No abstract

Currently available procedures for determination of total nitrogen in petroleum distillates were found unsatisfactory when the nitrogen content was below 0.01% (100 p.p.m.). A high pressure catalytic hydrogenation process for determining total nitrogen in petroleum distillates in the range of 1 to 100 p.p.m. consists essentially of quantitatively reducing organic nitrogen to ammonia by high pressure hydrogenation in an autoclave with a nickel catalyst and absorbing the resulting ammonia on acidic alumina which is in admixture with the catalyst proper. The absorbed ammonia is determined by a conventional Kjeldahl distillation of the catalyst mixture. Interference due to sulfur is eliminated by proper choice of sample size. Data are presented on synthetic samples containing the types of nitrogen compounds found in petroleum as well as results on a variety of light petroleum distillates, both virgin and cracked.ICCEXT publications on the Kjeldahl (4, 6) and the ter R Rleulen (3) procedures for the determination of total nitrogen in petroleum distillates have demonstrated the utility of these methods for nitrogen in the range upwards of 0.01% (100 p.p.m,). Howevei, attempts in this laboratory to use the Kjeldah1 method on naphthas containing less than 0.01 7 0 nitrogen failed, largely because the amount of sample which can be digested is small, with the consequence that the ammonia blank for the reagents usually exceeded that recovered from the sample. The ter Meulen method q-as not tried in this laboratory, but the recent work of Holov-chak, Wear, and Baldeschwieler ( 3 ) showed that the lower limit of detection was 100 p.p.m.. with a possibility that refinement of technique would enable detection of 10 p.p.m.The procedure sought was one which would enable detection of nitrogen in the range of 1 to 100 p.p.m. present in petroleum distillate fractions. The low nitrogen concentration dictated that the reagent blank be negligible, and that a large sample, up to 1 liter, be used to give a convenient and accurate analysis. These requirements seemed to be fulfilled by a catalytic hydrogenation technique in which the organic nitrogen is quantitatively converted to ammoniaThe first efllort5 along these lines were with a high pressure bench scale hydrogenation apparatus in which the naphtha was pumped, along with hydrogen, over a suitable catalyst bed. These preliminai y results showed considerable promise for the use of UOP nickel-kieselguhr catalyst for the quantitative reduction of organic nitrogen to ammonia, but the technique had to tie abandoned for several practical reasons-it was difficult to recovei all the ammonia and the practical aspect of repeated heating and cooling of the reactor vewel, changing of catalyst, etc., made it very difficult to maintain a leak-free system. Although it vas ahandoned, this v-oik led to the idea that ammonia might be iecovered by using an acidic solid in admixture with the hydrogenation catalyst. The batch-type reaction run in an autoclave proved to be a successful technique for low n...

No abstract