Hydrogenolysis Operations Manual

Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown
Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass
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Web Site: www.GBHEnterprises.com
GBH Enterprises, Ltd.
Operating Manual
Hydrogenation Catalysts
VHT-S101 hydrogenation catalyst

Contents
Introduction
VULCAN Series VHT-S101
Catalyst storage, handling, charging
Health and safety precautions
Start-up of VHT-S101 hydrogenation catalyst
Operation of VHT-S101 hydrogenation catalyst
Shut-down of VHT-S101 hydrogenation catalyst
Sulfiding of hydrodesulfurization catalysts
Catalyst Discharge
Information contained in this publication or as otherwise supplied to Users is
believed to be accurate and correct at time of going to press, and is given in good
faith, but it is for the User to satisfy itself of the suitability of the product for its
own particular purpose.
GBH Enterprises, Ltd., Catalyst Process Technology gives no warranty as to the
fitness of the Product for any particular purpose and any implied warranty or
condition (statutory or otherwise) is excluded except to the extent that exclusion
is prevented by law. GBH Enterprises, Ltd., Catalyst Process Technology accepts
no liability for loss or damage, resulting from reliance on this information.

INTRODUCTION
Sulfur and chlorine compounds are particularly severe poisons for nickel, iron
and copper catalysts used in plants utilizing steam reforming technology for the
production of hydrogen and hydrogen/carbon monoxide mixtures for downstream
use in oil refining, petrochemical, ammonia and methanol production. The large
volumes of hydrocarbon feedstock to be processed mean that even small traces
of these poisons have a cumulative detrimental effect on the performance of
downstream catalysts. It is therefore extremely important to purify all the
hydrocarbon feedstocks before they are processed to achieve the long
production runs needed for economic operation.
Organic sulfur compounds must be hydrogenolysed over VHT-S101 or VHT-
S103 to convert the sulfur to hydrogen sulfide (H2S). Where present, organic
chloride compounds are also hydrogenolysed over VHT-S101 or VHT-S103 to
give hydrogen chloride (HCI), which is then removed by absorption with VSG-
CL101. Lastly, the H2S is removed by absorption with VSG-S201 or VSG-
EZ200.
This manual discusses the principles of start-up, operation and shut down and
the information provided is sufficient for the preparation of detailed operating
instructions, which of necessity will be plant specific.

VULCAN Series VHT-S101
Hydrodesulfurization catalysts
GBH Enterprises, Ltd., Catalyst Process Technology supplies two catalysts for
hydrodesulphurization (HDS), namely VHT-S101 and VHT-S103 which are
respectively based on cobalt oxide/molybdenum oxide and nickel oxide/molybdenum
oxide, in both cases supported on alumina. VHT-S101 is more commonly used for
ammonia and hydrogen duties while VHT-S103 is usually used in methanol plants.
The catalysts achieve their highest activity when sulfided but can also operate under low
sulfur conditions when partially sulfided. In most applications, the catalysts do not need a
special sulfiding stage and an appropriate level of sulfiding is attained by reaction with
the sulfur compounds in the hydrocarbon feed.
VHT-S101 and VHT-S103 normally operate at temperatures in the range of 300-
400ºC (570-750ºF) and at pressures of 25-40 bar (363-580 psi). The preferred operating
temperature is towards the upper end of this range.
In certain circumstances, it is advisable to pre-sulfide the HDS catalyst. These
circumstances are limited to situations where the carbon oxides concentration is
high presenting a risk of exothermic methanation; the sulfur concentration is very
low such that inadequate sulfiding will occur; the operating temperature is low
such that maximum HDS activity is necessitated from start of run; the organic
sulfur level is high again necessitating maximum activity immediately on
commissioning; and the nature of the hydrocarbon feed and partial pressure of
hydrogen present a risk that an exothermic hydrocracking reaction may initiate.
Pre-sulfiding of the catalyst is achieved either by an in situ sulfide pre-treatment
or by supply of pre-sulfided catalyst. In these situations, GBH Enterprises, Ltd.,
Catalyst Process Technology will advise on the appropriate catalyst selection and
procedures.
Composition
VHT-S101 Cobalt oxide/ Molybdenum Oxide/Alumina
Physical and Chemical Properties
Appearance Blue Gray Extrude Cylinder
Size, mm Φ3.0
Components Co, Mo, γ-Al2O3
Bulk Density, kg/l 0.65-0.75 (typically 0.72)
Crushing Strength, N/cm ≥80
Attrition loss, % ≤3.0

Catalyst storage, handling, charging and discharging
Before charging, discharging and handling shift catalysts any potential risk to
health during these activities should be assessed and appropriate precautions
taken. In addition the GBH Enterprises Catalysts brochure on “Catalyst
Handling” should be consulted.
Drum storage
Shift catalysts are generally supplied in mild steel drums, fitted with polythene
liners, and having the following packaging details. Precise information will be
recorded in the documentation covering the goods when supplied.
Drums must not be stacked on their sides or stacked more than four drums high,
even when held on pallets. Taller stacks tend to be unstable and there is the risk
that the top drums may fall off the stack, and the lower drums can be crushed
due to the weight of the drums above them. The metal drums are usually suitable
for outside storage for a few months but should be protected against rain and
standing water. If prolonged storage is expected, they should be kept under
cover and away from damp walls and floors. The lids should be left on the drums
until just before the catalyst is to be charged. If the lids are removed it is
important that they should be replaced as soon as possible, so that
contamination of the catalyst is avoided. If the drum lid cannot be replaced, then
the catalyst should be redrummed without delay. If any contamination occurs it is
difficult to assess the extent of any damage without full examination of the
catalyst. If there is any doubt about the state of the catalyst it is best not to
charge it to the reactor.
Drum handling
Catalyst drums should be handled as carefully as possible. They must not be
rolled. Catalyst drums are often supplied on pallets, which reduces the likelihood
of damage in transit but requires suitable fork-lift trucks and a paved area to
handle the pallets. The fork-lift truck to be used for dismantling the pallets should
be fitted with rim or body clamps to avoid damage to the drums. The use of
shipping containers for either catalyst drums or palleted drums eases shipment
and further reduces the likelihood of damage in transit. It is important not to use
standard forks to lift the drums under the rolling hoops, as damage to the drums
and catalyst is almost inevitable.

Sieving catalyst
Catalysts are screened before they are packed into drums for dispatch, hence
sieving on site is not usually required, but in some instances attrition can occur in
transit if the drums are roughly handled. In this case some form of screening is
advisable before charging, especially if the catalyst appears to contain dust on
delivery. A good method of sieving is to pass the catalyst over a simple inclined
screen. This is often the most satisfactory method, since vibrating screens can
cause additional unnecessary damage and loss. The screen should contain
provision to collect the dust, and at the same time avoid generating a dusty
atmosphere. The mesh spacing should be about half the smallest dimension of
the catalyst pellet. While the catalyst is being poured over the screen, the use of
a vacuum system situated close to the sieve will control the dust effectively.
Pre-charging checks
Before the catalyst is charged it is important that the condition of the catalyst
support grid in the vessel and any supporting materials such as inert balls be
checked. Some form of light metal shield or “spider” fitted into the discharge
manhole prevents inadvertent catalyst discharge when the manhole cover is
removed. The vessel should be clean, dry and free from loose scale and debris.
It is important to ensure that the charging level is clearly defined, so as to avoid
under filling or overfilling. The desired level can be marked with chalk before
charging is commenced.
It can be valuable to check that thermocouples are correctly installed before
charging is commenced by warming them in turn to ensure that the correct
indication is given on the instrument panel.

Charging the Hydrogenation Vessel
The catalyst may be loaded directly from the drums or from intermediate bulk
containers. The general rules for charging catalysts into vessels are:
• The catalysts should have a free fall of between 50 and 100 cm (20-40
inches) to ensure a suitable packed density is achieved. (More than 100
cm/40 inches may damage the catalyst)
• The catalyst must be distributed evenly as the bed is filled, with a
maximum height difference of 15 cm (6 inches) across the bed when
completed.
Health and safety precautions
Operators should be aware of the hazards associated with the use of catalyst
and draw up the appropriate safety instructions.
Discharge of pyrophoric catalyst
Catalysts discharged in the pyrophoric state must be kept separate from
flammable materials. Transport of such catalyst should only be in metal skips or
metal sided trucks. Dumps of the catalyst should be within reach of water hoses
so that any overheating that occurs can be controlled. High temperatures can
build up in heaps and it is a prudent precaution to spread the catalyst thinly over
the ground until the oxidations is complete. Under no circumstances should
personnel be allowed to walk over the catalyst until it has been fully stabilized.
The normal shut-down procedure for inert discharge is as follows
Dust exposure
Short term exposure to the metals and metal oxides used in catalysts may give
rise to irritation of the skin, eyes and respiratory system. Over-exposure can give
rise to more serious effects. Product safety data sheets should be consulted for
information. Catalysts should be handled as far as possible in well-ventilated
areas and in a way which avoids the excessive formation of dust. Operators who
handle catalyst must wear suitable protective body clothing, gloves and goggles.
Inhalation of dust should be avoided, and the appropriate occupational exposure
limits should be strictly observed. If these limits are likely to be exceeded, then
respiratory protections should be used. Everyone involved in the handling
operation should clean up afterwards and, in particular, must wash before eating.

Clothing should be changed at the end of each shift, and more frequently if
contamination is heavy.
Ergonomics
Physical hazards arise from the handling of drums, materials and lifting
equipment. Personnel should be aware of these and appropriate precautions
taken.
Note: The European Union has decided that it is prudent to classify all insoluble
nickel compounds as Category 1 carcinogens. Appropriate information is
contained in the Material Safety Data Sheet sent with all orders.
Start-up of VULCAN Series VHT-S101
When using VHT-S101 for the hydrodesulphurization of light hydrocarbons and
gaseous feedstocks no special activation procedures are usually necessary.
Conversion to the more active sulfided form is achieved to a sufficient extent by
reaction with sulfur compounds in the feed gas.
1 Purge the vessel free of oxygen using an inert gas or natural gas. The
latter is used of necessity where there is no available nitrogen system, for
example in certain ammonia plant designs.
2 Heat the catalyst in a flow of inert gas or natural gas at a rate not
exceeding 50ºC (90ºF) per hour. The alumina support will usually contain
adsorbed moisture which will be evolved during the heating stage. The
HDS catalyst and downstream absorbents should be heated to at least
300°C (572°F) (and ideally to design operating temperature) before the
system is commissioned for hydrodesulfurization with feed forward to the
steam reforming section.
3 If the catalyst is heated up with natural gas, care is needed with regard to
any sulfur compounds. Organic sulfur impurities will not be absorbed by
the H2S removal absorbent downstream and may not react effectively over
the HDS catalyst until the hydrogen flow has been introduced and the
catalyst temperature exceeds 300°C (572°F). Care is required, therefore,
that impure natural gas does not pass to the steam reformer during the
heating phase and conditions are such that sulfur impurities are being
removed before feeding gas forward.

4 Raising the pressure will aid heat transfer. The HDS catalyst vessel may
be brought up to operating pressure at any time during the heating stage,
however, a lower pressure may be preferred at this stage depending on
the status of the reduction of the downstream steam reforming catalyst. If
this is the case, pressure should be raised later in line with the
requirements of the steam reformer commissioning.
5 The feed gas and hydrogen, or hydrogen rich gas, may be introduced with
the temperature below 300°C (572°F) in order to begin sulfiding of the
catalyst with the more reactive sulfur compounds in the feed as long as it
is possible to route this gas elsewhere than the steam reforming section.
Important: If hydrogen rich gas contains carbon oxides then these could
methanate over the unsulfided catalyst at temperatures above 300ºC
(570ºF). The gas temperature will increase by about 50ºC (90ºF) for every
1% of carbon oxides which reacts. If the catalyst temperature can then
exceed the design value it will be necessary to introduce the hydrocarbon
feedstock before the hydrogen rich gas at an inlet temperature below
300ºC (570ºF) in order to dilute the carbon oxides to an acceptable level.
Hydrocarbon that is not completely desulfurized during this stage should
not pass to the primary reformer.
When VHT-S101 is used to desulfurize steam reformer feedstocks,
commissioning often proceeds with the start-up of the reforming furnace. The
desulphurization vessel may be included in the reformer recycle loop and
hydrocarbon feedstock can only be added at the appropriate stage in the
reforming catalyst reduction.
This may mean that the unsulfided catalyst is in contact with hydrogen at the
normal operating temperature before sulfur containing gas can be admitted.
Prolonged exposure to hydrogen alone should be avoided as this can lead to
over reduction of the catalyst but experience indicates that subsequent problems
are very rare.
Several variations of the recommended start-up procedure are possible in
particular plants. For example, if VHT-S101 is being used to hydrodesulfurize
gas streams the gas feedstock can be used to heat the vessel in stage 2 of the
start up procedure. It is also possible to desulfurize gas at low throughput rates
for steam reforming plants as soon as the catalyst bed temperature exceeds
300ºC (570ºF), but is still less than the design temperature, if this is an
advantage. It is always important, however, on these occasions to monitor the
sulfur content of gas leaving the zinc oxide. This is to confirm that adequate
purification has been achieved before passing it to the reformer.

Operation of VULCAN Series VHT-S101
VHT-S101 is robust and gives trouble-free operation for many years.
Performance is usually checked by measuring the feedstock sulfur content and
the sulfur content of gas leaving the final bed of zinc oxide. Any instantaneous
changes in sulfur slip will often be noticed first from the performance of the
reformer.
It is possible to check on the extent of hydrogenolysis of organic sulfur
compounds across the bed of cobalt catalyst but this requires sophisticated
analytical equipment.
VHT-S101 evolves or absorbs sulfur as the sulfur content of process gas
changes. This corresponds to changes in the sulfide content of the catalysts due
to equilibration with the changing process gas sulfur level. Any evolved sulfur will
be in the form of H2S which is removed in the downstream absorbent beds.
There will normally be no detectable temperature rise across the catalyst bed
unless olefins are present which will then be hydrogenated. Depending on the
temperature rise observed it may be necessary to decrease the inlet temperature
to the vessel to maintain the exit temperature at the design maximum.
When operating with VHT-S101 it should be remembered that:
1 Performance is closely related to the quantity of sulfur and the particular
sulfur compounds present in the feed gas.
2 Hydrodesulphurization is not possible in the absence of hydrogen.
3 Activity is strongly temperature dependent so that operation below design
conditions is not recommended.
4 Operation above 400ºC (750ºF) should be avoided to achieve best results
and to prevent hydrocracking.
5 Olefins present will hydrogenate and consume hydrogen. Not only will this
produce an exotherm but also it may not leave enough hydrogen for the
hydrogenolysis of organic sulfur compounds.

6 This catalyst is an effective shift catalyst therefore if CO2 is present in the
feed an allowance should be made for the hydrogen consumed in the
reverse water gas shift reaction.
CO2 + H2 CO + H2O
Shut-down of VHT-S101
During a plant shut-down, hydrodesulphurization catalyst may normally be left in
an atmosphere of the process gas without any damage to the catalyst.
Where there is a likelihood of some condensation of the hydrocarbon feedstock,
for example in a naphtha based plant, the reactor should be purged with an inert
gas. Similarly if carbon oxides are present the reactor should be purged with an
inert gas to avoid the risk of methanation occurring.
Hydrodesulphurization catalysts in the sulfided from are potentially pyrophoric,
due to finely-divided carbon that can be present. This and any adsorbed
hydrogen or feedstock can ignite when the catalyst is discharged hot from the
vessel. For this reason if the catalyst is to be discharged the procedure outlined
under “Catalyst Discharge” must be used. Under no circumstances should air be
passed through the catalyst until it has been cooled to below 50ºC (90ºF).
Sulfiding of hydrodesulphurization catalysts
HDS catalysts can be sulfided if required by doping with a sulfur compound to
ensure maximum activity during initial operation and also to inhibit methanation
of carbon oxides in feed gas or hydrogen recycle. During normal operation the
HDS catalyst will reach an equilibrium sulfur content which depends on the level
of sulfur in the feedstock. If more sulfur than this is added during sulfiding the
excess will be displaced when operation begins and shorten the life of the zinc
oxide bed. It is recommended, therefore, that only about 2% w/w sulfur be added
during the procedure.

1 Purge the reactor free of oxygen using an inert gas.
2 Heat the catalyst to 200ºC (392ºF) in a flow of inert gas or natural gas at a
rate not exceeding 50ºC (90ºF) per hour. Pressure may be in the range of
10-20 bar (150-300 psi). Introduce about 5-10% hydrogen and add about
1% of carbon disulfide, dimethyl disulfide, mercaptan or hydrogen sulfide.
The space velocity should be about 400-600 hr-1 and sulfiding should
continue until the catalyst has picked up 1-2% w/w sulfur.
3 Discontinue sulfur addition.
4 If feedstock plus hydrogen has been used as the carrier the catalyst bed
temperature should be increased at a rate not exceeding 50ºC (90ºF) per
hour to the operating temperature. It is ready for use. If an inert gas plus
hydrogen has been used as the carrier during sulfiding it should be
replaced with feedstock plus hydrogen before increasing the temperature
to the operating level.
The importance of sulfiding HDS catalysts when high concentrations (greater
than 10% v/v) of carbon oxides are present in either recycle hydrogen, or
feedstock, must always be remembered. It is also very important to monitor the
sulfur content of gas leaving the zinc oxide catalyst during the commissioning
period to check that adequate purification has been achieved when presulfided
HDS catalysts are being used and excess sulfur is being evolved.
Catalyst discharge and disposal
The catalyst or absorbent is usually discharged from the reactor with large mobile
vacuum units or by gravity flow from the bottom of the vessel.
The spent material should be assumed to be potentially combustible because of
adsorbed hydrogen and hydrocarbons or finely-divided carbon that can be
present. When discharging from the vessel the following procedure should be
used.
1 Purge the reactor free of hydrocarbon using an inert gas and reduce the
pressure.
2 Cool the reactor to below 50ºC (90ºF) in a flow of inert gas.

3 Discharge the catalyst or absorbent under a positive pressure of inert gas.
This may be by vacuum extraction or by gravity flow from the bottom of
the converter. In the latter case, as the material falls from the bottom
manhole, water hoses should be available to wet it in case it overheats.
If the material has to be discharged when it is hot it should be assumed that it is
pyrophoric and the following procedure used.
1 Purge the desulfurizer vessel with an inert gas and reduce the pressure.
Maintain a positive pressure of the inert gas in the vessel.
2 Discharge the catalyst or absorbent into metal bins or metal-sided lorries
with only the discharge manhole open. Air must NOT be allowed to enter
the vessel otherwise local overheating could take place.
3 Water hoses should be available in case of overheating. Water should not
be used unless necessary as this could cause breakdown of the catalyst
or absorbent particles.
GBH Enterprises, Ltd., Catalyst Process Technology offers advice on the
environmentally safe disposal of its complete product range.

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