Synthesis of mordenite by solvent-free method and its application in the dimethyl ether carbonylation reaction

Mordenite with different Si/Al ratios were synthesized by solvent-free method and used for dimethyl ether(DME)carbonylation reaction.The influence of Si/Al ratio in the feedstock on the structure,porosity and acid sites were systematically investigated.The characterization results showed that with the increase of Si/Al ratio in the feedstock,part of silicon species fail to enter the skeleton and the specific surface area and pore volume of the samples decreased.The amount of weak acid and medium strong acid decreased alongside with the increasing Si/Al ratio,and the amount of strong acid slightly increased.The Al atoms preferentially enter the strong acid sites in the 8 member ring(MR)channel during the crystallization process.The high Si/Al ratio sample had more acid sites located in the 8 MR channel,leading to more active sites for carbonylation reaction and higher catalytic performance.Appropriately increasing the Si/Al ratio was beneficial for the improvement of carbonylation reaction activity over the mordenite(MOR)catalyst.

Preparation of CIP@TiO_(2) composite with broadband electromagnetic wave absorption properties

Scholars aim for the improved impedance matching (Z) of materials while maintaining their excellent wave absorption properties. Based on the hydrolysis characteristics of isopropyl titanate, a simple preparation process for the coating of carbonyl iron powder(CIP) with TiO_(2) was designed. Given the TiO2coating, the Z of the CIP@TiO_(2) composite was adjusted well by decreasing the dielectric constant. Moreover, the interfacial polarization of CIP@TiO_(2) was enhanced. Ultimately, the electromagnetic-wave (EMW) absorption property of the CIP@TiO_(2)composite was improved substantially, the minimum reflection loss reached-46.07 dB, and the effective absorption bandwidth can reach 8 GHz at the composite thickness of 1.5 mm. Moreover, compared with CIP, the oxidation resistance of CIP@TiO_(2)showed remarkable improvement. The results revealed that the oxidation starting temperature of CIP@TiO_(2) as about 400℃,whereas the uncoated CIP had an oxidation starting temperature of approximately 250℃. Moreover, the largest oxidation rate temperature of CIP@TiO_(2) increased to around 550℃. This work opens up a novel strategy for the production of high-performance EMW absorbers via structural design.

构筑开放锡位点实现酸性增强的二甲醚羰基化丝光沸石催化剂设

Due to their tunable acidity,shape selectivity,and excellent stability,zeolites are of great importance as solid acid materials in industrial catalysis.Tuning the properties of the acid sites in zeolites allows for the rational design and fabrication of catalysts for target reactions.Dimethyl ether(DME)carbonylation,a critical chain-growth reaction for C1 resource utilization,is selectively catalyzed by the Brønsted acid sites within the eight-membered rings(8-MRs)of mordenite(MOR).It is anticipated that strengthening the Brønsted acidity—particularly in 8-MRs—will improve the catalytic performance of MOR.In this work,density functional theory(DFT)calculations are first employed and the results used to design a modified MOR with stannum(Sn)and to predict the corresponding changes in acidity.Guided by the theoretical studies,a series of Sn-modified MOR are synthesized via a defect-engineering and subsequent heteroatom-substitution strategy.After partial desilication,isolated tetrahedral Sn species in an open configuration are successfully synthesized for the first time,within which tetrahedrally coordinated Al sites are preserved.An acidic characterization is used to confirm that the acidity of the Brønsted acid sites is enhanced by the introduction of the Sn species;as a result,the sample exhibits excellent activity in DME carbonylation reaction.Kinetic and DFT studies reveal that this strengthened acidity facilitates the adsorption of DME and reduces the activation barriers of DME dissociation and acetyl formation,accounting for the improved activity.The work demonstrates mechanistic insights into the promoting effects of strong acidity on DME carbonylation and offers a promising strategy to precisely control the acidic strength of zeolites.

Mechanism of CO_(2)reduction in carbonylation reaction promoted by ionic liquid additives:A computational and experimental study

The Ru-catalyzed carbonylation of alkenes with CO_(2)as a C1 surrogate and imidazole chlorides as the promotor is investigated by a combination of computational and experimental study.The conversion rate of CO_(2)to CO is positively correlated with the efficiency of both hydroesterification and hydroformylation,which is found facilitated in the presence of chloride additives with a decreasing order of BmimCl~B3MimCl>BmmimCl~LiCl.Taking the hydroesterification with MeOH as a representative example,BmimCl bearing C-H functionality at the C^(2)site of the cation assists the reduction of CO_(2)to CO as a hydrogen donor medium,with the anion and cation acting in a synergistic fashion.Subsequent insertion of CO_(2)into the formed Ru-H bond with the assistance of chloride anion produces the Ru-COOH species,which ultimately accelerates the activation of CO_(2).

A review on photo-, electro- and photoelectro- catalytic strategies for selective oxidation of alcohols

Traditional conversion of alcohols into carbonyl compounds exists a few drawbacks such as harsh reaction conditions,production of large amounts of hazardous wastes,and poor selectivity.The newly emerging conversion approaches via photo-,electro-,and photoelectro-catalysis to oxidize alcohols into high value-added corresponding carbonyl compounds as well as the possible simultaneous production of clean fuel hydrogen(H_(2))under mild conditions are promising to substitute the traditional approach to form greener and sustainable reaction systems and thus have aroused tremendous investigations.In this review,the state-of-the-art photocatalytic,electrocatalytic,and photoelectrocatalytic strategies for selective oxidation of different types of alcohols(aromatic and aliphatic alcohols,single alcohol,and polyols,etc.)as well as the simultaneous production of H_(2) in certain systems are discussed.The design of photocatalysts,electrocatalysts,and photoelectrocatalysts as well as reaction mechanism is summarized and discussed in detail.In the end,current challenges and future research directions are proposed.It is expected that this review will not only deepen the understanding of environmentally friendly catalytic systems for alcohol conversion as well as H_(2) production,but also enlighten significance and inspirations for the follow-up study of selective oxidation of various types of organic molecules to value-added chemicals.

Microwave absorption properties of carbonyl iron-based paint coatings for military applications

The paper explores the possibilities of using carbonyl iron in the form of a powder for the manufacture of radar-absorbing paints-reducing the radar signature of the objects that they cover.The attenuation values in the range of 4-18 GHz for various coating thicknesses,ranging from 0.5 to 2.00 mm with 0.5 mm increment,and for different absorber content-75%and 80%,as well as the use of two different binders in the form of epoxy resins with hardeners,were investigated.For the frequency of 18 GHz and a 1.5 mm thick coating with a 75%absorber content,Epidian 112 resin and Saduramid 10/50 hardener used as a binder,and the maximum attenuation level obtained equalled 20.2 d B at 16 GHz.Additionally,the absorber particle size ranging from 3 to 4μm and its higher mass content resulted in achieving the reflection loss above-12 d B in the entire 8-12.5 GHz range for layers between 1-and 1.5 mm thickness.The qualitative assessment of the tested samples in the context of camouflage in the radar range was also performed,using statistical analysis.

Effect of polytetrafluoroethylene hollow fiber microstructure on formaldehyde carbonylation performance in membrane contactor

Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane contactor has been proved in our previous study. In this paper, the effect of membrane microstructure on process performance was further investigated. Three porous PTFE hollow fibers with different pore sizes and one polydimethylsiloxane(PDMS)/PTFE composite membrane with dense layer were fabricated for comparison. The physical and chemical properties of four membranes, including chemical composition, morphology, contact angle, liquid entry pressure, thermodynamic analysis and gas permeability, were systemically characterized. Experiments of formaldehyde carbonylation under different reaction conditions were conducted. The results indicated that the yield of glycolic acid increased with decreasing pore size for porous membranes, which was due to the improvement of wetting behavior. The dense layer of PDMS in composite hollow fiber could effectively prevent the solvent from entering membrane pores, thus the membrane exhibited the best performance. At reaction temperature of 120℃ and operation pressure of 3.0 MPa, the yield of glycolic acid was always higher than 90% as the mass ratio of trioxane and phosphotungstic acid increased from 0.2:1 to 0.8:1. The highest turnover frequency was up to 26.37 mol·g^(-1)·h^(-1). This study provided a reference for the understanding and optimization of membrane contactors for the synthesis of glycolic acid using solvent with low surface tension.

GDX203色谱固定相的改性及在羰基合成醋酸中的应用

甲醇羰基化反应制醋酸,是一个重要的化学反应[1],无论在实验室或在工业生产上,其反应过程的监测均是以色谱为分析手段[2,3]。由于该反应产物的组分多(甲醇、水、碘甲烷、乙酸甲酯、醋酸),通常采用色谱程序升温的方法才可达到各组分的分离[4],这种方法由于存在分析周期长和由于反应物在色谱柱中的保留时间长而发生变化影响了定量的准确性的缺点,给对该反应进行的快速、准确的监测带来诸多不便。

The Oxidative Stress Balance Measured in Humans with Different Markers, Following a Single Oral Antioxidants Supplementation or a Diet Poor of Antioxidants

Four different markers of oxidative stress [OS] (8-OHdG in urine, 8-Iso-PGF, hydroperoxides and carbonylated proteins in plasma, a new marker of antioxidant capacity (AC) in plasma/urine/saliva, and hs-CRP were determined concomitantly in twelve apparently healthy volunteers. All the markers were determined at 8 am, 10 am, 12 am in three different moments: after a week of normal diet (baseline), after an acute supplementation with an antioxidant pool, and finally following a week of a diet poor in antioxidant. The supplementation of antioxidants determined a significant (t test p < 0.05) decrease up to 12% of 8-OHdG in urine and up to 46% of carbonylated proteins in plasma, whereas hydroperoxides and 8-Iso-PGF were unmodified;the antioxidant capacity increased significantly (t test p < 0.05) up to 19%, 78%, and 67%, respectively in plasma, urine and saliva. Hs-CRP was unchanged.The diet poor in antioxidant caused significant increases (t test p< 0.01) of hydroperoxides (up to 24%), 8-Iso-PGF 23 (up to 69%), carbonylated proteins (up to 76%) and 8-OHdG (up to 16%): hs-CRP increase reached 72% despite the levels were still within the normal range. Any reduction of soluble antioxidants activity in plasma was detected, whereas in urine and saliva a reduction of 45% and 38% respectively was shown. In conclusion, the antioxidant surplus determined by a single antioxidants pool administration seems to protect DNA and proteins from oxidation. On the contrary the shortage of antioxidant intake increases all the markers of OS, particularly those related to lipids and proteins, whereas the DNA seems to be protected more efficiently. The AC in plasma tends to be constant, and the limitation of antioxidants intake is followed by reduction of AC in urine and saliva.

Dimethyl ether carbonylation over zeolites

Syngas to ethanol, consisting of dimethyl ether(DME) carbonylation to methyl acetate(MA) over zeolites and MA hydrogenation to ethanol on copper catalyst, has been developed in recent years.DME carbonylation over zeolites, a key step in this new process, has attracted increasing attention due to the high reaction efficiency and promising industrial application.In recent years, continuous efforts have been made on improving the activity and stability of the zeolites.From a mechanistic point of view, DME carbonylation to MA, involving the formation of C–C bond, is achieved via the Koch-type CO insertion into DME within the 8-member ring(8-MR) pores of zeolites, typically HMOR and HZSM-35.The unique geometric configuration of the 8-MR pore endowed the formation of the key intermediate(acetyl, CH3CO^*), possibly by a spatial confinement of the transition state during CO insertion into the surface O–CH3 group.This review article summarizes the main progress on zeolite-catalyzed DME carbonylation, including reaction kinetics and mechanism, theoretical calculations, and experimental strategies developed for populating acid sites and engineering pore structure of the zeolites in order to enhance the overall performance.

Influence of shape anisotropy on microwave complex permeability in carbonyl iron flakes/epoxy resin composites

To explore the mechanism of carbonyl iron flake composites for microwave complex permeability, this paper investigates the feature of the flakes. The shape anisotropy was certified by the results of the magnetization hysteresis loops and the Mossbauer spectra. Furthermore, the shape anisotropy was used to explain the origin of composite microwave performance, and the calculated results agree with the experiment. It is believed that the shape anisotropy dominates microwave complex permeability, and the natural resonance plays main role in flake.

LC-MS/MS法对卷烟主流烟气中8种羰基化合物的测定

A liquid chromatography-tandem mass spectroscopy(LC-MS/MS)method was developed for analysis of carbonyl compounds in cigarette mainstream smoke.The cigarette smoke was collected using a Cambridge filter treated with acidic solution of 2,4-dinitrophenylhydrazine,then extracted with acetonitrile.The extract was diluted with acetonitrile-water and analyzed by LC-MS/MS in negative electro-spray ionization mode.Formaldehyde,acetaldehyde,acetone,acrolein,propionaldehyde,methyl ethyl ketone,butyraldehyde and crotonaldehyde in mainstream cigarette smoke were analyzed with the recovery at the range of 83% to 103%.The minimum detectable quantity for the carbonyls ranged from 0.08 to 0.28 μg/L,and relative standard deviations were below 6%.This new method had higher selectivity and sensitivity compared to conventional methods.5 kinds of foreign and domestic cigarette were analyzed.

Removal of carbonyl sulfide from CO_2 stream using AgNO_3-modified NaZSM-5

Removal of carbonyl sulfide(COS) from CO2 stream is significant for the production and utilization of food grade CO2. This study investigates the adsorption performance of Ag/NaZSM-5 as adsorbent prepared by incipient wetness impregnation for the removal of COS from a CO2 stream in a fixed-bed adsorption apparatus. Effects of various conditions on the preparation of adsorbent, adsorption and desorption were intensively examined. The results revealed that COS can be removed to below 1×10-9from a CO2stream(1000 ppm COS/CO2) using Ag/NaZSM-5(10 wt% AgNO3) with an adsorption capacity of 12.86 mg·g-1. The adsorbent can be fully regenerated using hot air at 450 C. The adsorption ability remained stable even after eight cycles of regeneration.

Levels of Crotonaldehyde and 4-hydroxy-(E)-2-nonenal and Expression of Genes Encoding Carbonyl-Scavenging Enzyme at Critical Node During Rice Seed Aging

The critical node(CN) is an important stage during seed aging, which is related to effective genebank conservation. Previous studies have demonstrated that proteins undergo carbonylated modification at the CN in rice, indicating oxidative damage. However, the levels of reactive carbonyl species(RCS) and the associated scavenging system at the CN are largely unknown. In this study, we optimized methods for the extraction and analysis of RCS from dry rice embryos. In order to acquire seeds at the CN, rice seeds were subjected to natural conditions for 7, 9, 11 and 13 months, and the seed germination rates were reduced to 90%, 82%, 71% and 57%, respectively. We chose the stage with seed germination rate of 82% as the CN according to the rice seed vigor loss curve. The levels of crotonaldehyde and 4-hydroxy-(E)-2-nonenal(HNE) were significantly increased at the CN. In addition, genes encoding carbonyl-scavenging enzyme, including Os ALDHs and Os AKRs, were significantly down-regulated at the CN, and reductions in the expression of Os ALDH2-2, Os ALDH2-5, Os ALDH3-4, Os ALDH7, Os AKR1 and Os AKR2 in particular could be responsible for RCS accumulation. Thus, the accumulations of crotonaldehyde and HNE and down-regulation of genes encoding carbonyl-scavenging enzyme might be related to an accelerating loss of seed viability at the CN.

Simultaneous catalytic hydrolysis of carbonyl sulfide and carbon disulfide over Al_2O_3-K/CAC catalyst at low temperature

In this work, a series of coal-based active carbon （CAC） catalysts loaded by A1203 were prepared by sol-gel method and used for the simulta- neous catalytic hydrolysis of carbonyl sulfide （COS） and carbon disulfide （CS2） at relatively low temperatures of 30-70 ℃. The influences of calcinations temperatures and operation conditions such as： reaction temperature, 02 concentration, gas hourly space velocity （GHSV） and relative humidity （RH） were also discussed respectively. The results showed that catalysts with 5.0 wt% A1203 calcined at 300 ℃ had supe- rior activity for the simultaneous catalytic hydrolysis of COS and CS2. When the reaction temperature was above 50 ℃, catalytic hydrolysis activity of COS could be enhanced but that of CS2 was inhibited. Too high RH could make the catalytic hydrolysis activities of COS and CS2 decrease. A small amount of 02 introduction could enhance the simultaneous catalytic hydrolysis activities of COS and CS2.

Corrosion inhibition of α,β-unsaturated carbonyl compounds on steel in acid medium

Corrosion inhibition of three α,β-unsaturated carbonyl compounds on N80 steel at high temperature and in concentrated acid medium was evaluated, and the inhibition mechanism was investigated. The results proved that both cinnamaldehyde and benzalacetone had an evident anticorrosion effect and could reduce the corrosion of steel effectively in acid medium, α,β-unsaturated carbonyl compounds with a benzene ring structure had good adsorption on steel surface. The experiments proved that polymerization of α,β-unsaturated carbonyl compounds on the steel surface at a high temperature and in concentrated acid medium resulted in a good corrosion inhibiting effect, which was attributed to the structures of α,β-unsaturated carbonyl compounds.

Enabling Multi-Chemisorption Sites on Carbon Nanofibers Cathodes by an In-situ Exfoliation Strategy for High-Performance Zn–Ion Hybrid Capacitors

Carbon nanofibers films are typical flexible electrode in the field of energy storage,but their application in Zinc-ion hybrid capacitors(ZIHCs)is limited by the low energy density due to the lack of active adsorption sites.In this work,an in-situ exfoliation strategy is reported to modulate the chemisorption sites of carbon nanofibers by high pyridine/pyrrole nitrogen doping and carbonyl functionalization.The experimental results and theoretical calculations indicate that the highly electronegative pyridine/pyrrole nitrogen dopants can not only greatly reduce the binding energy between carbonyl group and Z n2+by inducing charge delocalization of the carbonyl group,but also promote the adsorption of Zn2+by bonding with the carbonyl group to form N–Zn–O bond.Benefit from the multiple highly active chemisorption sites generated by the synergy between carbonyl groups and pyridine/pyrrole nitrogen atoms,the resulting carbon nanofibers film cathode displays a high energy density,an ultralong-term lifespan,and excellent capacity reservation under commercial mass loading(14.45 mg cm-2).Particularly,the cathodes can also operate stably in flexible or quasi-solid devices,indicating its application potential in flexible electronic products.This work established a universal method to solve the bottleneck problem of insufficient active adsorption sites of carbon-based ZIHCs.Imoproved should be changed into Improved.

Highly active Pd containing EMT zeolite catalyst for indirect oxidative carbonylation of methanol to dimethyl carbonate

Palladium containing EMT zeolite catalyst(Pd/EMT) was prepared and used for the indirect oxidative carbonylation of methanol to dimethyl carbonate(DMC).The EMT zeolite was employed as a new catalyst support and compared with the conventional Pd containing FAU zeolite catalyst(Pd/FAU).The Pd/EMT in contrast to the Pd/FAU catalyst exhibited high intrinsic activity with the turnover frequency of 0.25 s^(-1) vs.0.11 s^(-1).The Pd/EMT catalyst showed high CO conversion of 82% and DMC selectivity of 79%,that maintained for at least 130 h,while the activity of the Pd/FAU catalyst rapidly deteriorated within 12 h.The enhanced interactions between Pd and EMT zeolite inhibited the sintering of palladium clusters and maintained the Pd2+ active sites in the Pd/EMT catalyst.The stabilization of the mono-dispersed Pd clusters within the EMT zeolite is paramount to the excellent performance of the catalyst for the indirect oxidative carbonylation of methanol to DMC.

Unregulated emissions from a diesel engine equipped with vanadium-based urea-SCR catalyst

The present work is aimed at the study of number-size distribution of particles, volatile organic compounds （VOCs）, and carbonyl compounds （CC） or carbonyls emitted from a 4-cylinder turbocharged diesel engine equipped with a vanadium-based urea selective catalytic reduction catalyst. The engine was run on an electric dynamometer in accordance with the European steady-state cycle. Pollutants were analyzed using an electric low pressure impactor, a gas chromatograph/mass spectrometer, and a high performance liquid chromatography system for the number-size distribution of particles, VOCs, and CC emissions, respectively. Experimental results revealed that total number of particles were decreased, and their number-size distributions were moved from smaller sizes to larger sizes in the presence of the catalyst. The VOCs were greatly reduced downstream of the catalyst. There was a strong correlation between the conversion of styrene and ethyl benzene. The conversion rate of benzene increased with increase of catalyst temperature. Formaldehyde, acetaldehyde, acrolein and acetone were significantly reduced, resulting in a remarkable abatement in carbonyls with the use of the vanadium-based urea-SCR system.