Upgrading By Hydrocracking: Selected Areas Of R&D Interest At CANMET
Authors: Kriz J.F. , Ternan M. , Denis J.M. 
Published: March 2010

Hydro-cracking is one of the recognized routes for converting low-grade petroleum resources, such as oil-sand bitumens, heavy oils or refinery residual oils, to liquid fuels. High-pressure operation and substantial hydrogen requirements are common to most hydro-cracking processes, but the reactor arrangement and catalyst used may differ. The major objective to maximize conversion of the high-boiling pitch fraction into liquids competes with the objective of trouble-free operation. Using low-cost additives or developing fouling-resistant, catalysts can offer significant process improvements. Catalysts can improve liquid product quality, but this is offset by deactivation problems. It appears desirable to incorporate into the catalyst a strong hydrogenation component which would stabilize the reaction intermediates. Feedstock characteristics also affect process operability. Process performance can be determined experimentally by observing the sensitivity to feedstock properties and to gaseous components.

Introduction

It is generally believed that utilization of unconventional sources of liquid fuels will increase substantially as conventional crude oils become too scarce to satisfy the demand. Oil sands and heavy oils are important unconventional sources of hydrocarbons in Canada. From the refining point of view, these are low-grade materials from which useable liquids have to be obtained through chemical conversion, resulting in the production of "synthetic crudes ".

Hydro-cracking is one of the recognized conversion routes. Being a hydrogen addition process, as opposed to carbon extraction processes, it upgrades the original material by raising its over-all hydrogen : carbon ratio while reducing the average relative molecular mass. Such a conversion is brought about by contacting the material with hydrogen at high pressure and elevated temperature.

The operating commercial upgrading plants and the projects under development in Canada have selected coking processes in all cases. Hydro-cracking processes, as opposed to coking, do not generate by-product coke. This results in increased liquid product yield per unit volume of feedstock. The high liquid yield and flexibility in operation of hydro-crackers can offer considerable economic benefits.

Effects of operating conditions and catalyst properties on product quality and on ease of operation are of fundamental importance in the development of hydro-cracking processes. For example, the key factor to operation at moderate pressure and high conversions achieved in the CANMET Process is the presence of an inexpensive additive in the feed (Lunin et al., 1981). The feed properties are equally important when applying the hydro-cracking process. Catalysts or additives could be optimized for use with a selected feedstock.

Increasing quantities of bitumen and heavy-oil derived liquids are expected to stimulate new developments in secondary refining as well. Work at CANMET's Energy Research Laboratories has dealt with hydroprocessing of both virgin and derived materials to assess the effects of catalysts and processing conditions. This paper, intended to present a brief review of findings related to hydro-cracking, deals with selected aspects of thermal and catalytic hydro-cracking of bituminous oils and briefly comments on the co-processing of these materials with coal. For brevity, the findings collected from a number of published studies are presented without supporting data or illustrations.