ZSM-5分子筛的P改性研究进展

P改性是调变ZSM-5分子筛催化性能的重要手段。ZSM-5分子筛的P改性方法主要由磷酸、磷酸盐水溶液及有机P化合物浸渍或通过气相沉积等方法进行。改性ZSM-5分子筛中,P与Al物种相互作用, P物种主要以四配位形式存在,调变分子筛的酸性,通过对表面的修饰阻止骨架Al的脱除,提高ZSM-5分子筛的水热稳定性。P改性后,HZSM-5分子筛的酸密度,尤其是表面强酸密度下降,降低正碳离子机理反应中的二次反应,减少氢转移及齐聚,促进轻烯烃的生成。P改性修饰HZSM-5分子筛的孔口,提高择形性能,部分进入体相的P减少裂化过程中ZSM-5交叉口处大分子正碳离子的形成,减少双分子裂化机理中间体的生成,提高轻烯烃选择性。P改性ZSM-5分子筛强酸密度降低,择形效应提高,焦炭生成得到抑制,催化剂寿命延长。     

蓖麻酸甲酯水解反应性能研究

以自制蓖麻酸甲酯为原料,对其进行了水解反应性能的研究。采用单因素试验考察了反应温度、水与蓖麻酸甲酯体积比、酸碱性及反应时间对蓖麻酸甲酯水解率的影响。结果表明:按碱性、中性、酸性水解顺序蓖麻酸甲酯水解率依次减小;反应温度越低,蓖麻酸甲酯水解率越小;水与蓖麻酸甲酯体积比越小,蓖麻酸甲酯水解率越小;反应时间缩短,蓖麻酸甲酯水解率减小;在酸性介质、水与蓖麻酸甲酯体积比1∶1、反应温度25℃、反应时间60 min条件下,蓖麻酸甲酯水解率为4.2%。选择在酸性介质、较低温度、较少水量条件下对蓖麻酸甲酯进行快速水洗对降低其水解损失是有利的。     

分子筛酸性对异丁烷/丁烯烷基化反应性能的影响研究进展

概述分子筛的酸性特点,介绍固体酸催化的异丁烷/丁烯烷基化反应机理,并对已用于异丁烷/丁烯烷基化反应的分子筛情况进行总结,重点阐述分子筛的酸性对烷基化反应性能的影响。结果表明,分子筛应有合适的酸强度,综合来看,中强B酸更有利于反应。今后的机理研究中应当关注L酸及酸位空间分布对烷基化反应的影响。     

Predominant yeasts in the sourdoughs collected from some parts of Turkey

In the present study, a total of eight sourdough samples were collected from three different bakeries at two different times in Turkey. Also, laboratory-scale sourdough production was conducted by daily back-slopping for 7 days. Microbiological and chemical properties of the sourdoughs were investigated. Yeast species in the sourdoughs were identified by subjecting all presumptive yeast cultures to internal transcribed spacer region amplification of the 5.8S rRNA gene, restriction fragment length polymorphism analysis using Hae III, Hha I, and Hinf I endonucleases, and sequence analysis of the D1/D2 domain of the 26S rDNA gene. A total of seven profiles were determined according to the restriction fragments. Totally, 148 yeast isolates were identified at the species level (≥400 bp , 99% identity) as Saccharomyces cerevisiae (106), Kazachstania bulderi (11), Pichia fermentans (nine), Pichia membranifaciens (eight), Kazachstania servazzii (seven), Kazachstania unispora (four), and Hanseniaspora valbyensis (three). Although collected sourdoughs were produced without using baker's yeast, S. cerevisiae was the most frequently isolated yeast species. This can be related to the contamination of the bakery environment with commercial baker's yeast during the production of other bakery products. The pH and acidity levels of the collected sourdough samples ranged from 3.71 to 3.96 and 6.78 to 23.93 mL 0.1 N NaOH/10 g dough, respectively. Mean values of the content of maltose + sucrose, glucose, fructose, lactic acid, and acetic acid were 2.43, 1.57, 2.67, 7.30, and 1.40 g/kg, respectively. Due to the artisan and region-dependent handling of the sourdough, different biochemical patterns were observed among the collected samples.     

Brönsted方程动力学模型研究ZSM-5催化乙烯齐聚及芳构化活性和酸强度分布之间的定量关系

乙烯催化齐聚和芳构化是烯烃高值化和合成液体燃料的关键过程，采用NH₃-TPD谱图分析计算方法得到的探针分子脱附活化能作为催化剂的酸位点强度分布的参数，结合线性自由能理论在Br?nsted方程中引入酸强度对反应的影响因子γ作为动力学方程参数关联探针分子脱附活化能与反应活化能，明确固体酸酸强度的基准在催化动力学方程中的物理意义。建立同为MFI拓扑结构 Si /Al摩尔比为12.5、19、25、60、70的ZSM-5分子筛催化剂上不同酸强度位和乙烯齐聚及芳构化中氢转移、齐聚、芳构化各单元步骤以及对应的烷烃、低碳烯烃和芳烃产物分布的定量关系。根据拟合得到动力学参数γ可以发现不同强度的酸位点对乙烯齐聚及芳构化具有不同的作用系数。氨脱附活化能(DAE)为90 kJ·mol^-1的酸位点是氢转移反应的主要活性位点，而对于乙烯齐聚反应中主要的活性酸位点为DAE 90 kJ·mol^-1和124 kJ·mol^-1，DAE为150 kJ·mol^-1的酸位点是芳构化反应的主要活性位点。     

Enhancing cation exchange capacity of chars through ozonation

The use of ozone to increase the cation exchange capacity (CEC) of two chars produced from pyrolysis of Douglas fir (Pseudotsuga menziessii) and a control bituminous coal activated carbon (AC) is reported. Chars were produced from the wood fraction of Douglas fir (DFWC) and the bark (DFBC) at 500 °C using an auger driven reactor with a nitrogen sweep gas under mild vacuum. Five ozone treatment times, ranging from 5 min to 60 min, were investigated. The initial properties of each char were found to differ significantly from the other samples in terms of surface area, proximate composition, and elemental composition. DFWC did not show significant mass loss or temperature variation during ozone treatment; however, after 1 h of oxidation both DFBC and AC samples resulted in 20% and 30% mass loss, respectively, and reactor temperatures in excess of 60 °C. Analysis of the pore size distribution of each treatment shows that ozone treatment did not significantly affect small micropores after 30 min of treatment for any material, but did reduce the apparent surface area of mesopores. Increases in carboxylic groups were identified with ozone treatment and found to correlate strongly with changes in measured CEC. The formation of lactone was found to correlate positively with reactor temperature during oxidation. These results indicate that the properties of chars, including surface area, pore structure, and chemical composition, as well as reactor conditions strongly affect the ozone oxidation of chars.     

孔结构与酸性质对多孔氧化铝材料催化性能的影响研究

选用两种自制氧化铝材料和三种工业氧化铝材料，采用XRD，XRF，BET，FT-IR，NH3-TPD等方法对水热老化前后的氧化铝材料进行详细的结构表征，并使用重油微反评价装置进行裂化性能评价。结果表明，五种氧化铝材料均具有拟薄水铝石结构，平均孔径介于5～16 nm均属于介孔范围，且仅含有L酸中心；制备方法的不同导致氧化铝材料的结晶程度、孔结构参数以及酸性质均有所不同，水热稳定性及裂化活性也存在较大差异；转化能力及产品分布同时与孔结构参数和酸性质（水热老化后）密切相关，在不同的孔径范围内两者的作用程度不同，对于平均孔径约10 nm的氧化铝材料，孔道性质对裂化性能的影响程度更大，平均孔径达13～25 nm时，总酸量对裂化性能的影响相对强于孔道性质的影响。     

FCC废催化剂镁改性催化裂化性能再生研究

提出并证实了高的强酸性位可接近性导致FCC废催化剂失活的机制。基于所提出的失活机制，采用浸渍法对FCC废催化剂进行镁改性再生。对所制备的再生FCC废催化剂进行了表征并考察了其重油催化裂化性能。表征结果表明，与未改性的FCC废催化剂相比，再生FCC废催化剂表面酸强度被一定程度地削弱，而表面总酸量和结构性质参数未出现显著改变。重油催化裂化结果表明，得益于适宜的表面酸性，再生FCC废催化剂的催化裂化反应性能得到极大改善。与未改性的FCC废催化剂相比，再生FCC废催化剂的汽油产率显著增加了3.04个百分点，同时干气、液化气、焦炭和重油产率则分别下降了0.36、0.81、1.28和0.87个百分点，这使得所制备的再生FCC废催化剂可以代替部分新鲜FCC催化剂使用。最后，探讨了再生FCC废催化剂表面酸性改变机理。