Catalytic fixed bed membrane reactor operation for hydrocarbon conversion processes

摘要

Dry/CO2 reforming is one the hydrocarbon processes that recently has beeninteresting due to it is ability of producing a lower synthesis gas ratio (H2/CO).This synthesis gas is a highly significant product since it costs more than 50%of the total capital cost of gas to liquid (GTL) process. However, since thisreaction is thermodynamically limited, higher temperature or lower pressure isrequired to achieve higher conversion. Typically, reaction temperaturesbetween 1073 and 1173 K are used for catalytic dry reforming reactions.Consequently, these extreme temperatures lead to a severe carbondeposition causing a catalyst deactivation which is the major difficulty relatedto CO2 reforming reaction. This has pushed the efforts to be focused mainlyon the development of new catalysts. In fact, dry reforming of propane is anequilibrium-limited reaction which can be shifted to the product side byremoving one of the products out of the system which can be achieved usinga selective membrane reactor.This research is dedicated to investigate and study the catalytic performanceof dry reforming of propane over cobalt-nickel catalyst under the temperaturerange of 773-973 K. This bimetallic catalyst supported on δ-Al2O3 has beenutilized in this research since it exhibits better activity, selectivity, anddeactivation resistance than monometallic catalysts. Based on this, theprimary aims of this thesis are to examine this catalyst and to study the impactof using membrane reactor. In addition, the reaction mechanism and kineticare investigated using a fixed-bed reactor.Experimental observations have exposed that the catalyst is offering goodresults under this reaction. The catalysts analysis has confirmed the presenceof metal oxides in the catalyst. However, only at a lower carbon dioxide topropane ratio, i.e. lower than 3.5, a carbon signal has been reported. Theactivation energy study indicates that the process is unlimited by diffusion.The reaction order for propane and carbon dioxide has been found to be zeroand 1.17 respectively. This in turn has indicated that C3H8 activation reactionis taking place rapidly and carbon dioxide is suggested to be involved in therate determining step. In membrane reactor operation, the production rates forH2 and CO have been reported to increase as the sweep gas flow rateincreases. The co-current mode offers higher production rate and morestability than counter-current mode over the range of feed ratio. On the otherhand, fixed bed reactor shows stable performance and produces more COand H2 for both modes.