F:Flammable;
79-20-9Relevant articles and documents
Insights into the Pyridine-Modified MOR Zeolite Catalysts for DME Carbonylation
Cao, Kaipeng,Fan, Dong,Li, Lingyun,Fan, Benhan,Wang, Linying,Zhu, Dali,Wang, Quanyi,Tian, Peng,Liu, Zhongmin
, p. 3372 - 3380 (2020)
Pyridine-modified mordenite (MOR) zeolite catalysts have attracted great attention in recent years due to their unique shape selectivity within eight-membered ring (8-MR) side pockets for dimethyl ether (DME) carbonylation to methyl acetate (MA) and syngas conversion to ethylene. Herein, aimed at elucidating pyridine modification-carbonylation activity relationships and developing high-performance catalysts, we investigated the adsorption/desorption behaviors of pyridine on MOR zeolites with varying Si/Al ratios and their impact on DME carbonylation. Instead of the previously proposed selective adsorption of pyridine in 12-MR channels, pyridine is revealed to penetrate into 8-MR side pockets of MOR zeolites and interact with acidic hydroxyls therein. Upon heating, pyridine in pockets desorbs preferentially, likely arising from the lower stability of pyridine adspecies in constrained spaces. This well explains the observed increment of carbonylation activity following the increase of pretreatment temperature. Unprecedentedly, high MA yield (7.2 mmol/(h g)) has been achieved on pyridine-modified MOR (Si/Al = 13.8) under controlled pyridine desorption conditions, resulting from the joint contributions of better diffusion properties and larger amounts of active acid sites. Moreover, the catalytic activity of Br?nsted acid sites within 8-MR pockets is demonstrated to be inhomogeneous, closely associated with their locations.
Mesoporous MCM-48 Immobilized with Aminopropyltriethoxysilane: A Potential Catalyst for Transesterification of Triacetin
Bandyopadhyay, Mahuya,Tsunoji, Nao,Sano, Tsuneji
, p. 1040 - 1050 (2017)
Abstract: The ordered mesoporous silicas MCM-48, MCM-41, and SBA-15 were synthesized and functionalized with 3-aminopropyltriethoxysilane (APTES). The X-ray diffraction patterns before and after functionalization revealed no structural degradation during the process. FT-IR spectra of the materials clearly indicated the anchoring of the aminopropyl moiety with silanol groups. The amine concentrations were calculated using TG-DTA and CHN analysis. The amine-loaded materials were assessed as catalysts for the transesterification of triacetin with methanol. MCM-48-NH2, in which the pores are interconnected in a three-dimensional manner, exhibited superior catalytic activity to one- dimensional MCM41-NH2 and SBA-15-NH2, even with lower concentrations of the amine group. Graphical Abstract: [Figure not available: see fulltext.]
Chemiluminescence upon isomerization of dimethyldioxirane in the gas phase and on a sorbent surface
Kazakov,Voloshin,Kabal'Nova,Shereshovets,Kazakov
, p. 2452 - 2453 (1996)
Chemiluminescence (CL) was found upon the isomerization of dimethyldioxirane in the gas phase under argon atmosphere. The intensity of CL increases as temperature increases and decreases with time at constant temperature. If Silipor is placed in a cell containing the dimethyldioxirane vapor in argon, the intensity of CL sharply increases (more than 10 times) and then decreases following the exponential law. In all cases tripletly excited methyl acetate is the emitter of Chemiluminescence. 1997 Plenum Publishing Corporation.
Direct observation of DME carbonylation in the different channels of H-MOR zeolite by continuous-flow solid-state NMR spectroscopy
He, Ting,Ren, Pengju,Liu, Xianchun,Xu, Shutao,Han, Xiuwen,Bao, Xinhe
, p. 16868 - 16870 (2015)
The dynamic evolution of acetyl intermediates in the two different channels of H-mordenite (H-MOR) zeolite during dimethyl ether (DME) carbonylation is tracked by using in situ solid-state NMR spectroscopy under continuous-flow conditions. Thus, the reaction path via methyl acetate produced over active sites in 8 member ring (MR) channels, followed by diffusion into 12 MR channels, is proposed.
Purification of EMIMOAc used in the acetylation of lignocellulose
Shi, Jin-Zhi,Stein, Juergen,Kabasci, Stephan,Pang, Hao
, p. 197 - 202 (2013)
Up to now, several methods of purifying ionic liquids (ILs), such as the extraction with supercritical carbon dioxide, crystallization, column chromatography, and so forth were reported. The IL that was used in the acetylation of lignocellulose with the help of acetic anhydride contains an elevated amount of acetic acid. In this paper our investigations on the separation of acetic acid from synthetic mixtures with 1-ethyl-3- methylimidazolium acetate (EMIMOAc) are described. The separation was performed by evaporation, extraction, and esterification. While impurities like ethyl acetate, n-propyl acetate, isopropyl acetate, and tetrahydrofuran (THF) can easily be evaporated from EMIMOAc, it is difficult to remove acetic acid from EMIMOAC or EMIMCl by evaporation below certain concentration levels. In extraction tests acetic acid could be separated from EMIMOAc to some degree, especially with extractants immiscible with EMIMOAc having a high value of ET(30) and a dielectric constant near that of acetic acid. The most successful removal of acetic acid was found to be an esterification of acetic acid at a large excess of alcohol, a long reaction time, and an intensive contact of the educts in the liquid phase at elevated temperature and pressure with subsequent evaporation of the produced acetic acid ester.
Selective dealumination of mordenite for enhancing its stability in dimethyl ether carbonylation
Xue, Huifu,Huang, Xiumin,Zhan, Ensheng,Ma, Meng,Shen, Wenjie
, p. 75 - 79 (2013)
Selective dealumination of mordenite by high-temperature steam treatment improved its stability in dimethyl ether carbonylation. Most of the framework Al species in the 12-membered ring channels of mordenite was removed while those in the 8-membered ring
Novel synthesis and catalytic performance of hierarchical MOR
Lu, Jiaxin,Wang, Yaquan,Sun, Chao,Zhao, Taotao,Zhao, Jingjing,Wang, Ziyang,Liu, Wenrong,Wu, Shuhui,Shi, Mingxue,Bu, Lingzhen
, p. 8629 - 8638 (2021)
A novel route was developed to synthesize hierarchical MOR through introduction of BEA/MOR zeolite embryos as the structural growth inducer (SGI) in the presence of hexadecyltrimethylammonium (CTA+). The morphologies, physicochemical properties and possible formation mechanism of the hierarchical MOR were studied systematically. In the process of crystallization, CTA+ might act as a crystal growth inhibitor for the formation of BEA zeolite; therefore, the MOR embryos have the chance to induce the growth of MOR. Besides, CTA+ ions interact with the primary crystals formed and result in the formation of mesopores. Through changing the addition of CTAB and SGI, the crystal sizes, the mesopore volume and the acidity of the hierarchical MOR could be adjusted. Compared with commercial MOR, the catalytic stability of the hierarchical MOR is much higher in the carbonylation of dimethyl ether.
Dimethyl ether carbonylation to methyl acetate over highly crystalline zeolite seed-derived ferrierite
Kim, Jihyeon,Ham, Hyungwon,Jung, Hyun Seung,Wang, Yang,He, Yingluo,Tsubaki, Noritatsu,Cho, Sung June,Han, Gui Young,Bae, Jong Wook
, p. 3060 - 3072 (2018)
Gas-phase carbonylation of dimethyl ether (DME) to methyl acetate (MA) was investigated on ferrierite (FER) zeolite having different Si/Al molar ratios of 10.4-12.5 as well as high crystallinity synthesized by using various zeolite seed materials such as MOR, ZSM-5 and USY. The enhanced crystallinity of the FER prepared by simply using FER seeds (denoted as FER@FER) having newly formed mesopore structures was responsible for an increased amount of active Br?nsted acid sites, which resulted in a higher MA productivity of 2.94 mmol gcat h-1 with MA selectivity of above 99%. The highly crystalline FER@FER revealed the suppressed deposition of aromatic coke precursors due to the presence of fewer defect sites. Compared to other zeolite seed-derived FER zeolites, the lesser amount of defect sites (extra-framework Lewis acid Al species, EFAL) on the FER@FER was successfully controlled through a recrystallization process. The active Br?nsted acid sites for the DME carbonylation reaction mainly originated from the preferential formation of stable tetrahedral Al sites (especially the T2 sites of the Al-O-Si-O-Al framework of FER) on the 8- and 10-membered ring channels of the FER@FER. On those stable T2 sites having proper acid strength, the adsorbed methyl intermediates formed by the dissociation of DME can be transformed to acetyl adsorbates by a relatively faster CO insertion rate on the vicinal Br?nsted acid sites, which results in a high catalytic stability and activity of the highly crystalline FER@FER.
Stability enhancement of H-mordenite in dimethyl ether carbonylation to methyl acetate by pre-adsorption of pyridine
Liu, Junlong,Xue, Huifu,Huang, Xiumin,Wu, Pei-Hao,Huang, Shing-Jong,Liu, Shang-Bin,Shen, Wenjie
, p. 729 - 738 (2010)
The carbonylation of dimethyl ether to methyl acetate over H-mordenite (HMOR) and pyridine-modified HMOR was compared. The catalytic stability of HMOR was improved significantly by pyridine pre-adsorption, and a yield of methyl acetate ～30 was still obtained after 48 h on stream at 473 K. In situ infrared spectroscopy and ammonia temperature-programmed desorption revealed that pyridine preferentially occupied the acidic sites in 12-membered ring pores but not the acidic sites in 8-membered ring pores. 129Xe NMR studies suggested that the channels of HMOR were blocked by coke in the reaction but those in the pyridine-modified HMOR were not. The acidic sites in the 12-membered ring pores were responsible for the deactivation of HMOR, and the reaction can be directed to occur mainly on the acidic sties in the 8-membered ring pores by the selective adsorption of pyridine in the 12-membered ring pores.
Selective carbonylation of dimethyl ether to methyl acetate catalyzed by acidic zeolites
Cheung, Patricia,Bhan, Aditya,Sunley, Glenn J.,Iglesia, Enrique
, p. 1617 - 1620 (2006)
(Chemical Equation Presented) A simpler way: Acidic zeolites catalyze dimethyl ether carbonylation to methyl acetate at low temperatures with high selectivity and catalyst stability. This approach provides a halide-free heterogeneous catalytic route to acetic acid and methyl acetate.
