Pre-combustion CO2 Capture Research Articles

Green fabrication of cost-effective and sustainable nanoporous carbons for efficient hydrogen storage and CO2/H2 separation

In this study, sustainable nanoporous carbon materials that are efficient, renewable, cost-effective and adaptable were developed. These microporous feature carbon adsorbents were synthesized utilizing a straightforward and efficient method. Plum stones are residual fruit materials that offer a financially feasible and sustainable carbon source with exceptional porosity and desirable elemental composition. The plum stones underwent carbonization and were subsequently chemically modified with polyaniline nanofibers and then subjected to chemical activation using different activating agents. This yielded sustainable nanoporous carbon with a high degree of porosity, in conjunction with doping with precious high electron density elements such as O, N and S. The sustainable nanoporous carbons that have been developed exhibits exceptional microporosity, with BET-SSA of 1705 m2 g−1 and a pore volume of 0.726 cm3 g−1, besides, the dominance of ultramicropores of 0.6 nm size. This in addition to convenient doping of oxygen, nitrogen and sulfur elements which are crucial for H2 uptake. The developed nanoporous carbon demonstrated highly promising capabilities for storing H2 molecules at cryogenic and ambient temperatures. The sustainable adsorbent achieved hydrogen storage capacities of 4.63 and 0.45 wt% at 77, 296 K, and a pressure of 40 and 80 bar, respectively. This H2 storage capacity at RT is often regarded as one of the highest reported in the literature for nanoporous adsorbents. Moreover, study investigated the separation selectivity of developed adsorbents for CO2/H2 based on uptake ratio at 30 bar and RT. The results demonstrated a significant separation selectivity reaching a value of 382.5 for the CO2/H2, which is regarded as one of the most elevated values documented in the existing literature for nanoporous carbon materials. Thus, the presented sustainable nanoporous materials have shown great promise for hydrogen storage, pre-combustion CO2 capture and H2 purification applications at ambient temperature.

Facile infiltration of polyethyleneimine as a strong CO2 retardant in scalable dual-polymer membranes for H2/CO2 separation

Successful pre-combustion CO2 capture from synthetic gas for H2 production requires effective membrane separation technology. While polymer-based membrane materials offer promising industrial scalability, they generally lack a sufficiently high H2/CO2 selectivity to make this process energy-efficient. In this work, we have designed a scalable dual-polymer blend membrane consisting of sulfonated polyphenylsulfone (sPPSU) and polybenzimidazole (PBI), and then being infiltrated with amine-rich poly(ethyleneimine) (PEI) molecules as effective CO2 retardants to substantially elevate the H2/CO2 selectivity. PEI molecules were infiltrated into the dual-polymer matrix via solution-treatment to crosslink the polymer network and retard CO2 transport using its amine-rich nature. The PEI infiltration dramatically increased the H2/CO2 selectivity of the dual-polymer matrix from 4.6 to up to 59.3 while maintaining a minimum H2 permeability of 2.49 Barrer at a low temperature of 35 °C, which not only surpasses the Robeson upper bound but also places the newly developed membrane among the best-performing polymer-based membranes. More importantly, the solution infiltration of PEI incurs no phase segregation, maintaining the polymer mechanical robustness, which is crucial for industrial scaling. This study offers promising opportunities to develop three-polymer membrane systems for H2/CO2 separation using synergistic polymer blends and CO2-retarding molecules.

Near-zero carbon emission power generation system enabled by staged coal gasification and chemical recuperation

Generating clean, efficient, and low-carbon electricity from coal is imperative for limiting the global temperature rise to 1.5 °C. This study presents a near-zero-carbon-emission power generation system that utilizes staged coal gasification. The innovation of this system is the division of coal gasification into two stages: intermediate-temperature pyrolysis, followed by high-temperature gasification. This process begins with utilizing waste heat from the exhaust of a gas turbine to drive the partial gasification of coal during pyrolysis. The nongaseous products from this stage are then completely gasified in the gasifier, and chemical recuperation is performed, in which heat from the syngas at the gasifier's outlet preheats the reactants at the inlet and aids in reforming pyrolysis gas. For CO2 capture, an oxyfuel combustion strategy is used. Our system produced net electricity and exergy efficiencies of 43.01 and 47.57 %, respectively, surpassing both pre-combustion CO2 capture systems based on staged coal gasification (improvements of 3.04 and 5.37 %, respectively) and coal-water slurry gasification (improvements of 3.55 and 5.8 %, respectively). Moreover, the carbon emissions from our system are approximately 90 g/kWh lower than those from these systems. Thus, this study offers an environmentally sustainable approach to utilizing coal that may facilitate achieving global environmental goals.

Blended-amine CO2 capture process without stripper for high-pressure syngas

With the emergence of the hydrogen economy, advanced CO2 capture technologies are essential for cost-effective H2 production until renewable-energy based H2 production technologies gains competitiveness. A novel stripper-free pre-combustion CO2 capture process, in which the stripper was replaced with a low-pressure (LP) flash column, was developed for cost-effective pre-combustion CO2 capture from H2-rich syngas at high pressure. The developed process could regenerate the blended N-methyldiethanolamine/piperazine (MDEA/PZ) solvent at relatively low temperature (<373.15 K). After the sensitivity analysis using key operating parameters, process optimization was performed by the deep learning-based surrogate models using non-dominated sorting genetic algorithm-II (NSGA-Ⅱ). The heat duty of 1.881GJ/tonCO2 was required at the optimal condition, but the required energy could be supplied through the utilization of a waste heat recovery (WHR) system because the regeneration was possible at low temperatures. Compared with advanced stripper-incorporated amine processes, the equivalent work of the developed process with WHR system using a heat source at 370 K was lowered by 50 % and more cost-effective (32.89$/tonCO2 at the discount rate of 10 %) from the economic analysis considering carbon emission price. The performance assessment of the stripper-free CO2 capture process provided design guidelines for effective CO2 capture from H2-rich syngas and emphasized the importance of CO2 capture unit in net-zero scenario.

Semiclathrate-based CO2 capture from pre-combustion fuel gas using tetra-n-butylammonium chloride: A thermodynamic, kinetic, and spectroscopic study

The primary objective of this study was to investigate the feasibility of pre-combustion CO2 capture using tetra-n-butylammonium chloride (TBAC) semiclathrate in a fuel gas mixture comprising CO2 (40%) + H2 (60%), with a primary focus on examining the thermodynamic, kinetic, and spectroscopic aspects of this process. Phase equilibria measured at various TBAC concentrations revealed that the CO2 + H2 + TBAC semiclathrates exhibited maximum thermodynamic stability at a stoichiometric concentration (3.3 mol%). CO2 concentrations in both the vapor and semiclathrate phases, along with gas consumption during and after semiclathrate formation, were measured to assess CO2 selectivity and gas uptake in the semiclathrate phase. Notably, CO2 enrichment was approximately 90% in the semiclathrate phase. In-situ Raman spectroscopy provided clear confirmation of the enclathration of both CO2 and H2 in the semiclathrate lattices, while powder X-ray diffraction analysis revealed the tetragonal (P42/m) structure of the CO2 + H2 + TBAC (3.3 mol%) semiclathrate. Furthermore, a high-pressure micro-differential scanning calorimeter was used to measure the dissociation enthalpies of the CO2 + H2 + TBAC (3.3 mol%) semiclathrate at various pressures. The comprehensive results obtained in this study strongly support the potential use of TBAC semiclathrate as a material for pre-combustion CO2 capture.

Field-Scale Testing of a High-Efficiency Membrane Reactor (MR)-Adsorptive Reactor (AR) Process for H2 Generation and Pre-Combustion CO2 Capture.

The study objective was to field-validate the technical feasibility of a membrane- and adsorption-enhanced water gas shift reaction process employing a carbon molecular sieve membrane (CMSM)-based membrane reactor (MR) followed by an adsorptive reactor (AR) for pre-combustion CO2 capture. The project was carried out in two different phases. In Phase I, the field-scale experimental MR-AR system was designed and constructed, the membranes, and adsorbents were prepared, and the unit was tested with simulated syngas to validate functionality. In Phase II, the unit was installed at the test site, field-tested using real syngas, and a technoeconomic analysis (TEA) of the technology was completed. All project milestones were met. Specifically, (i) high-performance CMSMs were prepared meeting the target H2 permeance (>1 m3/(m2.hbar) and H2/CO selectivity of >80 at temperatures of up to 300 °C and pressures of up to 25 bar with a <10% performance decline over the testing period; (ii) pelletized adsorbents were prepared for use in relevant conditions (250 °C < T < 450 °C, pressures up to 25 bar) with a working capacity of >2.5 wt.% and an attrition rate of <0.2; (iii) TEA showed that the MR-AR technology met the CO2 capture goals of 95% CO2 purity at a cost of electricity (COE) 30% less than baseline approaches.

Highly efficient separation and equilibrium recovery of H2/CO2 in hydrate-based pre-combustion CO2 capture

Gas hydrate-based CO2 capture processes have attracted considerable attention due to their potentials for energy-efficient pre-combustion CO2 capture. Recent investigations have explored the use of tailored-wettability porous silica gels, highlighting benefits in thermodynamic and kinetic efficiencies, specifically characterized by low energy requirements and rapid formation. However, achieving high purity levels for both H2 and CO2 is crucial for practical implementation. Consequently, identifying and optimizing an effective separation route becomes imperative. In this study, we examined the thermodynamic stability, gas uptake, and separation factors of THF (5.56 mol%) + H2 + CO2 hydrates with varying compositions (H2:CO2 = 80:20, 60:40, 30:70, or 20:80 mol%) in C0 and C1 silica gel (functionalized by monofunctional alkylsilanes (X-(CH3)2-Si-Cn)) systems with SDS (0 or 500 ppm). Pressure-composition diagrams for THF + H2 + CO2 systems in C0 and C1 silica gel were meticulously measured. Notably, the C1 silica gel system without SDS demonstrated good thermodynamic stability, substantial gas uptake, and a significant separation factor. Based on the pressure-composition diagram of the C1 silica gel system, we proposed a highly efficient route for separating H2 and CO2. This proposed cyclic process involves a three-stage reactor and achieve to gas hydrate-based pre-combustion CO2 capture, yielding a purity of approximately 91 % H2 and 94 % CO2. The present findings provide valuable insights into optimizing the wettability of porous media and efficient separation routes, demonstrating the feasibility of a gas hydrate-based pre-combustion carbon dioxide capture process.

Energy, Exergy &amp; Environmental Analysis of a Combined Cycle with Pre-combustion CO2 Capture and N2 Injected into the Compressor of the Gas Turbine

Power plants are a major source of CO2 emissions in the environment, which cause global warming; due to this issue, CO2 capture from hydrocarbon fuels is one of the key technology options to reduce greenhouse gases. Pre-combustion capture of CO2 in the combined gas and steam turbine cycle has been investigated in this paper. The first step in the pre-combustion method is to react the fuel with oxygen, which comes from the air separation unit and produces a mixture of hydrogen and carbon monoxide. The CO is converted to CO2 in a water-shift reactor, and a physical absorbent removes the CO2; a hydrogen-rich fuel is produced, which can be burnt in a gas turbine with minimal CO2 emissions. This paper presents a thermodynamic cycle analysis, where pre-combustion CO2 capture is applied in a combined cycle where the main goal is to reduce the CO2 emission into the atmosphere. The main parameters are varied to examine the influence on cycle performance. The cycle performance results for the combined cycle with CH4 as fuel are presented and compared to the combined cycle with precombustion CO2 capture, both with and without Nitrogen injection into the compressor. An exergy analysis is carried out to determine which case has more exergy destruction. The results indicate that at 45 oC the combined cycle efficiency is raised by around 3 % when the pre-combustion CO2 capture without Nitrogen injection into the compressor is used, and the power output has been increased by 29 %. The performance of combined cycle with CO2 capture can be further enhanced by the N2 acquired from the air separation process and injected into the compressor’s middle stage. The results demonstrate a good improvement in the performance; the power output increases by 48 % and efficiency by 4.2 %. However, exergy destruction is increased when the CO2 capture, both with and without N2 injection into the compressor is used. Nevertheless, pre-combustion capture requires large monetary investment for a new-build plant where also the CO2 emission is reduced by 100 %.

Ultra-low emission flexible plants for blue hydrogen and power production, with electrically assisted reformers

This study investigates the potential of natural gas-based plants designed to produce blue hydrogen and decarbonized electric power, conceived to operate flexibly depending on the electricity price. This paper considers plants based on fired-tubular reforming (FTR) and auto-thermal reforming (ATR) technologies, with MDEA-based pre-combustion CO2 capture process and partial electrification of the reformer, designed to achieve CO2 capture efficiency higher than 95 %. Heat and mass balances for the chemical and power island are evaluated at both full and part load to define the corresponding operating maps. With pre-combustion CO2 capture only, FTR plants can achieve CO2 capture rates higher than 90 %, H2 production efficiency of 73–74 % and power generation efficiency of around 47 %. Reformer electrification allows increasing overall capture efficiency to 95 %. Plants based on ATR can approach 95 % capture efficiency without electrification and achieve H2 efficiency similar to FTR but higher electric efficiency, close to 51 %. An economic analysis is performed to assess profitability of the plants under electricity price scenarios with different penetration of renewables. The economic analysis shows that flexible plants may be profitable in future scenarios with high penetration of renewables and high price variance, resulting in IRR around 10–17 % for hydrogen selling prices of 2.0–2.5 €/kg, natural gas price of 9 €/GJ and carbon tax of 100 €/tCO2.

Construction of N-Rich Aminal-Linked Porous Organic Polymers for Outstanding Precombustion CO2 Capture and H2 Purification: A Combined Experimental and Theoretical Study.

A large number of scientific investigations are needed for developing a sustainable solid sorbent material for precombustion CO2 capture in the integrated gasification combined cycle (IGCC) that is accountable for the industrial coproduction of hydrogen and electricity. Keeping in mind the industrially relevant conditions (high pressure, high temperature, and humidity) as well as good CO2/H2 selectivity, we explored a series of sorbent materials. An all-rounder player in this game is the porous organic polymers (POPs) that are thermally and chemically stable, easily scalable, and precisely tunable. In the present investigation, we successfully synthesized two nitrogen-rich POPs by extended Schiff-base condensation reactions. Among these two porous polymers, TBAL-POP-2 exhibits high CO2 uptake capacity at 30 bar pressure (57.2, 18.7, and 15.9 mmol g-1 at 273, 298, and 313 K temperatures, respectively). CO2/H2 selectivities of TBAL-POP-1 and 2 at 25 °C are 434.35 and 477.93, respectively. On the other hand, at 313 K the CO2/H2 selectivities of TBAL-POP-1 and 2 are 296.92 and 421.58, respectively. Another important feature to win the race in the search of good sorbents is CO2 capture capacity at room temperature, which is very high for TBAL-POP-2 (15.61 mmol g-1 at 298 K for 30 to 1 bar pressure swing). High BET surface area and good mesopore volume along with a large nitrogen content in the framework make TBAL-POP-2 an excellent sorbent material for precombustion CO2 capture and H2 purification.

Development and evaluation of FINEX off-gas capture and utilization processes for sustainable steelmaking industry

FINEX process was proposed as an environmentally friendly option for steelmaking. To further its environmental friendliness, this study proposes and evaluates three options for FINEX off-gas (FOG) capture and utilization: post-combustion CO2 capture (Case 1), pre-combustion CO2 capture (Case 2), and methanol production following the pre-combustion CO2 capture (Case 3). These options are designed through simulation and are comparatively evaluated in terms of their net CO2 emissions and economics by conducting CO2 lifecycle assessment (LCA) and techno-economic analysis (TEA). In the latter, CO2 avoidance cost is estimated to assess the economic feasibility of each option. Case 1 was observed to give the largest amount of CO2 emission reduction, which is 35% lower than the current FOG utilization method of burning it for electricity generation. Case 2 showed the lowest CO2 avoidance cost of 68 USD/ton. Although Case 3 was estimated to give higher net CO2 emissions than Case 1 and higher CO2 avoidance cost than Case 2, sensitivity analysis revealed that the outcome depends strong on the global warming impact of the mixed electricity, carbon credit price, and methanol price and it can become an attractive option in the future.

Synergistic dual-polymer blend membranes with molecularly mixed macrocyclic cavitands for efficient pre-combustion CO2 capture

In this work, scalable polyphenylsulfone (PPSU) and polybenzimidazole (PBI) polymers were homogeneously blended to create an enhanced polymer matrix that could utilize both the higher permeability and mechanical flexibility of the former and the excellent selectivity and thermal stability of the latter. Within this blend matrix, calix[6]arene (CA6), an organic macrocyclic cavitand (OMC) with versatile solubility and high affinity for polymers, was also incorporated to further enhance the H2/CO2 selectivity using its polymer-intruded, partially open cavity that exhibits strong size-sieving nature. At 20 wt% CA6 loading, the nanocomposite blend membrane obtained a 103% higher H2/CO2 selectivity with an only mild permeability loss at 100 °C, which enabled both its overall pure- and mixed-gas separation performances to substantially surpass the Robeson upper bound. Most importantly, the ability of CA6 to molecularly mix with PPSU and PBI without phase segregation perfectly maintains the mechanical robustness of the pristine polymers, which is essential for potential industrial upscaling. This work presents exciting possibilities in designing molecularly mixed composite membranes (MMCMs) using synergistic polymer blends that offer clearly better scalability over the conventional phase-segregated mixed-matrix designs.

Synchronous Design of Membrane Material and Process for Pre-Combustion CO2 Capture: A Superstructure Method Integrating Membrane Type Selection

Membrane separation technology for CO2 capture in pre-combustion has the advantages of easy operation, minimal land use and no pollution and is considered a reliable alternative to traditional technology. However, previous studies only focused on the H2-selective membrane (HM) or CO2-selective membrane (CM), paying little attention to the combination of different membranes. Therefore, it is hopeful to find the optimal process by considering the potential combination of H2-selective and CO2-selective membranes. For the CO2 capture process in pre-combustion, this paper presents an optimization model based on the superstructure method to determine the best membrane process. In the superstructure model, both CO2-selective and H2-selective commercial membranes are considered. In addition, the changes in optimal membrane performance and capture cost are studied when the selectivity and permeability of membrane change synchronously based on the Robeson upper bound. The results show that when the CO2 purity is 96% and the CO2 recovery rate is 90%, the combination of different membrane types achieves better results. The optimal process is the two-stage membrane process with recycling, using the combination of CM and HM in all situations, which has obvious economic advantages compared with the Selexol process. Under the condition of 96% CO2 purity and 90% CO2 recovery, the CO2 capture cost can be reduced to 11.75$/t CO2 by optimizing the process structure, operating parameters, and performance of membranes.

Performance of hydrophobic physical solvents for pre-combustion CO2 capture at a pilot scale coal gasification facility

Here, we present the first pilot plant data for hydrophobic physical solvents for CO2 and H2S removal from coal-derived H2-rich syngas. Four physical solvents were tested under pre-combustion CO2 capture conditions at bench scale and pilot plant scale: one baseline hydrophilic solvent and three hydrophobic solvents. The solvents were: (1) polyethylene-glycol-dimethyl ether (PEGDME), a hydrophilic solvent analog for the commercial process Selexol, (2) tributyl- phosphate (TBP), a commercially available hydrophobic solvent, (3) polyethylene glycol-poly(dimethylsiloxane) (PEG-PDMS-3), and (4) diethyl sebacate (CASSH-1), a novel, computationally screened hydrophobic solvent developed by the National Energy Technology Laboratory (NETL). All solvents were studied under pure gas (CO2/N2/H2/CH4) equilibrium conditions at NETL followed by pilot plant testing with syngas at the University of North Dakota Energy & Environmental Research Center (UND EERC). Long term performance of CASSH-1 and PEDGME was then assessed with results compared to process simulation predictions. Within experimental uncertainties, all solvents showed comparable CO2 absorption performance at above room temperature operation while the hydrophobic solvents had limited water uptake and low vapor pressure, which alleviates concerns related to corrosion, water absorption, and solvent loss to evaporation. These results indicate low viscosity, low vapor pressure hydrophobic solvents are a promising option for lower cost CO2 capture from high pressure syngas applications.

BECCS opportunities in Brazil: Comparison of pre and post-combustion capture in a typical sugarcane mill

In order to make feasible the efforts that would limit the rise of Earth's temperature to no more than 2 °C, profound changes are required in the energy systems. In this sense, BECCS are considered instrumental to attain possible negative emissions. This draws attention to the sugarcane industry in Brazil, where it is possible to produce fuel ethanol at a relative low cost and a large amount of relatively cheap biomass is available. This paper is part of a research that aims to study the combined production of liquid fuels and electricity, using sustainable sources of biomass and maximizing carbon capture. Two cases related to an innovative technology were evaluated and in both the capture is based on amine technology: pre-combustion capture of CO2 from the fuel gas derived from biomass gasification, and post-combustion capture from gas turbine exhaust gases. Information from the scientific literature was used in modelling the systems, as well as estimating energy penalties and costs associated with capturing, transporting and storing CO2. The results indicate technical feasibility of both capture options, but difficulties in setting the full integration of the power unit (BIG-CC) with the sugarcane mill and the CCS system, due to the high demand for thermal energy as low-pressure steam. The estimated CO2 abatement cost is in the range 60–71 €/tCO2 for pre-combustion capture, and 52–63 €/tCO2 in the case of post-combustion. Feasibility results are impacted by the scale of CO2 capture (0.82–1.44 MtCO2/year), particularly in the pre-combustion case, and the relatively high cost of electricity generation.

Power and Hydrogen Co-Production in Flexible “Powdrogen” Plants

Abstract This study investigates the potential of “Powdrogen” plants for blue hydrogen and decarbonized electric power production, conceived to operate flexibly depending on the electricity price and to increase the capacity factor of the hydrogen production and CO2 separation units. The hydrogen production is based on fired tubular reforming or autothermal reforming technologies with precombustion CO2 capture by a methyl diethanolamine (MDEA) process. The power island is based on a combined cycle with an H2-fired gas turbine and a triple pressure reheat heat recovery steam generator (HRSG). The analysis considers three main plant operating modes: hydrogen mode (reformer at full load with hydrogen export and combined cycle off) and power mode (reformer at full load with all hydrogen burned in the combined cycle), plus an intermediate polygeneration mode, producing both hydrogen and electricity. The possibility of integrating the HRSG and the reformer heat recovery process to feed a single steam turbine has been explored to allow keeping the steam turbine hot also in hydrogen operating mode. The economic analysis investigates the competitivity of the plant for different operating hours in hydrogen and power modes. Results suggest that these plants are likely to be a viable way to produce flexibly low-carbon hydrogen and electricity following the market demand.

Advanced pre-combustion CO2 capture by clathrate hydrate formation with water-to-gas molar ratio optimization

Capturing CO2 from exhaust gases by formation of clathrate hydrates, which consist mainly of water (∼85 %), is highly promising owing to the mild operating conditions, economic feasibility, and environment-friendliness. Although tremendous efforts have been made, hydrate-based CO2 capture has not yet been realized primarily due to insufficient CO2 uptake kinetics and separation efficiency. To overcome these, the effect of the water-to-gas molar ratio (W/G ratio), which was not previously considered important despite its significance, on clathrate hydrate-based pre-combustion capture was investigated. Changes in phase equilibrium temperatures for structure Ⅰ CO2/H2 and structure Ⅱ CO2/H2/tetrahydrofuran (THF) hydrates with the W/G ratio were characterized to establish suitable operation temperature and pressure conditions. In addition, a novel strategy utilizing the residual liquid water to capture extra CO2 in structure Ⅰ hydrates was demonstrated. Contrary to the general premise, limiting the THF concentration was found to be effective in preventing unfavorable H2 capture, thus dramatically improving the separation efficiency. Through a comprehensive evaluation in terms of hydrate phase equilibria, formation kinetics, and separation efficiency, 3 mol% THF + high W/G ratio was derived as the optimal condition. The present findings demonstrate that the effect of the W/G ratio and its combined effects with other parameters on phase equilibria, formation kinetics, and separation efficiency should be emphasized to achieve an advanced pre-combustion capture using clathrate hydrates toward carbon neutrality.

Blue, green, and turquoise pathways for minimizing hydrogen production costs from steam methane reforming with CO2 capture

Rising climate change ambitions require large-scale clean hydrogen production in the near term. “Blue” hydrogen from conventional steam methane reforming (SMR) with pre-combustion CO2 capture can fulfil this role. This study therefore presents techno-economic assessments of a range of SMR process configurations to minimize hydrogen production costs. Results showed that pre-combustion capture can avoid up to 80% of CO2 emissions cheaply at 35 €/ton, but the final 20% of CO2 capture is much more expensive at a marginal CO2 avoidance cost around 150 €/ton. Thus, post-combustion CO2 capture should be a better solution for avoiding the final 20% of CO2. Furthermore, an advanced heat integration scheme that recovers most of the steam condensation enthalpy before the CO2 capture unit can reduce hydrogen production costs by about 6%. Two hybrid hydrogen production options were also assessed. First, a “blue-green” hydrogen plant that uses clean electricity to heat the reformer achieved similar hydrogen production costs to the pure blue configuration. Second, a “blue-turquoise” configuration that replaces the pre-reformer with molten salt pyrolysis for converting higher hydrocarbons to a pure carbon product can significantly reduce costs if carbon has a similar value to hydrogen. In conclusion, conventional pre-combustion CO2 capture from SMR is confirmed as a good solution for kickstarting the hydrogen economy, and it can be tailored to various market conditions with respect to CO2, electricity, and pure carbon prices.

Development of Natural Hydrophobic Deep Eutectic Solvents for Precombustion CO2 Capture

Hydrophobic deep eutectic solvents (DESs) have been designed as effective solvents for precombustion CO2 capture by using a conductor-like screening model for real solvents (COSMO-RS). Reliable CO2 solubilities in various compounds and binary solvents were estimated. We have developed new DESs from 38 selected, nature-derived, hydrophobic, and CO2 affinitive compounds. The possibilities of any two of these substances to form DESs were assessed from predicted activity coefficients, followed by an estimation of the CO2 solubilities of the theoretically feasible DESs. 58 promising hypothetical DESs were screened out. Subsequently, eight DESs were successfully prepared and characterized. Most of these DESs have a density larger than 1.0 g/mL at 298.15 K. The DESs have a similarly low volatility as decanoic acid–menthol (1:2) and are thermally stable below 420 K. Vanillin-4-oxoisophorone (1:3) and methyl salicylate-4-oxoisophorone (1:1) have been identified to be very promising for precombustion capture, showing comparable CO2 solubility and viscosity to the well-known, conventionally used Selexol solvent.

High efficient pre-combustion CO2 capture by using porous slurry formed with ZIF-8 and isoparaffin C16

Integrated gasification combined cycle (IGCC) power generation has drawn more and more attention because of the increasing demand for zero CO2 emission. H2/CO2 mixture with middle/higher pressure like IGCC gas is usually separated by using low energy consumption physical absorption approach. Here, for upgrading traditional physical absorbents, we report a new porous slurry formed with ZIF-8 and isoparaffin C16 to raise CO2 capture capacity and selectivity. The properties and sorption behaviors of this slurry have been experimentally investigated, and the content of ZIF-8 is optimized as 20 wt%. The optimized slurry exhibits low viscosity (11.02–2.75 mPa·s when temperature ranges from 273.15 to 303.15 K), sufficiently high sorption speed, low CO2 sorption heat (9.39–18.47 kJ/mol, decreasing with increasing CO2 loading). More importantly, the slurry exhibits much higher CO2 sorption capacity (e.g., 3.39 mol/L/MPa at 0.1 MPa and 273.15 K, vs. 2.48 mol/L/MPa for dimethyl ethers of polyethylene glycol (DEPG) and 2.22 mol/L/MPa for propylene carbonate (PC)) and selectivity over H2 (17.4–205, which could be one time higher than DEPG and three times higher than PC). The recyclability of this slurry system is also excellent. The 98% sorption capacity is recovered by vacuuming for 5 min without heating, showing that the easy sorption-desorption cycle can be completed only via pressure swing. We believe ZIF-8/isoparaffin C16 slurry would be a promising alternative to existing commercial CO2 absorbent for separating IGCC gas with higher efficiency and lower energy cost.