106-42-3Relevant articles and documents
Boosting the synthesis of value-added aromatics directly from syngasviaa Cr2O3and Ga doped zeolite capsule catalyst
Gao, Weizhe,Gao, Xinhua,Ma, Qingxiang,Tsubaki, Noritatsu,Wang, Kangzhou,Wang, Yang,Wu, Mingbo,Yang, Guohui,Zhang, Baizhang,Zhang, Peipei,Zhao, Heng
, p. 7786 - 7792 (2021)
Even though the transformation of syngas into aromatics has been realizedviaa methanol-mediated tandem process, the low product yield is still the bottleneck, limiting the industrial application of this technology. Herein, a tailor-made zeolite capsule catalyst with Ga doping and SiO2coating was combined with the methanol synthesis catalyst Cr2O3to boost the synthesis of value-added aromatics, especiallypara-xylene, from syngas. Multiple characterization studies, control experiments, and density functional theory (DFT) calculation results clarified that Ga doped zeolites with strong CO adsorption capability facilitated the transformation of the reaction intermediate methanol by optimizing the first C-C coupling step under a high-pressure CO atmosphere, thereby driving the reaction forward for aromatics synthesis. This work not only reveals the synergistic catalytic network in the tandem process but also sheds new light on principles for the rational design of a catalyst in terms of oriented conversion of syngas.
Biotransformation of thymol by Aspergillus niger
Esmaeili, Akbar,Khodadadi, Abas,Safaiyan, Shila
, p. 966 - 968 (2012)
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Continuous process for the production of aromatic hydrocarbons from n-hexane and C5+ natural gas liquid over Pd-loaded ZSM-5 zeolite
Suwanprasop, Somsaluay,Khamnuansiri, Pharkpoom,Nhujak, Thumnoon,Roengsumran, Sophon,Petsom, Amorn
, p. 577 - 582 (2003)
A continuous process for the production of aromatic hydrocarbons from n-hexane and C5+ natural gas liquid (C5+ NGL) over Pd-loaded ZSM-5 zeolite in a tubular reactor was developed. The optimal conditions for continuous aromatization of n-hexane and C5+ NGL were found at 400°C reaction temperature and 0.4 cm3/min reactant feeding rate, employing ZSM-5 (0.5% Pd content) as a catalyst; under these conditions, n-hexane conversion and aromatic contents in reaction product were found to be 99.7% and 92.3%, respectively. GC and GC/MS analysis revealed that this continuous process for n-hexane aromatization yielded both benzene derivatives and naphthalene derivatives, including benzene (5.7%), toluene (23.6%), xylenes (25.0%), 4-ethyltoluene (3.5%), 1,3,5-trimethylbenzene (4.9%), 1-methylnaphthalene (4.3%), and 1,5-dimethylnaphthalene (3.6%). Under the same reaction conditions, C5+ NGL gave 94.3% conversion and 92.6% aromatic contents in reaction product. The composition of product included benzene (8.1%), toluene (23.3%), xylenes (22.8%), 4-ethyltoluene (4.3%), 1,3,5-trimethylbenzene (3.7%), 1-methylnaphthalene (4.1%), and 1,5-dimethylnaphthalene (2.9%).
Guest-selected formation of Pd(II)-linked cages from a prototypical dynamic library [15]
Hiraoka, Shuichi,Fujita, Makoto
, p. 10239 - 10240 (1999)
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Pyrolysis of 3-carene: Experiment, Theory and Modeling
Sharath,Chakravarty,Reddy,Barhai,Arunan
, p. 2119 - 2135 (2015)
Thermal decomposition studies of 3-carene, a bio-fuel, have been carried out behind the reflected shock wave in a single pulse shock tube for temperature ranging from 920 K to 1220 K. The observed products in thermal decomposition of 3-carene are acetylene, allene, butadiene, isoprene, cyclopentadiene, hexatriene, benzene, toluene and p-xylene. The overall rate constant for 3-carene decomposition was found to be k / s-1 = 10(9.95 ± 0.54) exp (- 40.88 ± 2.71 kcal mol-1/RT). Ab-initio theoretical calculations were carried out to find the minimum energy pathway that could explain the formation of the observed products in the thermal decomposition experiments. These calculations were carried out at B3LYP/6-311 + G(d,p) and G3 level of theories. A kinetic mechanism explaining the observed products in the thermal decomposition experiments has been derived. It is concluded that the linear hydrocarbons are the primary products in the pyrolysis of 3-carene.
Renewable p-Xylene from 2,5-Dimethylfuran and Ethylene Using Phosphorus-Containing Zeolite Catalysts
Cho, Hong Je,Ren, Limin,Vattipalli, Vivek,Yeh, Yu-Hao,Gould, Nicholas,Xu, Bingjun,Gorte, Raymond J.,Lobo, Raul,Dauenhauer, Paul J.,Tsapatsis, Michael,Fan, Wei
, p. 398 - 402 (2017)
p-Xylene is a major commodity chemical used for the production of polyethylene terephthalate, a polymer with applications in polyester fibers, films, and bottles. The Diels–Alder cycloaddition of 2,5-dimethylfuran and ethylene and the subsequent dehydration of the cycloadduct intermediate is an attractive reaction pathway to produce renewable p-xylene from biomass feedstocks. However, the highest yields reported previously do not exceed 75 %. We report that P-containing zeolite Beta is an active, stable, and selective catalyst for this reaction with an unprecedented p-xylene yield of 97 %. It can catalyze the dehydration reaction selectively from the furan-ethylene cycloadduct to p-xylene without the production of alkylated and oligomerized products. This behavior is distinct from that of Al-containing zeolites and other solid phosphoric acid catalysts and establishes a commercially attractive process for renewable p-xylene production.
Effect of extra-framework Al formed by successive steaming and acid leaching of zeolite MCM-22 on its structure and catalytic performance
Mihályi,Kollár,Király,Karoly,Mavrodinova
, p. 76 - 86 (2012)
Dealuminated MCM-22 samples have been prepared by a two-step dealumination procedure. Detailed assessment of the properties of the materials obtained at each one of the successive stages, i.e. steaming (at 500 °C, 700 °C and 800 °C) and acid reflux (HCl and oxalic), has been made by XRD, N 2 adsorption-desorption, m-xylene adsorption, 27Al MAS NMR and FT-IR of pyridine adsorption. It was found that steaming generates extra-framework aluminum (EFAl) species and the majority of them cannot be extracted by the consecutive acid leaching. These extra-lattice entities block the zeolite micropores which makes the remaining Broensted acid sites isolated and inefficient. It is shown that the presence of such species vastly affects the catalytic performance of zeolite MCM-22 in the reaction of m-xylene conversion. The consequences are reduced adsorption capacity and catalytic activity, modified reaction products distribution, enhanced p-xylene selectivity, as well as altered mode of coke formation and composition of the coke precursors.
Interference by Phosphine Decomposition in Oxidative Additions of Aryl Halides to Methyl-, and Trimethylsilyl-tris(triphenylphosphine)Cobalt
Michman, M.,Chocron, S.,Nussbaum, S.,Schumann, H.,Montachemi, R.,Kannert, G.
, p. 113 - 118 (1986)
The oxidative addition of aryl halides, ArX, to 3CoCH3 yield ArAr and ArCH3 when Ar= 4-CH3C6H4, but exclusively ArCH3 for 1- and 2-bromo-naphthalene and 4-bromobiphenyl.Decomposition of the phosphine ligand in 3CoCH3 interfers with these reactions to varying extents depending on the relative rates of the reactions; ArCl mostly gives PhPh with some ArPh and ArAr; ArI gives mostly ArAr; ArBr shows intermediate behaviour.Other cobalt compounds such as 3CoSi3, 3CoCH3, 3CoPh and 3CoCH3 and several other organic halides examined show a low activity in the oxidative addition.
A Simple and Mild Approach for the Synthesis of p-Xylene from Bio-Based 2,5-Dimethyfuran by Using Metal Triflates
Ni, Lingli,Xin, Jiayu,Dong, Huixian,Lu, Xingmei,Liu, Xiaomin,Zhang, Suojiang
, p. 2394 - 2401 (2017)
The production of aromatic platform chemicals from biomass-derived feedstocks is of considerable importance in biomass conversion. However, the development of effective routes with simple steps and under mild conditions is still challenging. In this work, we report an original route for the direct synthesis of p-xylene from 2,5-dimethylfuran and acrylic acid catalyzed by scandium(III) triflate (Sc(OTf)3) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim]NTf2) under mild conditions. An overall 63 % selectivity towards p-xylene and 78 % selectivity towards aromatics were obtained at 90 % conversion of 2,5-dimethylfuran by enhancing the dehydration and introducing an extra one-pot decarboxylation step. Furthermore, various dienes and dienophiles were employed as reactants to extend the substrate scope. The aromatic compounds were obtained in moderate yields, which proved the potential of the method to be a generic approach for the conversion of bio-based furanics into renewable aromatics.
The miracle role of lattice imperfections in benzene alkylation with methanol over mordenite
Yun, Hongfei,Meng, Jiale,Li, Guixian,Dong, Peng
, p. 1423 - 1430 (2020)
Mordenite (MOR) has demonstrated potential as a catalyst for alkylation due to high variability, intrinsic porosity, and outstanding stability. However, the contact probability of benzene and methanol has been limited by typical layered structures of MOR and there is no connection between layers. Here, we report the preparedness of H-MOR via a sequential post-treatment method based on a commercial MOR. H-MOR sample had appeared lattice imperfections inferred from characterization means. The samples were tested with benezene methylation reaction. Results show that the high conversion of benzene and the high selectivity of toluene were obtained from the miracle role of lattice imperfections in the H-MOR sample. Sequentially, based on the study of all catalyst structure and physical properties, a plausible reaction mechanism for the selectivity of the desired toluene was proposed.
Preparation of active Cs2HPW12O40 catalyst with the 'core-shell' secondary structure by a self-organizing process
Matachowski,Drelinkiewicz,Mucha,Kry?ciak-Czerwenka,Rachwalik
, p. 239 - 249 (2014)
By mixing and ageing of the powdered H3PW12O 40 acid and the Cs3PW12O40 salt, at the molar ratio of 1:2, the Cs2HPW12O40 salt with a unique 'core-shell' secondary structure is being formed. The self-organizing process proceeds in a solid state at ambient temperature and its rate depends on the humidity of air atmosphere. The formation of new secondary structure of the Cs2HPW12O40 salt was proved by number of techniques (XRD, DRIFT, DSC/TG and N2-sorption). Its properties were compared with those of the Cs2HPW12O40 salt prepared by the standard method, with the 'solid solution' secondary structure. The characterization techniques evidenced the substantial differences between various structures of the Cs2HPW12O40 salt. The microcalorimetric method showed that the process of ammonia sorption on the Cs2HPW12O40 salt with the new structure is quite similar to that on the K2HPW12O40 salt with well-known 'core-shell' structure. The catalytic activity of the Cs 2HPW12O40 samples with different secondary structure was compared in the dehydration of ethanol and in the transformation of m-xylene. It turn out that the Cs2HPW12O40 salt with the 'core-shell' structure exhibited significantly higher catalytic activity than the same salt with the 'solid solution' structure and was also more active than the Cs2.5H0.5PW12O 40 salt. It can be suggested that in the 'core-shell' structure of the Cs2HPW12O40 salt the protons are easily accessible for the reactants.
Preparation and characterization of mesoporous Cs2HPW 12O40 salt, active in transformation of m-xylene
Matachowski,Drelinkiewicz,Rachwalik,Zimowska,Mucha,Ruggiero-Miko?ajczyk
, p. 19 - 27 (2013)
The samples of Cs2HPW12O40 salt were precipitated with CsCl, CsBr or CsI reagent as well as with commonly used Cs2CO3. The use of cesium halides resulted in the Cs 2HPW12O40 samples of mesoporous structure composed of relatively loosely aggregated primary particles. It was observed that the type of halogen ion influenced textural properties of the Cs 2HPW12O40 samples. As the atomic size of halogen ion increased (from Cl to I), the specific surface area and microporosity decreased. The so-obtained samples exhibited textural and morphological features similar to those of Cs2.5H 0.5PW12O40 salt. In the transformation of m-xylene, the pore-size sensitive reaction, the catalytic activity of the Cs2HPW12O40 samples prepared with CsBr and CsI reagents was about two-fold higher than that of Cs2.5H 0.5PW12O40 salt. All these samples exhibited similar strength of acid sites. Therefore, high catalytic activity of the samples prepared with CsBr and CsI could be ascribed to their open pore structure, which allowed the accessibility of almost all active sites for m-xylene molecules.
Lewis acid zeolites for tandem Diels-Alder cycloaddition and dehydration of biomass-derived dimethylfuran and ethylene to renewable p-xylene
Chang, Chun-Chih,Je Cho, Hong,Yu, Jingye,Gorte, Ray J.,Gulbinski, Jason,Dauenhauer, Paul,Fan, Wei
, p. 1368 - 1376 (2016)
Lewis acid zeolites including Zr-, Sn-, and Ti-BEA were examined for tandem [4 + 2] Diels-Alder cycloaddition of 2,5-dimethylfuran (DMF) and ethylene to oxanorbornene with subsequent dehydration to produce biorenewable p-xylene. Zr-BEA (Si/Zr = 168) exhibited superior performance with improved recalcitrance to deactivation, which was attributed to its low activity for the hydrolysis of DMF to 2,5-hexanedione and subsequent condensation. Zr-BEA also achieved the highest selectivity to p-xylene of 90% at 99% conversion of DMF. For low catalyst loading within a three-phase reactor, the reaction rate to form p-xylene was linearly proportional to the number of Lewis acid sites, while high catalyst loading exhibited zero order dependence on Lewis acid sites. A maximum achievable reaction rate was shown to be consistent with a transition in rate-limiting reactions from dehydration of oxanorbornene, the Diels-Alder product, to the Diels-Alder cycloaddition of DMF and ethylene.
Atmospheric pressure microwave assisted heterogeneous catalytic reactions
Chemat-Djenni, Zoubida,Hamada, Boudjema,Chemat, Farid
, p. 1399 - 1409 (2007)
The purpose of the study was to investigate microwave selective heating phenomena and their impact on heterogeneous chemical reactions. We also present a tool which will help microwave chemists to answer to such questions as "My reaction yields 90% after 7 days at reflux; is it possible to obtain the same yield after a few minutes under microwaves?" and to have an approximation of their reactions when conducted under microwaves with different heterogeneous procedures. This model predicting reaction kinetics and yields under microwave heating is based on the Arrhenius equation, in agreement with experimental data and procedures.
Excellent Performances of Dealuminated H-Beta Zeolites from Organotemplate-Free Synthesis in Conversion of Biomass-derived 2,5-Dimethylfuran to Renewable p-Xylene
Zhao, Rongrong,Zhao, Zhenchao,Li, Shikun,Parvulescu, Andrei-Nicolae,Müller, Ulrich,Zhang, Weiping
, p. 3803 - 3811 (2018)
Direct synthesis of renewable p-xylene (PX) by cycloaddition of biomass-derived 2,5-dimethylfuran (2,5-DMF) and ethylene was achieved over Al-rich H-beta zeolites synthesized by an organotemplate-free approach and their dealuminated counterparts with different Si/Al ratios. Among them, H-beta zeolite with an Si/Al ratio of 22, obtained from an Al-rich parent by dealumination, was found to be an excellent catalyst for the synthesis of PX. A PX yield of 97 % and 2,5-DMF conversion of 99 % were obtained under optimized conditions. These results are even better than those of a commercial H-beta zeolite prepared using a organotemplate synthesis with a similar Si/Al ratio of 19. The excellent performance of the H-beta zeolite with Si/Al ratio of 22 is closely related to its acidity and porous structure. A moderate Br?nsted/Lewis acid ratio can improve the conversion of 2,5-DMF to as high as 99 %. Furthermore, dealuminated H-beta zeolite has a secondary pore system that facilitates product diffusion, which increases the selectivity to PX. In addition, this catalyst shows better regeneration. After five successive regeneration cycles, the yield of PX was still as high as 85 % without obvious dealumination. This work provides a deeper understanding of the more general Diels–Alder cycloaddition of furan-based feedstocks and olefins and significantly improves the potential for the synthesis of chemicals from lignocellulosic biomass.
Regeneration of Pentasil Zeolite Catalysts using Ozone and Oxygen
Copperthwaite, Richard G.,Hutchings, Graham J.,Johnston, Peter,Orchard, S. Walter
, p. 1007 - 1018 (1986)
A novel procedure for the removal of carbonaceous deposits from zeolites using ozone-enriched oxygen is described.Pentasil zeolites (SiO2/Al2O3 mole ratios 35, 70) were studied and deactivated using methanol conversion to hydrocarbons and o-xylene isomerisation.Low temperature ozone reactivation was found to restore the catalyst activity for these reactions and hence can be considered as an alternative procedure to high temperature oxygen reactivation currently utilised industrially.Ozone reactivation was found to increase slightly the catalyst lifetime and also to reduce the initial methane yield when compared with oxygen reactivation.
Kinetic Study of Carbonylation of α-Bromo-p-xylene with Iron Pentacarbonyl by Phase-Transfer Catalysis
Wu, Ho-Shing,Tan, Wen-Han
, p. 604 - 610 (1998)
The reaction kinetics of the carbonylation of α-bromo-p-xylene (BrCH2C6H4CH3, BX) with iron pentacarbonyl (Fe(CO)5) by phase-transfer catalysis was studied in an organic solvent/alkaline solution. The concentration of tetra-n-butylammonium bromide ((n-C4H9)4NBr, TBAB), NaOH, NaBr, aqueous volume and temperature were evaluated to achieve the optimum reaction condition. The reaction behavior was discussed by the apparent reaction-rate constants for BX and bis(p-methylbenzyl) ketone ((p-CH3C6H4CH2)2CO, BMBK), respectively, and the relationship of consumption of BX and Fe(CO)5. The product distributions of BX with Fe(CO)5 on various reactions conditions were measured. The activation energies was obtained at TBAB = 1.24 and 0 mmol as Well.
Synthesis of HZSM-5@silicalite-1 core-shell composite and its catalytic application in the generation of p-xylene by methylation of toluene with methyl bromide
Deng, Yi-Qiang,Zhou, Wei-Fang,Lv, Hao-Ming,Zhang, Ying-Ying,Au, Chak-Tong,Yin, Shuang-Feng
, p. 37296 - 37301 (2014)
A core-shell HZSM-5@silicalite-1 composite was synthesized by overgrowing silicalite-1 on the external surface of HZSM-5, and was characterized by XRD, SEM, TEM, NH3-TPD, 1,3,5-triisopropylbenzene (TIPB) cracking and N2 adsorption-desorption techniques. When used as a catalyst for the formation of p-xylene through toluene methylation with methyl bromide, the HZSM-5@silicalite-1 composite exhibits para-selectivity of up to 76% with no evidence of deactivation in an on stream period of 3 h. The excellent catalytic performance is attributed to the inactive silicalite-1 shell that extends the diffusion path length of xylenes while having the acid sites on the external surface of HZSM-5 fully covered. the Partner Organisations 2014.
Route to Renewable PET: Reaction Pathways and Energetics of Diels-Alder and Dehydrative Aromatization Reactions between Ethylene and Biomass-Derived Furans Catalyzed by Lewis Acid Molecular Sieves
Pacheco, Joshua J.,Labinger, Jay A.,Sessions, Alex L.,Davis, Mark E.
, p. 5904 - 5913 (2015)
Silica molecular sieves that have the zeolite beta topology and contain framework Lewis acid centers (e.g., Zr-β, Sn-β) are useful catalysts in the Diels-Alder and dehydrative aromatization reactions between ethylene and various renewable furans for the production of biobased terephthalic acid precursors. Here, the main side products in the synthesis of methyl 4-(methoxymethyl)benzene carboxylate that are obtained by reacting ethylene with methyl 5-(methoxymethyl)-furan-2-carboxylate are identified, and an overall reaction pathway is proposed. Madon-Boudart experiments using Zr-β samples of varying Si/Zr ratios clearly indicate that there are no transport limitations to the rate of reaction for the synthesis of p-xylene from 2,5-dimethylfuran and ethylene and strongly suggest no mass transport limitations in the synthesis of methyl p-toluate from methyl 5-methyl-2-furoate and ethylene. Measured apparent activation energies for these reaction-limited systems are small (13C kinetic isotope effects (KIE) in the synthesis of MMBC and MPT measured by gas chromatography/isotope-ratio mass spectrometry in reactant-depletion experiments support the Madon-Boudart result that these systems are not transport-limited and the KIE values agree with those previously reported for Diels-Alder cycloadditions.
Pairera,Trimm
, p. 485,486 (1973)
Quantification of Bronsted acid sites of grafted amorphous silica-alumina compounds and their turnover frequency in m-xylene isomerization
Caillot, Maxime,Chaumonnot, Alexandra,Digne, Mathieu,Bokhoven, Jeroen A. Van
, p. 3644 - 3656 (2013)
The number and types of acid sites and the catalytic activity of amorphous silica-alumina, obtained by grafting silicon species to the surface of γ-alumina, varies with the synthesis conditions and the amount of grafted silicon. IR spectroscopy of the OH region proves that deposition occurs selectively, first on the (1 0 0) and then on the (1 1 0) facets. Grafting onto the (1 0 0) surface lowers the number of active sites in ethanol dehydration. Grafting onto the (1 1 0) surface yields Bronsted acid sites that are active in the dehydration of ethanol and that catalyze the isomerization of m-xylene. Strong Lewis acid sites, or "defect sites", as detected by CO adsorption, also appear, although they are absent on the parent alumina. The stoichiometric dehydration of ethanol on Bronsted sites, monitored by using thermogravimetric analysis, enables the calculation of the turnover frequency of these sites in m-xylene isomerization (1.410-3 s -1 site-1 at 350 °C, atmospheric pressure, 0.6 cm 3 h-1 of m-xylene, and 0.5 g of catalyst). This number is 22 times lower than on a USY zeolite without extraframework aluminum. Multifaceted γ-alumina: Under mild conditions, tetraethyl orthosilicate (TEOS) is first deposited on the (1 0 0) surface of γ-alumina, and then on the (1 1 0) surface. The latter step enables the formation of Bronsted acid sites upon calcination, which are less active than those present in an H-USY zeolite. Copyright
Preparation of an MCM-22/Hydrotalcite Framework Composite and Its Catalytic Application
Baskaran, Thangaraj,Christopher, Jayaraj,Mariyaselvakumar, Mariyamuthu,Sakthivel, Ayyamperumal
, p. 2396 - 2405 (2017)
A composite material (MAMCM), possessing both a layered cationic MgAl-hydrotalcite (MA-HT) and an anionic MCM-22 framework, was prepared by a simple coprecipitation method. The resulting composite material has features of both MCM-22 and the HT layered framework, as shown by powder XRD, FTIR, 29Si and 27Al-MAS NMR spectroscopy, and SEM studies. Electron microscopy revealed that the layer sheets are arranged in a spherical morphology. The composite material was utilized for the vapor-phase alkylation of toluene. The MAMCM material showed better toluene conversion than MCM-22 and MA-HT materials.
Komatsu
, p. 167 (1968)
ORBITAL-CONTROLLED REACTIONS CATALYSED BY ZEOLITES: ELECTROPHILIC ALKYLATION OF AROMATICS
Corma, A.,Zicovich-Wilson, C.,Viruela, P.
, p. 364 - 370 (1994)
The role of orbital control in product selectrivity during electrophilic alkylation catalysed by zeolites was studied both theoretically and experimentally.In order to discuss this, the alkylation of toluene and m-xylene by methanol was carried out on a series of large-pore zeolites (HY).The changes in the para to ortho ratio observed on changing the framework Si/Al ratio of the zeolites were related to ab initio molecular orbital calculations of the LUMO energy of structurally alike model clusters but containing different tetrahedral cations around the active site.The observed correlation is discussed in terms of the HSAB principle by taking into account the influence of the catalyst composition on the reactivity of the electrophilic reagent.
Transformation of aromatic hydrocarbons over isomorphously substituted UTL: Comparison with large and medium pore zeolites
?ilková, Nadě?da,Shamzhy, Mariya,Shvets, Oleksiy,?ejka, Ji?í
, p. 22 - 29 (2013)
Isomorphously substituted UTL zeolite with heteroatoms Al, Ga and Fe was synthesized, characterized by X-ray powder diffraction, scanning electron images, nitrogen adsorption isotherms and pyridine adsorption followed by FTIR spectroscopy and tested in disproportionation of toluene, toluene alkylation with isopropyl alcohol and trimethylbenzene disproportionation/isomerization. The catalytic properties of UTL zeolites were compared with those of BEA and MFI zeolites and the observed differences are discussed. Isomorphously substituted (Al, Ga, Fe) UTL zeolites show in most cases lower conversions for the reactions studied but higher selectivities to more valuable products. For toluene disproportionation reaction UTL zeolites shown higher selectivity to xylenes compared with BEA and MFI. In toluene alkylation with isopropyl alcohol no n-propyltoluenes are formed(Ga)UTL or (Fe)UTL while some traces of this undesired product were observed(Al)UTL. (Al)UTL shows high selectivity to cymenes and iso-/n-propyltoluene ratio orders of magnitude higher than for MFI. The initial selectivity to xylenes in trimethylbenzene disproportionation/ isomerization decreases in the order (Ga)UTL > (Al)UTL ≈ BEA > MFI and correlates with increasing of acid centres strength, showing that isomorphously substituted extra-large pore zeolites can be enough active and more selective catalysts in some aromatic hydrocarbon transformation reaction.
Rational Design of Zinc/Zeolite Catalyst: Selective Formation of p-Xylene from Methanol to Aromatics Reaction
Chen, Biaohua,Chen, Congmei,Chen, Xiao,Hou, Yilin,Hu, Xiaomin,Li, Jing,Qian, Weizhong,Sun, Wenjing,Wang, Ning,Yang, Yifeng,Zhang, Lan
supporting information, (2022/02/16)
The production of p-xylene from the methanol to aromatics (MTA) reaction is challenging. The catalytic stability, which is inversely proportional to the particle size of the zeolite, is not always compatible with p-xylene selectivity, which is inversely proportional to the external acid sites. In this study, based on a nano-sized zeolite, we designed hollow triple-shelled Zn/MFI single crystals using the ultra-dilute liquid-phase growth technique. The obtained composites possessed one ZSM-5 layer (≈30 nm) in the middle and two silicalite-1 layers (≈20 nm) epitaxially grown on two sides of ZSM-5, which exhibited a considerably long lifetime (100 % methanol conversion >40 h) as well as an enhanced shape selectivity of p-xylene (>35 %) with a p-xylene/xylene ratio of ≈90 %. Importantly, using this sandwich-like zeolite structure, we directly imaged the Zn species in the micropores of only the ZSM-5 layer and further determined the specific structure and anchor location of the Zn species.
Comparison of Physicochemical Properties and Catalytic Activity in the m-Xylene Isomerization of Catalysts Based on ZSM-12 Zeolites Prepared at Hydrothermal Conditions and under the Action of Microwave Radiation
Tsaplin,Ostroumova,Kulikov,Naranov,Egazar’yants,Karakhanov
, p. 1292 - 1301 (2021/12/29)
The properties of ZSM-12 zeolites prepared under hydrothermal conditions and microwave radiation influence were investigated. The prepared zeolites were characterized by various physicochemical methods of analysis, e.g., X-ray diffraction analysis, low-temperature nitrogen adsorption/desorption, scanning electron microscopy, solid-state 27Al and 29Si NMR spectroscopy, IR spectroscopy, temperature-programmed desorption of ammonia, IR spectroscopy of adsorbed pyridine, and X-ray fluorescence elemental analysis. The calcined zeolites were impregnated with 0.5 wt.% Pt, which performed the hydrogenation function in the reaction under study. The obtained materials were evaluated in the m-xylene isomerization reaction under the following conditions: Т = 300°С–440°С, WHSV = 1/hr, Р(Н2) = 10 atm. On the ZSM-12 MW catalyst, due to its high acidity and fine particles, which promoted high mass transfer, it is possible to increase the yields of m-xylene isomers, in particular p-xylene, to 36%–65%.
Selective upgrading of biomass-derived benzylic ketones by (formic acid)–Pd/HPC–NH2 system with high efficiency under ambient conditions
Chen, Yuzhuo,Chen, Zhirong,Gong, Yutong,Mao, Shanjun,Ning, Honghui,Wang, Yong,Wang, Zhenzhen
, p. 3069 - 3084 (2021/11/16)
Upgrading biomass-derived phenolic compounds provides a valuable approach for the production of higher-value-added fuels and chemicals. However, most established catalytic systems display low hydrodeoxygenation (HDO) activities even under harsh reaction conditions. Here, we found that Pd supported on –NH2-modified hierarchically porous carbon (Pd/HPC–NH2) with formic acid (FA) as hydrogen source exhibits unprecedented performance for the selective HDO of benzylic ketones from crude lignin-derived oxygenates. Designed experiments and theoretical calculations reveal that the H+/H? species generated from FA decomposition accelerates nucleophilic attack on carbonyl carbon in benzylic ketones and the formate species formed via the esterification of intermediate alcohol with FA expedites the cleavage of C–O bonds, achieving a TOF of 152.5 h?1 at 30°C for vanillin upgrading, 15 times higher than that in traditional HDO processes (~10 h?1, 100°C–300°C). This work provides an intriguing green route to produce transportation fuels or valuable chemicals from only biomass under mild conditions.