No abstract

In this work, a lignin-based concrete water reducer was prepared through organic solvent fractionation and chemical modification of lignin extracted from pine wood with formic acid. The fractionated lignin with different molecular weight was modified via oxidation–sulfomethylation (OS), and the effects of fractionation on the performance of lignin-based concrete water reducer were investigated. It was found that the sulfonation degree (SD) of the fractionated lignin after OS was clearly higher compared to the unfractionated lignin, and the SD of fractionated lignin was linearly correlated with its workability (i.e., the fluidity of cement paste) based on the results obtained. By adding the same quantity of modified lignin-based concrete water reducer, the fluidity of cement paste with the fractionated lignin (by pure acetone) after OS modification was 21% higher than the sulfonated FAL (M-FAL) without fractionation. The organic solvents used in this study could be easily recovered and reused. Thus, the whole fractionation process was sustainable. In addition, the structure changes of lignin samples before and after fractionation and OS modification were characterized by gel permeation chromatography, FTIR, and 1H NMR, respectively.

Carbon dioxide is a sufficient and important carbon resource, which has been widely used as a C1 building block in synthetic chemistry. Carbonylations with CO are important processes in industry. However, due to the toxicity of CO, its storage and transport are problematic. Attentions are gradually focused on using other safe reagents to be the CO surrogates in carbonylation reactions. This review focuses on the summary of recent developments in using CO2 as a CO surrogate in homogeneous catalysis. Reductive processes by using H2, Si‐H, alcohols, etc and redox‐neutral processes are separately summarized.