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Polyamines confined within mesoporous supports have shown great potential as materials for postcombustion CO2capture. However, previous research has focused on improving adsorption performance, with little attention given to identifying practical desorption temperatures that can enable fast desorption and preserve the thermal stability of the sorbent. To address this, we impregnated pentaethylenehexamine (PEHA) and branched polyethylenimines (PEIs) onto silica gel and studied the effects of polymer structural and physical properties, polymer loading, and temperature on adsorption/desorption efficiency and cyclic thermal stability. At 40 °C, the adsorption efficiency and capacity followed this order: PEHA-40 < PEI12-40 < PEI8-40, which was consistent with their structural openness and primary/secondary (P/S) amine ratio. At 60 °C, the efficiency followed the same order, whereas the highest capacity was reached by PEHA-40, the sorbent with the polymer having the smallest molecule and highest amine density. The desorption kinetics was influenced by the S/P amine ratio, polymer loading, and temperature. PEHA-40, the sorbent with the lowest isosteric heats, likely due to its high S/P amine ratio, exhibited the fastest desorption of CO2at 60 °C followed by PEI12-40 and PEI8-40. Nevertheless, when performing the desorption at 100 °C, all three sorbents exhibited similar desorption rates. The sorbent with the lowest polymer loading (PEI8-30) enabled the fastest CO2desorption because of high CO2diffusion. The results from the thermal stability analysis indicated that the use of high-molecular-weight polymers (PEI MW 1200) and high polymer loadings (filled pores) can effectively suppress polymer leaching, the latter being attributed to a denser hydrogen bond network and reduced polymer concentration gradient. Through this systematic study, the identification of a sorbent with excellent thermal stability and rapid regeneration at 100 °C (PEI12-40) was made possible. This sorbent has significant promise for use in CO2capture systems utilizing vacuum-assisted desorption, and using unmodified polymer structures can lead to substantial cost savings in sorbent preparation.

Valorization of biomass-derived oxygenates to jet fuel range aromatics harbors tremendous practical value due to growing concerns about the sustainable production of fuels and chemicals. Herein, bioderived C3oxygenates with different functional groups including aldehydes, ketones, and alcohols were converted to jet fuel range hydrocarbons with high yield (maximum 86.1%) and purity (maximum 98.2%) and remarkably enhanced stability in a single continuous-flow reactor using nonprecious dual-bed catalysts. Instead of the conventional pathway (i.e., olefin generation following oligomerization), our strategy first transforms pronanal, propanol, and acetone into C9–C12oxygenates via aldol condensation and ring closure reactions on the upstream Cu/SiO2+ TiO2catalyst and subsequently converts the aldol-derived oxygenates through hydrogenation–dehydration–aromatization reactions on the downstream Ni/HZSM-5 catalyst at a relatively moderate temperature (573 K) and atmospheric pressure. This versatile and atom-economic strategy opens new opportunities for the efficient upgradation of bio-oil-derived oxygenates to renewable jet fuel range aromatics.

The autothermal gas-phase oxidative dehydrogenation of ethane (ODHE) in a tubular reactor was analyzed by one-dimensional (1D) and two-dimensional (2D) reactor simulations coupling with a detailed kinetic model, where effects of the reactor configuration and operating conditions such as the C2H6/O2ratio, inlet temperatures, and oxygen distribution on the ethylene yield were analyzed and optimized. An inlet temperature of 1023 K and a C2H6/O2ratio of 3.3 were found as the best-operating conditions for the gas-phase oxidative dehydrogenation of ethane with autothermal operations. Multiple injections of oxygen feed are analyzed and used to optimize the ethylene yield using an overall C2H6/O2ratio of 3.3. An ethylene yield of 57.8% (C2H4selectivity 70.2%) is predicted for an inlet temperature of 1023 K. The results demonstrated the importance of small gradients of oxygen and temperature in the reactor for both the axial and radial directions to gain a high ethylene yield. A multitubular reactor with a relatively small diameter and multiple axial oxygen injections is recommended.

Research in the sustainable conversion of biomass to fuels and chemicals is a necessity for the reduction of the carbon footprint in transport energy. Herein, we demonstrate an efficient tandem catalyst to selectively convert (simulated) bio-oil to hydrocarbons with enhanced C4+fuel yield in a fixed bed reactor of a small pilot plant. The tandem catalytic system is a multifunctional dual bed system; carbon coupling catalysts (0.2 wt % X-TiO2(X: Ru, Pd, Au) at the upper layer and hydro-deoxygenation (Ru-MoFeP/Al2O3) at the bottom layer in a single fixed bed reactor. The upper-bed catalysts facilitated the carbon coupling reaction of C2–C4light oxygenates and significantly reduced the light gases yield (C1–C5) to ca. 40% and increased the organic (C4+) phase ca. 15%. The analysis of the organic phase suggests that among the screened upstream catalysts, 0.2 wt % Ru/TiO2||Ru-MoFeP/Al2O3recorded the optimum activity. The coupled light oxygenates (acetone) alkylated with the phenolic compounds and sequentially hydro-deoxygenated to yield higher C4+hydrocarbons. This versatile tandem catalytic approach has a potential application in the emerging biorefinery concept.

The development of an energy-efficient and cost-effective technology for the purification of a hydrogen rich stream to achieve a CO concentration below 10 ppm, suitable for low temperature fuel cell applications, is one of the major objectives of energy research. Here we report the sorption enhanced Boudouard (SEB) reaction as an effective route for pure hydrogen production on metal-free catalysts by the highly selective removal of CO and CO2from a hydrogen rich stream, where CaO serves as both a catalyst and a CO2sorbent. We reveal that the in situgenerated oxygen vacancy by CO adsorption on CaO catalyzes the sorption enhanced Boudouard reaction, hence the Boudouard reaction and CO2removal occur simultaneously in a single step. The capture of CO2in the presence of H2by the solid sorbent shifts the chemical equilibrium towards complete CO conversion. The results demonstrate a remarkable decrease in the CO concentration from 0.5% in a hydrogen rich stream to less than 5 ppm, suitable for low temperature fuel cells. It avoids a subsequent preferential oxidation process or methanation reaction, as well as an additional CO2capture process. The feasibility of applying the sorption enhanced Boudouard reaction in the production of highly pure hydrogen (CO content less than 10 ppm) was demonstrated by multicycle tests of Boudouard-carbonation/regeneration on Ca-based oxides with stable cyclic operation.

Monitoring and simulating the events occurring on the catalysts under the real reaction conditions has significant meaning for elucidating the dynamic changes of the active sites during the reactions and for a better understanding of the reaction mechanisms. Herein, we use the operando ultraviolet–visible and near-infrared (UV–vis–NIR) spectroscopy to study the CuCl2/γ-Al2O3-based catalyst in ethylene oxychlorination, one of the most important processes for producing vinyl chloride in the industry, to elucidate the dynamic changes of the copper active sites. The full spectra of Cu species such as CuCl2, CuCl2with vacancies, CuCl, and Cu2OCl2were detected and identified for the first time, and their transient changes and contribution in the reduction, oxidation, and hydrochlorination steps as well as at the steady-state operation in the catalytic cycle can be accurately “imaged” by resolving the UV–vis–NIR spectra dataset using the multivariate curve resolution (MCR) analysis. The distribution and changes of the Cu species are correlated to the catalytic activity, selectivity, and stability. The time-resolved spectra and their correlation with the catalytic performance provide better insights into the dynamic nature of the active sites and their role in the Mars–van Krevelen-type reaction. This method is expected to be exploited to analyze the dynamics of the active sites and kinetic studies in other catalytic redox systems.