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1.
The batch simultaneous saccharification and fermentation (SSF) of microwave/acid/alkali/H 2O 2 pretreated rice straw to ethanol was optimized using cellulase from Trichoderma reesei and Saccharomyces cerevisiae YC-097 cells prior to the fed-batch SSF studies. The batch SSF optima were 10% w/v substrate, 40°C, 15 mg cellulase/g substrate, initial pH 5.3, and 72 hours. Under the optimum conditions the ethanol concentration and its yield were 29.1 g/L and 61.3% respectively. Based on the optimal batch SSF, the fed-batch SSF was investigated and its operation parameters were optimized. Under its optimal conditions the ethanol concentration reached 57.3 g/L, while its productivity and yield were only slightly less than those in the batch SSF. This suggests that fed-batch SSF is a potential operation mode for effective ethanol production from microwave/acid/alkali/H 2O 2 pretreated rice straw. 相似文献
2.
Layered -titanate materials, Na xM x/2Ti 1−x/2O 2 (M=Co, Ni and Fe, x=0.2–0.4), were synthesized by flux reactions, and electrical properties of polycrystalline products were measured at 300–800 °C. After sintering at 1250 °C in Ar, all products show n-type thermoelectric behavior. The values of both d.c. conductivity and Seebeck coefficient of polycrystalline Na 0.4Ni 0.2Ti 0.8O 2 were ca. 7×10 3 S/m and ca. −193 μV/K around 700 °C, respectively. The measured thermal conductivity of layered -titanate materials has lower value than conductive oxide materials. It was ca. 1.5 Wm −1 K −1 at 800 °C. The estimated thermoelectric figure-of-merit, Z, of Na 0.4Ni 0.2Ti 0.8O 2 and Na 0.4Co 0.2Ti 0.8O 2 was about 1.9×10 −4 and 1.2×10 −4 K −1 around 700 °C, respectively. 相似文献
3.
H 2O 2改性稻杆作为Pb 2+吸附剂,具有改性工艺环保、简单、成本低,以及对Pb 2+吸附率高等特点,是一种优良的改性剂。优化改性工艺,制备优良吸附性能的H 2O 2改性稻杆具有较强的实用价值。详细探讨了改性工艺的影响因素如pH值、H 2O 2用量、Fe 2+/H 2O 2物质的量之比、改性温度、改性时间、稻杆颗粒度和稻杆用量等对改性效果的影响,在单因素实验的基础上,通过正交实验和对比实验对改性工艺进行了进一步优化。得出最适宜的改性工艺为:在100 mL的溶液中,不加FeSO 4的情况下,稻杆用量为3 g,改性pH值为8,H 2O 2用量为稻秆用量的30%,稻杆颗粒度为40目,改性温度为20℃,改性时间为4 h。用2 g H 2O 2改性稻秆处理100 mL 200 mg/L的Pb 2+废水时,对Pb 2+的吸附率为94.45%,吸附容量为9.445 mg/g,表明H 2O 2改性稻秆具有优良的吸附性能。 相似文献
4.
The effect of TiO 2 on the grain growth of the ZnO–Bi 2O 3–CoO–MnO ceramic system prepared by chemical coprecipitation, was studied between 1150 and 1300 °C in air. Bi 2O 3 melts during firing, and then TiO 2 dissolves into Bi 2O 3-rich liquid. TiO 2 initially reacts with Bi 2O 3 to form Bi 4Ti 3O 12. Above ≈1050 °C, Bi 4Ti 3O 12 reacts with ZnO to form Zn 2TiO 4 spinel phase. The kinetic study of grain growth carried out using the expression Gn– Gon= Ko· t·exp(− Q/ RT) gave grain exponent ( n) value as 6 and the apparent activation energy ( Q) as 226.46 kJ/mol. 1.00 mol% TiO 2 addition increased the grain growth exponent value from 6 to 7 and apparent activation energy with 1.00 mol% TiO 2 addition was found to be 197.10 kJ/mol. The ZnO grain size gradually increases with increasing TiO 2 content. Addition of TiO 2 may increase the reactivity of the Bi 2O 3-rich liquid towards the ZnO grain, thus affecting the ZnO grain growth. 相似文献
5.
The phase evolution and microstructural development of a series of geopolymer mixtures comprising SiO 2, Al 2O 3, Na 2O and H 2O prepared by alkali reaction of metakaolin, have been studied. The study also included the effects of cure duration and its impact on physical properties such as compressive strength. The characteristic molar ratios of the geopolymer mixtures were of the range SiO 2/Al 2O 3 [2.50–5.01] and Al 2O 3/Na 2O [0.60–1.70], respectively. The formulations were subjected to continuous curing at 40 °C for 7 months, and were analyzed periodically by XRD and SEM techniques. Amorphous Na–Al–Si phase(s), observed at early ages, gradually transformed to crystalline phase(s) with prolonged curing. The initial SiO2, Na2O, and Al2O3 contents of mixtures appeared to be critical factors governing the observed amorphous → crystalline transformation. Well-developed crystalline zeolitic phases, including chabazite, faujasite, zeolite A and zeolite P, were identified in some of the mixtures investigated. In most cases, with prolonged curing, some correlation emerged relating compressive strength development with corresponding phase changes. In essence, the mixture formulations that developed crystalline phases after prolonged curing tended to produce low strengths. The relevance of these findings on the phase development of mild- to warm-temperature prolonged curing of geopolymer systems is discussed. 相似文献
6.
以己内酰胺-八水氧氯化锆低共熔溶剂为添加组分,采用溶胶-凝胶法合成含锆的硅胶,再经过高温煅烧得到 n-ZrO 2/SiO 2 ( n=2%,4%,6%) 负载型催化剂。并用红外光谱(FT-IR)、X射线衍射(XRD)、扫描电镜(SEM)、N 2吸附-脱附、X射线光电子能谱(XPS)对其进行结构表征,确定ZrO 2成功负载到SiO 2上。以ZrO 2/SiO 2为催化剂和吸附剂,H 2O 2为氧化剂组成催化氧化脱硫体系,并应用于模拟油脱硫。分别考察了氧化锆负载量、反应温度、氧硫比、催化剂加入量及不同类型的硫化物对脱硫效果的影响。实验结果表明,在反应温度为70℃、 n(H 2O 2)/ n(S)=4(摩尔比)、4%-ZrO 2/SiO 2的加入量为0.2 g的最佳反应条件下,氧化脱硫体系对二苯并噻吩(DBT)、4,6-二甲基二苯并噻吩(4,6-DMDBT)和苯并噻吩(BT)的脱除率分别为98.7%、93%和65.9%。且4%-ZrO 2/SiO 2回收利用5次后,DBT脱除率仍可达到91.8%。 相似文献
7.
This work investigates performances of supported transition-metal oxide catalysts for the catalytic reduction of SO 2 with C 2H 4 as a reducing agent. Experimental results indicate that the active species, the support, the feed ratio of C 2H 4/SO 2, and pretreatment are all important factors affecting catalyst activity. Fe 2O 3/γ-Al 2O 3 was found to be the most active catalyst among six γ-Al 2O 3-supported metal oxide catalysts tested. With Fe 2O 3 as the active species, of the supports tested, CeO 2 is the most suitable one. Using this Fe 2O 3/CeO 2 catalyst, we found that the optimal Fe content is 10 wt.%, the optimal feed ratio of C 2H 4/SO 2 is 1:1, and the catalyst presulfidized by H 2+H 2S exhibits a higher performance than those pretreated with H 2 or He. Although the feed concentrations of C 2H 4:SO 2 being 3000:3000 ppm provide a higher conversion of SO 2, the sulfur yield decreases drastically at temperatures above 300 °C. With higher feed concentrations, maximum yield appears at higher temperatures. The C 2H 4 temperature-programmed desorption (C 2H 4-TPD) and SO 2-TPD desorption patterns illustrate that Fe 2O 3/CeO 2 can adsorb and desorb C 2H 4 and SO 2 more easily than can Fe 2O 3/γ-Al 2O 3. Moreover, the SO 2-TPD patterns further show that Fe 2O 3/γ-Al 2O 3 is more seriously inhibited by SO 2. These findings may properly explain why Fe 2O 3/CeO 2 has a higher activity for the reduction of SO 2. 相似文献
8.
A lost of culturability of bacteria Escherichia coli K12 was observed after exposition to a solar simulator (UV–vis) in a laboratory batch photoreactor. The bacterial inactivation reactions have been carried out using titanium dioxide (TiO 2) P25 Degussa and FeCl 3 as catalysts. At the starting of the treatment, the suspensions were at their “natural” pH. An increase in the efficiency in the water disinfection was obtained when some advanced oxidation processes such as UV–vis/TiO 2, UV–vis/TiO 2/H 2O 2, UV–vis/Fe 3+/H 2O 2, UV–vis/H 2O 2 were applied. The presence of H 2O 2 accelerates the rate of disinfection via TiO 2. The addition of Fe 3+ (0.3 mg/l) to photocatalytic system decreases the time required for total disinfection (<1 CFU/ml), for TiO 2 concentrations ranging between 0.05 and 0.5 g/l. At TiO 2 concentrations higher than 0.5 g/l the addition of Fe 3+ does not significantly increase the disinfection rate. The systems: Fenton (H 2O 2/Fe 3+/dark), H 2O 2/dark, H 2O 2/TiO 2/dark showed low disinfection rate. The effective disinfection time (EDT 24) was reached after 60 and 30 min of illumination for the Fe 3+ and TiO 2 photoassisted systems, respectively. EDT 24 was not reached for the system in the absence of catalyst (UV–vis). The effect on the bacterial inactivation of different mixture of chemical substance added to natural water was studied. 相似文献
9.
采用分步浸渍法制备了碱/碱土金属修饰Ni基催化剂Ni-M/Al 2O 3 (M=K 2CO 3, Na 2CO 3, MgO, CaO)。探究了碱/碱土金属的添加对改性Ni基催化剂CO 2吸附和甲烷化性能的影响。研究发现,碱/碱土金属的添加提高了Ni/Al 2O 3催化剂表面的碱性活性位点密度,强化了其CO 2吸附性能。碱/碱土金属类型影响Ni-M/Al 2O 3催化剂碱性活性位点的分布、NiO物相的转化及Ni的分散度,进而影响其甲烷化性能。MgO添加使NiO物相转化为与载体呈强相互作用的β型和γ型NiO,降低了催化剂表面的强碱性活性位点比例,有利于CO 2吸附活化。Ni-MgO/Al 2O 3的CO 2吸附容量最高为0.68mmolCO 2/g,其CO 2转化率和CH 4选择性分别高达58.4%和95.4%,其在烟气CO 2捕集与原位甲烷化中极具应用前景。 相似文献
10.
Two series of catalysts, V 2O 5/TiO 2 and modified V 2O 5/TiO 2, were prepared with a conventional impregnation method. They were tested in the selective oxidation of toluene to benzoic acid under microwave irradiation. The reaction conditions were optimized over V 2O 5/TiO 2. It was found that in the microwave catalytic process the optimum reactor bed temperature of the titled reaction decreases to 500 K (600 K in the conventional process). The modification of V 2O 5/TiO 2 with MoO 3, WO 3, Nb 2O 5 or Ta 2O 5, which has no negative influence on the reaction in the conventional catalytic process, can greatly promote the catalytic activities in the microwave process, leading to a high yield of benzoic acid (41%). The effects of microwave electromagnetic field on the catalysts are discussed. 相似文献
11.
以碱共沉淀法制备Mg-Al水滑石,然后采用浸渍法负载活性组分Pt,经焙烧、氢气还原得到Pt/Al_2O_3与Pt/Mg O-Al_2O_3催化剂,采用XRD、N2吸附-脱附、FT-IR、H2-TPR和Py-IR等分析Mg O的加入对Pt/Al_2O_3催化剂结构性能的影响,并在甲基环己烷连续脱氢反应中对比两种催化剂活性。结果表明,Pt/Mg O-Al_2O_3催化剂比表面积小于Pt/Al_2O_3催化剂,且表面基本无酸性活性中心,但表现出与Pt/Al_2O_3催化剂相同的脱氢活性。在Pt负载质量分数2%、催化剂用量0.5 g、甲基环己烷0.1 m L·min-1纯样进料和325℃反应10 h后,原料平均转化率79.9%,脱氢产物只有甲苯,对应的产氢速率192.8 mmol·(g-metal·min)-1,表现出优良的脱氢活性。 相似文献
12.
The effects of pretreatment of catalyst on its surface properties and the HDS activity of a 0.49% Ru/Al 2O 3 catalyst were studied in a single-pass, differential microreactor. The surface properties of the catalyst were measured by NH 3-TPD and XPS analysis. The Ru/Al 2O 3 catalyst was pretreated in three ways: reduced in H 2 (Ru-R catalyst), oxidized in air and subsequently reduced in H 2 (Ru-OR catalyst), or sulfided in H 2S/H 2 (Ru-S catalyst). Three types of peaks (low, middle, and high temperatures) were observed in the NH 3-TPD study. The predominant high-temperature peak was observed for both the Ru-OR and Ru-S catalyst, pretreated at 300°C. Mass spectrometry showed that the high-temperature peak in NH 3-TPD consisted of N 2 and H 2 formed from the decomposition of NH 3 on the ruthenium sites. NO adsorption of unsaturated Ru species was related to the low-temperature peak in the NH 3-TPD. The XPS analysis showed that the peaks at 279.9 eV, 280.6 eV, and 282.5 eV were ascribed to metallic ruthenium, RuO 2, and RuO 3, respectively. The low-, middle-, and high-temperature peaks were assigned to RuO 2, acid sites on alumina, and metallic Ru, respectively. Metallic ruthenium was effective in the HDS of thiophene and the decomposition of NH 3. 相似文献
13.
The inhibition effect of H 2O on V 2O 5/AC catalyst for NO reduction with NH 3 is studied at temperatures up to 250 °C through TPD, elemental analyses, temperature-programmed surface reaction (TPSR) and FT-IR analyses. The results show that H 2O does not reduce NO and NH 3 adsorption on V 2O 5/AC catalyst surface, but promotes NH 3 adsorption due to increases in Brønsted acid sites. Many kinds of NH 3 forms present on the catalyst surface, but only NH 4+ on Brønsted acid sites and a small portion of NH 3 on Lewis acid sites are reactive with NO at 250 °C or below, and most of the NH 3 on Lewis acid sites does not react with NO, regardless the presence of H 2O in the feed gas. H 2O inhibits the SCR reaction between the NH 3 on the Lewis acid sites and NO, and the inhibition effect increases with increasing H 2O content. The inhibition effect is reversible and H 2O does not poison the V 2O 5/AC catalyst. 相似文献
14.
Ta 3N 5 was synthesized by nitridation of Ta 2O 5 under NH 3 flow at 700 °C. The catalyst was pure Ta 3N 5 according to X-ray diffraction (XRD), and was about 5 nm in size with a BET specific surface area 52.8 m 2/g. When Ta 3N 5 was added to Fe 3+/H 2O 2 solution (known as Fenton-like system), most Fe 3+ were adsorbed on the Ta 3N 5 surface and could not react with H 2O 2 in the dark, which is different from the general Fenton reaction. Under visible light irradiation, adsorbed Fe 3+ ions were reduced to Fe 2+ rapidly and Fe 2+ were reoxidized by H 2O 2 on the Ta 3N 5 surface, thus a fast Fe 3+/Fe 2+ cycling was established. Kinetics and ESR measurements supported this mechanism. The Ta 3N 5/Fe 3+/H 2O 2 system could efficiently decompose H 2O 2 to generate hydroxyl radicals driven by visible light, which could accelerate significantly the degradation of organic molecules such as N, N-dimethylaniline (DMA), and 2,4-dichlorophenol (DCP). A mechanism was proposed for iron cycling on the basis of experimental results. 相似文献
15.
This article discusses a mechanism for preparing perovskite powders, 0.75Pb(Ni 1/3Nb 2/3)O 3-0.25PbTiO 3 (PNN-PT), using a semichemical method (SCM).Precursors were prepared by adding aqueous Ni(Ac) 2 solutions to an alcohol slurry of PbO, Nb 2O 5, and TiO 2. The TG-DTG and DSC analysis of the precursors and XRD analysis of the powders at different thermal treatment temperatures showed that the reaction mechanisms in this method differ from those in the conventional mixed-oxide method. The aqueous Ni(Ac) 2 solution reacted with PbO to form Pb(Ac) 2 · Pb(OH) 2 · H 2O and Ni(OH) 2, which decomposed to form nascent PbO and NiO, thereby improving the reactivity and distribution of PbO and NiO. Pb 3Nb 2O 8 and NiNb 2O 6 formed and were easily converted into the perovskite phase during the thermal treatment process. At a thermal treatment temperature of 850°C, the content of the perovskite phase reached 98%. Pyrochlore-free PNN-PT ceramic was obtained after 2 h of sintering at 1100°C, and its dielectric properties were found to be excellent at temperatures ranging between -55 and 120°C. 相似文献
16.
Fe3O4 magnetic nanoparticles (MNPs) were synthesised, characterised, and used as a peroxidase mimetic to ac-celerate levofloxacin sono-degradation in an ultrasound (US)/H2O2 system. The Fe3O4 MNPs were in nanometre scale with an average diameter of approximately 12 to 18 nm. The introduction of Fe3O4 MNPs increased levofloxacin sono-degradation in the US/H2O2 system. Experimental parameters, such as Fe3O4 MNP dose, initial solution pH, and H2O2 concentration, were investigated by a one-factor-at-a-time approach. The results showed that Fe3O4 MNPs enhanced levofloxacin removal in the pH range from 4.0 to 9.0. Levofloxacin removal ratio in-creased with Fe3O4 MNP dose up to 1.0 g·L?1 and with H2O2 concentration until reaching the maximum. More-over, three main intermediate compounds were identified by HPLC with electrospray ionisation tandem mass spectrometry, and a possible degradation pathway was proposed. This study suggests that combination of H2O2, Fe3O4 MNPs and US is a good way to improve the degradation efficiency of antibiotics. 相似文献
17.
Silica hollow microspheres containing phosphorous have been prepared by a sol-gel/emulsion method which uses tetraethoxysilane (TEOS) as the precursor for the SiO 2 and phosphoric acid (H 3PO 4) as the precursor for P 2O 5. The hollow structure forms an emulsion system which is composed of an oil phase (kerosene, sorbitan monooleate (Span 80)) and an aqueous phase (a viscous sol solution of ethanol, TEOS and H 3PO 4). Some of the phosphorous remains in the final silica shell structure even after calcination at 650°C. The hollow structure of the P 2O 5-SiO 2 (silicophosphate) was characterized by X-ray diffraction (XRD), polarized optical microscopy (POM), scanning electron microscopy (SEM), nitrogen adsorption measurement and Fourier transform infrared spectroscopy (FTIR). 相似文献
18.
Combined effect of H 2O and SO 2 on V 2O 5/AC the activity of catalyst for selective catalytic reduction (SCR) of NO with NH 3 at lower temperatures was studied. In the absence of SO 2, H 2O inhibits the catalytic activity, which may be attributed to competitive adsorption of H 2O and reactants (NO and/or NH 3). Although SO 2 promotes the SCR activity of the V 2O 5/AC catalyst in the absence of H 2O, it speeds the deactivation of the catalyst in the presence of H 2O. The dual effect of SO 2 is attributed to the SO 42− formed on the catalyst surface, which stays as ammonium-sulfate salts on the catalyst surface. In the absence of H 2O, a small amount of ammonium-sulfate salts deposits on the surface of the catalyst, which promote the SCR activity; in the presence of H 2O, however, the deposition rate of ammonium-sulfate salts is much greater, which results in blocking of the catalyst pores and deactivates the catalyst. Decreasing V 2O 5 loading decreases the deactivation rate of the catalyst. The catalyst can be used stably at a space velocity of 9000 h −1 and temperature of 250 °C. 相似文献
19.
采用浸渍法制备了一系列具有不同CuO含量的Pd-CuO/Al 2O 3催化剂,并将其用于乙醇氧化反应,其结构与性质通过XRD、H 2-TPR和NH 3-TPD等手段进行分析。结果发现,催化剂的活性并不是随着CuO含量的增加而增强,Pd-1.0%CuO/Al 2O 3催化剂表现出最佳的活性,其点火温度和完全转化温度比Pd/Al 2O 3催化剂至少降低了50℃。与Pd/Al 2O 3催化剂相比,含CuO催化剂增强的衍射峰强度以及氢化钯分解峰的消失,说明Pd-Cu合金结构的形成有利于Pd、Cu物种之间的协同作用。对于Pd-1.0%CuO/Al 2O 3催化剂来说,还原峰向低温的移动以及还原峰面积的增大说明该催化剂上氧化性物质更易被还原且数量在增加,这对于氧化反应是十分有利的,新出现的还原峰表示Pd、Cu的相互作用生成了新物种。NH 3-TPD结果中更高含量的低温酸有利于高活性,而且新出现的脱附峰说明形成了新的酸性位点。 相似文献
20.
Two process concepts have been developed for a microbial contribution to the problem of flue gas desulfurization and NO x removal. We have demonstrated that the sulfate-reducing bacterium Desulfovibrio desulfuricans can be grown in a mixed culture with fermentative heterotrophs in a medium in which glucose served as the only carbon source. Beneficial cross-feeding resulted in vigorous growth of D. desulfuricans, which used SO 2(g) as a terminal electron acceptor, with complete reduction of SO 2 to H 2S in 1–2 s of contact time. We have proposed that the concentrated SO 2 stream, obtained from regeneration of the sorbent in regenerable processes for flue gas desulfurization, could be split with two-thirds of the SO 2 reduced to H 2S by contact with a culture of sulfate-reducing bacteria. The resulting H 2S could then be combined with the remaining SO 2 and used as feed to a Claus reactor to produce elemental sulfur. However, the use of glucose as an electron donor in microbial SO 2 reducing cultures would be prohibitively expensive. Therefore, if microbial reduction of SO 2 is to be economically viable, less expensive electron donors must be found. Consequently, we have evaluated the use of municipal sewage sludge and elemental hydrogen as carbon and/or energy sources for SO 2 reducing cultures. Heat and alkali pretreated sewage sludge has been successfully used as a carbon and energy source to support SO 2 reduction in a continuous, anaerobic mixed culture containing D. desulfuricans. The culture operated for nine months with complete reduction of SO 2 and H 2S. Another sulfate-reducing bacterium, Desulfotomaculum orientis, has also been grown in batch cultures on a feed of SO 2, H 2 and CO 2. Complete reduction of SO 2 to H 2S was observed with gas-liquid contact times of 1–2 s. We have also demonstrated that the facultative anaerobe and chemoautotroph, Thiobacillus denitrificans, can be cultured anoxically in batch reactors using NO(g) as a terminal electron acceptor with reduction to elemental nitrogen. We have proposed that the concentrated stream of NO x, as obtained from certain regenerable processes for flue gas desulfurization and NO x removal, could be converted to elemental nitrogen for disposal by contact with a culture T. denitrificans. Two heterotrophic bacteria have also been identified which may be grown in batch cultures with succinate or heat and alkali pretreated sewage sludge as carbon and energy sources and NO as a terminal electron acceptor. These are Paracoccus denitrificans and Pseudomonas denitrificans. 相似文献
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