Isobutane production

Isobutane Production. The importance of isobutane domestically prompted experimentation aimed at maximizing the isobutane yield. Indications had been obtained from Figures 2 and 3 and discussed previously that as the catalyst aged, isobutane yields increased (at the expense of propane). It appeared likely that processing at less severe conditions would be beneficial towards increasing isobutane yields. 

Fig. 2. Turnover frequencies for isobutane production of 723 K and 0.0033 atm isobutylene pressure (a) and 0.13 atm hydrogen pressure (b) for reaction catalyzed by Pt/Sn/Si02 (O), Pt/Sn/K/Si02 ( ), and Pt/Sn/K-L (O). Adapted from (40). Solid lines represent the fit for each set of data using the Horiuti-Polanyi mechanism.

The distillate product from the DIB is the isobutane product. It has a specification of 2 mol % iC4. Since the fresh feed contains some propane, there is also some propane in the distillate product. All of the propane in the feed leaves the process in the distillate stream. 

Step 1. In this process we want to achieve the desired production rate and control the impurity of normal butane in the isobutane product at 2 mol %. Reactor pressure cannot exceed the design operating pressure... 

Step 5. The final isobutane product is the distillate from the DIB column, and we want to keep the composition of the nC4 impurity at 2 mol %. Nothing can be done about the propane impurity. Whatever propane is in the fresh feed must leave in the product stream. Because the separation involves two isomers, the temperature profile is flat in the DIB column. Use of an overhead composition analyzer is necessary. 

This study is on the development of high-purity isobutane production from isobutane-enriched stream by gaseous adsorption technology. Isobutane purification from Ci mixture, in which not only isobutane, but also n-butane and several kinds of Ct olefins in small or in trace are involved, is very difficult by a traditional distillation method because of their close relative volatilities between constituting components. The continuous layered 3-bed process in which was comprised of six steps as follows pressurization-1 by the cocurrent effluent gas from the other bed, pressurization-2 by isobutane (noduct, adsorption, cocurrent depressurization, countercurrent blowdown, and low pressure purge by isobutane product, was applied. From the experiment, isobutane product with over 99.9% purity and with the trace levels of olefin components could be obtained at ambient temperature. Silver impregnated cliq prefers to CMS for the removal of Ci olefins... 

From the process experiment, isobutane product with over 99.9% purity can be continuously obtained with the trace levels of olefin components. Silver impregnated clay prefers to CMS in viewpoint of product purity and productivity. 

Figure 1. Reaction scheme of the acid-catalyzed two-step condensation of phenol with formaldehyde (a) and isobutanal (b), and dehydration and cyclization of the primary phenol/isobutanal product (c).

Now suppose the refinery crude unit that contributes feed to the butane splitter suddenly increases the propane content of its butane product. Assume this change raises the propane content in the splitter s feed by 20%. If the tower top temperature is maintained at 140°F, the isobutane product composition would be 13% propane, 66% isobutane, and 21% normal butane. 

In effect, the light nonkey component propane is pulling the heavy key, normal butane, up the tower. After all, the distillate product must be at its dew point when it leaves the tower as a vapor. The normal butane content of the isobutane product will now considerably exceed the 10% specification. 

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