Hydrotreating of gas-oils: A comparison of trickle-bed and upflow fixed bed lab scale reactors

Hydrotreating reactions of distillates and gas-oils are industrially performed in trickle bed reactors, on the scale of several meters in diameter and height. For the development of new catalysts and processes in the laboratory, a realistic scale down of this process is necessary. The smaller the scale of the laboratory unit, the lower the investment and operating costs, smaller amounts of materials to handle and dispose off, and increased safety of the operation. Lab-scale reactors are usually much shorter than the industrial reactors and thus have different height to diameter ratios, leading to much lower linear gas and liquid velocities when operated at similar residence times. For catalyst testing with the purpose of discriminating among commercial catalysts not only should the ranking of catalysts be correct, the lab-scale or pilot testing operation should also allow the prediction of the full scale operation with respect to feedstock/operating conditions, catalyst, and product quality. To fulfill this ambition it follows that the testing must be done with real feedstocks. The choice of reactor type is then limited to either using trickle bed reactors, or up-flow fixed bed reactors. The purpose of this chapter is to give some experimental results comparing catalyst testing in bench scale/small pilot scale units employing trickle bed as well as upflow reactors, and comparing with activity data from commercial use of the same catalyst.