Raw material from biomass and green preparation processes are the two key features for the development of green products. As a bio-lubricant in metalworking fluids, estolides of ricinoleic acid are considered as the promising substitute to mineral oil with a favorable viscosity and viscosity index. Thus, an efficient and sustainable synthesis protocol is urgently needed to make the product really green. In this work, an environment-friendly Brønsted acidic ionic liquid (IL) 1-butanesulfonic acid diazabicyclo[5.4.0]undec-7-ene dihydrogen phosphate ([HSO₃-BDBU]H₂PO₄) was developed as the efficient catalyst for the production of oligomeric ricinoleic acid from ricinoleic acid under solvent-free conditions. The reaction parameters containing reaction temperature, vacuum degree, amount of catalyst and reaction time were optimized and it was found that the reaction under the conditions of 190 °C and 50 kPa with 15 wt % of the [HSO₃-BDBU]H₂PO₄ related to ricinoleic acid can afford a qualified product with an acid value of 51 mg KOH/g (which corresponds to the oligomerization degree of 4) after 6 h. Furthermore, the acid value of the product can be adjusted by regulating the reaction time, implying this protocol can serve as a versatile method to prepare the products with different oligomerization degree and different applications. The other merit of this protocol is the facile product separation by stratification and decantation ascribed to the immiscibility of the product and catalyst at room temperature. It is also worth mentioning that the IL catalyst can be used at least for five cycles with high catalytic activity. As a result, the protocol based on the IL catalyst, i.e. [HSO₃-BDBU]H₂PO₄ shows great potential in industrial production of oligomeric ricinoleic acid from ricinoleic acid.

中文翻译：

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高效，可回收的布朗斯台德酸性离子液体促进了低聚蓖麻油酸的制备

来自生物质和绿色制备过程的原材料是开发绿色产品的两个关键特征。作为金属加工液中的生物润滑剂，蓖麻油酸的雌二醇被认为是具有良好粘度和粘度指数的矿物油的有前途的替代品。因此，迫切需要一种有效且可持续的合成方案，以使产品真正绿色环保。在这项工作中，环境友好的布朗斯台德酸性离子液体（IL）1-丁烷磺酸二氮杂双环[5.4.0]十一碳-7-烯丙基磷酸二氢（[HSO ₃ -BDBU] H ₂ PO ₄）被开发为在无溶剂条件下从蓖麻油酸生产低聚蓖麻油酸的有效催化剂。优化了反应参数，包括反应温度，真空度，催化剂量和反应时间，发现在190℃和50kPa的条件下与15wt％的[HSO ₃ -BDBU] H ₂ PO反应₄与蓖麻油酸相关的产品在6小时后可提供酸值为51 mg KOH / g（对应于4的低聚度）的合格产品。此外，可以通过调节反应时间来调节产物的酸值，这表明该方案可以作为制备具有不同低聚度和不同用途的产物的通用方法。该方案的另一个优点是通过分层和倾析法容易地分离产物，这归因于产物和催化剂在室温下的不溶混性。还值得一提的是，IL催化剂可以以高催化活性至少使用五个循环。结果，基于IL催化剂的方案，即[HSO ₃ -BDBU] H ₂ PO ₄ 在蓖麻油酸的低聚蓖麻油酸的工业生产中显示出巨大的潜力。