Showing papers in "Frontiers of Chemical Engineering in China in 2010"

In situ DRIFTS study of photocatalytic CO 2 reduction under UV irradiation

Abstract: Photocatalytic reduction of CO2 on TiO2 and Cu/TiO2 photocatalysts was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) under UV irradiation. The photocatalysts were prepared by sol-gel method via controlled hydrolysis of titanium (IV) butoxide. Copper precursor was loaded onto TiO2 during sol-gel procedure. A large amount of adsorbed H2O and surface OH groups was detected at 25°C on the TiO2 photocatalyst after being treated at 500°C under air stream. Carbonate and bicarbonate were formed rapidly due to the reaction of CO2 with oxygen-vacancy and OH groups, respectively, on TiO2 surface upon CO2 adsorption. The IR spectra indicated that, under UV irradiation, gas-phase CO2 further combined with oxygen-vacancy and OH groups to produce more carbonate or bicarbonate. The weak signals of reaction intermediates were found on the IR spectra, which were due to the slow photocatalytic CO2 reduction on photocatalysts. Photogenerated electrons merge with H+ ions to form H atoms, which progressively reduce CO2 to form formic acid, dioxymethylene, formaldehyde and methoxy as observed in the IR spectra. The well-dispersed Cu, acting as the active site significantly increases the amount of formaldehyde and dioxymethylene, thus promotes the photoactivity of CO2 reduction on Cu/TiO2. A possible mechanism of the photocatalytic CO2 reduction is proposed based on these intermediates and products on the photocatalysts.

Purification and crystallization of xylitol from fermentation broth of corncob hydrolysates

Abstract: Xylitol, a five-carbon sugar alcohol, is a valuable sugar substitute, and widely used in the pharmaceutical, odontological and food industry due to its interesting properties. In the past decades, the xylitol industry has grown rapidly and more attention has been focused on xylitol purification, which possesses an important proportion of the whole industry. In our paper, the purification and crystallization of xylitol fermentation broth by biotechnology using corncob hydrolysates as substance were studied. An initial xylitol fermentation broth was decolored with activated carbon (1% M−1, 60°C, 165 rpm), desalted with a combination of two ionexchange resins (732 and D301), and residual sugars were separated with UBK-555(Ca2+). Then the solution was vacuum-concentrated up to supersaturation (750 g/L xylitol). After adding 1% xylitol crystal seeds, the supersaturated solution was cooled to −20°C for 48 h. The crystalline xylitol of a regular tetrahedral shape with purity 95% and crystallization yield 60.2% was obtained from the clarified xylitol fermentation broth. An intact, economical and environmental-friendly route of purification and crystallization of xylitol from fermentation of corncob hydrolysates was obtained, and its experimental procedure and data provided a sound basis for large-scale industrial production.

Assessment of postcombustion carbon capture technologies for power generation

Abstract: A significant proportion of power generation stems from coal-combustion processes and accordingly represents one of the largest point sources of CO2 emissions worldwide. Coal power plants are major assets with large infrastructure and engineering units and an operating life span of up to 50 years. Hence, any process design modification to reduce greenhouse gas emissions may require significant investment. One of the best options to utilize existing infrastructure is to retrofit the power station fleet by adding a separation process to the flue gas, a practice known as postcombustion capture (PCC). This review examines the recent PCC development and provides a summary and assessment of the state of play in this area and its potential applicability to the power generation industry. The major players including the various institutes, government, and industry consortia are identified along with flue gas PCC demonstration scale plants. Of the PCC technologies reviewed, amine-based absorption is preeminent, being both the most mature and able to be adapted immediately, to the appropriate scale, for power station flue gas with minimal technical risk. Indeed, current commercial applications serve niches in the merchant CO2 market, while a substantial number of smaller scale test facilities are reported in the literature with actual CO2 capture motivated demonstrations now commencing. Hybrid membrane/absorption systems, also known as membrane contactors, offer the potential for the lowest energy requirements, possibly 10% of current direct scrubbers but are at an early stage of development. Other methods being actively pursued as R&D projects include solid absorbents, solid adsorbents, gas membrane separators, and cryogenic separation. The variety and different maturities of these competing technologies make technical comparison largely subjective, but useful insights could be gained through the development and application of econometric techniques such as ‘real options’ within this context. Despite these limitations, it is clear from this review that amine scrubbing is likely to be adapted first into the existing power station fleet, while less mature technologies will grow and become integrated with the development of future power stations.

A stepwise process for carbon dioxide sequestration using magnesium silicates

Abstract: This work involves the production of magnesium in the form of Mg(OH)2 from serpentinite rock (nickel mine tailing) material followed by conversion into MgCO3 using a pressurised fluidised bed (PFB) reactor operating at 400°C–600°C and pressures up to 2.85 MPa. Our approach is rooted in the thermodynamic fact that the reaction between Mg(OH)2 and gaseous CO2 forming MgCO3 and water releases significant amounts of heat. The main problem is, however, the chemical kinetics; the reaction is slow and has to be accelerated in order to be used in an economically viable process for large-scale (∼1 Mt/a) CO2 sequestration. We have constructed a labscale PFB reactor test-setup for optimising the carbonation reaction. At high enough temperatures and conversion levels the reaction should provide the heat for the proceeding Mg(OH)2 production step, making the overall process energy neutral. So far we have been able to achieve a conversion degree of 26% at 500°C and 2.85 MPa after 30 min (particle size 125–212 μm). In this paper the test facility and our latest results and progress on CO2 mineral carbonation are summarised. Also, the possible integration of the iron as a feedstock for iron and steel production will be briefly addressed. An interesting side-effect of this carbon dioxide capture and storage (CCS) route is that significant amounts of iron are obtained from the serpentinite rock material. This is released during the Mg(OH)2 production and can be of great interest to the iron- and steel producing sector, which at the same time is Finland’s largest CO2 producer.

Carbon dioxide: a renewable feedstock for the synthesis of fine and bulk chemicals

Abstract: The syntheses of carbon dioxide (CO2) based industrially important chemicals have gained considerable interest in view of the sustainable chemistry and “green chemistry” concepts. In this review, recent developments in the chemical fixation of CO2 to valuable chemicals are discussed. The synthesis of five-member cyclic carbonates via, cycloaddition of CO2 to epoxides is one of the promising reactions replacing the existing poisonous phosgene-based synthetic route. This review focuses on the synthesis of cyclic carbonates, vinyl carbamates, and quinazoline-2,4(1H,3H)-diones via reaction of CO2 and epoxide, amines/phenyl acetylene, 2-aminobenzinitrile and other chemicals. Direct synthesis of dimethyl carbonate, 1,3-disubstituted urea and 2-oxazolidinones/2-imidazolidinones have limitations at present because of the reaction equilibrium and chemical inertness of CO2. The preferred alternatives for their synthesis like transesterification of ethylene carbonate with methanol, transamination of ethylene carbonate with primary amine and transamination reaction of ethylene carbonate with diamines/β-aminoalcohols are discussed. These methodologies offer marked improvements for greener chemical fixation of CO2 in to industrially important chemicals.

Experimental study on the laminar flame speed of hydrogen/natural gas/air mixtures

Abstract: Laminar flame speeds of hydrogen/natural gas/air mixtures have been measured over a full range of fuel compositions (0–100% volumetric fraction of H2) and a wide range of equivalence ratio using Bunsen burner. High sensitivity scientific CCD camera is use to capture the image of laminar flame. The reaction zone area is employed to calculate the laminar flame speed. The initial temperature and pressure of fuel air mixtures are 293 K and 1 atm. The laminar flame speeds of hydrogen/air mixture and natural gas/air mixture reach their maximum values 2.933 and 0.374 m/s when equivalence ratios equal to 1.7 and 1.1, respectively. The laminar flame speeds of hydrogen/natural gas/air mixtures rise with the increase of volumetric fraction of hydrogen. Moreover, the increase in laminar flame speed as the volumetric fraction of hydrogen increases presents an exponential increasing trend versus volumetric fraction of hydrogen. Empirical formulas to calculate the laminar flame speeds of hydrogen, natural gas, and hydrogen/natural gas mixtures are also given. Using these formulas, the laminar flame speed at different hydrogen fractions and equivalence ratios can be calculated.

Ni-Co bimetallic catalyst for CH 4 reforming with CO 2

Abstract: A co-precipitation method was employed to prepare Ni/Al2O3-ZrO2, Co/Al2 O3-ZrO2 and Ni-Co/Al2O3-ZrO2 catalysts. Their properties were characterized by N2 adsorption (BET), thermogravimetric analysis (TGA), temperature-programmed reduction (TPR), temperature-programmed desorption (CO2-TPD), and temperature-programmed surface reaction (CH4-TPSR and CO2-TPSR). Ni-Co/Al2O3-ZrO2 bimetallic catalyst has good performance in the reduction of active components Ni, Co and CO2 adsorption. Compared with mono-metallic catalyst, bimetallic catalyst could provide more active sites and CO2 adsorption sites (C + CO2 = 2CO) for the methane-reforming reaction, and a more appropriate force formed between active components and composite support (SMSI) for the catalytic reaction. According to the CH4-CO2-TPSR, there were 80.9% and 81.5% higher CH4 and CO2 conversion over Ni-Co/Al2O3-ZrO2 catalyst, and its better resistance to carbon deposition, less than 0.5% of coke after 4 h reaction, was found by TGA. The high activity and excellent anti-coking of the Ni-Co/Al2O3-ZrO2 catalyst were closely related to the synergy between Ni and Co active metal, the strong metal-support interaction and the use of composite support.

Synthesis of methanol and ethanol over CuZnAl slurry catalyst prepared by complete liquid-phase technology

Abstract: A new method, named the complete liquid-phase technology, has been applied to prepare catalysts for methanol synthesis. Its main innovative thought lies in preparing slurry catalysts directly from raw solution. Activity tests indicate that the CuZnAl slurry catalyst prepared by the new method can efficiently catalyze conversion of syngas to ethanol in a slurry reactor, while CO conversion reaches 35.9% and ethanol selectivity is more than 20%, with a total alcohol selectivity of more than 87%. No deactivation was found during the 192 h reaction.

Effect of PEG additives on properties and morphologies of polyetherimide membranes prepared by phase inversion

Abstract: This study investigated the effect of poly (ethylene glycol) (PEG) additive as a pore-former on the structure formation of membranes and their permeation properties connected with the changes in thermodynamic and kinetic properties in the phase inversion process. The membranes were prepared by using polyetherimide/N-methyl-2-pyrrolidone/PEG (PEI/NMP/PEG) casting solution and water coagulant. The resulting membranes, prepared by changing the ratio of PEG to PEI, were characterized by scanning electron microscope (SEM) observations, measurements of water flux and γ-globin rejection. The thermodynamic and kinetic properties of the membrane-forming system were studied through viscosity. The pore radius distribution curves were especially obtained by differential scanning calorimetry (DSC). Furthermore, the membranes were characterized for pure water flux and rejection of solute and by SEM observation. The filtration results agreed well with the SEM observations. As expected, PEG with a fixed molecular weight (PEG 600) acted as a pore forming agent, and membrane porosity increased as the PEG content of the casting solution increased.

Evaluation of strategies for the subsequent use of CO2

Abstract: If substantial amounts of CO2, which according to actual scenarios may in the future be captured from industrial processes and power generation, shall be utilized effectively, scalable energy efficient technologies will be required. Thus, a survey was performed to assess a large variety of applications utilizing CO2 chemically (e.g., production of synthesis-gas, methanol synthesis), biologically (e.g., CO2 as fertilizer in green houses, production of algae), or physically (enhancement of fossil fuel recovery, use as refrigerant). For each of the processes, material and energy balances were set up. Starting with pure CO2 at standard conditions, expenditure for transport and further process specific treatment were included. Based on these calculations, the avoidance of greenhouse gas emissions by applying the discussed technologies was evaluated. Based on the currently available technologies, applications for enhanced fossil fuel recovery turn out to be most attractive regarding the potential of utilizing large quantities of CO2 (total capacity > 1000 Gt CO2) and producing significant amounts of marketable products on one hand and having good energy and material balances on the other hand \( \left( {{{t_{CO_2 - emitted} } \mathord{\left/ {\vphantom {{t_{CO_2 - emitted} } {t_{CO_2 - utilized} 0.34}}} \right. \kern- ulldelimiterspace} {t_{CO_2 - utilized} > 0.34}} \)). Biological processes such as CO2 fixation using micro-algae look attractive as long as energy and CO2 balance are considered. However, the development of effective photo-bioreactors for growing algae with low requirements for footprint area is a challenge.

Surface modification of biomaterials by photochemical immobilization and photograft polymerization to improve hemocompatibility

Abstract: Thrombus formation and blood coagulation are serious problems associated with blood contacting products, such as catheters, vascular grafts, artificial hearts, and heart valves. Recent progresses and strategies to improve the hemocompatibility of biomaterials by surface modification using photochemical immobilization and photograft polymerization are reviewed in this paper. Three approaches to modify biomaterial surfaces for improving the hemocompatibility, i.e., bioinert surfaces, immobilization of anticoagulative substances and biomimetic surfaces, are introduced. The biomimetic amphiphilic phosphorylcholine and Arg-Gly-Asp (RGD) sequence are the most effective and most often employed biomolecules and peptide sequence for improving hemocompatibility of material surfaces. The RGD sequence can enhance adhesion and growth of endothelial cells (ECs) on material surfaces and increase the retention of ECs under flow shear stress conditions. This surface modification is a promising strategy for biomaterials especially for cardiovascular grafts and functional tissue engineered blood vessels.

Study on the microwave-assisted extraction of polyphenols from tea

Abstract: This study demonstrated a promising method for quickly extracting tea polyphenol (TP) by microwave-assisted extraction (MAE) technology. Some influential parameters, including MAE temperature, microwave power, concentration of extraction solvent, MAE time and the solid/liquid ratio, were investigated. The optimum condition of MAE was obtained by dual extraction with 60% ethanol (v/v) and the solid/liquid ratio 1:12 g/mL at 80°C for 10 minutes under the microwave power 600W. The yield of TP was 96.5% under the described condition. Compared with traditional methods, including hot reflux extraction (HRE), ultrasound-assisted extraction (UAE) and supercritical fluid extraction (SFE), the extraction time was saved 8 times than that of HRE, and the yield was increased by 17.5%. The extraction time at comparable levels of production was saved 2 times, and the energy consumption was one fourth that of UAE. The extraction time was saved 5 times than that of SFE, and the yield of TP was increased by 40%. Moreover, compared with MAE of TP studied by others, it decreased the solid/liquid ratio from 1: 20 to 1: 12 g/mL without 90-min pre-leaching time, and the yield of TP was increased by 6%–40%.

Polymorphism of pharmaceutical molecules: perspectives on nucleation

Abstract: Polymorphism is a widespread phenomenon observed in more than half of all drug substances. Various polymorphs frequently possess different physical, chemical, mechanical and thermal properties that can profoundly affect the bioavailability, stability and other performance characteristics of the drug. Accordingly, the elucidation of the relationship between the particular polymorph of a pharmaceutical molecule and its functional properties is crucial to select the most suitable polymorph of the pharmaceutical molecule for development into a drug product. This review briefly introduces recent advances in the discovery and control of the polymorphs of pharmaceutical molecules, in terms of the enhancement of the selective nucleation of a particular polymorph. In the light of this, some cases discussed in the following is to be considered controversial.

Carbonation of calcium-containing mineral and industrial by-products

Abstract: The use of carbon dioxide (CO2) and calcium-containing by-products from industrial activities is receiving increasing interest as a route to valuable carbonate materials while reducing CO2 emissions and saving natural resources. In this work, wet-chemical experimental data was assessed, which involved the carbonation of three types of materials in aqueous solutions, namely, 1) wollastonite, a calcium silicate mineral, 2) steelmaking slag, a by-product of steel production, and 3) paper bottom ash (PBA) from waste paper incineration. Aims were to achieve either a high carbonation degree and/or a pure carbonate product with potential commercial value. Producing a pure precipitated calcium carbonate (PCC) material that may find use in paper industry products puts strong requirements on purity and brightness. The parameters investigated were particle size, CO2 pressure, temperature, solid/liquid ratio, and the use of additives that affect the solubilities of CO2 and/or calcium carbonate. Temperatures and pressures were varied up to 180°C and 4 MPa. Data obtained with the wollastinite mineral allowed for a comparison between natural resources and the industrial by-product materials, the latter typically being more reactive. With respect to temperature and pressure trends reported by others were largely confirmed, with temperatures above 150°C introducing thermodynamic limitations depending on CO2 pressure. The influence of additives showed some promise, although costs may make recycling and reuse of additives a necessity for a large-scale process. When using steelmaking slag, magnetic separation may remove some iron-containing material from the process (although this is far from perfect), while the addition of bicarbonate supported the removal of phosphorous, aside from improving calcium extraction. The experiments with paper bottom ash (PBA) gave new data, showing that its reactivity resembles that of steelmaking slag, while its composition results in relatively pure carbonate product. Also, with PBA no additives were needed to achieve this.

Study of ultrasound-promoted, lipase-catalyzed synthesis of fructose ester

Abstract: The effect of low energy ultrasound in biochemistry and biotechnology has attracted great attention in recent years. It can enhance substrate dissolution and improve mass transfer within and outside of a cell, both of which are beneficial to the synthesis of fructose ester. Here we describe the experimental study of the effect of ultrasounds of different intensity on the lipase-catalyzed synthesis of fructose ester in the solvent butanone. The results were compared with control reactions performed with no ultrasound. High performance liquid chromatography (HPLC) and thin layer chromatography (TLC) were used for qualitative and quantitative analyses. The results show the following: 1) the concentration of mono-ester and diester increased with the reaction time, either with or without ultrasonic irradiation. Low energy ultrasound accelerated the reaction due to the effect of ultrasonic steady cavitations, and high energy ultrasound was not beneficial to the reaction. 2) The application of ultrasound played an important role in our lipase-catalyzed reaction. It decreased reaction time as compared to a reaction without ultrasound that resulted in the same yield, increased reaction rate, and enhanced the amount of fructose ester produced. When the frequency was 10 kHz and sound intensity was 0.16 W·m−2, the concentration of ester was twofold more than without ultrasonic irradiation after a reaction time of up to 12 h. With the proper ultrasonic parameters, the overall concentration of production appeared to increase exponentially with the reaction time. 3) Ultrasound had little effect on the initial reaction rate, and continuous ultrasonic irradiation was favorable for the reaction. The longer the reaction continued, the more obvious the effects of the ultrasound became in our experiments.

Applications of the crystallization process in the pharmaceutical industry

Abstract: The applications of the crystallization technique in the pharmaceutical industry as a purification and separation process for the isolation and synthesis of pure active pharmaceutical ingredients (API), co-crystals, controlled release pulmonary drug delivery, and separation of chiral isomers are briefly discussed using a few case studies. The effect of process variables and solvent on the polymorphism and morphology of stavudine is discussed. The implementation of external control in the form of feedback and real-time optimal control using cooling and antisolvent crystallization of paracetamol in water-isopropyl alcohol is introduced. Two methods to prepare micronsized drug particles, namely, micro-crystallization and polymer-coated API-loaded magnetic nanoparticles for pulmonary drug delivery, are discussed. The significance of co-crystals in drug administration is highlighted using the theophylline-nicotinamide co-crystal system. Resolution of chloromandelic acid derivatives, a racemic compound, is achieved using direct crystallization and diastereomeric salts crystallization. The crystal structures of diastereomeric salts of chloromandelic acid and phenylethylamine are determined. The structure comparison between the less soluble and more soluble salts shows that weak interactions such as CH/π interactions and van der Waals forces contribute to chiral recognition when the hydrogen bonding patterns are similar.

A mini review on chemical fixation of CO2: Absorption and catalytic conversion into cyclic carbonates

Abstract: In this article, we present our research results on chemical fixation of CO2 using organobismuth compounds. We fabricated bismuth biphenoate complex, Zn-Mg-Al composite oxides, and SBA-15 or Al-SBA-15 immobilized hydroxyl ionic liquid for CO2 cycloaddition onto epoxides. The hypervalent bismuth compounds show good ability for association and dissociation with CO2. The bismuth biphenolate complexes are catalytically effective for the cycloaddition reaction. The heterogeneous catalysts, viz. Zn-Mg-Al oxides and SBA-15 or Al-SBA-15 immobilized ionic liquid, are efficient for the synthesis of cyclic carbonate from CO2 and epoxide. It is found that the presence of a trace amount of water can improve the catalytic activity of the immobilized ionic liquid.

Desulfurization mechanism of FCC gasoline: A review

Abstract: This paper reviews the most important developments on the desulfurization mechanism of Fluid Catalytic Cracking (FCC) gasoline. First, the origin of sulfur compounds in FCC gasoline and the current developed desulfurization approaches and technologies are briefly introduced, and then the researches on desulfurization mechanism are summarized from experimental and theoretical perspectives. Further researches on the desulfurization mechanism will lay a foundation for optimizing desulfurization sorbents and technologies.

Effect of pressure on gasification reactivity of three Chinese coals with different ranks

Abstract: The gasification reactivities of three kinds of different coal ranks (Huolinhe lignite, Shenmu bituminous coal, and Jincheng anthracite) with CO2 and H2O was carried out on a self-made pressurized fixed-bed reactor at increased pressures (up to 1.0 MPa). The physicochemical characteristics of the chars at various levels of carbon conversion were studied via scanning electron microscopy (SEM), X-ray diffraction (XRD), and BET surface area. Results show that the char gasification reactivity increases with increasing partial pressure. The gasification reaction is controlled by pore diffusion, the rate decreases with increasing total system pressure, and under chemical kinetic control there is no pressure dependence. In general, gasification rates decrease for coals of progressively higher rank. The experimental results could be well described by the shrinking core model for three chars during steam and CO2 gasification. The values of reaction order n with steam were 0.49, 0.46, 0.43, respectively. Meanwhile, the values of reaction order n with CO2 were 0.31, 0.28, 0.26, respectively. With the coal rank increasing, the pressure order m is higher, the activation energies increase slightly with steam, and the activation energy with CO2 increases noticeably. As the carbon conversion increases, the degree of graphitization is enhanced. The surface area of the gasified char increases rapidly with the progress of gasification and peaks at about 40% of char gasification.

The catalytic effect of both oxygen-bearing functional group and ash in carbonaceous catalyst on CH4-CO2 reforming

Abstract: A kind of new catalyst—carbonaceous catalyst—for CH4-CO2 reformation has been developed in our laboratory. The effect of both oxygen-bearing functional group such as phenolic hydroxyl, carbonyl, carboxyl, and lactonic, and ash such as Fe2O3, Na2CO3, and K2CO3 in the carbonaceous catalyst on the CH4-CO2 reforming has been investigated with a fixed-bed reactor. It has been found that the carbonaceous catalyst is an efficient catalyst on CO2-CH4 reforming. With the decrease of oxygen-bearing functional group, the catalytic activity of carbonaceous catalyst decreases quickly. The oxygen-bearing functional groups play a significant role in the carbonaceous-catalyzed CO2-CH4 reforming; the ash components in carbonaceous catalyst also have an important influence on the CO2-CH4 reforming. Fe2O3, Na2CO3, and K2CO3 in the ash can catalyze the CO2-CH4 reforming reaction; CaO has little effect on CO2-CH4 reforming reaction. CaO can catalyze the gasification between carbonaceous catalyst and CO2; Al2O3 and MgO inhibit the CO2-CH4 reforming.

Effects of pressure and temperature on fixed-site carrier membrane for CO2 separation from natural gas

Abstract: In this paper, the effect of testing temperature on the performance of fixed carrier membrane for CO2 separation were studied. The blend composite membranes were developed respectively with a blend of PEI-PVA (polyetheleneimine-polyvinyl alcohol) as separation layer and PS (polysulfone) ultrafiltration membranes as the substrates. The permselectivity of the membranes was measured with CO2/CH4 mixed gas. The effect of testing temperature on membrane separation performance was investigated. The results showed that both the permeances of CO2 and CH4 decreased with the increase of temperature, and the permeances decreased more quickly under low pressure than those under high pressure. At the feed pressure of 0.11 MPa, the CO2/ CH4 selectivity of PEI-PVA/PS blend composite membrane reduced along with temperature increment. Under the feed pressure of 0.21 MPa, as well as 1.11 MPa, the selectivity decreased with the increase of temperature.

Synthesis and electrocatalytic property of cubic and spherical nanoparticles of cobalt platinum alloys

Abstract: This paper describes the morphological control and electrocatalytic property of CoPt nanoparticles. Both cubic and spherical CoPt nanoparticles were made using cobalt carbonyl and platinum 2,4-pentanedionate under different reaction temperatures in the presence of capping reagents, which included adamantanecarboxylic acid and hexadecylamine. Effects of heterogeneous species on shape of the CoPt nanoparticles were examined by replacing cobalt carbonyl with silver acetylacetonate. Our results suggest that the formation of different shapes of CoPt particles could be attributed to the affinity between cobalt and platinum, and the effects of capping agents. The size and shape dependent electrocatalytic properties of these nanoparticles were examined based on the direct methanol oxidation reaction.

Konjac glucomannan and xanthan gum as compression coat for colonic drug delivery: experimental and theoretical evaluations

Abstract: Compression coated tablets for oral colon specific delivery systems were developed with a mixture polysaccharide of konjac glucomannan (KGM) and xanthan gum (XG) as the compression coat. Diffusion of cimetidine from compression coated tablets was investigated by release experiment in Vitro. 0.22U/mL β-mannanase was applied in the mimic colon solution. The structure of the mixture polysaccharide was studied by an atomic force microscope (AFM). The experimental results indicate that a KGM70 tablet with a 0.4 g coat is of good design, due to a less than 5% drug loss in the mimic upper gastrointestinal solution by the synergistic interaction between XG and KGM, and due to about 50% cumulative release in the mimic colon solution by degradation after 24 hours. The release mechanism and model are discussed based on different periods of drug release including the delay of the drug, the constant release without an enzyme and the delay of degradation. Under hydrolysis by β-mannanase, drug release from the tablet with KGM coat shows an exponential increase, while that from the dosage with the mixture polysaccharide coat is an approximately zero-order process in which the constant release rate relates to the release velocity of a non-degraded system, the content of KGM within the coat and the average molecular weight ratio of KGM to XG. It was found that XG was the framework of the polysaccharide mixtures by AFM, which is similar to the analysis results from experiments on drug release.

Synthesis of crystals and particles by crystallization and polymerization in droplet-based microfluidic devices

Abstract: The recent advances in crystallization and polymerization assisted by droplet-based microfluidics to synthesize micro-particles and micro-crystals are reviewed in this paper. Droplet-based microfluidic devices are powerful tools to execute some precise controls and operations on the flow inside microchannels by adjusting fluid dynamics parameters to produce monodisperse emulsions or multiple-emulsions of various materials. Major features of this technique are producing particles of monodispersity to control the shape of particles in a new level, and to generate droplets of diverse materials including aqueous solutions, gels and polymers. Numerous microfluidic devices have been employed to generate monodisperse droplets of range from nm to μm, such as T junctions, flow-focusing devices and co-flow or cross-flow capillaries. These discrete, independently controllable droplets are ideal microreactors to be manipulated in the channels to synthesize the nanocrystals, protein crystals, polymer particles and microcapsules. The generated monodisperse particles or crystals are to meet different technical demands in many fields, such as crystal engineering, encapsulation and drug delivery systems. Microfluidic devices are promising tools in the synthesis of micron polymer particles that have diverse applications such as the photonic materials, ion-exchange and chromatography columns, and field-responsive rheological fluids. Processes assisted by microfluidic devices are able to produce the polymer particles (including Janus particles) with precise control over their sizes, size distribution, morphology and compositions. The technology of micro-fluidics has also been employed to generate core-shell microcapsules and solid microgels with precise controlled sizes and inner structures. The chosen “smart” materials are sensitive to an external stimulus such as the change of the pH, electric field and temperature. These complex particles are also able to be functionalized by encapsulating nanoparticles of special functions and by attaching some special groups like targeting ligands. The nucleation kinetics of some crystals like KNO3 was investigated in different microfluidic devices. Because of the elimination of the interactions among crystallites in bulk systems, using independent droplets may help to measure the nucleation rate more accurately. In structural biology, the droplets produced in microfluidic devices provide ideal platforms for protein crystallization on the nanoliter scale. Therefore, they become one of the promising tools to screen the optimal conditions of protein crystallization.

Developing macromolecular therapeutics: the future drug-of-choice

Abstract: Macromolecular drugs including peptides, proteins, antibodies, polysaccharides and nucleic acids have been widely used for therapy of major diseases such as carcinoma and AIDS as well as cardiovascular and neurodegenerative disorders among other medical conditions. Due to their unmatched properties of high selectivity and efficiency, macromolecular drugs have been recognized as the drug-of-choice of the future. Since worldwide progress on macromolecular therapeutics still remains in the infant stage and is therefore wide open for equal-ground competition, R&D related to macromolecular drugs should be considered as the main point of focus in China in setting up its strategic plans in pharmaceutical development. In this article, research strategies and drug delivery approaches that should be adopted to enhance the therapeutic effects of macromolecular drugs are reviewed. In addition, comments concerning how to implement such strategies to excel from competition in this challenging research field, such as the design of innovative and highly effective delivery systems of macromolecular drugs with self-owned intellectual property rights, are provided.

Structure controlling and process scale-up in the fabrication of nanomaterials

Abstract: Nanotechnology is already having a significant commercial impact, and will very certainly have a much greater impact in the future. The research on process engineering and scale-up will be very important for the commercial production and application of nanomaterials, because the properties and structure of nanomaterials are not only determined by the nucleation and growth process, but also strongly affected by the engineering properties, such as the mixing, the heat and mass transfer, and also the distribution of temperature, concentration, etc. This paper will present some research work in our laboratory on the fabrication of nanomaterials. Based on the chemical engineering principle and methods, many kinds of novel nanomaterials can be synthesized and their structure can be easily controlled through adjusting the parameters of the fluid mixing, and the distribution of temperature, residence time and concentration, etc. By using the micro-mixing, heat and mass transfer and reaction control methods, the host-guest nanocomposites have been assembled and assumed as the novel electroanalytical sensing nanobiocomposite materials. Based on the principles of chemical engineering, the manufacturing technologies for magnetic powders, calcium carbonate, and titanium dioxide have been developed for commercial-scale production, and the largest production scale has reached 15 kt/year.

Preparation of Cu/ZnO/Al2O3 catalyst under microwave irradiation for slurry methanol synthesis

Abstract: Cu/ZnO/Al2O3 catalysts with Cu/Zn/Al ratios of 6/3/1 were precipitated and aged by conventional and microwave heating methods and tested in the slurry phase reactor for methanol synthesis. The effect of technological condition of precipitation and aging process under microwave irradiation on the catalytic performance was investigated to optimize the preparing condition of Cu/ZnO/Al2O3 catalyst. The results showed that the microwave irradiation during precipitation process could improve the activity of the catalyst, but had little effect on the stability. While the microwave irradiation during aging process has a great benefit to both the activity and stability of the catalyst, the catalyst aged at 80°C for 1 h under microwave irradiation possessed higher methanol space time yield (STY) and more stable catalytic activity. The activity and stability of the catalyst was further enhanced when microwave irradiation was used in both precipitation and aging processes; the optimized condition for the catalyst precursor preparation was precipitation at 60°C and aging at 80°C under microwave irradiation.

Molecular size characterization of heavy oil fractions in vacuum and solution by molecular dynamic simulation

Abstract: Two kinds of heavy oils were fractionated into eight fractions by Liquid-Solid Adsorption Chromatography, respectively, and samples were collected to measure properties. According to the elemental analysis, molecular weight and 1H-NMR data, average molecular structures of polycyclic aromatic and heavy resin were constructed with improved Brown-Ladner (B-L) method and several corrections. And then, the most stable conformations of polycyclic aromatic and heavy resin in vacuum and toluene solution were obtained by molecular dynamic simulation, and the molecular size was gotten via the radius of gyration analysis. The results showed that the radius of gyration of polycyclic aromatic and heavy resin was 0.55–0.70 nm in vacuum and 0.60–0.90 nm in toluene solution. With molecular weight increasing, the molecular size in vacuum and toluene solution also increased. Due to the swelling behavior of solvent, the alkyl side chains of heavy oil molecule in solution were more stretched. Thus, the molecular size in toluene solution was larger than that in vacuum.

Study on direct alcohol/ether fuel synthesis process in bubble column slurry reactor

Abstract: The recent studies of direct alcohol/ether synthesis process in slurry reactors were reviewed, and the research work in our laboratory was carried out in this paper. a global kinetics model for direct dimethyl ether (DME) synthesis from syngas over a novel Cu-Zn-Al-Zr slurry catalyst was established according to the total of 25 experimental data, and a steady-state one-dimensional mathematical model was further developed in bubble column slurry reactor (BCSR), which was assumed that the bubble phase was plug flow, and the liquid phase was fully mixed flow. The numerical simulations of reactor design of 100000 t/a dimethyl ether pilot plant indicate that higher pressure and lower temperature were favorable to the increase of CO conversion, selectivity of dimethyl ether, product yield and height of slurry bed. The optimal operating conditions for DME synthesis process were obtained: reaction temperature at 240°C, reactor pressure at 5 MPa and reactor diameter of 2.5 m.

Numerical simulation and experimental verification of chemical reactions for SCR DeNOx

Abstract: Selective catalytic reduction (SCR) is a major commercial technology for NOx removal in power plants. There are a lot of complex chemical reactions in SCR reactors, and it is of great significance to understand the internal process of chemical reactions for SCR DeNOx and study the impact of various factors on NOx removal efficiency. In this paper, the impact of reaction temperature, ammonia-nitrogen molar ratio and resident time in the catalyst bed layer on NOx removal efficiency were studied by simulation of chemical reactions. Then calculated results were compared with catalyst activity test data in a power plant, which proved that the simulated results were accurate. As a result, the reaction conditions were optimized in order to get the best removal efficiency of NO, so that we can provide a reference for optimal running of SCR in power plants.