Novel carbon microtube based solid acid from pampas grass stick for biodiesel synthesis from waste oils

Insights into Preparation Methods and Functions of Carbon-Based Solid Acids

With the growing emphasis on green chemistry and the ecological environment, researchers are increasingly paying attention to greening materials through the use of carbon-based solid acids. The diverse characteristics of carbon-based solid acids can be produced through different preparation conditions and modification methods. This paper presents a comprehensive summary of the current research progress on carbon-based solid acids, encompassing common carbonization methods, such as one-step, two-step, hydrothermal, and template methods. The composition of carbon source material may be the main factor affecting its carbonization method and carbonization temperature. Additionally, acidification types including sulfonating agent, phosphoric acid, heteropoly acid, and nitric acid are explored. Furthermore, the functions of carbon-based solid acids in esterification, hydrolysis, condensation, and alkylation are thoroughly analyzed. This study concludes by addressing the existing drawbacks and outlining potential future development prospects for carbon-based solid acids in the context of their important role in sustainable chemistry and environmental preservation.

Synthesis of Novel Magnetic Carbon Microtube-Based Solid Acid and Its Catalytic Activities for Biodiesel Synthesis

Novel magnetic carbon microtube-based solid acid was synthesized via the carbonization of FeCl3-doped willow catkin and benzenediazoniumsulfonate acid-based sulfonation. The biomass willow catkin provided the special microtube structure and the high surface area of 215 m2/g for the novel solid acid. The microtube structure was well conserved during the mild carbonization (400 °C) and sulfonation process. The large number of acidic sites (2.3 mmol/g) on the microtube surface was quite accessible to reactants. Its magnetic properties offered a simple separation process. The novel solid acid showed very high activity for biodiesel synthesis, using cooking oils as raw material, which gave a total yield of 99% and free fatty acid conversion of 98.7% under mild conditions (70 °C). The facile synthetic process, high activity, high stability, and high recovery simplicity were the main properties of the novel magnetic solid acid, which is one of the best choices for biodiesel synthesis.

Development of Magnetic Multi-Shelled Hollow Catalyst for Biodiesel Production

The magnetic CaO-based catalyst has endorsed great enhancements in biodiesel synthesis. In the present work, novel multi-shelled hollow γ-Fe2O3 stabilized CaO microspheres were synthesized using a facile one-step hydrothermal method. The strategy revealed that the well-defined multi-shelled hollow structures were formed with magnetism; the presence of γ-Fe2O3 was the key for the effective structural stabilization, and the multi-shelled hollow structures provided the sites for the active material. The synthesized catalyst was employed for the preparation of biodiesel by transesterification of palm oil and methanol. A four factors response surface methodology was adopted for optimizing the reaction conditions. Ca80Fe20 with a yield of 96.12% performed the highest catalytic activity under reaction conditions of 2 h, a methanol to oil ratio of 12:1, 65 °C and 11 wt. % of catalyst dosage. The catalyst under the optimum transesterification conditions also performed a better recyclability (>85%). In addition, the response surface methodology (RSM) based on the Box–Behnken design was used to optimize the four reaction parameters.