• Should we expect some return on our original purchase cost if we send spent catalyst for metals recovery?



  • Erick D Gamas, The Business Shop-Chemical Engineering Services, edgamas@hotmail.com

    Yes, Spent catalysts containing precious metals (PM), or any other metals used as active component on solid catalysts, have a market value. However, the value of PM metals on solid catalysts goes beyond a simple valuation of their metal content based on the price of metals in the market.The proper assessment of the value of PM in spent catalysts requires the involvement of an accounting department in addition to catalyst engineering estimations.

    a.- A refining operation using PM catalysts will need to pay for the metals on the new catalyst load, the value of PM on spent materials will contribute to defray the cost of the PM on fresh catalyst. Whether the metals market indicates a loss or a gain of value of metals, The price change might have some implications of capital gains or depreciation of assets (the PM on the solid catalyst)

    b. The value of a spent catalyst might also contribute to abate the cost of spent catalyst disposition, in particular if the spent catalysts contain additional materials (originally in the catalyst, or from deposition of contaminants from the process) that could cause a classification of Hazardous Waste. This item could contribute to reduce operating expenses.

    c. For low severity operations where spent catalysts might still maintain an acceptable level of activity. A regeneration step, whether in situ or external at a reclaimer's site, also contribute to decrease the cost of catalyst utilisation in processing operations. Some level of loss should be expected during unloading, regeneration, transportation and reloading. These losses can also impact operating costs and the corresponding tax implications.

    d. One model that used to be practiced in the recent past was PM  catalyst leasing. While apparently convenient for  catalyst as the ownership of the catalyst remains with a catalyst vendor, the model of leasing creates complications of the custody of the catalyst assets that could potentially disrupt the process operations when plant upsets happen, equipment failure occurs, or scheduled plant shutdowns take place. Representatives from catalyst vendors would need to be present on the site to ensure that proper care and custody of materials is exercised.

    In summary, PM on solid catalysts must be classified as an asset in processing operations, their valuation goes far beyond a simple arithmetic calculation based on the price of metals. As such there are tax implications that might impact the assessment of value of the PM in spent materials.


  • Brad Cook, Sabin Metal, bcook@sabinmetal.com

    In terms of precious metals (PM) catalysts, the answer is “absolutely”. In most recycling scenarios, the net value returned to PM catalyst users exceeds 90% of the PM original loading, including the cost of all recovery services and shipping charges. In order to ensure that the full value of the PM content is returned, however, far more crucial and costly details are always in play: the honesty/integrity of the precious metals refiner; the accuracy of sampling and analysis; and the hidden contractual and technical details (loss on ignition, splitting limits, and lot size).

    Learn more about these topics at www.sabinmetal.com/knowledge-center.



  • Meritxell Vila, MERYT Catalysts & Innovation, mvila@meryt-chemical.com

    Catalysts are used on a large scale in refineries, petrochemical plants, and chemical plants in general, as they are used in 90% of the chemical processes. The value of purchasing fresh catalysts is a very significant part of the production costs. Most of the catalysts are heterogeneous containing metals, and when the catalyst reaches the end of its cycle life, it is time for recycling and metal recovery.

    It is definitely possible to get some return on your original purchase cost by sending the catalyst for metal recovery. Depending on the type of catalyst/metal used, these returns could be from low to high. There are certain thresholds that the catalyst needs to have in order to get value back. However, even small returns on your metals are better then landfilling spent catalysts.

    Metals that are great for recovery are nickel, copper, zinc, cobalt, molybdenum, tungsten, and, of course, precious metals such as platinum, rhodium, palladium, and ruthenium.

    Most recovery processes are done using either a hydro-metallurgic process or a pyro-metallurgic process. The best method is selected depending on the percentage of metals, contaminants, and final product. The final product could be used again for new catalysts or used in a completely different industry (for example, car batteries).

    The limit of quantity of metal required on spent catalyst for an economic return also depends on the market rate of the metals. Catalysts without metallic value are also interesting for recycling or reuse. In general, landfilling can be reduced significantly in an economy that tends to reuse, recycle, and be circular.



  • Rainer Rainer Rakoczy, Clariant Catalysts, Rainer.Rakoczy@clariant.com

    A large number of catalysts for the petrochemical and pharmaceutical industries contain precious metals (PM), such as palladium, platinum, rhodium, ruthenium, and gold. These represent a high economic value even if only present in low percentage amounts. Precious metal reclaiming is, therefore, a common practice in the industry. Several specialised companies – typically locally active, rather than globally – have developed methods to recover a high percentage of those metals from spent catalysts. In general, the recycling company will credit the value of the recovered material to your account minus a fee for their service.

    Catalysts using base metals like copper, nickel, cobalt, iron, or molybdenum are used in even larger amounts than PM catalysts. They generally contain a much higher content of base metals than their PM counterparts. The business case for recycling those metals is not as obvious as in the case of PM, and it depends on a number of factors such as the base metal content, overall composition, metal price, and recovery efficiency. It needs to be determined case by case if reclaiming those metals is sensible. This will be done by the reclaimer, who will perform a detailed analysis weighing the influencing parameters upon receiving a representative sample of the spent catalyst. The reclaimer will share their findings, recommend a way to recycle the catalyst, explain the economics, and discuss the logistics with you.

    From a sustainability standpoint, it makes sense for most spent catalysts to reclaim the precious and base metals, as mining and refining those metals are resource and energy-intensive endeavours, which generally result in a large carbon footprint.



  • Francis Humblot, Arkema, francis.humblot@arkema.com

    The catalyst manufacturer has a prescribed procedure to sulphide the catalyst. The catalyst manufacturer has a prescribed procedure to sulphide the catalyst, and they should review and approve any deviation from this procedure.

    Spiked feed sulphiding of a metal oxide hydrotreating catalyst is a process where a spiking agent such as dimethyl disulphide (DMDS) in the presence of H2 converts to hydrogen sulphide (H2S) in-situ, which then reacts with the metal oxide to generate an active metal sulphide catalyst. This exothermic process has to be controlled by appropriate heat removal to maintain  temperatures prescribed by the catalyst manufacturer. Dimethyl disulphide (DMDS) is one of the most efficient sulphiding agents. With a high active sulphur content (68% w/w), it decomposes at relatively low     temperatures to generate H2S that reaches stoichiometric levels in the DMDS decomposition at around 240⁰C.

    CH3SSCH3 + 3H2           à 2 CH4 + 2H2S     
    Typical reactions of DMDS with the catalysts are shown below:

    MoO3 + 4H2 + CH3SSCH3à MoS2 + 3H2O + 2 CH4     ΔH = -319 kJ.mol-1

    9CoO + 13H2 + 4 CH3SSCH3 à Co9S8 + 9H2O + 8 CH4 ΔH = -629 kJ.mol-1

    3NiO + 4H2 + CH3SSCH3 à Ni3S2 + 3H2O + 2 CH4     ΔH = -374 kJ.mol-1

    WO3 + 4H2 + CH3SSCH3  à WS2 + 3H2O + 2 CH4      ΔH = -303 kJ.mol-1

    All hydrotreating catalysts require a stoichiometric amount of sulphur to be activated. The process of catalyst activation involves both sulphiding coupled with controlled metals reduction. Knowing that the whole process is exothermic, the rate at which the sulphiding agent (DMDS) is introduced into the feed oil must be controlled. Both the sulphiding reaction and the reduction reaction are accelerated by increasing temperature. One needs to be cognizant that there is a time delay between the increase in DMDS flow rate and the concomitant increase in reactor outlet temperature.

    Below 240⁰C, the reduction reaction is not pronounced and thus, as we increase the sulphiding agent flow rate in the temperature range of 220-240⁰C, we are accelerating mainly the sulphiding reaction. For faster sulphiding, one needs to have higher H2S concentrations in the reactor while controlling the temperature. This can be done by the independent control of the liquid feed rate into the reactor if feasible and the sulphiding agent flow rate into the liquid feed. Sulphiding is carried out in two phases: primary and secondary. Primary sulphiding is done at temperatures below 250⁰C, and secondary sulphiding is carried out from above 250⁰C to >300⁰C or start-of-run temperatures (SOR) (>300-350⁰C). Different sulphiding agents decompose differently to H2S as a function of temperature. DMDS is used extensively as a sulphiding agent because it starts to generate H2S at temperatures as low as 190⁰C and decomposes exclusively to H2S and methane at temperatures as low as 240⁰C. Maximising DMDS flow rate above 220⁰C, ascertaining a controlled exotherm by intermittent changes in DMDS flow rate while continuing oil feed, will allow for a quick breakthrough of H2S (3000 ppm in the recycle gas). At this point after breakthrough, DMDS feed needs to be continued to establish an H2S concentration significantly higher than 3000 ppm in the recycle gas at a temperature of about 240⁰C. A vent of the recycle gas can then be taken, to purge the CH4 and some of the H2S**. Fresh H2 is then introduced to restore at least 60% H2 purity of the recycle gas (the minimum value prescribed by the catalyst manufacturer). The H2S concentration should still be significantly higher than 3000 ppm

    After H2S breakthrough, DMDS flow rate is adjusted to maintain H2S, typically in the 1.5-2.0% in the recycle gas, while the temperature is increased 15-20⁰C per hour (or the catalyst manufacturer’s prescribed increase). Remember, as the temperature is increased, the H2S is consumed to sulphide the catalyst. DMDS flow is continued at a rate that maintains the H2S concentration well above 3000 ppm. Once there is no more consumption of H2S, and the temperature is >300⁰C, the catalyst is deemed to be completely sulphided, and DMDS feed is stopped. The catalyst is sometimes soaked in recycle gas with high H2S concentrations at this high temperature for about an hour or more. The recycle gas is then partially purged**, fresh H2 is brought in, a value of H2S >5000 ppm in the recycle gas is ascertained, and the unit is prepared to accept sour feed in the production mode.

    ** All venting and purges require the amines gas treating unit to be online.