NEW JOURNAL OF CHEMISTRY
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2018
·Vol. 42
·期 15
·13054-13064
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IF 3.201
Qingwen Gu,Jian Fang,Zichen Xu,Wenxiu Ni,Kang Kong,Zhenshan Hou
1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) is an effective nucleophilic catalyst for the transesterification of dimethyl carbonate (DMC) with various alcohols and amines, which afforded unsymmetrical organic carbonate and carbamate. It was observed that the transesterification was accelerated under pressurized CO2 in this work. The activity is very high and the best result (89% conversion with 98% selectivity to unsymmetrical carbonate) was obtained for the DBU/alcohol/DMC/CO2 system. The addition of CO2 to DBU/ethanol generated the DBU cation salt, [DBUH][OCOOCH2CH3], which dissociated more favorably under increasing reaction temperature even under pressurized CO2. The salt could also help to activate DMC by H-bond interaction. The reaction system can be extended easily for the catalytic synthesis of carbamates from amines and DMC. After the reaction, the salt was separated from the reaction mixture and DBU can be recovered by the feasible thermal decomposition, offering a straightforward strategy for the recycling of DBU. On the basis of these results, a plausible mechanism involving the role of both DBU and CO2 has been proposed.
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ACS Applied Materials & Interfaces
·
2018
·
IF 8.097
Dongxing Tan,Jianling Zhang,Jinbiao Shi,Shaopeng Li,Bingxing Zhang,Xiuniang Tan,Fanyu Zhang,Lifei Liu,Dan Shao,Buxing Han
To develop photocatalysts with desirable compositions and structures for improving the efficiency and selectivity of CO2 conversion to CH4 under mild conditions is of great importance. Here, we design an effective photocatalyst of bimetal (Ag/Pd) nanoalloys supported on nitrogen-doped TiO2 nanosheet for CO2 conversion. Such a novel photocatalyst combines multiple advantages of abundant Ti3+ ions, oxygen vacancies, and substitutional nitrogen that are favorable for catalyzing CO2 reduction. It was found that CO2 could be efficiently transformed to CH4 under mild conditions, i.e., in aqueous solution and at atmospheric pressure and room temperature. The maximum production rate of CH4 can reach 79.0 μmol g–1 h–1. Moreover, the Ag/Pd bimetals supported on N-doped TiO2 nanosheet exhibit high selectivity to CH4. The as-synthesized photocatalyst can be well recycled for CO2 reduction.
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高影响因子
MICROPOROUS AND MESOPOROUS MATERIALS
·
2018
·
IF 3.649
Yunzhe Jiang,Chuanyao Liu,Jürgen Caro,Aisheng Huang
A new UiO-66-NH 2 based MOF named UiO-66-NH 2 @ICA has been prepared by grafting imidazole-2-carbaldehyde (ICA) to UiO-66-NH 2 through a post-synthesis reaction via amine condensation. FESEM , XRD , 1 H NMR, FT-IR and N 2 adsorption were used to characterize the morphology and structure of UiO-66-NH 2 @ICA. The grafted ICA mainly reduces the pore volume of UiO-66-NH 2 but increases the number of nitrogen atom as binding site of CO 2 . The UiO-66-NH 2 @ICA showed less BET surface area but a higher CO 2 /CH 4 adsorption selectivity in comparison with UiO-66-NH 2 . UiO-66-NH 2 @ICA and UiO-66-NH 2 crystals were dispersed in Matrimid ® 5218 to form mixed-matrix membranes (MMMs). Single gas permeation and mixed gas separation was carried out to investigate the effects of filler loading and feed gas pressure on the separation performances of the MMMs. The UiO-66-NH 2 @ICA/Matrimid ® MMM with 10 wt % filler showed a high CO 2 /CH 4 selectivity with a separation factor of 64.7, which is an increase by 40% in comparison with UiO-66-NH 2 /Matrimid ® MMM.
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PHYSICAL CHEMISTRY CHEMICAL PHYSICS
·
2018
·Vol. 20
·期 30
·19900-19905
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IF 3.906
Caili Dai,Qianru Yang,Mingwei Gao,Mingwei Zhao,Jianfeng Jiang
To indicate the difference between pH and CO2 stimuli mechanisms, a dual responsive system is constructed with the aid of N-[3-(dimethylamino)propyl]docosanamide (NDPD) and sodium salicylate (NaSal), which is responsive to pH and CO2. The dual responsive system is characterized by rheometry, cryo-TEM and 1H NMR spectroscopy. After bubbling CO2 or adjusting the pH, the rheological properties indicate the formation of wormlike micelles. The cyro-TEM images also confirmed wormlike micelles. The effect of temperature is also clarified. By comparing the rheological properties of the wormlike micelles with pH and CO2 stimuli conditions, combined with cryo-TEM and 1H NMR results, the stimuli mechanisms of pH and CO2 to the dual responsive system are shown. Through this work, we expect to deepen our understanding of the responsiveness of a self-assembled system.
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Inorganic Chemistry Frontiers
·
2019
·Vol. 6
·期 7
·1799-1812
·
IF 5.934
Xiaosong Hu,Chaoyue Zhao,Qingxin Guan,Xin Hu,Wei Li,Jun Chen
The chemical transformation of CO2 not only mitigates CO2 released into the atmosphere but also produces fuels and chemicals with important additional value. The activation of stable CO2 molecules is the key difficulty for the efficient conversion of CO2. Herein, we designed a ternary catalyst containing Cu, ZnO, and CeOx and dispersed them in SBA-15 using incipient wetness impregnation. Interestingly, the catalytic performances were improved greatly when the related active components were dispersed inside and outside the pore channels of SBA-15 using the incipient wetness impregnation method. Methanol and CO were controllably produced on the interface of Cu and metal oxides (ZnO and CeOx) due to the synergistic effects between the three active components. The metal oxides play a more important role in CO2 conversion as well as the product selectivity compared to Cu. CeO2 is more efficient than ZnO in promoting the dispersion of Cu nanoparticles and methanol generation. The suitable pore channels of SBA-15 promote the mass transfer and heat transfer while the high specific surface area is favorable to the dispersion of active components, which will facilitate the production of methanol and CO. After continuous hydrogenation evaluation for 100 h, the catalytic performance of the catalyst was still very stable. This work provides a viable strategy to prepare a supported catalyst with highly dispersed active sites, and the catalyst exhibits an efficient catalytic effect on producing methanol and CO.
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JOURNAL OF MOLECULAR LIQUIDS
·
2019
·
IF 4.561
Xiangrui Meng,Yijin Mi,Dongling Jia,Ning Guo,Yarui An,Yuqing Miao
Co hydroxide polymorphs (green α-Co(OH) 2 , red β-Co(OH) 2 and brown β-Co(OH) 3 ) formed at separate positions in a test-tube. Diffusion of hydrazine hydrate downward in agar gel facilitated the reaction between hydrazine and Co 2+ leading a dilatational wave of reactant concentration. The resulting periodic Liesegang bands of α-Co(OH) 2 were observed due to the diffusion hindrance of reactants. It can be deduced that the high concentration of Co 2+ causes formation of α-Co(OH) 2 while the low concentrations produce β-Co(OH) 2 . β-Co(OH) 2 is oxidized readily to form brown β-Co(OH) 3 at the upper area of agar gel with high alkali condition and O 2 distribution. This study is helpful to learn the formation of more than one product and prepare multiple materials in single chemical reaction system. In addition, the obtained α-Co(OH) 2 has been stabilized in the gel medium for at least 3 months. It may facilitate its application in many areas especially in electrochemical area since α-Co(OH) 2 typically exhibits higher conductivity and electrocatalysis than β-Co(OH) 2 while in the past its application often is limited by thermodynamically instability.
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Royal Society Open Science
·
2019
·Vol. 6
·期 3
·
IF 2.515
Fei Wang,Juangang Wang,Yunhuan Cheng
In this paper, a novel photocatalyst CNCC with excellent visible light photocatalytic performance was successfully prepared to optimize the CO2 photoreduction performance. The results showed that the methanol formation rate of CNCC was 24.7 µmol g−1 h−1, which was 1.42 times higher than that of NCC. The enhanced photoactivity is attributed to the rapid propagation of charge carriers induced by light from the constructed composite structure.
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NANOTECHNOLOGY
·
2019
·Vol. 30
·期 39
·394001
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IF 3.399
Qijie Mo,Liuqing He,Jiachang Zeng,Qingsheng Gao
Exploring noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) is a key issue in a hydrogen economy blueprint. As one of the promising candidates, transition metal phosphides unfortunately suffer from inevitable surface oxidation which obstructs active-site exposure. Herein, a facile reduction followed by a surface phosphorization is introduced to convert surface-oxidized cobalt phosphides to a Co2(P2O7)-CoP heterostructure embedded in N-doped carbon (Co2(P2O7)-CoP/NC), accomplishing an efficient HER in both acidic and alkaline electrolytes. It affords low overpotentials (η10) of 88 and 97 mV to reach a current density of −10 mA cm−2, and small Tafel slopes of 51 and 61 mV dec−1 in 0.5 M H2SO4 and 1.0 M KOH, respectively, outperforming the parent surface-oxidized Co2P and most previously-reported Pt-free electrocatalysts. The remarkably improved electrocatalysis should be ascribed to the strong surface acidity of the Co2(P2O7) component and thereby the promoted HER kinetics on Co2(P2O7)-CoP interfaces. This work will encourage the development of cost-efficient electrocatalysts via surface engineering.
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FUEL
·
2017
·
IF 4.601
Yannan Li,Jun Cheng,Leiqing Hu,Jianzhong Liu,Junhu Zhou,Kefa Cen
In order to reduce energy consumption of absorbent regeneration, an amine absorbent piperazine (PZ) was dissolved in an organic solvent N , N -dimethylformamide (DMF) to prepare a phase-changing PZ/DMF solution for CO 2 absorption with solid precipitate of PZ-carbamate. The CO 2 absorption capacity and peak rate of PZ/DMF solution were 22.9% and 29% higher than those of PZ/water solution, respectively. Based on differential scanning calorimetry/thermogravimetry experiments, biscarbamate PZ(CO 2 ) 2 2− and protonation PZ(H) 2 2+ compositions (34.5 wt%) in the PZ-carbamate precipitate mainly decomposed at peak temperature of 91.9 °C due to their instability, and then PZ(CO 2 ) composition (65.5 wt%) in the PZ-carbamate precipitate decomposed at peak temperature of 125.7 °C. The electrochemical corrosion tests and scanning electron microscopy revealed that PZ/DMF solution had much lower corrosivity than PZ/water solution.
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CATALYSIS TODAY
·
2017
·
IF 4.636
Zhibiao Shi,Haiyan Yang,Peng Gao,Xiaopeng Li,Liangshu Zhong,Hui Wang,Hongjiang Liu,Wei Wei,Yuhan Sun
A series of TiO 2 supported Co–Cu catalysts with the weight percent of potassium oxides ranged from 0 to 3.5 wt.% were synthesized. This work investigates the influence of potassium promoter on CO 2 hydrogenation to long-chain (C 5+ ) hydrocarbons. The introduction of suitable amount of K into the CoCu/TiO 2 catalyst remarkably promoted the formation of C 5+ hydrocarbons and suppressed methane formation. The temperature-program desorption measurements demonstrate that the addition of K increases the chemisorption of CO 2 , whereas H 2 adsorption is decreased, which enhanced production of liquid fuels. However, these effects were not obvious with the addition of excess amount of K due to the slight change of surface K content. A maximum C 5+ yield with CO 2 conversion of 13% and C 5+ selectivity of 35.1 C-mol% is obtained over the CoCu/TiO 2 catalyst with 2.5 wt.% of potassium promoter loading, which also exhibits a substantial stability.
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APPLIED CLAY SCIENCE
·
2017
·
IF 3.101
Jing Ouyang,Wei Gu,Chenghui Zheng,Huaming Yang,Xiangchao Zhang,Yelin Jin,Jing Chen,Jinlong Jiang
CO 2 capture and storage (CCS) by advanced materials and technologies will play a significant role in reducing industrial or human caused CO 2 emissions. In this article, a clay mineral based CO 2 absorbent was prepared by impregnating polyethyleneimine (PEI) onto acid modified fibrous sepiolite . X-ray diffraction (XRD), Fourier transform microscopy (FTIR), thermogravimetric analysis (TGA), and N 2 adsorption - desorption isotherms accompanied BET (Brunauer-Emmett-Teller) analysis were used to characterize the raw mineral and the prepared absorbents as well as their CO 2 adsorption performances. After the acid treatment, the raw sepiolite changed into amorphous silica (SiO 2 ) containing a small amount of MgO , but maintained their nanowire morphology, the S BET value of acid treated Sep was 4 times larger and pore volume was about 2 times higher than the raw mineral. The MgO-SiO 2 nanowires and polyethyleneimine (PEI) successfully formed an organic-inorganic hybrid composite. A maximized adsorption capacity of 2.48 mmol/g at 75 °C was reached in CO 2 adsorption/desorption measurement when the composite contained 50 wt% PEI. The product also showed an excellent adsorption repeatability, above 98% of the optimized CO 2 adsorption capacity could be maintained after 10 circles tests, which confirmed that the fibrous MgO-SiO 2 assembly optimal amount of PEI is a promising solid absorbent in CO 2 gases controlling fields.
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HIGH PERFORMANCE POLYMERS
·
2017
·
IF 1.179
Xin Fu,Xueqin Li,Ruili Guo,Jianshu Zhang,Xingzhong Cao
A series of block copolymer membranes was designed using polyetheramine (PEA) and methyl-containing polyisophthalamides (MPA) for the separation of carbon dioxide (CO2)/methane (CH4) gas mixtures. PEA consists of abundant ethylene oxide units, which show good affinity with CO2, and MPA consists of methyl (Me) substituents, which can increase the fractional free volume of block copolymer membranes. The Me substituents were introduced into MPA via polymerization from isophthaloyl dichloride (IPC), 2,5-dimethyl-1,4-phenylenediamine (DPD), and 4,4′-bis(3-aminophenoxy)diphenyl sulfone (BADS). Therefore, the CO2 solubility and diffusivity in the membranes could be improved by tailoring the PEA/MPA mass ratio and BADS/DPD mole ratio, respectively. The membrane with a PEA/MPA mass ratio of 6/4 and a BADS/DPD mole ratio of 1/10 exhibited optimum CO2 separation performance with a CO2 permeability of 629 Barrer and CO2/CH4 selectivity of 23 at 2 × 105 Pa and 25°C.
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