Effects of adding Pd or Ni in Cu-Ti-Al-O catalyst on regulating products in selective hydrogenation or maleic anhydride

The selective hydrogenation of maleic anhydride over copper-based catalyst supported on TiO2-Al2O3 was studied at 200 similar to 280 V and atmospheric pressure, and palladium or nickel as the promoter was added in the catalyst. In the reaction, there are many products, such as 1,4-butanediol, tetrahydrofuran, gamma-butyrolactone and so on. Cu-Ni/TiO2-Al2O3 exhibits excellent catalytic performance for hydrogenation of maleic anhydride, and the change of the loading of CuO or NiO affects the product distribution. When the loading of CuO is higher than that of NiO, 1 4-butanediol and tetrahydrofuran are obtained with similar to 17.3% total selectivity at 270degreesC; When the loading of NiO is higher than that of CuO, the selectivity for gamma-butyrolactone reaches 100% with 100% conversion of maleic anhydride. Adding I'd into Cu/TiO2-Al2O3 catalyst makes the selectivity for I 4-butanediol or tetrahydrofuran increase remarkably, such as at 240degreesC using Cu-Pd/TiO2-Al2O3 (n (Pd) In (Cu) = 0.08%) catalyst, 38.5% selectivity for 1,4-butanediol and tetrahydrofuran with 100% conversion of maleic anhydride is obtained, but using Cu/TiO2-Al2O3 catalyst, the selectivity for I 4-butanediol and tetrahydrofuran is zero. The presence of Pd in CuO/-TiO2-Al2O3 can promote the reduction of Cu+ and Cu2+ to Cu-0 obviously, which enable the crystallite size of Cu-0 in the catalyst to decrease from 9.1 nm to 2.4 nm and the micro-strain value of Cu-0 to increase from 0.32 X 10 to 5.8 X 10(-3). This leads that the catalyst with Pd behaves much higher activity than that without Pd.