Development of High Performance Catalyst Used for Reformulating Diesel Oils

�@ According to the report (dated December 14, l998) issued by Central Environment Council of Environment Agency, long term objective for the achievement in high specification for diesel oil will be decided by the end of fiscal year 2002. Furthermore, the reinforcement of diesel exhaust emission by Tokyo Metropolitan Government requires the reduction of sulfur level to 50 ppm (-30 ppm) and less even earlier.

�A In EU, reduction of sulfur level to less than 50 ppm will be required as of year 2005. Regulation regarding polyaromatics control is being discussed at present.

�B Improvement of the diesel oil specification is the technique which complements to the techniques for improving engine itself or for the catalysts used for treating exhaust gases. It is, at the same time, considered to be effective in decreasing particulate matters from the vehicles of models conforming to current emission control standards and older used cars, and moreover, specified vehicles used in specified areas such as construction, industrial and agricultural sites which have been exempted from emission standards.

�C Using the clean diesel oil from which sulfur and polyaromatics are reduced helps to decrease particulate matters to a certain level without installing exhaust filter or oxidation catalyst for particulate matters (possible to decrease from all types of diesel engines widely). This enables to reduce suspended particulate matters (SPM) rate by approximately 20 to 30 %.

�D According to the special research project on environment carried out from l994 to l997 fiscal year (collaborative research with National Institute for Resources and Environment of Agency of Industrial Science and Technology), when aromatic level of diesel oil is decreased to 7.2%(polyaromatics 0.8%) and sulfur to 43 ppm, the particulate matters decreased approximately to 20% compared to that of raw diesel oil [aromatic level = about 26% (in which polyaromatics contained less than 5%) sulfur level = about 240 ppm]. The catalyst developed is palladium-platinum/cerium modified ultrastable Y type zeolite catalyst.

The characteristics of the newly developed catalyst

�@ Research on palladium - platinum/cerium modified ultrastable Y type zeolite catalyst developed by our Institute has been continuously carried out in order to improve its sulfur resistance, nitrogen resistance and durability. Consequently, we have developed the following catalyst:
@Catalyst developed: palladium - platinum/ytterbium modified ultrastable Y type zeolite catalyst(Pd-Pt/Yb-USY zeolite catalyst).
@@Ytterbium Yb is one of the rear earth elements.
@@The total content of palladium and platinum is 1.2% weight.

@The raw material diesel oil (same product as the diesel oil sold commercially) used for the reaction
@sulfur level = 263 ppm
@@total aromatics level - 26.3% weight (of which, polyaromatics level =
@@6.9% weight)
@@distillation property: IBP (217��), 10% distillation temperature (253��)
@@50% distillation temperature (299��), 90% distillation temperature (350��)
@EP (374��)

@Reaction condition: reaction pressure = 40kg/cm²G, reaction temperature 280��,
@@WHSV = 4h - 1, hydrogen/raw material diesel oil feeding ratio (volume ratio)=
@@500Nl/l
@@time on stream = approximately 200 hrs (short term life test)

@Properties of the obtained reformulate diesel oil:
@@sulfur level = 17 ppm,
@@total aromatics level = 4.5% weight (of which, polyaromatics level =
@@0.8% weight)
@@distillation property: IBP (187��), 10% distillation temperature (238��)
@@50% distillation temperature (294��), 90% distillation temperature (348��)
@@EP (373��)

�A Using this newly developed catalyst, it is possible to achieve deep hydrodesulfurization (S<20ppm) and lower the levels of aromatics simultaneously when used to reformulate hydrotreated diesel oils under mild condition. The condition of the normal commercial hydrodesulfurization reaction is approximately 50kg/cm² pressure, and WHSV being under 4h -1, the use of this catalyst with the commercial refining condition, it can be predicted that both sulfur and aromatics levels to decrease further at the same time.

�B Because the zeolite's solid acidity is controlled, nitrogen resistance is improved and also over cracking (lessen gasoline fraction or gas generation) of diesel oil component is controlled. Partly, diesel oil is converted into kerosene oil fraction.

�C When the condition is S<30 - 50ppm, use of sulfide catalyst has to be increased to more than double the current level [i.e. reduction in oil yield (WHSV reduction), increase of catalyst loading amount and further installment of reactor, etc. are indispensable]. Higher the reaction temperature the more hydrodesulfurization progresses, thus by increasing the reaction temperature as the activity falls (temperature compensation), hydrodesulfurization activity can be maintained. However, aromatics level increases when reaction temperature increases
(thermodynamic limitation that hydrogenated compounds are dehydrogenated and changed to aromatics).

�D The catalyst developed is assumed to be used in the next system (two-stage reaction). Raw material diesel oil (sulfur volume = approximately 1 - 2%) �� present deep hydrodesulfurization reaction tower (first stage)
(Sulfur level<500ppm) �� developed noble metal catalyst reaction tower (second stage)(sulfur volume<10 - 30 ppm, polyaromatics<1wt%)
However, inbetween the first and second stage reaction towers, manipulation for removing certain amount of hydrogen sulfide or ammonium will be needed.

�E On the assumption that the developed catalyst be industrialized, the sample catalyst for industrial use is manufactured together in this joint project with Catalyst & Chemicals Ind. Co. Ltd.
Pd-Pt/Yb-USY-Al203-B203 and Pd-Pt/Yb-USY-Al203 catalyst(1/16 inch extrusion mold)
The performance of the catalyst is confirmed by the experiment using model compound
(tetralin).

The long term life test (time on stream = 2000h) is being carried out using bench scale equipment at Wakamatsu factory of Catalysts & Chemicals Ind. Co. Ltd., at present.