Hβ/MCM-41复合分子筛催化剂上苯甲醚与乙酸酐酰化反应研究

以β沸石为硅源,制备了不同硅铝比的Hβ/MCM-41复合分子筛,考察了该复合分子筛对苯甲醚与乙酸酐酰化反应的催化效果,并与介孔MCM-41、微孔Hβ分子筛的催化效果进行了比较,研究了分子筛硅铝比、酸性及孔道结构对酰化反应催化性能的影响。结果表明,对于苯甲醚和乙酸酐酰化反应,Hβ/MCM-41复合分子筛具有较好的催化稳定性,反应过程中的积炭量较少,积炭的碳氢比较低。该复合分子筛不仅具有微孔沸石的强酸性,而且具有较大孔径的介孔,产物分子能及时从孔道中扩散出来,催化活性位不易中毒失活。     

非贵金属催化剂在羟甲基糠醛电氧化增值中的应用

羟甲基糠醛是呋喃类化合物,具有价格低廉及来源广泛的优点,可作为平台化合物用于制备其它高附加值产品.传统的热催化氧化增值方法需要高温、高压及贵金属催化剂,造成经济效益的下降.而电氧化方法不需要高温、高压条件;同时,通过对电催化剂的合理设计,非贵金属催化剂表面的羟甲基糠醛选择性转化已经得以实现,从而避免使用大量贵金属.因此,通过电氧化方法对羟甲基糠醛平台化合物进行高附加值转化受到了广泛关注.在羟甲基糠醛氧化的多种产物中,羟基和醛基被全部氧化为羧基的产物——2,5-呋喃二甲酸,被美国能源部列为“最具有价值的12种生物质衍生化学品”之一.鉴于此,本文介绍了羟甲基糠醛电氧化增值生产2,5-呋喃二甲酸的重要研究价值及相关非贵金属电催化剂的最新进展,并对催化羟甲基糠醛电氧化反应的非贵金属催化剂的发展前景进行了展望.     

利用空间位阻和氢溢流协同作用促进5-羟甲基糠醛选择性加氢制备5-甲基糠醛

化学工业生产中，用氢气为还原剂，通过选择性加氢可以制备多种重要化学品。5-羟甲基糠醛是重要的生物质基平台化合物，而5-甲基糠醛是用途广泛的化学品。由5-羟甲基糠醛加氢得到5-甲基糠醛是一条非常理想的路径，但是选择性活化C-OH非常困难。本文设计并制备了Pt@PVP/Nb₂O₅(PVP: 聚乙烯吡咯烷酮)催化剂，该催化体系巧妙地结合了位阻效应、氢溢流和催化剂界面的电子效应，系统研究了该催化剂对5-羟甲基糠醛选择性加氢制备5-甲基糠醛催化性能，在最优条件下，5-甲基糠醛的选择性可达92%。利用密度泛函理论计算研究了5-羟甲基糠醛选择性加氢制备5-甲基糠醛反应路径。     

超高效液相色谱法同时测定烟用香精料液中的糠醛、5-羟甲基糠醛与5-甲基糠醛

建立了同时测定烟用香精料液中糠醛、5-羟甲基糠醛和5-甲基糠醛的超高效液相色谱(UPLC)方法。样品经流动相稀释、振荡、过滤后,采用C18(2.1 mm i.d.×100 mm,1.7μm)柱,以乙腈-水(10∶90)为流动相,在流速0.3 m L/min条件下等度洗脱分离,以二极管阵列检测器在波长280 nm下检测,外标法定量。该方法5 min内即可实现3种目标物的分离,5-羟甲基糠醛、糠醛和5-甲基糠醛的线性范围分别为0.004 2~40.00 mg/kg,0.004 6~30.00 mg/kg,0.006 9~30.00 mg/kg;相关系数(r2)分别为0.999 2,0.999 9和0.999 8;检出限(S/N=3)分别为1.24,1.37,2.06μg/kg;相对标准偏差(RSD,n=11)为0.1%~0.4%;加标水平为0.005 0~10.18 mg/kg时,3种化合物的回收率为91.7%~106.0%。该方法操作简便、分析快速、结果准确,适用于烟用香精料液中5-羟甲基糠醛、糠醛和5-甲基糠醛的检测。     

固体离子交换法将钒引入高硅分子筛

通过固体离子交换方法将V引入高硅分子筛HM(氢型丝光沸石)和HZSM-5中。XRD、LRS和BIE表明V_2O_5晶相在HM和HZSM-5表面上消失, 并以VO离子形式进入分子筛。吡啶吸附-IR表明VO离子主要与HM、HZSM-5分子筛中的质子发生交换。ESR的两个信号表明进入分子筛的孤立VO离子具有两种不同的配位结构: 压缩的八面体六配位和平面四方锥五配位。     

双功能[Sn,Al]-Beta分子筛一步催化葡萄糖生成5-羟甲基糠醛

以部分脱铝的Beta分子筛为母体,采用同晶置换法将Sn植入骨架制备双功能[Sn,Al]-Beta分子筛,并应用于葡萄糖一步催化生成5-羟甲基糠醛(5-HMF)反应中.样品中Sn与Al的含量通过酸洗的浓度和酸洗的时间以及SnCl4处理的时间来控制.由于骨架中有与Al相关为B酸位,和Sn相关的L酸位,[Sn,Al]-Beta可作为一种双功能的固体酸催化剂.优化了[Sn,Al]-Beta催化葡萄糖一步催化生成5-HMF的反应参数,在最优Sn/Al比条件下,葡萄糖转化率为60.0%,5-HMF选择性为62.1%.     

HZSM-5沸石中Lewis酸与Brönsted酸协同作用下的甲基环己烷开环反应

由于水蒸气处理HZSM-5生成的骨架外铝在分子筛中体现Lewis酸性, 分子筛中骨架外铝物种的可移动性导致Lewis酸与分子筛本身的Brönsted酸在空间上具有临近性. 当甲基环己烷分子在HZSM-5的笼中转化时, Lewis酸与Brönsted酸的协同作用加快了甲基环己烷分子的转化速率, 且骨架外铝物种浓度越高, 这种协同效应越明显. 而产物的选择性只与催化剂的孔道结构有关, 与水蒸气处理所导致的酸性质的变化无关.     

离子液体中树脂催化转化果糖为5-羟甲基糠醛

开发了以离子液体1-丁基-3-甲基咪唑氯盐([BMIM]Cl)为溶剂, 固体酸离子交换树脂NKC-9为催化剂转化果糖为5-羟甲基糠醛的绿色工艺. 在此催化体系中, 100 ℃下反应10 min时5-HMF的产率达到78.0%, 其反应时间远远小于已有文献报道的长达数小时的反应时间. 在此催化体系中, 果糖起始浓度的增加对5-HMF产率影响不大, 因而此工艺同样适用于处理高浓度的果糖溶液. 离子液体[BMIM]Cl和树脂组成的催化体系可以循环使用, 经过9次重复使用后仍能保持稳定的催化活性.     

高效液相色谱法测定牛膝颗粒中5-羟甲基糠醛和蜕皮甾酮的含量

提出了高效液相色谱法同时测定牛膝配方颗粒中5-羟甲基糠醛和蜕皮甾酮的含量的方法。采用SHIMADZU shim-pack VP-ODS(4.6mm×250mm,4.6μm)柱;用两种不同配比的乙腈和水混合溶液作为流动相,梯度洗脱;检测波长为279nm(5-羟甲基糠醛)和245nm(蜕皮甾酮)。5-羟甲基糠醛和蜕皮甾酮的质量浓度分别在0.390～100mg.L-1和3.125～100mg.L-1范围内与峰面积呈线性关系,方法的检出限(3S/N)分别为1.95,2.01ng。5-羟甲基糠醛和蜕皮甾酮的平均回收率分别为99.7%,99.1%;相对标准偏差(n=5)分别为0.80%,0.67%。     

Ru/C催化5-羟甲基糠醛选择氧化高效合成2,5-呋喃二甲醛

在活性炭负载金属钌(Ru/C)催化剂上实现了5-羟甲基糠醛的高效选择氧化.以甲苯为反应溶剂,在383 K和2.0 MPa O₂的反应条件下,2,5-呋喃二甲醛(DFF)收率高达95.8%.与活性炭负载的具有相似粒径的Pt,Rh,Pd,Au等其它贵金属催化剂相比,Ru/C具有更加优良的活性和DFF选择性.同时Ru/C催化剂结构稳定,具有良好的重复使用性能.在相似的反应条件下,采用水代替甲苯作为溶剂,同时添加少量水滑石固体碱,可便捷地将主要产物从DFF调变为5-甲酰基-2-呋喃甲酸或2,5-呋喃二甲酸,显示出Ru/C催化剂在控制5-羟甲基糠醛选择氧化反应产物方面的优异性能.     

Acylation of Anisole Catalyzed by Hierarchical Porous Hβ Zeolite Modified with Cr

Modified hierarchical porous Hβ zeolite was obtained by metal modification of Hβ zeolite, which was treated with alkaline solution, and the catalysts before and after modification were characterized by means of X-ray diffraction(XRD), nitrogen adsorption-desorption, scanning electron microscopy(SEM), X-ray fluorescence(XRF), NH₃ temperature-programmed desorption and Fourier-transform infrared spectroscopy(FTIR). The activities of acylation of anisole with acetic anhydride were also investigated. The results show that the Hβ zeolite, which was treated with alkaline solution has microporous and mesoporous structures that could improve the diffusion performance of chemical reaction. The amount of acid was modulated with metal modification. The Hβ zeolite modified by 5%(mass fraction) metal chromium had the best catalytic performance. The conversion of acetic anhydride acylation was 93.01% under the optimal conditions, which was higher than that of other catalysts. The catalyst not only showed good activity, but also exhibited a stable performance in regeneration tests.     

Conversion of carbohydrates into 5-hydroxymethylfurfural catalyzed by ZnCl2 in water

The incompletely coordinated zinc ions in the concentrated aqueous ZnCl(2) solution catalyze the direct conversion of carbohydrates into 5-hydroxymethylfurfural, and a moderate HMF yield up to 50% can be achieved.     

NaOH后处理对多级孔Hβ分子筛上木质素催化热解性能的影响

采用碱性条件下"后处理"脱硅的方法,制备了一系列多级孔Hβ分子筛,考察了Na OH浓度对Hβ分子筛上木质素催化热解性能的影响。结果表明,当Na OH浓度小于0.2 mol/L时,碱处理后的多级孔Hβ分子筛的介孔数量增加,木质素热解液体产物的收率随着Na OH浓度提高而显著增加。当Na OH浓度小于0.5 mol/L时,碱处理可以保持多级孔Hβ分子筛的微孔结构基本不被破坏,木质素催化热解具有较好的脱氧效果;产物以芳烃为主,含氧化合物的收率始终小于3%。当Na OH的浓度增加到1 mol/L时,会造成Hβ分子筛过度脱硅,骨架坍塌;由于Hβ分子筛的多级孔结构被破坏,此时不仅木质素热解液体产物的收率降低,而且脱氧效果变差。     

甜高粱茎秆生产燃料乙醇

本文对甜高粱茎秆原料的贮藏、汁液液态发酵、茎秆直接粉碎固态发酵以及榨汁后剩余的秆渣预处理同步糖化发酵4个方面的研究情况进行了综述,重点论述了甜高粱茎秆生产燃料乙醇的瓶颈问题即原料的贮藏和秆渣木质纤维素预处理技术。提出了一种更经济合理的甜高粱茎秆生产燃料乙醇工艺流程。     

Factors to decrease the cellulose conversion of enzymatic hydrolysis of lignocellulose at high solid concentrations

The enzymatic hydrolysis of lignocelluloses is a key step in the production of ethanol. Economic considerations for large-scale implementation of the process require operation at high solid concentrations. However, the decrease in cellulose conversion offsets the advantages of working at high solid concentrations. The conversion showed a linear decrease in the reaction of pretreated corn stover (PCS) from 2 to 20 % (w/w) and filter paper from 1 to 10 % (w/w) initial total solid content. Hydrolysis experiments with PCS at various mixing speeds showed that the mass transfer limitation could not restrict the cellulose conversion except the solid concentrations over 5 % DM(w/w). The lignin, if added separately, does not correspond directly to the decrease. At increased concentrations, furfural and 5-hydroxymethylfurfural played a part in the effect, and 5-hydroxymethylfurfural only affected exoglucanase. Product inhibition caused by glucose accumulation at increased solid concentrations was found to be a significant and perhaps principal factor. The decrease in yield was caused by the synergetic inhibition, which was more serious with increased solid concentrations.     

碱催化促进Ni-W/β分子筛催化剂氢解纤维素产1,2-丙二醇的研究

为提高纤维素催化氢解产醇类产物中1,2-丙二醇(1,2-PG)的收率,采用等体积浸渍法制备了以β分子筛为载体负载Ni和W的催化剂。结果表明,当7Ni-20W/β分子筛作为催化剂时,在240℃反应温度和6.0 MPa H_2的条件下反应30 min后,纤维素实现完全转化,1,2-PG和乙二醇(EG)产率分别达到19.3%和45.3%;不同于其他载体催化剂,β分子筛可以明显提高1,2-PG选择性。当不同碱催化剂加入到Ni-W/β分子筛催化剂反应体系后,可以进一步提高1,2-PG的选择性。尤其是当加入Ba(OH)_2后,1,2-丙二醇产率从19.3%提高了32.5%。为了探究碱催化剂在反应中的作用,以葡萄糖为底物进行了一系列的碱催化反应。结果表明,碱催化剂主要作用是有助于将葡萄糖异构化为果糖,从而促进纤维素转化为1,2-PG。催化剂在两次回收重复利用之后1,2-PG的收率只下降3.9%,乙二醇产率收率下降4.1%。     

Sweet Sorghum as Feedstock for Ethanol Production: Enzymatic Hydrolysis of Steam-Pretreated Bagasse

Sweet sorghum is an attractive feedstock for ethanol production. The juice extracted from the fresh stem is composed of sucrose, glucose, and fructose and can therefore be readily fermented to alcohol. The solid fraction left behind, the so-called bagasse, is a lignocellulosic residue which can also be processed to ethanol. The objective of our work was to test sweet sorghum, the whole crop, as a potential raw material of ethanol production, i.e., both the extracted sugar juice and the residual bagasse were tested. The juice was investigated at different harvesting dates for sugar content. Fermentability of juices extracted from the stem with and without leaves was compared. Sweet sorghum bagasse was steam-pretreated using various pretreatment conditions (temperatures and residence times). Efficiency of pretreatments was characterized by the degree of cellulose hydrolysis of the whole pretreated slurry and the separated fiber fraction. Two settings of the studied conditions (190 °C, 10 min and 200 °C, 5 min) were found to be efficient to reach conversion of 85–90%.     

Characterization and Activity of Cr, Cu and Ga Modified ZSM—5 for Direct Conversion of Methane to Liquid Hydrocarbons

Direct conversion of methane using a metal-loaded ZSM-5 zeolite prepared via acidic ion exchange was investigated to elucidate the roles of metal and acidity in the formation of liquid hydrocarbons. ZSM-5 (SiO2/A12O3=30) was loaded with different metals (Cr, Cu and Ga) according to the acidic ion-exchange method to produce metal-loaded ZSM-5 zeolite catalysts. XRD, NMR, FT-IR and N2 adsorption analyses indicated that Cr and Ga species managed to occupy the alllmlnum positions in the ZSM-5 framework. In addition, Cr species were deposited in the pores of the structure. However, Cu oxides were deposited on the surface and in the mesopores of the ZSM-5 zeolite. An acidity study using TPD-NH3, FT-IR, and IR-pyridine analyses revealed that the total number of acid sites and the strengths of the BrSusted and Lewis acid sites were significantly different after the acidic ion exchange treatment.Cu loaded HZSM-5 is a potential catalyst for direct conversion of methane to liquid hydrocarbons. The successful production of gasoline via the direct conversion of methane depends on the amount of aluminum in the zeolite framework and the strength of the BrSnsted acid sites.     

Oxidation of cyclohexane catalyzed by metal-ion-exchanged zeolites

The ion-exchange rates and capacities of the zeolite NaY for the Cu(II), Co(II), and Pb(II) metal ions were investigated. Ion-exchange equilibria were achieved in approximately 72 h for all the metal ions. The maximum ion exchange of metal ions into the zeolite was found to be 120 mg Pb(II), 110 mg Cu(II), and 100 mg Co(II) per gram of zeolite NaY. It is observed that the exchange capacity of a zeolite varies with the exchanged metal ion and the amount of metal ions exchanged into zeolite decreases in the sequence Pb(II) > Cu(II) > Co(II). Application of the metal-ion-exchanged zeolites in oxidation of cyclohexane in liquid phase with visible light was examined and it is observed that the order of reactivity of the zeolites for the conversion of cyclohexane to cyclohexanone and cyclohexanol is CuY > CoY > PbY. It is found that conversion increases by increase of the empty active sites of a zeolite and the formation of cyclohexanol is favored initially, but the cyclohexanol is subsequently converted to cyclohexanone.     

Dealuminated ZSM-5 Zeolite Catalyst for Ethylene Oligomerization to Liquid Fuels

Ethylene oligomerization using ZSM-5 zeolite was investigated to study the role of Bronsted acid sites in the formation of higher hydrocarbons. The oligomerization of olefins, dependent on the acidity of ZSM-5 zeolite, is an important step in the conversion of natural gas to liquid fuels. The framework Si/Al ratio reflects the number of potential acid sites and the acid strength of the ZSM-5 catalyst. ZSM-5 with the mole ratio SiO2/Al2O3 equal to 30 was dealuminated for different periods of time according to the acidic ion-exchange method to produce ZSM-5 with various Si/Al ratios. The FT-IR analysis revealed that the integrated framework aluminum band, non-framework aluminum band, and silanol groups areas of the ZSM-5 zeolites decreased after being dealuminated. The performance of the dealuminated zeolite was tested for ethylene oligomerization. The results demonstrated that the dealumination of ZSM-5 led to higher ethylene conversion, but the gasoline selectivity was reduced compared to the performance