금속산화물을 이용한 Mg-Al 하이드로탈사이트 합성 및 염기적 촉매 특성에 관한 연구

이기훈 명지대학교 대학원 2017 국내석사

점토광물 중 하나인 하이드로탈사이트는 촉매, 음이온 교환제, 흡착제 및 센서 등 다양한 분야에서 활용되고 있으며, 특히 촉매로 활용될 경우 염기적 촉매특성을 요구하는 크뇌베나겔 축합반응, 에스터교환반응, 알킬화 반응 및 이성질화반응 등에 활용할 수 있다고 알려져 있다. 이러한 하이드로탈사이트의 경우 공침법, 졸-겔법, Urea법, 수열합성법 등 다양한 제조방법을 통해 제조할 수 있으나, 이러한 촉매 제조방법의 경우 제조과정 중 조절해야 하는 변수들이 다양하여 촉매의 재현성이 떨어지며, 다양한 변수에 의해 생성되는 하이드로탈사이트의 물리화학적 특성이 달라지는 문제점을 지니고 있고, 촉매 제조비용이 비싸다는 단점을 지니고 있다. 따라서 다양한 분야에서 활용될 수 있는 하이드로탈사이트를 특정한 변수의 조절을 하지 않고, 비교적 간단한 방법으로 제조할 수 있는 제조방법에 대한 연구의 필요성이 대두되고 있다. 따라서 본 연구에서는 제조과정 중에 특정한 변수를 조절하지 않고, 비교적 간단한 방법을 통해 하이드로탈사이트를 제조할 수 있는 새로운 제조방법을 제안하고자 하였다. Mg-Al 하이드로탈사이트를 제조하기 위해 각각의 금속산화물인 산화마그네슘과 산화알루미늄을 촉매의 전구체로 사용하였으며, 각각의 금속산화물로부터 Mg-Al 하이드로탈사이트가 제조되는 일련의 반응들을 확인하여 새로운 제조방법의 반응경로를 규명하였다. 또한 생성된 Mg-Al 하이드로탈사이트의 염기적 촉매성능을 향상시키기 위해 하이드로탈사이트의 특징인 메모리효과를 이용하여 촉매의 염기적 성능을 향상시켰다. 제조된 Mg-Al 하이드로탈사이트의 물리화학적 특성을 확인하기 위해 XRD, ICP-AES, SEM 및 TGA 분석 방법을 적용하였으며, 염기적 촉매특성을 확인하기 위해 포도당 이성질화반응과 유기산 흡착실험을 수행하였다. 다양한 특성분석을 진행하여 각 금속산화물로부터 Mg-Al 하이드로탈사이트가 형성되는 것을 확인하였으며, 다른 제조방법을 통해 제조된 하이드로탈사이트와 동일한 물리화학적 특성을 나타내는 것을 확인하였다. 또한 각 금속산화물로부터 Mg-Al 하이드로탈사이트가 생성되는 일련의 화학반응들을 조사한 결과, 전구체로 사용된 금속산화물들이 수용액 내에서 수화반응이 진행되어 Mg2+ 와 Al(OH)4- 가 생성되며, 생성된 Mg2+와 Al(OH)4- 들 간의 반응을 통해 Mg-Al 하이드로탈사이트가 생성되는 것을 확인하였다. 이때 전구체로 사용된 금속산화물의 형태에 따라 Mg-Al 하이드로탈사이트가 생성되기 위한 반응조건이 상이한 것을 확인 하였다. 이후 Mg-Al 하이드로탈사이트의 염기적 촉매성능을 향상시키기 위해 다양한 재수화 방법을 적용하였으며, 이를 통해 촉매의 염기적 특성을 효과적으로 증진시킬 수 있는 재수화 방법을 확인하였다. 재수화 방법의 경우 기계적교반을 이용한 재수화 방법과 초음파를 이용한 재수화 방법으로 총 2가지의 재수화 방법을 적용하여 Mg-Al 하이드로탈사이트를 재수화 하였으며, 재수화된 촉매를 이용하여 포도당이성질화 반응 및 유기산 흡착실험을 진행한 결과, 초음파를 이용한 재수화 방법이 하이드로탈사이트의 염기적 촉매성질을 효과적으로 증진시키는 것을 확인 할 수 있었다. 이는 재수화 과정 중 초음파로 인한 공동현상으로 인해 촉매가 박리되며 이에 따라 촉매의 표면적이 증가되고 표면의 염기점이 증가하기 때문이라고 판단된다. Hydrotalcite (HT), one of the various clay, can be used as catalysis, anion-exchanger, adsorbent, and sensor. In case of hydrotalcite used as catalysts, hydrotalcite can be applied in basic-catalysis such as knoevenagel-condensation, transesterification, alkylation and isomerization. Although hydrotalcite can be synthesized by various preparation method such as co-precipitation, sol-gel method, urea method or hydrothermal method, there are some drawbacks such as existence of many synthetic parameters during preparation processes, low reproducibility, and high preparation cost. Therefore, the research on the preparation method, which has no controlled parameters and non-complex preparation processes is required to overcome the disadvantage of conventional preparation method. In this study, we report the simple preparation method for Mg-Al hydrotalcite as base catalyst via hydration of their corresponding metal oxides (MgO and Al2O3) without any particular controlled variables. Also, we propose a reasonable explanation for a series of reaction pathways in which Mg-Al HTs are formed from their metal oxides. For enhancement on basic property of the formed Mg-Al hydrotalcite via hydration of metal oxides, reconstruction processes was conducted. To check the physicochemical properties on the synthesized Mg-Al hydrotalcites, XRD, ICP-AES SEM and TGA analysis were conducted and glucose isomerization and organic adsorption test was applied to confirm the catalytic basic properties. It is revealed that the Mg-Al hydrotalcites was formed via hydration of both metal oxides and synthesized Mg-Al hydrotalcite has a similar physicochemical properties respected with Mg-Al hydrotalcite prepared by a co-precipitation. The Mg-Al HTs were formed by the reation of Mg2+ and Al(OH)4-, which resulted from the hydration of both metal oxides. In addition, to improve the basic properties of Mg-Al hydrotalcite, two reconstruction methods (mechanical stirring method (HT_RM) and sonication assisted method (HT_RS)) were applied to reconstruction process of the Mg-Al hydrotalcite. From the experimental results, it is revealed that sonication assisted method is more efficient method than mechanical stirring method to enhance the catalytic basic properties, because vertical break and exfoliation of layers structure in the hydrotalcite during the reconstruction processes result in increasement of specific surface area and the number of weak base site on the catalyst surface.

乾燥묵의 再水化에 관한 硏究

황정섭 大邱가톨릭大學校 保健大學院 2001 국내석사

The developments of various processed foods and the high quality instant foods are urgently needed for the enhancement of competitive values. But there was not fundamental research for drying and rehydration process of Mook, a tradition gel food in Korea, has been made from various starches. The estimation of moisture gain, rehydration efficiency was analyzed statistically. The color and textural properties were studied and sensory evaluation was undertaken to evaluate the rehydrated Mook quality. The objectives of this study are to establish efficient pretreatment concentration and rehydration process for the production of the high quality of dried Mook as instant food. The obtained results were as follows : 1. The optimum rehydration time was decided to 15 minutes and it takes 3 minutes for the cooling time 2. Effect of salt concentration in rehydration medium on the rehydration efficiency was investigated. The moisture gain increased as the rehydration temperature increased. And the moisture gain and moisture gain rate was higher at 1% than other concentration. 3. As the color and sensory properties of rehydrated Mook, 1% treatment was superior but felt salt taste, and then non-salt medium was selected to optimum rehydration medium 4. Effect of immersion in sucrose solution before freeze-drying as pretreatment on the rehydration efficiency and quality characteristics was studied. The rehydration efficiency of non-treated Mook was highest. The rehydration efficiency increased as the concentration of sucrose increased. 5. The texture of rehydrated Mook treated sucrose solution was decreased by rehydration temperature increased. At the 60% of sucrose concentration treatment was similar to market selling in the quality and prevented color and texture degradation.

고온환경에서 훈련 중의 수분섭취가 체수분 균형과 체온 반응에 미치는 영향

손윤선 국민대학교 대학원 2008 국내석사

본 연구는 고온 환경(38~40도)에서 운동 중 체수분보충훈련이 체수분 균형과 체온 반응에 미치는 영향을 규명하여, 더위에서 장시간 운동 시 수분섭취 권장에 대한 기초 자료를 제시하는데 그 목적이 있다. 본 연구에 참여한 피험자들은 대사기능과 더위 관련 질병력이 없는 건강한 남자 대학생 8명으로서, 특정 운동프로그램에 참여하지 않았고 실험 전 더위적응과정이 없었다. 피험자들은 충분한 수분섭취 조건(Active Rehydration Condition;ARC)과 불충분한 수분섭취 조건(Passive Rehydration Condition;PRC)의 수분섭취훈련을 7일간 총2회 수행하였고, 각 수분섭취훈련 전?후에 이루어진 사전?사후검사도 모두 수행하였다. ARC?PRC의 수분섭취훈련 사이에는 3주간의 Wash-out 기간이 있었으며 훈련의 적응으로 나타나는 영향을 고려하여 훈련의 순서는 무선으로 선정하였다. 수분섭취훈련은 90분간 60~70% VO2max의 운동 강도로 트레드밀에서 달리기를 하며 체수분손실량의 1.5배의 수분을 섭취하는 ARC와 0.5배의 수분을 섭취하는 PRC로 나뉘어 진행되었다. ARC와 PRC의 훈련을 통한 체수분 균형의 차이를 알아보기 위해 체중, 뇨비중, 뇨삼투, 혈청삼투, 헤모글로빈, 헤마토크릿, 총단백질을 검사하였고, 체온반응은 심부온과 피부온을 측정하였다. 운동수행능력은 RPE, 목마름척도, 더위척도로 측정하였다. 모든 자료는 평균과 표준편차를 산출하였으며, with in subjects Factorial ANOVA with repeated measure 통계를 사용하였다. ARC와 PRC 조건의 수분섭취훈련으로 나타나는 사전?사후검사를 비교 분석한 결과 체수분 균형을 알아본 모든 변인들에서 통계적으로 유의한 차이는 없었고, 체온 반응에도 유의한 영향을 미치지 못했다. 운동수행능력을 측정한 결과 ARC의 수분섭취훈련이 PRC의 수분섭취훈련 보다 수치가 다소 감소하는 경향을 보였지만 조건*시기*시간 간의 통계적으로 유의한 차이는 없었다. 본 연구에서 진행된 고온환경에서의 수분보충훈련은 인체의 체수분 조절에 주요한 요인으로 작용하지 않은 것으로 사료된다. 이는 인체가 극단적인 상황에서도 항상성을 유지하려는 본질적인 생리적 성향과 관계가 있으며, 특히 체수분 조절은 개인의 컨디션이나 개인의 생리적 변화의 폭에 따라 그 범위가 매우 넓기 때문일 것이다. This study examined the effects of an habitual hydration maneuver during exercise training in a hot environment (38-40 C) at 60-70% VOzm. for 90 min on body fluid balance and thermoregulatory responses, and intended to provide informations related to rehydration strategies while exercising in heat for long duration. Eight healthy collegiate men who had not experienced any heat related diseases and were not know for metabolic diseases were recruited. They were not in a regular exercise program prior to the study. All subjects underwent two experimental conditions; active rehydration condition (ARC) and passive rehydration condition (PRC). Each condition of experiment was designed in three phases; pre-testing, a 7-day training program, and post-testing. Two conditions were separated by a 3-week wash-out period. The order of experiments were randomly selected and balanced, For the ARC, each subject actively consumed fluid during exercise training, and for the PRC, they restriced fluid consumption during the training sessions. During the tests, body weight, urine specific gravity, urine osmolality, plasma osmolality, hemoglobin, hematocrit, total protein were analyed for fluid balance status and the core and skin temperatures were monitored. In additiion, ratio of perceived exertion and thirst sensation were evaluated. All values were reported in mean and standard deviation and the Factorial ANOVA with repeated measure was employed to test three factors (condition, period, and time). For the fluid balance parameters and thermoregulatory responses, no differences were found between pre- and post-test in both ARC and PRC. Although the perception during exercise tended to be lower in ARC than PRC, there were no statistical significances. Based on the results, the habitual rehydration maneuver while exercise training in heat did not modify the major fluid balance responses. It is considered that human can maintain a body fluid homeostasis even at a strenuous condition without sufficient fluid supplements. It has to be noted that the control of body fluid balance can be widely varied by an individual physiological adjustment.

Optimization of Semi Drying Process for Advancing Eating Quality and Extending Shelf Life of Ginseng

권인숙 세종대학교 대학원 2021 국내석사

Recently, as consumers’ desire for health increases, the demand for ginseng that has the effect of improving immune system, anticancer, blood pressure control, and antioxidant activity is steadily increasing. The ginseng contains a high moisture content of about 70%, so it is mainly processed and distributed in the form of dried ginseng with a moisture content of 14% through drying or steaming for the purpose of long-term storage and quality stabilization. However, dried ginseng cannot be restored to its original shape even if it is cooked in hot water for a long time. Due to its tough texture, it is limited in food application, so it is used in other forms such as powder or extract. Therefore, in this study, the development of semi-dried ginseng was attempted to improve the texture, which is the biggest drawback of dried ginseng. And hot air drying (HA) and infra-red (IR) were performed to calculate the optimal conditions for improving the rehydration capacity and shelf life of fresh ginseng. To investigate the effect of drying conditions on the quality of semi-dried ginseng, HA (40°C, 50°C, 60°C) and IR (58.5±1.5°C, 56±4°C) were dried by time (6-24 h). Based on the above results, the optimum moisture content was found and the shelf life was measured through accelerated experiments. As a results, the moisture content after drying decreased rapidly at the initial drying time and then became constant. Overall, IR dried faster than HA. As a result of rehydration of dried ginseng in hot water for 15 min, rehydration capacity (RC) is higher in IR (1.5-1.7) than HA (1.2-1.6) regardless of drying time. The RC increased with decreasing moisture content, and rehydration properties were proportional to dryness. After drying, as the drying temperature was higher and the drying time was longer, L* (brightness) decreased and a* (redness) increased due to non-enzymatic browning reaction. These results were more evident after rehydration than after drying. In addition, this study focused on the optimal semi-drying conditions of ginseng, and the shear force, which had a high correlation with consumer preference, was measured with rehydrated ginseng. As a result, the longer the drying time, the higher the shear force was measured. Ginseng dried with HA 40-50°C showed slightly lower shear force than the control, but ginseng dried at HA60°C showed 3.6 times higher shear force than the control. However, the IR-treated ginseng showed much lower shear force than the ginseng dried at HA 60°C, and particularly, it showed similar shear force to the control in the initial drying time. When applied to food, it showed the possibility of improving the texture, the biggest drawback of dried ginseng. Therefore, in order to calculate the optimal semi-drying process, semi-dried ginseng with a moisture content of 40% (wet weight basis) prepared through HA was added and boiled in chicken porridge, which is the food most commonly used in ginseng. As a result, ginseng containing a moisture content of 0.67 g/g solid showed excellent rehydration capacity and a texture close to that of the control. In addition, as a result of accelerated testing of ginseng containing 0.67 g/g solid of moisture through HA and IR, the shelf life of semi-dried ginseng was increased compared to fresh ginseng. In particular, in the case of IR-treated ginseng, the activation energy increased about 10 times compared to fresh ginseng. In this study, the optimal processing condition of semi-dried ginseng is 0.67 g/g sloid, and it is expected that IR-treated semi-dried ginseng can be applied to various foods by improving the tough structure and short shelf life of dried ginseng.

凍結乾燥 粉末고추장의 再水化時 리올로지 特性

김석신 忠南大學校 大學院 1985 국내석사

Rheological properties of rehydrated suspensions of two kinds of freeze dried KOCHUJANG. Brookfield wide-gap rotational viscometer was used to study their rheological proper-ties at 25~60'C. Shear rates ranged from 0.1965 sec-1 to 1.9650 sec-1 and solid content ranged from 47% to 56%. Results obtaind were as follows. Rehydrated suspensions of quickly frozen KOCHUJANG powder and slowly frozen KOCHUJANG powder, and raw KOCHUJANG exhibited pseudoplastic behaviors with yield stress and presented thixotropic properties which showed time-dependent structural decays. Rehydrated suspensions of powdered KOCHUJANG exhibited considerably lower values for the consitency index and yield stress than raw KOCHUJANG. And there wher no significant differences in the consistency index between two KOCHUJANG powers, and in the flow behavior index among three samples. From the beginning of shearing up to 20 minutes the structure breakdown of rehydrated suspensions of quickly frozen KOCHUJANG powder and slowly frozen KOCHUJANG powder, and raw KOCHUJANG followed the second-order kinetic behavior proposed by Tiu and the decaying rates of the structure were increased with shear rates. The decaying rates of suspensions of KOCHUJANG powders exhibited considerably higher than that of raw KOCHUJANG, while quickly frozen KOCHUJANG powder and slowly frozen KOCHUHANG powder showed no significant differneces in th rate constants.The dependency of the equilibrium structure parameter on the shear rate was weak, and there were no significant differences among the values of structure paramenters of three samples. The temperature dependency of the apparent visnosity of KOCHUJANG suspension was fully expressed by Arrhenius equation and activation energies of quickly frozen KOCHUJANG powder, slowly frozen KOCHUJANG powder, and raw KOCHUJANG were 2.21, 2.18, and 2.32 kcal/g·mole, respectively. Consistency indices of three samples increased with solid contnt and decreased with temperature. Flow behavior indices of three samples showed no considerable dependency on temperature and solid content.