Zeolite nanosheets with a short b-axis thickness are highly desirable in lots of catalytic reactions due to their reduced diffusion resistance. Nevertheless, conventional synthesis methods usually require expensive st...Zeolite nanosheets with a short b-axis thickness are highly desirable in lots of catalytic reactions due to their reduced diffusion resistance. Nevertheless, conventional synthesis methods usually require expensive structure-directing agents(SDAs), pricey raw materials, and eco-unfriendly fluorine-containing additives. Here, we contributed a cost-effective and fluoride-free synthesis method for synthesizing high-quality MFI zeolite nanosheets through a Silicalite-1(Sil-1) seed suspension and urea cooperative strategy, only with inexpensive colloidal silica as the Si source. Our approach was effective for synthesizing both Sil-1 and aluminum-containing ZSM-5 nanosheets. By optimizing key synthesis parameters,including seed aging time, seed quantity, and urea concentration, we achieved precise control over the crystal face aspect ratio and b-axis thickness. We also revealed a non-classical oriented nanosheet growth mechanism, where Sil-1 seeds induced the formation of quasi-ordered precursor particles, and the(010)crystal planes of these particles facilitated urea adsorption, thereby promoting c-axis-oriented growth.The obtained ZSM-5 nanosheets exhibited exceptional catalytic performance in the benzene alkylation with ethanol, maintaining stability for over 500 h, which is 5 times longer than traditional ZSM-5 catalysts. Furthermore, large-scale production of ZSM-5 nanosheets was successfully carried out in a 3 L highpressure autoclave, yielding samples consistent with those from laboratory-scale synthesis. This work marks a significant step forward in the sustainable and efficient production of MFI nanosheets using inexpensive and environmentally friendly raw materials, offering the broad applicability in catalysis.展开更多
Direct enantioselective allylic C—H functionalization has emerged as a powerful strategy for the asymmetric syn-thesis of highly valuable chiral products.Herein,a Rh(III)-catalyzed enantioselective allylic C—H alkyl...Direct enantioselective allylic C—H functionalization has emerged as a powerful strategy for the asymmetric syn-thesis of highly valuable chiral products.Herein,a Rh(III)-catalyzed enantioselective allylic C—H alkylation of unactivated alkenes withα-diazo carbonyl compounds is described,enabling direct access to chiral products with high efficiency(up to 77%yield,92%ee,and>10∶1 B/L(branched/linear)selectivity).This atom-and step-economical protocol directly converts simple,unactivated substrates into valuable enantioenriched products under mild conditions,providing an efficient catalytic system for asymmetric allylic C—H functionalization.展开更多
The cerium-silicate pillared MWW zeolites are fabricated by introducing Ce species into the silica pillars within adjacent MWW layers through a liquid-phase pillaring method,and the multiple-layer structure of MWW zeo...The cerium-silicate pillared MWW zeolites are fabricated by introducing Ce species into the silica pillars within adjacent MWW layers through a liquid-phase pillaring method,and the multiple-layer structure of MWW zeolites is well maintained.However,it's found that these Ce^(3+)species can produce the Bronsted acid sites by the dissociation of water molecules owing to the electrostatic field of Ce^(3+)cations,the splitting of water molecules occurs following[Ce(H_2O)_n]^(3+)■Ce[(OH)(H_2O)_(n-1)]^(2+)+H^(+)equation based on the Plank-Hirschler mechanism,leading to superior activity of resultant cerium-silicate pillared MWW zeolites in the alkylation between benzene with 1-dodecene.Moreover,the additional Ce species located in the silica pillars can be easily accessed by vip molecules due to the presence of mesopores between neighboring MWW layers,which can strongly active benzene molecules by polarization effect,and dodecyl carbenium ions are preferred to attack the carbon atoms located in activated benzene molecules,resulting in the long lifetime of cerium-silicate pillared MWW zeolites since the oligomerization of long-chain olefins is suppressed.Under harsh reaction conditions(benzene/1-dodecene=10,WHSV=20 h^(-1)),the optimized cerium-silicate pillared MWW zeolite shows outstanding activity(>40%)and excellent selectivity(>85%)of 2-LAB in the alkylation of benzene with 1-dodecene.展开更多
Polyfluoroarenes represent an essential group of compounds in the fields of medical and material chemistry.It is still a challenge to synthesize alkylated polyfluoroarenes.Herein,a Ni-catalyzed reductive alkylation of...Polyfluoroarenes represent an essential group of compounds in the fields of medical and material chemistry.It is still a challenge to synthesize alkylated polyfluoroarenes.Herein,a Ni-catalyzed reductive alkylation of polyfluoroarenes with alkyl halides under mild conditions is reported.Polyfluoroarenes(3~6 F)can reacted smoothly with a diverse range of alkyl halides,such as primary,secondary,and tertiary alkyl iodides.The efficient formation of C(sp2)—C(sp3)can be achieved through the combination of Ni catalysis and(Bpin)2/K2CO3 as terminal reductant.展开更多
An Hβ-supported heteropoly acid （H3PW12O40 （HPW）/Hβ） catalyst was successfully prepared by wetness impregnation, and investigated in the alkylation of toluene with tert-butyl alcohol for the synthesis of 4-tert-...An Hβ-supported heteropoly acid （H3PW12O40 （HPW）/Hβ） catalyst was successfully prepared by wetness impregnation, and investigated in the alkylation of toluene with tert-butyl alcohol for the synthesis of 4-tert-butyltoluene （PTBT）. X-ray diffraction, scanning electron microscopy, transmis- sion electron microscopy, fourier-transform infrared spectroscopy, inductively coupled plas- ma-optical emission spectrometry, the brunauer emmett teller （BET） method, tempera- ture-programmed NH3 desorption, and pyridine adsorption infrared spectroscopy were used to characterize the catalyst. The results showed that loading HPW on Hβ effectively increased the B acidity and decreased the pore size of Hβ. The B acidity of HPW/Hβ was 142.97 μmol/g, which is 69.74% higher than that of Hβ （84.23 μmol/g）. The catalytic activity of the HPW/Hβ catalyst was much better than that of the parent Hβ zeolite because of its high B acidity. The toluene conversion over HPW/Hβ reached 73.1%, which is much higher than that achieved with Hβ （54.0%）. When HPW was loaded on Hβ, the BET surface area of Hβ decreased from 492.5 to 379.6 m2/g, accompa- nied by a significant decrease in the pore size from 3.90 to 3.17 nm. Shape selectivity can therefore play an important role and increase the product selectivity of the HPW/Hβ catalyst compared with that of the parent Hβ. PTBT （kinetic diameter 0.58 nm） can easily diffuse through the narrowed pores of HPW/Hβ, but 3-tert-butyltoluene （kinetic diameter 0.65 nm） diffusion is restricted because of steric hindrance in these narrow pores. This results in high PTBT selectivity over HPW/Hβ （around 81%）. The HPW/Hβ catalyst gave a stable catalytic performance in reusability tests.展开更多
The development of low-cost,earth-abundant and environmentally benign transition metal catalysts,which can catalyze multiple different types of asymmetric reactions,is an important objective in mod-ern asymmetric cata...The development of low-cost,earth-abundant and environmentally benign transition metal catalysts,which can catalyze multiple different types of asymmetric reactions,is an important objective in mod-ern asymmetric catalysis.Herein we demonstrate that a chiral Ni/P-Phos catalyst achieves three types of asymmetric reactions:allenylic substitution of racemic allenic ethers,1,4-hydroalkylation of prochiral 1,3-enynes and double alkylation of newly designed enynyl ether reagents.Three methods complement each other and produce various axially chiral allene derivatives bearing a pyrazolidine-3,5-dione unit,which is widely present in drugs and biologically active molecules with versatile pharmacological activities.展开更多
Enantiomerically pure a-substituted bamino esters were prepared from natural L-a-amino acids through Arndt-Eistert homologation and diastereoselective aalkylation.
An operationally simple and efficient method for the synthesis of a wide range of alkylated nucleotides under mild conditions was developed. This improved method furnishes alkylated nucleotides fi＇om both single nucl...An operationally simple and efficient method for the synthesis of a wide range of alkylated nucleotides under mild conditions was developed. This improved method furnishes alkylated nucleotides fi＇om both single nucleotides and oligonucleotides, and were prepared in high yields of 81% to 91%. Alkyl modified aptamer AS1411s were synthesized using this method and the biological activity screening results demonstrated that alkylation at the 1^st P-S site on yielded stronger target protein binding capacity, greater growth suppression effects against K562 and HL-60 cell lines, and improved serum stability, as compared with AS1411. This modified aptamer may be useful in tumor detection and treatment.展开更多
The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with t...The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with the presence of appropriate amount of phosphorus. Meanwhile, side reactions such as methanol to olefins related with the formation of by-product ethylbenzene formation and isomerization of xylene to meta-xylene were suppressed efficiently. The acid strength and sites amount of Br?nsted acid of the catalyst were crucial for improving benzene conversion and yield of xylene, whereas passivation of external surface acid sites played an important role in breaking thermodynamic equilibrium distribution of xylene isomers.展开更多
With the shape selective zeolite catalyst,toluene alkylation with methanol to para-xylene(MTPX)technology could produce highly pure para-xylene(PX)in one step.The lower feedstock cost and less energy consumption in pr...With the shape selective zeolite catalyst,toluene alkylation with methanol to para-xylene(MTPX)technology could produce highly pure para-xylene(PX)in one step.The lower feedstock cost and less energy consumption in products separation make it more competitive compared to the current toluene disproportionation route.Thus,MTPX is regarded as the most reasonable production route for PX production.This article reviews the strategies that applied to the preparation of high-performance catalysts for MTPX,with special focus on the precise control of pore dimension and acid sites distribution in zeolite to achieve the highest selectivity to PX.The outlook of the MTPX catalyst is also proposed to guide the catalyst development in the field.展开更多
A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the...A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the addition of NaC1 and crystal seed. X-ray diffraction （XRD）, scanning electron microscope （SEM）, X-ray fluorescence （XRF） and temperature-programmed desorption of ammonia （NH3-TPD） were used to characterize these samples. The samples were tested with toluene methylation reaction. The modified sample composed of spherical particles with 3 μm crystal particles on the surface had a para-xylene selectivity of 95% and maintained 79% of the initial conversion after running the reaction for 50 h. This modified samole showed the best stability amonz the tested three modified samoles.展开更多
The alkylation of benzene with isopropanol over beta-zeolite is a more cost-effective solution to cumene production. During the benzene alkylation cycles, the cumene selectivity slowly increased, while the benzene con...The alkylation of benzene with isopropanol over beta-zeolite is a more cost-effective solution to cumene production. During the benzene alkylation cycles, the cumene selectivity slowly increased, while the benzene conversion presented the sharp decrease due to catalyst deactivation. The deactivation mechanism of betazeolite catalyst was investigated by characterizing the fresh and used catalysts. The XRD, SEM and TEM results show that the crystalline and particle size of the beta-zeolite catalyst almost remained stable during the alkylation cycles. The drop in catalytic activity and benzene conversion could be explained by the TG, BET,NH_3-TPD and GC–MS results. The organic matters mainly consisted of ethylbenzene, p-xylene and 1-ethyl-3-(1-methyl) benzene produced in the benzene alkylation deposited in the catalyst, which strongly reduced the specific surface area of beta-zeolite catalyst. Moreover, during the reaction cycles, the amount of acidity also significantly decreased. As a result, the catalyst deactivation occurred. To maintain the catalytic performance,the catalyst regeneration was carried out by using ethanol rinse and calcination. The deactivated catalyst could be effectively regenerated by the calcination method and the good catalytic performance was obtained.展开更多
A novel industrial process was designed for the highly selective production of ethylbenzene. It comprised of a reactor vessel, vapor phase ethylene feed stream, benzene and transalkylation feed stream. Especially the ...A novel industrial process was designed for the highly selective production of ethylbenzene. It comprised of a reactor vessel, vapor phase ethylene feed stream, benzene and transalkylation feed stream. Especially the product stream containing ethylbenzene was used to heat the reactor vessel, which consisted of an alkylation section, an upper heat exchange section, and a bottom heat exchange section. In such a novel reactor, vapor phase benzene and liquid phase benzene were coexisted due to the heat produced by isothermal reaction between the upper heat exchange section and the bottom heat exchange section. The process was demonstrated by the thermodynamic analysis and experimental results. In fact, during the 1010 hour-life-test of gas phase ethene with gas phase-liquid phase benzene alkylation reaction, the ethene conversion was above 95%, and the ethylbenzene selectivity was above 83% （only benzene feed） and even higher than 99% （benzene plus transalkylation feed）. At the same time, the xylene content in the ethylbenzene was less than 100 ppm when the reaction was carried out under the reaction conditions of 140-185℃ of temperature, 1.6-2.1 MPa of pressure, 3.0-5.5 of benzene/ethylene mole ratio, 4-6 v% of transalkylation feed/（benzene＋transalkylation feed）, 0.19-0.27 h^-1 of ethene space velocity, and 1000 g of 3998 catalyst loaded. Thus, compared with the conventional ethylbenzene synthesis route, the transalkylation reactor could be omitted in this novel industrial process.展开更多
Aim To investigate the alkylation of 2-thiopyrimidine. Methods Treating the starting material 2-thiopyrimidine with chloromethyl ethers via a procedure of K2CO3 in DMF or with alkyl halide in CH3ONa-CH3OH at room temp...Aim To investigate the alkylation of 2-thiopyrimidine. Methods Treating the starting material 2-thiopyrimidine with chloromethyl ethers via a procedure of K2CO3 in DMF or with alkyl halide in CH3ONa-CH3OH at room temperature, to obtain the corresponding regioselective 2-S-allkyl pyrimidines. The products were determined by JH NMR, 2D NMR, IR and MS spectra. Results 2-S-alkyl-pyrimidines were regioselectively synthesized. Conclusion In different conditions with different alkyl halides, 2- thiouracil could be converted into the corresponding 2-S-alkylpyrimidines regioselectively.展开更多
Abstract The study on the catalysis of ionic liquids for alkylation of benzene with 1-octadecene to synthesize LAB （linear alkylbenzenes） was performed. The results showed that the most important factor that governe...Abstract The study on the catalysis of ionic liquids for alkylation of benzene with 1-octadecene to synthesize LAB （linear alkylbenzenes） was performed. The results showed that the most important factor that governed the conversion of olefin and selectivity of LAB was reaction temperature. Moreover, the effects of different ionic liquids and molar ratio of benzene to 1-octadecene on the conversion and selectivity were obviously in different degrees. The reaction temperature, molar ratio of benzene to 1-octadecene and the amount of catalyst were lower, compared with the traditional reaction technologies. The experimental results demonstrated that the ionic liquid had higher activity at 30℃, with over 98% selectivity of monoalkylbenzene and 100% conversion of the olefin at the molar ratio 0.08 of FeCl3 in ionic liquid to 1-octadecene and 10 for benzene to 1-octadecene.展开更多
In our present work,the high-silica hierarchical porous ZSM-5 with appropriate Br(o|¨)nsted acidity and hierarchical porous structure was synthesized by sol-gel method for continuously catalytic conversion of ben...In our present work,the high-silica hierarchical porous ZSM-5 with appropriate Br(o|¨)nsted acidity and hierarchical porous structure was synthesized by sol-gel method for continuously catalytic conversion of benzene alkylation with methanol to xylene.The effects of temperature,pressure,benzene/methanol molar ratio and weight hour space velocity(WHSV)on the catalytic performance of the catalyst were investigated as well.As a result,the high-silica hierarchical porous ZSM-5 showed great performance as the yield of xylene was up to 41.1%under the optimum reaction conditions(500℃,0.1 MPa,M_(benzene)/M_(methanol)=1:1.5 and WHSV=4 h 1),while the selectivity to by-product,ethylbenzene,was well suppressed(below 0.1%).In addition,the catalyst structure and properties were characterized by the means of XRD,IR,TPD,SEM,TEM and N_2 physical adsorption technologies.展开更多
Ball milling modification was performed on Cs/X catalysts before or after cesium ion exchange.Multiple characterization results(such as pyridine-FTIR,XPS,and solid-state NMR)demonstrated that ball milling played a dis...Ball milling modification was performed on Cs/X catalysts before or after cesium ion exchange.Multiple characterization results(such as pyridine-FTIR,XPS,and solid-state NMR)demonstrated that ball milling played a distinct role in these two different preparation procedures of the catalyst.Ball milling performed after the cesium modification has a strong influence on the Cs/X structure and acid-base properties,which results in the enhancement of the catalytic performance for side-chain methylation of toluene with methanol.Detailed studies revealed that ball milling intensified the interactions between oxides and molecular sieves,which not only increased the dispersion of the Cs species but also generated some weaker basic centers.It is proposed that the new basic centers could be Si-O-Cs and Al-O-Cs,which are produced by breaking of the Si-O-Al bonds of the zeolite framework under the synergetic effect of ball milling and alkali treatment.These new active sites may help to promote the side-chain methylation reaction.However,excessive ball milling will lead to the vanishing of zeolite micropores,thus deactivating side-chain methylation activity,which indicates that microporosity plays a key role in side-chain methylation and individual basic centers cannot catalyze this reaction.展开更多
A series of Cu-based catalysts were developed for alkylation of benzene with syngas. The catalyst samples were prepared by the impregnation method, and were characterized by XRD, XRF, NH3-TPD, and TEM and evaluated in...A series of Cu-based catalysts were developed for alkylation of benzene with syngas. The catalyst samples were prepared by the impregnation method, and were characterized by XRD, XRF, NH3-TPD, and TEM and evaluated in a fixed bed reactor. The optimized reaction temperature of Cu/Al2O3/ZSM-5 catalyst was 350 ℃, while higher contents of copper were conducive to alkylation of benzene with syngas. The new medium strength acid centers in the catalyst created by Cu were beneficial to alkylation. Hydrogenation reaction of CO was executed on the metal centers without dissociation, Dimethyl ether(DME) was the major intermediate over Cu-based catalysts. Higher selectivity of methylation and lower selectivity of heavy aromatics were confirmed after the second metal(Zn, Mn, or V) was added to the copper catalyst. Cu was partly covered by Zn in the Cu-Zn/Al2O3/ZSM-5 catalyst leading to low dispersion and low activity of copper. Cu-Mn/Al2O3/ZSM-5 catalyst possessed the best yield of methylation product. Cu-Mn composite oxides were probably formed in fresh catalyst, which blocked the sintering of Cu in the reaction process. The loading of Cu decreased dramatically after the introduction of V, while causing an increase of the amount of medium strength acid centers at the same time. V prevented the sintering of copper particles during the reducing process and had a promoting effect on the activity of Cu.展开更多
A series of calcined HTLcs catalysts were prepared and modified with potassium phosphate by impregnation method to clarify the influence of catalyst alkalinity on the side chain alkylation of toluene with methanol for...A series of calcined HTLcs catalysts were prepared and modified with potassium phosphate by impregnation method to clarify the influence of catalyst alkalinity on the side chain alkylation of toluene with methanol for synthesis of ethylbenzene and styrene.The catalysts were characterized by X-ray diffraction(XRD),N_(2)physical adsorption-desorption,Fourier-transform infrared spectroscopy(FT-IR),Scanning electron microscopy(SEM),X-ray photoelectron spectrometry(XPS),NH_(3)temperature-programmed desorption(NH_(3)-TPD)and CO_(2)temperature-programmed desorption(CO_(2)-TPD).It was found that the selectivity of styrene was highest(39.25%)when the K_(3)PO_(4)loading was 7.5 wt%.And the total yield of styrene and ethylbenzene could reach 65.08%with 10 wt%K_(3)PO_(4)loading.This might due to the fact that the addition of K_(3)PO_(4)could adjust the acid and basic sites of catalysts.In addition,appropriate strength and amount of basic sites were favorable to producing more styrene.展开更多
The alkylation of toluene with methanol to selective formation of p-xylene has been systematically studied. ZSM-12 （MTW）/ZSM-5 co-crystalline zeolite in 40：60 proportions have been synthesized by the same molar gel...The alkylation of toluene with methanol to selective formation of p-xylene has been systematically studied. ZSM-12 （MTW）/ZSM-5 co-crystalline zeolite in 40：60 proportions have been synthesized by the same molar gel composition, but at different temperatures and periods than that of ZSM-12 and ZSM-5, separately. All the prepared samples are characterized by XRD, SEM, BET, and XRF. The activity of toluene alkylation was investigated with a mixture of toluene and methanol as a feed over the ZSM-12, ZSM-12/ZSM-5 co-crystalline, ZSM-5, and physical mixture of ZSM-12/ZSM-5. From characterization, it is observed that the ZSM-12/ZSM-5 co-crystalline material is different from that of ZSM-12, ZSM-5, and their physical mixture. Further, the ZSM-12/ZSM-5 co-crystalline zeolite produces the highest content of xylene and has better selectivity for p-xylene than ZSM-12, ZSM-5, and their physical mixture.展开更多
基金Joint Project of Dalian University of Technology-Dalian Institute of Chemical Physics (HX20230236)。
文摘Zeolite nanosheets with a short b-axis thickness are highly desirable in lots of catalytic reactions due to their reduced diffusion resistance. Nevertheless, conventional synthesis methods usually require expensive structure-directing agents(SDAs), pricey raw materials, and eco-unfriendly fluorine-containing additives. Here, we contributed a cost-effective and fluoride-free synthesis method for synthesizing high-quality MFI zeolite nanosheets through a Silicalite-1(Sil-1) seed suspension and urea cooperative strategy, only with inexpensive colloidal silica as the Si source. Our approach was effective for synthesizing both Sil-1 and aluminum-containing ZSM-5 nanosheets. By optimizing key synthesis parameters,including seed aging time, seed quantity, and urea concentration, we achieved precise control over the crystal face aspect ratio and b-axis thickness. We also revealed a non-classical oriented nanosheet growth mechanism, where Sil-1 seeds induced the formation of quasi-ordered precursor particles, and the(010)crystal planes of these particles facilitated urea adsorption, thereby promoting c-axis-oriented growth.The obtained ZSM-5 nanosheets exhibited exceptional catalytic performance in the benzene alkylation with ethanol, maintaining stability for over 500 h, which is 5 times longer than traditional ZSM-5 catalysts. Furthermore, large-scale production of ZSM-5 nanosheets was successfully carried out in a 3 L highpressure autoclave, yielding samples consistent with those from laboratory-scale synthesis. This work marks a significant step forward in the sustainable and efficient production of MFI nanosheets using inexpensive and environmentally friendly raw materials, offering the broad applicability in catalysis.
文摘Direct enantioselective allylic C—H functionalization has emerged as a powerful strategy for the asymmetric syn-thesis of highly valuable chiral products.Herein,a Rh(III)-catalyzed enantioselective allylic C—H alkylation of unactivated alkenes withα-diazo carbonyl compounds is described,enabling direct access to chiral products with high efficiency(up to 77%yield,92%ee,and>10∶1 B/L(branched/linear)selectivity).This atom-and step-economical protocol directly converts simple,unactivated substrates into valuable enantioenriched products under mild conditions,providing an efficient catalytic system for asymmetric allylic C—H functionalization.
基金supported by the National Natural Science Foundation of China(22278090,21978055)Natural Science Foundation of Guangdong Province,China(2022A1515012088)。
文摘The cerium-silicate pillared MWW zeolites are fabricated by introducing Ce species into the silica pillars within adjacent MWW layers through a liquid-phase pillaring method,and the multiple-layer structure of MWW zeolites is well maintained.However,it's found that these Ce^(3+)species can produce the Bronsted acid sites by the dissociation of water molecules owing to the electrostatic field of Ce^(3+)cations,the splitting of water molecules occurs following[Ce(H_2O)_n]^(3+)■Ce[(OH)(H_2O)_(n-1)]^(2+)+H^(+)equation based on the Plank-Hirschler mechanism,leading to superior activity of resultant cerium-silicate pillared MWW zeolites in the alkylation between benzene with 1-dodecene.Moreover,the additional Ce species located in the silica pillars can be easily accessed by vip molecules due to the presence of mesopores between neighboring MWW layers,which can strongly active benzene molecules by polarization effect,and dodecyl carbenium ions are preferred to attack the carbon atoms located in activated benzene molecules,resulting in the long lifetime of cerium-silicate pillared MWW zeolites since the oligomerization of long-chain olefins is suppressed.Under harsh reaction conditions(benzene/1-dodecene=10,WHSV=20 h^(-1)),the optimized cerium-silicate pillared MWW zeolite shows outstanding activity(>40%)and excellent selectivity(>85%)of 2-LAB in the alkylation of benzene with 1-dodecene.
文摘Polyfluoroarenes represent an essential group of compounds in the fields of medical and material chemistry.It is still a challenge to synthesize alkylated polyfluoroarenes.Herein,a Ni-catalyzed reductive alkylation of polyfluoroarenes with alkyl halides under mild conditions is reported.Polyfluoroarenes(3~6 F)can reacted smoothly with a diverse range of alkyl halides,such as primary,secondary,and tertiary alkyl iodides.The efficient formation of C(sp2)—C(sp3)can be achieved through the combination of Ni catalysis and(Bpin)2/K2CO3 as terminal reductant.
文摘An Hβ-supported heteropoly acid （H3PW12O40 （HPW）/Hβ） catalyst was successfully prepared by wetness impregnation, and investigated in the alkylation of toluene with tert-butyl alcohol for the synthesis of 4-tert-butyltoluene （PTBT）. X-ray diffraction, scanning electron microscopy, transmis- sion electron microscopy, fourier-transform infrared spectroscopy, inductively coupled plas- ma-optical emission spectrometry, the brunauer emmett teller （BET） method, tempera- ture-programmed NH3 desorption, and pyridine adsorption infrared spectroscopy were used to characterize the catalyst. The results showed that loading HPW on Hβ effectively increased the B acidity and decreased the pore size of Hβ. The B acidity of HPW/Hβ was 142.97 μmol/g, which is 69.74% higher than that of Hβ （84.23 μmol/g）. The catalytic activity of the HPW/Hβ catalyst was much better than that of the parent Hβ zeolite because of its high B acidity. The toluene conversion over HPW/Hβ reached 73.1%, which is much higher than that achieved with Hβ （54.0%）. When HPW was loaded on Hβ, the BET surface area of Hβ decreased from 492.5 to 379.6 m2/g, accompa- nied by a significant decrease in the pore size from 3.90 to 3.17 nm. Shape selectivity can therefore play an important role and increase the product selectivity of the HPW/Hβ catalyst compared with that of the parent Hβ. PTBT （kinetic diameter 0.58 nm） can easily diffuse through the narrowed pores of HPW/Hβ, but 3-tert-butyltoluene （kinetic diameter 0.65 nm） diffusion is restricted because of steric hindrance in these narrow pores. This results in high PTBT selectivity over HPW/Hβ （around 81%）. The HPW/Hβ catalyst gave a stable catalytic performance in reusability tests.
基金supported by the National Natural Science Foundation of China (No.22171240)
文摘The development of low-cost,earth-abundant and environmentally benign transition metal catalysts,which can catalyze multiple different types of asymmetric reactions,is an important objective in mod-ern asymmetric catalysis.Herein we demonstrate that a chiral Ni/P-Phos catalyst achieves three types of asymmetric reactions:allenylic substitution of racemic allenic ethers,1,4-hydroalkylation of prochiral 1,3-enynes and double alkylation of newly designed enynyl ether reagents.Three methods complement each other and produce various axially chiral allene derivatives bearing a pyrazolidine-3,5-dione unit,which is widely present in drugs and biologically active molecules with versatile pharmacological activities.
基金The project is generously supported by the National Natural Science Foundation of China (Grant No. 29972002 20172002)+1 种基金 the Trans-Century Training Programme Foundation for the Talents by Ministry of Education and Bayer Co. Ltd (Germany). We thank Dr
文摘Enantiomerically pure a-substituted bamino esters were prepared from natural L-a-amino acids through Arndt-Eistert homologation and diastereoselective aalkylation.
基金the Ministry of Science and Technology of China(Grant No.2012CB720604)National Natural Science Foundation of China(Grant No.21332010)
文摘An operationally simple and efficient method for the synthesis of a wide range of alkylated nucleotides under mild conditions was developed. This improved method furnishes alkylated nucleotides fi＇om both single nucleotides and oligonucleotides, and were prepared in high yields of 81% to 91%. Alkyl modified aptamer AS1411s were synthesized using this method and the biological activity screening results demonstrated that alkylation at the 1^st P-S site on yielded stronger target protein binding capacity, greater growth suppression effects against K562 and HL-60 cell lines, and improved serum stability, as compared with AS1411. This modified aptamer may be useful in tumor detection and treatment.
基金Supported by the National Natural Science Foundation of China(21476207,21506189)Zhejiang Postdoctoral Research Funded Projects(BSH1502147)
文摘The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with the presence of appropriate amount of phosphorus. Meanwhile, side reactions such as methanol to olefins related with the formation of by-product ethylbenzene formation and isomerization of xylene to meta-xylene were suppressed efficiently. The acid strength and sites amount of Br?nsted acid of the catalyst were crucial for improving benzene conversion and yield of xylene, whereas passivation of external surface acid sites played an important role in breaking thermodynamic equilibrium distribution of xylene isomers.
基金the funding support(Project No.:CF9300172922)from National Institute of Clean-and-low-carbon Energy.
文摘With the shape selective zeolite catalyst,toluene alkylation with methanol to para-xylene(MTPX)technology could produce highly pure para-xylene(PX)in one step.The lower feedstock cost and less energy consumption in products separation make it more competitive compared to the current toluene disproportionation route.Thus,MTPX is regarded as the most reasonable production route for PX production.This article reviews the strategies that applied to the preparation of high-performance catalysts for MTPX,with special focus on the precise control of pore dimension and acid sites distribution in zeolite to achieve the highest selectivity to PX.The outlook of the MTPX catalyst is also proposed to guide the catalyst development in the field.
文摘A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the addition of NaC1 and crystal seed. X-ray diffraction （XRD）, scanning electron microscope （SEM）, X-ray fluorescence （XRF） and temperature-programmed desorption of ammonia （NH3-TPD） were used to characterize these samples. The samples were tested with toluene methylation reaction. The modified sample composed of spherical particles with 3 μm crystal particles on the surface had a para-xylene selectivity of 95% and maintained 79% of the initial conversion after running the reaction for 50 h. This modified samole showed the best stability amonz the tested three modified samoles.
基金Supports by the National Key Research and Development Plan(2016YFB0301503)the Jiangsu Natural Science Foundation for Distinguished Young Scholars(BK20150044)+3 种基金the National Natural Science Foundation of China(91534110,21606124)the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province(14KJB530004)the Foundation from State Key Laboratory of Materials-Oriented Chemical Engineering(ZK201402,ZK201407)the Technology Innovation Foundation for Science and Technology Enterprises in Jiangsu Province(BC2015008)
文摘The alkylation of benzene with isopropanol over beta-zeolite is a more cost-effective solution to cumene production. During the benzene alkylation cycles, the cumene selectivity slowly increased, while the benzene conversion presented the sharp decrease due to catalyst deactivation. The deactivation mechanism of betazeolite catalyst was investigated by characterizing the fresh and used catalysts. The XRD, SEM and TEM results show that the crystalline and particle size of the beta-zeolite catalyst almost remained stable during the alkylation cycles. The drop in catalytic activity and benzene conversion could be explained by the TG, BET,NH_3-TPD and GC–MS results. The organic matters mainly consisted of ethylbenzene, p-xylene and 1-ethyl-3-(1-methyl) benzene produced in the benzene alkylation deposited in the catalyst, which strongly reduced the specific surface area of beta-zeolite catalyst. Moreover, during the reaction cycles, the amount of acidity also significantly decreased. As a result, the catalyst deactivation occurred. To maintain the catalytic performance,the catalyst regeneration was carried out by using ethanol rinse and calcination. The deactivated catalyst could be effectively regenerated by the calcination method and the good catalytic performance was obtained.
基金This work is supported by the National 973 Project of China (2009CB623501)
文摘A novel industrial process was designed for the highly selective production of ethylbenzene. It comprised of a reactor vessel, vapor phase ethylene feed stream, benzene and transalkylation feed stream. Especially the product stream containing ethylbenzene was used to heat the reactor vessel, which consisted of an alkylation section, an upper heat exchange section, and a bottom heat exchange section. In such a novel reactor, vapor phase benzene and liquid phase benzene were coexisted due to the heat produced by isothermal reaction between the upper heat exchange section and the bottom heat exchange section. The process was demonstrated by the thermodynamic analysis and experimental results. In fact, during the 1010 hour-life-test of gas phase ethene with gas phase-liquid phase benzene alkylation reaction, the ethene conversion was above 95%, and the ethylbenzene selectivity was above 83% （only benzene feed） and even higher than 99% （benzene plus transalkylation feed）. At the same time, the xylene content in the ethylbenzene was less than 100 ppm when the reaction was carried out under the reaction conditions of 140-185℃ of temperature, 1.6-2.1 MPa of pressure, 3.0-5.5 of benzene/ethylene mole ratio, 4-6 v% of transalkylation feed/（benzene＋transalkylation feed）, 0.19-0.27 h^-1 of ethene space velocity, and 1000 g of 3998 catalyst loaded. Thus, compared with the conventional ethylbenzene synthesis route, the transalkylation reactor could be omitted in this novel industrial process.
基金National Nature Science Foundation of China(NO.20172007).
文摘Aim To investigate the alkylation of 2-thiopyrimidine. Methods Treating the starting material 2-thiopyrimidine with chloromethyl ethers via a procedure of K2CO3 in DMF or with alkyl halide in CH3ONa-CH3OH at room temperature, to obtain the corresponding regioselective 2-S-allkyl pyrimidines. The products were determined by JH NMR, 2D NMR, IR and MS spectra. Results 2-S-alkyl-pyrimidines were regioselectively synthesized. Conclusion In different conditions with different alkyl halides, 2- thiouracil could be converted into the corresponding 2-S-alkylpyrimidines regioselectively.
基金Supported by the National Natural Science Foundation of China （No.20276038） and Beijing Natural Science Foundation （No.2052010）.
文摘Abstract The study on the catalysis of ionic liquids for alkylation of benzene with 1-octadecene to synthesize LAB （linear alkylbenzenes） was performed. The results showed that the most important factor that governed the conversion of olefin and selectivity of LAB was reaction temperature. Moreover, the effects of different ionic liquids and molar ratio of benzene to 1-octadecene on the conversion and selectivity were obviously in different degrees. The reaction temperature, molar ratio of benzene to 1-octadecene and the amount of catalyst were lower, compared with the traditional reaction technologies. The experimental results demonstrated that the ionic liquid had higher activity at 30℃, with over 98% selectivity of monoalkylbenzene and 100% conversion of the olefin at the molar ratio 0.08 of FeCl3 in ionic liquid to 1-octadecene and 10 for benzene to 1-octadecene.
基金financial support from the National Natural Science Foundation of China(Nos.NSFC-21476207 and NSFC21506189)National Basic Research Program of China(973 Program,No.2011CB710800)
文摘In our present work,the high-silica hierarchical porous ZSM-5 with appropriate Br(o|¨)nsted acidity and hierarchical porous structure was synthesized by sol-gel method for continuously catalytic conversion of benzene alkylation with methanol to xylene.The effects of temperature,pressure,benzene/methanol molar ratio and weight hour space velocity(WHSV)on the catalytic performance of the catalyst were investigated as well.As a result,the high-silica hierarchical porous ZSM-5 showed great performance as the yield of xylene was up to 41.1%under the optimum reaction conditions(500℃,0.1 MPa,M_(benzene)/M_(methanol)=1:1.5 and WHSV=4 h 1),while the selectivity to by-product,ethylbenzene,was well suppressed(below 0.1%).In addition,the catalyst structure and properties were characterized by the means of XRD,IR,TPD,SEM,TEM and N_2 physical adsorption technologies.
文摘Ball milling modification was performed on Cs/X catalysts before or after cesium ion exchange.Multiple characterization results(such as pyridine-FTIR,XPS,and solid-state NMR)demonstrated that ball milling played a distinct role in these two different preparation procedures of the catalyst.Ball milling performed after the cesium modification has a strong influence on the Cs/X structure and acid-base properties,which results in the enhancement of the catalytic performance for side-chain methylation of toluene with methanol.Detailed studies revealed that ball milling intensified the interactions between oxides and molecular sieves,which not only increased the dispersion of the Cs species but also generated some weaker basic centers.It is proposed that the new basic centers could be Si-O-Cs and Al-O-Cs,which are produced by breaking of the Si-O-Al bonds of the zeolite framework under the synergetic effect of ball milling and alkali treatment.These new active sites may help to promote the side-chain methylation reaction.However,excessive ball milling will lead to the vanishing of zeolite micropores,thus deactivating side-chain methylation activity,which indicates that microporosity plays a key role in side-chain methylation and individual basic centers cannot catalyze this reaction.
文摘A series of Cu-based catalysts were developed for alkylation of benzene with syngas. The catalyst samples were prepared by the impregnation method, and were characterized by XRD, XRF, NH3-TPD, and TEM and evaluated in a fixed bed reactor. The optimized reaction temperature of Cu/Al2O3/ZSM-5 catalyst was 350 ℃, while higher contents of copper were conducive to alkylation of benzene with syngas. The new medium strength acid centers in the catalyst created by Cu were beneficial to alkylation. Hydrogenation reaction of CO was executed on the metal centers without dissociation, Dimethyl ether(DME) was the major intermediate over Cu-based catalysts. Higher selectivity of methylation and lower selectivity of heavy aromatics were confirmed after the second metal(Zn, Mn, or V) was added to the copper catalyst. Cu was partly covered by Zn in the Cu-Zn/Al2O3/ZSM-5 catalyst leading to low dispersion and low activity of copper. Cu-Mn/Al2O3/ZSM-5 catalyst possessed the best yield of methylation product. Cu-Mn composite oxides were probably formed in fresh catalyst, which blocked the sintering of Cu in the reaction process. The loading of Cu decreased dramatically after the introduction of V, while causing an increase of the amount of medium strength acid centers at the same time. V prevented the sintering of copper particles during the reducing process and had a promoting effect on the activity of Cu.
基金financial support from the National Key Technology Research&Development Program(Grant No.2013BAC14B04)the National Natural Science Foundation of China(Grant No.21336006)+1 种基金the Shanxi Province Key Research&Development Program(international cooperation,Grant No.201803D421099)Supported by Shanxi Scholarship Council of China(Grant No.2017-035)。
文摘A series of calcined HTLcs catalysts were prepared and modified with potassium phosphate by impregnation method to clarify the influence of catalyst alkalinity on the side chain alkylation of toluene with methanol for synthesis of ethylbenzene and styrene.The catalysts were characterized by X-ray diffraction(XRD),N_(2)physical adsorption-desorption,Fourier-transform infrared spectroscopy(FT-IR),Scanning electron microscopy(SEM),X-ray photoelectron spectrometry(XPS),NH_(3)temperature-programmed desorption(NH_(3)-TPD)and CO_(2)temperature-programmed desorption(CO_(2)-TPD).It was found that the selectivity of styrene was highest(39.25%)when the K_(3)PO_(4)loading was 7.5 wt%.And the total yield of styrene and ethylbenzene could reach 65.08%with 10 wt%K_(3)PO_(4)loading.This might due to the fact that the addition of K_(3)PO_(4)could adjust the acid and basic sites of catalysts.In addition,appropriate strength and amount of basic sites were favorable to producing more styrene.
文摘The alkylation of toluene with methanol to selective formation of p-xylene has been systematically studied. ZSM-12 （MTW）/ZSM-5 co-crystalline zeolite in 40：60 proportions have been synthesized by the same molar gel composition, but at different temperatures and periods than that of ZSM-12 and ZSM-5, separately. All the prepared samples are characterized by XRD, SEM, BET, and XRF. The activity of toluene alkylation was investigated with a mixture of toluene and methanol as a feed over the ZSM-12, ZSM-12/ZSM-5 co-crystalline, ZSM-5, and physical mixture of ZSM-12/ZSM-5. From characterization, it is observed that the ZSM-12/ZSM-5 co-crystalline material is different from that of ZSM-12, ZSM-5, and their physical mixture. Further, the ZSM-12/ZSM-5 co-crystalline zeolite produces the highest content of xylene and has better selectivity for p-xylene than ZSM-12, ZSM-5, and their physical mixture.
