Fatores que afetam a produção de biodiesel utilizando óleos e gorduras residuais (OGRs): uma revisão

Abstract

Consumption and large-scale production have increased the demand for energy in the world. Given this situation for decades, fossil fuels such as oil, coal and natural gas were used, however, their use poses environmental risks. An alternative is the use of biofuels, which are fuels produced from biomass. Among these, biodiesel stands out as an excellent alternative, due to its renewability and similarity to petroleum diesel in its structure and behavior. Biodiesel can be produced from a process known as transesterification, in which triglycerides present in vegetable oil or animal fat react with a short-chain alcohol in the presence of catalysts. Production and yield are affected by some factors, such as: the type of oil, alcohol, catalyst and the technique used. A proposal for this process is the replacement of new oil by waste cooking oil (WCO), as in addition to reducing process costs, it enables solutions to the problem of improper disposal of oils and fats. The objective of this research was to compare, through a literature review, the different biodiesel production methods using residual oils and fats. Three factors that affect the yield of biodiesel production using OGRs were analyzed: type of alcohol, catalyst and process intensification techniques. By choosing the Science Direct database (Elsevier), 60 documents from the last 7 years were analyzed. It was observed that 56 studies used methanol due to its high reactivity, most of which found a yield greater than 90%. Three studies used ethanol, alcohol considered renewable, and all found a yield greater than 94%. Butanol was used in one study and promoted a yield of 95.6%. Homogeneous basic catalysts resulted in yields between 40 and 100%, heterogeneous basic catalysts between 45.52 and 100%, and heterogeneous acid catalysts between 78 and 96%. Enzymatic catalysts obtained a yield of 91.8 to 98.5%, bringing the possibility of recycling these reagents, which reinforces a sustainable production. There was a great use of conventional methods for the production of biodiesel, such as reactors equipped with mechanical and magnetic stirrers, heating plates and blankets, and reflux condensers. These methods

resulted in yields of 40 to 100% and reaction times between 30 and 2880 minutes. It was also noted the use of process intensification techniques, with the use of autoclaves, electrolytic cells, microwaves, microreactors, ultrasonic reactors and production assisted by UV irradiation. PI techniques resulted in yields of 71.1 to 98.8% with reaction times between 9.15 and 900 minutes. The choice of each of these variables significantly affected the production of this biofuel, interfering with reaction time and yield. Studies on the relationship between the variables and the respective yield can be one of the research topics in this area in Brazil, contributing to the scientific and sustainable development of biodiesel production.