tall a closed reactor operating at 10 atm would require a reactor volume roughly 140 cm 55 u2033 wide and 140 cm 55 u2033 tall would have almost 25 times the heated inner surface area and much more expensive construction pd membranes are extensively used for hydrogen separation in the petrochemical industry the following are a few arguments against the use of a pd membrane in hvpe and the counter arguments for its potential feasibility first the manufacturers of pd membranes johnson matthey for example caution against their use at temperatures higher than about 500 u00b0 c to avoid reactions between the pd and the underlying support material they also caution against their use in environments that contain chlorine since the pd membrane may be ruined by the formation of palladium chloride pdcl 2 hvpe reactors typically run at temperatures as high as 1050 u00b0 c and contain chlorides the pd cl phase diagram bell w e merten u tagami m j phys chem 65 1961 510 indicates that pdcl 2 is readily formed at the reactor temperatures common in the petrochemical industry i e 300 500 u00b0 c it also indicates that this compound is known to begin decomposing into pd and cl 2 at 738 u00b0 c and at temperatures above 980 u00b0 c there exists only pd metal and cl 2 gas thus a pd membrane that is exposed to chlorine only at temperatures higher than 738 u00b0 c would not react with it the presence of hcl in the reactor may also be considered but hcl ceases to be adsorbed on.