CHEMICAL ENGINEERING SCIENCE
·
2023
·
IF 4.7
Shidong Wang,Yaxi Wang,Xinru Wu,Cejun Hu,Hongwei Zhang,Qinyang Cui,Xiaojun Bao,Pei Yuan
Pore diffusion effect plays a crucial role in heterogeneous hydrogenation of unsaturated polymers. However, how large pore size can eliminate the pore diffusion limitation remains a controversial issue. Herein, we prepared a series of Pd/SiO 2 catalysts with graded pore sizes and investigated the effect of pore size on hydrogenation activity of nitrile butadiene rubber (NBR). It is found that when the catalyst pore size (D cat ) is 7 times of the diameter of NBR chains (D NBR ), the Weisz modulus Φ can be reduced to < 0.3 thus the internal mass transfer limitation can be eliminated, making NBR easier to approach the active sites. Consequently, the catalysts with the D cat /D NBR > 7 exhibit excellent catalytic activity (96.7%) and selectivity (100%) to C = C. This work emphasizes that the pore size of catalysts can regulate the pore transfer limitation and the accessibility of internal active sites, providing useful guidance for the design of efficient macromolecular hydrogenation catalysts.
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FUEL
·
2023
·
IF 7.4
Fukun Bi,Shuting Ma,Bin Gao,Yang Yang,Lexun Wang,Fuhao Fei,Jingcheng Xu,Yuandong Huang,Minghong Wu,Xiaodong Zhang
Herein, Pd and Pt-catalysts loaded on non-oxide support (g-C 3 N 4 ) were prepared and compared for CO and toluene co-oxidation, and Pt/C 3 N 4 presented excellent catalytic performance. A series of characterizations including TEM, H 2 -TPR, O 2 -TPR and XPS etc., indicated that Pt/C 3 N 4 exhibited the smaller Pt NPs, better low temperature reduction ability, more active oxygen species and positive charged Pt species, which could account for its better catalytic performance. Additionally, DFT calculations further confirmed that the lower activation barrier of O 2 and the higher adsorption for CO and toluene triggered the efficient CO and toluene degradation over Pt/C 3 N 4 . Interestingly, the introduction of H 2 O (10.0 vol%) suppressed the catalytic performance of Pd/C 3 N 4 , while expedited CO and toluene oxidation over Pt/C 3 N 4 , which was revealed by DFT calculations. Furthermore, the difference in degradation intermediates, corresponding distributions and toxicity generated during toluene oxidation under different conditions over Pd/C 3 N 4 and Pt/C 3 N 4 were exposed. Compared with Pd/C 3 N 4 , less variety, toxicity and content of intermediates produced over Pt/C 3 N 4 . This work would inspire many rational designs of supported noble metal catalysts for environmentally friendly catalysis.
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POLYMERS FOR ADVANCED TECHNOLOGIES
·
2023
·Vol. 34
·期 8
·2541-2553
·
IF 3.4
Li-Ying Ren,Qian-Qian Li,Yu-Xia Zhang
The 3,4-ethylenedioxy thiophene (EDOT)-based conjugated microporous polymers (CMPs) were readily constructed via facile one-step direct arylation polymerication of C H from simple EDOT as a linker and commercially available aryl bromides of different geometries as the knots, without preactivation of C H bonds of aromatic building blocks using organometallic reagents. In contrast to conventional coupling reactions, this synthesis strategy not only has atomic efficiency but also can use simple thiophene derivatives as building blocks for synthesizing thiophene-based CMPs of different structures, which avoids the synthesis of complex thiophene derivatives and are important for applications, for example, fluorescent sensors. The resulting EDOT-based CMPs were used to fluorescent sensing to 2,4-dinitrophenol (DNP), I 2 , and p-nitrophenol (p-NP), with high optimal Stern-Volmer quenching constants.
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Polymers
·
2023
·Vol. 15
·期 11
·2501
·
IF 5
Panpan Zhang,Qiongqiong Xu,Wenyu Mao,Jiaxing Lv,Haodong Tang,Huadong Tang
A novel synthesis of ultrahigh molecular weight poly(methyl methacrylate) (PMMA) using organosulfur compounds combined with a catalytical amount of transition metal carboxylates as an initiator has been developed. The combination of 1-octanethiol with palladium trifluoroacetate (Pd(CF3COO)2) was found to be a very efficient initiator for the polymerization of methyl methacrylate (MMA). An ultrahigh molecular weight PMMA with a number-average molecular weight of 1.68 × 106Da and a weight-average molecular weight of 5.38 × 106Da has been synthesized at the optimal formulation of [MMA]:[Pd(CF3COO)2]:[1-octanethiol] = 94,300:8:23 at 70 °C. A kinetic study showed that the reaction orders with respect to Pd(CF3COO)2, 1-octanethiol, and MMA are 0.64, 1.26, and 1.46, respectively. A variety of techniques such as proton nuclear magnetic resonance spectroscopy (1H NMR), electrospray ionization mass spectroscopy (ESI-MS), size exclusion chromatography (SEC), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electron paramagnetic resonance spectroscopy (EPR) were employed to characterize the produced PMMA and palladium nanoparticles (Pd NPs). The results revealed that Pd(CF3COO)2was firstly reduced by the excess of 1-octanethiol to form Pd NPs at the early stage of the polymerization, followed by the adsorption of 1-octanethiol on the surface of nanoparticles and subsequent generation of corresponding thiyl radicals to initiate the polymerization of MMA.Keywords:ultrahigh molecular weight;PMMA;polymerization;kinetics;mechanism
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CHEMICAL ENGINEERING JOURNAL
·
2023
·
IF 15.1
Hongye Li,Xunli Zhang,Qingqiang Wang,Nan Jin,Haisheng Wei,Yuchao Zhao
There are still technical challenges associated with surface fouling and clogging in microchannels when conducting multiphase catalytic reactions involving solid particles. In this study, a Pickering emulsion was employed to enhance the oxidation of benzyl alcohol (BNOH) catalyzed by Pd/SiO 2 nanoparticles under Taylor flow in a microchannel reactor. The reaction characteristics of benzyl alcohol/water Pickering emulsion in a microchannel reactor were studied experimentally. The characteristic results showed that the O/W Picking emulsion system was superior to the W/O Picking emulsion system for the catalytic oxidation reaction. The influences of a wide range of operational variables were characterized on the conversion of reactants and the selectivity of the desired product. The optimized reaction conditions included: reaction temperature 403 K, CB 5 wt%, O 2 /BNOH (mol/mol) 0.76 and tube length 8 m. Under the optimal operating conditions, the conversion of BNOH and the selectivity of benzaldehyde were found to be 86.53% and 99.79%, respectively. In addition, the interfacial transport-reaction mechanism in Pickering emulsions under Taylor flow in microchannels was proposed from the perspective of multiphase mass transfer. This development provided significant insights and guiding for effectively performing multiphase catalytic reactions involving solid catalyst particles in microchannel reactors.
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Journal of Energy Chemistry
·
2023
·
IF 13.1
Jun Li,Liying Cai,Xiaosi Liang,Shuke Huang,Xiaosha Wang,Yongshuai Kang,Yongjian Zhao,Lei Zhang,Chenyang Zhao
Light-metalloid-atom-doped Pd interstitial nanoalloy is promising candidate for electrocatalysis because of the favorable electronic effect. Herein, an innovative method was developed to synthesize C-doped Pd interstitial nanoalloy using palladium acetate both as metal precursor and C dopant. Elaborate characterizations demonstrated that C atoms were successfully doped into the Pd lattice via self-catalytic decomposition of acetate ions. The as-synthesized C-doped Pd catalysts showed excellent activity and durable stability for formic acid electrooxidation. The mass activity and specific activity at 0.6 V of C-doped Pd were approximately 2.59 A/mg and 3.50 mA cm −2 , i.e., 2.4 and 2.6 times of Pd, respectively. DFT calculations revealed that interstitial doping with C atoms induced differentiation of Pd sites. The strong noncovalent interaction between the Pd sites and the key intermediates endowed Pd with high-selectivity to direct routes and enhanced CO tolerance. This work presents a sites-differentiation strategy for metallic catalysts to improve the electrocatalysis.
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Nanoscale
·
2023
·Vol. 15
·期 8
·3772-3779
·
IF 6.7
Qiaoli Chen,Hui Jin,Tianchun Cheng,Zhi Wang,Yaoyao Ren,Jinshu Tian,Yihan Zhu
Proton-exchange membrane fuel cells are considered as promising energy-conversion devices. Alloying 3d transition metals with noble metals not only highly improves the performance of noble metal-based catalysts towards electrocatalytic reactions in fuel cells due to d–d hybridization interaction but also decreases the total cost. However, the rapid leaching of transition metal atoms leads to a fast decay of the activity, which seriously affects the performance of the fuel cell. Herein, alloyed Pd-main group metal (e.g. Pb, Bi, Sn) ultrathin nanowires were realized by a facile one-step wet-chemical strategy. The content of the main group metal could be tuned in a certain range while maintaining the same one-dimensional ultrathin nanowire morphology, which provided a large surface area and many more active sites. These Pd-based alloys showed a significant improvement in electrocatalytic activity and durability towards the oxygen reaction reaction as well as ethanol oxidation reaction. Optimal activity occurred when a small amount of main group metal existed, which could be explained through calculations by a strong p–d hybridization interaction between the main group metal and Pd to optimize the surface electronic structure collaboratively. Besides, high stability was achieved, which could be ascribed to the increased antioxidant activity of Pd by the main group metal. Furthermore, the low amount of the main group metal atoms also prevented them from leaching out of the crystal lattice.
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CATALYSIS LETTERS
·
2022
·
IF 2.936
Zhang Tingting,Li Guohua,Zhang Xinyu,Xu Longjun
Herein, the multiphase catalyst was prepared for catalytic Suzuki–Miyaura cross-coupling reactions by anchoring palladium nanoparticles on tris(pentaethylene-pentamine)triazine modified boron nitride nanosheets (BNNSs-TPEPTA-Pd). The synthesized catalysts were characterized using various spectroscopic and microscopic techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES). Subsequent experiments showed that BNNSs-TPEPTA-Pd is an excellent two-dimensional heterogeneous catalyst with a wide range of substrate tolerance, achieving an excellent yield of 95% within 45 min. On average, the catalyst improved the biaryl yield by about 12% and reduzced the reaction time by 4.6 h. In addition, the catalytic effect remained high after eight catalytic cycles. Graphical Abstract An efficient, stable, and recyclable heterogeneous catalyst was prepared by anchoring palladium nanoparticles on tris(pentaethylene-pentamine)triazine modified boron nitride nanosheets (BNNSs-TPEPTA-Pd). The catalyst was used in the Suzuki–Miyaura cross-coupling reaction to verify its activity.
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JOURNAL OF MATERIALS SCIENCE
·
2022
·Vol. 58
·期 1
·170-185
·
IF 4.682
Zang Yu,Gao Shan,Jing Boyu,Sun Hong,Wang Jianjun,Liu Jiao,Miao Fengjuan,Xu Liang
Four kinds of conjugated microporous polymers (CMPs) with imine structures were synthesized by a Sonogashira coupling reaction followed by a postreaction between aldehydes and amines. Palladium nanoparticles (Pd NPs) were successfully supported on the CMPs to prepare Pd/CMP heterogeneous catalysts and were used to catalyze the Suzuki–Miyaura coupling reaction. The number of aromatic nuclei and nitrogen atoms in the CMPs highly affects Pd loading. In the Suzuki–Miyaura coupling reaction, the Pd/CMP with good Pd NPs dispersibility and appropriate Pd content (Pd/CMP-NA) exhibited the highest catalytic efficiency with 100% conversion and 95.4% yield which can be used for many substrates. The Pd/CMP-NA heterogeneous catalyst was easy to recover and still exhibited good catalytic efficiency after 5 cycles. To further understand the catalytic mechanism of Pd/CMP-NA on the Suzuki–Miyaura coupling reaction, we proposed a rational catalytic cycle. This paper provides an idea for the structural design of CMPs used for Suzuki–Miyaura catalytic reaction.
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Journal of Energy Chemistry
·
2023
·
IF 13.1
Yuling Chen,Yali Wen,Qun Zhou,Lina Shen,Fanghui Du,Pai Peng,Yu Chen,Junwei Zheng
Herein, Pd nanoparticles loaded Co 3 O 4 catalysts (Pd@Co 3 O 4 ) are constructed from zeolitic imidazolate framework-67 (ZIF-67) for the ethanol oxidation reaction (EOR). It is demonstrated for the first time that the electrochemical conversion of Co 3 O 4 support would result in the charge distribution alignment at the Pd/Co 3 O 4 interface and induce the formation of highly reactive Pd-O species (PdO*), which can further catalyze the consequent reactions of the intermediates of the ethanol oxidation. The catalyst, Pd@Co 3 O 4 -450, obtained under the optimized conditions exhibits excellent EOR performance with a high mass activity of 590 mA mg −1 , prominent operational stability, and extraordinary capability for the electro-oxidation of acetaldehyde intermediates. Importantly, the detailed mechanism investigation reveals that Pd@Co 3 O 4 -450 could be benefit to the C–C bond cleavage to promote the desirable C1 pathway for the ethanol oxidation reaction. The present strategy based on the metal-support interaction of the catalyst might provide valuable inspiration for the design of high-performing catalysts for the ethanol oxidation reaction.
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ADVANCED FUNCTIONAL MATERIALS
·
2023
·Vol. 33
·期 44
·2302285
·
IF 19
Zhixuan Liang,Yiheng Li,Liu He,Zhi Gao,Zhenbin Tang,Yiting Xu,Birong Zeng,Weiang Luo,Guorong Chen,Conghui Yuan,Lizong Dai
Biological tissues grow or evolve through a series of complicated processes of matter and energy internalization, which are highly challenging to mimic in synthetic materials. Herein, a delayed cross-linking strategy is developed to program the reactivity of cross-linking sites and make hydrogels evolvable. The polymer networks are constructed by combining polyvinyl alcohol (PVA) with a polyzwitterion comprising both cationic quaternary ammonium and anionic phenylboronic acid groups (PQBA). Shielding of phenylboronic acid groups in ion pairs and polyzwitterion microdomains delays the cross-linking between PVA and PQBA. Mechanical stimulations unlock the phenylboronic acid groups and dramatically accelerate the cross-linking reaction. A simple stretching treatment makes the hydrogels stronger. Training the hydrogels with five cycles of 200% stretching results in up to ≈13.0- and ≈22.8-fold of enhancements in tensile strength and maximum Young's modulus, respectively. The hydrogels can also self-evolve in a damage-healing process, the fracture strength and maximum Young's modulus of the hydrogels increase by at most ≈7.5- and ≈27.2-fold after five times of repeated tensile rupture and self-healing. The study demonstrates the possibility of designing “living polymeric materials” by programming the cross-linking kinetics of polymer networks.
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ACS Applied Materials & Interfaces
·
2022
·
IF 10.383
Danying Zhao,Qiannan Cai,Xuanbo Zhu,Wenhan Xu,Qiwen Zhou,Sen Niu,Zhenhua Jiang,Yunhe Zhang
In energy storage and transportation systems, polymer dielectrics are widely applied in smart grids, electric vehicles, and power conditioning owing to their incomparable power density and high reliability. However, the dielectric constant (ε) and breakdown strength (Eb) normally cannot be increased simultaneously, which results in insufficient discharged energy density especially at high temperatures. In this work, enhanced Eb and high energy density are archived in multilayer polymer nanocomposites by introducing cross-linked dielectric transition layers. Specifically, the sandwiched composite achieves a huge discharge energy density of 4.64 J cm–3 with a charged–discharged efficiency of 84% at 150 °C and 500 MV m–1. The formation of cross-linked dielectric transition layers between layers of the multilayer nanocomposite could effectively restrain the growth of the electrical tree and greatly increase the Eb. This work presents a strategy for designing high-performance multilayered dielectric polymer nanocomposites by introducing cross-linked dielectric transition layers to reduce the loss from interlayer interfaces.
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