Improvement of Heavy Vacuum Gas Oil Quality via Bio and Hydrotreatment

Abstract

A primary role of hydrotreating processes is to improve the quality of the oil feedstock by removing impurities. The hydrotreating experiments were conducted on autoclave reactor at various operating conditions of Temperature (325-375) oC, pressure (20- 60) bar, time (2-6) h and cat/oil ratio of 1:75, 33 and 10. The performance of CoMoS/CNT catalysts was studied and compared with γ-Al2O3 Supported catalyst and experiments were carried out in a batch reactor. Bioremediation is recognized as an efficient, economic, and versatile alternative to physicochemical treatment of oil-contaminants. Over the last decade, extensive researches focused on oil bioremediation and crude oil degradation have been carried out with pure culture or mixed bacterial Consortia isolated from oil-contaminated soils. The works were classified as:- 1- In first part of work, biodegradation process of vacuum gas oil was carried out , in which nine crude-oil-degrading bacteria were isolated from oil-contaminated sites in the Suez Oil Petroleum Company using BH and MSM media with heavy vacuum gas oil (HVGO) as sole carbon source. The biodegradation of heavy vacuum gas oil by pure bacterial strains was analyzed after 7 days of incubation period using the GC for aliphatic compounds. The percentage of residual n- and iso-paraffins present in crude oil after biodegradation was calculated by comparing with the undegraded control. The biodegradation potential of the bacterial strains on polyaromatics was detected by HPLC analysis. For enhancing the biodegradation of heavy vacuum gas oil (HVGO) sample, the authors selected two groups of bacterial isolates (Bb1, Bb2, Bb3 and Bb4) and (Bb5, Bb6, Bb7, Bb8 and Bb9) at different time intervals (0, 7, 14, 21, 30 days). The total paraffins were remarkably decreased from 29.73 in control sample to 20.53 after 21 days in microcosm containing mixed culture (1) of bacterial isolates (Bb5, Bb6, Bb7, Bb8 and Bb9). While, the best decreased in the total concentration of polyaromatics from residue heavy vacuum gas oil (HVGO) was obtained after 21 days in microcosm containing mixed culture (1) from 2574.71 control sample to 390.9. Determination of the nucleotide sequence of the 16S rRNA gene showed that these isolated strains belonged to genera Halomonas zincidurans strain B6, Halomonas xianhensis strain A-1, Halomonas salifodinae strain BC7, Pseudomonas xanthomarina KMM 1447 and Pseudomonas stutzeri ATCC 17588. (Bb5, Bb6, Bb7, Bb8 and Bb9) bacterial strains which consider as the best group, reduce sulfur content of HVGO by 15%, decrease the amount of aromatic from (34) to (28.5) % and decease resin from (2.12) to (1.94) % i.e. decrease the poly aromatic component of HVGO which can easily the hydrotreating process and enhanced it by applying biodegradation process before hydrotreatment process. 2- In second part of work, CoMo/CNT and CoMo/Al2O3 was prepared by impregnation method, and then several characterization techniques were applied to the MWCNTs and γ-alumina both before and after the impregnation of transition metal catalysts. These methods were used to define the structure and morphology of the MWCNTs and γ-alumina as well as to explain the exhibited behavior of the catalyst. 3- In third part of work, hydrotreating of HVGO divided into two parts. A: Hydrotreating of HVGO directly, which conducted on autoclave reactor (parr.model7575) using HVGO as feed and CoMoS/CNT and CoMoS/Al2O3 as a catalyst under the following conditions, temperature 325-375, pressure 20-60 bar, time 2-6h and cat/oil ratio (1:75,1:33 and 1:10) % . Effect of reaction temperature: - the data revealed that the characteristic of HVGO are affected, especially on sulfur content. The HDS was observed to be increased from (77.1 to 94.8) %. DI and aniline point were improved; these properties give an indication on the hydrogenation activity of catalyst. As the reaction temperature increased, the aromatic content was decreased from (25) to (17.6) % at 325 and 375 respectively at the same time the total saturate increased from (75) to (82.4) % due to the hydrogenation of aromatics. The effect of reaction temperature on the characteristic of HVGO by CoMoS/Al2O3 as the same direction but in case of CoMoS/Al2O3, the improvement of properties less than in case of CoMoS/CNT, due to the higher activity of the CNT supported which related on to the surface properties of the CNT.