Hydroprocessing of renewable feedstocks

Testing Vegetable Oil hydrotreating catalysts in high-throughput micro-pilot plants

 

  • With the current megatrend of renewable feedstocks (vegetable oils, liquefied waste plastics), refineries face new technical challenges. With limited renewable feedstock availability for testing, Avantium small-scale reactors technology offers new opportunities to scout process conditions and new designs of catalyst loading sequences.
  • Avantium Catalysis developed small-scale parallel fixed bed reactor systems designed for catalyst intake up to 1 ml, trade name Flowrence®, in order to enhance catalyst development and selection. Flowrence® high-throughput technology is extensively used for the parallel testing of hydroprocessing catalysts over a wide range of process conditions and applications.
  • We continuously evaluate the feasibility of processing new feedstocks. Our micro-pilot plant technology allows for the highly efficient testing of hydroprocessing catalysts; smaller volumes will reduce the amount of feed required, avoiding the typical issues associated with obtaining large quantities like handling, shipping, and storage (also for longer-term availability of reference feed material).

Introduction

Accurate catalyst evaluation is an important step in optimizing catalytic processes with respect to product yield, energy efficiency and overall product quality. High-throughput catalyst testing and small-scale reactors offers several advantages when compared to larger reactor systems (C. Ortega, 2021).

Avantium Catalysis continuously evaluates the feasibility of processing new feedstocks at our Flowrence® systems. In this paper, we present the results of processing blends of soybean oil and Straight Run Gas Oil (SRGO) and 100% Vegetable Oil (VO) for renewable diesel production.

In this testing program, we used a commercial ULSD NiMo catalyst to hydrotreating the VO.

Methology

The Micro-Pilot Plant

This testing program was conducted in a 16-parallel fixed bed reactors system with a diameter of 2.0-2.6 mm. Figure 1 shows a schematic overview of the 16-parallel reactors micro-pilot plant. This unit employs Flowrence® Technology, which enables the tight control of process conditions – temperature, flow rates, and pressure. See (C. Ortega, 2021) for a detailed description of the Micro-Pilot Plant.

Experimental

We performed this testing program in collaboration with a catalyst supplier global market leader. For this program, only 8 reactors were used; the high-throughput 16-reactors system allows for the selective isolation of unused reactors.

Reactor Loading

The catalyst packing in the Single-String-Pellet Reactors (SPSR) is straightforward and does not require special procedures. A single string of catalyst particles is loaded in the reactors with an internal diameter (ID) that closely matches the particle average diameter. To enhance hydrodynamics, an inert nonporous diluent material (with a defined average particle size distribution) is used as a filler. Before doing the final loading in a steel reactor tube, we often perform a trial loading in quartz reactors to confirm the packing (Figure 3). The extrudates are not sorted for length or otherwise.

Operating Conditions

A commercial ULSD NiMo catalyst was loaded in 8 reactors (561.0 mm length and 2.0 mm internal diameter) with 2 different bed lengths to test 2 different LHSVs (Liquid Hourly Space Velocity) simultaneous (Figure 4). All reactors were tested at 70 barg pressure.

Feedstock

Pressure drop issues is one of the main challenges when processing vegetable oils in hydroprocessing units.  This is even more evident when using pilot plants with small diameter reactors as catalyst fouling can quickly lead to plugging. For this reason, the approach of the current test was the co-feeding of the vegetable oil (soybean oil, see properties in Table 2) blended with a SRGO at different ratios as shown in Table 1.

Table 1 lists the different feed blends tested over a period of 400 hours on stream (HOS) and 100% vegetable oil (VO) over 150 hours (6 days). The feed blends with 70%VO and 100%VO were spiked with DMDS up to 2 wt.% sulfur.

Results

Mass Balance

An accurate mass balance is an internal control of the data quality obtained.

The mass balance calculation includes the water in the gas stream measured with the online GC.

Reactor pressure regulation and pressure drop over the reactors

Reactor pressure regulation is not only important to ensure accurate pressure control at operating pressures, but also to help maintaining equal distribution of the inlet flow over all reactors.

The pressure drop for all reactors is very small with an overall average of 0.2 barg.

VO Conversion

At the predefined testing conditions, we obtained a total conversion of the VO without apparent effect of the LHSV.

Figure 7 shows an example SimDist for the 40% VO feedstock where we can see the conversion of triglycerides (BP > 480°C) into paraffins (apparently mostly C16 to C18).

Liquid Product Yields

Figure 8 presents the Diesel, Kerosene and Naphtha yields for 40% VO, 70% VO and 100%VO feedstocks.

The Yield to Diesel is around 80% for the 100% VO feedstock

  • Liquid product analysis (ASTM D5291) confirmed that there was no Oxygen left
  • As expected, there isn’t any Naphtha or Kerosene produced from the conversion of the VO – there is a direct conversion of triglycerides to C12+ paraffins
  • The small effect of the higher LHSV (1.5 l/l/h) on the VO products yield
  • Overall a good reactor-to-reactor repeatability for the product yields

Gas Product Yield

Figure 9 shows the gas make yield (C1, C3 and C4) – only traces of C2 were observed (not presented in the graph) – for all feedstocks tested.

As expected, methane and propane are the main gas hydrocarbons products

  • Increasing gas product yields as the amount of VO is increased on the feed
  • Up to 5 wt.% propane produced when processing 100% VO
  • Good reactor to reactor repeatability for the gas product yields
  • Small but consistent effect of LHSV on the gas yields

Figure 10 shows the CO, CO2 and H2O yields.

Increasing gas product yields as the amount of VO increases

  • Up to 3 wt.% CO and 5 wt.% CO2 produced when processing 100% VO
  • The yield to water presented does not include the small amount of water remaining in the liquid product
  • Good reactor to reactor repeatability for the gas product yields
  • Clear differences in CO and CO2 yield when using a higher LHSV

Hydrogen Consumption

Hydrogen consumption was measured using the online GC by comparing the outlet flow of hydrogen with the inlet flow.

As we can see in Figure 11, there is an expected step increase in the hydrogen consumption with increasing amount of VO in the feedstock.

  • Around 20% of the hydrogen fed into the system is consumed when processing the 100%VO feed
  • Good reproducibility for H2 consumption among duplicated reactors
  • Clear effect of LHSV on the LGO and LGO blends hydrotreating

Product Sulfur

The product sulfur was measured for the 40% and 70% VO blends at ULSD conditions. Note the very good repeatability of the S results for the duplicate reactors at such high conversion.

The reactors temperature was adjusted in order to produce < 5 ppmw S for the LHSV = 1 l/l/h

  • Very good reproducibility for product sulfur among duplicated reactors

Conclusions

  • No plugging was observed of any of small-scale reactors during the test of 23 days with various VO blends and 6 days running 100% VO
  • Quantifying the amount of water in the gas effluent using the online GC is a feasible method for closing the mass balance
  • The accuracy of the Mass Balance and Yields obtained during the test are similar to conventional hydroprocessing catalyst testing
  • High temperature SimDis is a feasible method for evaluating the conversion of triglycerides during VO hydrogenation tests
  • The reactor-to-reactor repeatability obtained during this test is similar to conventional hydroprocessing tests
  • The test allowed measuring accurately the HDS capacity of the catalyst at SOR conditions when processing LGO / VO blends
  • The Flowrence high-throughput 16-parallel reactors system produces consistent and reliable high data quality with outstanding reactor-to-reactor repeatability for Hydrotreating of Vegetable Oils
  • This opens new options for R&D in the field of renewables processing, reducing the amount of the scarcely available feedstocks required for studies

Flowrence® products specifications

Reactor Section

Easy and quick reactor exchange system. Possibility to use quartz reactors at high pressure.

1 block of 4 reactors

HT = High Temperature max. 800°C nominal, limited to 925°C (<0.5°C reactor to reactor deviation)

4 blocks of 4 reactors

HT  or MT = Medium Temperature max. 525°C (<0.5°C block-to-block deviation)

16 reactors with iRTC

individual Reactor Temperature Control
max. 550°C (<0.5°C reactor-to-reactor)

4 reactors with iRTC

individual Reactor Temperature Control
max. 550°C (<0.5°C reactor-to-reactor)

Temperature Ranges (°C)

100 – 800°C
up 925°C (Option)

50 – 525°C
100 – 800°C
up 925°C (Option)

50 – 550°C

50 – 550°C

Reactor Types

L= Length
OD= Outer Diameter
ID= Inner Diameter
SS= Stainless Steel (< 550⁰C)
Qz= Quartz (< 925⁰C)

L 300 mm 561 mm
OD 3 mm 6 mm
ID SS 2 / 2.6 mm 2 / 3 / 4 / 5 mm
ID Qz 2 mm 2 / 4 mm
300 mm 561 mm 561 mm
3 mm 3 mm 6 mm
2 / 2.6 mm 2 / 2.6 mm 2 / 3 / 4 / 5 mm
2 mm 2 mm 2 / 4 mm
561 mm
3 mm
2 / 2.6 mm
2 mm
561 mm
3 mm
2 / 2.6 mm
2 mm

Maximum Catalyst Bed Length

(isothermal zone tolerance ± 1°C)
Note: isothermal length is dependent on the temperature range

300 / 3 HT 561 / 6 HT
>120 mm @ 450°C >200 mm @ 500°C
>90 mm @ 800°C >150 mm @ 800°C
>140 mm @ 925°C
300 / 3 HT 561 / 3 MT 561 / 6 HT
>120 mm @ 450°C >310 mm @ 450°C >200 mm @ 500°C
>90 mm @ 800°C >150 mm @ 800°C
>140 mm @ 925°C
561 / 3 MT iRTC
250°C ±0.5°C 41cm (4reactors)
350°C±0.5°C 38cm (4reactors)
550°C±0.5°C 28cm (4reactors)
3 reactors at 550°C, 1 reactor 350°C:
550°C=27cm 350°C=41cm ±0.5°C
561 / 3 MT iRTC
250°C ±0.5°C 41cm (4reactors)
350°C±0.5°C 38cm (4reactors)
550°C±0.5°C 28cm (4reactors)
3 reactors at 550°C, 1 reactor 350°C:
550°C=27cm 350°C=41cm ±0.5°C

Catalyst Volume (mL)

(isothermal zone)

0.2 - 0.6 mL 0.4 - 2.0 mL
0.2 - 0.6 mL 0.4 - 1.0 mL 0.4 - 2.0 mL
0.4 - 1.0 mL
0.4 - 1.0 mL

Pressure Ranges (barg)

2 – 80 barg
0.5 – 180 barg (option)

2 – 100 barg
0.5 – 180 barg

2 – 80 barg
0.5 – 180 barg

2 – 20 barg
2 – 50 barg (option)

Reactor Pressure Control

Advanced control RSD ±0.1 barg at reference conditions (gas phase only and 20 barg). For trickle flow Advanced control RSD ±0.5barg.

Standard (±0.5 barg)
Advanced (±0.1 barg) (option)

Standard (±0.5 barg)
Advanced (±0.1 barg) (option)

Advanced (±0.1 barg)

Advanced (±0.1 barg)

Gas Feed Lines

(#Gas Feeds)

Up to 6 + Diluent gas

He, Ar, N2, H2, CH4, CO2, C2H4, C2H6, O2/Inert (≤5%), CO, Other gases

Up to 7 + Diluent gas

He, Ar, N2, H2, CH4, CO2, C2H4, C2H6, O2/Inert (≤5%), CO, Other gases

Up to 7 + Diluent gas

He, Ar, N2, H2, CH4, CO2, C2H4, C2H6, O2/Inert (≤5%), CO, Other gases

Up to 6 + Diluent gas

He, Ar, N2, H2, CH4, CO2, C2H4, C2H6, O2/Inert (≤5%), CO, Other gases

Online Analysis

Full integration GC, MS , GC/MS with data visualisation (option)

Full integration GC, MS , GC/MS with data visualisation

Full integration GC, MS , GC/MS with data visualisation

Full integration GC, MS , GC/MS with data visualisation

Liquid Feed

 Split feeding 8 + 8 reators (option)

Pump-Coriolis dosing system
(ambient, cooled)

Pump-Coriolis dosing system
(ambient, cooled, heated 80°C)

Pump-Coriolis dosing system
(ambient, cooled, heated 80°C)

Pump-Coriolis dosing system
(ambient, cooled, heated 80°C)

Liquid Distribution

Microfluidic Distribution
(4-channel glass-chip)

Microfluidics Distribution
(4x4-channel glass-chip)
(16-channel glass-chip)
Active Liquid Distribution (option)
(with automatic isolation valves)

Active Liquid Distribution
(with automatic isolation valves)

Microfluidic Distribution
(4-channel glass-chip)

Liquid Sampling

(G/L Separation)

Parallel liquid sampling (4 x 20ml vials) with sequential on-line gas phase sampling (option)

Automated liquid sampling (4 rows x 16 vials x 8ml) with sequential on-line gas phase sampling (option)

Automated liquid sampling (4 rows x 16 vials x 8ml) with sequential on-line gas phase sampling (option)

Parallel liquid sampling (4 x 20ml vials) with sequential on-line gas phase sampling (option)

Reactors Effluent Handling

(Off-line Analysis Connection)

Full heated circuit up to 180°C with sequential on-line full gas phase sampling (option)

Full heated circuit up to 200°C with sequential on-line full gas phase sampling

Full heated circuit up to 200°C with sequential on-line full gas phase sampling

Full heated circuit up to 200°C with sequential on-line full gas phase sampling

Offline Analysis

Integrated Workflow: SimDist, total S/N, liquid density, balance, label printer, barcode (option)

Integrated Workflow: SimDist, total S/N, liquid density, balance, label printer, barcode

Integrated Workflow: SimDist, total S/N, liquid density, balance, label printer, barcode

Integrated Workflow: SimDist, total S/N, liquid density, balance, label printer, barcode

Waste Handling

Ambient temperature
Heated wax trapping (option)

Ambient temperature / Cooled containers / Heated compartment (wax trapping, heavies)

Ambient temperature / Cooled containers / Heated compartment (wax trapping, heavies)

Ambient temperature / Cooled containers / Heated compartment (wax trapping, heavies)

Safety

Gas sensors and control box (CO, LEL, VOC)

Gas sensors and control box (CO, LEL, VOC)

Gas sensors and control box (CO, LEL, VOC)

Gas sensors and control box (CO, LEL, VOC)

Flowrence® Software

Flowrence® recipe builder, control & database builder

Flowrence® recipe builder, control & database builder

Flowrence® recipe builder, control & database builder

Flowrence® recipe builder, control & database builder

Microfluidics modular gas distribution

Unrivalled accuracy in gas distribution with patented glass-chips for 4 and 16 reactors, with a guaranteed flow distribution of 0.5% RSD. Quick exchange of glass-chips for different operating conditions. Flexibility to cover a wide range of applications.

TinyPressure glass-chip holder with integrated pressure measurement

Compact modular design for gas and liquid distribution. No high-temperature pressure sensors required. Quick exchange of the microfluidic glass-chips, without the need for time-consuming leak testing.

Tube-in-tube reactor technology with effluent dilution

Unique tube-in-tube design with easy and rapid exchange of the reactor tubes (within minutes!). No need for any connections. Use of inert diluent gas (outside of reactor) to maintain the pressure prevents dead volumes and back flow. Possibility to use quartz reactors at high pressure applications.

Automated liquid sampling system

Programmable, fully automated liquid product sampling robot for 24/7 hands-off operation. Robot equipped with a compact manifold aiming at depressurizing the effluent immediately after each reactor to atmospheric pressure. Eliminates the use of high pressure valves.

Reactor Pressure Control (RPC)

The most accurate and stable pressure regulator for a 16-parallel reactors with just ±0.1bar RSD. The RPC uses microfluidics technology to regulate the pressure of each reactor, maintaining equal distribution of the inlet flow over the 16 reactors.

Auto-calibrating liquid feed distribution, measurement, and control

Distribution of difficult feedstocks e.g., VGO, HVGO, DAO. Liquid distribution 0.2% RSD, making it the most accurate liquid distribution device on the market. Option to selectively isolate each reactor.

Single-Pellet-String-Reactors (SPSR)

No dead-zones, no bed packing & distribution effects. The catalyst packing is straightforward and does not require special procedures. A single string of catalyst particles is loaded in the reactors avoiding maldistribution, eliminating channeling and incomplete wetting.

EasyLoad®

Unique reactor closing system with no connections. Rapid reactor replacement minimizing delays, improving uptime and reliability. Stable evaporation by liquid injection into reactor.

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