Merrow Scientific Blog

20 years of high pressure sorption measurement!!

Merrow Scientific are pleased to announce this year is the 20th Anniversary of the formation of Rubotherm GmbH.

Rubotherm are the manufacturers of the unique patented magnetic suspension balance used for high pressure gravimetric sorption.  Originally this instrument was developed in the world renown Thermodynamics Dept in the Ruhr University, Bochum (Germany) when they had a specific application and found that nothing commerically available would allow them to measure at raised pressures and to the accuracy required.  After this successful first project a spin out company was formed from the Ruhr Uni Bochum Thermodynamics Dept (you can see where the name comes from now!!) and since then for the last 20 years the Rubotherm MSB gravimetric system has been supplied worldwide for many applications, including:

• gas sorption
• measurement of gas density
• corrosion and degradation studies
• vapour sorption
• separation
• catalyst characterisation
• supercritical extraction
• thermo gravimetric analysis

There are countless applications possible and many leading research groups using the system for cutting edge work - please look at the Rubotherm section of this blog for further information.

Due to the unique design of the Rubotherm system we can very accurately measure small mass changes of sample while dosing gases or vapours across in all conditions - from ultra high vacuum to 2000bar; from 4K up to 1600degC; and in corrosive environments.  In addition due to the expertise and knowledge built up at Rubotherm over the last 20+ years the accuracy and versatility of the system can be fine tuned to suit the exact research requirements - including unique high pressure thermodynamics expertise not available elsewhere.

Merrow Scientific are the exclusive partner in the UK and Ireland for Rubotherm and to celebrate 20 years of Rubotherm leading the way for high pressure sorption we have a number of special deals available - please contact us for further information.

Great value for money high pressure stirred reactors!

Merrow Scientific are the UK representative for Autoclave Engineers, who have been designing and manufacturing high pressure systems since the 1940s. 

Autoclave Engineers, who lead the way in terms of innovation, design quality and custom configuration, also lead in terms of value for money!  Sure there are companies who'll offer to make a pressure vessel or stirred reactor for a slightly lower price, but I wonder if these same companies can say they've never had a failure of a vessel in their 70 year history, or that they have customers running stirred reactors still that were supplied in the 1960s?

All Autoclave Engineers systems have serial numbers on all components, metal to metal precision engineered seals used on all VFT components, and all systems supplied since the 60s have detailed drawings in pdf format quickly available.  These makes it easy to keep all of our customers, even those with 50 year old systems, supplied with spares when needed.

One benefit of metal to metal engineered seals on the VFT is the fact that this means there are no welded ports (when they break that's it for the reactor), no teflon tape and compression threads (not a high temperature or precision pressure sealing method), so when a customer needs to replace a component they can do that easily and quickly.

So the return on investment when a £10K reactor lasts for over 50 years is pretty impressive!!

New compact high temperature high pressure stirred reactor launched

Autoclave Engineers have added a new reactor to their extensive range of custom configurable stirred reactors (available in the UK through Merrow Scientific).

Featuring the inline Mag3 magnedrive this results in a very small footprint stirred reactor that can easily be configured to suit many research applications.  Rated to 454degC and 227bar using metal to metal engineered seals throughout this unit can be easily integrated with MFCs, back pressure regulators, automated sampling systems and other devices.

Available in a range of materials and with 10 ports that can be set up with whatever fittings are required, plus a wide range of catalyst baskets.

Further information can be seen on the Mini-Ezeseal HTHP page or by contacting Merrow Scientific

Higher temperature activates porous material increasing adsorption

New research carried out by the Kitagawa group has resulted in the development of a new porous coordination polymer that is essentially triggered (in terms of its adsorption behaviour) as temperature increases - opposite to the behaviour of most porous materials.  Further work has shown that oxygen is adsorbed more as temperature increases, whereas little adsorption of argon takes place so potentially this material could be used for separation of argon and oxygen (normally difficult due to similarities of these molecules). 

Further details on this work can be seen here where they used BEL volumetric and Rubotherm gravimetric systems in combination with other techniques for characterising the material.

Experts in high pressure vessel manufacture

Our US partner Autoclave Engineers have yet again proven themselves to be leading the world in the design and manufacture of high pressure equipment.

Terms such as "experts", "leading the world" and even "high pressure" are often used in marketing speak without really much substance, so let me back up my statement with a couple of bits of information:

• Autoclave Engineers have been in this business of designing and manufacturing high pressure vessels, stirred reactors, VFT and other pieces of equipment since the 1940s and have never had a failure!  They have been certified to the highest levels of the PED (pressure equipment directive - law in the EU for the supply of pressure vessels), ASME and other pressure equipment legislation.
• A good example which illustrates their high levels of competence perfectly is one of their latest vessels.  This was to meet a requirement for a company supplying components for oilfields - they needed to test the components at high pressures and raised temperatures to check their performance before they were used in the field where those conditions would be experienced.   The vessel supplied was required to be operated at 40,000 PSI and 260degC, and due to the size of the components to be tested the vessel had to be 45 feet long and 15" ID - so a large high pressure system indeed.  The below pictures show the vessel being moved by crane lift and also the pressure gauges during the testing cycles (yes that's 60,000PSI they're being tested at!! Really shows the safety margins factored in).

So when it comes to high pressure vessels - Autoclave Engineers really are experts and leading the world.  If you'd like any further information please don't hesitate to contact us (Merrow Scientific are the UK partner for Autoclave Engineers' vessels and reactors) or look at our pressure vessel page.

Just drifting along: Removing the influence of balance drift on your measurement

One fact of life is that all balances used for measuring mass (and therefore mass change) drift over time. 

Drift occurs gradually and randomly over time and can be due to a number of factors (including changes in temperature, static, radio frequency interference) and happens to all balances.  Typically the drift could be something between 5ug (microgram) and 10 ug (maybe higher) on a 0.1ug resolution balance. 

This drift doesn't really effect one off measurements (e.g. measuring the mass of an item) as the user can tare (re-zero) the balance and even re-calibrate before measurement, so maximising the accuracy of the balance.

But in experiments where the user is measuring continual mass change over time (such as gas sorption, material degradation and other thermal gravimetric type measurements) the drift can have a large effect on the measurement.

Let's look at this a bit further, say a researcher is investigating mass change of a solid over a certain time period (e.g hydrogen gas storage into a solid or thermal degradation) and they're using a system that is listed on the brochure as having a resolution of 0.1ug, and as part of their studies are happy to report mass changes of 20ug. (200 times the reported resolution) Sounds ok? Well maybe not...

As mentioned all balances drift over time,  some companies take steps to limit this drift by trying to control the temperature around the balance which is certainly possibly for ambient to moderate temperature range experiments, but even then they quote for a 0.1ug balance drift of <5ug.  So using a maximum drift of 5ug when the researcher reports mass changes of 20ug it could be in fact 15ug or 25ug (drift can be upwards or downwards) so 20ug +/- 25%.  Sound ok still?  Probably not.... But lets look further at a balance that is not temperature controlled or maybe is in an environment such that temperature control around the balance is very difficult, so lets give that a conservative drift of 10ug.  So same results would be in fact 10ug or 30ug so 20ug +/- 50%....  Probably not worth reporting the result until you're able to get to mass changes of perhaps a reading +/- 1% maybe so with that balance it'd be 1000ug (even though the brochure says 0.1ug resolution) as that would be 1000ug +/- the max balance drift of 10ug. (1000ug = 1mg)

So I think from the above we can safely assume for continual mass change measurement the resolution of 0.1ug is pretty irrelevant and is probably no more than a marketing spec on the brochure.  For one off measurements though resolution is relevant.

Hopefully you're still with me at this point, but what I wanted to highlight is something Rubotherm have been doing for a number of years, in fact this year they celebrate 20years as a company supplying their patented magnetic suspension balance for gravimetric analysis.

As mentioned elsewhere on our site the Rubotherm system uses a patented technique where the precision balance is magnetically coupled to where the sample is located unlike all other gravimetric system where the sample is directly connecteed to the sample.

 

So what does that mean?  Well normally we highlight the fact that we can subject the sample to a wide range of conditions - gases and vapours, corrosive environments, pressures up to 2000bar, temperature to 1600degC all while measuring mass changes - without any risk to the balance as it's in a separate chamber completely untouched by (or lets say "blissfully unaware of") whats happening to the sample.

But another major benefit of being magnetically coupled between the sample and the balance is that we can re-zero/tare and even re-calibrate the balance at any point during our analysis!

So the high resolution version that Rubotherm supply has a resolution of 1ug.  But because we can re-zero the balance (typically we advise re-zeroing every 10mins) that means we have absolutely no effect of balance drift on the measurements.  The balance does drift still of course, but we can re-zero whenever we wish to (a bit like re-zeroing before a one off mass measurement on a normal balance) so the mass change is precisely measured.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Hopefully the above pictures shows how easily we can do this zero point measurement to remove the influence of balance drift (the user can easily set this in the software)

So our 1ug balance is able to measure to +/-1ug.

Going back to the previous example of reporting 20ug mass changes during a continuous gravimetric experiment, with the Rubotherm system we're able to say that this mass change is 19ug up to 21ug so 20ug +/-5% - does that sound ok - probably better than the previous examples even though we have a "lower resolution balance"!.

Sorry for the long post but it's an area very often overlooked.  Next time looking at a gravimetric system don't just look at the resolution on the brochure ask about the balance drift likely......

Gas to Liquids, Fischer-Tropsch, Advanced Energy Technology, Future's Pathway - new book by Peter Tijm

A new book is available looking in detail at the history of the Fischer-Tropsch reaction (including how it developed, how it works and why it is becoming so popular now over 60 years since it's first use).

The book is written by Peter Tijm who's worked in the GTL industry and related fields for over 30 years and provides an insight into his experiences and where he considers the industry is heading.  Available to purchase and download on the following website:  http://www.booklanddirect.com/

Catalyst Characterisation Group - Linkedin

If you're involved in any aspect of catalyst characterisation please join the Catalyst Characterisation Group recently set up on Linkedin

This group is intended to be an open place for researchers to do some networking and discuss their latest techniques, new research findings, meetings and conferences or anything related to this subject field.

Binary Vapour Sorption - measured gravimetrically at Warwick University

Professor Critoph's group at Warwick University have just taken delivery of their new state of the art Rubotherm system for measuring binary vapour sorption. 

Situated in their recently refurbished laboratory with their existing Rubotherm system this Magnetic Suspension Balance gravimetric system and dosing system is specifically designed to allow two vapours to be created and mixed (to known amounts) before dosing over a sample to measure selective sorption.  The system can also be used for single vapour or gas dosing and also mixtures of gases where temperature control is important when they are pressurised (e.g. CO2 for carbon capture work)

Merrow Scientific launch range of economical gravimetric systems for sorption research

Available in the UK and Ireland from Merrow Scientific (elsewhere in the world from Rubotherm) the Isosorp HyGrA range is an economically priced range allowing researchers with limited budgets the opportunity to utilise the Rubotherm patented technology to carry out gravimetric studies while subjecting samples to a wide range of conditions.

No longer are researchers limited to doing research to 20bar - simply because that's all the instrument can go to; the Isosorp HyGrA system allows sample mass change to be measured from Ultra High Vacuum to 200bar and from 77K to 770K (a wide range of other conditions including much higher pressures can be analysed using other systems from the Rubotherm range)

Systems are available for sorption research using gases, vapours and supercritical fluids so opening a wide range of applications such as hydrogen, CO2, methane storage; vapour adsorption and supercritical extraction.  Further information can be seen on the economical gravimetric sorption analysis page