Dow Chemical Research Articles

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Reinforced Plastics spoke to Peter Cate from Dow Automotive Systems about advanced composites developed at Dow Chemical.

Heat Transfer Fluid Life Time Analysis of Diphenyl Oxide/Biphenyl Grades for Concentrated Solar Power Plants

Abstract To gain a better understanding of how purity affects fluid degradation in concentrated solar power (CSP) plants, commercially available eutectic diphenyl oxide/ biphenyl heat transfer fluids were tested for their thermal stability at different temperatures and for their chlorine content. A model for thermal degradation of the eutectic diphenyl oxide/ biphenylfluids in a parabolic trough CSP plant was built based on laboratory testing results and average fluid analysis results from operating CSP plants. Fluid degradation was compared between high quality product at 99.9% purity such as DOWTHERM™ AHeat Transfer Fluid and commercially available products with purities around 99.5%. A range of 1.7-2.4 times more degradation was determined for 99.5% purity fluids compared to the 99.9% quality for the operating conditions in a CSP plant. More frequent degradation separation operations are needed for lower 99.5% purity fluids, which ultimately means extra operating cost. In addition to that, the additional new fluid refills needed over a 25 years of operation is $2/kg. DOWTHERM™ is a trademark of The Dow Chemical Company.

Modeling of Proton Conductivity through Perfluorosulfonate Acid Electrolyte Membranes

Proton conductivity (σ) through perfluorosulfonate acid (PFSA) polymer electrolyte membranes was modelled from the unsaturated hydraulic conductivity, which was described as a power-law function of water content; i.e.,λ q , where λ is the water content and the exponent q is a porosity factor. In this study, the membrane was modeled as a network of nanopores with the anionic groups (i.e., –SO3 –) assumed to be fixed along the pore wall according to an indeterminate distribution consistent with the material’s equivalent weight (EW) and dry membrane density. The transport of the hydronium ions inside the porous network was expressed using the extended Nernst-Einstein equation, which was modified using continuum percolation theory to reveal the relevant transport mechanisms at different water contents and temperatures. The power q in the modification was compatible with the critical path analysis simulation results; i.e., q=1.28±0.07 in two dimensions and q=1.86±0.19 in three dimensions, depending singularly on the dimensionality of the transport system. The average electrical conductivity of the membrane was deduced in terms of the following quantities: water content, equivalent weight, and the nature of the perfluorosulfonate acid polymer side chain. Theoretical predictions of this model were compared against experimental data of conductivity for four different membranes: DuPont’s Nafion 117 (EW = 1100), Membrane C (EW = 900) of Chlorine Engineers Corp., Japan, Dow Chemical’s XUS 13204.10 (EW = 800), and a 3M membrane developed by 3M Corp. (EW = 1000) for different water contents and temperatures. The theoretical predictions of the model matched the experimental data with reasonable quantitative accuracy in most cases.

First Principles Investigation of Stable LiMn2O4 Surfaces for Lithium-Ion Batteries

The spinel LiMn2O4 (LMO) has been widely studied as a lithium-ion battery cathode to replace the currently-used LiCoO2 materials due to its low cost and fast Li+ diffusivity.[1] However, a severe capacity fading during LMO cycling occurs because of the Mn dissolution, possibly initiating from the cathode surface. Thus, it is essential to completely understand the stable LMO surface structure to overcome current limitations and further to suppress the Mn dissolution in LMO. In this work, we investigate the effects of surface termination, slab reconstruction, relaxation schemes, magnetic ordering, and different U value for Mn to determine the relative stabilities of the LMO surfaces. We find that it is necessary to relax all atomic positions with symmetry-broken DFT calculations to fully capture the local variation of Mn-O and Li-O polyhedral clusters to obtain the most consistent surface energies. We finally comment on the possible implication of our work on the future surface studies of the mixed-valence transition metal complex oxides such as the LMO system. Acknowledgement: This work has been supported by Northwestern-Argonne Institute of Science and Engineering (NAISE) and by The Dow Chemical Company. Reference: [1] R. J. Gummow, A. Kock, M.M. Thackeray, Solid State Ionics 1994, 69, 59. Figure 1

A High-Throughput Search for Functional Cathode Coatings for Lithium-Ion Batteries By First-Principles Thermodynamics

A widely employed remedy to slow down the degradation of the electrochemical performances of lithium-ion batteries (LIBs) is to apply coating materials on cathode surfaces.[1] Such coatings can serve as physical barriers to inhibit electrode-electrolyte side reactions, and they can possess an additional functionality such as scavenging the detrimental acids (e.g., the hydrofluoric acid, HF) in electrolytes. Recently, we introduced a density functional theory (DFT) based framework to find promising HF-scavenging binary metal oxide coatings by considering their HF-scavenging tendencies and lithiation voltages.[2] Building on that framework, here we present a new high-throughput (HT) coating design strategy to search among thousands of candidate oxide materials and find the most promising candidates. In the current framework, we consider three main thermodynamic criteria to assess the effectiveness of a compound A a B b C c …O1/2 as a coating. First criterion is the thermodynamic stability of the candidate material. We evaluate this criterion by finding whether the material is stable against decomposition to other phases in its chemical space A-B-C-…-O. The second criterion is the electrochemical stability. This criterion tests whether the material is stable against reduction and oxidation during cycling. The third criterion is the HF-scavenging tendency. We evaluate this criterion for systems where an HF-scavenging functionality is preferred, by identifying the HF-scavenging reactions and free energies. In addition, we take into account the effect of different cathode-electrolyte chemistries on these three criteria, namely, presence of common cathode materials (LiCoO2, LiMn2O4, etc.), as well as presence of HF-free or HF-bearing electrolytes. Utilizing the HT-coating design framework described above, we screen more than ~100,000 oxide materials available in the Open Quantum Materials Database (OQMD)[3] to find coating materials with different target properties. We suggest promising multi-component oxide cathode coatings that can prolong the cycle-lives of LIBs, and surpass the effectiveness of common coatings used such as Al2O3, MgO and ZrO2. Acknowledgement This work has been supported by The Dow Chemical Company.

Revealing the Thermodynamics of Magnesium and Lithium Ion Insertion Chemistry in Ultrafast Discharging Hybrid Rechargeable Batteries

We present a combined experimental and theoretical strategy to design dual-salt Mg2+/Li+ batteries with very high electrochemical performance.[1] In this work, we first investigate the (co)-insertion mechanisms of Mg2+ and Li+ ions into the Mo6S8 cathode by using density functional theory (DFT) calculations together with the Nernst relation. We show that there exists a threshold for the Li+ activity in the electrolyte above which lithiation is preferred instead of magnesiation. Based on the DFT results, to achieve high electrochemical performance, we suggest an approach to control the insertion chemistry by varying the Li salt content of the electrolyte. Using this approach, we have carefully revealed the ion insertion chemistry for the Mg-metal anode/Mo6S8cathode hybrid Mg/Li batteries with all-phenyl complex (APC) and LiCl electrolytes. Our experimental results confirm that at low Li+ activities in the electrolyte, Mg2+ insertion dominates and the battery can cycle only below 80 mAh g-1, whereas at high Li+ activities, fast Li+ ionic transport in the entire intercalation range leads to higher voltage, capacity and rate capability. We find that the Mg/Li hybrid rechargeable battery with an APC 0.2 M and LiCl 0.5 M dual-salt electrolyte has a remarkable electrochemical performance. This hybrid battery with optimized insertion chemistry achieves 93.6% capacity retention at 20 C and 87.5% at 30 C at room temperature. Our combined computational and experimental study suggests an effective route to develop new dual-salt hybrid systems with controlled insertion chemistry. Acknowledgement This work has been supported by The Dow Chemical Company and Northwestern-Argonne Institute of Science and Engineering (NAISE).

Cheese whey treated by membrane separation as a valuable ingredient for barley sourdough preparation

Utilisation of cheese whey for production of healthier food has been the main task of this study. Cheese whey, which is often considered as a waste material, was treated by a series of processes including fermentation, membrane filtrations, mixing with barley flour, drying, and/or extrusion to produce barley sourdough.In the first series of experiments, the effect of membrane ultrafiltration (UF) and nanofiltration (NF) on separation of whey components has been studied. Non-fermented sweet cheese whey was treated by pilot-plant membrane ultrafiltration (50kDa tubular ceramic membrane, TAMI Industries, France), followed by three step diafiltration to minimise losses of lactose, glucose, galactose, and organic acids (namely lactic acid) in retentate. The UF permeates were used for the subsequent nanofiltration and diafiltrations (spiral wound membrane NF 270-2540, Filmtec, Dow Chemicals, USA). The results showed high recovery of proteins (81%) during UF and reduction of lactose and propionate losses by using diafiltration. Rejections of components on the NF membrane were: 93% lactose, 77% galactose, and 76% lactic acid. However, the diafiltration on the NF membrane reduced the relative recovery both for carbohydrates and organic acids.In the second series of experiments, cheese whey was concentrated by reverse osmosis (RO) and the obtained retentate was fermented with Lactobacillus plantarum, Lactobacillus sanfranciscensis and Propionibacterium freudenreichii subsp. freudenreichii. Part of the fermented whey was mixed with barley flour and dried by cold air fluid drying to produce sourdough pellets. The other part of fermented whey was filtered by nanofiltration and both permeate and retentate were sprayed on the surface of sourdough pellets in several layers and dried again. The extrusion of a mixture containing barley flour and fermented whey was tested for pellet production as well. The main aims were to obtain sourdough rich in natural preservatives, and maintain the present microorganisms active. That is why all the technological processes, including drying, were carried out under low temperatures. The content of organic acids (lactic, acetic and propionic) was analysed in final sourdough samples.

Industrialized watersheds have elevated risk and limited opportunities to mitigate risk through water trading

Businesses are increasingly concerned about water scarcity and its financial impacts, as well as competing needs of other stakeholders and ecosystems. Industrialized watersheds may be at more serious risk from water scarcity than previously understood because industrial and municipal users have inelastic demand and a high value for water. Previous water risk assessments have failed to sufficiently capture these economic aspects of water risk. We illustrate how hydro-economic modeling can be used to improve water risk assessments at a basin scale and we apply the methodology to the industrialized Brazos River Basin (85% municipal and industrial withdrawals) and consider implications for The Dow Chemical Company׳s Freeport Operations in Texas, US. Brazos water right holders pay only operating and maintenance costs for water during normal periods; however, when shortages occur, leasing stored water or reducing production may be the only mitigation option in the short-run. Modeling of water shortages and the theoretical cost of leasing water under nine combined scenarios of demand growth and climate change suggests that water lease prices to industry could increase by 9–13X. At best, a more developed water rights and storage lease market could result in lower lease prices (2–3X); however, given that transactions would be limited it is more likely that prices would still increase by 4–13X. These results suggest that markets are unlikely to be a robust solution for the Brazos because, in contrast to other watersheds in the Western US, there is little reliable water to trade from low value users (agricultural) to high value users (industry and municipalities). Looking at demand trends across the contiguous US as an indicator of water risk, 2% of watersheds have municipal and industrial demands that outstrip total surface and ground water supplies and in these watersheds industry has historically paid higher lease prices for water. This study provides new ways for businesses to characterize water risk and forecast water prices that uncovers hidden water risk and highlights the positive but diminished mitigating effects of water markets in a highly industrialized basin.

Firm’s knowledge creation structure for new product development

AbstractKnowledge has many different characteristics and scholars in epistemology, economics and management have dealt with them ever since knowledge has emerged as the leading source of firms’ competitive advantages. New product development requires new ideas and new ideas are stemming from knowledge. Knowledge originates from tacit knowledge. Therefore, firms need to enact tacit knowledge. Enactment takes different forms depending on the context of knowledge and organizational characteristics. This paper conducts an in-depth literature review on the nature of knowledge and knowledge creation structure and investigates how The Dow Chemical Company uses a knowledge creation structure to elicit tacit knowledge and exploit knowledge for new product development. The Dow Chemical Company is known as one of the leading innovative firms in the world. We believe that this case enriches research on knowledge creation and new product development although it has limitations in generalizing its findings and practice...

Driving innovation through life-cycle thinking

The concept of sustainability is critical for businesses and individuals to understand and apply. Although there are many ways to define sustainability, at The Dow Chemical Company (Dow) we say that sustainability requires making every decision with the future in mind. Sustainable innovation is driven by a clear corporate strategy, global accountability to goals, and a variety of tools to track and improve business performance. The ability to articulate aspirational goals for some areas and quantitative measurements for others is critical. Individual awareness of the four themes of sustainable chemistry and engineering (atom economy, energy efficiency, reduced hazard, and holistic design) is a firm foundation for sustainable innovation. The Dow Chemical Sustainability Footprint Tool©, life-cycle assessment, and a product-based Sustainable Chemistry Index are very useful in positioning and quantifying sustainability as a target for innovation—and a source of business growth. The development, application, and use of these tools in Dow are described.

Finding solutions to water scarcity: Incorporating ecosystem service values into business planning at The Dow Chemical Company’s Freeport, TX facility

Water scarcity presents a major risk to businesses, but it can be hard to quantify. Ecosystem service valuation methods may help businesses better understand the financial impacts of water shortages and identify solutions. At The Dow Chemical Company’s facility in Freeport, TX, we used natural capital asset valuation to assess the risk from future changes in industrial water supplies. We found that the value of industrial water rights may increase in the future with increased demand but that potential decreases in reliability of water rights due to demand growth and climate change could reduce their value. Using this information, experts identified 16 potential nature-based and collaborative (involving other water users) solutions to future water scarcity. We used multi-criteria analysis to select five of the 16 solutions for further analysis. Two solutions (marsh wastewater treatment, land management) were not cost-competitive and three solutions (reservoir flood pool reallocation/floodplain restoration, irrigation efficiency, municipal rebate program) were cost-competitive with the business-as-usual solution (expanding reservoir storage). However, these solutions have significant technical, legal, and political hurdles. We also found that these solutions provide substantial collective benefits to the public and biodiversity, suggesting that such solutions may be appropriate for implementation via multi-stakeholder collaboration.

Characterization of Chemical/Mechanical Properties of Surface Films in Copper CMP

The chemical and mechanical properties of wafer materials have a direct impact on the performance of the CMP process. This report presents a systematic study to characterize surface films on copper wafers in the presence of simple peroxide solutions as well as representative bulk copper and copper barrier CMP slurries offered by the Dow Chemical Company. Measurements are made of chemical composition, thickness, modulus, and removal rate of films formed under both static etch and CMP conditions. Sample aging—a major obstacle in past efforts of this type—is minimized by temporarily setting up the equipment for wafer film preparation in close proximity to the surface analytical instruments. It is found that Dow's commercial bulk and barrier Cu CMP slurries form permeable surface films less than 4 nm deep consisting of reaction products with copper. Compared to native copper, the films have compressive and shear moduli that are 5X and 2X lower respectively—enabling mechanical removal by sliding contact with pad asperities at a lower threshold contact pressure. The results provide insight into the mechanism of surface film formation during CMP and lay groundwork for modeling the mechanical and chemical steps in the wafer planarization process.

Performance of New Biodegradable Di‐Sulfonate Surfactants as Hydrotropes in High‐Temperature and Salinity Environments

AbstractPropyl alkyl ether sulfonate (PAES) surfactants, recently developed by The Dow Chemical Company, show excellent electrolyte, hard water and caustic solubility, with attractive ECOTOX profile and biodegradability. Due to their unique structure and properties, they are good candidates for use as hydrotropes in formulations containing nonionic surfactants. The goal of these studies was to evaluate hydrotropic efficiency of PAES materials via cloud point analysis. The effects of PAES alkyl tail length, concentration, and mono‐ and di‐sulfonate components on the cloud point of TERGITOL™ 15‐S‐9 in solutions of varying electrolyte strength were investigated. In the presence of high electrolyte levels, PAES 12C had the highest hydrotropic efficiency of all materials tested, including commonly used commercial hydrotropes. Di‐sulfonate components of the PAES materials were found to be more efficient hydrotropes than mono‐sulfonate in high electrolyte environments for all tail lengths tested. The di/mono ratio and tail length were found to be critical parameters.

Utilization of Fly Ash Nanofluids in Two-phase Closed Thermosyphon for Enhancing Heat Transfer

This study investigates how fly ash nanofluids affect the thermal performance of a two-phase closed thermosyphon at various states of operation. The utilization of nanofluids obtained from X2O3-type oxides, such as Al2O3, Fe2O3, or CuO, on the improvement of two-phase closed thermosyphon performance was reported in a number of studies in the literature. The present study experimentally demonstrated the effect of using a nanofluid obtained from fly ash comprised of various types of metal oxides in varying ratios on improving the performance of a two-phase closed thermosyphon. The fly ash was obtained from the flue gas that was captured in the cyclones of the Yatagan thermal power plant (Turkey). Triton X-100 (Dow Chemical Company) dispersant was used in the study to produce the 0.2% (wt) fly ash/water nanofluid via direct synthesis. A straight copper tube with an inner diameter of 13 mm, outer diameter of 15 mm, and length of 1 m was used as the two-phase closed thermosyphon. The nanofluid filled 33.3% (44.2 ml) of the volume ofthe two-phase closed thermosyphon. Three heating power levels (200, 300, and 400 W) were used in the experiments with three different flow rates of cooling water (5, 7.5, and 10 g/s) used in the condenser for cooling the system. A increase of 26.39% was achieved in the efficiency of the two-phase closed thermosyphon when 4% (wt) fly ash containing nanofluid was used to replace deionized water at a heat load of 200 W and with a cooling water flow rate of 5 g/s.

Some Items of Interest to Process R&D Chemists and Engineers

ADVERTISEMENT RETURN TO ISSUEPREVHighlights from the ...Highlights from the LiteratureNEXTSome Items of Interest to Process R&D Chemists and EngineersWenyi Zhao, Dongbo Zhao, Sylvain Guizzetti, Arjun Raghuraman, James A. Schwindeman, and John Knight*View Author Information Jacobus Pharmaceutical Co. Inc., Princeton, New Jersey 08540, United States. E-mail: [email protected] Bayer MaterialScience (China) Company Limited, 33 Qinqiao Rd, Jinqiao Export Processing Zone, Pudong District, Shanghai 201206, P. R. China. E-mail: [email protected] NovAlix, Building A: Chemistry, Bioparc, Bld Sébastien Brant BP 30170, F-67405 Illkirch Cedex, France. E-mail: [email protected] Polyurethane Process R&D, The Dow Chemical Co., Freeport, Texas 77541, United States. E-mail: [email protected] Rohner Inc., 4066 Belle Meade Circle, Belmont, North Carolina 28012, United States. E-mail: [email protected] Scientific Update LLP, Maycroft Place, Stone Cross, Mayfield, East Sussex TN20 6EW, U.K.*E-mail: [email protected]Cite this: Org. Process Res. Dev. 2014, 18, 10, 1156–1163Publication Date (Web):October 8, 2014Publication History Published online8 October 2014Published inissue 17 October 2014https://doi.org/10.1021/op5002897Copyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views2450Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (916 KB) Get e-AlertsSUBJECTS:Cyclization,Hydrocarbons,Ketones,Organic compounds,Reagents Get e-Alerts

Solidarity after Bhopal: Building a Transnational Environmental Justice Movement

Abstract This article documents the history of the U.S.-based campaign that emerged around the ongoing Bhopal disaster, since the 2001 merger of Union Carbide Corporation (Union Carbide) and the Dow Chemical Company (Dow). Based on interviews with key organizers and former and current campaigners in the United States and in Bhopal, the article discusses how this movement has worked to keep the Bhopal disaster alive and relevant for its three target constituencies in the United States. By appealing to social and environmental justice (EJ) groups, students, and the Indian diaspora, the campaign has won small victories in India and has challenged Dow's greenwashing attempts. Members of the diaspora have been instrumental in setting in motion what scholars have called the boomerang effect through exerting pressure on the Indian government. We also see the double boomerang at work in the United States when EJ activists make strategic references to Bhopal in times of crisis. More needs to be done, however, to b...

Some Items of Interest to Process R&D Chemists and Engineers

ADVERTISEMENT RETURN TO ISSUEPREVHighlights from the ...Highlights from the LiteratureNEXTSome Items of Interest to Process R&D Chemists and EngineersWenyi Zhao, Dongbo Zhao, Sylvain Guizzetti, Arjun Raghuraman, and John Knight*View Author InformationJacobus Pharmaceutical Co. Inc., Princeton, New Jersey 08540, United States. E-mail: [email protected]Bayer Technology & Engineering (Shanghai) Co. Ltd., 82 Mu Hua Road, Shanghai Chemical Industry Park, Shanghai 201507, P. R. China. E-mail: [email protected]NovAlix, Building A: Chemistry, Bioparc, Bld Sébastien Brant BP 30170, F-67405 Illkirch Cedex, France. E-mail: [email protected]Polyurethane Process R&D, The Dow Chemical Co., Freeport, Texas 77541, United States. E-mail: [email protected]Scientific Update LLP, Maycroft Place, Stone Cross, Mayfield, East Sussex, TN20 6EW, U.K.*E-mail: [email protected]Cite this: Org. Process Res. Dev. 2014, 18, 8, 922–927Publication Date (Web):August 1, 2014Publication History Published online1 August 2014Published inissue 15 August 2014https://doi.org/10.1021/op5002269Copyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views2327Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSUBJECTS:Alcohols,Anions,Catalysts,Organic compounds,Sulfones Get e-Alerts

Development of phosphors with high thermal stability and efficiency for phosphor-converted LEDs

This article briefly reviews the developments of the phosphors with high thermal stability and high efficiency for use in phosphor-converted LED (pcLED) packages by Lightscape Materials Inc. (wholly owned by The Dow Chemical Company). The current industry design objectives for pcLED packages are first outlined with emphasis on the emission spectral features required for target brightness and color characteristics for general illumination and back light unit for liquid crystal displays. There is a growing demand on thermal stability of the phosphor emission as the LED package power increases. A phenomenological analysis is described on luminescence loss and its relation to thermal stability of luminescence emission at elevated temperatures, which serves as an empirical guide in the search for new phosphor materials of high thermal stability. Finally, the formulations and luminescence properties of the proprietary carbidonitride and oxycarbidonitride phosphors are discussed.

Multinuclear group 4 catalysis: olefin polymerization pathways modified by strong metal-metal cooperative effects.

Polyolefins are produced today catalytically on a vast scale, and the manufactured polymers find use in everything from artificial limbs and food/medical packaging to automotive and electrical components and lubricants. Although polyolefin monomers are typically cheap (e.g., ethylene, propylene, α-olefins), the resulting polymer properties can be dramatically tuned by the particular polymerization catalyst employed, and reflect a rich interplay of macromolecular chemistry, materials science, and physics. For example, linear low-density polyethylene (LLDPE), produced by copolymerization of ethylene with linear α-olefin comonomers such as 1-butene, 1-hexene, or 1-octene, has small but significant levels of short alkyl branches (C2, C4, C6) along the polyethylene backbone, and is an important technology material due to outstanding rheological and mechanical properties. In 2013, the total world polyolefin production was approximately 211 million metric tons, of which about 11% was LLDPE. Historically, polyolefins were produced using ill-defined but highly active heterogeneous catalysts composed of supported groups 4 or 6 species (usually halides) activated by aluminum alkyls. In 1963, Karl Ziegler and Giulio Natta received the Nobel Prize for these discoveries. Beginning in the late 1980s, a new generation of group 4 molecule-based homogeneous olefin polymerization catalysts emerged from discoveries by Walter Kaminsky, a team led by James Stevens at The Dow Chemical Company, this Laboratory at Northwestern University, and a host of talented groups in Germany, Italy, Japan, the United Kingdom, and the United States. These new "single-site" catalysts and their activating cocatalysts were far better defined and more rationally tunable in terms of structure, mechanism, thermodynamics, and catalyst activity and selectivity than ever before possible. An explosion of research advances led to new catalysts, cocatalysts, deeper mechanistic understanding of both the homogeneous and heterogeneous systems, macromolecules with dramatically altered properties, and large-scale industrial processes. It is noteworthy that many metalloenzymes employ multiple active centers operating in close synergistic proximity to achieve high activity and selectivity. Such enzymes were the inspiration for the research discussed in this Account, focused on the properties of multimetallic olefin polymerization catalysts. Here we discuss how modifications in organic ligand architecture, metal···metal proximity, and cocatalyst can dramatically modify polyolefin molecular weight, branch structure, and selectively for olefinic comonomer enchainment. We first discuss bimetallic catalysts with identical group 4 metal centers and then heterobimetallic systems with either group 4 or groups 4 + 6 catalytic centers. We compare and contrast the polymerization properties of the bimetallic catalysts with their monometallic analogues, highlighting marked cooperative enchainment effects and unusual polymeric products possible via the proximate catalytic centers. Such multinuclear olefin polymerization catalysts exhibit the following distinctive features: (1) unprecedented levels of polyolefin branching; (2) enhanced enchainment selectivity for linear and encumbered α-olefin comonomers; (3) enhanced polyolefin tacticity and molecular weight; (4) unusual 1,2-insertion regiochemistry for styrenic monomers; (5) modified chain transfer kinetics, such as M-polymer β-hydride transfer to the metal or incoming monomer; (6) LLDPE synthesis with a single binuclear catalyst and ethylene.

Technoeconomic Analysis for the Production of Mixed Alcohols via Indirect Gasification of Biomass Based on Demonstration Experiments

An integrated biomass-to-mixed alcohol process was demonstrated at the pilot scale, including indirect gasification, tar and hydrocarbon reforming, gas conditioning, and gas to liquids operations. Additional bench-scale experiments were conducted to gather insights into reforming and fuel synthesis operations under more extensive conditions. Data from these experiments were combined with tools and knowledge owned by industrial partners—Rentech and The Dow Chemical Company—to validate a conceptual commercial-scale cellulosic ethanol refinery. Results suggest that both reforming and mixed alcohol processes are scalable and economical, with a modeled mature plant ethanol production cost of $0.54/L ($0.82/L of gasoline equivalent). Sustainability metrics for the conversion process are also presented.