This invention relates to an apparatus, comprising: a plurality of plates in a stack defining at least one process layer and at least one heat exchange layer, each plate having a peripheral edge, the peripheral edge of each plate being welded to the peripheral edge of the next adjacent plate to provide a perimeter seal for the stack, the ratio of the average surface area of each of the adjacent plates to the average penetration of the weld between the adjacent plates being at least about 100 cm.sup.2/mm. The stack may be used as the core assembly for a microchannel processor. The microchannel processor may be used for conducting one or more unit operations, including chemical reactions such as SMR reactions.

The disclosed invention relates to a process for converting ethylbenzene to styrene, comprising: flowing a feed composition comprising ethylbenzene in at least one process microchannel in contact with at least one catalyst to dehydrogenate the ethylbenzene and form a product comprising styrene; exchanging heat between the process microchannel and at least one heat exchange channel in thermal contact with the process microchannel; and removing product from the process microchannel. Also disclosed is an apparatus comprising a process microchannel, a heat exchange channel, and a heat transfer wall positioned between the process microchannel and heat exchange channel wherein the heat transfer wall comprises a thermal resistance layer.

Reactors are provided that can include a first set of fluid channels and a second set of fluid channels oriented in thermal contact with the first set of fluid channels. The reactor assemblies can also provide where the channels of either one or both of the first of the set of fluid channels are non-linear. Other implementations provide for at least one of the first set of fluid channels being in thermal contact with a plurality of other channels of the second set of fluid channels. Reactor assemblies are also provided that can include a first set of fluid channels defining at least one non-linear channel having a positive function, and a second set of fluid channels defining at least another non-linear channel having a negative function in relation to the positive function of the one non-linear channel of the first set of fluid channels. Processes for distributing energy across a reactor are provided. The processes can include transporting reactants via a first set of fluid channels to a second set of fluid channels, and thermally engaging at least one of the first set of fluid channels with at least two of the second set of fluid channels.

A plurality of microfluidic chips are prepared in which a main chip having a minute space into which a liquid is introduced is held in a guide. These microfluidic chips are connected in a row, and the minute spaces provided in two adjacent main chips are connected by a joint chip. The joint chip is held half each by the respective guides so as to straddle the two adjacent main chips to form a portion of a flow channel including the minute spaces provided in the two main chips. The minute spaces included in the two adjacent main chips and a communication flow path built into the joint chip are connected by a main communication hole of the main chip and a joint communication hole of the joint chip to form a flow channel.