Search

It is of fundamental importance to transform carbon monoxide (CO) to petrochemical feedstocks and fine chemicals. Many strategies built on the activation of C=O bond by π-back bonding from the transition metal center were developed during the past decades. Herein, a new CO activation method, in which the CO was converted to the active acyl-like metalloradical, [(por)Rh(CO)]* (por = porphyrin), was reported. The reactivity of [(por)Rh(CO)]* and other rhodium porphyrin compounds, such as (por)- RhCHO and (por)RhC(O)NHnPr, and corresponding mechanism studies were conducted experimentally and computationally and inspired the design of a new conversion system featuring 100% atom economy that promotes carbonylation of amines to formamides using porphyrin rhodium(II) metalloradical. Following this radical based pathway, the carbonylations of a series of primary and secondary aliphatic amines were examined, and turnover numbers up to 224 were obtained. [ABSTRACT FROM AUTHOR]

Biogenic silica has been considered as a potential feedstock for producing a variety of silicon-containing products. A new synthesis pathway of tetraethyl orthosilicate from silica that is contained in rice hull ash has been recently proposed. Requiring only one-step processing, it is expected to offer advantages over conventional routes which are derived from silicon metal. This study aims to investigate the optimal synthesis conditions for which this new technology can sustainably replace the conventional method. Experiments employing different reaction conditions are performed to provide the necessary information for a conceptual process design and an economic and environmental viability evaluation. The results obtained by comparison with a selected conventional process show that, under the optimal synthesis conditions, the new process can decrease the production cost and markedly reduce the high greenhouse gas emissions. The competitiveness of the new process is further examined with a sensitivity analysis considering fluctuations in key feedstock and utility prices and alternative sources of electricity supplied to the conventional process. The new synthesis technology shows high potential as a sustainable alternative to the conventional one. [ABSTRACT FROM AUTHOR]

The use of biomass for adsorption of rare earth elements (REEs) has been the subject of many recent investigations. However, REE adsorption by bioengineered systems has been scarcely documented, and rarely tested with complex natural feedstocks. Herein, we engineered E. coli cells for enhanced cell surface-mediated extraction of REEs by functionalizing the OmpA protein with 16 copies of a lanthanide binding tag (LBT). Through biosorption experiments conducted with leachates from metal-mine tailings and rare earth deposits, we show that functionalization of the cell surface with LBT yielded several notable advantages over the nonengineered control. First, the efficiency of REE adsorption from all leachates was enhanced as indicated by a 2-10-fold increase in distribution coefficients for individual REEs. Second, the relative affinity of the cell surface for REEs was increased over all non-REEs except Cu. Third, LBT-display systematically enhanced the affinity of the cell surface for REEs as a function of decreasing atomic radius, providing a means to separate high value heavy REEs from more common light REEs. Together, our results demonstrate that REE biosorption of high efficiency and selectivity from low-grade feedstocks can be achieved by engineering the native bacterial surface. [ABSTRACT FROM AUTHOR]

The design and operation of a circulating fluid catalytic cracking (FCC) riser pilot plant is presented in the paper. Emphasis is given on the effect of riser length on feedstock conversion and coke yield. Riser lengths considered in the study were 1.46 and 9.95 m. The effect of catalyst residence time on feedstock conversion and coke yield at constant feed rate and reactor temperature (526 °C) is presented. The catalyst residence time varies with reactor volume and catalyst circulation rate. It is shown that for the same feed conversion, high catalyst circulation rates are required with the lower riser volume. Lower gasoline and lower coke yields are experimentally observed with the short riser length. A second-order kinetic model is used to correlate the variation in conversion and coke yield. Commercial results validate the pilot plant design as a useful tool for guiding commercial operations. [ABSTRACT FROM AUTHOR]

Poly(oxymethylene) dimethyl ethers (OME) are environmentally benign alternative fuels. This work presents the conceptual design of a novel OME process which employs aqueous solutions of formaldehyde and methanol as feedstock. In this process, OME of the desired chain lengths n = 3-5 and water are separated from the reactive mixture (formaldehyde + water + methanol + methylal + OME). Thermodynamic limits are identified by studying distillation boundaries and chemical equilibria. By that it is shown that OME of chain lengths n = 3-5 can be separated from the reactor outlet by distillation. The separation of water is carried out using either an adsorption or a membrane process. Adsorption isotherms of water on Zeolite 3A are determined experimentally. The OME process is simulated and optimized using a reduced process model accounting for the mass balances and the thermodynamic limits. Favorable operating points of the process are identified using multi-objective optimization. [ABSTRACT FROM AUTHOR]

The current approach for technological projects must fulfill sustainability indexes. In this work, we use a multiobjective optimization framework to analyze the convenient product distribution in a lignocellulosic biorefinery, considering economic, environmental, and safety indexes. Corn cob was selected as feedstock due to the high annual volume produced as residue of maize crop. Products selection was based on the existing demand and economic value; bioethanol, lactic acid, succinic acid, xylitol, and lignosulfonates were chosen. Through the multiobjective optimization strategy an efficient solution with an Economic Potential Index of 0.16 is achieved, generating an annual utility of nearly 70 kUSD when bioethanol and xylitol production is favored over succinic acid and lactic acid. This tool can be applied with different feedstocks and products in a biorefinery scheme, with kinetic and yield data for corresponding processes. [ABSTRACT FROM AUTHOR]

Simulation of the evaporation process of a naphtha feedstock in the convection section of a steam cracking furnace is reported in this article. A two-step evaporation model was developed to determine component changes in the vapor and liquid phases. First, a feedstock-simplifying method, based on the work of Eckert and Vaněk ( Comput. Chem. Eng. 2005, 30, 343-356), was developed in which the original hydrocarbon mixture is represented by a system of real components. Second, the component distribution was determined by vapor-liquid equilibrium theory, using an activity coefficient method. The group contribution method (GCM) was employed to calculate the interaction parameters in the activity coefficient method. Using a mechanistic heat-transfer method, a comparison was made between the evaporation model developed in this work and a simplified evaporation model. The simulation results are in good agreement with industrial data. Some parameter profiles for the heat-transfer process are provided, as are the flow patterns of the naphtha feedstock. [ABSTRACT FROM AUTHOR]

Different types of crude oils, including heavy sour crudes, are usually processed in oil refineries. They are suitably mixed in multipipeline crude oil blending systems (MCOBS) to get qualified feedstocks for the crude distillation units (CDUs) that separate them into various fractions or cuts. Current research on the scheduling of such refinery operations seeks to minimize the total operating cost while limiting the concentration of some impurities in the feedstock. However, an essential property like the feedstock composition usually approximated by the true boiling point (TBP) distribution curve is often ignored. In fact, one of the major goals of the blending process is to supply feedstocks to the CDUs that consistently produce the desired proportions of final cuts to match refined product demands. This work introduces a novel slot-based mixed-integer nonlinear programming (MINLP) formulation for the MCOBS scheduling problem that explicitly accounts for the TBP curves of the crude oils to get a series of suitable and stable feedstocks for the CDUs. An MILP-NLP solution strategy is proposed to find near-optimal schedules in reasonable CPU times. [ABSTRACT FROM AUTHOR]

Under the conditions of oxidative gold catalysis, exposure of ethylene to aryl silanes and alcohols generates products of 1,2-oxyarylation. This provides a rare example of a process that allows catalytic differential 1,2-difunctionalization of this feedstock chemical. [ABSTRACT FROM AUTHOR]

An integrated, modular and multifunctional process is conceptually designed, simulated and optimized for direct utilization of CO2 from dilute flue gas to produce high-quality syngas, a precursor for many value-added chemicals and liquid transportation fuels. The process is intensified to simultaneously capture and convert CO2 using methane, natural gas, or excess fuel gas from the same plant, or using nearby unconventional methane from biogas or landfill gas. It is an integrated adsorption-purge-reaction system where CO2 is first adsorbed and then desorbed using methane-rich feed leading to a mixture suitable for dry-reforming. The merging of concentration-based CO2 desorption with the reactor feed premixing step eliminates the need for pressure or temperature swings and significantly reduces the energy penalty and cost of CO2 capture and utilization. The process is simulated at different conditions using a high-fidelity process model to elucidate the effects of key decision variables as well as the trade-offs and interactions between the capture and reforming sections. The technology is flexible to handle different feedstock compositions and is amenable to both centralized and distributed production of syngas. A constrained grey-box optimization method is employed to achieve a maximum of 99.7% net overall CO2 utilization considering auxiliary emissions at a total cost ranging from $110-130 per ton of syngas. As much as 14.6% of the total CO2 input to the process comes "directly" from flue gas without additional cost for CO2 capture while maintaining about 91% overall CO2 utilization. The technology is also computationally found to be robust in terms of CO2 utilization and cost for different natural gas feeds with CO2 contamination as high as 60%. This can be attributed to the novel process intensification concept and the gray-box constrained optimization method presented in this work. [ABSTRACT FROM AUTHOR]

Many refineries use hydrogen to upgrade heavy fuel feedstocks, and therefore, hydrogen solubility is an important parameter. Shale oil is a fuel for which hydrotreatment is of interest, but no data about its hydrogen solubility can be found in the literature. This Article presents experimental data for the hydrogen solubility of two shale oil samples measured at high temperatures and pressures (423-527 K and 40-140 bar). Experiments were performed using a continuous flow apparatus. Results show that the shale oil had a lower hydrogen solubility than most other fuels, probably due to the high content of polar phenolic compounds in the oil. Removing about 80% of the phenolic compounds increased the hydrogen solubility by approximately 0.1 mol H2/kg oil (which is about 15 to 45%, depending on the solubility). Analysis also showed that current prediction methods used for petroleum and coal liquids cannot reliably be used for predicting the hydrogen solubility of this shale oil and other similar fuels. [ABSTRACT FROM AUTHOR]

The family of hemicelluloses stands out as a very promising natural resource that can be utilized as a biobased materials feedstock. An in-depth understanding of the hemicellulose inherent structural and property features as well as the structure-property relationships induced by the specific supramolecular hierarchical organization of lignocellulosic biopolymers will be a key enabling technology in the emerging biorefinery sector. This Review aims to give a perspective on these issues and demonstrate how the transfer of molecular wood cell interactions into hemicellulose-based materials may offer new design principles for material formulations. [ABSTRACT FROM AUTHOR]

Innovative valorization of naturally abundant and renewable lignocellulosic biomass is of great importance in the pursuit of a sustainable future and biobased economy. Ionic liquids (ILs) as an important kind of green solvents and functional fluids have attracted significant attention for the catalytic transformation of lignocellulosic feedstocks into a diverse range of products. Taking advantage of some unique properties of ILs with different functions, the catalytic transformation processes can be carried out more efficiently and potentially with lower environmental impacts. Also, a new product portfolio may be derived from catalytic systems with ILs as media. This review focuses on the catalytic chemical conversion of lignocellulose and its primary ingredients (i.e., cellulose, hemicellulose, and lignin) into value-added chemicals and fuel products using ILs as the reaction media. An outlook is provided at the end of this review to highlight the challenges and opportunities associated with this interesting and important area. [ABSTRACT FROM AUTHOR]

This paper presents research undertaken on pyrolytic coconut shell char to evaluate its potential as a sustainable and renewable substitute filler for carbon black in rubber. Carbon black is the most widely used filler in rubber. Its manufacture from nonrenewable feedstock is unsustainable and energy-consuming and contributes significantly to global CO2 emissions. The pyrolytic properties of coconut shell were evaluated; response surface methodology was applied to model the relationship between the pyrolysis conditions and char properties. Coconut shells were pyrolyzed using a laboratory-scale furnace under various temperatures (400-800°C), residence times (0-2 h), and atmospheric flow rates. Comparisons were made between the char and commercial carbon blacks for their physical and chemical properties (surface area and pH). Comparable char pH and surface area properties were achieved (optimal char exhibited 300 m²/g surface area). Selected samples were tested in-rubber, with the performance of the filled styrene-butadiene rubber showing 2 MPa at M100%. [ABSTRACT FROM AUTHOR]

Compared to microalgae, macroalgae are larger in size, thereby imposing lower separation and drying costs. This study demonstrates the feasibility of cultivating macroalgae Chaetomorpha linum in different types of municipal wastewaters, their ability to remove nutrient and their biomass composition for downstream biofuel production. Screening experiments indicated that C. linum grew well on primary (PW) and secondary wastewaters (SW), as well as centrate wastewater (CW) diluted to less than 20%. In a subsequent experiment, a step feeding approach was found to significantly increase biomass productivity to 10.7 ± 0.2 g AFDW-m-2-d-1 (p < 0.001), a 26.5% improvement in comparison to the control with single feeding, when grown on 10-CW; meanwhile, nitrogen and phosphorus removal efficiencies rose to 86.8 ± 1.1% (p < 0.001) and 92.6 ± 0.2% (p < 0.001), respectively. The CO2-supplemented SW cultures (10.1 ± 0.4 g AFDW-m-2-d-1) were 1.20 times more productive than the corresponding controls without CO2 supplementation (p < 0.001); however, similar improvements were not observed in PW (p = 0.07) and 10-CW cultures (p = 0.07). Moreover, wastewater type and nutrient concentration influenced biomass composition (protein, carbohydrate and lipid). These findings indicate that the application of the macroalgae C. linum could represent an effective wastewater treatment alternative that could also provide a feedstock for downstream processing to biofuels. [ABSTRACT FROM AUTHOR]

Land availability for growing feedstocks at scale is a crucial concern for the bioenergy industry. Feedstock production on land not well-suited to growing conventional crops, or marginal land, is often promoted as ideal, although there is a poor understanding of the qualities, quantity, and distribution of marginal lands in the United States. We examine the spatial distribution of land complying with several key marginal land definitions at the United States county, agro-ecological zone, and national scales, and compare the ability of both marginal land and land cover data sets to identify regions for feedstock production. We conclude that very few land parcels comply with multiple definitions of marginal land. Furthermore, to examine possible carbon-flow implications of feedstock production on land that could be considered marginal per multiple definitions, we model soil carbon changes upon transitions from marginal cropland, grassland, and cropland-pastureland to switchgrass production for three marginal land-rich counties. Our findings suggest that total soil organic carbon changes per county are small, and generally positive, and can influence life-cycle greenhouse gas emissions of switchgrass ethanol. [ABSTRACT FROM AUTHOR]

A life cycle-based model, OSTUM (Oil Sands Technologies for Upgrading Model), which evaluates the energy intensity and greenhouse gas (GHG) emissions of current oil sands upgrading technologies, is developed. Upgrading converts oil sands bitumen into high quality synthetic crude oil (SCO), a refinery feedstock. OSTUM's novel attributes include the following: the breadth of technologies and upgrading operations options that can be analyzed, energy intensity and GHG emissions being estimated at the process unit level, it not being dependent on a proprietary process simulator, and use of publicly available data. OSTUM is applied to a hypothetical, but realistic, upgrading operation based on delayed coking, the most common upgrading technology, resulting in emissions of 328 kg CO2e/m3 SCO. The primary contributor to upgrading emissions (45%) is the use of natural gas for hydrogen production through steam methane reforming, followed by the use of natural gas as fuel in the rest of the process units' heaters (39%). OSTUM's results are in agreement with those of a process simulation model developed by CanmetENERGY, other literature, and confidential data of a commercial upgrading operation. For the application of the model, emissions are found to be most sensitive to the amount of natural gas utilized as feedstock by the steam methane reformer. OSTUM is capable of evaluating the impact of different technologies, feedstock qualities, operating conditions, and fuel mixes on upgrading emissions, and its life cycle perspective allows easy incorporation of results into well-to-wheel analyses. [ABSTRACT FROM AUTHOR]

Biomass has been long exploited as an anthropogenic energy source; however, the 21st century challenges of energy security and climate change are driving resurgence in its utilization both as a renewable alternative to fossil fuels and as a sustainable carbon feedstock for chemicals production. Deconstruction of cellulose and hemicellulose carbohydrate polymers into their constituent C5 and C6 sugars, and subsequent heterogeneously catalyzed transformations, offer the promise of unlocking diverse oxygenates such as furfural, 5-hydroxymethylfurfural, xylitol, sorbitol, mannitol, and gluconic acid as biorefinery platform chemicals. Here, we review recent advances in the design and development of catalysts and processes for C5â€"C6 sugar reforming into chemical intermediates and products, and highlight the challenges of aqueous phase operation and catalyst evaluation, in addition to process considerations such as solvent and reactor selection. [ABSTRACT FROM AUTHOR]

We report a two-step chemical vapor deposition growth method for rapid synthesis of isolated large-domain graphene. The key feature of the two-step growth method is to separate nucleation from growth, performing the nucleation in step one with a low carbon feedstock (methane) gas flow rate, and rapid growth in step two with a high flow rate. We find empirically that, even under the high flow rate conditions of step two, the nucleation density on the inside of the copper pocket used for growth is suppressed (preventing merging of domains into full films) until the graphene growing on the outside of the pocket merges into a full film, fully covering the outside. The mechanism for this suppression is believed to be related to oxygen-assisted passivation of nucleation sites, a decreased energetic barrier for edge-attachment growth, and diffusion of carbon through the copper bulk. These conditions enable us to finely tune the local carbon concentration on the inside surface for fast growth and minimum nucleation density and achieve a growth of 5 mm isolated graphene domains in under 5 h of total growth time, much faster than traditional one-step growth methods. [ABSTRACT FROM AUTHOR]

Variability in silk's rheology is often regarded as an impediment to understanding or successfully copying the natural spinning process. We have previously reported such variability in unspun native silk extracted straight from the gland of the domesticated silkworm Bombyx mori and discounted classical explanations such as differences in molecular weight and concentration. We now report that variability in oscillatory measurements can be reduced onto a simple master-curve through normalizing with respect to the crossover. This remarkable result suggests that differences between silk feedstocks are rheologically simple and not as complex as originally thought. By comparison, solutions of poly(ethylene-oxide) and hydroxypropyl-methyl-cellulose showed similar normalization behavior; however, the resulting curves were broader than for silk, suggesting greater polydispersity in the (semi)synthetic materials. Thus, we conclude Nature may in fact produce polymer feedstocks that are more consistent than typical man-made counterparts as a model for future rheological investigations. [ABSTRACT FROM AUTHOR]

Inherent tracers--the "natural" isotopic and trace gas composition of captured CO2 streams--are potentially powerful tracers for use in CCS technology. This review outlines for the first time the expected carbon isotope and noble gas compositions of captured CO2 streams from a range of feedstocks, CO2-generating processes, and carbon capture techniques. The C-isotope composition of captured CO2 will be most strongly controlled by the feedstock, but significant isotope fractionation is possible during capture; noble gas concentrations will be controlled by the capture technique employed. Comparison with likely baseline data suggests that CO2 generated from fossil fuel feedstocks will often have δ13C distinguishable from storage reservoir CO2. Noble gases in amine-captured CO2 streams are likely to be low concentration, with isotopic ratios dependent on the feedstock, but CO2 captured from oxyfuel plants may be strongly enriched in Kr and Xe which are potentially valuable subsurface tracers. CO2 streams derived from fossil fuels will have noble gas isotope ratios reflecting a radiogenic component that will be difficult to distinguish in the storage reservoir, but inheritance of radiogenic components will provide an easily recognizable signature in the case of any unplanned migration into shallow aquifers or to the surface. [ABSTRACT FROM AUTHOR]

Amino acids are important in human and animal diet, as well as being potential feedstocks for chemical production. Amino acids can be obtained from protein after hydrolysis. In addition, several agro-industrial residues already contain a mixture of free amino acids. The objective of this study was to develop a method for amino acids separation, starting from mixtures containing amino acids, and using antisolvent precipitation with ethanol. Protamylasse, rubber seed protein hydrolysates, and grass juice were used in the experiments, representing existing and potential agro-industrial residues. Our results show that in a water-ethanol system, some amino acids had lower solubility in mixtures than as a single component, thereby facilitating precipitation. A sufficiently high total amino acid concentration in the mixture is needed to achieve precipitation; therefore, a concentration step is sometimes required. Ethanol precipitation can be applied as a pretreatment to separate mixtures into groups of amino acids or a polishing step to increase purity. [ABSTRACT FROM AUTHOR]

A systematic methodology to critically assess and screen among early stage design alternatives was developed for the use of glycerol. Through deterministic sensitivity analysis it was found that variations in the product and feedstock prices, total production cost, fixed capital investment, and discount rate, among others, have high impact on the project's profitability analysis. Therefore, the profitability was tested under uncertainties by using NPV and MSP as economic metrics. The robust ranking of solutions is presented with respect to minimum economic risk of the project being nonprofitable (failure to achieve a positive NPV times the consequential profit loss). It was found that the best potential options for glycerol valorization is through the the production of either (i) lactic acid (9 MM$ economic risk with 63% probability of failure to achieve a positive NPV); (ii) succinic acid (14 MM$ economic risk with 76% probability of failure to achieve a positive NPV); or finally, (iii) 1,2-propanediol (16 MM$ economic risk with 68% probability of failure to achieve a positive NPV). As a risk reduction strategy, a multiproduct biorefinery is suggested which is capable of switching between the production of lactic acid and succinic acid. This solution comes with increased capital investment; however, it leads to more robust NPV and decreased economic risk by approximately 20%, therefore creating a production plant that can continuously adapt to market forces and thus optimize profitability. [ABSTRACT FROM AUTHOR]

Microalgae can grow significantly faster than terrestrial plants and are a promising feedstock for sustainable value added products encompassing pharmaceuticals, pigments, proteins and most prominently biofuels. As the biomass productivity of microalgae strongly depends on the cultivation temperature, detailed information on the reactor temperature as a function of time and geographical location is essential to evaluate the true potential of microalgae as an industrial feedstock. In the present study, a temperature model for an array of vertical flat plate photobioreactors is presented. It was demonstrated that mutual shading of reactor panels has a decisive effect on the reactor temperature. By optimizing distance and thickness of the panels, the occurrence of extreme temperatures and the amplitude of daily temperature fluctuations in the culture medium can be drastically reduced, while maintaining a high level of irradiation on the panels. The presented model was developed and applied to analyze the suitability of various climate zones for algae production in flat panel photobioreactors. Our results demonstrate that in particular Mediterranean and tropical climates represent favorable locations. Lastly, the thermal energy demand required for the case of active temperature control is determined for several locations. [ABSTRACT FROM AUTHOR]

In light of the depletion of fossil fuels and the increased daily requirements for liquid fuels and chemicals, CO2 should indeed be regarded as a valuable C1 additional feedstock for sustainable manufacturing of liquid fuels and chemicals. Development and deployment of CO2 capture and chemical conversion processes are among the grand challenges faced by today's scientists and engineers. Very few of the reported CO2 capture and conversion technologies have been employed for industrial installations on a large scale, where high-efficiency, cost/energy-effectiveness, and environmental friendliness are three keys factors. The CO2 capture technologies from stationary sources and ambient air based on solvents, solid sorbents, and membranes are discussed first. Transforming CO2 to liquid fuels and chemicals, which are presently produced from petroleum, through thermochemical, electrochemical, photochemical, and biochemical routes are discussed next. The relevant state-of-the-art computational methods and tools as a complement to experiments are also briefly discussed. Finally, after pointing out the advantages and disadvantages of the currently available technologies for CO2 capture and conversion, ideas and perspectives for the development of new techniques, opportunities, and challenges are highlighted. [ABSTRACT FROM AUTHOR]

Capture and utilization of CO2 as alternative carbon feedstock for fuels, chemicals, and materials aims at reducing greenhouse gas emissions and fossil resource use. For capture of CO2, a large variety of CO2 sources exists. Since they emit much more CO2 than the expected demand for CO2 utilization, the environmentally most favorable CO2 sources should be selected. For this purpose, we introduce the environmental-merit-order (EMO) curve to rank CO2 sources according to their environmental impacts over the available CO2 supply. To determine the environmental impacts of CO2 capture, compression and transport, we conducted a comprehensive literature study for the energy demands of CO2 supply, and constructed a database for CO2 sources in Europe. Mapping these CO2 sources reveals that CO2 transport distances are usually small. Thus, neglecting transport in a first step, we find that environmental impacts are minimized by capturing CO2 first from chemical plants and natural gas processing, then from paper mills, power plants, and iron and steel plants. In a second step, we computed regional EMO curves considering transport and country-specific impacts for energy supply. Building upon regional EMO curves, we identify favorable locations for CO2 utilization with lowest environmental impacts of CO2 supply, so-called CO2 oases. [ABSTRACT FROM AUTHOR]

Greenhouse gas (GHG) regulations affecting U.S. transportation fuels require holistic examination of the life-cycle emissions of U.S. petroleum feedstocks. With an expanded system boundary that included land disturbance-induced GHG emissions, we estimated well-to-wheels (WTW) GHG emissions of U.S. production of gasoline and diesel sourced from Canadian oil sands. Our analysis was based on detailed characterization of the energy intensities of 27 oil sands projects, representing industrial practices and technological advances since 2008. Four major oil sands production pathways were examined, including bitumen and synthetic crude oil (SCO) from both surface mining and in situ projects. Pathway-average GHG emissions from oil sands extraction, separation, and upgrading ranged from ∼6.1 to ∼27.3 g CO2 equivalents per megajoule (in lower heating value, CO2e/MJ). This range can be compared to ∼4.4 g CO2e/MJ for U.S. conventional crude oil recovery. Depending on the extraction technology and product type output of oil sands projects, the WTW GHG emissions for gasoline and diesel produced from bitumen and SCO in U.S. refineries were in the range of 100-115 and 99-117 g CO2e/MJ, respectively, representing, on average, about 18% and 21% higher emissions than those derived from U.S. conventional crudes. WTW GHG emissions of gasoline and diesel derived from diluted bitumen ranged from 97 to 103 and 96 to 104 g CO2e/MJ, respectively, showing the effect of diluent use on fuel emissions. [ABSTRACT FROM AUTHOR]

Substituting biomass for fossil-based feedstock is a potential scenario of chemical production. To achieve sustainable production, various issues must be considered, such as the constraints of limited biomass resources, feasibility of production technologies, and competitiveness of bio-based chemical products. In this study, we developed a new framework for the design and assessment of bio-based chemical processes. Both monetary and nonmonetary indicators including production cost, energy consumption, environmental impact, and safety hazards are considered. The framework was applied to the design and assessment of both existing and emerging new bio-based processes producing potential platform chemicals from bioethanol. On the basis of the design and assessment results, the suitable biomass feedstock, a sustainable synthesis process, a competitive bio-based product, and an appropriate production scenario can be selected. Using data available at the conceptual design stage, the framework can be applied to synthesize high-potential bio-based chemical processes for future sustainability development. [ABSTRACT FROM AUTHOR]

The straightforward large-scale synthesis and the ability to adjust the properties of polymers make polymers very attractive materials. Polymers have been used in numerous applications and an increased demand is foreseeable. However, a serious issue is the accumulation of enormous amounts of end-of-life polymers, which are currently recycled by thermal degradation, undergo downcycling, or buried in landfills. In contrast, only a minor fraction of polymers is recycled by selective depolymerization processes to produce low molecular weight chemicals that can be polymerized to new polymers. Polysiloxanes (silicones) are widely used polymers, and recycling is challenging due to their intrinsic properties. A few high temperature or less environmentally friendly protocols have been reported for recycling silicones. To circumvent these problems, a low-temperature process was developed for the depolymerization of polysiloxanes using catalytic amounts of cheap, iron salts as a precatalyst and benzoyl fluoride as a depolymerization reagent. Low molecular weight products (difluorodimethylsilane and 1,3-difluoro-1,1,3,3-tetramethyldisiloxane) are used for the synthesis of new polysiloxanes; hence, overall a recycling process is feasible. This inorganic chemistry experiment introduces second-year undergraduate students to the concept of feedstock recycling via depolymerization/polymerization processes and exemplifies modern advances in sustainable chemistry. [ABSTRACT FROM AUTHOR]

Itaconic acid, a renewable feedstock obtained by fermentation of carbohydrates, is used as a key substrate to produce aliphatic unsaturated polyesters as well as polynorbornenes. Renewable unsaturated polyesters were prepared by direct polycondensation of dimethyl itaconate (DMI) with diols, whereas the ring-opening-metathesis polymerization (ROMP) of a DMI derived norbornene led to polynorbornenes. The direct polycondensation of DMI was performed with tin(II) ethylhexanoate as catalyst, 4-methoxyphenol as radical inhibitor, and different diols to yield linear unsaturated polyesters with a molecular weight up to 11500 Da without isomerization or cross-linking of the vinylic double bond. Further modification of the unsaturated polyesters by thia-Michael addition yielded polysulfides, which were subsequently oxidized to polysulfones. Moreover, the solvent-free and straightforward Diels-Alder reaction of DMI and cyclopentadiene was used to prepare a partially renewable norbornene monomer, which was used in ROMP with different catalysts to prepare polymers with low dispersities and adjustable molecular weights. The thereof derived unsaturated and functionalized renewable polynorbornenes were further modified by hydrogenation, and their thermal properties were evaluated. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO2) removalis a key component of manyindustrial processes, especially coal-fired power generation. ControllingSO2emissions is vital to maintaining environmental quality,as SO2is a contributor to acid rain, but has value asa chemical feedstock. Although a number of novel solvents/materialsincluding ionic liquids (ILs) have recently been proposed for alternativesto limestone scrubbing for SO2capture/removal from pointsources, the imidazole architecture presents a convenient, inexpensiveand efficient class of low volatility and low viscosity solvents toaccomplish this goal. On the basis of our prior work with imidazolesfor CO2capture, we have extended our interests towardunderstanding the relationship between imidazole structure and SO2absorption. Using a series of imidazole compounds with varioussubstituents at the 1, 2 and/or 4(5) positions of the five-memberedring, SO2absorption via both chemical and physical mechanismswas observed. The chemical absorption product is a relatively stable1:1 SO2–imidazole complex, while physical absorptionof SO2is dependent on pressure and temperature. Becauseimidazoles are relatively small molecules, they are an efficient absorptionmedium for SO2and can form adducts wherein the mass fractionof bound SO2is >40 wt %. The SO2–imidazolecomplexes were also observed to produce distinct color and/or phasechanges that are associated with the nature of the substituents present.The chemically bound SO2can be released under vacuum atmoderate temperature (∼100 °C) and vacuum, yielding theoriginal neat solvent, while the physically dissolved SO2can be readily removed at ambient temperature under vacuum. Thisbehavior corresponds to a much smaller enthalpy of absorption forphysical dissolution (−4 to −13 kJ/mol) as determinedvia thermodynamic relationships compared to the binding energies ofchemical complexation (−35 to −42 kJ/mol) as determinedvia density functional theory calculations. Increasing chemical complexationenergies are correlated with increased substitution on the imidazolering. Simulations were also employed to gain insight into the structuresof the SO2–imidazole complexes, illustrating changesin partial charge distribution before and after complexation as wellas confirming a charge transfer complex is formed based on the N–Sbond length. [ABSTRACT FROM AUTHOR]

Solidacid catalysts are an important class of catalysts becauseof their applications in various organic reactions. A 12-tungstophosphoricacid (TPA) is a member of heteropoly acid (HPA) compounds, which grabbedattention because of its low volatility, low corrosivity, higher activity,and acidity compared to sulfuric acid. However, the major problemsof using TPA are its solubility in polar media, and its lower surfacearea. Therefore, various techniques are applied to use it as heterogeneouscatalysts. Biodiesel is a diesel substitute renewable fuel, whichis produced from various renewable feedstocks through transesterificationor esterification reactions. Acid catalysts can catalyze both transesterificationand esterification reactions. For this reason, research has been conductedto study the catalytic activity of various TPA precursory solid acidcatalysts for biodiesel production. In this Review, a data miningtechnique has been applied to extract valuable information from thepreviously published literature. For this purpose, an artificial neuralnetwork (ANN) model has been developed based on the published researchdata to capture the general trends or to make predictions. Both catalystproperties and reaction conditions are trended and predicted usingthe network model. [ABSTRACT FROM AUTHOR]

A biomass-based trigeneration systemproduces heat, power and coolingenergy simultaneously. To synthesize a biomass-based trigenerationsystem, decision makers are required to consider a wide range of technologiesbased on various factors (e.g., capital investment, operating cost,availability and reliability of the technologies, etc.). In addition,both short-term and long-term uncertainties that may arise duringthe course of operations should also be taken into consideration.If not considered at the synthesis stage, uncertainties would preventthe designed energy system from meeting the required energy demandsand cause possible bottlenecks during operation. With such consideration,not all available technologies are economically and operationallysensible. Thus, it is essential to develop a systematic approach tosynthesize a biomass-based trigeneration system with considerationof uncertainties. In this work, a multiperiod optimization approachfor the systematic synthesis of a biomass-based trigeneration systemwith variations in raw material supply and corresponding energy demandis presented. Following the concept of multiperiod optimization approach,the fraction of occurrence for each biomass supply and energy demandscenario is included. Meanwhile, the maximum capacities of each technologythat can operate in all scenarios are determined. In addition, selectionof design capacities based on available sizes in the market is alsoperformed simultaneously. To illustrate the proposed approach, a trigenerationsystem with palm-based biomass as feedstock is solved. [ABSTRACT FROM AUTHOR]

Fluidcatalytic cracking (FCC) is an important refinery processby which heavy hydrocarbons are cracked to form lighter valuable productsover catalyst particles. FCC plants consist of the riser (reactor),the regenerator, and the fractionator that separates the riser effluentinto the useful end products. In FCC plants the product specificationsand feedstocks change due to varying economic and market conditions.In addition, FCC plants operate with large throughputs and a smallimprovement realized by optimization and control yields significanteconomic return. In previous work, we developed a nonlinear dynamicmodel and validated it with industrial data. In this study, our focusinvolves the development and application of a real-time optimizationframework. We propose a hierarchical structure which includes a two-layerimplementation of economic model predictive control (EMPC). EMPC providesthe optimal riser and the regenerator temperature reference trajectorieswhich are determined from a dynamic optimization problem maximizingthe plant profit. A regulatory model predictive controller (RMPC)manipulates the catalyst circulation rate and the air flow rate totrack the reference trajectories provided by EMPC. We consider changesin product prices and the feed content, both of which necessitateonline optimization. Dynamic simulations show that the proposed hierarchicalcontrol structure achieves optimal tracking of plant profit duringtransitions between different operating regimes thanks to the combinedefforts of EMPC and RMPC. [ABSTRACT FROM AUTHOR]

Thethermochemical conversion of coal and biomass to liquid transportationfuels from a synthesis gas intermediate is investigated using an optimization-basedprocess synthesis framework. Two distinct types of coal (LV bituminousand coal commonly found in the province of Anhui, China) and two typesof biomass (hardwood and duckweed) are considered as feedstocks. Thesuperstructure incorporates alternative conversion pathways of synthesisgas which include methanol formation and conversion into Fischer–Tropschhydrocarbons. Methanol may be converted to gasoline or olefins, andthe olefins may be subsequently converted to gasoline and distillate.A rigorous deterministic global optimization branch-and-bound frameworkis utilized to determine the optimal process topology that producesliquid fuels at the lowest possible cost. Economies of scale are evidentas the refinery capacity increases and it is observed that the fuelratios of the final liquid products have a significant impact on theoptimal topology of the plant. The results suggest that liquid fuelsproduction from coal and biomass can be competitive with petroleum-basedprocesses. [ABSTRACT FROM AUTHOR]

Thepurpose of this paper was to evaluate the shrinkage behavior of a316L molding feedstock. The methodology adopted a statistical approach(design of experiment) and a standard microshrinkage measurement approach.The statistical approach identified the mold temperatureparallelto the flow directionand the combined effect of the holdingand injection pressurenormal to the flow directionascritical factors. In comparison with the polymer on which the feedstockwas based, lower shrinkage values and fewer critical factors wereobserved. In conclusion, the lower shrinkage values were a consequenceof the powder loading. The critical factors identified in the presentwork have found confirmation in the literature, except the absenceof melt temperature between feedstock critical factors. [ABSTRACT FROM AUTHOR]

Weaddress the problem of biorefinery supply chain network designunder competitive corn markets. Unlike existing methods, the purchaseprices of corn are considered to vary not only across time but alsoacross competing biorefineries in a given region for all time periodsin the design horizon. As the feedstock cost for purchasing corn isthe largest cost component for producing ethanol, it is critical toconsider the formation of corn prices in real-world markets involvingcompetition and interactions among biorefineries, among farmers, andbetween biorefineries and the food market. However, these competitivemarkets are difficult to formulate in a mathematical program. To simulatethe corn markets, an agent-based model is developed. In each market,the dynamic corn prices are determined by a double-auction processparticipatedin by biorefinery agents,farmer agents, and a food market agent. The determined corn pricesare then returned to the supply chain design problem, which is a mixed-integernonlinear program (MINLP) with black-box functions. However, sucha problem cannot be solved directly by a MINLP solver. Thus, we usea genetic algorithm to solve the optimization problem and determinethe location and capacity of each biorefinery in the network. Theproposed method is demonstrated by a case study on a corn-based biorefinerysupply chain network design in Illinois in which the optimal net presentvalue of a network of 10 biorefineries increased by 10.7% comparedto that of the initial supply chain network. [ABSTRACT FROM AUTHOR]

Waste to energy (WTE) performance is evaluated by maximization of electrical energy production and throughput, while maintaining low operational costs and complying with emission limits. Uncertainty in the quantities, composition and heating values of received wastes, pose severe operability problems and impair performance and emissions. The present work demonstrates and quantifies the possibility of improving WTE efficiency under feedstock uncertainty via oxygen enrichment of the combustion air. Acting essentially as a nitrogen depletion mechanism, oxygen enrichment has reverse effects compared to excess air (EA); synergistic use provides extended capabilities for performance improvement, without impairing final emissions, while satisfying capacity constraints. Increased oxygen enrichment is required at higher EA to maintain temperature. Lower charging rates of rich wastes (plastics, paper, etc.) or diminishing heating values, require higher oxygen enrichment or lower EA The opposite holds for lower charging rates of poor wastes (biodegradables, biosludge, inerts, etc.) or rising heating values. The results establish the possibility of nominal designs to respond to feedstock variations and may be useful for low range excess air operation (low cost) or adiabatic operation (high EA, combustor temperature controlled by large fluegas volumes). The vector formulation facilitates digital coding for applications featuring multiple waste mixture variability. A 700000 tpa WTE facility in Athens, now under publicprivate-partnership contract tender is investigated. [ABSTRACT FROM AUTHOR]

Theworldwide demand of activated carbon is expected to increaseby 58% until 2016 [FredoniaWorld Activated Carbon;2013; p 415], owing to tighter pollution controls andincreased production of consumer goods. To cope up with high demand,new sustainable and energy efficient processes are being explored.Microwave assisted production of activated carbon from biomass feedstockuse selective heating which makes the process energy efficient andsustainable in nature. Recent studies used domestic microwave ovenwith open loop temperature control to prepare activated carbon, withouttaking into consideration the dielectric properties of biomass andactivating agents, and safety issues. As a result, these studies donot provide necessary information for the scale-up of the reactorfor high throughputs. In this research, the critical issues in thepresent research are analyzed, and appropriate remedies have beensuggested to overcome them, as a step forward toward the scale-upof technology for industrial scale production. [ABSTRACT FROM AUTHOR]

Lignocellulosic feedstock can beconverted to bio-oil by directliquefaction in a phenolic solvent such as guaiacol with an oil yieldof >90 C% at 300–350 °C without the assistance of catalystor reactive atmosphere. Despite good initial performance, the liquefactionwas rapidly hindered by the formation of heavy components (molecularweight > 1000 Da), which increased the viscosity of the bio-oiluponrecycling the bio-oil or a fraction of it as a liquefaction solvent.This paper explores the possibility to minimize the production ofthis undesirably heavy fraction by optimizing the process parameterssuch as temperature, heating rate, reaction time, and concentrationof water. This study allowed us to find a compromise between maximizingthe bio-oil yield and minimizing its heavy fraction. It also providesinsight onto the reaction network of the liquefaction reaction, showingfor instance that all product fractions, including the heaviest productsand the char, are mainly direct liquefaction products rather thansecondary reaction products, e.g. from bio-oil recondensation. However,the resulting heavy fraction is still too high to allow effectiverecycling of the bio-oil. Complementary approaches need to be investigated. [ABSTRACT FROM AUTHOR]

As an alternative transportation fuel to petrodiesel, biodiesel has been promoted within national energy portfolio targets across the world. Early estimations of low lifecycle greenhouse gas (GHG) emissions of biodiesel were a driver behind extensive government support in the form of financial incentives for the industry. However, studies consistently report a high degree of uncertainty in these emissions estimates, raising questions concerning the carbon benefits of biodiesel. Furthermore, the implications of feedstock blending on GHG emissions uncertainty have not been explicitly addressed despite broad practice by the industry to meet fuel quality standards and to control costs. This work investigated the impact of feedstock blending on the characteristics of biodiesel by using a chance-constrained (CC) blend optimization method. The objective of the optimization is minimization of feedstock costs subject to fuel standards and emissions constraints. Results indicate that blending can be used to manage GHG emissions uncertainty characteristics of biodiesel, and to achieve cost reductions through feedstock diversification. Simulations suggest that emissions control policies that restrict the use of certain feedstocks based on their GHG estimates overlook blending practices and benefits, increasing the cost of biodiesel. In contrast, emissions control policies which recognize the multifeedstock nature of biodiesel provide producers with feedstock selection flexibility, enabling them to manage their blend portfolios cost effectively, potentially without compromising fuel quality or emissions reductions. [ABSTRACT FROM AUTHOR]

Ethanol is an attractive end product and a versatilefeedstockbecause a widespread market exists for its commercial use as a fueladditive or a potential substitute for gasoline. Currently, ethanolis produced primarily by fermentation of biomass-derived sugars, particularlythose containing six carbons, but coproducts 5-carbon sugars and ligninremain unusable. Another major process for commercial production ofethanol is hydration of ethylene over solid acidic catalysts, yetnot sustainable considering the depletion of fossil fuels. Catalyticconversion of synthetic gas (CO + H2) could produce ethanolin large quantities. However, the direct catalytic conversion of syntheticgas to ethanol remains challenging, and no commercial process existsas of today although the research has been ongoing for the past 90years, since such the process suffers from low yield and poor selectivitydue to slow kinetics of the initial C–C bond formation andfast chain growth of the C2intermediates. [ABSTRACT FROM AUTHOR]

Vapor–liquid equilibrium (VLE)data for hydrogen/hydrocarbonmixtures based on real feedstocks at high temperature and pressureis scarce and is needed to model hydrocracking systems accurately.Experiments with a vacuum gas oil have been used to generate VLE datafor real hydrogen/hydrocarbon mixtures under hydrocracking conditionsin a semibatch reactor with a range of compositions. Flash calculationswere performed using a process simulation program and compared tothe experimental results. The data was used to verify the existenceof equilibrium conditions in the reactor and to show that the GraysonStreed activity coefficient model, combined with Peng–Robinsonequation of state, provides a good estimate of liquid phase and vaporphase compositions and individual component volatility. [ABSTRACT FROM AUTHOR]

Ethylene production process and thefeedstock management are thecritical activities in an olefin plant. Better analysis of these twoproblems gives rise to better use of the plant feeding material andenhanced production capabilities. It is important to ensure the feedingmaterial loaded and unloaded continuously and consistently from upstreamto downstream in case of any insufficient supply or increased productionburden. Besides, considering the changing yield characteristic ofthe furnace cracking operation and the naphtha blending constraints,how to incorporate the real world operational characteristics intothe integrated full space problem from upstream to downstream andimprove its economic performance in the strategic level is quite significant.Facing this challenge, this paper develops a novel synchronized decision-supportingframework for the long-term planning and scheduling problem of anethylene plant by simultaneously considering the upstream naphthainventory management and the downstream ethylene furnace operationwith a subcooperative model, which also incorporate more logisticand operational characteristics of the subproblems in practice. Moreover,the solution performance of both two subproblems is enhanced by thenew solving approach. The resulting framework is shown to be robustand seamlessly integrated. The efficacy and the economic potentialof this proposed integration framework are illustrated through a comprehensivecase study from the real world ethylene plant. [ABSTRACT FROM AUTHOR]

Converting hydrocarbon feedstocks into value-added chemicals continues to offer challenges to contemporary preparative chemists. A particularly important remaining challenge is the selective activation and functionalization of the C(sp3)–H linkages of alkanes, which are relatively abundant but chemically inert. [ABSTRACT FROM AUTHOR]

Air pollution emissions regulation can affect the location, size, and technology choice of potential biofuel production facilities. Difficulty in obtaining air pollutant emission permits and the cost of air pollution control devices have been cited by some fuel producers as barriers to development. This paper expands on the Geospatial Bioenergy Systems Model (GBSM) to evaluate the effect of air pollution control costs on the availability, cost, and distribution of U.S. biofuel production by subjecting potential facility locations within U.S. Clean Air Act nonattainment areas, which exceed thresholds for healthy air quality, to additional costs. This paper compares three scenarios: one with air quality costs included, one without air quality costs, and one in which conversion facilities were prohibited in Clean Air Act nonattainment areas. While air quality regulation may substantially affect local decisions regarding siting or technology choices, their effect on the system as a whole is small. Most biofuel facilities are expected to be sited near to feedstock supplies, which are seldom in nonattainment areas. The average cost per unit of produced energy is less than 1% higher in the scenarios with air quality compliance costs than in scenarios without such costs. When facility construction is prohibited in nonattainment areas, the costs increase by slightly over 1%, due to increases in the distance feedstock is transported to facilities in attainment areas. [ABSTRACT FROM AUTHOR]

The article offers information on the conversion of biosourced feedstocks into chemicals in presence of metal catalysts. Topics discussed include synthesis of sorbitol from D-glucose and its use as an additive in food, cosmetic, and paper industry, acid catalyzed hydrolysis of hemicelluloses to furfural and synthesis of levulinic acid by depolymerization and dehydration of cellulose. Also discussed are fermentation of carbohydrates to form lactic acid and synthesis of oleochemicals.

Hydrogenations of CO or CO2 are important catalytic reactions as they are interesting alternatives to produce fine chemical feedstock hence avoiding the use of fossil sources. Using monodisperse nanoparticle (NP) catalysts, we have studied the CO/H2 (i.e., Fischer-Tropsch synthesis) and CO2/H2 reactions. Exploiting synchrotron based in situ characterization techniques such as XANES and XPS, we were able to demonstrate that 10 nm Co NPs cannot be reduced at 250 °C while supported on TiO2 or SiO2 and that the complete reduction of cobalt can only be achieved at 450 °C. Interestingly, cobalt oxide performs better than fully reduced cobalt when supported on TiO2. In fact, the catalytic results indicate an enhancement of 10-fold for the CO2/H2 reaction rate and 2-fold for the CO/H2 reaction rate for the Co/TiO2 treated at 250 °C in H2 versus Co/ TiO2 treated at 450 °C. Inversely, the activity of cobalt supported on SiO2 has a higher turnover frequency when cobalt is metallic. The product distributions could be tuned depending on the support and the oxidation state of cobalt. For oxidized cobalt on TiO2, we observed an increase of methane production for the CO2/H2 reaction whereas it is more selective to unsaturated products for the CO/H2 reaction. In situ investigation of the catalysts indicated wetting of the TiO2 support by CoOx and partial encapsulation of metallic Co by TiO2-x. [ABSTRACT FROM AUTHOR]

Ionic liquids have been consideredas “green” replacementsfor volatile organic compounds in modern and clean industrial processessince the beginning of the 1990s. It has been shown recently thatwhen combined with renewable feedstocks derived from biomass (likecarbohydrates) they form systems attractive for sustainable chemicalengineering and technology. Promising features of such systems haveinduced research activity in various areas of pure and applied chemistry.In particular, new experimental data on different thermodynamic propertiesof biomaterials dissolved in ionic liquids are required. In this paperwe present both experimental and theoretical thermodynamic studiesof binary mixtures composed of sugars and two low-viscous ionic liquidsbased on 1-butyl-3-methylimidazolium cation and dicyanamide or trifluoroacetateanion. Solubility of d-(+)-glucose, d-(−)-fructose,and sucrose in the ionic liquids was determined as a function of temperature.The results indicate that both ionic liquids under consideration canbe successfully applied as alternative solvents for sugars. Additionally,thermal characterization of pure sugars was performed with differentialscanning calorimetry. The obtained solid–liquid equilibriumphase diagrams were analyzed in terms of perturbed-chain statisticalassociating fluid theory (PC-SAFT). It was shown that the PC-SAFTmodel is capable of representing phase behavior of the studied systemsquantitatively. [ABSTRACT FROM AUTHOR]

Inthis work, the viability of using aqueous-phase sugars derivedfrom the pyrolysis of lignocellulosic biomass was analyzed using high-throughputscreening in microtiter plates. To standardize results, a syntheticaqueous phase of pyrolytic bio-oil was constructed based on typicalconstituents and composition ranges and then used to determine thefermentation viability of Saccharomyces cerevisiae. The effects of inhibitory compounds in pyrolytic bio-oil were assessedby fitting measured growth kinetics to the model of Baranyi and Roberts(Int. J. Food Microbiol.1994, 23, 277), specifically on the fitted growth rates, initial microorganismadaptation, and maximum biomass densities. It was found that evena dilution to approximately 10% of the hypothetical inhibitor concentrationin aqueous bio-oil was significantly inhibitory to growth, althoughthe presence of additional sugars was able to moderate this impactslightly. The high-throughput screening used in this work allowedfor the rapid measurement of a variety of inhibitors at differentconcentrations, as well as inhibitory mixtures. [ABSTRACT FROM AUTHOR]