Cooperative catalytic effects between the penta-coordinated Al and Al2O3 in Al2O3-AlPO4 for aldol condensation of methyl acetate with formaldehyde to methyl acrylate

Leveraging the Proximity and Distribution of Cu-Cs Sites for Direct Conversion of Methanol to Esters/Aldehydes

Methanol serves as a versatile building-block for various commodity chemicals, and the development of industrially promising strategies for its conversion remains the ultimate goal in methanol chemistry. In this study, we design a dual Cu-Cs catalytic system that enables a one-step direct conversion of methanol and methyl acetate/ethanol into high value-added esters/aldehydes, with customized chain length and saturation by leveraging the proximity and distribution of Cu-Cs sites. Cu-Cs at a millimeter-scale intimacy triggers methanol dehydrogenation and condensation, involving proton transfer, aldol formation, and aldol condensation, to obtain unsaturated esters and aldehydes with selectivities of 76.3 % and 31.1 %, respectively. Cu-Cs at a micrometer-scale intimacy significantly promotes mass transfer of intermediates across catalyst interfaces and their subsequent hydrogenation to saturated esters and aldehydes with selectivities of 67.6 % and 93.1 %, respectively. Conversely, Cu-Cs at a nanometer-scale intimacy alters reaction pathway with a similar energy barrier for the rate-determining step, but blocks the acidic-basic sites and diverts the reaction to byproducts. More importantly, an unprecedented quadruple tandem catalytic production of methyl methacrylate (MMA) is achieved by further tailoring Cu and Cs distribution across the reaction bed in the configuration of Cu-Cs||Cs, outperforming the existing industrial processes and saving at least 15 % of production costs.

Efficient and Stable O-Methylation of Catechol with Dimethyl Carbonate over Aluminophosphate Catalysts

The O-methylation of catechol is an effective method for the industrial production of guaiacol used as an important chemical. However, the low catechol conversion and poor catalyst stability are the most critical issues that need to be addressed. Herein, the O-methylation of catechol with dimethyl carbonate was investigated over aluminophosphate (APO) catalysts, using a continuous-flow system to produce guaiacol. APO catalysts were synthesized with varying P/Al molar ratios and calcination temperatures to study their effects on catalytic performance for the reaction. The physico-chemical properties of the APO catalysts were thoroughly investigated using XRD, NH3-TPD, CO2-TPD, FTIR, and Py-FTIR. The P/Al molar ratio and catalyst calcination temperature significantly influenced the structure and texture, as well as the surface acid-base properties of APO. Both the medium acid and medium base sites were observed over APO catalysts, and the Lewis acid sites acted as the main active sites. The APO (P/Al = 0.7) exhibited the highest catalytic activity and excellent stability, due to the suitable medium acid-base pairs.