Biodiesel Production over Niobium-Containing Catalysts: A Review

Abstract

Nowadays, the synthesis of biofuels from renewable raw materials is very popular. Among the various challenges involved in improving these processes, environmentally benign catalysts compatible with an inexpensive feedstock have become more important. Herein, we report the recent advances achieved in the development of Niobium-containing heterogeneous catalysts as well as their use in routes to produce biodiesel. The efficiency of different Niobium catalysts in esterification and transesterification reactions of lipids and oleaginous raw materials was evaluated, considering the effect of main reaction parameters such as temperature, time, catalyst load, and oil:alcohol molar ratio on the biodiesel yield. The catalytic performance of Niobium compounds was discussed considering the characterization data obtained by different techniques, including NH3-TPD, BET, and Pyr-FT-IR analysis. The high catalytic activity is attributed to its inherent properties, such as the active sites distribution over a high specific surface area, strength of acidity, nature, amount of acidic sites, and inherent mesoporosity. On top of this, recycling experiments have proven that most Niobium catalysts are stable and can be repeatedly used with consistent catalytic activity.

Síntese de óxido de nióbio(V) dopado com lantânio e sua aplicação na reação esterificação do ácido oleico com etanol

“…Catalisadores desempenham um papel de destaque nas reações orgânicas, representando um extenso campo de investigação no cenário científico contemporâneo [6][7][8][9][10]. Compostos de nióbio estão atualmente sob investigação para tal finalidade, incluindo haletos de nióbio, óxidos de nióbio, silicatos de nióbio e outros materiais correlatos [11][12][13][14][15][16][17][18][19].…”

“…Esta reação é de significativa relevância para a sociedade contemporânea, uma vez que é a partir dela que se torna possível a produção de biodiesel e ésteres alquílicos de cadeias longas [14]. É importante ressaltar que quando se menciona a utilização da reação de esterificação na produção de biodiesel, isso é aplicável somente quando o reagente inicial é um ácido graxo; no caso de triglicerídeos, ocorre a reação de transesterificação [13,29]. Observa-se, na Figura 1, a presença de uma seta dupla na equação química, indicando que a reação é reversível, isto é, os ésteres podem ser hidrolisados pela água para a formação de ácido graxo e álcool [30].…”

Chitosan with Sulfonic Groups: A Catalyst for the Esterification of Caprylic Acid with Methanol

“…Biodiesel is a mixture of fatty acid methyl ester. It can be obtained by esterification of fatty acids with an alcohol (methanol, ethanol) and by transesterification of triglycerides with an alcohol (methanol, ethanol, propanol, or butanol) [1][2][3][4]. The transesterification of triglycerides has been performed using homogenous catalysts, such as NaOH or KOH.…”

“…Traditionally, this reaction is carried out in the presence of homogenous catalysts, such as H 2 SO 4 . However, homogenous catalysts have some disadvantages such as being difficult to recover the catalyst from the reaction mixture and its reutilization [1][2][3][4]. To overcome the problems associated with the homogenous catalyst, esterification reactions have been carried out using solid acid materials, which can be easily removed from the mixture and reused [5][6][7][8][9][10][11].…”