Method and apparatus for continuous flow microwave-assisted chemistry techniques

Abstract

The invention is a method and associated instrument for microwave assisted chemistry. The invention includes the steps of directing a continuous flow of fluid through a microwave cavity while applying microwave radiation to the cavity and to the continuous flow of materials therein, monitoring the pressure of the fluid in the cavity; and cooling the fluid in the cavity when the pressure exceeds a predetermined setpoint pressure.

1 . A method of microwave assisted chemistry comprising: 
 directing a continuous flow of fluid through a microwave cavity while applying microwave radiation to the cavity and to the continuous flow of materials therein;    monitoring the pressure of the fluid in the cavity; and    cooling the fluid in the cavity when the pressure exceeds a predetermined setpoint pressure.    
     
     
         2 . A method according to  claim 1  wherein the cooling step comprises moderating the degree of cooling in response to the monitored pressure.  
     
     
         3 . A method according to  claim 1  wherein the step of cooling the fluid in the cavity comprises circulating a coolant in the cavity in response to the pressure setpoint determination.  
     
     
         4 . A method according to  claim 3  comprising circulating air as the coolant in the cavity.  
     
     
         5 . A method according to  claim 1  comprising directing the continuous flow of fluid through a single mode microwave cavity.  
     
     
         6 . A method according to  claim 1  wherein the step of directing the fluid comprises directing the fluid in the presence of a catalyst.  
     
     
         7 . A method according to  claim 1  wherein the step of directing the fluid comprises directing the fluid in the presence of a scavenging composition.  
     
     
         8 . A method according to  claim 1  wherein the steps of monitoring and cooling comprise: 
 sending a signal representative of the pressure from a pressure monitor to a processor;  
 using the processor to compare the monitored pressure to the setpoint pressure; and  
 sending a signal from the processor that initiates and runs a cavity cooling device whenever the monitored pressure exceeds the setpoint pressure.  
 
     
     
         9 . A method according to  claim 1  wherein the steps of directing and cooling the fluid comprise: 
 directing the fluid through a tube; and  
 externally cooling the tube.  
 
     
     
         10 . A method according to  claim 9  wherein the step of externally cooling the tube comprises directing a cooling fluid over the exterior of the tube.  
     
     
         11 . A method of microwave assisted chemistry comprising 
 carrying out a chemical reaction in batch format while irradiating the reactants with microwave radiation and while concurrently externally cooling the reaction vessel to thereby identify an optimum power level for the reaction and without exceeding a temperature at which the reactants decompose;    thereafter directing a continuous flow of corresponding reactants through a single mode microwave cavity while applying microwave radiation to the cavity and to the continuous flow of materials therein at the power level identified during batch format reaction of the same reactants; and    externally cooling the flowing reactants while applying the microwave radiation in order to continue at the identified power level while avoiding an undesired increase in the temperature of the reaction.    
     
     
         12 . A method of microwave assisted chemistry comprising: 
 directing a continuous flow of fluid that includes reactants through a single mode microwave cavity while applying microwave radiation to the cavity and to the continuous flow of materials therein; and    purifying the reaction products with a scavenging composition in a single-mode microwave cavity.    
     
     
         13 . A method according to  claim 1  wherein the scavenging step comprises directing the fluid through a column filled with a solid support that includes a scavenging functional group selected from the group consisting of electrophilic scavengers, nucleophilic scavengers, and combinations thereof.  
     
     
         14 . A method according to  claim 12  and further comprising: 
 monitoring the pressure of the fluid in the cavity; and  
 cooling the fluid in the cavity when the pressure exceeds a predetermined setpoint.  
 
     
     
         15 . A method according to  claim 12  and further comprising: 
 monitoring the pressure of the fluid in the cavity; and  
 moderating the applied microwave power when the pressure exceeds a predetermined setpoint.  
 
     
     
         16 . A method according to  claim 12  and further comprising: 
 monitoring the temperature in the cavity; and  
 cooling the fluid in the cavity when the temperature exceeds a predetermined setpoint.  
 
     
     
         17 . A method according to  claim 12  and further comprising: 
 monitoring the temperature in the cavity; and  
 moderating the applied microwave power when the temperature exceeds a predetermined setpoint.  
 
     
     
         18 . A method according to  claim 12  and further comprising immediately directing the purified reaction products to a separation step.  
     
     
         19 . A method according to  claim 18  wherein the separation step comprises chromatography.  
     
     
         20 . A method according to  claim 19  wherein the chromatography step comprises high pressure liquid chromatography.  
     
     
         21 . An instrument for microwave assisted chemistry comprising: 
 a microwave cavity;    a flow cell in said cavity;    a pump for directing fluid reactants from at least one source to said flow cell;    a pressure meter in fluid communication with said flow cell for measuring the pressure of fluid in said flow cell; and    a cooling system for cooling said flow cell in said cavity.    
     
     
         22 . A microwave instrument according to  claim 21  and further comprising: 
 a processor in communication with said pressure meter and said cooling system for moderating the cooling of said flow cell in said cavity in response to the pressure measured by said pressure meter.  
 
     
     
         23 . A microwave instrument according to  claim 22  and further comprising: 
 a microwave source in communication with said cavity  
 and wherein said processor is in communication with said source for moderating the application of microwaves from the source in response to the pressure detected by said pressure meter.  
 
     
     
         24 . A microwave instrument according to  claim 23  and further comprising a temperature detector in said cavity and in communication with said processor for moderating the application of microwaves from said source or moderating the cooling of said flow cell by said cooling system in response to the temperature measured by said detector.  
     
     
         25 . A microwave instrument according to  claim 21  comprising a single mode cavity.  
     
     
         26 . A microwave instrument according to  claim 21  wherein said flow cell comprises: 
 a microwave-transparent support structure; and  
 microwave transparent tubing on said support structure.  
 
     
     
         27 . A microwave instrument according to  claim 21  comprising a scavenging cell in said cavity.