Evan S. Beach

Algae as a source of renewable chemicals: opportunities and challenges

Algae are being explored as a sustainable energy feedstock, having potential to reduce dependence on petrofuels and offset greenhouse gas emissions. Economic considerations and principles of green design suggest that if algae-to-fuel technology is to be successful, biofuels must be produced simultaneously with value-added co-products. At present, the algae industry is centered around a limited number of products, such as low-volume/high-value speciality nutrients. New products for medium- and high-volume markets will be needed as biomass production increases in scale. This Perspective highlights non-fuel applications of algal biomass that have received relatively little attention to date but are promising for future development. It is our goal to draw attention to some of the unique opportunities that algae present with respect to biochemical composition as compared to lignocellulosic energy crops.

Depolymerization of organosolv lignin to aromatic compounds over Cu-doped porous metal oxides

Isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in methanol with an added pressure of H2, using a porous metal oxide catalyst (PMO) derived from a Cu-doped hydrotalcite-like precursor. The Cu-PMO was effective in converting low-molecular weight lignin into simple mixtures of aromatic products in high yield, without char formation. Gel permeation chromatography was used to track changes in molecular weight as a result of the catalytic treatments and product mixtures were characterized by 1H and 13C NMR spectroscopy. In the temperature range 140–220 °C, unusual C9 catechols were obtained with high selectivity. Lignin conversion of >90% and recovery of methanol-soluble products in yields of was >70% was seen at 180 °C with optimized catalyst and biomass loadings. At 140 °C, 4-(3-hydroxypropyl)-catechol was the major product and could be isolated in high purity.

Green Chemistry: A design framework for sustainability

In this review we will highlight some of the science that exemplifies the principles of Green Chemistry, in particular the efficient use of materials and energy, development of renewable resources, and design for reduced hazard. Examples are drawn from a diverse range of research fields including catalysis, alternative solvents, analytical chemistry, polymer science, and toxicology. While it is impossible for us to be comprehensive, as the worldwide proliferation of Green Chemistry research, industrial application, conferences, networks, and journals has led to a wealth of innovation, the review will attempt to illustrate how progress has been made toward solving the sustainability goals of the 21st century by engaging at the molecular level.

Preferential technological and life cycle environmental performance of chitosan flocculation for harvesting of the green algae Neochloris oleoabundans

Dewatering of the green algae Neochloris oleoabundans by flocculation was investigated for chitosan biopolymer, ferric sulfate, and alum. Chitosan was found to be most effective flocculant, with an optimum dose of 100mg/L algae broth. Zeta potential measurements suggest the mechanism involves both adsorption and charge neutralization processes. Life cycle assessment (LCA) was used to compare the chitosan method to other flocculation methods as well as centrifugation and filtration/chamber press processes. LCA showed that among these techniques, flocculation by chitosan is the least energy intensive and had the lowest impacts across all other categories of environmental impacts. The results are discussed in the overall context of biofuel production from algal biomass.

Green chemistry: the emergence of a transformative framework

Abstract Since the Twelve Principles of Green Chemistry were formulated in the 1990s, there have been tremendous successes in developing new products and processes to be more compatible with human health, the environment, and sustainability goals. This review gives a sampling of research successes from the last 20years, including advances in synthetic efficiency, application of alternative synthetic methods, use of less hazardous solvents and reagents, and development of renewable resources for chemical feedstocks. The future of green chemistry will depend on innovations that consolidate and integrate these achievements that have been made, using all Twelve Principles as a framework for intentional design. Designing for sustainability and reduced hazard should not be viewed as constraining, but rather as providing the freedom to explore and invent, bridging continents and scientific disciplines to create new solutions.

Depolymerization of organosolv lignin using doped porous metal oxides in supercritical methanol

An isolated, solvent-extracted lignin from candlenut (Aleurites moluccana) biomass was subjected to catalytic depolymerization in the presence of supercritical methanol, using a range of porous metal oxides derived from hydrotalcite-like precursors. The most effective catalysts in terms of lignin conversion to methanol-soluble products, without char formation, were based on copper in combination with other dopants based on relatively earth-abundant metals. Nearly complete conversion of lignin to bio-oil composed of monomers and low-mass oligomers with high aromatic content was obtained in 6h at 310°C using a catalyst based on a Cu- and La-doped hydrotalcite-like precursor. Product mixtures were characterized by NMR spectroscopy, gel permeation chromatography, and GC-MS.

Life cycle inventory improvement in the pharmaceutical sector: assessment of the sustainability combining PMI and LCA tools

Pharmaceutical chemicals are complex, high value added products that typically impose significantly greater impacts on the environment per kilogram compared to basic chemicals. A variety of green metrics have been developed to guide the design of chemistries and processes that are more sustainable. Among these, Process Mass Intensity (PMI) was selected by the American Chemical Society Green Chemistry Institute Pharmaceutical Roundtable as the key parameter to express sustainability. However, researchers were concerned that these metrics could miss relevant factors that would be addressed by a more comprehensive Life Cycle Assessment (LCA). Lack of inventory data for many chemicals poses a significant barrier to more extensive implementation of LCA for pharmaceuticals. A cradle-to-gate LCA of Viagra™ is used to present a practical approach to construct inventories using patent and literature data. Details of the improved inventory data were presented for four chemicals to illustrate the methodology and highlight the importance of considering out-sourced processing of reagents used in pharmaceutical synthesis. A more comprehensive impact assessment was conducted using ReCiPe v1.11 at both midpoint and endpoint levels. A comparison of two synthesis routes rated them well against results from the simpler green metrics. An area for future work is to address the lack of characterization factors for toxicity and other impact categories for many chemicals.

Rapid, biomimetic degradation in water of the persistent drug sertraline by TAML catalysts and hydrogen peroxide.

Iron TAML activators (oxidation catalysts based upon tetraamido macrocyclic ligands) at nanomolar concentrations in water activate hydrogen peroxide to rapidly degrade sertraline, the persistent, active pharmaceutical ingredient (API) in the widely used drug Zoloft. Although all the API is readily consumed, degradation slows significantly at one intermediate, sertraline ketone. The process occurs from neutral to basic pH. The pathway has been characterized through four early intermediates which reflect the metabolism of sertraline, providing further evidence that TAML activator/peroxide reactive intermediates mimic those of cytochrome P450 enzymes. TAML catalysts have been designed to exhibit considerable variability in reactivity and this provides an excellent tool for observing degradation intermediates of widely differing stabilities. Two elusive, hydrolytically sensitive intermediates and likely human metabolites, sertraline imine and N-desmethylsertraline imine, could be identified only by using a fast-acting catalyst. The more stable intermediates and known human metabolites, desmethylsertraline and sertraline ketone, were most easily detected and studied using a slow-acting catalyst. The resistance of sertraline ketone to aggressive TAML activator/peroxide treatment marks it as likely to be environmentally persistent and signals that its environmental effects are important components of the full implications of sertraline use.

Fe-TAML/hydrogen peroxide degradation of concentrated solutions of the commercial azo dye tartrazine

Here we describe a catalytic oxidation process for decomposing concentrated dye solutions, as a model for the treatment of concentrated industrial effluent streams. The prototype Fe-TAML/H2O2 oxidizing system rapidly and extensively degrades the recalcitrant azo dye, tartrazine, in water at ambient temperatures and at dye concentrations that are industrially important. Nearly complete dye removal can be obtained with performance-optimized dosing and pH control. At higher, but still remarkably low catalyst and oxidant concentrations, the dye is removed to below detection limits. 3D surface plots reveal that optimum decolorization at high dye concentration (16.5 g L−1, 30.9 mM) requires 50 times less catalyst and 5 times less oxidant per substrate than at low dye concentration (16.5 mg L−1, 30.9 μM), demonstrating a clear process benefit of higher substrate concentrations. The Fe-TAML/H2O2 system generates environmentally benign and/or biodegradable products from tartrazine: small organic acids, 4-phenolsulfonic acid, and a small amount of 4-nitrobenzenesulfonic acid. The acute toxicity of the Fe-TAML/H2O2/tartrazine reaction mixture toward luminescent bacteria is approximately half that of tartrazine as determined by the Microtox® assay. The results suggest a potential utility of the Fe-TAML/H2O2 technology for treating wastewaters containing high substrate concentrations from the dyeing industry in a straightforward manner to ameliorate environmental impacts, and because of the degradation resistance of tartrazine, that this potential utility might extend to other industries.

Linear and cyclic C-glycosides as surfactants

Carbohydrate-based surfactants have long been of interest due to their desirable performance properties and their potential to be derived from renewable feedstocks. Although most carbohydrate based surfactants utilize an O-glycosidic linkage, recent advances in carbohydrate C–C bond formation allows for the facile synthesis of new classes of carbohydrate-based surfactants on a C-glycosidic linkage. Herein is described an approach that can generate a wide variety of C-glycoside surfactants in moderate to very good yield by treating the nonulose C-glycoside intermediate first described by Lubineau et al. with pyrrolidine in the presence of an alkyl aldehyde. Depending on the stoichiometry and reaction conditions, this chemistry will result in either a linear enoneC-glycoside, or a cyclohexenoneC-glycoside, both of which demonstrate interesting surfactant properties. Further, the linear enone series can be photochemically modified or reacted with other alkyl aldehydes to generate additional analogs.