95-63-6Relevant articles and documents
Centrifugation-free and high yield synthesis of nanosized H-ZSM-5 and its structure-guided aromatization of methanol to 1,2,4-trimethylbenzene
Shen, Kui,Qian, Weizhong,Wang, Ning,Su, Chang,Wei, Fei
, p. 19797 - 19808 (2014)
Nanosized H-ZSM-5 has been proven to be an efficient way to improve mass transport properties with shape selectivity in many catalytic reactions. Generally, the synthesis of very fine nanosized H-ZSM-5 always suffers from low product yield and requires a complicated centrifugal separation process, both of which severely hinder its large-scale preparation and industrial applications. Herein, we report a centrifugation-free and high yield synthesis route for hierarchically nanosized ZSM-5 with a wide Si/Al ratio range by a combination of pre-aging process and steam-assisted conversion method using alkalis-free powder as the ZSM-5 precursor. This facile route not only avoids the energy-intensive centrifugal separation and ion-exchange process, but also significantly increases the crystallization efficiency along with a high yield. The obtained nanosized ZSM-5 possesses an ultrafine uniform size, high surface area, high total pore volumes, tunable Si/Al molar ratio, and high crystallinity. As a result, the nanosized ZSM-5 shows excellent catalytic performance when used in the catalytic conversion of methanol to aromatics. Notably, the nanosized ZSM-5 with a Si/Alth of 60 (NZS-60) shows an almost 25-fold longer catalytic lifetime, as well as up to 16% higher total aromatic selectivity when compared with conventional ZSM-5. Furthermore, the selectivity of 1,2,4-trimethylbenzene over this catalyst can be up to 44% in all products and 64% in aromatics products. Characterization results of the spent samples reveal that the most-improved catalytic performance and high selectivity of 1,2,4-trimethylbenzene over the nanosized ZSM-5 could be attributed to its small crystal size and hierarchical structure, which not only prevents the deposition of polyaromatic hydrocarbon in the microspores, but also sharply increases the reaction efficiency of bulky intermediate products on the surface of the catalyst.
Highly effective and chemoselective hydrodeoxygenation of aromatic alcohols
Han, Buxing,He, Mingyuan,Mei, Xuelei,Wu, Haihong,Wu, Wei,Xu, Caiyun,Zhai, Jianxin,Zhang, Kaili,Zhang, Zhanrong,Zheng, Bingxiao
, p. 1629 - 1635 (2022/02/21)
Effective hydrodeoxygenation (HDO) of aromatic alcohols is very attractive in both conventional organic synthesis and upgrading of biomass-derived molecules, but the selectivity of this reaction is usually low because of the competitive hydrogenation of the unsaturated aromatic ring and the hydroxyl group. The high activity of noble metal-based catalysts often leads to undesired side reactions (e.g., saturation of the aromatic ring) and excessive hydrogen consumption. Non-noble metal-based catalysts suffer from unsatisfied activity and selectivity and often require harsh reaction conditions. Herein, for the first time, we report chemoselective HDO of various aromatic alcohols with excellent selectivity, using porous carbon-nitrogen hybrid material-supported Co catalysts. The C-OH bonds were selectively cleaved while leaving the aromatic moiety intact, and in most cases the yields of targeted compounds reached above 99% and the catalyst could be readily recycled. Nitrogen doping on the carbon skeleton of the catalyst support (C-N matrix) significantly improved the yield of the targeted product. The presence of large pores and a high surface area also improved the catalyst efficiency. This work opens the way for efficient and selective HDO reactions of aromatic alcohols using non-noble metal catalysts.
Probing the pore structure of hierarchical EU-1 zeolites by adsorption of large molecules and through catalytic reaction
Guo, Zaibin,Hao, Wenming,Ma, Jinghong,Li, Ruifeng
, p. 187 - 193 (2020/07/04)
The adsorption of toluene and 1,3,5-trimethylbenzene and the catalytic transformation of 1,3,5-trimethylbenzene are applied as probing approaches to characterize the pore system of hierarchical EU-1 zeolites prepared using organofunctionalized fumed silica as the silicon source. The adsorption and diffusion of toluene and 1,3,5-trimethylbenzene are significantly improved in the hierarchical EU-1 zeolites compared with the conventional microporous EU-1 zeolite. The adsorption kinetics of toluene and 1,3,5-trimethylbenzene suggested that introducing mesopores significantly increases the rate of adsorption and improved the diffusion of large molecules. In the catalytic transformation of 1,3,5-trimethylbenzene, the conversion of 1,3,5-trimethylbenzene on the hierarchical EU-1 zeolites is doubled compared with the conventional microporous EU-1 zeolite, due to the improved diffusion of bulky molecules and enhanced accessibility of active sites in the hierarchical EU-1 structure. Although isomerization is the main reaction, differences are observed in the product ratios of isomerization to disproportionation between the hierarchical EU-1 zeolites and the microporous counterpart with different times on stream. The transformation of 1,3,5-trimethylbenzene over the hierarchical EU-1 zeolites has a higher isomerization to disproportionation ratio than that over the microporous EU-1 zeolite; this is due to the increased mesoporosity.
Selective production of bio-based: Para -xylene over an FeOx -modified Pd/Al2O3catalyst
Fu, Zaihui,Li, Changzhi,Meng, Qingwei,Pan, Xiaoli,Xiao, Yuxue,Zhang, Chao
, p. 4341 - 4349 (2020/07/14)
para-Xylene (PX) is a basic building block of polyethylene terephthalate, which is currently produced from petroleum resources. Developing a renewable route to PX is highly desirable to address both economic and environmental concerns. Several attempts used noble metal catalysts, e.g. Pd/Al2O3, to synthesize PX from biomass-derived 4-methyl-3-cyclohexene-1-carboxaldehyde (4-MCHCA), but suffered from a severe decarbonylation reaction, resulting in toluene as the main product. In this paper, we report an FeOx modification strategy to suppress the decarbonylation reaction on a Pd/Al2O3 catalyst, leading to a drastic shift in selectivity towards PX with a yield up to 81percent via a cascade dehydroaromatization-hydrodeoxygenation (DHA-HDO) pathway. Characterization and control experiments revealed that the electron density of Pd sites decreased in an FeOx-modified Pd/Al2O3 catalyst compared to Pd/Al2O3, thus tuning the preferential adsorption mode of the substrate from η2-(C,O), the key transition state of the decarbonylation reaction, to the η1-(O) mode that favors the hydrodeoxygenation process. Notably, this designed catalyst is highly stable and is readily applicable in the selective synthesis of a broad range of desired aromatic chemicals via the same DHA-HDO pathway from cyclohex-3-enecarbaldehyde derivatives. Overall, this work develops a controllable catalyst modification strategy that tailors an efficient catalyst for petroleum-independent bio-PX synthesis.
PROCESS FOR CO-PRODUCTION OF MIXED XYLENES AND HIGH OCTANE C9+ AROMATICS
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Paragraph 0067-0072, (2019/10/23)
Disclosed is a process for producing mixed xylenes and C9+ hydrocarbons in which an aromatic hydrocarbon feedstock comprising benzene and/or toluene is contacted with an alkylating agent comprising methanol and/or dimethyl ether under alkylation conditions in the presence of an alkylation catalyst to produce an alkylated aromatic product stream comprising the mixed xylenes and C9+ hydrocarbons. The mixed xylenes are subsequently converted to para-xylene, and the C9+ hydrocarbons and its components may be supplied as motor fuels blending components. The alkylation catalyst comprises a molecular sieve having a Constraint Index in the range from greater than zero up to about 3. The molar ratio of aromatic hydrocarbon to alkylating agent is in the range of greater than 1:1 to less than 4:1.
Methods for preparing benzene-ring-containing compounds from pinacol
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Paragraph 0057; 0058; 0059; 0061, (2018/08/04)
The invention relates to methods for preparing durene, 1,2,3-trimethylbenzene, o-xylene, pyromellitic acid and trimellitic acid from pinacol. Durene, 1,2,3-trimethylbenzene and o-xylene are prepared through three steps of reaction, and pyromellitic acid and trimellitic acid are prepared through four steps of reaction. A catalytic system used in the invention is green and environment-friendly, andcan be recycled. The raw materials of method, i.e., pinacol, crotonaldehyde, acrolein and crotonate can all be derived from biomass, and are cheap and easily available. All the reaction processes aresimple and are high in activity and selectivity in the dehydration of pinacol and the dehydrogenation, decarbonylation and oxidation of D-A products. The invention provides novel methods for preparingfine chemicals including durene, 1,2,3-trimethylbenzene, o-xylene, pyromellitic acid and trimellitic acid from lignocellulose-based platform chemicals.
Selective Production of Renewable para-Xylene by Tungsten Carbide Catalyzed Atom-Economic Cascade Reactions
Dai, Tao,Li, Changzhi,Li, Lin,Zhao, Zongbao Kent,Zhang, Bo,Cong, Yu,Wang, Aiqin
supporting information, p. 1808 - 1812 (2018/02/10)
Tungsten carbide was employed as the catalyst in an atom-economic and renewable synthesis of para-xylene with excellent selectivity and yield from 4-methyl-3-cyclohexene-1-carbonylaldehyde (4-MCHCA). This intermediate is the product of the Diels–Alder reaction between the two readily available bio-based building blocks acrolein and isoprene. Our results suggest that 4-MCHCA undergoes a novel dehydroaromatization–hydrodeoxygenation cascade process by intramolecular hydrogen transfer that does not involve an external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W2C surface. Notably, this process is readily applicable to the synthesis of various (multi)methylated arenes from bio-based building blocks, thus potentially providing a petroleum-independent solution to valuable aromatic compounds.
Pushing the Limits on Metal-Organic Frameworks as a Catalyst Support: NU-1000 Supported Tungsten Catalysts for o-Xylene Isomerization and Disproportionation
Ahn, Sol,Nauert, Scott L.,Buru, Cassandra T.,Rimoldi, Martino,Choi, Hyeju,Schweitzer, Neil M.,Hupp, Joseph T.,Farha, Omar K.,Notestein, Justin M.
supporting information, p. 8535 - 8543 (2018/06/25)
Acid-catalyzed skeletal C-C bond isomerizations are important benchmark reactions for the petrochemical industries. Among those, o-xylene isomerization/disproportionation is a probe reaction for strong Br?nsted acid catalysis, and it is also sensitive to the local acid site density and pore topology. Here, we report on the use of phosphotungstic acid (PTA) encapsulated within NU-1000, a Zr-based metal-organic framework (MOF), as a catalyst for o-xylene isomerization at 523 K. Extended X-ray absorption fine structure (EXAFS), 31P NMR, N2 physisorption, and X-ray diffraction (XRD) show that the catalyst is structurally stable with time-on-stream and that WOx clusters are necessary for detectable rates, consistent with conventional catalysts for the reaction. PTA and framework stability under these aggressive conditions requires maximal loading of PTA within the NU-1000 framework; materials with lower PTA loading lost structural integrity under the reaction conditions. Initial reaction rates over the NU-1000-supported catalyst were comparable to a control WOx-ZrO2, but the NU-1000 composite material was unusually active toward the transmethylation pathway that requires two adjacent active sites in a confined pore, as created when PTA is confined in NU-1000. This work shows the promise of metal-organic framework topologies in giving access to unique reactivity, even for aggressive reactions such as hydrocarbon isomerization.
Sustainable Production of o-Xylene from Biomass-Derived Pinacol and Acrolein
Hu, Yancheng,Li, Ning,Li, Guangyi,Wang, Aiqin,Cong, Yu,Wang, Xiaodong,Zhang, Tao
, p. 2880 - 2885 (2017/07/25)
o-Xylene (OX) is a large-volume commodity chemical that is conventionally produced from fossil fuels. In this study, an efficient and sustainable two-step route is used to produce OX from biomass-derived pinacol and acrolein. In the first step, the phosphotungstic acid (HPW)-catalyzed pinacol dehydration in 1-ethyl-3-methylimidazolium chloride ([emim]Cl) selectively affords 2,3-dimethylbutadiene. The high selectivity of this reaction can be ascribed to the H-bonding interaction between Cl? and the hydroxy group of pinacol. The stabilization of the carbocation intermediate by the surrounding anion Cl? may be another reason for the high selectivity. Notably, the good reusability of the HPW/[emim]Cl system can reduce the waste output and production cost. In the second step, OX is selectively produced by a Diels–Alder reaction of 2,3-dimethylbutadiene and acrolein, followed by a Pd/C-catalyzed decarbonylation/aromatization cascade in a one-pot fashion. The sustainable two-step process efficiently produces renewable OX in 79 % overall yield. Analogously, biomass-derived crotonaldehyde and pinacol can also serve as the feedstocks for the production of 1,2,4-trimethylbenzene.
Standard and rapid scan infrared spectroscopic studies of: O -xylene transformations in terms of pore arrangement of 10-ring zeolites-2D COS analysis
Go?bek, Kinga,Tarach, Karolina A.,Góra-Marek, Kinga
, p. 9934 - 9950 (2017/08/10)
This study attempts to offer an insight into o-xylene isomerization process in terms of steric constraints of 10-ring zeolites. The zeolites under investigation, i.e. ZSM-5, IM-5 and TNU-9, have purely microporous structures and crystals with the same shape and offer comparable protonic functionality, both in manner of amount and strength of Si(OH)Al groups. Under these conditions, micropore topology is recognised to deliver differentiated catalytic performance of each zeolitic structure. Moreover, 10-ring zeolites of reduced dimensionality, i.e. TNU-10 and ZSM-22, are chosen as reference materials. The 2D COS analysis of IR spectra reveal that interaction and catalytic activity in o-xylene isomerization process are strongly influenced by diffusion of reagents in rigid microporous environment and the formation of intermediate species is characterised by IR bands at 1485 and 1455 cm-1. With a prolonged time of the reaction (15 min), the formation of the latter species is observed for zeolite IM-5 characterised by limited 3-dimensionality. Rapid scan experiments show that in a shorter reaction time (4 min), these intermediate moieties are present for all the structure studied. The intermediate species are believed to originate from arenium ions such as methylbenzenium CH3-C6H5+-CH3 and/or methyl-substituted cycloheptatrienyl ions CH3-C7H7+. Their amount is strictly related to the rigidity of the microporous system: the most spacious environment for o-xylene transformation, e.g. TNU-9, is characterised by the lowest population of intermediates, whereas structures offering sufficiently tight geometry, e.g. TNU-10, can accommodate intermediate species in higher quantities, finally leading to the production of p-xylene with high selectivity.
