Supercritical Methanol Biodiesel (SMB) Process

RPS offers Biodiesel Production Process through Supercritical method. The Supercritical Biodiesel Production Process is the third generation technology that does not require any catalyst whatsoever to convert Feedstocks (Oils & Fats) with a wide range of Fatty Acid range between 0 to 100 percent to Methyl Esters and high-quality Glycerin. This production method has simplified operations compared to a conventional production process (such as esterification, glycerolysis, enzymatic and transesterification production methods) and involves minimal monitoring. The overall processing cost compared to a traditional production process is reduced by 30 percent including the carbon footprint. 

RPS has built to date two Supercritical Biodiesel Production facilities and are the largest facilities in the world. We have the exclusive rights to the Patents related Supercritical Biodiesel Production Process. The future of renewable fuels such as Biodiesel and its intrinsic value is dependent on energy efficient processing method and processing capability of low-value feedstocks. The Supercritical Biodiesel Production Process fits very well in the above criteria. 

Supercritical Biodiesel Process Flow Diagram

Supercritical Process Advantages


  1. Process can handle Oils & Fats with Fatty Acid up to 100 percent.
  2. No use of Acid or Base Catalyst whatsoever.
  3. Processing cost far below Conventional Process.
  4. No Soaps, No Salts and No Side Products formed during the process.
  5. Glycerin Purity greater than 95 percent and sold as Technical Grade.
  6. Hands free operation with low maintenance and no downtime.
  7. Finished Biodiesel exceeds ASTM-6751 Standards.
RPS provides a wide range of Feedstock Filtration processes depending on the impurity of the primary feedstock.

Usually, the feedstocks consumed in the Biodiesel industry range from vegetable oils to animal fats. The impurities in Vegetable oils such as gums, phospholipids, proteins, etc that are insoluble in oils when hydrated and are extracted using centrifugal force. The same applies to particulate matter and protein in animal fats.

Any residual impurity left in the feedstock after the first stage of washing can is reduced by either second stage water-washing the oil or through special sorbents and filtration.

We have developed a simplified Feedstock Filtration process that maintains the feedstock quality for Biodiesel production.

Feedstocks both Vegetable Oils and Animal Fats with a wide range of Fatty Acid level ranging from 0 to 100 percent are blended with Methanol to convert to Methyl Esters in our Supercritical System. The system operates under high pressure and temperature where Methanol is under Supercritical state. Both Esterification and Transesterification reactions occur at the same time. The conversion rates to Methyl Ester are greater than 99.5 percent in a single step depending on the molar ratios of various compounds. The side-product Glycerin purity is higher than 95 percent.

RPS is the only firm that offers Supercritical systems. We hold the patent rights for this method. We have deployed several Supercritical facilities and built the largest supercritical based Biodiesel production facility to date. The Supercritical step is a continuous hands-free operation that needs no monitoring and extremely safe. We have mastered, high pressure and temperature reactions over several years of research, development and operation experience.

The Supercritical Process output stream which is a mixture of majority Methyl Ester, Methanol and Glycerin is fed to the Methanol Evaporator to recover and recycle the Methanol to the purity required for the Supercritical step.

Our Methanol Evaporator operates with very low energy requirement due to efficient energy management between Supercritical process and Methanol Evaporator. Our evaporator has both stripping and rectification sections to separate Methanol from Methyl Esters and Glycerin streams.

RPS has deployed several evaporators around the world, and we have extensive experience for any complex feed compositions. Read more…

The Wet Methyl Esters produced from the Supercritical steps are washed with recycled process water in a high-speed centrifuge. The Disc Stack Centrifuge used for the washing step allow less use of process water compared to a Conventional washing step. Also, due to high G-forces inside the centrifuge, the impurity levels in Methyl Esters such as soaps and free glycerin are maintained far below the ASTM-6751 specifications. RPS deployed several Disc Stack Centrifuges over the years for the washing step, and we work with GEA Westfalia for our Centrifuge needs.

In the washing step, we use water between 5 to 10 percent ratio to the Methyl Ester flow. Also, the process water used in the washing step is recovered and reused.

The washed Methyl Ester is distilled under deep vacuum and high temperature to produce clear Biodiesel that exceeds ASTM-6751 specification. Our distillation columns are far more efficient compared to the competition. Our distillation columns use far less reflux feedback to the column, which helps reduce energy. The loss incurred from column bottoms is less than 2 percent. The column bottoms are fed back into the filtration unit to improve yields, and some part of it separated for storage. Read more…

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