V_(2)O_(5)/ZrO_(2)-Al_(2)O_(3)催化甲醇选择性氧化合成二甲氧基甲烷

The Synthesis of Dimethoxymethane through Selective Oxidation of Methanol with V_(2)O_(5)/ZrO_(2)-Al_(2)O_(3) Catalysts

采用浸渍法制备了V_(2)O_(5)质量分数不同的V_(2)O_(5)/Al_(2)O_(3)催化剂,采用Zr对Al_(2)O_(3)载体进行改性并应用于催化甲醇选择性氧化制备二甲氧基甲烷(DMM)的反应中。经X-射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见分光光谱(UV-Vis)、傅里叶变换红外光谱(FTIR)、拉曼光谱(Raman)、N2吸附-脱附(BET)、H2程序升温还原(H_(2)-TPR)和NH3程序升温脱附(NH_(3)-TPD)表征分析,结果表明:与单一Al_(2)O_(3)负载的钒基催化剂相比,Zr改性提高了钒氧化物的分散性与稳定性,加强了催化剂中各组分间的相互作用,有效调变了催化剂的酸性和氧化性,进而提高了DMM的选择性。考察了反应条件对甲醇选择性氧化制备DMM的影响,最佳反应温度为175℃,经20%V_(2)O_(5)/12%ZrO_(2)-Al_(2)O_(3)催化氧化,甲醇转化率为27.9%,DMM选择性为99.9%。

V_(2)O_(5)/Al_(2)O_(3) catalysts with different V_(2)O_(5) mass fraction were prepared with the impregnation method.The support of V_(2)O_(5)/Al_(2)O_(3) catalyst was modified with Zr.The catalysts were applied to the selective oxidation of methanol to prepare dimethoxymethane(DMM).The as-prepared catalysts were characterized with X-ray diffraction(XRD),scanning electron microscope(SEM),ultraviolet and visible spectrophotometry(UV-Vis),fourier transform infrared(FTIR),raman spectra(Raman),N_(2) adsorption-desorption isotherm(BET),H2 temperature-programmed reduction(H_(2)-TPR)and NH_(3) temperature-programmed desorption(NH3-TPD).The results indicated that the performance of Zr modification could effectively improve the dispersibility and stability of vanadium oxide and the interaction between the substances in the catalyst.In addition,compared with vanadium-based catalysts supported on the single oxide Al_(2)O_(3),the Zr modification could effectively regulate the acidity and oxidation properties of the catalyst,which improved the selectivity of DMM.The effect of reaction conditions on the preparation of DMM through methanol oxidation was investigated.For the catalyst 20%V_(2)O_(5)/12%ZrO_(2)-Al_(2)O_(3),the value of methanol conversion and DMM selectivity were 27.9%and 99.9%at 175℃,respectively.