Process denitrogenation

A two phase process, in which the feedstock (e.g., petroleum) was mixed with water and an organic solvent to improve denitrogenation of aromatic nitrogen compounds [102], led to an improvement of the process. Additionally, a surfactant was used to increase the interfacial area. Carbazole and quinoline and their alkyl derivatives were used as primary compounds for demonstration. The biocatalyst is used in resting stage and is continuously fed to the system to keep the reaction rate at an acceptable level. It was observed that quinoline was hardly removed under the conditions at which carbazole was decomposed and assimilated. 

The major goal of hydroconversion is the cracking of residua with desulfurization, metal removal, denitrogenation, and asphaltene conversion. The residuum hydroconversion process offers production of kerosene and gas oil, and production of feedstocks for hydrocracking, fluid catalytic cracking, and petrochemical applications. 

In the process (Figure 9-37), the residue feed is slurried with a small amount of finely powdered additive and mixed with hydrogen and recycle gas prior to preheating. The feed mixture is routed to the liquid phase reactors. The reactors are operated in an up-flow mode and arranged in series. In a once through operation conversion rates of >95% are achieved. Typically the reaction takes place at temperatures between 440 and 480°C and pressures between 150 and 250 bar. Substantial conversion of asphaltenes, desulfurization and denitrogenation takes place at high levels of residue conversion. Temperature is controlled by a recycle gas quench system. 

However, several assumptions are inherent in this interpretation of the data. First, it is assumed that the change in the observed effect (such as conversion of 850°F+, percentage denitrogenation, etc.) is linear with respect to time. Thus a linear delta-effect per period of time could be established and intermediate data could be adjusted to a MfreshM activity corresponding to that observed at the reference period and at any desired temperature. Second, it is assumed that the intermediate process parameter variations had no adverse effect on the catalyst deactivation function. For example, operation at constant temperature for a given interval of time would produce the same catalyst deactivation as varying temperatures (within limits) over the same interval of time. 

These results are not meant to suggest that the percentage denitrogenation for the overall TSL process will necessarily be the same as obtained in the LC-Finer. 

Thermal Baseline Study. PDU Run 2LCF-21 (Thermal Baseline) processed a 70/30 volume percent SRC-I/500°F IBP KC-Oil feed blend over an inert 1/32 inch Shell catalyst support. The inert support was the extrudate base for the modified Shell 324 catalyst and had been calcined at 1100-1150°C. The purpose of this run was to determine the extent of conversion and denitrogenation in the absence of an active catalyst ingredient - nickel and molybdenum (Ni/Mo). 

Short contact time coal extracts show a greater percentage denitrogenation in the total liquid product than SRC-I coal extract when processed by LC-Fining. Also, short contact time coal extracts show a lower C1-C4 gas yield. 

HDN of oils obtained from the solvent process (0.97 wt% N) and COED (1.73wt% N) has been investigated on CoMo/A1203 catalyst by Ahmed and Crynes 20 the COED oil is more difficult to denitrogenate than the other oils (nitrogen in products respectively 0.39 and 0.66%). 

The heavy gas oils were processed at 1300 psig, 3000 SCF H2/bbl, 1 LHSV, and at temperatures of 625°, 675°, and 725°F. Desulfurization eflBciency of the coal heavy distillate was greater than that for the petroleum. Results show that at 725°F the coal heavy distillate was 91% desulfurized, the petroleum fraction was 83% at 725°F, and the shale heavy distillate analyzed at 61% sulfur removal. Here again, the nitrogen compounds proved very diflBcult to remove. At 725°F the petroleum fraction underwent 69% nitrogen removal, the shale cut revealed a 56% denitrogenation, and the coal heavy distillate exhibited 17% introgen removal. 

Over the last 15 years, the homogeneous studies of HDS and HDN processes have been extremely useful to understand many mechanistic details regarding the coordination of sulfur and nitrogen heterocycles to metal centers, hydrogen transfer from metal to coordinated heterocycle, metal insertion into C-S and C-N bonds, and the desulfurization/denitrogenation paths. Recently, however, there has been a qualitative leap in molecular catalysis so that crossing the border-... 

Ishihara, A., Wang, D.H., Dumeignil, F., Amano, H., Qian, E.W.H., and Kabe, T. Oxidative desulfurization and denitrogenation of a light gas oil using an oxidation/adsorption continuous flow process. Applied Catalysis. A, General, 2005, 279, 279. 

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