Qatar Foundation Annual Research Conference Proceedings Volume 2016 Issue 1

In recent years, increasing concerns about climate change and the liberalisation of the energy market have provided the necessary impetus for a revolutionary restructuring of the electricity network. Traditional power networks are designed to operate in a passive and unidirectional way as their main functionality encompasses the transfer of energy from the power stations to the customer, with minimum loss. Increased electricity production from renewable energy sources (RES) coupled with energy efficiency lie at the heart of the ambitious targets set by Europe and globally in the quest to curb greenhouse gas emissions and to reach energy sustainability. As a result, complete restructuring of the electricity networks will have to take place in order to accommodate increased penetration of RES and distributed generation (DG) which is associated with electricity production from RES. Especially in regions with high solar irradiance, the penetration of photovoltaic (PV) systems is expected to increase in the near future as the technology becomes more competitive. High penetration of PV systems will definitely have serious consequences on the operation of the electricity grid and further challenges will arise as penetration levels increase. Thereafter the security and stability of the power system should be considered carefully to identify possible impacts due to uncontrolled deployment. The occurrence of power quality problems is not only negatively affecting utility customers but is also affecting the generated energy from Photovoltaic (PV) systems and the stability of the power system. The severity and frequency of occurrence of power quality issues can be the result of distribution grid topology/dynamics, arising due to high PV system concentration or even abnormal PV system operation. Analytical tools and accurate models of PV systems must be developed in order to evaluate their behaviour in the context of the full network. The utilization of accurate simulation models is of great importance in an attempt to assess the real consequences of localized energy production from distributed energy sources and in particular PV.

A common detailed PV system model is formed by a PV array, an inverter and a power grid interface as shown in Fig. 1.

Figure 1: General schematic of a Detailed Photovoltaic System.

The PV array is affected by the solar irradiance, the temperature and the specific characteristics of the chosen PV module technology. The PV array converts the solar irradiance into DC power which is then delivered to the distribution grid via the PV inverter. A Maximum Power Point Tracking (MPPT) Controller is used to absorb the maximum available energy. The MPPT Controller varies the duty cycle of a DC/DC converter to adjust the voltage at the output of the PV array (DC link A). The DC/DC converter is connected to a DC link (DC link B) of which the voltage is maintained constant by a DC/AC inverter circuit topology. In more detail, the DC/AC inverter is set to inject the power reaching the DC link B into the electricity grid and in that way the DC link B remains constant. A filter is always placed at the output of the inverter to eliminate undesirable harmonic currents produced by the switching operation of the inverter [1].

A generic PV system model for transient studies, the parameters of which can be tuned using transient data is developed in this work. The adopted analysis utilizes existing knowledge to formulate an accurate transient representation that considers the PV system control circuit and dynamics [2], [3]. The model is tuned and validated using transient data obtained from a detailed PV system circuit topology developed in Matlab Simulink via the Nelder-Mead simplex algorithm [4]. Its abstract representation is shown in Fig. 2. The proposed model is actually a three phase representation capable of simulating with sufficient accuracy normal/unbalanced operating conditions and voltage regulation. Harmonics are also incorporated into the model to reveal its capability for use in complete power quality studies.

Figure 2: Proposed Transient Photovoltaic System Model (TPVSM).

This PV system model is able to characterize the transient behaviour of PV systems in a generic way via a parameter estimation process. In addition, it enables the analysis of more aspects of power quality and voltage stability with higher accuracy under balanced and unbalanced conditions. It must also be pointed out that the proposed model is simpler and faster, thus allowing the computationally efficient simulation of complex problems.

Figure 3: Output current response to a step change in active power input.

The transient response of both the detailed and the proposed PV system model during a step change in active power input is shown in Fig. 3 (the reactive power input is kept at a zero value). In the next step, the developed model is used to assess the voltage transient response of a distribution grid busbar (point of common coupling of the PV system with the electricity grid) and the results are shown in Fig. 4.

The comparison is made with the “Theil inequality coefficient”. The specific inequality coefficient provides a measure of how well a time series of observed values compares to a corresponding time series of estimated values. A value of 0 indicates zero difference or perfect predictions, whereas a value of 1 indicates poor model performance. Values lower than 0.3 depict good agreement between estimated and observed data. As can be seen from the results and inequality coefficient in Figs. 3 and 4, good agreement has been obtained between the detailed and the proposed PV system model. It is important to stress that the proposed generic model can been tuned by using experimental data as well.

Figure 4: Transient reponse of voltage during a step change in reactive power reference.

In summary, the proposed generic model is in line with current DG standards as it can be used for studies of voltage regulation/power quality. The aim of the aforementioned research is to enhance the effort of assessing the consequences of high PV penetration and facilitate corrective action with appropriate technical solutions so as to enable the safe and unrestricted deployment of these technologies in electricity grids [5].

References

[1] S.-K. Kim, J.-H. Jeon, C.-H. Cho, E.-S. Kim, and J.-B. Ahn, “Modeling and simulation of a grid-connected PV generation system for electromagnetic transient analysis,” Sol. Energy, vol. 83, no. 5, pp. 664–678, May 2009.

[2] M. Liang and T. Q. Zheng, “Synchronous PI control for three-phase grid-connected photovoltaic inverter,” in 2010 Chinese Control and Decision Conference, CCDC 2010, 2010, no. 2, pp. 2302–2307.

[3] Z. Xueguang, X. Dianguo, and L. Weiwei, “A novel PLL design method applied to grid fault condition,” in Conference Proceedings-IEEE Applied Power Electronics Conference and Exposition-APEC, 2008, pp. 2016–2020.

[4] W. Bao, X. Zhang, and L. Zhao, “Parameter estimation method based on parameter function surface,” Sci. China Technol. Sci., vol. 56, no. 6, pp. 1485–1498, 2013.

[5] M. Patsalides, A. Stavrou, V. Efthymiou, and G. E. Georghiou, “A Generic Transient PV System Model for use in Power Quality Studies,” Renew. Energy, 2015, Accepted.

Energy is an expensive and scare resource and the world faces an energy crisis given our dependence on the limited supply of fossil fuels. Similar to other countries, in Qatar, energy consumption and the subsequent production of greenhouse gas emissions are becoming a major challenge that the society is facing. Recent statistics in Qatar indicated that the per-capita use of electricity and production of CO2-emission has been rising continually since 1971. Population growth and industrial development are the main sources of these problems. In 2004, the electricity consumption per capita reached 17000 kWh which puts Qatar as one of the highest energy consumer per capita in the world as it surpasses the average per-capita electricity consumption of the developed countries. Due to the high contribution of buildings in overall energy consumption, building energy performance has become a key approach to reduce energy consumption and the associated greenhouse gas emissions. Since the building energy performance depends on the numerous variables related to the building characteristics, installed equipment, occupants' behavior, and environmental loadings, selecting the most efficient combination of variables is highly complicated. Considering other objectives such as reduction of financial costs and minimizing the life cycle emission will increase the complexity of the decision making process. To solve these problems, different numerical methods such as optimization algorithms are proposed and utilized. Multi-objective design optimization is a powerful tool to assist decision makers identify and implement the most efficient strategies. The multi objective optimization algorithms are capable of determining the proper variables to obtain the optimum design. Therefore, the objective of this work is to tackle the problem of determining the best design by implementing a harmony search (HS) based optimization algorithm to minimize the life cycle cost and life cycle CO2 equivalent emissions of a small office building. Parameters considered in the current investigation model are building materials and their associated thickness in different building components including wall, floor, roof, and ceiling. In addition, different HVAC systems are considered as design variables. HS algorithm was conceptualized using the musical process to identify the perfect state of harmony. HS was initially developed for the discrete variable optimization problems and then expanded to include continuous variable problems as well. Simplicity in implementation and flexibility of the algorithm has increased the utilization of this method in many research fields. In difference with other optimization methods which are usually based on the numerical linear and nonlinear programing methods that require gradient information to seek the solution, HS algorithm does not utilize gradient information. To achieve this objective, price data and emission data are collected and magnitudes of each one calculated according to the simulation results. The first objective is to minimize the life cycle cost of the design. To identify the life cycle cost of each model, the summation of present value of initial costs, operation and maintenance costs, and energy costs are calculated. The data for construction costs are taken from construction handbooks. In this study, the building life is assumed to be 40 years. For the life cycle assessment, all phases of pre-use (extraction, transfer, and processing of materials), use (service and maintenance), and end-of-life (demolishing and transfer of wastes) of the modeled building have been considered. The pre-use phase costs include the material prices, labor costs, replacement, and equipment. The use-phase includes the service energy costs (heating, cooling, water heating, lighting, equipment, etc.) which are determined by the energy simulation. The second objective of this study is to minimize the life cycle emission of the design. The life cycle emission of each design is determined based on the emission of global warming potential (GWP) data of different materials during pre-use, use, and end-of-life. The pre-use emission can be calculated by having the weight of each material used in construction of the building and multiplying with the emission amount per unit weight. The environmental emission data are collected through different LCA datasets such as DEAM and EcoPack. The use phase emission includes two types of emissions: energy related and service-maintenance. For the energy related emissions, the emission factor of electricity consumption is determined according to the location and source of energy generator systems. To calculate the maintenance emission during the use period, a list of materials and mass of each which should be replaced was prepared. The post-use phase energy consumption includes all the emissions related to demolition and disposal of wastes and the regarding data were gathered through life cycle analysis data bases. In order to optimize the process of designing of the small office building in this study, a C++ code which is capable of modifying model characteristics, perform energy simulation, evaluate the results, and identify the next simulation magnitudes was developed. The proposed HS optimization algorithm, first selects and assigns random magnitudes for the initial values of variables. This selection is a random selection through the defined ranges for variables. Then a simulation of the initial model is performed to attain the first sets of results (objective functions). HS algorithm evaluates the objectives and sets the new values for variables for next simulation. The results of next simulations will be compared with results of previous simulations. If the results in each simulation are better than worst solution, worst solution will be replaced by new results. The solution of the optimization problem improves by having multiple simulations gradually. To determine the energy consumption of the building in the use phase, EnergyPlus model of the building including building envelope system details, thermal zones temperature set points, occupants' activity type and schedule, types of HVAC system, equipment loadings, lighting system schedule, and design year weather data was prepared. EnergyPlus is a powerful energy simulation program for modeling building energy performance and capable of modeling multi-zone airflow, thermal comfort and natural ventilation systems, as well as determining the amount of energy was utilized to determine the total building energy consumption. The focus of this study is to determine the optimum building construction materials and their associated thickness as well as HVAC system of a small office building located in Doha, Qatar. Heat pump air to air ventilation system is assigned to this building and zones' temperature set points are fixed on 22 °C for heating and 26 °C for cooling. Running the simulation process parallel to the optimization algorithm evaluation resulted in identifying multiple optimum solutions of building construction materials and their associated thickness as well as HVAC system. In order to offer decision makers the chance to evaluate the tradeoff between cost and emissions, the Pareto front is plotted. In addition, comparing designs with different life cycle costs and emissions resulted in the following conclusions: By comparing the life cycle cost and carbon dioxide emission of different designs, it was concluded that assigning a small modification in life cycle cost can significantly change the CO2 equivalent emissions. Foundations, floors, and ceilings are emitting the highest amounts of carbon dioxide equivalent in building. Using of high emission materials with higher thickness comparing to other construction materials are the main reasons of this contribution. The outcomes of this research, assists designers in identifying the best combination of envelope materials to design energy efficient buildings. It remains for future to investigate the effects of working schedule, and control strategies in optimum design of buildings.

Oilfield reservoir characterization with a nonradioactive Kr isotope tracers with collinear fast beam laser spectroscopy (CFBLS) has been developed in our laboratory and has unprecedented sensitivity, selectivity and dynamic range. It provides efficient method of reservoir mapping, which is much safer than commercially available radioactive isotope based enhanced oil recovery approaches. Our approach can be used in far and near borehole surveys and to quantify fracturing efficiency. The analytical system uses mass separation in conjunction with highly selective laser excitation and sensitive optical detection. For similar applications we also implemented a novel optical spectroscopy based on frequency comb lasers (FCL) that have a regular comb structure of millions of laser modes for ultra broad band detection. Especially in the infrared, a plethora of green house and other gases have molecular fingerprint spectra that can be studied with FCL, based mainly on the Er-, Yb-doped fiber lasers with their wavelength ranges extended by optical parametric oscillation processes, supercontinuum or difference-frequency generation. We present our work on trace isotope detection that utilized both techniques. As examples we describe analysis of crude oil and well gas samples based on the research in Qatar, and the monitoring of the methane content of seawater in the aftermath of the oil spill in the Gulf of Mexico. This work was supported by the by the Robert A. Welch Foundation grant No. A1546 and the Qatar Foundation under the grant NPRP 5-994-1–172.

Global environmental and resource concerns dictate that future energy supply and security will become increasingly dependent upon the development of accessible, sustainable and scalable energy technologies. State-of-art polymer solar cells (PSCs) has been considered as one of the renewable important technologies which can harvest solar energy from sunlight to generate electricity. Intensive research efforts from both academia and industry have been dedicated into solution-processed organic solar cells due to development of the next-generation solar cells technology 1,2. Owing to the readily available carbon feedstock as well as the numerous and flexible synthetic pathways, polymer solar cells (PSCs) gained tremendous attentions over silicon solar cell in the past decay due to low- cost and quick energy pay-back, solution-processable, lightweight, and flexible/stretchable, large area photovoltaic panels. 1,2 So as to achieve the high performance solar cells it is very important to develop novel kinds of active materials, which have to cover entire solar spectrum i.e. from ultraviolet to infrared (IR) regions, suitable molecular energy levels morphologies and high mobilities. Several donor-acceptor (D-A) conjugated polymers are reported recently with photovoltaic performance over 10%. 3 However, in D-A PSC materials have high intrinsic torsional defects, which impacts the negative impact on performance of the OPV devices. The torsional defects partially break the conjugation pathways of the polymers, leading to shortened coherent lengths along the polymer chain and decreased carrier mobilities. Meanwhile, the torsional defects perturb the intermolecular packing of the polymer materials so that the electronic coupling between the polymer chains are interrupted, adding an energy barrier for the charge carriers and excitons to transport within the active layer. 4 Moreover, the torsional defects increase the band gap of conjugated polymers, hence to prevent their photo-absorption in longer wavelength region. Overall the torsional defects often lead to larger π–π stacking distances in the polymer thin film, making the thin film more susceptible to the permeation of oxygen and water, hence decreasing the stability of the overall OPV devices. Our approach looks into ways to overcome the drawbacks raised by torsional defects on a fundamental level. By definition, Ladder polymers consist of cyclic subunits, connected to each other by two links that are attached to different sites of the respective subunits, comparable to a graphene nanoribbon. Consequently, ladder polymers have two or more independent strands of bonds which are tied together regularly without merging to a single or double bond or crossing each other. 4 As a result, ladder polymers have large planar core structures with no torsional defects. Such defect-free feature grants them with rigid and hence highly conjugated core structures. On one hand, the highly conjugated cores not only afford low band gaps that allow strong optical absorption at long wavelength in terms of energy absorption, but also lead to low beta value for coherent tunneling and low activation energy for electron hopping, in terms of charge transport alongside the polymer chains. There were many carbazole-containing organic D-A polymer materials has been demonstrated for high performance solar cell applications and no such types of ladder polymers reported by utilizing carbazole core. 5 Herein, we report the synthesis of fully conjugated carbazole-based ladder polymer with low level of unreacted defects, by utilizing the controlled ring-closing olefin metathesis (RCM) reaction. The designed ladder polymer is well soluble in common organic solvents for solution processability. We also discussed the photo-physical, electrochemical and optoelectronic properties of torsional defect-free ladder polymers.

References

[1] L. Lu, T. Zheng, Q. Wu, A. M. Schneider, D. Zhao, L. Yu, Chem. Rev. 2015, DOI: 10.1021/acs.chemrev.5b00098.

[2] L. Dou, Y. Liu, Ziruo Hong, Gang Li, Y. Yang, Chem. Rev. 2015, DOI: 10.1021/acs.chemrev.5b00165.

[3] J-D. Chen, C. Cui, Y.-Q. Li, L. Zhou, Q.-D. Ou, C. Li, Y. Li, J.-X. Tang, Adv. Mater. 2015, 27, 1035.

[4] A.-D. Schluter Adv. Mater. 1991, 3, 283.

[5] J. Lee, B. B. Rajeeva, T. Yuan, Z. Guo, Y. Lin, M. Al-Hashimi, Y. Zheng and L. Fang, Chem. Sci., 2015, DOI: 10.1039/C5SC02385H.

Managed aquifer recharge focuses on increasing the availability of potable water within the subsurface. Under managed aquifer recharge, recycled or excess water is diverted into large infiltration basins that allow water to percolate into the subsurface thus increasing the volume of water within the shallow aquifer. Water can then be extracted during periods of increased demand and provided water security. This widely used technique has low energy costs and can significantly enhance the amount of groundwater recharge. However, infiltration rates can decrease as a result of clogging of sand grains within these infiltration basins and thus increase the percentage of water lost to evaporation. Rapid detection of decreases in infiltration can trigger remedial action in order to prevent further water loss. The research presented here focuses the development of passive thermal tomography; a new technology to (1) quantifying infiltration rates of managed aquifer recharge at meter scale resolution and (2) to determine aquifer heterogeneity within the subsurface. Passive thermal tomography uses temperature as a groundwater tracer to monitor infiltration rates over large areas, such as infiltration basins. The temperature of the surface water in infiltration basins fluctuates due to the daily solar heating and cooling cycle, and the resulting diel signal propagates down into the subsurface. As the rate of infiltration increases or decrease, the thermal signal produced at the land surface will shift at depth as a result of the advective transport of groundwater. Through the monitoring of shifts in the temperature signals at two discrete depths it is possible to quantify the rate of groundwater infiltration. By extracting the amplitude ratio or diel phase-shift at these two depths, recharge rates can be quantified across the infiltration basin. These methods assume vertical and steady flow of water, quasi-steady (cyclic) flow of heat, through homogeneous, isotropic, fully saturated sediments, and temperature measurements collected in a vertical profile. It should be noted that sensitivity analyses have demonstrated the uncertainty of flux calculations due to inaccurate thermal properties and sensor spacing. Uncertainties in both thermal properties and sensor spacing have been evaluated in this research using a fully coupled numerical model. Taking advantage of this natural passive signal, it is possible to detect temporal changes in the daily rate of groundwater recharge as well as seasonal changes, due to clogging of the pores. Using the calculated rates of groundwater infiltration, an inverse, fully coupled groundwater flow and heat transport model is run in order to determine heterogeneity in hydraulic conductivity within the aquifer. Using thermal and hydraulic boundary conditions at the surface and groundwater flux estimates based on the evaluation of amplitude/phase-shits in the thermal signature with depth, it is possible to determine a suite of hydraulic conductivity scenarios that match the true conditions within the aquifer. This inverse modeling approach using thermal tomography allows for the quantification of changes in hydraulic conductivity across the infiltration basin. While groundwater flux is based on a two dimensional grid, the inversion of the numerical model is able to represent a quasi three-dimensional change in hydraulic conductivity. Passive thermal tomography addresses the protection and management of groundwater resources through the quantification of artificial recharge. Current techniques to quantify artificial recharge are either based on point measurements or simple conservation of mass calculations. Through the use of this new technique it is possible to better monitor and maintain artificial infiltration basins in order to support sustainable and secure groundwater resources in Qatar.

Controlling the operation of polymer reactors is a highly important task that aims at maximizing the production rate and the product quality and also minimizing the transition losses due to the high consumer demands, as well as the tight market competition for producing different grades of polymers. However, the control design task is nontrivial due to the nonlinear behavior of polymer reactor systems which exhibit strong dependence on multiple operating regimes, unstable modes at some operating points as well as time-varying parameters. In this work, linear parameter-varying (LPV) control techniques are considered to control a free radical solution copolymerization reactor. LPV systems describe a class of nonlinear/time-varying systems that can be represented in terms of parameterized linear dynamics in which the model coefficients depend on a number of measurable variables called scheduling variables. The LPV controller synthesis tools extend the well-known methods of controlling linear time-invariant (LTI) systems to control nonlinear systems with guaranteed stability and high performance over a wide range of operation. In this work, the LPV representation of the copolymerization reactor is obtained through a transformation capturing the system nonlinearities in 15 scheduling variables. With this high number of scheduling variables, the design of LPV controller involves two major problems. On one hand, for control synthesis design, the number of linear matrix inequalities (LMIs) to be solved increases exponentially with the number of scheduling variables, hence the problem becomes computationally intractable. On the other hand, overbounding the range of the scheduling variables often renders the LPV model to include some behaviors that are not exhibited by the original plant, which results in conservatism. In order to cope with the high number of scheduling variables, two approaches for reduced LPV model development for the copolymerization reactor are introduced. The aim of this work is to emphasize the capability of the LPV controllers, designed on the basis of reduced models, to provide high performance control of the polymerization reactor by enhancing the settling time of the output and reducing the control effort. In the first approach, the number of scheduling variables is reduced via the parameter set mapping (PSM) procedure based on principal component analysis (PCA). PSM is an effective way to reduce the conservatism in LPV modeling by resizing the scheduling range such that the reduced model matches the original system behavior as closely as possible. With this method, the complexity of the LPV model of the copolymerization reactor is ideally reduced into one scheduling variable, which allows a minimal design complexity. However, the synthesized controllers may not guarantee the closed-loop stability and performance with the full nonlinear model of the copolymerization reactor since they are designed based on an approximation of the nonlinear model. The second method is based on an alternative conversion of the nonlinear model to an LPV form by truncating the state variables that have no significant role in the state evolution. This method is a specific model reduction approach aiming at reducing the complexity, as well as the number of scheduling variables of the model while the input-output behavior of the original system is preserved. The resulting reduced LPV model of the copolymerization reactor has 4 scheduling variables, which is a relatively large number. However, the stability and performance of the original plant are guaranteed with such controller. Once the operating region and the resulting LPV models are determined, a control design methodology is applied on each produced model. For the LPV-PSM approach, LPV H_infty control synthesis is used to synthesize an LPV controller for the reduced LPV model of the reactor. For the reduced order based model, a linear fractional transformation (LFT) based LPV controller synthesis approach is used since it is capable of handling plants with relatively large number of scheduling variables while maintaining low design complexity. However, the implementation of the designed LPV controllers requires the availability of all the scheduling variables, some of which are not measurable in the reactor model. Therefore, an extended Kalman filter (EKF) is designed for the nonlinear model of the copolymerization reactor in order to estimate its state vector. A comparative analysis of the closed-loop performance is done between the synthesized LPV controllers and the model predictive controller (MPC) developed in the literature. The PSM based LPV controller, based on one scheduling dimension LPV model, has shown a better disturbance rejection without either output oscillation or input saturation and a convergence time of 9 hours, which is lower than the reduced order based LPV controller and the MPC controller whose convergence times are 10 hours and 15 hours, respectively. This enhancement in the closed-loop performance is due to the low conservatism of the design by the PSM approach. However, the inability to guarantee the closed-loop stability with the nonlinear reactor model remains the main drawback of the PSM procedure, whereas the stability is guaranteed with the LPV controller based on reduced order LPV model. As a conclusion, a trade-off is illustrated by the low complexity and good performance on one hand, and the stability guarantee of the closed-loop system with the nonlinear model of the reactor on other hand.

Carbon emission is a concern across the industry due to its environmental impact. In order to reduce carbon emissions, industry have to look not only at their processes but also in the generation of emissions in the whole supply chain that it belongs to. This is more necessary when various forms of carbon emissions policies are faced by the industry. The current focus on research is either in the economics of supply chain or mainly on the forward or reverse supply chains when it pertains to the carbon emissions. However, as lifecycle of the product is also becoming important, the isolated treatment of supply chains should be avoided for an integrated (forward and reverse) supply chain, also called the closed loop supply chain (CLSC). The complexity arises when the supply chain is faced with different kind of carbon policies implemented by the governments, for example, carbon tax, carbon cap, and carbon-cap and tax. The design of CLSC may change with the change in the carbon emission policy. In this research, a stochastic model is developed for the design of a CLSC by considering carbon emission policies. This work is one of the first attempts to understand the implication of carbon emission policy on the design of a CLSC. The model is applied to a sample case of aluminum industry with a life cycle assessment of emission.

Our preliminary findings include:

(1) When the more scenarios are taken into account, the total cost and emission would increase, because more uncertain information is considered in CSSC design.

(2) Given the same carbon cap, in a broad sense, the amount of emission credit traded in market changes in line with the total emission. It indicates that the emission trading is determined by the actual emission rather than the carbon price, even the uncertain carbon price is considered. However, a higher emission does not always lead to a bigger amount of emission to be traded.

(3) The network structure obtained by the deterministic formulation is not able to be easily adapted to changes in demand and supply.

(4) In order to deal with the uncertain demand, the CLSC has to enlarge its handling capacity by using the facilities with a higher capacity or incorporating more facilities with the same function. With the same purpose, the supplier selection decisions are also changed associate the increasing scenarios.

(5) The fuel of diesel is selected regardless of the scenarios. It means the current carbon price level would not motivate the firms to gain profit or reduce costs by employing future fuels in transportation. This conclusion is also proved by the further investigation when the total cost and emission are observed under decreasing cap. A further investigation reveals the transportation mode doesn't change when the carbon price increase from 9 to 234. Consequently, the future fuels would be attractive to firms only when the transportation price reduced or other policy environment changes, such as government subsidy. The efforts in reducing the transportation cost with future fuels have never ceased and the advanced technologies in automobile industry provide opportunity for green transportation promoters.

N-Heterocyclic Carbenes (NHCs): Over the last two decades N-Heterocyclic carbenes (NHCs) have immensely attracted chemists in nearly all fields of chemistry. N-Heterocyclic carbenes are commonly encountered in coordination chemistry, they are extensively used as ligands for organometallic complexes. Perhaps the biggest hit of NHCs ligands was their use in Grubbs II catalyst for olefin metathesis chemistry. It is noteworthy that the success of NHCs ligands in catalysis is due to several factors favoring their high activity, selectivity and stability when compared to the phosphine counterparts in Grubbs I catalyst [1]. Supported Catalysts: Increased environmental and health awareness requires that designing new metal-catalysts should focus not only on increasing activity and selectivity but also on finding new strategies that help chemists recycle and separate the metal-catalyst from the reaction mixture. In general, homogenous catalysis is preferred over heterogeneous catalysis. This is due to the higher turnover number, better selectivity and usually lower operating temperatures required. On the other hand, heterogeneous catalysis has the advantage of the ease of separation of the catalyst from the final products and is generally less expensive. One important strategy is to use catalysts attached to a heterogeneous support and separate them from the products by simple filtration. Alternatively, homogeneous catalysts that can self-separate from the products by selective solvent extraction would be of great interest. The frequency of their reuse would be environmentally beneficial and to a higher extent this should overcome the lower activity of conventional heterogeneous catalysts. Metal catalysts that can self-separate from the reaction mixture are of great importance due to the reduced metal leaching into the product mixture. In addition, their reuse and recovery make this overall process much greener compared to the conventional homogeneous/heterogeneous catalysis systems. Ever since Herrmann et al. [2] reported the polystyrene supported NHC-palladium catalyst, studies have largely been focused on the use of polymeric supports for NHC-palladium catalysts. While polyethylene-glycol-supported catalyst can be extracted with a polar solvent, Bergbreiter et al. [3] and others have showed that polyisobutylene (PIB) is a useful support for ligands and their metal catalysts (Pd, Ru…) having preferable solubility towards solvents with low polarities such as hexanes, heptanes and decanes. In all of these biphasic systems for cross-coupling/olefin metathesis, the design is mainly focused on the recovery and the reuse of the supported catalysts. Biphasic catalysis having thermomorphic behavior have witnessed great developments due to their temperature-dependent miscibility [4]. While reactions in these biphasic mixtures can be conducted under homogeneous conditions at high-temperatures, the supported catalysts and the products/by-products can be efficiently separated by restoring the biphasic conditions at a low-temperature (Scheme 1). Herein we report the synthesis of new PIB-supported N-heterocyclic carbenes ligands having two different frameworks and their Pd-complexes, 1 and 2. The use, recovery and effectiveness of catalysts are detailed in both Heck and Suzuki cross-coupling reactions (Scheme 2). Metal leaching to the polar phase will be discussed too. Scheme 2: Heck cross-coupling and Suzuki cross-coupling using catalysts 1 and 2.

References:

[1] Scholl, M.; Ding, S.; Woo-Lee, C.; Grubbs, R. H. Org. Lett. 1999, 1, 953.

[2] Schwarz, J.; Böhn, V. P. W.; Gardiner, M. G.; Grosche, M.; Herrmann, W. A.; Hieringer, W.; Raudaschl-Sieber, G. Chem. Eur. J. 2000, 6, 1773–1780.

[3] (a) Bergbreiter, D. E.; Su, H-L.; Koizumi, H.; Tian, J. J. Organomet. Chem, 2011, 696, 1272. (b) Bergbreiter, D. E.; Tian, J. Tetrahedron Lett. 2007, 48, 4499–4503.

[4] J. A. Gladysz, Dr. C. Rocaboy Chem. Eur. J. 2003, 9, 88. (b) Al-Hashimi, M.; Hongfa, C.; George, B.; Bazzi, H.S.; Bergbreiter, D. E. J. Polym Sci Part A: Polym. Chem., 2012, 50, 3954. (c) Al-Hashimi, M.; Abu Bakar, M.D.; Elsaid, K.; Bergbreiter, D. E.; Bazzi, H.S. RSC Advances, 2014, 4, 43766.

“Research for the future” is the roadmap of research at Qatar University for 2014–2019 [i]. It identifies the research priority themes based on Qatar's needs and on National Development Strategy 2011–2016. The following themes are the research priorities of Qatar University 1) Energy, Environment and Resource Sustainability, 2) Social Change and Identity, 3) Population, Health and Wellness and 4) Information and Communication Technologies. This strategy is also aligned with the Qatar National Research Strategy 2012 with a vision for Qatar to be a leading center for research and development excellence and innovation [ii]. Materials Science is the heart of economic growth as it is related to all areas of energy, environment and sustainability. This presentation will show the Center for Advanced Material (CAM) as a leading model for theme number one “Energy, Environment and Resource Sustainability”. CAM has grown from a small unit with five people in 2008 to a state-of-the-art center that has more than fifty-five members in 2015 working in various leading projects, this includes a high contribution of female scientists. This number does not include the students, short period visitors and daily visiting QU members. Examples of current research projects in the Materials Science and Nanotechnology subtheme will be presented. This will include research done in collaboration with the industry, mainly local oil and gas industries, and international institutes around the world. Projects such as corrosion protections, energy conservations techniques, medical application and sustainable materials are some examples. Emphasis will be made on emerging trends in technology to manipulate the atoms at the nano level for various technology applications. These improvements in this small scale can lead to improvement in the performance of traditional materials to reduce the energy consumption and cost. The state-of-the-art equipment and high quality accredited labs will also be shown. The presentation will explain a wide range of equipment in synthesis, processing and characterization stages. Graduate and undergraduate students' involvement in the activities as part of their courses, thesis dissertations or working as RAs in projects will be shown. Scientific trips to external institutes and industry as well as continuous exposure of the students to the local industry improved their learning abilities. The presentation will also show selected projects contributing to the other themes, especially in the Health and Wellness. This will include new synthesized nanoparticles that can fight the diseases such as cancer and new biomedical nanofibres for medical applications. Social Change and Identity is another priority that CAM is contributing through many leading projects such as the WISE 2015 wining project AlBairaq and the archeology studies in collaboration with the Qatar Museum Authorities.

Qatar National Research Strategy, Qatar University Research road map, Center for Advance Materials, Nanotechnology

[i] Research for the Future, Road map of research at Qatar University 2014–2019.

[ii] Qatar National Research Strategy (QNRS) 2012.

1. Abstract:

This work aimed to explore common methods for the extraction of pesticide and to perform qualitative and quantitative analysis by gas chromatography coupled with electron impact mass spectrometry (GC-EI-MS). Extraction was conducted using QuEChERS and Liquid–Liquid (L–L). Calibration curve and standard addition curve were both plotted for different concentration of mixtures. Additionally, the efficiency of the QuEChERS extraction methods was examined by spiking the organic rice and tomato with standard mixture of pyrethroid and carbamate and applying the extraction. Results showed that, in general, carbamate species (especially the aliphatic types) were eluted at earlier times compared to pyrethroids species. Carbamates were more susceptible to degradation during GC separation compared to pyrethroids. A chromatographic resolution of 3.24 was obtained for the two permethrin isomers. Good linearity of the three quantitative methods (R2 > 0.99) were obtained for most compounds. Based on using the standard addition curve, the recovery for the different pyrethroid and carbamate compounds were determined.

2. Introduction

Pesticides poisoning of farmers are largely attributed to the inappropriate pesticide handling, improper use of personal protective equipment (e.g., gloves, respirators, and masks) and lack of knowledge about the toxicity of chemicals that they contain. Common misuses of pesticides in farming include the use of large volumes or concentration of pesticides than indicated on labels, ineffective use of protective equipment while mixing or applying the pesticides, improper management and disposal of pesticides, and lack of awareness of pre-harvest intervals following application. This causes high level of pesticides residues in fruits and vegetables. Therefore, pesticide management is of great necessity. Common methods used to extract pesticides can be classified into three types: liquid–liquid extraction, solid phase extraction (SPE), and Soxhlet extraction. One important and recently developed extraction method is QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) [1]. QuEChERS offers simple simultaneous extraction and clean-up steps of a wide range of analytes, in both polar and non-polar samples. It is a faster, convenient and cost-effective method than conventional liquid–liquid extraction producing premium results in a few steps with minimum solvent amount used. Two types of pesticides (carbamates and pyrethroids) were the focal points of this research. Carbamates are a group of pesticides which contain carbamic acid backbone. The high solubility of carbamate derivatives allows plants to absorb them by the root and the leaves [2]. Pyrethroids are synthetic insecticides derived from the naturally found pyrethrins. Although pyrethroids are more specific to insects, with less impact on human and environment, they are not widely used because of their short life-time compared to other synthetic pesticides [3–4].

3. Objectives

The primary aim of the research is to explore the use of common methods for the extraction of pesticides from foodstuffs and to qualitatively and quantitatively analyze them by GC-MS method. Calibration curve and standard addition were utilized as quantitative methods. The recoveries of QuEChERS extraction of carbamates and pyrethroids from spiked rice and tomato were evaluated. This work was also aimed to improve the skill of mass spectra interpretation and conducting scientific literature surveys.

4. Experimental

4.1. Instrumentation and operational conditions

GC-MS (Shimadzu QP-2010) was used for the analysis of the pesticides. DB5 (30 m, 0.25 mm, 0.25 μm) column was used for the separation of pesticides. Scanning mode was used to identify the pesticides, while selective ion monitoring mode was used to determine their concentrations. The operational condition of the GC and MS are shown in Table 1 and 2.

4.2. Materials

The standards (Carbamate & Pyrethroids) pesticides were purchases from Dr. Ehrenstorfer GmbH, Germany. The contents of each mixture are shown in Table 3. The QuEChERS kit was purchased from Agilent Technology (U.S.A). The QuEChERS kit (Agilent, U.S.A), consisted of premeasured packet of MgSO4/Na-acetate mixture, and three types of DSP cleanup kit, which came in three different led-colors (red, blue and green), containing MgSO4/PSA DSP in different ratios.

4.3. Preparation of standards for quantitative analysis

Four standard samples containing mixture of both pyrethroids and carbamates were prepared. The standards only differed in concentration (0.125, 0.25, 0.50, and 1.0 ppm). These standards were analyzed by the GC-MS to obtain the calibration curve. The standards were also used in standard addition analysis.

4.4. QuEChERS extraction

About 15 ml of tomato juice was transferred into 50 mL tubes. 15 mL of acetonitrile was added to the tube. The extraction of rice is performed following similar steps, but prior to the addition of acetonitrile, the rice was mixed with equal amount of distilled water. Then the 50 mL tube was shaken for 30 seconds. After that, premeasured packet of mixture (MgSO4/Na-acetate) was added to each tube and shaken again vigorously for 1 min. The tubes were placed in ice for five minutes to allow the liquids to separate in two layers. The upper liquid layer was collected into another 50 mL tube.

4.5. Liquid–Liquid (L–L) extraction

About 200 g of blended tomato was placed in an Erlenmeyer flask. 150 mL of solvent mixture (3:2:1) (n-hexan:DCM:ACN) was added to the sample. The mixture was shaken for about one hour. The two immiscible phases were left overnight to separate into two layers. The upper layer was transferred into graduated cylinders.

4.6. The cleanup steps

Extracts (each one mL) from the two previous extraction procedures (L–L and QuEChERS) were transferred into two dispersive cleanup tubes, containing 150 mg of MgSO4 and 25 mg PSA. The extracts in the tubes were shaken for one minute and centrifuged for 5 min. The extracts were then transferred into vials and stored in the refrigerator, ready to be analyzed by the GC-MS.

4.7. Recovery study of QuEChERS method

For the recovery study of QuEChERS extraction method, the organic tomato and rice were spiked before the extraction with known amount of mixture consisting of carbamates and pyrethroids. The mixture was prepared by mixing 15 mL of carbamates (20 ppm) with 15 mL of pyrethroids (20 ppm) to produce a concentration of 10 ppm for each compound in the mixture. Then, 200 g of organic tomato and organic rice were spiked with 15 mL of the prepared mixture. Based on this spiking, the concentration of each pesticide compound in the tomato and rice before extraction should be ∼0.70 ppm. To determine the concentration of pesticides after extraction, standard addition method was used. The QuEChERS extract was first diluted to half its original concentration. Then the extract was divided into three 1.0 mL portions. In the first, second, and third portion, 0.50 mL of standards mixture with concentration of 0.125 ppm, 0.250 ppm, 0.50 ppm were added, respectively.

5. Results and discussion

5.1. Qualitative and Quantitative Analysis of Pesticides

The chromatograms of carbamates and pyrethroids are shown in Fig. 1 and Fig. 2, respectively. Generally carbamates species were eluted at lower retention time (tr) compared to pyrethroids. Aliphatic carbamate derivatives were even observed at lower tr compared to the aromatic species, and they were more susceptible to degradation. Isomers of both resmethrin and permethrin were very well resolved with resolution > 3. The peaks in the chromatogram can be identified based on their fragmentation and isotopic pattern in the mass spectra by matching the patterns with those available in the GC-MS software library. Two peaks, at 7.08 & 8.85 minutes belong to promecarb. The first peak was attributed to the degradation while the second was attributed to the fragmentation of promecarb as shown in their mass spectra in Fig. 3 (a, b). Observing the parent ion peak at m/z =  207 Da confirm that the mass spectrum in Fig. 3 (b) belong to the fragmentation (not the degradation) of promecarb. Also, logically, the degradation product of any compound is expected to be observed at earlier retention time. It was notices that the C–O bond of the carbamate backbone is more likely to break down. According to Wang and Schnuta [5], carbamates are polar and/or thermally labile and not suitable for GC analysis. Aromatic compounds (resmethrin and permethrin) were less susceptible to degradation as observed, for instant, in the mass spectrum of permethrin (Fig. 4). According to the isotopic pattern, two chloride atoms are present in the fragment at m/z =  163 Da. The proposed fragments for permethrin are shown in the spectrum in Fig. 4.

5.2. Quantitative analysis and recovery results

Calibration curves for all standard pesticides were plotted. Also, standard addition method was used to determine the recovery of QuEChERS extraction method for these pesticides. The unknown concentration of carbamate residues in the tomato extract (after extraction) was determined by adding different concentrations of standards and plotting the curve as shown for 3-Hydroxycarbofuran (3-HCF) in Fig. 5. The lines are extrapolated to obtain the concentrations of the extracts before the addition of standards. The recovery was calculated as following, taking 3-HCF as example. Since the extract before addition of standard was diluted to half of its original concentration, the concentration of 3-HCF in the original extract is calculated as: 0.28 ppm ×  2 =  0.56 ppm, where 0.28 is the value intercepted by extrapolation in the x-axis. Then, the recovery was calculateda as follows: Recovery =  (Extracted conc/original conc) × 100 =  (0.56/0.70) ×  100 =  80%. The linearity of the standard addition curves was acceptable, with correlation coefficient (R2) higher than 0.99. The recoveries of the other pesticides were calculated similarly and they are shown in the Table 4.

6. Conclusions

Fragmentation of compounds by GC-MS allowed identification of peaks in the chromatograms. Most of the carbamate compounds degrade in the GC-column, especially the non-aromatic species. The chromatograms illustrate that the non-aromatic carbamate compounds are found at low retention time unlike the aromatic ones. The C-O bond of the carbamate backbone is more likely to break down by either degradation in the GC column prior MS ionization, or fragmentation in the MS via the ionization source. The quantitative analysis is performed chiefly by three methods, which are standard calibration curve, standard addition. All these methods gave acceptable linearity with R2 > 90%. Standard addition is an alternative to the calibration curve technique that is useful to determine compounds in complex matrices and to measure the recovery of extraction methods.

Acknowledgment

This research work was made possible by UREP grant # UREP 13-040-1-007 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.

References

[1] Wilkowska A, Biziuk M (2010). Determination of pesticide residues in food matrices using the QuEChERS methodology. Food Chemistry, 125, 803–812.

[2] Gupta RC (2006). Toxicology of organophosphate and carbamate compounds. Amsterdam: Elsevier Academic Press. 673–681.

[3] Mishra D, Tripathi S, Srivastav SK, Suzuki N, Srivastav AK (2010). Corpuscles of Stannius of a teleost Heteropneustes fossilis following intoxication with a pyrethroid (cypermethrin), 6, 2013–208

[4] Palmquist K, Salatas J, Fairbrother A (2012). Pyrethroid Insecticides: Use, Environmental Fate, and Ecotoxicology, Insecticides - Advances in Integrated Pest Management. 251–262.

[5] Wang J, Schnuta W (2011). Quantitative determination of ultratrace Level N-methyl carbamates in rice samples by accelerated solvents extraction (ASE) and Ultrahigh performance liquid chromatography tandem mass.