Transesterification in Microreactors—Overstepping Obstacles and Shifting Towards Biodiesel Production on a Microscale

Abstract

Biodiesel, which was earlier used only as an alternative fuel, is now an indispensable component of commercial diesel. Conventional production processes are unable to cope with the increasing demand for biodiesel, and therefore more and more work is being done to intensify the existing processes. The intensification of the biodiesel production process, taking into account the environmental and economic factors, is based on increasing productivity. One way to achieve that is by reducing the volume of production units. The application of the enzymatic reaction path, while reducing the volume of process equipment to the micro-level, has significantly magnified the productivity of the biodiesel production process, which is primarily due to better mass transfer in microsystems. Additional breakthrough is the use of deep eutectic solvents (DES) instead of buffers for enzyme stabilization. In this study, a lipase from Thermomyces lanuginosus (TlL) (both commercial and produced by solid-state fermentation) was used as a catalyst for biodiesel production. Edible and waste sunflower oil, as well as methanol, were used as substrates. The reaction mediums were buffer and DES. The transesterification reaction was carried out in a batch reactor and the emphasis was made on different microreactor configurations. The highest yield of 32% for residence time of only τ = 30 min was obtained in the microreactor system with an emulsion of waste oil and a commercial enzyme suspended in a buffer. This indicates that enzymatic transesterification could be a valuable reaction path for dealing with waste oils. Furthermore, biodiesel synthesis in DES showed somewhat lower yields, but by increasing the water content in the system, the reaction could prove much better results. In the end, the effects of reaction conditions on the volumetric productivity of the process were analyzed.

Transesterification of Sunflower Oil over Waste Chicken Eggshell-Based Catalyst in a Microreactor: An Optimization Study

“…This technology can achieve rapid and high reaction rates due to the high surface-to-volume ratio and short diffusion distance, thus intensifying the transesterification process [ 15 ]. Another additional important aspect is the easier scale-up by multiplying the number of microreactor units without change of the channel geometry [ 16 , 17 ]. In the process of biodiesel production, time, temperature, type and amount of used catalyst, mixing intensity, alcohol and oil type and their molar ratio are the effective parameters of reaction efficiency.…”

Let the Biocatalyst Flow

“…75 thus phase separation problems, this obstacle is reduced in microflow reactors. 39,78 Applications of slug flow include various reactions and enzymes, from reactions catalyzed by alcohol-dehydrogenase (ADH), [79][80][81][82] to hydroxynitrile lyase-catalyzed C-C bond formation, 83 a reduction with pentaerythritol tetranitrate reductase, 84 terpene production catalyzed by aristolochene synthase, 77 penicillin acylase-catalyzed antibiotic synthesis, 75,85,86 and lipase-assisted biodiesel production, 87,88 among others.…”

“…The reaction, which was carried out in a Y-Yshaped microchannel as well as in a mm-scale tube, resulted in a 3-4-fold higher productivity than in the stirred tank reactor operated in batch mode. 88 Environmentally friendly ATPS prepared from PEG and phosphate buffer was used for an enzyme-catalyzed synthesis of the β-lactam antibiotic cephalexin, which is produced industrially on a multi-tones annual scale. The microfluidic setup shown in Figure 6 b included a slugflow microreactor that supported efficient mass transfer between penicillin acylase dissolved in the bottom ATPS phase and the substrates in the ATPS's top phase, as well as in situ product separation in the latter.…”

Continuous Integrated Process of Biodiesel Production and Purification—The End of the Conventional Two-Stage Batch Process?

“…Biodiesel, a mixture of fatty acid methyl esters, stands as a suitable replacement for fossil diesel due to its reduced greenhouse gas and impurity emissions compared to fossil diesel combustion [2][3][4][5]. The use of biodiesel in a mixture with fossil diesels such as B5, B7, and B20 blends has become common in Europe [6]. Therefore, the production of significant quantities of biodiesel for the lowest possible price is required for its competitiveness on the market [7].…”

“…Furthermore, DESs are increasingly being investigated in the context of their use as reaction media, especially in biocatalysis, because some studies have shown that lipases have high activity and stability in DESs in the presence of a certain percentage of water [3,31,34]. Since the simultaneous use of DESs as reaction and extraction media is still unexplored, it is necessary to optimize such an integrated process [6]. An optimization method that is very popular among researchers is response surface methodology (RSM) [35].…”