Evaluation of total residual oxidant generation and removal efficiency of quinolone antibiotics using catalytic ozonation in seawater-based wastewater

Kim, Taehun Sungkyunkwan University 2023 국내석사

Owing to recent developments in aquaculture, the discharge of seawater containing antibiotics has become a growing concern. Quinolone antibiotics, which cause central nervous system disorders and cardiac conduction, are commonly detected in aquaculture. For this seawater-based wastewater treatment, an ozone process with high oxidation power has been introduced. In this process, bromide ions (Br−) produce total residual oxidants (TRO), such as hypobromous acid (HOBr) and hypobromite ions (OBr−). However, oxidation by TRO demonstrates a low oxidizing power. Therefore, the seawater ozone process requires a relatively higher ozone injection than the freshwater. This study evaluated an ozone-catalytic process using gamma alumina (ɤ-Al2O3) to improve antibiotic removal efficiency. Various factors affecting TRO production were evaluated to derive the optimal ozone process. The removal rates of representative quinolone antibiotics such as enrofloxacin, ciprofloxacin, and oxolinic acid were evaluated using liquid chromatography-fluorescence detection. For 3.0 mg/min of ozone and 1 g/L of ɤ-Al2O3, the removal kinetic rate constant increased by 45.37%, 43.95%, and 37.68% for enrofloxacin, ciprofloxacin, and oxolinic acid, respectively. In addition, the time required for non-detection has also been decreased. These results show that the seawater ozone-catalytic process can be attempted to efficiently remove the pollutants in aquaculture. 최근 선박 무역 및 수산물 수입 증가로 인해, 선박평형수 또는 양식장 폐수 배출수가 다량 발생하고 있으며, 특히 병원성 미생물 또는 잔류 항생제가 근해 수질 오염 및 수생태계 교란을 일으키는 것으로 알려져 사회적 및 환경적으로 문제를 일으키고 있다. 오존 공정은 높은 산화력, 빠른 반응속도 등으로 인해 널리 사용되고 있으나, 해수 내에 브롬이온으로 인해 오존은 수초 이내에 하이포아브롬산(HOBr/OBr-)의 형태로 전환된다. 이러한 하이포아브롬산은 해수 오존 공정에서의 주된 잔류산화물질로써, 총잔류산화물질(Total residual oxidant; TRO)로서의 대표성을 지닌다. 총 잔류산화물질은 병원성 미생물 살균을 위해 일정한 농도로 유지되어야하나 상대적으로 낮은 산화력을 지니는 하이포아브롬산(Oxidation potential of ozone = 2.07 V and HOBr = 1.59 V)으로 인해 높은 항생제 제거율을 얻기 위해서는 담수 조건에 비해 해수 조건에서 고농도의 오존 주입이 필요하다. 따라서, 본 연구에서는 해수 오존 공정의 성능을 향상시키기 위해, 촉매 주입이 TRO 생성과 항생제 제거에 미치는 영향에 대해 평가하였다. 60mg/L-Br 및 0.5mg/L-NH3인공 해수 조건에서, 촉매를 주입할 경우 퀴놀린계열 항생제의 제거 반응속도(k)값은 37.68~45.37% 증가하였다. 이와 유사하게 TRO 생성 속도도 증가하는 것을 확인하였다(촉매 미 첨가: 0.159 mg·L-1·min1-TRO, 촉매 첨가: 0.169 mg·L-1·min1-TRO). 결과적으로, 해수 내에 촉매 오존 공정은 항생제 제거율을 높일 뿐 아니라 TRO 농도를 유지하기 위해 오존을 고농도로 주입시키지 않아도 될 것으로 사료된다.

Interrogating Catalytic Processes with Data Science, Computational Chemistry, and Synthesis

Grosslight, Samantha Marie The University of Utah ProQuest Dissertations & Th 2021 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation utilizes data-driven workflows to gain a deeper understanding of the features influencing selective catalytic processes. Selectivity within catalytic processes can be affected by numerous components, such as the reacting partners, ligand, and additives. Additionally, the degree to which different reaction components affect selectivity may not be the same. This can make gaining mechanistic insight into catalytic processes challenging. Furthermore, this complexity can pose challenges in predicting the outcome when a reaction component is changed. This dissertation investigates different types of catalytic processes using various tools within data science and computational chemistry to gain insight into mechanistic details. A particular focus is placed upon utilizing data-driven workflows that use tools such as multivariate linear regression (MLR), transition state analysis (TS), and experimentation.An overview of all general considerations and tools applied within this dissertation is discussed in Chapter 1. Variations of this data-driven workflow are used for three diverse projects within this dissertation. Chapter 2 evaluates the site-selective acylation of steroidal natural products with BINOL derived chiral phosphoric acids (CPA). Catalyst features that were uncovered to be critical for site-selectivity were the proximal steric bulk in addition to the non-covalent interactions between the substrate and catalyst. Chapter 3 integrates an atroposelective Pd catalyzed Negishi cross-coupling with pyridine heterocycles. MLR and TS analysis are being used to decipher the reaction components that are critical for dictating atroposelectivity. Finally, Chapter 4 extends these tools to the site-selective Pd-catalyzed cross-coupling of polychlorinated heterocycles, focusing on understating the role that phosphine ligands can have on selectivity.By utilizing a data-driven workflow, diverse catalytic processes can be studied to understand the implications that various reaction components can have upon selectivity. This can guide the changes, such as using new ligands, that should be made to affect the desired outcome.

Heterogeneous catalytic dehydrative reactions for the conversion of biomass-derived C4 chemicals

김태용 서울대학교 대학원 2016 국내박사

The utilization of biomass for the production of fine chemicals has been attracted as an alternative way to conventional petrochemical processes. As biomass-derived feedstocks contain abundant oxygen atoms, selective removal of oxygen is required to produce fine chemicals previously obtained from petroleum. Dehydrative reactions such as dehydration and esterification are effective to reduce oxygen content of biomass-derived feedstock as well as to produce desired functional groups. In this thesis, heterogeneous dehydrative reactions for the conversion of biomass-derived C4 chemicals including 2,3-butanediol and 1-butanol are studied. At first, a novel type of dehydration reaction that produces 2,3-epoxybutane from 2,3-butanediol (dehydrative epoxidation) is discovered and explored. Among a number of tested basic catalysts, the CsOx/SiO2 catalyst showed outstanding performance for the dehydrative epoxidation of 2,3-butanediol and is considered to be the most promising catalyst for this type of reaction. In order to identify the superiority of the CsOx/SiO2 catalyst and a mechanism of the reaction, structure-activity relationships were studied along with density functional theory (DFT) calculations. The following features are found to be responsible for the excellent activity of the CsOx/SiO2 catalyst: i) strong basic sites formed by Cs+, ii) low penetration of Cs+ into SiO2 which permits basic sites to be accessible to the reactant, iii) stable basic sites due to the strong interactions between Cs+ and SiO2 surface, and iv) mildly acidic surface of SiO2 which is advantageous for the elimination to H2O. In addition, the dehydrative epoxidation involves an inversion of chirality (e.g. meso-2,3-butanediol (R,S) to trans-2,3-epoxybutane (R,R or S,S)), which is in agreement with DFT results that the reaction follows a stereospecific SN2-like mechanism. The 2,3-epoxybutane produced from the dehydrative epoxidation of 2,3-butanediol can be further utilized to produce fine chemicals. When 2,3-epoxybutane was reacted over basic lithium phosphate catalyst, isomerized product, 3-buten-2-ol, was obtained with high selectivity. Furthermore, it was found that 3-buten-2-ol is an ideal precursor for the production of 1,3-butadiene. Reaction of 3-buten-2-ol over acidic mesoporous aluminosilicate (Al-MCM-41) led to dominant formation of 1,3-butadiene via acid-catalyzed dehydration. On the basis of the results, heterogeneous catalytic process for the production of 1,3-butadiene from 2,3-butanediol is proposed. Esterification of 1-butanol with carboxylic acid produces various esters which can be utilized to environmentally friendly solvents and precursors for fragrances. Esterification reactions are industrially conducted with homogeneous mineral acid catalysts, which causes process and environmental problems. Heterogeneous acid catalyst for the esterficiation reactions is essential to overcome the current problems. Zr-WOx clusters on WOx/ZrO2 catalyst are known to be active sites for the acid catalyzed reactions, such as dehydration of alcohols and alkane isomerization reactions. However synthetic methods for producing high density of Zr-WOx clusters with high surface areas are not currently available. A facile method for preparing mesoporous Zr-WOx/SiO2 is proposed and the effect of Zr/W ratio on its structure and acidity was examined. Results showed that the sequential hydrolysis of zirconium and tungsten via soft-templating resulted in the formation of Zr-WOx clusters with uniform mesopore structures and a high acidity. The prepared Zr-WOx/SiO2 was characterized by N2 physisorption, XRD, TEM, XPS, UV-Vis spectroscopy, NH3-TPD and in-situ FTIR. Catalytic performance for the esterification of 1-butanol with acetic acid was evaluated. The materials had a high surface area of over 500 m2/g and ordered cylindrical pores with a uniform size of ca. 5 nm. Below a Zr/W ratio of ≈0.5, the zirconium was primarily associated with tungstate rather than SiO2, which indicates the formation of Zr-WOx clusters. The highest density of Zr-WOx clusters was obtained at a Zr/W ratio of 0.3 with a strong Brønsted acidity. Consequently, Zr-WOx/SiO2, as a Zr/W ratio of 0.3 exhibited the highest activity with a significantly improved performance compared to HZSM-5 and WOx/ZrO2 catalysts.

Prediction of Reaction Performance and Analysis of Selectivity Bias in Catalytic Processes via Multivariate Linear Regression Models

Santiago, Laura Celine Bunag The University of Utah ProQuest Dissertations & Th 2018 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

Multivariate linear regression (MLR) modeling is a data-driven strategy for investigating molecular reactivity to identify key mechanistic features of the reaction that influence reaction performance. Catalytic reactions are often multifaceted, which renders the reaction development challenging and conventionally requires synthesis of multiple analogs of the catalyst. In this dissertation, MLR models that quantitatively evaluate molecular descriptors as a function of various catalytic reaction outcomes (enantioselectivity, site selectivity, and turnover frequency) were utilized concurrent to reaction optimization, enabling prediction of an optimal ligand and providing mechanistic understanding of the reaction. In Chapter 2, an extensive library of molecular descriptors for aryl ring substituent effects was collected from simulated structures of ortho-, meta-, and para-substituted benzoic acids. Proximal and remote steric effects were accounted for in the obtained selectivity-MLR models investigating various arene substrates.The effect of the catalyst on the 1) enantioselectivity in an intermolecular dehydrogenative Heck arylation of indoles and alkenyl alcohols and 2) site selectivity in palladium-catalyzed 1,3-arylfluorination of chromenes and boronic acids in the presence of Selectfluor was evaluated in Chapter 3 by using molecular descriptors of [N,N]-bidentate ligands in MLR models. From a virtual screening library of ligand parameters, a new chiral pyridine oxazoline ligand was identified affording improved enantioselectivity in the Heck arylation. The mechanistic study of the arylfluorination reaction revealed that the site selectivity was influenced by the denticity and electronic nature of the ligand. To further explore catalyst reactivity, metathesis catalyst ligand parameters were utilized in MLR models described in Chapter 4 to quantitative evaluate 1) turnover frequency in self-metathesis of cis-nonene using silica-supported tungsten catalysts and 2) selectivity for ethenolysis of cis-cyclooctene using ruthenium N-heterocyclic carbene metathesis catalysts.The generation and utilization of a significant-sized library of simulated ligand parameters for MLR modeling provides a platform for accelerated catalyst development by virtual prediction of reaction outcome a priori. Harnessing the predictive power of MLR models is advantageous in reducing the synthetic effort invested on screening multiple analogs of a particular catalyst. Ultimately, the mechanistic rationale obtained from these parameterization studies can lead to the design of new catalysts and reaction optimization strategies.

먼지와 질소산화물의 동시처리를 위한 촉매필터의 질소산화물 제거특성에 대한 연구

최현덕 연세대학교 대학원 2003 국내석사

본 연구는 실제 발전소 등에서 집진공정과 NOx저감 SCR공정이 함께 설치된 공정에서 나타나는 촉매의 활성저하 및 plugging 현상과 재 가열해야하는 에너지 손실 등의 문제점들을 해결하여 열효율 향상과 처리비용 절감 및 장치설비 공간, 설치비용 등의 절감 등의 효과를 얻기 위해 질소산화물 제거를 위한 촉매공정과 먼지제거를 위한 집진공정을 일체화한 hybrid system의 촉매필터를 고안하여 제작하였다. 일차적으로 촉매필터의 NOx 전환율에 대한 실험을 수행하였으며, 그에 따른 필터에 담지된 촉매의 양, NH₃/NOx 몰비, Face velocity, 시간, 온도 등에 대해 각각 NOx 전환율 test 및 slip되는 NH₃ 검출 등 기초적인 실험을 실시하여 실험결과를 토대로 NOx 저감용 촉매필터개발에 필요한 조건들을 알아보았다. 촉매를 코팅시키기 위해서는 필터의 표면뿐만 아니라 내부까지 코팅하기 위해 코팅장치를 제작하여 실시한 결과 SEM분석을 통해 필터의 각 fiber에 촉매가 내부까지 고르게 코팅이 되었으며, 필터의 pore를 막는 현상은 없었다. 하지만 바인더의 영향으로 고정층에서의 실험과 비교하여 전환율이 낮아졌으며, 이점에 대해서는 새로운 바인더의 개발을 필요로 한다. 촉매필터의 반응성 실험결과 먼저 face velocity 결과로부터 촉매필터는 불규칙하게 구성된 fiber에 의해 유체의 흐름이 불규칙하여 반응gas와 촉매와의 mass transfer를 증가시키게 되므로 honeycomb에 비해 space velocity가 2.5배 크더라도 같은 전환율을 얻었다. 촉매의 담지량은 필터의 압력손실을 감안하여 그 양을 결정해야하며, 촉매의 담지량별 실험결과 촉매의 담지량이 증가할수록 높은 전환율을 보였으나 그 담지량을 10.97g 이상 증가시킬 경우 증가율이 감소되는 경향을 나타냈다. 따라서 촉매의 최적 담지량을 10.97g로 결정했으며, 단위면적당 촉매코팅양은 0.46g/㎠이다. 반응온도는 230℃이상에서 NH₃가 자체산화와 고온에서의 NO₂생성으로 인해 반응에 필요한 NH₃의 감소로 전환율이 약간 감소하는 결과를 얻었으며, NH₃의 배출은 온도전역에서 NH₃/NOx mole ratio 1.0부터 배출되기 시작하므로 NH₃로 인한 2차 오염을 방지하기 위해 0.9 이하에서 결정해야한다. 또한 face velocity 실험결과 0.8에서 2.0사이에서 90~82%의 전환율을 얻었다. 따라서 0.46g/㎠의 촉매를 코팅한 필터에, 반응온도 190~230℃, face velocity 0.8~1.6m/min, NH₃/NOx mole ratio 0.9로 실험조건을 할 경우, NOx를 85% 제거할 수 있으며, 또한 NH₃에 의한 2차 오염도 방지할 수 있는 것으로 나타났다. The typical air pollution control devices (Bag filter or Selectively Catalyst Reactor) were used to have some troubles, such as plugging, catalyst activity drop, and energy loss for flue gas re-heating, during the operation to control the particulate matters and NOx from power plant as the emission source. This study was focused on the energy, cost, and spatial effective process which referred as hybrid system; combined process of catalytic process for NOx and particulate matter control. The NOx conversion rate and detection of slipped NH₃ were investigated to estimate the appropriate amount of catalyst, NH₃/NOx mole ratio, face velocity of flue gas, residence time, and temperature. To coat filter with catalyst, the coater, which was available to coat not only surface but also inner space of filter fiber, was needed. It was regarded that the catalyst was fluently coated on surface and inside without any stopping pore of filter as the result of SEM analysis. However, the NOx conversion rate in the experiment of coated filter was lower than the fixed bed experiment's because of the binder. The advanced binder will be required in further research. Even though the catalytic filter had 2.5 times faster space velocity than honeycomb's, it showed similar NOx conversion rate with honeycomb type because of its irregular flow by porous fiber. The amount of catalyst loaded on the fiber must be decided with the consideration of pressure drop of filter. The NOx conversion rate was increased with the amount of catalyst loaded on the filter; however, after more than 10.97g of catalyst loaded, the conversion rate was decreased. Thus, the optimum amount of catalyst loaded was regarded as 0.46g catalyst per unit area of filter. The NOx conversion rate was decreased at the temperature 230℃ and above, because NH₃ was oxidized by itself and was decreased by forming NO₂ under the high temperature. The drawing off of NH₃ was observed after the NH₃/NOx mole ratio 1.0 in all experimented temperature (150-230℃), so that the mole ratio must be below 0.9 to prevent secondary contamination. Additionally, the NOx conversion rate showed 90% and 82% at the mole ratio 0.8 and 2.0, respectively, as results from the face velocity experiment. As the conclusions, the optimum conditions of NOx control in hybrid system were regarded to the conditions such as 0.46g catalyst coated per unit area of filter, 190~230℃ of reaction temperature, 0.8~1.6m/min of face velocity, and 0.9 of NH₃/NOx mole ratio to eliminate 85% of NOx and to prevent the secondary contamination.

Dynamics simulation and optimization of fluidized catalytic cracking processes

한인수 全南大學校 1999 국내박사

Catalytic metal induced crystallization of metal oxide semiconductors

신재철 중앙대학교 대학원 2021 국내석사

본 논문을 통해 기존 금속 산화물의 결정화를 위한 고온 열처리 공정의 한계를 극복하고, 비교적 저온의 열처리를 통해 고품질의 박막을 형성하여 차세대 반도체 소자 개발에 기여하고자 한다. 본 연구에서는 촉매 금속을 이용한 산화물 반도체의 저온 결정화 가속 공정 방법을 개발했다. 이 공정 방법을 통해, 촉매 금속은 졸-겔 공정 증착된 금속 산화물 박막을 비정질에서 결정질 상으로의 변이를 가속화한다. 일반적으로 졸-겔 공정 TiO2 박막의 결정화를 위해서, 500-600 °C 이상의 고온이 요구되며, 형성된 박막은 다량의 결점 밀도와 낮은 전기적 특성을 갖는다. 해당 연구 결과, 촉매 금속을 이용한 결정화 가속 공정은 더 낮은 온도에서 결정화를 이루며, 고품질의 anatase 결정질 구조를 갖는 TiO2 박막을 형성함으로써 효과적으로 결점 밀도를 감소시킬 수 있었다. 비정질 TiO2 박막 위에 다양한 촉매 금속 (알루미늄 (Al), 몰리브데늄 (Mo), 티타늄 (Ti))을 증착하여 다양한 조건 하에 비교 분석을 진행했으며, 최적의 촉매 금속인 Al을 이용한 산화물 반도체 결정화 가속 공정을 진행한 결과, 300 °C의 낮은 열처리 온도에서 결정화가 진행되었고, 전계 이동도, 온/오프 스위칭, 동작 안정성에 대한 반도체 소자 성능이 향상되었다. To overcome conventional high-temperature crystallized metal oxide (MO) layers, the catalytic metal induced crystallization (CMIC) process is introduced for low-temperature crystallized MO semiconductors by using the catalytic metal. Through the CMIC process, the catalytic metal accelerates sol-gel processed MO layer phase transition from amorphous to crystalline phase. Commonly, the sol-gel processed TiO2 layer is needed high-temperature condition for crystallization (≥500− 600 °C), indicating low electrical performance related to high defect density. Contrary to conventional method, the suggested CMIC process accomplished lower crystallization temperature, enabling high-quality crystalline-TiO2 (c-TiO2) layers with well-aligned anatase structure grains and effectively decreased defect density. The various catalytic metals were deposited on the amorphous titanium oxide (a-TiO2) layers. Then, the CMIC process was performed for low-temperature transition of sol-gel processed a-TiO2 to effectively crystallized states. Particularly, the Al-CMIC process applying the crystalline aluminum (Al) catalytic seed layer promotes lower temperature (≥300 °C) crystallization of sol-gel processed a-TiO2 layers and the characteristic of high-performance sol-gel processed c-TiO2 thin-film transistors with improved field-effect mobility, good on/off switching, and enhanced operational stability.

Biodiesel production through thermally induced non-catalytic transesterification

정종민 세종대학교 대학원 2022 국내박사

Biodiesel is one of the promising alternative fuels which can replace petro-diesel to reduce CO2 emission from a sector of transportation. Despite an increase in global demand for biodiesel, more biodiesel production from edible oils is discouraged due to ethical dilemmas. As such, it is highly desirable to discover promising alternative biodiesel feedstocks from non-edible resources. In addition, the development of efficient biodiesel production process is required. To establish a new technical platform for biodiesel production using low quality and non-edible biodiesel feedstocks, this dissertation particularly studies an alternative method for biodiesel production, namely thermally induced non-catalytic transesterification. This study is composed of five detailed themes; 1) comparison of biodiesel yield and reaction kinetics observed from both conventional and thermally induced transesterifications of edible oils (Chapter II), 2) systematical study of relationships between reaction parameters and resulting process efficiency (Chapters III and IV), 3) development of efficient porous material for thermally induced transesterification (Chapter V), 4) conversion of low quality alternative biodiesel feedstocks (microalgae and food waste) into biodiesel through thermally induced transesterification and fuel property characterization (Chapters VI and VII), and 5) heating values and thermodynamic calculation of biodiesels obtained from thermally induced transesterification to be used as a different biofuel (bio-jet fuel) (Chapter VIII). In Chapter II, the technical feasibility of biodiesel production through thermally induced non-catalytic transesterification was assessed using an oil-bearing biomass (sesame oil and seed). In detail, biodiesel productions from both conventional base-catalyzed transesterification and thermally induced transesterification of sesame oil (oil extract from sesame seed) were compared. From both conventional and thermally induced transesterifications, sesame extract was converted into biodiesel, also confirming that thermally induced one has much faster reaction kinetics than conventional method. Thermally induced reaction was highly active around 350 ˚C, showing higher than 90 wt.% within 1 min of reaction. Sesame seed was also directly converted into biodiesel without oil extraction through thermally induced transesterification. At the temperature of 380 ˚C, 96.4 wt.% of biodiesel yield was achieved. Therefore, it was concluded that thermally induced non-catalytic transesterification offers a high tolerance against impurities. Such facts led to the high yield of biodiesel through the fast reaction kinetics. In Chapter III and IV, the relationships between reaction parameters (molar ratio of acyl acceptor to lipid and mass ratio of porous material to lipid) and biodiesel yield were systematically studied. When the molar ratio of acyl acceptors (methanol and dimethyl carbonate) to lipid was 12, biodiesel yield reached to about 50 wt.% through thermally induced transesterification. Biodiesel yield was proportionate to the amount of acyl acceptors. The best mass ratio of silica to lipid was 8 in this study. In Chapter V, a cheap and effective porous medium was developed to enhance biodiesel production efficiency. An agricultural waste, chicken manure, was used as a raw material to produce porous biochar. The performance of chicken manure biochar was compared with that of SiO2. Chicken manure biochar was produced at 350, 450, 550, and 660 ˚C. The surface morphology and the pore structures of biochar were characterized using XRD, SEM, and BET. Identification and quantification of metals in chicken manure were determined using an elemental analyzer and induced coupled plasma spectroscopy. As a result, biodiesel yield reached to 95 wt.% at 350 ˚C when chicken manure biochar fabricated at 350 ˚C was used as a porous medium, while SiO2 showed the maximum biodiesel yield at 380 ˚C. The reduction of the reaction temperature for the maximum biodiesel yield was likely due to the catalytic effect of alkaline earth metal in chicken manure (CaCO3). Therefore, it was demonstrated that the application of porous medium containing alkaline earth metals can lower the reaction temperature for biodiesel production. Moreover, the experimental findings showed that the utilization of waste-derived porous material containing alkaline earth metals can be considered a strategic means to enhance reaction efficiency of biodiesel production. In Chapter VI and VII, low quality non-edible lipids were used as alternative feedstocks of biodiesel: (1) microalga (Euglena gracilis) and (2) food waste using black soldier fly larva as a medium. Due to high acid value of E. gracilis (8.12 mg KOH g−1), acid-catalyzed transesterification should be used in the conventional biodiesel production process, which is even slower than base-catalyzed transesterification. Thermally induced transesterification of E. gracilis extract improved biodiesel yield 30 wt.% in reference to acid-catalyzed transesterification. Thermally induced reaction also directly converted lipid in E. gracilis into biodiesel without lipid extraction. Considering that the lipid productivity of microalgae highly depends on cultivation methods, lipid productivity from different cultivation methods (phototrophic, heterotrophic and mixotrophic cultivations) and nutrient concentrations was also studied. The high dose of nutrients under the heterotrophic cultivation was determined as the favorable conditions for lipid production (24.81 wt.%, dry basis) during 10 d of cultivation, and the maximum lipid productivity of E. gracilis was shown after 6 d of cultivation (0.131 g lipid L-1 d-1). Food waste was utilized as a resource for biodiesel production using black soldier fly larvae as a medium, because black soldier fly larvae convert carbohydrate and lipid in food waste into fat body through their metabolism. The larvae digested the food waste and accumulated lipid (34.0 wt.% in dried biomass). Thermally induced transesterification transformed the lipid of black soldier fly larvae into biodiesel, showing 94.7 wt.% of biodiesel yield without lipid extraction. In the following studies, fuel properties of biodiesel produced from black soldier fly larvae were tested, and the results met the European Union and Korean biodiesel fuel standards. In Chapter VIII, the feasibility of biodiesels as an aviation fuel was evaluated. Six biodiesels obtained from thermally induced transesterification of plant oils (olive, coconut, canola, soybean, avocado and sesame oils) were used as model compounds. Heating values and air to fuel ratios of biodiesels and jet fuels (Jet-A and JP-4) in line with their fuel performances as an aviation fuel were compared. When the combustion through turbojet engine was completely done, 14 ~ 18% more fuel was required when biodiesels were used as jet fuels. However, the more biodiesel fuel consumption resulted in higher engine and specific thrusts than conventional jet fuels. As such, propulsion and thermal efficiencies of biodiesels were nearly same with those of conventional jet fuels. Considering that biodiesels are carbon neutral fuels, the results suggested that jet fuel and biodiesel blends can contribute to reduction of greenhouse gas without fuel performance change. In this dissertation, a new technical platform for biodiesel production was studied. The thermally induced non-catalytic transesterification showed superior performance in reference to conventional acid/base-catalyzed (trans)esterification, because it showed higher biodiesel yield and reaction kinetics, and tolerance to impurities. The thermally induced reaction also converted low-quality lipid feedstocks into biodiesel without lipid extraction. Fuel properties of biodiesel obtained from thermally induced transesterification met biodiesel fuel standards of European Union and Korea. Lastly, fuel performances of biodiesels obtained from thermally induced transesterification were similar with those of jet fuels during combustion in turbojet engines.

Lignocellulosic biomass pyrolysis and hydrodeoxygenation of bio-oil using transition metals (Ni, Co, Fe) based catalysts

Quoc Khanh Tran 강원대학교 대학원 2022 국내박사

Biomass is a promising renewable resource to generate energy owing to its abundance and low cost. Lignocellulosic biomass is known as a strong candidate due to their advantages compare to other biomass, e.g. high energy, but low costs, low ash content, and very low nitrogen and sulfur contents. Lignocellulosic biomass is consisted of hemicellulose, cellulose, and lignin. Among several thermal conversion technologies, pyrolysis is a feasible approach to convert biomass into energy and chemicals due to reasonable coast and simple operation. To understand the pyrolysis kinetic of lignocellulosic biomass, the main components of lignocellulosic biomass such as cellulose and lignin were used to investigate systematically using thermal gravimetric analysis (TGA) and micro-tubing reactor. The simulated data of α-cellulose is in good agreement with the experimental data in the aspects of the conversion and the conversion rate versus temperature. The decomposition of α-cellulose, mainly occurring at 270–420℃, induced an apparent activation energy ranging from 175.42 kJ/mol to 197.73 kJ/mol at a conversion of 10–90%. With 0.1–0.2 wt% K or Ca impregnation into the α-cellulose, the mean activation energy for pyrolysis was lowered (from 181.47 kJ/mol (for α-cellulose) to 141.11 kJ/mol (for 0.2 wt% K/α-cellulose) and 159.46 kJ/mol (for 0.1 wt% Ca/α-cellulose)) and higher amounts of liquid and gas products were produced. Furthermore, the addition of potassium and calcium increased the production of lower molecular weight components, such as furfural and its derivatives. The kinetic rate constants indicate that the predominant reaction pathway is from α-cellulose into a liquid product, rather than from α-cellulose into a gas product. The pyrolysis characteristics and kinetics of Organosolv lignin from pine trees were also investigated. Through these approaches, the activation energy of Organosolv lignin pyrolysis was calculated. The activation energy by the Friedman method ranged from 70.11–355.92 kJ/mol, while relatively lower values (48.51–302.47 kJ/mol) were calculated by the peak separation method. Thermodynamic parameters such as entropy (ΔSo), Gibbs free energy (ΔGo), and enthalpy (ΔHo) were also calculated to understand the reaction pathways from a thermodynamic perspective. Based on the pyrolysis mechanisms proposed in this study, the reaction rate constants of different steps were determined. The primary reaction route was identified to be the pyrolysis of Organosolv lignin to liquid products such as bio-oils. Finally, the compositions of gaseous and liquid products formed by pyrolysis were analyzed using the micro-tubing reactor. The Organosolv lignin was polymerized into lower molecular weight structures by the pyrolysis process. CO, CO2, and CH4 were mainly produced as gaseous products, while Organosolv lignin was primarily decomposed into guaiacol, 3-methoxy-1,2-benzendiol, vanillin, vanillic acid, acetovanillate, and syringaldehyde. Pine trees is considered as promising candidate biomass sources compare to other lignocellulosic biomasses for the production of high liquid yield bio-oil. Pyrolysis of pitch pine has been investigated in a bubbling fluidized bed reactor. In this system, silica sand and nitrogen were used as the fluidizing bed material and fluidizing medium, respectively. The experimental was systemically perform on different temperature, fluidized velocity, and particle size of biomass. The optimum temperature condition at which the bio-oil yields reached the highest value (65.5%) was 500 ℃. In addition, the higher heating values of bio-oils from pitch pine biomass were reached in the range 22 MJ/kg to 24 MJ/kg. Moreover, this bio-oil had high content of useful chemicals including such as levoglucosan, furfural, and guaiacol. The large amount of C5–C11 (gasoline fraction) produced make the pyrolyzed oil originating from pitch pine trees a promising biofuel candidate. Since guaiacol is a key compound obtained from lignocellulosic biomass pyrolysis bio-oil, it is often utilized as a model compound in most studies. Additionally, it contains methoxy (-OCH3) and hydroxy (-OH) groups, which are important in ascertaining its value as a fuel source. Spherical -Al2O3-SiO2 catalysts with varying Al/Si ratios were prepared by combining the sol-gel and spray pyrolysis (SP) methods to examine in hydrodeoxygenation process. The effectiveness of the product catalysts was then tested via the hydrodeoxygenation (HDO) of guaiacol, a model compound of bio-oil obtained from the pyrolysis of lignocellulosic biomass. Our results showed that the -Al2O3-SiO2 catalyst with a 50:50 Al/Si ratio after calcination at 450 C exhibited the highest guaiacol conversion (81.79%) at a reaction temperature of 300 C, atmospheric pressure, and a weight hourly space velocity (WHSV) of 6.5 h-1. During guaiacol HDO, the carbon–oxygen cleavage and methyl group transfer reactions occurred on the -Al2O3-SiO2 catalyst, which converted the guaiacol into the respective deoxygenated products, including 2,6-xylenol, 2,3,5,6-tetramethyl phenol, pentamethyl benzene, and hexamethyl benzene. In addition, Ni/γ-Al2O3 and Fe/activated carbon (AC) catalysts were prepared by an incipient impregnation method and then also utilized for hydrodeoxygenation (HDO) of guaiacol (GUA). The AC used in the process was derived from bamboo through steam activation. At 300 °C and atmospheric pressure, 91.52% of GUA was successfully transformed into cresol and 1,2-dimethoxybenzene in liquid phase using 10 wt% of the Fe/AC catalyst, which was calcined at 550 ℃. Under the same reaction conditions, utilizing 10 wt% of the Ni/γ-Al2O3 catalyst, which was calcined at 450 ℃, resulted in 96.88% GUA conversion, producing 13.03% of cresol, 58.98% of 1,2-dimethoxybenzene, and 27.99% of 3-methyl guaiacol. The reaction pathways for the conversion of guaiacol HDO were also proposed in this study. The catalytic hydrodeoxygenation (HDO) processes for upgrading pyrolysis bio-oils from wood pallet sawdust (WPS) were studied using activated carbon (AC) as a support of mono- (Co/AC and Fe/AC) and bi-metallic (Co-Fe/AC) catalysts. At 350 ℃ and 60 bar, 20 wt% Co/AC showed the highest liquid yield (70.46 wt%) along with HHV of 34.22 MJ/Kg. Among the tested bimetallic catalysts, comparable liquid yield (68.85 wt%) and HHV (34.16 MJ/kg) were achieved with 20 wt% 4Co-1Fe/AC catalyst. Methyl phenol derivatives were found to be the main component in upgraded bio-oil. The carbon number of upgraded bio-oil was mainly distributed in C5–C11 fraction, especially with the C8 component (20.40 wt%). The catalysts were deactivated by the formation of carbonaceous compounds on the external surface, oxidation of metal species, and blocking of active sites on catalysts.

Preparation of Metal Oxide Nanoparticles Using Catalytic Biomimetic Molecules

안성준 연세대학교 대학원 2011 국내석사

This research focused on preparation of metal oxides with functionality of photo energy conversion through biomineralization. The outcomes of this study is that mineralization with catalytic effects of a biomimetic molecule provides low energy consumption process, while the property of the products is similar to those of high energy consumption process.Single crystalline zinc tin oxide (ZTO) nanocrystallites were prepared at room temperature through association with a peptide-containing bolaamphiphile molecule in a strong acidic environment. ZTO nanocrystallite synthesis was achieved only when the bolaamphiphile molecule was added, while a mixture of amorphous Sn and Zn precipitates was formed in the absence of the bolaamphiphile molecule. The prepared ZTO nanocrystallites had almost the same band gap energy as ZTO nanoparticles prepared by the conventional hydrothermal process.Titanium dioxide was prepared by biomineralization with lysine along with investigation of influence of lysine on the mineralization of titanium dioxide. Oligo (L-lysine) with various numbers of lysine was used for the in vitro mineralization of titanium dioxide. Observation of the titanium source residue after reaction using a UV-vis spectroscopy revealed the influence of lysine numbers on the mineralization.