碱处理浓度对预脱铝ZSM-5成孔过程及其MTG反应性能的影响  

Effect of Alkaline Concentration on Mesopore Formation in Acid Pre-treated HZSM-5 Zeolite and Its Catalytic Performance in the Methanol-to-Gasoline Reaction

作　　者：常江伟[1] 付廷俊[1] 张洪建[1] 周浩[1] 李忠[1] 

机构地区：[1]f太原理工大学煤化工研究所,煤科学与技术教育部和山西省重点实验室,太原030024

出　　处：《无机化学学报》2015年第11期2119-2127,共9页Chinese Journal of Inorganic Chemistry

基　　金：太原理工大学人才资助项目(No.tyut-rc201454a)

摘　　要：在80℃水浴条件下,对ZSM-5分子筛进行酸碱处理改性;重点考察了碱处理溶液浓度对酸预处理脱铝后ZSM-5分子筛微观结构及其催化甲醇制汽油(MTG)性能的影响。通过BET、XRD、FT-IR、NH3-TPD和TEM等手段对样品进行表征。结果表明,单独酸处理没有改变分子筛孔结构,单独碱处理产生了并不明显的介孔。酸预处理后再碱处理可促进介孔的产生,产生更为显著的介孔结构;而且随着碱处理强度的增加,分子筛样品的介孔/微孔比表面积比例和孔体积均先增大后降低。酸浓度2 mol·L-1,碱浓度0.4 mol·L-1条件处理得到的分子筛,介孔比表面积比例和孔容均达到最大,酸量和酸强度最低。在400℃,0.1 MPa,WHSV=2.1 h-1条件下,甲醇制汽油反应性能最佳:汽油收率由未改性时的30wt%提高到34wt%,寿命更是由16 h延长到135 h,芳烃含量由原来的73wt%降至20wt%。Modifying of ZSM-5 molecular sieve in acid and alkaline solution was studied at 80 ℃. For the post synthesis, dealumination prior to desilication step was critical for the following mesopore formation by desilication and the effect of alkaline concentration on the crystallinity, porosity, morphology and acidity of zeolite was investigated by deep characterization of BET, XRD, FT-IR, NH3-TPD, and TEM. It was found that the microporous structure was well reserved in acid dealumination alone, alkaline desilication could promote smaller mesopore. However, acid dealumination before desilication facilitated the mesopore formation resulting in larger pore volume. When the concentration of alkaline solution was increased to 0.6 mol·L^-1, both the pore volume and Sext/Smicro firstly increased and then decreased. The sample via post treatment of 2 mol·L^-1 HC1 and 0.4 mol·L^-1 NaOH solution was found to have higher proportion of mesopores, less amount of acid sites, especially strong acidity. Methanol conversion to gasoline reaction was carried out in a fixed reactor at 400℃, 0.1 MPa and WHSV=2.1 h^-1. The sample subjected to 2 mol· L^-1 HC1 acid solution and 0.4 mol·L^-1 NaOH solution exhibited greater improvement： the yield of gasoline range increased to 34wt% from 30wt%, the lifetime was prolonged to 135 h relative to parent ZSM-5 and the content of aromatics was decreased from 73wt% to 20wt%. The results were well rationalized by alterations of acidic properties, mesopore formation and improved diffusivity.

关 键 词：酸预处理 脱硅 HZSM-5 甲醇制汽油 介孔 

分 类 号：O643.36[理学—物理化学]