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影响天然气（甲烷）蒸汽转化反应速度的主要因素有哪些？

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参考答案：

主要有以下几个方面：

没有催化剂存在时，即使在相当高的温度下，甲烷蒸汽转化反应速度也很缓慢。当有催化剂存在时，能大大加快反应速度，在600-800℃就可获得很高的反应速度；

反应温度愈高，转化反应速度愈快；

氢气对反应有阻碍作用，因此反应初期速度快，随着反应的进行，氢含量增加，反应速度就会逐渐下降；

反应物由催化剂外表面，通过毛细孔扩散到内表面的内扩散过程，对甲烷蒸汽转化反应速度有明显的影响，因此采用粒度较小的催化剂，减少内扩散影响，能加快反应速度。

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The first two stages in the development of civilized man were probably the invention of primitive weapons and the discovery of fire, although nobody knows exactly when he acquired the use of the latter.
41) ______ Animals have a few cries that serve as signals, but even the highest apes have not been found able to pronounce words, even with the most intensive professional instruction. The superior brain of man is apparently a necessity for the mastering of speech. When man became sufficiently intelligent, we must suppose that he gradually increased the number of cries for different purposes. It was a great day when he discovered that speech could be used for narrative. There are those who think that in this respect picture language preceded oral language. A man could draw a picture on the wall of his cave to show in which direction he had gone, or what prey he hoped to catch. 42) ______
Two important stages came not so long before the dawn of written history. The first was the domestication of animals; the second was agriculture. Agriculture made possible an immense increase in the number of the human species in the regions where it could be successfully practiced. 43) ______
44) ______
These inventions and discoveries--fire, speech, weapons domestic animals, agriculture, and writing--made the existence of civilized communities possible. From about 3000 B. C. until the beginning of the Industrial Revolution less than two hundred years ago there was no technical advance comparable to these. During this long period man had time to become accustomed to his technique, and to develop the beliefs and political organizations appropriate to it. There was, of course, an immense extension in the area of civilized life. At first it had been confined to the Nile, the Euphrates, the Tigris, and the Indus, but at the end of the period in question it covered much the greatest part of the inhabitable globe. I do not mean to suggest that there was no technical progress during the time. 45) ______ (512 words)
Notes: ape 猿。pastoral nomad 田园式的游牧部落的人。the Euphrates 幼发拉底河。the Tigris底格里斯河。the Indus 印度河。in question 所谈的(在名词后作后置定语)。
[A] Probably picture language and. oral language developed side by side. I am inclined to think that language has been the most important single factor in the development of man.
[B] Another fundamental technical advance was writing, which, like spoken language, developed out of pictures, but as soon as it had reached a certain stage, it was possible to keep records and transmit information to people who were not present when the information was given.
[C] With the development of civilization, primitive people who lived in caves at that time badly needed a language, which would help them to communicate with one another.
[D] The origin of language is also obscure. No doubt it began very gradually.
[E] In fact, there was progress--there were even two inventions of very great importance, namely, gunpowder and the mariner’s compass--but neither of these can be compared in their revolutionary power to such things as speech and writing and agriculture.
[F] These were, at first, only those in which nature fertilized the soil after each harvest. Agriculture met with violent resistance from the pastoral nomads, but the agricultural way of life prevailed in the end because of the physical comforts it provided.
[G] But industry was a step in human progress to which subsequently there was nothing comparable until our own machine age.
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