Article
Engineering, Chemical
Xiuxiu Ren, Shengjie Yang, Rong Xu, Meng Guo, Weiqiu Huang, Ming Ding, Jing Zhong
Summary: By exchanging Na+ with mono- and divalent cations, the structure and performance of Na-mordenite zeolite membranes were modified, resulting in higher water capacity and improved separation efficiency in the dehydration of acetic acid by pervaporation.
JOURNAL OF MEMBRANE SCIENCE
(2022)
Article
Chemistry, Applied
Stefanie C. M. Mizuno, Siriwan Dulnee, Tassia C. P. Pereira, Ricardo J. Passini, Ernesto A. Urquieta-Gonzalez, Jean Marcel R. Gallo, Joao B. O. Santos, Jose M. C. Bueno
Summary: This study investigates the influences of Cu content, Si/Al ratio, and sample preparation method on the active Cu species in mordenite (MOR). The XANES spectra indicate that isolated Cu+ species were formed after interaction with CH4 and were re-oxidized under a flow of water steam, showing the impact of different Cu species on CH4 oxidation.
Article
Chemistry, Multidisciplinary
Matthieu Balas, Asma Mayoufi, Richard Villanneau, Franck Launay
Summary: Since its first report in the early 1990s, Mukaiyama-type aerobic epoxidation involving the presence of an aldehyde as an electron donor is considered as an interesting oxidation reaction. Among the various metal catalysts efficient for this process, salen-type complexes have many advantages: i) cheap Schiff-base ligands can be easily synthesized and functionalized, ii) their metal complexes are described with most transition metals from the periodic table and iii) these compounds are also efficient for the catalytic formation of cyclic carbonates from epoxides and CO2, which makes them ideal candidates for the oxidative carboxylation of alkenes. The present work aimed at revisiting the aerobic oxidation of styrene using Cr(iii) and Mn(iii) salen complexes in the presence of isobutyraldehyde with the idea to further use these complexes (without any work-up), as co-catalysts for the formation of styrene carbonate under CO2 pressure. However, contrary to what is often described in the literature, the present study showed that the introduction of a metal catalyst is not necessary for the epoxidation of styrene at 80 degrees C in benzonitrile. In our hands, yields of ca. 15% of styrene carbonate were obtained from styrene using O-2 (3.5 bar) and CO2 (11 bar) as reagents in the presence of isobutyraldehyde (2.5 eq), tetrabutylammonium bromide (ca. 2 mol%) and the Cr(iii) salen complex (ca. 1 mol%). Apparently, the oxidation of Cr(iii) to Cr(vi) species in the presence of O-2 and isobutyraldehyde is detrimental to the kinetics of the tetrabutylammonium bromide-catalyzed cycloaddition of CO2 to styrene oxide.
REACTION CHEMISTRY & ENGINEERING
(2023)
Article
Chemistry, Multidisciplinary
Panxia Zhao, Jie Chen, Nana Ma, Jingfei Chen, Xiangquan Qin, Chuanfei Liu, Fuquan Yao, Lishan Yao, Longyi Jin, Zhiqi Cong
Summary: The study demonstrates the efficient H2O2-dependent (R)-enantioselective epoxidation of unfunctionalized styrene and its derivatives by site-mutated variants of a unique non-natural P450BM3 peroxygenase in combination with a dual-functional small molecule. The synergistic use of protein engineering and an exogenous DFSM represents an effective strategy to control the enantioselectivity of styrene epoxidation, significantly expanding the chemical scope of P450 enzymes as useful bio-oxidative catalysts.
Article
Chemistry, Multidisciplinary
Chenlong Wang, Hongju Zhan, Xinhuan Lu, Run Jing, Haifu Zhang, Lu Yang, Xixi Li, Fanfan Yue, Dan Zhou, Qinghua Xia
Summary: In this study, ammonia complexes were synthesized for the epoxidation of alpha-pinene, with [Co(NH3)(6)]Cl-3 showing excellent catalytic activity. When using CHP as the initiator, the conversion rate for alpha-pinene reached 97.4%, with a selectivity of 98.3% for the epoxide product. Recycling experiments demonstrated that the catalyst is stable and efficient for the epoxidation process.
NEW JOURNAL OF CHEMISTRY
(2021)
Article
Chemistry, Physical
H. Yousefzadeh, Selmi E. Bozbag, C. Erkey
Summary: The new technique of Supercritical Ion Exchange (SCIE) was used to synthesize Cu-MORS, demonstrating site selective ion-exchange inferred by the equilibrium isotherm. Cu-MORS showed 16% higher methanol productivity compared to Cu-MORA in the stepwise direct methane to methanol process. This highlights the importance of site selective ion-exchange for zeolite catalysis.
JOURNAL OF SUPERCRITICAL FLUIDS
(2022)
Article
Chemistry, Multidisciplinary
Sii Hong Lau, Meredith A. Borden, Talia J. Steiman, Lucy S. Wang, Marvin Parasram, Abigail G. Doyle
Summary: This study introduces a Ni/photoredox-catalyzed enantioselective reductive coupling of styrene oxides and aryl iodides, yielding enantioenriched 2,2-diarylalcohols. Analysis shows that enantioselectivity is correlated with the electronic properties of the ligands, with more electron-donating ligands leading to higher ee values. Experimental and computational studies support the hypothesis that reductive elimination is enantiodetermining and ligand electronic properties affect enantioselectivity by altering the position of the transition state structure.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Chemistry, Physical
Hu Xiao, Shuang Dong, Yan Liu, Xiao-Qiong Pei, Hui Lin, Zhong-Liu Wu
Summary: New (R)-selective styrene monooxygenases have been identified, showing high enantioselectivity in converting styrene analogues into (R)-epoxides with purity up to >99% ee. Site 46 was identified as a critical residue affecting the enantioselectivity of SMOs, providing a valuable green alternative for the synthesis of enantiopure (R)-epoxides.
CATALYSIS SCIENCE & TECHNOLOGY
(2021)
Article
Energy & Fuels
Qiuchen Wang, Xiaoxu Deng, Wenguang Chen, Peng Chen, Fei Liu, Shuang-Feng Yin
Summary: A novel bismuth complex-based metallopolymer (BiTMT) was prepared by a wet-chemical method and demonstrated excellent stability and conversion efficiency in the selective oxidation of organic compounds using air as the oxidant under visible light irradiation, opening up a new avenue for photocatalytic selective oxidation and other applications.
Article
Metallurgy & Metallurgical Engineering
M. L. Strauss, L. A. Diaz, J. McNally, J. Klaehn, T. E. Lister
Summary: The paper introduces an efficient extraction strategy to separately recover nickel and cobalt from waste lithium-ion batteries, without the need for additional impurity removal operations. The developed process allows for high purity metal products with minimum chemical addition and pH adjustment.
Article
Chemistry, Multidisciplinary
Hao Wang, Tiantian Jin, Simon Tricard, Xuhong Peng, Kun Liang, Peizhu Zheng, Jian Fang, Jihua Zhao
Summary: This study focuses on the development of efficient heterogeneous catalysts for the styrene epoxidation reaction. FeCo double metal cyanide (DMC) modified with linear alcohols showed promising catalytic performance. The conversion rate of styrene was mainly affected by the modification with alcohols, while the selectivity in styrene oxide was influenced by the solvent. The presence of MeOH significantly promoted the adsorption of the oxidant on the surface of FeCo DMC, leading to improved catalytic activity.
Article
Engineering, Chemical
Yuxin Wu, Zhuo Chen, Fajun Wang, Jianhong Xu, Yundong Wang
Summary: The study focused on a highly efficient microreaction system for epoxidation of styrene, achieving high conversion and excellent product selectivity. Various factors such as temperature, residence time, catalyst molar fraction, MeCN/t-BuOH molar ratio, H2O2 flow rate, and buffer solution were investigated. A kinetic equation was established based on experimental data, aiding in verifying the rationality of the reaction mechanism and optimizing experimental conditions.
CHEMICAL ENGINEERING SCIENCE
(2022)
Article
Chemistry, Physical
Perla Sanchez-Lopez, Yulia Kotolevich, Joel Antunez-Garcia, Fernando Chavez-Rivas, Evgeny Khramov, Gloria Berlier, Luis Moreno-Ruiz, Yan Zubavichus, Vitalii Petranovskii, Sergio Fuentes-Moyado, Alexey Pestryakov
Summary: In this study, experimental and theoretical methods were used to investigate the effect of differences in the deposition order of components on the state of silver in bimetallic iron-silver samples based on mordenite. The results showed that different varieties of silver were formed in each silver-containing sample, which varied in size and type compared to the other samples. The formation of large silver nanoparticles on the outer surface of mordenite was explained by the redox interaction between Ag+-Fe2+ and the selectivity of ion exchange. The local environment of silver in the studied samples also varied, with different silver species present. Partially charged silver clusters were formed inside the mordenite channels due to partial reduction of Ag+ and subsequent agglomeration. Most of the silver in the zeolite existed in a cationic state attached to the mordenite framework through electrostatic forces, and the arrangement of cations in the side pockets allowed for free transport channels, which is favorable for catalytic and adsorption applications.
Article
Chemistry, Multidisciplinary
Xiaoxue Luo, Xiaoxia Tang, Jingtian Ni, Baijing Wu, Cunpu Li, Minhua Shao, Zidong Wei
Summary: In this study, MnO2 with an asymmetric electronic configuration was designed to discriminate the spin-paired pi electrons of styrene. On the MnO2/(Ru0.3Ti0.7)O-2/Ti bifunctional anode, one of these discriminated pi electrons combined with reactive oxygen species (ROS) such as (OH)-O-center dot, (OOH)-O-center dot, etc., to form benzaldehyde via Grob fragmentation instead of benzoic acid. However, only benzoic acid was obtained from the oxidation of styrene on the anodes MOs/(Ru0.3Ti0.7)O-2/Ti, where MOs are other metal oxides with symmetric electronic configurations.
Article
Chemistry, Applied
Zhanyu Zhang, Jun Tang, Junbao Chen, Peixin Cui, Siyu Jiao, Wei Yi, Qingping Ke, Hengquan Yang
Summary: In this study, MnOx nanocatalysts with abundant oxygen vacancies were prepared using reverse-micelle as a template and endowed with an amphiphilic surface through post-modification. These catalysts were utilized to formulate Pickering emulsion and create compartmentalized droplet microreactors for the epoxidation of styrene. The oxygen defects on MnOx improved the chemisorption of t-butylhydroperoxide and facilitated the formation of superoxide radicals for the synthesis of styrene oxide. The compartmentalization effects from Pickering emulsion droplets enhanced the radical reaction path, resulting in higher selectivity and catalytic efficiency.
