Towards sustainable catalysts in hydrodeoxygenation of algae-derived oils: A critical review

Frustrated Lewis pair catalyst realizes efficient green diesel production

Hydrotreating renewable oils over sulfided metal catalysts is commercially applied to produce green diesel, but it requires a continuous sulfur replenishment to maintain catalyst activity, which inevitably results in sulfur contamination and increases production costs. We report a robust P-doped NiAl-oxide catalyst with frustrated Lewis pairs (i.e., P atom bonded with the O atom acts as an electron donor, while the spatially separated Ni atom acts as an electron acceptor) that allows efficient green diesel production without sulfur replenishment. The catalyst runs more than 500 h at a weight hourly space velocity (WHSV) of 28.3 h-1 without deactivation (methyl laurate as a model compound), and is able to completely convert a real feedstock of soybean oil to diesel-range hydrocarbons with selectivity >90% during 500 h of operation. This work is expected to open up a new avenue for designing non-sulfur catalysts that can make the green diesel production greener.

Fundamentals in applications of algae biomass: A review

Algae play an extremely important ecological role. They form the basis of trophic webs, produce oxygen that allows the respiration of many of the organisms in aquatic environments, absorb CO₂, and serve as refuge areas and habitats for thousands of species. Many species can also absorb organic pollutants from seawater. Algae have been used for many centuries by humans as a source of food, fertilizer, fodder, and for the extraction of compounds with antifungal, antiviral, anticancer, and antibacterial properties. More recently, some species have been used for the production of biofuels. It has been shown that mixing small proportions of algae with the feed of cattle can reduce methane emissions from their digestive activity by more than 95%. One of the most widespread but least known applications of algae is the extraction of their phycocolloids for utilization in food, pharmaceutical, wine, and textile industries, among others. These compounds have gelling, stabilizing, and thickening properties and are therefore frequently included in creams, ice creams, cheeses, jellies, flavored milks, sauces, shampoos, medications, toothpaste, and many other products. The phycocolloids agar and carrageenan are extracted from red algae, whereas alginate is extracted from brown algae, being used in dental impressions, emulsifying lotions, and paints, among others, and in the preparation of wine and beer. Algae are of particular interest in the research and development of new biosorbent materials, not only because of their high adsorption capacity, but also because they are present in the seas and oceans in abundant and easily accessible quantities. Marine algae are a promising biosorbent for the removal of heavy metals and various pollutants and, due to their intrinsic characteristics, have received increasing attention in recent decades. Their application as biosorbents for the sorption of heavy metals and radionuclides could be interpreted as the use of waste to remove waste. Algae have attracted particular interest in the field of biotechnology for economic reasons, given that large amounts are naturally produced and left lying on beaches as waste material. The composition of algae biomass makes it a promising candidate for an extensive list of applications that continues to lengthen. The development of appropriate technologies and policies can transform the presence of algae in coastal ecosystems from an unpleasant and potentially harmful phenomenon into a source of major benefits. This review discusses the capacity of algae biomass to remove pollutants and also delves into its applicability in the production of dyes, oils, and biofuels and for animal feed and fertilizer industries, among others. Further research is warranted on strategies to convert a biomass that is currently considered waste into a means of addressing environmental problems.