Heterogeneous catalyst application in biodiesel production: Needs to focus on cost effective and reusable catalysts

Heterogeneous base catalysts: Synthesis and application for biodiesel production – A review

Towards sustainable biodiesel and chemical production: Multifunctional use of heterogeneous catalyst from littered Tectona grandis leaves

Heteropoly acids as supported solid acid catalysts for sustainable biodiesel production using vegetable oils: A review

Chapter 16 - Sustainable production of biodiesel over heterogeneous acid catalysts

Over the last decades, advanced oxidation processes (AOPs) have been widely used in surface and ground water pollution control. The heterogeneous electro-Fenton (EF) process has gained much attention due to its properties of high catalytic performance, no generation of iron sludge, and good recyclability of catalyst. As of October 2022, the cited papers and publications of EF are around 1.3 × 10-5 and 3.4 × 10-3 in web of science. Among the AOP techniques, the contaminant removal efficiencies by EF process are above 90% in most studies. Current reviews mainly focused on the mechanism of EF and few reviews comprehensively summarized heterogeneous catalysts and their applications in wastewater treatment. Thus, this review focuses on the current studies covering the period 2012-2022, and applications of heterogeneous catalysts in EF process. Two kinds of typical heterogeneous EF systems (the addition of solid catalysts and the functionalized cathode catalysts) and their applications for organic contaminants degradation in water are reviewed. In detail, solid catalysts, including iron minerals, iron oxide-based composites, and iron-free catalysts, are systematically described. Different functionalized cathode materials, containing Fe-based cathodes, carbonaceous-based cathodes, and heteroatom-doped cathodes, are also reviewed. Finally, emphasis and outlook are made on the future prospects and challenges of heterogeneous EF catalyst for wastewater treatments.

Application of heterogeneous catalysts in olefin hydroformylation

Biodiesel has been considered as one of the interesting alternative and environmentally benign fuels. The development of environmental friendly heterogeneous catalyst for the esterification/transesterification process seems to be promising route and the reason why it is more preferred to conventional homogeneous and enzymatic catalyzed reactions is discussed. However, investigation on heterogeneous catalyst for biodiesel production is extensively carried out based on previous research studies. In order to reduce cost of biodiesel production, evaluation and characterization of heterogeneous catalytic materials before and after its preparation provide facts on the process that have significant impact on the desired activity and selectivity properties. This review study provides a comprehensive overview of common process techniques usually employ in producing biodiesel. Different materials that serve as sources of heterogeneous catalysts to transesterify oils or fats for production of biodiesel with emphasis on selection criteria of solid catalytic materials are also highlighted. The potential heterogeneous catalyst that could be derived from anthill, various methods of preparing solid catalysts, as well as reusability and leaching analysis are discussed in details

The need for fossil fuels and the emissions generated from these fuels are increasing daily. Researchers are concerned with global warming as well as climate change; and energy sustainability and material usages are important issues today. Waste cooking oil (WCO) can be processed into biodiesel as an alternative fuel to replace diesel. Production of biodiesel using WCO as the feedstock has been of growing interest for the last two decades. A number of research papers related to the improvements in production, raw materials and catalyst selection have been published. This paper reviews the various types of heterogeneous solid catalyst in the production of biodiesel via the transesterification of WCO. The catalysts used can be classified according to their state presence in the transesterification reaction as homogeneous or heterogeneous catalysts. Homogeneous catalysts act in the same liquid phase as the reaction mixture, whereas heterogeneous catalysts act in a solid phase with the reaction mixture. Heterogeneous catalysts are non-corrosive, a green process and environmentally friendly. They can be recycled and used several times, thus offering a more economic pathway for biodiesel production. The advantages and drawbacks of these heterogeneous catalysts are presented. Future work focuses on the application of economically and environmentally friendly solid catalysts in the production of biodiesel using WCO as the raw material.

Current application of MOFs based heterogeneous catalysts in catalyzing transesterification/esterification for biodiesel production: A review

Fossil fuel depletion, increased world energy demand, and the environmental crisis linked to petroleum-based energy instigated the quest for its substitute. The sustainability of biodiesel affords it a high prospect over fossil fuels. It has been receiving attention as a result of its biodegradability, renewability, low toxicity, and good transport and storage properties. The main shortcomings of biodiesel are the production cost and choice of catalyst. Three types of catalysts mainly used for biodiesel production are basic, acidic, or enzyme. Industrial production of biodiesel typically employed homogeneous catalysts due to their ability to facilitate the reaction quickly. However, catalyst separation and biodiesel purification are tormenting, requiring a large amount of water. Thus, heterogeneous catalysts, with several advantages over homogenous catalysts, have been searched. Heterogeneous catalysts can be separated from the products effortlessly, thus allowing for recycling. Furthermore, the process is simpler, cheaper, and more environmentally benign. This review aims to evaluate the performance of different types of catalysts in the transesterification reaction, with special emphasis on heterogeneous base catalysts. The review also gives insight into the key catalytic properties that need to be tailored economically and eco-friendly to reduce cost, to give better biodiesel yield/conversion. Additionally, the various conditions necessary for the optimum yield of biodiesel have also been explored. Lastly, the future challenges and prospects of heterogeneous base catalysts are proposed. Keywords: Biodiesel, Catalyst performance, Heterogeneous catalyst, Transesterification

The continuous increase in the growth of the world's population is also drastically increasing energy demands in both industrial and domestic sectors. Moreover, public awareness about pollution due to overuse of fossil fuels has led to a rise in interest in research into alternative renewable energy sources. Among the various options for renewable energies for road transportation, biodiesel is considered the most suitable replacement for petro-diesel. In terms of industrial applications for biodiesel production, homogeneous catalysts such as NaOH, KOH, H2SO4, and HCl are usually preferred, but their removal is rather complex and somewhat polluting, bringing extra cost to the final product. The application of heterogeneous catalysts, both solid acid and solid base, for the transesterification reaction can resolve the biodiesel purification problems associated with homogeneous catalysts. However, heterogeneous catalysts are currently somewhat slow and inefficient, and present some mass-transfer limitations. In this context, nanocatalysts represent a new generation of heterogeneous catalysts with promising advantages over homogeneous and conventional heterogeneous ones. Other alternatives also exist. Enzymatic catalysis has been used in biodiesel production, employing lipases as biocatalysts. However, for economic reasons and due to issues of reusability and recycling, the lipases must be immobilized on suitable supports, bringing into play the concept of heterogeneous biocatalysis. Like other heterogeneous catalytic materials, this presents similar issues with inefficiency and mass-transfer limitations. A solution may be the use of nanostructured supports for enzyme immobilization as new heterogeneous biocatalysts. This chapter mainly focuses on the application of heterogeneous basic, acidic, and enzymatic catalysts, as well as nanocatalysts and nano(bio)catalysts, in transesterification reactions, and their multiple methods of synthesis.

Synthesis of biomass as heterogeneous catalyst for application in biodiesel production: State of the art and fundamental review

The relevance of heterogeneous catalysis in biodiesel production cannot be overemphasized, as heterogeneous catalysts have eliminated the demerits associated with a homogeneous catalysts. Some heterogeneous catalysts experience drawbacks such as partial recoverability and reusability, energy and waste conservation issues during biodiesel processing and leaching of active catalyst sites. This paper highlights and summarizes several heterogeneous catalysts used in biodiesel production. The catalyst preparation, reaction conditions, feedstock, and biodiesel yield for the heterogeneous base and acid catalysts were emphasized. The inability of heterogeneous base catalysts to trans-esterify low-grade oil with high free fatty acid (FFA) is a primary concern; the cost of processing low-grade oil with high FFA using heterogeneous acid catalysts is also a big issue. Nano-doped heterogeneous catalysts with unique properties were recommended because they can process oil with high FFA transesterification, improve reaction efficiency, simplify production, reduce the leaching of active sites, enable better biodiesel yield by minimizing energy and waste, and increase catalyst recoverability, activity, selectivity and durability.

Ever-increasing energy demand, spiralling fossil fuel prices, and global warming due to unwarranted exploitation of fossil fuels have resulted in the emerge of biodiesel as a promising eco-friendly and renewable substitute for fossil-based fuels. Chemically, biodiesel stands for fatty acid alkyl (usually ethyl or methyl) esters, which are prepared via transesterification of vegetable oils and animal fats. Biodiesel has many advantages over petro-based diesel fuel, as it is free of harmful hydrocarbons, and causes lower emissions of harmful greenhouse gases, particulate matter, and sulphur compounds. Despite its many benefits, biodiesel has not attracted the interest and popularity in the commercial sector in India due to the high production cost coupled with the deficiency of sufficient feedstock. In a country like India, which imports a significant portion of its edible oil, the use of second-generation feedstock (non-edible oils, waste cooking oil, and animal fat) could be advantageous to avoid a food versus fuel conflict. However, such feedstock usually has high free fatty acid contents, and thus, conventionally used homogeneous alkali catalysts could not be employed here for transesterification. Heterogeneous catalysts offer a wide range of advantages over homogeneous counterparts, viz. ease of catalyst separation, regeneration, and reuse. In the recent past, diverse solid catalysts have been extensively explored for biodiesel (BD) production utilizing second-generation feedstock. In this context, mesoporous silica offers attractive properties, such as ease of surface modification via impregnation or grafting of catalytically active species, high thermal stability, variable pore size, and high surface area. In this chapter, properties of second-generation feedstock and its application for biodiesel production in the presence of various heterogeneous catalysts is reviewed.

Chapter 16 - Applications of Heterogeneous Catalysts in the Production of Biodiesel by Esterification and Transesterification