117,072 research outputs found
KOH-Induced Oxygen-Deficient VO<sub>2</sub> for High-Rate Aqueous Zn-Ion Batteries
No full textDue
to its high safety and low cost,
aqueous Zn-ion batteries (AZIBs) have become one of the most promising
energy storage devices. However, the development of a stable cathode
with fast kinetics and high-energy density is crucial to realize AZIBs
for large-scale application. In this work, KOH-induced oxygen-deficient
VO2 (K-VO2) was developed by activating doughnutlike
VO2 by KOH. Benefiting from the combination of a unique
morphology with abundant active sites and the oxygen vacancy, increasing
the interlayer spacing, both improved kinetics and enhanced Zn-ion
storage capability in the VO2 cathode are achieved. The
optimized K-VO2-3:4 delivers a specific capacity of 260.9
mA h g–1 at 0.2 A g–1, an excellent
high-rate capability of 166.1 mA h g–1 at 5 A g–1, and long-term cyclic stability with a capacity retention
of 88.1% after 3000 cycles. The electrochemical performance of K-VO2-3:4 has been greatly improved compared with untreated VO2. The KOH activation strategy proposed here also presents
an encouraging pathway for developing other high-energy and stable
cathodes
Ionization energy of KOH and the dissociation energies of KOH and KOH+
No full textHigh level ab initio, up to RCCSD(T), and B3LYP calculations were employed to calculate thermochemical properties for KOH and KOH+. Basis sets were of both all-electron and effective core potential (ECP) types: in both cases large, flexible valence basis sets were used, and the largest basis sets were of quintuple-zeta quality. Both KOH and KOH+ were found to be linear; in the latter case, the Renner-Teller effect is discussed. The results are close to convergence with regard to both basis sets and levels of theory. The most reliable quantities are: first AIE(KOH)=7.38+/-0.02 eV; D-0(K...OH)=82+/-1 kcal mol(-1); D-0(K+...OH)=11.4+/-1 kcal mol(-1); DeltaH(f)(KOH, 298 K) = -53+/-1 kcal mol(-1); and DeltaH(f)(KOH+, 298 K)=119+/-1 kcal mol(-1)
การศึกษาเปรียบเทียบระหว่างตัวเร่งปฏิกิริยา KOH/Al2O3 และ KOH/NaY สำหรับการผลิตไบโอดีเซลโดยปฏิกิริยาทรานเอสเทอร์ริฟิเคชันจากน้ำมันปาล์ม
No full textThesis (M.S.) -- Chulalongkorn University, 2007Typically, biodiesel, a possible substitute for diesel fuel, is produced from the transesterification of vegetable oil or animal fat with methanol in the presence of a homogeneous base catalyst. In the conventional homogeneous catalysts, however, undesired side reactions occur and a separation step to remove the catalysts is required. Therefore, heterogeneous catalysts have been receiving the most attention for replacing homogeneous catalysts. This research is focused on the production of biodiesel from palm oil by using heterogeneous catalysts. Two types of catalysts, KOH/Al2O3 and KOH/NaY, were applied to determine the optimum condition for biodiesel production. Several parameters which may influence the quality of the produced biodiesel were investigated, including the reaction time, %wt. KOH loading, molar ratio of oil to methanol, amount of catlyst, reaction temperature and stirrer speed. The best result was obtained with Al2O3 loaded with 25% wt. KOH at 60C, with a 1:15 molar ratio of palm oil to methanol, a reaction time of 2 hours, and a catalyst amount of 3 g. The biodiesel yield was 91.07%, while NaY gave the same yield with 10% wt. KOH at 60C, with a 1:15 molar ratio of palm oil to methanol, a reaction time of 3 hours and a catlyst amount of 6 g.ไบโอดีเซลเป็นเชื้อเพลิงทดแทนชนิดใหม่ที่มีความเป็นไปได้ที่จะเข้ามาแทนที่น้ำมันดีเซลที่ใช้กันอยู่ในปัจจุบัน โดยทั่วไปไบโอดีเซลสามารถผลิตได้จากปฏิกิริยาทรานเอสเทอร์ริฟิเคชันจากน้ำมันพืชหรือไขมันสัตว์กับเมทิลแอลกอฮอล์ในสภาวะที่มีตัวเร่งปฏิกิริยาชนิดเบสแบบเอกพันธุ์ อย่างไรก็ตามในการใช้ตัวเร่งปฏิกิริยาชนิดเบสแบบเอกพันธุ์นั้นมีข้อเสียหลายประการ เช่นเกิดปฏิกิริยาข้างเคียงที่มีผลทำให้ลดปริมาณของไบโอดีเซล และจำเป็นต้องมีการกำจัดตัวเร่งปฏิกิริยาออกจากไบโอดีเซล ซึ่งการกำจัดตัวเร่งปฏิกิริยาแบบเอกพันธุ์นั้นกระทำได้ยากและก่อให้เกิดปัญหากับสิ่งแวดล้อมทางด้านน้ำเสียอีก ดังนั้นการใช้ตัวเร่งปฏิกิริยาแบบวิวิธพันธุ์มาแทนที่การใช้ตัวเร่งปฏิกิริยาแบบเอกพันธุ์ จึงได้รับความสนใจเป็นอย่างมากเนื่องจากสามารถแยกออกจากไบโอดีเซลได้ง่ายและไม่ก่อให้เกิดปัญหาสิ่งแวดล้อมอีกด้วย จากข้อดีนี้เอง จึงเป็นจุดสนใจในงานวิจัยนี้คือการผลิตไบโอดีเซลจากน้ำมันปาล์มโดยการใช้ตัวเร่งปฏิกิริยาแบบวิวิธพันธุ์ ซึ่งตัวเร่งปฏิกิริยาสองชนิด คือ KOH/Al1O3 และ KOH/NaY ถูกใช้เป็นตัวเร่งปฏิกิริยาเพื่อทดสอบหาสภาวะที่เหมาะสมในการผลิตภบโอดีเซล โดยศึกษาตัวแปรที่มีผลต่อคุณภาพของไบโอดีเซลได้แแก่ เวลาในการทำปฏิกิริยา, ปริมาณของ KOH บนตัวเร่งปฏิกิริยา, อัตราส่วนระหว่างน้ำมันพืชและเมทิลแอลกอฮอล์, ปริมาณตัวเร่งปฏิกิริยา, อุณหภูมิในการเกิดปฏิกิริยาและความเร็วรอบในการกวน จากผลการทดลองแสดงให้เห็นว่า ตัวเร่งปฏิกิริยาชนิด KOH/Al2O3 ให้ร้อยละผลได้ของไบโอดีเซล 91.07% ที่สภาวะเวลาในการทำปฏิกิริยา 2 ชั่วโมง, 25% KOH, อัตราส่วนระหว่างน้ำมันพืชและเมทิลแอลกอฮอล์ 1:15, ปริมาณตัวเร่งปฏิกิริยา 3 กรัม, อุณหภูมิในการเกิดปฏิกิริยา 60 องศาเซลเซียส และความเร็วรอบในการกวนที่ 300 รอบต่ำนาที ในขณะที่ตัวเร่งปฏิกิริยาชนิด KOH/NaY ให้ร้อยละผลได้ของไบโอดีเซล 91.07% ที่สภาวะเวลาในการทำปฏิกิริยา 3 ชั่วโมง, 10% KOH, อัตราส่วนระหว่างน้ำมันพืชและเมทิลแอลกอฮอล์ 1:15, ปริมาณตัวเร่งปฏิกิริยา 6 กรั
Viewpoints: Dual-blocking antibody against VEGF-A and angiopoietin-2 for treating vascular diseases of the eye
No full text© 2022 Elsevier LtdFaricimab, a bispecific antibody that targets the endothelial cell growth factors vascular endothelial growth factor-A (VEGF-A) and angiopoietin-2 (Angpt2), was recently approved for treating neovascular age-related macular degeneration and diabetic macular edema. Here, Koh and Augustin review how mechanistic studies have translated into therapies, while Campochiaro evaluates their impact and value for clinical practice.11Nsciescopu
Karakteristik Biodiesel Kemiri Sunan dengan Katalis NaOH dan KOH
No full textMinyak non pangan seperti minyak biji kemiri sunan berpeluang digunakan sebagai bahan baku biodiesel. Masalah yang muncul dalam pembuatan biodiesel adalah reaksi transesterifikasi tanpa katalis berlangsung sangat lambat sehingga dikhawatirkan reaksinya tidak stabil, serta kebutuhan input energi yang sangat tinggi menjadikan tidak layak teknis. Oleh karena itu, untuk mempercepat reaksi transesterifikasi diperlukan katalis. Penggunaan KOH 1% dan NaOH 0,75% sebagai katalis pada proses transesterifikasi dapat mempercepat reaksi. Penelitian ini bertujuan untuk mengetahui karakteristik biodiesel dari minyak biji kemiri sunan, campuran dari beberapa aksesi, yang dihasilkan dengan katalis NaOH 0,75% dan KOH 1 % dibandingkan dengan SNI 04-7182-2015 tentang Biodiesel. Metode pembuatan biodiesel yang digunakan meliputi tahapan degumming, transesterifikasi, separasi dan pencucian. Penelitian dilakukan di Laboratorium Kimia Tanaman Balai Penelitian Tanaman Pemanis dan Serat, Malang pada bulan Agustus-Desember 2019. Biodiesel kemiri sunan menggunakan katalis NaOH 0,75% memiliki nilai kadar air 0,03%, densitas 0,89 (g/cm3 ), angka asam 0,38 mg/KOH/g, angka iod 42,67, viskositas kinematik pada suhu 40 °C 5,45 °C, dan titik nyala 173 °C. Biodiesel dengan penambahan katalis NaOH 0,75% menghasilkan mutu lebih baik dari penambahan katalis KOH 1%. Biodiesel dengan katalis NaOH 0,75% sudah memenuhi SNI 04-7182-2015 tentang Biodiesel pada parameter mutu yang diukur (kadar air, densitas, angka asam, angka iod, viskositas kinematik, dan titik nyala). Parameter lain dalam SNI 04-7182-2015 yang belum dilaporkan dalam penelitian ini perlu dilakukan penelitian lebih lanjut untuk biodiesel minyak kemiri sunan menggunakan katalis NaOH 0,75%.Characteristics of Toxic-Candlenut Biodiesel with NaOH and KOH CatalystsNon-food oils, such as toxic candlenut seed oil, have the opportunity to be used as raw material for biodiesel. The problem that arises in biodiesel process is the slowly transesterification reaction, when without a catalyst will cause unstable reaction, need very high energy inputs, so that makes it technically unfeasible. Therefore, a catalyst is needed to accelerate the transesterification reaction. The use of 1% KOH and 0.75% NaOH in the transesterification process can accelerate the reaction. This study was aimed to determine the characteristics of biodiesel from toxic candlenut oil, a mixture of several accessions of the toxic candlenuts, which was produced with 1% KOH and 0.75% NaOH catalyst. The results were then compared to the characteristics of those determined in SNI 04-7182-2015 of Biodiesel. The method in producing biodiesel included the stages of degumming, transesterification, separation and washing. The experiment was conducted in Phytochemical Laboratory of IRSFCRI in August to December 2019. Toxic candlenut biodiesel using 0.75% NaOH catalyst has a value of moisture content (0.03%), density (0.89 g/cm3), acid number (0.38 mg/KOH/g), iodine number (42.67), kinematic viscosity at temperature 40°C (5.45°C), and flash point (173°C). Biodiesel quality with 0.75% NaOH is better than that of 1% KOH catalyst. Biodiesel with 0.75% NaOH catalyst has achieved the requirement of the SNI 04-7182-2015 on Biodiesel on almost all parameters (i.e., water content, density, acid number, iodine number, kinematic viscosity, and flash point). Other parameters in SNI 04-7182-2015 that have not been reported in this study need further research on biodiesel of toxic candlenut oil using 0.75% NaOH catalyst. Toxic candlenut biodiesel is expected to be used for biofuel
Impact of the carbonisation temperature on the activation of carbon fibres and their application for hydrogen storage
No full textSpecial issue: 2nd World Congress of Young Scientists on Hydrogen Energy Systems.Porous materials are gaining interest due to their potential for storing hydrogen via physisorption. In the present work, two carbon fibres, carbonised at 973 and 1273 K, have been chemically activated with KOH and NaOH, in order to obtain materials with optimised characteristics for hydrogen storage application. Highly microporous activated carbon fibres were obtained from both precursors, especially from the fibre carbonised at the lower carbonisation temperature, remarking its importance on its subsequent activation process. As activation agent, KOH is more effective for developing the narrow microporosity, and higher yields are obtained. H2 adsorption isotherms were measured at 298 K for pressures up to 20 MPa, and at 77 K up to 4 MPa. The maximum excess adsorption of hydrogen reached 1 wt% at 298 K and 3.8 wt% at 77 K. The total volumetric storage capacity is of 17 g/l at 298 K, and 32 g/l at 77 K.Financial help from the European Union (Marie Curie Research Training Network—HyTRAIN Project reference:512443), MEC (Accion complementaria; ENE2005-23824-E/CON), the Generalitat Valenciana (Accion complementaria; ACOMP06/089) and MEC-CTQ2006-08958PPQ. Samples supplied by Osaka gas Co., Ltd
Esterification and Deacidification of a Waste Cooking Oil (TAN 68.81 mg KOH/g) for Biodiesel Production
No full textOils with high content of free fatty acid (FFA) can be treated by acid esterification where an alcohol reacts with the given oil in the presence of acid catalyst. The investigated parameters include methanol to oil ratio, temperature and amount of catalyst. The optimum conditions for acid esterification which could reduce FFA content in the feedstock to less than 1.88% (acid value 3.76 mg KOH/g waste cooking oil) were 50 °C, 20% methanol to oil ratio (by volume) and 0.4 vol.% H<sub>2</sub>SO<sub>4</sub> after 5 h. However, oil with an acid value of more than 1 mg KOH/g oil cannot meet the alkaline catalyzed transesterification conditions. Under the conditions of NaOH concentration 0.5 N, excess alkali 15%, 60 °C, 40 min, the FFA removal rate for deacidification reached 77.11% (acid value 0.86 mg KOH/g esterified oil). The acid value of deacidification product was reduced below 0.86 mg KOH/g esterified oil, thus meeting the base-catalyzed trans-esterification conditions
KOH capture by coal fly ash
No full textThe KOH-capture reaction by coal fly ash at suspension-fired conditions was studied through entrained flow reactor (EFR) experiments and chemical equilibrium calculations. The influence of KOH-concentration (50–1000 ppmv), reaction temperature (800–1450 °C), and coal fly ash particle size (D50 = 6.03–33.70 μm) on the reaction was investigated. The results revealed that, at 50 ppmv KOH (molar ratio of K/(Al + Si) = 0.048 of feed), the measured K-capture level (CK) of coal fly ash was comparable to the equilibrium prediction, while at 250 ppmv KOH and above, the measured data were lower than chemical equilibrium. Similar to the KOH-kaolin reaction reported in our previous study, leucite (KAlSi2O6) and kaliophilite (KAlSiO4) were formed from the KOH-coal fly ash reaction. However, coal fly ash captured KOH less effectively compared to kaolin at 250 ppmv KOH and above. Studies at different temperatures showed that, at 800 °C, the KOH-coal fly ash reaction was probably kinetically controlled. At 900–1300 °C it was diffusion limited, while at 1450 °C, it was equilibrium limited to some extent. At 500 ppmv KOH (molar ratio of K/(Al + Si) = 0.481), and a gas residence time of 1.2 s, 0.063 g K/(g additive) and 0.087 g K/(g additive) was captured by coal fly ash (D50 = 10.20 μm) at 900 and 1450 °C, respectively. Experiments with coal fly ash of different particle sizes showed that a higher K-capture level were obtained using finer particle sizes, indicating some internal diffusion control of the process
Relative Cariostatic Effects of KOH-soluble and KOH-insoluble Fluoride in situ
No full textThe relative cariostatic effects of fluoride as fluorapatite, CaF2, loosely-bound fluoride, or KOH-soluble fluoride are debated. The present study was carried out to investigate this further in an intra-oral caries model. Pairs of premolars extracted for orthodontic reasons were used. Enamel from one tooth of each pair was used as control (untreated). Two slabs were cut from the enamel of the other contralateral premolar. These slabs were treated with 2% NaF for 24 h. One slab was then treated with 1 mol/L KOH twice for 24 h for removal of all loosely-bound fluoride. The slabs treated with 2% NaF and then with 1 mol/L KOH would contain the KOH-insoluble fluoride. Those treated with only 2% NaF would, in addition, contain KOH-soluble fluoride. Each slab, control, KOH-insoluble F, and KOH-soluble and insoluble F was mounted on different upper removable appliances. The slabs were covered with orthodontic banding material, thus allowing space for plaque accumulation. Five individuals wore the appliance in three separate four-week periods. The slabs were analyzed by quantitative microradiography. The average mineral loss (delta Z) was 1680 +/- 1000 vol% x microns in the control teeth, 620 +/- 76 vol% x microns in the KOH-soluble and -insoluble F teeth, and 2167 +/- 1278 vol% x microns in the KOH-insoluble F teeth. The average lesion depths were 90 +/- 41 microns in the control teeth, 35.3 +/- 5.5 microns in the KOH-soluble F teeth, and 88 +/- 35 microns in the KOH-insoluble F teeth. It was concluded that only KOH-soluble fluoride reduced mineral loss and lesion depths significantly, compared with the untreated teeth
The Effect of Variation Concentration Potassium Hydroxide ( KOH ) Added Against Prevention of rancidity in Tanak Oil
No full textThis study aimed to determine the effect of KOH concentration on the prevention of rancidity in tanak oil produced and to determine the condition of the oil tanak after up to 6 weeks. This study uses a completely randomized design ( CRD ) comprised of 5 treatments and 3 repetitions . Data were analyzed statistically using ANOVA and continued by Duncan's New Multiple Range Test ( DNMRT ) at 5% level . The treatment in this study is to neutralize the oil tanak with KOH with treatment A ( 0.59 g KOH in 200 g of tanak oil ) , treatment B ( 0.65 g KOH in 200 g of tanak oil ) , treatment C ( 0.72 g KOH in 200 g of tanak oil) , treatment D ( 0.79 g KOH in 200 g of tanak oil ) , treatment E ( 0.87 g KOH in 200 g of tanak oil ) . The results showed that the addition of KOH concentration gives a significantly different effect on levels of dirt , moisture , free fatty acids and peroxide , but has not been able to lower free fatty acids and the water content of the tanak oil SNI (7381-2008) of VCO. Oil condition is kept for 6 weeks had a TBA figures obtained very low at 0.015 mol MA / MA kg to 0.031 mol / kg , and this shows that the oil tanak neutralized with KOH have not experienced rancidity
Keywords : tanak Oil, rancidity , KOH concentratio
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