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CATALYSTS FOR PROCESSES OF HYDROCARBON FEED DEMERCAPTANIZATION AND WASTE WATER TREATMENT

J.S.”VNIIUS”  has developed and implementated heterogeneous and homogeneous catalysts for demercaptanization of light hydrocarbon feed (LHF) and treatment of sulfide-containing waste waters.

Heterogeneous catalysts of KS and UVKO types  passed pilot-commercial tests on a number of plants and commercial check at long operation. An advantage of heterogeneous catalysts is ease of use as compared to homogeneous catalysts which should be periodically added during plant operation. Another advantage of these catalysts is absence or small quantity of metal salts (cobalt phthalocyanine salts) in waste waters, which are inevitably formed in desulfurization processes.  However, experience of operation of plants with heterogeneous catalysts show that their disadvantages are more important than their advantages, therefore J.S.”VNIIUS” does not recommend to use heterogeneous catalysts of KS and KSM types neither in  liquefied gas demercaptanization processes nor in sulfur-alkaline waste water treatment. For gasoline and kerosene demercaptanization a heterogeneous catalyst of UVKO type – activated carbon with cobalt phthalocyanine applied on its surface – is recommended (Ukhta, Kharg).
A major disadvantage of heterogeneous catalysts is contamination of their active surface with mechanical impurities or reaction products (e.g. with elemental sulfur formed during sodium hydrosulfide oxidation) and subsequent inevitable loss of activity. Causes of the catalyst deactivation due to surface contamination are described in a publication of one of  inventors of the catalyst of KS type /XX/.
Another serious disadvantage is low catalytic activity of heterogeneous catalysts, especially of KS and KSM types, as compared to that of homogeneous catalysts because an oxidation reaction of mercaptides and sulfides is catalyzed only by geometric surface. Therefore a reactor-regenerator volume is almost two times larger as compared to a volume of a regenerator, operating with a homogeneous catalyst and, consequently, energy consumption for supplying process air and alkaline solution into the regenerator is higher as compared to that when a homogeneous catalyst is used.
Using heterogeneous catalysts it is impossible to control the process of an alkaline solution regeneration promptly, while when using a homogeneous catalyst it is possible, if necessary, to intensify quickly the regeneration process by increasing a volume or concentration  of the catalyst solution dosed into the system.
Incomplete regeneration of the alkaline solution on KSM catalyst results in incomplete removal of mercaptans from feed.  Unfortunately, some sites contain incorrect information about an ostensibly new KSM catalyst possesing many positive properties.  KSM catalyst is only another form of KS catalyst, an author's certificate on which was given to J.S.”VNIIUS” as long ago as1980. Inventors of KSM catalyst allege that the “new”  catalyst allows to decrease an amount of waste waters from plants of light hydrocarbon feed demercaptanization. Chemical principles of mercaptan extraction with an alkaline solution and mechanism of catalytic action of both homogeneous and heterogeneous catalysts are similar, therefore composition and amount of waste waters depend only on composition of the supplied feed.
Statement of KSM inventors that total sulfur content in the treated feed  in case of heterogeneous catalyst is lower than in case of homogeneous catalyst is incorrect.  Data of operation of plants for light hydrocarbon feed demercaptanization confirm that the statement about the disadvantages of heterogeneous catalysts is correct.
Advantages of homogeneous catalysts are confirmed also by a fact that several thousands of plants for light hydrocarbon feed demercaptanization of such companies as UOP, Merichem, Axens, etc. use only homogeneous water-soluble phthalocyanine catalysts.
Homogeneous desulfurization catalyst – IVKAZ is a water-soluble sodium salt of cobalt phthalocyanine. It is produced on a commercial scale according to TU 2175-037-00151638-2009 by J.S.”VNIIUS”, Kazan. The catalyst is used in the processes of treatment of associated petroleum gases for hydrogen sulfide, in demercaptanization of liquefied gases, light oil products, crude feed and gas condensates and in treatment of sulfur-alkaline waste waters. The catalyst is delivered by J.S.”VNIIUS”, Kazan. IVKAZ catalyst is supplied to oil and gas refineries of Russia: Orenburg, Astrakhan, Kuibyshev, Ryazan, Perm, Tatneft, etc. and also to plants of Kazakhstan, Iran, Netherlands, Bulgaria, Lithuania, Latvia (see reference-list of VNIIUS desulfurization plants). The catalyst is supplied in a form of thin powder in polyethylene bags or plastic containers by 1-3 kg or in a form of liquid suspension in 5 or 10 liter polymer fuel cans. Photo shows the catalyst samples.