Microalgae Biomass as a New Potential Source of Sustainable Green Lubricants

Lubricants are materials able to reduce friction and/or wear of any type of moving surfaces facilitating smooth operations, maintaining reliable machine functions, and reducing risks of failures while contributing to energy savings. At present, most worldwide used lubricants are derived from crude oil. However, production, usage and disposal of these lubricants have significant impact on environment and health. Hence, there is a growing pressure to reduce demand of this sort of lubricants, which has fostered development and use of green lubricants, as vegetable oil-based lubricants (biolubricants). Despite the ecological benefits of producing/using biolubricants, availability of the required raw materials and agricultural land to create a reliable chain supply is still far from being established. Recently, biomass from some microalgae species has attracted attention due to their capacity to produce high-value lipids/oils for potential lubricants production. Thus, this multidisciplinary work reviews the main chemical-physical characteristics of lubricants and the main attempts and progress on microalgae biomass production for developing oils with pertinent lubricating properties. In addition, potential microalgae strains and chemical modifications to their oils to produce lubricants for different industrial applications are identified. Finally, a guide for microalgae oil selection based on its chemical composition for specific lubricant applications is provided.     

Lubricants from renewable energy sources – a review

Lubricant oils are known to decrease the friction coefficient between two contacting surfaces. It is essential for the correct function of almost the totality of mechanical machinery working in the entire world. Lubricant oils consist of about 80% of oily base stocks which attributes to their properties of viscosity, stability, and pour point to the lubricant plus additives supplemented to improve these properties. Petroleum lubricants are usually environmentally unacceptable due to their low biodegradability and toxicity. These oils contaminate the air, soil, and drinking water and affect human and plant life to a great extent. Thus, the demand for environmentally acceptable lubricants is increasing along with the public concerns for a pollution-free environment. Plant oils are promising as base fluid for biolubricants because of their excellent lubricity, biodegradability, viscosity–temperature characteristics, and low volatility. The purpose of this paper is to present a survey of the current status of biolubricating oil. This research provides an overview on the synthesis, tribochemical behavior; the effect of structure on friction/wear, load-bearing capacity, resistance to rise in specimen temperature, and varying response of antiwear/extreme-pressure additives in the presence of vegetable oil/derivative structures has also been discussed. Though a significant number of papers have been published in this area, there is still much to explore. A proper selection of base oil and additives is therefore essential for an efficient synthesis of biolubricating oil.     

Surface forces between bottlebrush polymer layers

In this review, I summarize recent experimental investigations of surface and friction forces between bottlebrush structure macromolecules including biolubricants and biomimetic ones by direct force measurements. I also discuss recent experimental investigations of synergy in lubrication in which a question, ‘How do lubricants act together?’, is aimed to be answered. Lastly, challenges and opportunities for developing efficient lubricating systems are outlined.     

Industrial development and applications of plant oils and their biobased oleochemicals

In the concepts for new products, performance, product safety, and product economy criteria are equally important. They are taken into account already when the raw materials base for a new industrial product development is defined. Here, renewable resources gain-again after the earlier “green trend” in the 1980s—increasing attention as an alternative raw materials source compared to fossil feedstock. The industrial use of carbohydrates, proteins, and plant oils aligns perfectly with the principles of Responsible Care and is an important part of green chemistry and sustainability in general. Since the 1950s, oleochemistry has grown to a major research and technology area in several institutions and industries. A large variety of products based on fats and oils have been developed since then for different uses, such as specialties for polymer applications, biodiesel, surfactants, emollients for home and personal-care industries, pesticides and biodegradable mineral oil replacements for lubricants. However, at present it seems that the use of renewable resources, especially plant oils, has to compete more and more with the increasing demand for bioenergy, which could cause an unbalanced supply and demand in the future or even a threat for the increasing demand for food in certain areas of the world.     

Plant oils: The perfect renewable resource for polymer science?!

Already for a long time, plant oils and their derivatives have been used by polymer chemists due to their renewable nature, world wide availability, relatively low price, and their rich application possibilities. Although many different synthetic approaches have been used, more recent examples are pointing in the direction of catalytic transformations and other efficient reactions to achieve a more sustainable production of polymers from these renewable resources. In this context, olefin metathesis, thiol–ene additions, and other processes can contribute not only to a more efficient synthesis of plant oil based polymers, but also to broaden the application possibilities of plant oils. This feature article provides an overview of the present situation with special attention to the use of olefin metathesis and thiol–ene chemistry as synthetic methods and as polymerization techniques.     

Nachhaltige Bausteine für die Kunststoff‐Herstellung

Plant oils are currently the principle resource for the production of bio‐based, high performance polymers, such as polyamides. This process is facilitated by giant strides in chemical catalysis and biotechnology, which allows conversion of vegetable oils in “drop‐in” chemical building blocks. These bio‐based polymer building blocks have equivalent chemical and physical properties as well as similar cost structures compared to conventional petrochemical synthesis feedstock. This allows integration of bio‐based resources into industrial production processes without significant adaptations in logistics or process configuration. However, only use of synergies between chemical and biotechnological unit operations will in future provide for sustainable and eco‐efficient process designs. To allow sustainable supply of bio‐oils to a growing chemical industry without a significant impact on food production demands development of alternative bio‐oil sourcing strategies. In this respect the development of processes for the production of microbial oils, which have equivalent chemical properties to their plant counterparts is imperative. One leading option is the biotechnological conversion of agricultural and food waste streams into microbial oils by combining enzymatic hydrolysis and fermentative production using oleaginous organisms, such as yeasts.     

Fluoroarylphosphines as ligands

This short review concentrates on important aspects of fluoroarylphosphines, in particular their synthesis, ligand properties and chemical and catalytic properties of their complexes. Although the electronic, steric and chemical properties of fluoroarylphosphines have been known for 30 years, their use as ligands for homogeneous catalysis and in the synthesis of elaborate multidentate ligands has occurred more recently. The number of recent reports suggests that their importance is growing.     

Plant wastes and sustainable refineries: What can we learn from fungi?

The valorization of plant wastes allows access to renewable carbon feedstocks without increasing the demand for plant biomass production. Plant wastes are the non-edible residues and waste streams from agriculture, agroindustry and forestry. The chemical diversity and recalcitrance to degradation of such wastes challenge our ability to transform and valorize these resources into value-added compounds. Fungi that thrive on plant tissues have gained a huge diversity of enzymatic toolkits for the finely-tuned degradation of glycan and lignin polymers. Our knowledge on the enzymatic systems developed by fungi now guides innovations for plant waste bioprocessing. Here, we provide an overview of the most recent findings in the hydrolytic and oxidative systems used by fungi for the degradation of recalcitrant plant polymers. We present recent promising success in applying fungal enzymes or fungal fermentations on plant wastes, and discuss the forthcoming developments that could reinforce fungal biotechnology entering a variety of industrial applications.     

Waste cooking oil as a promising source for bio lubricants- A review

The development of renewable and sustainable products to replace fossil fuels is a key topic in this decade from an industrial, environmental, and scientific perspective. There is an inescapable flow of mineral-based lubricants into the environment due to the increasing use of numerous lubricant types, most of which are mineral-based. Waste cooking oil is another problem, and the disposal of this oil pollutes the environment. Making bio-based lubricant from used cooking oil can solve both of these problems. Lubricating oils that can be created from waste cooking oil are the subject of this article. Bio-lubricants are an attractive alternative to conventional petro-based lubricants because of a number of physical properties, including as biodegradability, high lubricity, and high flash points. Despite this, they are expected to displace petroleum-based lubricants in a range of applications because to their inefficient chemical structure. This allows waste oil to be used as a lubricant while still keeping its tribological and environmental properties through chemical modification. Biodegradable lubricants may benefit from lower prices for waste natural oils, which may help them compete on the market. This article provides a brief introduction of waste cooking oil and its possible use as a bio-based lubricant, as well as the many elements and trends within it.     

Biodiesel Production from Vegetable Oils and Animal Fat over Solid Acid Double-Metal Cyanide Catalysts

Biodiesel comprises of fatty acid alkyl esters prepared from vegetable oils or animal fat by esterification/transesterification with short-chain alcohols (methanol or ethanol, for example). It is a biodegradable renewable fuel. Its production is growing exponentially due to greater concerns about environmental protection and depletion of fossil fuel resources. Further, its production from non-edible oils and animal fat is more desirable than from edible oils due to lower cost of non-edible feedstocks and elimination of food verses fuel issues. Solid acid catalysts are ideal for conversion of such low-grade oils to biodiesel. Biodiesel from non-edible oils can be produced by two methods: (1) simultaneous esterification of fatty acids and transesterification of fatty acid glycerides and (2) hydrolysis of glycerides followed by esterification. This account reports the catalytic performance of solid, Fe–Zn double-metal cyanide (DMC) complexes and other acid catalysts in these transformations for biodiesel production. The factors influencing the catalytic performance of the solid acid catalysts in biodiesel production are discussed.     

Chemical modification of waste cooking oil for the biolubricant production through transesterification process

Concerns and restrictions around contamination and environmental pollution are developing. The production of waste cooking oil and the pollution brought on by mineral oils are two important issues. The FSSAI's new standards state that cooking oil that contains more than 25% polar compounds is inappropriate for use and should be discarded. Therefore, both issues can be resolved with the aid of chemical modifications to waste cooking oil. Waste cooking oils are an attractive alternative to mineral oils because they are biodegradable and renewable sources of lubricants. The goal of the current research work is to create an environmentally friendly lubricant through transesterification reaction. Fatty acid methyl esters (FAMEs) of WCO with various alcohols (1-Heptanol, 2-Ethyl-1-Hexanol & Neopentyl Glycol) with diverse branching were used to create bio lubricant. As a heterogeneous catalyst, zinc acetate was used to carry out the reaction. Complex esters, which have been produced, have the potential to be used as biodegradable lubricants in industrial lubricant applications. Using the GC-MS technique, the structure of the generated bio lubricant was examined. The structural modification of waste cooking oil resulted in improvement in both physicochemical and tribological properties. The created bio lubricant had improved flash and fire points as well as a superior viscosity index (>120). The generated bio lubricant possesses friction characteristics that are comparable to those of commercial mineral oil-based lubricants. According to the results of this study, waste cooking oil lubricant has a lot of potential for use as a base stock due to its favorable biodegradability and tribological performance.     

Environmentally Friendly Recovery and Characterization of Oil from Used Engine Lubricants

The present paper demonstrates the review of some acid processes as well as development of some new solvent processes for reclamation of used lubricating oils. The conventional processes are found to be of low yield (? 50%), laborious, time consuming and environmentally hazardous, because of residual acidic sludge. Based on the findings, a new modified Aluminium sulphate‐sodium silicate‐acid‐base method employing a small quantity of acid and giving a high yield (? 60%) is proposed. Further, to avoid use of acid, new regeneration processes based on solvent extraction were investigated. They are termed CCl₄‐alcohol method, Dodecane‐alcohol method and Toluene‐alcohol method. These processes are not only cost effective in terms of complete solvent recovery, but are rapid, less time consuming, more environmentally friendly and gave a high yield (70–75%). The virgin lubricants (Castrol GTX and Rimula‐C) as well as oils recovered by different methods were also characterized physicochemically to determine kinematic viscosity, density, refractive index, carbon distribution, wear scar diameter, % Conradson carbon residue, % ash, % chloride, pour point, etc. Results obtained show that many of the physico‐chemical properties of the recovered oils are in good agreement with those of virgin oils. The n.d.M analysis was also performed which shows that virgin oils have 73 ± 3% paraffinic carbon, 26 ± 3% naphthenic carbon and about 1% aromatic carbon. The recovered oils also showed nearly the same chemical composition. The UV‐Visible spectra of the recovered oils are all similar to those of virgin lubricants. The results suggest that the oils recovered by solvent treatments, particularly Dodecan‐alcohol and Toluene‐alcohol methods, may serve for lubrication purposes and can be rendered as excellent as virgin lubricants with the addition of certain additives. The proposed methods may be considered as alternative cost effective green techniques for acid reclamation processes and being the motivation of the present investigation.     

Conversion of biomass to selected chemical products

This critical review provides a survey illustrated by recent references of different strategies to achieve a sustainable conversion of biomass to bioproducts. Because of the huge number of chemical products that can be potentially manufactured, a selection of starting materials and targeted chemicals has been done. Also, thermochemical conversion processes such as biomass pyrolysis or gasification as well as the synthesis of biofuels were not considered. The synthesis of chemicals by conversion of platform molecules obtained by depolymerisation and fermentation of biopolymers is presently the most widely envisioned approach. Successful catalytic conversion of these building blocks into intermediates, specialties and fine chemicals will be examined. However, the platform molecule value chain is in competition with well-optimised, cost-effective synthesis routes from fossil resources to produce chemicals that have already a market. The literature covering alternative value chains whereby biopolymers are converted in one or few steps to functional materials will be analysed. This approach which does not require the use of isolated, pure chemicals is well adapted to produce high tonnage products, such as paper additives, paints, resins, foams, surfactants, lubricants, and plasticisers. Another objective of the review was to examine critically the green character of conversion processes because using renewables as raw materials does not exempt from abiding by green chemistry principles (368 references).     

Aurones: interesting natural and synthetic compounds with emerging biological potential

Aurones [2-benzylidenebenzofuran-3(2H)-ones] are either natural or synthetic compounds, belonging to the flavonoid family. They are isomeric to flavones and provide a bright yellow color to the plants in which they occur. Today, a literature survey indicates that the related flavonoids have been studied not only for their physiological properties and effects on Nature, but also for their therapeutic potential. Aurones are recently attracting the interest of an increasing number of research groups, and, since the last review, some interesting advances have been made in understanding the aurones. In this review, we report the recent advances made on the synthetic routes towards aurones. We also highlight their activity in different biological areas, as well as applied genetic plant modifications to produce these colored compounds. Their synthesis, structure-activity relationships and the importance of the substitution pattern will also be mentioned. Finally, some aspects regarding the possible development of aurones will be discussed briefly.     

Synthesis,chemistry, physicochemical properties and industrial applications of amino acid surfactants: A review

Surfactant use throughout mankind is extensive, from their initial applications as detergents extending to use in medicine, lubricant, cosmetics and even enhanced oil recovery. However, the image of surfactant use has in the past been tarnished by issues with low biodegradability and their synthesis from nonsustainable resources. Amino acid–based surfactants are a class of surfactants derived from a hydrophobe source coupled with simple amino acids, mixed amino acids from synthesis or from protein hydrolysates, and as such can be derived solely from renewable resources. There are several pathways for their synthesis and this allows for extensive structural diversity in this class of surfactants, resulting in widespread tuneable functionality in their physiochemical properties. This review includes the details of most of the available routes of synthesis for amino acid surfactants (AASs) and the impact of the diverse routes on their final physiochemical properties, including solubility, dispersability, toxicity and biodegradability. The diversity offered by the structural variation in AASs offers many exciting commercial opportunities for this ever-growing class of surfactants. It also includes a discussion on current and future potential uses of AASs.     

Plant oil renewable resources as green alternatives in polymer science

The utilization of plant oil renewable resources as raw materials for monomers and polymers is discussed and reviewed. In an age of increasing oil prices, global warming and other environmental problems (e.g. waste) the change from fossil feedstock to renewable resources can considerably contribute to a sustainable development in the future. Especially plant derived fats and oils bear a large potential for the substitution of currently used petrochemicals, since monomers, fine chemicals and polymers can be derived from these resources in a straightforward fashion. The synthesis of monomers as well as polymers from plant fats and oils has already found some industrial application and recent developments in this field offer promising new opportunities, as is shown within this contribution. (138 references.)     

How well can renewable resources mimic commodity monomers and polymers?

This highlight discusses the recent progress aimed at maximizing the potential of biomass for commodity monomers and polymers. These efforts are no longer solely academic issues. In recent years, a variety of alkene, diene, aromatic, and condensation type monomers have utilized renewable resources, such as cellulose, lignin, plant oils, starches, and monoterpenes in commercial polymers. Generally, these multifaceted efforts involve pretreatment of biomass with thermal, chemical, or physical methods followed by a catalyst sequence that entails a combination of acid‐catalysis, bio‐catalysis, or metal‐based catalysis. In this regard, synthesis strategies for ethylene, propylene, α‐olefins, methylmethacrylate, 1,3‐butadiene, 1,3‐cyclohexadiene, isoprene, 1,3‐propanediol, 1,4‐butanediol, and terephthalic acid are discussed as well as opportunities for other renewable‐based monomers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Potentiality of plants as source of insecticide principles

In the search for alternatives to conventional insecticides, essential oils extracted from aromatic plants have been widely investigated. Their toxicities toward insects were of special interest during the last decade. The purpose of this paper is to provide an overview of the data published mostly in the past 10 years on aromatic plant and plant’s essential oils that have been reported to possess insecticidal activity and practical methods and recent techniques for screening these compounds. The review refers to 230 plants, their geographical distribution and the organism tested. Some aspects of recent insecticidal activity directed research on natural products are discussed.     

Synthetic mimicking of plant oils and comparison with naturally grown products in polyurethane synthesis

The use of plant oils as industrial feedstocks can often be hampered by their lack of optimization towards a particular process, as well as their development being risky; growing suitable volumes of crops to test can take up to five years. To circumvent this, we aimed to discover a method that would mimic plant oil profiles in the laboratory, and show that they exhibited similar properties to the naturally grown plant oils in a given process. Using the synthesis of polyurethanes as an example, we have synthesized six different polymers and demonstrated that plant oils will produce polymers with similar physical properties to those oils mimicked in the laboratory. The use of this mimicking process can be extended to other types of polymers to obtain a method for predicting the properties of a given material based on the plant oil composition of a crop before it is grown in bulk.     

Recent Advances in the Chemical Synthesis of Glycosylphosphatidylinositols (GPIs): Expanding Synthetic Versatility for Investigating GPI Biology

Carbohydrate chemists have been remarkably successful at developing methods for the chemical synthesis of glycosylphosphatidylinositols (GPIs), a highly complex and structurally diverse family of glycolipids that anchor proteins to eukaryotic cell surfaces. With the goal of generating new tools for GPI biological research, several groups in this field have recently shifted their attention from narrowly focused target-oriented total synthesis to the development of more versatile synthetic strategies that allow access to a broad variety of GPIs, GPI analogs, and GPI-anchored proteins. These recent efforts are the topic of this review article.