Methanol synthesis from syngas is an effective method for producing fuel additives, oxygenated fuels, and other chemicals. Several promoted catalytic systems have been tested for the synthesis of methanol. Catalysts based on noble metals are extremely active in generating methanol from syngas. However, sintering, poisoning, and related expenses accounted for the switch to Cu-based catalysts. The promotion of Cu-based catalysts, even with small doses of an effective promoter, resulted in a considerable change in product selectivity. A suitable promoter is required for Cu-based catalysts used in the synthesis of methanol because it significantly impacts the electronic, geometric, or acid/base surface properties, which in turn affect the catalyst's activity and selectivity. It also significantly impacts the interactions between the catalyst's active ingredients. However, the interactions between the active component and the promoter can be adjusted or influenced by appropriate support. The present paper primarily focuses on several promoters in the copper-based catalyst for synthesizing methanol from syngas. We briefly deliberated on the need for copper-based catalysts for methanol synthesis, their reaction and mechanism, the reasons for promoter addition concerning their role and influence, the importance of CO 2 addition in feed synthesis gas and their impact on the catalyst. This paper mainly highlights the selectivity and activity of various promoted Cu-based catalysts, although different reaction parameters are the cause of promotion and inhibition in the catalyst. The effects of reaction conditions, including pressure, temperature, gas hourly space velocity (GHSV), and syngas composition, are briefly reported. This paper also comprehensively compares the effects of adding various promoters in small amounts to copper-based catalysts. This review intends to be illustrative rather than exhaustive.

Internationally emerging energy trend, depletion of existing fossil fuel reserves along with growing population and alarming pollution all together has diverted the research towards the use of renewable fuels such as biodiesel. Biodiesel being eco‐friendly and climate neutral is a better alternative to vastly depleting petrodiesel fuels. Biodiesel is frequently produced by combining vegetable oil and alcohol with catalyst in a transesterification reaction. Catalyst is a key factor that is known to affect the kinetics and output of a transesterification reaction. Moreover, one of the most critical features of a catalyst‘s catalytic activity is the particle size. The present review is an account of the widely used heterogeneous nanocatalyst for biodiesel synthesis. Heterogeneous nanocatalyst are novel for FAME synthesis as they are economical, recyclable, reusable, readily available, active, selective, non‐corrosive, stable and conveniently separable. Metal oxide (MO), Nano ferrites, Nano zeolites, Nano hydrotalcite and Metal Organic Frameworks (MOFs) based heterogeneous nanocatalyst and their reusability have been discussed. Critical factors like time duration, alcohol‐to‐oil ratio, reaction temperature, intensity of mixing, catalyst loading etc. have also been accounted in this review.

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