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自从沸石分子筛问世以来,由于其独特的结构,在气体和液体的分离、净化、干燥、环保等方面取得了广泛的应用。特别是由于分子筛的微孔中存在着强大的吸附力场,使其在真空情况下,对气体仍具有较大的吸附量,已在低温吸附泵中得到广泛的应用。近年来在各种电真空器件的应用中,亦取得明显的效果,日益受到重视。六十年代中期,已有学者对分子筛在低压下对空气及其主要成份如N_2,O_2、Ar等非极性分子的吸附性能进行了研究。首先测定了在1×10~(-2)～5000帕压强下,在液氮温度时,A、X型分子筛对N_2、Ar等的吸附等温线。结果表明5A、13X分子筛有明显的吸附能力,并且对N_2的吸附能力显著大于Ar。等测定了在1×10~(-3)～10帕的压强下,液氮温度时,A、X型分子筛对空气的吸附等温线也有类似的结果。本文提供了能在1.0×10(-2)～1.0×10~(-5)帕高真空范围内测量分子筛的吸附量和吸附速率的实验方法。这就是真空定容法和高真空定压法,分别测定吸附量和吸附速率。这两个方法比较合理地解决了国产分子筛的吸气速率的测试。本文比较了5A,13X,M型和ZSM—5型四种分子筛在不同平衡压强下对氮气的吸附量,发现5A,13X在1.33×10~(-3)～1.33×10~(-2)帕范围内吸附量较大,但在1.33×10~(-4)～1.33×10~(-3)帕范围内不理想,不能将它用在真空器件中。而把这几种分子筛用离子交换法进行改性后,M型分子筛交换Ca~(++)离子后,在1.33×10~(-4)～1.33×10~(-2)帕范围内吸附量明显上升,在1.33×10~(-3)～1.33×10~(-2)帕范围内吸附量也和13X差不多。而且测量出交换了Ca~(++)离子的M型分子筛在较高真空度时对空气吸附速率大于13X。离子交换法是分子筛改性的好方法,它能提高分子筛的吸附量和吸附速率。M型分子筛是一种较新型的分子筛,进行改性后在高真空状况下吸附量和吸速率又较大,因此它是一种理想的吸气剂。我们将这种M型分子筛加入适当的粘结剂在国内红外探测器的真空元件中得到了应用,使该器件真空度提高2—3个数量级,寿命也明显增加。本文也比较了加入适量的粘结剂分子筛的吸附量和吸附速率的影响,与其他吸气剂一样,吸气量和吸气速率略有降低。
Since the advent of zeolite, its unique structure has been widely used in the separation of gases and liquids, purification, drying and environmental protection. In particular, due to the presence of a strong adsorptive force field in the pores of the molecular sieve, it still has a larger adsorption capacity for gases under vacuum, and has been widely used in low-temperature adsorption pumps. In recent years in a variety of electrical vacuum device applications, but also achieved significant results, more and more attention. In the mid-1960s, some scholars studied the adsorption of zeolite under low pressure on non-polar molecules such as N 2 O 2 and Ar in air and its main components. First, the adsorption isotherms of A, X molecular sieves for N 2, Ar and the like at a pressure of 1 × 10 -2 to 5 000 Pa at liquid nitrogen temperature were measured. The results show that 5A, 13X zeolite has obvious adsorption capacity, and adsorption capacity of N_2 is significantly greater than Ar. The results showed that the adsorption isotherms of A and X zeolites to air were similar under the pressure of 1 × 10 ~ (-3) ~ 10 Pa and liquid nitrogen temperature. This article provides experimental methods for measuring the adsorption capacity and adsorption rate of zeolites in the high vacuum range of 1.0 × 10 -2 to 1.0 × 10 -5 Pa. This is the vacuum volume method and high vacuum pressure method, were measured adsorption and adsorption rate. These two methods more reasonable solution to the domestic molecular sieve breathing rate test. In this paper, the adsorption capacities of four zeolites 5A, 13X, M and ZSM-5 at different equilibrium pressures were compared. It was found that the adsorption capacities of 5A, 13X at 1.33 × 10 -3 -3.3 × 10 -2, The adsorption capacity in the range of PAS is large, but it is not ideal in the range of 1.33 × 10 -4 to 1.33 × 10 -3 Pa. It can not be used in vacuum devices. After these molecular sieves were modified by ion exchange method, M type molecular sieve exchanged Ca ~ (++) ions and adsorbed in the range of 1.33 × 10 ~ (-4) ~ 1.33 × 10 ~ (-2) Pa The amount of adsorption increased obviously in the range of 1.33 × 10 -3 ~ 1.33 × 10 -2 Pa. Moreover, it was also measured that the M-type molecular sieve exchanged with Ca ~ (++) ion has an air adsorption rate greater than 13X at a higher degree of vacuum. Ion exchange method is a good method of molecular sieve modification, it can increase the molecular sieve adsorption and adsorption rate. M-type molecular sieve is a relatively new type of molecular sieve, after modification in the high vacuum adsorption capacity and absorption rate and larger, so it is an ideal getter. We will M type molecular sieve with a suitable binder in the domestic infrared detector vacuum components has been applied to the device to increase the degree of vacuum 2-3 orders of magnitude, life expectancy also increased significantly. In this paper, we also compare the adsorption capacity and adsorption rate of the zeolite with the proper amount of binder. Compared with other getters, the inspiratory capacity and inspiratory rate slightly decrease.