摘要
开发低温、高活性和良好稳定性的催化剂成为甲醇气相脱水制二甲醚乃至合成气一步法制二甲醚反应的核心.在氧化铝挤条成型的纳米HZSM-5沸石上负载Keggin结构12-磷钨酸制备了复合固体酸催化剂,通过FT-IR、UV-Raman、31P MAS-NMR和XRD对所制备的样品进行表征.以甲醇气相脱水制二甲醚为探针反应的研究结果表明,在选定的操作条件下连续运转超过300 h,甲醇摩尔转化率大于87%(理论转化率90.9%),二甲醚摩尔选择性高于99.0%,是目前该反应非常有效的催化剂之一.
Exploiting the catalysts with higher activity and stability for methanol dehydration at low temperature has become the central part of research dimethyl ether from synthesis gas or methanol. The crystal size of HZSM-5 zeolite is 50~ 100 nm. The nanocrystalline HZSM-5 zeolite is thought to be an ideal material for the encapsulation of heteropoly acid （HPA） molecules having a Keggin or Dawson structure since they have the intergranular secondary pores. A HPA/nanocrystalline HZSM-5 complex solid acidic catalyst was prepared by an impregnation method and characterized by FT-IR, UV-Raman, XRD and 31p MAS-NMR. The 12-phosphotungstic acid （HPW） loaded on nanocrystalline HZSM-5 zeolites was prepared by the following steps. The strip （qb 1 mmX 2 mm） nanocrystalline HZSM-5 （Si/A1=4.2） catalyst was prepared by the procedure that reported in the literature. 1.00 g HPW was dissolved in 15 mL deionized water. 10.0 g of the strip nanocrystalline HZSM-5 zeolite were added into the solution and steeped the mixture for 12 h. The slurry mixture was calcined at 350 ~C for 4 h. This catalyst is denoted HPW-HZSM-5. The FT-IR spectroscopy, UV-Raman spectroscopy and 31p MAS-NMR of HPW-HZSM-5 characterization results show that the Dawson type structure was well preserved after calcination of the cata- lysts. The reaction was carried out in a continuous flow fixed-bed reactor （diameter 10 mm）. Reaction conditions are listed as following： temperature 200℃, WHSV= 1.6, Fp, H （methanol flow rate）=0.08 mL/min; FRH （N2 flow rate）=8.0 mL/min; catalyst 2.05 g; system pressure 0.8 MPa. The composition of the products was analyzed by a GC-8820 gas chromatograph equipped with FID and a GDX-403 （2 m±4 mm）. The reaction performance results, including methanol conversion and di- methyl ether selectivity were subsequently calculated. Under steady state conditions, the catalyst shows good stability, and the conversion of methanol maintains above 87.0 mol% （90.9 mol%） during 300 h, it also shows the selectivity （99.0 mol%） of dimethyl ether under the experimental conditions.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2013年第5期810-814,共5页
Acta Chimica Sinica
基金
中国博士后科学基金面上项目(No.20080441109)
国家自然科学基金(No.21171082)资助~~
关键词
12-磷钨酸
纳米HZSM-5沸石
甲醇脱水
二甲醚
12-phosphotungstic acid
nanocrystalline HZSM-5 zeolite
methanol dehydration
dimethyl ether
