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Our zeolite promote and lubricate your efficiency of creating value.
Some gas oils and lube oil base stocks, particularly those produced by hydrocracking, have cold flow properties that do not comply with specifications. The molecules responsible for these problems are mainly the long straight-chain alkyls, including those linked to a naphthene or aromatic ring (Table 1).
First let we find out some characteristics of the principal petroleum fractions and which kind of the various hydrocarbon families contribute to these characteristics by three typical catalytic refining process(cracking, hydrocracking, hydroisomerization ).
Generally, we achieve it by Dewaxing of gas oils and lube oil base stocks, and there are two ways to remove these chains (table 1)—by selective hydrocracking or by selective hydroisomerization.
Dewaxing of Jet Fuels, Gas Oils, and Lube Oil Base Stocks by Selective Hydrocracking.
In 1977, Mobil announced that it developed a selective acid ZSM-5-based catalyst for dewaxing jet fuels and gas oils.The pores of this zeolite (diameter around 0.55 nm) readily allow the penetration of straight-chain paraffins and long straight-chain alkyls juxtaposed to a ring, and to a lesser degree, alkyl chains that include a branched methyl group. These chains are cracked by the ZSM-5 zeolite at a temperature of between 300–400 C into smaller fragments that are distributed between the LPG and gasoline fractions. At the beginning of the 1980s, this application was extended to lube oil base stocks using the same zeolite.
Cracking all or part of the straight-chain paraffins improves cold-flow characteristics of the hydrocarbon cut processed, but on the other hand, it has the disadvantage of reducing its yield and of slightly deteriorating some important properties of the cut—the jet fuel smoke point, gas oil cetane number, and lube oil viscosity index. The dewaxing operation should therefore offer the best possible compromise between the desired cold-flow characteristics, the yield requirements, and the combustion or viscosity characteristics.
The feed does not require previous hydrotreating before dewaxing, because the organic base nitrogen molecules that it contains are too large to penetrate the pores of the ZSM-5 zeolite and inhibit its acidity. Hydrotreating would lead to the conversion of these bulky nitrogeneous organic molecules into ammonia that would penetrate the pores of the zeolite and inhibit its acidity. In such a case, this would impose the separation of ammonia upstream of the dewaxing reactor. A large amount of the cracked products is present in the gasoline cut. In the absence of any strong hydrogenation function, the acid ZSM-5 zeolite produces olefinic gasoline with a high octane number as a by-product.
Dewaxing of Jet Fuels, Gas Oils, and Lube Oil Base Stocks by by HydroIsomerization
The second way of catalytically improving the cold-flow characteristics of a petroleum cut is to isomerize the paraffins while minimizing cracking so as to obtain a very high distillate or lube oil base stock yield.[20,23,24] This is an attractive solution in the case of lube oil base stocks. Their added value is much higher than that of distillates and so provides an incentive to minimize cracking into light by-products of lower value.
With the acid ZSM-5 zeolite used in dewaxing by selective hydrocracking, the cracking of n-paraffins is preceded by their isomerization into branched paraffins. The most branched of them are retained in the pores and are cracked into smaller fragments that may break free. There are two ways of avoiding or restricting the cracking: by using a more open zeolite such as the Beta zeolite (BEA structure), for example, which allows multibranched isomers to escape from the pores before they are cracked, or by finding a zeolite with a pore size and shape that do not allow the formation of multibranched isomers that are easily cracked. The first solution cannot prevent significant cracking, whereas the second solution appears more promising, provided the appropriate zeolite(s) can be found. The first results of removing linear paraffins by selective hydroisomerization were published around 1987 and concern the treatment of lube oil base stocks by the SAPO-11 zeolite (Table 2). This zeolite has intermediate pore apertures (with a diameter of around 0.5 nm) and the required shape selectivity to inhibit the formation of easily cracked multibranched isomers and to allow the formation, even at a very high rate of conversion, of only slightly branched isomers that are difficult to crack. The catalyst used is bifunctional and possesses a strong hydrogenation function based on a noble metal (Pt or Pd) that requires operating with feeds that have low concentrations of organic sulfur and nitrogen compounds. Other zeolites possess properties comparable to those of the SAPO-11 zeolite: ZSM-22 and ZSM-23, and ferrierite, for example. The first process for dewaxing by hydroisomerization was commercialized in 1993 for lube oil base stock treatment.
Our designed zeolite ZSM-23 and ZSM-48 is good choice for your nobel metal isomerization dewaxing catalysts to improve your Cold Flow Properties of Jet Fuels, Gas Oils, and Lube Oil Base Stocks by hydroisomerization with advantages of:
-Catalyst with strong Hydro-Isomerization activity transforms waxy molecules into non-waxy iso-paraffins plus small distillates
-Improved selectivity for wax Conversion gives more yield and higher VI Lube
-Highly refined base oils substantially reduced S&N from feed such as Lube Hydrocrakates, Fuel Hydrocracker Bottom or Hydroconverted raffinates
-Higher VI & Better yield of base oils than Solvent Dewaxing
