Lactic acid esterification over three carbon based solid acid catalysts were compared: sulfonated carbonised wood, graphene oxide (GO) and Amberlyst 15(A15) with the aim to address their water tolerance related to their acidity and hydrophobicity. The acidic properties of the carbon materials were measured by calorimetry of NH₃ adsorption and their hydrophobicity was evaluated by water vapor adsorption isotherms. Here, we disclose the exceptional strong acidity of GO with differential heat of NH₃ adsorption (Q_diffNH₃) higher than 200 kJ mol⁻¹ while A15 and sulfonated carbon have significant lower acid strength with Q_diffNH₃ lower than 150 kJ mol⁻¹. The super-acidity of GO is tentatively ascribed to the presence of “free” protons explained by the delocalization of the negative charges of counter anions within the graphene sheet. In presence of the minimum water content (3 mol L⁻¹), GO is the most active catalyst with a TOF of 52 h⁻¹ and its activity is also less inhibited upon water addition compared to A15. These results are rationalized considering that TOF depends intrinsically on the strength of Br∅nsted active sites and on the active site accessibility more or less controlled by the its micro-environment hydrophobicity seen to be equivalent for A15, sulfonated carbon and GO.

比较了在三种碳基固体酸催化剂上的乳酸酯化反应：磺化碳化木，氧化石墨烯（GO）和Amberlyst 15（A15），目的是解决它们与酸度和疏水性有关的耐水性。通过NH ₃吸附量热法测量碳材料的酸性，并通过水蒸气吸附等温线评估其疏水性。在这里，我们公开了GO具有非凡的强酸性，其中NH ₃吸附差热（Q _diff NH ₃）高于200 kJ mol ^-1，而A15和磺化碳的酸强度显着降低，Q _diff NH ₃低于150 kJ mol^-1。GO的超酸性暂时归因于“游离”质子的存在，这可以通过石墨烯片中抗衡阴离子的负电荷的离域来解释。在最低水含量（3 mol L ^-1）的情况下，GO是最具活性的催化剂，TOF为52 h ^-1，并且与A15相比，加水后其活性受到的抑制也较小。考虑到TOF本质上取决于布朗斯台德活性位点的强度以及活性位点可及性或多或少地受其微环境疏水性（与A15，磺化碳和GO相当）控制，这些结果是合理的。