol·kg−1 at 100 kPa; 1.9 mol·kg−1 at 500 kPa) and the best selectivity for CO2/CH4 separation (95 at 500 kPa) is obtained using 1.5% (m/v) of chitosan solution dried under supercritical CO2. This material combines a good CO2 adsorption capacity with one of the highest selectivities for CO2/CH4 separation of the literature, arising as a promising alternative adsorbent for natural gas or biogas upgrading at reduced cost. The presence of high nitrogen content together with pores of diameter around 2 nm leads to an increase of the CO2 adsorption capacity. In the case of chitosan-PMO-based materials, the activation step using both acid and crushing methods is crucial to increase the CO2 adsorbed amount. Here, the highest CO2 adsorption capacity and the highest selectivity are obtained by the chitosan-PMO crushed adsorbent and the chitosan-PMO material activated with sulfuric acid, respectively. These observations indicate the importance of the controlled attack of the material surface to enhance the diffusion of the target gases within the adsorbent, avoiding the adsorption of other species.publishe

Properties and Applications of Metal Phosphates and Pyrophosphates as Proton Conductors

We review the progress in metal phosphate structural chemistry focused on proton conductivity properties and applications. Attention is paid to structure–property relationships, which ultimately determine the potential use of metal phosphates and derivatives in devices relying on proton conduction. The origin of their conducting properties, including both intrinsic and extrinsic conductivity, is rationalized in terms of distinctive structural features and the presence of specific proton carriers or the factors involved in the formation of extended hydrogen-bond networks. To make the exposition of this large class of proton conductor materials more comprehensive, we group/combine metal phosphates by their metal oxidation state, starting with metal (IV) phosphates and pyrophosphates, considering historical rationales and taking into account the accumulated body of knowledge of these compounds. We highlight the main characteristics of super protonic CsH2PO4, its applicability, as well as the affordance of its composite derivatives. We finish by discussing relevant structure–conducting property correlations for divalent and trivalent metal phosphates. Overall, emphasis is placed on materials exhibiting outstanding properties for applications as electrolyte components or single electrolytes in Polymer Electrolyte Membrane Fuel Cells and Intermediate Temperature Fuel Cells.This research was funded by PID2019110249RB-I00 (MICIU/AEI, Spain) and PY20-00416 (Junta de Andalucia, Spain/FEDER) research projects. M.B.-G. thanks PAIDI2020 research grant (DOC_00272 Junta de Andalucia, Spain) and R.M.P.C. thanks University of Malaga under Plan Propio de Investigación for financial support

Study on the Effect of Coal Drying in AdsorbingC02 at Different Temperature and pH

C02 is the primary green house gas representing roughly 83% of the anthropogenic effect. One of the options to mitigate the rising atmospheric concentration of CO2 is through CO2 geologic sequestration in coal seams process. Part of understanding the sequestration is to study what is the effect on the rate of CO2 adsorption at different temperature and pH in a coal mine environment. The objectives of this study are to investigate CO2 gas adsorption patterns on local coal sample at different temperature,pH and particle sizes. It is also to determine the basic properties of the local coal sample and determine how the characteristic of the coal sample affects the adsorption rate of CO2 gas. In the characterization ofthe coal sample process, there were a number ofparameters which was studied and tested. They were the moisture content, the ash content, carbon content and mineral content of the coal sample. For the study on the effect of varying parameters on the CO2 adsorption on coal seams, the CO2 adsorption behavior was investigated using a manometric apparatus. The experimental set-up will be used in the investigation of the effects of temperature (24.6°C, 30°C, 40°C and 55°C) pH (acidic of pH 0.51, near neutral of pH 5.97 and alkali of pH 12.40), and particle size (lOOOum and 2000um) of the CO2 adsorption rate on the local coal sample. The moisture content of the coal sample was found to be 37.4%. The ash content analysis gave a percentage ash of 11.02%). The elemental composition analysis gave an elemental carbon content of 56% to 60%. The mineral matter in the coal sample was found to be 12.09%. The chemical elements analysis indicated silica as having the highest amount in the coal sample. The experiments conducted for the study of the CO2 adsorption in coal seams showed that smaller particle size lOOOum had a higher adsorption rate per mass of coal sample as compared to the 2000um sample. The effect of increasing the temperature is to decrease the equilibrium adsorption capacity of the coal samples. It can be observed that the untreated coal sample has the highest extent of adsorption capacity followed by the acidic, alkali and neutral conditions. The coal samples were found to be of lignite type. From literature review, coals of lignite type were found to exhibit the most sorption tendency towards CO2 as compared to coals of other ranks

Synthesis and modification of porous boron nitride materials for application in carbon dioxide capture

Global warming, which is often confused with “climate change”, can cause longlasting, irreversible, catastrophic and far-reaching effects on the earth and the lives of the future generations. There is a unanimous agreement that global warming is mainly due to human activities and above all, burning fossil fuels for industrial applications and emission of CO2 as one of the major contributors of global warming. To mitigate the amount of CO2 emission and to offset its effect, the governments around the world have united to take necessary actions in an effective and efficient way by a variety of policy changes and adoption of technologies such as carbon capture and storage. For instance, the UK government has set out measures to tackle climate change with a plan for the UK to be a pioneering economy in the world towards a zero-emission economy by 2050. Among the technologies used for carbon capture, those derived from solid sorbents for CO2 capture attract growing interest in industrial applications. The popularity of using these technologies is attributed to their lower energy penalty, high selectivity, recyclability and ease of manufacturing. Developments of new materials with low cost is fundamental, even though numerous solid sorbents have been examined for CO2 capture to date. Porous boron nitride (BN) has been recognised as a promising alternative to be used in carbon adsorption process due to its unique advantages including its bond polarity, tuneability and high thermal and chemical stabilities. So far, a systematic understanding of how its distinctive properties (pore structure and chemistry) contributes to capture carbon dioxide is still lacking. To develop a favourable porous BN, further work is required to establish the viability of these materials as cost-effective adsorbents. This research presents synthesis and modification strategies of porous BN and a characterisation of the material for carbon capture application. Various synthesis conditions have been developed to obtain high surface area (>700 m2/g) pristine BN material via template free method. The study pursued two distinct strategies to modify pristine porous BN, aiming to enhance its CO2 adsorption performance. Firstly, a focus on controlling the pure BN porosity has been implemented by tuning with a polymeric surfactant as non-metal modification approach. The capacity of pure CO2 on nonmetal modified porous BN has been enhanced by about 34.5% compared to pristine BN in ambient conditions. The study highlights the significant role of porosity/pore size of BN for CO2 adsorption. Secondly, a novel approach has been implemented for modifying pore structure and surface chemistry of pristine BN by introduction of Ni (II) into BN framework. The pure CO2 capture experiment has been assessed, considering three different temperatures and the results confirmed that the basic sites on porous BN contribute to its ability to adsorb more CO2 relative to pure BN. The method has been validated as a feasible route to improve porous BN performance in CO2 adsorption process even at realistic flue gas temperatures (above 298 K). Finally, the stability and reusability of pristine BN samples with various porosity and chemistry have been examined over the eight adsorption-desorption cycles. Overall, this dissertation demonstrated that porous BN materials possess a combination of desirable properties with flexibility for functionalisation and lower regeneration energy. Thus, it can be considered as an effective adsorbent for future large-scale carbon capture technologies

Doctor of Philosophy

dissertationWith the consistently growing demand for liquid hydrocarbons there have been new technologies to meet those demands. Some of the new technologies focus on removing a resource from an underground repository using some form of thermal treatment to pyrolyze the material in the formation, either coal or oil shale, to create and produce hydrocarbons. In order to offset some of the carbon dioxide that would be produced in heating underground formations, the possibility of long-term sequestration was investigated for the remnants of said pyrolysis processes. There are four mechanisms for subsurface storage of CO2: adsorption, mineralization, pore volume storage, and dissolution into the connate water. Sequestration in a pyrolyzed coal seam relies heavily on the adsorption of CO2 and is similar in concept to enhanced coal bed methane. Utah Skyline bituminous, Illinois Carlinville bituminous, and Wyoming North Antelope subbituminous coals were pyrolyzed to final temperatures of 325, 450, or 600°C with heating rates of either 10 or 0.1°C/minute. Adsorption isotherms, pore size studies, and permeability measurements were performed on the reacted and unreacted coals. The adsorption of CH4 and CO2 on the thermally treated coals increases with treatment temperature and is related to the pore size distributions. Pore size studies found a fraction of the surface area and micro- and mesopores can are attributable to residual tars. Permeability measured on the treated coals generally shows increases with treatment temperature. Sequestration in a pyrolyzed oil shale demonstrates all four sequestration mechanisms. Mineralization studies were carried out with a retorted Green River oil shale in the liquid and gas phase. Results of the mineralization study showed that the dissolution of pyrrhotite with siderite was the most prevalent path for CO2 mineralization. The combined effects of mineralization, pore volume, and adsorption were also simulated and found the most common result to be 40 kg/tonne of CO2 stored

Measurement and Modeling of Sorption-Induced Strain and Permeability Changes in Coal

Strain caused by the adsorption of gases was measured in samples of subbituminous coal from the Powder River basin of Wyoming, U.S.A., and high-volatile bituminous coal from the Uinta-Piceance basin of Utah, U.S.A. using a newly developed strain measurement apparatus. The apparatus can be used to measure strain on multiple small coal samples based on the optical detection of the longitudinal strain. The swelling and shrinkage (strain) in the coal samples resulting from the adsorption of carbon dioxide, nitrogen, methane, helium, and a mixture of gases was measured. Sorption-induced strain processes were shown to be reversible and easily modeled with a Langmuir-type equation. Extended Langmuir theory was applied to satisfactorily model strain caused by the adsorption of gas mixtures using the pure gas Langmuir strain constants. The amount of time required to obtain accurate strain data was greatly reduced compared to other strain measurement methods. Sorption-induced changes in permeability were also measured as a function of pres-sure. Cleat compressibility was found to be variable, not constant. Calculated variable cleat-compressibility constants were found to correlate well with previously published data for other coals. During permeability tests, sorption-induced matrix shrinkage was clearly demonstrated by higher permeability values at lower pore pressures while holding overburden pressure constant. Measured permeability data were modeled using three dif-ferent permeability models from the open literature that take into account sorption-induced matrix strain. All three models poorly matched the measured permeability data because they overestimated the impact of measured sorption-induced strain on permeabil-ity. However, by applying an experimentally derived expression to the measured strain data that accounts for the confining overburden pressure, pore pressure, coal type, and gas type, the permeability models were significantly improved