The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by ...The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by the impregnation of the ZSM-5 type zeolites（Si/Al=64：1）with the corresponding RE nitrate aqueous solutions.The catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD,and IR spectroscopy of adsorbed pyridine.The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor.The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins,especially to propylene,thus increasing the total yield of olefins in the catalytic cracking of butane.Among the RE-modified HZSM-5 samples,Ce/HZSM-5 gave the highest yield of total olefins,and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600℃.The presence of rare earth metal on the HZSM-5 sample,not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type,that is,the ratio of L/B（Lewis acid/Brnsted acid）,but also altered the basic properties of it,which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.展开更多
Te-promoted （1%） vanadium phosphate catalyst （VPDTe） was prepared via VOPO4·2H2O by calcining its precursor VOHPO4·0.5H2O in a flow of n-butane/air.VPDTe catalyst has resulted a higher existence of V5＋ ...Te-promoted （1%） vanadium phosphate catalyst （VPDTe） was prepared via VOPO4·2H2O by calcining its precursor VOHPO4·0.5H2O in a flow of n-butane/air.VPDTe catalyst has resulted a higher existence of V5＋ phase with V5＋/V4＋ ratio of 0.23.SEM micrographs show that Te addition altered the arrangement of the platelets from ＂rose-like＂ clusters to layer with irregular shape.Te addition has also markedly lowered the reduction activation energies of the vanadium phosphate catalyst as revealed by TPR profile.The amount of active oxygen species associated with V4＋ phase of the Te promoted catalyst was significantly higher than those of the unpromoted catalyst.These observations suggest that high mobility and availability of reactive oxygen species contributed to the enhancement of n-butane conversion up to 80% at 673 K,while only 47% over unpromoted catalyst （2400 h^-1,1.7% n-butane in air）.展开更多
The title coordination polymer 1,{[Cu8（btb）2（CN）8].3H2O}n（btb = 1,4-bis（1,2,4-triazol-1-yl）butane）,has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction.Complex...The title coordination polymer 1,{[Cu8（btb）2（CN）8].3H2O}n（btb = 1,4-bis（1,2,4-triazol-1-yl）butane）,has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction.Complex 1 crystallizes in monoclinic,space group C2/c with a = 1.2938（3）,b = 1.9422（5）,c = 0.9406（2） nm,β = 121.891（4）°,V = 2.0066（9） nm3,C24H30Cu8N20O3,Mr = 1155.00,Dc = 1.912 g/cm3,μ（MoKα） = 4.209 mm？1,F（000） = 1140,GOF = 1.184,Z = 2,the final R = 0.0634 and wR = 0.1503 for I 2σ（I）.In complex 1,one-dimensional CuCN zigzag chains are linked by triazolyl groups of btb ligands to form two-dimensional networks,which are further bridged by 1,4-butyl moieties of btb ligands to fabricate a three-dimensional order framework,in which one-dimensional ellipsoid-like channels are observed.展开更多
An efficient technology of impregnation of carbonate crushed stone by oil-product based on SCF-impregnation process usage with propane/butane solvent was developed. Regular impregnation throughout the volume of crushe...An efficient technology of impregnation of carbonate crushed stone by oil-product based on SCF-impregnation process usage with propane/butane solvent was developed. Regular impregnation throughout the volume of crushed stone sample is achieved. As a result of the appliance of proposed technology, the humidity of the treated crushed stone samples decreased down to 0.54%.展开更多
The oxidative dehydrogenation of butane to butadiene and butene was studied using a conventional fixed-bed ractor (FBR), inert membrane reactor (IMR) and mixed inert membrane reactor (MIMR). When IMR and MIMR were emp...The oxidative dehydrogenation of butane to butadiene and butene was studied using a conventional fixed-bed ractor (FBR), inert membrane reactor (IMR) and mixed inert membrane reactor (MIMR). When IMR and MIMR were employed, a ceramic membrane modified by partially coating with glaze was used to distribute oxygen to a fixed-bed of 24-V-Mg-O catalyst. The oxygen partial pressure in the catalyst bed could be decreased. The effect of feeding modes and operation conditions were investigated. The selectivity of C4 dehydrogenation products (butene and butadiene) was found to be higher in IMR than in FBR. The feeding mode with 20% of air mixing with butane in MIMR was found to be more efficient than the feeding mode with all air permeating through ceramic membrane. The MIMR gave the most smooth temperature profile along the bed.展开更多
Eight new macrocyclic complexes were synthesized by template reaction of 1,4-bis（3-aminopropoxy）butane with metal nitrate and 1,3-bis（2-formylphenyl）propane or 1,4-bis（2-formylphenyl）butane and their structures ...Eight new macrocyclic complexes were synthesized by template reaction of 1,4-bis（3-aminopropoxy）butane with metal nitrate and 1,3-bis（2-formylphenyl）propane or 1,4-bis（2-formylphenyl）butane and their structures were proposed on the basis of elemental analysis, FTIR, UV-vis, molar conductivity measurements, ^1H NMR and mass spectra. The metals to ligand molar ratios of the complexes were found to be 1： 1. The complexes are 1：2 electrolytes for Pb（II）, Zn（II） and Cd（II） complexes and 1：3 electrolytes for La（III） as shown by their molar conductivities （Am） in DMSO at 10^-3 mol L^-1. Due to the existence of free ions in these complexes, such complexes are electrically conductive. The configurations of La（III） and Pb（II） were proposed to probably octahedral and Zn（II） and Cd（II） complexes were proposed to probably tetrahedral.展开更多
The new ligand bis-（1,4-sodium thiolactate） butane （L）-O2CCH3S-（CH2）4SCHCH3CO2- has been prepared from the reaction of disodium salt of thiolactic acid and 1,4-dichlorobutane, while the disodium thiolactate was ...The new ligand bis-（1,4-sodium thiolactate） butane （L）-O2CCH3S-（CH2）4SCHCH3CO2- has been prepared from the reaction of disodium salt of thiolactic acid and 1,4-dichlorobutane, while the disodium thiolactate was prepared instanteously through the reaction of thiolactic acid with NaOH. Mono and dinuclear complexes were obtained by direct reaction of the above ligands with H[AuCI4] in 1 ： 1, 2：1, 1：2, 2：2 and 3：1 ligands to metal molar ratio. The prepared complexes were characterized by elemental analysis, spectral studies FTIR （Fourier transform Infrared） and UV-Vis, magnetic measurement, conductivity measurement and IHNMR for the ligand （L） and some of the complexes. The conductance data indicate that the complexes of the formulas Na[Au（SCH3CHCOO）2], Na[Au（SCH3CHCOO）（OOCCHCH3SH）2] and [Au（L）]Cl are 1：1 electrolyte. Electronic spectra and magnetic moment values indicate the presence of square planner geometry around Au（III） ions.展开更多
Dearomative photocycloaddition of heteroarenes is an efficient method for replacing planar arenes with three-dimensional(3D)scaffolds,such as bicyclo[2.1.1]-hexane(BCH)containing heterocycles.Herein,we report intramol...Dearomative photocycloaddition of heteroarenes is an efficient method for replacing planar arenes with three-dimensional(3D)scaffolds,such as bicyclo[2.1.1]-hexane(BCH)containing heterocycles.Herein,we report intramolecular dearomative[2π+2σ]photocycloadditions of bicyclo[1.1.0]butanes(BCBs)with(benzo)furans and(benzo)thiophenes.These photocycloadditions are initiated through an energy transfer pathway(EnT)or single electron transfer pathway(SET),efficiently yielding unique BCHpyrrolidinone-fused heterocyclic scaffolds.Moreover,the synthetic utility of this photochemical reaction was demonstrated on the basis of large-scale synthesis and diversified transformations.Mechanistic investigations,in conjunction with density functional theory(DFT)calculations,were taken to support the proposed reaction mechanisms.展开更多
NMR hyperpolarization dramatically improves the detection sensitivity of magnetic resonance through the increase in nuclear spin polarization.Because of the sensitivity increase by several orders of magnitude,addition...NMR hyperpolarization dramatically improves the detection sensitivity of magnetic resonance through the increase in nuclear spin polarization.Because of the sensitivity increase by several orders of magnitude,additional applications have been unlocked,including imaging of gases in physiologically relevant conditions.Hyperpolarized ^(129)Xe gas recently received FDA approval as the first inhalable gaseous MRI contrast agent for clinical functional lung imaging of a wide range of pulmonary diseases.However,production and utilization of hyperpolarized ^(129)Xe gas faces a number of translational challenges including the high cost and complexity of contrast agent production and imaging using proton-only(i.e.,conventional)clinical MRI scanners,which are typically not suited to scan ^(129)Xe nuclei.As a solution to circumvent the translational challenges of hyperpolarized ^(129)Xe,we have recently demonstrated the feasibility of a simple and cheap process for production of proton-hyperpolarized propane gas contrast agent using ultralow-cost disposable production equipment and demonstrated the feasibility of lung ventilation imaging using hyperpolarized propane gas in excised pig lungs.However,previous pilot studies have concluded that the hyperpolarized state of propane gas decays very fast with an exponential decay T1 constant of∼0.8 s at 1 bar(physiologically relevant pressure);moreover,the previously reported production rates were too slow for potential clinical utilization.Here,we investigate the feasibility of high-capacity production of hyperpolarized butane gas via heterogeneous parahydrogen-induced polarization using Rh nanoparticle-based catalyst utilizing butene gas as a precursor for parahydrogen pairwise addition.We demonstrate a remarkable result:the lifetime of the hyperpolarized state can be nearly doubled compared to that of propane(T1 of∼1.6 s and long-lived spin-state TS of∼3.8 s at clinically relevant 1 bar pressure).Moreover,we demonstrate a production speed of up to 0.7 standard liters of hyperpolarized gas per second.These two synergistic developments pave the way to biomedical utilization of proton-hyperpolarized gas media for ventilation imaging.Indeed,here we demonstrate the feasibility of phantom imaging of hyperpolarized butane gas in Tedlar bags and also the feasibility of subsecond 2D ventilation gas imaging in excised rabbit lungs with 1.6×1.6 mm^(2) in-plane resolution using a clinical MRI scanner.The demonstrated results have the potential to revolutionize functional pulmonary imaging with a simple and inexpensive on-demand production of protonhyperpolarized gas contrast media,followed by visualization on virtually any MRI scanner,including emerging bedside low-field MRI scanner technology.展开更多
2-Azabicyclo[2.1.1]hexanes(aza-BCHs)are constrained pyrrolidine analogues with improved physicochemical characteristics in drug design.Here,we report a direct visible light-mediated photocycloaddition of 4-aza-coumari...2-Azabicyclo[2.1.1]hexanes(aza-BCHs)are constrained pyrrolidine analogues with improved physicochemical characteristics in drug design.Here,we report a direct visible light-mediated photocycloaddition of 4-aza-coumarins with mono-or disubstituted bicyclo[1.1.0]butanes for synthesizing aza-BCHs without an external catalyst.The introduction of the ester group on 4-aza-coumarin is critical for direct imine excitation and versatile synthetic utility.Preliminary mechanistic studies indicated that the reaction took place primarily at the triplet hypersurface.展开更多
Background and Originality Content Cyclobutane moieties are an important class of motifs since they are frequently found in the medicinally relevant compounds such as alkaloids and pharmaceuticals.[1] Therefore,the de...Background and Originality Content Cyclobutane moieties are an important class of motifs since they are frequently found in the medicinally relevant compounds such as alkaloids and pharmaceuticals.[1] Therefore,the development of efficient synthetic strategies for the construction of cyclobutanes and their derivatives has always been a focus of inter-est.[2a] Photochemical reactions are powerful tools for synthesizing compounds with high complexity and diversity.[2b-h] Among them,photochemical[2+2]cycloaddition is a widely used protocol for the preparation of such compounds.[2h]However,this kind of reaction always suffers from the challenges of controlling the resulting products of the intermolecular[2+2]photodimerization.In principle,to achieve cyclobutanes via[2+2]cycloaddition,the two olefins should be oriented in a parallel fashion keeping the distance less than 4.2 A apart from each other.展开更多
A copper catalyzed stereoselective[2+2]cyclization has been developed,providing a concise protocol to the direct construction of diaryl-substituted cyclobutanes in up to 99%yield with up to>95/5 dr.Meanwhile,the en...A copper catalyzed stereoselective[2+2]cyclization has been developed,providing a concise protocol to the direct construction of diaryl-substituted cyclobutanes in up to 99%yield with up to>95/5 dr.Meanwhile,the enantioselective version of this reaction has also been achieved,leading to a series of optically active diaryl-substituted cyclobutanes with up to 94%ee.展开更多
of main observation and conclusion We herein report the first example of iridium-catalyzed enantioselective C(sp^3)-H borylation of cyclobutanes using benzoxazoline as the directing group.The combination of a chiral b...of main observation and conclusion We herein report the first example of iridium-catalyzed enantioselective C(sp^3)-H borylation of cyclobutanes using benzoxazoline as the directing group.The combination of a chiral bidentate boryl ligand and an iridium precursor has found to effectively catalyze C(sp)-H borylation to afford a variety of cyclobutylboronates with good to excellent enantioselectivities.We also demonstrate the synthetic utility of the current method by converting the stereogenic C—B bond to other functionalities.展开更多
A N,N＇-bisferrocenesulfonyl bisbenzimidazole compound 1,4-bis（1-ferrocenesulfonyl-2-benzimidazolyl） butane was prepared. Its crystal structure was determined. The crystal belongs to triclinic with space group P-1 a...A N,N＇-bisferrocenesulfonyl bisbenzimidazole compound 1,4-bis（1-ferrocenesulfonyl-2-benzimidazolyl） butane was prepared. Its crystal structure was determined. The crystal belongs to triclinic with space group P-1 and a= 0.87241（13） nm, b=0.97553（15） nm, c= 1.4120（2） rim, and α= 83.041（2）°, β= 72.454（2）°,γy= 69.732（2）°, the unit cell volume V= 1.0746（3） nm3, the molecule number in one unit cell Z= 1, the absorption coefficient u= 1.191 mm 1, the calculated density Dc= 1.584 g/cm3. The theoretical investigation of the compound as a structure unit was fully optimized by B3LYP/6-31G method in Gaussian 03 package, and the most stable structure of the compound in theory was obtained. The two results were compared. The optimized structure was in accordance with the crystal structure in the main, suggesting that the molecular geometry optimization of the structures was reliable and the calculation method used was reliable. The distribution of atomic charges and the energy, and composition of frontier molecular orbits were analyzed. Thermal analysis indicated that it is stable before melting.展开更多
On September 26,2016 Algerian Space Agency launched AlSat-1B,the second in a series of medium resolution earth observation satellites mission.AlSat-1B electro-thermal propulsion system follows the classic design princ...On September 26,2016 Algerian Space Agency launched AlSat-1B,the second in a series of medium resolution earth observation satellites mission.AlSat-1B electro-thermal propulsion system follows the classic design principle that has been used on previous SSTL-100 missions.With a total dry weight of 5.17 kg,the system is filled with 2.35 L selfpressurized butane.The thruster assembly is designed to use 15 W(at 28 V)redundant heater elements,it is designed to have an average mission thrust of 50 mN.With a warm up time of 10 min,the temperature of the butane will be increased by over 250℃.This is the equivalent of about 35%gain in specific impulse over ambient temperature butane.The spacecraft dry weigh at launch site was 107 kg,the propulsion system is designed to provide at least 19 m/s Delta-v to meet the spacecraft’s mission requirement.To investigate the system readiness for flight,a series of performance tests have been completed at the Surrey Satellite Technology Ltd laboratories(United Kingdom),Satellite Development Centre(Algeria)and Satish Dhawan Space Centre rocket launch site(India),the results of these tests as well as initial flight test results are presented in this paper.展开更多
Six new macrocyclic complexes were synthesized by a template reaction of 1,4-bis（2-formylphenoxy）butane with diamines and Cu（NO3）2·3H2O and their structures were proposed on the basis of elemental analysis, F...Six new macrocyclic complexes were synthesized by a template reaction of 1,4-bis（2-formylphenoxy）butane with diamines and Cu（NO3）2·3H2O and their structures were proposed on the basis of elemental analysis, FT-IR, UV-Vis, magnetic susceptibility measurements, molar conductivity measurements and mass spectra. The metal to ligand molar ratios of the Cu（Ⅱ） complexes were found to be 1 ： 1. The Cu（Ⅱ） complexes are 1 ： 2 electrolytes as shown by their molar conductivities （∧m） in DMF at 10^-3 mol·L^-1. Due to the existence of free ions the Cu（Ⅱ） complexes are electrically conductive. Their configurations were proposed to be probably distorted octahedral.展开更多
The permeation properties of n-butane, i-butane and n-butane/i-butane mixture （n-butane 24.3% （molar ratio）, i-butane 75.7%） through a tubular silicalite1 zeolite membrane were studied at 298 and 473 K respectivel...The permeation properties of n-butane, i-butane and n-butane/i-butane mixture （n-butane 24.3% （molar ratio）, i-butane 75.7%） through a tubular silicalite1 zeolite membrane were studied at 298 and 473 K respectively. The permselectivities of n-butane and i-butane under pressure difference of 0.06 MPa at 298 and 473 K were 16.3 and 7.4 respectively. The separation factors of n-butane/i-butane mixture were between 2.0 and 2.5 at 298 and 473 K. At 298 K, the permeances of n-butane in the mixture were lower than those of single component while the permeances of i-butane in the mixture were almost the same as those of single component. At 473 K, the permeances of n-butane and i-butane in the mxiture were decreased compared with those of the single component, and the permeance of n-butane decreased more rapidly than that of i-butane.展开更多
Boron nitride(BN)aerogels,composed of nanoscale BN building units together with plenty of air in between these nanoscale building units,are ultralight ceramic materials with excellent thermal/electrical insulation,gre...Boron nitride(BN)aerogels,composed of nanoscale BN building units together with plenty of air in between these nanoscale building units,are ultralight ceramic materials with excellent thermal/electrical insulation,great chemical stability and high-temperature oxidation resistance,which offer considerable advantages for various applications under extreme conditions.However,previous BN aerogels cannot resist high temperature above 900℃ in air atmosphere,and hightemperature oxidation resistance enhancement for BN aerogels is still a great challenge.Herein,a calcium-doped BN(Ca-BN)aerogel with enhanced high-temperature stability(up to~1300℃ in air)was synthesized by introducing Ca atoms into crystal structure of BN building blocks via high-temperature reaction between calcium phosphate and melamine diborate architecture.Such Ca-BN aerogels could resist the burning of butane flame(~1300℃)and keep their megashape and microstructure very well.Furthermore,Ca-BN aerogel serves as thermal insulation layer,together with Al foil serving as both low-infrared-emission layer and high-infrared-reflection layer,forming a combination structure that can effectively hide high-temperature target(heated by butane flame).Such successful chemical doping of metal element into crystal structure of BN may be helpful in the future design and fabrication of advanced BN aerogel materials,and further extending their possible applications to extremely high-temperature environments.展开更多
BACKGROUND Colorectal polyps refer to all neoplasms that protrude into the intestinal cavity.Researchers believe that 50%-70%of colorectal cancers originate from adenomatous polyps.AIM To investigate the endoscopic mo...BACKGROUND Colorectal polyps refer to all neoplasms that protrude into the intestinal cavity.Researchers believe that 50%-70%of colorectal cancers originate from adenomatous polyps.AIM To investigate the endoscopic morphologic features,pathologic types,and clinical situation;evaluate the efficacy and safety of endoscopic mucosal resection(EMR);and guide clinicians in their daily practice.METHODS Two hundred thirty-four patients who underwent EMR in our hospital from January 1,2018 to December 31,2019 were recruited.Data including sex,age,endoscopic morphology of the polyps,and pathological characteristics were analyzed among groups.RESULTS A total of 295 polyps were resected from the 234 subjects enrolled in the study,of which 4(1.36%)were Yamada type I.There were 75(25.42%)type II,101(34.24%)type III,and 115(38.98%)type IV adenomas.Among them,41 were nonadenomas,110 were low-risk adenomas,139 were high-risk adenomas,and 5 were carcinomas.The differences in distribution were not statistically significant,with P values greater than 0.05.The risk of cancer significantly increased for polyps≥1 cm in diameter(c2=199.825,P=0.00).Regarding the endoscopic morphological features,congestion,erosion,and lobulation were more common on the surface morphology of high-risk adenomas and cancerous polyps(c2=75.257,P=0.00),and most of them were Yamada types III and IV.In all,6 of the 295 polyps could not be removed completely,with a one-time resection rate of 97.97%.There were two cases of postoperative bleeding and no cases of perforation,with an overall complication rate of 0.09%.CONCLUSION Colorectal polyps ranging from non-adenomatous polyps,low-risk adenomas,and high-risk adenomas to adenocarcinomas each has their own endoscopic features,while EMR,as a mature intervention,has good safety and operability and should be promoted clinically,especially at the primary care level.展开更多
Two new Cu（Ⅱ） coordination polymers, [Cu2（tbph）2（btb）2]n （1） and {[Cu2（tbph）2- （bth）2]·H2O}n （2）, （H2tbph = 4-tert-butyl-phthalic acid, btb = 1,4-bis（1,2,4-triazol-1- yl）butane, bth = 1,6-bis（1...Two new Cu（Ⅱ） coordination polymers, [Cu2（tbph）2（btb）2]n （1） and {[Cu2（tbph）2- （bth）2]·H2O}n （2）, （H2tbph = 4-tert-butyl-phthalic acid, btb = 1,4-bis（1,2,4-triazol-1- yl）butane, bth = 1,6-bis（1,2,4-triazol-l-yl）hexane）, have been synthesized and characterized by elemental analysis, FT-IR and X-ray single-crystal diffraction. Complex 1 has a 2D sql layer. Complex 2 shows a （3,4）-connected 2D sheet with a （4.6^4.8）（4.8^2） topology. The thermal behavior of the two cor- responding complexes has briefly been investigated.展开更多
基金Project supported by the National Basic Research Program of China(2004CB2178062005CB221402)+1 种基金the National NaturalScience Foundation of China(20373043)Young Scientists Innovation Foundation of CNPC(04E7025)
文摘The effects of rare earth（RE）on the structure,acidity,and catalytic performance of HZSM-5 zeolite were investigated.A series of RE/HZSM-5 catalysts,containing 7.54% RE（RE=La,Ce,Pr,Nd,Sm,Eu or Gd）,were prepared by the impregnation of the ZSM-5 type zeolites（Si/Al=64：1）with the corresponding RE nitrate aqueous solutions.The catalysts were characterized by means of FT-IR,UV-Vis,NH3-TPD,and IR spectroscopy of adsorbed pyridine.The catalytic performances of the RE/HZSM-5 for the catalytic cracking of mixed butane to light olefins were also measured with a fixed bed microreactor.The results revealed that the addition of light rare earth metal on the HZSM-5 catalyst greatly enhanced the selectivity to olefins,especially to propylene,thus increasing the total yield of olefins in the catalytic cracking of butane.Among the RE-modified HZSM-5 samples,Ce/HZSM-5 gave the highest yield of total olefins,and Nd/HZSM-5 gave the highest yield of propene at a reaction temperature of 600℃.The presence of rare earth metal on the HZSM-5 sample,not only modified the acidic properties of HZSM-5 including the amount of acid sites and acid type,that is,the ratio of L/B（Lewis acid/Brnsted acid）,but also altered the basic properties of it,which in turn promoted the catalytic performance of HZSM-5 for the catalytic cracking of butane.
文摘Te-promoted （1%） vanadium phosphate catalyst （VPDTe） was prepared via VOPO4·2H2O by calcining its precursor VOHPO4·0.5H2O in a flow of n-butane/air.VPDTe catalyst has resulted a higher existence of V5＋ phase with V5＋/V4＋ ratio of 0.23.SEM micrographs show that Te addition altered the arrangement of the platelets from ＂rose-like＂ clusters to layer with irregular shape.Te addition has also markedly lowered the reduction activation energies of the vanadium phosphate catalyst as revealed by TPR profile.The amount of active oxygen species associated with V4＋ phase of the Te promoted catalyst was significantly higher than those of the unpromoted catalyst.These observations suggest that high mobility and availability of reactive oxygen species contributed to the enhancement of n-butane conversion up to 80% at 673 K,while only 47% over unpromoted catalyst （2400 h^-1,1.7% n-butane in air）.
基金Supported by Nanjing University of Posts and Telecommunications (No. NY209032)the National Natural Science Foundation of China (No. 21001065)the Major State Basic Research Development Program of China (973 Program,No. 2009CB930600)
文摘The title coordination polymer 1,{[Cu8（btb）2（CN）8].3H2O}n（btb = 1,4-bis（1,2,4-triazol-1-yl）butane）,has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction.Complex 1 crystallizes in monoclinic,space group C2/c with a = 1.2938（3）,b = 1.9422（5）,c = 0.9406（2） nm,β = 121.891（4）°,V = 2.0066（9） nm3,C24H30Cu8N20O3,Mr = 1155.00,Dc = 1.912 g/cm3,μ（MoKα） = 4.209 mm？1,F（000） = 1140,GOF = 1.184,Z = 2,the final R = 0.0634 and wR = 0.1503 for I 2σ（I）.In complex 1,one-dimensional CuCN zigzag chains are linked by triazolyl groups of btb ligands to form two-dimensional networks,which are further bridged by 1,4-butyl moieties of btb ligands to fabricate a three-dimensional order framework,in which one-dimensional ellipsoid-like channels are observed.
文摘An efficient technology of impregnation of carbonate crushed stone by oil-product based on SCF-impregnation process usage with propane/butane solvent was developed. Regular impregnation throughout the volume of crushed stone sample is achieved. As a result of the appliance of proposed technology, the humidity of the treated crushed stone samples decreased down to 0.54%.
基金Supported by the National Natural Science Foundation of China(No.29776005).
文摘The oxidative dehydrogenation of butane to butadiene and butene was studied using a conventional fixed-bed ractor (FBR), inert membrane reactor (IMR) and mixed inert membrane reactor (MIMR). When IMR and MIMR were employed, a ceramic membrane modified by partially coating with glaze was used to distribute oxygen to a fixed-bed of 24-V-Mg-O catalyst. The oxygen partial pressure in the catalyst bed could be decreased. The effect of feeding modes and operation conditions were investigated. The selectivity of C4 dehydrogenation products (butene and butadiene) was found to be higher in IMR than in FBR. The feeding mode with 20% of air mixing with butane in MIMR was found to be more efficient than the feeding mode with all air permeating through ceramic membrane. The MIMR gave the most smooth temperature profile along the bed.
文摘Eight new macrocyclic complexes were synthesized by template reaction of 1,4-bis（3-aminopropoxy）butane with metal nitrate and 1,3-bis（2-formylphenyl）propane or 1,4-bis（2-formylphenyl）butane and their structures were proposed on the basis of elemental analysis, FTIR, UV-vis, molar conductivity measurements, ^1H NMR and mass spectra. The metals to ligand molar ratios of the complexes were found to be 1： 1. The complexes are 1：2 electrolytes for Pb（II）, Zn（II） and Cd（II） complexes and 1：3 electrolytes for La（III） as shown by their molar conductivities （Am） in DMSO at 10^-3 mol L^-1. Due to the existence of free ions in these complexes, such complexes are electrically conductive. The configurations of La（III） and Pb（II） were proposed to probably octahedral and Zn（II） and Cd（II） complexes were proposed to probably tetrahedral.
文摘The new ligand bis-（1,4-sodium thiolactate） butane （L）-O2CCH3S-（CH2）4SCHCH3CO2- has been prepared from the reaction of disodium salt of thiolactic acid and 1,4-dichlorobutane, while the disodium thiolactate was prepared instanteously through the reaction of thiolactic acid with NaOH. Mono and dinuclear complexes were obtained by direct reaction of the above ligands with H[AuCI4] in 1 ： 1, 2：1, 1：2, 2：2 and 3：1 ligands to metal molar ratio. The prepared complexes were characterized by elemental analysis, spectral studies FTIR （Fourier transform Infrared） and UV-Vis, magnetic measurement, conductivity measurement and IHNMR for the ligand （L） and some of the complexes. The conductance data indicate that the complexes of the formulas Na[Au（SCH3CHCOO）2], Na[Au（SCH3CHCOO）（OOCCHCH3SH）2] and [Au（L）]Cl are 1：1 electrolyte. Electronic spectra and magnetic moment values indicate the presence of square planner geometry around Au（III） ions.
基金supported by the National Key R&D Program of China(2022YFC2303100)the National Natural Science Foundation of China(22305261,21372250,21121062,21302203,20732008,21772037,21772226,21861132014,91956115,22171078)+1 种基金the Shanghai Municipal Science and Technology Major Project(2018SHZDZX03)the Fundamental Research Funds for the Central Universities(222201717003)。
文摘Dearomative photocycloaddition of heteroarenes is an efficient method for replacing planar arenes with three-dimensional(3D)scaffolds,such as bicyclo[2.1.1]-hexane(BCH)containing heterocycles.Herein,we report intramolecular dearomative[2π+2σ]photocycloadditions of bicyclo[1.1.0]butanes(BCBs)with(benzo)furans and(benzo)thiophenes.These photocycloadditions are initiated through an energy transfer pathway(EnT)or single electron transfer pathway(SET),efficiently yielding unique BCHpyrrolidinone-fused heterocyclic scaffolds.Moreover,the synthetic utility of this photochemical reaction was demonstrated on the basis of large-scale synthesis and diversified transformations.Mechanistic investigations,in conjunction with density functional theory(DFT)calculations,were taken to support the proposed reaction mechanisms.
基金supported by DOD CDMRP W81XWH-20-10576,W81XWH-20-10578,NSF CHE-1905341 and CHE-1904780,NHLBI R21HL154032 and F32HL160108,R01NS114972,R01NS117146,and R01NS130258.I.V.K.and O.G.S.thank the Russian Science Foundation(Grant#22-43-04426)for financial support.
文摘NMR hyperpolarization dramatically improves the detection sensitivity of magnetic resonance through the increase in nuclear spin polarization.Because of the sensitivity increase by several orders of magnitude,additional applications have been unlocked,including imaging of gases in physiologically relevant conditions.Hyperpolarized ^(129)Xe gas recently received FDA approval as the first inhalable gaseous MRI contrast agent for clinical functional lung imaging of a wide range of pulmonary diseases.However,production and utilization of hyperpolarized ^(129)Xe gas faces a number of translational challenges including the high cost and complexity of contrast agent production and imaging using proton-only(i.e.,conventional)clinical MRI scanners,which are typically not suited to scan ^(129)Xe nuclei.As a solution to circumvent the translational challenges of hyperpolarized ^(129)Xe,we have recently demonstrated the feasibility of a simple and cheap process for production of proton-hyperpolarized propane gas contrast agent using ultralow-cost disposable production equipment and demonstrated the feasibility of lung ventilation imaging using hyperpolarized propane gas in excised pig lungs.However,previous pilot studies have concluded that the hyperpolarized state of propane gas decays very fast with an exponential decay T1 constant of∼0.8 s at 1 bar(physiologically relevant pressure);moreover,the previously reported production rates were too slow for potential clinical utilization.Here,we investigate the feasibility of high-capacity production of hyperpolarized butane gas via heterogeneous parahydrogen-induced polarization using Rh nanoparticle-based catalyst utilizing butene gas as a precursor for parahydrogen pairwise addition.We demonstrate a remarkable result:the lifetime of the hyperpolarized state can be nearly doubled compared to that of propane(T1 of∼1.6 s and long-lived spin-state TS of∼3.8 s at clinically relevant 1 bar pressure).Moreover,we demonstrate a production speed of up to 0.7 standard liters of hyperpolarized gas per second.These two synergistic developments pave the way to biomedical utilization of proton-hyperpolarized gas media for ventilation imaging.Indeed,here we demonstrate the feasibility of phantom imaging of hyperpolarized butane gas in Tedlar bags and also the feasibility of subsecond 2D ventilation gas imaging in excised rabbit lungs with 1.6×1.6 mm^(2) in-plane resolution using a clinical MRI scanner.The demonstrated results have the potential to revolutionize functional pulmonary imaging with a simple and inexpensive on-demand production of protonhyperpolarized gas contrast media,followed by visualization on virtually any MRI scanner,including emerging bedside low-field MRI scanner technology.
基金supported by the National Key R&D Program of China(No.2022YFA1503200)the National Natural Science Foundation of China(Nos.22071028,21921003)。
文摘2-Azabicyclo[2.1.1]hexanes(aza-BCHs)are constrained pyrrolidine analogues with improved physicochemical characteristics in drug design.Here,we report a direct visible light-mediated photocycloaddition of 4-aza-coumarins with mono-or disubstituted bicyclo[1.1.0]butanes for synthesizing aza-BCHs without an external catalyst.The introduction of the ester group on 4-aza-coumarin is critical for direct imine excitation and versatile synthetic utility.Preliminary mechanistic studies indicated that the reaction took place primarily at the triplet hypersurface.
文摘Background and Originality Content Cyclobutane moieties are an important class of motifs since they are frequently found in the medicinally relevant compounds such as alkaloids and pharmaceuticals.[1] Therefore,the development of efficient synthetic strategies for the construction of cyclobutanes and their derivatives has always been a focus of inter-est.[2a] Photochemical reactions are powerful tools for synthesizing compounds with high complexity and diversity.[2b-h] Among them,photochemical[2+2]cycloaddition is a widely used protocol for the preparation of such compounds.[2h]However,this kind of reaction always suffers from the challenges of controlling the resulting products of the intermolecular[2+2]photodimerization.In principle,to achieve cyclobutanes via[2+2]cycloaddition,the two olefins should be oriented in a parallel fashion keeping the distance less than 4.2 A apart from each other.
基金We thank the NSFC(Nos.21432011,21772224)the CAS(Nos.QYZDY-SSW-SLH016,XDB20000000,2017301)the STCSM(Nos.17JC1401200,17ZR1436900)for the financial support.We also thank Dr.Xue-Bing Leng(SIOC)for X-ray crystal analysis.
文摘A copper catalyzed stereoselective[2+2]cyclization has been developed,providing a concise protocol to the direct construction of diaryl-substituted cyclobutanes in up to 99%yield with up to>95/5 dr.Meanwhile,the enantioselective version of this reaction has also been achieved,leading to a series of optically active diaryl-substituted cyclobutanes with up to 94%ee.
基金We thank the National Natural Science Foundation of China(21573262,21776260,21873261,and 91956116)the Natural Science Foundation of Jiangsu Province(BK20170422)for thegenerous support.
文摘of main observation and conclusion We herein report the first example of iridium-catalyzed enantioselective C(sp^3)-H borylation of cyclobutanes using benzoxazoline as the directing group.The combination of a chiral bidentate boryl ligand and an iridium precursor has found to effectively catalyze C(sp)-H borylation to afford a variety of cyclobutylboronates with good to excellent enantioselectivities.We also demonstrate the synthetic utility of the current method by converting the stereogenic C—B bond to other functionalities.
基金Project supported by the Natural Science Foundation of Shaanxi Province （No. 2010JM2019）, the Postdoctoral Science Foundation of Northwest University （No. BK08008）, the National Science Fund for Fostering Talents in Basic Science （No. J0830417）, and the State Key Program of National Natural Science of China （No. 20931005）.
文摘A N,N＇-bisferrocenesulfonyl bisbenzimidazole compound 1,4-bis（1-ferrocenesulfonyl-2-benzimidazolyl） butane was prepared. Its crystal structure was determined. The crystal belongs to triclinic with space group P-1 and a= 0.87241（13） nm, b=0.97553（15） nm, c= 1.4120（2） rim, and α= 83.041（2）°, β= 72.454（2）°,γy= 69.732（2）°, the unit cell volume V= 1.0746（3） nm3, the molecule number in one unit cell Z= 1, the absorption coefficient u= 1.191 mm 1, the calculated density Dc= 1.584 g/cm3. The theoretical investigation of the compound as a structure unit was fully optimized by B3LYP/6-31G method in Gaussian 03 package, and the most stable structure of the compound in theory was obtained. The two results were compared. The optimized structure was in accordance with the crystal structure in the main, suggesting that the molecular geometry optimization of the structures was reliable and the calculation method used was reliable. The distribution of atomic charges and the energy, and composition of frontier molecular orbits were analyzed. Thermal analysis indicated that it is stable before melting.
文摘On September 26,2016 Algerian Space Agency launched AlSat-1B,the second in a series of medium resolution earth observation satellites mission.AlSat-1B electro-thermal propulsion system follows the classic design principle that has been used on previous SSTL-100 missions.With a total dry weight of 5.17 kg,the system is filled with 2.35 L selfpressurized butane.The thruster assembly is designed to use 15 W(at 28 V)redundant heater elements,it is designed to have an average mission thrust of 50 mN.With a warm up time of 10 min,the temperature of the butane will be increased by over 250℃.This is the equivalent of about 35%gain in specific impulse over ambient temperature butane.The spacecraft dry weigh at launch site was 107 kg,the propulsion system is designed to provide at least 19 m/s Delta-v to meet the spacecraft’s mission requirement.To investigate the system readiness for flight,a series of performance tests have been completed at the Surrey Satellite Technology Ltd laboratories(United Kingdom),Satellite Development Centre(Algeria)and Satish Dhawan Space Centre rocket launch site(India),the results of these tests as well as initial flight test results are presented in this paper.
文摘Six new macrocyclic complexes were synthesized by a template reaction of 1,4-bis（2-formylphenoxy）butane with diamines and Cu（NO3）2·3H2O and their structures were proposed on the basis of elemental analysis, FT-IR, UV-Vis, magnetic susceptibility measurements, molar conductivity measurements and mass spectra. The metal to ligand molar ratios of the Cu（Ⅱ） complexes were found to be 1 ： 1. The Cu（Ⅱ） complexes are 1 ： 2 electrolytes as shown by their molar conductivities （∧m） in DMF at 10^-3 mol·L^-1. Due to the existence of free ions the Cu（Ⅱ） complexes are electrically conductive. Their configurations were proposed to be probably distorted octahedral.
文摘The permeation properties of n-butane, i-butane and n-butane/i-butane mixture （n-butane 24.3% （molar ratio）, i-butane 75.7%） through a tubular silicalite1 zeolite membrane were studied at 298 and 473 K respectively. The permselectivities of n-butane and i-butane under pressure difference of 0.06 MPa at 298 and 473 K were 16.3 and 7.4 respectively. The separation factors of n-butane/i-butane mixture were between 2.0 and 2.5 at 298 and 473 K. At 298 K, the permeances of n-butane in the mixture were lower than those of single component while the permeances of i-butane in the mixture were almost the same as those of single component. At 473 K, the permeances of n-butane and i-butane in the mxiture were decreased compared with those of the single component, and the permeance of n-butane decreased more rapidly than that of i-butane.
基金financially supported by the Royal Society Newton Advanced Fellowship(NA170184)the National Natural Science Foundation of China(52173052)the Natural Science Foundation of Jiangsu Province(BK20210133).
文摘Boron nitride(BN)aerogels,composed of nanoscale BN building units together with plenty of air in between these nanoscale building units,are ultralight ceramic materials with excellent thermal/electrical insulation,great chemical stability and high-temperature oxidation resistance,which offer considerable advantages for various applications under extreme conditions.However,previous BN aerogels cannot resist high temperature above 900℃ in air atmosphere,and hightemperature oxidation resistance enhancement for BN aerogels is still a great challenge.Herein,a calcium-doped BN(Ca-BN)aerogel with enhanced high-temperature stability(up to~1300℃ in air)was synthesized by introducing Ca atoms into crystal structure of BN building blocks via high-temperature reaction between calcium phosphate and melamine diborate architecture.Such Ca-BN aerogels could resist the burning of butane flame(~1300℃)and keep their megashape and microstructure very well.Furthermore,Ca-BN aerogel serves as thermal insulation layer,together with Al foil serving as both low-infrared-emission layer and high-infrared-reflection layer,forming a combination structure that can effectively hide high-temperature target(heated by butane flame).Such successful chemical doping of metal element into crystal structure of BN may be helpful in the future design and fabrication of advanced BN aerogel materials,and further extending their possible applications to extremely high-temperature environments.
文摘BACKGROUND Colorectal polyps refer to all neoplasms that protrude into the intestinal cavity.Researchers believe that 50%-70%of colorectal cancers originate from adenomatous polyps.AIM To investigate the endoscopic morphologic features,pathologic types,and clinical situation;evaluate the efficacy and safety of endoscopic mucosal resection(EMR);and guide clinicians in their daily practice.METHODS Two hundred thirty-four patients who underwent EMR in our hospital from January 1,2018 to December 31,2019 were recruited.Data including sex,age,endoscopic morphology of the polyps,and pathological characteristics were analyzed among groups.RESULTS A total of 295 polyps were resected from the 234 subjects enrolled in the study,of which 4(1.36%)were Yamada type I.There were 75(25.42%)type II,101(34.24%)type III,and 115(38.98%)type IV adenomas.Among them,41 were nonadenomas,110 were low-risk adenomas,139 were high-risk adenomas,and 5 were carcinomas.The differences in distribution were not statistically significant,with P values greater than 0.05.The risk of cancer significantly increased for polyps≥1 cm in diameter(c2=199.825,P=0.00).Regarding the endoscopic morphological features,congestion,erosion,and lobulation were more common on the surface morphology of high-risk adenomas and cancerous polyps(c2=75.257,P=0.00),and most of them were Yamada types III and IV.In all,6 of the 295 polyps could not be removed completely,with a one-time resection rate of 97.97%.There were two cases of postoperative bleeding and no cases of perforation,with an overall complication rate of 0.09%.CONCLUSION Colorectal polyps ranging from non-adenomatous polyps,low-risk adenomas,and high-risk adenomas to adenocarcinomas each has their own endoscopic features,while EMR,as a mature intervention,has good safety and operability and should be promoted clinically,especially at the primary care level.
基金Supported financially by Henan Province basic and frontier technology research projects of Henan Provincial Department of Science and Technology(No.142300410083)
文摘Two new Cu（Ⅱ） coordination polymers, [Cu2（tbph）2（btb）2]n （1） and {[Cu2（tbph）2- （bth）2]·H2O}n （2）, （H2tbph = 4-tert-butyl-phthalic acid, btb = 1,4-bis（1,2,4-triazol-1- yl）butane, bth = 1,6-bis（1,2,4-triazol-l-yl）hexane）, have been synthesized and characterized by elemental analysis, FT-IR and X-ray single-crystal diffraction. Complex 1 has a 2D sql layer. Complex 2 shows a （3,4）-connected 2D sheet with a （4.6^4.8）（4.8^2） topology. The thermal behavior of the two cor- responding complexes has briefly been investigated.
