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Gallium as a solvent liquid metal catalyst is used in an energy efficient, high yield and controlled reaction between lithium and CO2. A liquid metal electrode and the naturally formed surface products are used as a supercapacitor.

CO2 hydrogenation to methanol is attracting specific interest because of its potential economic and environmental benefits in transforming waste CO2 to value-added hydrocarbons. Copper-based catalysts are documented as efficient and widely applied, whereas insufficient catalytic properties of conventional catalysts hinder their application. Herein, catalysts using Mg-Al hydrotalcite (HT) as the carrier of Cu/ZnO/ZrO2 (CZZ) nanoparticles were prepared to exploit special advantages of hydrotalcite on copper dispersion and catalytic performance. The results show that CZZ nanoparticles can be uniformly dispersed on external surfaces of HT, elevating BET surface areas of CZZ-HT samples by at least 2.5 times compared to pure CZZ. The HT carrier also enriches strong basic sites and hence elevates CO2 adsorption capabilities in the range of reaction temperature. Both copper surface area and copper dispersion of CZZ-HT samples are improved dramatically. A catalyst containing 45.1 wt% of CZZ shows 1.1 times higher copper surface area per gram CZZ and 1.6 times higher copper dispersion than the reference CZZ. Subsequent reactions demonstrate the CZZ-HT samples show remarkably promoted turnover frequency (TOF) for methanol synthesis and retain considerable catalyst stability. The typical catalyst prepared in this research, at the reaction temperature of 523 K and pressure of 3.0 MPa, presents a 68.2% higher methanol STYCu per gram copper and an 117.0% higher SMeOH/SCO ratio than the commercial catalyst. The support HT plays a crucial role for the enhanced catalytic performance physically and chemically. Thus, the as-prepared CZZ-HT catalyst provides a significant improvement for CO2 utilization.

Adsorption materials play a key role in determining the efficiency of the pressure swing adsorption process. The selectivity of CO2 over CH4 on most zeolite adsorbents drops dramatically with incre...

In this study, we report the solubility of the gases carbon monoxide (CO) and hydrogen (H2) in methanol and methyl formate using the synthetic isothermal method via total pressure measurement. The ...

In this study, a novel green strategy through fusion hydrothermal method was adopted for in-situ synthesis of chabazite. The morphological and physiochemical characteristic of the prepared adsorbent was determined by X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. The characterization results revealed that prepared chabazite posses fine particles (2–5 µm) and porous structure which could be employed for capture of CO2 molecules. In order to gain an understanding of the adsorption performance of prepared adsorbent, different types of adsorption isotherms and kinetic adsorption models were studied. The results indicated that synthesized adsorbent has shown significant high CO2 adsorption capacity as well as CO2/N2 selectivity. As compare to pseudo-first-order, pseudo-second-order and Elovich model, the kinetics data of CO2 adsorption on chabazite fitted well with the Bangham model. This strategy may be a novel approach for large-scale synthesis of chabazite that exhibits excellent adsorption performance for industrial CO2 capture.

CO2 hydrogenation to methanol plays an increasingly important role in fields of chemical engineering, energy generation and H2/CO2 utilization, and the prohibitive costs result partially from the high operating pressures required for practical application. Thus, a hybrid catalyst/adsorbent consisting of Cu-ZnO-ZrO2 supported on hydrotalcite (named CZZ@HT) was synthesized, characterized and analyzed in this study with the intent that the adsorbent hydrotalcite would enhance the local concentration of CO2 and assist in catalyst dispersion. The as-prepared CZZ@HT catalyst containing 43.4 wt% of CuO-ZnO-ZrO2 in the form of well dispersed nanoparticles possessed a considerable BET surface area and external surface area after reduction. A remarkable copper dispersion of 58.7% was thereby achieved. This reduced catalyst displayed elevated uptakes of H2O and CO2 at 473 K compared to the reference adsorbent-free catalyst and presented enhanced adsorption capacities of CO2 at reaction temperatures due to collective effects of physisorption and chemisorption. Catalysis experiments on a fixed bed reactor using the rCZZ@HT catalyst showed a methanol selectivity of 83.4% and a SMeOH/SCO ratio of 5.0 in products. A control experiment in which hydrotalcite was replaced with quartz (named rCZZ&QS) showed considerably lower conversion at low pressure and demonstrated the enhancing effect of the hydrotalcite support. The new catalyst could achieve the same methanol productivity as the control catalyst at 2.45 MPa lower reaction pressure. This lower pressure corresponds to a ∼61.3% savings in energy consumption for compression. Accordingly, the CZZ@HT is a promising candidate for CO2 hydrogenation to methanol at moderate pressures.

Upgrading coal mine methane (CMM) with adsorption method is an effective way to enhance the energy utilizing efficiency and reduce greenhouse gas emissions. In this work, adsorption equilibrium and kinetics of CH4, N2 and O2, as typical components in CMM, on three carbon molecular sieves (CMSs) and the corresponding separation performances were studied. The equilibrium and kinetic selectivity were obtained from adsorption isotherms fitted with the Langmuir model and uptake curves fitted with the micropore-diffusion model, respectively. O2 with the highest diffusion time constant among three gases suggests the advantage of CMS-based kinetic separation in deoxygenation of CMM and the critical role that N2/CH4 kinetic separation plays in CH4 enrichment. CMS-1 with the highest microporosity has the largest adsorption capacities, and CMS-3 with a proper average pore size has the greatest N2/CH4 kinetic selectivity. The actual separation performances shown by CH4/N2/O2 breakthrough curves according to the principle for practical CMM upgrading processes exhibit the order of CMS-1 > CMS-3 > CMS-2 which is inconsistent with that of the conventional N2/CH4 selectivity highly due to the underestimation of effects of N2 equilibrium adsorption relative to N2 kinetic selection without covering specific adsorption range corresponding to practical working capacity region. A modified selectivity with consideration of actual N2 amount adsorbed was therefore developed, showing the correct performance order and the potential to be used as a practical adsorbent selection parameter. An advanced CMS materials design with proper existence of microporosity would benefit practical CMM upgrading in terms of reaching an optimal balance between adsorption equilibrium and kinetics.

Electrical swing adsorption (ESA) is an interesting cyclic adsorption technology which relies on rapid Joule heating of the adsorbent to liberate adsorbed molecules such as CO2. In this study we used a novel hybrid zeolite/activated carbon honeycomb to implement ESA and compared it to conventional vacuum swing adsorption (VSA) for CO2 capture. We then combined electrical and vacuum swing adsorption (VESA) to assess the merits of this dual regeneration technology for recovering CO2 from a 15% CO2/N2 gas stream at low pressure. With a simple VSA-only cycle, a CO2 downstream purity of only 17–23% was achievable when the desorption pressures varied from 30 to 10 kPa. This was primarily due to the adsorbent’s poor adsorption characteristics which provided little change in CO2 adsorption capacity over this pressure range. A CO2 product purity of 15–34% and a recovery of 29–78% was achieved with ESA as the electrification time was extended from 30 s to 180 s. The combined VESA process provided a CO2 purity of 33% and recovery of 72% with a short electrification time of 30 s at a mild desorption pressure of 10 kPa. Energy calculations indicate that the total specific energy for VESA was lower than ESA alone but still higher than VSA, although the latter suffered from low purity.

Methanol synthesis via CO2 hydrogenation is an important part of the strategy for generating clean energy as we attempt to reduce our dependency on fossil fuels. Conventional catalysts for this reaction need improvement in their methanol selectivity. In this work, a layered double hydroxide (Mg-Al LDH) was used as a carrier for Cu-ZnO-ZrO2 to produce a catalyst by co-precipitation. From characterization results, CuO-ZnO-ZrO2 nanoparticles were formed and were uniformly dispersed and attached to the surface of LDH. BET surface area and copper dispersion of the catalysts were significantly improved by 4.3 times and 2.9 times, respectively, compared with a reference catalyst without the support. In a catalytic reaction, the catalyst showed dramatic methanol selectivity of 78.3% at 523 K and 3.0 MPa, which is 14.4% higher than the commercial catalyst measured in this investigation and about 50% higher than conventional copper-based catalysts in literatures. It also showed over twice the space time yield based on active metal sites compared to a commercial catalyst in the temperature range 473 K–573 K. Therefore, the prepared catalyst can be efficiently applied at relatively mild reaction temperatures and pressures.

Modelling dynamic adsorption of sulfur dioxide (SO2) on activated carbons (ACs) is significant in guiding practical desulphurization processes and making highly efficient use of adsorbents in terms of the adsorption rate which largely depends on particle size. In this work, models derived from the Vermeulen and an improved linear driving force (LDF) rate equation were studied for the first time on SO2 adsorption over AC particles with different sizes. For larger particles (≥3 mm), breakthrough curves predicted by the Vermeulen equation showed good agreement with experimental data, demonstrating that intraparticle diffusion resistance varied with particle size, feed concentration, adsorption time and location. For smaller particles (1 mm), a correction on the volume-averaged adsorption capacity as a function of adsorption time and saturation in the rate equation was developed to avoid the underestimation of adsorption rate due to the inappropriate parabolic concentration profile inherent in the conventional LDF model. By providing a concentration gradient and adsorption rate closer to actual values, the improved LDF equation was confirmed to provide excellent prediction results on 1-mm particles. Different modelling characteristics of the two models indicates varying effects of intraparticle diffusion on adsorption rate with particle size regarding the specificity of SO2 physisorption on ACs.

The CO2CRC, in collaboration with The University of Melbourne (UoM) and the University of New South Wales (UNSW), tested two novel CO2 capture technologies aimed for both on-shore and off-shore natural gas applications. The tests involved materials testing in a state-of-the-art experimental capture rig at CO2CRC’s Otway International Test Centre followed by simulation and techno-economic activities for scaled up facilities. The goal was to develop robust and compact technology for high pressure natural gas separation over a range of adjusted high CO2 concentrations mimicking various gas field conditions. The tests were conducted for adsorbents and membranes in a high-pressure rig incorporating both pressure swing adsorption (PSA) and membrane technologies. It was found that adsorption, a second-generation technology with a low footprint is very suitable for natural gas separation with higher separation efficiency, contrary to the general perception. The stable separation performance of the thin film composite hollow fibre membranes was particularly encouraging among all membranes tested. This paper will discuss novel adsorbent and membrane development and their quantitative performance in the test campaigns followed by suggested next steps in the TRL towards commercial application. It is anticipated further research and testing at higher Technology Readiness Level (TRL) levels 5/6 would be necessary to make them commercial ready. These technologies, if successful, would facilitate developing new gas fields to recover methane in a cost-effective manner which is currently uneconomical with conventional technologies.

There is an increasing global attention toward hydrogen as a green energy carrier, primarily because of the environmental concerns associated with global warming issues. It is expected that the produced hydrogen from various sources may be injected to the natural gas grid for economical transportation and use. One interesting option is to evaluate technologies for extracting the hydrogen from the natural gas pipeline for applications using high purity hydrogen. However, natural gas is a complex mixture including CH4, C2H6, CO2, N2 and trace amounts of C3-C6 hydrocarbons. This function requires a natural gas/hydrogen separation technology which must not only operate with low capital and energy cost, but must also provide hydrogen of sufficient purity. The goal of current work therefore was to take a mixture of hydrogen/natural gas of representative concentrations and produce high purity hydrogen using a bespoke pressure swing adsorption (PSA) cycle. A six-bed PSA system with 12 steps was developed and simulated in Aspen Adsorption software to this end. A three-layered adsorption column was designed to capture different groups of components of the mixture selectively within each layer. Informed by measured and literature equilibrium isotherm data, silica gel was chosen as the pre-layer to remove heavy hydrocarbon components and most of the CO2; activated carbon in the main-layer to mainly adsorb methane, and LiLSX zeolite in the top-layer to remove trace nitrogen which had eluted from the earlier layers, for obtaining pure hydrogen product. High purity hydrogen product (>99%) with high recovery (>85%) was achieved with the PSA system for different hydrogen concentrations (5–30%) in the 30 bar feed stream. We also compared the PSA system against an electrolyzer generating hydrogen onsite. Our analysis suggests that the PSA competes favorably, even at a low hydrogen recovery of 40% in cases where the PSA plant is built at a pressure reduction station.

High iron content is one of the challenges in utilizing the refractory bauxites in China. An improved method for treating the high-iron bauxite by roasting with (NH4)2SO4 was proposed, which offers a possible alternative method for utilizing the high-iron bauxite. The influences of the roasting time, roasting temperature, material ratio, and ore particle size on the extraction ratios of Fe and Al were studied, and the orthogonal test was used to optimize the reaction conditions. The optimized reaction conditions were proposed as follows: roasting temperature of 450 °C, roasting time of 120 min, material ratio of (NH4)2SO4 to ore of 2.5:1.0, and ore particle size below 80 μm. The roasting mechanism and kinetic parameters including the apparent activation energy and reaction rate constant were investigated. The results showed that the control step of the roasting process was the internal diffusion on the product layer and the apparent activation energy was 19.22 kJ mol−1 in the reaction temperature range. The kinetic equation was obtained finally.

The structure of ZSM-25, a RHO family zeolite, was resolved recently. Recent reports focused on Na-ZSM-25 as a promising CO2 adsorbent with high CO2 working capacity and exceptional CO2/CH4 ideal s...

Pure Cu nanowires as catalyst were prepared by electrochemical deposition and were used in CO2 hydrogenation to methanol. The active sites of the Cu based catalyst were discussed. The performance and structural development of the catalyst were observed during CO2 hydrogenation. A mechanism for the deactivation of the catalyst was discussed. The key factors that affect the deactivation of the catalyst were found. Cu nanowire sample was characterized by SEM, EDS, XRD, and BET. The results show that Cu nanowires have very high sintering resistance and catalytic stability. This helps to develop high performance catalysts. The changes in the grain size, SEM morphology and catalytic properties of the sample during CO2 hydrogenation show that the migration of the Cu atoms on the surface of the Cu nanowires can occur. Continuous migration of Cu atoms and sintering of Cu grains can lead to flow blockage in gas channels. The gas channel flow blockage or the sintering of Cu grains can lead to deactivation of the catalyst. However, the shape of catalytic performance curve indicates that the main reason for the deactivation of the catalyst is the gas channel flow blockage.

Electrical Swing Adsorption is a version of temperature swing adsorption in which the adsorbent is regenerated by Joule heating. To accomplish this feature, the adsorbent must be a continuous, electrically conducting member, which usually restricts the application to activated carbon samples. Unfortunately, the CO2 adsorption capacity and selectivity of activated carbon is not as good as silica-alumina materials such as zeolites. In addition, the low resistance of activated carbon samples often means that the dominant heat generation occurs at the contact resistance between the electrodes and the sample, depriving the bulk sample of temperature increase. Use of the silica-alumina materials though, is prevented by its electrically insulating properties. In the current work, we present a novel approach to solve this dilemma. We have synthesized a novel hybrid activated carbon (from phenolic resin) and zeolite NaUSY monolith with attractive electrical and adsorption properties. The adsorption capacity of CO2 on the novel adsorbent was more than twice that of an AC-only material prepared from phenolic resin. The electrical resistance increased from 4.59 × 10−4 Ω m for activated carbon to 1.18 × 10−2 Ω m for the hybrid adsorbent so that energy loss in the contacting surfaces between the adsorbent surface and copper electrode was reduced significantly from 73% of the total resistance to 18%. This novel hybrid adsorbent has excellent potential in ESA applications.

Improvement on oxygen (O2) concentrator using pressure swing adsorption (PSA) technology according to variable product demands is of great significance, which, for instance, provides the key step for success in practical O2 therapy for COVID-19 patients who need to be delivered with a wide product flow rate range (1–15 standard liter per minute (SLPM)) of medical O2 (purity > 82%). This work studied the individual effects of major PSA process parameters on O2 production performance at the product flow rate of 3.46–19.88 SLPM (0.64–3.68 SLPM per kilogram of adsorbent (SLPM/kg)), based on a self-designed two-bed PSA unit with a modified Skarstom cycle using Li-LSX zeolite adsorbents. The improvement strategies were accordingly proposed based upon influential mechanisms of each parameter: 1) at lower product flow rates (≤2.00 SLPM/kg), increasing the purge flow rate and decreasing the adsorption pressure to suppress excess O2 adsorption, and decreasing the feed flow rate to ensure low energy consumption; 2) at higher product flow rates (≥2.00 SLPM/kg), decreasing the purge flow rate and increasing the adsorption pressure to eliminate N2 breakthrough and O2-rich product waste, and appropriately increasing the feed flow rate to enhance cost-effectiveness. An improved set of parameters rendered O2 purity (95.67–74.86%), recovery (11.28–49.05%), productivity (0.47–2.04 mmol/kg/s) increased by up to 3.52–20.08%, 0.36–20.47%, 6.82–19.61%, and energy consumption (4.07–0.95 kWh/kgO2) decreased by up to 10.56–18.10%, in comparison to two conventional sets, respectively. The results are beneficial for developing intellectualized and flexibly-controlled O2 concentrators for practical applications.

Electrical Swing Adsorption (ESA) technology is an interesting option for rapid temperature swing adsorption to capture CO2 due to its highly efficient and rapid regeneration with the Joule effect. Electric current, electrification time and N2 purge rate have strong effects on ESA processing performance. In this study, these operating parameters were investigated experimentally and theoretically, for their effect on CO2 product purity, recovery, harvest time and energy consumption. For a feed stream of 15% CO2 balanced with N2 using a MAST© carbon monolith, CO2 purity and energy consumption significantly increased as electric current and electrification time increased; CO2 recovery increased as N2 purge rate increased; these three factors all impacted on CO2 productivity positively, that is, productivity increased with increase of each of electric current, electrification time and N2 purge rate. The optimal conditions obtained for CO2 capture using MAST© monolith in this study are electric current of 12 A, electrification time of 80 s and N2 purge rate of 600 ml/min (0.088 m/s). Under such optimal condition, a CO2 purity of 52%, and a recovery of 76% was achieved with an energy consumption of 5.64 MJ/kg.CO2.

High-purity NO2 and SO2 have significant economic values and are widely used in many fields. The large amounts of NO2 and SO2 in industrial flue gases are worthy of recovery for environmental protection and economic benefits. In this work, a dual-column distillation separation process was proposed to further separate and upgrade NO2 and SO2 following a flue gas adsorption capture process. The feasibility of distillation separation of NO2/SO2 from the desorbed gas, and the advantage of liquid-phase feeding way over gas-phase counterpart in terms of lower energy consumption (1286.39 kW) were demonstrated. Key process parameters such as the number of total stages, the feed stage number, the mole flow rate at bottom of column, the reflux ratio and operating pressure for the two columns (15, 6, 16.66 kmol/h, 0.16, 4 bar; 21, 10, 4.43 kmol/h, 0.50, 1 bar) were determined. Heat and mass transfers along the column height as well as the process robustness against feed composition fluctuation indicate its applicability for practical operation and adaptation to industrial needs. An economic analysis shows a significant annual revenue of 14,333.52 thousand USD based on high-purity (>99.5%) SO2 and NO2 products recovered from a typical scale (~1000,000 m3/h) of iron-ore sintering flue gas, not only offsetting the total operating cost of the entire adsorption capture-distillation recovery process but also generating net profit.

Nanoporous carbon-based composites derived from metal–organic frameworks (MOFs) have drawn increasing attention and hold promising potential in the application of gas adsorption and separation. Herein, we report the preparation and characterization of four novel carbon-based materials, converted from a non-porous Mg-MOF and a porous Zn-MOF which were both constructed by biphenyl-4,4′-dicarboxylic acid (BPDC) as bridging linkers in the structures. The phase transformation and structural evolution of the material were studied by in situ synchrotron powder X-ray diffraction with variable temperature. Interestingly, the results indicate the porosity generated by carbonization would be more dependent on the thermal stability rather than crystallographic intactness of the template MOFs. Moreover, the derived carbon materials selectively adsorb CO2 over N2 at moderate conditions, which would be promising for post-combustion carbon dioxide capture.

We reported a new polymorphous core-shell metal-organic framework (MOF) in the form of a three-dimensional MOF core wrapped in a two-dimensional layered MOF shell by applying a general acid-solvent synergy synthesis. This hybrid material can achieve high adsorptive selectivity/capacity simultaneously, which is validated by the unary isotherms of CO

The main objective of the current capture R&D at Otway Research Facility in Victoria, Australia is to facilitate field testing and evaluation of the state-of-the-art CO2CRC membrane and adsorption technologies for separation of CO2 during real natural gas (NG) processing. The ultimate goal is to develop robust and efficient capture technologies for high CO2 content NG separation at high pressure over a range of adjusted CO2 concentrations mimicking various gas field conditions. A skid mounted fully automated capture rig comprising of both the technologies has been in operation since early 2017 implementing a research plan developed by The University of Melbourne (UOM) and UNSW Australia. The testing plan has been going forward in stage campaigns, started first with commercial materials followed by testing new innovative materials which will then be tested against impurities, like H2S, one of the worst impurities found in natural gas production. This would facilitate firstly to develop new gas fields to recover methane, which is uneconomical with currently available technologies and at the same time to open up a cost-effective way of CCS implementation in gas processing fields.

CO2CRC’s capture program has established a formidable reputation over the past decade, not only for identifying practical advancements in solvent, membrane, adsorption, membrane contactor and cryogenic technologies for CO2 separation from flue gas, syngas and acid gas, but also for advancing the understanding of the principles that underpin these. CO2CRC, has successfully operated in-field pilot test facilities providing it with knowledge and expertise in the development of cost-effective solutions for carbon capture in local conditions thus making CO2 capture and utilization an attractive option to bring down the greenhouse gas emissions. CO2CRC is looking beyond energy and power sector and actively engaged in providing services and consultancy to carbon intensive industries like iron and steel industry, cement plants and production of hydrogen from coal with carbon capture.

Methane (CH4) is a cleaner fuel resource with relatively low carbon emissions and negligible particulate matters, heavy metals, and sulphur oxides, compared with those emission intensive fuels like coal. However, large amounts of CH4 emitted to the atmosphere drive significant greenhouse gas (GHG) effects due to the low value of its low concentration sources and technical difficulty of CH4/N2 separation. Therefore, it becomes crucial to advance the technology for separating low concentration CH4 from N2. In this study, a commercial activated carbon was used to separate CH4 from N2 with a 4-column vacuum swing adsorption (VSA) facility. Both light and heavy streams were firstly collected and stored in gas tanks, and then used for light/heavy purge. Four process modes involving A) 2-column and 8 steps, B) 3-column and 9 steps, C) 4-column and 16 steps, and D) 4-column and 20 steps were employed to investigate the effects of process design factors on their separation performance. Results showed that both pressure equalization and heavy product purge steps have significant impacts on product purity, recovery and productivity. In the case of 11.7 and 17.0% (CH4) feed gases, the methane products reached a purity around/above 30% and these gases can be compressed and transported for industrial utilization. Furthermore, the recovery of these low concentration methane gases will bring extra incentives with GHG mitigation benefits.

Different VSA (Vacuum Swing Adsorption) cycles and process schemes have been evaluated to find suitable process configurations for effectively separating CO2 from flue gases from different industrial sectors. The cycles were studied using an adsorption simulator developed in our research group, which has been successfully used to predict experimental results over several years. Commercial zeolite APGIII and granular activated carbon were used as the adsorbents. Three-bed VSA cycles with- and without-product purge and 2-stage VSA systems have been investigated. It was found that for a feed gas containing 15% CO2 (representing flue gas from power plants), high CO2 purities and recoveries could be obtained using a three-bed zeolite APGIII VSA unit for one stage capture, but with more stringent conditions such as deeper vacuum pressures of 1–3 kPa. 2-stage VSA process operated in series allowed us to use simple process steps and operate at more realistic vacuum pressures. With a vacuum pressure of 10 kPa, final CO2 purity of 95.3% with a recovery of 98.2% were obtained at specific power consumption of 0.55 MJ·(kg CO2)− 1 from feed gas containing 15% CO2. These numbers compare very well with those obtained from a single stage process operating at 1 kPa vacuum pressure. The feed CO2 concentration was very influential in determining the desorption pressure necessary to achieve high separation efficiency. For feed gases containing > 30% CO2, a single-stage VSA capture process operating at moderate vacuum pressure and without a product purge, can achieve very high product purities and recoveries.

We report an advanced synthesis strategy, termed "exchange method using acid-solvent synergy for metal-organic framework synthesis" (EASY-MOFs), which can generally be applied to pillar-layered MOFs to generate new structures. Superior to de novo synthesis, EASY-MOFs provides an alternative synthesis route with advantages of high product purity, structural versatility and controllability. In addition, high product yield is possible without the need for tedious optimization of the synthetic conditions, which is often the case for de novo synthesis. More importantly, novel structures that are not obtainable by direct synthesis or conventional ligand-exchange strategies can be achieved by EASY-MOFs. Based on our experimental observations, we attribute the unique advantages of EASY-MOFs to the nucleation rate control during the disassembly-exchange-reassembly process and the seeding effect of the parent crystals promoted by the acid.

Temperature swing adsorption (TSA) is an attractive technology for CO2 removal from gas streams. CO2 capture by a TSA process in which the recovered CO2 product is heated and used as regeneration purge gas has been examined. Our study is based on cyclic experiments performed on a single adsorption column packed with the commercially available zeolite NaUSY adsorbent. The commercial Aspen adsorption simulator was used to simulate the experimental system, where the model predictions agreed quite well with experimental results in terms of breakthrough and results for cycle designs based on indirect heating followed by hot product gas purge. The validated model was used to simulate the case of regeneration using only hot product gas purge, which was difficult to examine experimentally due to constraints of the experimental system used. With a three-step cycle of (1) adsorption, (2) hot gas purge, and (3) cooling, this case yielded product purities of >91% CO2 and maximum recoveries of 55.5, 76.2, and 83.6% at...

Although a considerable amount of the research is focussed in carbon capture specifically towards flue gas separations, another area that is of interest is CO 2 /CH 4 separation for the natural gas industries. It is believed that 40% of the world’s reserves of natural gas are sour, and these gas reserves are typically left unexploited due to their high CO 2 content and the costs associated with separation and transport. One recent class of adsorbents, metal organic frameworks (MOFs) has been advocated as potential candidates for CO 2 removal from natural gas at high pressure. This can be attributed to their high CO 2 capacities, which could be exploited in high pressure separations. In this work we synthesised ZIFs -8, -14 and -71 and measured CO 2 and CH 4 isotherms over a range of temperatures and pressures. The CO 2 capacity for these materials at 303 K and 45 bar(a) was in the order of ZIF-8 (9.1 mol kg −1 ) > ZIF-71 (8.1 mol kg −1 ) > ZIF-14 (5.0 mol kg −1 ). The CH 4 loading at 303 K and 100 bar(a) was in the order of ZIF-8 (6.8 mol kg −1 ) > ZIF-14 (4.8 mol kg −1 ) > ZIF-71 (4.4 mol kg −1 ). The ideal selectivity of these materials for a 15% mol CO 2 , 85% mol CH 4 feed mixture at 100 bar(a) and 303 K was found to be 5.6 for ZIF-8, 4.5 for ZIF-14 and 13 for ZIF-71. This isotherm data was then used to design and simulate a pressure swing adsorption process for CO 2 /CH 4 separation. Feed CO 2 concentrations between 15% mol and 35% mol were investigated at a condition of 100 bar(a) and 303 K. It was found that only ZIFs -8 and -71 could achieve the 98% mol CH 4 product purity required. ZIF-8 and ZIF-71 were able to achieve CH 4 recoveries of 46% mol and 48% mol respectively. Furthermore, it was also found that ZIFs -8 and -71 behaved very similarly when compared on a volume of adsorbent basis. The CH 4 uptake of ZIF-14 was found to be abnormally high, which resulted in a very low CO 2 /CH 4 selectivity. The loading of CH 4 was higher than CO 2 for both the 15% mol and 25% mol CO 2 feed cases, with only the 35% mol CO 2 feed resulting in a higher CO 2 capacity, 4.6 mol kg −1 of CO 2 in comparison to 4.1 mol kg −1 of CH 4 . Although their CO 2 capacities at high pressures are high, there is little discrimination between the adsorption of small molecules. Consequently, their CH 4 loadings also increase substantially at those increased pressures. This results in a poor separation with the CO 2 product becoming diluted with the co-adsorbed CH 4 gas.

A Ni5Ga3 catalyst synthesized from hydrotalcite-like compound (HTlc) precursors was examined for CO2 hydrogenation to methanol. HTlc precursors with a nickel atomic percentage of 65 % balanced with gallium were prepared by a urea hydrolysis hydrothermal method, and fully characterized. The HTlc phase in the nickel–gallium precipitant became better crystallized and the structure became more stable as the synthesis reaction temperature increased. Bimetallic alloy Ni5Ga3 was obtained by reducing the as-prepared HTlc precursors in a flow of 5 % H2 balanced with Ar at a temperature of 700 °C. Ni–Ga HTlc precursor prepared at a hydrothermal temperature of 110 °C resulted in the formation of bimetallic alloy, Ni5Ga3, which produces smaller crystal size and a stable structure. Enhanced catalytic performance was demonstrated by an endurance test with a constant CO2 conversion and 100 % methanol selectivity at 200 °C, and a turnover frequency of 0.27 s−1.

CO2 hydrogenation, in which CO2 conversion to methanol plays a key role, is of increasing importance in mitigating the climate crisis. However, high reaction pressures are required to conduct methanol synthesis because of poor catalytic performance of conventional catalysts, leading to high energy consumption. In this study, a novel strategy was applied to promote methanol synthesis by adsorption-enhanced CO2 hydrogenation. Catalysts made from Cu-ZnO-Al2O3 mixed with different hydrotalcite contents (named CZA-HT) were prepared by physically mixing a commercial copper-based catalyst for methanol synthesis with hydrotalcite for high temperature CO2 adsorption. In these catalysts, only the commercial copper-based component contains the active part for CO2 hydrogenation and its copper surface area is 48.1 m2 g−1 with an optimal reaction temperature of 523 K. Hydrotalcite exhibits no catalytic activity, yet the catalytic performance of the CZA-HT catalysts were clearly facilitated by CO2 adsorption on HT. The sample containing 40 wt% hydrotalcite and 60 wt% CZA showed the highest methanol selectivity of 73.4% and a methanol yield of 4.4% among all samples. The reaction was conducted at a low reaction pressure of 30 bar (much lower than conventional pressure), so that the methanol yield was not high. However, it is observed that the methanol formation rate based on a unit mass of active CZA always increases as the hydrotalcite content in CZA-HT increases, confirming the promotion effects of CO2 adsorption on HT on catalytic performance. The mechanism of adsorption enhanced catalytic reaction was also analysed and discussed, in which the well mixed finer particles of CZA and HT perform better than CZA alone with a 73.9% higher methanol yield.

The potential of novel polyethyleneimine (PEI) based sorbent and process designs to safeguard the stability of the PEI type sorbent stability for CO2 post combustion capture (PCC) via vacuum swing adsorption (VSA) application was investigated. In-situ thermogravimetric analysis (TGA) combined with CO2 partial pressure swing adsorption (PPSA) processing, Fourier Transform Infrared (FTIR) spectroscopy and lab scale VSA processing of adsorber columns were employed for this purpose. The inventions were found to inhibit the dehydration of ammonium carbamates into ureas, and, thereby, better maintain the integrity of the sorbent and its CO2 working capacity under key process conditions.

The performance of a 4-bed/16-step vacuum swing adsorption cycle containing three pressure equalization (PE) steps has been analysed in order to understand the role played by the multiple PE steps in the process performance. The cycle was designed for CO2 capture from a feed gas mixture of 15 %CO2/85 %N2, with zeolite ×13 adsorbent from UOP (PSO2HP). Simulations were performed with the help of the commercial Aspen Adsorption simulator to help interpret the experimental results. It was found that CO2 loading decreased only slightly, but N2 loading decreased significantly and uniformly across the bed after each PE step. Thus, while CO2 working capacity remained almost constant, working selectivity and CO2 product purity increased with the number of PE steps. An experimental purity of 91.3 mol% CO2 could be obtained at a recovery of 77 % at 3 kPa desorption pressure, with a cycle containing 3 pressure equalisation steps. Specific energy consumption (calculated with a constant pump efficiency of 70 %) was calculated as 0.3 MJ/kg CO2, which was lower than the 1 and 2 pressure equalisation cycles. We evaluated 2-bed and 3-bed cycles containing one and two pressure equalisation steps respectively, by means of simulation in order to compare their performance with the base 4-bed 3PE cycle. For a constant recovery of 75–77 %, CO2 product purities increase by 7.4 and 4.2 % (relative) in going from 1PE, to 2PE and 3PE cycles respectively, at an evacuation pressure of 3 kPa. Specific energy consumption also decreased with the number of PE steps, owing to the lowering of the starting pressure for desorption and some savings in repressurization energy with the number of PE steps. The specific energy dropped by 13 % in going from 1PE to 2PE and 3PE steps. However, the extra beds and extra cycle time required for the 3PE steps led to a reduction in productivity by almost 33 % in going from the 2PE to 3PE cycles. The choice for including additional PE steps therefore relies on the tradeoff of capital and operating costs which is strongly location and project specific.

Vacuum swing adsorption (VSA) is a commercial technology for gas separation, and is promising for CO 2 removal from a range of process gases. In this study, a parametric analysis and process characterisation was conducted of VSA for CO 2 capture from a variety of gas steams, using the commercial zeolite 13X-APIII as a benchmark adsorbent. Because deep vacuum levels ( 2 concentrations of 15%, 30% and 50% with varying operation temperatures from 20 to 120 °C were studied to cover the range of concentration and temperatures expected in industry. The studies were conducted using both single and double bed CO 2 VSA systems. CO 2 product purity and recovery are significantly affected by the vacuum pressure, operating temperature and inlet CO 2 concentration. In addition to the detrimental effect of higher vacuum levels, the rate of evacuation can also impact the performance. Rapid evacuation results in high pressure drop which leads to inadequate desorption of the adsorbed CO 2 . High desorption flow rates also limit CO 2 release from the solid phase to the gas phase due to mass transfer limitations. Pressure equalisation between two adsorption beds can remarkably improve the purity of CO 2 product, compared with single-bed cycle. Based on our experimental work, a set of intrinsic “recovery-purity” curves for APGIII were generated to guide the user in selecting appropriate conditions for achieving desired performance. We found that achieving high purity (>90% CO 2 ) at high recovery (>90%) for APGIII was not possible unless very deep vacuum levels are used (1 kPa) if the feed contains 15% CO 2 or less.

Performance of four adsorbents (three zeolites and one molecular sieve carbon) for CO2–CH4 separation from simulated biogas feed containing 42% CO2 (balance methane) is compared in a simple four step dual bed vacuum swing adsorption (VSA) cycle. The VSA cycle consisted of four sequential steps in each column namely adsorption, cocurrent depressurization, evacuation and pressure equalization. Among the adsorbents tested, zeolite NaUSY appears to give the best results for producing pipeline grade methane (>98%) at recoveries exceeding 85%. The methane productivity obtained by the present process is in the range of 11–16 mol/h/kg, which is considerably higher than the literature reported values with zeolite and carbon based adsorbents. The high methane productivity of the present process is due to the absence of purge step during regeneration with methane rich adsorption product as well as due to absence of any blow down step in the VSA cycle. Another advantage of the present process is that operation for bi...

Zeolite NaA was successfully prepared from nickel laterite residue for the first time via a fusion-hydrothermal procedure. The structure and morphology of the as-synthesized zeolite NaA were characterized with a range of experimental techniques, such as X-ray diffraction, scanning electronic microscopy, and infrared spectroscopy. It was revealed that the structures of the produced zeolites were dependent on the molar ratios of the reactants and hydrothermal reaction conditions, so the synthesis conditions were optimized to obtain pure zeolite NaA. Adsorption of nitrogen and carbon dioxide on the prepared zeolite NaA was also measured and analyzed. The results showed that zeolite NaA could be prepared with reasonable purity, it had physicochemical properties comparable with zeolite NaA made from other methods, and it had excellent gas adsorption properties, thus demonstrating that zeolite NaA could be prepared from nickel laterite residue.

The influence of water vapor on the adsorption of CO2 in carbon capture by vacuum swing adsorption (VSA) was described. VSA experiments with single and multilayered columns using alumina and zeolite 13X were conducted to understand the migration of water. The penetration depth of water in the column could be controlled by maintaining the purge-to-feed ratio above a critical value. At high water content in the feed (>4%), employment of a water adsorbing prelayer was essential to prevent failure of the carbon capture process. A simple axial working capacity model predicts the penetration depth of water in the column for a given feed temperature and adsorption isotherm, and the layering ratio can be selected accordingly. Although water is detrimental to CO2 capture with polar adsorbents, long-term recovery of CO2 is still possible by appropriate layering and ensuring an adequate purge-to-feed ratio. © 2013 American Institute of Chemical Engineers AIChE J 60: 673–689, 2014

The capture of CO2 with adsorption processes is greatly complicated by the presence of high water levels in most process and flue gas streams. One option is to use activated carbon of appropriate hydrophobicity. The interaction of water and CO2 on carbon materials in VSA processes is therefore of great interest and it is this feature which the current study addresses. The adsorption equilibrium isotherms of H2O, CO2 and N2 on activated carbon (coconut shell Acticarb GC1200) were measured over the range 25–60 °C and 0–1 bar. The Type V isotherm exhibited by water required a non-Langmuir type representation. In this case, Rutherford’s extended CMMS model was employed to describe water adsorption. Breakthrough experiments as well as one bed vacuum swing adsorption studies were undertaken to investigate the impact of water on CO2 adsorption and its eventual impact on a separation process. Simulations were also conducted to help interpret the data. Our analysis showed that there was little effect of CO2 and water on each other’s adsorption on the carbon material beyond the dilution effect on partial pressure of each component. The single bed vacuum swing experiment showed almost identical recovery and purity of CO2 in the presence of water as in the dry case. However, the presence of water required additional pumping energy and led to an increase in CO2 capture energy of about 35%. There is a need to improve carbon materials to further exclude water without substantially decreasing CO2 capacity and selectivity.

This paper reports a phase inversion method for the preparation of macroporous polysulfone (PS) composite spheres through a single orifice spinneret. Surfactant F127 was pre-added in the polymer solution as a surface pore-forming agent, and different amount of zeolitic imidazolate framework-8 (ZIF-8) particles were incorporated to form the ZIF-8/polysulfone (ZIF-8/PS)-composite spheres. ZIF-8 and polymer acted as the adsorbent and binder in the final composite spheres, respectively. The fabrication conditions, such as the types of the surfactant, the amount of the surfactant, and ZIF-8 added in the polymer solution, were investigated. Nitrogen and carbon dioxide sorption analysis indicated the ZIF-8/PS composite spheres had similar properties as the pure ZIF-8 particles, and the active sites of ZIF-8 in the polymer composites were well exposed. The composite spheres exhibited advantages of easy handling and recycling over ZIF-8 particles, and this phase inversion method can be extended to prepare other polymer composite spheres.