1120句英语运动短句
Elderly people are worn with age, so it is even more important for them to take part in exercise 老年人年老体衰更应该参加一些适当的体育锻炼。 He goes for a long-distance run every day at a specific time 他每天都定时进行长跑锻炼。
Doing sit-ups is an effective way to exercise abdominal muscles 仰卧起坐是锻炼腹部肌肉的有效办法。 Early in the morning people may be seen doing exercise Martial arts (like Chinese boxing) which formerly were cultivated for self-defense, now have become a form of physical exercise and are practiced in parks, streets, gardens, or on campuses In addition young and old people are also often seen running in order to build up their bodies 每天早上,都可看见很多人在运动。
武术(像太极拳)以前都是用于防卫的,现在已经变成是一种强身健体的运动了。每天都可看见人们在公园、大街、花园或校园里锻炼身体。
还有,经常看见不论老人还是青年都在跑步,他们也是为了强身健体。 He keeps exercising all year around, even in the hottest days in summer and the coldest days in winter 他常年坚持锻炼,冬练三九,夏练三伏。
In morning, there are a lot of old men doing exercise in the park 早上在公园锻炼的老头儿特别的多。 I've just learned how to exercise with clubs 我新学了一套棒操锻炼身体。
My grandfather exercises with his healthcare balls every day 我爷爷每天都拿着保健球锻炼。 No matter how cold it gets, we must all stick to our exercise routine 不管天气多么寒冷,我们都要坚持锻炼。
People are toughened by difficult experiences 艰苦的环境锻炼人的意志。 Regular physical exercises can strengthen one's resistance against illness 经常锻炼身体,能够提高人体的抵抗力。
She fixed the exercise time for Saturday afternoons 她把锻炼的时间固定在星期六下午。 She was very busy at work, but she managed to stick to her exercise regime 工作很忙,但是她还坚持锻炼。
Thanks to his persistent physical exercise, he looks healthy, with white hair and a ruddy complexion 由于长期坚持体育锻炼,他看起来鹤发童颜。 The army is a place where people can build their character 部队是一个锻炼意志的大熔炉。
The child has a weak constitution and is struck ill from time to time Lack of exercise is part of the reason 这孩子从小就体弱多病,这都是缺乏体育锻炼造成的。 The sportsmen are exercising to improve the strength of the muscles on their legs 运动员们正在锻炼,以便加强腿部肌肉的力量。
We should keep on developing our ability to think logically and exercise speculative thinking 我们要不断地培养自己的思辨能力、锻炼思辨性思维。 We should take exercise to build up resistance to disease 我们应该坚持锻炼以增强对疾病的抵抗力。
You should exercise more, you've already out of breath after completing such a small task 你应该多锻炼锻炼了,才干了这么点力气活就抽气得不行。 Doing sit-ups is an effective way to exercise abdominal muscles 仰卧起坐是锻炼腹部肌肉的有效办法。
Early in the morning people may be seen doing exercise Martial arts (like Chinese boxing) which formerly were cultivated for self-defense, now have become a form of physical exercise and are practiced in parks, streets, gardens, or on campuses In addition young and old people are also often seen running in order to build up their bodies 每天早上,都可看见很多人在运动。武术(像太极拳)以前都是用于防卫的,现在已经变成是一种强身健体的运动了。
每天都可看见人们在公园、大街、花园或校园里锻炼身体。还有,经常看见不论老人还是青年都在跑步,他们也是为了强身健体。
Elderly people are worn with age, so it is even more important for them to take part in exercise 老年人年老体衰更应该参加一些适当的体育锻炼。 He goes for a long-distance run every day at a specific time 他每天都定时进行长跑锻炼。
He keeps exercising all year around, even in the hottest days in summer and the coldest days in winter 他常年坚持锻炼,冬练三九,夏练三伏。 In morning, there are a lot of old men doing exercise in the park 早上在公园锻炼的老头儿特别的多。
I've just learned how to exercise with clubs 我新学了一套棒操锻炼身体。 My grandfather exercises with his healthcare balls every day 我爷爷每天都拿着保健球锻炼。
No matter how cold it gets, we must all stick to our exercise routine 不管天气多么寒冷,我们都要坚持锻炼。 People are toughened by difficult experiences 艰苦的环境锻炼人的意志。
Regular physical exercises can strengthen one's resistance against illness 经常锻炼身体,能够提高人体的抵抗力。 She fixed the exercise time for Saturday afternoons 她把锻炼的时间固定在星期六下午。
2用英语表达关于运动好处的句子Playing sports is good for our health When you are playing sports, your heart will beating fast and force it to pump more blood to your whole body This could improve your cardiorespiratory function It's also a good way for people to comunicate with each other When you play basket ball with your friends, you will feel happier than staying home alone 望采纳 谢谢。
3体育锻炼的英语短语aerobics 有氧操,body-building 健美,jogging 慢跑,judo 柔道,wresting 摔跤,ball games 球类运动,football 足球,basketball 篮球,tennis 网球,squash 壁球,rugby 橄榄球,volleyball 排球,golf 高尔夫球,table tennis 乒乓球,badminton 羽毛球,baseball 棒球,cricket 板球,hockey 曲棍球,billiard 台球,softball 垒球,ice hockey 冰球,aquatic sports 水上运动,country sports 乡间户外活动(如打猎, 钓鱼, 射击, 赛马等)a favourite sport 受人喜爱的运动项目,the school sports 学校运动会,sports extra 体育增刊,a sports meet [meeting] 运动会,a sports field 运动场,sportscast n, v[美](播送)体育节目,sportscaster n 体育节目广播员,sports-down n [美]运动界,sports-minded adj 关心体育的,sportswriting n 体育新闻的报道或写作,sports-wear n运动服装,sports-writer 体育运动专栏作家,sportsdom [美]体育界有关运动的人员:amateur 业余运动员,爱好者,contestant, competitor, player 运动员,enthusiast, fan 迷,爱好者,guide 领队,instructor 教练,技术指导,linesman, touch judge (橄榄球)裁判,manager 经纪人 ,professional 职业运动员,referee, umpire (网球棒球)裁判,trainer 助理教练,batsman 板球运动员,batter 击球运动员,men's singles 单打运动员,in the mixed doubles 混合双打足球运动员 a football player守门员 the goalkeeper运动员,田径运动员 an athlete / a sportsman / a sports-woman 职业/ 业余运动员(球类运动员)a professional / amateur player教练 the coach 他的对手 his opponents / rivals体育设施词汇:sports stadium 露天运动场,football stadium 有看台的大型足球场,children's stadium 儿童运动场,ice stadium 冰场,swimming stadium 有看台的游泳场,football pitch足球场,rugby pitch橄榄球场,hockey pitch 曲棍球场,cricket pitch 板球场,swimming pool 游泳池,natatorium(室内游泳池),tennis court网球场,basketball court 篮球场,squash court 壁球场,volleyball court 排球场,badminton court 羽毛球场,golf course 高尔夫球场,exercise area 运动区,ice [skating] rink 溜冰场,ping pong tables 乒乓球案奥运会 the Olympic Games 东道国 the host nation火把点燃仪式 the flame-lighting ceremony 开幕式 / 闭幕式 the opening / closing ceremony发奖仪式 the prize-awarding ceremony(田径)比赛 a competition / contest锦标赛 a championship(球类)比赛 a match / game奥运中常见比赛项目:badminton羽毛球, basketball篮球, baseball棒球, football足球, handball手球, hockey曲棍球, tennis 网球, volleyball排球, canoeing划艇, diving跳水, rowing划船, swimming游泳, synchronised swimming 同游表演, water polo水球, high jump跳高, hurdles 跳栏赛跑, the high [low] 高[低]栏赛跑, long jump跳远, Marathon马拉松长跑, pole vault撑杆跳, 20 km and 50 km road walk, triathlon三项全能运动, Floor Exercises自由体操, gymnastics体操, balance bars平衡杆, horizontal bar单杠, parallel bars双杠, rings吊环, archery箭术, boxing拳击, cycling骑自行车比赛, discus 掷铁饼, equestrian骑马, fencing剑术, javelin投枪, judo 柔道, Pommel Horse鞍马, shooting射击, shot put推铅球, taekwondo跆拳道(亦作T-K-D), weightlifting举重, wrestling摔跤, track and field athletics田径赛, 田径运动favourite 可望取胜者 (美作:favorite),outsider 无取胜希望者,championship 冠军赛,锦标赛,champion 冠军,record 纪录,record holder 纪录创造者,ace 网球赛中的一分,Olympic Games, Olympics 奥林匹克运动会,Winter Olympics 冬季奥林匹克运动会 ,stadium 运动场,track 跑道,ring 圈,ground, field 场地,pitch (足球、橄榄球)场地,court 网球场,team, side 队滑雪滑冰运动:skiing 滑雪,ski 滑雪板,滑雪橇,downhill race 速降滑雪赛,滑降,slalom 障碍滑雪,ski jumping competition 跳高滑雪比赛,ski jump 跳高滑雪,ice skating 滑冰,figure skating 花样滑冰,roller skating 滑旱冰,bobsleigh, bobsled 雪橇游泳运动:swimming pool 游泳池,changing room 更衣室,shower 淋浴,diving platform 跳台,diving pool 跳水池,non-swimmer's pool 浅水池,swimmer's pool 深水池,swimming lane 泳道,lifesaver, lifeguard 救生员,breaststroke 蛙泳,crawl stroke 爬泳,back stroke 仰泳,side stroke 侧泳,butterfly stroke 蝶泳,surfing 冲浪,surfboard 冲浪板,water ski 滑水橇自行车:cyclist 骑自行车者,bicycle, cycle, bike 自行车,cycle track 自行车赛车道,cycling 自行车赛,to ride a bicycle 骑自行车,hand signals 手势, tandem 双轮双座自行车,racing cycle 公路赛车,cycling stadium 自行车赛车场。
4关于健身的英汉互译名言有哪些1、生命在于运动。
Life is movement2、身体健康者常年轻。Good health is always young3、活动是生活的基础!Activity is the foundation of life!4、更高、更快、更强!Higher, faster, stronger!5、活动有方,五脏自和。
Well, five zang-organs and6、缓慢而有恒赢得竞赛。Slow and persistence won the competition7、从小不动,长大无用。
Grew up, useless8、我健身,所以我健康。So I am healthy, I exercise9、磨练肌胳,防病御症。
Hone muscle, preventing disease10、运动运动,病魔难碰。Exercise, the disease is difficult to touch11、人怕不动,脑怕不用。
People fear, afraid of brain12、健身不断,健康相伴。By the fitness, health13、跳绳踢毽,病少一半。
Jump rope, kick the shuttlecock, half14、运动是一切生命的源泉。Sport is the source of all life15、人是动物,不动成废物。
Man is an animal, and not move into waste16、丰收靠劳动健身靠运动。Harvest by labor fitness by movement17、如果你想聪明,跑步吧!If you want to smart, running!18、健身能长寿,不容再等候。
Fitness can live a long life, not wait19、以自然之道,养自然之身。In a natural way, nature's body20、同一个世界,同一个梦想。
One world, one dream21、多一分运动,少一分病痛。More exercise and less pain22、卫生是妙药,锻炼是金丹。
Health is a bullet, exercise are then23、科学的基础是健康的身体。Science is the foundation of a healthy body24、饭后百步走,活到九十九。
After supper walk, live to be ninety-nine25、站如松,坐如钟,走如风。Stop such as pine, such as bell, the wind26、墙靠基础坚,身强靠锻炼。
Wall on the basis of strong, body strong by exercise27、练出一身汗,小病不用看。Build a sweat, ailment without looking at28、迷雾打拳操,毒气冲七窍。
The fog QuanCao, gas and 729、体育是全社会共同的语言。Sports is the whole society's common language30、枪不擦不亮,人不练不壮。
Guns don't wipe not bright, people don't practice is not strong31、练足精气神,不进医院门。Asana vitality, not the hospital door32、生命像河流,运动防腐臭。
Life is like a river, movement against the moldy33、天天练身子,远离药铺子。Every day to practice body, away from the medicine shop34、一日舞几舞,活到九十五。
One day a few dance dance, live to be ninety-five35、天天练长跑,年老变年少。Practice running every day, old young36、运动劲出来,歇着病出来。
Sports strength, against the disease37、人胖多运动,人丑多看书!People move more fat, ugly many books!38、今日不运动,来日悔晚矣。Today don't exercise, every regret later in the future39、多做运动,强化身体机能。
Do more exercise, strengthen the body function40、早起活活腰,一天精神好。
5有哪些经典英语句子可以用来周旋客户If you insist on your price and refuse to make any concession, there will be not much point in further discussion。 如果你方坚持自己的价格,不作让步,我们没有必要再谈下去了。
9。 Let's have your counteroffer。
请还个价。 熟记还价十二句商务英语 订货交流没问题 10。
Still, I think it unwise for either of us to insist on his own price。 不过,我认为彼此都坚持自己的价格是不明智的。
11。 We think your offer is too high, which is difficult for us to accept。
我们认为你方的报价太高了,我方难以接受。 订票托运等怎么说 商务英语疯狂口语三十句 12。
Our offer is reasonable and realistic。 It comes in line with the prevailing market。
我方的报价是合理的、现实的,符合当前市场的价格水平。
6像体育运动的锻炼有益于身心健康的英语的句子Exercise has a major part to play in preventing and combating disease 体育锻炼在疾病防治方面发挥着重要作用。
Physical exercise administers to the circulation of the blood 体育锻炼有助于血液循环Exercise is conducive to good health 体育锻炼有助于增强体质体育锻Pro or con, commitment to physical exercise is valuable to your health 不管赞成还是反对, 参加体育锻炼有益于健康 Physical exercise is beneficial to health of body and mind体育运动的锻炼有益于身心健康Sports can improve the immune function, improve the body's ability to resist disease体育运动能提高机体免疫功能,提高机体抗御疾病的能力Sports can cultivate good will quality体育运动能培养良好的意志品质。
一、英语作文:
Title: A Story About Going to the Gym
Once upon a time, there was a young woman named Sarah who decided to start going to the gym She had always been interested in fitness but had never taken the leap to join a gym before Determined to improve her health and well-being, Sarah signed up for a gym membership
At first, Sarah felt overwhelmed by the array of equipment and the intense workouts happening around her However, with the help of friendly gym staff and fellow members, she gradually gained confidence and began to enjoy her gym sessions
One of the biggest challenges Sarah faced was staying motivated Some days, she felt tired and tempted to skip her workouts However, she reminded herself of her goals and the progress she had made so far Sarah found that having a workout buddy was immensely helpful in keeping her accountable and motivated
As Sarah continued her gym journey, she discovered the importance of proper form and technique The gym instructors guided her through various exercises, emphasizing the significance of posture and alignment Sarah learned that executing exercises correctly not only maximized the benefits but also minimized the risk of injury
Over time, Sarah started noticing positive changes in her physical and mental well-being She felt stronger, more energetic, and happier overall Going to the gym became a habit and a source of personal fulfillment for her
In conclusion, Sarah's story highlights the transformative power of going to the gym Despite initial challenges and moments of doubt, she persevered and reaped the rewards of her dedication Through her journey, Sarah learned the value of motivation, proper technique, and the positive impact of regular exercise on both the body and mind
二、中文翻译:
标题:关于去健身房运动的故事
从前,有一个名叫莎拉的年轻女子决定开始去健身房运动。她一直对健身很感兴趣,但以前从未加入过健身房。下定决心改善自己的健康和福祉,莎拉报名参加了健身房会员。
起初,莎拉对周围琳琅满目的器械和激烈的锻炼感到不知所措。然而,在友好的健身房员工和会员的帮助下,她逐渐建立了自信,并开始享受健身房的运动。
莎拉面临的最大挑战之一是保持积极性。有些日子,她感到疲倦,很想跳过锻炼。然而,她提醒自己她的目标和迄今为止取得的进展。莎拉发现找一个一起运动的伙伴对她来说非常有帮助,可以让她保持责任感和积极性。
随着莎拉继续她的健身之旅,她发现正确的姿势和技巧的重要性。健身房的教练指导她进行各种锻炼,强调姿势和身体对齐的重要性。莎拉学到了正确执行锻炼不仅可以最大化效果,还可以将受伤的风险降到最低。
随着时间的推移,莎拉开始注意到她的身心福祉出现了积极的变化。她感到更强壮、更有活力,整体上更快乐。去健身房成为了她的一种习惯和个人成就的源泉。
总而言之,莎拉的故事突出了去健身房运动的变革力量。尽管一开始面临挑战和犹豫不决的时刻,她坚持下来,并收获了她的付出所带来的回报。通过她的旅程,莎拉学到了积极性、正确技巧的价值,以及定期锻炼对身心健康的积极影响。
三、重要词汇:
Gym - a place equipped for various physical exercises and fitness activities
健身房:设备齐全,用于各种体育锻炼和健身活动的场所。
Membership - the state of being a member of a group or organization
会员资格:成为某个团体或组织的成员的状态。
Array - a wide range or variety of things
多样性:广泛的范围或种类。
Overwhelmed - feeling a strong emotional effect
不知所措的:感受到强烈的情感影响。
Accountability - the state of being accountable or responsible
责任感:承担责任或责任的状态。
Transformative - causing a marked change in someone or something
变革性的:引起某人或某物明显变化的。
Dedication - the quality of being dedicated or committed to a task or purpose
奉献精神:对任务或目标的专注和承诺的品质。
Technique - a particular method or way of doing something
技巧:做某事的特定方法或方式。
Fulfillment - a feeling of satisfaction or happiness as a result of one's efforts or achievements
成就感:由于个人努力或成就而产生的满足感或幸福感。
四、重要句子解释:
"She had always been interested in fitness but had never taken the leap to join a gym before"
"她一直对健身很感兴趣,但以前从未加入过健身房。"
解释:这句话表达了莎拉一直对健身感兴趣,但以前没有行动加入健身房的意愿和勇气。
"One of the biggest challenges Sarah faced was staying motivated"
"莎拉面临的最大挑战之一是保持积极性。"
解释:这句话指出莎拉在坚持锻炼中最大的困难是保持积极性和动力。
"Sarah found that having a workout buddy was immensely helpful in keeping her accountable and motivated"
"莎拉发现找一个一起运动的伙伴对她来说非常有帮助,可以让她保持责任感和积极性。"
解释:这句话说明莎拉发现与一个一起锻炼的伙伴相伴可以极大地帮助她保持责任感和积极性。
"She felt stronger, more energetic, and happier overall"
"她感到更强壮、更有活力,整体上更快乐。"
解释:这句话描述了莎拉在锻炼后身心的积极变化,包括更强壮、更有活力和整体上更快乐的感觉。
你的文献篇幅浩瀚,百度只允许上传这么长,余下部分到我的贴吧去拷贝吧!明天见!
利用超声技术改性的氨基多孔硅合成丙二醇甲醚
摘要
在温和条件下采用超声技术合成了氨基改性多孔硅。用BET、29Si核磁共振谱、元素分析和指示剂染料吸附等方法表征的样品在用甲醇和环氧丙烷合成丙二醇甲醚的反应中呈现出令人鼓舞的催化特性。 它们在反应中有高的产率和循环使用性,表明超声技术在有机改性硅催化剂的制备方面是有效的。而且我们还推测了用此类催化剂合成丙二醇甲醚的可能的反应机理。
关键词:改性多孔硅; 超声技术;环氧丙烷;甲醇;丙二醇甲醚。
前言
对均相催化剂的异质化的努力来代替传统试剂和催化剂已经成为一个兴趣越来越浓厚的研究领域。大量的工作集中在有机改性的固体碱的制备方面来异质化均相氨基催化剂。改性的过程一般是振荡、加热、回流等[1–3]。 最近,声化学合成反应的兴趣有所增加[4]。超声技术因其优点例如高精度和快度已被广泛用于两相反应体系中。多数此类反应涉及非均相化学反应[5]。 然而在多孔材料的有机功能化领域,超声技术仅得到有限的应用 [6,7]。当前工作中,我们用超声能开发了一个合成氨基改性硅的替代合成路线,超声能可以产生空化现象从而对固体进行化学改性[8]。带有‘‘单一碱基位点’’的氨基改性硅是各种反应中令人鼓舞的催化剂[9]。利用碱性催化剂合成丙二醇醚类是重要的有机合成反应。 已经有过几个关于丙二醇甲醚合成方法的报道[10,11]。其中环氧丙烷法最方便、最适合工业应用。一般来说,环氧丙烷通过酸性或碱性催化剂和脂肪醇反应。这个过程中使用的催化剂包括早期的均相酸催化剂或均相碱催化剂(氢氧化钠、乙醇钠和三氟化硼)以及后来的固体酸催化剂和碱催化剂。 然而,很少有报道氨基改性硅用作丙二醇甲醚合成的催化剂,尽管有机固体碱性催化剂 在该反应中表现出良好的活性。氨基官能团接枝到多孔支持体上会形成带有单一碱性位点的催化剂,可以加速这类反应。当前的工作中,氨基官能团化的硅催化剂,包括NH2/SiO2、NH(CH2)2NH2/SiO2、TAPM/SiO2(化合物翻译略)和TBD/SiO2(化合物翻译略),用APTMS、EDPTMS和CPTMS作为偶联剂在温和的实验条件下用超声技术制备。同时,为了证实超声技术的优点,我们也用传统方法制备了NH2/SiO2,以便理解超声技术在官能团改性的多孔硅的制备中的有效性。此外,有机固体碱催化剂的催化活性用甲醇+环氧丙烷=丙二醇甲醚这样的合成反应来估计。并且,我们还推测了在此类催化剂上合成丙二醇甲醚可能的反应机理。
2 实验
21 催化材料的合成
氨基化硅催化剂可用以前报道的在相似的条件下用两种方法获得 [7]。氨基丙基硅官能团化的SiO2用下述方法制备:100 g 二氧化硅在473 K下真空预热12 h除去除表面OH-官能团之外的所有吸附的水分,然后在真空下冷却到室温并转移到250 mL圆底烧瓶中。和400 mL 环己烷及50 mL APTMS混合后,圆底烧瓶中的混合物放入超声浴中在室温下保持2 h (日本Sheshin公司制造,操作功率60 W)。然后在索氏提取器中用甲苯提取24 h并在333 K温度下真空干燥获得催化剂。NH(CH2)2NH2/SiO2制备采用同样的方法。
TBD/SiO2用两步法制备:采用和氨基丙基硅官能团化的SiO2相同的改性方法,首先用3-氯丙基三甲氧基硅烷对硅改性,然后3-氯丙基三甲氧基硅烷改性的SiO2和 TBD (10 g)在环己烷 (400 mL)中反应。反应产物超声震动1 h。之后,在索氏提取器中用甲苯提取24 h并在333 K温度下真空干燥获得催化剂。TAPM/SiO2制备采用同样的方法。
22 表征
所有样品中碳、氮和氢的含量使用Vario EL元素分析仪测定。特异性表面积、总孔容和平均孔径用N2吸附-解吸法在Micromeritics ASAP-2000孔隙表面积测定仪(Norcross,GA)上测定。表面积用BET法计算,孔径大小分布用BJH孔径分析法和其他孔径的氮吸附-解吸进行比较获得。用Bruker MSL-400光谱仪记录29Si核磁共振谱。样品的碱基堆积力用 hammett指示剂检测。
23 催化性能测试
催化性能在75 ml批量反应容器中测定,使用的反应物甲醇和环氧丙烷的物质的量之比为5:1。在403 K的温度下磁力搅拌反应10 h后, 反应器冷却到室温。反应产物经过滤并用离心法和催化剂分离后,用配置氢焰离子化检测器的气相色谱进行分析。催化剂用溶剂洗涤后用于回收率测试。
3 结果与讨论
31 多孔硅的氨基官能团改性
带游离氨基的多孔硅和所有改性样品中碳、氮和氢的百分含量用元素分析测定(表1)。结果表明,带游离氨基的多孔硅中不含碳、氮。改性材料中的碳、氮来自有机硅。元素分析表明,用文献描述的传统方法[12]制备的接枝有机官能团的有机官能团含量是113 mmol/g,远低于超声技术制备的样品中的含量(2 00 mmol/g) (表1)。这应归功于超声能对固体和液体的作用,因为超声能够提供一些物化性质的变化,包括空化(液体中形成小泡)和化学反应 (化学反应的加速)等[13]。结果是,粒子大小改性、新制备催化剂的表面净化 [14,15] 这些过程可以通过在固液界面上引入非均相介质来完成。对于多孔硅的有机改性,超声引起的空化现象能加速液体在多孔材料和液固界面的小孔中的传递速率。结果是,液体有机硅烷类可以和多孔硅内壁上的硅醇官能团良好接触并短时间内与它们反应,而振荡不能达到这种效果。因此,用超声完成催化剂的改性过程简单、快捷。固体催化剂的29Si核磁共振谱分析表明硅烷基化试剂和硅表面上的硅醇官能团之间形成共价键(图1)。109和99 ppm两个共振频段可分别使29Si原子核带上4个Si–O–Si连接(Q4)及3个Si–O–Si连接和一个羟基(Q3) [16]。58和67 ppm两个共振频段分别对RSi(OSi)(OH)2和RSi(OSi)3的形成起作用 [17],这表明用有机官能团通过共价键连接可成功地使多孔硅有机官能团化。C/N价(分子比)也能反映硅醇官能团和有机硅烷之间的接枝反应进行的程度[18]。NH2/SiO2、NH(CH2)2NH2/SiO2和 TBD/SiO2的C/N价分别是3–35、25–30 和33–36。 The results also suggested the anchorage of 氨基官能团 by Si–O–Si 键。这和29Si核磁共振的结果是一致的。
32催化剂样品的结构和碱度
图2是其他样品和供试样品N2吸收比较图。在毛细管吸附作用下,呈现典型IV型的官能团化催化剂样品比其他催化剂样品有清晰的滞后回线。这表明用不同有机硅烷对材料进行官能团化和改性的前后这些材料保留了多孔结构。BET 表面积和孔溶剂随着接枝有机官能团的百分比的增加逐渐下降(表2)。这可能是由于官能团的存在。接枝到微孔硅上的部分氨基官能团也能导致BET表面积的缩小。有机官能团对NH2/SiO2和NH(CH2)2NH2/SiO2的孔径的影响很弱。但对于TBD/SiO2和TAPM/ SiO2,或许是由于(CH2)3/TAPM和(CH2)3/TBD官能团具有大的分子骨架,催化剂样品的平均孔径分别减小到 790 和882 nm。然而平均孔径由于样品具有较低的有机物百分含量而并未严重下降。固体表面的碱度定义为样品表面把它吸附的电中性的酸转化成其共轭碱的活性。当一种电中性的酸指示剂吸附在非极性溶液中的固体碱上时,颜色变成了其共轭碱的颜色,表明固体有足够的碱度把电子对转移到酸上[19]。 带有大量阳性HH的固体具有强大的碱性位点。与不同官能团接枝键合可形成不同碱度。如表3所示,TBD/SiO2碱性最高(PH值= 150),而NH2/SiO2和NH(CH2)2NH2/SiO2 的碱性较低,PH值分别是93和93-150之间。和其他改性样品相比,TAPM/SiO2碱性最弱,PH值< 72。 因此,样品的碱性强度顺序是: TBD/SiO2 > NH(CH2)2NH2/SiO2 > NH2/SiO2 > TAPM/SiO2。
33 催化性能
用甲醇和环氧丙烷合成丙二醇甲醚来测试催化活性(表3)。如表 3所示,不使用催化剂时PO转化率和异构体选择性 (1-甲氧基-2-丙醇和丙二醇甲醚总量之比)分别达到 273 和723%。 在使用的催化剂中,带有游离氨基的多孔硅因其表面硅醇官能团的弱酸性而表现出较低的催化活性。对于锚定的氨基官能团,NH(CH2)2NH2/SiO2和NH2/SiO2 的对于反应10 h后1-甲氧基-2-丙醇的催化合成活性和选择性比其他催化剂要强。TAPM/SiO2做催化剂时环氧丙烷转化率较低(890%),异构体选择性是666%。 TBD/SiO2、NH(CH2)2NH2/SiO2和NH2/SiO2做时环氧丙烷转化率很高(>94%),但其异构体选择性不同。带有弱碱性的NH(CH2)2NH2/SiO2 和NH2/SiO2异构体选择性更高(>82%),而中等碱性的TBD/SiO2异构体选择性较低(737%)。 对于固体碱性催化剂, 中等碱性的催化剂理论上应当具有良好的异构体选择性 [20]。TBD/SiO2的异构体选择性较低可能是由于TBD 具有大的分子骨架结构。催化剂可用过滤法很容易地回收并再利用,利用7次后环氧丙烷的转化率仍然在89%以上,而且在403 K的温度下多次循环利用后异构体选择性还能保持不变(表 4),表明接枝到硅表面的氨基官能团在实验条件下是稳定的。其他样品的可重复利用性和NH2/SiO2相似。
34 可能的反应机理
无机固相催化剂已被广泛用于甲醇+环氧丙烷=丙二醇甲醚的合成中[31],该反应中甲氧基离子和质子分别吸附在催化剂表面酸性位点和碱性位点上,然后甲氧基离子进攻C(1)位点。然而在目前情况下,用于该反应的催化剂特征是仅有一个反应位点,例如,带有和均相碱性催化剂相似的独有的碱性反应位点。由于催化剂上不存在路易斯酸位点,反应机理应当不同于那些双官能团的催化剂。1-甲氧基-2-丙醇在NH2/SiO2上合成的推测机理见线图1。第一步在甲醇和氨基官能团之间形成H-键。在第二步中,由于PO上CH3-官能团的空间位阻效应,甲醇上的O原子进攻C(1) 位点 ,质子吸附在催化剂的碱性位点上,然后C(1)–O键断裂夺取质子形成 1-甲氧基-2-丙醇。似乎可以合理地认为,NH(CH2)2NH2/SiO2、NH2/SiO2和TBD/SiO2具有更高催化活性是由于其适中的碱度,不仅能形成H-键而且也能很容易断裂H-键。带有弱碱性的TAPM/SiO2 仅能形成更多不稳定的H-键。 因此,TAPM/SiO2的活性低于其他样品。 如果这个机理是合理的,那么有机官能团的大骨架分子结构能够影响甲醇中O原子的进攻位点。 结果造成了大分子骨架的TBD异构体选择性较低。因此,具有合适碱度和简单分子骨架的有机官能团对于1-甲氧基-2-丙醇的高转化率和良好的选择性是非常重要的。
4 结论
上述结果可得出下列结论:
(1) 高效的超声技术能成功地制备氨基官能化的多孔硅催化剂;
(2) 表征结果表明,氨基官能团以共价键的形式接枝到硅表面;
(3) 合适碱度和简单分子骨架的有机官能团对于1-甲氧基-2-丙醇的高转化率和良好的选择性是非常重要的;
(4)催化剂可以通过过滤回收并循环利用而保持恒定的活性。
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