问题 问答题 简答题

丙烯低压氢甲酰化法生产丁辛醇的工艺有什么优缺点?

答案

参考答案:

主要优点如下:

(1)由于低压法反应条件缓和,不需要特殊高压设备,也不需要特殊材质,耗电少,操作容易控制,工作人员少,操作和维修费用少。

(2)副反应少,正/异醛比率高达12~15:1,高沸点产物少,而且没有醇生成,产品收率高,原料消耗少。

(3)催化剂容易分离,利用率高,损失少,虽然铑比较昂贵,但仍能在工业上大规模使用。

(4)污染排放物非常少,接近无公害工艺。

低压法的主要不足是:作为催化剂的铑资源稀少,价格十分昂贵。此外,配位体三苯基膦有毒性,对人体有一定的危害性,使用时要注意安全。

单项选择题

Passage Three

If you had asked me then if I would accept a job as a restaurant critic for The New York Times, or any established publication, I would have replied, without a second thought, "Of course not!" And not just because I did not want to think of myself as an ambitious sort. Working in restaurants was honest labor; anyone could see that. Writing about them for the mainstream press was not; it felt like joining the enemy.

But reviewing was fun, so much fun that when mainstream publishers started paying me for my opinions, I didn’t do the decent thing. Before I knew it, I had stopped cooking professionally. Then I stopped cooking altogether. "She’s joined the leisure class," my friends said.

I disarmed my critics by inviting them along; nobody I knew could afford to eat out and nobody refuseD. We went with equal amounts of guilt and pleasure, with a feeling that we were trespassing on the playgrounds of the rich.

We didn’t belong in those starchy restaurants. We always got the worst table. And then, because I didn’t own a credit card, I had to pay in cash. The year turned into two, and three, and more. I got a credit carD. I got good clothes. I was writing for increasingly prestigious publications. Meanwhile, a voice inside me kept whispering, "How could you"

When I receive weekly letters from people who think it is indecent to write about $100 meals while half the world is hungry, the voice yacks right along. "They’re absolutely right," it whispers. And when it asks, "When are you going to grow up and get a real job" it sounds a lot like my mother.

And just about then is when I tell the voice to shut up. Because when my mother starts telling me that all I’m doing with my life is telling rich people where to eat, I realize how much the world has changed.

Yes, there are still restaurants where rich people go to remind themselves that they are different from you and me. But there are fewer and fewer of them. As American food has come of age, American restaurants have changeD. Going out to eat used to be like going to the opera; today, it is more like going the movies.

The word "decent" in "doing the decent thing" in paragraph 2 is closest in meaning to ().

A.very profitable

B.morally acceptable

C.fairly attractive

D.very pleasant

判断题