GB723114A - Improvements in or relating to a method of producing diphenyl and homologues thereof - Google Patents

Abstract

<PICT:0723114/IV (b)/1> Diphenyl and its homologues are produced by passing a monocyclic aryl hydrocarbon through a tubular reactor heated substantially throughout its entire length to a temperature which is constant and lies within the limits of 773 DEG and 1073 DEG K. thereby converting from 1-30 per cent by weight of said hydrocarbon in a sojourn time of from 0.56-100 seconds. The reaction temperature and sojourn time are correlated in accordance with the equation <FORM:0723114/IV (b)/1> <FORM:0723114/IV (b)/2> where k is the reaction velocity constant, t is the sojourn time, a is the initial concentration of the hydrocarbon, x is the amount decomposing in time t, A has values of 4x108 and 1.1x109 when E has values of 45738 and 49006 cal./mol. DEG K. respectively, e is the base of the natural logarithms, R is the gas constant having the value 1.986, and K is the absolute temperature. It is also desirable to correlate the diameter of the reactor tube (d), the vapour velocity (u), the vapour density (p), and the vapour viscosity (U), so that the Reynolds' number (d.u.p/U) is from 600-100,000, particularly 3000-70,000. By recycling unreacted benzene, an overall conversion to diphenyl of about 93 per cent is obtained with 5 per cent conversion per pass or about 65 per cent with 30 per cent conversion per pass. The pressure may range from 0-100, preferably 0-40, p.s.i.g. A graph is given wherein conversion is plotted against sojourn time at different temperatures. Time and temperature having been selected, the conversion (x) is read off when the value of k can be determined from the above equation. The activation energy E is determined from the equation <FORM:0723114/IV (b)/3> and hence the values of A. Apparatus may comprise coiled preheater tube 1, heated from power lines 12, 15 connected to copper plates 11, 14, and connected to exit tube 13 from which samples of product can be collected via line 20. Tube 13 is connected to reactor tube 24 surrounded by alundum pipe 26 wrapped in nichrome heater ribbon. Tube 24 terminates in straight section 32 connected to exit pipe 33. Thermocouples 7, 29, 34, 35 are provided. Product vapours pass to condensers 42, 43, 44. Tubes 1, 24 may be of nickel steel, mild steel, iron, copper or copper-manganese alloys. Promoters such as acetone may be present during the pyrolysis. In addition to benzene, toluene, xylene, ethylbenzene, propylbenzene, and their mixtures may be pyrolyzed.