Search

The efficient conversion of low-grade acidic oils to biodiesel is still a great challenge due primarily to the presented free fatty acids (FFAs) and moisture that significantly activate the used catalysts. In this premise, the acidic aluminosilicates (AAS) were employed as catalyst supports for loading of molybdenum and zirconium metals to synthesize the solid acid catalysts of molybdenum and zirconium doped aluminosilicates (ZrMo-AAS). The so-synthesized composite catalysts were characterized by various physicochemical techniques, and their catalytic activities were evaluated for the efficient biodiesel production by using acidic soybean oils as feedstocks. Results revealed that the targeted solid catalysts featured dual Bronsted-Lewis acidic sites and mesoporous structure with the acidity of 719 μmol/g and surface area of 459.7 m2/g, displaying high catalytic performances for the concurrent transesterification of triglycerides and esterification of FFAs with 92.3% of oil conversion and full FFA conversion to biodiesel at a reaction temperature of 130 °C for 12 h with a methanol/oil molar ratio of 30. This solid catalyst had good water and FFA-resistance capacity even with water content to 1% and FFA content of 40%, and moreover could be easily recovered by filtration with a steady reusability with a slight attenuation in the activity after five time reuses, rendering it to have the potential of cost-effective production of biodiesel from the low-grade oils. [ABSTRACT FROM AUTHOR]

BACKGROUND: The exploration of a robust solid acid catalyst for the efficient hydrolysis of cellulose is a research hotspot due to the need for clean production and sustainable development. KIT‐6 silica offers abundant three‐dimensionally interconnected mesopores, which are expected to be superior to mesoporous structures with one‐ or two‐dimensional channels due to faster diffusion of reactants and products during reaction. The catalytic conversion of microcrystalline cellulose is examined in detail over a functionalized KIT‐6 catalyst prepared by the method of Zr addition and subsequent sulfation. RESULTS: In terms of cellulose conversion and product yield, the activity of the catalysts followed the order of sulfated Zr‐KIT‐6 > Zr‐KIT‐6 > SO42−‐KIT‐6 > KIT‐6. Over the sulfated Zr‐KIT‐6 catalyst with a Si/Zr molar ratio of 7:1, a maximum cellulose conversion of 95.0% was achieved with glucose yield of 23.4%, 5‐hydroxymethylfufural yield of 4.9% and levulinic acid yield of 11.7% under the optimized reaction conditions: reaction temperature of 200 °C, reaction time of 2 h, catalyst amount of 0.3 g, cellulose‐to‐water mass ratio of 1:1. CONCLUSION: The sulfated Zr‐KIT‐6 catalyst possessed the strongest and richest Brønsted acid sites, which readily provided protons for the cleavage of β‐1,4 glycosidic bonds in cellulose, thus conferring superior catalytic activity in cellulose hydrolysis. A plausible pathway at the initial stage of cellulose hydrolysis over the catalyst was proposed. © 2023 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

[Display omitted] • 35% H 6 PV 3 MoW 8 O 40 /AC-Ag catalyst was prepared. • A high oil conversion of 91.3% was achieved over the solid catalyst. • The catalyst has good recyclability and high resistance of acid and water. • Transesterification and esterification reactions can be achieved simultaneously. The heterogenization of Keggin-structure heteropoly acids (HPAs) has been proposed as a strategy to improve their application in biodiesel production in an attempt to comply the green and clean production demand. Herein, the commercial activated carbon (AC) was firstly modified with different metal ions (Cs+, K+ and Ag+), and then the H 6 PV 3 MoW 8 O 40 acid was incorporated into as-modified AC supports, so as to prepare HPAs-based solid catalysts. By screening tests, the 35%H 6 PV 3 MoW 8 O 40 /AC-Ag hybrid solid catalyst showed highly catalytic performance for transesterification of soybean oil. The best oil conversion of 91.3% was achieved under optimized conditions: methanol/oil molar ratio of 30:1, reaction time of 10 h, reaction temperature of 140 °C and catalyst dosage of 8 wt.%. Characterization results of XRD, IR, ICP and TG indicated that H 6 PV 3 MoW 8 O 40 was highly dispersed on the AC-Ag support as the loading was less than 35%. Proton exchange with Ag may contribute to the highly dispersion of H 6 PV 3 MoW 8 O 40 on the support and thus enhance the interaction of the heteropoly acids with the support, thereof leading to the increased catalytic stability. The as-prepared 35%H 6 PV 3 MoW 8 O 40 /AC-Ag catalyst was easily recycled and had good resistance to free fatty acid (FFA) and water, which were usually included in the low-quality oils. Moreover, as a bifunctional catalyst, the solid acid catalyst could simultaneously catalyze the transesterification of soybean oil and esterification of FFAs, and a probable mechanism of the catalytic process was also proposed. All the features of this novel solid catalyst are more advantageous than the homogenous H 6 PV 3 MoW 8 O 40 catalyst, successfully creating an efficient and sustainable approach of biodiesel production especially from the low-quality oils. [ABSTRACT FROM AUTHOR]

Improving the reactant mass transfer on the catalyst surface is a feasible approach to fabricate a robust solid catalyst for efficiently promoting the biomass macromolecules-involving reactions, specifically for biodiesel production by using non-edible acidic oils as feedstocks. In this premise, to reduce the mass transfer resistance, the hierarchical porous SOM-ZIF-8 was firstly synthesized using polystyrene spheres (PS) as templates and then employed as catalyst supports for loading of Keplerate-type polyoxomolybdates {Mo 132 } to prepare a novel {Mo 132 }@SOM-ZIF-8 solid acid catalyst. The catalyst characterization results revealed that the active species of {Mo 132 } clusters were well-dispersed on the SOM-ZIF-8 support and the primary framework of the SOM-ZIF-8 support remained nearly unaltered after the preparation processes. This prepared catalyst featured three-dimensional ordered hierarchical porous structure and dual Bronsted-Lewis acid sites, with a large surface area of 736.26 m2/g and high acidity of 903 μmol/g, presenting high activities for concurrent triglyceride transesterification and free fatty acids (FFAs) esterification. With the acidic soybean oils as feedstocks, 93.9 % of oil conversion and full FFA conversion to biodiesel were achieved over this solid catalyst at 130 °C for 8 h with a catalyst loading of 2 wt%, thus imparting the great potential for a one-pot efficient biodiesel manufacture from the acidic oils to comply with the demand of green and clean production. The synergy between the hierarchical porous structure and the strong acidity emerged, thus boosting the catalytic performance of this solid catalyst for the heterogeneous biodiesel production. The good FFA and moisture-resistance capacity was shown for this catalyst even in the case of moisture content of 3 % and FFA content of 25 %. Further, this catalyst showed excellent reusability without significantly losing its catalytic performance even after five runs, providing a deeper insight into constructing efficient solid catalysts with hierarchical porous structure that are utilized for cost-effective production of biodiesel from the non-edible acidic oils. [Display omitted] [ABSTRACT FROM AUTHOR]

The development of feasible ecofriendly processes for biodiesel production is highly desirable to meet the requirement of green chemistry and sustainable development. To reach this goal, the molybdenum and zirconium oxides were incorporated into commercial available KIT-6, mesoporous silica nanoparticle, by a solvothermal method, to form MoO 3 /ZrO 2 /KIT-6 catalyst. The targeted solid composite catalysts were structurally characterized using XRD, TEM, SEM, XPS, EDS, TG, and nitrogen porosimetry measurement. The characterization results showed that the ordered porous structure of the support was well persevered with high surface area, and the molybdenum and zirconium oxides could be highly dispersed on the mesoporous support. The acidic nature of the solid catalyst was evaluated in detail by means of NH 3 -TPD and infrared spectra of adsorbed pyridine techniques. It was indicated that the acidities of the solid catalysts, with both Brønsted and Lewis acid sites, could greatly affected their catalytic activity. This catalyst displayed high activities to the transesterification of triglycerides and esterification of free fatty acids (FFAs) simultaneously owing to the synergistic effect of Brønsted and Lewis acid sites, thus achieving one-pot heterogeneous production of biodiesel as the low-quality oil was used as feedstocks. The influence of reaction parameters and the catalyst reusability were also investigated, and the best oil conversion of 92.7% was obtained under the optimized reaction conditions. The targeted catalyst exhibited a better FFAs and water tolerant for the reaction, advantageously with no noticeable decline in the catalytic performance even after five reaction cycles. [Display omitted] • MoO3/ZrO2/KIT-6 catalysts with both Brönsted and Lewis acid site were prepared. • The catalyst was effective for one-pot biodiesel production from low-quality oils. • The solid acid catalysts were characterized by various techniques. • Transesterification and esterification reactions can be achieved simultaneously. • The catalyst has good recyclability and high resistance to acid and water. [ABSTRACT FROM AUTHOR]

The exploration of efficient and recyclable catalysts is highly desirable for catalytic biodiesel manufacture from low-grade acidic oils, in response to the demand of clean production and environmental concerns. For this aim, phosphotungstic acid (HPW) was firstly modified by tin metal, and then embedded on ZIF-8 metal-organic formworks (MOFs) to synthesize the SnPW@ZIF-8 catalyst. Catalyst characterization results revealed that the active species of Sn-doped HPW with Keggin-type anion structure were well-dispersed on the ZIF-8 support, and this catalyst featured high surface area with dual Brönsted-Lewis acid sites, posing enhanced catalytic performances to the oil transesterification and esterification of free fatty acids (FFAs) presented in oils. By applying this catalyst, 92.8 % of oil conversion and 97.4 % of FFAs conversion were concurrently achieved under the optimized conditions, rendering one-pot conversion of low-grade acidic oils to biodiesel and minimizing the complex and tedious separation processes. Moreover, the higher water and FFA-resistance capacity was shown for this catalyst, imparting its more suitable for the efficient biodiesel production particularly with the acidic oils as feedstocks. Further, this catalyst could still remained high catalytic efficiency after five cycle reuses due to the strong interactions of the SnPW with the imidazole groups in the ZIF-8, making it to have the potential of cost-effective and efficient production of biodiesel from the low-grade acidic oils. [Display omitted] • SnPW@ZIF-8 solid catalyst with duai Brönsted-Lewis acid site were prepared. • This catalyst was effective for one-pot biodiesel production from low-grade oils. • Oil transesterification and FFA esterification can be achieved simultaneously. • This catalyst has good recyclability and high resistance to acid and moisture. [ABSTRACT FROM AUTHOR]

For the purpose of fabricating an efficient solid acid catalyst for biodiesel production from low-grade acidic oils, bimetallic silica mesoporous composites with different Zr/Al molar ratios were initially synthesized via a facile one-step hydrothermal method, and then sulfated with sulfuric acid at different concentrations to get a series of sulfated Zr x -Al y -KIT-6 catalysts (denoted as SZA-K, where x/y represents the molar ratio of Zr to Al). The sulfated bimetallic solid catalysts were fully characterized by using XRD, FT-IR, TEM, SEM, EDS, NH 3 -TPD, and nitrogen porosimetry measurements. Results showed that the remarkable amount of acidic sites in the catalysts was derived from the Zr and Al incorporation and further sulfation, and specifically, the Zr4+ and Al3+ could afford abundant weak acid sites while the inductive effect of SO 4 2− species greatly influences the acidic strength of this solid catalyst. In combination with the enhancement in mass transfer resulting from the inherent interconnected mesoporous structure, the SZA-K catalyst could facilitate the transesterification reaction to take place efficiently. The sulfated Zr 5 –Al 1 -KIT-6 catalyst (Zr/Al molar ratio of 5/1, treated using 0.75 mol/L sulfuric acid for 12 h) exhibited enhanced acid strength with larger number of acidic sites (7.81 mmol/g), resulting in a high catalytic performance to the oil transesterification reaction. An oil conversion of 96.3% was attained for the transesterification reaction performed at 120 °C for 7 h by using a methanol/oil molar ratio of 20:1 and a catalyst dosage of 6 wt%. Further, this solid catalyst exhibited better acid and water-resistance capacity with above 80% of oil conversion even with 10% of free fatty acid (FFA) and 2% of moisture present in the low-grade acidic oils. Meanwhile, the good reusability was shown for this catalyst with 80.1% conversion even after reusing for three cycles. The good stability of the solid catalyst was resulted from the strong interactions between the acidic species and the bimetallic composite support. Bimetallic Zr x -Al y -KIT-6 modified with sulfate as acidic catalyst for biodiesel production from low-grade acidic oils. [Display omitted] [ABSTRACT FROM AUTHOR]