Huilin Yi,Shuliang Lu,Jiajia Wu,Yujun Wang,Guangsheng Luo
In this paper, we present a parallelized microfluidic device with improved ladder–tree distributors for the scaled-up production of monodisperse microspheres. Owing to the improved distribution form comprising a ladder distributor in the center and tree distributors around the circumference, the uniformity of the generated droplets for our device was improved by 32.9% and 86.1% compared to those achieved in devices with conventional tree and ladder distributors, respectively, in the final production stage with 32 droplet generators, indicating the potential of our device for further scale-up while maintaining the monodispersity of the generated droplets. The effect of the 2D scale-up of our device was investigated by varying the continuous-phase flow rate and viscosity. Using our device, γ-Al 2 O 3 microspheres with a diameter of 598.1 μm and a CV of 2.58%, as catalyst support for microreactors, were continuously synthesized at high production rate. The nickel-based catalyst prepared from γ-Al 2 O 3 microspheres with large specific surface area and pore volume had an average NiO size of 14 nm, which was 60.9% of that supported on industrial support. The CO methanation conversion of the Ni@Al 2 O 3 microspheres was 1.7 times larger than Ni@Al 2 O 3 industrial support at 140 °C.
CaO-doped γ-Al2O3 beads were prepared by an alginate assisted sol–gel method, followed by grafting with alkyl groups and impregnation of NbCl5 to construct multi-functionalized γ-Al2O3 beads for efficient catalytic conversion of glucose to 5-hydroxymethylfurfural (5-HMF). Doping with CaO improved the binding capacity of the catalyst with glucose and increased the Lewis acid amount. However, a high CaO content would cover the Lewis acid sites of γ-Al2O3, resulting in a lower isomeric conversion of glucose to fructose. When the C8–Ca(10%)–γ-Al2O3 catalyst was loaded with Nb2O5, intermediate fructose was consumed rapidly resulting in complete conversion of glucose, which indicated that conversion of glucose to 5-HMF involved the isomeric conversion of glucose to fructose followed by dehydration of fructose to 5-HMF. This was necessary to balance hydrophilic isomerization reactions with restraining the rehydration of 5-HMF by hydrophobic modification. This is similar to the reaction in which a medium with a certain amount of water was beneficial for glucose isomerization. Under the synergistic effect of Lewis acid provided by γ-Al2O3 and Brønsted acid offered by Nb2O5, C8–Ca(10%)–γ-Al2O3–Nb(3%), a glucose conversation rate of 100% and the highest yield of 5-HMF (68.4%) were achieved in the reaction medium with a dimethylsulfoxide/H2O (V/V) ratio of 4 : 1, a catalyst amount of 33 mg, a reaction temperature of 140 °C and a reaction time of 4 h.
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