Design and operation of integrated pilot-scale dimethyl ether synthesis system via pyrolysis/gasification of corncob

The integrated pilot-scale dimethyl ether (DME) synthesis system from corncob was demonstrated for modernizing utilization of biomass residues. The raw bio-syngas was obtained by the pyrolyzer/gasifier at the yield rate of 40-45 Nm(3)/h. The content of tar in the raw bio-syngas was decreased to less than 20 mg/Nm(3) by high temperature gasification of the pyrolysates under O-2-rich air. More than 70% CO2 in the raw bio-syngas was removed by pressure-swing adsorption unit (PSA). The bio-syngas (H-2/CO approximate to 1) was catalytically converted to DME in the fixed-bed tubular reactor directly over Cu/Zn/Al/HZSM-5 catalysts. CO conversion and space-time yield of DME were in the range of 82.0-73.6% and 124.3-203.8 kg/m(cat)(3)/h, respectively, with a similar DME selectivity when gas hourly space velocity (GHSV, volumetric flow rate of syngas at STP divided by the volume of catalyst) increased from 650 h(-1) to 1500 h(-1) at 260 degrees C and 4.3 MPa. And the selectivity to methanol and C-2(+) products was less than 0.65% under typical synthesis condition. The thermal energy conversion efficiency was ca. 32.0% and about 16.4% carbon in dried corncob was essentially converted to DME with the production cost of ca. (sic) 3737/ton DME. Cu (111) was assumed to be the active phase for DME synthesis, confirmed by X-ray diffraction (XRD) characterization.

Scale study of direct synthesis of dimethyl ether from biomass synthesis gas

We investigated the synthesis of dimethyl ether (DME) from biomass synthesis gas using a kind of hybrid catalyst consisting of methanol and HZSM-5 zeolite in a fixed-bed reactor in a 100 ton/year pilot plant. The biomass synthesis gas was produced by oxygen-rich gasification of corn core in a two-stage fixed bed. The results showed that CO conversions reached 82.00% and 73.55%, the selectivities for DME were 73.95% and 69.73%, and the space-time yields were 124.28 kg m- 3 h- 1 and 203.80 kg m- 3 h- 1 when gas hourly space velocities were 650 h- 1 and 1200 h- 1, respectively. Deoxidation and tar removal from biomass synthesis gas was critical to the stable operation of the DME synthesis system. Using single-pass synthesis, the H2/CO ratio improved from 0.98-1.17 to 2.12-2.22. The yield of DME would be increased greatly if the exhaust was reused after removal of the CO2.

液晶聚芳醚酮/聚芳醚酮共混体系的相行为、凝聚态结构与流变性能研究

聚芳醚酮是一种高性能热塑性材料，但其熔融温度高，熔体粘度大，流动性较差。液晶聚芳醚酮则具有非常丰富的液晶相织构和复杂的相转变行为，并且其熔体粘度低，流动性较好。将二者共混，液晶的加入势必降低聚芳醚酮的熔融粘度，改善其熔体流动性，另一方面液晶聚芳醚酮的液晶织构和相行为等势必受很大影响。因此开展这一研究工作不但有重要的理论意义，同时对改善这类材料的性能和拓宽其应用范围具有重要的实际意义。发现液晶聚芳醚酮／聚醚醚酮共混物的复杂相行为与组成密切相关。在以液晶聚芳醚酮为主的共混物中，高分子量的聚醚醚酮易于从低分子量的液晶聚芳醚酮基质相中分离出来，形成了特殊的环带结构。在50：50液晶聚芳醚酮／聚醚醚酮共混物中，两个组分在熔融状态下发生了液一液相分离，导致环带结构和聚醚醚酮球晶同时形成。在以聚醚醚酮为基质相的共混物中，低分子量的液晶聚芳醚酮很难从高分子量的聚醚醚酮基质相中分离出来，最后只能在聚醚醚酮球晶的边界形成单独的相区。当聚醚醚酮含量很高时，仅生成聚醚醚酮球晶。首次在液晶聚芳醚酮与聚醚醚酮共混物中发现了环带球晶，并利用溶剂选择性蚀刻的方法确定了其相结构和组成。环带球晶中的亮心和亮环是液晶聚芳醚酮相，其c轴（分子链方向）垂直于膜平面，而。和b轴则在膜平面内没有固定的取向。暗环则是聚醚醚酮与部分液晶聚芳醚酮的共存相，其中液晶聚芳醚酮晶体的分子链也垂直于膜平面，但聚醚醚酮片晶则呈现复杂的结晶取向。确定环带球晶的形成机理，从分子水平上提出环带球晶的生长模型，即间歇式增长过程，符合结构不连续模型。总结了环带球晶的形成规律和必要条件为：（l）液晶聚芳醚酮为主要成分；（2）液晶聚芳醚酮与聚醚醚酮有一定相容性，至少在熔融态分子相容；（3）液晶聚芳醚酮的各向同性相向液晶相的转变温度要高于聚芳醚酮的结晶温度；（4）液晶聚芳醚酮相转变（或结晶）速率与共混物的相分离速率相匹配或前者略大于后者；（5）降温速率或等温结晶温度适当。聚醚醚酮／含氟液晶聚芳醚酮共混物在熔体状态下的流动行为与共混物的组成、两相的相容性及相的转变有着密切的关系。在聚醚醚酮／含氟液晶聚芳醚酮共混物中，当前者为主要成份时，流动曲线形状与纯PEEK的相似，而当后者为主要成份时，表现出与含氟液晶聚芳醚酮相似的流变行为。共混物的复数粘度、储存模量和损失模量总体来说随F一队EK含量的增加而逐渐下降，只有当含氟液晶聚芳醚酮含量为50％时，共混物的复数粘度、储存模量和损失模量出现了局部极大值。

稀土三元催化剂下二氧化碳/环氧丙烷/缩水甘油醚共聚物的合成与性能研究

为拓宽PPC的应用范围，本论文在CO2与PO的共聚反应中，引入第三单体缩水甘油醚（烯丙基缩水甘油醚AGE、丁基缩水甘油醚BGE和苯基缩水甘油醚GPE），制备得到不同结构和性能的二氧化碳共聚物。主要工作总结如下：1．在CO2与PO的共聚反应中，引入第三单体 AGE，合成了侧链带双键的官能化二氧化碳共聚物Pol（PO-co-CO2-co-AGE）；2．在CO2-PO-BGE的共聚反应中，控制PO／B GE的摩尔比，可制得不同结构和 性能的二氧化碳共聚物Poly（P0-co-CO2-co-BGE），其Tg为-26.8-36.1℃，大幅度拓展了二氧化碳共聚物的最低使用温度区间；3．在CO2与PO的共聚反应中，引入第三单体GPE，合成了侧链带刚性苯环的 二氧化碳共聚物Poty（PO-co-CO2-co-GPE），提高了聚合产物的热稳定性。

Laterally Electrostatically Driven Poly 3C-SiC Folded-Beam Resonant Microstructures

Micromachined comb-drive electrostatic resonators with folded-cantilever beams were designed and fabricated. A combination of Rayleigh＇s method and finite-element analysis was used to calculate the resonant frequency drift as we adjusted the device geometry and material parameters. Three micromachined lateral resonant resonators with different beam widths were fabricated. Their resonant frequencies were experimentally measured to be 64.5,147.2, and 255.5kHz, respectively, which are in good agreement with the simulated resonant frequency. It is shown that an improved frequency performance could be obtained on the poly 3C-SiC based device structural material systems with high Young＇s modulus.

RTCVD工艺制备poly-Si薄膜太阳电池的研究

报道了快速热化学气相沉积(RTCVD)工艺制备多晶硅(poly -Si)薄膜及电池的实验和结果。采用SiH_2Co_2作为原料气体，衬底温度为1030℃时，薄膜的生长速率为10nm/s。发现薄膜的平均晶粒度及载流子迁移率与衬底温度和材料有关。用该薄膜在未抛光重掺杂磷的硅衬底上制备1cm~2的p~+n结样品电池，无减反射涂层，其转换效率为4.54%(AM1.5,100mW/cm~2,25℃)。

Electrical bistability and negative differential resistance in diodes based on silver nanoparticle-poly(N-vinylcarbazole) composites

An electrically bistable device has been fabricated using nanocomposite films consisting of silver nanoparticles and a semiconducting polymer by a simple spin-coating method. The current-voltage characteristics of the as-fabricated devices exhibit an obvious electrical bistability and negative differential resistance effect. The current ratio between the high-conducting state and low-conducting state can reach more than 103 at room temperature. The electrical bistability of the device is attributed to the electric-filed-induced charge transfer between the silver nanoparticles and the polymer, and the negative differential resistance behavior is related to the charge trapping in the silver nanoparticles. The results open up a simple approach to fabricate high quality electrically bistable devices by doping metal nanoparticles into polymer.