Towards sustainable fuels: Nano‐catalysts for hydrodeoxygenation to green diesel

Green diesels are excellent alternatives to fossil fuels because these are non‐toxic to the environment and renewable. These green biodiesels are produced through the upgradation of bio‐oil by the Hydro deoxygenation method (HDO). Various feedstocks like comestible and non‐comestible oil, animal fats, and algal oil are used. HDO is a viable route to produce liquid fuel through fat pyrolysis. Several kinds of catalysts are reported for HDO; among them noble and non‐noble metals have received great attention. The current study critically comprehends Nano catalyst usage, their advances, and challenges with a detailed summarization of the literature review about HDO. In this review study, other nanocatalysts like oxides, reduced transition metals, phosphide, carbide, and many other alternative catalysts are discussed in detail. HDO of several lignin and the literature on carbohydrate‐derived oxygenates are collated, and their techniques are addressed. It has been reported in this study that the HDO process is also influenced by variables including temperature, hydrogen/oil ratio, pressure, catalyst, and space velocity. Finally, the catalyst deactivation and key challenges are explained in depth. The obstacle in HDO industrialization is catalyst deactivation and short lifespan; hence, HDO catalysts must be regenerated to save operating cost. The aforementioned causes are the main challenges of using nanocatalysts in the HDO process for green diesel production.