| Gas-water-solid three-phase catalysis reactions are widely used in laboratory synthesisand industrial production. Traditional chemical reaction is carried out in an organic solvent,while the addition of organic solvent will cause harm to humans and the environment anddoes not match the requirements of green chemistry. Therefore, water, as a green,pollution-free solvent, is favored by researchers. However, because gas has lower solubility inwater, catalytic reaction rate is greatly limited, as a result of which to find an efficientcatalytic reaction mode to speed up the reaction rate and improve the yield is becomingmore and more essential. Due to the bubbles can thoroughly mix gas, liquid and solid, thethree-phase contact area has been significantly improved, which further accelerates thereaction rate and improve the reaction yield. Therefore, it is a crucial task to synthesize akind of solid particle that can stabilize the bubbles and apply it into catalytic reaction.This paper prepared a catalyst which is interfacially active, and researched on its abilityto stabilize bubbles when as a foaming agent. Also the TEM, FT-IR, nitrogen adsorption,contact angle and elemental analysis were used to characterize the appearence, surfacefunctional groups and wettability of materials and catalysts and study the solid particleshaving interfacial activity for the first time when, as foaming agent, applied to the aqueousphase catalytic hydrogenation and aqueous-phase catalytic oxidation reaction.First, the interfacially active materials were obtained by using hydrophobicoctyltrimethoxysilane(C8) to make functional modification on the surface of SiO2nanoparticles(SN), and then studied how do the materials(SN-C8) stabilize the foam. Also, theinfluences of the amount of grafted silane, the mass of materials, the concentration of NaCland temperature on the formation and stability of bubbles were investigated. The resultsshowed that the bubble formed when the amount of grafted silane was0.6mmol/g,0.2g SN-C8-0.6was added to2mL NaCl solution at a concentration of0.05g/mL can stabilize for72hours under25℃; when the temperature reaches100℃, the bubbles began to collapse;secondly, based on the above study,we prepared catalyst, SN-Pd-C8,which wasinterfacially and loaded with Pd, and first applied it into the aqueous phase catalytichydrogenation reaction. With2-butene-1,4-diol as substrates, the effects of bubble formationon the aqueous phase of the hydrogenation reaction rate was studied, and reaction cycles,examined into the bubble stability and catalytic activity stability of the catalyst. Experimentalresults show that the formation of bubbles can increase the reaction yield, when there is nobubbles formation, the reaction yield is only31%and the reaction rate is slow; when there aremore bubbles the yield can reach100%, and the reaction is faster. Cycle experiments werecarried out7times, and in the course of the reaction cycle a large of bubbles were formed;the yield of the reaction is still about80%after seven times cycle, which shows catalysts hasgood foaming stability and catalytic activity stability.Finally, nanoparticles were modified with hydrophilic triaminesilane and hydrophobicoctylsilane, then noble metal Au was loaded on the modified particles to obtain Au/SN-C8N.It was used as a foam agent to form a foam and first used into the aqueous phase catalyticoxidation reaction, the effect of the foam on the oxidation reaction yield was studied, thecycling reaction used saligenin as substrate. Experimental results show that, the formation ofbubbles can make the reaction yield of the oxidation reaction improve2to3times. Cyclingreaction were carried out10times, and can form fine bubbles during the reactions, and10cycles of the reaction yield does not change a lot, the reaction is still of around80%after10times, indicating that the prepared catalyst has good foaming stability and catalytic activitystability. |
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