莫来石-二氧化硅催化剂载体制备

PREPARATION OF A_3S_2-SiO_2 CATALYST SUPPORT

莫来石具有膨胀均匀、热震稳定性好、硬度大、化学稳定性好等性质,二氧化硅具有耐磨性好、化学性能稳定、熔点高等性质。为此,以此两种矿物为主要矿相的材料作为催化剂载体,其性能稳定。这里利用固体废弃物矾土尾矿、粘土和纤维素为原料制备了莫来石-石英多孔催化剂载体,研究结果表明:为满足制品中更多地形成莫来石矿物相,同时满足各种原料配合后能够实现可塑成形的要求,较为合理的配方是矾土尾矿与紫木节粘土质量比160g:40g,纤维素和水分别为矾土尾矿与紫木节粘土总质量外加计1%和25%。为使载体中形成合适的气孔,在载体中加入成孔剂,对所选成孔剂,成孔剂M较为理想,可以实现载体内不留残留物,载体不会受到污染,成孔剂M合理的加入量为4%,此时其载体气孔率较高为41.3%;合理的烧成温度为1250℃;烧成温度下的保温时间选取2h为宜。所制得的多孔催化剂载体经X-射线表征主要矿物相为莫来石和石英,载体线膨胀率为0.68-0.72%,载体具有较好的化学稳定性及耐热性能。

Mullite was characterized by uniform expansion, good thermal-shock resistance, high hardness and good chemical stability. Silica had good abrasive resistance, good chemical stability and high melting point. In this way, catalyst support mostly prepared by the two mineral facies had good stability. The catalyst support was prepared using gangue of bauxite tailing which was a solid waste material, clay and cellulose. In order to get more mullite and well-molded support after mixing, it was found that the mass ratio of gangue of bauxite and knar clay was 4 ： 1. The masses of cellulose and water were individually lwt% and 25wt% of the total mass of gangue of bauxite tailing and knar clay. In order to form suitable pores, pore forming agent was added into the clay. The pore forming agent M was optimum among the selected pore forming agents. The pore forming agent M didn＇ t residue in support after sintering so that the support wasn＇ t polluted. The appropriate addition of the pore forming agent M was 4%, and the catalyst support with the porosity of 41.3% was preparated. The appropriate sintering temperature and holding time were 1250°C and 2h, respectively. The X-ray diffraction pattern of the catalyst support showed that mullite and quartz were the main mineral facies of the catalyst support. The linear shrinkage rate of the support ranged from 0.68% to 0.72%. The catalyst support had good chemical stability and heat-resisting property.