System for operating parallel reactors, which system comprises: - a plurality of reactor assemblies, each reactor assembly comprising: - a flow-through reactor, said flow-through reactor comprising a reactor inlet and a reactor outlet, - a reactor feed line, which reactor feed line has a first end and a second end, said second end being connected to the reactor inlet of the flow-through reactor, said reactor feed line being adapted to supply a fluid to the flow-through reactor, - a reactor effluent line, which reactor effluent line has a first end, which first end is connected to the reactor outlet of the flow-through reactor, said reactor effluent line being adapted to discharge reactor effluent from the reactor, - a primary fluid source, which primary fluid source is adapted to provide a pressurized fluid to the flow-through reactors, - a flow splitter which is arranged downstream of the primary fluid source and upstream of the reactor assemblies, said flow splitter having an inlet and multiple passive flow restrictors, wherein the inlet of the flow splitter is connected to the primary fluid source and each passive flow restrictor is in fluid communication with said inlet, and wherein each passive flow restrictor has an outlet, which outlet is connected to the first end of the reactor feed line of its own dedicated reactor assembly, and wherein all passive flow restrictors have an substantially equal resistance to fluid flow wherein the system further comprises a feed line pressure measurement device, said feed line pressure measurement device being adapted to measure the pressure in the fluid flow in the reactor feed lines, and wherein in each reactor effluent line an individually controllable backpressure regulator is provided, said backpressure regulator being adapted to regulate the pressure in each reactor effluent line individually, and wherein further a pressure control arrangement is provided, said pressure control arrangement being linked to said feed line pressure measurement device and said backpressure regulators, said pressure control arrangement comprising an input device allowing to input at least a feed line pressure setpoint into the pressure control arrangement, said feed line pressure setpoint representing a desired feed line pressure, said desired feed line pressure being the same for all reactor assemblies, wherein said pressure control arrangement is adapted and/or programmed to individually control the backpressure regulators such that for each reactor assembly the pressure measured in the reactor feed line by the feed line pressure measurement device is compared to said feed line pressure setpoint and in case of a difference between the measured feed line pressure and the feed line pressure setpoint, the corresponding backpressure regulator being adjusted such that the measured feed line pressure becomes substantially the same as the feed line pressure setpoint, and therewith substantially the same as the feed line pressures in the other reactor assemblies. - a plurality of reactor assemblies, each reactor assembly comprising: - a flow-through reactor, said flow-through reactor comprising a reactor inlet and a reactor outlet, - a reactor feed line, which reactor feed line has a first end and a second end, said second end being connected to the reactor inlet of the flow-through reactor, said reactor feed line being adapted to supply a fluid to the flow-through reactor, - a reactor effluent line, which reactor effluent line has a first end, which first end is connected to the reactor outlet of the flow-through reactor, said reactor effluent line being adapted to discharge reactor effluent from the reactor, - a flow-through reactor, said flow-through reactor comprising a reactor inlet and a reactor outlet, - a reactor feed line, which reactor feed line has a first end and a second end, said second end being connected to the reactor inlet of the flow-through reactor, said reactor feed line being adapted to supply a fluid to the flow-through reactor, - a reactor effluent line, which reactor effluent line has a first end, which first end is connected to the reactor outlet of the flow-through reactor, said reactor effluent line being adapted to discharge reactor effluent from the reactor, - a primary fluid source, which primary fluid source is adapted to provide a pressurized fluid to the flow-through reactors, - a flow splitter which is arranged downstream of the primary fluid source and upstream of the reactor assemblies, said flow splitter having an inlet and multiple passive flow restrictors, wherein the inlet of the flow splitter is connected to the primary fluid source and each passive flow restrictor is in fluid communication with said inlet, and wherein each passive flow restrictor has an outlet, which outlet is connected to the first end of the reactor feed line of its own dedicated reactor assembly, and wherein all passive flow restrictors have an substantially equal resistance to fluid flow