It's pretty straightforward, except maybe for the use of XAttribute to add a named namespace:
XNamespace ns1 = "http://localhost:8080/WsNFe2/lote";
XNamespace tipos = "http://localhost:8080/WsNFe2/tp";
XNamespace xsi = "http://www.w3.org/2001/XMLSchema-instance";
var doc = new XElement(ns1 + "ConsultaSeqRps",
new XAttribute(XNamespace.Xmlns + "ns1", ns1),
new XAttribute(XNamespace.Xmlns + "tipos", tipos),
new XAttribute(XNamespace.Xmlns + "xsi", xsi),
new XAttribute(xsi + "schemaLocation",
"http://localhost:8080/WsNFe2/lote http://localhost:8080/WsNFe2/xsd/ConsultaSeqRps.xsd")
);