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GCCES2016 Invited Lectures

 

Design Catalysts for the catalytic wet air oxidation of aqueous nitrogen containing compounds

Professor Binghui Chen, Xiamen University

Catalytic wet air oxidation (CWAO) is considered to be a promising technology to deal with sewage disposal due to its high efficiency, low cost and general applicability[1]. However, the deactivation, low activity, and sometimes high cost of catalysts extremely hinder the utilization of this technology, especially for wastewater comprising nitrogen-containing compounds such as ammonia [2] and N,N-dimethylformamide (DMF) [3]. The typical property of nitrogen-containing compounds is that they normally have lone pair electrons, which could form strong chemical bonds with metals on catalysts and cause leaching of the metals on catalysts. Therefore, understanding the mechanism for nitrogen-containing compounds catalytic decomposition in wastewater and then constructing highly active and stable catalysts for selectively decompose nitrogen-containing compounds into harmless nitrogen in wastewater are critical in use of CWAO.
Based on literature as well as our experimental results, oxygen affinity could be the key factor for the catalytic activity of nitrogen-containing compounds decomposition. However, an appropriate oxygen affinity towards nitrogen production selectivity.
In this work, 4 nitrogen-containing compounds, DMF, dimethylamine (DMA), methylamine (MA), and ammonia were examined for catalytic decomposition. It was found that different catalyst structures have to be construct as the molecular structure of the compounds changed. Characterization techniques such as TPR, HADDF-STEM etc. were used to determine the structure-effect results   
References
[1]          S. Keav, J. Barbier, D. Duprez, Catalysis Science & Technology 1 (2011) 342-353.
[2]          L. Oliviero, J. Barbier Jr, D. Duprez, Applied Catalysis B: Environmental 40 (2003) 163-184.
[3]          N. Grosjean, C. Descorme, M. Besson, Applied Catalysis B: Environmental 97 (2010) 276-283.

 

 

 

 

Chemical conversion processes at ultra-high temperatures in thermal plasma reactors

Professor Yi Cheng, Department of Chemical Engineering, Tsinghua University

Chemical conversion processes are most often operated at the temperatures below 1000°C. However, challenges have been encountered when the feedstock can be hardly converted using conventional means. This presentation will overview our recent efforts to convert coal, coal tar, asphaltene, SiCl4 and MgCl2 to valuable chemicals or materials at ultra-high temperatures in thermal plasmas. The interest in the potential applications of thermal plasma techniques in chemical engineering field comes from their unique thermodynamic and transport properties, for example, high efficiency of the transformation of electrical energy into thermal energy; the possibility of stationary heating of the gas to the mean mass temperature of the order of 103-104 K; high rate of the chemical reactions, leading to high-productivity reactors; high concentration of energy in the small volume of plasma; and the possibility of heating almost any gases: reduction, oxidation, inert gases and mixtures. To deeply understand the thermal conversion processes at extreme conditions, experimental and theoretical researches have been carried out in my group in the past ten years, involving the representative processes of (1) pyrolysis of coal, coal tar, asphaltene or other gas/liquid hydrocarbons to acetylene and other light gases; (2) fabrication of high-purity materials of nc-Si, nc-SiC, MgO and graphene. Perspectives on these unique chemical processes will be discussed.

 

 

 

Ultrasensitive microchip based on smart microgel for real-time on-line detection of trace threat analytes

Professor Liang-Yin Chu, Sichuan University

Real-time on-line detection of trace threat analytes is critical for global sustainability, while the key challenge is how to efficiently convert and amplify analyte signals into simple readouts.  Here we report an ultrasensitive microfluidic platform incorporated with smart microgel for real-time on-line detection of trace threat analytes.  The microgel can swell responding to specific stimulus in flowing solution, resulting in efficient conversion of the stimulus signal into significantly amplified signal of flow rate change; thus highly sensitive, fast and selective detection can be achieved.  We demonstrate this by incorporating ion-recognizable microgel for detecting trace Pb2+, and connecting our platform with pipelines of tap water and wastewater for real-time on-line Pb2+-detection to achieve timely pollution warning and terminating.  This work provides a generalizable platform for incorporating myriad stimuli-responsive microgels to achieve ever-better performance for real-time on-line detection of various trace threat molecules, and may expand the scope of applications of detection techniques.

 


 

 

 

Development of novel electrodes for water splitting
Professor Guoqing Guan, Hirosaki University
Hydrogen production by electrochemical splitting of water using natural energy such as solar and wind energy has attracted increasing interest. In this talk, the state of art of on electrode development for water splitting will be reviewed and discussed. The try in our group on this area will be introduced. In our lab, electro-deposition combined with thermal oxidation method has been developed to fabricate various composite electrodes. It is found that some special electrodes with 3D hierarchical structure showed excellent performance for the water splitting. Based on these researches, the prospects and challenges for the development of novel electrode will be also discussed.

 

 

 

 

 

Enzyme sensitive, surface engineered nanoparticles for enhanced delivery of camptothecin
Professor Yong Hu, Nanjing University
To achieve a drug delivery system combining the programmable long circulation and targeting ability, surface engineering nanoparticles (NPs), having a sandwich structure consisting of a long circulating outmost layer, a targeting middle layer and a hydrophobic innermost core were constructed by mixing a matrix metalloproteinase MMP2 and MMP9-sensitive copolymers (mPEG-Pep-PCL) and folate receptor targeted copolymers (FA-PEG-PCL). Their physiochemical traits including morphology, particle size, drug loading content, and in vitro release profiles were studied. In vitro studies validated that the inhibition efficiency of tumor cells was effectively correlated with NPs concentrations. Furthermore, The PEG layer would detach from the NPs due to the up-regulated extracellular MMP2 and MMP9 in tumors, resulting in the exposure of folate to enhance the cellular internalization via folate receptor mediated endocytosis, which accelerated the release rate of CPT in vivo. The antitumor efficacy, tumor targeting ability and bio-distribution of the NPs were examined in a B16 melanoma cells xenograft mouse model. These NPs showed improved tumor target ability and enhanced aggregation of camptothecin (CPT) in tumor site and prominent suppression of tumor growth. Thus this mPEG-Pep-PCL@FA-PEG-PCL core-shell structure NP could be a better candidate for the tumor specific delivery of hydrophobic drug.

Keywords: nanoparticles; matrix metalloproteases; camptothecin; targeting; polycaprolactone

 

 

 

 

Biochar as Enabling Material for Sustainability
Professor Charles Q. Jia , University of Toronto

Biochar is carbon created from photosynthetic biomass using a carbonization or pyrolysis process. Traditionally, it is used as a solid fuel which is renewable and carbon neutral. As carbon in biochar is originated from atmospheric carbon dioxide (CO2), the production and utilization of biochar in non-fuel applications represent a net removal of CO2 from the global carbon cycle – a carbon-negative process. A wide range of biomass has been used as raw material for biochar production, from agriculture wastes to various woody materials. While highly carbonized with carbon contents over 90 wt%, biochar can become chemically stable under ambient conditions. Biochar derived from biomass can also have a porous structure that mimics that of its precursor. Its porous nature, associated internal surface area and chemical stability make biochar desirable in many environmental and energy applications, from air and water purification to soil amendment. In this study, we explore the potential of biochar as material in other areas. We suggest that large-scale utilizations of biochar in diverse, non-fuel applications can be a viable mechanism of offsetting CO2 emissions from human activities and enhancing sustainability. As an example, we demonstrate the potential of biochar as an active electrode material for supercapacitor - a physical energy storage device that can be rapidly charged and discharged for over half million times. Some synthetic porous carbons, such as carbon nanotubes (CNTs) and graphene sheets, have been studied as electrode material and shown promising performance due to their superior capacity of conducting electrons and ions in electrolyte. Our work demonstrates that the structure of monolithic biochar can facilitate both electron conduction and ion transport in electrolyte, but with the added benefits of having a continuous macrostructure that can be scaled more readily and economically than CNTs and other synthetic carbon nanomaterials. Hence, biochar can be a viable choice for electrode material in large-scale, high-performance supercapacitors.

 

 

 

Design and fabrication of graphene-based membranes for molecular separation
Professor Wanqin Jin, Nanjing Tech University
Graphene is a well-known two-dimensional material that exhibits preeminent electrical, mechanical and thermal properties owing to its unique one-atom-thick structure. Graphene and its derivatives (e.g., graphene oxide (GO)) have become emerging nano-building blocks for separation membranes featuring distinct laminar structures and tunable physicochemical properties. Extraordinary molecular separation properties for purifying water and gases have been demonstrated by graphene-based membranes, which have attracted a huge surge of interest during the past few years.[1]

However, most of the graphene-based membranes are polymeric supported or free-standing, whose practical application is limited due to the lack of mechanical strength and thermal and chemical stability. To address this problem, a facile silane-graft modification approach proposed by our group was demonstrated to be an efficient way to improve the quality of the GO film formed on the porous ceramic substrate.[2] Based on this, we further demonstrated a scalable fabrication of GO membranes on ceramic hollow fiber substrate and showed good PV dehydrotion of aqueous organic solution.[3] Moreover, we demonstrated a novel bio-inspired strategy that utilizes the synergistic effect of a hydrophilic polymer and GO laminates to realize fast water-transport channels for constructing high-efficiency membrane.[5] For gas separation, we proposed a novel type of membrane with fast and selective gas-transport channels of GO laminates enabled by polymer-GO hydrogen bonding.[4] The as-prepared GO-based membrane showed excellent CO2 permeation performance and extraordinary operational stability. Also, the effect of GO lateral size and oxidation degree were systematically studied. Recently, we proposed several strategies including the facile spray-evaporation and integrated external forces driven assembly (EFDA) approaches to precisely manipulate the GO membranes with highly ordered two-dimensional microstructure for precise molecular gas separation. [6]

Because GO nanosheets can be easily mass-produced by chemical oxidization and ultrasonic exfoliation from inexpensive raw graphite, it is expected that GO-based material is promising for membrane based process. Future efforts should be taken to further develop high-quality graphene-based membranes for efficient water desalination and enhance the membrane stability for practical application.

Keywords: graphene • graphene oxide • membranes •ceramic • molecular separation

Reference:

[1] G. Liu, W. Jin, N. Xu, Chem. Soc. Rev., 44 (2015) 5016-5030.

[2] Y. Lou, W. Jin, et al., Appl. Surf. Sci., 307 (2014) 631-637.

[3] K. Huang, W. Jin, et al., Angew. Chem. Int. Ed., 53 (2014) 6929-6932.

[4] J. Shen, W. Jin, et al., Angew. Chem. Int. Ed., 54 (2015) 578-582.

[5] K. Huang, W. Jin, et al., Adv. Funct. Mater., 25 (2015) 5809–5815.

[6] J. Shen, W. Jin, et al., ACS Nano, (2016) DOI: 10.1021/acsnano.5b07304.

 

 

 

Asymmetric polymeric membrane fine structure characterization by PAS
Professor Kueir-Rarn Lee, Chung Yuan University
To increase the permeation rate of polymeric membranes without sacrificing selectivity, the membrane must be converted from a dense thick structure into an asymmetrical structure. Thus, how to characterize the asymmetric polymeric membrane fine structure to correlate the separation performance become more and more important. Recently, there is an increasing interest in positron annihilation spectroscopy (PAS) and in its use in studies on free volume size and distribution in asymmetric polymeric membranes. PAS is an important method for detecting vacancy defects, from single atom vacancies to large voids, and it is used for probing the variation in the free volume in the active layers of asymmetric polymeric membranes. With this method, a variable energy positron beam with an adjustable energy and a narrow energy distribution allows depth-resolved measurements useful in asymmetric polymeric membranes defect studies.

 

 

 

Microchemical systems for reaction process intensification
Professor Guangsheng Luo, Tsinghua University

Microchemical systems have high promising prospects for the development of green and low-carbon chemical industries, because these new systems can provide several advantages in safety, mass and heat transfer, energy and mass consumption, and controllable. Since 1990s, the group of microstructured chemical systems at Tsinghua University began to develop new microdevices and to realize multiphase microflows in microchannels. Monodispersed droplets or bubbles have been successfully generated and general mathematical models for the prediction of the dispersed phase size have been suggested. The mass transfer performances of multiphase microflows have been determined. The applications of multiphase microflows in separation, chemical reaction, and nanoparticle preparation have been carried out. In this presentation some new development and applications of multiphase microflows for the reaction process intensification will be introduced.

Keywords: multiphase; microflows; mass transfer; separation process; applications

 

 

 

Filtered CFD model for gas-solid flow and reaction in a large-scale fluidized bed reactor
Professor Zheng-Hong Luo, Shanghai Jiao Tong University
In this report, using a large-scale methanol-to-olefin (MTO) fluidized bed reactor (FBR) as case, a filtered CFD model at coarse-grid conditions is developed for describing the gas–solid flow and MTO reaction behaviors in this large-scale MTO FBR. The filtered model is based on a cold-model filtered two-fluid model (FTFM) used by our group in a previous work (Zhu et al., Chem. Eng. Sci. doi:10.1016/j.ces.2016.01.006) and incorporated with a filtered-interphase heat-transfer model and a MTO kinetic model. The efficiency of some representative interphase heat-transfer and kinetic models was evaluated by comparing predicted results with industrial data. Two important operation conditions, i.e., reaction temperature and water-to-methanol ratio, were investigated based on the above model. Some simulated results will also be described in this report. This is the first work that the filtered CFD model at coarse-grid conditions is developed for an industrial MTO FBR with the effects of both water content and coke deposition.
References
Chen X. M., Luo Z. H., Zhu Y. P., Xiao.J., Chen X. D., 2013. Chem. Eng. Sci. 104, 690.
Igci Y., Andrews IV, A. T., Sundaresan S., Brien T. O., 2008.  AIChE J. 54, 1431.
Liu C., Wang W., Zhang N., Li J., 2015. Chem. Eng. Sci. 122, 114.
Yan W.C., Luo, Z.H., Lu, Y.H., Chen, X.D., 2012. AIChE J. 58, 1717.
Zhu L.T., Xie L., Xiao J., Luo Z. H., 2016. Chem. Eng. Sci. doi: 10.1016/j.ces.2016. 01. 006.

 

 

 

 

Performance of fluidized beds for methane dehydro-aromatization

Professor Xiaoxun Ma, Northwest University

A pilot-scale experimental facility was constructed for methane dehydro-aromatization. The facility consists mainly of two fluidized beds and catalyst feeder. One fluidized bed was used as the reactor (50 mm i.d.), another was used as the regenerator (50 mm i.d.). Catalysts of Mo/HZSM-5 were circulated between two fluidized beds (reactor and regenerator) in steady state in the experiment. In this paper, performance of the experimental facility of two fluidized beds for methane dehydro-aromatization, catalyst evaluation and effects of operating conditions (reaction/regeneration temperature, reaction/regeneration VHSV, catalyst circulating speed etc.) were investigated by a series of tests. Experimental results showed the tests were running continuously, stably and smoothly in the experimental system of two fluidized beds, the catalyst reactivity and regeneration performance of deactivated catalyst were better than those in fixed-bed reactor/ regenerator.

Key words: Methane dehydro-aromatization, Fluidized bed, Catalysis, Hydrogen regenerate

 

 

 

 

Understanding cell homing-based tissue regeneration from the perspective of materials
Professor Hemin Nie, Hunan University

Homing of cells to their target organs for tissue defect repair poses a significant challenge to biomaterials scientists and tissue engineers, due to the low efficiency of homing of effective cells to defect sites as well as the difficulties in coordinating cell migration, adhesion, spreading and differentiations. Recent advances in biomaterials have successfully improved the efficiency of homing of mesenchymal stem cells (MSCs) and cell homing-based tissue regeneration. In this review, the process of cell-homing based tissue regeneration was discussed from three different perspectives, including cell surface engineering, scaffold optimization and signaling molecules interactions. Cell surface modification by using polymeric materials offers a simple way to administrate cell migration. Besides, the ordered or anisotropic structures are proved to be more efficient for cell adhesion, spreading and infiltration than relatively random or isotropy structures. Moreover, the coordinated release of different growth factors (GFs), e.g. achieved via core-shell microspheres, can orchestrate the biological processes, including cell growth and differentiations, and significantly enhance the osteogenic differentiation of low population density of MSCs. These developments in biomaterials are not only important for fundamental understanding of materials-cell interactions, but also help understand cell homing-based tissue regeneration from the perspective of materials, which is crucial for the design and fabrication of a new generation of highly functional biomaterials for tissue regeneration.

 

 

 

Protein aggregation and its inhibition
Professor Yan Sun, Tianjin University

A nascent protein (peptide) needs to fold to its specific tertiary structure to function in a living system, so how a protein folds is an essential issue under study in life sciences. If a protein fails to fold correctly or protein misfolding occurs in vivo, the misfolded peptide will accumulate and aggregate in the living system, resulting in serious diseases. Currently, over 50 diseases have been identified to be related to protein misfolding and aggregation, including neurodegenerative diseases (e.g., Alzheimer’s disease, AD), metabolic diseases and cancers. Hence, inhibition of protein aggregation is a major concern in medical science. On the other hand, there are lots of therapeutic proteins that need large-scale production by overexpression of foreign proteins in bacteria such as E. coli. This often results in the formation of insoluble aggregates known as inclusion bodies (IBs). Hence, in vitroprotein folding from isolated and solubilized IBs is a crucial step in the downstream processing of therapeutic proteins. This presentation will describe our efforts on the studies of in vitro protein refolding and inhibition of amyloid b-protein (Ab) aggregation (fibrillogenesis), which is recognized as the main hallmark of AD. 

Recently, we found that electrostatic repulsion between the protein to be refolded and like-charged ion exchange resins can greatly suppress the aggregation of folding intermediates, leading to the significant increase of native protein recovery. The working mechanism of like-charged particles is considered due to the charge repulsion near like-charged surfaces. The charge repulsion at a solid (or polymer) surface can induce oriented alignment of protein molecules, which increases electrostatic repulsion between neighboring proteins and leads to the inhibition of protein aggregation.

On the inhibition of Ab aggregation, we have discovered a natural compound that inhibits Ab fibrillogenesis, remodels amyloid fibrils and reduces amyloid cytotoxicity. In addition, we have designed new peptide inhibitors and developed peptide-nanoparticle conjugates and acidulated albumin, which showed significant inhibitory effects on Ab aggregation. It is remarkable that the like-charge effect mentioned above on suppressing protein aggregation has also been observed in the inhibition of Ab aggregation using acidulated albumin and nanoparticles. Therefore, charge repulsion is an important factor for modulation in protein folding and inhibition of protein aggregation.

 

 

Rational design of photocatalysts for water splitting and CO2 conversion

Professor Junwang Tang, University College London

CO2 concentration in the atmosphere reached its record (400ppm) this year, which causes a serious concern about catastrophic climate change and global warming. The major contributor is by far the combustion of fossil fuel. There are two potential solutions to solve the problem. One is to replace fossil fuel by renewable energy and the other is to help nature maintain the carbon cycle by artificial conversion of CO2.
image1As the most abundant renewable energy source available on the Earth, solar energy has the potential to meet the increasing global energy demands. Therefore solar energy conversion and storage, via water splitting has been attracting substantial interest over the last ten years, which can provide renewable H2 fuel with a strong potential to replace fossil fuel. In parallel, CO2 photoreduction by sunlight has also drawn increasing attention, which can not only provide a renewable fuel but also dramatcially reduce CO2 emission, thus facilitating carbon cycle.
The key in these technologies is an efficient photocatalyst which can convert a photon to a pair of charge carriers and then utilise them to drive the expected chemical reactions. The current low efficiency in these processes is contributed to fast charge recombination in an inorganic semiconductor.1 In this talk, carbon-based photocatalysts, e.g C3N4, covalent triazine etc will be presented and their excellent performance for both water splitting and CO2 conversion will be discussed. The reaction mechanism behind their novel properties will also be pointed out.  image2Stimulated by our recent research outcomes on the charge dynamics in inorganic semiconductor photocatalysts,1 we developed novel materials for solar driven hydrogen synthesis and CO2 reduction. The first example is pure water splitting for simultaneous H2 and O2 evolution by C3N4 semiconductor based system in a suspensions solution under visible light (Figure 1).2,3 In parallel a few junction structures for CO2 photoreduction under visible light irradiation have been developed. For example, Figure 2 shows CO2 reduction by a junction composed of C3N4 and the major product is methanol instead of CO. More recently, covalent triazine photocatalysts exhibit excellent water oxidation ability, active from UV till IR when using silver ions as electron scavenger apart from its activity for H2 production from water. This is to our knowledge the first photocatalyst showing such a wide operation window for water oxidation which is the rate-determined step in solar driven water splitting. These novel properties were attributed to efficient charge separation by a junction and good charge transport pathway in these photocataysts, which were evidenced by diverse spectroscopies, elementary analysis and theoretical modelling.

References

1. J. Tang, J. R. Durrant and D. R Klug, J. Am. Chem. Soc., 130(42) (2008) 13885-13891.

2. D. J. Martin, K. Qiu, S. A Shevlin, A.D. Handoko, X. Chen, Z, Guo, and J. Tang, Angewandte Chemie-International Edition, 53 (35) (2014) 9240-9245.

3. D.J. Martin, P. J. T. Reardon, S. J. A. Mon, and J. Tang,, J. Am. Chem. Soc. 136 (2014)  12568.  Highlighted in Chemical & Engineer News on Sep. 10, 2014.

4. D. Kong, S. A. Shevlin, Z. Guo, and  J. Tang.  Submitted.

 

Numerical investigation of liquid-liquid two-phase flow in a mixer-settler

Professor Yundong Wang, Tsinghua University

Mixer-settler is one of the most widely used extraction equipments in rare earth industry. Liquid-liquid two-phase flow has been studied using computational fluid dynamics (CFD) simulation combined with population balance model (PBM) and verified with particle image velocimetry (PIV) experiment. A prediction of flow field in a single-stage mixer-settler was performed with the aid of CFD software. Multiple reference frames (MRF) model and the standard turbulence model were employed for simulating the fluid flow. Effects of impeller speed, flow ratio and droplet diameter on flow field and dispersed phase holdup were investigated. Structures of settler were optimized. Results showed that novel structures in the settler could increase the residential time of the fluid and reduce the dispersed phase entrainment. CFD simulation with PBM could predict droplet size distribution. Results showed that small droplets were mainly in the bottom region of the mixer, large droplets were in the top part of the mixer and the largest were in the impeller region. Keywords: Solvent extraction; mixer-settler; Flow characteristic; CFD; PBM

 

 

 

Achieving a Marvelous Performance by Carefully Modulating Catalyst Structure /p>

Professor Zidong Wei, Chongqing University

Developing catalytic materials for oxygen reduction reactions (ORR) with high performance and low cost has been one of the major challenges for large-scale applications of fuel cells. Among various catalytic materials, Sp2 carbon materials having abundant free-flowing π-electrons are potential catalysts for the ORR. Breaking the electroneutrality of graphitic materials by doping with heteroatoms to create charged sites favorable for O2 adsorption is the key factor in enhancing ORR activity, regardless of whether the dopant is electron-rich (e.g. N) or electron-deficient (e.g. P, B). Recently, we presented a strategy for the selective synthesis of pyridinic- and pyrrolic-nitrogen-doped graphene (NG) by the use of layered montmorillonite (MMT) as a quasi-closed flat nanoreactor. The confinement effect of MMT extensively constrains the formation of quaternary N because of its tetrahedral sp3 configuration but facilitates the formation of planar N, i.e. pyridinic and pyrrolic N which have planar sp2 configuration. In consideration of the active sites only appearing in large quantities on the edges of numerous pores, a three dimensional network catalyst with a large amount of pores, was constructed. The cathode catalyst in a proton exchange membrane fuel cell produces a peak power of 600 mWcm-2, making this among the best non-precious metal catalysts for the ORR reported so far.

References

1. Wen-Jie Jiang, Lin Gu, Li Li, Yun Zhang, Xing Zhang, Lin-Juan Zhang, Jian-Qiang Wang, Jin-Song Hu, Zidong Wei, and Li-Jun Wan, J. Am. Chem. Soc., 2016, 138 (10), 3570.

2. Yao Nie, Xiaohong Xie, Siguo Chen, Wei Ding, Xueqiang Qi, Yao Wang, Jun Wang, Wei Li, Zidong Wei,and Minhua Shao, Electrochimica Acta, 2016 (187)1:153.

3. Guangping Wu, Jun Wang, Wei Ding, Yao Nie, Li Li, Xueqiang Qi, Siguo Chen, and Zidong Wei, Angew. Chem. Int. Ed. 2016, 55(4), 1340.

4. Rong Li, Zidong Wei, and Xinglong Gou, ACS Catal., 2015, 5, 4133.

5. Li Li , Xianghong Feng, Yao Nie , Siguo Chen, Feng Shi , Kun Xiong, Wei Ding, XueQiang Qi , Jinsong Hu , Zidong Wei , Li-Jun Wan, and Meirong Xia, ACS Catal., 2015, 5 (8), 4825.

6. Ding, Wei; Li, Li; Xiong, Kun; Wang, Yao; Li, Wei; Nie, Yao; Chen, Siguo; Qi, XueQiang; Wei, Zidong, J. Am. Chem. Soc., 2015, 137 (16), 5414.

7. Yao Nie, Li Li and Zidong Wei, Chem Soc Rev, 2015, 44 (8), 2168 -2201.

8. Wei Ding, Zidong Wei, Siguo Chen, Xueqiang Qi, Tao Yang, Jinsong Hu, Dong Wang, Li-Jun Wan, Shahnaz Fatima Alvi, and Li Li, Angew. Chem. Int. Ed. 2013, 52 (45), 11755-11759.

 

 

 

 

Innovative and efficient conversion of lignocellulose to lactic acid

Professor Jin Chuan Wu, Institute of Chemical and Engineering Sciences, A*SATR

The demand for optically pure lactic acid is increasing owing to the rapid growth of poly lactic acid (PLA) industry. Lactic acid is currently produced by microbial fermentation from starchy materials. To avoid the competition with the supply of foods and feeds, it is essential to produce lactic acid from lignocellulose, the most abundant renewable resource on earth. Oil palm empty fruit bunch (EFB) was hydrolyzed to get fermentable sugars at a total sugar yield of 90% by the combined use of dilute H2SO4 and H3PO4 in a 20 L Parr reactor. Furfural, 5-hydroxymethyl furfural and acetic acid in hydrolysate were sequentially degraded by simply adding the whole cells of the bacteria that were isolated from nature. Thermophilic Bacillus coagulans strains were isolated from the natural environment and used to convert all lignocellulose sugars to L-lactic acid at 50°C under no-sterilization conditions. In a simultaneous detoxification, saccharification and fermentation process, 129.7 g/L of L-lactic acid was obtained at a productivity of 4.6 g/L/h from EFB using cheap dry yeast cells as the nitrogen source. However, Ca(OH)2 was needed to control the pH during fermentation, which leads to the formation of CaSO4 during downstream processing. Effort is now being made to increase the acid tolerance of the thermophilic strains by whole cell mutagenesis to make the fermentation conduct at lower pH without the need of neutralization to further reduce the production cost.

 

 

 

On the electrostatics of granules and granular flows
Professor Jun Yao, China University of Petroleum-Beijing
In solid processing systems, electrostatic problems are commonly observed for granules and granule flows but a complete understanding of the basic dependence of electrostatic charge generation on single granule and granules has yet to be established. In this work, electrostatics was characterized for single granule based on the effects of granular front-facing angle, length-ratio, sliding area, sliding orientation, sliding times, relative humidity and granule surface roughness and then for granular flows based on the effects of pipe wall material, particle composition and relative humidity of the conveying air used. It was found that these factors are much important in determining the electrostatic charge generation characteristics and granular flow patterns observed. In addition, the methodology of coupling large eddy simulation (LES) with the discrete element method was applied for computational studies of pneumatic transport of granular materials through vertical and horizontal pipes in the presence of electrostatic effects. Based on dynamic analyses of forces acting on individual particles, it was concluded that electrostatic effects played a dominant role in influencing particle behaviours during pneumatic conveying at low flow rates, whereas drag forces became more important at high flow rates.

 

 

 

 

Optimal Design of methanol to olefin reactor: Effect of internal diffusion and coking

Professor Wen-De Xiao, Shanghai Jiao Tong University

Methanol conversion to olefins over zeolite catalyst has been being an active topic in the chemical and energy industries since 1980s, though it comes into practices lately in recent years. This process is divided into two kinds: ZSM-5 based and SAPO-34 based. The ZSM-5 based process produces propylene on-purpose with a trademark of MTP by the Lurgi Company using fixed-bed reactor, and the SAPO-34 based one produces both ethene and propene with a logogram of MTO using fluidized-bed reactor. Practically, MTO achieves much higher yield (over 85%) than MTP (about 60%), thus MTP process leaves much incentive to researchers for performance improvement. The author's group has carried out modest detailed investigations on MTP process in the reaction mechanism [1,2], kinetics [3-5] and reactor modeling [6-8], and found the reasons why the yield of the desired product is inferior to MTO: internal diffusion due to the coarse catalyst pellet and the lengthy contact time due to requirement for the interval regeneration of the coked and deactivated zeolites. The fluidized-bed reactor used in MTO is able to eliminate the internal diffusion and to regenerate the coked catalyst continuously, which can restrict effectively the side reactions for the undesired products: higher olefins, paraffins and aromatics and achieve satisfactory yield. Based on our fundamental researches, several strategies have been proposed for improvement of the current MTP industrial process and reactor. One is to optimize the recycling of the undesired higher olefins and make them contact the catalyst as little as possible. The second is to optimize the methanol conversion efficiency for each stage of the six-staged fixed-bed adiabatic reactor to count for the activity variation with time by the coking. The 3rd measures is to operate the multi-staged reactor stage by stage in full parallel other than in parallel for methanol feeding but in series for introducing the recycled higher olefins in the current mode. The 4th and the best one is to replace the fixed-bed by the fluidized-bed, which needs changes both in catalyst manufacturing and reactor configuration, and the operational scheme as well with the interval regeneration turned to continuous regeneration. This presentation will address the comparison of these four routes by the modeling and simulation based on our previous fundamental works and gives a hint for the reasonable choice of the reactors for methanol to olefins as a rule.

References:

[1] W. Wu, W. Guo, W. Xiao, M. Luo, Dominant reaction pathway for methanol conversion to propene over high silicon H-ZSM-5, Chemical Engineering Science, 66 (2011) 4722–4732;

[2] W. Wu, W. Guo, W. Xiao, M. Luo, Methanol conversion to olefins (MTO) over H-ZSM-5: Evidence of product distribution governed by methanol conversion, Fuel Processing Technology, 108 (2013) 19-24;

[3] X. Huang, D. Aihemaitijiang, W.D. Xiao, Reaction pathway and kinetics of C3-C7 olefin transformation over high-silicon HZSM-5 zeolite at 400-490ºC, Chemical Engineering Journal 280 (2015) 222-232;

[4] X. Huang, D. Aihemaitijiang, W.D. Xiao, Co-reaction of methanol and olefins on a high silicon HZSM-5 catalyst: a kinetic study, Chemical Engineering Journal, 286 (2016) 150-164;

[5] X. Huang, H. Li, W.D. Xiao, D Chen, Insight into the side reactions in methanol-to-olefin process over HZSM-5: a kinetic study, Revised to Chemical Engineering Journal;

[6] W. Guo, W. Xiao, M. Luo, Comparison among monolithic and randomly packed reactors for the methanol-to-propylene process, Chemical Engineering Journal, 207–208 (2012) 734-745;

[7] W. Guo, W. Wu, M. Luo, W. Xiao, Modeling of diffusion and reaction in monolithic catalysts for the methanol-to-propylene process, Fuel Processing Technology, 108 (2013) 133-138;

[8] X. Huang, H. Li, H. L, W.D. Xiao, A computationally efficient multi-scale simulation of a multi-stage fixed-bed reactor for methanol to propylene reactions, Revised to Fuel Processing Technology.

 

 

 

 

Controlling Enzymatic Enantioselectivity by Adjusting Molecular Interactions

Professor Hongwei Yu, Zhejiang University

Stereoselectivity is one of the most significant properties of enzymes, which makes them the preferred choice in the pharmaceutical and fine chemical industries. Therefore, discovery or creation of biocatalysts with excellent and desired stereoselectivity is of great interest.  However, tailoring of biocatalysts with desired stereoselectivity remains a major challenge due to the elusive nature of enzyme stereo-recognition.
To provide an improved understanding of the molecular basis for the stereoselectivity control, the esterases (BioH from Escherichia coli and RspE from Rhodobacter sphaeroides) and short-chain dehydrogenase/reductase (PpYSDR from Pseudomonas putida) were chosen for rational design. Since dimethyl 3-arylglutarate (for BioH and RspE) and halogenated acetophenones (for PpYSDR) were chosen as the target substrates, special attention was given to enzyme-substrate interactions involving the aromatic ring and halogen atom of the substrates considering their possible roles in the control of stereoselectivity. Thus, strategies involving the introduction/elimination of enzyme-substrate interactions (noncanonical interactions, including π-π interactions and anion-π interaction) and the decrease of steric hindrance were proposed for the stereoselectivity control of these enzymes.
As a result, the enantiomeric excess (ee) of the S-product of dimethyl 3-phenylglutarate was increased from 25% (BioH wild type) to 96% (B_L83F/L86F) and from 13% (RspE wild type) to >99% (R_Y27R), respectively, while another variant of RspE R_M121F gave a reversed ee of 50% (R-product). The stereopreference towards halogenated acetophenones of PpYSDR was successfully switched from Prelog to anti-Prelog through the introduction/elimination of noncanonical interactions and the decrease of steric hindrance. Mutants M85T/L136E and M85V/M187D completely inversed the stereoselectivity toward 3,5-bis(trifluoromethyl) acetophenone to the (R)-product with >95% ee, even the wild type PpYSDR was shown to be an excellent S-selective SDR for 3,5-bis(trifluoromethyl) acetophenone, with ee value of S-products >99%.
These results demonstrate that the enzyme-substrate interactions involving aromatic ring and halogen atom play critical roles in determining the stereoselectivity of these ketone reductions besides the steric repulsion. It is a new insight regarding the role of noncanonical interactions in protein engineering. This strategy could also be applied in altering enzyme stereoselectivity and/or activity toward other substrates with special functional groups.

 

 

 

Selective production of guaiacol using lignin extracted from black liquor

Professor Ying Zheng,University of New Brunswick

Lignin extracted from black liquor is selectively decomposed in hydrocarbon solvents - hexadecane (C16) and 1-methylnaphthalene (1-MN) to guaiacol and its derivatives, as high as 68% was obtained. Compositions of liquid products are also different with liquid products obtained from other thermal chemical methods, such as pyrolysis, liquefaction (with solvents of water, ethanol etc.). Hydrocarbon molecules are identified as active catalyst to promote the production of guaiacol compounds. According to bond dissociation energy, the decomposition mechanism of lignin was proposed. The selectivity for the guaiacol type compounds decreases in the following order: 4-methyl guaiacol < 4-ethyl guaiacol < guaiacol. The decomposed intermediate radicals can abstract H from hexadecane or 1- methylnaphthalene.


Key words: thermolysis; black liquor; lignin, guaiacol, 1-methylnaphthelene

 

 

 

 

 

 

 

 



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