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Bio-based pentamethylene dicarbamate (PDC) belongs to N-substituted carbamates, which are important fine chemicals and organic intermediates. In this work, well-defined CeO2rods, cubes, and octahedrons were successfully prepared to catalyze the synthesis of PDC by carbonylation of 1,5-pentanediamine (PDA) with methyl carbamate (MC). Among them, CeO2rods with higher amounts of acid–base sites and abundant oxygen vacancies showed superior intrinsic activity in the PDA carbonylation reaction. In situFTIR results showed that intermediate polyureas were readily formed in the reaction, and then, CeO2rods promoted the alcoholysis of polyureas to PDC. In situDRIFTS results indicated that the surface of CeO2rods is more favorable for the adsorption and activation of the reactants. CeO2rods can also be used for the efficient synthesis of a series of N-substituted carbamates. We believe that this work will contribute to the efficient, green, and sustainable production of N-substituted carbamates.

Silicon-rich lye (SRL), a characteristic byproduct from desilication during high-value utilization of coal-based solid wastes, can be applied as special silicon resources to prepare tobermorite. Herein, nanoflake tobermorite can be obtained at optimal conditions with a silicon conversion rate up to 94.65%. Increase in temperature and duration leads to an increase in crystallinity of tobermorite with less incorporation of impurities such as sodium and aluminum and promotes the transition of crystal growth from the radial to axial direction. Aluminum preferentially exists in the form of replacing silicon atoms at Q3branching sites, possibly decreasing the polymerization degree and increasing basal spacing. The uptake of sodium occurs in Si–O–Na and is held near Al(IV) sites. The crystallization mechanism of tobermorite mainly consists of three stages, the formation of calcium silicate hydrate (C–S–H) (I) gel, the transformation of C–S–H (I) gel to tobermorite crystal, and the growth and agglomeration of tobermorite particle. The addition of foil-like tobermorite can reduce the thermal conductivity of energy-saving products by nearly 50%. This study can provide fundamental information on the structure and formation of tobermorite in highly alkaline environments and broaden its synthetic application.