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用XRD、IR及ESR等方法,考察了P_2O_6-V_2O_5的晶相结构,结果证明(VO)_2P_2O_7(B相)对于丁烷氧化制顺酐,有良好的催化效果。P/V=1.15的催化剂,S_(BET)在20m~2·g~(-1),主要孔分布在80~90A,ESR信号强度最大,且有V4+V5+容易可逆转变的特点。NH_3-IR结果证明,P/V=1.15时有强B酸中心,而0.9和2.0时都没有,这是B相的一个重要特征。强的P—OH酸性中心,在催化过程中,将同显著伸长了的V=O键有协同作用。催化剂的六种不同制法,虽然P/V原子比相同,所得晶相却差别很大,C、E、F在p/V=1.0—1.2主要生成B相,A、B、D则主要是α相和无定形相。C、E、F和A、B、D不仅相结构不同,在NHs不可逆吸附丁烯异构化活性和丁烷转化为MA的选择性上,也有明显的区别。
The crystal structure of P_2O_6-V_2O_5 was investigated by XRD, IR and ESR. The results showed that (VO) _2P_2O_7 (B phase) had a good catalytic effect on the oxidation of butane to maleic anhydride. The catalyst with P / V = 1.15 has a BET specific surface area of 20 m 2 · g -1 and a dominant pore distribution of 80-90 A with the highest ESR signal intensity and reversible V4 + V5 + conversion. NH_3-IR results showed strong B acid sites at P / V = 1.15, but not at 0.9 and 2.0, which is an important feature of B phase. Strong P-OH acidic centers, in the catalytic process, will have a synergistic effect with the significantly elongated V = O bond. Although the P / V atomic ratio is the same, the obtained crystalline phases are quite different. C, E and F mainly generate B phase at p / V = 1.0-1.2, while A, B and D are mainly α-phase and amorphous phase. C, E, F and A, B, D not only have different phase structures, but also have obvious differences in the irreversible adsorption of butane on isomerization activity of NHs and the selectivity of butane conversion to MA.