State Key Laboratory of Heavy Oil Processing; Key Laboratory of Catalysis, CNPC, China University of Petroleum, Qingdao 266580, People's Republic of China ; Department of Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China.
State Key Laboratory of Heavy Oil Processing; Key Laboratory of Catalysis, CNPC, China University of Petroleum, Qingdao 266580, People's Republic of China ; Lanzhou Petrochemical Research Center, Petrochemical Research Institute, PetroChina Company Limited, Lanzhou 730060, People's Republic of China.
Nanoscale Res Lett. 2014 Oct 3;9(1):550. doi: 10.1186/1556-276X-9-550. eCollection 2014.
Three kinds of HZSM-5 nanoparticles with different acidity were tailored by impregnating MgO or varying Si/Al ratios. Both the textural and acidic properties of the as-prepared nanoparticles were characterized by nitrogen adsorption-desorption measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), ammonia temperature-programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR or Py-FTIR). It was found that the intensity of Lewis acid sites with weak strength was enhanced by impregnating MgO or reducing Al concentration, and such an enhancement could be explained by the formation of Mg(OH)(+) or charge unbalance of the MgO framework on the surface of HZSM-5 support. The effect of HZSM-5 nanoparticles' acidity on methyl bromide dehydrobromination as catalyst was evaluated. As the results, MgHZ-360 catalyst with the highest concentration of Lewis acid sites showed excellent stability, which maintained methyl bromide conversion of up 97% in a period of 400 h on stream. Coke characterization by BET measurements and TGA/DTA and GC/MS analysis revealed that polymethylated naphthalenes species were formed outside the channels of the catalyst with higher acid intensity and higher Brønsted acid concentration during the initial period of reaction, while graphitic carbon formed in the channels of catalyst with lower acid intensity and higher Lewis acid concentration during the stable stage.
三种具有不同酸度的 HZSM-5 纳米粒子通过浸渍 MgO 或改变 Si/Al 比来进行调变。通过氮气吸附-脱附测量、X 射线衍射 (XRD)、扫描电子显微镜 (SEM)、氨程序升温脱附 (NH3-TPD) 和傅里叶变换红外光谱 (FTIR 或 Py-FTIR) 对所制备的纳米粒子的结构和酸性进行了表征。结果发现，通过浸渍 MgO 或降低 Al 浓度，可以增强具有较弱强度的 Lewis 酸位的强度，这种增强可以通过 HZSM-5 载体表面上形成的 Mg(OH)(+)或 MgO 骨架的电荷不平衡来解释。评估了 HZSM-5 纳米粒子的酸度对甲基溴化物脱氢溴化作为催化剂的影响。结果表明，Lewis 酸位浓度最高的 MgHZ-360 催化剂表现出优异的稳定性，在 400 小时的连续运行期间，保持了高达 97%的甲基溴化物转化率。通过 BET 测量、TGA/DTA 和 GC/MS 分析对积碳进行了表征，结果表明，在反应初期，具有较高酸强度和较高 Brønsted 酸浓度的催化剂通道外形成了多甲基萘类物质，而在稳定阶段，具有较低酸强度和较高 Lewis 酸浓度的催化剂通道内形成了石墨碳。
