甲醇气相氧化羰化法合成碳酸二甲酯的Cu-AC催化剂活性研究

采用连续流动固定床反应器,研究了用于甲醇直接氧化羰化合成碳酸二甲酯的负载型Cu-AC催化剂。分别考察了铜离子价态、浸渍溶剂、铜含量和载体活性炭孔修饰对催化剂活性的影响。结果表明,由浓氨水为浸渍溶剂,AC为载体,CuCl活性组分制得的Cu-AC催化剂具有较高的催化活性和DMC选择性;催化剂中Cu质量分数达7.5%时,催化剂的活性最高,Cu质量分数过高,易使催化剂表面富集大量CuO物种,导致DMC选择性及收率明显下降;以CuCl_2为活化剂,制得的AC可明显改善载体的孔结构性质和孔径分布,孔径分布主要由修饰前的1.5 nm较大微孔区转变为2.5 nm左右的中孔区域;中孔分布比例较大且孔径范围在2.5 nm左右的AC载体有利于该活性组分的分散及甲醇氧化羰化催化活性的提高;在Cu质量分数5%时,甲醇转化率可达35.0%,DMC时空收率为211.9 g/(kg·h),且DMC选择性仍在95%以上。

Cu-AC CATALYST FOR SYNTHESIS OF DIMETHYL CARBONATE BY DIRECT VAPOR PHASE OXIDATIVE CARBONYLATION OF METHANOL

The Cu-AC supported catalyst for dimethyl carbonate (DMC) synthesis by direct oxidative carbonylation of methanol was studied in a continuous fixed-bed reactor.Effects of cupper valence states,impregnation solvents,cupper content and modification of the activated carbon (AC) support were investigated.The results showed that the Cu-AC catalyst prepared using ammonia as impregnation solvent,CuCl as active component and activated carbon as support showed high catalytic activity and DMC selectivity.When Cu content was 7.5%,the catalytic activity was the highest.Excessive cupper in the catalyst resulted in more CuO enrichment on the surface of the catalyst,and then further resulted in the decrease of DMC selectivity and yield.Chemical modification of cola-based AC using CuCl_2 as activator increased the mesopore distribution and changed the range of the pore diameter: the pore distribution changed mainly from 1.5 nm micropore region to 2.5 nm mesopore region.AC with the highest proportion of mesopore distribution at about 2.5 nm pore diameter was appropriate for the dispersion of the active component and improvement of the catalytic activity of methanol oxycarbonylation. On the catalyst with 5% cupper content,methanol conversion,DMC selectivity and space time yield (STY) reached 35.0%,95% and 211.9 g/(kg·h),respectively.